JP2013017323A - Cell equalization control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell equalization control system for equalizing remaining capacities of battery cells or battery blocks constituting a battery pack which ensures insulation and uses a reduced number of components.SOLUTION: Voltage detection terminal groups 102a, 102b are connected to both sides of each battery cell constituting a battery pack 101. First and second changeover switch groups 103, 104 selectively connect the odd-numbered and even-numbered voltage detection terminal groups 102a, 102b to terminals T1, T2, respectively. A transformer 106 has a primary coil connected with an output terminal of the battery pack 101 or a regenerative energy output terminal via a switch element 107. A control section 109 controls the first and second changeover switch groups 103, 104 and a polarity switching relay group 105 to connect predetermined battery cells of the battery pack 101 or predetermined battery blocks aggregating such battery cells to a secondary coil of the transformer 106 and then controls the switch element 107 to execute equalization control.

Description

  The present invention relates to a cell equalization control system for equalizing the remaining capacity of battery cells or battery blocks constituting an assembled battery.

  A so-called hybrid car, plug-in hybrid car, hybrid vehicle, hybrid electric vehicle, or other vehicle or transport machine (hereinafter referred to as “vehicle etc.”) equipped with a motor (electric motor) as a power source in addition to the engine is practical. It has become. Furthermore, an electric vehicle that does not include an engine and drives the vehicle only by a motor is being put into practical use. As a power source for driving these motors, a lithium ion battery having a small size and a large capacity has been frequently used. In such an application, an assembled battery in which a plurality of batteries (hereinafter, each battery is referred to as a “cell”, and a plurality of the “cells” connected to each other is referred to as a “block”) is connected to each other. Often supplied.

  In this case, the characteristics of the lithium ion battery or the like greatly change depending on the temperature, and the remaining capacity and charging efficiency of the battery greatly change depending on the temperature of the environment in which the battery is used. This is especially true in environments where automobiles are used. As a result, in the battery cells constituting the assembled battery, the remaining capacity and the output voltage of each cell vary. When the voltage generated by each cell varies, it becomes necessary to stop or suppress the entire power supply when the voltage of one cell falls below the driveable threshold, resulting in reduced power efficiency. Resulting in. For this reason, control for equalizing the voltage or capacity of each cell is required.

  As a first conventional technique for cell equalization control, a passive system shown as an example of the configuration in FIG. 6 is known. In this system, a circuit in which a resistor 602 and a switch 603 are connected in series is connected in parallel to each battery cell 601 with respect to N battery cells 601 of # 1 to #N connected in series. Then, if necessary, each battery cell 601 (# 1 to # 1) is discharged by short-circuiting the switch 603 connected in parallel to the battery cell 601 and discharging the battery cell 601 through the resistor 602 connected thereto. #N) are aligned.

  However, such a passive method is a method of performing equalization control by discharging the energy stored in the battery cell 601, and thus has a problem that power efficiency is discarded and power efficiency is poor. It was. In addition, since equalization control is executed for each cell using a resistor, there is a problem that it takes time for convergence to equalize. Furthermore, since the number of times the battery can be used is limited, there has been a problem that the battery deteriorates when repeated overcharge / discharge (overcharge / discharge) many times.

  As a second conventional technique of cell equalization control, a conventional active 1 system shown as a configuration example in FIG. 7 is known. This method includes (N + 1) voltage detection terminals 702a and 702b connected to the N battery blocks of an assembled battery 701 in which N battery blocks including one or a plurality of secondary batteries are connected in series. The capacitor means 706 for storing the battery voltage, the first multiplexer 703 having a plurality of switches for selectively connecting the odd-numbered voltage detection terminal 702a to the first terminal T1, and the even-numbered voltage detection terminal 702b A second multiplexer 704 having a plurality of switches that are selectively connected to the second terminal T2, and the first terminal T1 is selectively connected to one end or the other end of the capacitor means 706, and the second terminal T2 is a capacitor. The switch 706 has a switch selectively connected to the other end or one end of the means 706, and the voltage between the first terminal T1 and the second terminal T2 is set to a predetermined polarity, and the capacity means 706 It has a configuration comprising a polar correcting unit 705 for applying. In this method, the first multiplexer 703, the second multiplexer 704, and the polarity correction means 705 are controlled to temporarily store the energy of the battery cell having a high remaining capacity in the capacity means 706, and to the battery cell having a low remaining capacity. The electric power stored in the capacity means 706 is charged. Thus, charging can be performed even during traveling, power efficiency is high, the number of switches is small, and an inexpensive capacitor can be used as the capacity unit 706, so that low-cost cell equalization control is realized.

  However, this method uses a capacitor as the capacity means 706, and therefore, if a voltage higher than the charging voltage of the capacitor is not supplied to the capacitor, the power cannot be delivered well and it is difficult to adjust the power transfer. Was. In addition, since there is no power adjustment circuit, if there is too much voltage difference between the battery cells, a current flows at a stretch and a burden is imposed on the parts, which may cause a failure. Further, since the current flowing through the circuit is large, there is a problem that the loss is large. In addition, it is inefficient to directly charge the capacitor with a voltage, and the convergence time becomes long when a time constant is imposed on the current. In addition, a considerable part of the charging power to the capacitor is used as a loss, and there is a possibility that the energy efficiency of the power is lower than that of the passive method. Moreover, insulation is not ensured.

  As a third conventional technique for equalization control, a conventional active 2 system shown as an example of the configuration in FIG. 8 is known. In this system, an assembled battery 801 configured by connecting a plurality of battery cells in series, a primary coil side is connected to both output terminals of the assembled battery 801 via a switch 804, and a secondary coil side is a rectifier diode 805. And a transformer 803 that is selectively connected to both side terminals of each battery cell in the assembled battery 801 via the changeover switch group 802.

  In this method, in a battery cell with a small remaining capacity, both terminals are connected to the secondary coil side of the transformer 803 by the switch group 802, and the switch 804 is turned on / off. As a result, electric power or regenerative energy from the assembled battery 801 is transmitted from the primary coil of the transformer 803 to the secondary coil, rectified by the rectifier diode 805, and then supplied to the battery cell whose remaining capacity is reduced. Is charged. With this configuration, a part of the regenerative current from the assembled battery 801 can be supplied to the battery cell with a small remaining capacity through the transformer 803, so that the charge amount can be finely adjusted. Moreover, since there is insulation by the transformer 803, there are few short-circuit failures between battery cells.

  However, this method has a problem that the number of switches constituting the changeover switch group 802 is large and the cost is high.

JP 2010-220413 A JP 2005-328642 A JP 2001-339865 A

  An object of this invention is to implement | achieve the cell equalization control system which can ensure insulation and has few number of parts.

  The present invention includes a voltage detection terminal group connected to both sides of each battery cell constituting the assembled battery, a first changeover switch group that selectively connects the odd-numbered voltage detection terminal group to the first terminal, A second changeover switch group that selectively connects the even-numbered voltage detection terminal group to the second terminal, and an output terminal of the assembled battery or an output terminal of regenerative energy is connected to the primary coil side via a switch element. A polarity switching relay group that connects the transformer, the first terminal, and the second terminal to the secondary coil side of the transformer through a rectifier diode by controlling the connection polarity; a first selector switch group; Controlling the switch element after connecting a predetermined battery cell constituting the assembled battery or a predetermined battery block including the battery cell to the secondary coil of the transformer by controlling the switch group and the polarity switching relay group. By And a control unit for executing equalization control for the battery cell or a predetermined cell block.

  According to the present invention, the equalization operation can be performed even while the vehicle is traveling, and it is possible to take time for equalization even when the ignition is off. Therefore, the accuracy of the equalization control is improved and the convergence time of the equalization control is shortened. It becomes possible.

  According to the present invention, since all the battery voltages are stable even during traveling, it is possible to avoid a situation in which the battery voltage drops by one cell and stops suddenly, and traveling without being disturbed by variations in voltage. As a result, drivability (drivability, drive performance) is improved.

According to the present invention, since optimal overcharge / discharge suppression is realized, the battery life can be extended.
According to the present invention, a cell equalization control system that can be easily implemented can be realized.

  According to the present invention, it is possible to secure insulation between current sensors and realize safe cell equalization control.

It is a block diagram of embodiment. It is operation | movement explanatory drawing of embodiment. It is a flowchart which shows the control operation of embodiment. It is a timing chart which shows control operation of an embodiment. It is a comparison figure of embodiment and the conventional active system. It is a figure which shows the structural example of a 1st prior art (passive system). It is a figure which shows the structural example of the 2nd prior art (conventional active 1 system). It is a figure which shows the structural example of the 3rd prior art (conventional active 2 system).

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention. The present embodiment is implemented as a cell equalization control system that equalizes the remaining capacity of battery cells or battery blocks of an assembled battery mounted on a vehicle.

  The assembled battery 101 is, for example, a lithium ion battery that has a configuration in which a plurality of battery blocks each having a plurality of battery cells connected in series are connected, and drives a vehicle or the like. Outputs on both sides of the assembled battery 101 are connected to output terminals OUT1 and OUT2. The output terminals OUT1 and OUT2 are connected to a drive motor control circuit.

  Voltage detection terminal groups 102 a and 102 b are connected to both sides of each battery cell constituting the assembled battery 101. The odd-numbered voltage detection terminal group 102a is selectively connected to the first terminal T1 by the first changeover switch group 103. The even-numbered voltage detection terminal group 102b is selectively connected to the second terminal T2 by the second changeover switch group 104.

The first terminal T <b> 1 and the second terminal T <b> 2 are connected to the secondary coil side of the transformer 106 via the rectifier diode 108 with the connection polarity controlled by the polarity switching relay group 105.
An output terminal OUT1 and an output terminal OUT2 are connected to the primary coil side of the transformer 106 via a switching element 107 for generating alternating current.

  The control unit 109 monitors the voltage of each battery cell or battery block in the assembled battery 101 via the control signal terminal S1. The control unit 109 controls the first changeover switch group 103 and the second changeover switch group 104 via the control signal terminals S2 and S3. The control unit 109 controls the polarity switching relay group 105 via the control signal terminal S4. Further, the control unit 109 controls the switch element 107 via the control signal terminal S5. In addition, the control unit 109 monitors the current value detected by the current sensor installed at the position of the first terminal T1 (may be the second terminal T2) via the control signal terminal S6.

The operation of the embodiment having the above configuration will be described below.
FIG. 2 is an operation explanatory diagram of the present embodiment. This explanatory diagram shows a current path when the control unit 109 in FIG. 1 determines that the remaining battery capacity of the top battery cell in the assembled battery 101 is the smallest and needs charging through the control signal terminal S1. It is.

  First, the control unit 109 in FIG. 1 brings the switch sw1 in the first changeover switch group 103 in FIG. 1 into a conductive state via the control signal terminal S2. Further, the control unit 109 brings the switch sw1 ′ in the second changeover switch group 104 in FIG. 1 into a conductive state via the control signal terminal S3. Thereafter, the control unit 109 brings the relays s1 and s4 in the polarity switching relay group 105 in FIG. 1 into a conductive state via the control signal terminal S4. Thereafter, the control unit 109 starts the on / off operation of the switch element 107 via the control signal terminal S5.

  As a result, the output of the assembled battery 101 flows in the AC state into the primary coil side of the transformer 106 through the path indicated by the broken line arrow 201 or the regenerative energy from the drive motor along the path indicated by the broken line 202. This intermittent current is transmitted to the secondary coil side by the electromagnetic induction effect as indicated by a solid line arrow 203, and is transmitted from the rectifier diode 108 to the inside of the assembled battery 101 via the relay s1, the first terminal T1, and the switch sw1. Flows to the positive electrode side of the uppermost battery cell. Further, the battery cell returns to the secondary coil side of the transformer 106 via the switch sw1 ′, the second terminal T2, and the relay s4 from the negative electrode side of the battery cell.

In this way, the uppermost battery cell in the assembled battery 101 can be charged.
When the second battery cell needs to be charged, the switch sw2 of the first changeover switch group 103 and the switch sw1 ′ of the second changeover switch group 104 are turned on. Then, the relays s2 and s3 of the polarity switching relay group 105 are turned on. As a result, the output of the rectifier diode 108 → relay s3 → second terminal T2 → switch sw1 ′ → second battery cell → switch sw2 → first terminal T1 → relay s2 → secondary coil side of the transformer 106 A current flows, and the second battery cell can be charged.

  When the third battery cell needs to be charged, the switch sw2 of the first changeover switch group 103 and the switch sw2 ′ of the second changeover switch group 104 are made conductive. Then, the relays s1 and s4 of the polarity switching relay group 105 are turned on. As a result, the output of the rectifier diode 108 → relay s1 → first terminal T1 → switch sw2 → third battery cell → switch sw2 ′ → second terminal T2 → relay s4 → secondary coil side of the transformer 106 A current flows, and the third battery cell can be charged.

  As described above, in the present embodiment, the first changeover switch group 103, the second changeover switch group, and the polarity changeover relay group 105 are provided, and the transformer 106, the switch element 107, and the rectifier diode 108 are provided as means for supplying power. A regenerative circuit consisting of With this configuration, it is possible to reduce the number of switches while ensuring insulation between battery cells, and to realize a cell equalization control system that can always perform equalization control even during traveling.

  3 and 4 are a flowchart and a timing chart showing the control operation of the present embodiment. The control operation of the flowchart of FIG. 3 is executed by the control unit 109 of FIG. The control unit 109 is realized as a computer system including, for example, a CPU (Central Processing Unit), a program ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Then, the control operation of the flowchart of FIG. 3 is realized as a process in which the CPU executes the control program stored in the program ROM.

  First, the control unit 109 calculates the lowest block voltage, the lowest cell voltage, the target block voltage, and the target cell voltage via the control signal terminal S1 (step S301). The assembled battery 101 of FIG. 1 is configured by a plurality of battery cells. Among these, some of the battery cells are further configured in units of battery blocks. That is, one battery block is composed of a plurality of battery cells, and the assembled battery 101 is composed of a plurality of battery blocks. Therefore, equalization control is performed in units of both battery blocks and battery cells. First, the block voltage output from each battery block is monitored in units of battery blocks, the lowest block voltage is calculated as the lowest block voltage, and the corresponding battery block is recorded. Also, the cell voltage output by each battery cell is monitored in the unit of battery cell, the lowest cell voltage is calculated as the cell voltage being the lowest among them, and the corresponding battery cell is recorded. Further, the target block voltage and the target cell voltage are voltage values that the battery block having the lowest block voltage and the battery cell having the lowest cell voltage should reach. These may be fixed values or may be calculated by a predetermined calculation from all current block voltages and cell voltages in the assembled battery 101.

  Next, the control unit 109 compares the cell voltage deviation, which is the difference between the lowest cell voltage and the target cell voltage, and the block voltage deviation, which is the difference between the lowest block voltage and the target block voltage (step S302).

  If the cell voltage deviation is larger than the block voltage deviation, a control process for selecting a battery cell corresponding to the lowest cell voltage as a charging cell is executed (steps S302 → S303). On the other hand, if the block voltage deviation is greater than or equal to the cell voltage deviation, a control process for selecting a battery block corresponding to the lowest block voltage as a charging block is executed (steps S302 → S304).

  In the charging cell selection process in step S303, the following process is executed. First, the control unit 109 controls the control signal terminals S2 and S3 so that the terminals on both sides of the battery cell corresponding to the lowest cell voltage can be selected. The selector switch group 104 is controlled. In the example of FIG. 2, the switches sw1 and sw1 ′ are selected when the top battery cell is determined to be a charge cell. Next, the control unit 109 controls the polarity switching relay group according to the polarities of the first changeover switch group 103 and the second changeover switch group 104 connected to the selected battery cell via the control signal terminal S4. 105 is controlled. In the example of FIG. 2, relays s1 and s4 are selected. Thereafter, the control unit 109 turns on the selected switch and relay to bring them into a conductive state. 4A and 4D are timing charts showing ON timings of selected switches in the first changeover switch group 103 and the second changeover switch group 104. FIG. The ON timings of the switches sw1 and sw1 ′ are shown corresponding to the example of FIG. 4B and 4C are timing charts showing ON timings of selected relays in the polarity switching relay group 105. FIG. The ON timings of the relays s1 and s4 are shown corresponding to the example of FIG. Accordingly, the relay ON timing is controlled to be slightly behind the switch ON timing.

  Subsequently, the control unit 109 acquires the current value at the position of the first terminal T1 in FIG. 1 from the current sensor via the control signal terminal S6 in FIG. 1, and the current sensor value is a predetermined dark current value (almost most). It is determined whether it is smaller than (a value close to zero) (step S305). Now, if the rectifier diode 108 in FIG. 1 is damaged and short-circuited, even if the transformer 106 has not started the regenerative operation, the short-circuited rectifier diode 108 is caused to flow backward, and steps S303 or S304 are performed. A large current flows from the positive side to the negative side of the current cell or battery block connected by (for example, in the direction opposite to the solid arrow 203 in FIG. 2). Therefore, in the present embodiment, the control unit 109 can detect the short-circuit state of the secondary coil side circuit by performing the determination in step S305.

  When the current sensor value is equal to or greater than the dark current value and the determination in step S305 is NO, the control unit 109 turns off all the relays in the polarity switching relay group 105 to stop the regenerative operation, and the abnormality is detected by a lamp or the like. A warning is given (step S307).

  FIG. 4E is a timing chart showing the output value of the current sensor installed at the first terminal T1 of FIG. Immediately after the first changeover switch group 103, the second changeover switch group 104, and the polarity changeover relay group 105 are turned on, the current value is close to zero if it is normal, and the output current rises according to the subsequent regenerative operation.

  On the other hand, when the current sensor value is smaller than the dark current value and the determination in step S305 is YES, the control unit 109 starts the intermittent operation of the switch element 107 via the control signal terminal S5 in FIG. The charging operation by the regenerative circuit 107 and the rectifier diode 108 is started (step S306). The timing chart is as shown in FIG.

  After the above charging process, the control unit 109 performs the following operation when it is confirmed through the control signal terminal S1 that the target charging cell or charging block has reached the target cell voltage or the target block voltage. That is, the control unit 109 turns off the relay selected by the polarity switching relay group 105 via the control signal terminal S4, and the first changeover switch group 103 and the second switching point via the control signal terminals S2 and S3. The switch selected in the selector switch group 104 is turned off (step S308).

Then, it returns to the control process of step S301 and continues cell equalization control.
In the present embodiment described above, the number of parts constituting the cell equalization control system is first determined by combining the first changeover switch group 103, the second changeover switch group 104, and the polarity changeover relay group 105. Can be reduced. FIG. 5 is a comparison diagram of the number of parts in the conventional active 1 system illustrated in FIG. 7, the conventional active 2 system illustrated in FIG. 8, and the present embodiment in FIG. 1. Here, an assembled battery 101 is assumed in which the number of battery cells is 14 in series, and 8 battery blocks configured thereby are configured in parallel. As a result, in this embodiment, the number of parts can be reduced to almost half compared with the conventional active 2 system having excellent insulation, and the number of parts is almost the same as that of the conventional active 1 system having a small number of parts but poor insulation. It can be seen that it can be implemented with points.

  In the present embodiment, cell equalization control can be performed at any time, such as when the vehicle is stopped, traveling, or charging. For this reason, it is not necessary to worry about the convergence time required for charging, and it is possible to supply energy to a plurality of battery cells or battery blocks by switching between the charging cells or the charging blocks.

  In this embodiment, since the transformer 106 is used, insulation between the primary coil side and the secondary coil side is ensured. Further, the polarity switching relay group 105 enables quick insulation in the event of a short circuit failure or the like, and ensures insulation between battery cells.

  In the present embodiment, by performing equalization control at all times, overcharging / discharging during traveling can be suppressed, and traveling time can be extended. By equalizing the voltage during running, the duration of the battery can be extended, and the drivability is stabilized because no sudden voltage change occurs.

  In the present embodiment, since the regenerative energy and the like sent from the outside are directly adjusted using the transformer 106, the power efficiency is increased by the absence of energy saving loss. Passive waste energy can be reused, and regenerative / charging energy can be directly equalized.

In this embodiment, since equalization control is always possible, it is not necessary to flow a large current, and it is possible to cope with parts having a small capacity, and the cell equalization control system can be downsized.
In this embodiment, since the number of parts is small and the control is not complicated, mounting is easy.

101, 701, 801 assembled battery 101
102a, 102b, 702a, 702b Voltage detection terminal group 103, 703 First changeover switch group 104, 704 Second changeover switch group 105 Polarity change relay group 106, 803 Transformer 107 Switch element 108, 805 Rectifier diode 109 Control unit 601 Battery cell 602 Resistance 603 Switch 705 Polarity correction means 706 Capacity means 802 Changeover switch group 804 Switch T1 First terminal T2 Second terminal S1, S2, S3, S4, S5, S6 Control signal terminal

Claims (2)

Voltage detection terminal groups connected to both sides of each battery cell constituting the assembled battery;
A first changeover switch group for selectively connecting an odd-numbered voltage detection terminal group to the first terminal;
A second switch group for selectively connecting the even-numbered voltage detection terminal group to the second terminal;
A transformer in which an output terminal of the assembled battery or an output terminal of regenerative energy is connected to the primary coil side via a switch element;
A polarity switching relay group for controlling the connection polarity and connecting the first terminal and the second terminal to the secondary coil side of the transformer via a rectifier diode;
The first changeover switch group, the second changeover switch group, and the polarity changeover relay group are controlled so that a predetermined battery cell constituting the assembled battery or a predetermined battery block in which the battery cells are collected is transferred to the transformer. A control unit that performs equalization control on the predetermined battery cell or the predetermined battery block by controlling the switch element after being connected to the secondary coil of
A cell equalization control system comprising: A current sensor for measuring a current value at the position of the first terminal or the second terminal;
The control unit controls the first changeover switch group, the second changeover switch group, and the polarity changeover relay group to form a predetermined battery cell constituting the assembled battery or a predetermined battery cell. After connecting the battery block to the secondary coil of the transformer and before operating the switch element, if the current value measured by the current sensor exceeds a predetermined dark current value, the polarity switching Turn off all relays in the relay group.
The cell equalization control system according to claim 1.