JP2018191406A - Equalization device and power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equalization device and a power storage system that can adjust a state of charge of a power storage cell even in a charged state or a discharged state.SOLUTION: An equalization device (1) includes: a voltage detection circuit (20); a discharge circuit (10); and an equalization control unit (30). The voltage detection circuit (20) detects voltages of a plurality of storage cells (61). The discharge circuit (10) discharges the storage cells (61). The equalization control unit (30) calculates a discharge time in a case of discharging capacity required for discharge in the storage cell (61) with a reference voltage and a reference duty ratio in the discharge circuit (10) and sets a duty ratio based on the voltages detected by the voltage detection circuit (20).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an equalizing device and a power storage system that adjust a state of charge (SOC) of a power storage cell.

  The equalization apparatus described in Patent Literature 1 includes a discharge circuit that discharges the storage cell and a control circuit. The control circuit determines the discharge time or the end of discharge for the storage cell to be discharged based on the charge state evaluation value before the start of discharge, the change rate of the evaluation value during discharge, and the change rate of the evaluation value during non-discharge. Means for deriving a value; The control circuit has means for ending the discharge when the discharge time elapses after the discharge circuit starts discharging the discharge target cell or when the charge state evaluation value reaches the discharge end value. .

International Publication No. 2009/113530

  The equalization apparatus described in Patent Document 1 equalizes power storage cells when the power storage cells are not being charged or discharged. In this case, the execution of the equalization process that suppresses the variation among the storage cells mounted on the vehicle is limited to the case where the vehicle is parked and the power is turned off, and the storage cell is not charged from the charging device. There was a problem that it was.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an equalization device and a power storage system that can adjust the charge state of a power storage cell even in a charged state or a discharged state. Is to provide.

  An equalization device according to an aspect of the present invention is based on a voltage detection circuit that detects voltages of a plurality of power storage cells included in a power storage unit, a discharge circuit that discharges the power storage cells, and a voltage detected by the voltage detection circuit. And an equalization control unit that controls an operating state of the discharge circuit. The equalization control unit discharges a capacity that needs to be discharged in the storage cell at a reference voltage and a reference duty ratio in the discharge circuit. In this case, the discharge time is calculated, and the duty ratio is set based on the voltage detected by the voltage detection circuit.

  According to the present invention, it is possible to adjust the state of charge of the storage cell even when it is in a charged state or a discharged state.

It is a block diagram which shows the structure of the electrical storage system which concerns on embodiment. It is a schematic diagram for demonstrating the dispersion | variation in the voltage of an electrical storage cell. It is a flowchart which shows the procedure of the equalization process by an equalization control part. It is a graph which shows the voltage of the electrical storage cell at the time of charge.

  Hereinafter, the present invention will be described based on preferred embodiments with reference to FIGS. The same or equivalent components and members shown in the drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. Also, in the drawings, some of the members that are not important for describing the embodiment are omitted.

(Embodiment)
FIG. 1 is a block diagram illustrating a configuration of a power storage system 100 according to the embodiment. The power storage system 100 includes the power storage unit 6 and the equalization device 1, equalizes the voltages of a plurality of power storage cells 61 included in the power storage unit 6, and supplies power from the power storage unit 6 to various loads 7 mounted on the vehicle. To do. The load 7 is, for example, an in-vehicle device such as a traveling motor, a headlight, a power window, an electronic control device, and the like, and is connected to the power storage unit 6 by turning on and off the switch 71.

  In the power storage system 100, the power storage unit 6 is connected to the load 7 and discharged, and the power storage unit 6 is charged by receiving power from an external charging device or the like. The power storage cell 61 included in the power storage unit 6 is charged and discharged repeatedly, so that the state of charge varies among the power storage cells 61. The state of charge (SOC) here means the ratio of the charge amount to the full charge capacity. If there is a variation in the state of charge of the plurality of power storage units 6 connected in series, overcharge or overdischarge may occur, so it is necessary to eliminate the variation in the state of charge using the equalization device 1. Specifically, since there is a correlation between the state of charge of power storage unit 6 and the voltage, equalization apparatus 1 eliminates the voltage variation of power storage unit 6 by discharging. In the present embodiment, a configuration in which the state of charge of the power storage unit 6 is adjusted using the voltage of the power storage unit 6 as an example will be described as an example, but the voltage need not necessarily be the target. As a method for adjusting the state of charge of the power storage unit 6, the target power storage unit 6 can be discharged so that the amount of charge and the state of charge of the battery are uniform.

  The power storage unit 6 is formed by connecting a plurality of power storage cells 61, for example, lithium ion battery cells in series. In addition to the lithium ion battery cell, the storage cell 61 may be a nickel hydrogen battery cell, a lead battery cell, an electric double layer capacitor cell, a lithium ion capacitor cell, or the like.

  The equalization apparatus 1 includes a plurality of discharge circuits 10, a voltage detection circuit 20, and an equalization control unit 30. Although the discharge circuit 10 includes the resistor 11 and the switch 12 and is provided for each storage cell 61, the plurality of adjacent storage cells 61 may be provided as a block, and may be provided for each block. The resistor 11 is connected between both terminals of the power storage cell 61, and the current from the power storage cell 61 flows, so that the charge of the power storage cell 61 is consumed and the voltage of the power storage cell 61 is lowered.

  FIG. 2 is a schematic diagram for explaining variations in the voltage of the storage cell 61. The variation in the voltage of the storage cell 61 is suppressed by the discharge by the discharge circuit 10. The equalization apparatus 1 functions to match the variation of the storage cells 61 to the minimum voltage among the voltages of the storage cells 61.

  The switch 12 is connected to the resistor 11 in series, and is opened and closed by an on / off signal from the equalization control unit 30. When the switch 12 is in the closed state, a current flows through the resistor 11, and the discharge amount can be adjusted by setting and changing the duty ratio in the closed state. Note that the switch 12 is periodically switched between open and closed states by a signal from the equalization control unit 30. The duty ratio is a ratio of the time of the closed state to one cycle of the open state and the closed state in the switch 12.

  The voltage detection circuit 20 is connected to both terminals by connection lines for each storage cell 61 and measures the voltage between the terminals. The voltage detection circuit 20 is configured by, for example, an ASIC (Application Specific Integrated Circuit), and outputs the detected voltage of the storage cell 61 to the equalization control unit 30.

  The equalization control unit 30 is configured by a microcomputer, functions by executing a program stored in a built-in storage circuit, and performs processing by software while storing the calculated numerical value in the storage circuit. The equalization control unit 30 acquires the voltage of each storage cell 61 from the voltage detection circuit 20 and calculates the capacity that needs to be discharged to suppress voltage variation based on the SOC-OCV curve of the storage cell 61.

  The equalization control unit 30 calculates the discharge time when the storage cell 61 needs to be discharged at the reference voltage and the reference duty ratio. The equalization control unit 30 sets an initial duty ratio based on the ratio of the voltage detected by the voltage detection circuit 20 to the reference voltage. At this time, the storage cell 61 is not being charged or discharged due to load connection, and the voltage detection circuit 20 detects a state in which no current flows through the storage cell 61, that is, a voltage when the storage cell 61 is opened. . The equalization control unit 30 controls the switch 12 of the discharge circuit 10 to be closed according to the set initial duty ratio.

  The equalization control unit 30 estimates the voltage when the storage cell 61 is opened based on the voltage detected by the voltage detection circuit 20 when the storage cell 61 is charged and the voltage increases. The equalization control unit 30 varies the duty ratio based on the ratio of the estimated voltage to the reference voltage. In this case, the equalization control unit 30 controls the duty ratio to be lowered because the voltage of the storage cell 61 is increased by charging. For example, the voltage detection circuit 20 calculates a voltage change amount with respect to a capacity change amount obtained by integrating the current from the SOC-OCV curve, and uses the calculated voltage change amount as the voltage of the storage cell 61 detected by the voltage detection circuit 20. By adding, the voltage when the storage cell 61 is opened is estimated.

  In addition, the equalization control unit 30 determines the voltage when the storage cell 61 is opened based on the voltage detected by the voltage detection circuit 20 when the storage cell 61 is connected to a load and becomes in a discharge state and the voltage is lowered. Is estimated. The equalization control unit 30 varies the duty ratio based on the ratio of the estimated voltage to the reference voltage. In this case, the equalization control unit 30 controls to increase the duty ratio because the voltage of the storage cell 61 decreases due to discharge.

  Next, the operation | movement in the equalization process by the equalization apparatus 1 is demonstrated based on a flowchart etc. FIG. 3 is a flowchart showing the procedure of the equalization process by the equalization control unit 30, and FIG. 4 is a graph showing the voltage of the storage cell 61 during charging. As described above, the equalization control unit 30 sets the duty ratio for closing the switch 12 in the discharge circuit 10, and even when the storage cell 61 is in a charged state or a discharged state (when connected to a load), the storage cell A control process for estimating the voltage 61 and varying the duty ratio is executed. Hereinafter, the procedure of the equalization process will be described based on FIG. 3 with reference to FIG. 4 in the case where the vehicle is parked and turned off, and then the storage cell 61 is charged.

At time T1 (see FIG. 4) before the start of charging, the equalization control unit 30 acquires the voltage of each storage cell 61 from the voltage detection circuit 20 (S1), and obtains the minimum voltage value of each storage cell 61 ( S2). The equalization control unit 30 calculates the capacity that needs to be discharged in order to align the voltage of each storage cell 61 with the minimum voltage obtained in S <b> 2 based on the SOC-OCV curve of the storage cell 61. The equalization control unit 30 calculates a discharge time when the capacity of the storage cell 61 that needs to be discharged is discharged at the reference voltage and the reference duty ratio (S3). The equalization control unit 30 calculates the discharge time Td by the following equation, where Q is the capacity that needs to be discharged, Vs is the reference voltage, Ds (%) is the reference duty ratio, and R is the resistance value of the resistor 11.
Td = Q × (R / Vs) × (Ds / 100)

  The equalization control unit 30 sets an initial duty ratio based on the ratio of the voltage detected by the voltage detection circuit 20 to the reference voltage (S4). At this time, the storage cell 61 is not being charged or discharged by load connection, and the voltage detection circuit 20 detects a state in which no current flows through the storage cell 61, that is, a voltage when the storage cell 61 is opened. And For example, assuming that the reference voltage Vs is 3.5 V, the reference duty ratio Ds is 50%, and the voltage of the storage cell 61 is 3.6 V, the equalization control unit 30 sets the initial duty ratio D to 3.5. /3.6×50=48.6(%). The equalization control unit 30 controls the open / close state of the switch 12 of the discharge circuit 10 according to the set initial duty ratio, and starts discharging the storage cell 61 (S5).

  When the actual voltage of the storage cell 61 is higher than the reference voltage, the equalization control unit 30 decreases the duty ratio because the current flowing in the discharge circuit 10 increases. Further, when the actual voltage of the storage cell 61 is lower than the reference voltage, the equalization control unit 30 increases the duty ratio because the current flowing in the discharge circuit 10 decreases. Since the equalization control unit 30 can perform the equalization process by controlling the opening and closing of the discharge circuit 10 using the duty ratio, regardless of whether the voltage of the storage cell 61 is higher or lower than the reference voltage, the discharge circuit can be simplified. And can be configured at low cost.

  The equalization control unit 30 estimates the voltage when the storage cell 61 is opened based on the voltage detected by the voltage detection circuit 20 (S6). The equalization control unit 30 can estimate the voltage when the storage cell 61 is opened by a method such as current integration as described above. Prior to the start of charging, the load 7 is not connected to the storage cell 61, or even if it is connected, a minute current is passed, and the voltage of the storage cell 61 is considered to be substantially constant. When the storage cell 61 is charged at time T2 (see FIG. 4), the voltage increases.

  The equalization control unit 30 varies the duty ratio based on the estimated voltage ratio with respect to the reference voltage (S7). When the storage cell 61 is in a charged state, the equalization control unit 30 controls the duty ratio to decrease because the voltage of the storage cell 61 increases due to charging. The equalization control unit 30 calculates and varies the duty ratio based on the estimated voltage in the same manner as the calculation of the initial duty ratio. For example, when the estimated voltage is 3.8 V, the equalization control unit 30 changes the duty ratio to 3.5 / 3.8 × 50 = 46.1 (%). Moreover, the equalization control part 30 is 3.5 / 4.2 * 50 = 41.7 (%), when the estimated voltage in the time T3 (refer FIG. 4) when charge was completed was 4.2V, for example. Change the duty ratio to.

  The equalization control unit 30 determines whether or not the discharge time Td has elapsed (S8), and if not (S8: NO), returns to S6 to estimate the voltage of the storage cell 61 and store The discharge by the discharge circuit 10 of the cell 61 is continued. If the equalization control unit 30 determines that the discharge time Td has elapsed at time T4 (see FIG. 4) at which time Td has elapsed from time T1 (S8: YES), it controls the switch 12 of the discharge circuit 10 to be in the open state. Then, the discharge is stopped and the equalization process is finished (S9).

  The equalization control unit 30 varies the capacity to be discharged by varying the duty ratio of the discharge circuit 10 even when the state of charge occurs during the equalization process of the energy storage cell 61 and the voltage of the energy storage cell 61 changes. Then, the equalization process can be executed with the discharge time Td. The equalization control unit 30 performs control to lower the duty ratio when a charged state occurs during the equalization process of the storage cells 61.

  In addition, the equalization control unit 30 can similarly perform the equalization process with the discharge time Td by varying the duty ratio when the storage cell 61 is connected to the load to be in a discharge state and the voltage is lowered. . The equalization control unit 30 estimates the voltage when the storage cell 61 is opened based on the voltage detected by the voltage detection circuit 20. The equalization control unit 30 varies the duty ratio based on the ratio of the estimated voltage to the reference voltage. In this case, the equalization control unit 30 controls to increase the duty ratio because the voltage of the storage cell 61 decreases due to discharge.

  The equalization control unit 30 sets the reference voltage Vs to a value that the power storage cell 61 can typically take by using the power storage unit 6 in the vehicle, so that the discharge circuit in the equalization process has a value close to the initial duty ratio. The opening and closing of the ten switches 12 can be controlled. Further, the reference duty ratio may be determined to be about 50%, which is a middle level in consideration of the charged state and the discharged state of the storage cell 61, but is not limited thereto. For example, in order to shorten the discharge time Td and finish the equalization process relatively quickly, the reference duty ratio Ds may be increased. Further, the equalization control unit 30 may change the reference duty ratio Ds according to the temperature of the power storage unit 6. In this case, when the temperature of the power storage unit 6 is low, the reference duty ratio Ds is increased. When the temperature of the section 6 is high, the reference duty ratio Ds is set low.

  In the above, it demonstrated based on embodiment of this invention. Those skilled in the art will understand that these embodiments are examples, and that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes are also within the scope of the claims of the present invention. It is where it is done. Accordingly, the description and drawings herein are to be regarded as illustrative rather than restrictive.

In addition, embodiment and the modification may be specified by the following items.
[Item 1]
A voltage detection circuit (20) for detecting voltages of a plurality of power storage cells (61) included in the power storage unit (6), a discharge circuit (10) for discharging the power storage cells (61), and the voltage detection circuit (20 In an equalization apparatus (1), comprising an equalization control unit (30) for controlling the operating state of the discharge circuit (10) based on the voltage detected by
The equalization control unit (30) calculates a discharge time in the case where a discharge capacity in the storage cell (61) is discharged at a reference voltage and a reference duty ratio in the discharge circuit (10), and the voltage An equalizing device (1) characterized in that a duty ratio is set based on a voltage detected by a detection circuit (20). Thereby, the equalization apparatus (1) can equalize the voltage of the electrical storage cell (61) and adjust the state of charge even when the electrical storage cell (61) is in a charged state or a discharged state.
[Item 2]
The equalization control unit (30) estimates the voltage of the power storage cell (61) when the power storage cell (61) is in a charged state or a discharged state, and determines the duty ratio based on the estimated voltage. 2. The equalizing device (1) according to item 1, wherein the equalizing device (1) is variable. Thereby, the equalization apparatus (1) can equalize the voltage of an electrical storage cell (61) by the calculated discharge time by the control using a duty ratio, and can adjust a charge condition.
[Item 3]
The equalization apparatus (1) according to item 2, wherein the equalization control unit (30) reduces the duty ratio when the power storage cell (61) is in a charged state. Thereby, the equalization apparatus (1) can equalize the voltage of the electrical storage cell (61) and adjust the state of charge by reducing the duty ratio even when the electrical storage cell (61) is in the charged state. .
[Item 4]
The equalization apparatus (1) according to item 2, wherein the equalization control unit (30) increases the duty ratio when the power storage cell (61) is in a discharged state. Thereby, the equalization apparatus (1) can equalize the voltage of an electrical storage cell (61), and can adjust a charge condition, even when the electrical storage cell (61) is in a discharge state by raising a duty ratio. .
[Item 5]
A power storage unit (6);
The equalization apparatus (1) according to any one of items 1 to 4,
A power storage system (100) comprising: Thereby, the electrical storage system (100) can equalize the voltage of the electrical storage cell (61) and adjust the electrical charge state even when the electrical storage cell (61) is in a charged state or a discharged state.

1 equalization device, 10 discharge circuit, 20 voltage detection circuit,
30 equalization control unit, 6 power storage unit, 61 power storage cell,
100 Power storage system.

Claims (5)

A voltage detection circuit that detects voltages of a plurality of power storage cells included in the power storage unit, a discharge circuit that discharges the power storage cells, and an operation state of the discharge circuit is controlled based on the voltage detected by the voltage detection circuit An equalization control unit comprising:
The equalization control unit calculates a discharge time when discharging a capacity that needs to be discharged in the storage cell at a reference voltage and a reference duty ratio in the discharge circuit, and based on the voltage detected by the voltage detection circuit An equalizing device characterized by setting a duty ratio.   The said equalization control part estimates the voltage of the said electrical storage cell when the said electrical storage cell is a charge state or a discharge state, The variable duty ratio is varied based on the estimated voltage. 1. The equalizing apparatus according to 1.   The equalization apparatus according to claim 2, wherein the equalization control unit reduces the duty ratio when the power storage cell is in a charged state.   The equalization apparatus according to claim 2, wherein the equalization control unit increases the duty ratio when the power storage cell is in a discharged state. A power storage unit;
The equalizing device according to any one of claims 1 to 4,
A power storage system comprising:

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