Multilevel inverter and multilevel inverter device

Abstract

We provide a multi-level inverter that can lower the voltage rating of the switch. [Solution] The multilevel inverter (24) receives a multilevel voltage formed based on the voltages output from multiple series-connected batteries (26a, 26b) and switches the output voltage to one of the multilevel voltages. The multilevel inverter includes multiple series-connected high-voltage switches (Su1, Su2, Sv1, Sv2, Sw1, Sw2) that receive a total voltage obtained by summing the voltages of the multiple batteries and switch between outputting and cutting off the total voltage, and multiple changeover switches (41, 42) that switch the voltage input to the multiple high-voltage switches to one of the voltages output from the terminals and connection points (CP) of the multiple batteries that is lower than the total voltage and higher than 0.

Description

Technical Field

[0004] , , , ,

[0005] , , ,

[0001] The present invention relates to a multilevel inverter.

Background Art

[0002] For example, there is an inverter device including a neutral point clamped type three-level inverter having a plurality of switching elements and a plurality of diodes as elements of each phase, and driving a three-phase motor, and a control device that controls the three-level inverter so that a three-level voltage is applied to each phase of the three-phase motor (see Patent Document 1). When any one of the elements of each phase experiences a short-circuit failure, the control device described in Patent Document 1 controls the three-level inverter so that a two-level voltage is applied to each phase of the three-phase motor using the elements that have not experienced a short-circuit failure among the elements of each phase.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Each phase of the three-level inverter described in Patent Document 1 has first to fourth switches connected in series in order from the positive line to the negative line on the DC side. The U-phase, V-phase, and W-phase of the motor are connected to the connection points of the second and third switches of each phase, respectively.

[0005] Incidentally, when the first and second switches are turned off and the third and fourth switches are turned on, the DC voltage is interrupted by the first and second switches. For this reason, the required voltage rating for the first and second switches is half the DC voltage. However, if the first switch short-circuits, the DC voltage must be interrupted by the second switch alone. In this case, the required voltage rating for the second switch is the entire DC voltage. Therefore, in order to interrupt the DC voltage even if either the first or second switch short-circuits, the voltage rating of the first and second switches must be increased, which may increase the cost of the first and second switches.

[0006] Furthermore, these conditions are generally common not only to 3-level inverters but also to multi-level inverters with 4 or more levels.

[0007] The present invention was made to solve the above problems, and its main objective is to provide a multilevel inverter that can reduce the voltage withstand capability of a switch. [Means for solving the problem]

[0008] The first means to solve the above problem is, A multilevel inverter (24) that takes a multilevel voltage formed based on the voltages output from multiple batteries (26a to 26f) connected in series as input and switches the output voltage to one of the multilevel voltages, A series-connected high-voltage switch (Su1, Su2, Sv1, Sv2, Sw1, Sw2, S1, S3, S5, S7) receives the total voltage obtained by summing the voltages of the aforementioned batteries and switches between outputting and shutting off the total voltage. Multiple selector switches (41-46) switch the voltage input to the multiple high-voltage switches to one of the voltages output from the terminals and connection points (CP, CP1-CP3) of the multiple batteries that is lower than the total voltage and higher than 0. It is equipped with.

[0009] According to the above configuration, the multilevel inverter receives a multilevel voltage formed based on the voltages output from multiple batteries connected in series. The multilevel voltage may be formed by dividing the total voltage obtained by summing the voltages of the multiple batteries by multiple capacitors connected in series, or it may be formed by the voltages output from the terminals and connection points of the multiple batteries. The multilevel inverter switches the output voltage to one of the multilevel voltages.

[0010] Here, multiple high-voltage switches are connected in series and receive the total voltage as input, switching between outputting and shutting off the total voltage. Therefore, the voltage withstand capability required for each of the multiple high-voltage switches to shut off the total voltage is the total voltage divided by the number of high-voltage switches. However, if, for example, one high-voltage switch short-circuits, the total voltage must be shut off by only the functioning high-voltage switches. Consequently, in order to shut off the total voltage even if any of the multiple high-voltage switches short-circuit, the voltage withstand capability of the high-voltage switches must be increased, which may increase the cost of the high-voltage switches.

[0011] In this regard, the multilevel inverter is equipped with multiple changeover switches that switch the voltage input to the multiple high-voltage switches to one of the voltages output from the terminals and connection points of the multiple batteries that is lower than the total voltage and higher than zero. Therefore, for example, if one high-voltage switch short-circuits, the voltage input to the multiple high-voltage switches can be switched to a voltage lower than the total voltage by the multiple changeover switches. Consequently, it is not necessary to keep the voltage withstand capability of the multiple high-voltage switches high, and the voltage withstand capability of the multiple high-voltage switches can be reduced. Furthermore, even if one high-voltage switch short-circuits, for example, a voltage lower than the total voltage and higher than zero can be input to the multiple high-voltage switches, allowing the multilevel inverter to continue outputting voltage. [Brief explanation of the drawing]

[0012] [Figure 1] Circuit diagram of the multilevel inverter device, battery, and motor of the first embodiment. [Figure 2] Circuit diagram showing the switching of the switching switch during a short-circuit fault of switch Su1. [Figure 3] Flowchart showing the switching procedure between normal running control and evacuation running control. [Figure 4] Circuit diagram showing an example of changing a plurality of batteries. [Figure 5] Circuit diagram showing an example of changing the multilevel inverter of the first embodiment. [Figure 6] Circuit diagram of the multilevel inverter device, battery, and motor of the second embodiment. [Figure 7] Circuit diagram showing the switching of the switching switch during a short-circuit fault of switch Su1. [Figure 8] Circuit diagram of the multilevel inverter device, battery, and motor of the third embodiment. [Figure 9] Circuit diagram showing the first example of the switching of the switching switch during a short-circuit fault of switch Su1. [Figure 10] Circuit diagram showing the second example of the switching of the switching switch during a short-circuit fault of switch Su1. [Figure 11] Circuit diagram of the multilevel inverter device, battery, and motor of the fourth embodiment. [Figure 12] Circuit diagram of the multilevel inverter device, battery, and motor of the fifth embodiment. [Figure 13] Circuit diagram showing the switching of the switching switch during a short-circuit fault of switch S1. [Figure 14] Circuit diagram of the multilevel inverter and battery of the sixth embodiment. [Figure 15] Circuit diagram showing the first example of the switching of the switching switch during a short-circuit fault of switch S1. [Figure 16] Circuit diagram showing the second example of the switching of the switching switch during a short-circuit fault of switch S1. [Figure 17] Circuit diagram showing an example of changing the multilevel inverter of the sixth embodiment.

Embodiments for Carrying Out the Invention

[0013] (First Embodiment) Hereinafter, a first embodiment embodied in a multilevel inverter device mounted on an electric vehicle or a hybrid vehicle and driving a motor will be described with reference to the drawings.

[0014] As shown in FIG. 1, for example, an electric vehicle includes a traveling motor 22, an inverter device 20, and a battery 26 (batteries 26a and 26b). The battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The inverter device 20 (corresponding to a multilevel inverter device) includes an inverter 24 and an electronic control unit (ECU: Electronic Control Unit) 30. The battery 26 is connected to the inverter 24 via a power line 28. The ECU 30 (corresponding to a control device) controls the inverter 24 (corresponding to a multilevel inverter).

[0015] The battery 26 is composed of batteries 26a and 26b connected in series (that is, a plurality of batteries). The batteries 26a and 26b are composed of one or more cells (single cells). The rated voltages of the batteries 26a and 26b are both VH / 2, and the rated voltage of the battery 26 is VH.

[0016] The motor 22 is configured as, for example, a three-phase synchronous generator motor, and has a rotor in which permanent magnets are embedded in a rotor core and a stator in which three-phase coils are wound around a stator core.

[0017] <​​​ The U-phase switching elements Su1 to Su4 are connected in series with the positive electrode line 28p and the negative electrode line 28n of the power line 28 in that order. Each of the U-phase switching elements Su1 to Su4 has a U-phase diode Du1 to Du4 connected in parallel (with the forward direction from the negative electrode line 28n side to the positive electrode line 28p side of the power line 28). The U-phase of the motor 22 is connected to the connection point of the U-phase switching elements Su2 and Su3. The cathode of clamp diode Dc1 is connected to the connection point of the U-phase switching elements Su1 and Su2 (corresponding to multiple high-voltage switches). The cathode of clamp diode Dc2 is connected to the anode of clamp diode Dc1. The connection point of the U-phase switching elements Su3 and Su4 (corresponding to multiple low-voltage switches) is connected to the anode of clamp diode Dc2.

[0019] The V-phase switching elements Sv1 to Sv4 are connected in series with the positive electrode line 28p and the negative electrode line 28n of the power line 28 in that order. Each of the V-phase switching elements Sv1 to Sv4 has a V-phase diode Dv1 to Dv4 connected in parallel (with the negative electrode line 28n side of the power line 28 being the forward direction to the positive electrode line 28p side). The V-phase of the motor 22 is connected to the connection point of the V-phase switching elements Sv2 and Sv3. The cathode of clamp diode Dc3 is connected to the connection point of the V-phase switching elements Sv1 and Sv2 (corresponding to multiple high-voltage switches). The cathode of clamp diode Dc4 is connected to the anode of clamp diode Dc3. The connection point of the V-phase switching elements Sv3 and Sv4 (corresponding to multiple low-voltage switches) is connected to the anode of clamp diode Dc4.

[0020] The W-phase switching elements Sw1 to Sw4 are connected in series with the positive electrode line 28p and the negative electrode line 28n of the power line 28 in that order. Each of the W-phase switching elements Sw1 to Sw4 has a W-phase diode Dw1 to Dw4 connected in parallel (with the forward direction from the negative electrode line 28n to the positive electrode line 28p of the power line 28). The W-phase of the motor 22 is connected to the connection point of the W-phase switching elements Sw2 and Sw3. The cathode of the clamp diode Dc5 is connected to the connection point of the W-phase switching elements Sw1 and Sw2 (corresponding to multiple high-voltage switches). The cathode of the clamp diode Dc6 is connected to the anode of the clamp diode Dc5. The connection point of the W-phase switching elements Sw3 and Sw4 (corresponding to multiple low-voltage switches) is connected to the anode of the clamp diode Dc6.

[0021] Capacitors C1 and C2 are configured to have the same rated capacitance and are connected in series in that order to the positive line 28p and negative line 28n of the power line 28. The connection point of capacitors C1 and C2 (neutral point NP) is connected to the connection points of clamp diodes Dc1 and Dc2, the connection points of clamp diodes Dc3 and Dc4, and the connection points of clamp diodes Dc5 and Dc6.

[0022] The ECU30, though not shown in the diagram, is configured as a microprocessor centered around a CPU. In addition to the CPU, it includes a ROM for storing processing programs, a RAM for temporarily storing data, and input / output ports. Signals from various sensors are input to the ECU30 via its input ports. Examples of signals input to the ECU30 include the rotational position θm from the rotational position sensor 22a, which detects the rotational position of the rotor of the motor 22, and the currents Iu and Iv of each phase from the current sensors 14u and 14v, which detect the current of each phase of the motor 22. The temperatures from temperature sensors (not shown) attached to the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 and diodes Du1~Du4, Dv1~Dv4, Dw1~Dw4 and clamp diodes Dc1~Dc6 of each phase of the inverter 24 can also be listed as signals input to the ECU30.

[0023] Various control signals are output from the ECU30 via its output ports. For example, control signals to the switching elements Su1~Su4, Sv1~Sv4, and Sw1~Sw4 of each phase of the inverter 24 are output via the output ports from the ECU30. Based on the rotational position θm of the rotor of the motor 22 from the rotational position sensor 22a, the ECU30 calculates the electrical angle θe and rotational speed Nm of the motor 22.

[0024] In the inverter device 20, the ECU 30 controls the switching of the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of the inverter 24 by pulse width modulation control (PWM control) so that, for example, the motor 22 is driven by a torque command Tm*.

[0025] In controlling the inverter 24, first, assuming that the sum of the currents flowing through each phase of the motor 22 is 0, the currents Iu and Iv of the U and V phases are transformed (3-phase to 2-phase conversion) to the currents Id and Iq of the d and q axes using the electrical angle θe of the motor 22. Next, the current commands Id* and Iq* of the d and q axes are set based on the torque command Tm* of the motor 22, and the voltage commands Vd* and Vq* of the d and q axes are set so that the difference between the currents Id and Iq of the d and q axes and the current commands Id* and Iq* cancels out. Then, the voltage commands Vd* and Vq* of the d and q axes are transformed (2-phase to 3-phase conversion) to the voltage commands Vu*, Vv*, and Vw* of the U, V, and W phases using the electrical angle θe of the motor 22. Then, based on the voltage commands Vu*, Vv*, Vw* for the U-phase, V-phase, and W-phase, PWM signals are generated for the U-phase, V-phase, and W-phase switching elements Su1~Su4, Sv1~Sv4, and Sw1~Sw4. The switching of the switching elements Su1~Su4, Sv1~Sv4, and Sw1~Sw4 is then controlled using the generated PWM signals.

[0026] The inverter 24 includes a first changeover switch 41, a high-voltage bypass 51, and a second changeover switch 42.

[0027] The first changeover switch 41 and the second changeover switch 42 are configured, for example, by relays. The high-voltage bypass 51 connects the connection point CP of batteries 26a and 26b to the connection point HP of battery 26a and capacitor C1 on the positive electrode line 28p. The first changeover switch 41 is connected between battery 26a and connection point CP. When the first changeover switch 41 is turned on, it connects battery 26a and connection point CP, and when it is turned off, it disconnects battery 26a and connection point CP. In other words, the first changeover switch 41 connects and disconnects the connection point CP (a predetermined connection point) of batteries 26a and 26b (multiple batteries) and the high-voltage battery 26a closest to connection point CP.

[0028] In the high-voltage bypass 51, a second changeover switch 42 is provided between connection point CP and connection point HP. When the second changeover switch 42 is turned on, it connects connection point CP and connection point HP, and when it is turned off, it disconnects connection point CP and connection point HP. In other words, the second changeover switch 42 connects and disconnects connection point CP to the switching element Su1, Sv1, Sw1, Sw2 (multiple high-voltage side switches), specifically the switching element Su1, Sv1, Sw1, which is the highest voltage side. The first changeover switch 41 and the second changeover switch 42 are controlled by the ECU 30.

[0029] Next, we will explain the operation of the inverter device 20 configured in this way, and in particular, the control mode when generating PWM signals for the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase based on the voltage commands Vu*, Vv*, Vw* of each phase and performing switching control of these elements.

[0030] If none of the elements in each phase of the inverter 24 (switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 and diodes Du1~Du4, Dv1~Dv4, Dw1~Dw4 and clamp diodes Dc1~Dc6) are short-circuited, the ECU 30 operates in normal mode. Normal mode is the mode used for normal driving control of an electric vehicle. In normal mode, PWM signals are generated for the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase based on the voltage commands Vu*, Vv*, Vw* for each phase, and these switching control is performed so that three levels of voltage—high level (H level), middle level (M level), and low level (L level)—are applied to each phase of the motor 22. The H level is voltage VH, the M level is voltage VH / 2, and the L level is voltage 0. In other words, the inverter 24 receives H-level, M-level, and L-level (equivalent to multi-level) voltages formed based on the voltages output from the series-connected batteries 26a and 26b (equivalent to multiple batteries), and switches the output voltage to one of the H-level, M-level, and L-level voltages.

[0031] When the ECU 30 is running in normal mode, it connects the connection point CP to the high-voltage battery 26a closest to the connection point CP using the first changeover switch 41, and disconnects the connection point CP from the highest-voltage switching elements Su1, Sv1, Sw1 (high-voltage switches) using the second changeover switch 42. This state corresponds to the first state in which the voltage VH (corresponding to the total voltage), which is the sum of the voltages VH / 2 of batteries 26a and 26b (corresponding to multiple batteries), is input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (corresponding to multiple high-voltage switches).

[0032] Here, we will explain the relationship between the on / off state of the U-phase switching elements Su1 to Su4 and the U-phase voltage Vu of the motor 22. When switching elements Su1 and Su2 are turned on and switching elements Su3 and Su4 are turned off, current flows from the positive terminal line 28p of the power line 28 to the U-phase of the motor 22 via the switching elements Su1 and Su2. At this time, the voltage at the input terminal of the U-phase of the motor 22 becomes approximately equal to the voltage at the positive terminal line 28p of the power line 28, and the U-phase voltage Vu of the motor 22 becomes high. In other words, switching elements Su1 and Su2 are switched to take a high-level voltage VH (corresponding to the total voltage), which is the sum of the respective voltages VH / 2 of batteries 26a and 26b, as input and output a high-level voltage VH.

[0033] When switching elements Su3 and Su4 are turned on and switching elements Su1 and Su2 are turned off, current flows from the U-phase input terminal of the motor 22 through switching elements Su3 and Su4 to the negative terminal line 28n of the power line 28. At this time, the voltage at the U-phase input terminal of the motor 22 becomes approximately equal to the voltage at the negative terminal line 28n of the power line 28, and the U-phase voltage Vu of the motor 22 becomes L level. Also at this time, switching elements Su1 and Su2 are switched to receive an H-level voltage VH and to interrupt the H-level voltage VH. In this state, the H-level voltage VH is interrupted by the series-connected switching elements Su1 and Su2. For this reason, the required withstand voltage for switching elements Su1 and Su2 is voltage VH / 2, respectively.

[0034] When switching elements Su2 and Su3 are turned on and switching elements Su1 and Su4 are turned off, current flows from the connection point (neutral point NP) of capacitors C1 and C2 to the input terminal of motor 22 via clamp diode Dc1 and switching element Su2, and current flows from the input terminal of motor 22 to the connection point of capacitors C1 and C2 via switching element Su3 and clamp diode Dc2. At this time, the voltage at the U-phase input terminal of motor 22 becomes approximately equal to the voltage at the connection point of capacitors C1 and C2, and the U-phase voltage Vu of motor 22 becomes M level.

[0035] The relationship between the on / off state of the V-phase switching elements Sv1 to Sv4 and the V-phase voltage Vv of the motor 22 is similar, as is the relationship between the on / off state of the W-phase switching elements Sw1 to Sw4 and the W-phase voltage Vw of the motor 22.

[0036] The ECU30 executes HL mode when it detects a short-circuit failure in any of the switching elements Su1, Sv1, Sw1 or diodes Du1, Dv1, Dw1. In HL mode, it generates PWM signals for the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase based on the voltage commands Vu*, Vv*, Vw* for each phase, and controls their switching so that two levels of voltage, H level and L level, are applied to each phase of the motor 22.

[0037] The ECU30 executes HM mode when it detects a short-circuit failure in any of the switching elements Su2, Sv2, Sw2 or diodes Du2, Dv2, Dw2. In HM mode, it generates PWM signals for the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase of the motor 22 to apply two voltage levels, H level and M level, to each phase, and controls their switching.

[0038] The ECU30 executes ML mode when it detects a short-circuit failure in any of the switching elements Su3, Sv3, Sw3 or diodes Du3, Dv3, Dw3. In ML mode, PWM signals are generated for the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase based on the voltage commands Vu*, Vv*, Vw* for each phase, and switching control is performed so that two levels of voltage, M level and L level, are applied to each phase of the motor 22.

[0039] The ECU30 executes HL mode when it detects a short-circuit failure in any of the switching elements Su4, Sv4, Sw4 or diodes Du4, Dv4, Dw4. In HL mode, it generates PWM signals for the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase based on the voltage commands Vu*, Vv*, Vw* for each phase, and controls their switching so that two levels of voltage, H level and L level, are applied to each phase of the motor 22.

[0040] By executing these modes, the motor 22 can be driven with a certain degree of accuracy even if any of the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 or diodes Du1~Du4, Dv1~Dv4, Dw1~Dw4 in each phase experience a short-circuit failure.

[0041] However, in order to execute HL mode when, for example, switching element Su1 or diode Du1 short-circuits, the H-level voltage VH must be blocked by switching element Su2 alone. Therefore, in order to block the H-level voltage VH even when switching element Su1 or diode Du1 short-circuits, the voltage rating of switching element Su2 must be set to voltage VH. In other words, the voltage rating of switching element Su2 must be twice the voltage rating required when no short-circuit occurs, which may increase the cost of switching element Su2. Furthermore, in order to execute HM mode when switching element Su2 or diode Du2 short-circuits, the H-level voltage VH must be blocked by switching element Su1 alone. For this reason, the voltage rating of switching element Su1 must be twice the voltage rating required when no short-circuit occurs, which may increase the cost of switching element Su1. The same applies when any element in the V-phase and W-phase short-circuits, not just the U-phase, short-circuits.

[0042] Therefore, in this embodiment, when the ECU 30 detects a short-circuit failure in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (multiple high-voltage switches) or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the first changeover switch 41 disconnects the connection point CP from the high-voltage battery 26a closest to the connection point CP, and the second changeover switch 42 connects the connection point CP to the highest-voltage switching element Su1, Sv1, Sw1 (high-voltage switch). In other words, when the ECU 30 detects a short-circuit failure in any of the multiple high-voltage switches, it controls the first changeover switch 41 and the second changeover switch 42 (corresponding to multiple changeover switches) to switch the voltage input to the multiple high-voltage switches to a voltage VH / 2, which is lower than the voltage VH (corresponding to the total voltage) and higher than 0, among the voltages VH, VH / 2, and 0 output from the terminals of batteries 26a, 26b (multiple batteries) and connection point CP, respectively. This state corresponds to the second state in which the voltage VH / 2 at the connection point CP (i.e., a voltage lower than the sum of the voltages and higher than zero) is input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (corresponding to multiple high-voltage switches).

[0043] For example, when the ECU 30 controls the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase so that an M-level voltage is applied to the U-phase of the motor 22 during HM mode execution, if it determines that a short-circuit current (a current different from the normal current) has flowed based on the currents Iu and Iv of each phase detected by the current sensors 14u and 14v, the ECU 30 detects that a short-circuit failure has occurred in the switching element Su1 or diode Du1. However, when the ECU 30 controls the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase so that an H-level voltage is applied to the U-phase of the motor 22 during HM mode execution, it determines that no short-circuit current is flowing based on the currents Iu and Iv of each phase detected by the current sensors 14u and 14v.

[0044] Furthermore, when the ECU 30 controls the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase so that an L-level voltage is applied to the U-phase of the motor 22 during ML mode execution, and determines that a short-circuit current (a current different from the normal state) has flowed based on the currents Iu and Iv of each phase detected by the current sensors 14u and 14v, the ECU 30 detects that a short-circuit failure has occurred in the switching element Su2 or diode Du2. In addition, when the ECU 30 controls the switching elements Su1~Su4, Sv1~Sv4, Sw1~Sw4 of each phase so that an M-level voltage is applied to the U-phase of the motor 22 during ML mode execution, the ECU 30 determines that no short-circuit current is flowing based on the currents Iu and Iv of each phase detected by the current sensors 14u and 14v.

[0045] Furthermore, if the temperature from a temperature sensor (not shown) attached to each element of each phase of the inverter 24 is higher than a threshold, it can be detected that a short-circuit failure has occurred in that element. This is because thermal damage due to overheating is a possible cause of short-circuit failure in each element of each phase of the inverter 24. In addition, it is also possible to determine that a short-circuit current has flowed based on the result of detecting the current flowing through the neutral point NP.

[0046] Then, as shown in Figure 2, when the ECU 30 detects a short-circuit failure in, for example, the switching element Su1 or the diode Du1, it turns off the first changeover switch 41 and turns on the second changeover switch 42 to execute HL mode. This enables the ECU 30 to perform a maneuver to move the electric vehicle to a safe location.

[0047] On the other hand, as shown in Figure 1, if the ECU 30 does not detect any short-circuit faults among the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, and diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, it turns on the first changeover switch 41 and turns off the second changeover switch 42 to execute normal mode. This enables normal driving control to operate the electric vehicle in normal driving conditions.

[0048] Figure 3 is a flowchart showing the procedure for switching between normal driving control and evasive driving control. This series of processes is performed by the ECU 30 when the electric vehicle is in operation.

[0049] First, normal driving control is performed (S11).

[0050] Next, it is determined whether or not a short-circuit fault has been detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, and diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2. If, in this determination, it is determined that no short-circuit fault has been detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2 (S12: NO), the first changeover switch 41 is turned ON and the second changeover switch 42 is turned OFF (S13). After that, the process from S11 is executed again.

[0051] On the other hand, if the determination in S12 determines that a short-circuit fault has been detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2 (S12: YES), the first changeover switch 41 is turned off and the second changeover switch 42 is turned on (S14).

[0052] Next, the electric vehicle's evasive driving control is executed (S15). Specifically, if a short-circuit fault is detected in any of the switching elements Su1, Sv1, Sw1 or diodes Du1, Dv1, Dw1 during the S12 process, the HL mode is executed to evacuate the electric vehicle. Also, if a short-circuit fault is detected in any of the switching elements Su2, Sv2, Sw2 or diodes Du2, Dv2, Dw2 during the S12 process, the HM mode is executed to evacuate the electric vehicle.

[0053] The embodiment described in detail above has the following advantages.

[0054] The inverter 24 is equipped with a first changeover switch 41 and a second changeover switch 42 that switch the voltage input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (corresponding to multiple high-voltage switches) to a voltage VH / 2, which is lower than the H-level voltage VH and higher than 0, among the voltages VH, VH / 2, and 0 output from the terminals VH, VH / 2, and connection point CP of batteries 26a, 26b, respectively. Therefore, for example, if one high-voltage switch short-circuits, the voltage input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 can be switched to a voltage VH / 2, which is lower than the H-level voltage VH, by the first changeover switch 41 and the second changeover switch 42. Consequently, it is not necessary to keep the withstand voltage of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 high, and the withstand voltage of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 can be reduced. Furthermore, even if, for example, one high-voltage switch experiences a short-circuit failure, a voltage VH / 2, which is lower than the H-level voltage VH and higher than 0, can be input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, and Sw2, allowing the inverter 24 to continue outputting voltage (HL mode or HM mode).

[0055] By using the first changeover switch 41 to connect the connection point CP of batteries 26a and 26b to the high-voltage battery 26a closest to the connection point CP, and by using the second changeover switch 42 to disconnect the connection point CP from the highest-voltage switching elements Su1, Sv1, and Sw1, a high-level voltage VH, which is the sum of the voltage at the connection point CP and the voltage of all batteries (one battery 26a in this embodiment) higher than the connection point CP, can be input to the high-voltage side switch. On the other hand, by using the first changeover switch 41 to disconnect the connection point CP from the high-voltage battery 26a closest to the connection point CP, and by using the second changeover switch 42 to connect the connection point CP to the highest-voltage switching elements Su1, Sv1, and Sw1, the voltage at the connection point CP can be input to the high-voltage side switch. Therefore, the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 can be switched between a first state in which a high-level voltage VH is input and a second state in which the voltage VH / 2 at the connection point CP (i.e., a voltage lower than the high-level voltage VH and higher than 0) is input, using two selector switches 41 and 42.

[0056] The ECU 30 controls the inverter 24, enabling it to output multi-level voltages VH, VH / 2, and 0. When the ECU 30 detects a short-circuit fault in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, it controls the first changeover switch 41 and the second changeover switch 42 to switch the voltage input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 to a voltage VH / 2, which is lower than the high-level voltage VH. Therefore, it is not necessary to keep the voltage withstand capability of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 high, and the voltage withstand capability of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 can be reduced.

[0057] If a short-circuit fault is not detected in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, a high-level voltage VH can be input to the high-voltage side switch. This high-level voltage VH is the sum of the voltage VH / 2 at connection point CP and the voltages of all batteries on the high-voltage side of connection point CP (in this embodiment, one battery 26a). If a short-circuit fault is detected in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, a high-voltage side switch can be input to the high-voltage side switch.

[0058] The first embodiment can also be implemented with the following modifications. Parts identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are used accordingly.

[0059] As shown in Figure 4, the electric vehicle may be equipped with batteries 26c, 26d (multiple batteries) that output voltage VH / 4 respectively instead of battery 26a, and batteries 26e, 26f (multiple batteries) that output voltage VH / 4 respectively instead of battery 26b. In this case, the first changeover switch 41 connects and disconnects the connection point CP (predetermined connection point) between batteries 26c, 26d and batteries 26e, 26f, and the high-voltage battery 26d closest to connection point CP.

[0060] If the ECU30 does not detect any short-circuit faults in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (multiple high-voltage switches) or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the first changeover switch 41 connects the connection point CP to the high-voltage battery 26d closest to the connection point CP, and the second changeover switch 42 disconnects the connection point CP from the highest-voltage switching elements Su1, Sv1, Sw1. Furthermore, when the ECU 30 detects a short-circuit fault in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the first changeover switch 41 disconnects the connection point CP from the high-voltage battery 26d closest to the connection point CP, and the second changeover switch 42 connects the connection point CP to the highest-voltage switching element Su1, Sv1, Sw1.

[0061] According to the above configuration, if a short-circuit fault is not detected in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, a high-level voltage VH can be input to the high-voltage side switch. This is the voltage VH / 2 of the connection point CP plus the respective voltages VH / 4 of all batteries 26c and 26d on the high-voltage side of connection point CP. Furthermore, if a short-circuit fault is detected in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, the voltage VH / 2 of the connection point CP (the voltage VH / 2 obtained by adding the respective voltages VH / 4 of all batteries 26e and 26f on the low-voltage side of connection point CP) can be input to the high-voltage side switch.

[0062] As shown in Figure 5, a reverse current blocking diode 49 may be provided in the high-voltage bypass 51. The anode of the reverse current blocking diode 49 is connected to the connection point CP, and the cathode of the reverse current blocking diode 49 is connected to the second changeover switch 42. Alternatively, the anode of the reverse current blocking diode 49 may be connected to the second changeover switch 42, and the cathode of the reverse current blocking diode 49 may be connected to the connection point HP. The reverse current blocking diode 49 prevents current from flowing back into the battery 26b when the first changeover switch 41 is turned off and the second changeover switch 42 is turned on. In other words, the reverse current prevention diode 49 prevents current from flowing back into battery 26b when the ECU 30 detects a short-circuit fault in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, controls the first changeover switch 41 and the second changeover switch 42, and the voltage input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 is switched to a voltage VH / 2, which is lower than the H level voltage VH and higher than 0, among the voltages VH, VH / 2, and 0 output from the terminals and connection point CP of batteries 26a and 26b.

[0063] With the above configuration, when the ECU 30 detects a short-circuit fault in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, and a voltage VH / 2 lower than the H level voltage VH and higher than 0 is input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2, the reverse current prevention diode 49 can prevent current from flowing back into battery 26b. Therefore, when the motor 22 is performing regenerative power generation, etc., it is possible to suppress the application of an excessive voltage to battery 26b (corresponding to some of the batteries) or the overcharging of battery 26b. In turn, it is possible to suppress the uneven distribution of the remaining capacities of batteries 26a and 26b.

[0064] (Second Embodiment) The following description focuses on the differences between the second embodiment and the first embodiment. Parts identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are used accordingly.

[0065] Instead of the first changeover switch 41, high-voltage bypass 51, and second changeover switch 42 in Figure 1, the inverter 24 of this embodiment, as shown in Figure 6, is equipped with a third changeover switch 43, a low-voltage bypass 52, and a fourth changeover switch 44.

[0066] The third changeover switch 43 and the fourth changeover switch 44 are configured, for example, by relays. The low-voltage bypass 52 connects the connection point CP of batteries 26a and 26b to the connection point LP of battery 26b and capacitor C2 in the negative electrode line 28n. The third changeover switch 43 is connected between battery 26b and connection point CP. When the third changeover switch 43 is turned on, it connects battery 26b and connection point CP, and when it is turned off, it disconnects battery 26b and connection point CP. In other words, the third changeover switch 43 connects and disconnects the connection point CP (a predetermined connection point) of batteries 26a and 26b (multiple batteries) and the low-voltage battery 26b closest to connection point CP.

[0067] In the low-voltage bypass 52, a fourth changeover switch 44 is provided between connection point CP and connection point LP. When the fourth changeover switch 44 is turned on, it connects connection point CP and connection point LP, and when it is turned off, it disconnects connection point CP and connection point LP. In other words, the fourth changeover switch 44 connects and disconnects connection point CP from voltage 0 (ground). The third changeover switch 43 and the fourth changeover switch 44 are controlled by the ECU 30.

[0068] As shown in Figure 6, when the ECU 30 does not detect any short-circuit faults in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (corresponding to multiple high-voltage switches) or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the third changeover switch 43 connects the connection point CP to the low-voltage battery 26b closest to the connection point CP, and the fourth changeover switch 44 disconnects the connection point CP from ground. On the other hand, as shown in Figure 7, when the ECU 30 detects any short-circuit fault in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the third changeover switch 43 disconnects the connection point CP to the low-voltage battery 26b closest to the connection point CP, and the fourth changeover switch 44 connects the connection point CP to ground.

[0069] The second embodiment has the following advantages. Here, only the advantages that differ from the first embodiment will be described.

[0070] By using the third changeover switch 43 to connect the connection point CP of batteries 26a and 26b to the low-voltage battery 26b closest to the connection point CP, and by using the fourth changeover switch 44 to disconnect the connection point CP from ground, a high-level voltage VH, which is the sum of the voltage VH / 2 of the connection point CP and the voltage VH / 2 of all batteries on the high-voltage side of the connection point CP (one battery 26a in this embodiment), can be input to the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (high-voltage side switches). On the other hand, by using the third changeover switch 43 to disconnect the connection point CP and the low-voltage battery 26b closest to the connection point CP, and by using the fourth changeover switch 44 to connect the connection point CP to ground, a voltage VH / 2, which is the high-level voltage VH minus the voltage of all batteries on the low-voltage side of the connection point CP (one battery 26b in this embodiment), can be input to the high-voltage side switch. Therefore, the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 can be switched between a first state in which a high-level voltage VH is input, and a third state in which a voltage VH / 2 (i.e., a voltage lower than the high-level voltage VH and higher than 0), obtained by subtracting the voltages of all batteries on the lower-voltage side of the connection point CP from the high-level voltage VH, is input. This can be switched using the two selector switches 43 and 44.

[0071] If no short-circuit fault is detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, or Sw2, a high-level voltage VH can be input to the high-voltage side switch. This VH is the voltage at connection point CP plus the voltage of all batteries on the high-voltage side of connection point CP (in this embodiment, one battery 26a). If a short-circuit fault is detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, or Sw2, a high-level voltage VH / 2 can be input to the high-voltage side switch. This VH can be the high-voltage side switch.

[0072] (Third embodiment) The third embodiment will be described below, focusing on the differences from the first and second embodiments. Parts identical to those in the first and second embodiments will be denoted by the same reference numerals for further explanation.

[0073] As shown in Figure 8, the inverter 24 of this embodiment includes a first changeover switch 41, a second changeover switch 42, a third changeover switch 43, a fourth changeover switch 44, and bypasses 53 to 55.

[0074] The first changeover switch 41 and the second changeover switch 42 are configured, for example, by relays. Bypasses 53 and 55 connect the connection point CP of batteries 26a and 26b to the connection point HP of battery 26a and capacitor C1 on the positive electrode line 28p. The first changeover switch 41 is connected between battery 26a and connection point CP. When the first changeover switch 41 is turned on, it connects battery 26a and connection point CP, and when it is turned off, it disconnects battery 26a and connection point CP. In other words, the first changeover switch 41 connects and disconnects the connection point CP (a predetermined connection point) of batteries 26a and 26b (multiple batteries) and the high-voltage battery 26a closest to connection point CP.

[0075] In the bypass 53, a second changeover switch 42 is provided between connection point CP and connection point HP. When the second changeover switch 42 is turned on, it connects connection point CP and connection point HP, and when it is turned off, it disconnects connection point CP and connection point HP. In other words, the second changeover switch 42 connects and disconnects connection point CP to the switching element Su1, the highest-voltage switching element among the switching elements Su1 and Su2 (multiple high-voltage side switches). The first changeover switch 41 and the second changeover switch 42 are controlled by the ECU 30.

[0076] The third changeover switch 43 and the fourth changeover switch 44 are configured, for example, by relays. Bypasses 54 and 55 connect the connection point CP of batteries 26a and 26b to the connection point LP of battery 26b and capacitor C2 in the negative electrode line 28n. The third changeover switch 43 is connected between battery 26b and connection point CP. When the third changeover switch 43 is turned on, it connects battery 26b and connection point CP, and when it is turned off, it disconnects battery 26b and connection point CP. In other words, the third changeover switch 43 connects and disconnects the connection point CP (a predetermined connection point) of batteries 26a and 26b (multiple batteries) and the low-voltage battery 26b closest to connection point CP.

[0077] In the bypass 54, a fourth changeover switch 44 is provided between connection point CP and connection point LP. When the fourth changeover switch 44 is turned on, it connects connection point CP and connection point LP, and when it is turned off, it disconnects connection point CP and connection point LP. In other words, the fourth changeover switch 44 connects and disconnects connection point CP from voltage 0 (ground). The third changeover switch 43 and the fourth changeover switch 44 are controlled by the ECU 30.

[0078] Bypass 55 connects the connection point MP of the second changeover switch 42 and the fourth changeover switch 44 to the connection point CP.

[0079] As shown in Figure 8, when the ECU 30 does not detect any short-circuit faults in the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 (corresponding to multiple high-voltage switches) or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the first changeover switch 41 connects the connection point CP to the high-voltage battery 26a closest to the connection point CP, the second changeover switch 42 disconnects the connection point CP from the switching elements Su1, Sv1, Sw1 (corresponding to the highest-voltage switch), the third changeover switch 43 connects the connection point CP to the low-voltage battery 26b closest to the connection point CP, and the fourth changeover switch 44 disconnects the connection point CP from ground. Furthermore, as shown in Figure 9, when the ECU 30 detects a short-circuit fault in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, the first changeover switch 41 disconnects the connection point CP from the high-voltage battery 26a closest to the connection point CP, the second changeover switch 42 connects the connection point CP from the switching elements Su1, Sv1, Sw1, the third changeover switch 43 connects the connection point CP from the low-voltage battery 26b closest to the connection point CP, and the fourth changeover switch 44 disconnects the connection point CP from ground. Alternatively, as shown in Figure 10, when the ECU 30 detects a short-circuit fault in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2 or diodes Du1, Du2, Dv1, Dv2, Dw1, Dw2, it connects the connection point CP to the high-voltage battery 26a closest to the connection point CP using the first changeover switch 41, disconnects the connection point CP from the switching elements Su1, Sv1, Sw1 using the second changeover switch 42, disconnects the connection point CP from the low-voltage battery 26b closest to the connection point CP using the third changeover switch 43, and connects the connection point CP to ground using the fourth changeover switch 44.

[0080] The third embodiment has the following advantages. Here, only the advantages that differ from the first and second embodiments are described.

[0081] By using the first changeover switch 41 to connect the connection point CP of batteries 26a and 26b to the high-voltage battery 26a closest to the connection point CP, and using the second changeover switch 42 to disconnect the connection point CP from the switching elements Su1, Sv1, Sw1, and using the third changeover switch 43 to connect the connection point CP to the low-voltage battery 26b closest to the connection point CP, and using the fourth changeover switch 44 to disconnect the connection point CP from ground, a high-level voltage VH, which is the sum of the voltage VH / 2 of the connection point CP and the voltage VH / 2 of all batteries (one battery 26a in this embodiment) on the high-voltage side of the connection point CP, can be input to the high-voltage side switches (switching elements Su1, Su2, Sv1, Sv2, Sw1, Sw2).

[0082] By using the first changeover switch 41 to disconnect the connection point CP from the high-voltage battery 26a closest to the connection point CP, connecting the connection point CP from the switching elements Su1, Sv1, and Sw1 with the second changeover switch 42, connecting the connection point CP from the low-voltage battery 26b closest to the connection point CP with the third changeover switch 43, and disconnecting the connection point CP from ground with the fourth changeover switch 44, the voltage VH / 2 at the connection point CP (the sum of the voltages of all batteries lower than the connection point CP) can be input to the high-voltage switch.

[0083] By connecting the connection point CP to the high-voltage battery 26a closest to the connection point CP using the first changeover switch 41, disconnecting the connection point CP from the switching elements Su1, Sv1, and Sw1 using the second changeover switch 42, disconnecting the connection point CP to the low-voltage battery 26b closest to the connection point CP using the third changeover switch 43, and connecting the connection point CP to ground using the fourth changeover switch 44, a voltage VH / 2, obtained by subtracting the voltages of all batteries lower than the connection point CP from the H-level voltage VH, can be input to the high-voltage switch.

[0084] The switching elements Su1, Su2, Sv1, Sv2, Sw1, and Sw2 can be switched between three states using four selector switches 41 to 44: a first state (Figure 8) in which a high-level voltage VH is input; a second state (Figure 9) in which a voltage VH / 2, which is the sum of the voltages of all batteries on the lower-voltage side of the connection point CP, is input; and a third state (Figure 10) in which a voltage VH / 2, which is the high-level voltage VH minus the voltages of all batteries on the lower-voltage side of the connection point CP, is input.

[0085] If a short-circuit fault is not detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, or Sw2, a high-level voltage VH can be input to the high-voltage side switch. This high-level voltage VH is obtained by adding the voltages of all batteries on the high-voltage side of connection point CP to the voltage VH / 2 at connection point CP. If a short-circuit fault is detected in any of the switching elements Su1, Su2, Sv1, Sv2, Sw1, or Sw2, a high-voltage side switch can be input either a high-level voltage VH minus the voltages of all batteries on the low-voltage side of connection point CP (VH / 2), or a high-level voltage VH minus the voltages of all batteries on the low-voltage side of connection point CP (VH / 2). Therefore, when inputting a voltage VH / 2 lower than the high-level voltage VH and higher than 0 to the switching elements Su1, Su2, Sv1, Sv2, Sw1, or Sw2, it is possible to select either the second or third state, thereby suppressing uneven distribution of the remaining capacity of batteries 26a and 26b.

[0086] (Fourth Embodiment) The fourth embodiment will be described below, focusing on the differences from the first embodiment. Parts identical to those in the first embodiment will be denoted by the same reference numerals, and their descriptions will be referenced accordingly.

[0087] As shown in Figure 11, the inverter 24 of this embodiment does not have the capacitors C1 and C2 shown in Figure 1. The connection point CP of batteries 26a and 26b is connected to the connection points of clamp diodes Dc1 and Dc2, the connection points of clamp diodes Dc3 and Dc4, and the connection points of clamp diodes Dc5 and Dc6. Batteries 26a and 26b have a rated capacity that is sufficiently larger than that of capacitors C1 and C2 and are identical to each other.

[0088] According to the above configuration, the inverter 24 receives a multilevel voltage formed based on the voltages output from batteries 26a and 26b (corresponding to multiple batteries) connected in series. The multilevel voltage is formed by the voltages VH, VH / 2, and 0 output from the terminals and connection point CP of batteries 26a and 26b. The inverter 24 switches the output voltage to one of the multilevel voltages. This configuration can also achieve the same effects as the first embodiment.

[0089] (Fifth embodiment) The fifth embodiment will be described below, focusing on the differences from the first embodiment. Parts identical to those in the first embodiment will be denoted by the same reference numerals for further explanation.

[0090] The phases of the inverter 24 in Figure 1 can also be changed to the circuits shown in Figure 12. Each phase of the inverter 24 is equipped with switching elements S1 to S4 and diodes D1 to D4. The inverter 24 is equipped with a first changeover switch 41 and a second changeover switch 42 common to each phase. That is, the switching elements S1 to S4 and diodes D1 to D4 of each phase are connected in parallel to connection points HP, CP, and LP.

[0091] The inverter 24 receives three voltage levels (VH, VH / 2, 0) as input and switches the output voltage Vo to each phase of the motor 22 to one of the three voltage levels. Specifically, the ECU 30 (not shown) outputs a high-level voltage VH by turning on switching elements S1 and S3 and turning off switching elements S2 and S4. The ECU 30 outputs a medium-level voltage VH / 2 by turning on switching elements S2 and S3 and turning off switching elements S1 and S4. The ECU 30 outputs a voltage of 0 by turning off switching element S3 and turning on switching element S4.

[0092] As shown in Figure 12, when the ECU 30 does not detect any short-circuit faults in the switching elements S1 and S3 of each phase (corresponding to multiple high-voltage switches) or the diodes D1 and D3 of each phase, it connects the connection point CP to the high-voltage battery 26a closest to the connection point CP using the first changeover switch 41, and disconnects the connection point CP from the highest-voltage switching element S1 of each phase using the second changeover switch 42. On the other hand, as shown in Figure 13, when the ECU 30 detects any short-circuit fault in the switching elements S1 and S3 of each phase or the diodes D1 and D3, it disconnects the connection point CP from the high-voltage battery 26a closest to the connection point CP using the first changeover switch 41, and connects the connection point CP to the highest-voltage switching element S1 of each phase using the second changeover switch 42. In other words, when the ECU 30 detects a short-circuit fault in any of the multiple high-voltage switches for each phase, it controls the first changeover switch 41 and the second changeover switch 42 (corresponding to multiple changeover switches) to switch the voltage input to the multiple high-voltage switches for each phase to a voltage VH / 2, which is lower than voltage VH (corresponding to the total voltage) and higher than voltage 0, among the voltages VH, VH / 2, and 0 output from the terminals and connection points CP of batteries 26a and 26b (multiple batteries), respectively. This configuration can also achieve the same effects as the first embodiment.

[0093] (Sixth Embodiment) The sixth embodiment will be described below, focusing on the differences from the fifth embodiment. Parts identical to those in the fifth embodiment will be denoted by the same reference numerals, and their descriptions will be referenced accordingly.

[0094] The 3-level inverter 24 in Figure 12 can also be changed to a 5-level inverter 24, as shown in Figure 14. Each phase of the inverter 24 in this embodiment is equipped with switching elements S1 to S8 and diodes D1 to D8. The inverter 24 is equipped with first changeover switches 41 and 45 and second changeover switches 42 and 46 common to each phase. That is, the switching elements S1 to S8 and diodes D1 to D8 of each phase are connected in parallel to connection points HP, CP1 to CP3, and LP.

[0095] The inverter 24 receives five voltage levels (VH, 3VH / 4, 2VH / 4, VH / 4, 0) as input and switches the output voltage Vo to each phase of the motor 22 to one of the five voltage levels. For example, the ECU 30 (not shown) outputs a high-level voltage VH by turning on switching elements S1, S3, 5, and 7 and turning off switching elements S2, S4, S6, and S8. The ECU 30 outputs a voltage VH / 2 by turning on switching elements S4, S5, and S7 and turning off switching elements S1~S3, S6, and S8. The ECU 30 outputs a voltage 0 by turning off switching element S7 and turning on switching element S8.

[0096] As shown in Figure 14, when the ECU 30 does not detect any short-circuit faults in the switching elements S1, S3, S5, S7 of each phase (corresponding to multiple high-voltage switches) or the diodes D1, D3, D5, D7 of each phase, it connects connection point CP1 (a predetermined connection point) to the high-voltage battery 26c closest to connection point CP1 using the first changeover switch 41, connects connection point CP2 (a predetermined connection point) to the high-voltage battery 26d closest to connection point CP2 using the first changeover switch 45, disconnects connection point CP1 from the highest-voltage switching element S1 of each phase using the second changeover switch 42, and disconnects connection point CP2 from the highest-voltage switching element S1 of each phase using the second changeover switch 46.

[0097] On the other hand, as shown in Figure 15, when the ECU 30 detects a short-circuit fault in any of the switching elements S1, S3, S5, S7 of each phase or the diodes D1, D3, D5, D7 of each phase, it disconnects connection point CP1 from the high-voltage battery 26c closest to connection point CP1 using the first changeover switch 41, connects connection point CP1 from the highest-voltage switching element S1 of each phase using the second changeover switch 42, connects connection point CP2 from the high-voltage battery 26d closest to connection point CP2 using the first changeover switch 45, and disconnects connection point CP2 from the highest-voltage switching element S1 of each phase using the second changeover switch 46. In other words, when the ECU 30 detects a short-circuit failure in any of the multiple high-voltage switches, it controls the first changeover switches 41, 45 and the second changeover switches 42, 46 (corresponding to multiple changeover switches) to switch the voltage input to the multiple high-voltage switches to a voltage of 3VH / 4, which is lower than the voltage VH (corresponding to the total voltage) and higher than the voltage 0, among the voltages VH, 3VH / 4, 2VH / 4, VH / 4, and 0 output from the terminals and connection points CP1 to CP3 of the batteries 26c to 26f (multiple batteries), respectively.

[0098] Alternatively, as shown in Figure 16, when the ECU 30 detects a short-circuit fault in any of the switching elements S1, S3, S5, S7 of each phase or the diodes D1, D3, D5, D7 of each phase, it connects connection point CP1 to the high-voltage battery 26c closest to connection point CP1 using the first changeover switch 41, disconnects connection point CP1 to the highest-voltage switching element S1 of each phase using the second changeover switch 42, disconnects connection point CP2 to the highest-voltage battery 26d closest to connection point CP2 using the first changeover switch 45, and connects connection point CP2 to the highest-voltage switching element S1 of each phase using the second changeover switch 46. In other words, when the ECU 30 detects a short-circuit failure in any of the multiple high-voltage switches, it controls the first changeover switches 41, 45 and the second changeover switches 42, 46 (corresponding to multiple changeover switches) to switch the voltage input to the multiple high-voltage switches to a voltage 2VH / 4, which is lower than voltage VH (corresponding to the total voltage) and higher than voltage 0, among the voltages VH, 3VH / 4, 2VH / 4, VH / 4, and 0 output from the terminals and connection points CP1 to CP3 of the batteries 26c to 26f (multiple batteries), respectively. The above configuration can also produce the same effects as the fifth embodiment.

[0099] As shown in Figure 17, a reverse current blocking diode 49 may be provided in the bypass 56 connecting the connection point CP1 and connection point HP of batteries 26c and 26d. The anode of the reverse current blocking diode 49 is connected to connection point CP1, and the cathode of the reverse current blocking diode 49 is connected to the second changeover switch 42. Alternatively, the anode of the reverse current blocking diode 49 may be connected to the second changeover switch 42, and the cathode of the reverse current blocking diode 49 may be connected to connection point HP. The reverse current prevention diode 49 prevents current from flowing back into batteries 26d to 26f when the ECU 30 detects a short-circuit failure in any of the switching elements S1, S3, S5, or S7, controls the changeover switches 41, 42, 45, or 46, and switches the voltage input to the switching elements S1, S3, S5, or S7 to a voltage 3VH / 4, which is lower than the high-level voltage VH and higher than 0, among the voltages VH, 3VH / 4, 2VH / 4, VH / 4, and 0 output from the terminals of batteries 26c to 26f and connection points CP1 to CP3.

[0100] Furthermore, a reverse current blocking diode 49 may be provided in the bypass 57 connecting the connection point CP2 and connection point HP of batteries 26d and 26e. The anode of the reverse current blocking diode 49 is connected to connection point CP2, and the cathode of the reverse current blocking diode 49 is connected to the second changeover switch 46. Alternatively, the anode of the reverse current blocking diode 49 may be connected to the second changeover switch 46, and the cathode of the reverse current blocking diode 49 may be connected to connection point HP. The reverse current prevention diode 49 prevents current from flowing back into batteries 26e and 26f when the ECU 30 detects a short-circuit failure in any of the switching elements S1, S3, S5, or S7, and controls the changeover switches 41, 42, 45, or 46, causing the voltage input to the switching elements S1, S3, S5, or S7 to be switched to a voltage 2VH / 4, which is lower than the H-level voltage VH and higher than 0, among the voltages VH, 3VH / 4, 2VH / 4, VH / 4, and 0 output from the terminals of batteries 26c to 26f and connection points CP1 to CP3.

[0101] Furthermore, the above embodiments and their modifications can be combined and implemented to the extent possible.

[0102] The following describes the characteristic configurations extracted from each of the embodiments and modifications described above. [Configuration 1] A multilevel inverter (24) that takes a multilevel voltage formed based on the voltages output from multiple batteries (26a to 26f) connected in series as input and switches the output voltage to one of the multilevel voltages, A series-connected high-voltage switch (Su1, Su2, Sv1, Sv2, Sw1, Sw2, S1, S3, S5, S7) receives the total voltage obtained by summing the voltages of the aforementioned batteries and switches between outputting and shutting off the total voltage. Multiple selector switches (41-46) switch the voltage input to the multiple high-voltage switches to one of the voltages output from the terminals and connection points (CP, CP1-CP3) of the multiple batteries that is lower than the total voltage and higher than 0. A multilevel inverter equipped with the following features. [Configuration 2] The multilevel inverter according to configuration 1, wherein the plurality of changeover switches include first changeover switches (41, 45) that connect and disconnect predetermined connection points (CP, CP1, CP2) of the plurality of batteries to the high-voltage batteries (26a, 26c, 26d) closest to the predetermined connection points, and second changeover switches (42, 46) that connect and disconnect the predetermined connection points to the high-voltage side switches (Su1, Sv1, Sw1, S1) closest to the high voltage. [Configuration 3] The multilevel inverter according to configuration 1, wherein the plurality of changeover switches include a third changeover switch (43) that connects and disconnects a predetermined connection point of the plurality of batteries to the low-voltage battery (26b) closest to the predetermined connection point (CP), and a fourth changeover switch (44) that connects and disconnects the predetermined connection point to ground. [Structure 4] The multilevel inverter according to configuration 1, wherein the plurality of changeover switches include a first changeover switch (41) that connects and disconnects a predetermined connection point (CP) of the plurality of batteries to the high-voltage battery (26a) closest to the predetermined connection point; a second changeover switch (42) that connects and disconnects the predetermined connection point to the high-voltage side switch (Su1, Sv1, Sw1) on the highest voltage side; a third changeover switch (43) that connects and disconnects the predetermined connection point to the low-voltage battery (26b) closest to the predetermined connection point; and a fourth changeover switch (44) that connects and disconnects the predetermined connection point to ground. [Composition 5] A multilevel inverter as described in one of configurations 1 to 4, A control device (30) that controls the multilevel inverter, A multilevel inverter device (20) comprising, The control device, when it detects a short-circuit failure in any of the multiple high-voltage switches, controls the multiple changeover switches to switch the voltage input to the multiple high-voltage switches to one of the voltages output from the terminals and connection points of the multiple batteries that is lower than the total voltage and higher than zero, and is a multilevel inverter device. [Composition 6] The multilevel inverter described in Configuration 2, A control device (30) that controls the multilevel inverter, A multilevel inverter device (20) comprising, The control device is If a short-circuit failure is not detected in the plurality of high-voltage switches, the first changeover switch connects the predetermined connection point to the high-voltage battery closest to the predetermined connection point, and the second changeover switch disconnects the predetermined connection point from the high-voltage switch on the highest voltage side. A multilevel inverter device that, when a short-circuit failure is detected in any of the plurality of high-voltage switches, disconnects the predetermined connection point from the high-voltage battery closest to the predetermined connection point using the first changeover switch, and connects the predetermined connection point from the high-voltage switch on the highest voltage side using the second changeover switch. [Composition 7] The multilevel inverter described in Configuration 3, A control device (30) that controls the multilevel inverter, A multilevel inverter device (20) comprising, The control device is If a short-circuit failure is not detected in the plurality of high-voltage switches, the third changeover switch connects the predetermined connection point to the low-voltage battery closest to the predetermined connection point, and the fourth changeover switch disconnects the predetermined connection point from ground. A multilevel inverter device that, when a short-circuit failure is detected in any of the plurality of high-voltage switches, disconnects the predetermined connection point from the low-voltage battery closest to the predetermined connection point using the third changeover switch, and connects the predetermined connection point from the ground using the fourth changeover switch. [Structure 8] The multilevel inverter described in Configuration 4, A control device (30) that controls the multilevel inverter, A multilevel inverter device (20) comprising, The control device is If a short-circuit failure is not detected in the plurality of high-voltage switches, the first changeover switch connects the predetermined connection point to the high-voltage battery closest to the predetermined connection point, the second changeover switch disconnects the predetermined connection point from the high-voltage switch closest to the predetermined connection point, the third changeover switch connects the predetermined connection point to the low-voltage battery closest to the predetermined connection point, and the fourth changeover switch disconnects the predetermined connection point from the ground. A multilevel inverter device that, when a short-circuit failure is detected in any of the plurality of high-voltage switches, disconnects the predetermined connection point from the high-voltage battery closest to the predetermined connection point using the first changeover switch, connects the predetermined connection point from the high-voltage switch closest to the predetermined connection point using the second changeover switch, connects the predetermined connection point from the low-voltage battery closest to the predetermined connection point using the third changeover switch, and disconnects the predetermined connection point from ground using the fourth changeover switch, or connects the predetermined connection point from the high-voltage battery closest to the predetermined connection point using the first changeover switch, disconnects the predetermined connection point from the high-voltage switch closest to the predetermined connection point using the second changeover switch, disconnects the predetermined connection point from the low-voltage battery closest to the predetermined connection point using the third changeover switch, and connects the predetermined connection point from ground using the fourth changeover switch. [Composition 9] A multilevel inverter device according to any one of configurations 5 to 8, wherein the control device detects a short-circuit failure in any of the plurality of high-voltage switches and controls the plurality of changeover switches, and when the voltage input to the plurality of high-voltage switches is switched to one of the voltages output from the terminals and connection points of the plurality of batteries that is lower than the total voltage and higher than 0, a reverse current prevention diode (49) is provided to prevent current from flowing back into the plurality of batteries. [Explanation of Symbols]

[0103] 20...Inverter device, 24...Inverter, 26a...Battery, 26b...Battery, 26c...Battery, 26d...Battery, 26e...Battery, 26f...Battery, 30...ECU, 41...First changeover switch, 42...Second changeover switch, 43...Third changeover switch, 44...Fourth changeover switch, 45...First changeover switch, 46...Second changeover switch, CP...Connection point, CP1...Connection point, CP2...Connection point, CP3...Connection point, S1...Switching element, S3...Switching element, S5...Switching element, S7...Switching element, Su1...Switching element, Su2...Switching element, Sv1...Switching element, Sv2...Switching element, Sw1...Switching element, Sw2...Switching element.

Claims

1. A multilevel inverter (24) that takes a multilevel voltage formed based on the voltages output from multiple batteries (26a to 26f) connected in series as input and switches the output voltage to one of the multilevel voltages, A series-connected high-voltage switch (Su1, Su2, Sv1, Sv2, Sw1, Sw2, S1, S3, S5, S7) receives the total voltage obtained by summing the voltages of the aforementioned multiple batteries, and switches between outputting and shutting off the total voltage. Multiple changeover switches (41-46) switch the voltage input to the multiple high-voltage side switches to one of the voltages output from the terminals and connection points (CP, CP1-CP3) of the multiple batteries that is lower than the total voltage and higher than 0, A multilevel inverter equipped with the following features.

2. The multilevel inverter according to claim 1, wherein the plurality of changeover switches include first changeover switches (41, 45) that connect and disconnect predetermined connection points (CP, CP1, CP2) of the plurality of batteries to the high-voltage batteries (26a, 26c, 26d) closest to the predetermined connection points, and second changeover switches (42, 46) that connect and disconnect the predetermined connection points to the high-voltage side switches (Su1, Sv1, Sw1, S1) closest to the highest voltage.

3. The multilevel inverter according to claim 1, wherein the plurality of changeover switches include a third changeover switch (43) for connecting and disconnecting a predetermined connection point of the plurality of batteries and the low-voltage battery (26b) closest to the predetermined connection point (CP), and a fourth changeover switch (44) for connecting and disconnecting the predetermined connection point and ground.

4. The multilevel inverter according to claim 1, wherein the plurality of changeover switches include a first changeover switch (41) for connecting and disconnecting a predetermined connection point (CP) of the plurality of batteries to the high-voltage battery (26a) closest to the predetermined connection point; a second changeover switch (42) for connecting and disconnecting the predetermined connection point to the high-voltage switch (Su1, Sv1, Sw1) closest to the high voltage; a third changeover switch (43) for connecting and disconnecting the predetermined connection point to the low-voltage battery (26b) closest to the predetermined connection point; and a fourth changeover switch (44) for connecting and disconnecting the predetermined connection point to ground.

5. A multilevel inverter according to any one of claims 1 to 4, A control device (30) for controlling the multilevel inverter, A multilevel inverter device (20) comprising, The control device, when it detects a short-circuit failure in any of the multiple high-voltage switches, controls the multiple changeover switches to switch the voltage input to the multiple high-voltage switches to one of the voltages output from the terminals and connection points of the multiple batteries that is lower than the total voltage and higher than zero, and is a multilevel inverter device.

6. The multilevel inverter according to claim 2, A control device (30) for controlling the multilevel inverter, A multilevel inverter device (20) comprising, The control device is If a short-circuit failure is not detected in the plurality of high-voltage switches, the first changeover switch connects the predetermined connection point to the high-voltage battery closest to the predetermined connection point, and the second changeover switch disconnects the predetermined connection point from the high-voltage switch on the highest voltage side. A multilevel inverter device that, when a short-circuit failure is detected in any of the plurality of high-voltage switches, disconnects the predetermined connection point from the high-voltage battery closest to the predetermined connection point using the first changeover switch, and connects the predetermined connection point from the high-voltage switch on the highest voltage side using the second changeover switch.

7. The multilevel inverter according to claim 3, A control device (30) for controlling the multilevel inverter, A multilevel inverter device (20) comprising, The control device is If a short-circuit failure is not detected in the plurality of high-voltage switches, the third changeover switch connects the predetermined connection point to the low-voltage battery closest to the predetermined connection point, and the fourth changeover switch disconnects the predetermined connection point from ground. A multilevel inverter device that, when a short-circuit fault is detected in any of the plurality of high-voltage switches, disconnects the predetermined connection point from the low-voltage battery closest to the predetermined connection point using the third changeover switch, and connects the predetermined connection point from the ground using the fourth changeover switch.

8. The multilevel inverter according to claim 4, A control device (30) for controlling the multilevel inverter, A multilevel inverter device (20) comprising, The control device is If a short-circuit failure is not detected in the plurality of high-voltage switches, the first changeover switch connects the predetermined connection point to the high-voltage battery closest to the predetermined connection point, the second changeover switch disconnects the predetermined connection point from the high-voltage switch closest to the highest voltage, the third changeover switch connects the predetermined connection point to the low-voltage battery closest to the predetermined connection point, and the fourth changeover switch disconnects the predetermined connection point from the ground. A multilevel inverter device in which, upon detecting a short-circuit failure in any of the plurality of high-voltage switches, the first changeover switch disconnects the predetermined connection point from the high-voltage battery closest to the predetermined connection point, the second changeover switch connects the predetermined connection point from the high-voltage switch closest to the predetermined connection point, the third changeover switch connects the predetermined connection point from the low-voltage battery closest to the predetermined connection point, and the fourth changeover switch disconnects the predetermined connection point from ground; or the first changeover switch connects the predetermined connection point from the high-voltage battery closest to the predetermined connection point, the second changeover switch disconnects the predetermined connection point from the high-voltage switch closest to the predetermined connection point, the third changeover switch disconnects the predetermined connection point from the low-voltage battery closest to the predetermined connection point, and the fourth changeover switch connects the predetermined connection point from ground.

9. The multilevel inverter device according to claim 5, further comprising a reverse current prevention diode (49) that prevents current from flowing back into the plurality of batteries when the control device detects a short-circuit failure in any of the plurality of high-voltage switches and controls the plurality of changeover switches, and the voltage input to the plurality of high-voltage switches is switched to one of the voltages output from the terminals and connection points of the plurality of batteries that is lower than the total voltage and higher than zero.

Images