JPWO2020246038A1 - Motor drive, blower, compressor and air conditioner - Google Patents

Abstract

The motor drive device (100) has a converter circuit (3) that converts the AC voltage output from the AC power supply (1) into a DC voltage and outputs the DC voltage to the DC bus (16a, 16b), and the DC voltage is output to the motor (500). An inverter circuit (18) that converts the AC voltage applied to the AC voltage and outputs it, a temperature sensor (22) that detects the temperature of the converter circuit (3), and a temperature sensor (24) that detects the temperature of the inverter circuit (18). , Equipped with. The converter circuit (3) outputs a DC voltage to the DC bus (16a, 16b) based on the temperature difference between the first temperature detected by the temperature sensor (22) and the second temperature detected by the temperature sensor (24). Change the voltage value of.

Description

The present invention relates to a motor drive device for driving a motor, a blower and a compressor equipped with the motor drive device, and an air conditioner equipped with the blower or the compressor.

The motor drive device includes a converter circuit that converts an AC voltage output from an AC power supply into a DC voltage, and an inverter circuit that converts the DC voltage into an AC voltage. In the motor drive device, for example, when the load of the motor fluctuates due to disturbance, the temperature rise of the inverter circuit or the converter circuit may become a problem. Therefore, the motor drive device is required to have a function of detecting a temperature rise of the inverter circuit and the converter circuit and protecting the switching element provided in the converter circuit and the inverter circuit from the temperature rise.

In Patent Document 1 below, in a power conversion device provided with a converter circuit and an inverter circuit, when the temperature of the circuit element reaches a threshold value, the input current value for the inverter circuit is updated to a low value, and the updated current is obtained. A technique for continuing the operation of the device by value is disclosed.

Japanese Unexamined Patent Publication No. 2011-139579

It is conceivable to apply the technique of Patent Document 1 to prevent damage to the switching element due to an excessive temperature rise due to disturbance or the like. However, in the technique of Patent Document 1, it is necessary to reduce the input current value for the inverter circuit, and there is a problem that the driving force of the motor is lowered and the performance of the motor driving device is lowered.

The present invention has been made in view of the above, and an object of the present invention is to obtain a motor drive device capable of protecting switching elements in a converter circuit and an inverter circuit while suppressing deterioration of the performance of the motor drive device. do.

In order to solve the above-mentioned problems and achieve the object, the present invention is a motor drive device for driving a motor. The motor drive device includes a converter circuit that converts the AC voltage output from the AC power supply into a DC voltage and outputs it to the DC bus, and an inverter circuit that converts the DC voltage into an AC voltage applied to the motor and outputs it. .. Further, the motor drive device includes a first temperature detector that detects the temperature of the converter circuit and a second temperature detector that detects the temperature of the inverter circuit. The converter circuit changes the voltage value of the DC voltage output to the DC bus based on the temperature difference between the first temperature detected by the first temperature detector and the second temperature detected by the second temperature detector. ..

According to the motor drive device according to the present invention, it is possible to protect the switching element in the converter circuit and the inverter circuit while suppressing the deterioration of the performance of the motor drive device.

A circuit diagram showing a configuration of a motor drive device according to a first embodiment. The figure provided for the description of the operation mode of the DC power supply device in Embodiment 1. The figure which shows one of the current paths in the passive synchronous rectification mode in the converter circuit of Embodiment 1. The figure which shows typically the current-loss characteristic in a general switching element. The figure which shows one of the current paths in the simple switching mode in the converter circuit of Embodiment 1. The figure which shows an example of the control block configured in the converter control part in Embodiment 1. The figure which shows an example of the control block configured in the DC voltage command value correction part shown in FIG. A flowchart showing the operation of the DC voltage command value correction unit shown in FIG. The first figure which shows the operation waveform when the control based on the method of Embodiment 1 was activated. FIG. 2 is a second diagram showing an operation waveform when the control based on the method of the first embodiment is activated. A block diagram showing an example of a hardware configuration that embodies the function of the control unit according to the first embodiment. A block diagram showing another example of a hardware configuration that embodies the function of the control unit according to the first embodiment. The figure which shows the structure of the air conditioner which concerns on Embodiment 2.

The motor drive device, the blower, the compressor, and the air conditioner according to the embodiment of the present invention will be described below with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below. Further, in the following, the electrical connection will be described simply as "connection".

Embodiment 1.
FIG. 1 is a circuit diagram showing a configuration of a motor drive device 100 according to a first embodiment. The motor drive device 100 according to the first embodiment converts the AC power supplied from the single-phase AC power supply 1 into DC power, converts the converted DC power into AC power again, and converts the converted AC power into the motor 500. It is a drive device that drives the motor 500 by supplying the electric power to the electric power.

As shown in FIG. 1, the motor drive device 100 according to the first embodiment includes a DC power supply device 50, a control unit 8, and an inverter 12. The DC power supply device 50 is a power supply device that converts AC power supplied from the single-phase AC power supply 1 into DC power. A breaker 10 which is a circuit breaker for wiring for protecting the motor driving device 100 is provided between the AC power supply 1 and the motor driving device 100. The DC power supply device 50 includes a reactor 2, a converter circuit 3, a gate drive circuit 15 which is a first drive circuit, a capacitor 4, a voltage detector 5 which is a first voltage detector, and a first current. It includes a current detector 6 which is a detector, a voltage detector 7 which is a second voltage detector, and a temperature sensor 22 which is a first temperature detector. One end of the reactor 2 is connected to the AC power supply 1 via the breaker 10, and the other end of the reactor 2 is connected to the converter circuit 3. The converter circuit 3 converts the AC voltage output from the AC power supply 1 into a DC voltage and outputs the AC voltage to the DC buses 16a and 16b. The voltage output by the converter circuit 3 to the DC bus 16a and 16b may be referred to as "bus voltage".

Further, the inverter 12 includes a gate drive circuit 17 which is a second drive circuit, an inverter circuit 18, a current detector 9 which is a second current detector, and a temperature sensor 24 which is a second temperature detector. , Equipped with. The inverter circuit 18 converts the DC voltage output from the DC power supply device 50 into an AC voltage applied to the motor 500 and outputs the AC voltage. Examples of equipment on which the motor 500 is mounted are blowers, compressors or air conditioners.

The temperature sensor 22 detects the temperature of the converter circuit 3. The temperature of the converter circuit 3 detected by the temperature sensor 22 is referred to as a "first temperature" and is referred to as "T1". The information of the first temperature T1 detected by the temperature sensor 22 is input to the control unit 8.

The temperature sensor 24 detects the temperature of the inverter circuit 18. The temperature of the inverter circuit 18 detected by the temperature sensor 24 is referred to as a "second temperature" and is referred to as "T2". The information of the second temperature T2 detected by the temperature sensor 24 is input to the control unit 8.

The temperature sensors 22 and 24 may be arranged in any place as long as the temperature of the switching element provided in the converter circuit 3 and the inverter circuit 18 can be estimated. The types of the temperature sensors 22 and 24 include a contact type and a non-contact type, and any type may be used.

The converter circuit 3 includes a first leg 31 and a second leg 32. The first leg 31 and the second leg 32 are connected in parallel. In the first leg 31, the first upper arm element 311 and the first lower arm element 312 are connected in series. In the second leg 32, the second upper arm element 321 and the second lower arm element 322 are connected in series. The other end of the reactor 2 is connected to a connection point 3a between the first upper arm element 311 and the first lower arm element 312 in the first leg 31. The connection point 3b between the second upper arm element 321 and the second lower arm element 322 is connected to the other end of the AC power supply 1. In the converter circuit 3, the connection points 3a and 3b form an AC terminal.

In FIG. 1, the reactor 2 is connected between one end of the AC power supply 1 and the connection point 3a, but is connected between another end of the AC power supply 1 and the connection point 3b. May be good.

In the converter circuit 3, the side where the connection points 3a and 3b are located is called the "AC side". Further, the AC voltage output from the AC power supply 1 is called a "power supply voltage", and the cycle of the power supply voltage is called a "power supply cycle".

The first upper arm element 311 includes a switching element Q1 and a diode D1 connected in antiparallel to the switching element Q1. The first lower arm element 312 includes a switching element Q2 and a diode D2 connected in antiparallel to the switching element Q2. The second upper arm element 321 includes a switching element Q3 and a diode D3 connected in antiparallel to the switching element Q3. The second lower arm element 322 includes a switching element Q4 and a diode D4 connected in antiparallel to the switching element Q4. Each of the switching elements Q1 to Q4 may be referred to as a "first switching element".

In FIG. 1, a metal oxide semiconductor field effect transistor (MOSFET) is illustrated for each of the switching elements Q1, Q2, Q3, and Q4, but the switching element is not limited to MOSFET. A MOSFET is a switching element capable of passing a current in both directions between a drain and a source. Any switching element may be used as long as it is a switching element capable of bidirectionally flowing a current between the first terminal corresponding to the drain and the second terminal corresponding to the source, that is, a bidirectional element.

Further, antiparallel means that the first terminal corresponding to the drain of the MOSFET and the cathode of the diode are connected, and the second terminal corresponding to the source of the MOSFET and the anode of the diode are connected. As the diode, a parasitic diode that the MOSFET itself has inside may be used. Parasitic diodes are also called body diodes.

Further, the switching elements Q1, Q2, Q3 and Q4 are not limited to MOSFETs formed of silicon-based materials, and may be MOSFETs formed of wide bandgap semiconductors such as silicon carbide, gallium nitride, gallium oxide or diamond.

In general, wide bandgap semiconductors have higher withstand voltage and heat resistance than silicon semiconductors. Therefore, by using a wide bandgap semiconductor for at least one of the switching elements Q1, Q2, Q3, and Q4, the withstand voltage resistance and the allowable current density of the switching element are increased, and the semiconductor module incorporating the switching element can be miniaturized. Can be converted.

One end of the capacitor 4 is connected to the DC bus 16a on the high potential side. The DC bus 16a is drawn from the connection point 3c between the first upper arm element 311 in the first leg 31 and the second upper arm element 321 in the second leg 32. The other end of the capacitor 4 is connected to the DC bus 16b on the low potential side. The DC bus 16b is drawn from the connection point 3d between the first lower arm element 312 in the first leg 31 and the second lower arm element 322 in the second leg 32. In the converter circuit 3, the connection points 3c and 3d form a DC terminal. Further, in the converter circuit 3, the side where the connection points 3c and 3d are located may be referred to as the "DC side".

The output voltage of the converter circuit 3 is applied to both ends of the capacitor 4. The capacitor 4 is connected to the DC bus lines 16a and 16b. The capacitor 4 smoothes the output voltage of the converter circuit 3. The voltage smoothed by the capacitor 4 is applied to the inverter circuit 18.

The voltage detector 5 detects the power supply voltage and outputs the detected value Vs of the power supply voltage to the control unit 8. The power supply voltage is an absolute value of the instantaneous voltage of the AC power supply 1. The effective value of the instantaneous voltage may be used as the power supply voltage. The current detector 6 detects the alternating current flowing between the alternating current power supply 1 and the converter circuit 3, and outputs the detected value Is of the alternating current to the control unit 8. An example of the current detector 6 is a current transformer (CT). The voltage detector 7 detects the bus voltage and outputs the detected value Vdc of the bus voltage to the control unit 8.

The inverter circuit 18 includes a leg 18A in which the upper arm element 18UP and the lower arm element 18UN are connected in series, a leg 18B in which the upper arm element 18VP and the lower arm element 18VN are connected in series, and an upper arm element 18WP. It includes a leg 18C in which a lower arm element 18WN is connected in series. The legs 18A, 18B and 18C are connected in parallel to each other. The upper arm elements 18UP, VP, WP and the lower arm elements 18UN, VN, WN may be referred to as "second switching elements".

FIG. 1 illustrates a case where the upper arm elements 18UP, 18VP, 18WP and the lower arm elements 18UN, 18VN, 18WN are insulated gate bipolar transistors (Insulated Gate Bipolar Transistors: IGBTs), but the present invention is not limited thereto. MOSFETs may be used instead of the IGBTs.

The upper arm element 18UP includes a transistor 18a and a diode 18b connected in antiparallel to the transistor 18a. The same configuration is used for the other upper arm elements 18VP and 18WP and the lower arm elements 18UN, 18VN and 18WN. In antiparallel, as in the case of the converter circuit 3, the anode side of the diode is connected to the first terminal corresponding to the emitter of the IGBT, and the cathode side of the diode is connected to the second terminal corresponding to the collector of the IGBT. means.

Note that FIG. 1 has a configuration including three legs in which the upper arm element and the lower arm element are connected in series, but the configuration is not limited to this configuration. The number of legs may be four or more. The circuit configuration shown in FIG. 1 is adapted to the motor 500, which is a three-phase motor. When the motor 500 is a single-phase motor, the inverter circuit 18 is also configured to correspond to the single-phase motor. Specifically, the configuration includes two legs in which the upper arm element and the lower arm element are connected in series. When the motor 500 is either a single-phase motor or a three-phase motor, one leg may be composed of a plurality of pairs of upper and lower arm elements.

When the transistor 18a of the upper arm elements 18UP, 18VP, 18WP and the lower arm elements 18UN, 18VN, 18WN is a MOSFET, the upper arm elements 18UP, 18VP, 18WP and the lower arm elements 18UN, 18VN, 18WN are silicon carbide, gallium nitride. It may be formed of a system material or a wide bandgap semiconductor such as diamond. If a MOSFET formed of a wide bandgap semiconductor is used, the effects of withstand voltage and heat resistance can be enjoyed.

The connection point 26a between the upper arm element 18UP and the lower arm element 18UN is connected to the first phase (for example, U phase) of the motor 500, and the connection point 26b between the upper arm element 18VP and the lower arm element 18VN is the first phase of the motor 500. It is connected to two phases (for example, V phase), and the connection point 26c between the upper arm element 18WP and the lower arm element 18WN is connected to the third phase (for example, W phase) of the motor 500. In the inverter circuit 18, the connection points 26a, 26b, and 26c form an AC terminal.

The current detector 9 is arranged on the DC bus 16b on the inverter 12 side. The current detector 9 detects the direct current flowing through the direct current bus 16b on the inverter 12 side, and outputs the detected value Idc of the direct current to the control unit 8. An example of the current detector 9 is a shunt resistor. Further, although the current detector 9 is arranged on the DC bus 16b in FIG. 1, it may be arranged on the DC bus 16a on the inverter 12 side.

The control unit 8 includes a converter control unit 11 and an inverter control unit 14. The converter control unit 11 in the converter circuit 3 is based on the DC voltage command value Vdc *, the detection value Vs of the voltage detector 5, the detection value Is of the current detector 6, and the detection value Vdc of the voltage detector 7. Control signals S311 to S322 for controlling each switching element are generated. The DC voltage command value Vdc * is a command value of the DC voltage output to the DC bus 16a and 16b by the converter circuit 3. The control signal S311 is a control signal for controlling the switching element Q1, and the control signal S322 is a control signal for controlling the switching element Q4. The switching elements Q2 and Q3 are also controlled by the control signal from the control unit 8. The control signals S311 to S322 generated by the control unit 8 are input to the gate drive circuit 15.

Further, the inverter control unit 14 has a speed command value ω * which is a command value of the rotation speed of the motor 500, a detection value Vs of the voltage detector 5, a detection value Is of the current detector 6, and a detection value of the voltage detector 7. Based on Vdc, control signals S1 to S6 for controlling each switching element provided in the inverter circuit 18 are generated. The inverter circuit 18 has a three-phase circuit configuration, and has six switching elements corresponding to the three-phase circuit configuration. Further, six control signals S1 to S6 are generated corresponding to the six switching elements. The control signals S1 to S6 generated by the control unit 8 are input to the gate drive circuit 17.

The gate drive circuit 15 generates drive pulses G311 to G322 for driving each switching element in the converter circuit 3 based on the control signals S311 to S322. The drive pulse G311 is a drive pulse for driving the switching element Q1, and the drive pulse G322 is a drive pulse for driving the switching element Q4. The switching elements Q2 and Q3 are also driven by the drive pulse from the gate drive circuit 15.

The gate drive circuit 17 generates drive pulses G1 to G6 for driving each switching element in the inverter circuit 18 based on the control signals S1 to S6.

FIG. 2 is a diagram provided for explaining the operation mode of the DC power supply device 50 according to the first embodiment. FIG. 2 shows three operation modes: a passive synchronous rectification mode, a simple switching mode, and a pulse width modulation (PWM) control mode. FIG. 3 is a diagram showing one of the current paths in the passive synchronous rectification mode in the converter circuit 3 of the first embodiment. FIG. 4 is a diagram schematically showing a current-loss characteristic in a general switching element. FIG. 5 is a diagram showing one of the current paths in the simple switching mode in the converter circuit 3 of the first embodiment.

The upper part of FIG. 2 shows the power supply voltage and the power supply current in the passive synchronous rectification mode. This operation mode is a mode in which synchronous rectification is performed without boosting. Non-boosting means suppressing the output voltage of the converter circuit 3 to be equal to or lower than the peak value of the power supply voltage. On the contrary, boosting means that an output voltage exceeding the peak value of the power supply voltage is output from the converter circuit 3. Further, synchronous rectification is a control method in which a switching element connected in antiparallel to a diode is turned on at the timing when a current flows through the diode.

FIG. 3 shows a charging path for the capacitor 4 when the power supply voltage is positive and synchronous rectification is performed. As shown in FIG. 3, it is assumed that the polarity of the power supply voltage is positive when the upper terminal of the AC power supply 1 has a positive potential. Further, it is assumed that the polarity of the power supply voltage is negative when the upper terminal of the AC power supply 1 has a negative potential.

In FIG. 3, when the switching elements Q1 and Q4 are not turned on when the capacitor 4 is charged by the current supplied from the AC power supply 1, the AC power supply 1, the reactor 2, the diode D1, the capacitor 4, the diode D4, and the AC power supply are used. Current flows in the order of 1. The diode does not conduct unless a voltage corresponding to the voltage drop is applied in the direction in which the current flows, that is, in the forward direction. Therefore, as shown in the upper part of FIG. 2, in the period of the half cycle T01 where the power supply voltage is positive, the current flows in the period T02 shorter than the half cycle T01. In the passive synchronous rectification mode, the switching elements Q1 and Q4 are controlled to be ON in the period T02 according to the conduction timing of the diodes D1 and D4. Therefore, in the period T02, the current flows in the order of the AC power supply 1, the reactor 2, the switching element Q1, the capacitor 4, the switching element Q4, and the AC power supply 1.

The same operation is performed in the half cycle when the power supply voltage is negative. However, in the period T03 in the half cycle in which the power supply voltage is negative, the switching elements Q2 and Q3 are controlled to be ON according to the conduction timing of the diodes D2 and D3.

FIG. 4 shows the loss characteristic of the diode and the loss characteristic when the switching element is turned on. As shown in FIG. 4, in the region R where the current is smaller than the current value I0, the loss of the diode is larger than the loss of the switching element. By utilizing this characteristic and using synchronous rectification that turns on the switching element connected to the diode in antiparallel to the timing when the current flows through the diode, the device can be operated with high efficiency.

Further, in the middle part of FIG. 2, the power supply voltage and the power supply current in the simple switching mode are shown. This operation mode is an operation mode in which the power supply short-circuit operation is performed one or several times in a half-cycle period of the power supply voltage. In the example of the middle part of FIG. 2, the power supply short-circuit operation is performed once in the half-cycle period of the power supply voltage. By using the simple switching mode, the output of the converter circuit 3 can be boosted.

FIG. 5 shows a short-circuit path of the AC power supply 1 via the reactor 2 when the power supply voltage is positive and synchronous rectification is performed. As shown in FIG. 5, the switching elements Q1 and Q3 are turned on during the period T04. In this way, the current flows in the order of the AC power supply 1, the reactor 2, the switching element Q1, the switching element Q3, and the AC power supply 1, and the electric energy is stored in the reactor 2.

After the period T04, the operation is performed in the passive synchronous rectification mode shown in the upper part of FIG. Immediately after the period T04, the sum of the voltage of the AC power supply 1 and the voltage generated in the reactor 2 is applied to the converter circuit 3. Therefore, the diodes D1 and D4 of the converter circuit 3 are conductive. Then, the switching elements Q1 and Q4 are turned on in accordance with the conduction timing of the diodes D1 and D4, and the power supply current flows.

In FIG. 5, the switching elements Q1 and Q3 are turned on, but instead of this, the switching elements Q2 and Q4 may be turned on. In this case, the current flows in the order of the AC power supply 1, the reactor 2, the switching element Q2, the switching element Q4, and the AC power supply 1.

The same applies to the negative half cycle, and after one or several power short-circuit operations, the passive synchronous rectification operation is performed. In the power supply short-circuit operation, the switching elements Q1 and Q3 may be turned on, or the switching elements Q2 and Q4 may be turned on.

Further, the lower part of FIG. 2 shows the power supply voltage and the power supply current in the PWM control mode. In this operation mode, the power supply short-circuit operation in which the electric energy is stored in the reactor 2 and the charging operation in which the capacitor 4 is charged by using the electric energy stored in the reactor 2 are alternately repeated. Switching between the power short-circuit operation and the charging operation is performed at a high frequency of several kHz to several tens of kHz. As a result, as shown in the lower part of FIG. 2, the power supply current is controlled to a sinusoidal current. By using the PWM control mode, the power supply current can be brought closer to a sine wave while boosting the output of the converter circuit 3.

The above-mentioned three modes can be switched according to the load conditions. This makes it possible to operate the DC power supply device 50 with high efficiency.

Next, the operation of the main part of the motor drive device 100 according to the first embodiment will be described with reference to FIGS. 6 to 10. FIG. 6 is a diagram showing an example of a control block configured in the converter control unit 11 according to the first embodiment. FIG. 7 is a diagram showing an example of a control block configured in the DC voltage command value correction unit 11a shown in FIG. FIG. 8 is a flowchart showing the operation of the DC voltage command value correction unit 11a shown in FIG. FIG. 9 is a first diagram showing an operation waveform when the control based on the method of the first embodiment is activated. FIG. 10 is a second diagram showing an operation waveform when the control based on the method of the first embodiment is activated.

As shown in FIG. 6, the converter control unit 11 includes a control system including a DC voltage command value correction unit 11a, a differencer 11b, a feedback compensator 11c, and a control signal generation unit 11d.

The first temperature T1 detected by the temperature sensor 22, the second temperature T2 detected by the temperature sensor 24, and the DC voltage command value Vdc * are input to the DC voltage command value correction unit 11a. The DC voltage command value Vdc * is a command value of the DC voltage output to the DC bus 16a and 16b by the converter circuit 3. The DC voltage command value correction unit 11a performs an operation to correct the DC voltage command value Vdc * based on the first temperature T1 and the second temperature T2. The new DC voltage command value obtained by the correction is called a "correction command value" and is expressed as "Vdc_r *".

As shown in FIG. 7, the DC voltage command value correction unit 11a includes a control system including a difference device 11a1 and a correction value calculation unit 11a2. The absolute value ΔT (= | T1-T2 |) of the temperature difference between the first temperature T1 and the second temperature T2 and the zero value which is the target value of ΔT are input to the diffifier 11a1. In the diffifier 11a1, the difference value −ΔT between the zero value and the absolute value ΔT is calculated and input to the correction value calculation unit 11a2. The correction value calculation unit 11a2 calculates a correction value X that brings the absolute value ΔT closer to the target value based on the absolute value ΔT. The correction value X includes a correction value generated when the first temperature T1 is higher than the second temperature T2 and a correction value generated when the first temperature T1 is lower than the second temperature T2. In the flowchart of FIG. 8 described later, the former is referred to as a correction value A and the latter is referred to as a correction value B.

Returning to FIG. 6, the correction command value Vdc_r * corrected by the DC voltage command value correction unit 11a is input to the diffifier 11b. In the diffifier 11b, the difference value between the correction command value Vdc_r * and the detected value Vdc of the bus voltage is calculated. The calculated difference value (Vdc_r * -Vdc) is input to the feedback compensator 11c. An example of the feedback compensator 11c is a Proportional-Integral (PI) controller. When the feedback compensator 11c is a PI controller, the proportionally integrated output of the difference value (Vdc_r * -Vdc) is input to the control signal generation unit 11d. The control signal generation unit 11d generates the control signals S311 to S322 described above based on the output of the feedback compensator 11c.

Next, the detailed operation of the DC voltage command value correction unit 11a will be described with reference to the flowchart of FIG. First, the absolute value ΔT of the temperature difference between the first temperature T1 and the second temperature T2 is calculated (step S101). Next, the first temperature T1 and the second temperature T2 are compared (step S102). When the second temperature T2 is equal to or higher than the first temperature T1 (step S102, Yes), the absolute value ΔT and the first threshold value ΔTlim are further compared (step S103). When the absolute value ΔT is equal to or greater than the first threshold value ΔTlim (step S103, Yes), the correction value A is calculated (step S104). The correction value A is a correction value that raises the bus voltage. Therefore, in order to raise the bus voltage, the value obtained by adding the correction value A to the DC voltage command value Vdc * is set as the correction command value Vdc_r * (step S105), and the flow of FIG. 8 ends.

Further, in step S103, when the absolute value ΔT is less than the first threshold value ΔTlim (steps S103, No), the determination result of the previous step S103 is “whether or not the absolute value ΔT is equal to or more than the first threshold value ΔTlim”. Is confirmed (step S106), and when “the absolute value ΔT is equal to or greater than the first threshold value ΔTlim” (step S106, Yes), the previous correction command value Vdc_r * is maintained (step S107), and FIG. Finish the flow.

Further, in step S106, when the determination result of the previous step S103 is confirmed and "the absolute value ΔT is less than the first threshold value ΔTlim" (steps S106, No), the DC voltage command value Vdc * is the correction command value. It is set to Vdc_r * (step S108). That is, the current DC voltage command value Vdc * is maintained or returned to the current DC voltage command value Vdc *, and the flow of FIG. 8 ends.

Further, in step S102, when the second temperature T2 is less than the first temperature T1 (steps S102, No), the absolute value ΔT and the first threshold value ΔTlim are further compared (step S109). When the absolute value ΔT is equal to or greater than the first threshold value ΔTlim (step S109, Yes), the correction value B is calculated (step S110). The correction value B is a correction value that lowers the bus voltage. Therefore, in order to reduce the bus voltage, the value obtained by subtracting the correction value B from the DC voltage command value Vdc * is set as the correction command value Vdc_r * (step S111), and the flow of FIG. 8 ends.

Further, in step S109, when the absolute value ΔT is less than the first threshold value ΔTlim (steps S109, No), the determination result of the previous step S109 is “whether or not the absolute value ΔT is equal to or more than the first threshold value ΔTlim”. Is confirmed (step S112), and when “the absolute value ΔT is equal to or greater than the first threshold value ΔTlim” (step S112, Yes), the previous correction command value Vdc_r * is maintained (step S113), and FIG. Finish the flow.

Further, in step S112, when the determination result of the previous step S109 is confirmed and "the absolute value ΔT is less than the first threshold value ΔTlim" (step S112, No), the DC voltage command value Vdc * is the correction command value. It is set to Vdc_r * (step S114). That is, the current DC voltage command value Vdc * is maintained or returned to the current DC voltage command value Vdc *, and the flow of FIG. 8 ends.

In step S102 described above, the case where the second temperature T2 and the first temperature T1 are equal is determined by "Yes", but it may be determined by "No". That is, the case where the second temperature T2 and the first temperature T1 are equal may be determined by either "Yes" or "No".

Further, in steps S103 and S109 described above, the case where the absolute value ΔT and the first threshold value ΔTlim are equal is determined by “Yes”, but it may be determined by “No”. That is, the case where the absolute value ΔT and the first threshold value ΔTlim are equal may be determined by either “Yes” or “No”.

Further, in the above step S106, in the determination process of the previous step S103, the case where the absolute value ΔT and the first threshold value ΔTlim are equal is determined by “Yes”, but it may be determined by “No”. .. That is, the case where the absolute value ΔT and the first threshold value ΔTlim are equal may be determined by either “Yes” or “No”.

Further, in step S112 described above, in the determination process of the previous step S109, the case where the absolute value ΔT and the first threshold value ΔTlim are equal is determined by “Yes”, but it may be determined by “No”. .. That is, the case where the absolute value ΔT and the first threshold value ΔTlim are equal may be determined by either “Yes” or “No”.

Further, in steps S106 and S112, confirmation of whether or not the absolute value ΔT is equal to or greater than the first threshold value ΔTlim is confirmed only for the previous determination result, but the present invention is not limited to this. The object of confirmation of whether or not the absolute value ΔT is equal to or greater than the first threshold value ΔTlim may be expanded to the determination results of a plurality of times before including the previous time. As an example of this case, if at least one of the determination results of the previous multiple times including the previous time is "the absolute value ΔT is equal to or greater than the first threshold value ΔTlim", the process of maintaining the previous correction command value Vdc_r * is performed. be able to. This process is effective when the processing interval of the determination result is short, and it is possible to suppress the fluttering of the bus voltage due to the control of the DC voltage.

9 and 10 show operation waveforms in the main part when the above-mentioned control is activated. In FIGS. 9 and 10, the horizontal axis is time, and in the vertical axis direction, the absolute value ΔT (= | T1-T2 |) of the temperature difference and the first temperature T1 which is the temperature of the converter circuit 3 are in order from the upper part. , The second temperature T2 which is the temperature of the inverter circuit 18, the detection value Vdc of the bus voltage corresponding to the output voltage of the converter circuit 3, and the operation waveform of the inverter output current output from the inverter circuit 18 toward the motor 500 are shown. Has been done.

In FIG. 9, at time t1, ΔT exceeds the first threshold value ΔTlim. Therefore, the DC voltage command value Vdc * is corrected by the correction value A that raises the bus voltage, and the bus voltage rises. Since the bus voltage rises, the inverter output current drops less. Due to the decrease in the inverter output current, the conduction loss in the inverter circuit 18 decreases, and the temperature of the inverter circuit 18 decreases. On the other hand, as the bus voltage rises, the current flowing through the converter circuit 3 increases, and the temperature of the converter circuit 3 rises. As a result, the absolute value ΔT of the temperature difference becomes small, ΔT becomes equal to or less than the first threshold value ΔTlim, and the increase of the bus voltage stops. Although the inverter output current decreases, the bus voltage increases, so that the power supplied to the motor 500 is maintained. As a result, the switching element of the inverter circuit 18 can be reliably protected by the temperature rise without stopping or stalling the motor 500.

Further, in FIG. 10, at time t2, ΔT exceeds the first threshold value ΔTlim. Therefore, the DC voltage command value Vdc * is corrected by the correction value B that lowers the bus voltage, and the bus voltage drops. As the bus voltage drops, the inverter output current increases. The control that lowers the bus voltage lowers the current flowing through the converter circuit 3, and the reduction in the conduction loss in the converter circuit 3 lowers the temperature of the converter circuit 3. On the other hand, as the bus voltage drops, the inverter output current increases and the temperature of the inverter circuit 18 rises. As a result, the absolute value ΔT of the temperature difference becomes small, ΔT becomes equal to or less than the first threshold value ΔTlim, and the decrease of the bus voltage stops. Although the bus voltage decreases, the inverter output current increases, so that the power supplied to the motor 500 is maintained. As a result, the switching element of the converter circuit 3 can be reliably protected by the temperature rise without stopping or stalling the motor 500.

As described above, according to the first embodiment, the converter circuit is based on the temperature difference between the first temperature detected by the first temperature detector and the second temperature detected by the second temperature detector. The voltage value of the DC voltage output to the DC bus is changed. In this control, when the first temperature is higher than the second temperature and the absolute value of the temperature difference exceeds the first threshold value, the voltage value of the DC voltage output by the converter circuit to the DC bus increases. Further, when the first temperature is lower than the second temperature and the absolute value of the temperature difference exceeds the first threshold value, the voltage value of the DC voltage output to the DC bus by the converter circuit decreases. In this control, the power supplied to the motor is maintained. As a result, it is possible to reliably protect the switching element in the converter circuit and the inverter circuit while suppressing the deterioration of the performance of the motor drive device.

In the conventional one, the switching element is protected at each of the temperature of the converter circuit and the temperature of the inverter circuit, and the performance of the motor drive device is inevitably deteriorated. On the other hand, in the motor drive device according to the first embodiment, since the switching element is protected by the temperature control by the cooperative operation of the converter circuit and the inverter circuit, the performance deterioration of the motor drive device can be suppressed in the prior art. No remarkable effect can be obtained.

The control of the first embodiment is a control focusing on the conduction loss in the converter circuit 3 or the inverter circuit 18, but may be further controlled by focusing on the switching loss. For example, in a normal state, the modulation method for the inverter circuit 18 is three-phase modulation, but when the absolute value of the temperature difference exceeds the first threshold value and the temperature of the inverter circuit 18 continues to be high for a certain period of time or longer. Also uses a control for switching the modulation method for the inverter circuit 18 to two-phase modulation in order to eliminate the continuous high temperature state of the inverter circuit 18. Specifically, a state in which the second temperature T2 is higher than the first temperature T1, the absolute value ΔT of the temperature difference exceeds the first threshold value, and the second temperature T2 exceeds the second threshold value. If it continues for a preset first time or longer, the three-phase modulation is switched to the two-phase modulation. By switching to the two-phase modulation, the switching loss in the inverter circuit 18 is reduced, so that it is possible to suppress the deterioration of the performance of the motor drive device 100 and prevent the temperature of the inverter circuit 18 from continuing to be high.

Further, in the first embodiment, as shown in FIG. 1, a converter having a reactor on the AC power supply side and boosting the voltage on the AC side before rectification has been illustrated, but the present invention is not limited to this. It may be a type of converter that boosts the voltage on the output side of the converter, that is, on the DC side after rectification. The type of converter that boosts the voltage on the DC side after rectification includes a so-called one-stone boost converter in which the boost circuit is composed of one stage, or a so-called interleaved converter in which the boost circuit is composed of a plurality of stages. All of these are converters having a boosting function, and can be applied to the motor drive device of the first embodiment.

Next, the hardware configuration for realizing the function of the control unit 8 in the first embodiment will be described with reference to the drawings of FIGS. 11 and 12. FIG. 11 is a block diagram showing an example of a hardware configuration that embodies the function of the control unit 8 according to the first embodiment. FIG. 12 is a block diagram showing another example of the hardware configuration that embodies the function of the control unit 8 according to the first embodiment.

When the function of the control unit 8 according to the first embodiment is realized, as shown in FIG. 11, the processor 300 that performs the calculation, the memory 302 that stores the program read by the processor 300, and the input / output of the signal are input / output. It can be configured to include the interface 304 to be performed.

The processor 300 may be a computing means such as an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Further, the memory 302 includes a non-volatile or volatile semiconductor memory such as a RAM (Radom Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (registered trademark) (Electrically EPROM). Examples thereof include magnetic disks, flexible disks, optical disks, compact disks, mini disks, and DVDs (Digital Versaille Discs).

The memory 302 stores a program that executes the function of the control unit 8 according to the first embodiment. The processor 300 sends and receives necessary information via the interface 304, the processor 300 executes a program stored in the memory 302, and the processor 300 refers to a table stored in the memory 302 to perform the above-described processing. It can be carried out. The calculation result by the processor 300 can be stored in the memory 302.

Further, when the function of the control unit 8 in the first embodiment is realized, the processing circuit 305 shown in FIG. 12 can also be used. The processing circuit 305 corresponds to a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The information input to the processing circuit 305 and the information output from the processing circuit 305 can be obtained via the interface 306.

Note that some processing in the control unit 8 may be performed by the processing circuit 305 having the configuration shown in FIG.

Embodiment 2.
In the second embodiment, an application example of the motor drive device 100 described in the first embodiment will be described. FIG. 13 is a diagram showing the configuration of the air conditioner 400 according to the second embodiment. The motor drive device 100 described in the first embodiment can be applied to products such as a blower, a compressor, and an air conditioner. In the second embodiment, as an application example of the motor drive device 100 according to the first embodiment, an example in which the motor drive device 100 is applied to the air conditioner 400 will be described.

In FIG. 13, a motor 500 is connected to the output side of the motor drive device 100, and the motor 500 is connected to the compression element 504. The compressor 505 includes a motor 500 and a compression element 504. The refrigeration cycle unit 506 is configured to include a four-way valve 506a, an indoor heat exchanger 506b, an expansion valve 506c, and an outdoor heat exchanger 506d.

The flow path of the refrigerant circulating inside the air conditioner 400 is from the compression element 504 via the four-way valve 506a, the indoor heat exchanger 506b, the expansion valve 506c, the outdoor heat exchanger 506d, and again via the four-way valve 506a. Therefore, it is configured to return to the compression element 504. The motor drive device 100 receives AC power from the AC power supply 1 and rotates the motor 500. The compression element 504 executes a compression operation of the refrigerant by rotating the motor 500, and the refrigerant can be circulated inside the refrigeration cycle unit 506.

Since the air conditioner 400 according to the second embodiment is equipped with the motor drive device 100 according to the first embodiment, the effects obtained in the first embodiment can be enjoyed.

Further, the configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is configured without departing from the gist of the present invention. It is also possible to omit or change a part of.

1 AC power supply, 2 reactors, 3 converter circuits, 3a, 3b, 3c, 3d, 26a, 26b, 26c connection points, 4 capacitors, 5,7 voltage detectors, 6,9 current detectors, 8 controls, 10 breakers , 11 converter control unit, 11a DC voltage command value correction unit, 11a1, 11b differential, 11a2 correction value calculation unit, 11c feedback compensator, 11d control signal generation unit, 12 inverter, 14 inverter control unit, 15, 17 gate drive Circuit, 16a, 16b DC bus, 18 inverter circuit, 18A, 18B, 18C leg, 18a transistor, 18b, D1, D2, D3, D4 diode, 18UN, 18VN, 18WN lower arm element, 18UP, 18VP, 18WP upper arm element , 22, 24 Temperature sensor, 31 1st leg, 32 2nd leg, 50 DC power supply, 100 motor drive, 300 processor, 302 memory, 304, 306 interface, 305 processing circuit, 311 1st upper arm Element, 312 1st lower arm element, 321 2nd upper arm element, 322 2nd lower arm element, 400 air conditioner, 500 motor, 504 compression element, 505 compressor, 506 refrigeration cycle part, 506a four-way valve , 506b indoor heat exchanger, 506c expansion valve, 506d outdoor heat exchanger, Q1, Q2, Q3, Q4 switching element.

Claims (15)

A motor drive that drives a motor
A converter circuit that converts the AC voltage output from the AC power supply into a DC voltage and outputs it to the DC bus,
An inverter circuit that converts the DC voltage into an AC voltage applied to the motor and outputs it.
A first temperature detector that detects the temperature of the converter circuit,
A second temperature detector that detects the temperature of the inverter circuit, and
With
The converter circuit outputs the DC voltage to the DC bus based on the temperature difference between the first temperature detected by the first temperature detector and the second temperature detected by the second temperature detector. Motor drive that changes the voltage value. When the first temperature is higher than the second temperature and the absolute value of the temperature difference exceeds the first threshold value, the voltage value of the DC voltage output by the converter circuit to the DC bus increases. The motor drive device according to claim 1. When the first temperature is lower than the second temperature and the absolute value of the temperature difference exceeds the first threshold value, the voltage value of the DC voltage output by the converter circuit to the DC bus is lowered. The motor drive device according to claim 1 or 2. The voltage value of the DC voltage is calculated based on the DC voltage command value which is the command value of the DC voltage, and the first correction value for increasing the voltage value of the DC voltage is calculated.
When the first temperature is higher than the second temperature and the absolute value of the temperature difference exceeds the first threshold value, it is corrected by adding the first correction value to the DC voltage command value. The motor drive device according to any one of claims 1 to 3, wherein the correction command value of this time is a new DC voltage command value. The voltage value of the DC voltage is calculated based on the DC voltage command value which is the command value of the DC voltage, and the first correction value for increasing the voltage value of the DC voltage is calculated.
When the first temperature is higher than the second temperature and the absolute value of the temperature difference is smaller than the first threshold value, the absolute value of the temperature difference is the first in the previous determination process regarding the temperature difference. The motor drive device according to any one of claims 1 to 3, wherein the previous DC voltage command value is maintained when the threshold value of is exceeded. The voltage value of the DC voltage is calculated based on the DC voltage command value which is the command value of the DC voltage, and the first correction value for increasing the voltage value of the DC voltage is calculated.
When the first temperature is higher than the second temperature and the absolute value of the temperature difference is smaller than the first threshold value, the absolute value of the temperature difference is the first in the previous determination process regarding the temperature difference. The motor drive device according to any one of claims 1 to 3, wherein the current DC voltage command value is maintained or returned to the current DC voltage command value when the temperature does not exceed the threshold value of. The voltage value of the DC voltage is calculated based on the DC voltage command value which is the command value of the DC voltage, and the second correction value for lowering the voltage value of the DC voltage is calculated.
When the first temperature is lower than the second temperature and the absolute value of the temperature difference exceeds the first threshold value, it is corrected by subtracting the second correction value from the DC voltage command value. The motor drive device according to any one of claims 1 to 3, wherein the current correction command value is a new DC voltage command value. The voltage value of the DC voltage is calculated based on the DC voltage command value which is the command value of the DC voltage, and the second correction value for lowering the voltage value of the DC voltage is calculated.
When the first temperature is lower than the second temperature and the absolute value of the temperature difference is smaller than the first threshold value, the absolute value of the temperature difference is the first in the previous determination process regarding the temperature difference. The motor drive device according to any one of claims 1 to 3, wherein the previous DC voltage command value is maintained when the threshold value of is exceeded. The voltage value of the DC voltage is calculated based on the DC voltage command value which is the command value of the DC voltage, and the first correction value for lowering the voltage value of the DC voltage is calculated.
When the first temperature is lower than the second temperature and the absolute value of the temperature difference is smaller than the first threshold value, the absolute value of the temperature difference is the first in the previous determination process regarding the temperature difference. The motor drive device according to any one of claims 1 to 3, wherein the current DC voltage command value is maintained or returned to the current DC voltage command value when the temperature does not exceed the threshold value of. The first time is a state in which the second temperature is higher than the first temperature, the absolute value of the temperature difference exceeds the first threshold value, and the second temperature exceeds the second threshold value. The motor drive device according to any one of claims 1 to 9, wherein when the above is continued, the modulation method for the inverter circuit is switched from three-phase modulation to two-phase modulation. The motor drive device according to any one of claims 1 to 10, wherein the switching element of the converter circuit is formed of a wide bandgap semiconductor. The motor drive device according to claim 11, wherein the wide bandgap semiconductor is silicon carbide, gallium nitride, gallium oxide, or diamond. A blower comprising the motor driving device according to any one of claims 1 to 12. A compressor comprising the motor driving device according to any one of claims 1 to 12. An air conditioner including at least one of the blower according to claim 13 and the compressor according to claim 14.

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