CN116232138A - Motor drive control device, motor drive control method, and refrigerating air conditioner - Google Patents

Abstract

The invention provides a motor drive control device, a motor drive control method and a refrigeration air conditioner, which control a motor used in a refrigeration cycle. Provided is a drive control device for controlling a motor used in a refrigeration cycle. The drive control device (100) comprises: an inverter circuit (122) connected to the motor (102); and a control unit (128) that controls the inverter circuit (122) so that a positioning current for fixing or adjusting the rotor position of the motor (102) flows through the motor (102) when the motor (102) is started, wherein the control unit (128) adjusts the magnitude of the positioning current according to the state of the refrigeration cycle.

Description

Motor drive control device, motor drive control method, and refrigerating air conditioner

Technical Field

The present invention relates to a motor drive control device, a motor drive control method, and a refrigeration air conditioner having a compressor, wherein the compressor is provided with a motor.

Background

In the case of controlling the permanent magnet synchronous motor by the inverter, it is preferable to detect the phase of the motor rotor, but since the inside of the device such as the compressor is usually at high temperature and high pressure, it is difficult to provide a phase detector such as a hall element in the device. Conventionally, an inverter circuit for a device such as a compressor has been used, which is called sensorless control, that is, a technique of estimating a phase from a current (motor current) flowing through a motor winding.

On the other hand, the sensorless control is a control method using an induced voltage generated when the motor rotates, and therefore, in a low rotation region when the device such as a compressor is started, the estimation accuracy of the phase of the motor rotor is lowered. Therefore, a control method called positioning control is known as follows: a direct current called a detent current is caused to flow in the motor windings to generate a fixed magnetic field, thereby fixing the phase of the rotor. After the positioning control, the motor current phase is gradually advanced, that is, the motor is rotated by changing the direct current to the alternating current.

In order to prevent the motor from failing to start at the time of starting, a motor current sufficiently larger than the expected load torque is required. Therefore, the motor current is currently determined according to the hardware specification of the inverter circuit and is set to a fixed value.

Patent document 1 (japanese patent application laid-open No. 2008-157182) discloses the following structure: in the synchronous operation mode performed at the time of starting, the starting current value is determined based on the low-pressure side pressure of the compressor or the ambient temperature in order to stabilize the driving of the compressor at the time of starting. In the prior art of patent document 1, a start current value that becomes an amplitude in the synchronous operation mode is determined, and on the other hand, in the initial excitation mode before the synchronous operation mode, the current value flowing in each phase is gradually increased from zero in a range equal to or less than the maximum current value (current peak value) that can flow in each phase during the normal operation. Although a current of a direct current component such as a positioning current applies thermal stress to an inverter circuit, patent document 1 does not disclose improvement of such positioning current, and there is still room for improvement in positioning control.

Patent document 1: japanese patent laid-open No. 2008-157182

Disclosure of Invention

The present disclosure has been made in view of the above-described problems in the related art, and an object of the present invention is to provide a drive control device and a drive control method for a motor, which can stabilize the start of the motor used in a refrigeration cycle, reduce thermal stress applied to an inverter circuit at the start, suppress fatigue and deterioration of elements of the inverter circuit, prevent malfunction of a device including the inverter circuit, and realize a long lifetime.

In order to solve the above problems, the present disclosure provides a drive control device for controlling a motor used in a refrigeration cycle, the drive control device having the following features. The drive control device includes an inverter circuit connected to the motor and a control unit. The control unit controls the inverter circuit so that a positioning current for fixing or adjusting the position of the motor rotor flows through the motor when the motor is started. The control unit adjusts the magnitude of the positioning current according to the state of the refrigeration cycle.

Also, according to the present disclosure, a refrigerating and air-conditioning apparatus having the following features may be provided. A refrigerating air conditioner is provided with: a heat exchanger; a compressor provided with a motor; an inverter circuit connected to the motor; and a control unit that controls the inverter circuit. When starting the motor, the control unit controls the inverter circuit so that a positioning current for fixing or adjusting the position of the motor rotor flows through the motor. The control unit determines the magnitude of the positioning current according to the state of the refrigeration cycle.

Also, according to the present disclosure, a drive control method of controlling an electric motor used in a refrigeration cycle may also be provided having the following features. The driving control method comprises the following steps: determining a magnitude of a positioning current flowing for fixing or adjusting a position of a motor rotor according to a state of a refrigeration cycle; and controlling an inverter circuit connected to the motor so that a positioning current flows to the motor in accordance with the determined magnitude when the motor is started.

Further, the problems disclosed in the present application and the solutions thereof will become clear from the columns and the drawings for implementing the embodiments of the present invention.

According to the above configuration, the start-up of the motor used in the refrigeration cycle can be stabilized, the thermal stress applied to the inverter circuit at the start-up can be reduced, fatigue and deterioration of the elements of the inverter circuit can be suppressed, and the malfunction of the device including the inverter circuit can be prevented and the lifetime can be prolonged.

Drawings

Fig. 1 is a configuration diagram of an air conditioner according to an embodiment of the present invention.

Fig. 2 is a block diagram of a motor drive control device according to an embodiment of the present invention.

Fig. 3 is a flowchart showing a process of determining the magnitude of a current value at the time of starting a compressor executed by an inverter controller in the motor drive control device according to the embodiment of the present invention.

Fig. 4 schematically shows time variations of current values in positioning control and synchronization control based on the determination made by the motor drive control device of the present embodiment.

Fig. 5 is a graph depicting time changes in current values and load torques at the time of positioning control, synchronization control, and sensorless control in the motor drive control device of the present embodiment.

Fig. 6 is a graph depicting time changes in current values and changes in rotor phases when positioning control and synchronization control are performed at the time of starting from various initial phases.

Fig. 7 schematically shows time variations of current values during positioning control and synchronization control accompanied by phase adjustment in the preferred embodiment.

Fig. 8 is a graph depicting time changes in current values and changes in rotor phases at the time of positioning control and synchronization control with phase adjustment in the preferred embodiment when starting from various initial phases.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings, but the embodiments of the present invention are not limited to the specific embodiments described below. In the drawings, like reference numerals designate identical or corresponding parts.

The present disclosure targets the following: a drive control device for controlling a motor used in a refrigeration cycle, a drive control method for controlling a motor used in a refrigeration cycle, and a refrigeration air conditioner (hereinafter, air conditioning may be simply referred to as air conditioning) provided with the drive control device. The drive control device according to an embodiment of the present invention includes, for example: an inverter circuit connected to a motor used in a compressor, for example, in a refrigeration cycle of a refrigeration air conditioner; and a control unit that controls the inverter circuit so that a positioning current for fixing or adjusting the position of the motor rotor flows through the motor when the motor is started, and adjusts the magnitude of the positioning current according to the state of the refrigeration cycle. This stabilizes the start-up of the motor used in the refrigeration cycle, reduces thermal stress applied to the inverter circuit at the start-up, suppresses fatigue and deterioration of the elements of the inverter circuit, prevents malfunction of the device, and realizes a long life.

Hereinafter, a drive control device for controlling a motor used in a refrigeration cycle, a drive control method for controlling a motor used in a refrigeration cycle, and a refrigeration air conditioner provided with the drive control device will be described in more specific embodiments with reference to the accompanying drawings.

A motor drive control device and a motor drive control method according to an embodiment of the present invention will be described below with reference to fig. 1 to 5. The embodiment shown in fig. 1 to 5 corresponds to a motor drive control device and a drive control method thereof used in an air conditioner, which is an example of a refrigerating air conditioner. Here, a refrigeration air conditioner (refrigeration air conditioning apparatus) is a generic term for apparatuses such as an air conditioner, a refrigerator, and a freezer that use a refrigerant and a refrigeration cycle. Examples of the refrigerating air conditioner include an air conditioner such as an indoor air conditioner and a gas engine heat pump air conditioner, a heat source device such as a refrigerator and a cooling unit, a refrigerator for use in a display case, a freezer and refrigerator, a unit cooler, a refrigerator for use in a commercial use such as an ice maker, a refrigerating device for use in transportation such as an automobile air conditioner, a heat pump water heater, and the like, and the air conditioner will be described as an example in the following description.

Hereinafter, referring first to fig. 1, an overall configuration of an air conditioner 1, which is an example of a refrigeration air conditioner to which a drive control device of a motor and a drive control method thereof are attached, will be described.

Fig. 1 is a structural diagram of an air conditioner 1 according to the present embodiment. The air conditioner 1 shown in fig. 1 is a device for switching between a cooling operation and a heating operation, and includes a refrigerant circuit Q and a control device 30. In fig. 1, the direction of the flow of the refrigerant in the refrigerant circuit Q is indicated by a solid arrow in the cooling operation, and the cooling operation is described below on the premise that the cooling operation is not described in particular, but the refrigerant is circulated in the reverse direction in the heating operation.

The refrigerant circuit Q is configured by sequentially connecting the compressor 11, the outdoor heat exchanger 13, the indoor expansion valve 21, and the indoor heat exchanger 22. The refrigerant circuit Q includes devices provided in the outdoor unit 10, devices provided in the indoor unit 20, and connection pipes k1 and k3.

The outdoor unit 10 includes a compressor 11, a receiver 12, an outdoor heat exchanger 13, an outdoor fan 14, a four-way valve 15, a gas blocking valve 18a, a liquid blocking valve 18b, and sensors 19.

The compressor 11 compresses the gaseous refrigerant flowing in through the accumulator 12 in accordance with a command from the control device 30. The compressor 11 includes a motor as a target to be controlled and driven by the inverter circuit in the present embodiment. The compressor 11 is not particularly limited, and a scroll compressor can be used.

The accumulator 12 is provided on the suction side of the compressor 11, and performs gas-liquid separation of the refrigerant flowing in from the indoor heat exchanger 22. By providing the accumulator 12, the liquid can be prevented from being compressed in the compressor 11, and the dryness of the refrigerant sucked into the compressor 11 can be appropriately adjusted.

Therefore, the outdoor heat exchanger 13 is a heat exchanger that exchanges heat between the high-temperature and high-pressure refrigerant discharged from the compressor 11 and the outside air sent by the outdoor fan 14. The outdoor heat exchanger 13 functions as a condenser that condenses the refrigerant compressed by the compressor 11 during the cooling operation. In the example shown in fig. 1, the upstream end of the outdoor heat exchanger 13 is connected to the discharge port of the compressor 11 via a four-way valve 15. The downstream end of the outdoor heat exchanger 13 is connected to the indoor heat exchanger 22 via the liquid blocking valve 18b, the connection pipe k3, and the indoor expansion valve 21 in this order.

The outdoor fan 14 is provided near the outdoor heat exchanger 13, and sends outside air into the outdoor heat exchanger 13 in response to a command from the control device 30.

The four-way valve 15 is used to switch the direction in which the refrigerant flows in the refrigerant circuit Q. During the cooling operation, the four-way valve 15 is switched to the flow path shown by the solid line, and the refrigerant circulates through the refrigerant circuit Q that connects the compressor 11, the outdoor heat exchanger 13 (functioning as a condenser during the cooling operation), the indoor expansion valve 21, and the indoor heat exchanger 22 (functioning as an evaporator during the cooling operation) in this order in a loop. In contrast, during the heating operation, the four-way valve 15 is switched to the flow path shown by the broken line, and the refrigerant circulates through the refrigerant circuit Q that connects the compressor 11, the indoor heat exchanger 22 (functioning as a condenser during the heating operation), the indoor expansion valve 21, and the outdoor heat exchanger 13 (functioning as an evaporator during the heating operation) in this order in a loop.

The gas preventing valve 18a and the liquid preventing valve 18b are opened after the air conditioner 1 is installed, so that the refrigerant sealed in the outdoor unit 10 is distributed throughout the refrigerant circuit Q. One side (downstream side in the cooling operation) of the gas blocking valve 18a is connected to the four-way valve 15, and the other side (upstream side in the cooling operation) is connected to the indoor heat exchanger 22 via the connection pipe k 1. One side (upstream side in the cooling operation) of the liquid blocking valve 18b is connected to the outdoor heat exchanger 13, and the other side (downstream side in the cooling operation) is connected to the indoor expansion valve 21 via the connection pipe k 3.

The sensors 19 of the outdoor unit 10 include a suction pressure sensor 19a, a discharge pressure sensor 19b, a discharge temperature sensor 19c, a temperature sensor 19d, an outside air temperature sensor 19g, and an outdoor heat exchanger intermediate temperature sensor 19h.

The suction pressure sensor 19a is provided on the suction side of the compressor 11, and detects the pressure of the refrigerant sucked into the compressor 11. The discharge pressure sensor 19b is provided on the discharge side of the compressor 11, and detects the pressure of the refrigerant discharged from the compressor 11. The discharge temperature sensor 19c is provided near the discharge port of the compressor 11, and detects the temperature of the refrigerant discharged from the compressor 11. The temperature sensor 19d is provided on the upstream side of the reservoir 12, and detects the temperature thereof. The outside air temperature sensor 19g is provided at a predetermined portion of the outdoor unit 10, and detects the temperature of the outside air. The outdoor heat exchanger intermediate temperature sensor 19h is provided in the outdoor heat exchanger 13, and detects a temperature near an intermediate portion (intermediate portion of a heat transfer pipe through which the refrigerant flows) of the outdoor heat exchanger 13 (hereinafter, referred to as an intermediate temperature).

In fig. 1, signal lines are indicated by broken arrows, and detection values of the sensors 19 are output to the control device 30.

The indoor unit 20 includes an indoor expansion valve 21, an indoor heat exchanger 22, an indoor fan 23, an indoor solenoid valve 24, and an indoor heat exchanger intermediate temperature sensor 25.

The indoor expansion valve 21 is a valve for decompressing the refrigerant condensed by the outdoor heat exchanger 13. The indoor expansion valve 21 has a function of decompressing the refrigerant flowing from the outdoor heat exchanger 13 to the indoor heat exchanger 22 via the connection pipe k3 during the cooling operation. The opening degree of the indoor expansion valve 21 is adjusted by the control device 30.

Accordingly, the indoor heat exchanger 22 is a heat exchanger that exchanges heat between the refrigerant depressurized by the indoor expansion valve 21 and indoor air (air in the air-conditioning space). In the cooling operation, the indoor heat exchanger 22 functions as an evaporator that evaporates the refrigerant depressurized by the indoor expansion valve 21. The indoor air is cooled by the latent heat of vaporization of the refrigerant flowing through the indoor heat exchanger 22.

The indoor fan 23 is provided near the indoor heat exchanger 22, and sends indoor air into the indoor heat exchanger 22 in response to a command from the control device 30. The indoor solenoid valve 24 is provided upstream of the indoor expansion valve 21, and is opened to allow the refrigerant to circulate when the indoor unit 20 is operated. If the indoor expansion valve 21 is of a fully closable construction, the indoor solenoid valve 24 can be omitted.

The indoor heat exchanger intermediate temperature sensor 25 is provided in the indoor heat exchanger 22, and detects the temperature near the intermediate portion of the indoor heat exchanger 22.

In fig. 1, a signal line is indicated by a broken arrow, and a detection value of the indoor heat exchanger intermediate temperature sensor 25 is output to the control device 30.

Although not shown, the control device 30 includes a CPU (Central Processing Unit: central processing unit), a ROM (Read Only Memory), a RAM (Random Access Memory: random access Memory), and various interfaces. The programs stored in the ROM are read out and developed in the RAM, and various processes are executed by the CPU. The control device 30 includes a motor drive control device described later, and controls the respective devices including the compressor 11 and the indoor expansion valve 21 based on the detection values of the sensors 19 and 25 and an operation signal from a remote controller.

A motor drive control device 100 and a drive control method thereof according to an embodiment of the present invention will be described below with reference to fig. 2. The embodiment shown in fig. 2 corresponds to a drive control device and a drive control method for the motor 102 of the air conditioner provided in the compressor 11. The motor 102 is an alternating current motor, more specifically a synchronous motor, typically a permanent magnet synchronous motor (PMSM, permanent Magnet Synchronous Motor) using a predetermined number of poles.

Fig. 2 shows the overall configuration of the motor drive control device 100 according to the present embodiment. The motor drive control device 100 shown in fig. 2 is not particularly limited, and can be mounted in the control device 30 shown in fig. 1. As shown in fig. 2, an ac power source 101 and a motor 102 are connected to a motor drive control device 100, and the motor drive control device 100 mainly includes a converter unit 110 and an inverter unit 120.

The converter 110 includes a rectifier circuit 111, a smoothing reactor 113, and a smoothing capacitor 114.

The ac power supply 101 is a 3-phase ac power supply, and the rectifier circuit 111 is a 3-phase full-wave rectifier circuit. The rectifier circuit 111 has a 3-phase bridge structure using 6 diodes (a thyristor may be used instead of the diode) 112. The rectifier circuit 111 is connected to the ac power supply 101, converts an ac voltage from the ac power supply 101 into a dc voltage, and outputs the dc voltage to the inverter unit 120.

Smoothing reactor 113 and smoothing capacitor 114 are connected to a dc output terminal of rectifying circuit 111. The smoothing reactor 113 and the smoothing capacitor 114 constitute a dc filter for smoothing the dc voltage output from the rectifier circuit 111.

The inverter unit 120 includes a dc voltage detection unit 121, an inverter circuit 122, current sensors 125 and 126, a gate drive circuit 127, and an inverter controller 128. The dc current from the converter unit 110 is input to the inverter unit 120.

The dc voltage detection unit 121 is provided on the input side of the inverter circuit 122, detects a dc voltage of the output of the rectifier circuit 111 (both ends of the smoothing capacitor 114), and outputs the detected voltage value to the inverter controller 128.

The inverter circuit 122 converts the dc power from the converter unit 110 into ac power, and outputs the ac power to the motor 102, which is an ac load. The inverter circuit 122 is configured by 6 semiconductor switching elements 123 and diodes 124 connected in antiparallel with the respective semiconductor switching elements 123 to form a 3-phase bridge circuit corresponding to 3-phase alternating current. The diode 124 connected in anti-parallel with each switching element 123 is a diode for the commutation operation when each switching element 123 is turned off.

The gate drive circuit 127 is a circuit that performs pulse width modulation (hereinafter, pulse width modulation may be referred to as PWM (Pulse Width Modulation)) driving of the inverter circuit 122 under the control of the inverter controller 128.

The inverter circuit 122 turns on and off a Semiconductor switching element 123 such as an IGBT (Insulated Gate Bipolar Transistor) or a power MOS (Metal-Oxide-Semiconductor) FET (Field-Effect Transistor) in accordance with a PWM signal input from the gate drive circuit 127, converts a dc voltage, which is an output of the converter 110, into an ac voltage, and outputs the ac voltage, thereby controlling the rotation speed of the motor 102.

The current sensors 125 and 126 detect ac voltages of ac outputs, and output measured values to the inverter controller 128.

The inverter controller 128 controls the gate drive circuit 127 based on the dc voltage value from the dc voltage detection unit 121 and the detection signal of the ac current value from the current sensors 125 and 126, thereby generating a PWM signal. As the inverter controller 128, an arithmetic processing device such as a microcomputer or DSP (Digital Signal Processor: digital signal processor) can be used. The inverter controller 128 further includes a sample-and-hold circuit and an a/D (Analog/Digital) converter, and converts the input detection signals of the voltages and currents into Digital signals.

In the circuit configuration shown in fig. 2, in response to satisfaction of a condition (power on, etc.) that is a trigger for starting the compressor 11, the inverter controller 128 inputs a predetermined PWM signal to the inverter circuit 122 via the gate drive circuit 127, thereby starting the compressor 11 (and the motor 102 thereof) and operating the compressor at the obtained rotation speed 11.

As described above, in the case of inverter control of a motor (for example, a permanent magnet synchronous motor) incorporated in a compressor, it is preferable to detect the phase (mechanical angle) of the motor rotor. However, since the inside of the compressor is at high temperature and high pressure, it is difficult to provide an element for phase detection such as a hall element in the compressor. Therefore, sensorless control is generally performed in which the phase is estimated from the current (motor current) flowing through the motor winding.

On the other hand, the sensorless control is a control method using an induced voltage generated when the motor rotates, and therefore, in a low rotation region at the time of starting the compressor, there is a possibility that the accuracy of estimating the rotor phase is lowered. This is because the induced voltage of the motor becomes high in proportion to the rotation speed. Therefore, the phase information of the motor rotor is not required at the time of starting the compressor 11, and specifically, the following positioning control is performed: a direct current called a detent current is caused to flow through the motor winding to generate a fixed magnetic field, whereby the phase of the rotor is fixed, and thereafter the following synchronous control is performed: the phase of the motor current is gradually advanced, i.e., the motor is rotated by changing the dc current to ac current.

On the other hand, the direct current (direct current component) such as the positioning current may cause a large thermal stress to be applied to the inverter circuit, and may cause fatigue or deterioration of elements constituting the inverter circuit, and may cause malfunction or a reduction in lifetime of the inverter circuit and the device including the inverter circuit. Therefore, the initial dc current at the time of starting the motor is preferably as small as possible and short. On the other hand, if the detent current is reduced, the generated torque becomes small, and therefore, the step-out is caused in the case where the generated torque is lower than the load torque, and the start-up of the compressor 11 fails.

Therefore, conventionally, from the viewpoint of preventing the motor from being out of step and preventing the start failure of the compressor 11, a design is adopted in which importance is attached to the stability at the time of start, and in order to set a motor current sufficiently larger than the envisaged load torque, a fixed value is used which can ensure that a sufficient torque is generated according to the hardware specifications of the inverter circuit. However, since the fixed value is a value having a margin, there is room for further reducing the positioning current.

Therefore, in the present embodiment, the motor drive control device 100 includes the inverter circuit 122 connected to the motor 102 used in the compressor 11 in the refrigeration cycle of the air conditioner 1 shown in fig. 1, and the motor drive control device 100 is configured such that the inverter controller 128 controls the inverter circuit so that a positioning current for fixing or adjusting the position of the motor rotor flows through the motor when the motor 102 is started, and at this time, the magnitude of the positioning current is adjusted according to the state of the refrigeration cycle. This stabilizes the start-up of the motor used in the refrigeration cycle, reduces thermal stress applied to the inverter circuit at the start-up, suppresses fatigue and deterioration of the elements of the inverter circuit, prevents malfunction of the device, and realizes a long life.

The inverter controller 128 receives information about the measured values of the various sensors 19a, 19b, 19h, 25 and the operating state of the air conditioner. The state of the refrigeration cycle detected for adjusting the positioning current may be detected based on at least one unit selected from the group consisting of the discharge pressure sensor 19b for detecting the discharge pressure of the compressor 11, the suction pressure sensor 19a for detecting the suction pressure of the compressor 11, the intermediate temperature sensors 19h and 25 for detecting the intermediate temperatures of the heat exchangers 13 and 22, and means for measuring the elapsed time after stopping the compressor and until starting the compressor 11, as shown in fig. 1.

More specifically, for example, the state of the refrigeration cycle may be detected based on the differential pressure between the discharge pressure and the suction pressure of the compressor 11 immediately before the start, and in this case, the positioning current may be adjusted to be large when the differential pressure is large. In this case, the positioning current can be adjusted to be large when the intermediate temperature of the outdoor heat exchanger is high during the cooling operation, and the positioning current can be adjusted to be large when the intermediate temperature is low during the heating operation. In addition, in 1 or more embodiments, the stop elapsed time from the temporary stop of the compressor 11 to the start may be measured, and the state of the refrigeration cycle may be detected based on the measured stop elapsed time, in which case the positioning current may be adjusted to be large when the elapsed time is short.

Hereinafter, how to detect the state of the refrigeration cycle and how to adjust the positioning current based on the detected state of the refrigeration cycle will be described in more detail with reference to fig. 3 and 4.

Fig. 3 is a flowchart illustrating a process for determining the magnitude of a current value at the time of starting the compressor 11, which is executed by the inverter controller 128 in the motor drive control device 100 according to the embodiment of the present invention.

The process shown in fig. 3 starts in step S100, and in step S101, the inverter controller 128 obtains a pressure difference (differential pressure) between the discharge pressure and the suction pressure of the compressor 11 before (immediately before) starting, an intermediate temperature of the outdoor heat exchanger, and a stop duration of the compressor 11. The measured values of the discharge pressure sensor 19b and the suction pressure sensor 19a are read at a point in time immediately before the start, and the differential pressure (differential pressure) is obtained by calculating the difference. The intermediate temperature is obtained by reading the measurement value of the intermediate temperature sensor 19h (intermediate temperature sensor 25 when the indoor heat exchanger is used) at the point immediately before the start-up. The difference and the intermediate temperature may be 1 time point before the start-up, or may be an average value of a plurality of time points before the start-up. At the time of stopping the compressor 11, the time is stored, and the time is acquired at the time point before the start, and the stop duration of the compressor 11 can be obtained from the difference from the stored stop time.

In step S102, the inverter controller 128 compares the calculated pressure difference between the discharge pressure and the suction pressure with a threshold value (hereinafter, referred to as a threshold value 1 with respect to the differential pressure), and determines whether or not the calculated pressure difference exceeds the threshold value 1. When it is determined in step S102 that the determined pressure difference exceeds the threshold value 1 (yes), the routine proceeds to step S103. In step S103, 1 stage is lifted, and the process advances to step S104. This is because, when the differential pressure is large, the load torque applied to the compressor 11 is large, and therefore, the motor current needs to be further increased. On the other hand, when it is determined in step S102 that the determined pressure difference does not exceed the threshold value 1 (no), the process proceeds directly to step S104.

In step S104, the inverter controller 128 compares the intermediate temperature thus obtained with a threshold value (hereinafter, referred to as a threshold value 2 with respect to the intermediate temperature), and determines whether or not the intermediate temperature thus obtained exceeds the threshold value 2. When it is determined in step S104 that the intermediate temperature obtained exceeds the threshold value 2 (yes), the routine proceeds to step S105. In step S105, 1 stage is lifted, and the process advances to step S106. For example, in the cooling operation, when the intermediate temperature of the outdoor heat exchanger 13 is higher than the outside air temperature, the estimated discharge pressure is high, and therefore, the motor current needs to be increased. On the other hand, when it is determined in step S104 that the intermediate temperature thus obtained does not exceed the threshold value 2 (no), the process proceeds directly to step S106. In the heating operation, since the load torque increases when the intermediate temperature of the outdoor heat exchanger 13 is lower than the outside air temperature, the motor current needs to be further increased by 1 step when the intermediate temperature is lower than other thresholds. In addition, when the intermediate temperature of the indoor heat exchanger is used, the above is contrary to the case.

In step S106, the inverter controller 128 compares the obtained stop duration with a threshold (hereinafter, the threshold for the stop duration is referred to as a threshold 3), and determines whether or not the obtained stop duration is lower than the threshold 3. When it is determined in step S106 that the determined stop duration is less than the threshold 3 (yes), the routine proceeds to step S107. In step S107, 1 stage is lifted, and the process advances to step S108. This is because, when the stop elapsed time from the stop of the compressor 11 to the start is short, it is assumed that a pressure difference remains in the refrigeration cycle, and therefore, it is necessary to increase the motor current. On the other hand, when it is determined in step S106 that the determined stop duration is not less than the threshold 3 (no), the process proceeds directly to step S108.

In step S108, the inverter controller 128 determines the magnitude of the motor current (the positioning current and the arbitrary synchronization current) at the initial stage of the start-up based on the determination result up to this point. In the illustrated embodiment, the initial value of the stage is set to 0, and any one of the 4 stages 0 to 3 is determined by steps S102 to S107. In step S108, the magnitude of the current in the corresponding stage can be selected according to the magnitude of the predetermined positioning current and the arbitrary synchronization current prepared for each of the stages 0 to 3. In this way, the thresholds are set for the differential pressure between the discharge pressure and the suction pressure, the intermediate temperature of the heat exchanger, and the stop elapsed time from the stop of the compressor to the start of the compressor, and the magnitude of the motor current at the start is adjusted stepwise according to the magnitude relation with the thresholds.

In the embodiment described above, the determination results are described by setting 1 determination condition for each of 3 determination items, and setting the respective determination conditions to the same score, and adding up the determination results of 4 stages. However, the number of stages may be less than 4 or 5 or more, or the stages may be obtained by weighted addition. In addition, a table may be prepared in which 8 cases are held for each authenticity of the determination result. Further, a plurality of threshold determinations may be provided for each item of the differential pressure, the intermediate temperature of the heat exchanger, and the stop duration, or any item may be excluded from the conditions, or other determination items may be added. Instead of using the threshold value determination, the magnitude of the motor current may be determined using a function of the pressure difference, the intermediate temperature, and the stop duration.

Next, in step S109, the present process ends. Then, positioning control and synchronization control are performed based on the determined magnitude of the motor current.

Fig. 4 (a) and (B) schematically show time variations of current values when positioning control and synchronization control are performed based on the determination of the motor drive control device 100 according to the present embodiment. The control states (different between the positioning control and the synchronization control) of the inverter are indicated by double arrows. In the above description, the determination results are described as 4-stage determination results, but fig. 4 (a) schematically shows a case where the motor current in the positioning control and the synchronous control is maximized (a case where the determination conditions of the 3 items are all satisfied), and fig. 4 (B) schematically shows a case where the motor current in the positioning control and the synchronous start control is minimized (a case where the determination conditions of the 3 items are all not satisfied). Fig. 4 shows a time change in the current value of 3 phases, and signals of 3 phases are identified by solid lines, broken lines, and one-dot chain lines.

The time change of the 3-phase current during the positioning control and the synchronization control is represented by the following equation

(1)

Iu＝A(t)×sin(ωt)

Iv＝A(t)×sin(ωt+120°)

Iw＝A(t)×sin(ωt+240°)

ω is the angular frequency and is a function of the gradual increase to a predetermined frequency during the synchronization control. A (t) is a function indicating the current amplitude, and is a function that monotonically increases (e.g., linearly increases) from 0 at time 0 in a range equal to or less than the maximum current that can flow through each phase and in a range equal to or less than the upper limit value corresponding to the determination result during normal operation. The increase rate (slope in the case of linear increase) of a (t) may be set to a value corresponding to the determination result. A (t) is a function of time, and the upper limit value and the increase rate can be determined uniquely by determining the upper limit value and the increase rate based on the determination result in step S108 shown in fig. 3. Since ωt is fixed during the positioning control, the current is dc during the positioning control, and the current is ac at the frequency ω of the amplitude a (t) (a function of the time added during the synchronization control) during the synchronization control. In the example shown in fig. 4, ωt in the positioning control period is fixed to 90 ° for convenience of explanation. The 3-phase current maintains a state in which the phases are shifted from each other by 120 °.

Fig. 4 (a) shows a case where the current becomes maximum, and a (t) shown by a thick dotted line linearly increases to an upper limit value (maximum value) throughout the entire period of the positioning control, and thereafter becomes constant in the synchronization control. On the other hand, fig. 4 (B) shows a case where the current becomes the minimum, and a (t) shown by the thick dotted line linearly increases during the positioning control and the synchronization control. In the example shown in fig. 4 (B), a (t) is limited to a range lower than the upper limit value in the case of fig. 4 (a). However, the present invention is not limited to this, and the increase rate (slope in the case of linear increase) may be changed without changing the upper limit value.

In fig. 4 (a), the peak value of the motor current in the synchronous control is constant, but in fig. 4 (B), the peak value of the motor current in the synchronous control is gradually increased. Since the motor current during the positioning control and the synchronous control is adjusted to reduce the thermal stress applied by the direct current (component), if the frequency is high during the synchronous control, the necessity of reducing the peak value of the motor current is reduced, and on the contrary, the motor current is increased, whereby the stability of the start-up can be ensured.

The time change of the current value shown in fig. 4 is an example, and there is also an intermediate stage in fig. 4 (a) and 4 (B), and the rate of increase of a (t) can be appropriately set according to each stage. The shape of the function of a (t) is described as linear, but the present invention is not limited to this, and any monotonically increasing function may be used.

Fig. 5 (a) and (B) are graphs depicting time changes in current values and load torques at the time of positioning control and synchronization control of the motor drive control device of the present embodiment. The control state of the inverter is indicated by double arrows. In addition, in fig. 5, a temporal change in the 1-phase current is representatively illustrated.

As shown in fig. 4 and 5, the inverter control state starts by the positioning control, and is followed by the synchronization (start-up) control, and as shown in fig. 5, the inverter control state shifts to the sensorless control (normal control). In the positioning control, a positioning current (direct current) is caused to flow through the motor. I.e. the polarity of the positioning current does not change. In the synchronous control, an alternating current called a synchronous current flows. The frequency of the alternating current gradually increases, and the rotational speed of the compressor increases. If the rotational speed of the compressor 11 reaches a predetermined value, the control is shifted to sensorless control.

In the sensorless control, the phase of the motor rotor is estimated from the motor current detection value, and the load torque is estimated from the motor current detection value and the phase of the rotor. If the load torque can be estimated, the motor current can be adjusted to a minimum required value corresponding to the load torque. On the other hand, in the positioning control and the synchronous start control at the initial stage of start-up, the open loop control is performed in such a way that the phase information of the rotor is not used for the adjustment of the motor current. In the open loop control, a sufficiently large motor current needs to flow to the load torque, but in the embodiment described above, the magnitude of the current value is adjusted according to the determination result indicating the state of the refrigeration cycle. Therefore, it is possible to avoid such a phenomenon that the motor is out of step due to the small current flow of the motor, and to adjust the motor current to a required minimum value in the positioning control (and in the synchronous starting control). Therefore, a reduction in the lifetime of the inverter circuit can be prevented. In this way, by adjusting the motor current during the positioning control at the initial stage of start-up and during any synchronization control to a value as small as possible within a range where no step-out occurs based on the state of the refrigeration cycle at the time of start-up, it is possible to reduce the losses of the inverter circuit and the motor, and to achieve high efficiency.

As described above, fig. 5 traces back the process of shifting to the sensorless control after performing the positioning control and the synchronization control, but is not necessarily limited thereto. For example, it is possible to make an ac current having a small frequency (for example, about 1 or less) during positioning control, which is not clearly classified into positioning control (dc) and synchronization control (ac). At this time, the dc component in the region having the frequency ω close to 0 acts as a positioning current.

In the above embodiment, the configuration is assumed that the number of compressors 11 is only 1. However, in other embodiments, a plurality of compressors 11 may be provided. When a plurality of compressors 11 are arranged in 1 refrigeration cycle, it is assumed that the load torque differs from that in the case where the other compressors are being driven, as compared with the case where the compressors have been stopped. For example, when starting up the compressors from a state where all the compressors have been stopped, the difference in starting up is low and the load torque is small compared to when starting up the compressors in a state where 1 or more other compressors have been driven. Therefore, the former can lower the peak value of the motor current at the start of the positioning control and the synchronous control, and the latter can set the peak value of the motor current at the start of the positioning control and the synchronous start control higher. That is, when the motor provided in one of the compressors is started, the state of the refrigeration cycle can be detected based on whether or not the other compressors are being driven, and at this time, the positioning current can be adjusted to be large when any one of the other compressors is being driven. The determination condition may be used alone or in combination with a part or all of the differential pressure, the intermediate temperature, and the stop duration.

Hereinafter, a preferred embodiment will be described with reference to fig. 6 to 8. In the above embodiment, since the current of each phase is direct current in the positioning control, the phase of the motor current in the positioning control does not change. In contrast, in the preferred embodiment described below, by further adjusting the phase of the positioning current in the positioning control, the stability of the start-up can be further improved even when the positioning current is reduced.

As described above, the phase of the motor current in the positioning control does not change. However, the phase (mechanical angle) of the motor rotor varies according to the initial phase of the rotor. Fig. 6 is a graph depicting time changes in current values and phase changes of the rotor when positioning control and synchronization control are performed at the time of starting from various initial phases.

In fig. 6, the initial phases (a) to (C) of the 3 kinds of rotors are shown, but the phases of the motor currents in the positioning control are all 0rad (0 °). In fig. 6 (a), the initial phase of the rotor is-0.87 rad (-50 °) and is delayed. Therefore, in the positioning control, the phase of the rotor varies from-0.87 rad (-50 °) to 0rad (0 °). In fig. 6 (B), the initial phase of the rotor is 0rad (0 °), which coincides with the phase of the current. Therefore, in the positioning control, the phase of the rotor does not change. In fig. 6 (C), the initial phase of the rotor is advanced by 1.04rad (+60°). Therefore, in the positioning control, the phase of the rotor is changed from 1.04rad (+60°) to 0rad (0 °).

As described above, when the phase of the rotor is delayed from the phase of the motor current at the initial stage of the rotor phase, the phase of the rotor advances in the positive direction during the positioning control, whereas when the initial phase of the rotor advances, the phase of the rotor advances in the negative direction during the positioning control. Fig. 6 shows the operation of a 3-pole permanent magnet synchronous motor, and in the case of 3 poles, attention is paid to the phase change amount of the rotor with respect to the phase change amount of the motor current being 1/3.

Here, when the change in the phase of the rotor and the compression of the refrigerant are examined, a load torque due to the compression of the refrigerant is generated when the phase of the rotor is advanced in the positive direction, whereas when the phase of the rotor is advanced in the negative direction, a load torque due to the compression of the refrigerant is not generated. Therefore, the load torque when advancing the phase of the rotor in the negative direction is small compared to advancing the phase of the rotor in the positive direction, which means that the margin for reducing the positioning current is further increased.

Therefore, in the preferred embodiment, the inverter controller 128 performs control of advancing the phase of the rotor in the negative direction in the positioning control regardless of the initial phase of the rotor.

The time change of the 3-phase current during the positioning control associated with the phase adjustment is represented by the following equation, for example.

(2)

Iu＝A(t)×sin(ωt+θ(t))

Iv＝A(t)×sin(ωt+120°+θ(t))

Iw＝A(t)×sin(ωt+240°+θ(t))

As described above, ω is an angular frequency, and is a function gradually increasing to a predetermined frequency during the synchronization control. A (t) is a function indicating the current amplitude, and is a function that monotonically increases (e.g., linearly increases) from 0 at time 0 in a range equal to or less than the maximum current that can flow through each phase during normal operation and in a range equal to or less than the upper limit value corresponding to the determination result. The increase rate (slope in linear increase) of a (t) may be set to a value corresponding to the determination result. Like the above-described embodiment, ωt is fixed during the positioning control, but the phase θ (t) is added, and the phase of the 3-phase current is maintained in a state shifted by 120 ° from each other, but the amount of phase change θ (t) during the positioning control is shown. More specifically, θ (t) is a function that varies to-2pi rad (reverse rotation 360 °) throughout the entire period of positioning control.

Fig. 7 schematically shows time variations of current values during positioning control and synchronization control accompanied by phase adjustment in the preferred embodiment. Fig. 7 also shows a time change of the 3-phase current value as in fig. 4, and the 3-phase signal is identified by a solid line, a broken line, and a one-dot chain line. Fig. 8 is a graph depicting time changes in current values and changes in phases of the rotor during positioning control and synchronization control accompanied by phase adjustment in a preferred embodiment when starting from various initial phases. In fig. 8, the time variation of the current of phase 1 is representatively shown. Fig. 8 also shows the operation of a 3-pole permanent magnet synchronous motor, and in the case of 3 poles, it is noted that the amount of change in the phase of the rotor relative to the amount of change in the phase of the motor current is 1/3.

As shown in fig. 7 and 8, in the positioning control, the phase of the motor current is changed by 2pi rad (360 °) at an electrical angle in the negative direction. In fig. 8 (a), the phase of the rotor is changed from-0.87 rad (-50 °) to-2.09 rad (-120 °) in the positioning control. In fig. 8 (C), the phase of the rotor is changed from 1.04rad (60 °) to 0rad in the positioning control. By advancing the positioning current with the fixed phase in the negative direction in this way, the phase of the rotor can be reliably advanced in the negative direction regardless of the initial phase of the rotor. Therefore, the load torque is reduced because the load torque is not generated by the compression of the refrigerant, and the positioning current can be further reduced accordingly.

As described above, according to the present disclosure, it is possible to provide a drive control device and a drive control method for a motor, which can stabilize the start of the motor used in a refrigeration cycle, reduce thermal stress applied to the inverter circuit at the time of start, suppress fatigue and deterioration of elements of the inverter circuit, and prevent malfunction of the device including the inverter circuit, and realize a long lifetime.

In the motor drive control device, the motor drive control method, and the inverter circuit in the refrigerating and air-conditioning apparatus according to the present embodiment, the current flowing at the time of starting the motor becomes the minimum current corresponding to the state of the refrigerating cycle, and the thermal stress is reduced as much as possible. Particularly, in a device such as a compressor of a refrigeration air conditioner, by appropriately reducing the loss of an inverter circuit for driving a motor, the failure of the device such as the refrigeration air conditioner can be prevented and the lifetime can be prolonged.

In the prior art of patent document 1, regarding an initial excitation mode in which each phase is caused to flow a dc current before the synchronous operation mode, only a point is disclosed in which the dc current of each phase is gradually increased from zero in a range of not more than a maximum current peak value that each phase can flow during normal operation, and the peak value in the synchronous control is also controlled to be constant. In contrast, in the control of the present disclosure, the magnitude of the current value during the positioning control and the arbitrary synchronization control is adjusted according to the differential pressure between the discharge pressure and the suction pressure, the intermediate temperature of the heat exchanger, the stop duration, and the operation state of the other compressors, whereby the start current more suitable for the load of the compressor can be determined.

The embodiments of the present invention are not limited to the above embodiments, and various modifications can be included. For example, the above-described embodiments are described in detail for easy understanding of the description, and are not limited to the embodiments having all the described structures. In addition, a part of the structure of one embodiment may be replaced with the structure of another embodiment, and the structure of another embodiment may be added to the structure of one embodiment. In addition, some of the structures of the embodiments may be added, deleted, or replaced with other structures.

A part or all of the above-described structures, functions, processing units, and the like may be realized by hardware, for example, by designing an integrated circuit. Some or all of the above-described structures, functions, and the like can be realized by a computer-executable program for realizing the respective functions by a processor described in a conventional programming language such as an assembly program, C, C ++, c#, java (registered trademark), or the like, or an object-oriented programming language, and information such as a program, a table, a file, and the like realizing the respective functions can be stored in a HDD (Hard Disk Drive), an SSD (Solid State Drive: solid state Drive) ROM, EEPROM, EPROM, a storage device such as a flash memory, a computer-readable recording medium such as a floppy Disk, a CD-ROM, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW, a blu-ray disc, an SD (registered trademark) card, an MO, or the like, or distributed via an electric communication line.

Some or all of the above-described structures, functions, and the like can be mounted on a Programmable Device (PD) such as a Field Programmable Gate Array (FPGA), and the like, and can be distributed via a recording medium as circuit configuration data (bit stream data) downloaded to the PD for realizing the above-described functions on the PD, HDL (Hardware Description Language: hardware description language) for generating circuit configuration data, VHDL (Very High Speed Integrated Circuits Hardware Description Language: ultra-high speed integrated circuit hardware description language), verilog-HDL, and the like. The control lines and the information lines are considered to be required for explanation, and not necessarily all the control lines and the information lines are shown in the product. In practice, almost all structures can be considered to be connected to each other. The various data formats illustrated in the above description can be configured by, for example, comma-Separated Values, XML (eXtensible Markup Language: extensible markup language), binary (binary), or the like, but are not limited thereto.

Description of the reference numerals

1 …, Q … refrigerant circuit, 10 … outdoor unit, 11 … compressor, 12 … accumulator, 13 … outdoor heat exchanger, 14 … outdoor fan, 15 … four-way valve, 18a … gas block valve, 18b … liquid block valve, 19a … suction pressure sensor, 19b … discharge pressure sensor, 19c … discharge temperature sensor, 19d … temperature sensor, 19g … outside air temperature sensor, 19h … outdoor heat exchanger intermediate temperature sensor, 20 … indoor unit, 21 … indoor expansion valve, 22 … indoor heat exchanger, 23 … indoor fan, 24 … indoor solenoid valve, 25 … indoor heat exchanger intermediate temperature sensor, 30 … control device, 100 … motor drive control device 100, 101 … ac power supply, 102 … motor, 110 … converter section, 111 … rectifier circuit, 112 … diode, 113 … smoothing reactor, 114 … smoothing capacitor, 120 … inverter section, 121 … dc voltage detection section, 122 … inverter circuit, 123 … semiconductor switching element, 124 … diode, 125, 126 … current sensor, 127 … gate drive circuit, 128 … inverter controller.

Claims (10)

1. A drive control device for controlling an electric motor used in a refrigeration cycle, characterized in that,

the drive control device includes:

an inverter circuit connected to the motor; and

and a control unit that controls the inverter circuit so that a positioning current for fixing or adjusting a rotor position of the motor flows through the motor when the motor is started, and adjusts the magnitude of the positioning current according to a state of the refrigeration cycle.

2. The drive control apparatus according to claim 1, wherein,

the control unit changes the positioning current to an alternating current after the positioning current is caused to flow for a predetermined period, and controls the inverter circuit so that a synchronous current flows in the motor, and further adjusts the magnitude of the synchronous current according to the state of the refrigeration cycle.

3. The drive control apparatus according to claim 1 or 2, wherein,

the motor is provided in a compressor, detects a state of the refrigeration cycle based on a pressure difference between a discharge pressure and a suction pressure of the compressor, and adjusts the positioning current to be large when the pressure difference is large.

4. The drive control apparatus according to any one of claims 1 to 3, characterized in that,

The motor is provided in a compressor connected to a heat exchanger, detects a state of the refrigeration cycle based on a temperature of the heat exchanger and a stop elapsed time from when the compressor is stopped to when the compressor is started, and adjusts the positioning current to a value corresponding to the temperature or the stop elapsed time or both of them.

5. The drive control apparatus according to any one of claims 1 to 4, characterized in that,

the motor is provided in the compressor, and includes a plurality of compressors, and detects the state of the refrigeration cycle based on whether any other compressor is being driven when the motor provided in 1 compressor is started, and adjusts the positioning current to be large when the other compressors are being driven.

6. The drive control apparatus according to any one of claims 1 to 5, characterized in that,

the control unit starts a forward rotation by advancing a rotor phase of the motor in a reverse direction by at least one turn by an electric angle during a period in which the positioning current is caused to flow when the motor is started.

7. The drive control apparatus according to any one of claims 1 to 6, characterized in that,

The motor is a permanent magnet synchronous motor.

8. A refrigerating air conditioner is characterized by comprising:

a heat exchanger;

a compressor provided with a motor;

an inverter circuit connected to the motor; and

a control unit that controls the inverter circuit,

the control unit controls the inverter circuit so that a positioning current for fixing or adjusting a rotor position of the motor flows through the motor when the motor is started, and adjusts a magnitude of the positioning current according to a state of the refrigeration cycle.

9. The refrigerating air conditioner according to claim 8, wherein,

the refrigerating air conditioner further includes at least one unit selected from the group consisting of detecting a state of the refrigerating cycle based on the at least one unit,

wherein the combination is composed of the following units: a discharge pressure sensor for detecting a discharge pressure of the compressor, a suction pressure sensor for detecting a suction pressure of the compressor, a temperature sensor for detecting a temperature of the heat exchanger, a unit for measuring a stop elapsed time from stopping the compressor until starting, and a unit for detecting a driving state of other compressors.

10. A drive control method for controlling an electric motor used in a refrigeration cycle, characterized in that,

the driving control method comprises the following steps:

determining a magnitude of a positioning current flowing for fixing or adjusting a rotor position of the motor according to a state of the refrigeration cycle; and

when the motor is started, an inverter circuit connected to the motor is controlled so that the positioning current flows through the motor according to the determined magnitude.

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