Abnormality determination method of power converter and abnormality determination system of power converter

Abstract

To provide an abnormality determination method of a power converter capable of determining abnormality of the power converter without rotating a motor, and an abnormality determination system of the power converter.SOLUTION: In an abnormality determination method of a power converter in which multiple serial circuits in which two switching elements are connected in series are connected in parallel with respect to a battery 1, a connection middle point of one of the two switching elements in the serial circuit and the other switching element is connected to a motor 4, and power is supplied and received between the battery 1 and the motor 4 by controlling an operation of the two switching elements, remaining switching elements other than the selected single switching element in the multiple serial circuits are made an off state, a current value flowing through the serial circuits or the motor 4 when the selected single switching element is switched from the off state to an on state is measured, and presence / absence of abnormality of the selected switching element is determined based on the current value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for determining an abnormality in a power conversion device and a system for determining an abnormality in a power conversion device. [Background technology]

[0002] Patent Document 1 discloses a technique for detecting a phase current flowing through a coil of a motor and determining whether an abnormality exists in an inverter (power conversion device) based on the detected phase current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-215328 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the technique disclosed in Patent Document 1 detects the value of a current supplied to a coil to drive a motor, it is not possible to determine whether an abnormality has occurred in the power conversion device when the motor is not being driven (rotating).

[0005] An object of the present invention is to provide a method for determining an abnormality in a power conversion device, and a system for determining an abnormality in a power conversion device, which are capable of determining an abnormality in the power conversion device without rotating a motor. [Means for solving the problem]

[0006] The method for determining an abnormality of a power conversion device according to the present invention is a method for determining an abnormality of a power conversion device in which a plurality of series circuits, each having two switching elements connected in series, are connected in parallel to a battery, a midpoint between one of the two switching elements in the series circuits is connected to a motor, and power is exchanged between the battery and the motor by controlling the operation of the two switching elements. In this method for determining an abnormality, one switching element is selected from the plurality of series circuits. Then, the remaining switching elements other than the selected switching element in the plurality of series circuits are turned off, and the value of a current flowing through the plurality of series circuits or the motor when the selected switching element is switched from the off state to the on state is measured, and the presence or absence of an abnormality in the selected switching element is determined based on the current value. Effect of the Invention

[0007] According to the present invention, if the selected switching element is normal, a current flows through the parasitic capacitance contained in the switching element, and if the selected switching element is abnormal, no current flows, so the difference between these two can be used to detect the presence or absence of an abnormality. Also, the current flowing through the parasitic capacitance is very small, so it does not rotate the motor. Therefore, it is possible to determine the presence or absence of an abnormality in the switching element without rotating the motor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an abnormality determination system for a power conversion device according to a first embodiment. [Diagram 2] FIG. 2 is an overall control flow of the abnormality determination system for the power conversion device according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing a current that flows through a parasitic state when a switching element (Tr1) is set to an ON state and switching elements (Tr2-Tr6) are set to an OFF state. [Figure 4] FIG. 4 is a diagram showing a state when the switching element (Tr1) is set to an OFF state in the state of FIG. [Diagram 5]FIG. 5 is a control flow of the open circuit abnormality determination of the abnormality determination system for the power conversion device of the first embodiment. [Figure 6] FIG. 6 shows a modified example of the control flow for open circuit abnormality determination in the abnormality determination system for the power conversion device of the first embodiment. [Figure 7] FIG. 7 is a time chart of the power conversion device abnormality determination system of the first embodiment, showing a case where no abnormality exists in the switching element. [Figure 8] FIG. 8 is a time chart of the power conversion device abnormality determination system of the first embodiment, showing a case where an abnormality occurs in a switching element. [Figure 9] FIG. 9 is a diagram showing the current flowing through the parasitic capacitance when the switching element (Tr1) is set to the off state in the state of FIG. 5 and then the switching element (Tr2) is set to the on state immediately thereafter in the abnormality determination system for the power conversion device of the second embodiment. [Figure 10] FIG. 10 is a flow chart (first half) of control for determining an abnormality in the power conversion device abnormality determination system according to the second embodiment. [Figure 11] FIG. 11 is a flow chart (latter stage) of control for determining an abnormality in the power conversion device abnormality determination system of the second embodiment. [Figure 12] FIG. 12 is a time chart of the power conversion device anomaly determination system of the second embodiment, showing a case where no anomaly occurs in the switching elements (Tr1, Tr2). [Figure 13] FIG. 13 is a time chart of the abnormality determination system for the power conversion device of the second embodiment, showing a case where an abnormality exists in the switching element (Tr1) and an abnormality does not exist in the switching element (Tr2). [Figure 14] FIG. 14 is a time chart of the power conversion device anomaly determination system of the second embodiment, showing a case where an anomaly occurs in the switching elements (Tr1, Tr2). [Figure 15] FIG. 15 is a schematic diagram of an abnormality determination system for a power conversion device according to the third embodiment. [Figure 16]FIG. 16 shows the current detected by the current sensor (A1) when each of the switching elements (Tr1, Tr2, Tr3, Tr4, Tr5, and Tr6) is selected and set to the on state. [Figure 17] FIG. 17 is a flow chart showing an abnormality determination control flow of the abnormality determination system for a power conversion device according to the third embodiment. [Figure 18] FIG. 18 is a schematic diagram of a modified example of the abnormality determination system for the power conversion device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] [First embodiment] 1 is a schematic diagram of an abnormality determination system for a power conversion device (inverter 3) according to the first embodiment. The abnormality determination system for a power conversion device according to the first embodiment is configured with a battery 1, a relay 2, an inverter 3 (power conversion device), a motor 4, a smoothing capacitor 5, a current sensor 6, a magnetic pole position detection sensor 7, a voltage sensor 8, a gate drive circuit 9, a motor controller 10, and a vehicle controller 11, and is mounted on an electric vehicle (or a hybrid vehicle).

[0011] The battery 1 is connected to the DC side of the inverter 3 via a relay 2 .

[0012] Relay 2 is in an on state (conductive state) when the vehicle key switch is in an on state, and in an off state (non-conductive state) when the key switch is in an off state.

[0013] The inverter 3 is composed of a plurality of switching elements (IGBTs: Insulated Gate Bipolar Transistors) (Tr1-Tr6) and feedback diodes (D1-D6).

[0014] More specifically, a U-phase series circuit is constructed by connecting in series, for example, a first parallel circuit of an NPN switching element (Tr1) and a feedback diode (D1) that connects the emitter and collector of the switching element (Tr1) to allow a current from the emitter to the collector and block the current in the reverse direction, and a first parallel circuit of a similarly connected switching element (Tr2) and feedback diode (D2). The first parallel circuit is connected to the positive electrode side of the battery 1 (smoothing capacitor 5), the second parallel path is connected to the negative electrode side of the battery 1 (smoothing capacitor 5), and the connection midpoint (UM) of the first parallel circuit and the second parallel circuit is connected to the U-phase of the motor 4.

[0015] The inverter 3 also has a V-phase series circuit and a W-phase series circuit with a configuration similar to that of the U-phase series circuit, and the U-phase series circuit, V-phase series circuit, and W-phase series circuit are connected in parallel to the battery 1 (smoothing capacitor 5). The connection midpoint (VM) of the V-phase series circuit is connected to the V-phase of the motor 4, and the connection midpoint (WM) of the W-phase series circuit is connected to the W-phase of the motor 4.

[0016] When gate signals (GUP, GUN, GVP, GVN, GWP, GWN) are input from the gate drive circuit 9, the inverter 3 converts the DC power output by the battery 1 into AC power and outputs it to the motor 4, or converts the regenerative power generated by the motor 4 into DC power and outputs it to the battery 1.

[0017] The motor 4 is, for example, a permanent magnet type three-phase synchronous motor, and is used as a power source for the vehicle.

[0018] The smoothing capacitor 5 is connected in parallel with the battery 1 between the relay 2 and the inverter 3. The smoothing capacitor 5 smoothes the DC power.

[0019] The current sensor 6 detects the currents Iu, Iv, Iw flowing through the respective phases of the motor 4, and outputs the detection signals to the motor controller 10.

[0020] The magnetic pole position detection sensor 7 is a device such as a resolver that detects the electrical angle of the motor 4 (rotor) and outputs a detection signal to the motor controller 10.

[0021] The voltage sensor 8 detects the voltage of the smoothing capacitor 5 and outputs the detection signal to the gate drive circuit 9.

[0022] The vehicle controller 11 calculates a torque command value based on the vehicle's accelerator signal, brake signal, shift position signal, etc., and outputs the calculated torque command value to the motor controller 10, and also outputs a start request command and a stop request command to the motor controller 10. The vehicle controller 11 also outputs a relay control signal for opening and closing the relay 2 based on the shift position signal, and simultaneously outputs relay opening and closing information to the motor controller 10. When the shift position signal is, for example, parking, the vehicle controller 11 outputs a relay control signal for disconnecting the relay 2 to the relay 2, and also outputs relay opening and closing information indicating that the relay 2 has been disconnected to the motor controller 10. When the shift position is, for example, other than parking, the vehicle controller 11 also outputs a relay control signal for connecting the relay 2 to the relay 2, and outputs relay opening and closing information indicating that the relay 2 has been connected to the motor controller 10.

[0023] The motor controller 10 controls the operation of the inverter 3. The motor controller 10 generates a pulse width modulation (PWM) signal based on a torque command value input from the vehicle controller 11, and outputs this to the gate drive circuit 9.

[0024] The gate drive circuit 9 controls the on / off of each switching element (Tr1-Tr6) constituting the inverter 3 at a predetermined timing based on a PWM signal input from the motor controller 10. The gate drive circuit 9 also has a function of detecting an overheating abnormality or an overcurrent abnormality state of the switching elements (Tr1-Tr6) and outputting an IGBT abnormality signal to the motor controller 10.

[0025] [Overall control flow of the anomaly detection system] 2 is an overall control flow of the abnormality determination system for the power conversion device (inverter 3) of the first embodiment. The abnormality determination system for the power conversion device (inverter 3) of the present embodiment is controlled by the motor controller 10, for example.

[0026] In step S101, the motor controller 10 determines whether or not the relay 2 has been disconnected based on the relay open / close information input from the vehicle controller 11. If YES, the process proceeds to step S102, and if NO, the process remains in step S101.

[0027] In step S102, the motor controller 10 determines whether the motor rotation speed calculated from the detection signal of the magnetic pole position detection sensor 7 has become lower than a predetermined value (the rotation speed at which the motor is considered to have stopped), and if the answer is YES, the process proceeds to step S103, and if the answer is NO, the process remains in step S102.

[0028] In step S103, the motor controller 10 determines whether the voltage of the smoothing capacitor 5 represented by the voltage sensor signal input from the voltage sensor 8 is higher than the determinable voltage required to execute the subsequent step S104, and if the result is YES, proceeds to step S104, and if the result is NO, proceeds to END.

[0029] In step S104, the motor controller 10 executes an open circuit abnormality determination for the switching elements (Tr1-Tr6). The details of the open circuit abnormality determination will be described later.

[0030] In step S105, the motor controller 10 determines whether or not an open abnormality occurs in any of the switching elements (Tr1-Tr6) based on the open abnormality determination in step S104.

[0031] In step S106, the motor controller 10 stops the gate drive circuit 9 if an open abnormality is detected in step S105.

[0032] [How to determine open abnormality] Fig. 3 is a diagram showing the current flowing through the parasitic state when the switching element (Tr1) is set to the ON state and the switching elements (Tr2-Tr6) are set to the OFF state. Fig. 4 is a diagram showing the state when the switching element (Tr1) is set to the OFF state in the state of Fig. 3.

[0033] As shown in FIG. 3, the switching elements (Tr1-Tr6) and the feedback diodes (D1-D6) each have a parasitic capacitance (C1-C6), and when the smoothing capacitor 5 is discharged, a transient current, that is, a current until the parasitic capacitance stores a charge, or a current when the charge stored in the parasitic capacitance is discharged, flows through the parasitic capacitance (C1-C6).

[0034] 3 and 4 show a case where there is no open circuit abnormality in the switching elements (Tr1-Tr6). Note that the switching elements (Tr1, Tr3, Tr5) may be called the first switching elements, and the switching elements (Tr2, Tr4, Tr6) may be called the second switching elements.

[0035] For example, as shown in FIG. 3, when switching element (Tr1) is turned on and other switching elements (Tr2-Tr6) are turned off, a current flows through inverter 3 in such a manner that the charges of smoothing capacitor 5, the charge of the parasitic capacitance (C1) of switching element (Tr1), the charge of the parasitic capacitance (C3) of switching element (Tr3), and the charge of the parasitic capacitance (C5) of switching element (Tr5) flow toward switching element (Tr1).

[0036] At this time, the U phase of the motor 4 has a higher potential than the V and W phases, so that a current flows from the U phase to the V and W phases. However, since this current is very small, it does not cause the motor 4 to rotate.

[0037] In addition, since the second switching elements (Tr2, Tr4, Tr6) are all in the off state, a current flows to the smoothing capacitor 5 through the parasitic capacitance (C2) of the switching element (Tr2), the parasitic capacitance (C4) of the switching element (Tr4), and the parasitic capacitance (C6) of the switching element (Tr6), and charge is stored in the parasitic capacitance (C2), the parasitic capacitance (C4), and the parasitic capacitance (C6).

[0038] Thereafter, as shown in Fig. 4, when the switching element (Tr1) is turned off, all switching elements (Tr1-Tr6) are turned off, and no current flows through the inverter 3. However, since the charges stored in the parasitic capacitances (C2), (C4), and (C6) are very small, these charges are naturally discharged. Therefore, by repeating the states shown in Fig. 3 and Fig. 4, it is possible to cause a current to flow through the inverter 3 by discharging the charge of the smoothing capacitor 5 through the parasitic capacitances (C1-C6).

[0039] Here, if the capacitance (C) of the smoothing capacitor 5 and the voltage (V) of the smoothing capacitor 5 are used, the charge (Q) stored in the smoothing capacitor 5 is Q=CV, and the current (Icap) flowing through the smoothing capacitor 5 is Icap=C(dV / dt). Here, dV / dt can be regarded as the amount of voltage change (ΔV, described later), so the current (Icap) flowing through the smoothing capacitor 5 can be calculated simply from the amount of voltage change in the smoothing capacitor 5.

[0040] In addition, if it is considered that the switching elements (Tr1-Tr6) and feedback diodes (D1-D6) have the same characteristics and that the parasitic capacitances (C1-C6) are also the same, the current flowing through the selected switching element is Icap×2.

[0041] In addition, in FIG. 3, the current flowing through the U phase (Iu), the current flowing through the V phase (Iv), and the current flowing through the W phase (Iw) are Iu+Iv+Iw=0, but if we consider the characteristics to be identical as described above, then |Iu|=2|Iv|=2|Iw|.

[0042] On the other hand, if the selected switching element (Tr1) has an open circuit abnormality, the switching element (Tr1) will not be turned on even if the gate signal (GUP) of the switching element (Tr1) is set to HIGH (high potential). Therefore, as shown in Fig. 3, the charge of the smoothing capacitor 5 and the charge of the parasitic capacitances (C1, C3, C5) of the switching element (Tr1) will not flow into the switching element (Tr1), and as a result, no current will flow to the smoothing capacitor 5 via the parasitic capacitances (C2, C4, C6).

[0043] In addition, if an open circuit abnormality occurs in a non-selected switching element (any of Tr2 to Tr6), the current flowing through the inverter 3 is not affected because the non-selected switching element is set to the off state in the first place.

[0044] As described above, when the selected switching element is normal, a current flows through the inverter 3, and when the selected switching element is abnormal, no current flows through the inverter 3. Therefore, it is possible to determine whether or not the selected switching element has an abnormality by utilizing this current difference. In the prior art, it was necessary to rotate the motor 4 to detect an open abnormality in the switching element. In this case, when the vehicle starts driving from a stopped state, the determination of the open abnormality is delayed, and the motor 4 does not rotate because a starting torque cannot be generated, or the motor 4 is rotated in an open abnormality state, which may cause unexpected vibrations and noise, causing discomfort to the driver. However, in this embodiment, the presence or absence of an open abnormality in the switching element is determined without rotating the motor 4, i.e., before starting the vehicle, so that the discomfort caused to the driver can be reduced.

[0045] Even if there is an abnormality in the selected switching element, a small amount of current may flow through the parasitic capacitances (C1-C6) due to variations in the characteristics of the switching elements (Tr1-Tr6) and feedback diodes (D1-D6), fluctuations in the neutral point potential of the motor 4, etc.

[0046] Therefore, in this embodiment, the voltage change (ΔV) of the smoothing capacitor 5 is obtained after repeatedly switching the selected switching element between the on and off states a predetermined number of times, so that the voltage change (ΔV) caused by the characteristics of the inverter 3 and the motor 4 and the voltage change (ΔV) caused by an open abnormality in the switching element can be easily distinguished.

[0047] Furthermore, in this embodiment, the current value flowing through the inverter 3 is obtained each time the selected switching element is switched between the on and off states, and the sum of the current values ​​is calculated by repeatedly switching the switching element between the on and off states a predetermined number of times, making it possible to easily distinguish between the sum of the current values ​​resulting from the characteristics of the inverter 3 and the motor 4 and the sum of the current values ​​resulting from an open abnormality in the switching element.

[0048] When the vehicle system is stopped, the smoothing capacitor 5 can be discharged by using the parasitic capacitances (C1-C6). For example, all the first switching elements (Tr1, Tr3, Tr5) are set to the ON state, and all the second switching elements (Tr2, Tr4, Tr6) are set to the OFF state. Then, since all the first switching elements are in the ON state, a current flows through all the first switching elements, and the charge stored in the parasitic capacitances (C1, C3, C5) is discharged. Then, since the U phase, V phase, and W phase are at the same potential with respect to the motor 4, no voltage is applied to the motor 4, and no current flows through the motor 4. On the other hand, since all the second switching elements are in the OFF state, a current flows so that the parasitic capacitances (C2, C4, C6) are charged. Then, the generation of the above current discharges the smoothing capacitor 5.

[0049] Next, all the first switching elements (Tr1, Tr3, Tr5) are set to the OFF state, and all the second switching elements (Tr2, Tr4, Tr6) are set to the ON state. Then, since all the second switching elements are in the ON state, a current flows through all the second switching elements, and the charge stored in the parasitic capacitances (C2, C4, C6) is discharged. Then, since the U phase, V phase, and W phase are at the same potential with respect to the motor 4, no voltage is applied to the motor 4, and no current flows through the motor 4. Meanwhile, since all the first switching elements are in the OFF state, a current flows so that the parasitic capacitances (C1, C3, C5) are charged. Then, the generation of the above-mentioned current discharges the smoothing capacitor 5.

[0050] Therefore, by repeatedly switching between the on and off states of all of the first switching elements (Tr1, Tr3, Tr5) and all of the second switching elements (Tr2, Tr4, Tr6) in a manner such that the on / off oscillations of all of the first switching elements (Tr1, Tr3, Tr5) and all of the second switching elements (Tr2, Tr4, Tr6) are in opposite phase to each other, a current flows through the inverter 3 via the parasitic capacitances (C1-C6), generating heat and discharging the charge in the smoothing capacitor 5.

[0051] [Control flow of open circuit abnormality determination in the first embodiment] 5 is a control flow of open circuit abnormality determination of the abnormality determination system of the power conversion device (inverter 3) of Embodiment 1. In the first embodiment, the open circuit abnormality determination of step S104 in FIG. 2 is composed of steps S201 to S213 shown in FIG.

[0052] In step S201, the motor controller 10 selects a switching element (X) (X: any one of Tr1-Tr6) for which an open circuit abnormality determination is to be performed from the switching elements (Tr1-Tr6). The order in which the switching elements (X) are selected can be set arbitrarily. For example, when the selected switching element (X) is the switching element (Tr1), the gate signal (GUP) is set to a HIGH (high potential) or LOW (low potential) state.

[0053] In step S202, the motor controller 10 sets the non-selected switching elements to the OFF state. For example, when the selected switching element (X) is the switching element (Tr1), the gate signals (GUN, GVP, GVN, GWP, GWN) are set to LOW (low potential).

[0054] In step S203, the motor controller 10 acquires the voltage value detected by the voltage sensor 8 as the initial value (V0) of the voltage of the smoothing capacitor 5 before the abnormality is determined.

[0055] In step S204, the motor controller 10 sets the switching element (X) to the ON state. At this time, as described above, a current flows through the parasitic capacitances (C1-C6) of the switching elements (Tr1-Tr6) and the like, and the smoothing capacitor 5 is discharged.

[0056] In step S205, the motor controller 10 sets the switching element (X) to the OFF state.

[0057] In step S206, the motor controller 10 counts up the number of switching operations k.

[0058] In step S207, the motor controller 10 determines whether the number of switching times k has reached a predetermined number, and if YES, proceeds to step S208, and if NO, proceeds to step S204. The predetermined number of times is determined in advance based on the resistance-temperature characteristics of the smoothing capacitor 5 used, the magnitude of the parasitic capacitance component of the switching element, the change over time in the voltage of the smoothing capacitor 5, and the like, but may be once or twice or more.

[0059] In step S208, the motor controller 10 calculates the voltage value detected by the voltage sensor 8 as the final value (V k ) is obtained.

[0060] In step S209, the motor controller 10 calculates the initial value (V0) and the final value (V k ) and the voltage change amount (ΔV=V0-V k ) is calculated.

[0061] In step S210, the motor controller 10 judges whether the voltage change amount (ΔV) is less than a predetermined amount. If the answer is YES, the process proceeds to step S211. If the answer is NO, the process proceeds to step S212. If the voltage change amount (ΔV) is less than the predetermined value, the flowing current (amount of charge discharged from the parasitic capacitance) is judged to be smaller than expected, and the selected switching element (X) is judged to have an open circuit abnormality (open circuit failure: not turned on, or the on state is incomplete). Conversely, if the voltage change amount (ΔV) is equal to or greater than the predetermined value, the switching element (X) is judged to be normal. The predetermined value that is the reference for the voltage change amount (ΔV) is determined in advance based on the resistance temperature characteristics of the smoothing capacitor 5 to be used, the magnitude of the parasitic capacitance component of the switching element, the time change in the voltage of the smoothing capacitor 5, and the like, in the same manner as the predetermined number of times described above.

[0062] In step S211, the motor controller 10 determines that an abnormality has occurred in the switching element (X).

[0063] In step S212, the motor controller 10 determines that there is no abnormality in the switching element (X).

[0064] In step S213, the motor controller 10 judges whether the open circuit abnormality judgment of all the switching elements is completed. If the result is YES, the process proceeds to END. If the result is NO, the process proceeds to step S201. When the open circuit abnormality judgment is completed, the motor controller 10 outputs judgment information to the vehicle controller 11. The judgment information is, for example, information having the same number of digits (6) as the number of switching elements (Tr1-Tr6) and arranged in the order of the switching elements (Tr1-Tr6), and for example, each digit displays "1" when there is an open circuit abnormality and displays "0" when there is no open circuit abnormality. For example, when there is an open circuit abnormality in the switching element (Tr1) and there is no open circuit abnormality in the other switching elements (Tr2-Tr6), the judgment information is "100000". When the vehicle controller 11 receives the judgment information "100000", it displays on the display panel for the driver of the vehicle that there is an open circuit abnormality in the switching element (Tr1).

[0065] [Modification of the control flow for determining an open abnormality in the first embodiment] 6 is a modified control flow of open circuit abnormality determination in the abnormality determination system for the power conversion device (inverter 3) of the first embodiment. In the first embodiment, the modified control flow of the open circuit abnormality determination in step S104 in FIG. 2 is composed of steps S301 to S316 shown in FIG.

[0066] In step S301, the motor controller 10 selects a switching element (X) (X: any one of Tr1-Tr6) for which an open abnormality determination is to be performed from the switching elements (Tr1-Tr6).

[0067] In step S302, the motor controller 10 sets the non-selected switching elements to the OFF state.

[0068] In step S303, the motor controller 10 counts up the number of switching operations k.

[0069] In step S304, the motor controller 10 sets the switching element (X) to the ON state.

[0070] In step S305, the motor controller 10 determines whether the selected switching element (X) is the switching element (Tr1) or the switching element (Tr2), and if YES, proceeds to step S307, and if NO, proceeds to step S306.

[0071] In step S306, the motor controller 10 determines whether the selected switching element (X) is the switching element (Tr3) or the switching element (Tr4), and if YES, proceeds to step S308, and if NO, proceeds to step S309.

[0072] In step S307, the motor controller 10 detects the current (I k ) to get the

[0073] In step S308, the motor controller 10 detects the current (I k ) to get the

[0074] In step S309, the motor controller 10 detects the current (I k ) to get the

[0075] In step S310, the motor controller 10 calculates the current (I k ) (S k =S k-1 +I k ) is calculated.

[0076] In step S311, the motor controller 10 sets the switching element (X) to the OFF state.

[0077] In step S312, the motor controller 10 determines whether the number of switching times k has reached a predetermined number of times, and if YES, the process proceeds to step S313, and if NO, the process proceeds to step S303.

[0078] In step S313, the motor controller 10 calculates the current (I k ) (S k ) absolute value (|S k |) is a given value (S th If the answer is YES, the process proceeds to step S314. If the answer is NO, the process proceeds to step S315. k ) (S k ) absolute value (|S k |) is a given value (S th ), it is determined that the current that has flowed (the amount of charge discharged from the parasitic capacitance) is smaller than expected, and the selected switching element (X) is determined to have an open circuit abnormality (open circuit failure: the switching element does not turn on, or the on circuit is incomplete). Conversely, if the current (I k ) (S k ) absolute value (|S k |) is a given value (S th ) or more, the switching element (X) is determined to be normal. k ) (S k ) absolute value (|S k The predetermined value serving as the reference for |) is determined in advance based on the resistance-temperature characteristics of the smoothing capacitor 5 to be used, the magnitude of the parasitic capacitance component of the switching element, the change in voltage of the smoothing capacitor 5 over time, and the like, similar to the predetermined number of times described above.

[0079] In step S314, the motor controller 10 determines that an abnormality has occurred in the switching element (X).

[0080] In step S315, the motor controller 10 determines that there is no abnormality in the switching element (X).

[0081] In step S316, the motor controller 10 determines whether or not the open circuit abnormality determination for all switching elements has been completed. If YES, the process proceeds to END. If NO, the process proceeds to step S301. k ) or the sum (S k When determining whether or not there is an open circuit abnormality in the switching elements (Tr1-Tr6) using the above-mentioned method, the determination is not made using the voltage of the smoothing capacitor 5, and therefore this can be performed even when the relay 2 is in a connected state.

[0082] [Time chart of the first embodiment] Fig. 7 is a time chart of the abnormality determination system of the power conversion device (inverter 3) of the first embodiment, showing a case where there is no abnormality in the switching element (Tr1). Fig. 8 is a time chart of the abnormality determination system of the power conversion device (inverter 3) of the first embodiment, showing a case where there is an abnormality in the switching element (Tr1).

[0083] 7 and 8 show a case where a switching element (Tr) is selected and alternately switched between the on and off states, and switching elements (Tr2-Tr6) are set to the off state.

[0084] As shown in Fig. 7, when there is no open circuit abnormality in the switching element (Tr1), the switching element (Tr1) repeats ON and OFF states in accordance with the gate signal (GUP: HIGH or LOW). When the switching element (Tr1) is ON, a current flows through the switching element (Tr) via the smoothing capacitor 5 and parasitic capacitances (C1, C3, C5), and the current sensor 6 detects the U-phase current (Iu), and detects the V-phase current (Iw) and W-phase current (Iw), which are in opposite phase to the U-phase and have half the absolute value. At this time, the voltage (V) of the smoothing capacitor 5 decreases, a current (Icap) flows through the smoothing capacitor 5, and the current value (I k ) (S k ) is added. When the switching element (Tr1) is in the off state, no current flows in the inverter 3.

[0085] In addition, even if there is an open circuit abnormality in switching elements (Tr2-Tr6) other than the switching element (Tr1), these switching elements (Tr2-Tr6) are set to the off state and no current flows, so there is no effect on the open circuit abnormality determination of the switching element (Tr1).

[0086] As shown in FIG. 8, when an open circuit occurs in the switching element (Tr1), the switching element (Tr1) does not turn on regardless of the gate signal (GUP: HIGH or LOW), and the current sensor 6 does not detect the current (Iu), the current (Iw), or the W-phase current (Iw). At this time, the voltage (V) of the smoothing capacitor 5 does not decrease, the current (Icap) does not flow through the smoothing capacitor 5, and the current value (I k ) (S k ) is not added.

[0087] From the above, the difference in the voltage change (ΔV) of the voltage (V) or the current value (I k The presence or absence of an open circuit anomaly can be determined by using the difference between the sums (Sk) of the

[0088] [Second embodiment] FIG. 9 is a diagram showing the current flowing through the parasitic capacitance when the switching element (Tr1) is set to the off state in the state of FIG. 5 and then the switching element (Tr2) is set to the on state immediately thereafter in the abnormality determination system for the power conversion device (inverter 3) of the second embodiment.

[0089] The configuration of the abnormality determination system for the power conversion device of the second embodiment is the same as that of the first embodiment (FIG. 1). In the second embodiment, one switching element is selected from the first switching elements (Tr1, Tr3, Tt5), one switching element is selected from the second switching elements (Tr2, Tr4, Tr6), and the on-state and the off-state of the selected first switching element and the selected second switching element are alternately repeated so that the on-off states of the selected first switching element and the selected second switching element oscillate in opposite phases to each other, thereby performing open abnormality determination for the selected first switching element and the selected second switching element.

[0090] For example, when a switching element (Tr1) is selected as the first switching element, a switching element (Tr2) is selected as the second switching element, and the first switching element (Tr1) is turned on and the second switching element (Tr2) is turned off, a current flows through the inverter 3 as in Fig. 3. Then, the current (U-phase current) that flows when the first switching element (Tr1) is set to the on state, or the voltage of the smoothing capacitor 5 is measured.

[0091] Thereafter, as shown in FIG. 9, when the first switching element (Tr1) is turned off and the second switching element (Tr2) is turned on, all of the first switching elements (Tr1, Tr3, Tr5) are turned off, and the charge in the smoothing capacitor 5 flows via the parasitic capacitances (C1, C3, C5).

[0092] At this time, since the second switching element (Tr2) is in the ON state, the U phase has a lower potential than the V and W phases for the motor 4, so the charge of the parasitic capacitance (C4) passes through the V phase, and the charge of the parasitic capacitance (C6) passes through the W phase and flows to the U phase, but the current associated with this charge is very small, so this does not cause the motor 4 to rotate. Then, the charge of the parasitic capacitances (C2, C4, C6) flows into the smoothing capacitor 5 via the second switching element (Tr2). Then, the current that flows when the second switching element (Tr2) is set to the ON state (current of the U phase) or the voltage of the smoothing capacitor 5 is measured.

[0093] When the selected switching elements (Tr1, Tr2) each have an open circuit abnormality, no current flows as shown in FIGS.

[0094] As described above, the currents that flow when the two selected switching elements are on are measured separately, and since current flows when the selected switching elements are normal and no current flows when the selected switching elements are abnormal, this current difference can be used to simultaneously determine whether or not there is an abnormality in the two selected switching elements.

[0095] [Modification of the control flow for determining an open abnormality in the second embodiment] Fig. 10 is an abnormality determination control flow (first half) of the abnormality determination system for the power conversion device (inverter 3) of the second embodiment. Fig. 11 is an abnormality determination control flow (second half) of the abnormality determination system for the power conversion device (inverter 3) of the second embodiment. In the second embodiment, a modified example of the open abnormality determination in step S104 in Fig. 2 is composed of steps S401 to S424 shown in Figs. 10 and 11.

[0096] In step S401, the motor controller 10 selects a switching element for which open abnormality determination is to be performed from the first switching elements (Tr1, Tr3, Tr5).

[0097] In step S402, the motor controller 10 selects a switching element for which open abnormality determination is to be performed from the second switching elements (Tr2, Tr4, Tr6).

[0098] In step S403, the motor controller 10 acquires the voltage value detected by the voltage sensor 8 as the initial value (V0) of the voltage of the smoothing capacitor 5 before the abnormality is determined.

[0099] In step S404, the motor controller 10 counts up the number of switching operations k.

[0100] In step S405, the motor controller 10 sets the non-selected switching elements to the OFF state.

[0101] In step S406, the motor controller 10 sets the selected first switching element to an ON state, and sets the selected second switching element to an OFF state.

[0102] In step S407, the motor controller 10 calculates the voltage value detected by the voltage sensor 8 when the selected first switching element is in the ON state as the voltage of the smoothing capacitor 5 (V1 k ) is obtained.

[0103] In step S408, the motor controller 10 calculates the voltage change amount (ΔV1 k =V2 k-1 -V1 k ) is calculated. Here, V2 k-1 is the previous value of the voltage value detected by the voltage sensor 8 when the second switching element is in the ON state, and when k=initial value (for example, 1), the previous value becomes the initial value (V0).

[0104] In step S409, the motor controller 10 calculates the voltage change amount (ΔV k =V2 k-1 -V1 k ) Sum of (S1 k =S1 k-1 +ΔV1 k ) is calculated. Here, when k = initial value (for example, 1), S1 k-1 will be zero.

[0105] In step S410, the motor controller 10 sets the selected first switching element to an OFF state, and sets the selected second switching element to an ON state.

[0106] In step S411, the motor controller 10 calculates the voltage value detected by the voltage sensor 8 when the selected second switching element is in the ON state as the voltage of the smoothing capacitor 5 (V2 k ) is obtained.

[0107] In step S412, the motor controller 10 calculates the voltage change amount (ΔV k =V1 k -V2 k ) is calculated. Here, V1 k is the voltage (V1 k ).

[0108] In step S413, the motor controller 10 calculates the voltage change amount (ΔV k =V1 k-1 -V2 k ) Sum of (S2 k =S2 k-1 +ΔV2 k ) is calculated. Here, if k = initial value (for example, 1), S2 k-1 will be zero.

[0109] In step S414, the motor controller 10 determines whether the number of switching times k has reached a predetermined number of times, and if YES, the process proceeds to step S415, and if NO, the process proceeds to step S404.

[0110] In step S415, the motor controller 10 calculates the voltage change amount (ΔV k ) Sum of (S1 k If the answer is YES, the process proceeds to step S416, and if the answer is NO, the process proceeds to step S417. The first predetermined value is determined in advance based on the resistance-temperature characteristics of the smoothing capacitor 5 to be used, the magnitude of the parasitic capacitance component of the switching element, the change in the voltage of the smoothing capacitor 5 over time, and the like, in the same manner as the predetermined number of times.

[0111] In step S416, the motor controller 10 determines that the selected first switching element has an abnormality.

[0112] In step S417, the motor controller 10 determines that there is no abnormality in the selected first switching element.

[0113] In step S418, the motor controller 10 calculates the voltage change amount (ΔV k ) Sum of (S1 k If the answer is YES, the process proceeds to step S419, and if the answer is NO, the process proceeds to step S420. The second predetermined value is determined in advance, similar to the first predetermined value.

[0114] In step S419, the motor controller 10 determines that the selected second switching element has an abnormality.

[0115] In step S420, the motor controller 10 determines that there is no abnormality in the selected second switching element.

[0116] In step S421, the motor controller 10 determines whether or not the open abnormality determination for all switching elements has been completed, and if YES, the process proceeds to END, and if NO, the process proceeds to step S401.

[0117] In the second embodiment, following the modified example of the first embodiment, the sum of the current when the first switching element is in the on state and the sum of the current when the second switching element is in the on state may be calculated, and each sum may be compared with a corresponding threshold value to individually determine whether or not an open circuit abnormality has occurred in the first switching element and whether or not an open circuit abnormality has occurred in the second switching element.

[0118] [Time chart of the second embodiment] Fig. 12 is a time chart of the abnormality determination system of the power conversion device (inverter 3) of the second embodiment, showing a case where there is no abnormality in the switching elements (Tr1, Tr2). Fig. 13 is a time chart of the abnormality determination system of the power conversion device (inverter 3) of the second embodiment, showing a case where there is an abnormality in the switching element (Tr1) but not in the switching element (Tr2). Fig. 14 is a time chart of the abnormality determination system of the power conversion device (inverter 3) of the second embodiment, showing a case where there is an abnormality in the switching elements (Tr1, Tr2).

[0119] As shown in Fig. 12, there is no open circuit abnormality in the first switching element (Tr1) and the second switching element (Tr2), and the first switching element (Tr1) alternates between on and off states according to the gate signal (GUP), and the second switching element (Tr2) alternates between on and off states according to the gate signal (GUN). Note that the gate signals (GUP) and (GUN) oscillate in opposite phases to each other.

[0120] At this time, the voltage of the smoothing capacitor 5 drops from the point where the first switching element (Tr1) is first turned on, and thereafter, even when the first switching element (Tr1) is turned off and the second switching element (Tr2) is turned on, the voltage (V) of the smoothing capacitor 5 drops. Therefore, while the first switching element (Tr1) and the second switching element (Tr2) alternate between the on state and the off state so as to oscillate in opposite phases to each other, a current (Icap) flows through the smoothing capacitor 5, and a voltage change amount (ΔV1 k ) Sum of (S1 k ) and voltage change (ΔV2 k ) Sum of (S2 k ) also increases stepwise.

[0121] On the other hand, as shown in FIG. 13, if there is an open circuit abnormality in the first switching element (Tr1), the first switching element (Tr1) will not be turned on regardless of the gate signal (GUP). Therefore, when the gate signal (GUP) is HIGH, the voltage (V) of the smoothing capacitor 5 will not drop, and when the gate signal (GUN) is HIGH, that is, when the second switching element (Tr2) is on, the voltage (V) of the smoothing capacitor 5 drops and a current (Icap) flows. Also, the amount of voltage change (ΔV2 k ) Sum of (S2 k ) increases like a step function, but the voltage change (ΔV1 k ) Sum of (S1 k ) does not increase.

[0122] Furthermore, as shown in FIG. 14, when an open circuit occurs in the first switching element (Tr1) and the second switching element (Tr2), the first switching element (Tr1) does not turn on regardless of the gate signal (GUP), and the second switching element (Tr2) does not turn on regardless of the gate signal (GUN). Therefore, regardless of the gate signals (GUP, GUN), the voltage (V) of the smoothing capacitor 5 does not decrease and the current (Icap) does not flow. In addition, the voltage change amount (ΔV2 k ) Sum of (S2 k ) and voltage change (ΔV1 k ) Sum of (S1 k ) does not increase.

[0123] [Third embodiment] Fig. 15 is a schematic diagram of an abnormality determination system for a power conversion device (inverter 3) according to the third embodiment. Fig. 16 shows a current detected by a current sensor (A1) when each of switching elements (Tr1-Tr6) is selected and set to an on state.

[0124] The configuration of the abnormality determination system for the power conversion device (inverter 3) of the third embodiment is the same as that of the first embodiment, except that a current sensor is connected in series to any one of the switching elements (Tr1-Tr6). In the third embodiment, for example, the switching element (Tr1) is a specific switching element, and a current sensor (A1) is connected in series to the specific switching element. More specifically, a second series circuit is constructed by connecting the current sensor (A1) in series to a first parallel circuit of the specific switching element (Tr1) and a feedback diode (D1), and a series circuit for the U phase is constructed by connecting a second parallel circuit of the switching element (Tr2) and a feedback diode (D2) and the second series circuit in series. A connection midpoint (UM) of the second series circuit and the second parallel circuit is connected to the U phase of the motor 4.

[0125] As the current sensor (A1), for example, a detection element for detecting a shunt current built into the switching element (Tr1) can be used, and a shunt resistor or a Hall sensor can also be used.

[0126] Although not shown, a bypass circuit is provided for the current sensor (A1), and when the shift position is other than parking (when the inverter 3 is receiving and transmitting power from the motor 4), the bypass circuit is connected to the switching element (Tr1) and the current sensor (A1) is disconnected from the switching element (Tr1), and when the shift position is parking, the current sensor (A1) is connected to the switching element (Tr1) and the bypass circuit is disconnected from the switching element (Tr1). This prevents damage to the current sensor (A1).

[0127] Here, by turning on the switching element (Tr1) and turning off the switching elements (Tr2-Tr6), charges from the smoothing capacitor 5 and the parasitic capacitances (C1, C3, C5) flow into the switching element (Tr1) (see FIG. 3). Here, the current flowing from the smoothing capacitor 5 is equivalent to the current caused by the charge of the parasitic capacitances (C2, C4, C6) flowing in, so that a current equivalent to the current flowing in when the charge of the parasitic capacitances (C1-C6) flows in the switching element (Tr1) and the current sensor (A1) can detect this current.

[0128] In addition, when any of the first switching elements (Tr3, Tr5) other than the switching element (Tr1) is turned on, the charge of the parasitic capacitance (C1) flows in, and the current sensor (A1) can detect the current at that time.

[0129] Furthermore, when any of the second switching elements (Tr2, Tr4, Tr6) is turned on, a current flows toward the parasitic capacitance (C1), and the current sensor (A1) can detect this current.

[0130] Here, similarly to the first embodiment, a case will be considered in which the switching elements (Tr1-Tr6) and feedback diodes (D1-D6) have the same characteristics and the same parasitic capacitances (C1-C6).

[0131] In this case, as shown in FIG. 16, when each of the switching elements (Tr2-Tr6) is turned on, the current values ​​detected by the current sensor (A1) are the same.

[0132] However, the direction of the current detected by the current sensor (A1) when each of the switching elements (Tr2, Tr4, Tr6) is turned on is opposite to the direction of the current detected by the current sensor (A1) when each of the switching elements (Tr3, Tr5) is turned on.

[0133] The direction of the current detected by the current sensor (A1) when the switching element (Tr1) is turned on is the same as the direction of the current detected by the current sensor (A1) when each of the switching elements (Tr2, Tr4, Tr6) is turned on. Also, as described above, the current flowing through the switching element (Tr1) is equivalent to the total current when discharging the charge of the parasitic capacitances (C1-C6), so the current value detected by the current sensor (A1) when the switching element (Tr1) is turned on is six times larger than the current value detected by the current sensor (A1) when any of the switching elements (Tr2-Tr6) is turned on.

[0134] In the third embodiment, the current flowing when the selected switching element is alternately switched between the on state and the off state is acquired by a current sensor (A1), and the presence or absence of an open circuit abnormality in the selected switching element is detected by calculating the total current when the operation of alternately switching the selected switching element between the on state and the off state is repeated a predetermined number of times. At this time, a judgment threshold value (S th_tr1 ) is the judgment threshold (S th_tr2 -S th_tr6 ) can be set to a value six times larger than the

[0135] In addition, when there is variation in the characteristics of the switching elements (Tr1-Tr6), etc., the corresponding judgment threshold (S th_tr1 -S th_tr6 ) can also be set individually.

[0136] [Control flow of open circuit abnormality determination in the third embodiment] 17 is a flow chart showing an abnormality determination control flow of the abnormality determination system for the power conversion device (inverter 3) of the third embodiment. In the third embodiment, the open circuit abnormality determination in step S104 of FIG. 2 is composed of steps S501 to S513 shown in FIG.

[0137] In step S501, the motor controller 10 selects a switching element (X) (X: any one of Tr1-Tr6) for which an open abnormality determination is to be performed from the switching elements (Tr1-Tr6).

[0138] In step S502, the motor controller 10 sets the non-selected switching elements to the OFF state.

[0139] In step S503, the motor controller 10 counts up the number of switching operations k.

[0140] In step S504, the motor controller 10 sets the switching element (X) to the ON state.

[0141] In step S505, the motor controller 10 detects the current (I k ) to get the

[0142] In step S506, the motor controller 10 calculates the current (I k ) (S Xk =S X(k-1) +I k ) is calculated. Here, if k = initial value (for example, 1), S x(k-1) will be zero.

[0143] In step S507, the motor controller 10 sets the switching element (X) to the OFF state.

[0144] In step S508, the motor controller 10 determines whether the number of switching times k has reached a predetermined number of times, and if YES, the process proceeds to step S509, and if NO, the process proceeds to step S503.

[0145] In step S509, the motor controller 10 determines the determination threshold value (S th_tr1 , S th_tr2 , S th_tr3 , S th_tr4, S th_tr5 , S th_tr6 ) among the switching elements (X), the judgment threshold (S th_x ) to extract the

[0146] In step S510, the motor controller 10 calculates the current (I k ) (S Xk ) absolute value (|S Xk |) is the decision threshold (S th_X If the answer is YES, the process proceeds to step S511. If the answer is NO, the process proceeds to step S512. k ) (S Xk ) absolute value (|S Xk |) is the decision threshold (S th_X ), it is determined that the current that has flowed (the amount of charge discharged from the parasitic capacitance) is smaller than expected, and the selected switching element (X) is determined to have an open circuit abnormality (open circuit failure: the switching element does not turn on, or the on circuit is incomplete). Conversely, if the current (I k ) (S Xk ) absolute value (|S Xk |) is the decision threshold (S th_X ), the switching element (X) is determined to be normal. The determination threshold is determined in advance based on the resistance-temperature characteristics of the smoothing capacitor 5 used, the magnitude of the parasitic capacitance component of the switching element, the time change in the voltage of the smoothing capacitor 5, and the like, in the same manner as the above-mentioned predetermined number of times.

[0147] In step S511, the motor controller 10 determines that an abnormality has occurred in the switching element (X).

[0148] In step S512, the motor controller 10 determines that there is no abnormality in the switching element (X).

[0149] In step S513, the motor controller 10 determines whether or not the open abnormality determination for all switching elements has been completed, and if YES, the process proceeds to END, and if NO, the process proceeds to step S501.

[0150] [Modification of the third embodiment] FIG. 18 is a schematic diagram of a modified example of the abnormality determination system for the power conversion device (inverter 3) of the third embodiment.

[0151] The configuration of the modified example of the abnormality determination system for the power conversion device (inverter 3) of the third embodiment is the same as that of the first embodiment, except that current sensors (A1-A6) are individually connected in series to all switching elements (Tr1-Tr6). In the third embodiment, the current sensor (A1) is connected in series to the switching element (Tr1), the current sensor (A2) is connected in series to the switching element (Tr2), the current sensor (A3) is connected in series to the switching element (Tr3), the current sensor (A4) is connected in series to the switching element (Tr4), the current sensor (A5) is connected in series to the switching element (Tr5), and the current sensor (A1) is connected in series to the switching element (Tr6). The current sensors (A2-A6) have the same configuration as the current sensor (A1).

[0152] The control flow for determining an open circuit abnormality in the modified example of the third embodiment is similar to the control flow shown in FIG. 17, but in step S505, the motor controller 10 detects a current (I Xk ) is detected.

[0153] [Effects of this embodiment] The method for determining an abnormality in the power conversion device of this embodiment is a method for determining an abnormality in a power conversion device (inverter 3) in which a plurality of series circuits in which two switching elements (Tr1, Tr2), (Tr3, Tr4), (Tr5, Tr6)) are connected in series are connected in parallel to a battery 1, a connection midpoint (e.g., UM) between one (e.g., Tr1) and the other (e.g., Tr2) of the two switching elements in the series circuits is connected to a motor 4, and power is exchanged between the battery 1 and the motor 4 by controlling the operation of the two switching elements. One switching element (e.g., Tr1) is selected from the plurality of series circuits, the remaining switching elements (e.g., Tr2-Tr6) other than the selected switching element (e.g., Tr1) in the plurality of series circuits are turned off, and the current value flowing through the plurality of series circuits or the motor 4 is measured when the selected switching element (e.g., Tr1) is switched from the off state to the on state, and the presence or absence of an abnormality (open abnormality) in the selected switching element (e.g., Tr1) is determined based on the current value.

[0154] With the above method, if the selected switching element (Tr1) has no abnormality (open circuit abnormality), current flows through the parasitic capacitances (C1-C6) contained in the switching elements (Tr1-Tr6) and the like, and if there is an abnormality (open circuit abnormality), no current flows, so the presence or absence of an abnormality (open circuit abnormality) can be detected by utilizing this difference. Also, since the current flowing through the parasitic capacitances (C1-C6) is very small, it does not rotate the motor 4. Therefore, it is possible to determine the presence or absence of an abnormality (open circuit abnormality) in the switching element (Tr1) without rotating the motor 4.

[0155] In this embodiment, the presence or absence of an abnormality in all of the switching elements constituting the plurality of series circuits is determined by sequentially switching switching elements selected from the plurality of series circuits and measuring the current value.

[0156] By using the above method, it is possible to identify which of the switching elements (Tr1-Tr6) has an abnormality (open abnormality).

[0157] In this embodiment, the sum of current values ​​is calculated by repeating the operation of switching the selected switching element between the on state and the off state a predetermined number of times, and the presence or absence of an abnormality in the selected switching element is determined based on this sum.

[0158] The above method can improve the accuracy of determining whether or not there is an abnormality (open abnormality). In this embodiment, when a plurality of series circuits are connected in parallel to a smoothing capacitor 5 and are disconnected from the battery 1, a current value is calculated based on the amount of change in voltage (amount of voltage change (ΔV)) applied to the smoothing capacitor 5 when a selected switching element is switched from an off state to an on state.

[0159] The above method makes it possible to calculate the current value required to determine the presence or absence of an abnormality (open abnormality) without installing a dedicated current sensor for determining the presence or absence of an abnormality (open abnormality), thereby simplifying the circuit and reducing costs.

[0160] In this embodiment, when one of the two switching elements in the series circuit is connected to one terminal of the battery 1 as a first switching element (Tr1, Tr3, Tr5) and the other is connected to the other terminal of the battery 1 as a second switching element (Tr2, Tr4, Tr6), one first switching element (e.g., Tr1) and one second switching element (e.g., Tr2) are selected from the multiple series circuits, and the first switching element (Tr1) and the second switching element (Tr2) are switched between the on state and the off state at different timings for the on / off states of the selected first switching element (Tr1) and the second switching element (Tr2) are switched between the on state and the off state a predetermined number of times, thereby obtaining a first sum (S1 k ) and the second sum (S2 k ) and the first sum (S1 k ), the presence or absence of an abnormality in the first switching element (Tr1) selected based on the second sum (S2 k) is used to determine whether or not there is an abnormality in the selected second switching element (Tr2).

[0161] The above method makes it possible to obtain a current value for determining whether an open circuit abnormality exists in the selected first switching element when the selected second switching element is in the off state, and to obtain a current value for determining whether an open circuit abnormality exists in the selected second switching element when the selected first switching element is in the off state.Therefore, it is possible to determine whether an open circuit abnormality exists in two switching elements in the time it takes to determine whether an open circuit abnormality exists in one switching element, and a highly accurate determination can be performed in a short time.

[0162] In this embodiment, in the case where one of the plurality of series circuits is formed by connecting in series a current sensor (e.g., A1) and a specific switching element (Tr1) that is one of two switching elements (e.g., Tr1), and a connection midpoint (UM) between the second series circuit and the other of the two switching elements (Tr2) is connected to the motor 4, when the specific switching element (Tr1) is selected from the plurality of series circuits, the remaining switching elements (Tr2-Tr6) other than the specific switching element (Tr1) are turned off, and the specific switching element (Tr1) is switched from the off state to the on state, a first current value (I k ) and the first current value (I k ), and when any one (e.g., Tr2) of the switching elements (Tr2-Tr6) other than the specific switching element (Tr1) is selected from the plurality of series circuits, the remaining switching elements (Tr1, Tr3-Tr6) other than the selected switching element (Tr2) in the plurality of series circuits are turned off, and when the selected switching element (Tr2) is switched from the off state to the on state, a second current value (I k ) and the second current value (I k) to determine whether or not there is an abnormality in the switching element (Tr2) selected based on the first current value (I k ) decision threshold (S th_tr1 ) and a second current value (I k ) decision threshold (S th_tr2 -S th_tr6 ) and are set to be different from each other.

[0163] By using the above method to set a judgment threshold according to the switching element, it is possible to judge the presence or absence of an open circuit abnormality in all switching elements by connecting a current sensor (e.g., A1) in series to any one of the switching elements (e.g., Tr1). Therefore, the number of current sensors (e.g., A1) can be reduced, simplifying the circuit and reducing costs.

[0164] The abnormality determination system for the power conversion device of this embodiment is an abnormality determination system for the power conversion device (inverter 3) including: a power conversion device (inverter 3) in which a series circuit in which two switching elements ((Tr1, Tr2), (Tr3, Tr4), (Tr5, Tr6)) are connected in series is connected in parallel to a battery 1; and a control unit (motor controller 10) that controls the operation of the two switching elements to exchange power between the battery 1 and the motor 4. The control unit (motor controller 10) selects one switching element (e.g., Tr1) from the multiple series circuits, turns off the remaining switching elements (Tr2-Tr6) other than the selected switching element (Tr1) in the multiple series circuits, measures the current value flowing through the selected switching element (Tr1) when the selected switching element (Tr1) is turned on from the off state, and determines whether or not there is an abnormality in the selected switching element (Tr1) based on the current value.

[0165] With the above configuration, if the selected switching element (Tr1) has no abnormality (open abnormality), current flows through the parasitic capacitances (C1-C6) contained in the switching elements (Tr1-Tr6), etc., and if there is an abnormality (open abnormality), no current flows, so the difference can be used to detect the presence or absence of an abnormality (open abnormality). Also, since the current flowing through the parasitic capacitances (C1-C6) is very small, it does not rotate the motor 4. Therefore, it is possible to determine the presence or absence of an abnormality (open abnormality) in the switching element (Tr1) without rotating the motor 4.

[0166] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and the technical scope of the present invention is not limited to the specific configurations of the above-mentioned embodiments. In addition, the above-mentioned embodiments can be appropriately combined. [Explanation of symbols]

[0167] 1 Battery, 4 Motor, 10 Motor controller, Tr1-Tr6 Switching element

Claims

1. A method for determining an abnormality in a power conversion device in which a plurality of series circuits, each having two switching elements connected in series, are connected in parallel to a battery, a midpoint between one of the two switching elements in the series circuits is connected to a motor, and power is exchanged between the battery and the motor by controlling operations of the two switching elements, selecting one switching element from the plurality of series circuits; turning off the remaining switching elements other than the selected switching element in the plurality of series circuits; measuring a current value flowing through the plurality of series circuits or the motor when a selected switching element is switched from an off state to an on state; The method for determining whether or not an abnormality exists in a switching element selected based on the current value.

2. The method for determining an abnormality in a power conversion device according to claim 1 , wherein the presence or absence of an abnormality in all of the switching elements constituting the plurality of series circuits is determined by sequentially switching switching elements selected from the plurality of series circuits and measuring the current value.

3. calculating a sum of the current values ​​by repeating an operation of switching the selected switching elements between an on state and an off state a predetermined number of times; 3. The method for determining an abnormality in a power conversion device according to claim 1, further comprising the step of determining whether or not an abnormality exists in the selected switching element based on the sum.

4. When a plurality of the series circuits are connected in parallel to a smoothing capacitor and disconnected from the battery, 2. The method for determining an abnormality in a power conversion device according to claim 1, wherein the current value is calculated based on an amount of change in voltage applied to the smoothing capacitor when a selected switching element is switched from an off state to an on state.

5. When the one of the two switching elements of the series circuit connected to one terminal of the battery is defined as a first switching element and the other switching element connected to the other terminal of the battery is defined as a second switching element, selecting one of the first switching elements and one of the second switching elements from the plurality of series circuits; by repeating an operation of switching the first switching element and the second switching element between an on state and an off state at different timings when the on / off states of the selected first switching element and the selected second switching element are different from each other a predetermined number of times, a first sum of the current values ​​related to the selected first switching element and a second sum of the current values ​​related to the selected second switching element; determining whether or not the first switching element selected based on the first sum has an abnormality; 2. The method for determining an abnormality in a power conversion device according to claim 1, further comprising the step of determining whether or not the selected second switching element has an abnormality based on the second sum.

6. One of the plurality of series circuits is formed by connecting in series a second series circuit in which a current sensor and a specific switching element that is one of the two switching elements are connected in series with the other of the two switching elements, and a connection midpoint between the second series circuit and the other of the two switching elements is connected to the motor; When the specific switching element is selected from the plurality of series circuits, a first current value is measured by the current sensor when the remaining switching elements other than the specific switching element are turned off and the specific switching element is switched from the off state to the on state; determining whether or not the specific switching element is abnormal based on the first current value; When any of the switching elements other than the specific switching element is selected from the plurality of series circuits, a second current value is measured by the current sensor when the remaining switching elements other than the selected switching element in the plurality of series circuits are turned off and the selected switching element is switched from the off state to the on state; determining whether or not an abnormality exists in the selected switching element based on the second current value; 2. The method for determining an abnormality in a power conversion device according to claim 1, wherein the first current value determination threshold for determining the presence or absence of an abnormality in the specific switching element and the second current value determination threshold for determining the presence or absence of an abnormality in a switching element selected other than the specific switching element are set to be different from each other.

7. a power conversion device in which a plurality of series circuits, each having two switching elements connected in series, are connected in parallel to a battery, and a midpoint of connection between one of the two switching elements in the series circuit is connected to a motor; A control unit that controls the operation of the two switching elements to exchange power between the battery and the motor, The control unit is selecting one switching element from the plurality of series circuits; turning off the remaining switching elements other than the selected switching element in the plurality of series circuits; measuring a value of a current flowing through the plurality of series circuits or the motor when a selected switching element is changed from an off state to an on state; An abnormality determination system for a power conversion device that determines whether or not a selected switching element has an abnormality based on the current value.

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