JP2016171637A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system which selectively executes a parallel connection mode for supplying electric power to a load circuit (an inverter) with two DC power supplies (storage batteries) connected in parallel to each other and a series connection mode for supplying electric power to the load circuit with the two DC power supplies connected in series to each other and which, when a switching failure occurs while a specific switching element is conducting, detects occurrence of the failure.SOLUTION: The power supply system controls, when one switching element to be detected is failed, the other switching elements so that a specific closed circuit is formed, and detects occurrence of the failure of the specific switching element on the basis of a change in a voltage across terminals of a capacitor provided at the power supply system, which appears when the closed circuit is formed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system that includes two DC power supplies and can selectively connect these DC power supplies in series or in parallel to a load circuit.

  Patent Document 1 discloses a power supply system (hereinafter also referred to as “conventional device”) including two DC power supplies capable of charging and discharging, four switching elements, and two reactors. In the conventional device, a parallel circuit that supplies power to a load circuit in a state where two DC power sources are connected in parallel with each other by maintaining a specific switching element among four switching elements in a conductive state (on state). Connected mode is executed. Furthermore, in the conventional device, a series connection mode in which power is supplied to the load circuit in a state where two DC power sources are connected in series with each other by maintaining another switching element among the four switching elements. Is executed.

  In addition, the conventional device switches a specific switching element that is not maintained in a conductive state among the four switching elements between a conductive state and a cut-off state (off state), and thus energy stored in the reactor. By controlling the voltage, the voltage between the terminals of the two DC power supplies can be boosted, and the boosted voltage can be applied to the load circuit. In other words, the conventional device can operate a specific switching element as the lower arm element of the step-up chopper circuit.

  Alternatively, when the load circuit generates a DC voltage (output voltage), the conventional device switches the other specific switching element between the conductive state and the cut-off state, and controls the energy stored in the reactor to output The voltage can be stepped down and the stepped down voltage can be applied to two DC power supplies. In other words, the conventional device can operate a specific switching element as the upper arm element of the step-down chopper circuit.

  For example, the conventional apparatus executes the parallel connection mode when the voltage required by the load circuit (required voltage) is low, and executes the series connection mode when the required voltage is high. More specifically, if the required voltage is lower than the sum of the voltages between the terminals of the two DC power supplies, the conventional device executes the parallel connection mode. On the other hand, if the required voltage is higher than the sum of the voltages between the terminals of the two DC power supplies, the conventional device executes the series connection mode.

JP2013-93923A

  However, when the switching element is in a conductive state and cannot be switched (hereinafter also referred to as “short-circuit failure”), the parallel connection mode and / or the series connection mode cannot be executed. In addition, when a short circuit failure of the switching element occurs, it may be impossible to boost the voltage between the terminals of the DC power supply. That is, there is a risk that it is difficult for the conventional device to stably supply power to the load circuit due to a short circuit failure of the switching element.

  Accordingly, one of the objects of the present invention is to provide a power supply system that can detect the occurrence of a short-circuit fault in a specific switching element.

  A power supply system for achieving the above object (hereinafter also referred to as “the device of the present invention”) is connected to a load circuit and used to supply DC power to the load circuit, A negative electrode connection point, a feed line, a first DC power source, and a second DC power source are provided. The device of the present invention further includes first to fourth semiconductor switches, a high-voltage side capacitor, a high-voltage side voltage sensor and a low-voltage side voltage sensor, and a control unit.

  The power supply line connects the positive electrode connection point and the negative electrode connection point, a first connection point between the positive electrode connection point and the negative electrode connection point, and the first connection point and the negative electrode connection point A second connection point in between, a third connection point between the second connection point and the negative connection point, and a fourth connection point between the third connection point and the negative connection point .

  A positive electrode of the first DC power supply is connected to the first connection point, and a negative electrode of the first DC power supply is connected to the third connection point. A positive electrode of the second DC power supply is connected to the second connection point, and a negative electrode of the second DC power supply is connected to the fourth connection point. Each of the first DC power supply and the second DC power supply can be charged and discharged.

  The first semiconductor switch is interposed between the positive electrode connection point and the first connection point of the power supply line, and cuts off only a current flowing from the positive electrode connection point to the first connection point. it can. The second semiconductor switch is interposed in a portion between the first connection point and the second connection point of the feeder line, and cuts off only a current flowing from the first connection point to the second connection point. be able to. The third semiconductor switch is interposed between the second connection point and the third connection point of the power supply line, and cuts off only a current flowing from the second connection point to the third connection point. be able to. The fourth semiconductor switch is interposed in a portion between the third connection point and the fourth connection point of the feeder line, and cuts off only a current flowing from the third connection point to the fourth connection point. be able to.

  Each of the first to fourth semiconductor switches is configured by combining, for example, a switching element such as an IGBT and a MOSFET and a diode connected in reverse parallel to the switching element. Each of the first semiconductor switch to the fourth semiconductor switch cuts off only one-way current when the included switching element is in a cut-off state, and the state of the semiconductor switch at this time is also referred to as a “cut-off state”. On the other hand, each of the first to fourth semiconductor switches conducts current in both directions when the enclosing switching element is in a conducting state, and the state of the semiconductor switch at this time is also referred to as a “conducting state”.

  The high-voltage side capacitor has one end connected to the positive electrode connection point and the other end connected to the negative electrode connection point. That is, the high-voltage side capacitor is connected between the positive electrode connection point and the negative electrode connection point. The high voltage side voltage sensor detects a high voltage side voltage that is a voltage between the positive electrode connection point and the negative electrode connection point (that is, a voltage across terminals of the high voltage side capacitor). The low voltage side voltage sensor detects a low voltage side voltage which is a voltage between terminals of the second DC power supply.

  The control unit controls the conduction state of each of the first semiconductor switch to the fourth semiconductor switch (that is, by switching the state of each semiconductor switch between a conduction state and a cutoff state), A parallel connection mode in which the first DC power source and the second DC power source are connected in parallel to the load circuit, and the first DC power source and the second DC power source are connected in series to the load circuit. The series connection mode is selectively executed.

  In addition, the control unit boosts a voltage between the terminals of the first DC power source and / or the second DC power source by controlling a conduction state of each of the first to fourth semiconductor switches. The voltage is applied between the positive electrode connection point and the negative electrode connection point, or the voltage between the positive electrode connection point and the negative electrode connection point is stepped down and applied to the first DC power source and / or the second DC power source.

  Further, when the high-voltage side voltage is higher than the low-voltage side voltage by the charge accumulated in the high-voltage side capacitor, the control unit controls the first semiconductor switch from the cut-off state to the conductive state, If the high-voltage side voltage is equal to the low-voltage side voltage, it is determined that a short circuit fault has occurred in the second semiconductor switch.

  If both the first semiconductor switch and the second semiconductor switch are in a conductive state, a closed circuit including a high-voltage side capacitor and a second DC power supply is formed (see a thick line B1 in FIG. 8). If a charge is accumulated in the high-voltage side capacitor, the closed circuit is formed if the voltage between the terminals of the capacitor (ie, the high-voltage side voltage) is higher than the voltage between the terminals of the second DC power supply (ie, the low-voltage side voltage). When this is done, the charge moves from the high voltage side capacitor to the second DC power source. That is, the second DC power supply is charged. As a result, the high voltage and the low voltage are equal to each other.

  For example, in order to smooth the low-voltage side voltage, a capacitor (also referred to as “low-voltage side capacitor” for convenience) is connected in parallel with the second DC power supply to the second connection point and the fourth connection point. There is a case. Even in this case, if the high-voltage side voltage is higher than the low-voltage side voltage, when the closed circuit is formed, the charge moves from the high-voltage side capacitor to the second DC power source and the low-voltage side capacitor. That is, the high-voltage side voltage and the low-voltage side voltage are equal to each other.

  Therefore, when the high-voltage side voltage is higher than the low-voltage side voltage, if the high-voltage side voltage becomes equal to the low-voltage side voltage when the control unit controls only the first semiconductor switch from the cutoff state to the conductive state, the closed circuit is Thus, it can be determined that a short-circuit fault has occurred in the second semiconductor switch.

  Therefore, according to the device of the present invention, it is possible to detect the occurrence of a short circuit fault in the second semiconductor switch.

1 is a schematic diagram of a vehicle on which a power supply system (first system) according to a first embodiment of the present invention is mounted. It is the table | surface which showed the presence or absence of the pressure | voltage rise operation | movement of the 1st system determined based on the relationship between the voltage between terminals of two storage batteries, and a high voltage side voltage. It is the table | surface which showed each state of the semiconductor switch with respect to each of the connection mode of a 1st system. It is the schematic showing the equivalent circuit in case a 1st system performs parallel connection mode. It is the schematic showing the equivalent circuit in case the 1st system performs another parallel connection mode. It is the schematic showing the equivalent circuit in case a 1st system performs series connection mode. It is a time chart showing the mode of control with respect to a system main relay and a semiconductor switch when the control part of a 1st system performs a short circuit fault detection process. It is a partial circuit diagram showing the closed circuit formed when the short circuit fault has generate | occur | produced in the 2nd semiconductor switch. It is a flowchart showing the short circuit fault detection processing routine which the control part of a 1st system performs. It is a time chart showing the mode of control to a system main relay and a semiconductor switch when a control part of a power supply system (second system) concerning a 2nd embodiment of the present invention performs a short circuit fault detection processing. It is a partial circuit diagram showing the closed circuit formed when the short circuit failure has not generate | occur | produced in the 2nd semiconductor switch. It is a partial circuit diagram showing the closed circuit formed when the short circuit fault has generate | occur | produced in the 2nd semiconductor switch. It is a flowchart showing the short circuit fault detection processing routine which the control part of a 2nd system performs.

<First Embodiment>
Hereinafter, a power supply system 10 (hereinafter also referred to as “first system”) according to a first embodiment of the present invention will be described with reference to the drawings. The first system is mounted on a vehicle 1 whose schematic configuration is shown in FIG. The vehicle 1 is an electric vehicle.

  The first system includes a first power supply unit 20, a second power supply unit 30, a switch unit 40, a high-voltage side capacitor 51, and an ECU (electronic control unit) 60. The vehicle 1 further includes an inverter 70 and an electric motor 80.

  The first power supply unit 20 includes a first storage battery 21, a first capacitor 22, a first reactor 23, and a first system main relay 24 (SMR1).

  The first storage battery 21 is a lithium ion battery that can be charged and discharged. The positive electrode (P1) and the negative electrode (N1) of the first storage battery 21 are connected to one end of each of the pair of power supply lines (PL1, NL1). The other ends of the pair of power supply lines (PL1, NL1) are connected to the switch unit 40.

The first capacitor 22 is connected between a pair of power supply lines (PL1, NL1). That is, the first capacitor 22 is connected in parallel with the first storage battery 21. The first capacitor 22 smoothes the inter-terminal voltage V <b> 1 between the positive electrode and the negative electrode of the first storage battery 21.
The 1st reactor 23 is interposed in the part between the 1st capacitor | condenser 22 and the switch part 40 of a feeder (PL1).

  The first system main relay 24 includes a first positive electrode switch 24a and a first negative electrode switch 24b. The first positive electrode switch 24a is interposed in a portion between the first storage battery 21 and the first capacitor 22 of the power supply line (PL1). The first negative electrode switch 24b is interposed in a portion between the first storage battery 21 and the first capacitor 22 of the power supply line (NL1). The first system main relay 24 can block the current flowing through the first storage battery 21.

  The 2nd electric power feeding part 30 contains the 2nd storage battery 31, the 2nd capacitor | condenser 32, the 2nd reactor 33, and the 2nd system main relay 34 (SMR2).

  The second storage battery 31 is a lithium ion battery that can be charged and discharged. The positive electrode (P2) and the negative electrode (N2) of the second storage battery 31 are connected to respective one ends of the pair of power supply lines (PL2, NL2). The other ends of the pair of power supply lines (PL2, NL2) are connected to the switch unit 40.

The second capacitor 32 is connected between a pair of power supply lines (PL2, NL2). That is, the second capacitor 32 is connected in parallel with the second storage battery 31. The second capacitor 32 smoothes the inter-terminal voltage V <b> 2 between the positive electrode and the negative electrode of the second storage battery 31.
The 2nd reactor 33 is interposed in the part between the 2nd capacitor | condenser 32 and the switch part 40 of a feeder (PL2).

  The second system main relay 34 includes a second positive electrode switch 34a and a second negative electrode switch 34b. The second positive electrode switch 34a is interposed in a portion between the second storage battery 31 and the second capacitor 32 of the power supply line (PL2). The second negative electrode switch 34b is interposed in a portion between the second storage battery 31 and the second capacitor 32 of the power supply line (NL2). The second system main relay 34 can block the current flowing through the second storage battery 31.

  The switch unit 40 includes a first diode 41a to a fourth diode 44a, a first IGBT 41b (SW1) to a fourth IGBT 44b (SW4), and a feeder line (FR).

  The feeder line (FR) includes a connection point C0 to a connection point C4. The connection point C0 to the connection point C4 are arranged in the order of the connection point C0, the connection point C1, the connection point C2, the connection point C3, and the connection point C4. A connection point C0 at one end of the feeder line (FR) is connected to one end of the feeder line (PH). A connection point C4 at the other end of the power supply line (FR) is connected to one end of the power supply line (NH).

  The first diode 41a is interposed between the connection point C0 and the connection point C1 of the feeder line (FR), the cathode is on the connection point C0 side, and the anode is on the connection point C1 side. The first IGBT 41b is connected in reverse parallel to the first diode 41a. The combination of the first IGBT 41b and the first diode 41a is also referred to as a “first semiconductor switch” for convenience.

  The second diode 42a is interposed between the connection point C1 and the connection point C2 of the feeder line (FR), the cathode is on the connection point C1 side, and the anode is on the connection point C2 side. The second IGBT 42b is connected in antiparallel to the second diode 42a. The combination of the second IGBT 42b and the second diode 42a is also referred to as a “second semiconductor switch” for convenience.

  The third diode 43a is interposed between the connection point C2 and the connection point C3 of the power supply line (FR), the cathode is on the connection point C2 side, and the anode is on the connection point C3 side. The third IGBT 43b is connected in reverse parallel to the third diode 43a. The combination of the third IGBT 43b and the third diode 43a is also referred to as a “third semiconductor switch” for convenience.

  The fourth diode 44a is interposed between the connection point C3 and the connection point C4 of the power supply line (FR), the cathode is on the connection point C3 side, and the anode is on the connection point C4 side. The fourth IGBT 44b is connected in antiparallel to the fourth diode 44a. The combination of the fourth IGBT 44b and the fourth diode 44a is also referred to as a “fourth semiconductor switch” for convenience.

  A power supply line (PL1) of the first power supply unit 20 is connected to the connection point C1. A power supply line (PL2) of the second power supply unit 30 is connected to the connection point C2. A power supply line (NL1) of the first power supply unit 20 is connected to the connection point C3. The power supply line (NL2) of the second power supply unit 30 is connected to the connection point C4.

  The other end of the feed line (PH) is connected to the positive electrode connection point (P3). The other end of the power supply line (NH) is connected to the negative electrode connection point (N3). Each of the positive electrode connection point (P3) and the negative electrode connection point (N3) is connected to an inverter 70 described later.

  The switch unit 40 boosts the DC voltage output from the first storage battery 21 and / or the second storage battery 31 by controlling the conduction state of the first IGBT 41b to the fourth IGBT 44b described later, and applies the boosted voltage to the inverter 70. .

  The high voltage side capacitor 51 is connected between the power supply line (PH) and the power supply line (NH). The high voltage side capacitor 51 smoothes the high voltage side voltage VH, which is a voltage between the positive electrode connection point (P3) and the negative electrode connection point (N3).

  The ECU 60 is a microcomputer including a CPU 62, a ROM 63 that stores a program executed by the CPU 62, a map, and the like, and a RAM 64 that temporarily stores data. ECU 60 controls first IGBT 41b to fourth IGBT 44b, first system main relay 24 and second system main relay 34 (conductive state and cut-off state), and inverter 70. The ECU 60 is connected to a first current sensor 81, a second current sensor 82, a first voltage sensor 83, a second voltage sensor 84 and a high voltage side voltage sensor 85 which will be described later.

  The inverter 70 includes a plurality of switching elements (in this example, IGBT) not shown, and the DC power output by the switch unit 40 between the positive electrode connection point (P3) and the negative electrode connection point (N3) It is converted into V-phase and W-phase three-phase AC power and output to the motor 80. For convenience, the inverter 70 is also referred to as a “load circuit”.

  When the electric motor 80 operates as a generator, the inverter 70 converts the alternating current power output from the electric motor 80 into direct current power, between the positive electrode connection point (P3) and the negative electrode connection point (N3), that is, the switch unit 40. Output to. In this case, the switch unit 40 steps down the DC voltage and applies the stepped-down voltage to the first storage battery 21 and / or the second storage battery 31 by controlling the conduction state of the first IGBT 41b to the fourth IGBT 44b described later. As a result, the first storage battery 21 and / or the second storage battery 31 is charged.

  The electric motor 80 includes a stator including a three-phase winding (coil) that generates a rotating magnetic field, and a rotor including a permanent magnet that generates torque by a magnetic force attracted or repelled by the rotating magnetic field. The electric motor 80 can operate as a generator as well as an electric motor. When the electric motor 80 operates as an electric motor, it generates a driving force of the vehicle 1 (torque for running the vehicle).

  The first current sensor 81 generates a signal that represents the current A <b> 1 that flows through the first reactor 23. When current flows from the first reactor 23 toward the connection point C1, the current A1 is a positive value. The second current sensor 82 generates a signal that represents the current A <b> 2 that flows through the second reactor 33. When current flows from the second reactor 33 in the direction of the connection point C2, the current A2 has a positive value.

  The first voltage sensor 83 generates a signal representing the terminal voltage V <b> 1 of the first storage battery 21. The second voltage sensor 84 generates a signal representing the inter-terminal voltage V <b> 2 of the second storage battery 31. For convenience, the voltage V2 is also referred to as “low voltage side voltage”. The high voltage side voltage sensor 85 generates a signal representing the high voltage side voltage VH.

(Operation)
The CPU 62 of the ECU 60 (hereinafter also simply referred to as “CPU”) detects a short-circuit failure of the second IGBT 42b to the fourth IGBT 44b when the vehicle 1 is started (that is, when the ECU 60 is started). Execute the process. When a short circuit failure occurs, the CPU executes a degenerate operation in which the vehicle 1 travels only with the electric power generated by the second storage battery 31.

  First, control of the states (conducting state and blocking state) of the first IGBT 41b to the fourth IGBT 44b executed by the CPU will be described. While the vehicle 1 is operating, the CPU maintains the first system main relay 24 and the second system main relay 34 in a conductive state.

  The CPU executes a parallel connection mode in which power is supplied to the inverter 70 in a state where the first storage battery 21 and the second storage battery 31 are connected in parallel with each other by maintaining one of the second IGBT 42b and the fourth IGBT 44b in a conductive state. . When there is a request to execute the parallel connection mode, each of the inter-terminal voltage V1 of the first storage battery 21 and the inter-terminal voltage V2 of the second storage battery 31 becomes the high-voltage side voltage VH (that is, V1 = V2 = VH). Further, when the voltage V1 and the voltage V2 are boosted by a boosting operation described later, each of the boosted voltage V1 and the boosted voltage V2 is equal to the high-voltage side voltage VH.

  Or CPU performs the series connection mode which supplies electric power to the inverter 70 in the state in which the 1st storage battery 21 and the 2nd storage battery 31 were mutually connected in series by maintaining the 3rd IGBT43b in a conduction | electrical_connection state. When there is a request to execute the series connection mode, the sum of the inter-terminal voltage V1 of the first storage battery 21 and the inter-terminal voltage V2 of the second storage battery 31 becomes the high-voltage side voltage VH (that is, V1 + V2 = VH). Further, when the voltage V1 and the voltage V2 are boosted by a boosting operation described later, the sum of the boosted voltage V1 and the boosted voltage V2 becomes equal to the high voltage VH.

  The CPU selectively executes the parallel connection mode and the series connection mode. FIG. 2 shows the connection mode determined based on the magnitude relationship among the voltage V1 and the voltage V2 and the target high-voltage side voltage VH * and the presence or absence of the boost operation. FIG. 3 shows the states (conductive state and cut-off state) of the first IGBT 41b to the fourth IGBT 44b for each of the connection modes. Details of the parallel connection mode and the series connection mode will be described below.

1 Parallel connection mode When there is a request to execute the parallel connection mode, the CPU operates the first system according to the magnitude relationship between the terminal voltage V1 of the first storage battery 21 and the terminal voltage V2 of the second storage battery 31. Switch.

1-1 When Voltage V1 <Voltage V2 When there is a request to execute the parallel connection mode, if the voltage V1 is lower than the voltage V2, the CPU maintains the second IGBT 42b in a conductive state. As a result, the first storage battery 21 and the second storage battery 31 are connected in parallel to the inverter 70. An equivalent circuit of the first system in this case is shown in FIG. The parallel connection mode realized by maintaining the second IGBT 42b in the conductive state is also referred to as “first parallel connection mode”.

(1a) In this state, when the third IGBT 43b is in a conductive state and the fourth IGBT 44b is in a disconnected state, a current flows from the positive electrode of the first storage battery 21 to the negative electrode of the first storage battery 21 through the first reactor 23. Energy is accumulated in one reactor 23. Thereafter, when the third IGBT 43 b changes to the cutoff state, the energy accumulated in the first reactor 23 is released and supplied to the inverter 70. As a result, the voltage V1 generated by the first storage battery 21 is boosted to the boosted voltage Vpa1, and the boosted voltage Vpa1 is applied to the inverter 70. That is, in this case, the first power supply unit 20 and the switch unit 40 operate as a boost chopper circuit in which the third IGBT 43b functions as a lower arm element.

Assuming that the duty ratio of the lower arm element (that is, the third IGBT 43b) is the duty ratio Dpa1, the boosted voltage Vpa1 is expressed by the following equation (1).

Vpa1 = {1 / (1-Dpa1)} · V1 (1)

Here, the duty ratio (conduction ratio) is the time from the time when the switching element is switched from the cut-off state to the conductive state until the time when the switching element is switched from the cut-off state to the conductive state again (that is, the switching cycle). It is the ratio of the time during which the switching element is in a conducting state.

(1b) On the other hand, when the third IGBT 43b and the fourth IGBT 44b are both in a conductive state, a current flows from the positive electrode of the second storage battery 31 to the negative electrode of the second storage battery 31 through the second reactor 33, so in addition to the first reactor 23 Energy is also accumulated in the second reactor 33. Thereafter, when at least one of the third IGBT 43b and the fourth IGBT 44b is changed to the cutoff state, the energy accumulated in the second reactor 33 is released and supplied to the inverter 70. As a result, the voltage V2 generated by the second storage battery 31 is boosted to the boosted voltage Vpa2, and the boosted voltage Vpa2 is applied to the inverter 70. That is, in this case, the second power feeding unit 30 and the switch unit 40 operate as a boost chopper circuit in which the third IGBT 43b and the fourth IGBT 44b function as lower arm elements.

Assuming that the duty ratio of the lower arm elements (that is, the third IGBT 43b and the fourth IGBT 44b) is the duty ratio Dpa2, the boosted voltage Vpa2 is expressed by the following equation (2).

Vpa2 = {1 / (1-Dpa2)} · V2 (2)

  As understood from the above formulas (1) and (2), the boost rate Rv1 (boost rate Rv1 = post-boost voltage Vpa1 / inter-terminal voltage V1) of the first storage battery 21 increases as the duty ratio Dpa1 increases. . Furthermore, the boost rate Rv2 (boost rate Rv2 = post-boost voltage Vpa2 / inter-terminal voltage V2) of the second storage battery 31 increases as the duty ratio Dpa2 increases.

  Since the time during which both the third IGBT 43b and the fourth IGBT 44b are in the conducting state is shorter or equal to the time during which only the third IGBT 43b is in the conducting state, the duty ratio Dpa2 is equal to or less than the duty ratio Dpa1 (that is, Dpa1 ≧ Dpa2). Therefore, the boost rate Rv1 ≧ the boost rate Rv2.

  On the other hand, the boosted voltage Vpa1 and the boosted voltage Vpa2 are both equal to the high voltage VH (that is, Vpa1 = Vpa2 = VH). Since the step-up rate Rv1 ≧ the step-up rate Rv2, it is necessary that the voltage V1 ≦ the voltage V2 in order to boost both the voltage V1 and the voltage V2 to the high voltage VH. In other words, when the execution request for the parallel connection mode is generated, the CPU selects the first parallel connection mode if the voltage V1 is lower than the voltage V2 (that is, V1 <V2). On the other hand, when the execution request for the parallel connection mode is generated, the CPU selects the second parallel connection mode described later if the voltage V1 is higher than the voltage V2 (that is, V1> V2).

(2a) When the first storage battery 21 and / or the second storage battery 31 is charged by the DC voltage generated by the inverter 70, the first IGBT 41b is controlled. More specifically, when the first IGBT 41b is in the conducting state and the fourth IGBT 44b is in the cut-off state, the second reactor is connected from the positive connection point (P3) by the DC voltage generated by the inverter 70 (that is, the high-voltage side voltage VH). Since current flows through the negative electrode connection point (N 3) through 33, energy is stored in the second reactor 33. Thereafter, when the first IGBT 41b changes to the cutoff state, the energy accumulated in the second reactor 33 is released. That is, in this case, the voltage generated by the inverter 70 is stepped down, and the stepped down voltage is applied to the second storage battery 31. That is, the second power feeding unit 30 and the switch unit 40 operate as a step-down chopper circuit in which the first IGBT 41b functions as an upper arm element.

(2b) When both the first IGBT 41b and the fourth IGBT 44b are in a conductive state, current flows from the positive electrode connection point (P3) through the first reactor 23 to the negative electrode connection point (N3) due to the DC voltage generated by the inverter 70. Energy is stored in the first reactor 23 in addition to the two reactors 33. Thereafter, when at least one of the first IGBT 41b and the fourth IGBT 44b is changed to the cutoff state, the energy accumulated in the first reactor 23 is released. That is, in this case, the voltage generated by the inverter 70 is stepped down, and the stepped down voltage is applied to the first storage battery 21. In other words, the first power supply unit 20 and the switch unit 40 operate as a step-down chopper circuit in which the first IGBT 41b and the fourth IGBT 44b function as upper arm elements.

1-2 When Voltage V1> Voltage V2 As described above, when there is a request to execute the parallel connection mode, if the voltage V1 is higher than the voltage V2, the CPU maintains the fourth IGBT 44b in a conductive state. As a result, the first storage battery 21 and the second storage battery 31 are connected in parallel to the inverter 70. An equivalent circuit of the first system in this case is shown in FIG. The parallel connection mode realized by maintaining the fourth IGBT 44b in the conductive state is also referred to as “second parallel connection mode”.

(1a) In this state, when the third IGBT 43b is in a conducting state and the second IGBT 42b is in a disconnected state, a current flows from the positive electrode of the second storage battery 31 to the negative electrode of the second storage battery 31 through the second reactor 33. Energy is stored in the two reactors 33. Thereafter, when the third IGBT 43 b changes to the cutoff state, the energy accumulated in the second reactor 33 is released and supplied to the inverter 70. As a result, the voltage V2 generated by the second storage battery 31 is boosted to the boosted voltage Vpb2, and the boosted voltage Vpb2 is applied to the inverter 70. That is, in this case, the second power feeding unit 30 and the switch unit 40 operate as a boost chopper circuit in which the third IGBT 43b functions as a lower arm element.

Assuming that the duty ratio of the lower arm element (that is, the third IGBT 43b) is the duty ratio Dpb2, the boosted voltage Vpb2 is expressed by the following equation (3).

Vpb2 = {1 / (1-Dpb2)} · V2 (3)

(1b) On the other hand, when both the second IGBT 42b and the third IGBT 43b are in a conducting state, a current flows from the positive electrode of the first storage battery 21 to the negative electrode of the first storage battery 21 through the first reactor 23, so in addition to the second reactor 33 Energy is also accumulated in the first reactor 23. Thereafter, when at least one of the second IGBT 42b and the third IGBT 43b changes to the cut-off state, the energy stored in the first reactor 23 is released and supplied to the inverter 70. As a result, the voltage V1 generated by the first storage battery 21 is boosted to the boosted voltage Vpb1, and the boosted voltage Vpb1 is applied to the inverter 70. That is, in this case, the first power supply unit 20 and the switch unit 40 operate as a boost chopper circuit in which the second IGBT 42b and the third IGBT 43b function as lower arm elements.

Assuming that the duty ratio of the lower arm elements (that is, the second IGBT 42b and the third IGBT 43b) is the duty ratio Dpb1, the boosted voltage Vpb1 is expressed by the following equation (4).

Vpb1 = {1 / (1-Dpb1)} · V1 (4)

(2a) When the first storage battery 21 and / or the second storage battery 31 is charged by the DC voltage generated by the inverter 70, the first IGBT 41b is controlled. More specifically, when the first IGBT 41b is in the conducting state and the second IGBT 42b is in the cut-off state, the first reactor 23 is connected from the positive connection point (P3) by the DC voltage (high-voltage side voltage VH) generated by the inverter 70. As a result, current flows to the negative electrode connection point (N3), so that energy is accumulated in the first reactor 23. Thereafter, when the first IGBT 41b changes to the cutoff state, the energy accumulated in the first reactor 23 is released. That is, in this case, the voltage generated by the inverter 70 is stepped down, and the stepped down voltage is applied to the first storage battery 21. That is, the first power supply unit 20 and the switch unit 40 operate as a step-down chopper circuit in which the first IGBT 41b functions as an upper arm element.

(2b) When both the first IGBT 41b and the second IGBT 42b are in a conducting state, current flows from the positive electrode connection point (P3) through the second reactor 33 to the negative electrode connection point (N3) by the DC voltage generated by the inverter 70. Energy is stored in the second reactor 33 in addition to the first reactor 23. After that, when at least one of the first IGBT 41b and the second IGBT 42b changes to the cutoff state, the energy accumulated in the second reactor 33 is released. That is, in this case, the voltage generated by the inverter 70 is stepped down, and the stepped down voltage is applied to the second storage battery 31. In other words, the second power feeding unit 30 and the switch unit 40 operate as a step-down chopper circuit in which the first IGBT 41b and the second IGBT 42b function as upper arm elements.

2 Series Connection Mode When there is a request to execute the series connection mode, the CPU maintains the third IGBT 43b in a conductive state. As a result, the first storage battery 21 and the second storage battery 31 are connected in series to the inverter 70. An equivalent circuit of the first system in this case is shown in FIG.

(1a) In this state, when the second IGBT 42b is in a conductive state, current flows from the positive electrode of the first storage battery 21 through the first reactor 23 to the negative electrode of the first storage battery 21, so that energy is accumulated in the first reactor 23. The Thereafter, when the second IGBT 42 b changes to the cutoff state, the energy accumulated in the first reactor 23 is released and supplied to the inverter 70. As a result, the voltage V1 generated by the first storage battery 21 is boosted to the boosted voltage Vs1. That is, in this case, the first power supply unit 20 and the switch unit 40 operate as a boost chopper circuit in which the second IGBT 42b functions as a lower arm element.

When the duty ratio of the lower arm element (that is, the second IGBT 42b) is the duty ratio Ds1, the boosted voltage Vs1 is expressed by the following equation (5).

Vs1 = {1 / (1-Ds1)} · V1 (5)

(1b) On the other hand, when the fourth IGBT 44b is in a conducting state, current flows from the positive electrode of the second storage battery 31 through the second reactor 33 to the negative electrode of the second storage battery 31, so that energy is accumulated in the second reactor 33. Thereafter, when the fourth IGBT 44b changes to the cutoff state, the energy accumulated in the second reactor 33 is released and supplied to the inverter 70. As a result, the voltage V2 generated by the second storage battery 31 is boosted to the boosted voltage Vs2. That is, in this case, the second power feeding unit 30 and the switch unit 40 operate as a boost chopper circuit in which the fourth IGBT 44b functions as a lower arm element.

Assuming that the duty ratio of the lower arm element (that is, the fourth IGBT 44b) is the duty ratio Ds2, the boosted voltage Vs2 is expressed by the following equation (6).

Vs2 = {1 / (1-Ds2)} · V2 (6)

  When the series connection mode is executed, the high-voltage side voltage VH is equal to the sum of the boosted voltage Vs1 and the boosted voltage Vs2 (that is, VH = Vs1 + Vs2). That is, a voltage equal to the sum of the boosted voltage Vs1 and the boosted voltage Vs2 is applied to the inverter 70.

(2) When the first storage battery 21 and / or the second storage battery 31 is charged by the DC voltage generated by the inverter 70, the first IGBT 41b is controlled. More specifically, when the first IGBT 41b is in a conductive state, the DC voltage (high voltage side voltage VH) generated by the inverter 70 is changed from the positive electrode connection point (P3) to the negative electrode connection point (N3) through the first reactor 23. Since current flows, energy is accumulated in the first reactor 23. Similarly, when the first IGBT 41b is in a conducting state, current flows from the positive electrode connection point (P3) through the second reactor 33 to the negative electrode connection point (N3), so that energy is accumulated in the second reactor 33.

  Alternatively, energy is accumulated only in the first reactor 23 when both the first IGBT 41b and the fourth IGBT 44b are in a conductive state. On the other hand, when both the first IGBT 41b and the second IGBT 42b are in a conductive state, energy is stored only in the second reactor 33.

  Thereafter, when the first IGBT 41b is changed to the cutoff state, the energy accumulated in each of the first reactor 23 and the second reactor 33 is released. In this case, the voltage generated by the inverter 70 is stepped down, and the stepped down voltage is applied to each of the first storage battery 21 and the second storage battery 31. That is, in this case, the first power supply unit 20 and / or the second power supply unit 30 and the switch unit 40 operate as a step-down chopper circuit in which the first IGBT 41b functions as an upper arm element.

3. Selection of Parallel Connection Mode and Series Connection Mode The CPU selects either the parallel connection mode or the series connection mode as the connection mode according to the target high voltage VH * which is the target value of the high voltage VH. The CPU sets the target high-voltage side voltage VH * to a higher value as the required output of the electric motor 80 becomes higher.

  When the target high-voltage side voltage VH * is low, the CPU selects a parallel connection mode (specifically, one of the first parallel connection mode and the second parallel connection mode). When there is a request to execute the parallel connection mode, if the voltage V1 and / or the voltage V2 is lower than the target high-side voltage VH * (that is, if V1 <VH * and / or V2 <VH * is satisfied). ), The boosting process in the parallel connection mode described above is executed.

  The CPU sets the duty ratio Dpa1 and the duty ratio Dpa2 or the duty ratio Dpb1 and the duty ratio Dpb2 to higher values as the target high-voltage side voltage VH * becomes higher. As the duty ratio increases, the energy stored in the first reactor 23 and / or the second reactor 33 increases. Therefore, when the duty ratio is high, the accumulated energy may exceed the capacity of the first reactor 23 and / or the second reactor 33 (substantial maximum value of energy that can be accumulated).

  On the other hand, if the duty ratio is the same, the shorter the switching period is, the shorter the time during which the switching element (in this example, the lower arm element) is in the conductive state, the maximum amount of energy accumulated in the reactor is Get smaller. Therefore, when the duty ratio is high, it is necessary to shorten the switching cycle of the switching element in order to reduce the maximum value of the energy amount accumulated in the first reactor 23 and / or the second reactor 33.

  However, if the duty ratio is the same, the shorter the switching cycle, the greater the number of times the switching element switches between the conductive state and the cutoff state per unit time. growing. In other words, the switching loss can increase as the duty ratio increases. Therefore, when the target high-voltage side voltage VH * becomes higher than the sum of the voltage V1 and the voltage V2 (that is, if voltage V1 + voltage V2 <target high-voltage side voltage VH * is established), the CPU selects the series connection mode.

  When the boosting process in the series connection mode is executed, the duty ratio becomes smaller as compared with the case where the boosting process is executed in the parallel connection mode if the target high-voltage side voltage VH * is the same. As a result, an increase in switching loss can be avoided even when the target high-voltage side voltage VH * increases.

(Overview of battery short-circuit detection processing)
Next, short-circuit fault detection processing executed by the CPU will be described with reference to the time chart shown in FIG. The CPU maintains the switching element included in the inverter 70 in the cut-off state after the ECU 60 is activated until at least the short-circuit fault detection process is completed. Therefore, no current flows from the first storage battery 21 and / or the second storage battery 31 into the inverter 70 during execution of the short-circuit failure detection process.

  After the ECU 60 is activated, the CPU controls the second system main relay 34 to the conductive state at time t0. After that, at time t1, the CPU alternately executes ON control for switching the fourth IGBT 44b from the cutoff state to the conduction state and OFF control for switching the fourth IGBT 44b from the conduction state to the cutoff state until the time t1a alternately. .

  If a short circuit failure has occurred in the third IGBT 43b, a current that flows from the positive electrode of the second storage battery 31 to the negative electrode of the second storage battery 31 through the third IGBT 43b and the fourth IGBT 44b is generated when the fourth IGBT 44b is in a conductive state. In addition, in this case, a self-induced electromotive force is generated in the second reactor 33 by the current flowing from the positive electrode of the second storage battery 31.

  Therefore, when a short-circuit failure occurs in the third IGBT 43b, the current A2 starts to increase when the ON control is performed on the fourth IGBT 44b, and the current A2 is increased when the OFF control is performed on the fourth IGBT 44b. It begins to decrease. Therefore, when the current A2 exceeds a predetermined current threshold Ath (where Ath> 0) between time t1 and time t1a, the CPU determines that a short circuit fault has occurred in the third IGBT 43b.

  At time t2, the CPU executes ON control and OFF control alternately for the third IGBT 43b a plurality of times until reaching time t2a. If a short-circuit failure has occurred in the fourth IGBT 44b, a current that flows from the positive electrode of the second storage battery 31 to the negative electrode of the second storage battery 31 through the third IGBT 43b and the fourth IGBT 44b is generated when the third IGBT 43b is in a conductive state.

  Therefore, when a short-circuit failure has occurred in the fourth IGBT 44b, the current A2 starts to increase when the ON control is performed on the third IGBT 43b, and the current A2 is increased when the OFF control is performed on the third IGBT 43b. It begins to decrease. Therefore, when the current A2 exceeds the current threshold Ath between time t2 and time t2a, the CPU determines that a short-circuit failure has occurred in the fourth IGBT 44b.

  At time t3, the CPU boosts the voltage V2 by performing ON control and OFF control alternately on the third IGBT 43b and the fourth IGBT 44b multiple times at the same time until time t3a, and increases the boosted voltage to a high voltage. Applied to the side capacitor 51. That is, the CPU operates the third IGBT 43b and the fourth IGBT 44b as lower arm elements of the “boost chopper circuit in which energy is stored in the second reactor 33”.

  As a result of the boosted voltage being applied to the high-voltage side capacitor 51, electric charges are accumulated in the high-voltage side capacitor 51, and eventually the high-voltage side voltage VH becomes equal to the boosted voltage. In other words, at this time, the high-voltage side voltage VH is higher than the voltage V2 (that is, voltage VH> voltage V2).

  At time t4, the CPU performs on control on the first IGBT 41b. If a short circuit failure has occurred in the second IGBT 42b, a closed circuit in which the second storage battery 31 and the second capacitor 32 are connected in parallel to the high-voltage side capacitor 51 as shown by the thick line B1 in FIG. It is formed.

  When this closed circuit is formed, since the high-voltage side voltage VH is higher than the voltage V2, a part of the charge accumulated in the high-voltage side capacitor 51 flows into the second storage battery 31, and the other part is the second capacitor. 32. That is, a time when the current A2 takes a negative value occurs, and as a result, the second storage battery 31 is charged and the charge accumulated in the second capacitor 32 increases. When the movement of charges is completed, the high-voltage side voltage VH and the voltage V2 become equal to each other (that is, the voltage VH = the voltage V2).

  On the other hand, if no short-circuit failure has occurred in the second IGBT 42b, the closed circuit indicated by the thick line B1 in FIG. 8 is not formed, so that the high-voltage side voltage VH is maintained higher than the voltage V2 (that is, voltage VH> Voltage V2).

  Therefore, the CPU determines whether or not there is a short-circuit failure in the second IGBT 42b at time t4a when the "time required for the charge to move from the high voltage side capacitor 51 to the second storage battery 31 and the second capacitor 32" has elapsed from time t4. . Specifically, the CPU determines that a short-circuit fault has occurred in the second IGBT 42b if the high-voltage side voltage VH and the voltage V2 are equal to each other, and short-circuits to the second IGBT 42b if the high-voltage side voltage VH is higher than the voltage V2. It is determined that no failure has occurred.

  When the CPU determines whether or not there is a short circuit failure in the second IGBT 42b, the CPU executes an off control on the first IGBT 41b. This off control ends the short circuit failure detection process.

  If no short-circuit failure has occurred in any of the second IGBT 42b to the fourth IGBT 44b, the CPU controls the first system main relay 24 to the conductive state in addition to the second system main relay 34, and starts normal operation of the vehicle 1. To do.

  On the other hand, if a short circuit failure has occurred in at least one of the second IGBT 42b to the fourth IGBT 44b, the CPU starts the degenerate operation of the vehicle 1 from time t5 in FIG. More specifically, the CPU maintains the first system main relay 24 in the disconnected state. In addition, the CPU maintains the first IGBT 41b and the second IGBT 42b in a conductive state. As a result, the inter-terminal voltage V2 of the second storage battery 31 is applied to the inverter 70 without being boosted. Therefore, the vehicle 1 travels only with the electric power output from the second storage battery 31.

(Specific operation)
A specific operation of the CPU at the time of execution of the inter-battery short-circuit detection process will be described with reference to a “short-circuit fault detection process routine” represented by a flowchart in FIG. 9. The CPU executes this routine when the activation of the ECU 60 is completed.

  That is, at an appropriate timing (time t0 in FIG. 7 described above), the CPU starts the process from step 900 and proceeds to step 905 to control the second system main relay 34 from the cutoff state to the conductive state.

  Next, the CPU proceeds to step 910, and during the period from time t1 to time t1a, the fourth IGBT 44b is alternately subjected to on control and off control at predetermined time intervals. Further, the CPU proceeds to step 915 to determine whether or not there is a time during which the current A2 exceeds the current threshold value Ath from time t1 to time t1a.

  If there is a time during which the current A2 exceeds the current threshold Ath, the CPU makes a “Yes” determination at step 915 to proceed to step 920 to determine that a short circuit fault has occurred in the third IGBT 43b. Then, the process proceeds to step 925. On the other hand, if there is no time during which the current A2 exceeds the current threshold Ath, the CPU makes a “No” determination at step 915 to proceed directly to step 925.

  In step 925, the CPU alternately performs on control and off control on the third IGBT 43b at predetermined time intervals from time t2 to time t2a. Next, the CPU proceeds to step 930 to determine whether or not there is a time during which the current A2 exceeds the current threshold Ath between time t2 and time t2a.

  If there is a time during which the current A2 exceeds the current threshold Ath, the CPU makes a “Yes” determination at step 930 to proceed to step 935 to determine that a short-circuit fault has occurred in the fourth IGBT 44b. Then, the process proceeds to Step 940. On the other hand, if there is no time during which the current A2 exceeds the current threshold Ath, the CPU makes a “No” determination at step 930 to proceed directly to step 940.

  In step 940, the CPU executes ON control and OFF control alternately at both predetermined time intervals for both the third IGBT 43b and the fourth IGBT 44b from time t3 to time t3a. As a result, the voltage V2 is boosted, and the boosted voltage is applied to the high-voltage side capacitor 51.

  Next, the CPU proceeds to step 945 to execute on-control for the first IGBT 41b at the timing when time t4 is reached. Furthermore, the CPU executes the off control on the first IGBT 41b at the timing when the time t4a is reached.

  Next, the CPU proceeds to step 950 to determine whether or not the voltage VH and the voltage V2 are equal to each other at a timing immediately before the off control is performed on the first IGBT 41b. If the voltage VH and the voltage V2 are equal to each other, the CPU makes a “Yes” determination at step 950 to proceed to step 955, determines that a short-circuit fault has occurred in the second IGBT 42b, and then proceeds to step 960. On the other hand, if the voltage VH and the voltage V2 are not equal to each other (that is, if voltage VH> voltage V2), the CPU makes a “No” determination at step 950 to directly proceed to step 960.

  In step 960, the CPU determines whether or not a short circuit fault has occurred in at least one of the second IGBT 42b to the fourth IGBT 44b, that is, whether or not any of step 920, step 935, and step 955 has been executed. To do.

  If a short circuit failure has occurred in any of the switching elements (IGBTs), the CPU makes a “Yes” determination at step 960 to proceed to step 965, which is arranged on the dashboard of the driver's seat of the vehicle 1. Turn on a warning light (not shown). Next, the CPU proceeds to step 970 to start the degenerate operation of the vehicle 1.

  More specifically, the CPU performs on control on the first IGBT 41b and the second IGBT 42b. By maintaining the first IGBT 41b in a conductive state, the second storage battery 31 is charged by a DC voltage generated between the positive electrode connection point (P3) and the negative electrode connection point (N3) when the motor 80 operates as a generator. can do. In addition, by controlling the second IGBT 42b to be in a conductive state, the second storage battery 31 can be stably charged even if a short circuit failure of the second IGBT 42b occurs intermittently. After the start of the degeneration operation of the vehicle 1, the CPU proceeds to step 995 and ends this routine.

  On the other hand, if no short-circuit failure has occurred in any of the second IGBT 42b to the fourth IGBT 44b, the CPU makes a “No” determination at step 960 to proceed to step 975 to control the first system main relay 24 to the conductive state. To do. Further, the CPU proceeds to step 980 to start normal operation of the vehicle 1.

  More specifically, the CPU executes one of the parallel connection mode and the series connection mode described above, and further performs a boosting operation if necessary, and converts the high-voltage side voltage VH to the target high-voltage side voltage VH *. Equal to In addition, the CPU controls the switching element included in the inverter 70 and causes the electric motor 80 to generate torque requested by the driver of the vehicle 1. Next, the CPU proceeds to step 995.

As described above, the first system (power supply system 10) is
A positive connection point (P3) and a negative connection point (N3) connected to the load circuit (inverter 70) and used to supply DC power to the load circuit;
A first connection point (C1) between the positive connection point and the negative connection point, and between the positive connection point and the negative connection point, between the first connection point and the negative connection point. A second connection point (C2), a third connection point (C3) between the second connection point and the negative connection point, and a third connection point between the third connection point and the negative connection point. A feeder line (FR) having four connection points (C4);
A first DC power source (21) capable of charging and discharging, wherein a positive electrode is connected to the first connection point and a negative electrode is connected to the third connection point;
A second DC power source (31) capable of charging and discharging, wherein a positive electrode is connected to the second connection point and a negative electrode is connected to the fourth connection point;
A first semiconductor switch (first semiconductor switch) interposed between the positive electrode connection point and the first connection point of the power supply line and capable of interrupting only a current flowing from the positive electrode connection point to the first connection point. 1 diode 41a and first IGBT 41b),
A second semiconductor switch that is interposed in a portion between the first connection point and the second connection point of the power supply line and that can cut off only a current flowing from the first connection point to the second connection point. (Second diode 42a and second IGBT 42b);
A third semiconductor switch that is interposed in a portion between the second connection point and the third connection point of the power supply line and can cut off only a current flowing from the second connection point to the third connection point. (Third diode 43a and third IGBT 43b);
A fourth semiconductor switch interposed between the third connection point and the fourth connection point of the power supply line and capable of interrupting only a current flowing from the third connection point to the fourth connection point; (Fourth diode 44a and fourth IGBT 44b);
A parallel connection mode in which the first DC power supply and the second DC power supply are connected in parallel to the load circuit by controlling the conduction states of the first semiconductor switch to the fourth semiconductor switch (see FIG. 4 and FIG. 5) and a series connection mode (FIG. 6) in which the first DC power source and the second DC power source are connected in series to the load circuit are selectively executed. A voltage between terminals of the first DC power source and / or the second DC power source is boosted and applied between the positive electrode connection point and the negative electrode connection point, or a voltage between the positive electrode connection point and the negative electrode connection point is decreased. And a control unit (ECU 60) for applying the first DC power source and / or the second DC power source,
A power supply system comprising:
A high voltage side capacitor (51) connected between the positive electrode connection point and the negative electrode connection point;
A high-voltage side voltage sensor (85) for detecting a high-voltage side voltage that is a voltage between terminals of the high-voltage side capacitor;
A low voltage side voltage sensor (84) for detecting a low voltage side voltage which is a voltage between terminals of the second DC power supply;
With
The controller is
When the first semiconductor switch is controlled from the cut-off state to the conductive state when the high-voltage side voltage is higher than the low-voltage side voltage due to the electric charge accumulated in the high-voltage side capacitor (step 940 in FIG. 9) ( If the high-voltage side voltage is equal to the low-voltage side voltage (determined as “Yes” in step 950 in FIG. 9), a short-circuit fault occurs in the second semiconductor switch. It is configured to determine that it has occurred (step 955 in FIG. 9).

  According to the first system, it is possible to detect the occurrence of a short circuit failure in the second IGBT 42b to the fourth IGBT 44b (particularly, the second IGBT 42b). Furthermore, the first system can continue to supply power to the inverter 70 by executing a degenerate operation when a short circuit failure occurs.

Second Embodiment
Next, a power supply system according to a second embodiment of the present invention (hereinafter also referred to as “second system”) will be described. In the first system, when a short circuit fault has occurred in the second IGBT 42b during the execution of the short circuit fault detection process, each closed circuit including the second storage battery 31, the second capacitor 32, and the high voltage side capacitor 51 is formed. The switching element (IGBT) was controlled. In addition, the first system supplies only the power output from the second storage battery to the inverter 70 when the degenerate operation is executed.

  On the other hand, in the second system, if a short-circuit fault has occurred in the second IGBT 42b during the short-circuit fault detection process, the first capacitor 22 is added to the second storage battery 31, the second capacitor 32, and the high-voltage side capacitor 51. Each switching element (IGBT) is controlled so as to form a closed circuit including. In addition, the second system supplies the inverter 70 with the power output from the first storage battery 21 in addition to the power output from the second storage battery 31 when executing the degenerate operation. Hereinafter, this difference will be mainly described.

  The short-circuit fault detection process executed by the CPU 62 (hereinafter also simply referred to as “CPU”) of the ECU 61 of the second system will be described with reference to the time chart shown in FIG. Since the first system main relay 24 is in the cut-off state when the short-circuit fault detection process is performed, no charge is accumulated in the first capacitor 22 at least during the period from the time t0 to the time t4. 0 ".

  The CPU executes ON control on the first IGBT 41b and the fourth IGBT 44b at time t4. In this case, if no short-circuit failure has occurred in the second IGBT 42b, a closed circuit is formed in which the high-voltage side capacitor 51 and the first capacitor 22 are connected, as shown by the thick line B2 in FIG. By forming the closed circuit, the charge accumulated in the high voltage side capacitor 51 moves to the first capacitor 22. That is, a time when the current A1 takes a negative value occurs, and the high-voltage side voltage VH and the voltage V1 become equal to each other.

  At this time, the high-voltage side voltage VH is lower than that at time t3a, but is higher than the voltage V2 (that is, V2 <VH = V1). If the voltage V2 becomes higher than the high-voltage side voltage VH (that is, if V2> VH = V1), the charge moves from the second storage battery 31 to the first capacitor 22 via the second diode 42a. As a result, the voltage V1 and the voltage V2 are equal to each other. In other words, when the closed circuit is formed, the time between time t3 and time t3a is such that the voltage VH is still higher than the voltage V2 even if the charge moves from the high-voltage side capacitor 51 to the first capacitor 22. Sufficient charges are accumulated in the high-voltage side capacitor 51 by the boosting process to be executed.

  On the other hand, if a short circuit failure has occurred in the second IGBT 42 b, the second storage battery 31, the second capacitor 32, and the first capacitor 22 are in parallel to the high-voltage side capacitor 51, as shown by the thick line B <b> 3 in FIG. 12. A closed circuit to be connected is formed. By forming the closed circuit, the electric charge accumulated in the high-voltage side capacitor 51 moves to the second storage battery 31, the second capacitor 32, and the first capacitor 22, and eventually, the high-voltage side voltage VH, the voltage V1, and the voltage V2 Are equal to each other (ie, V1 = V2 = VH).

  Therefore, at time t4a, the CPU determines that a short-circuit fault has occurred in the second IGBT 42b if the high-voltage side voltage VH and the voltage V2 are equal to each other, and short-circuits to the second IGBT 42b if the high-voltage side voltage VH is higher than the voltage V2. It is determined that no failure has occurred.

(Specific operation)
A specific operation of the CPU during the execution of the inter-battery short-circuit detection process will be described with reference to the flowchart of FIG. In the flowchart of FIG. 13, steps in which the same processing as the steps shown in FIG. 9 is executed are denoted by the same step symbols as in FIG. 9. The CPU starts the process from step 1300 and proceeds to step 905 when the start of the ECU 61 is completed and the appropriate timing (time t0 in FIG. 10) is reached.

  When the CPU completes the process of step 940, the CPU proceeds to step 1345, and performs on-control for the first IGBT 41b and the fourth IGBT 44b at the time t4. Furthermore, the CPU executes the off control on the first IGBT 41b and the fourth IGBT 44b at the timing when the time t4a is reached. Next, the CPU proceeds to step 1350 to determine whether or not the voltage VH and the voltage V2 are equal to each other at a timing immediately before the off control is performed on the first IGBT 41b and the fourth IGBT 44b.

  If the voltage VH and the voltage V2 are equal to each other, the CPU makes a “Yes” determination at step 1350 to proceed to step 955, determines that a short-circuit fault has occurred in the second IGBT 42b, and then proceeds to step 1357. On the other hand, if the voltage VH and the voltage V2 are not equal to each other (that is, if voltage VH> voltage V2), the CPU makes a “No” determination at step 1350 to directly proceed to step 1357. In step 1357, the CPU controls the first system main relay 24 to a conductive state. Next, the CPU proceeds to step 960.

  Further, when the CPU makes a “No” determination at step 960, the CPU proceeds to step 980. In addition, when the CPU finishes the process of step 965, the CPU proceeds to step 1370 and starts the degenerate operation of the vehicle 1. More specifically, the CPU performs on control on the first IGBT 41b, the second IGBT 42b, and the fourth IGBT 44b. As a result, since the first storage battery 21 and the second storage battery 31 are connected in parallel to the inverter 70, the power output from the first storage battery 21 and the second storage battery 31 is supplied to the inverter 70 without being boosted. . After starting the degenerate operation of the vehicle 1, the CPU proceeds to step 1395 to end the present routine.

  Alternatively, the CPU proceeds to step 1395 when the process of step 980 is completed.

  According to the second system, it is possible to detect the occurrence of a short circuit failure in the second IGBT 42b to the fourth IGBT 44b (particularly, the second IGBT 42b). Furthermore, the second system can supply the power of both the first storage battery 21 and the second storage battery 31 to the inverter 70 even when a short circuit failure occurs.

  As mentioned above, although embodiment of the power supply system which concerns on this invention was described, this invention is not limited to the said embodiment, A various change is possible unless it deviates from the objective of this invention. For example, the present invention is applied not only to a vehicle power supply system applied to a vehicle equipped with an electric motor as a driving power source, but also to a power supply system applied to a vehicle further equipped with an internal combustion engine as a driving power source (ie, a hybrid vehicle). It also extends.

  In addition, the ECU 60 according to the first embodiment supplies only the electric power output from the second storage battery 31 to the inverter 70 during execution of the degenerate operation. However, the ECU 60 may supply electric power output from both the second storage battery 31 and the second storage battery 31 to the inverter 70 as in the ECU 61 according to the second embodiment when the degenerate operation is performed. Alternatively, the ECU 60, like the ECU 61, only when the difference between the terminal voltage V1 of the first storage battery 21 and the terminal voltage V2 of the second storage battery 31 is smaller than a predetermined value. The power output from both of the two may be supplied to the inverter 70.

  In addition, in the present embodiment, the first storage battery 21 and the second storage battery 31 are lithium ion batteries. However, the first storage battery 21 and / or the second storage battery 31 may be a different type of chargeable / dischargeable DC power source from a lithium ion battery such as a nickel metal hydride battery, an electric double layer capacitor, and a lithium ion capacitor.

  In addition, in the present embodiment, the switch unit 40 includes the first IGBT 41b to the fourth IGBT 44b as switching elements. However, the switch unit 40 may include a MOSFET, a GTO thyristor, or the like as a switching element.

  Vehicle 1, power supply system 10, first storage battery 21, first system main relay 24, second storage battery 31, second system main relay 34, switch unit 40, high-voltage side capacitor 51, ECU 60, inverter ... 70, electric motor ... 80.

Claims (1)

A positive electrode connection point and a negative electrode connection point connected to the load circuit and used to supply DC power to the load circuit;
A first connection point between the positive connection point and the negative connection point, a first connection point between the positive connection point and the negative connection point, and a second between the first connection point and the negative connection point. A feed line having a connection point, a third connection point between the second connection point and the negative connection point, and a fourth connection point between the third connection point and the negative connection point;
A first DC power source capable of charging and discharging, wherein a positive electrode is connected to the first connection point and a negative electrode is connected to the third connection point;
A second DC power source capable of charging and discharging, wherein a positive electrode is connected to the second connection point and a negative electrode is connected to the fourth connection point;
A first semiconductor switch interposed between the positive electrode connection point and the first connection point of the power supply line, and capable of cutting off only a current flowing from the positive electrode connection point to the first connection point;
A second semiconductor switch that is interposed in a portion between the first connection point and the second connection point of the power supply line and that can cut off only a current flowing from the first connection point to the second connection point. When,
A third semiconductor switch that is interposed in a portion between the second connection point and the third connection point of the power supply line and can cut off only a current flowing from the second connection point to the third connection point. When,
A fourth semiconductor switch interposed between the third connection point and the fourth connection point of the power supply line and capable of interrupting only a current flowing from the third connection point to the fourth connection point; When,
A parallel connection mode in which the first DC power supply and the second DC power supply are connected in parallel to the load circuit by controlling the conduction state of each of the first semiconductor switch to the fourth semiconductor switch; A series connection mode in which the first DC power source and the second DC power source are connected in series to the load circuit, and in addition, the first DC power source and / or the second DC power source. The voltage between the terminals of the power supply is boosted and applied between the positive electrode connection point and the negative electrode connection point, or the voltage between the positive electrode connection point and the negative electrode connection point is reduced and the first DC power supply and / or the same voltage is applied. A control unit for applying to the second DC power supply;
A power supply system comprising:
A high voltage side capacitor connected between the positive electrode connection point and the negative electrode connection point;
A high voltage side voltage sensor for detecting a high voltage side voltage which is a voltage between terminals of the high voltage side capacitor;
A low-voltage side voltage sensor that detects a low-voltage side voltage that is a voltage between terminals of the second DC power supply;
With
The controller is
When the first semiconductor switch is controlled from the cut-off state to the conductive state when the high-voltage side voltage is higher than the low-voltage side voltage due to the electric charge accumulated in the high-voltage side capacitor, the high-voltage side voltage is Configured to determine that a short-circuit fault has occurred in the second semiconductor switch if equal to a side voltage;
Power system.

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