CN111092563B - Power conversion device and diagnosis method for power conversion device - Google Patents
Power conversion device and diagnosis method for power conversion device Download PDFInfo
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- CN111092563B CN111092563B CN201910985749.9A CN201910985749A CN111092563B CN 111092563 B CN111092563 B CN 111092563B CN 201910985749 A CN201910985749 A CN 201910985749A CN 111092563 B CN111092563 B CN 111092563B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/40—Testing power supplies
- G01R31/42—AC power supplies
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- Power Conversion In General (AREA)
- Inverter Devices (AREA)
Abstract
The invention provides a power conversion device and a diagnosis method for the power conversion device, which monitor the operation state of the power conversion device on line and optimize the timing of equipment update independently. The device is provided with: a gate driving circuit for driving the switching element according to a PWM command signal for driving the switching element constituting the power conversion device; a current calculation unit and a voltage calculation unit for calculating a collector current or a drain current and a collector voltage or a drain voltage, respectively, at a timing when the switching element is turned off; a state monitoring unit for estimating the operation state of the power conversion device based on the PWM command signal, a feedback signal generated in response to the switching operation of the switching element, the estimated current of the collector current or the drain current, and the estimated voltage of the collector voltage or the drain voltage; and an abnormality diagnosis unit that determines an abnormality of the power conversion device based on the operation state of the power conversion device estimated by the state monitoring unit.
Description
Technical Field
The present invention relates to a power conversion device having an abnormality diagnosis function and a diagnosis method for the power conversion device, and is particularly suitable for abnormality diagnosis of a power conversion device having a large capacitance.
Background
A power conversion device used for controlling a motor for a railway or a large industrial facility, or a power conversion device used for frequency conversion of a large capacity for a power system or the like uses a semiconductor element for power of a large capacity to perform power control of a high voltage and a large current.
In such a device, if a failure occurs in operation, there is a possibility that: causing damage to the system, unplanned system outages, and large economic losses. In order to prevent such a situation, it is necessary to detect deterioration and abnormality of the power conversion device, prevent destruction by stopping the function, notify a person about the necessity of updating the equipment, and perform life-prolonging control of the power conversion device.
As a cause of failure of the power conversion device, overheat of the semiconductor switching element is known. The semiconductor switching element is destroyed when it is operated in a state where the junction temperature (Tj) is higher than or equal to the rated value. Therefore, a heat dissipation design is implemented for the power conversion device.
Here, since materials having a thermal expansion coefficient different from that of the semiconductor chip are stacked for mounting, it is unavoidable that solder and bonding wires deteriorate over time due to accumulation of thermal stress caused by self-heating of the semiconductor chip during operation.
Therefore, the thermal impedance of the semiconductor switching element may increase with time, and the semiconductor switching element may overheat.
On the other hand, since the power conversion device is not subjected to maintenance, the semiconductor switching element itself is rarely inspected in a normal maintenance operation, and the device itself is updated at a timing (timing) when a certain period of time elapses from the start of use.
However, the power conversion device is accelerated in the progress of deterioration according to the use environment thereof, and the life of the power conversion device is different. Therefore, it is preferable to monitor the status of each power conversion device on-line, and optimize the timing of the device update individually, thereby reducing maintenance costs.
Among them, as a technique for monitoring the state of a power conversion device by a simple method, a technique for measuring the junction temperature during the system operation is known.
Although there is a method of incorporating a temperature sensor in a semiconductor switching element, the integration of the sensor is costly, and there are many problems in terms of the response speed and reliability of the temperature sensor.
In addition, a technique for estimating a junction temperature by utilizing a temperature dependency of an electrical characteristic of a semiconductor switching element is known. For example, patent document 1 discloses the following method: in the gate-emitter voltage characteristics of the switching off phase of an IGBT (Insulated Gate Bipolar Transistor) element, the delay time from the start phase to the end phase of a Miller plateau (Miller plateau) is detected, the junction temperature of the IGBT element is determined, and when a continuous rise in the average junction temperature is recorded, the deterioration of the element is detected.
Prior art literature
Patent document 1: japanese patent laid-open publication No. 2013-142704
Disclosure of Invention
In the method described in patent document 1, the junction temperature of the IGBT element is estimated from the delay time of the switch turn-off from the start to the end of the miller stage, but the following is not mentioned: the switching off delay time varies not only depending on the junction temperature of the IGBT element but also depending on the collector current and collector voltage immediately before switching off.
The inventors found that the switching-off delay time is not only influenced by the junction temperature of the IGBT element, but also sensitively influenced by the collector current and collector voltage immediately before switching off.
Therefore, for example, as in the case of controlling a motor by a power conversion device, in a system in which a voltage applied to a semiconductor switching element provided in the power conversion device and a current flowing through the semiconductor switching element change at time intervals, it is necessary to accurately detect not only a switching off delay time but also a collector current and a collector voltage at the time of switching off, and calculate a junction temperature from a relationship between these currents, voltages, and switching off delay times.
As described above, since the semiconductor switching element is degraded with time by the accumulation of thermal stress in the solder and the bonding wire, monitoring of temperature vibration which is the origin of thermal stress is extremely important. For this reason, it is necessary to continuously monitor the junction temperature and monitor the accumulation of temperature vibrations under various conditions of current and voltage applied to the semiconductor switching element during operation.
However, since the current and the voltage change rapidly in the TURN-OFF (TURN OFF) operation of the semiconductor switching element, there is a problem that it is extremely difficult to detect the collector current in synchronization with the timing of the switching operation.
Accordingly, an object of the present invention is to provide a power conversion device having a semiconductor switching element, which can detect abnormality and wear level of the power conversion device itself with high accuracy by a simple configuration, and a diagnostic method therefor.
In order to solve the above-described problem, a power conversion device according to the present invention includes: a gate driving circuit for driving the switching element according to a PWM command signal for driving the switching element constituting the power conversion device; a current calculation unit and a voltage calculation unit for calculating a collector current or a drain current and a collector voltage or a drain voltage, respectively, at a timing when the switching element is turned off; a state monitoring unit for estimating the operation state of the power conversion device based on the PWM command signal, a feedback signal generated in response to the switching operation of the switching element, the estimated current of the collector current or the drain current, and the estimated voltage of the collector voltage or the drain voltage; and an abnormality diagnosis unit that determines an abnormality of the power conversion device based on the operation state of the power conversion device estimated by the state monitoring unit.
According to the present invention, it is possible to provide a power conversion device capable of detecting abnormality and wear level of the power conversion device itself with high accuracy by a simple configuration, and a diagnostic method therefor.
The problems, structures, and effects other than those described above will become apparent from the following description of the embodiments.
Drawings
Fig. 1 is a block diagram showing an example of the configuration of a power conversion device according to embodiment 1.
Fig. 2 is a block diagram showing an example of a configuration in which a current calculation unit, a voltage calculation unit, a state monitoring unit, and an abnormality diagnosis unit are integrated into a control unit in the power conversion device according to embodiment 1.
Fig. 3 is a diagram showing an example of a specific configuration of an inverter according to embodiment 1.
Fig. 4 is a diagram showing an example of a specific circuit configuration of the control section for calculating the switch off delay time.
Fig. 5 is a diagram showing the time relationship between the PWM command signal, the gate voltage, and the feedback signals, 3.
Fig. 6 is a diagram showing a switching waveform when the switch of the semiconductor switching element is turned on.
Fig. 7 is a diagram showing a switching waveform and a feedback signal waveform when the switch of the semiconductor switching element is turned off.
Fig. 8 is a diagram showing the relationship among the PWM command signal, the carrier signal, the motor phase current, the motor current value detected for motor control, and the estimated collector current at the time of off.
Fig. 9 is a graph showing a relationship with the junction temperature of the semiconductor switching element, a relationship with the collector current, and a relationship with the dc power supply voltage, respectively, with respect to the switching off delay time.
Fig. 10 is a graph showing the temporal change in motor phase current and the points at which the joining temperature is maximum and minimum.
Fig. 11 is a diagram showing an example of converting time-series data of joining temperature into temperature amplitude frequency data of a histogram.
Fig. 12 is a graph showing the relationship between the change in motor phase current, the switch off delay time, and the calculated estimated engagement temperature during normal operation and when the ground fault occurs according to example 2.
Fig. 13 is a diagram showing a part of the structure of the control unit according to embodiment 3 together with a gate driver circuit.
Fig. 14 is a diagram showing an example of the relationship between the pulse numbers of the PWM command signal and the feedback signal.
(symbol description)
1: a control unit; 2 (2 a to 2 f): a semiconductor switching element; 3 (3 a to 3 f): a gate driving circuit; 4: a current calculation unit; 5: a voltage calculation unit; 6: a state monitoring unit; 7: an abnormality diagnosis unit; 8: an inverter; 9: a motor; 10: a torque command calculation unit; 11: a current instruction calculation unit; 12: a current command/3-phase voltage command conversion unit; 13: a PWM converting unit; 14: a current feedback conversion unit; 15: a PWM command signal width calculation unit; 16: a feedback signal width calculation unit; 17: a direct current power supply; 18: a smoothing capacitor; 19 (19 a, 19 b): an insulating member; 20: a gate driving section; 21. 22: a comparator; 23. 24: a time measurement unit; 25: a time comparison unit; 26: and a pulse number measurement unit.
Detailed Description
Hereinafter, examples 1 to 3 according to the present invention will be described with reference to the drawings as modes for carrying out the present invention. In the drawings, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.
[ example 1 ]
Fig. 1 is a block diagram showing an example of the configuration of a power conversion device according to embodiment 1.
The control unit 1 outputs a PWM command signal and inputs a feedback signal (FB).
The gate drive circuit 3 drives the semiconductor switching element 2 in accordance with the PWM command signal received from the control section 1, and transmits a feedback signal (FB) to the control section 1 and the state monitoring section 6 in accordance with the result of the driving.
The state monitoring unit 6 monitors the operation state of the power conversion device including the semiconductor switching element 2 based on the estimated collector current at the time of turning off the semiconductor switching element 2 calculated by the current calculating unit 4, the estimated collector voltage at the time of turning off the semiconductor switching element 2 calculated by the voltage calculating unit 5, the previous PWM command signal, and the previous feedback signal (FB).
The abnormality diagnosis unit 7 determines an abnormal state in the power conversion device such as an abnormality and deterioration of the switching element 2 based on the monitoring result obtained by the state monitoring unit 6 monitoring the power conversion device.
Fig. 2 is a block diagram showing an example of a configuration in which the current calculation unit 4, the voltage calculation unit 5, the state monitoring unit 6, and the abnormality diagnosis unit 7 are integrated into the control unit 1 in the power conversion device according to embodiment 1.
The motor comprises an inverter 8 for converting direct current into alternating current, a 3-phase alternating current motor 9 driven by 3-phase alternating current (U-phase current ium, V-phase current ivm and W-phase current iwm) generated by the inverter 8, and a control unit 1 for transmitting a PWM command signal for control to the inverter 8.
The control unit 1 includes a microcomputer having a CPU, a memory, and the like, and includes, as constituent elements, a current calculation unit 4, a voltage calculation unit 5, a state monitoring unit 6, an abnormality diagnosis unit 7, a torque command calculation unit 10, a current command calculation unit 11, a current command/3-phase voltage conversion unit 12, a PWM conversion unit 13, a current feedback conversion unit 14, a PWM command signal width calculation unit 15, and a feedback signal width calculation unit 16.
The current feedback conversion unit 14 converts motor drive currents of the respective phases detected by the U-phase current sensor, the V-phase current sensor, and the W-phase current sensor (none of which are shown) into a d-axis current id and a q-axis current iq by coordinate conversion using the rotation angle θ of the motor 9, and inputs the d-axis current id and the q-axis current iq to the current command/3-phase voltage conversion unit 12.
The current command calculation unit 11 calculates a d-axis current command value id according to a table or the like prepared in advance, based on the torque command value input from the torque command calculation unit 10 * Q-axis current command value iq * And is input to the current command/3-phase voltage conversion unit 12.
The current command/3-phase voltage conversion unit 12 is based on the d-axis current command value id * Q-axis current command value iq * And a d-axis current id and a q-axis current iq input from the current feedback conversion unit 14, and then generates a d-axis and q-axis voltage command value, which is converted into a 3-phase alternating voltage command value Vu using the rotation angle θ of the motor 9 * 、Vv * Vw * And is input to the PWM conversion section 13.
The PWM converting unit 13 converts the input 3-phase alternating current voltage command value Vu * 、Vv * Vw * PWM command signals (uh, ul, vh, vl, wh and wl) are generated and input to the inverter 8.
The inverter 8 outputs a drive current to each phase of the motor 9 based on the PWM command signal input from the PWM conversion unit 13, and drives the motor 9.
Fig. 3 is a diagram showing an example of a specific configuration of the inverter 8 constituted by the switching elements 2.
The inverter 8 is connected between the positive electrode side and the negative electrode side of the dc power supply 17 and the smoothing capacitor 18, and converts an input current between dc power and ac power to output the converted input current. Accordingly, the inverter 8 includes a plurality of semiconductor switching elements (2 a to 2 f), and the output lines of the semiconductor switching elements are connected to windings of 3 phases (U-phase, V-phase, and W-phase) of the motor 9, and the ON/OFF (OFF) of the semiconductor switching elements (2 a to 2 f) is controlled to control the connection between the motor 9 and the dc power supply 17.
The gate driving circuits 3a to 3f drive the semiconductor switching elements (2 a to 2 f) according to the PWM command signals transmitted from the control unit 1, and transmit feedback signals (FB) to the control unit 1 according to the driving results thereof.
The semiconductor switching elements (2 a to 2 f) are not limited to the illustrated IGBTs, and various switching elements such as transistors and MOS-FETs can be used. In the case of using a MOS-FET, the emitter is changed to the source and the collector is changed to the drain.
Fig. 4 is a diagram showing an example of a specific circuit configuration of the control section 1 for calculating the switch off delay time from the PWM command signal and the feedback signal (FB).
The gate driving circuit 3 and the control unit 1 are insulated by insulating elements 19a and 19b (specifically, optical coupling type elements, magnetic coupling type elements, electrostatic coupling type elements, or the like).
The gate driving circuit 3 includes insulating elements 19a and 19b, a gate driving section 20 that drives the semiconductor switching element 2, a comparator 21 that compares a gate voltage with a switch-on reference voltage to determine switch-on, and a comparator 22 that compares the gate voltage with a switch-off reference voltage to determine switch-off. The feedback signal (FB) is sent from the gate drive circuit 3 to the control unit 1 according to the operations of the comparators 21 and 22.
In the control unit 1, a feedback signal (FB) received from the gate drive circuit 3 is input to a built-in time measurement unit 23, and a pulse width based on the feedback signal (FB) is measured. The PWM command signal output from the PWM conversion unit 13 is input not only to the gate drive circuit 3 but also to the time measurement unit 24 built in the control unit 1, and the pulse width of the PWM command signal is measured. Here, the time measuring unit 23 and the time measuring unit 24 have a time resolution of, for example, 10 nanoseconds or less. The feedback signal (FB) and the pulse width of the PWM command signal measured by the time measuring unit 23 and the time measuring unit 24 are input to the time comparing unit 25, respectively, and the switching off delay time can be calculated by comparing the values of both.
In the control unit 1, the respective pulse widths of the feedback signal (FB) and the PWM command signal are measured by the time measuring units 23 and 24, but instead of these, another time measuring unit (not shown) that measures the time from the switching off of the PWM command signal to the switching off of the feedback signal (FB) may be provided, and the switching off delay time may be calculated from the measured time.
Fig. 5 is a diagram showing the time relationship among the PWM command signal, the gate voltage, and the feedback signal (FB), 3.
As shown in fig. 5, regarding the PWM command signal for switching on outputted from the PWM conversion section 13, after a circuit delay caused by the gate drive circuit 3 including the insulating element 19b, the switch-on signal is inputted to the gate terminal of the semiconductor switching element 2. If a switch-on signal is input to the semiconductor switching element 2, the gate voltage rises according to a time constant corresponding to the gate resistance and the capacitance of the element. If the gate voltage reaches the switch-on reference voltage with an element delay based on the time constant, the comparator 21 operates to output a feedback signal (FB) for switch-on. The feedback signal (FB) is input to the time measuring section 23 after passing through a circuit delay caused by the gate driving circuit 3 including the insulating element 19 a.
In addition, similarly, if a PWM command signal for switching off is output from the PWM conversion section 13, a switching off signal is input to the gate terminal of the semiconductor switching element 2 after a circuit delay caused by the gate drive circuit 3 including the insulating element 19 b. If a switch-off signal is input to the semiconductor switching element 2, the gate voltage drops with a time constant corresponding to the gate resistance and the capacitance of the element. If the gate voltage reaches the switch-off reference voltage with an element delay based on the time constant, the comparator 22 operates to output a feedback signal (FB) for the switch-off. The feedback signal (FB) is input to the time measuring section 23 after passing through a circuit delay caused by the gate driving circuit 3 including the insulating element 19 a.
The time measurement unit 23 measures the pulse width of the feedback signal (FB) from the inputs of the feedback signal (FB) with the switch on and the feedback signal (FB) with the switch off.
Here, the inventors analyzed the correlation of the PWM command signal, the switching waveform of the semiconductor switching element 2, and the feedback signal waveform. As a result, the element delay is substantially constant regardless of the junction temperature, the collector current, and the dc power supply voltage during the switch on. On the other hand, it was found that the element delay in the switching off varies depending on the junction temperature, the collector current, and the dc power supply voltage.
Fig. 6 is a diagram showing switching waveforms in the case where the PWM command signal is output as the reference time when the switch is turned on under the condition that the circuit delay time is made constant in (a) to (c) thereof.
Fig. 6 (a) shows waveforms in the case where the junction temperature (in the case of 40 ℃ and 100 ℃ as an example) is varied in a wide range, fig. 6 (b) shows waveforms in the case where the collector current (in the case of 600A, 900A and 1200A as an example) is varied in a wide range, and fig. 6 (c) shows waveforms in the case where the dc power supply voltage (in the case of 1100V, 1300V and 1500V as an example) is varied in a wide range. Further, the switch-on reference voltage at which the switch is determined to be on is set to 5V as an example.
As shown in fig. 6 (a) to (c), the timing at which the gate voltage reaches the switch-on reference voltage is substantially constant, irrespective of the junction temperature, the collector current, and the dc power supply voltage. Therefore, it is found that the element delay at the time of switching on has very little dependence on the junction temperature, collector current, and dc power supply voltage.
Fig. 7 is a diagram showing switching waveforms ((a), (c), and (e)) and feedback signal waveforms ((b), (d), and (f)) in the case of outputting the PWM command signal as the reference time when the switch is turned off under the condition that the circuit delay time is made constant in the cases (a) to (f).
Fig. 7 (a) and (b) show waveforms in the case where the junction temperature (for example, 40 ℃ and 100 ℃) is varied variously, fig. 7 (c) and (d) show waveforms in the case where the collector current (for example, 600A, 900A and 1200A) is varied variously, and fig. 7 (e) and (f) show waveforms in the case where the dc power supply voltage (for example, 1100V, 1300V and 1500V) is varied variously. Further, the switch-off reference voltage for determining the switch-off is set to-5V as an example.
It is found that, when the junction temperature increases in fig. 7 (a), when the collector current decreases in fig. 7 (c), and when the dc power supply voltage increases in fig. 7 (e), the delay time until the gate voltage reaches the switch off reference voltage increases. It is known that these phenomena can be explained mainly by the dependency of the feedback capacitance of the element on the respective parameters.
As shown in fig. 7 (b), (d) and (f), it is understood that the timing of the feedback signal (FB) for switching off the output switch changes according to the delay time until the gate voltage reaches the switching off reference voltage.
Therefore, it is known that the element delay when the switch is turned off varies depending on the junction temperature, the collector current, and the dc power supply voltage.
From the above results, if the pulse widths of the PWM command signal and the feedback signal (FB) are compared, it is found that the change in the element delay when the switch is turned off can be measured.
Regarding the circuit delay, it was confirmed that the change was caused by the ambient temperature of the gate drive circuit 3, and that the change in the circuit delay when the switch was turned on was equal to the change in the circuit delay when the switch was turned off. As a result, if the pulse widths of the PWM command signal and the feedback signal (FB) are compared, it is found that the effects of the temperature variation of the circuit delay caused by the gate drive circuit can be canceled each other. In the case of a circuit configuration in which the temperature dependence of the circuit delay is different between when the switch is on and when the switch is off, a thermometer or the like may be provided to the gate driving circuit to correct the change in the circuit delay.
From the above-described results, in order to estimate the junction temperature of the semiconductor switching element 2, it is necessary to detect the dc power supply voltage and the collector current at the time of turn-off, and calculate the junction temperature from the relationship between the delay time of the element and the detected current and voltage.
In example 1, the voltage of the positive electrode side and the negative electrode side of the smoothing capacitor 18 was measured and calculated for detection of the dc power supply voltage. On the other hand, in the detection of the collector current, the collector current changes rapidly during the off operation, so that it is extremely difficult to sample the current in accordance with the off timing. As shown in fig. 2, the current of each phase of the motor is sampled for use in motor control, but in general, the current is sampled at each midpoint of on/off of the PWM command signal in synchronization with the carrier signal, so that the motor control does not use a scheme of detecting the current at the off timing.
Here, the inventors analyzed the relationship among the PWM command signal, the motor phase current value sampled in synchronization with the carrier signal for motor control, and the collector current at the time of turn-off. As a result, it was found that the collector current at the time of the off-state can be estimated from the voltage of each motor phase obtained by the combination of the PWM command signals of each phase, the rate of change of the motor phase currents (ium, ivm, and iwm) calculated based on the dc power supply voltage, the motor induced voltage Em, and the motor constant (inductance L), the motor phase current value sampled by carrier synchronization, and the phase difference due to the pulse width of the PWM command signals and the operation delay of the semiconductor switching element 2. In embodiment 1, the operation delay of the semiconductor switching element 2 is 10 μs or less and is set to be constant in advance, but in the case where the rate of change of the motor phase current is small, the current accuracy can be sufficiently improved even if the influence of the operation delay is ignored.
Fig. 8 is a diagram showing the relationship among the PWM command signal, the carrier signal, the motor phase current (Im), the motor current value (current sampling) detected for motor control, and the estimated collector current at the time of turn-off.
In embodiment 1, using the above relationship, the internal parameters for control such as PWM command signal width and carrier period and the motor phase current are input to the current calculation unit 4, and the collector current at the time of off is calculated. According to example 1, the collector current at the time of turning off can be estimated with high accuracy using the current value detected for motor control that has been conventionally used.
In fig. 9, regarding the switch-off delay, a relationship with the junction temperature (Tj) of the semiconductor switching element 2 is shown in (a), a relationship with the collector current (Ice) is shown in (b), and a relationship with the dc power supply voltage (Vce) is shown in (c).
The state monitoring unit 6 receives the switching off delay time calculated by the time comparing unit 25, the estimated collector current at the off time calculated by the current calculating unit 4, and the dc power supply voltage at the off time calculated by the voltage calculating unit 5, and estimates the junction temperature of the semiconductor switching element 2 for each switching on and off based on the relationship between these delay times and the current and voltage. This is shown schematically in fig. 9 (d).
As described above, one of the points in embodiment 1 is to monitor the wear level of the plurality of semiconductor switching elements 2 in the power conversion device, and to prevent the failure of the system and to notify the appropriate equipment update timing.
Fig. 10 is a graph showing the temporal change in motor phase current and the points at which the joining temperature becomes maximum and minimum.
The state monitoring unit 6 includes a unit that monitors the junction temperature at the time of switching operation at the maximum value (Tmax) and the minimum value (Tmin) in one cycle of each motor phase current (Im), and stores the temperature difference and the number of times in a memory or the like as a frequency distribution of thermal cycles, for example, as shown in fig. 10. As a method for converting the thermal cycle into a frequency, there is, for example, a rain flow (Rainflow) algorithm.
Fig. 11 is a diagram showing an example of time-series data of joining temperatures and frequency of temperature amplitudes converted into histograms. The temperature amplitude Δt of the horizontal axis is set on a scale of 5 ℃. The vertical axis is a logarithmic display of the number of cycles N (log N). As the thermal cycle rating, a power cycle test provided at the time of shipment of the semiconductor switching element 2 was used. In fig. 11, ni is the allowable maximum number of cycles of the temperature amplitude Ti, and Ni (the black part shown in fig. 11) is the number of cycles of the temperature amplitude Ti obtained by the state monitoring unit 6. The wear degree Di of each temperature amplitude Ti is given by Ni/Ni, and the overall wear degree is given by ΣDi.
The Σdi calculated by the state monitoring unit 6 is sent to the abnormality diagnosis unit 7. The abnormality diagnosis unit 7 determines that the wear of the element is degraded when the input Σdi exceeds a predetermined value, and notifies the determination result to the person concerned. At this time, the abnormality diagnosis unit 7 may include a GUI (Graphical User Interface ) for prompting the update of the device. In addition, if the abnormality determination result is included in the central monitoring system, the monitoring of a plurality of vehicles can be realized, and the optimization of the maintenance plan can be contributed.
As described above, according to embodiment 1, by storing time-series data of the change in the junction temperature of the semiconductor switching element and comparing and determining the time-series data with the reference value, it is possible to accurately detect the degree of wear of the semiconductor switching element and the power conversion device associated therewith, to accurately prevent failures and other adverse phenomena, and to optimize the equipment update and maintenance.
[ example 2 ]
Embodiment 2 provides a method of detecting sudden anomalies occurring in a power conversion device using the structure according to the present invention. Specifically, the present invention relates to a method for detecting an abnormality in a current value caused by a ground fault or the like of a power conversion device, and the method will be described below.
Fig. 12 is a diagram showing a change in motor phase current (Im) during normal operation and when a ground fault occurs in (a) thereof, and showing a relationship between a switch off delay time and a calculated estimated engagement temperature (Tj) in (b) thereof.
As shown in fig. 12 (a), since the rate of change of the motor phase current (Im) increases when the ground fault occurs as compared with that in the normal operation, the collector current at which the semiconductor switching element 2 is energized actually increases as compared with the estimated value of the collector current calculated by the current calculation unit 4.
As a result, as shown in fig. 12 (b), since the switching off delay time is shorter than that in the normal operation when the ground fault occurs, the junction temperature (Tj) of the semiconductor switching element 2 estimated by the state monitoring unit 6 is estimated to be lower than that in the normal operation based on the respective estimated values of the switching off delay time, the collector current, and the collector voltage. Further, since the current dependency of the switching off delay time is large, the state monitoring unit 6 outputs an abnormal result that the junction temperature (Tj) of the semiconductor switching element 2 is rapidly lowered.
As described above, it is possible to determine an abnormality in the collector current value due to a ground fault or the like from each estimated value of the switch off delay time, the collector current, and the collector voltage.
According to embodiment 2, in the time-series data of the junction temperature (Tj) input from the state monitoring unit 6 to the abnormality monitoring unit 7, when an abnormal value in which the junction temperature change is larger than a predetermined value is output, it is possible to determine an abnormality in the current value.
In general, a reference current value is set in advance for detection of a ground fault or a short circuit, and detection is performed when the reference current value exceeds an overcurrent state, so that there is a problem that detection timing is delayed. In the ground fault detection of embodiment 2, since whether or not there is an abnormality can be determined for each switching even in the operation in the low current region where the overcurrent state is not achieved, there is an advantage in that the protection of the system can be implemented more early.
Therefore, by the abnormality detection method according to embodiment 2, damage to the system can be prevented or reduced.
[ example 3 ]
Embodiment 3 provides another method of detecting sudden anomalies occurring in a power conversion device using the structure of the present invention. Specifically, a method for detecting a malfunction of the gate driving circuit is described below.
Fig. 13 is a diagram showing a part of the structure of the control unit 1 according to embodiment 3 together with the gate driving circuit 3.
In the foregoing embodiment 1, the respective pulse widths of the feedback signal (FB) and the PWM command signal are measured by the time measuring units 23 and 24, respectively, and the switch off delay time is calculated by the time comparing unit 25. In embodiment 3, in addition to the configuration of embodiment 1, a pulse number measuring unit 26 is provided, and the number of pulses of the feedback signal (FB) and the PWM command signal is counted based on the output results of the time measuring units 23 and 24.
Fig. 14 is a diagram showing the relationship between the number of pulses of the PWM signal and the feedback signal (FB) counted by the pulse number measurement unit 26 according to embodiment 3.
It is known that the gate driving circuit 3 may malfunction due to the influence of the surrounding environment and the operation of the power conversion device itself. If the gate drive circuit 3 is accidentally operated due to malfunction, a short circuit of the power conversion device may occur, and the system may be damaged.
Therefore, in general, the outputs of the PWM command signal and the feedback signal are compared to monitor whether the gate drive circuit is operating normally, and if the period of inconsistency between the outputs of the PWM command signal and the feedback signal is greater than a predetermined value, the gate drive circuit is determined to be malfunctioning.
However, as shown in fig. 5, in the normal operation, since there is an operation delay due to a circuit delay or an element delay between the PWM command signal and the feedback signal, it is necessary to increase the threshold value of the output inconsistency period for abnormality determination. In this way, if the threshold value of the output inconsistency period is increased, malfunction during a short period cannot be detected, and therefore, there is a possibility that the system may be deteriorated or damaged.
According to embodiment 3, since the malfunction of the gate driving circuit 3 is detected based on the comparison of the pulse numbers of the PWM command signal and the feedback signal (FB), there is an advantage that the malfunction in a short period can be detected. Further, as shown in fig. 14, the time measuring unit 23 can also measure the pulse width of the feedback signal (FB), so that the malfunction period can also be detected.
Therefore, by the abnormality detection method according to embodiment 3, damage to the system can be prevented or reduced.
Claims (12)
1. A power conversion device is provided with a switching element, wherein,
the power conversion device is provided with:
a gate driving circuit that drives the switching element according to a PWM command signal for driving the switching element;
a current calculation unit and a voltage calculation unit that calculate a collector current or a drain current and a collector voltage or a drain voltage, respectively, at a timing when the switching element is turned off;
a state monitoring unit configured to estimate an operation state of the power conversion device based on the PWM command signal, a feedback signal generated in response to a switching operation of the switching element, an estimated current of the collector current or the drain current, and an estimated voltage of the collector voltage or the drain voltage;
an abnormality diagnosis unit configured to determine an abnormality of the power conversion device based on the operation state of the power conversion device estimated by the state monitoring unit;
a 1 st time measurement unit configured to measure an on period or an off period of the PWM command signal; and
a 2 nd time measurement unit for measuring an on period or an off period of the feedback signal,
the power conversion device calculates a switching off delay time of the switching element based on an on period or an off period of the PWM command signal measured by the 1 st time measurement unit and an on period or an off period of the feedback signal measured by the 2 nd time measurement unit,
the state monitoring unit calculates a junction temperature of the switching element based on the switching off delay time, the estimated current of the collector current or the drain current, and the estimated voltage of the collector voltage or the drain voltage.
2. The power conversion apparatus according to claim 1, wherein,
the feedback signal is generated by comparing a voltage between the gate and the emitter or the source when the switching element is operated with a switch on reference voltage and a switch off reference voltage, respectively.
3. The power conversion apparatus according to claim 1 or 2, wherein,
the voltage calculation unit calculates the estimated voltage of the collector voltage or the drain voltage from the measured voltage of a capacitor provided between the positive electrode and the negative electrode of the power conversion device on the dc power supply side.
4. The power conversion apparatus according to claim 1 or 2, wherein,
the current calculation unit calculates an estimated current of the collector current or the drain current at a timing when the switching element is turned off, based on a measured current of each phase current outputted from the power conversion device, the PWM command signal, and an estimated voltage of the collector voltage or the drain voltage.
5. The power conversion apparatus according to claim 1, wherein,
the state monitoring unit calculates a temperature amplitude of the change in the joining temperature and the number of times the joining temperature is changed by the temperature amplitude based on the calculated time-series data of the joining temperature, and calculates the degree of wear of the switching element based on the temperature amplitude and the number of times.
6. The power conversion apparatus according to claim 1 or 2, wherein,
the abnormality diagnosis unit determines abnormality of the current value of the collector current or the drain current based on the switch off delay time, the estimated voltage of the collector voltage or the drain voltage, and the estimated current of the collector current or the drain current.
7. The power conversion apparatus according to claim 1 or 2, wherein,
the power conversion device includes a pulse number measurement unit that measures the number of pulses of the PWM command signal and the number of pulses of the feedback signal, respectively,
and detecting malfunction of the gate driving circuit based on the comparison result of the measured pulse numbers.
8. A diagnostic method for a power conversion device includes:
step 1, estimating a collector current or a drain current and a collector voltage or a drain voltage at a timing when a switching element constituting the power conversion device is turned off, respectively;
step 2, estimating an operation state of the power conversion device based on a PWM command signal for driving the switching element, a feedback signal generated in response to a switching operation of the switching element, an estimated current of the collector current or the drain current, and an estimated voltage of the collector voltage or the drain voltage;
step 3, judging abnormality of the power conversion device according to the estimated operation state of the power conversion device;
step 4, measuring the on period or off period of the PWM command signal and the on period or off period of the feedback signal;
step 5, calculating a switching off delay time of the switching element according to the measured on period or off period of the PWM command signal and the measured on period or off period of the feedback signal; and
and 6, calculating the junction temperature of the switching element according to the switch turn-off delay time, the estimated current of the collector current or the drain current and the estimated voltage of the collector voltage or the drain voltage.
9. The diagnostic method of a power conversion device according to claim 8, wherein,
the feedback signal is generated by comparing a voltage between the gate and the emitter or the source when the switching element is operated with a switch on reference voltage and a switch off reference voltage, respectively.
10. The diagnostic method of a power conversion apparatus according to claim 8, further comprising:
and 7, calculating the temperature amplitude of the change of the joint temperature and the number of times of the change of the joint temperature by the temperature amplitude according to the calculated time series data of the joint temperature, and calculating the abrasion degree of the switching element according to the temperature amplitude and the number of times.
11. The diagnostic method of a power conversion apparatus according to claim 8 or 9, further comprising:
and 8, judging abnormality of the current value of the collector current or the drain current according to the switch off delay time, the estimated voltage of the collector voltage or the drain voltage and the estimated current of the collector current or the drain current.
12. The diagnostic method of a power conversion apparatus according to claim 8 or 9, further comprising:
step 9, measuring the pulse times of the PWM command signal and the pulse times of the feedback signal respectively; and
and step 10, detecting malfunction of the gate driving circuit of the switching element according to the comparison result of the measured pulse times.
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| JP2018196372A JP7085453B2 (en) | 2018-10-18 | 2018-10-18 | Diagnostic method for power converters and power converters |
| JP2018-196372 | 2018-10-18 |
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| CN1445928A (en) * | 2002-01-17 | 2003-10-01 | 三菱电机株式会社 | Drive circuit of power semiconductor element |
| CN103733501A (en) * | 2011-09-05 | 2014-04-16 | 日产自动车株式会社 | Power conversion device and power conversion method |
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| JP2020065386A (en) | 2020-04-23 |
| JP7085453B2 (en) | 2022-06-16 |
| CN111092563A (en) | 2020-05-01 |
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