JP5949365B2 - Power system - Google Patents

Description

  The present invention relates to a power supply system, and more particularly to a power supply system including a plurality of power storage devices.

  Japanese Patent Laying-Open No. 2007-274834 (Patent Document 1) discloses a vehicle power supply device. The vehicle power supply device includes: a plurality of power storage devices; switch means for switching connection of the plurality of power storage devices between series connection and parallel connection; a limiting resistor; and control means for controlling the switch means. Prepare. In this vehicle power supply device, the inrush current at the time of connection switching is suppressed by the limiting resistance (see Patent Document 1).

JP 2007-274834 A JP 2007-274830 A Japanese Patent Laid-Open No. 5-236608

  However, in the vehicle power supply device as described above, it is necessary to provide a limiting resistor in order to suppress an inrush current at the time of connection switching. For this reason, an increase in cost and an increase in size of the apparatus due to the provision of the limiting resistor are problematic.

  Therefore, an object of the present invention is to suppress inrush current at the time of connection switching without providing a limiting resistor in a power supply system capable of switching the connection of a plurality of power storage devices.

  According to this invention, the power supply system includes first and second power storage devices, a switching device, and a control device. The switching device is configured to be able to switch the connection of the plurality of power storage devices to the load device between a serial connection and a parallel connection according to the load state of the load device. When the voltage difference between the first power storage device and the second power storage device exceeds the threshold value, the control device controls the switching device so that the connection becomes parallel connection regardless of the load state of the load device.

  According to the invention, the power supply system includes the first and second power storage devices, the switching device, and the control device. The switching device is configured to be able to switch the connection of the first and second power storage devices to the load device. The switching device includes a first switch, a second switch, and a third switch. The first switch is provided between the first power line connecting the positive electrode of the first power storage device to the load device and the positive electrode of the second power storage device. The second switch is provided between the negative electrode of the first power storage device and the positive electrode of the second power storage device. The third switch is provided between the negative electrode of the first power storage device and the second power line connecting the negative electrode of the second power storage device to the load device. When the control device is requested to switch the connection from series connection to parallel connection, the voltage difference between the first and second power storage devices is larger than a predetermined value, and the voltage value of the first power storage device is When the voltage value is larger than the voltage value of the second power storage device, the switching device is controlled so that the third switch is turned on and the first and second switches are turned off.

  According to the invention, the power supply system includes a plurality of power storage devices, a switching device, and a control device. The switching device is configured to be able to switch the connection of the plurality of power storage devices to the load device having the power storage element to any of serial connection, parallel connection, and non-connection. The control device controls the switching device so that the connection is switched from the serial connection to the non-connection when switching from the series connection to the parallel connection is requested, and the connection is disconnected after the voltage of the power storage element decreases. The switching device is controlled so as to switch from parallel connection to parallel connection.

  According to the invention, the power supply system includes a plurality of power storage devices, a switching device, and a control device. The switching device is configured to be able to switch the connection of the plurality of power storage devices to the load device having the power storage element to any of serial connection, parallel connection, and non-connection. The control device controls the load device to increase the voltage of the power storage element after switching the connection from the parallel connection to the non-connection when the connection is required to be switched from the parallel connection to the series connection. The switching device is controlled to switch the connection from non-connection to series connection after the voltage rises.

  According to the present invention, in a power supply system capable of switching the connection of a plurality of power storage devices, an inrush current at the time of connection switching can be suppressed without providing a limiting resistor.

1 is a block diagram showing an overall configuration of a vehicle to which a power supply system according to Embodiment 1 of the present invention is applied. It is a flowchart which shows the control structure of the process regarding the switching control from the serial connection performed by the control apparatus shown in FIG. 1 to a parallel connection. It is a graph which shows an example of the change of the voltage and output of an electrical storage apparatus in the power supply system by Embodiment 2 of this invention. It is a flowchart which shows the control structure of the process regarding the switching control from the serial connection to parallel connection which the control apparatus of the power supply system by Embodiment 2 of this invention performs. It is a flowchart which shows the control structure of the process regarding the switching control from the serial connection to parallel connection which the control apparatus of the power supply system by Embodiment 3 of this invention performs. It is a time chart which shows an example of the torque change of the motor generator in the vehicle to which the power supply system by the modification of Embodiment 3 of this invention is applied. It is a flowchart which shows the control structure of the process regarding the switching control from the serial connection to parallel connection which the control apparatus of the power supply system by the modification of Embodiment 3 of this invention performs. It is a flowchart which shows the control structure of the process regarding the switching control from the parallel connection performed to the serial connection which the control apparatus of the power supply system by Embodiment 4 of this invention performs. It is a block diagram which shows the whole structure of the vehicle with which the power supply system by the modification of Embodiment 4 of this invention is applied. It is a flowchart which shows the control structure of the process regarding the switching control from the parallel connection to a serial connection which the control apparatus shown in FIG. 9 performs.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
1 is a block diagram showing an overall configuration of a vehicle to which a power supply system according to Embodiment 1 of the present invention is applied. Referring to FIG. 1, vehicle 100 includes a motor generator MG, wheels 6, power storage devices B1 and B2, an electric device 10, an inverter 20, a capacitor C, a switching device 40, a control device 50, Voltage sensors 61, 62, and 63 are provided.

  Motor generator MG is an AC motor, for example, a three-phase AC synchronous motor. Motor generator MG generates drive torque of vehicle 100 by the three-phase AC voltage received from inverter 20. The driving torque of motor generator MG is transmitted to wheels 6 to cause vehicle 100 to travel.

  On the other hand, during regenerative braking of vehicle 100, motor generator MG is driven by wheel 6, and motor generator MG operates as a generator. Thereby, motor generator MG acts as a regenerative brake that converts braking energy into electric power. The electric power generated by motor generator MG is stored in power storage devices B1 and B2 via inverter 20.

  The power storage devices B1 and B2 are DC power sources that can be charged and discharged, and include, for example, secondary batteries such as nickel metal hydride batteries and lithium ion batteries, fuel cells, or capacitors. Power storage devices B1 and B2 supply power to inverter 20 that is a load device, and are charged by power from inverter 20 during power regeneration. Furthermore, the power storage device B <b> 2 supplies power to the electric device 10.

  Electrical device 10 includes a device that is connected in parallel to power storage device B2 and consumes the power of power storage device B2. The electric device 10 includes, for example, a DC / DC converter, an electric air conditioner, and the like for supplying power to an auxiliary machine mounted on the vehicle 100. The electric device 10 operates based on the signal LI from the control device 50.

  Inverter 20 operates based on signal PWI received from control device 50. Inverter 20 converts the DC voltage of capacitor C into a three-phase AC voltage and outputs it to motor generator MG. Inverter 20 converts the three-phase AC voltage generated by motor generator MG during regenerative braking of vehicle 100 into a DC voltage and outputs the DC voltage to capacitor C.

  Capacitor C is connected between power lines PL1 and PL2, and smoothes voltage fluctuations between power lines PL1 and PL2.

  Switching device 40 operates based on signal SE received from control device 50. Switching device 40 is for switching the connection of power storage devices B <b> 1 and B <b> 2 to inverter 20 between a serial connection and a parallel connection. Switching device 40 includes switching elements Q1 to Q3 and diodes D1 to D3.

  Switching element Q1 is provided between power line PL1 and the positive electrode of power storage device B2. Power line PL1 connects the positive electrode of power storage device B1 to inverter 20. Switching element Q2 is provided between the negative electrode of power storage device B1 and the positive electrode of power storage device B2. Switching element Q3 is provided between the negative electrode of power storage device B1 and power line PL2. Power line PL2 connects negative electrode of power storage device B2 to inverter 20. Switching elements Q1 to Q3 are in a conductive state when turned on, and are in a nonconductive state when turned off.

  Switching elements Q1-Q3 include, for example, an IGBT (Insulated Gate Bipolar Transistor). Diodes D1-D3 are connected in antiparallel to switching elements Q1-Q3, respectively.

  Switching elements Q1-Q3 are turned on / off in response to signal SE received from control device 50. When both switching elements Q1, Q3 are off and switching element Q2 is on, power storage devices B1, B2 are connected in series to inverter 20. When both switching elements Q1, Q3 are on and switching element Q2 is off, power storage devices B1, B2 are connected in parallel to inverter 20.

  Voltage sensor 61 detects voltage VB1 of power storage device B1 and outputs it to control device 50. Voltage sensor 62 detects voltage VB2 of power storage device B2 and outputs it to control device 50. The voltage sensor 63 detects the voltage VH of the capacitor C and outputs it to the control device 50.

  Control device 50 determines the required output of motor generator MG based on the accelerator opening, the brake depression amount, the vehicle speed, and the like. Control device 50 controls inverter 20 so that the output of motor generator MG matches the required output. The control device 50 generates a signal PWI for controlling the inverter 20 and outputs the signal PWI to the inverter 20.

  Control device 50 controls switching device 40 so as to switch the connection of power storage devices B1, B2 to inverter 20 between a serial connection and a parallel connection. The control device 50 generates a signal SE for controlling the switching device 40 and outputs the signal SE to the switching device 40.

  When the above connection is made in series, the maximum output of motor generator MG can be increased by increasing voltage VH. If the connection is parallel connection, the voltage VH decreases, so that loss in the inverter 20 can be suppressed. Therefore, the control device 50 controls the switching device 40 so as to switch the connection between the serial connection and the parallel connection according to the load state in the inverter 20.

  In addition, electric device 10 receives supply of power only from power storage device B2. For this reason, a difference arises between SOC (State Of Charge) which shows the charge state of electrical storage apparatus B1, and SOC of electrical storage apparatus B2. If only the SOC of one power storage device reaches the lower limit due to a difference between the SOC of power storage device B1 and the SOC of power storage device B2, if the above connection is a series connection, the other power storage device will receive power. Even if it is stored, it becomes impossible to supply power from the power storage devices B1 and B2 to the inverter 20.

  However, when switching from the series connection to the parallel connection is performed in a state where the difference between the voltage VB1 of the power storage device B1 and the voltage VB2 of the power storage device B2 is large, a large inrush current flows between the power storage devices B1 and B2. From the viewpoint of protecting the elements included in the power storage devices B1 and B2 and the switching device 40, it is desirable to suppress the inrush current.

  Therefore, in the first embodiment, when the voltage difference between power storage devices B1 and B2 exceeds the threshold value, the connection of power storage devices B1 and B2 to inverter 20 is connected from the series connection regardless of the load state of inverter 20. Switching control for switching to parallel connection is executed. Accordingly, an increase in voltage difference between power storage devices B1 and B2 is suppressed, and a current exceeding the allowable current of the elements included in power storage devices B1 and B2 and switching device 40 can be prevented from flowing. Hereinafter, the content of the switching control will be described in detail.

  FIG. 2 is a flowchart showing a control structure of processing related to switching control from serial connection to parallel connection executed by the control device 50 shown in FIG. Note that each step in the flowchart shown in FIG. 2 is executed in response to a predetermined cycle or a predetermined condition being established when a program stored in advance in the control device 50 is called from the main routine. (The same applies to the flowcharts shown in FIGS. 4, 5, 8, and 10 described below). Alternatively, for some steps, it is also possible to construct dedicated hardware (electronic circuit) and realize processing.

  Referring to FIG. 2, control device 50 determines in step (hereinafter, step is abbreviated as S) 110 whether or not connection of power storage devices B <b> 1 and B <b> 2 to inverter 20 is a serial connection. When it is determined that the connection is not a series connection (NO in S110), control device 50 does not perform a process of switching the connection from a series connection to a parallel connection.

  When it is determined that the connection is a series connection (YES in S110), control device 50 has a difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 greater than threshold value V1. It is determined whether or not (S120). When it is determined that the difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 is equal to or less than threshold value V1 (NO in S120), control device 50 switches from serial connection to parallel connection. Do not perform connection switching processing.

  Threshold value V1 is a value set based on the allowable current of the elements included in power storage devices B1 and B2 and switching device 40. That is, when the voltage difference is equal to or less than threshold value V1, the magnitude of the current flowing between power storage devices B1 and B2 is suppressed to an allowable current or less.

  When it is determined that the difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 is greater than threshold value V1 (YES in S120), control device 50 switches the connection to a parallel connection. Thus, the switching device 40 is controlled (S130). Specifically, control device 50 turns on switching elements Q1, Q3 and turns off switching element Q2.

  As described above, in the first embodiment, when the voltage difference between power storage devices B1 and B2 exceeds the threshold value, connection of power storage devices B1 and B2 to inverter 20 regardless of the load state of inverter 20 Is switched to switch from serial connection to parallel connection. Accordingly, an increase in voltage difference between power storage devices B1 and B2 is suppressed, and a current exceeding the allowable current can be prevented from flowing. Therefore, according to Embodiment 1, the inrush current flowing between power storage devices B1 and B2 when the connection is switched can be suppressed.

[Embodiment 2]
In the first embodiment, when the voltage difference between power storage devices B1 and B2 exceeds a threshold value, the connection of power storage devices B1 and B2 to inverter 20 is configured in parallel. For this reason, even when the required power of inverter 20 is large, when the voltage difference between power storage devices B1 and B2 exceeds a threshold value, the above connection is forcibly set in parallel. Therefore, the output from power storage devices B1 and B2 may be insufficient with respect to the required power of inverter 20.

  In the second embodiment, when the connection is switched from the serial connection to the parallel connection, the voltage is high if the difference between the voltage VB1 of the power storage device B1 and the voltage VB2 of the power storage device B2 is larger than the threshold value. Electric power is supplied to the inverter 20 only from the one power storage device. Then, after the difference between the voltages VB1 and VB2 becomes small, the connection is switched to the parallel connection. Thereby, it can suppress that a big electric current generate | occur | produces when the said connection is switched from a serial connection to a parallel connection. Therefore, even when the difference between the voltages VB1 and VB2 is large, it is possible to perform the process of switching from the serial connection to the parallel connection. Therefore, when the required power of the inverter 20 is large, it can be connected in series regardless of the difference between the voltages VB1 and VB2.

  The circuit configuration of the power supply system according to the second embodiment is the same as that of the power supply system according to the first embodiment shown in FIG.

  FIG. 3 is a graph showing an example of changes in voltages VB1 and VB2, output PB1 of power storage device B1, and output PB2 of power storage device B2 in the power supply system according to the second embodiment of the present invention. Referring to FIG. 3, when vehicle request output PREQ, which is the sum of outputs PB1 and PB2, is zero, voltage VB1 of power storage device B1 is higher than voltage VB2 of power storage device B2. At this time, the control device 50 controls the switching device 40 so that the switching elements Q1 and Q2 are turned off and the switching element Q3 is turned on. Thereby, electric power is supplied to inverter 20 only from power storage device B1. Therefore, the difference between the voltages VB1 and VB2 can be reduced.

  When vehicle request output PREQ increases from zero, output PB1 of power storage device B1 increases and voltage VB1 of power storage device B1 decreases.

  When the difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 decreases, control device 50 turns off switching element Q2 and turns on switching elements Q1 and Q3 when vehicle request output PREQ is P1. The switching device 40 is controlled. Thereby, connection of electrical storage apparatus B1, B2 with respect to the inverter 20 becomes parallel connection.

  When vehicle request output PREQ rises from P1, power is supplied from power storage devices B1 and B2 to inverter 20, so that voltages VB1 and VB2 similarly drop. Then, both outputs PB1 and PB2 of power storage device B1 rise.

  As described above, when the difference between the voltages VB1 and VB2 is large, the difference between the voltages VB1 and VB2 can be reduced by supplying power to the inverter 20 only from the power storage device having the higher voltage. Thereby, even if the difference between the voltages VB1 and VB2 is large, the process of switching from the serial connection to the parallel connection can be performed.

  FIG. 4 is a flowchart showing a control structure of processing relating to switching control from serial connection to parallel connection executed by control device 50 of the power supply system according to the second embodiment of the present invention.

  Referring to FIG. 4, control device 50 determines in S210 whether the connection of power storage devices B1, B2 to inverter 20 is a serial connection.

  When it is determined that the connection is a serial connection (YES in S210), control device 50 determines whether or not there is a switching request from a serial connection to a parallel connection (S220). When it is determined that there is no switching request (NO in S220), control device 50 does not perform the process of switching the connection.

  Note that the control device 50 determines whether or not there is a switching request based on the required power of the inverter 20. When the required power of inverter 20 is smaller than the threshold value, control device 50 determines that there is the switching request. On the other hand, when the required power of inverter 20 is equal to or greater than the threshold value, control device 50 determines that there is no switching request.

  If it is determined that there is the switching request (YES in S220), control device 50 determines whether or not the difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 is greater than threshold value V1. Is determined (S230). When it is determined that the difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 is equal to or less than threshold value V1 (NO in S230), control device 50 switches from serial connection to parallel connection. Thus, the switching device 40 is controlled (S270).

  If it is determined that the difference between voltage VB1 of power storage device B1 and voltage VB2 of power storage device B2 is greater than threshold value V1 (YES in S230), control device 50 causes voltage VB1 to be greater than voltage VB2. It is determined whether it is high (S240).

  If it is determined that voltage VB1 is higher than voltage VB2 (YES in S240), control device 50 controls switching device 40 to turn off switching elements Q1 and Q2 and to turn on switching element Q3 ( S250). Thereby, only the electric power of power storage device B <b> 1 is supplied to inverter 20. Further, no current flows between power storage devices B1 and B2. When it is determined that voltage VB1 is equal to or lower than voltage VB2 (NO in S240), control device 50 controls switching device 40 to turn on switching element Q1 and to turn off switching elements Q2 and Q3 ( S260). Thereby, only the electric power of power storage device B2 is supplied to inverter 20. Further, no current flows between power storage devices B1 and B2.

  When it is determined in S210 that the connection is not a series connection (NO in S210), control device 50 has only one of switching elements Q1 and Q3 turned on and switching element Q2 is turned off. It is determined whether or not there is (S280). If it is determined that only one of switching elements Q1, Q3 is on and switching element Q2 is off (YES in S280), the process proceeds to S230. If only one of switching elements Q1, Q3 is on and it is not determined that switching element Q2 is off (NO in S280), control device 50 does not perform the process of switching the connection.

  As described above, in the second embodiment, when the difference between voltages VB1 and VB2 is large, power is supplied to inverter 20 only from the power storage device having the higher voltage. Then, after the difference between the voltages VB1 and VB2 becomes small, the connection is switched to the parallel connection. Therefore, according to the second embodiment, when the connection of power storage devices B1, B2 to inverter 20 is switched from the series connection to the parallel connection according to the load state of inverter 20, power storage device B1, Inrush current flowing between B2 can be suppressed.

[Embodiment 3]
In the first and second embodiments, the configuration for suppressing the current flowing between the power storage devices B1 and B2 when the connection of the power storage devices B1 and B2 to the inverter 20 is switched has been described. In the third embodiment, a configuration for suppressing an inrush current flowing from capacitor C to power storage devices B1 and B2 when the connection is switched is shown.

  The circuit configuration of the power supply system according to Embodiment 3 is the same as that of the power supply system according to Embodiment 1 shown in FIG.

  FIG. 5 is a flowchart showing a control structure of processing relating to switching control from serial connection to parallel connection executed by control device 50 of the power supply system according to Embodiment 3 of the present invention.

  Referring to FIG. 5, control device 50 determines in S310 whether or not connection of power storage devices B1, B2 to inverter 20 is a series connection. If it is determined that the connection is not a series connection (NO in S310), control device 50 does not perform a process of switching the connection.

  If it is determined that the connection is a serial connection (YES in S310), control device 50 determines whether or not there is a request for switching from a serial connection to a parallel connection (S320). If it is determined that there is no switching request (NO in S320), control device 50 does not perform the process of switching the connection. Note that determination as to whether or not there is a switching request is the same as in the second embodiment, and thus description thereof will not be repeated.

  If it is determined that there is the switching request (YES in S320), control device 50 controls switching device 40 so as to turn off switching element Q2 (S330). Then, since all of switching elements Q1 to Q3 are turned off, connection of power storage devices B1 and B2 to inverter 20 is disconnected.

  Subsequently, in S340, the control device 50 determines that the difference between the voltage VP indicating the voltage of the power storage devices B1 and B2 when the power storage devices B1 and B2 are connected in parallel and the voltage VH of the capacitor C from the threshold value V2. It is determined whether or not it is smaller. When it is determined that the difference between voltage VP and voltage VH is equal to or greater than threshold value V2 (NO in S340), control device 50 determines that the difference between voltage VP and voltage VH is smaller than threshold value V2. Wait until At this time, the inverter 20 consumes the power stored in the capacitor C, so that the voltage VH decreases.

  Threshold value V2 is a value set based on the allowable current of the elements included in power storage devices B1 and B2 and switching device 40. That is, when the difference between voltage VP and voltage VH is equal to or less than threshold value V2, the current flowing between capacitor C and power storage devices B1 and B2 is suppressed to an allowable current or less.

  When it is determined that the difference between voltage VP and voltage VH is smaller than threshold value V2 (YES in S340), control device 50 controls switching device 40 to turn on switching elements Q1 and Q3. To do. Then, connection of power storage devices B1 and B2 to inverter 20 is parallel connection.

  As described above, in the third embodiment, when the connection is switched from the series connection to the parallel connection according to the load state of the inverter 20, the voltage VH of the capacitor C is switched after the connection from the series connection to the non-connection. After the voltage VH is reduced, control for switching from non-connection to parallel connection is executed. Therefore, the connection is made in parallel with a small difference between the voltage VP and the voltage VH. Therefore, according to the third embodiment, inrush current flowing from capacitor C to power storage devices B1 and B2 when the connection of power storage devices B1 and B2 to inverter 20 is switched can be suppressed.

[Modification of Embodiment 3]
In the third embodiment, when the connection is switched from the serial connection to the parallel connection according to the load state of the inverter 20, the voltage VH of the capacitor C is decreased after the connection is switched from the serial connection to the non-connection. The configuration in which the control for switching the connection from the non-connection to the parallel connection is executed after the VH has decreased has been described. However, when regenerative braking of the vehicle 100 is executed when the connection is not connected, the voltage VH rises due to regenerative power. For this reason, it may be difficult to make the connection in parallel.

  The circuit configuration of the power supply system according to the modification of the third embodiment is the same as that of the power supply system according to the first embodiment shown in FIG.

  Therefore, in the modification of the third embodiment, it is determined whether or not the switching process for switching from series connection to parallel connection can be completed before regenerative braking is started. Then, the execution of the switching process is permitted only when the switching process can be completed before the regenerative braking is started. As a result, it is possible to prevent the switching control from failing because the disconnected state is continued.

  FIG. 6 is a time chart showing an example of a change in torque of motor generator MG in vehicle 100 to which the power supply system according to the modification of the third embodiment of the present invention is applied.

  Referring to FIG. 6, at time t1, motor generator MG is in a state of power running operation. At this time, if there is a request to switch the connection from the series connection to the parallel connection, the control device 50 causes the motor generator MG to shift to the regenerative operation based on the torque Tr1 at this time and the maximum rate of torque change. Changes in torque and rotation speed of motor generator MG up to time t2 are predicted. The control device 50 calculates the power Pm based on the predicted torque and rotation speed. The electric power Pm is electric power consumed by the motor generator MG from this time until the motor generator MG enters the regenerative operation.

  Control device 50 calculates electric power Pc that must be discharged from capacitor C in order to make the difference between voltage VP and voltage VH smaller than threshold value V2, based on the capacitance of capacitor C and voltage VH. When the power Pm is larger than the power Pc, the control device 50 permits execution of a switching process for switching the connection from the serial connection to the parallel connection. That is, the control device 50 permits execution of the switching process only when the switching process can be completed before the regenerative braking starts.

  In addition, the control apparatus 50 can estimate on the conditions that electric power Pm becomes the minimum by using the maximum rate of a torque change rate. For this reason, it can be determined reliably whether the process which switches from serial connection to parallel connection can be completed.

  FIG. 7 is a flowchart showing a control structure of processing relating to switching control from serial connection to parallel connection executed by control device 50 of the power supply system according to the modification of the third embodiment of the present invention. Referring to FIG. 7, S310, S320, and S330 to S350 are the same as those in the third embodiment, and thus description thereof will not be repeated.

  If it is determined in S320 that there is a request for switching from series connection to parallel connection of power storage devices B1 and B2 with respect to inverter 20 (YES in S320), control device 50 determines whether the switching permission condition is satisfied. It is determined whether or not (S325). The switching permission condition is a condition for determining whether or not switching processing for switching from serial connection to parallel connection can be completed before regenerative braking starts. Specifically, the control device 50 determines that the switching permission condition is satisfied when the power Pm described above is larger than the power Pc. If it is determined that the switching permission condition is not satisfied (NO in S325), control device 50 does not perform the process of switching the connection.

  If it is determined that the switching permission condition is satisfied (YES in S325), control device 50 advances the process to S330 and disconnects power storage devices B1, B2 from inverter 20 to be disconnected. Then, a process for switching to parallel connection is performed as in the third embodiment.

  As described above, in the modification of the third embodiment, it is determined whether or not the switching process for switching from series connection to parallel connection can be completed before regenerative braking starts. Only when the switching process can be completed before regenerative braking starts, the execution of the switching process is permitted. As a result, it is possible to prevent the switching control from failing because the disconnected state is continued.

[Embodiment 4]
In the third embodiment, the configuration that suppresses the current flowing between the capacitor C and the power storage devices B1 and B2 when the connection of the power storage devices B1 and B2 to the inverter 20 is switched from the serial connection to the parallel connection has been described. In the fourth embodiment, a configuration is shown in which the current flowing between capacitor C and power storage devices B1 and B2 is suppressed when connection of power storage devices B1 and B2 to inverter 20 is switched from parallel connection to series connection.

  The circuit configuration of the power supply system according to the fourth embodiment is the same as that of the power supply system according to the first embodiment shown in FIG.

  FIG. 8 is a flowchart showing a control structure of processing relating to switching control from parallel connection to serial connection executed by control device 50 of the power supply system according to the fourth embodiment of the present invention.

  Referring to FIG. 8, control device 50 determines in S410 whether or not connection of power storage devices B1 and B2 to inverter 20 is a parallel connection. When it is determined that the connection is not parallel connection (NO in S410), control device 50 does not perform the process of switching the connection.

  When it is determined that the connection is a parallel connection (YES in S410), control device 50 determines whether or not there is a request to switch the connection of power storage devices B1 and B2 to the inverter 20 from the parallel connection to the series connection. Is determined (S420). If it is determined that there is no switching request (NO in S420), control device 50 does not perform the process of switching the connection.

  Note that the control device 50 determines whether or not there is a switching request based on the required power of the inverter 20. When the required power of inverter 20 is larger than the threshold value, control device 50 determines that there is the switching request. On the other hand, when the required power of inverter 20 is equal to or lower than the threshold value, control device 50 determines that there is no switching request.

  When it is determined that there is the switching request (YES in S420), control device 50 controls switching device 40 so as to turn off switching elements Q1, Q3 (S430). Then, since all of switching elements Q1 to Q3 are turned off, connection of power storage devices B1 and B2 to inverter 20 is disconnected.

  Subsequently, in S440, control device 50 determines that the difference between voltage VH indicating the sum of voltage VB1 and voltage VB2 when power storage devices B1 and B2 are connected in series and voltage VH of capacitor C is greater than threshold value V3. It is determined whether or not it is small. When it is determined that the difference between voltage VS and voltage VH is equal to or greater than threshold value V3 (NO in S440), control device 50 determines that the difference between voltage VS and voltage VH is smaller than threshold value V3. Until it becomes, regenerative control is performed (S460). In the regeneration control, the torque command of the motor generator MG is changed so as to be on the regeneration side. As a result, power is supplied from the inverter 20 to the capacitor C, whereby the voltage VH increases.

  Threshold value V3 is a value set based on the allowable current of the elements included in power storage devices B1 and B2 and switching device 40. That is, when the difference between voltage VS and voltage VH is equal to or smaller than threshold value V3, a current equal to or smaller than the allowable current flows between capacitor C and power storage devices B1 and B2.

  When it is determined that the difference between voltage VS and voltage VH is smaller than threshold value V3 (YES in S440), control device 50 controls switching device 40 to turn on switching element Q2. Then, connection of power storage devices B1 and B2 to inverter 20 is a series connection.

  As described above, in the fourth embodiment, when the connection is switched from the parallel connection to the series connection according to the load state of the inverter 20, the connection of the capacitor C is changed after the connection is switched from the parallel connection to the non-connection. After the voltage VH is increased and the voltage VH is increased, control for switching the connection from the non-connection to the series connection is performed. Therefore, the above connection is a series connection in a state where the difference between the voltage VS and the voltage VH is small. Therefore, according to the fourth embodiment, inrush current flowing from power storage devices B1 and B2 to capacitor C can be suppressed when connection of power storage devices B1 and B2 to inverter 20 is switched.

[Modification of Embodiment 4]
In the fourth embodiment, the configuration in which power storage devices B1 and B2 are charged only by regenerative electric power of motor generator MG while vehicle 100 is traveling has been described. In the modification of the fourth embodiment, a configuration that further includes a generator that can supply power to the capacitor C in addition to the configuration of the fourth embodiment will be described. For this reason, since it is not necessary to perform regenerative control of the motor generator when the connection of the power storage devices B1 and B2 to the inverter 20 is switched, the connection can be switched without impairing drivability.

  FIG. 9 is a block diagram showing an overall configuration of a vehicle to which a power supply system according to a modification of the fourth embodiment of the present invention is applied. Referring to FIG. 9, vehicle 100A includes an engine 2, motor generators MG1 and MG2, and power split device 4 instead of motor generator MG with respect to the configuration of the first embodiment.

  Vehicle 100A travels using engine 2 and motor generator MG2 as power sources. Power split device 4 is coupled to engine 2 and motor generators MG1 and MG2 to distribute power between them. Power split device 4 includes, for example, a planetary gear mechanism having three rotation shafts of a sun gear, a planetary carrier, and a ring gear, and these three rotation shafts are connected to the rotation shafts of engine 2 and motor generators MG1, MG2, respectively. It should be noted that engine 2 and motor generators MG1, MG2 can be mechanically connected to power split device 4 by hollowing the rotor of motor generator MG1 and passing the crankshaft of engine 2 through the center thereof. Further, the rotation shaft of motor generator MG2 is coupled to wheel 6 by a reduction gear or a differential gear (not shown).

  Motor generator MG1 operates as a generator driven by engine 2 and is incorporated in vehicle 100A as an electric motor that can start engine 2, and motor generator MG2 drives wheels 6. It is incorporated in the vehicle 100A as an electric motor.

  Control device 50 outputs a signal DRV for controlling engine 2 to engine 2. Control device 50 outputs to inverter 20 a signal PWI1 for controlling motor generator MG1 and a signal PWI2 for controlling motor generator MG2. Control device 50 executes power generation control for motor generator MG1 to generate power using the driving force of engine 2.

  FIG. 10 is a flowchart showing a control structure of processing related to switching control from parallel connection to series connection executed by the control device 50 shown in FIG. Referring to FIG. 10, since S410 to S450 are the same as those in the fourth embodiment, description thereof will not be repeated.

  If it is determined in S440 that the difference between voltage VS and voltage VH is greater than or equal to threshold value V3 (NO in S440), control device 50 determines that the difference between voltage VS and voltage VH is the threshold value V3. The power generation control is executed until it becomes smaller (S470). As a result, power is supplied from the inverter 20 to the capacitor C, whereby the voltage VH increases.

  As described above, in the modification of the fourth embodiment, a generator capable of charging power storage devices B1 and B2 is provided. For this reason, when switching the connection of power storage devices B1 and B2 to inverter 20, it is not necessary to perform regenerative control of motor generator MG, so that the connection can be switched without impairing drivability.

  In each of the above embodiments, the switching device 40 includes the switching elements Q1 to Q3 and the diodes D1 to D3. However, the circuit configured by the switching element Q1 and the diode D1, the switching element Q2 Each of the circuit constituted by the diode D2 and the circuit constituted by the switching element Q3 and the diode D3 may be a relay.

  In Embodiments 1 to 4 described above, the electric vehicle including motor generator MG has been described, but a hybrid vehicle further including an engine may be used. In the modification of the above-described fourth embodiment, the so-called series / parallel type hybrid vehicle in which the power of the engine 2 is distributed to the motor generator MG1 and the wheels 6 using the power split device 4 has been described. A so-called series-type hybrid vehicle may be used in which the power of the engine 2 is used only for power generation by the motor generator MG1, and the driving force of the vehicle is generated using only the motor generator MG2. Further, it may be a plug-in hybrid vehicle having a power generation function, an electric vehicle with a cruising range extension function (range extender), or a vehicle called a range extended electric vehicle.

  In the above embodiment, the configuration in which the power supply system includes the two power storage devices B1 and B2 has been described. However, the concept of the present invention can be applied to the case where the power supply system includes three or more power storage devices. Can do.

  In the above description, power storage devices B1 and B2 respectively correspond to “first power storage device” and “second power storage device” in the present invention, and inverter 20 corresponds to “load device” in the present invention. Switching elements Q1 to Q3 correspond to “first to third switches” in the present invention, and capacitor C corresponds to “power storage element” in the present invention.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  2 engine, 4 power split device, 6 wheels, 10 electrical equipment, 20 inverter, 40 switching device, 50 control device, 61, 62, 63 voltage sensor, 100, 100A vehicle, B1, B2 power storage device, C capacitor.

Claims (1)

First and second power storage devices;
A switching device configured to switch the connection of the first and second power storage devices to the load device between a serial connection and a parallel connection according to a load state of the load device;
A control device for controlling the switching device,
When the voltage difference between the first power storage device and the second power storage device is less than or equal to a threshold value and the load state is the first load state, the control device is configured so that the connection is a parallel connection. Controlling the switching device, and when the load state is a second load state larger than the first load state, controlling the switching device so that the connection is a series connection,
Wherein the controller, when the front SL voltage difference exceeds the threshold value, the even load state of the load device is a second load condition, the switching so that the connection is connected in parallel A power system that controls equipment.

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