JP5334566B2 - Voltage correction control method for power storage module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage correction control method of a power accumulation module which can surely correct voltages of power accumulation cells without making an excessively large current flow at the initial operation of a voltage correction circuit. <P>SOLUTION: In the voltage correction circuit 11, one end of an inductive element L1 is connected to a connecting point of the first power accumulation cell C1 and the second power accumulation cell C2, and a first switching element SW1 is interposed between the other end of the inductive element L1 and the positive-side terminal of the power accumulation cell C1. A second switching element SW2 is interposed between the other end of the inductive element L1 and the negative-side terminal of the power accumulation cell C2. A dead time at which both the switching elements SW1, SW2 are simultaneously turned off is set at the initial operation of the voltage correction circuit 11, and the dead time is controlled so as to be gradually shortened. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a voltage correction control method for a power storage module that equalizes cell voltages of a plurality of power storage cells connected in series to form a power storage module.

  Currently, power storage modules that are assembled into a battery by using a plurality of power storage cells such as electric double layer capacitors are used in power supply systems for electronic devices such as computers. Since the storage cell constituting the storage module has a low output voltage as a single unit, a voltage required for the power supply system is obtained by connecting the storage cells in series.

  By the way, when an electrical storage module is constituted by an electric double layer capacitor or the like, the leakage current differs in each cell, and the cell voltage may vary due to the influence of self-discharge. The variation in cell voltage in the power storage module is caused by manufacturing variation of each power storage cell, difference in use environment, secular change, and the like. In this power storage module, when each power storage cell is charged with the same current, there are power storage cells that are fully charged in a short time, while there are battery cells that are insufficiently charged. Therefore, in a power storage module in which a plurality of power storage cells are connected in series, it is desirable to use the cell voltages of each power storage cell equally from the viewpoint of effective use of power and extending the life.

  Various methods have been proposed as control for equalizing the cell voltages of power storage cells connected in series. As an example, a method (converter method) in which energy regeneration is performed using an inductive element from a high-voltage storage cell to a low-voltage storage cell has been put into practical use (see, for example, Patent Documents 1 and 2). This converter system is a useful method as a voltage correction method for a storage cell because it generates little heat during a voltage balancing operation and can evenly distribute voltages in a relatively short time.

FIG. 9 shows a schematic configuration of a voltage correction circuit for performing voltage correction by a converter method. As shown in FIG. 9, in the voltage correction circuit 21, one end of the inductive element L <b> 1 is connected to a connection point between two power storage cells C <b> 1 and C <b> 2 connected in series. Further, the first switching element SW1 is interposed between the other end of the inductive element L1 and the positive side terminal of the first storage cell C1, and the other end of the inductive element L1 and the second storage cell C2 are connected to each other. A second switching element SW2 is interposed between the negative terminal. Then, the switching elements SW1 and SW2 are complementarily turned on / off at a duty ratio of 50%, whereby charging / discharging is performed between the storage cells C1 and C2, and the cell voltage is controlled uniformly.
Japanese Patent No. 3328656 Japanese Patent No. 4140585

  However, in the conventional converter-type voltage correction method, when the voltage correction circuit 21 starts operating, if the cell voltage of each of the storage cells C1 and C2 is not properly controlled before the switching operation is stabilized. May cause excessive current to flow. In addition, the low-voltage storage cell that should be charged by the regenerative current is discharged, and the cell voltage may further decrease. In this case, there arises a problem that the balance operation time until the cell voltages are equalized becomes long. Further, in the conventional voltage correction circuit 21, it is necessary to use circuit components for a large current that can withstand an excessive current, resulting in an increase in the cost and mounting area of the components.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a voltage of a storage module that can appropriately perform voltage correction of a storage cell without flowing an excessive current during the initial operation of the voltage correction circuit. It is to provide a correction control method.

In order to solve the above problem, in the invention described in means 1, inductive elements having one end connected to a connection point of three or more power storage cells connected in series to form a power storage module, and the series connected A first switching element interposed between a positive terminal of three or more power storage cells and the other end of the inductive element; a negative terminal of the three or more power storage cells connected in series; and the inductive element And a second switching element interposed between the other end of the first and second terminals, and a voltage correction circuit connected so that the number of cells provided on the plus side differs from the number of cells provided on the minus side with respect to the connection point use, in particular controls to specific on-off the switching elements at a duty ratio corresponding to the cell number of the number of positive cells and the negative side A voltage correction control method for equalizing cell voltages of three or more power storage cells constituting the power storage module, wherein the first switching element and the first switching element and The gist of the voltage correction control method for a power storage module is to set a dead time in which both of the second switching elements are simultaneously turned off and to control the dead time to be gradually reduced.

Therefore, according to the invention described in Means 1, since the dead time during which both the first switching element and the second switching element are simultaneously turned off is set during the initial operation of the voltage correction circuit, The problem that an excessive current flows due to a long on-time is solved. Further, the dead time is gradually reduced with the passage of time, and finally turned on / off at a predetermined duty ratio. Accordingly, during the steady operation of the voltage correction circuit, the switching operation of each switching element is stably performed, and the cell voltage can be reliably corrected. In this way, it is not necessary to use large current components as in the conventional case, and the cost and space of the voltage correction circuit can be reduced . Also. By turning on / off each switching element with a duty ratio corresponding to the ratio between the number of plus-side cells and the number of minus-side cells, voltage correction of each storage cell can be performed accurately.

  The gist of the invention described in means 2 is that, in the means 1, the duty ratio for turning on each of the switching elements is controlled to gradually increase during the initial operation.

  Therefore, according to the invention described in the means 2, by controlling so that the duty ratio for turning on each switching element is gradually increased, the current flowing through the inductive element can be gradually increased, and the voltage correction is reliably performed. It can be carried out.

  According to a third aspect of the present invention, in the first aspect, in the initial operation, the cell voltages of the plurality of storage cells connected in series are detected and compared, and connected to the storage cell on the relatively high voltage side. For one switching element, the on-duty ratio is controlled to gradually increase, while for the other switching element connected to the relatively low voltage side storage cell, the on-duty of the one switching element is The gist of the present invention is to keep the off state until the ratio reaches a predetermined set value, and control to start on / off at the duty ratio after reaching the set value.

  Therefore, according to the invention described in the means 3, during the initial operation, the high-voltage side storage cell can be gradually discharged, and a large current can be prevented from flowing. At this time, since the switching element connected to the low-voltage side storage cell is kept off, discharge from the low-voltage side storage cell can be prevented. As a result, power consumption can be kept low, and the cell voltage of each storage cell can be corrected efficiently.

  The gist of the invention described in means 4 is that, in the means 1, in the initial operation, control is performed so as to gradually increase the operating frequency for turning on / off each of the switching elements.

  Therefore, according to the invention described in the means 4, it is possible to prevent a large current from flowing by gradually increasing the operating frequency for turning on / off each switching element during the initial operation. Further, in this case, since the on-duty ratio of each switching element gradually increases, the current flowing through the inductive element can be made constant, and voltage correction can be reliably performed.

  According to the invention described in means 5, the shortest operating time for operating the voltage correction circuit is set in advance in any one of means 1 to 4, and the voltage correction circuit is operated by turning on / off the switching elements. The gist is to control the switching elements to be turned off after the shortest operation time has elapsed.

  Therefore, according to the invention described in the means 5, since each switching element is turned off and the voltage correction circuit is stopped after the lapse of the shortest operation time, wasteful power consumption can be surely suppressed.

As described in detail above, according to the first to fifth aspects of the invention, the voltage correction of the storage cell can be reliably performed without flowing an excessive current.

[First Embodiment]

  DESCRIPTION OF EMBODIMENTS A first embodiment embodying the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a voltage correction circuit of a power storage module according to the present embodiment.

  As shown in FIG. 1, a power storage module 10 is configured by a first power storage cell C <b> 1 and a second power storage cell C <b> 2 connected in series. As each of the storage cells C1, C2, for example, an electric double layer capacitor is used. The voltage correction circuit 11 is interposed between the inductive element L1 having one end connected to the connection point between the storage cells C1 and C2, and the positive side terminal of the first storage cell C1 and the other end of the inductive element L1. On / off of the first switching element SW1, the second switching element SW2 interposed between the negative terminal of the second storage cell C2 and the other end of the inductive element L1, and the switching elements SW1 and SW2. And a controller 12 for controlling.

  In the voltage correction circuit 11, a first diode D1 is connected in parallel with the first switching element SW1, and a second diode D2 is connected in parallel with the second switching element SW2. Specifically, the first diode D1 has a cathode connected to the positive terminal of the first storage cell C1 and an anode connected to the other end of the inductive element L1. The second diode D2 has a cathode connected to the other end of the inductive element L1, and an anode connected to the negative terminal of the second storage cell C2.

  The first switching element SW1 and the second switching element SW2 are made of, for example, MOSFETs, and are turned on / off by a control signal input from the controller 12 to the gates of the elements SW1 and SW2.

  In the voltage correction circuit 11 of the present embodiment, the switching elements SW1 and SW2 are operated so as to be synchronous rectifiers, and control is performed so that the cell voltages of the storage cells C1 and C2 are equalized by flowing a rectification current from the inductive element L1. doing. For example, when the cell voltage of the first storage cell C1 is higher than the cell voltage of the second storage cell C2, the voltage correction circuit 11 is made to operate as a step-down converter by operating the switching elements SW1 and SW2. The rectified current (current in the arrow direction at the time of step-down in FIG. 1) flows so that the charge of the first power storage cell C1 is directed to the charge of the second power storage cell C2. Then, when the cell voltages of the storage cells C1 and C2 become the same voltage, the switching elements SW1 and SW2 are turned off to stop the operation of the voltage correction circuit 11.

  Further, when the cell voltage of the first power storage cell C1 is lower than the cell voltage of the second power storage cell C2, the voltage correction circuit 11 is made to operate as a boost converter by operating the switching elements SW1 and SW2. The rectified current (current in the arrow direction at the time of boosting in FIG. 1) flows so as to direct the charge of the second power storage cell C2 to the charge of the first power storage cell C1. Then, when the cell voltages of the storage cells C1 and C2 become the same voltage, the switching elements SW1 and SW2 are turned off to stop the operation of the voltage correction circuit 11.

  The controller 12 of the present embodiment detects the cell voltage by monitoring the potential between the terminals of each of the energy storage cells C1 and C2. When the detected cell voltages of the storage cells C1 and C2 are the same voltage, the controller 12 stops the operation of the switching elements SW1 and SW2 (cell voltage balancing operation), and the voltage difference between the cell voltages is When it occurs, the operation of the switching elements SW1 and SW2 is started.

  In the present embodiment, the voltage correction circuit 11 is controlled so that an excessive current does not flow through the circuit elements (switching elements SW1, SW2 and inductive element L1) by applying a soft start during the initial operation of the voltage correction circuit 11. doing.

  In the conventional voltage correction circuit 21 that turns on and off the switching elements SW1 and SW2 in a complementary manner, at the same time as the operation starts, the switching elements SW1 and SW2 can be turned on and off at a steady on-duty ratio of 50%. It ’s good. Specifically, as in the operation example shown in FIG. 2, the first switching element SW1 has an on-duty ratio smaller than 50%, and the second switching element SW2 has an on-duty ratio larger than 50%. . In this case, the second switching element SW2 is in the on state before the switching operation is started. For this reason, an excessive current flows through the inductive element L1, resulting in an operation that unbalances the cell voltage.

  On the other hand, in the present embodiment, as shown in FIG. 3, during the initial operation of the voltage correction circuit 11, the dead time Td during which both the first switching element SW1 and the second switching element SW2 are simultaneously turned off. And the dead time Td is controlled to be gradually reduced. That is, at the time of initial operation, control is performed so that the duty ratio for turning on each switching element SW1, SW2 is gradually increased, and finally, each switching element SW1, SW2 is turned on / off at a duty ratio of 50%. .

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the case of the present embodiment, the dead time during which both the first switching element SW1 and the second switching element SW2 are simultaneously turned off during the initial operation of the voltage correction circuit 11 is set. The problem that the ON time of the switching elements SW1 and SW2 becomes long and an excessive current flows to the inductive element L1 can be solved. In addition, the switching elements SW1 and SW2 are controlled so that the on-duty ratio is gradually increased by gradually reducing the dead time as time passes. Finally, the switching elements SW1 and SW2 are controlled at a duty ratio of 50%. Turned on / off. In this way, the current flowing through the inductive element L1 can be gradually increased, and the switching operation of the switching elements SW1 and SW2 can be stably performed to quickly perform the cell voltage balancing operation. In this way, it is not necessary to use large current components as in the conventional case, and the cost and space of the voltage correction circuit 11 can be reduced.

(2) In the voltage correction circuit 11 of the present embodiment, the cell voltages of the storage cells C1 and C2 are detected, and the operation of the switching elements SW1 and SW2 is started when a voltage difference between the cell voltages occurs. Thereafter, when the cell voltages of the storage cells C1 and C2 become equal, the operations of the switching elements SW1 and SW2 are stopped. In this way, since the voltage correction circuit 11 can be operated when a cell voltage balancing operation is required, wasteful power consumption can be suppressed.
[Second Embodiment]

  Next, a second embodiment embodying the present invention will be described. The configuration of the voltage correction circuit 11 of the present embodiment is the same as that of the first embodiment, and the voltage correction control method executed by the controller 12 is different from that of the first embodiment.

  That is, in the present embodiment, during the initial operation, the controller 12 detects and compares the cell voltages of the plurality of power storage cells C1 and C2 connected in series. Then, as shown in FIG. 4, the controller 12 controls the one of the switching elements connected to the relatively high voltage side storage cell so that the on-duty ratio gradually increases. On the other hand, for the other switching element connected to the storage cell on the relatively low voltage side, the on-duty ratio of one switching element reaches a predetermined set value (specifically, an on-duty ratio of 50%). Control is performed so that the off state is maintained until the set value is reached, and after the set value is reached, on / off is started at the duty ratio of 50%. In the control method according to the present embodiment, a dead time Td in which both the switching elements SW1 and SW2 are turned off is set in the initial operation, and the dead time Td is gradually reduced.

When the voltage correction circuit 11 is controlled as in the present embodiment, the storage cell on the high voltage side can be gradually discharged during the initial operation, and a large current can be prevented from flowing through the inductive element L1. it can. Further, in the initial operation, the switching elements connected to the low voltage side storage cells are kept off, and only the switching elements connected to the high voltage side storage cells are switched. Therefore, the low voltage side power storage cell is not discharged, and the low voltage side power storage cell can be reliably charged by the current flowing from the high voltage side power storage cell to the low voltage side power storage cell. As a result, power consumption can be kept low, and the cell voltages of the storage cells C1 and C2 can be corrected efficiently.
[Third Embodiment]

  Next, a third embodiment embodying the present invention will be described. The configuration of the voltage correction circuit 11 of the present embodiment is the same as that of the first embodiment, and the voltage correction control method executed by the controller 12 is different from that of the first embodiment.

  That is, in the present embodiment, in the initial operation, the controller 12 controls to gradually increase the operating frequency for turning on / off the switching elements SW1 and SW2 (see FIG. 5). Here, the ON times of the switching elements SW1 and SW2 are constant, and the dead time Td during which both the switching elements SW1 and SW2 are turned off is gradually reduced.

Even when the voltage correction circuit 11 is controlled as in the present embodiment, it is possible to prevent a large current from flowing through the inductive element L1. In this case, the on-duty ratios of the switching elements SW1 and SW2 are gradually increased, and the switching operation of the switching elements SW1 and SW2 is stably performed at the on-duty ratio of 50% during the steady operation. Therefore, the current flowing through the inductive element L1 can be made constant, and the cell voltage can be reliably corrected.
[Fourth Embodiment]

  Next, a fourth embodiment embodying the present invention will be described. FIG. 6 shows a voltage correction circuit 11A of the power storage module 10A in the present embodiment.

  As shown in FIG. 6, the power storage module 10A of the present embodiment includes four power storage cells C1, C2, C3, and C4 connected in series. The voltage correction circuit 11A includes three inductive elements L1, L2, and L3, six switching elements SW1, SW2, SW3, SW4, SW5, and SW6, and six diodes D1, D2, D3, D4, and D5. D6 and a controller 12 are provided.

  In the voltage correction circuit 11A, one end of the first inductive element L1 is connected to a connection point between the first storage cell C1 and the second storage cell C2, and the other end of the inductive element L1 and the first storage cell C1. The first switching element SW1 is interposed between the positive terminal and the first switching element SW1. The second switching element SW2 is interposed between the other end of the first inductive element L1 and the negative terminal of the second storage cell C2.

  Similarly, one end of the second inductive element L2 is connected to the connection point between the second power storage cell C2 and the third power storage cell C3, and the other end of the inductive element L2 and the positive side of the second power storage cell C2 A third switching element SW3 is interposed between the terminals. A fourth switching element SW4 is interposed between the other end of the second inductive element L2 and the negative terminal of the third storage cell C3.

  Furthermore, one end of the third inductive element L3 is connected to a connection point between the third power storage cell C3 and the fourth power storage cell C4, and the other end of the inductive element L3 and the positive side terminal of the third power storage cell C3. Is interposed a fifth switching element SW5. A sixth switching element SW6 is interposed between the other end of the third inductive element L3 and the negative terminal of the fourth storage cell C4. And each diode D1-D6 is connected in parallel with each switching element SW1-SW6.

Also in the voltage correction circuit 11A configured as described above, the switching elements SW1 to SW6 are operated so as to be a synchronous rectifier, and a rectification current is supplied to the inductive elements L1 to L3 so that the cell voltages of the storage cells C1 to C4 are equalized. It is controlled to do. Further, during the initial operation of the voltage correction circuit 11A, the circuit elements (switching elements SW1 to SW6 and inductive elements L1 to L3) are applied by performing a soft start by the same control method as in the first to third embodiments. ) Can be prevented from flowing an excessive current.
[Fifth Embodiment]

  Next, a fifth embodiment embodying the present invention will be described. FIG. 7 shows the voltage correction circuit 11B of the power storage module 11B in the present embodiment.

  As shown in FIG. 7, the power storage module 10B of the present embodiment is configured by three power storage cells C1, C2, and C3 connected in series. The voltage correction circuit 11B includes an inductive element L1, two switching elements SW1 and SW2, two diodes D1 and D2, and a controller 12. This voltage correction circuit 11B is based on the premise that no potential difference occurs between the first power storage cell C1 and the second power storage cell C2, and the third power storage for the cell voltages of the power storage cells C1 and C2. The balance operation is performed so that the cell voltage of the cell C3 becomes the same voltage.

  Specifically, in the voltage correction circuit 11B, one end of the inductive element L1 is connected to a connection point between the second power storage cell C2 and the third power storage cell C3, and the other end of the inductive element L1 and the first power storage cell. A first switching element SW1 is interposed between the positive terminal of the cell C1. The second switching element SW2 is interposed between the other end of the inductive element L1 and the negative terminal of the second storage cell C3. A first diode D1 is connected in parallel with the first switching element SW1, and a second diode D2 is connected in parallel with the second switching element SW2.

  Thus, in the present embodiment, the number of cells provided on the plus side (two) and the number of cells provided on the minus side (one) are based on the connection point to which one end of the inductive element L1 is connected. A voltage correction circuit 11B is connected so as to be different. In the voltage correction circuit 11B, the switching elements SW1 and SW2 are on / off controlled at a duty ratio corresponding to the ratio between the number of plus-side cells and the number of minus-side cells. Specifically, the switching elements SW1 and SW2 are operated so that the duty ratio at which the first switching element SW1 is turned on and the duty ratio at which the second switching element SW2 is turned on are 1: 2. Thus, a rectification current is supplied from the inductive element L1, and the total voltage of the storage cells C1 and C2 and the cell voltage of C3 are controlled to 2: 1.

Also in the present embodiment, during the initial operation of the voltage correction circuit 11B, circuit elements (switching elements SW1, SW2, and so on) are subjected to soft start by the same control method as in the first to third embodiments described above. It is possible to prevent an excessive current from flowing through the inductive element L1).
[Sixth Embodiment]

  Next, a sixth embodiment embodying the present invention will be described. FIG. 8 shows the voltage correction circuit 11C of the power storage module 10C in the present embodiment.

  As shown in FIG. 8, the power storage module 10C of the present embodiment is configured by four power storage cells C1, C2, C3, and C4 connected in series. The voltage correction circuit 11C includes two inductive elements L1, L2, four switching elements SW1, SW2, SW3, SW4, four diodes D1, D2, D3, D4, and a controller 12.

  In the voltage correction circuit 11C, one end of the first inductive element L1 is connected to a connection point between the second power storage cell C2 and the third power storage cell C3, and the other end of the inductive element L1 and the first power storage cell C1. The first switching element SW1 is interposed between the positive terminal and the first switching element SW1. The second switching element SW2 is interposed between the other end of the first inductive element L1 and the negative terminal of the third storage cell C3.

  Furthermore, one end of the second inductive element L2 is connected to a connection point between the third power storage cell C3 and the fourth power storage cell C4, and the other end of the inductive element L2 and the positive side terminal of the second power storage cell C2 The third switching element SW3 is interposed between the first switching element SW3 and the third switching element SW3. A fourth switching element SW4 is interposed between the other end of the second inductive element L2 and the negative terminal of the fourth storage cell C4. And each diode D1-D4 is connected in parallel with each switching element SW1-SW4.

  In the voltage correction circuit 11C of the present embodiment, the switching elements SW1, SW2 are set so that the duty ratio at which the first switching element SW1 is turned on and the duty ratio at which the second switching element SW2 is turned on are 1: 2. To work. Further, the switching elements SW3 and SW4 are operated so that the duty ratio at which the third switching element SW3 is turned on and the duty ratio at which the fourth switching element SW4 is turned on are 1: 2. Thereby, the rectified current is supplied to the inductive elements L1 and L2 to control the cell voltages of the storage cells C1 to C4 to be equal.

  Also in the present embodiment, during the initial operation of the voltage correction circuit 11C, the circuit elements (switching elements SW1 to SW4 and switching elements SW1 to SW4 and the like) are applied by performing a soft start by the same control method as in the first to third embodiments. It is possible to prevent an excessive current from flowing through the inductive elements L1, L2).

  In addition, you may change each embodiment of this invention as follows.

  In each of the above embodiments, the voltage correction circuits 11, 11A, 11B, and 11C detect the cell voltages of the storage cells C1 to C4 during circuit operation, and perform the circuit operation at the timing when the cell voltages become the same voltage. Although it stopped, it is not limited to this. Specifically, a minimum operation time for operating the voltage correction circuits 11, 11A, 11B, and 11C is set in advance, and the switching elements SW1 to SW1 of the voltage correction circuits 11, 11A, 11B, and 11C are set after the minimum operation time has elapsed. Control may be performed so that the circuit operation is stopped by turning off SW6. In this way, by stopping the circuit operation after the elapse of the shortest operation time, wasteful power consumption can be reliably suppressed.

  In each of the above embodiments, the number of power storage cells constituting the power storage modules 10, 10A, 10B, and 10C is two, three, and four, but is not limited to this number of cells and is five. The above power storage cells may be embodied in a power storage module connected in series.

  In each of the above embodiments, the electric double layer capacitors are used as the storage cells C1 to C4. However, in addition to this, a storage cell such as a lithium ion capacitor may be used.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows the voltage correction circuit of 1st Embodiment which actualized this invention. The timing chart which shows the conventional voltage correction control method. The timing chart which shows the voltage correction control method of 1st Embodiment. The timing chart which shows the voltage correction control method of 2nd Embodiment. The timing chart which shows the voltage correction control method of 3rd Embodiment. The schematic block diagram which shows the voltage correction circuit of 4th Embodiment. The schematic block diagram which shows the voltage correction circuit of 5th Embodiment. The schematic block diagram which shows the voltage correction circuit of 6th Embodiment. The schematic block diagram which shows the conventional voltage correction circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,10A, 10B, 10C ... Power storage module 11, 11A, 11B, 11C ... Voltage correction circuit C1-C4 ... Power storage cell L1-L3 ... Inductive element SW1-SW6 ... Switching element Td ... Dead time

Claims (5)

An inductive element having one end connected to a connection point of three or more power storage cells connected in series to form a power storage module, a positive terminal of the three or more power storage cells connected in series, and other inductive elements A first switching element interposed between the two ends, a second switching element interposed between the negative side terminals of the three or more storage cells connected in series and the other end of the inductive element; And using a voltage correction circuit connected so that the number of cells provided on the plus side differs from the number of cells provided on the minus side with reference to the connection point, the number of cells on the plus side and the cell on the minus side by controlling so as to turn on and off the switching elements at a duty ratio corresponding to the ratio of the number, three or more power storage cell constituting the battery module A The cell voltage is the voltage correction control method for equalizing,
In an initial operation when the voltage correction circuit starts operation, a dead time is set in which both the first switching element and the second switching element are simultaneously turned off, and the dead time is gradually reduced. A voltage correction control method for a power storage module, comprising:   2. The voltage correction control method for a power storage module according to claim 1, wherein a duty ratio for turning on each of the switching elements is controlled to gradually increase during the initial operation. During the initial operation, the cell voltages of the three or more storage cells connected in series are detected and compared, and one of the switching elements connected to the storage cell on the relatively high voltage side is turned on duty While the ratio is controlled to gradually increase, for the other switching element connected to the relatively low voltage side storage cell, the on-duty ratio of the one switching element reaches a predetermined set value. 2. The voltage correction control method for a power storage module according to claim 1, wherein control is performed such that the off state is maintained until the set value is reached, and on / off is started at the duty ratio after reaching the set value.   2. The voltage correction control method for a power storage module according to claim 1, wherein during the initial operation, control is performed so as to gradually increase an operating frequency for turning on / off each of the switching elements.   A minimum operation time for operating the voltage correction circuit is set in advance, the switching elements are turned on / off to operate the voltage correction circuit, and the switching elements are turned off after the shortest operation time has elapsed. The voltage correction control method for a power storage module according to any one of claims 1 to 4, wherein

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