JP2021132517A - Switching device, power storage system including switching device, vehicle including power storage system, and switching method - Google Patents

Abstract

To provide a switching device that can suppress the occurrence of energy loss due to switches such as a relay and the reduction of switch life when a plurality of batteries are connected in parallel, and can balance the voltages of the plurality of batteries with simple control, a power storage system including the device, a vehicle including the system, and a switching method.SOLUTION: A switching device includes a switching unit that switches the connection state of a plurality of batteries between a first state in which the plurality of batteries are connected in parallel and a second state other than the first state, a control unit that controls the switching unit, and a detection unit that detects a current value of a circulating current flowing in a closed circuit formed by connecting a plurality of batteries in parallel, and the control unit controls the switching unit such that the connection state of the plurality of batteries becomes the first state or the second state on the basis of the current value detected by the detection unit and a first threshold value.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a switching device, a power storage system including the device, a vehicle including the system, and a switching method.

Storage batteries (hereinafter referred to as batteries) are used in various electric devices and equipment including vehicles. For example, a vehicle such as a PHEV (Plug-in Hybrid Electric Vehicle) or an EV (Electric Vehicle) is equipped with an in-vehicle battery, an in-vehicle charger, a DC / DC converter, and a power conversion unit. As a result, the AC power of the system can be converted into DC power to charge the in-vehicle battery, and the output voltage of the in-vehicle battery can be converted into an appropriate voltage and supplied to each device inside the vehicle during traveling or the like.

In order to shorten the charging time of the in-vehicle battery, it is preferable to charge the vehicle at a higher voltage. Therefore, it is expected that a charger having a higher voltage (for example, 800V) than the charger for an in-vehicle battery currently generally used (for example, 400V) will be used in the future. In the future, even if the chargers are unified to higher voltage, two types of chargers with different charging voltages will be mixed transiently. To deal with this, the vehicle should be equipped with multiple in-vehicle batteries, and multiple in-vehicle batteries should be connected in parallel when charging at low voltage, and multiple in-vehicle batteries should be connected in series when charging at high voltage. Can be considered.

In addition to this, there is known a power storage system in which a plurality of power storage modules can be switched between series connection and parallel connection. When switching multiple batteries in series or in parallel using a relay, if there is a voltage imbalance between the multiple batteries, if the relay is switched as it is, energy loss due to short-circuit current flowing will occur. Occurs. There is also a problem that an arc is generated at the contacts and the life of the relay is shortened. In order to solve these problems, the following Patent Documents 1 and 2 disclose a power storage system that equalizes the voltages of a plurality of storage battery modules. In the power storage system disclosed in Patent Document 1, an in-vehicle charger is used to discharge between a plurality of batteries to balance the voltages of the plurality of batteries. In the power storage system disclosed in Patent Document 2, a battery is charged by a charger or discharged by a load to balance the voltages of a plurality of batteries.

JP-A-2019-80473 JP-A-2019-80474

However, in Patent Document 1, it is necessary to add a relay in addition to the battery charging / discharging function to the in-vehicle charger, which causes a problem of increasing the cost. Further, in order to balance the voltages of a plurality of batteries, it is necessary to control a complicated power converter, and there is a problem that the control and the function become complicated. In Patent Document 2, it is necessary to physically connect to an external charger, and it is also necessary to control communication with the outside, which is complicated. When the voltage of the battery is balanced by the load, there is a problem that wasteful energy loss occurs.

Therefore, the present disclosure can suppress the occurrence of energy loss due to a switch such as a relay and the decrease in the life of the switch when connecting a plurality of batteries in parallel, and can balance the voltages of the plurality of batteries by simple control. It is an object of the present invention to provide an apparatus, a power storage system including the apparatus, a vehicle including the system, and a switching method.

The switching device according to a certain aspect of the present disclosure switches between a switching unit that switches the connection state of a plurality of batteries between a first state in which the plurality of batteries are connected in parallel and a second state other than the first state. The control unit includes a control unit that controls the unit and a detection unit that detects the current value of the circulating current flowing through the closed circuit formed by connecting a plurality of batteries in parallel, and the control unit is the current detected by the detection unit. Based on the value and the first threshold value, the switching unit is controlled so that the connection state of the plurality of batteries becomes the first state or the second state.

A power storage system according to another aspect of the present disclosure includes a plurality of batteries and the above-mentioned switching device for switching a connection state between the plurality of batteries.

Vehicles according to yet another aspect of the present disclosure include the power storage system described above and a drive unit powered by a plurality of batteries.

The switching method according to still another aspect of the present disclosure is a switching method for switching the connection state of a plurality of batteries, in which the current value of the circulating current flowing through the closed circuit formed by connecting the plurality of batteries in parallel is used. Based on the first step to be detected, the current value detected by the first step, and the first threshold value, the connection states of the plurality of batteries are determined by the first state and the first state in which the plurality of batteries are connected in parallel. The first step and the second step are repeated, including a second step of switching between the second state other than the first state.

According to the present disclosure, when a plurality of batteries are connected in parallel, it is possible to suppress the occurrence of energy loss due to a switch such as a relay and the decrease in the life of the switch, and it is possible to balance the voltages of the plurality of batteries by simple control.

FIG. 1 is a circuit diagram showing a configuration of a power storage system according to the first embodiment of the present disclosure. FIG. 2 is a circuit diagram showing a state of charging the power storage system shown in FIG. FIG. 3 is a flowchart showing the operation of the power storage system shown in FIG. FIG. 4 is a graph showing a state in which the circulating current is suppressed. FIG. 5 is a schematic view showing a vehicle equipped with the power storage system shown in FIG. FIG. 6 is a circuit diagram showing the configuration of the power storage system according to the second embodiment of the present disclosure. FIG. 7 is a circuit diagram showing a configuration of a power storage system according to a third embodiment of the present disclosure. FIG. 8 is a flowchart showing the operation of the power storage system according to the first modification of the present disclosure. FIG. 9 is a circuit diagram showing a configuration of a power storage system according to a second modification of the present disclosure.

[Explanation of Embodiments of the present disclosure]
The contents of the embodiments of the present disclosure will be listed and described. At least a part of the embodiments described below may be arbitrarily combined.

(1) The switching device according to the first aspect of the present disclosure switches the connection state of a plurality of batteries between a first state in which the plurality of batteries are connected in parallel and a second state other than the first state. The control unit includes a switching unit, a control unit that controls the switching unit, and a detection unit that detects the current value of the circulating current flowing through the closed circuit formed by connecting a plurality of batteries in parallel. The switching unit is controlled so that the connection state of the plurality of batteries becomes the first state or the second state based on the current value detected by the above and the first threshold value.

As a result, when a plurality of batteries are connected in parallel, it is possible to suppress the generation of an excessive circulating current. Therefore, the energy loss due to the switching unit and the decrease in the life of the switching unit can be suppressed, and the voltages of a plurality of batteries can be balanced by simple control.

(2) Preferably, the control unit further controls the switching unit so that a plurality of batteries are connected in series, and in the first state, a first voltage is applied to both ends of the plurality of batteries connected in parallel, and the first voltage is applied in series. A second voltage larger than the first voltage is applied to both ends of the plurality of connected batteries. This makes it possible to support two types of chargers having different charging voltages.

More preferably, the control unit controls the switching unit so that the connection state of the plurality of batteries is in the first state when the current value is equal to or less than the first threshold value, and the current value is the first. If it is larger than the threshold value, the switching unit is controlled so that the connection state of the plurality of batteries becomes the second state. As a result, it is possible to easily suppress the generation of an excessive circulating current when a plurality of batteries are connected in parallel.

(4) More preferably, the control unit determines whether or not the voltage difference between the plurality of batteries is equal to or less than the second threshold value, and receives the determination that the voltage difference is equal to or less than the second threshold value. Then, the control of the switching unit is stopped. As a result, energy loss due to unnecessary control after the voltages of the plurality of batteries are balanced can be suppressed.

(5) Preferably, the first threshold value is set based on at least one of the life of the switching unit and the energy loss. As a result, it is possible to appropriately suppress the flow of an excessive circulating current that affects the life of the switching unit.

(6) More preferably, the switching unit includes a semiconductor switching element, and the control unit turns on the semiconductor switching element to set the connection state of a plurality of batteries to the first state and turns off the semiconductor switching element. , Set the connection state of multiple batteries to the second state. As a result, the connection state of the plurality of batteries can be switched at high speed, and the rapidly increasing circulating current can be appropriately suppressed. In addition, a switching device with low power consumption can be realized.

(7) More preferably, the detection unit is a current detection circuit. As a result, the current value of the circulating current used for determining the connection state of the plurality of batteries can be directly detected, and the switching unit can be quickly controlled.

(8) Preferably, the switching unit includes a plurality of switching elements, and the detection unit is a voltage between both terminals of the switching element that is turned on in both the first state and the second state of the plurality of switching elements. The control unit calculates the current value based on the voltage value detected by the voltage detection circuit, including the voltage detection circuit for detecting the voltage. As a result, the current value of the circulating current can be easily obtained in the existing power storage system.

(9) More preferably, the switching unit includes a plurality of switching elements, and the detection unit is located between both terminals of the switching element that are turned on in both the first state and the second state of the plurality of switching elements. It includes a voltage detection circuit that detects the voltage, and instead of detecting the current value, the voltage value is detected by the voltage detection circuit, and the control unit uses the voltage value detected by the detection circuit instead of the current value. Then, instead of the first threshold, a third threshold for voltage is used. As a result, in the existing power storage system, the voltage value due to the circulating current can be easily detected, and the switching unit can be quickly controlled.

(10) More preferably, the switching unit switches the connection state of three or more batteries. As a result, three or more batteries can be connected in series, and the batteries can be charged at a higher voltage, so that the charging time of the batteries can be further shortened.

(11) Preferably, the control unit includes a semiconductor integrated circuit or an arithmetic element that executes a computer program. By realizing the function of the control unit with a semiconductor integrated circuit, processing can be executed at high speed, and excessive circulating current can be suppressed with high accuracy. By realizing the function of the control unit by a computer program, it is easy to modify the process (change the timing, etc.), and it is possible to easily respond to the change of parts, etc.

(12) The power storage system according to the second aspect of the present disclosure includes a plurality of batteries and the above-mentioned switching device for switching the connection state between the plurality of batteries. As a result, in the power storage system, when a plurality of batteries are connected in parallel, it is possible to suppress the generation of an excessive circulating current. Therefore, the energy loss due to the switching unit and the decrease in the life of the switching unit can be suppressed, and the voltages of a plurality of batteries can be balanced by simple control.

(13) The vehicle according to the third aspect of the present disclosure includes the above-mentioned power storage system and a drive device to which electric power is supplied from a plurality of batteries. As a result, in a vehicle, when a plurality of batteries are connected in parallel, it is possible to suppress the generation of an excessive circulating current. Therefore, the energy loss due to the switching unit and the decrease in the life of the switching unit can be suppressed, and the voltages of a plurality of batteries can be balanced by simple control.

(14) The switching method according to the fourth aspect of the present disclosure is a switching method for switching the connection state of a plurality of batteries, and is a switching method of circulating current flowing in a closed circuit formed by connecting a plurality of batteries in parallel. Based on the first step of detecting the current value, the current value detected by the first step, and the first threshold value, the connection state of the plurality of batteries is determined by the first step in which the plurality of batteries are connected in parallel. The first step and the second step are repeated, including a second step of switching between the state and the second state other than the first state. As a result, when a plurality of batteries are connected in parallel, it is possible to suppress the generation of an excessive circulating current. Therefore, the energy loss due to the switching unit and the decrease in the life of the switching unit can be suppressed, and the voltages of a plurality of batteries can be balanced by simple control.

[Details of Embodiments of the present disclosure]
In the following embodiments, the same parts are given the same reference numbers. Their names and functions are also the same. Therefore, detailed explanations about them will not be repeated.

(First Embodiment)
The power storage system 100 according to the first embodiment of the present disclosure with reference to FIG. 1 includes a first battery unit 102, a second battery unit 104, a first switch 106, a second switch 108, a third switch 110, and a switch control unit. It includes 112, a current detection circuit 114, and terminals 120 and 122. The first battery unit 102 and the second battery unit 104 are units having the same specifications and are composed of rechargeable and dischargeable storage batteries. The first battery unit 102 and the second battery unit 104 are, for example, battery units having 400V specifications (charging voltage and output voltage ratings are 400V). The battery unit is not limited to the case where it is composed of a plurality of batteries, but also includes the case where it is composed of one battery. The first switch 106, the second switch 108, the third switch 110, the switch control unit 112, and the current detection circuit 114 are the first battery unit 102 and the second battery unit according to the state of the power storage system 100 (circulating current described later). A switching device 116 having a function of switching the connection state of the 104 is configured.

Under the control of the switch control unit 112, the first switch 106, the second switch 108, and the third switch 110 short-circuit (hereinafter, referred to as on) or open (hereinafter, referred to as off) both terminals. The first switch 106, the second switch 108, and the third switch 110 are, for example, relays. The first switch 106, the second switch 108, and the third switch 110 may be semiconductor elements having a switching function such as a FET (Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor).

One terminal (terminal of the same polarity (positive electrode)) of each of the first battery unit 102 and the second battery unit 104 is connected via the first switch 106. The other terminals of the first battery unit 102 and the second battery unit 104 (terminals having a polarity (negative electrode) different from that of one terminal) are connected via a third switch 110. The other terminal of the first battery unit 102 and one terminal of the second battery unit 104 (terminals having different polarities) are connected via the second switch 108. By being connected in this way, the first switch 106, the second switch 108, and the third switch 110 function as a switching unit for switching the connection state of the first battery unit 102 and the second battery unit 104. That is, when the first switch 106 and the third switch 110 are turned off and the second switch 108 is turned on, the first battery unit 102 and the second battery unit 104 are connected in series. When the first switch 106 and the third switch 110 are turned on and the second switch 108 is turned off, the first battery unit 102 and the second battery unit 104 are connected in parallel.

Chargers or loads may be connected to terminals 120 and 122. When charging the first battery unit 102 and the second battery unit 104, a charger is connected. When a load is connected, electric power can be supplied to the load by discharging the first battery unit 102 and the second battery unit 104.

When the first battery unit 102 and the second battery unit 104 are connected in parallel, the current detection circuit 114 is connected to a connection line (electrical wiring) forming a closed circuit including the first battery unit 102 and the second battery unit 104. Have been placed. The current detection circuit 114 is a specific example of the detection unit. The current detection circuit 114 is, for example, an ammeter connected in series with a closed circuit. The current detection circuit 114 may be a clamp-type ammeter that clamps the electrical wiring and electromagnetically measures the current. The current detection circuit 114 is a current that transiently flows in a closed circuit formed when the first switch 106 and the third switch 110 are turned on and the first battery unit 102 and the second battery unit 104 are connected in parallel. Hereinafter referred to as circulating current) is detected. The current detection circuit 114 inputs the current value of the circulating current to the switch control unit 112. Specifically, the current detection circuit 114 detects the current flowing through the line connecting the terminals of the same polarity of the first battery unit 102 and the second battery unit 104. By using the current detection circuit, as will be described later, the current value of the circulating current used for the determination of switching the connection state of a plurality of batteries can be directly acquired. Therefore, the first switch 106, the second switch 108, and the third switch 110 (switching unit) can be quickly controlled.

The switch control unit 112 controls the on and off of the first switch 106, the second switch 108, and the third switch 110, and connects the first battery unit 102 and the second battery unit 104 in parallel or in series as described above. do. As will be described later, the switch control unit 112 may output control signals of the first switch 106, the second switch 108, and the third switch 110 at preset timings, and may output an ASIC (Application Special Integrated Circuit) or programmable logic. It can be realized by a semiconductor integrated circuit such as a device (FPGA (Field Programmable Gate Array) or the like). The switch control unit 112 is configured as a control device (computer) including an arithmetic element (CPU: Central Processing Unit) and a storage element (memory), and the arithmetic element executes a computer program to execute the first switch 106 and the second. On and off control of the switch 108 and the third switch 110 may be performed. By realizing it with a semiconductor integrated circuit, it is possible to execute processing at high speed, and as will be described later, it is possible to accurately suppress an excessive circulating current. By realizing it by a computer program, it is easy to modify the process (change the timing, etc.), and it is possible to easily respond to the change of parts, etc.

(motion)
The operation of the power storage system 100 will be described with reference to FIGS. 2 and 3. With reference to FIG. 2, here, the charger 124 is connected to the terminals 120 and 122 of the power storage system 100 shown in FIG. 1, and the first battery unit 102 and the second battery unit 104 are connected by the switch control unit 112. Suppose they are connected in parallel and charged. That is, the switch control unit 112 sets the first switch 106 and the third switch 110 to ON, and the second switch 108 to OFF. If there is a difference (voltage difference) between the voltage of the first battery unit 102 and the voltage of the second battery unit 104, a circulating current flows. In FIG. 2, a broken line arrow indicates the circulating current i flowing when the voltage of the second battery unit 104 is larger than the voltage of the first battery unit 102 and its direction.

FIG. 3 shows a process executed by the switch control unit 112. In the initial state of the power storage system 100, it is assumed that the first switch 106, the second switch 108, and the third switch 110 are off. Further, the switch control unit 112 has a flag inside. For example, the switch control unit 112 includes a readable and writable memory, and uses a part of the memory area (for example, 1 bit) as a flag.

In step 300, the switch control unit 112 turns on the first switch 106 and the third switch 110 and sets the flag to “1” as described above. The flag is for storing the on / off state of the third switch 110. Here, if the flag is "1", it is turned on, and if it is "0", it is turned off. At this time, the switch control unit 112 maintains the initial state (off) of the second switch 108. As a result, the first battery unit 102 and the second battery unit 104 are connected in parallel. After that, control shifts to step 302.

In step 302, the switch control unit 112 acquires the current value of the circulating current detected by the current detection circuit 114. After that, control shifts to step 304.

In step 304, the switch control unit 112 determines whether or not the current value acquired in step 302 is equal to or less than a predetermined first threshold value (current value ≤ first threshold value). The first threshold value may be stored in the memory of the switch control unit 112. If it is determined that it is equal to or less than the first threshold value, the control shifts to step 308. Otherwise (current value> first threshold), control proceeds to step 306.

In step 306, the switch control unit 112 turns off the third switch 110 and sets the flag to “0”. The control then returns to step 302.

In step 308, the switch control unit 112 determines whether or not the flag is “1”. If the flag is "1", control proceeds to step 310. Otherwise (flag is “0”), control returns to step 300 and repeats the above process. When step 300 is executed again, the third switch 110, which was off, is turned on. At this time, since the first switch 106 is already on, that state is maintained.

In step 310, the switch control unit 112 determines whether or not the voltage difference between the first battery unit 102 and the second battery unit 104 is equal to or less than the second threshold value (voltage difference ≤ second threshold value). The second threshold value may be stored in the memory of the switch control unit 112. If it is determined that it is equal to or less than the second threshold value, this process is terminated. Otherwise (voltage> second threshold), control returns to step 302.

As described above, after the first switch 106 and the third switch 110 are turned on and the first battery unit 102 and the second battery unit 104 are connected in parallel, the circulating current is equal to or less than the first threshold value and the first one. As long as the voltage difference between the battery unit 102 and the second battery unit 104 is larger than the second threshold value, a closed circuit through which the circulating current flows is maintained (repetition of steps 302, 304, 308 and 310). When the current value of the circulating current becomes larger than the first threshold value (the determination result in step 304 is NO), the third switch 110 is turned off, the closed circuit is opened, and the circulating current decreases (step 306). As a result, it is possible to easily suppress the generation of an excessive circulating current when a plurality of batteries are connected in parallel.

After that, when the circulating current becomes smaller than the first threshold value again, the third switch 110 is turned on (the determination result in step 308 becomes YES, step 300 is executed), the closed circuit is formed again, and the circulation is performed. The current increases. After that, the above process is repeated until the voltage difference between the first battery unit 102 and the second battery unit 104 becomes equal to or less than the second threshold value. When the voltage difference between the first battery unit 102 and the second battery unit 104 becomes equal to or less than the second threshold value, the process ends. As a result, energy loss due to unnecessary control after the voltages of the plurality of batteries are balanced can be suppressed.

With reference to FIG. 4, the change in the circulating current when the above processing is executed will be described. The broken line indicates that after the first switch 106 and the third switch 110 were turned on to connect the first battery unit 102 and the second battery unit 104 in parallel, the third switch 110 was kept on without on / off control. The circulating current of the case is shown. The solid line shows the circulating current when the third switch 110 is turned on and off as described above. If the third switch 110 is not controlled on and off, the circulating current increases sharply immediately after the first switch 106 and the third switch 110 are turned on, and becomes larger than the current value that affects the relay life, and then. Decay. On the other hand, if the third switch 110 is controlled to be turned on and off, the circulating current increases sharply, but if it becomes larger than the first threshold value, the third switch 110 is turned off and the circulating current affects the relay life. Decreases before reaching the current value that exerts. After that, as described above, if the third switch 110 is repeatedly turned on and off (during the period Tc) and the voltage difference between the first battery unit 102 and the second battery unit 104 becomes smaller than the second threshold value. (After the lapse of the period Tc), the on / off control of the third switch 110 is terminated, the state in which the first switch 106 and the third switch 110 are turned on is maintained, and the circulating current is attenuated. Therefore, in a state where the voltages of the first battery unit 102 and the second battery unit 104 are balanced (the voltage difference is equal to or less than the second threshold value), the first battery unit 102 and the second battery unit 104 are charged by the charger 124. Can be charged.

In this way, immediately after the first switch 106 and the third switch 110 are turned on and the first battery unit 102 and the second battery unit 104 are connected in parallel, the third switch 110 is turned on and the third switch 110 is turned on according to the magnitude of the circulating current. By off-control, it is possible to suppress the generation of an excessive circulating current that affects the life of the relay, and it is possible to suppress the occurrence of energy loss due to the switch (relay) and the reduction of the life of the switch. Further, the voltages of a plurality of battery units can be balanced by a simple control of controlling the on and off of the third switch 110 according to the magnitude of the circulating current.

The first threshold value may be set in consideration of the specifications of the first switch 106 and the third switch 110 to be used. For example, the first threshold value can be set based on the life (durability) of the first switch 106 and the third switch 110. The first threshold value may be set based on the energy (energy loss) consumed by the first switch 106 and the third switch 110 because the circulating current flows. Further, it may be set based on the life and energy loss of the first switch 106 and the third switch 110. As a result, it is possible to appropriately suppress the flow of an excessive circulating current that affects the life of the switch (relay).

Since the circulating current increases sharply, it is preferable that the third switch 110 is controlled to be turned on and off at high speed. For example, it is preferable to be able to switch at several kHz to several tens of kHz. Therefore, it is preferable to use a semiconductor switching element (FET, IGBT, etc.) having a faster response speed than a mechanical relay (contact relay) for the third switch 110. By using the semiconductor switching element, the connection state of a plurality of batteries can be switched at high speed, and the rapidly increasing circulating current can be appropriately suppressed. In addition, a switching device with low power consumption can be realized.

In the above, the case where the third switch 110 for connecting the low voltage side (negative electrode) of the first battery unit 102 and the second battery unit 104 is controlled to be turned on and off according to the magnitude of the circulating current has been described. Not limited to this. The third switch 110 is kept on, and the first switch 106 for connecting the high voltage side (positive electrode) of the first battery unit 102 and the second battery unit 104 is turned on and off according to the magnitude of the circulating current. You may control it. Since it is sufficient that the closed circuit formed when the first battery unit 102 and the second battery unit 104 are connected in parallel can be opened, at least one of the first switch 106 and the third switch 110 is set according to the magnitude of the circulating current. It may be turned on and off. As described above, it is preferable to use a semiconductor switching element for the switch of the first switch 106 and the third switch 110 that is controlled to be turned on and off according to the magnitude of the circulating current.

In the above, when the charger 124 is connected to the terminals 120 and 122 to charge the first battery unit 102 and the second battery unit 104, the case where the first battery unit 102 and the second battery unit 104 are balanced will be described. However, it is not limited to this. Also when the load is connected to the terminals 120 and 122 and the first battery unit 102 and the second battery unit 104 are connected in parallel to supply the discharge power of the first battery unit 102 and the second battery unit 104 to the load. If there is a voltage difference between the 1 battery unit 102 and the 2nd battery unit 104, a large circulating current flows when the 1st switch 106 and the 3rd switch 110 are turned on. Therefore, even in such a case, it is preferable to balance the first battery unit 102 and the second battery unit 104. As described above, after balancing the first battery unit 102 and the second battery unit 104 by controlling the third switch 110 on and off according to the comparison result between the circulating current and the first threshold value. , Can power the load.

(Installation on vehicle)
With reference to FIG. 5, the power storage system 100 shown in FIG. 1 can be mounted on a vehicle 150 such as a PHEV or EV. The power storage system 100 mounted on the vehicle 150 constitutes a power supply unit. While the vehicle 150 is running, the power storage system 100 (switch control unit 112) controls the first switch 106, the second switch 108, and the third switch 110 on and off, for example, the first battery unit 102 and the second battery. The units 104 are connected in parallel, and the output voltage (direct current) thereof is supplied to the power converter 152. The power converter 152 has a DC / DC converter function and an AC / DC converter function. The voltage supplied to the power converter 152 is converted into a predetermined voltage (direct current) by the function of the DC / DC converter of the power converter 152 and supplied to the inverter 154. The voltage supplied to the inverter 154 is converted into AC power by the inverter 154 and used to drive a driving device 156 such as a motor. The output voltage of the power storage system 100 may be directly supplied to the inverter 154 without going through the power converter 152.

Further, the output voltage of the power storage system 100 is converted into a low voltage by the function of the DC / DC converter of the power converter 152 and supplied to the auxiliary machine system load 158. As a result, the auxiliary machine load 158 is operated. The auxiliary machine load 158 is an accessory device necessary for operating an engine, a motor, and the like, and mainly includes a cell motor, an alternator, a radiator cooling fan, and the like. The auxiliary machine load 158 may include lighting, a wiper drive unit, a navigation device, an air conditioner, a heater, and the like. The output voltage of the power storage system 100 may be directly supplied to a part of the auxiliary machine load 158 (for example, an air conditioner, a heater, etc.) without going through the power converter 152.

When charging the vehicle 150 (when charging the first battery unit 102 and the second battery unit 104 of the power storage system 100), the power converter 152 is an external charger (AC power supply) by the function of the AC / DC converter. The AC power supplied from the above is converted into the charging voltage of the first battery unit 102 and the second battery unit 104. The power storage system 100 (switch control unit 112) controls the first switch 106, the second switch 108, and the third switch 110 on and off, and controls the first battery unit 102 and the first battery unit 102 and the third switch 110 according to the voltage supplied from the external power source. The second battery unit 104 is connected in parallel or in series. For example, when the first battery unit 102 and the second battery unit 104 have a 400V specification and 400V is supplied from the charger, the first battery unit 102 and the second battery unit 104 are connected in parallel. When 800V is supplied from the charger, the first battery unit 102 and the second battery unit 104 are connected in series. As a result, the first battery unit 102 and the second battery unit 104 can correspond to two types of chargers having different charging voltages, and are charged with an appropriate charging voltage.

(Second Embodiment)
In the first embodiment, the case where the circulating current is directly detected by the current detection circuit has been described, but the present invention is not limited to this. The power storage system 140 according to the second embodiment of the present disclosure uses a voltage detection circuit. With reference to FIG. 6, the power storage system 140 is configured in the same manner as the power storage system 100 shown in FIG. The power storage system 140 differs from the power storage system 100 (FIG. 1) only in that it includes a voltage detection circuit 142 instead of the current detection circuit 114, and the switch control unit 118 has a function further added to the switch control unit 112. be. Other components of the power storage system 140 are the same as those of the power storage system 100. Therefore, the duplicate explanation will not be repeated, and the differences will be mainly described.

The first switch 106, the second switch 108, the third switch 110, the switch control unit 118, and the voltage detection circuit 142 of the first battery unit 102 and the second battery unit 104 according to the state (circulating current) of the power storage system 140. A switching device 144 having a function of switching the connection state is configured. The voltage detection circuit 142 is connected to both ends of the first switch 106 and detects the voltage across the first switch 106. The voltage detection circuit 142 is a specific example of the detection unit, for example, a voltmeter. Since the first switch 106 has a predetermined resistance when it is turned on, as described above, when a circulating current flows through the connection line constituting the closed circuit including the first battery unit 102 and the second battery unit 104, A potential difference (voltage drop due to resistance) occurs between both ends of the first switch 106. Here, it is assumed that the third switch 110 is controlled to be turned on and off and the first switch 106 is kept on, as in the first embodiment. The voltage detection circuit 142 inputs the detected voltage value to the switch control unit 118.

The switch control unit 118 controls on and off of the first switch 106, the second switch 108, and the third switch 110, similarly to the switch control unit 112. In addition to this, the switch control unit 118 converts the voltage value input from the voltage detection circuit 142 into a current value. The resistance value when the first switch 106 is turned on is stored in the memory of the switch control unit 118 in advance, and the switch control unit 118 reads this and divides the voltage value acquired from the switching device 144 by the resistance value. To calculate the current value. By using the voltage detection circuit, the current value of the circulating current can be easily obtained in the existing power storage system. When the existing power storage system is provided with a current detection circuit for detecting the circulating current, it is necessary to process a part of the existing circuit.

The switch control unit 118 executes a program having a control structure represented by the flowchart shown in FIG. In step 302, the switch control unit 118 calculates the current value of the circulating current from the voltage value acquired from the voltage detection circuit 142 as described above. Other processing is the same as that of the first embodiment.

Therefore, also in the power storage system 140, the circulating current is suppressed as shown by the solid line in FIG. That is, it is possible to suppress the generation of an excessive circulating current that affects the relay life, and to suppress energy loss and reduction in relay life. Further, the voltages of a plurality of battery units can be balanced by a simple control of controlling the on and off of the third switch 110 according to the magnitude of the circulating current.

In the above, the case where the switch control unit 118 calculates the current value of the circulating current from the voltage value detected by the voltage detection circuit 142 has been described, but the present invention is not limited to this. Using the voltage value corresponding to the first threshold value for limiting the circulating current (hereinafter referred to as the third threshold value), the voltage value is detected by the voltage detection circuit 142 instead of the determination process in step 304 of FIG. It may be determined whether or not the voltage value is equal to or less than the third threshold value. For the third threshold value, for example, the product of the first threshold value and the resistance value of the first switch 106 may be used. As a result, in the existing power storage system, the voltage value due to the circulating current can be easily acquired, and by using the voltage value detected by the voltage detection circuit, the switching unit can be quickly controlled.

(Third Embodiment)
The power storage system of the first and second embodiments has a configuration including two battery units, but is not limited thereto. In a power storage system, three or more battery units may be connected and used in parallel. The power storage system 200 according to the third embodiment of the present disclosure uses three battery units connected in parallel.

With reference to FIG. 7, the power storage system 200 includes a first battery unit 102, a second battery unit 104, and a third battery unit 202. The power storage system 200 includes a first switch 106, a second switch 108, a third switch 110, a fourth switch 206, a fifth switch 208, and a sixth switch 210 as switching units. The power storage system 200 further includes a first current detection circuit 204, a second current detection circuit 214, a switch control unit 216, and terminals 120 and 122. The first switch 106, the second switch 108, the third switch 110, the fourth switch 206, the fifth switch 208, the sixth switch 210, the first current detection circuit 204, the second current detection circuit 214, and the switch control unit 216 A switching device 218 having a function of switching the connection state of the first battery unit 102, the second battery unit 104, and the third battery unit 202 according to the state (circulating current) of the power storage system 200 is configured.

In the power storage system 200, the third battery unit 202, the fourth switch 206, the fifth switch 208, the sixth switch 210, and the second current detection circuit 214 are added to the power storage system 100 shown in FIG. 1, and the current detection circuit 114 Is replaced by the first current detection circuit 204, and the switch control unit 112 is replaced by the switch control unit 216. In FIG. 7, since the elements having the same reference numerals as those in FIG. 1 have the same functions as those described above, the duplicate description will not be repeated, and the differences will be mainly described.

The third battery unit 202 is a unit composed of a rechargeable and dischargeable storage battery, and has the same specifications as the first battery unit 102 and the second battery unit 104. The first battery unit 102, the second battery unit 104, and the third battery unit 202 are, for example, 400V specification battery units.

The first switch 106, the third switch 110, the fourth switch 206 and the sixth switch 210 are turned on, the first switch 106 and the fifth switch 208 are turned off, and the first battery unit 102, the second battery unit 104 and the second battery unit 104 and the first switch 208 are turned off. When the three battery units 202 are connected in parallel, three closed circuits are formed. Therefore, three types of circulating currents can flow. For example, before the first battery unit 102, the second battery unit 104, and the third battery unit 202 are connected in parallel, it is assumed that the magnitude relation of the respective voltages V1, V2, and V3 is V1 <V2 <V3. .. At this time, among the circulating currents i1 to i3 (arrows indicate the current direction) shown by the broken lines in FIG. 7, the circulating currents i1 and i2 flow according to the voltage difference (difference between V1, V2 and V3). And, the circulating currents i2 and i3 may flow.

The first current detection circuit 204 has the same function as the current detection circuit 114, and is arranged at the same position as the current detection circuit 114. That is, the first current detection circuit 204 is arranged on a connection line forming a closed circuit (path of circulating current i1) formed by connecting the first battery unit 102 and the second battery unit 104 in parallel. .. The second current detection circuit 214 has the same function as the first current detection circuit 204, and is a closed circuit (path of circulating current i2) formed by connecting the second battery unit 104 and the third battery unit 202 in parallel. ) Is located on the connection line. The first current detection circuit 204 and the second current detection circuit 214 are, for example, ammeters. As described above, the circulating current also flows in the closed circuit (path of the circulating current i3) formed by connecting the first battery unit 102 and the third battery unit 202 in parallel. Therefore, when the circulating currents i1 and i2 flow, the current detected by the first current detection circuit 204 is the circulating current i1, and the current detected by the second current detecting circuit 214 is the circulating current i2. When the circulating currents i2 and i3 flow, the current detected by the first current detection circuit 204 is the circulating current i3, and the current detected by the second current detection circuit 214 is the sum of the circulating currents i2 and i3 (i2 + i3). be. In either case, each of the first current detection circuit 204 and the second current detection circuit 214 inputs the detected current value to the switch control unit 216.

The switch control unit 216 controls on and off of the first switch 106, the second switch 108, the third switch 110, the fourth switch 206, the fifth switch 208, and the sixth switch 210, similarly to the switch control unit 112. .. As a result, the switch control unit 216 connects the first battery unit 102, the second battery unit 104, and the third battery unit 202 in parallel or in series. Like the switch control unit 112, the switch control unit 216 is realized by a semiconductor integrated circuit or a computer program.

Further, the switch control unit 216, like the switch control unit 112, uses the current values input from the first current detection circuit 204 and the second current detection circuit 214 to use the first battery unit 102 and the second battery unit 104. Control is performed to suppress the circulating currents i1 to i3 generated when the third battery unit 202 is connected in parallel. Specifically, the switch control unit 216 compares the current value (i1 or i3) input from the first current detection circuit 204 with the first threshold value, and the comparison result, similarly to the switch control unit 112. The third switch 110 is controlled to be turned on and off according to the above. Further, the switch control unit 216 compares the current value (i2 or i2 + i3) input from the second current detection circuit 214 with the first threshold value, and turns on the sixth switch 210 and turns on the sixth switch 210 according to the comparison result. Control off.

As a result, the current detected by each of the first current detection circuit 204 and the second current detection circuit 214 changes as shown by the solid line in FIG. 4, and the generation of excessive circulating current is suppressed even in the power storage system 200. can. That is, it is possible to suppress the generation of an excessive circulating current that affects the relay life, and it is possible to suppress the energy loss due to the switch (relay) and the decrease in the life of the switch. Further, it is as simple as controlling the on and off of the third switch 110 and the sixth switch 210 according to the magnitude of the current (circulating current) detected by the first current detection circuit 204 and the second current detection circuit 214. The voltage of the three battery units can be balanced by various controls. Therefore, when the charger is connected to the terminals 120 and 122, after the voltages of the first battery unit 102, the second battery unit 104, and the third battery unit 202 are balanced, the first battery unit 102, The second battery unit 104 and the third battery unit 202 are charged. When a load is connected to terminals 120 and 122, the voltages of the first battery unit 102, the second battery unit 104, and the third battery unit 202 are balanced, and then the first battery unit 102 and the second battery The discharge voltage of the unit 104 and the third battery unit 202 is supplied to the load. Further, since three batteries can be connected in series and the batteries can be charged at a higher voltage, the charging time of the batteries can be further shortened.

The third switch 110 and the sixth switch 210, which are turned on and off by the switch control unit 216, are preferably semiconductor switching elements (FET, IGBT, etc.). The switch control unit 216 may control the first switch 106 on and off instead of controlling the third switch 110 on and off. Further, the switch control unit 216 may control the fourth switch 206 on and off instead of controlling the sixth switch 210 on and off.

In the above, the case where V1 <V2 <V3 is described before the first battery unit 102, the second battery unit 104, and the third battery unit 202 are connected in parallel has been described, but the present invention is not limited to this. The voltages V1, V2 and V3 may have a magnitude relationship other than V1 <V2 <V3. That is, regardless of the magnitude relationship of the voltages V1, V2, and V3, the third switch 110 is turned on and off according to the comparison result between the current detected by the first current detection circuit 204 and the first threshold value. Just do it. Further, the sixth switch 210 may be controlled on and off according to the comparison result between the current detected by the second current detection circuit 214 and the first threshold value.

In the above, the case where three battery units are connected in parallel has been described, but the present invention is not limited to this. Even when four or more battery units are connected in parallel, the generation of an excessive circulating current can be suppressed by performing the same configuration and control as described above. For example, in the circuit configuration when four battery units are connected in parallel, a fourth battery unit, a current detection circuit, and three switches are added to the right side of the circuit of FIG. 7, similar to the change from FIG. 1 to FIG. do it.

When the number of battery units is N and all of them are connected in parallel, the current detection circuit for detecting the circulating current may be arranged on the connection line between the two battery units. For example, a current detection circuit is arranged on the connection line on the high voltage side (positive electrode) of the two battery units. The switching unit for parallel connection is composed of an N-1 switch for connecting the high voltage side (positive electrode) of the two battery units and an N-1 switch for connecting the low voltage side (negative electrode). (Total 2 × (N-1)). Therefore, the current value detected by each current detection circuit is compared with the first threshold value, and according to the comparison result, a switch arranged in a closed circuit including the current detection circuit and not including another current detection circuit. By controlling the on and off, the generation of an excessive circulating current can be suppressed as described above. Since four or more batteries can be connected in series and the batteries can be charged at a higher voltage, the charging time of the batteries can be further shortened.

(First modification)
The processing of the flowchart shown in FIG. 3 above ends when the voltage difference between the first battery unit 102 and the second battery unit 104 becomes equal to or less than the second threshold value. However, it is not limited to this. From the viewpoint of safety, for example, as shown in FIG. 8, the process of step 310 (FIG. 3) may not be performed. In the flowchart of FIG. 8, it is not determined whether or not the voltage difference between the first battery unit 102 and the second battery unit 104 is equal to or less than the second threshold value. Therefore, the process of turning on and off the third switch 110 is repeated according to the result of comparing the current flowing through the closed circuit including the first battery unit 102 and the second battery unit 104 with the first threshold value.

It is conceivable that an overcurrent will occur for some reason after the circulating current generated when the first battery unit 102 and the second battery unit 104 are connected in parallel disappears. By constantly repeating the process shown in FIG. 8, even if some factor that causes an overcurrent occurs after the circulating current generated when the first battery unit 102 and the second battery unit 104 are connected in parallel disappears. Overcurrent can be prevented. For example, when a short-circuit accident occurs on the load side, it is possible to prevent an overcurrent from flowing from the first battery unit 102 and the second battery unit 104.

(Second modification)
In FIGS. 1 and 2, the current detection circuit 114 is arranged on the connection line on the high voltage side (positive electrode) of the first battery unit 102 and the second battery unit 104, but the present invention is not limited to this. The position where the current detection circuit 114 is arranged may be any position where the circulating current can be detected. For example, as shown in FIG. 9, it may be arranged on the connection line on the low voltage side (negative electrode) of the first battery unit 102 and the second battery unit 104. The power storage system 230 of FIG. 9 is the power storage system 100 of FIG. 1 in which the position of the current detection circuit 114 is changed. By providing the current detection circuit 114 on the low voltage side (negative electrode) of the first battery unit 102 and the second battery unit 104 in this way, the ground of the control circuit (switch control unit or the like) becomes the first battery unit 102 and the second battery unit 102 and the second. If it is common to the low voltage side of the battery unit 104, it is not necessary to insulate the current detection circuit 114, which facilitates realization.

In the above, the power storage system in which a plurality of battery units are connected in parallel or in series has been described, but the present invention is not limited to this. For example, even in a system in which a plurality of battery units having the same specifications are always connected in parallel, an excessive circulating current may occur. For example, when one battery unit is replaced due to maintenance or the like, it is necessary to connect them in parallel again, and an excessive circulating current may be generated at that time. Therefore, even in such a case, as described above, the generation of an excessive circulating current can be suppressed by controlling the switch on and off according to the comparison result between the circulating current and the threshold value.

Although the present disclosure has been described above by explaining the embodiments, the above-described embodiments are examples, and the present disclosure is not limited to the above-described embodiments. The scope of the present disclosure is indicated by each claim of the claims, taking into consideration the description of the detailed description of the invention, and all changes within the meaning and scope equivalent to the wording described therein. include.

100, 140, 200, 230 Power storage system 102 1st battery unit 104 2nd battery unit 106 1st switch 108 2nd switch 110 3rd switch 112, 118, 216 Switch control unit 114 Current detection circuit (detection unit)
116, 144, 218 Switching device 120, 122 Terminal 124 Charger 142 Voltage detection circuit (detector)
150 Vehicle 152 Power converter 154 Inverter 156 Drive 158 Auxiliary system load 202 3rd battery unit 204 1st current detection circuit 206 4th switch 208 5th switch 210 6th switch 214 2nd current detection circuit 300, 302, 304 , 306, 308, 310 Steps i, i1, i2, i3 Circulating current V1, V2, V3 Voltage

Claims (14)

A switching unit that switches the connection state of a plurality of batteries between a first state in which the plurality of batteries are connected in parallel and a second state other than the first state.
A control unit that controls the switching unit and
Includes a detector that detects the current value of the circulating current flowing through the closed circuit formed by connecting the plurality of batteries in parallel.
The control unit switches the connection state of the plurality of batteries to the first state or the second state based on the current value detected by the detection unit and the first threshold value. A switching device that controls the unit. The control unit further controls the switching unit so that the plurality of batteries are connected in series.
In the first state, a first voltage is applied to both ends of the plurality of batteries connected in parallel, and the first voltage is applied.
The switching device according to claim 1, wherein a second voltage larger than the first voltage is applied to both ends of the plurality of batteries connected in series. The control unit
When the current value is equal to or less than the first threshold value, the switching unit is controlled so that the connection state of the plurality of batteries becomes the first state.
The switching device according to claim 1 or 2, wherein if the current value is larger than the first threshold value, the switching unit is controlled so that the connection state of the plurality of batteries becomes the second state. The control unit
It is determined whether or not the voltage difference between the plurality of batteries is equal to or less than the second threshold value.
The switching device according to any one of claims 1 to 3, wherein the control of the switching unit is stopped in response to the determination that the voltage difference is equal to or less than the second threshold value. The switching device according to any one of claims 1 to 4, wherein the first threshold value is set based on at least one of the life and energy loss of the switching unit. The switching unit includes a semiconductor switching element.
The control unit
By turning on the semiconductor switching element, the connection state of the plurality of batteries is changed to the first state.
The switching device according to any one of claims 1 to 5, wherein the connection state of the plurality of batteries is changed to the second state by turning off the semiconductor switching element. The switching device according to any one of claims 1 to 6, wherein the detection unit is a current detection circuit. The switching unit includes a plurality of switching elements.
The detection unit includes a voltage detection circuit that detects a voltage between both terminals of the switching element that is turned on in both the first state and the second state among the plurality of switching elements.
The switching device according to any one of claims 1 to 6, wherein the control unit calculates the current value based on the voltage value detected by the voltage detection circuit. The switching unit includes a plurality of switching elements.
The detection unit
Among the plurality of switching elements, a voltage detection circuit that detects a voltage between both terminals of the switching element that is turned on in both the first state and the second state is included.
Instead of detecting the current value, the voltage value is detected by the voltage detection circuit, and the voltage value is detected.
The control unit
Instead of the current value, the voltage value detected by the voltage detection circuit is used.
The switching device according to any one of claims 1 to 6, which uses a third threshold value for voltage instead of the first threshold value. The switching device according to any one of claims 1 to 9, wherein the switching unit switches the connection state of three or more batteries. The switching device according to any one of claims 1 to 10, wherein the control unit includes a semiconductor integrated circuit or an arithmetic element that executes a computer program. With multiple batteries
A power storage system including the switching device according to any one of claims 1 to 11, which switches a connection state between the plurality of batteries. The power storage system according to claim 12,
A vehicle including a drive device powered by the plurality of batteries. This is a switching method for switching the connection status of multiple batteries.
The first step of detecting the current value of the circulating current flowing through the closed circuit formed by connecting the plurality of batteries in parallel, and
Based on the current value detected by the first step and the first threshold value, the connection states of the plurality of batteries are set to other than the first state in which the plurality of batteries are connected in parallel and the first state. Includes a second step to switch between and the second state of
A switching method in which the first step and the second step are repeated.

Images