CN114002510A

CN114002510A - Capacitance detection device and method and motor control equipment

Info

Publication number: CN114002510A
Application number: CN202111341288.5A
Authority: CN
Inventors: 谭章德; 王长恺; 区均灌; 王岩; 郑培杰
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2021-11-12
Filing date: 2021-11-12
Publication date: 2022-02-01
Also published as: WO2023082712A1

Abstract

The invention discloses a capacitance detection device, a capacitance detection method and motor control equipment, wherein the device comprises: the switch unit is in a closed state under the condition that the motor control equipment needs to control the motor system to be electrified and started so as to electrify the motor control equipment; the detection unit is used for detecting the voltage at two ends of at least one capacitor module in the more than four capacitor modules and recording the voltage as capacitor voltage under the condition that the motor control equipment controls the motor system to be electrified and started; detecting the current flowing through more than four capacitor modules and recording the current as the capacitor current; the control unit determines whether the bus capacitor unit is abnormal or not according to at least one of the capacitor voltage and the capacitor current; and sending a protection signal under the condition that the bus capacitor unit is determined to be abnormal; and the switch unit is also switched from a closed state to an open state according to the protection signal. According to the scheme, the electrolytic capacitor is subjected to comprehensive fault detection in the power-on stage of the motor system, so that the safety of the motor system is improved.

Description

Capacitance detection device and method and motor control equipment

Technical Field

The invention belongs to the technical field of motor systems, and particularly relates to a capacitance detection device, a capacitance detection method and motor control equipment, in particular to a capacitance abnormality detection circuit and a capacitance abnormality detection method applied to a servo driver and motor control equipment (such as the servo driver, a frequency converter and the like).

Background

The servo driver is widely applied to the fields of industrial robots and numerical control machines, and the requirement of users on the reliability of products is higher and higher. The electrolytic capacitor has large storage charge amount per unit volume, and is applied to a rectifying filter and an energy storage circuit of a servo driver. The electrolytic capacitor for rectification and filtering influences the stability of the direct-current bus voltage, and is a key component for controlling performance of the servo driving system and long-term reliable operation of the servo driving system. The change of load causes the frequent charging and discharging of the electrolytic capacitor, and the temperature rise caused by heat loss is an important factor for the failure of the electrolytic capacitor. In the servo driver, an electrolytic capacitor is one of the devices with higher failure rate.

In the related scheme, for capacitor detection, only the voltage and the current of a main loop are generally detected, and the electrolytic capacitor is not subjected to comprehensive fault detection.

The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.

Disclosure of Invention

The invention aims to provide a capacitance detection device, a capacitance detection method and motor control equipment, so as to solve the problem that potential safety hazards exist in a motor system because the voltage and the current of a main loop are generally only detected and the electrolytic capacitor is not subjected to comprehensive fault detection in the related scheme for capacitance detection, and achieve the effect of improving the safety of the motor system by comprehensively detecting the fault of the electrolytic capacitor in the power-on stage of the motor system.

The present invention provides a capacitance detection device that can be applied to a motor control apparatus of a motor system; the motor control apparatus includes: the device comprises a rectifying unit, a bus capacitor unit, an inverter unit, a detection unit and a control unit; the bus capacitor unit includes: a capacitance module and a resistance module; the number of the capacitor modules is more than four, and the number of the resistor modules is the same as that of the capacitor modules; the four or more capacitor modules are divided into two capacitor groups, two capacitor modules in the first capacitor group are arranged in parallel, two capacitor modules in the second capacitor group are also arranged in parallel, and the first capacitor group and the second capacitor group are arranged in series; each capacitor module is connected with one corresponding resistor module in parallel; the capacitance detection device includes: a switch unit; the switch unit is configured to be in a closed state to enable the motor control equipment to be electrified under the condition that the motor control equipment needs to control the motor system to be electrified and started; the detection unit is configured to detect the voltage at two ends of at least one capacitor module in more than four capacitor modules and record the voltage as the capacitor voltage under the condition that the motor control equipment controls the motor system to be powered on and started; detecting the current flowing through more than four capacitor modules and recording the current as capacitor current; the control unit is configured to determine whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current; and sending a protection signal when the bus capacitor unit is determined to be abnormal; the switch unit is further configured to switch from the closed state to an open state according to the protection signal so as to power off the motor control device.

In some embodiments, four or more of the capacitive modules comprise: the first capacitor module, the second capacitor module, the third capacitor module and the fourth capacitor module; the first capacitor module and the third capacitor module are connected in series to form the first capacitor bank; the second capacitor module and the fourth capacitor module are connected in series to form the second capacitor bank; the detection unit includes: the device comprises a voltage sampling module and a current sampling module; the detecting unit detects a voltage across at least one of the four or more capacitor modules, and includes: the voltage sampling module is arranged between the positive end and the negative end of a bus of the output end of the bus capacitor unit and is configured to detect the voltage at two ends of at least one capacitor module in more than four capacitor modules; the detection unit detects currents flowing through four or more of the capacitor modules, and includes: the current sampling module is arranged between a bus negative end of an output end of the rectifier bridge and a bus negative end of an input end of the bus capacitor unit, and is configured to detect currents flowing through more than four capacitor modules.

In some embodiments, the voltage sampling module comprises: the device comprises a first sampling resistor module, a second sampling resistor module and a third sampling resistor module; the first sampling resistance module, the second sampling resistance module and the third sampling resistance module are arranged between the positive end and the negative end of a bus of the output end of the bus capacitance unit; the common end of the first sampling resistance module and the second sampling resistance module is connected to the common end of the first capacitor module and the second capacitor module and is connected to the common end of the third capacitor module and the fourth capacitor module; the current sampling module comprises: a fourth sampling resistance module; the fourth sampling module is arranged between the negative bus terminal of the output end of the rectifier bridge and the negative bus terminal of the input end of the bus capacitor unit.

In some embodiments, the motor control apparatus further includes: a regenerative braking unit; the regenerative braking unit is arranged between the bus capacitor unit and the inverter unit; the voltage sampling module is arranged between the bus capacitor unit and the regenerative braking unit.

In some embodiments, the switch unit is disposed between a positive dc bus terminal of the output terminal of the rectifier bridge and a positive dc bus terminal of the input terminal of the bus capacitor unit.

In some embodiments, the motor control apparatus further includes: a current-limited starting unit; the switch unit is arranged between the rectifier bridge and the current-limiting starting unit.

In some embodiments, the capacitor voltage comprises at least one of: a dc bus voltage at an output of the bus capacitor unit, a voltage between a first end of the first capacitor bank and a second end of the first capacitor bank, and a voltage between a first end of the second capacitor bank and a second end of the second capacitor bank; recording a voltage between a first end of the first capacitor bank and a second end of the first capacitor bank as a first voltage; recording a voltage between a first end of the second capacitor bank and a second end of the second capacitor bank as a second voltage; the capacitance current comprises at least one of the following: the current flowing through the whole of the four current modules and the current flowing through each of the four or more capacitor modules; the current flowing through the whole of the four current modules is recorded as charging current; the current flowing through the first capacitor module is recorded as a first current; the current flowing through the second capacitor module is recorded as a second current; the current flowing through the third capacitor module is recorded as a third current; and the current flowing through the fourth capacitor module is recorded as a fourth current.

In some embodiments, the determining, by the control unit, whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current includes: if the first voltage is equal to the direct-current bus voltage, determining that partial devices in the second capacitor bank have short-circuit faults; and if the second voltage is equal to the direct current bus voltage, determining that partial devices in the first capacitor bank have short-circuit faults.

In some embodiments, the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and further includes: if the difference value between the first voltage and the second voltage exceeds a first preset value in the process of charging the first capacitor bank and the second capacitor bank; after the first capacitor bank and the second capacitor bank are charged, if the first voltage is equal to the second voltage, determining that a capacitor open-circuit fault occurs in the first capacitor bank and the second capacitor bank; wherein a capacitive open fault is determined to occur in the first capacitive bank if the charging current is equal to the sum of the second current and the fourth current; determining that a capacitive open fault has occurred in the second capacitive bank if the charging current is equal to the sum of the first current and the third current.

In some embodiments, the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and further includes: after the first capacitor bank and the second capacitor bank are charged, if one of the first voltage and the second voltage changes fast, the other voltage changes slowly; and after the first voltage and the second voltage reach new balance, if the difference value of the first voltage and the second voltage exceeds a second preset value, determining that the resistance module in the bus capacitor unit has an open circuit fault or an aging phenomenon.

In some embodiments, the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and further includes: determining the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit according to the charging current, the capacitor voltage and the charging time of the capacitor module in the bus capacitor unit in the charging process; and determining the aging degree of the capacitor module in the bus capacitor unit according to the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit based on the corresponding relation among the set capacity, the set resistance value and the set aging degree.

In accordance with another aspect of the present invention, there is provided a motor control apparatus including: the capacitance detection device described above.

In accordance with the motor control device, a further aspect of the present invention provides a capacitance detection method, including: under the condition that the motor control equipment needs to control the motor system to be powered on and started, enabling a switch unit to be in a closed state so as to enable the motor control equipment to be powered on; under the condition that the motor control equipment controls the motor system to be powered on and started, detecting the voltage at two ends of at least one capacitor module in more than four capacitor modules and recording the voltage as capacitor voltage; detecting the current flowing through more than four capacitor modules and recording the current as capacitor current; determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current; and sending a protection signal when the bus capacitor unit is determined to be abnormal; and switching the switch unit from the closed state to an open state according to the protection signal so as to power off the motor control equipment.

In some embodiments, determining whether the bus capacitive unit is abnormal based on at least one of the capacitive voltage and the capacitive current includes: if the first voltage is equal to the direct-current bus voltage, determining that partial devices in the second capacitor bank have short-circuit faults; and if the second voltage is equal to the direct current bus voltage, determining that partial devices in the first capacitor bank have short-circuit faults.

In some embodiments, determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: if the difference value between the first voltage and the second voltage exceeds a first preset value in the process of charging the first capacitor bank and the second capacitor bank; after the first capacitor bank and the second capacitor bank are charged, if the first voltage is equal to the second voltage, determining that a capacitor open-circuit fault occurs in the first capacitor bank and the second capacitor bank; wherein a capacitive open fault is determined to occur in the first capacitive bank if the charging current is equal to the sum of the second current and the fourth current; determining that a capacitive open fault has occurred in the second capacitive bank if the charging current is equal to the sum of the first current and the third current.

In some embodiments, determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: after the first capacitor bank and the second capacitor bank are charged, if one of the first voltage and the second voltage changes fast, the other voltage changes slowly; and after the first voltage and the second voltage reach new balance, if the difference value of the first voltage and the second voltage exceeds a second preset value, determining that the resistance module in the bus capacitor unit has an open circuit fault or an aging phenomenon.

In some embodiments, determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: determining the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit according to the charging current, the capacitor voltage and the charging time of the capacitor module in the bus capacitor unit in the charging process; and determining the aging degree of the capacitor module in the bus capacitor unit according to the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit based on the corresponding relation among the set capacity, the set resistance value and the set aging degree.

Therefore, according to the scheme of the invention, the capacitance abnormity detection circuit is arranged in the frequency conversion equipment (such as a servo driver and a frequency converter) of the motor system, and the main capacitance circuit of the frequency conversion equipment is subjected to abnormity detection by using the capacitance abnormity detection circuit in the power-on stage of the motor system, so that fault treatment is carried out in time when the abnormity of the main capacitance circuit is detected; therefore, the electrolytic capacitor is subjected to comprehensive fault detection in the power-on stage of the motor system, and the safety of the motor system is favorably improved.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

FIG. 1 is a schematic structural diagram of a capacitance detection device according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an embodiment of a servo driver in a related art;

FIG. 3 is a schematic diagram of an embodiment of a main capacitor circuit;

FIG. 4 is a schematic diagram of an embodiment of a short circuit fault of a device in the main capacitor circuit portion;

FIG. 5 is a schematic diagram of an embodiment of a partial capacitive open circuit fault of the main capacitive circuit;

FIG. 6 is a schematic diagram of an embodiment of a voltage sharing resistor open fault in the main capacitor circuit portion;

FIG. 7 is a schematic structural diagram of an embodiment of an equivalent model of an electrolytic capacitor;

FIG. 8 is a schematic diagram of an embodiment of a main capacitor circuit with equivalent series resistance taken into account;

FIG. 9 is a schematic diagram of an embodiment of an additional capacitance anomaly detection circuit;

FIG. 10 is a voltage waveform schematic of a capacitor charging process;

FIG. 11 is a schematic diagram of a charging waveform when a portion of the capacitor is open;

FIG. 12 is a schematic diagram of a charging waveform when part of the equalizing resistors is abnormal;

FIG. 13 is a schematic diagram of a charging waveform for capacitance degradation detection;

FIG. 14 is a flowchart illustrating a capacitance detection method according to an embodiment of the invention;

fig. 15 is a flowchart illustrating an embodiment of determining the aging degree of the capacitor module in the bus capacitor unit according to the method of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Some schemes provide a method for identifying failure parameters of an electrolytic capacitor in a direct current converter, and the method is used for identifying Equivalent Series Resistance (ESR) by monitoring ripple current and ripple voltage of the electrolytic capacitor so as to judge whether the capacitor fails. In other schemes, the problem that the voltage sharing of two ends of a capacitor used in series is abnormal can be solved, and the reliability of the capacitor in the using process is improved. However, the capacitance state monitoring methods in these schemes all use additional hardware circuits, such as a capacitance current sensor, a voltage sensor, and the like, which affect the design of the main circuit.

According to an embodiment of the present invention, there is provided a capacitance detection device. Referring to fig. 1, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The capacitance detection device may include: the capacitance detection device can be applied to motor control equipment of a motor system. The motor control apparatus includes: the device comprises a rectifying unit, a bus capacitor unit, an inverter unit, a detection unit and a control unit. The bus capacitor unit includes: a capacitive module and a resistive module. The number of the capacitor modules is more than four, and the number of the resistor modules is the same as that of the capacitor modules. The capacitor modules are divided into two capacitor groups, two capacitor modules in the first capacitor group are arranged in parallel, two capacitor modules in the second capacitor group are also arranged in parallel, and the first capacitor group and the second capacitor group are arranged in series. Each capacitor module is connected in parallel with one corresponding resistor module.

The capacitance detection device includes: a switch unit.

The switch unit is configured to be in a closed state to enable the motor control device to be electrified when the motor control device needs to control the motor system to be electrified and started.

The detection unit is configured to detect a voltage across at least one of the four or more capacitor modules as a capacitor voltage when the motor control device controls the motor system to be powered on and started. And detecting the current flowing through more than four capacitor modules, and recording the current as the capacitor current (namely the charging current).

The control unit is configured to determine whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current. And sending a protection signal when the bus capacitor unit is determined to be abnormal.

The switch unit is further configured to switch from the closed state to an open state according to the protection signal so as to power off the motor control device.

The servo driver is mainly applied to the field of intelligent equipment such as industrial robots, numerical control machines and automatic production line equipment. FIG. 2 is a schematic structural diagram of an embodiment of a servo driver in a related art. As shown in fig. 2, the servo driver is composed of a power module and a control module, and the power module is composed of a rectifier bridge, a current-limiting starting circuit, a main capacitor circuit, a capacitor detection circuit, a regenerative braking circuit, an overcurrent detection circuit, and a three-phase inverter module. The power module is used for converting a three-phase alternating current input power frequency power supply into direct current voltage, and then converting the direct current voltage into three-phase alternating current output with controllable frequency amplitude through the three-phase inversion module. The control module consists of a main chip, various detection circuits and a control circuit, controls the work of the power module, realizes energy conversion, outputs three-phase variable frequency alternating current and drives the motor to operate.

In the example shown in fig. 2, the current limited start circuit includes: and a circuit formed by connecting the resistor R1 and the switch K1 in parallel, wherein the circuit is arranged between the rectifier bridge and the main capacitor circuit.

In the example shown in fig. 2, the main capacitor circuit includes: the capacitor C1, the capacitor C2, the capacitor C3 and the capacitor C4, and the resistor R1, the resistor R2, the resistor R3 and the resistor R4. The capacitor C1 and the capacitor C2 are connected in series to form a first capacitor branch, and the capacitor C3 and the capacitor C4 are connected in series to form a second series branch. The first series branch and the second series branch are connected in parallel. The resistor R1 is connected in parallel with the capacitor C1, the resistor R2 is connected in parallel with the capacitor C2, the resistor R3 is connected in parallel with the capacitor C3, and the resistor R4 is connected in parallel with the capacitor C4.

The main capacitor circuit is a key circuit module of the servo driver, is used for filtering and shaping and storing energy output by the rectifier bridge and is related to the power of the servo driver, and the larger the power is, the larger the required capacitor capacity is. The voltage of the industrial power grid in China is 380V alternating current, and capacitors are generally used in series in consideration of withstand voltage of the capacitors. The terminal voltage of the capacitors may be different due to the difference between the insulation resistance and the capacitance of the capacitors connected in series, so that the terminal voltages of the capacitors are different, which may cause the voltage of one of the capacitors to increase and break down. The equalizing resistors with the same resistance must be selected to be used in parallel, and the resistance is much smaller than the equivalent insulation resistance of the capacitor. The voltage-sharing resistor has the function of ensuring that the voltages at two ends of each capacitor connected in series are equal. Therefore, the main capacitor circuit consists of a capacitor C1-a capacitor C4, and a voltage-sharing resistor R1-a resistor R4. The number of capacitors and equalizing resistors is determined by the power capacity of the servo driver, and four capacitors are exemplified in the example shown in fig. 2.

The capacitor type of the main capacitor circuit generally selects a large-capacity aluminum electrolytic capacitor in the industry, and the aluminum electrolytic capacitor has simple manufacturing process and large stored charge amount per unit volume. The electrolytic capacitor is made of key components such as an anode foil, a cathode foil, electrolyte, an oxide film and the like. After long-term use, the electrolyte is dried up, the oxide film is deteriorated, and the like, and the capacity is further reduced. The oxide film and the insulating paper are damaged, which causes the short circuit phenomenon of the capacitor. If the lead-out wire in the electrolytic capacitor is not riveted with the aluminum foil or is subjected to external force, the contact between the aluminum foil and the lead-out wire is poor, and the phenomenon of capacitor disconnection is caused. Therefore, the main capacitor circuit is one of the modules with higher failure rate in the servo driver, and the main capacitor circuit can detect the abnormality in time, thereby improving the reliability of the system.

In the example shown in fig. 2, the voltage detection circuit includes: and a voltage division detection circuit composed of a resistor R5 and a resistor R6. The voltage detection circuit is provided between the main capacitor circuit and the regenerative braking circuit.

In the example shown in fig. 2, the regenerative braking circuit includes: and a power switch tube. Three-phase contravariant module includes: and an inverter bridge.

As shown in FIG. 2, the servo driver in the related scheme typically only detects the main loop voltage (i.e., the DC bus voltage) U_DCurrent I_DWhether the device of the main loop of the power module is abnormal or not is judged. When the servo driver is powered on, the output of the rectifier bridge charges a main capacitor (such as a capacitor C1-a capacitor C4) in a main capacitor circuit through a resistor R7, the charging current of the main capacitor is limited, and when the main capacitor in the motor system, such as an electrolytic capacitor, detects the voltage U of a direct current bus_DWhen the preset value is reached, the current-limiting starting circuit controls the switch K1 to act, the switch is closed, the resistor R7 is short-circuited, and the servo driver enters a normal working state. If the DC bus current I is detected in the process_DIf the current is higher than the overcurrent protection value, the main loop is abnormal, and overcurrent alarm is performed. Detect the DC bus voltage U_DAnd if the voltage is higher than the overvoltage protection value, the overvoltage alarm is given out. Detect the DC bus voltage U_DAnd if the voltage is lower than the undervoltage protection value, undervoltage alarm is carried out. Because the main capacitor circuit is formed by connecting capacitors in series and then in parallel, some abnormalities of the main capacitor circuit cannot be detected by related schemes, such as short circuit or open circuit of a certain capacitor, short circuit or open circuit of a certain voltage-sharing resistor, serious capacitor aging and the like.

The invention provides an abnormal detection scheme of a series capacitor, in particular to a circuit and a method for detecting abnormal capacitance of a servo driver. The capacitance anomaly detection circuit is designed in the servo driver, namely the circuit structure of the servo driver is improved, and a plurality of simple devices are added to the circuit structure of the servo driver, so that the anomaly detection of the main capacitance circuit is realized, and the design of a main circuit is not influenced. The method comprises the steps of detecting whether a capacitor and a voltage-sharing resistor in a main capacitor circuit are abnormal or not in a power-on stage of a motor system, specifically, monitoring the charging characteristic of the main capacitor circuit in a servo driver, detecting abnormal phenomena such as short circuit, open circuit and capacitor aging of the circuit in a starting stage of the motor system, and timely carrying out corresponding fault treatment. The voltage change of the capacitor and the charging current condition of the capacitor are monitored in the starting stage of the motor system, whether abnormity exists or not is judged, the reliability of the servo driver is improved, and the safety problem of the motor system is avoided.

In some embodiments, four or more of the capacitive modules comprise: the capacitive touch screen comprises a first capacitive module, a second capacitive module, a third capacitive module and a fourth capacitive module.

The first capacitor module and the third capacitor module are connected in series to form the first capacitor bank. A first capacitive module such as capacitor C1 and a third capacitive module such as capacitor C3.

The second capacitor module and the fourth capacitor module are connected in series to form the second capacitor bank. A second capacitive module such as capacitor C2 and a fourth capacitive module such as capacitor C4.

The detection unit includes: the device comprises a voltage sampling module and a current sampling module.

The detecting unit detects a voltage across at least one of the four or more capacitor modules, and includes: the voltage sampling module is arranged between the positive end and the negative end of the bus of the output end of the bus capacitor unit and is configured to detect the voltage at two ends of at least one capacitor module in more than four capacitor modules.

The detection unit detects currents flowing through four or more of the capacitor modules, and includes: the current sampling module is arranged between a bus negative end of an output end of the rectifier bridge and a bus negative end of an input end of the bus capacitor unit, and is configured to detect currents flowing through more than four capacitor modules.

Fig. 3 is a schematic structural diagram of an embodiment of the main capacitor circuit of fig. 2. As shown in FIG. 3, the main capacitor circuit is composed of a first capacitor set and a second capacitor set which are connected in series, and is divided into P, O, N three poles, wherein P is the anode of the direct current bus, N is the cathode of the direct current bus, and O is the midpoint of the two capacitors. Under normal condition, the DC bus voltage U_D＝U_PO+U_ONDue to the action of the equalizing resistor, U_PO、U_ONClose to equal, and regardless of error, U can be considered_PO＝U_ON. In the capacitor charging state, since the capacitors are used in series, the charging currents flowing through the two sets of capacitors are equal. Without adding additional current sensors, voltage sensors, there is no way to detect the state of each resistor, each capacitor, but the state of the first capacitor bank or the second capacitor bank can be detected.

In some embodiments, the voltage sampling module comprises: the device comprises a first sampling resistor module, a second sampling resistor module and a third sampling resistor module.

The first sampling resistor module, the second sampling resistor module and the third sampling resistor module are arranged between the positive end and the negative end of a bus of the output end of the bus capacitor unit. A first sampled resistance module, such as resistor R5. And a second sampling resistor module, such as resistor R6. And a third sampled resistance module, such as resistor R9.

And the common end of the first sampling resistance module and the second sampling resistance module is connected to the common end of the first capacitor module and the second capacitor module and is connected to the common end of the third capacitor module and the fourth capacitor module.

Fig. 9 is a schematic structural diagram of an embodiment of an additional capacitance abnormality detection circuit. In the example shown in fig. 2, a resistor R9 is added to the capacitance detection circuit formed by the resistors R5 and R6, and the connection point of the resistor R5 and the resistor R6 is connected to the connection point of the first capacitor bank and the second capacitor bank, so that the voltages of the two capacitors can be detected.

The current sampling module comprises: and the fourth sampling resistance module. The fourth sampling module is arranged between the negative bus terminal of the output end of the rectifier bridge and the negative bus terminal of the input end of the bus capacitor unit.

Referring to the example shown in fig. 9, the overcurrent detection circuit between the main capacitor circuit and the three-phase inverter module in the example shown in fig. 2 is moved between the rectifier bridge and the main capacitor circuit, so that the circuit function is expanded, and not only overcurrent but also charging current at the power-on time can be detected.

In some embodiments, the motor control apparatus further includes: a regenerative braking unit, such as a regenerative braking circuit.

And the regenerative braking unit is arranged between the bus capacitor unit and the inversion unit. The voltage sampling module is arranged between the bus capacitor unit and the regenerative braking unit.

In the example shown in fig. 9, a switch K2 is added to the current-limiting starting circuit in the example shown in fig. 2, so that the power supply can be cut off according to the fault condition, and the protection effect is achieved.

In some embodiments, the motor control apparatus further includes: a current limited start unit, such as a current limited start circuit.

The switch unit is arranged between the rectifier bridge and the current-limiting starting unit.

As shown in fig. 9, a switch K2 is connected in series in front of the current-limiting starting circuit, so that the power supply can be cut off in time when a short-circuit fault occurs. The overcurrent detection resistor R8 is moved between the negative electrode of the rectifier bridge and the negative electrode of the main capacitor, so that the current I of the main loop in normal operation can be detected_DAnd the charging current I of the main capacitor at the power-on time of the servo driver can be detected_C. Current flowing through resistor R8, etcIn I_D+I_C. At the power-on moment, the regenerative braking circuit and the three-phase inversion module do not work, so I_D0. During normal operation, the capacitor charging is completed to reach a balanced state, I_CVery small, the current through the resistor being mainly I_DTherefore, the operation of the overcurrent detection circuit is not affected. A resistor R9 is added to the capacitance detection circuit, and one end of a resistor R5 is connected to the midpoint of the series connection of the main capacitors C1 and C2, so that the direct current bus voltage U can be detected simultaneously_DThe voltage at the midpoint of the series capacitor (also the voltage across the second capacitor bank) U_ON. The voltage across the first capacitor bank is thus calculated: u shape_PO＝U_D-U_ON. Therefore, the voltage states of the main capacitor circuit in the charging process and after the charging can be detected in real time.

In some embodiments, the capacitor voltage comprises at least one of: the direct-current bus voltage of the output end of the bus capacitor unit, the voltage between the first end of the first capacitor bank and the second end of the first capacitor bank, and the voltage between the first end of the second capacitor bank and the second end of the second capacitor bank. And recording the voltage between the first end of the first capacitor bank and the second end of the first capacitor bank as a first voltage. And recording the voltage between the first end of the second capacitor bank and the second end of the second capacitor bank as a second voltage.

And determining the difference between the direct-current bus voltage output by the rectifying unit and the node voltage of the series node between the first capacitor bank and the second capacitor bank as the voltage at two ends of the first capacitor bank. And determining a node voltage of a series node between the first capacitor bank and the second capacitor bank as a voltage across the second capacitor bank.

The capacitance current comprises at least one of the following: the current flowing through the whole of the four current modules flows through each of the four or more capacitor modules. The current flowing through the whole of the four current modules is referred to as a charging current. The current flowing through the first capacitor module is denoted as a first current. And the current flowing through the second capacitor module is recorded as a second current. And the current flowing through the third capacitor module is recorded as a third current. And the current flowing through the fourth capacitor module is recorded as a fourth current.

In some embodiments, the determining, by the control unit, whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current includes: the method specifically comprises the following short-circuit fault situations according to the process of detecting whether the short-circuit fault occurs in the capacitor module in the bus capacitor unit according to the capacitor voltage.

First short circuit fault scenario: the control unit is specifically configured to determine that a short-circuit fault occurs in a part of devices in the second capacitor bank if the first voltage is equal to the dc bus voltage.

Second short circuit fault scenario: the control unit is specifically configured to determine that a short-circuit fault occurs in a part of devices in the first capacitor bank if the second voltage is equal to the dc bus voltage.

FIG. 4 is a schematic diagram of an embodiment of a short circuit fault of a device in the main capacitor circuit portion. During the initial power-up process of the servo driver, if only one group of capacitors is detected to be charged, the phenomenon that the main capacitor circuit is short-circuited is illustrated, as shown in fig. 4. If the detection of electrolytic capacitors in the motor system is detected, U is detected_PO＝U_DAnd the voltage at the point O is pulled to the negative electrode of the direct current bus, and the second capacitor bank is short-circuited. If the detection of electrolytic capacitors in the motor system is detected, U is detected_ON＝U_DAnd the voltage at the point O is pulled to the positive electrode of the direct current bus, and the first capacitor bank is short-circuited. That is, the voltage U across the capacitor can be detected_PO、U_ONAnd DC bus voltage U_DAnd judging whether the two are equal to each other or not to judge the short-circuit fault of the main capacitor circuit. When a short-circuit fault occurs, the power supply input is immediately cut off, otherwise, the short-circuit device may have potential safety hazard due to the rapid increase of heat. The voltage is only applied to one capacitor, and one capacitor is damaged due to overvoltage.

The servo driver is powered on, the switch K2 is closedAnd the switch K1 is turned off, and the current is limited by the resistor R7 to charge the main capacitor circuit. Fig. 10 is a voltage waveform diagram illustrating a capacitor charging process. The voltage change between the two ends of the capacitor is shown in FIG. 10, and under normal conditions, the voltage U_PO、U_ONClose to and finally stable in U_DAnd/2, after the charging is finished, the switch K2 is closed, the switch K1 is closed, and the servo driver enters a normal working state.

If only one group of capacitors is charged and the voltage of the other group of capacitors is always zero in the charging process, the main capacitor circuit has a short-circuit fault, the switch K2 is switched off, and the power supply is cut off.

In the scheme of the invention, the voltage of two groups of capacitors in the series capacitors is detected at the power-on time of the servo driver, so that whether a phenomenon that a certain group of capacitors is short-circuited exists or not is judged, and potential safety hazards in use of the servo driver are avoided. The problem of safety accidents caused by short-circuit faults of parts of main capacitor circuits used in series in the servo driver is solved.

In some embodiments, the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and further includes: the process of detecting whether the open circuit fault occurs in the capacitance module in the bus capacitance unit according to the capacitance voltage and the capacitance current is specifically referred to the following exemplary description.

The control unit is specifically configured to determine that a difference between the first voltage and the second voltage exceeds a first preset value in a charging process of the first capacitor bank and the second capacitor bank. And after the first capacitor bank and the second capacitor bank are charged, if the first voltage is equal to the second voltage, determining that a capacitance open circuit fault occurs in the first capacitor bank and the second capacitor bank.

Wherein a capacitive open fault is determined to occur in the first capacitive bank if the charging current is equal to the sum of the second current and the fourth current. Determining that a capacitive open fault has occurred in the second capacitive bank if the charging current is equal to the sum of the first current and the third current.

FIG. 5 is a schematic diagram of an embodiment of a partial capacitive disconnection fault of a main capacitive circuit. If the main capacitor circuit has the open circuit phenomena such as capacitor un-mounting, cold solder, poor connection of the internal pins of the capacitor, etc., as shown in fig. 5. If the capacitor C1 of the first capacitor set is open, the charging current only flows through the capacitor C3, and then flows into the capacitor C2 and the capacitor C4, respectively, and the charging current I is then obtained_C＝I₂+I₄At this time, the charging current of the capacitor C3 is larger, and the voltage across the capacitor rises faster. Assuming that the capacitor C2 of the second capacitor bank is open, the charging current flows only from the capacitor C4 to the rectifier bridge, and I is present_C＝I₁+I₃At this time, the charging current of the capacitor C4 is larger, and the voltage across the capacitor rises faster. Therefore, in the process of charging the capacitor, the capacitor bank with the open circuit phenomenon is charged more quickly, and the voltage at two ends rises more quickly. After the capacitors are charged, the voltage division between the capacitors mainly depends on the voltage-sharing resistors, and the voltage-sharing resistors are equal, so that U is formed_PO＝U_ON. Can detect the voltage U at two ends of the capacitor in the charging process_POAnd U_ONAnd judging the capacitor open circuit fault of the main capacitor circuit according to the difference value and whether the voltages at two ends of the capacitor tend to be equal after the charging is finished. When the fault occurs, if the servo driver continues to operate, the aging of the capacitor bank with the open circuit fault is aggravated because the ripple current is too high.

Wherein i_c、I_cAll represent the capacitor charging current and it is customary in the art to express this in lower case on an integral formula, meaning that this is a time-varying quantity, and upper case refers to a value at a certain time. Since this equation holds true at any time in the state shown in fig. 5, I is used here_cAre representative of capacitor charging current.

Fig. 11 is a schematic diagram of a charging waveform when a part of the capacitor is disconnected. If the charging process is performed for 0-T1, the voltage of one capacitor is detected to be larger and larger than that of the other capacitor. At the stage of time T1-T2, the voltage of the capacitor group rises faster, the voltage drops slowly, the other capacitor group rises slowly, and finally, the voltage is stabilized at U_DAround/2, as shown in FIG. 11. Fault indicating partial open circuit of capacitor in main capacitor circuitWhen the voltage difference U is smaller_Δ(U_Δ＝|U_PO-U_ON|) exceeds the preset value, the servo driver outputs a capacitance open circuit alarm signal, and the user needs to replace the main capacitance module.

In the scheme of the invention, whether the phenomenon of device disconnection exists is judged by detecting the power-on time of the servo driver, the charging characteristic of the capacitor and the change of the voltage of the capacitor, so that the abnormal work of the servo driver is avoided. The problem that when a main capacitor circuit part device used in series in a servo driver is subjected to open circuit failure, a motor system works abnormally is solved.

In some embodiments, the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and further includes: the process of detecting whether the resistance module in the bus capacitance unit has an open circuit fault according to the capacitance voltage is specifically referred to the following exemplary description.

The control unit is specifically further configured to equalize the first voltage and the second voltage during charging of the first capacitor bank and the second capacitor bank. After the first capacitor bank and the second capacitor bank are charged, if one of the first voltage and the second voltage changes fast, the other voltage changes slowly. And after the first voltage and the second voltage reach new balance, if the difference value of the first voltage and the second voltage exceeds a second preset value, determining that the resistance module in the bus capacitor unit has an open circuit fault or an aging phenomenon.

FIG. 6 is a schematic diagram of an embodiment of a voltage-sharing resistor open circuit fault in the main capacitor circuit portion. If the voltage equalizing resistor has open circuit phenomena such as insufficient soldering, missing soldering or improper connection, as shown in fig. 6. The voltage-sharing resistor mainly influences the voltage distribution after charging is finished, and the influence on the charging process of the capacitor is small. In the process of charging the capacitor, the voltage U between two ends of the capacitor_PO、U_ONClose. After the charging is finished, the voltage of the capacitor group with the broken voltage-sharing resistor increases slowly due to the increase of the resistance value, the voltage of the other capacitor group decreases slowly, after new balance is achieved, if the capacitor is in a state of being in charge ofIf the voltage difference between the two ends is large, the voltage equalizing resistor is likely to have an open circuit phenomenon. In addition to the problem that the voltage equalizing resistor is broken, which results in a large difference between the parallel resistance of the first capacitor bank and the second capacitor bank, the difference may also be caused by abnormal phenomena such as aging of the resistor, increase of the resistance, or wrong welding of the resistor. When the resistance value of the voltage equalizing resistor is abnormal, namely the resistance value of the resistor R1 and the resistor R3 after being connected in parallel is greatly different from the resistance value of the resistor R2 and the resistor R4 after being connected in parallel. In the process of charging the capacitor, the voltage U between two ends of the capacitor_PO、U_ONClose. After charging is finished, the voltage of the capacitor group with the larger resistance value can slowly rise, the voltage of the other capacitor group slowly falls, and after new balance is achieved, if the voltage difference value of the two ends of the capacitor is larger, the phenomenon that the resistance value of the voltage-sharing resistor is abnormal is probably shown. Can detect the voltage U at two ends of the capacitor after charging_PO、U_ONThe voltage-sharing resistor of the main capacitor circuit is judged to be in open circuit fault or abnormal resistance value. When this problem occurs, the capacitor bank with a large voltage division may be damaged by overvoltage.

Fig. 12 is a schematic diagram of a charging waveform in the case of a partial voltage-equalizing resistance abnormality. If the two groups of capacitors are detected to have substantially the same voltage rise during the charging process from time 0 to time T1, while one group of capacitors slowly rises and the other group slowly falls during the charging process from time T1 to time T2, and finally reaches a steady state, as shown in fig. 12. The circuit breaking fault of partial voltage-sharing resistors or the abnormal resistance value of the voltage-sharing resistors exist in the main capacitor circuit. When the voltage difference U is_ΔWhen the voltage-sharing abnormity alarm signal exceeds a preset value, the servo driver outputs a voltage-sharing abnormity alarm signal, and a user needs to replace the main capacitor module.

In some embodiments, the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and further includes: and determining the aging degree of the capacitor module in the bus capacitor unit.

The control unit is specifically configured to determine a resistance value of an equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit according to the charging current, the capacitor voltage and the charging time of the capacitor module in the bus capacitor unit in the charging process.

The control unit is specifically further configured to determine the aging degree of the capacitor module in the bus capacitor unit according to the resistance value of the equivalent series resistance of the capacity of the capacitor module in the bus capacitor unit based on the corresponding relationship between the set capacity, the set resistance value and the set aging degree.

FIG. 7 is a schematic structural diagram of an embodiment of an equivalent model of an electrolytic capacitor. The electrolytic capacitor has Equivalent Series Resistance (ESR) due to the structural characteristics and material characteristics, as shown in fig. 7. The equivalent series resistance influences the charging and discharging time of the capacitor, the ripple current generates loss on the equivalent series resistance, and the working temperature of the capacitor is increased. The temperature rise of the electrolytic capacitor can be determined by the ripple current, the ESR and the thermal resistance, and under the condition of assuming thermal balance, the temperature rise of the electrolytic capacitor is equal to the heat generated by power loss on the ESR. The most important harm of the heat generated by the ripple current of the electrolytic capacitor is that the service life of the capacitor is obviously shortened. Generally, the service life of the electrolytic capacitor is halved when the temperature rises by 10 ℃. However, when the internal core of the electrolytic capacitor approaches the maximum allowable temperature, the reduction in lifetime will no longer be halved by 10 ℃ per liter, but rather will be drastically reduced. This is because the electrolyte is subjected to thermal stress by the capacitor core, increasing the ESR by more than 10 times. Transient over-temperature or transient over-current can cause this condition to occur, causing the capacitor to fail. The aging degree of the electrolytic capacitor is generally represented by a capacitor value and a resistance value of ESR, and the service life judgment standard used in some schemes is that the resistance value of ESR is doubled or the capacitance value is reduced to 80% of the initial value, namely the safe service life is passed.

In electrolytic capacitors, there are two basic formulas:

C＝(1/U_C)∫i_C dt (1)。

R＝(U_DC-U_C)/i_C (2)。

wherein C is the capacitance of the electrolytic capacitor, U_CIs the voltage across the electrolytic capacitor, i_CCharging current of electrolytic capacitor, U_DCIs input voltage, t is charging time, R is equivalent series connection of electrolytic capacitorsThe resistance value of the resistor.

FIG. 8 is a schematic diagram of an embodiment of a main capacitor circuit with equivalent series resistance taken into account. As shown in fig. 8, considering the main capacitor circuit of the equivalent series resistor, the capacitance value of the first capacitor group is the capacitance value of the electrolytic capacitor C1 and the electrolytic capacitor C3 connected in parallel, and the equivalent series resistor resistance value of the first capacitor group is the resistance value of the ESR1 and ESR3 connected in parallel. The second capacitor bank works in the same way. The charging currents of the two sets of capacitor banks are equal. The capacity of the electrolytic capacitor and the resistance value of the equivalent series resistor can be calculated by detecting the charging current, the voltage at two ends of the capacitor and the charging time in the charging process of the electrolytic capacitor, so that the aging degree of the electrolytic capacitor is judged.

In summary, the present invention improves the circuit structure of the servo driver, and detects the states of the voltage and the charging current at the two ends of the series capacitor during and after the charging of the main capacitor of the servo driver, so as to determine whether the main capacitor circuit is abnormal. If no abnormity exists, the normal working state is entered. If the abnormality exists, corresponding protective measures are taken.

The invention also provides a capacitor aging detection method, which judges the aging degree of the capacitor by detecting the capacitance and the equivalent series resistance value and comparing with the initial parameter, adopts the detection mode of the charging current, the voltage and the charging time of the capacitor, and calculates the capacitance and the equivalent series resistance value according to the basic formula. The problem of main capacitor circuit because of the device ageing, lead to motor system work unusual is solved.

FIG. 13 is a schematic diagram of a charging waveform for capacitance degradation detection. In the charging process of the main capacitor circuit, the aging degree of the capacitor is detected, and the initial capacitance value of the electrolytic capacitor and the initial resistance value of the equivalent series resistor are firstly determined. First, according to the specification parameters of the selected electrolytic capacitor, the capacitance value of the first capacitor set, the resistance value of the equivalent series resistor, the capacitance value of the second capacitor set, and the resistance value of the equivalent series resistor are calculated. Then, as shown in fig. 13, two time points t1 and t2 are taken in the capacitor charging process, and U at two time points_POCan detect that each is U₁、U₂. Assume that the voltage across the capacitor is U_Ct1、U_Ct2. Two moments of capacitor charging current I_Ct1、I_Ct2. Substituting the data into the formula (1) and the formula (2) to obtain:

C＝(1/U_Ct1)∫i_C dt (3)。

R＝(U₁-U_Ct1)/I_Ct1 (4)。

C＝(1/U_Ct2)∫i_C dt (5)。

R＝(U₂-U_Ct2)/I_Ct2 (6)。

calculating U by integrating the currents of the equations (3) and (5)_Ct1、U_Ct2The multiple k value of (a), i.e.:

U_Ct2＝kU_Ct1 (7)。

substituting formula (7) for formula (6), and calculating U according to formula (4)_Ct1Thereby calculating the resistance value R of the equivalent series resistor and the capacitance value C of the electrolytic capacitor. Then the resistance value R of the equivalent series resistor is compared with the initial resistance value R₀Initial capacitance value C₀And comparing whether the judgment standard of capacitor aging is met. If the resistance value of the equivalent series resistor of a certain capacitor bank is doubled or the capacitance value is reduced to 80% of the initial value, namely the safe service life is over, the servo driver outputs a capacitor aging early warning signal to remind a user of replacing the main capacitor module in time.

The embodiment is directed at the condition that two groups of capacitors are used in series, when the motor system adopts three groups of capacitors or more capacitors in series, the same principle can be adopted to build a circuit for detecting the abnormal capacitance.

The above embodiment is a servo driver teaching scheme based on 380V ac input, and for other voltage class products, such as 220V input, 480V input, etc., if the main capacitor adopts a capacitor series connection mode, the scheme of the present invention is also applicable.

The scheme of the invention can be popularized to products with capacitor series structures, such as air conditioner frequency converters, photovoltaic inverters, motor controllers and the like.

The invention provides a capacitance abnormity detection circuit and method applied to a servo driver, in particular to a capacitance abnormity detection circuit of a series capacitor in the field of motor control such as the servo driver and a frequency converter. Therefore, whether the servo driver has potential safety hazards or not is detected in the starting stage of the motor system, and fault processing is carried out in time, so that the safe operation of the motor system is ensured.

By adopting the technical scheme of the invention, the capacitance abnormity detection circuit is arranged in the frequency conversion equipment (such as a servo driver and a frequency converter) of the motor system, and the main capacitance circuit of the frequency conversion equipment is subjected to abnormity detection by using the capacitance abnormity detection circuit in the power-on stage of the motor system, so that fault treatment is carried out in time when the abnormity of the main capacitance circuit is detected. Therefore, the electrolytic capacitor is subjected to comprehensive fault detection in the power-on stage of the motor system, and the safety of the motor system is favorably improved.

According to an embodiment of the present invention, there is also provided a motor control apparatus corresponding to the capacitance detection device. The motor control apparatus may include: the capacitance detection device described above.

Since the processing and functions implemented by the motor system of this embodiment substantially correspond to the embodiments, principles, and examples of the foregoing devices, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.

By adopting the technical scheme of the invention, the capacitance abnormity detection circuit is arranged in the frequency conversion equipment (such as a servo driver and a frequency converter) of the motor system, and the main capacitance circuit of the frequency conversion equipment is subjected to abnormity detection by using the capacitance abnormity detection circuit in the power-on stage of the motor system, so that fault treatment is carried out in time when the abnormity of the main capacitance circuit is detected. The charging characteristics of the main capacitor circuit are detected in the power-on stage of the servo driver, the fault problem is identified, corresponding fault processing is carried out, the servo driver is ensured to start working under the normal state of the main capacitor circuit, and the reliability of motor systems such as the servo driver and a frequency converter is improved.

According to an embodiment of the present invention, there is also provided a capacitance detection method corresponding to the motor control device, as shown in fig. 14, which is a schematic flow chart of an embodiment of the method of the present invention. The capacitance detection method may include: step S110 to step S140.

In step S110, in a case that the motor control device needs to control the motor system to be powered on and started, a switch unit is put in a closed state to power on the motor control device.

In step S120, when the motor control device controls the motor system to be powered on and started, the voltage across at least one of the four or more capacitor modules is detected and recorded as a capacitor voltage. And detecting the current flowing through more than four capacitor modules, and recording the current as the capacitor current (namely the charging current).

At step S130, it is determined whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current. And sending a protection signal when the bus capacitor unit is determined to be abnormal.

At step S140, the switch unit is switched from the closed state to an open state according to the protection signal, so as to power off the motor control device.

As shown in fig. 9, a switch K2 is connected in series in front of the current-limiting starting circuit, so that the power supply can be cut off in time when a short-circuit fault occurs. The overcurrent detection resistor R8 is moved between the negative electrode of the rectifier bridge and the negative electrode of the main capacitor, so that the current I of the main loop in normal operation can be detected_DAnd the charging current I of the main capacitor at the power-on time of the servo driver can be detected_C. The current flowing through the resistor R8 is equal to I_D+I_C. At the power-on moment, the regenerative braking circuit and the three-phase inversion module do not work, so I_D0. During normal operation, the capacitor charging is completed to reach a balanced state, I_CVery small, the current through the resistor being mainly I_DTherefore, the operation of the overcurrent detection circuit is not affected. A resistor R9 is added to the capacitance detection circuit, and one end of a resistor R5 is connected to the midpoint of the series connection of the main capacitors C1 and C2, so that the direct current bus voltage U can be detected simultaneously_DThe voltage at the midpoint of the series capacitor (also the voltage across the second capacitor bank) U_ON. The voltage across the first capacitor bank is thus calculated: u shape_PO＝U_D-U_ON. Therefore, the voltage states of the main capacitor circuit in the charging process and after the charging can be detected in real time.

In some embodiments, determining whether the bus capacitive unit is abnormal based on at least one of the capacitive voltage and the capacitive current includes: the method specifically comprises the following short-circuit fault situations according to the process of detecting whether the short-circuit fault occurs in the capacitor module in the bus capacitor unit according to the capacitor voltage.

First short circuit fault scenario: and if the first voltage is equal to the direct current bus voltage, determining that partial devices in the second capacitor bank have short-circuit faults.

Second short circuit fault scenario: and if the second voltage is equal to the direct current bus voltage, determining that partial devices in the first capacitor bank have short-circuit faults.

The servo driver is powered on, the switch K2 is closed, the switch K1 is opened, and the current is limited by the resistor R7 to charge the main capacitor circuit. Fig. 10 is a voltage waveform diagram illustrating a capacitor charging process. The voltage change between the two ends of the capacitor is shown in FIG. 10, and under normal conditions, the voltage U_PO、U_ONClose to and finally stable in U_DAnd/2, after the charging is finished, the switch K2 is closed, the switch K1 is closed, and the servo driver enters a normal working state.

In some embodiments, determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: the process of detecting whether the capacitor module in the bus capacitor unit has an open circuit fault according to the capacitor voltage and the capacitor current specifically comprises the following steps: if the difference value between the first voltage and the second voltage exceeds a first preset value in the process of charging the first capacitor bank and the second capacitor bank. And after the first capacitor bank and the second capacitor bank are charged, if the first voltage is equal to the second voltage, determining that a capacitance open circuit fault occurs in the first capacitor bank and the second capacitor bank.

Fig. 11 is a schematic diagram of a charging waveform when a part of the capacitor is disconnected. If the charging process is performed for 0-T1, the voltage of one capacitor is detected to be larger and larger than that of the other capacitor. Time of dayAt the stage T1-T2, the voltage rises faster, the voltage falls slowly, the other rises slowly, and finally stabilizes at U_DAround/2, as shown in FIG. 11. The fault that partial capacitors are disconnected exists in the main capacitor circuit is shown when the voltage difference value U is_Δ(U_Δ＝|U_PO-U_ON|) exceeds the preset value, the servo driver outputs a capacitance open circuit alarm signal, and the user needs to replace the main capacitance module.

In some embodiments, determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: the process of detecting whether the resistance module in the bus capacitor unit has an open circuit fault according to the capacitor voltage specifically comprises the following steps: the first voltage and the second voltage are equal during charging of the first capacitor bank and the second capacitor bank. After the first capacitor bank and the second capacitor bank are charged, if one of the first voltage and the second voltage changes fast, the other voltage changes slowly. And after the first voltage and the second voltage reach new balance, if the difference value of the first voltage and the second voltage exceeds a second preset value, determining that the resistance module in the bus capacitor unit has an open circuit fault or an aging phenomenon.

FIG. 6 is a schematic diagram of an embodiment of a voltage-sharing resistor open circuit fault in the main capacitor circuit portion. If the voltage equalizing resistor has open circuit phenomena such as insufficient soldering, missing soldering or improper connection, as shown in fig. 6. The voltage-sharing resistor mainly influences the voltage distribution after charging is finished, and the influence on the charging process of the capacitor is small. In the process of charging the capacitor, the voltage U between two ends of the capacitor_PO、U_ONClose. After the charging is finished, the capacitance group with the voltage-sharing resistor broken circuit has larger resistance value,the voltage will rise slowly, the other group will drop slowly, after reaching the new balance, if the voltage difference value at the two ends of the capacitor is larger, it indicates that the voltage-sharing resistance may have the phenomenon of open circuit. In addition to the problem that the voltage equalizing resistor is broken, which results in a large difference between the parallel resistance of the first capacitor bank and the second capacitor bank, the difference may also be caused by abnormal phenomena such as aging of the resistor, increase of the resistance, or wrong welding of the resistor. When the resistance value of the voltage equalizing resistor is abnormal, namely the resistance value of the resistor R1 and the resistor R3 after being connected in parallel is greatly different from the resistance value of the resistor R2 and the resistor R4 after being connected in parallel. In the process of charging the capacitor, the voltage U between two ends of the capacitor_PO、U_ONClose. After charging is finished, the voltage of the capacitor group with the larger resistance value can slowly rise, the voltage of the other capacitor group slowly falls, and after new balance is achieved, if the voltage difference value of the two ends of the capacitor is larger, the phenomenon that the resistance value of the voltage-sharing resistor is abnormal is probably shown. Can detect the voltage U at two ends of the capacitor after charging_PO、U_ONThe voltage-sharing resistor of the main capacitor circuit is judged to be in open circuit fault or abnormal resistance value. When this problem occurs, the capacitor bank with a large voltage division may be damaged by overvoltage.

In some embodiments, determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: and determining the aging degree of the capacitor module in the bus capacitor unit.

With reference to the flowchart of fig. 15 showing an embodiment of determining the aging degree of the capacitor module in the bus capacitor unit in the method of the present invention, a specific process for determining the aging degree of the capacitor module in the bus capacitor unit is further defined, which includes: step S201 and step S202.

Step S201, determining a resistance value of an equivalent series resistor of the capacitance of the capacitor module in the bus capacitor unit according to the charging current, the capacitor voltage and the charging time of the capacitor module in the bus capacitor unit in the charging process.

Step S202, based on the corresponding relation among the set capacity, the set resistance and the set aging degree, determining the aging degree of the capacitor module in the bus capacitor unit according to the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit.

In electrolytic capacitors, there are two basic formulas:

C＝(1/U_C)∫i_C dt (1)。

R＝(U_DC-U_C)/i_C (2)。

wherein C is the capacitance of the electrolytic capacitor, U_CIs the voltage across the electrolytic capacitor, i_CCharging current of electrolytic capacitor, U_DCIs the input voltage, t is the charging time, and R is the resistance of the equivalent series resistance of the electrolytic capacitor.

FIG. 13 is a schematic diagram of a charging waveform for capacitance degradation detection. In the charging process of the main capacitor circuit, the aging degree of the capacitor is detected, and the initial capacitance value of the electrolytic capacitor and the initial resistance value of the equivalent series resistor are firstly determined. Taking the first capacitor bank as an example, first, the first capacitor bank is based onAnd calculating the capacitance value of the first capacitor bank, the resistance value of the equivalent series resistor, the capacitance value of the second capacitor bank and the resistance value of the equivalent series resistor according to the selected specification parameters of the electrolytic capacitor. Then, as shown in fig. 13, two time points t1 and t2 are taken in the capacitor charging process, and U at two time points_POCan detect that each is U₁、U₂. Assume that the voltage across the capacitor is U_Ct1、U_Ct2. Two moments of capacitor charging current I_Ct1、I_Ct2. Substituting the data into the formula (1) and the formula (2) to obtain:

C＝(1/U_Ct1)∫i_C dt (3)。

R＝(U₁-U_Ct1)/I_Ct1 (4)。

C＝(1/U_Ct2)∫i_C dt (5)。

R＝(U₂-U_Ct2)/I_Ct2 (6)。

U_Ct2＝kU_Ct1 (7)。

Since the processing and functions implemented by the method of this embodiment substantially correspond to the embodiments, principles and examples of the motor system, reference may be made to the related descriptions in the foregoing embodiments without being detailed in the description of this embodiment.

By adopting the technical scheme of the embodiment, the capacitance abnormality detection circuit is arranged in the frequency conversion equipment (such as a servo driver and a frequency converter) of the motor system, and the capacitance abnormality detection circuit is utilized to perform abnormality detection on the main capacitance circuit of the frequency conversion equipment in the power-on stage of the motor system, so that fault processing is performed in time when the abnormality of the main capacitance circuit is detected; through designing a capacitance abnormity circuit in servo driver, through last electricity stage, detect the voltage variation of electric capacity, charging current realizes the unusual detection and corresponding protection processing of series connection electric capacity, has strengthened servo driver's reliability, can increase application scope according to the lectotype accommodate parameter of electric capacity, has promoted servo driver's market competition.

In summary, it is readily understood by those skilled in the art that the advantageous modes described above can be freely combined and superimposed without conflict.

The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A capacitance detection device is characterized in that the capacitance detection device can be applied to motor control equipment of a motor system; the motor control apparatus includes: the device comprises a rectifying unit, a bus capacitor unit, an inverter unit, a detection unit and a control unit; the bus capacitor unit includes: a capacitance module and a resistance module; the number of the capacitor modules is more than four, and the number of the resistor modules is the same as that of the capacitor modules; the four or more capacitor modules are divided into two capacitor groups, two capacitor modules in the first capacitor group are arranged in parallel, two capacitor modules in the second capacitor group are also arranged in parallel, and the first capacitor group and the second capacitor group are arranged in series; each capacitor module is connected with one corresponding resistor module in parallel;

the capacitance detection device includes: a switch unit; wherein the content of the first and second substances,

the switch unit is configured to be in a closed state to electrify the motor control equipment under the condition that the motor control equipment needs to control the motor system to be electrified and started;

the detection unit is configured to detect the voltage at two ends of at least one capacitor module in more than four capacitor modules and record the voltage as the capacitor voltage under the condition that the motor control equipment controls the motor system to be powered on and started; detecting the current flowing through more than four capacitor modules and recording the current as capacitor current;

the control unit is configured to determine whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current; and sending a protection signal when the bus capacitor unit is determined to be abnormal;

2. The capacitance detection device according to claim 1, wherein four or more of the capacitance modules comprise: the first capacitor module, the second capacitor module, the third capacitor module and the fourth capacitor module;

the first capacitor module and the third capacitor module are connected in series to form the first capacitor bank;

the second capacitor module and the fourth capacitor module are connected in series to form the second capacitor bank;

the detection unit includes: the device comprises a voltage sampling module and a current sampling module; wherein the content of the first and second substances,

the detection unit detects the voltage at two ends of at least one of the four or more capacitor modules, and includes:

the voltage sampling module is arranged between the positive end and the negative end of a bus of the output end of the bus capacitor unit and is configured to detect the voltage at two ends of at least one capacitor module in more than four capacitor modules;

the detection unit detects currents flowing through four or more of the capacitor modules, and includes:

the current sampling module is arranged between a bus negative end of an output end of the rectifier bridge and a bus negative end of an input end of the bus capacitor unit, and is configured to detect currents flowing through more than four capacitor modules.

3. The capacitance detection device of claim 2, wherein the voltage sampling module comprises: the device comprises a first sampling resistor module, a second sampling resistor module and a third sampling resistor module;

the first sampling resistance module, the second sampling resistance module and the third sampling resistance module are arranged between the positive end and the negative end of a bus of the output end of the bus capacitance unit;

the common end of the first sampling resistance module and the second sampling resistance module is connected to the common end of the first capacitor module and the second capacitor module and is connected to the common end of the third capacitor module and the fourth capacitor module;

the current sampling module comprises: a fourth sampling resistance module; the fourth sampling module is arranged between the negative bus terminal of the output end of the rectifier bridge and the negative bus terminal of the input end of the bus capacitor unit.

4. The capacitance detection device according to claim 3, wherein the motor control apparatus further comprises: a regenerative braking unit;

the regenerative braking unit is arranged between the bus capacitor unit and the inverter unit; the voltage sampling module is arranged between the bus capacitor unit and the regenerative braking unit.

5. The capacitance detection device according to claim 1, wherein the switch unit is disposed between a positive dc bus terminal of the output terminal of the rectifier bridge and a positive dc bus terminal of the input terminal of the bus capacitor unit.

6. The capacitance detection device according to claim 5, wherein the motor control apparatus further comprises: a current-limited starting unit;

7. The capacitance detection device according to any one of claims 1 to 6, wherein the capacitance voltage comprises at least one of:

a dc bus voltage at an output of the bus capacitor unit, a voltage between a first end of the first capacitor bank and a second end of the first capacitor bank, and a voltage between a first end of the second capacitor bank and a second end of the second capacitor bank; recording a voltage between a first end of the first capacitor bank and a second end of the first capacitor bank as a first voltage; recording a voltage between a first end of the second capacitor bank and a second end of the second capacitor bank as a second voltage;

the capacitance current comprises at least one of the following: the current flowing through the whole of the four current modules and the current flowing through each of the four or more capacitor modules; wherein the content of the first and second substances,

the current flowing through the whole of the four current modules is recorded as charging current; the current flowing through the first capacitor module is recorded as a first current; the current flowing through the second capacitor module is recorded as a second current; the current flowing through the third capacitor module is recorded as a third current; and the current flowing through the fourth capacitor module is recorded as a fourth current.

8. The capacitance detection device according to claim 7, wherein the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, and includes:

if the first voltage is equal to the direct-current bus voltage, determining that partial devices in the second capacitor bank have short-circuit faults;

and if the second voltage is equal to the direct current bus voltage, determining that partial devices in the first capacitor bank have short-circuit faults.

9. The capacitance detection device according to claim 7, wherein the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, further comprising:

if the difference value between the first voltage and the second voltage exceeds a first preset value in the process of charging the first capacitor bank and the second capacitor bank; after the first capacitor bank and the second capacitor bank are charged, if the first voltage is equal to the second voltage, determining that a capacitor open-circuit fault occurs in the first capacitor bank and the second capacitor bank;

wherein a capacitive open fault is determined to occur in the first capacitive bank if the charging current is equal to the sum of the second current and the fourth current; determining that a capacitive open fault has occurred in the second capacitive bank if the charging current is equal to the sum of the first current and the third current.

10. The capacitance detection device according to claim 7, wherein the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, further comprising:

after the first capacitor bank and the second capacitor bank are charged, if one of the first voltage and the second voltage changes fast, the other voltage changes slowly; and after the first voltage and the second voltage reach new balance, if the difference value of the first voltage and the second voltage exceeds a second preset value, determining that the resistance module in the bus capacitor unit has an open circuit fault or an aging phenomenon.

11. The capacitance detection device according to claim 7, wherein the control unit determines whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current, further comprising:

determining the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit according to the charging current, the capacitor voltage and the charging time of the capacitor module in the bus capacitor unit in the charging process;

and determining the aging degree of the capacitor module in the bus capacitor unit according to the resistance value of the equivalent series resistor of the capacity of the capacitor module in the bus capacitor unit based on the corresponding relation among the set capacity, the set resistance value and the set aging degree.

12. A motor control apparatus characterized by comprising: the capacitance detection device according to any one of claims 1 to 11.

13. A capacitance detecting method in a motor control apparatus according to claim 12, comprising:

under the condition that the motor control equipment needs to control the motor system to be powered on and started, enabling a switch unit to be in a closed state so as to enable the motor control equipment to be powered on;

under the condition that the motor control equipment controls the motor system to be powered on and started, detecting the voltage at two ends of at least one capacitor module in more than four capacitor modules and recording the voltage as capacitor voltage; detecting the current flowing through more than four capacitor modules and recording the current as capacitor current;

determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current; and sending a protection signal when the bus capacitor unit is determined to be abnormal;

and switching the switch unit from the closed state to an open state according to the protection signal so as to power off the motor control equipment.

14. The capacitance detection method according to claim 13, wherein the capacitance voltage comprises at least one of:

15. The capacitance detection method according to claim 14, wherein determining whether the bus capacitive unit is abnormal according to at least one of the capacitive voltage and the capacitive current comprises:

16. The capacitance detection method according to claim 14, wherein determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises:

17. The capacitance detection method according to claim 14, wherein determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises:

18. The capacitance detection method according to claim 14, wherein determining whether the bus capacitor unit is abnormal according to at least one of the capacitor voltage and the capacitor current further comprises: