阅读说明：本技术 异常判断系统 (Abnormality determination system ) 是由 山村雅纪 平井太郎 于 2019-07-11 设计创作，主要内容包括：一种异常判断系统,当输入驱动信号并且没有输入用于使开关元件的栅极驱动停止的关断信号时,信号切换部分将驱动信号输出到桥式电路。当输入关断信号时,信号切换部分停止驱动信号的输出并启动逆变器的关断功能。异常判断部分对关断功能中的异常进行判断。当电源继电器打开时,控制单元对桥式电路进行驱动以开始从平滑电容器释放电荷的放电过程,并在执行放电过程期间启动关断功能。当判断为在关断功能的操作期间平滑电容器的直接或间接检测到的电压已经下降时,异常判断部分判断为关断功能是异常的。(An abnormality determination system outputs a drive signal to a bridge circuit when the drive signal is input and a turn-off signal for stopping gate drive of a switching element is not input. When a shutdown signal is input, the signal switching section stops the output of the drive signal and starts the shutdown function of the inverter. The abnormality determination section determines an abnormality in the shutdown function. When the power supply relay is turned on, the control unit drives the bridge circuit to start a discharging process of discharging electric charges from the smoothing capacitor, and starts a turn-off function during execution of the discharging process. The abnormality determination section determines that the shutdown function is abnormal when it is determined that the voltage of the smoothing capacitor detected directly or indirectly during the operation of the shutdown function has dropped.)

1. An abnormality determination system comprising:

at least one inverter having a bridge circuit in which a plurality of switching elements are bridged, a smoothing capacitor provided at an input portion of the bridge circuit, and a control unit that drives driving of the bridge circuit, converts direct current input from a direct current power supply source to the bridge circuit into alternating current, and supplies the alternating current to a rotating electric machine; and

at least one power supply relay that is provided between the direct-current power supply and the smoothing capacitor and is capable of cutting off the supply of electric power from the direct-current power supply to the bridge circuit, wherein,

the control unit includes: a gate command section that generates a drive signal for driving gates of a plurality of the switching elements in the bridge circuit; a signal switching section that outputs the drive signal to the bridge circuit when the drive signal is input and a turn-off signal for stopping gate drive of a plurality of the switching elements of the bridge circuit is not input, and stops output of the drive signal and starts the turn-off function of the inverter when the turn-off signal is input; and an abnormality judgment section for judging an abnormality in the shutdown function,

the control unit drives the bridge circuit to start a discharging process of discharging electric charge from the smoothing capacitor when the power supply relay is turned on, and starts the shut-off function during execution of the discharging process, and the abnormality determination section determines that the shut-off function is abnormal when it is determined that a directly or indirectly detected voltage of the smoothing capacitor has dropped during operation of the shut-off function.

2. The abnormality determination system according to claim 1, wherein the abnormality determination portion determines that the discharging function of the inverter is abnormal when it is determined that the voltage of the smoothing capacitor is maintained in a period between a start of the discharging process and a start of the shutdown function.

3. The abnormality determination system according to claim 1,

the signal switching section activates the shutdown function based on any one or more of the shutdown signals of the plurality of inputs, and,

the abnormality determination portion determines abnormality in the plurality of off signals based on a voltage drop in the smoothing capacitor during a period in which each of the off signals is applied in a mutually exclusive manner.

4. The abnormality determination system according to claim 1,

at least one of the inverters comprises a plurality of inverters,

the control unit of the inverter performs abnormality diagnosis of the discharge process and the shutdown function at different timings.

5. The abnormality determination system according to claim 4, characterized in that the control unit of the inverter sequentially executes the discharge process of the inverter and the abnormality diagnosis of the shut-down function one by one after the turning on of the power supply relay.

6. The abnormality determination system according to claim 4, characterized in that the control unit of the inverter performs the abnormality diagnosis of the discharge process and the shutdown function of one or more inverters selected in sequence corresponding to one relay opening action.

7. The abnormality determination system according to claim 1,

at least one of the inverters comprises a plurality of inverters,

at least one of the power supply relays includes a plurality of power supply relays capable of individually cutting off the supply of electric power from the bridge circuit of the inverter.

8. The abnormality determination system according to claim 1, further comprising a boost converter provided between the DC power supply and the inverter to boost a voltage of the DC power supply and output the voltage to the inverter, wherein,

stopping the operation of the boost converter before the abnormality diagnosis of the shutdown function.

Technical Field

The present disclosure relates to an abnormality determination system that determines an abnormality in a shutdown function of an inverter.

Background

Conventionally, there is known a device in an inverter that drives a rotating electrical machine, which determines an abnormality in a shutdown function that stops gate driving of a switching element. For example, a drive device for a vehicle disclosed in japanese patent No. 5287705 determines an abnormality of a shut-off function of turning off a power converter after the vehicle runs.

The control unit for the driving device outputs a drive command for causing the drive current to flow and a shutdown command for shutting down the power converter at a higher priority than the drive command. The control unit determines that there is an abnormality in a shutdown function for shutting down the power converter when the drive current is detected while both the drive command and a shutdown command for shutting down the power converter are output.

In the following description, the term "approximately zero" in relation to the current means "approximately zero (a)" which means a current in a range where the current value is substantially regarded as "zero (a)" in consideration of the device resolution and the detection error. The command for allowing the flow of the drive current is generally judged in such a manner that the drive state is controlled with reference to the output values of the two phase current sensors. According to the apparatus described in japanese patent No. 5287705, the shutdown function is judged to be normal when the output value of the current sensor is approximately zero, and the drive current flows and the shutdown function is judged to be abnormal when the output value of the current sensor is greater than approximately zero or less than approximately zero.

For example, it is assumed that in the current sensors of two phases of V-phase and W-phase, an "approximately zero sticking failure" occurs in the V-phase current sensor. In this case, even if the drive current flows through the current path from the U-phase to the V-phase, the shutdown function is judged to be normal because the output of the V-phase current sensor is approximately zero. In addition, when the "near zero sticking failure" occurs in both the V-phase and W-phase current sensors, the shutdown function is judged to be normal even if the drive current flows through any phase. Therefore, an abnormality in the shutdown function cannot be accurately detected.

In the second embodiment described in japanese patent No. 5287705, when a voltage drop occurs in the smoothing capacitor and the flow of the drive current is detected, the shut-off function is determined to be abnormal. That is, even when the voltage in the smoothing capacitor drops, it is not possible to accurately detect an abnormality of the shutdown function by the "near zero sticking failure" of the current sensor of one phase or a plurality of phases. This is similar to the case where the voltage of the smoothing capacitor is not used for diagnosis.

Disclosure of Invention

The present disclosure has been devised in view of the above circumstances. An object of the present disclosure is to provide an abnormality determination system capable of detecting an abnormality of a shutdown function even in the case of an approximately zero sticking failure in a current sensor.

As an aspect of the embodiment, there is provided an abnormality determination system including: at least one inverter having a bridge circuit in which a plurality of switching elements are bridged, a smoothing capacitor provided at an input portion of the bridge circuit, and a control unit that controls driving of the bridge circuit, converts direct current input from a direct current power supply source to the bridge circuit into alternating current, and supplies the alternating current to the rotating electric machine; and at least one power supply relay that is provided between the direct-current power supply and the smoothing capacitor and is capable of cutting off the supply of electric power from the direct-current power supply to the bridge circuit. The control unit includes: a gate command section that generates a drive signal for driving gates of a plurality of switching elements in a bridge circuit; a signal switching section that outputs a drive signal to the bridge circuit when the drive signal is input and a shutdown signal for stopping gate drive of a plurality of switching elements of the bridge circuit is not input, and stops output of the drive signal and starts a shutdown function of the inverter when the shutdown signal is input; and an abnormality determination section for determining an abnormality in the shutdown function. When the power supply relay is turned on, the control unit drives the bridge circuit to start a discharging process of discharging electric charges from the smoothing capacitor and starts the shutdown function during execution of the discharging process, and when it is determined that the voltage of the smoothing capacitor detected directly or indirectly has dropped during operation of the shutdown function, the abnormality determination section determines that the shutdown function is abnormal.

Drawings

In the drawings:

fig. 1 is a diagram showing the overall configuration of an abnormality determination system according to a first embodiment;

FIG. 2 is a simplified diagram of the system architecture of FIG. 1;

fig. 3 is a diagram showing a structure relating to a drive signal and a turn-off signal according to the first embodiment;

FIG. 4 is a flowchart of a diagnostic process according to a first embodiment;

fig. 5 is a time chart of a diagnostic process according to the first embodiment;

fig. 6 is a flowchart of the diagnosis execution judgment by the diagnosis start voltage;

fig. 7 is a diagram showing a system in which another device is connected in parallel to a smoothing capacitor;

fig. 8 is a diagram showing the configuration of an abnormality determination system according to the second embodiment;

fig. 9 is a diagram showing the structure of the and drive signal and the off signal according to the third embodiment;

fig. 10 is a flowchart of a diagnostic process according to the third embodiment;

fig. 11 is a time chart of a diagnostic process according to the third embodiment;

fig. 12 is a diagram showing the configuration of an abnormality determination system according to the fourth embodiment;

fig. 13 is a diagram showing a structure relating to a drive signal and a shutdown signal according to the fourth embodiment;

fig. 14 is a flowchart of a diagnostic process according to the fourth embodiment;

fig. 15 is a flowchart of a diagnostic process according to the fifth embodiment;

fig. 16 is a diagram showing the configuration of an abnormality determination system according to the sixth embodiment;

fig. 17 is a diagram showing the configuration of an abnormality determination system according to the seventh embodiment;

fig. 18 is a diagram showing the configuration of an abnormality determination system according to the eighth embodiment;

fig. 19 is a diagram showing an abnormality determination system according to the eighth embodiment, in which an inverter to be diagnosed is restricted.

Detailed Description

Hereinafter, embodiments of the abnormality determination system will be described with reference to the drawings. Substantially the same components in the embodiments or substantially the same steps in the flowcharts will be given the same reference numerals or the same step numbers, and redundant description thereof will be omitted. In addition, the first to eighth embodiments will be collectively referred to as "the present embodiment". The abnormality determination system in the present embodiment is mounted in a hybrid vehicle or an electric vehicle that includes an electric motor, i.e., "rotating electric machine", as a power source.

During normal running of the vehicle, the abnormality determination system converts direct current of the battery as a "direct current power supply" into alternating current, and supplies the alternating current to the alternating current motor. After the vehicle stops, when the off ready state is established and the power supply relay provided between the battery and the inverter is turned on (i.e., turned off), the abnormality determination system cooperates with the vehicle control unit to diagnose an abnormality in the shutdown function. The "abnormality of the shutdown function" refers to an abnormality of a shutdown signal for stopping the gate of a switching element constituting a bridge circuit in the inverter.

(first embodiment)

An abnormality determination system in the first embodiment will be described with reference to fig. 1 to 7. Fig. 1 shows the overall configuration of an abnormality determination system 901 that supplies electric power from one inverter 30 to a three-phase alternating-current motor 80. The abnormal configuration system 901 mainly includes an inverter 30 and a power supply relay 15.

The inverter 30 includes: a bridge circuit 60 in which a plurality of switching elements 61 to 66 are bridged; a smoothing capacitor 50, the smoothing capacitor 50 being provided at an input portion of the bridge circuit; and a control unit 40, the control unit 40 controlling driving of the bridge circuit. In summary, here, not only the bridge circuit 60 is referred to as an "inverter", but the bridge circuit 60, the smoothing capacitor 50, and the control unit 40 are collectively defined as an "inverter". The inverter 30 converts direct current input to the bridge circuit 60 from the battery 10 as a "direct current power supply" into alternating current, and supplies the alternating current to the motor 80 as a "rotating electrical machine". The power supply relay 15 is provided between the battery 10 and the smoothing capacitor 50 to cut off the supply of electric power from the battery 10 to the bridge circuit 60.

Subsequently, these elements will be described in detail. The battery 10 is a chargeable and dischargeable secondary battery such as a lithium ion battery, which is a so-called high-voltage battery that can store a high voltage of several hundreds of volts. However, the high-voltage battery will be simply referred to as "battery 10" because an auxiliary battery, which is a so-called low-voltage battery, will not be mentioned here. The positive electrode of the battery 10 is connected to the high potential electrode of the smoothing capacitor 50 through the direct current bus line Lp, and the negative electrode of the battery 10 is connected to the low potential electrode of the smoothing capacitor 50 through the ground line Ln. The charge amount and the temperature of the battery 10 are monitored by the battery monitoring unit 12.

For example, as shown in fig. 1, the power supply relay 15 is provided on the direct current bus line Lp between the positive electrode of the battery 10 and the high potential electrode of the smoothing capacitor 50. The power supply relay may be provided across the direct current bus Lp and the ground line Ln similarly to the system main relay described in japanese patent No. 5287705, and may be combined with a precharge relay to prevent an inrush current at the time of closing. The power supply relay 15 is opened or closed by the vehicle control unit 20 that performs centralized control of the behavior of the entire vehicle or by the battery monitoring unit 12. When the battery monitoring unit 12 operates the power supply relay 15, information on the operation is provided to the vehicle control unit 20.

In the present embodiment applied to the vehicle, generally, when the ready state of the power switch of the vehicle is turned on, the power relay is turned on, i.e., closed. In the running state of the vehicle including the temporary stop, electric charge is accumulated in the smoothing capacitor 50. When the vehicle stops and the ready state of the power switch is turned off, the power relay 15 is turned off, i.e., opened. Thereafter, in order to ensure electrical safety during parking, generally, a discharging process is performed to discharge the residual electric charge from the smoothing capacitor 50.

The bridge circuit 60 of the inverter 30 has six switching elements 61 to 66 bridging upper and lower arms. Switching elements 61, 62, 63 are switching elements of the U-phase, V-phase, W-phase of the upper arm, respectively, and switching elements 64, 65, 66 are switching elements of the U-phase, V-phase, W-phase of the lower arm, respectively. The switching elements 61 to 66 are constituted by IGBTs, for example, and have free wheeling diodes connected in parallel to allow current to flow from the low potential side to the high potential side.

Hereinafter, the motor control during normal running of the vehicle is referred to as "normal control". During normal control, the bridge circuit 60 converts direct current into three-phase alternating current by operating the switching elements 61 to 66 according to the gate signals output from the control unit 40. Then, the bridge circuit 60 applies phase voltages corresponding to the voltage commands calculated by the control unit 40 to the respective phase windings 81, 82, 83 of the motor 80.

The smoothing capacitor 50 smoothes the dc voltage input to the bridge circuit 60. In the following description, the inter-electrode voltage of the smoothing capacitor 50, in other words, the voltage of the dc bus line Lp with reference to the potential of the ground line Ln will be referred to as "capacitor voltage Vc". In the first embodiment, the voltage sensor 51 is provided to directly detect the capacitor voltage Vc.

Current sensors that detect phase currents are provided in current paths connected to two or more of the three-phase windings 81, 82, 83 of the motor 80. In the example of fig. 1, current sensors 72 and 73 that detect phase currents Iv and Iw, respectively, are provided in current paths connected to a V-phase winding 82 and a W-phase winding 83, and a remaining U-phase current Iu is estimated according to kirchhoff's law. In other embodiments, any two-phase current may be detected, or a three-phase current may be detected.

Each detected phase current is coordinate-converted to a dq-axis current and fed back to the current command, whereby the PI calculates the voltage command. In the present embodiment, as described later, no current sensor is required, and therefore, for example, under normal control, the bridge circuit 60 can be always driven by feed-forward control without using the current detection value.

The motor 80 is a permanent magnet synchronous three-phase alternating current motor. The electric motor 80 of the present embodiment is a motor generator including a function of an electric motor that generates torque for driving the drive wheels of the hybrid vehicle and a function of a generator that collects energy from the torque transmitted from the engine and the drive wheels by generating electricity. In the motor control, a rotation angle sensor is generally provided to detect a rotation angle for coordinate conversion calculation or the like, although not shown or described in fig. 1.

The control unit 40 includes a microcomputer 41 and an and circuit 48 as a "signal switching section", wherein the microcomputer 41 has a gate command section 44 and an abnormality judgment section 45. The microcomputer 41 has a CPU, a ROM, an I/O unit, and a bus connecting these components, although not shown in the drawing. The microcomputer 41 performs control by software processing implemented by a program stored in advance being executed by the CPU, and by hardware processing implemented by a dedicated electronic circuit. The vehicle control unit 20 and the control unit 40 are communicable with each other via a network such as CAN communication.

During the normal control, the microcomputer 41 executes the general-purpose motor control by the vector control or the like. Specifically, the microcomputer 41 subjects the dq-axis voltage command calculated by the controller to three-phase conversion, thereby calculating three-phase voltage commands. The microcomputer 41 further subjects the three-phase voltage command to PWM modulation by a modulator, and outputs a gate command. In the current feedback control, the controller performs PI control of the current detection value to follow the current command, thereby calculating the dq-axis voltage command. In the voltage feedforward control, the controller operates, for example, on a dq-axis voltage command calculated from a current command by a voltage equation. The mechanism of the general motor control as described above is a well-known technique, and therefore, a detailed description thereof and an explanation of signal input and output will be omitted.

In the present embodiment, in particular, the gate command section 44 of the microcomputer 41 generates the drive signal DR for driving the gates of the plurality of switching elements 61 to 66 in the bridge circuit 60. The abnormality determination section 45 determines an abnormality of a turn-off function described below based on a change in the capacitor voltage Vc at the time of gate turn-off. Further, as described later, the abnormality determination portion 45 determines an abnormality of the discharge function of the inverter 30 based on the change in the capacitor voltage Vc at the time of the discharge process.

When the power supply relay 15 is turned on by the operation of the vehicle control unit 20 or the battery detection unit 12, the vehicle control unit 20 transmits a discharge command to the gate command portion 44 of the microcomputer 41 through CAN communication. Therefore, the driving signal DR is input from the gate command section 44 to one input terminal of the and circuit 48. In addition, the shutdown signal SO generated by the microcomputer 41 of the and circuit 48 or the vehicle control unit 20 is negatively input to the other input terminal of the and circuit 48. The off signal SO is a signal for stopping the gate drive of the plurality of switching elements 61 to 66 in the bridge circuit 60.

That is, when the drive signal DR is input and the off signal SO is not input, the and circuit 48 outputs the drive signal DR to the bridge circuit 60. At this time, the control unit 40 may activate the switching elements 61 to 66 of the bridge circuit 60 to perform the discharging process.

When the driving signal DR is not input or the off signal SO is input, the and circuit 48 does not output the driving signal DR. Therefore, when the shutdown signal SO is input from the microcomputer 41 or the vehicle control unit 20, the and circuit 48 stops the output of the drive signal DR. Therefore, the operation of stopping the gate drive of the bridge circuit 60, i.e., fixing the gate in the off state, regardless of the gate command will be referred to as "starting the shutdown function of the inverter 30". The control unit 40 may interrupt the discharge of the smoothing capacitor 50 by starting the shutdown function of the inverter 30 during the execution of the discharge process.

Fig. 2 is a simplified diagram of the system configuration in fig. 1. Fig. 3 is a diagram showing a communication configuration related to the drive signal DR and the shutdown signal SO in the vehicle control unit 20 and the control unit 40. Fig. 2 and 3 are diagrams showing the basic configuration of the first embodiment. Regarding the second embodiment and the subsequent embodiments, differences in configuration from the first embodiment will be described in drawings corresponding to fig. 2 and 3. Components not shown in the drawings of the following embodiments will be explained to be identical to those shown in fig. 1.

An abnormality in the off signal SO will cause an inconvenience that the gate drive of the bridge circuit 60 cannot be stopped even in an emergency. Therefore, it is necessary to diagnose an abnormality in the off signal SO. According to a technique disclosed in japanese patent No. 5287705 as a conventional technique, an abnormality of the shutdown function is judged based on an output value of a two-phase current sensor that detects a drive current. However, in the conventional technique, when the "near zero sticking failure" occurs in any current sensor, abnormality of the shutdown function cannot be correctly detected.

According to the conventional method of detecting an abnormality of the shutdown function by using the two-phase current sensor, the above-described problem occurs due to insufficient coverage of the shutdown function check. When the shutdown function is abnormal and a current flows from the smoothing capacitor 50, even if a part of the shutdown function fails as described above, energy will be supplied from the dc bus Lp to the inverter 30.

The idea to solve this problem is to prevent insufficient coverage by checking the energy supply. The present embodiment looks at the fact that the energy supply can be checked from the change in the energy accumulated in the smoothing capacitor 50 when the smoothing capacitor 50 is discharged. The energy accumulated in the smoothing capacitor 50 is proportional to the square of the capacitor voltage Vc, and therefore, the energy supply can be checked by the change in the capacitor voltage Vc.

Therefore, in the present embodiment, a solution is adopted that uses the capacitor voltage Vc during discharging the electric charge from the smoothing capacitor 50 to check the shutdown function. Specifically, when the capacitor voltage Vc falls while the discharging process is performed and the shutdown signal SO is output, the abnormality determination portion 45 determines that there is an abnormality in the shutdown function. That is, in the present embodiment, the output values of the current sensor 72 and the current sensor 73 are not used for abnormality diagnosis, but the abnormality of the shutdown function is judged only by the change in the energy accumulated in the smoothing capacitor 50. This ensures the detectability of the abnormality in the case of the near zero sticking failure in the current sensor 72 and the current sensor 73.

Fig. 4 is a flowchart of a diagnostic process according to the first embodiment. In this flowchart, symbol S denotes "step". In the steps shown in fig. 4, the step S10 of the discharging function diagnosis includes S13 and S14, and the step S20 of the turning off function diagnosis includes S22 to S24. In the description of fig. 4, "abnormality in the shutdown function" will be specifically referred to as "abnormality in the shutdown signal SO".

When the power supply relay is turned on in S01, the control unit 40 starts driving of the inverter 30 in S02, thereby starting discharging from the smoothing capacitor. Then, after the inverter 30 is driven to flow a current to the motor 80, when the driving of the inverter 30 is normal, the electric charge of the smoothing capacitor 50 is discharged, whereby the capacitor voltage Vc decreases. However, when the driving of the inverter 30 is abnormal, the capacitor voltage Vc is not decreased.

Therefore, the abnormality determination portion 45 determines in S13 whether there is a drop in the capacitor voltage Vc during the period before the start of the shutdown function. When there is a voltage drop, the abnormality determination section 45 determines that the discharge function of the inverter 30 is normal. When the capacitor voltage Vc is maintained without voltage drop, the abnormality determination portion 45 determines that the discharge function of the inverter 30 is abnormal. Specifically, when the capacitor voltage Vc is equal to or higher than the discharge threshold value α or when the capacitor voltage drop amount Δ Vc is equal to or smaller than the discharge drop amount threshold value Δ α, the abnormality determination portion 45 makes a determination of "no" in S13, and the present process proceeds to S14. In S14, abnormality determination portion 45 determines that the discharge function of inverter 30 is abnormal.

When the determination of "yes" is made, that is, when it is determined in S13 that the discharge function is normal, the off function diagnosis in S20 is performed. After the off signal SO is turned on in S22, the abnormality determination portion 45 determines whether the capacitor voltage Vc falls in S23. When there is no voltage drop, the abnormality determination section 45 determines that the off signal SO is normal, and when there is a voltage drop, the abnormality determination section 45 determines that the off signal SO is abnormal. Specifically, when the capacitor voltage Vc is equal to or smaller than the turn-off threshold value β, or when the capacitor voltage drop amount Δ Vc is equal to or larger than the turn-off drop amount threshold value Δ β, the abnormality determination portion 45 makes a determination of "yes" in S23, and the present process proceeds to S24. In S24, the abnormality determination section 45 determines that the off signal SO is abnormal.

Supplementary explanation of a method for judging the presence or absence of a voltage drop will be provided. The presence or absence of the voltage drop may be judged by sampling the voltage at least at two times and evaluating the voltage drop amount Δ Vc, or may be judged from the fact that the voltage equal to or lower than the turn-off threshold value continues for a predetermined period of time. When the discharge resistors are arranged in the dc bus line Lp, the voltage drop amount Δ Vc is evaluated in consideration of the voltage drop caused by the discharge from the discharge resistors. Specifically, it may be considered that the time rate of change of the capacitor energy caused by the discharge from the discharge resistance becomes "voltage²Resistance.

When the determination of "no" is made, that is, when it is determined in S23 that the off signal SO is normal, the abnormality determination portion 45 terminates the abnormality diagnosis in S30. In the process shown in fig. 4, the shutdown function diagnosis is performed after confirming that the discharge function is normal. This avoids erroneous judgment that the shutdown function is normal even in the case where the shutdown signal SO is abnormal. However, when it has been determined through another diagnostic process that the driving of the inverter 30 is normal, the discharge function diagnosis in S10 may be omitted. In this case, S02 may be followed by the step of turning on the off signal in S22.

Fig. 5 is a time chart showing the relationship between the gate operation timing and the variation in the capacitor voltage Vc in the diagnostic process according to the first embodiment. The period shown in the bar refers to a period in which the discharging process of the smoothing capacitor 50 is performed and a period in which the gate-off signal SO is output to the bridge circuit 60. Reference numerals "S02", "S22 and S23", and "S30" correspond to the step numbers shown in fig. 4. No communication delay is considered in fig. 5.

When the discharge process is started at time t1, the capacitor voltage Vc decreases from the voltage Vci at the start of diagnosis with a gradient according to the discharge rate. In the case where the off signal SO is output from time t2 to time t3, the capacitor voltage Vc is held at a constant value Vcs as shown by the solid line when the off signal SO is normal. At time t3, the abnormality determination section 45 determines that the off signal SO is normal, thereby completing the abnormality diagnosis. When the output of the off signal SO stops, the capacitor voltage Vc decreases again. At time t4, when the capacitor voltage Vc decreases to a convergent value Vcf (ideally zero), the discharge process is terminated.

Meanwhile, when the off signal SO is abnormal, the capacitor voltage Vc continues to decrease as shown by the broken line even after time t2, and then reaches the convergence value Vcf. At time t3, the abnormality determination section 45 determines that the off signal SO is abnormal based on the fact that, for example, the voltage drop amount Δ Vc is equal to or greater than the threshold value, thereby completing the abnormality diagnosis.

Hereinafter, other considerations in the abnormality diagnosis will be described.

< Current vector at inverter drive >

The current vector at the time of discharge of the inverter drive is desirably in the d-axis direction so as not to generate torque by the current. This makes it possible to avoid discomfort that the driver may feel when the discharging is performed immediately after the vehicle stops. Even when the current sensor 72 and the current sensor 73 fail, the driving inverter 30 can flow a current to realize the discharge.

< method for outputting drive command >

In order to control the driving of the inverter 30 during the discharging, if the current sensors 72 and 73 are normal, a current feedback control method of generating a voltage command from a difference between a current command and a current detection value may be used. Alternatively, a voltage feedforward control method of generating a voltage command without using a current detection value may be employed.

< switching of discharge Rate >

The discharge rate is desirably switched according to the capacitor voltage Vc. In particular, the discharge rate is accelerated in a high-voltage region higher than a voltage region for diagnosis, and the discharge rate is slowed in a low-voltage region equal to or lower than the voltage region for diagnosis. Slowing down the discharge rate helps in setting the diagnostic conditions. The discharge rate is increased to complete the discharge more quickly, thereby achieving an improvement in safety. The discharge rate may be switched stepwise or continuously according to the capacitor voltage Vc.

< Voltage Range at the beginning of diagnosis >

Preferably, a determination is made as to whether or not the diagnosis should be performed from the capacitor voltage Vc at the start of the diagnosis. This is because, when the voltage Vc at the start of diagnosis is lower than the lower limit value, the voltage will drop sharply due to discharge, so that normal diagnosis cannot be performed. When the voltage Vc at the start of diagnosis is higher than the upper limit value, the time elapsed until the completion of diagnosis becomes long, and safety is threatened, and it is possible to deal with this by not performing diagnosis. In the flowchart of fig. 6, in S04, the control unit 40 determines whether or not the voltage at the time of starting the diagnosis is within the range from the lower limit value to the upper limit value. When the determination of "yes" is made in step S04, the control unit 40 then determines in S05 that diagnosis is to be performed. When the determination of "no" is made in S04, the control unit 40 determines in S06 that the diagnosis is not to be performed.

< processing of System in which other device is connected to DC bus >

As shown in fig. 7, it is assumed that another device 19 is connected in parallel to the smoothing capacitor 50 and between the direct-current bus Lp and the ground line Ln so as to be closer to the inverter 30 than the power supply relay 15. The other devices 19 are, for example, dc-dc converters, air conditioning compressors, etc. In such a system, when the other device 19 is started after the power supply relay 15 is turned on, the electric charge in the smoothing capacitor 50 is consumed by the other device 19, and therefore, a correct determination cannot be made in the abnormality determination. Therefore, it is necessary to stop the start of the other device 19 before the opening of the power supply relay 15. The specific configuration of the connection with the boost converter will be described later with respect to the seventh embodiment and the eighth embodiment.

As described above, in the abnormality determination system 901 of the present embodiment, after the opening of the power supply relay 15, when it is determined that the voltage Vc of the smoothing capacitor detected during the execution of the turn-off function has dropped, the abnormality determination portion 45 determines that the turn-off function is abnormal. Since the abnormality of the shut-off function is determined based only on the capacitor voltage Vc without using the current values of the current sensor 72 and the current sensor 73 as in the conventional technique described in japanese patent No. 5287705, even if an approximately zero sticking failure occurs in at least one of the current sensor 72 and the current sensor 73, the abnormality diagnosis of the shut-off function can be appropriately performed.

In the abnormality determination system 901, when it is determined that the capacitor voltage Vc is maintained for the period between the start of the discharge process and the start of the shutdown function, the abnormality determination portion 45 determines that the discharge function of the inverter 30 is abnormal. Performing the shutdown function diagnosis after checking that the discharge function is normal makes it possible to avoid an erroneous determination that the shutdown function is normal regardless of whether the shutdown signal SO is abnormal.

(second embodiment)

Fig. 8 shows a second embodiment different from the first embodiment in a configuration for detecting a change in capacitor voltage. The abnormality determination system 902 in the second embodiment includes a current sensor 52 instead of the voltage sensor 51 shown in fig. 1 and 2. The current sensor 52 is provided on the dc bus Lp between the smoothing capacitor 50 and the bridge circuit 60 to detect the current Ic flowing from the high potential electrode of the smoothing capacitor 50. Since the current Ic flowing from the high potential electrode of the smoothing capacitor 50 to the bridge circuit 60 is correlated with the capacitor voltage Vc, a change in the capacitor voltage Vc is indirectly detected in this structure.

Specifically, when the output value of the current sensor 52 is about 0A, "no voltage drop" is determined, that is, a determination of "no" is made in S23 shown in fig. 4, and it is determined that the shutdown function is normal. On the other hand, when the output value of the current sensor 52 is not about 0A, it is determined that "there is a voltage drop", that is, a determination of "yes" is made in S23 shown in fig. 4, and it is determined that the shutdown function is abnormal. In this way, in the second embodiment, the abnormality diagnosis of the shutdown function can be performed as in the first embodiment.

However, in the case of an adhesion failure of the current sensor 52, an abnormality of the shutdown function may be erroneously determined. Therefore, in order to prevent such an erroneous determination, it is preferable to check whether or not the current sensor 52 outputs a current value during discharging before the shutdown function is activated. In the following embodiments, the capacitor voltage Vc may be detected by a method using the voltage sensor 51 as in the first embodiment or a method using the current sensor 52 as in the second embodiment.

(third embodiment)

A third embodiment is described with reference to fig. 9 to 11. As shown in fig. 9, a plurality of off signals are used in the abnormality determination system 903 in the third embodiment. The control unit 40 includes: a main microcomputer 42, the main microcomputer 42 performing centralized control of the inverter 30; a motor control microcomputer 43, the motor control microcomputer 43 performing control related to driving of the motor 80; or circuit 47; and circuit 48. The main microcomputer 42 includes an abnormality determination section 45, and the motor control microcomputer 43 includes a gate command section 44.

When the power supply relay 15 is opened, a diagnostic command from the vehicle control unit 20 is transmitted to the main microcomputer 42 of the control unit 40 via CAN communication. Based on this, the main microcomputer 42 generates A main off signal SO-A, and the motor control microcomputer 43 generates A motor control off signal SO-B. In addition, the vehicle control unit 20 transmits a vehicle control unit control signal SO-C. The OR circuit 47 outputs an open signal indicating "OFF signal present" when any one or more of the main OFF signal SO-A, the motor control OFF signal SO-B, and the vehicle control unit control signal SO-C are input.

When the drive signal DR is input from the motor control microcomputer 43 and no open-circuit signal is input from the or circuit 47, the and circuit 48 outputs the drive signal DR to the bridge circuit 60. On the other hand, when the or circuit 47 inputs the open signal to the and circuit 48, the and circuit 48 does not output the drive signal DR to the bridge circuit 60, thereby activating the shutdown function.

The plurality of shut down signals SO-A, SO-B and SO-C are redundantly generated by the plurality of microcomputers 42 and 43 of the control unit 40 and the vehicle control unit 20, SO that even when the generation of any shut down signal fails, the shut down function can be realized by the other shut down signals. This improves the reliability of ensuring the shutdown function.

The flow chart in fig. 10 and the timing chart in fig. 11 show the diagnostic process with multiple off signals. When the power supply relay is turned on in S01 shown in fig. 10, the control unit 40 starts discharging of the smoothing capacitor in S02, and performs a discharging function diagnosis in S10. Next, the control unit 40 performs the off function diagnosis of the main off signal SO-A in S20A, the off function diagnosis of the motor control off signal SO-B in S20B, and the off function diagnosis of the vehicle control unit off signal SO-C in S20C. When the diagnostic function diagnosis of all off signals is completed, the abnormality diagnosis is completed in S30.

When a plurality of off signals are simultaneously subjected to abnormality diagnosis, if any abnormality is detected, it is impossible to identify which off signal is abnormal. This is called "anomaly detection interference". In the conventional technique described in japanese patent No. 5287705, for example, it is not recognized which of the emergency shutdown command HSDN from the HV-ECU or the shutdown commands HSDN1# and HSDN2# from the control unit is abnormal. That is, the abnormality detection disturbance of a plurality of off commands is not considered.

In contrast, in the third embodiment, the control unit 40 sequentially performs the diagnosis of the off signals SO-A, SO-B and SO-C. Each shut down signal is off when the signal is not diagnosed. That is, during the period in which each of the off signals is applied in a mutually exclusive manner, the abnormality determination section 45 determines an abnormality in the plurality of off signals SO-A, SO-B, SO-C based on the voltage drop in the smoothing capacitor 50. Therefore, abnormality detection interference can be avoided.

As indicated by reference numeral "OL" in fig. 11, the on periods of the off signals preferably continuously overlap with each other. This is because, if any off period of the off signal occurs, the discharge is advanced to drop the capacitor voltage Vc, thereby narrowing the width of the voltage drop to be diagnosed. When all of the shutdown signals SO-A, SO-B and SO-C are normal, the capacitor voltage Vc is maintained at a constant value Vcs from time t2 to time t 3.

Although any off signal may be diagnosed first, it is preferable that the off signal of the control unit or the microcomputer is turned on first to make a judgment on the "discharge function diagnosis". This shortens the communication delay time from the completion of the "discharge function diagnosis" to the turning-on of the off signal. Therefore, it is possible to prevent unnecessary discharge of the smoothing capacitor 50 as much as possible and to increase the width of the voltage drop diagnosed in the subsequent diagnosis.

(fourth embodiment)

Next, a configuration example of an abnormality determination system including a plurality of inverters as a fourth embodiment will be described with reference to fig. 12 to 14. As shown in fig. 12, an abnormality determination system 904 in the fourth embodiment has a plurality of inverters 301 and 302 connected in parallel with a battery 10. The first inverter 301 supplies electric power to the first electric motor 801, and the second inverter 302 supplies electric power to the second electric motor 802. The first motor 801 and the second motor 802 may be configured as a double-winding motor. The fourth embodiment can also be applied to a system including three or more inverters in the same manner.

For the reference numerals of the elements shown in fig. 12, a numeral "1" is appended to the end of the reference numerals of the elements of the first inverter 301, and a numeral "2" is appended to the end of the reference numerals of the elements of the second inverter 302. The dc voltage of the battery 10 is input to the bridge circuit 601 of the inverter 301 and the bridge circuit 602 of the inverter 302 through a branch point B in the dc bus Lp. The power supply relay 15 is provided on the dc bus Lp closer to the battery 10 than the branch point B to the inverters 301 and 302.

The shutdown signal is input to the control unit 401 of the inverter 301 and the control unit 402 of the inverter 302 to shut down the respective inverters. Fig. 13 shows the input/output configuration of shutdown signals in the control unit 401 of the inverter 301 and the control unit 402 of the inverter 302. Fig. 13 shows a configuration using a plurality of shutdown signals for each inverter, consistent with the configuration of the third embodiment shown in fig. 9. Alternatively, the fourth embodiment may be configured to use one shutdown signal for each inverter, consistent with the configuration of the first embodiment shown in fig. 3. The main microcomputers 421 and 422 include abnormality determination sections 451 and 452, respectively, and the motor control microcomputers 431 and 432 include gate command sections 441 and 442, respectively.

When the power supply relay 15 is turned on, the vehicle control unit 20 transmits a diagnostic command to the main microcomputer 421 of the control unit 401 and the main microcomputer 422 of the control unit 402 via CAN communication. Based on this, the main microcomputers 421 and 422 generate main off signals SO-A1 and SO-A2, respectively, and the motor control microcomputers 431 and 432 generate motor control off signals SO-B1 and SO-B2, respectively. In addition, the vehicle control unit 20 transmits vehicle control unit control signals SO-C1 and SO-C2 to the control units 401 and 402. When any off signal is input to the or circuits 471 and 472, the and circuits 481 and 482 output the off signal to the bridge circuits 601 and 602 in preference to the drive signals DR1 and DR 2.

Fig. 14 shows a flowchart of a diagnostic process in the fourth embodiment. Reference numerals S100 and S200 in fig. 14 indicate respective steps of "inverter diagnosis", including abnormality diagnosis of the discharge process and shutdown function of the first inverter 301 and the second inverter 302. In the fourth embodiment, after the power supply relay 15 is turned on, the discharge process and the abnormality diagnosis of the shutdown function of the inverters 301 and 302 are sequentially performed one by one.

When the power relay 15 is opened in S01, the control unit 401 of the first inverter 301 first performs diagnosis of the first inverter in S100, and completes the diagnosis of the first inverter in S130. Next, the control unit 402 of the second inverter 302 performs diagnosis of the second inverter in S200, and completes diagnosis of the second inverter in S230. The diagnostic sequence of inverters 301 and 302 can be changed.

In the system configuration of the fourth embodiment, the high potential electrodes of the smoothing capacitors 501, 502 of the plurality of inverters 301, 302 are connected to each other via the direct current bus Lp, and the low potential electrodes thereof are connected to each other via the ground line Ln. Therefore, if the shutdown function of one of the plurality of inverters 301 and 302 is normal and the shutdown function of the other is abnormal, performing the abnormality diagnosis of the inverters at the same time will cause a current to flow from the normal inverter to the abnormal inverter. Therefore, it becomes difficult to independently detect and correctly lower the capacitor voltages Vc1 and Vc2 of the inverter.

In the following description, a phenomenon in which a current flows between a plurality of inverters through the dc bus Lp to confuse the capacitor voltages Vc1 and Vc2 will be referred to as "capacitor voltage disturbance". In addition, the influence of this phenomenon on the abnormality detection of the inverters 301 and 302 will be referred to as "abnormality detection disturbance".

According to the conventional technique in japanese patent No. 5287705, in a system configuration in which a common system main relay is provided for a plurality of inverters immediately after an electric power storage device, motor currents MCRT1 and MCRT2 of the inverters are input to a current detection section without distinguishing timings. That is, abnormality detection interference between a plurality of inverters is not taken into consideration. In contrast, in the fourth embodiment, the inverters 301 and 302 are diagnosed one by one in sequence, so that it is possible to avoid the disturbance of the abnormality detection caused by the disturbance of the capacitor voltage Vc and to perform the correct diagnosis.

(fifth embodiment)

Fig. 15 is a flowchart showing a diagnostic process of the fifth embodiment as another example of abnormality diagnosis in a system including a plurality of inverters as in the fourth embodiment. As for the system configuration in the fifth embodiment, fig. 12 and 13 will be referred to in common with the fourth embodiment. The control unit 401 of the inverter 301 and the control unit 402 of the inverter 302 perform abnormality diagnosis of the discharge process and the shutdown function of one or more inverters sequentially selected corresponding to one relay opening action.

In fig. 15, step number "S01-1" indicates a first opening action of the power supply relay 15 with reference to a certain point in time, and "S01-2" indicates a second opening action of the power supply relay 15 after the power supply relay 15 is closed once. For example, the time when the vehicle stops operating and the ready state is turned off for the first time corresponds to S01-1, then the ready state is turned on again and the vehicle travels, and the time when the vehicle stops and then the ready state is turned off for the second time corresponds to S01-2.

When the power supply relay 15 is turned on for the first time in S01-1, the control unit 401 of the first inverter 301 performs diagnosis of the first inverter in S100, and completes the diagnosis of the first inverter in S130. Then, the power supply relay 15 is closed in S09. Thereafter, when the power supply relay 15 is opened for the second time in S01-2, the control unit 402 of the second inverter 302 performs diagnosis of the second inverter in S200, and completes the diagnosis of the second inverter in S230. The diagnostic sequence of inverters 301 and 302 can be changed.

In the fifth embodiment, as in the fourth embodiment, abnormality detection disturbance at the time of diagnosis of the plurality of inverters 301 and 302 can be avoided. Also in the fifth embodiment, the dischargeable charge capacity amount of each inverter at one diagnosis increases, which makes it possible to secure a wide range of voltage drop for diagnosis. This widens the range of vehicle systems for which the diagnostics are applicable.

In a system including a plurality of inverters, the fourth embodiment and the fifth embodiment may be combined together to perform abnormality diagnosis. For example, when six inverters are to be diagnosed in turn, two of them may be diagnosed in turn at each relay opening action, so that the diagnosis of the six inverters is completed by three relay opening actions.

(sixth embodiment)

Fig. 16 shows another configuration example of an abnormality determination system including a plurality of inverters as a sixth embodiment. The abnormality determination system 906 in the sixth embodiment includes a plurality of inverters 301 and 302 and a plurality of power supply relays 151 and 152. The power supply relays 151 and 152 are disposed closer to the inverters 301 and 302 than the branch point B in the dc bus Lp, and can cut off the supply of electric power from the battery 10 to the respective bridge circuits 601 and 602 of the inverters 301 and 302. That is, the system configuration avoids anomaly detection interference.

In the abnormality determination system 906, the abnormality diagnosis of the discharge process and the shutdown function can be independently performed at the same time for each inverter corresponding to the turned-on power supply relay. Therefore, unlike the fourth and fifth embodiments, it is not necessary to perform the abnormality diagnosis of the discharge process and the shutdown function of the inverters 301 and 302 at different timings, thereby shortening the diagnosis time.

(seventh embodiment)

Next, an abnormality determination system 907 in a seventh embodiment in which a boost converter 18 is provided between the battery 10 and one inverter 30 will be described with reference to fig. 17. The boost converter 18 is constituted by a known chopper circuit or the like including an inductor and a switching element, and boosts the voltage of the battery 10 by a switching action and outputs the voltage to the inverter 30. The pre-converter capacitor 17 is provided on the battery 10 side of the boost converter 18, separately from the smoothing capacitor 50 of the inverter 30. However, the pre-converter capacitor 17 is not related to the "capacitor voltage Vc" for abnormality diagnosis. The boost converter 18 corresponds to an example of "another device 19" shown in fig. 7.

The abnormality determination system 907 performs abnormality diagnosis of the shutdown function of one inverter 30 by the method according to the first to third embodiments. In this case, the abnormality determination system 907 stops the switching operation of the boost converter 18 before performing the abnormality diagnosis of the shutdown function. This eliminates the influence of the voltage rise and current consumption of the boost converter 18 on the capacitor voltage Vc.

(eighth embodiment)

Next, an abnormality determination system 908 in an eighth embodiment in which a boost converter 18 is provided between a battery 10 and a plurality of inverters 301 and 302 will be described with reference to fig. 18 and 19. The configuration shown in fig. 18 is equivalent to the configuration in which the boost converter 18 is provided between the power supply relay 15 and the branch point B in the direct current bus Lp in the abnormality determination system 904 of the fourth embodiment shown in fig. 12.

The abnormality determination system 908 performs the abnormality diagnosis and shutdown functions of the plurality of inverters 301 and 302 by the method consistent with the fourth to sixth embodiments. In this case, the abnormality determination system 908 stops the switching action of the boost converter 18 before performing the abnormality diagnosis of the shutdown function. This eliminates the influence of the voltage rise and current consumption of the boost converter 18 on the capacitor voltages Vc1 and Vc 2.

As shown in fig. 19, in the abnormality determination system 908, the inverter to be diagnosed may be limited to one of the inverters (e.g., the first inverter 301). When the inverter to be diagnosed is limited to one inverter, the abnormality judgment system 908 performs abnormality diagnosis of the shutdown function by the method consistent with the first to third embodiments. In this case as well, the abnormality determination system 908 stops the switching action of the boost converter 18 before performing the abnormality diagnosis of the shutdown function. This eliminates the influence of the voltage rise and current consumption of the boost converter 18 on the capacitor voltage Vc 1.

(other embodiments)

(a) In the foregoing embodiment, the vehicle control unit 20 and the control unit 40 of the inverter 30 cooperate to realize the discharge process and the shutdown function. In this case, which functions are performed by which device can be appropriately designed. For example, the control unit 40 may directly operate the power supply relay 15. Alternatively, the vehicle control unit 20 may include the function of "a control unit of an inverter".

(b) The supply source of the direct current power supply is not limited to the battery but may be a double-layer capacitor, a converter that rectifies alternating current and outputs direct current, or the like. Alternatively, a boost converter may be provided between the battery and the inverter, as in the system described in japanese patent No. 5287705.

(c) The abnormality determination system of the present disclosure may not necessarily be applied to an inverter that supplies electric power to a motor of a vehicle, but may be applied to an inverter that supplies electric power to a rotating electrical machine for any other purpose. In this case, instead of the "vehicle control unit" in the above-described embodiment, a "centralized control unit" that manages the operation of the entire system including the inverter and its peripheral devices may issue a discharge instruction or a diagnosis instruction.

It should be noted that the present disclosure is not limited to the above-described embodiments, but may be implemented in various ways without departing from the spirit of the present disclosure.

The control units and methods described in this disclosure may be implemented by a special purpose computer, provided by constructing a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit and the control method described in the present disclosure may be implemented by a special purpose computer provided by constituting a processor by one or more dedicated hardware logic circuits. As another alternative, the control units and control methods described in this disclosure may be implemented by one or more special purpose computers comprising a combination of a processor and memory programmed to perform one or more functions and a processor comprised of one or more hardware logic circuits. In addition, the computer program may be stored in a non-transitory tangible recording medium readable by a computer as instructions executed by the computer.

Hereinafter, one aspect of the above-described embodiments will be summarized.

The abnormality determination system of the present disclosure includes at least one inverter (30) and at least one power supply relay (15). The inverter includes: a bridge circuit (60) in which a plurality of switching elements (61 to 66) are bridged; a smoothing capacitor (50), the smoothing capacitor (50) being provided at an input portion of the bridge circuit; and a control unit (40), wherein the control unit (40) controls the driving of the bridge circuit. The inverter converts direct current input from a direct current power supply (10) to a bridge circuit into alternating current, and supplies the alternating current to a rotating electrical machine (80). The power supply relay is provided between the direct-current power supply and the smoothing capacitor, and is capable of cutting off the supply of electric power from the direct-current power supply to the bridge circuit.

The control unit includes a gate command section (44), a signal switching section (48), and an abnormality determination section (45). The gate command section generates a drive signal for driving gates of a plurality of switching elements in the bridge circuit. The signal switching section outputs a drive signal to the bridge circuit when the drive signal is input and a turn-off signal for stopping gate driving of a plurality of switching elements of the bridge circuit is not input. When a shutdown signal is input, the signal switching section stops the output of the drive signal and starts the shutdown function of the inverter. The abnormality determination section determines an abnormality in the shutdown function.

When the power supply relay is turned on, the control unit drives the bridge circuit to start a discharging process of discharging electric charges from the smoothing capacitor, and starts a turn-off function during execution of the discharging process. The abnormality determination portion determines that the shutdown function is abnormal when it is determined that the voltage (Vc) of the smoothing capacitor detected directly or indirectly during the operation of the shutdown function has dropped. The "indirect detection" is, for example, detection of a current flowing from the high potential electrode of the smoothing capacitor to the bridge circuit, that is, detection of a voltage of the smoothing capacitor.

In the abnormality determination system of the present disclosure, unlike the conventional technique described in japanese patent No. 5287705, the abnormality of the shutdown function is determined based on only the voltage drop of the smoothing capacitor without using the current value of the current sensor. This allows the shutdown function to make an appropriate abnormality diagnosis even if the current sensor of one or more phases is in an approximately zero sticking failure.

In the conventional technique described in japanese patent No. 5287705, it is not specified which one of the plurality of off commands is abnormal. In addition, in the system configuration in which the common system main relay is provided in the plurality of inverters immediately after the power storage device, the motor current of the inverter is input to the current detection portion without distinguishing the timing. That is, abnormality detection disturbances of a plurality of shutdown commands or abnormality detection disturbances between a plurality of inverters are not considered. In contrast to this, in the present disclosure, when a plurality of shutdown signals are subjected to abnormality diagnosis or when a plurality of inverters are subjected to abnormality diagnosis, it is desirable to move the timing of the diagnosis to avoid abnormality detection interference.