JP7073669B2 - Power storage system - Google Patents

Description

The present invention relates to a power storage system.

Conventionally, a power storage system capable of switching a plurality of power storage modules in series or in parallel is known.

For example, the battery system for industrial machinery disclosed in Patent Document 1 is intended to enable quick charging under high voltage and to enable the use of low voltage components. This system selectively switches the charge / discharge switching means for selectively switching the connection state between the battery unit and the charging input unit or the power load, and the electrical connection between the plurality of battery units in parallel or in series. It is provided with parallel / serial switching means for switching to.

In the discharge control flow of this system, a plurality of battery units are discharged from a plurality of battery units to a power load in a state where a plurality of battery units are connected in parallel. Further, in the charge control flow, in a state where a plurality of battery units are connected in series, the plurality of battery units are charged from the quick charger via the charge input unit. After charging is completed, if the voltage difference between the plurality of battery units is equal to or greater than the threshold value, a balance process between the battery units is performed to eliminate the voltage difference.

Japanese Patent No. 5611400

In the balance processing between battery units of Patent Document 1, since a current flows between two battery units through a path provided with resistance, a loss due to resistance occurs. In addition, it takes time to balance because the current is suppressed by the resistance. In the system of Patent Document 1, after the completion of the balance processing between the battery units, the system is in a standby state, and it is presumed that the time required for balancing does not matter.

Hereinafter, in the present specification, "storage module" is used as a term of a superordinate concept including the battery unit of Patent Document 1. When the technology of Patent Document 1 is applied to external charging of an electric vehicle or a plug-in hybrid vehicle, after charging in series is completed, a plurality of power storage modules are switched to parallel connection and discharged to the main motor as a load to run. Is assumed. If, for example, the relay is operated to switch the connection while the potential difference between the plurality of power storage modules is large, the life of the relay may be shortened due to the arc of the contacts or the short-circuit current.

The present invention has been created in view of the above-mentioned problems, and an object of the present invention is to avoid the occurrence of loss and shortening of contact life when switching from series to parallel of a plurality of power storage modules. The purpose is to provide a power storage system that balances the voltage of the module.

The power storage system of the present invention includes a plurality of power storage modules (BT1, BT2, BT3), a series-parallel switch (RY1-RY10), a power converter (201, 202, 50, 61, 62), and a control circuit (. 45) and. Each of the plurality of storage modules includes one or more storage cells. The series-parallel switch can switch the connection state of a plurality of power storage modules in series or in parallel. The power converter transfers power between any two or more power storage modules among a plurality of power storage modules. The control circuit controls the series-parallel switch and the power converter.

Prior to the parallel switching of a plurality of power storage modules, the control circuit performs a "voltage balancing process" in which the power converter is operated so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the series-parallel switching. Switch the vessel.

In the present invention, the voltage of the power storage module is balanced by recirculating energy between arbitrary power storage modules to charge and discharge the energy through a power converter. As a result, the inrush current can be suppressed when the contacts of the series-parallel switch such as a relay are connected, so that the reliability and the life of the series-parallel switch can be improved. In addition, the loss can be reduced as compared with the conventional technique in which a current is passed between the storage modules via a resistor.

In one aspect of the invention, the power converter has one or more input / output ends connected to an object other than the power storage module, in addition to the plurality of input / output ends connected to the plurality of power storage modules. The power converter has a plurality of DC / DC converters (301, 302) having an input / output port connected to each of the plurality of power storage modules at one end and capable of bidirectionally energizing the power between the input / output ports. include.

For example, in a power storage system mounted on an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle, the main battery corresponds to a power storage module. Electric vehicles include DC / DC converters used as internal circuits of chargers that charge the main battery with AC power supplied from AC power, DC / DC converters for auxiliary batteries, and inverters that drive main motors and air conditioners. Etc. are already installed. By utilizing these power converters for voltage balancing processing, it is possible to reduce the number of devices and improve the utilization efficiency of the devices.

The block diagram of the power storage system of the 1st and 2nd embodiments. The block diagram which shows the battery voltage monitoring configuration of a power storage module. The figure which shows the relationship between a charge infrastructure and a load drive voltage. The figure explaining the problem at the time of switching from series to parallel. The figure which shows the characteristic example of the relay contact life with respect to the opening / closing current. The figure (1) explaining the principle of voltage balancing processing. The figure (2) explaining the principle of voltage balancing processing. Flowchart of parallel connection processing. Flowchart of parallel release processing. FIG. 6 is a configuration diagram of an in-vehicle charger in which a plurality of DC / DC converters, which are the power converters of the first embodiment, are arranged in parallel. The block diagram of the in-vehicle charger using the multi-port DC / DC converter which is the power converter of 2nd Embodiment. The block diagram of the power storage system of 3rd Embodiment. The flowchart of the series-parallel selection process at the time of the external charge by the 3rd Embodiment. Continuation of the flowchart of FIG. The block diagram of the power storage system of 4th Embodiment. The flowchart of the voltage balancing process during external charging according to 4th Embodiment. The block diagram of the power storage system of 5th Embodiment. The block diagram of the DC / DC converter for an auxiliary battery which is a power converter of 5th Embodiment. The block diagram of the power storage system of the 6th Embodiment. The block diagram of the inverter for an air conditioner compressor which is a power converter of 6th Embodiment. The block diagram of the power storage system of 7th Embodiment.

Hereinafter, embodiments of a power storage system including a plurality of power storage modules will be described with reference to the drawings. Substantially the same configurations in a plurality of embodiments are designated by the same reference numerals and description thereof will be omitted. The first to seventh embodiments are collectively referred to as "the present embodiment". Here, each power storage module includes one or more power storage cells. The power storage module in the present embodiment is a battery module including one or more battery cells. In particular, in the present embodiment, an in-vehicle power storage system including a main battery module that is a power source of a vehicle in an electric vehicle or a plug-in hybrid vehicle is assumed. In another embodiment, a capacitor or the like may be used as the power storage module.

The plurality of power storage modules are configured so that the connection state can be switched between series and parallel by the series-parallel switch. The series-parallel switch is typically a relay composed of a mechanical relay or a semiconductor switch. Further, the power storage system of the present embodiment includes a power converter that transfers power between any two or more power storage modules among a plurality of power storage modules, and a control circuit that controls the series-parallel switch and the power converter. Be prepared. Each of the following embodiments differs in the configuration of the power converter and the configuration related to charging / discharging of the power storage module.

(1st and 2nd embodiments)
First, with reference to FIG. 1, the configuration of the power storage system 401 common to the first and second embodiments will be described. The power storage system 401 includes two batteries BT1 and BT2 as "plurality of power storage modules", a relay RY1-RY7 as a "serial-parallel switch", an in-vehicle charger 20 as a "power converter", and a control circuit 45. To prepare for. The batteries BT1 and BT2 are chargeable / dischargeable, for example, 400 V high voltage battery modules such as lithium ion batteries. Hereinafter, the "battery module" is abbreviated as "battery". Further, in the fifth embodiment described later, a low voltage (for example, 12V) "auxiliary battery" is referred to, but any other "battery" is used to mean a high voltage battery.

In the power storage system 401, the batteries BT1 and BT2 are provided between the external charging connection portions 11 and 12 and the load 80. As the load 80, a device generally used in an electric vehicle or a plug-in hybrid vehicle is exemplified. The relays RY1 and RY3 open and close the paths between the positive electrodes of the batteries BT1 and BT2 and between the negative electrodes, respectively. The relay RY2 opens and closes the path between the negative electrode of the battery BT1 and the positive electrode of the battery BT2. The relays RY4 and RY5 open and close the path between the positive and negative electrodes of the battery BT2 and the load 80, respectively. The relay RY6 opens and closes the path between the positive electrode of the battery BT1 and the positive electrode terminal 11 of the external charging connection portion. The relay RY7 opens and closes the path between the negative electrode of the battery BT2 and the negative electrode terminal 12 of the external charging connection portion.

External chargers described in the third and fourth embodiments are connected to the external charging connection units 11 and 12. When an external charger compatible with 800V is used for external charging via the external charging connection units 11 and 12, series charging is performed with the batteries BT1 and BT2 connected in two series. On the other hand, when an external charger compatible with 400V is used, parallel charging is performed with the batteries BT1 and BT2 connected in two parallels.

In the following description of the relay opening / closing pattern, when "a certain relay is on" in RY1-RY7, it is assumed that "the other relays are off". During two-series charging, the relays RY2, RY6, and RY7 are turned on. During the two parallel charging, the relays RY1, RY3, RY6, and RY7 are turned on. The relays RY1, RY3, RY4, and RY5 are turned on during the two-parallel discharge in which the power of 400 V is supplied from the batteries BT1 and BT2 to the load 80. The opening and closing of these relays is operated by the command of the control circuit 45.

As a general function, the in-vehicle charger 20 converts AC power supplied from an external commercial power source via AC power supply connection portions 16 and 17 into DC power and charges the batteries BT1 and BT2. In the power storage system 401 of the first and second embodiments, the positive electrode and the negative electrode of the battery BT1 are connected to the input / output port P1 of the vehicle-mounted charger 20, and the positive electrode and the negative electrode of the battery BT2 are connected to the input / output port P2. To. The path between the batteries BT1 and BT2 and the input / output ports P1 and P2 of the vehicle-mounted charger 20 is called a balanced current path. As shown by the broken line G, the negative side connection destination of the balanced current path may be the load 80 side, and the relay may be shared. Further, the relay 28 that opens and closes the path between the batteries BT1 and BT2 and the in-vehicle charger 20 may not be provided.

Here, the input end of the vehicle-mounted charger 20 connected to the AC power supply connection units 16 and 17 is "connected to a target other than the power storage module, which is different from the plurality of input / output ends connected to the plurality of power storage modules. Corresponds to one or more input / output ends. Further, the operation of the vehicle-mounted charger 20 is controlled by the control circuit 45. The details of the operation of the in-vehicle charger 20 will be described later.

Next, with reference to FIG. 2, a configuration relating to information input of the control circuit 45 common to each embodiment will be supplemented. The control circuit 45 receives information on the battery voltage deviation (hereinafter, also referred to as “potential difference”) ΔVb (= | Vb1-Vb2 |) between the battery voltage Vb1 of the battery BT1 and the battery voltage Vb2 of the battery BT2 from the battery voltage monitoring unit 43. To get. The battery voltage monitoring unit 43 corresponds to the "module voltage monitoring unit". The control circuit 45 controls the operation of the vehicle-mounted charger 20, which is a power converter, based on the voltage detection value detected by the battery voltage monitoring unit 43, that is, by feeding back the current voltage deviation. Specifically, the control circuit 45 performs parallelization processing and parallelization cancellation processing, which will be described later, based on the information of the voltage deviation ΔVb and the relay current Iry flowing through the relays RY1 and RY3.

The battery voltage monitoring unit 43 may detect the voltage Vb1 and Vb2 between the terminals of the batteries BT1 and BT2 by the voltage sensors 71 and 72, and calculate ΔVb which is an absolute value of the difference. Alternatively, the battery voltage monitoring unit 43 may detect the voltage across the relay RY1 as the potential difference ΔVb by the voltage sensor 73. Further, the battery voltage monitoring unit 43 may obtain the relay current Iry by converting it from the potential difference ΔVb, or may detect it by a current sensor. The battery voltages Vb1 and Vb2 are voltages including a loss due to internal resistance when energized. Therefore, a symbol different from the open circuit voltages Vo_1 and Vo_2 in FIGS. 6 and 7 is used.

Further, the battery voltage monitoring unit 43 detects an abnormality when the voltages of the batteries BT1 and BT2 are out of the normal range, and transmits the abnormality to the control circuit 45. In addition, a battery temperature monitoring unit 44 may be provided that detects a temperature abnormality based on the temperatures Tb1 and Tb2 of the batteries BT1 and BT2 and transmits the temperature abnormality to the control circuit 45. The control circuit 45 cuts off the connection between the battery in which the abnormality is detected and the charger, load, or power converter. That is, the battery voltage monitoring unit 43 and the battery temperature monitoring unit 44 function as an "abnormality detection unit".

Subsequently, before moving on to the description of the specific configuration and the action and effect of each embodiment, the background and problems of the present embodiment will be described with reference to FIGS. 3 to 5. FIG. 3 shows the relationship between the charging infrastructure for the power storage module and the load drive voltage. Here, it is assumed that the voltage of the power storage module is 400V class as standard. In addition, it is assumed that there are two types of charging infrastructure such as charging stands, one that supports 400V class and the other that supports 800V class, and that there are two types of loads used, one that is driven by 400V class and the other that is driven by 800V class. do. There is no problem when charging the power storage module that drives the load at the 400V class with the charging infrastructure of the 400V class, or when charging the power storage module that drives the load at the 800V class with the charging infrastructure of the 800V class.

On the other hand, consider the case of charging the power storage module with a charging infrastructure having a voltage different from the load drive voltage. Then, if two power storage modules that drive a 400V class load are connected in series at the time of charging, charging can be performed with an 800V class charging infrastructure. Then, when the load is driven, that is, when the battery is discharged, the connection can be switched to parallel connection and used at 400 V class. On the contrary, if the power storage module charged by the 400V class charging infrastructure in the parallel connection state is switched to the two-series connection at the time of load driving, it can be used in the 800V class. By making it possible to switch the connection state of a plurality of power storage modules in series or in parallel in this way, it becomes possible to support many charging infrastructures.

Specifically, vehicle equipment such as main motors and auxiliary equipment of electric vehicles and plug-in hybrid vehicles and charging infrastructure are expected to shift from the current 400V class to the 800V class in the future in order to shorten the charging time. Then, there may be a situation where the vehicle specifications and the charging infrastructure specifications do not match, especially during the transitional period. Therefore, it is required to be able to switch the series-parallel of the battery module at the time of charging and at the time of load driving, that is, at the time of running in the case of driving the main engine motor. For that purpose, a series-parallel switch such as a mechanical relay or a relay composed of a semiconductor switch is inevitably provided in the circuit.

With reference to FIG. 4, it is assumed that a potential difference is generated between the two batteries BT1 and BT2 due to variations in internal resistance and the like. Assuming that the voltage when the two batteries BT1 and BT2 are connected in series is 100%, for example, it is assumed that the voltage of the battery BT1 is 52% and the voltage of the battery BT2 is 48%. The thick arrow means that the voltage is higher than that of the thin arrow. Then, when the relay is turned on and switched to the parallel connection after the series charging at the time of the external charger, a short-circuit current due to the potential difference between the batteries BT1 and BT2 flows, and an arc is generated at the relay contact.

FIG. 5 shows the relationship between the opening / closing current of the relay and the number of times of opening / closing durability, in other words, the relay contact life. The horizontal axis and the vertical axis are logarithmic scales. As can be seen from FIG. 5, the larger the opening / closing current, the smaller the opening / closing durability. Therefore, considering the design life of the device, it is necessary to suppress the switching current to a certain safety value or less based on the predetermined durability and the characteristics of the relay. For that purpose, it is necessary to balance the voltages of the batteries BT1 and BT2 and eliminate the potential difference before parallelizing them before connecting them in parallel.

Here, in the prior art disclosed in Patent Document 1 (Japanese Patent No. 5611400), a current flows between two battery units through a path provided with a resistance, so that a loss due to the resistance occurs. Further, there is a problem that it takes time to balance because the current is suppressed by the resistance. Further, the method for adjusting the assembled battery disclosed in Japanese Patent Application Laid-Open No. 2005-151679 also has a problem similar to the technique of Patent Document 1 in that a current is passed between modules through a resistor. Therefore, it is an object of the present embodiment to balance the potential difference between the power storage modules in a short time while avoiding the occurrence of loss and the shortening of the life of the contacts.

In order to achieve this object, in the present embodiment, a plurality of batteries connected in parallel, for example, the battery BT1 and the battery BT2 in the example of FIG. 1 are connected to the power converter. Then, prior to switching from series to parallel, a power converter is operated to transfer power between batteries having different terminal voltages. That is, energy is recirculated between a plurality of batteries by a power converter, and the voltage between the terminals causes a voltage drop and a voltage rise, so that the potential difference between the terminals of the plurality of batteries is made equal to or less than a predetermined threshold value. Then, in a state where the potential difference is equal to or less than the threshold value, the relays for parallel connection (RY1 and RY3 in the example of FIG. 1) are turned on. Hereinafter, this process according to the present embodiment is referred to as "voltage balancing process".

In the present embodiment, the voltage balancing process can turn on the contacts of the parallel connection relay without causing an excessive inrush current, and can improve the reliability and life of the relay. Further, unlike the conventional technique, the current is not passed through the resistor, so that the loss can be reduced and the voltage between the plurality of batteries can be balanced in a short time.

Next, the principle of the voltage balancing process will be described with reference to FIGS. 6 and 7. FIG. 6 shows a state in which a balanced current is passed between the batteries BT1 and BT2 using a power converter with the parallel relays RY1 and RY3 turned off, and FIG. 7 shows a state in which the parallelized relays RY1 and RY3 are turned on. The state after parallel connection is shown. The inrush current shown by the long broken line in FIG. 6 and the reflux current shown by the short broken line in FIG. 7 flow from the high voltage side to the low voltage side.

[Issues due to battery voltage difference]
When switching the batteries BT1 and BT2 from series to parallel, voltage variations may occur between the batteries BT1 and BT2 connected in parallel. For example, variations in battery capacity and the fact that each battery was used for a different load before parallel connection may be the factors.

The batteries BT1 and BT2 can be represented by an equivalent circuit using an open circuit voltage Vo, a series equivalent resistance R0, a polarization model Rn, and a capacitance Cn (n = 1 to N). The value of N is selected according to the model reproduction level, but is shown here as n = 1 and 2. For the battery BT1, the end of each symbol is described as "_1", and for the battery BT2, the end of each symbol is described as "_2".

For example, it is assumed that the open circuit voltage Vo_1 = 410V, Vo_2 = 390V, the equivalent series resistance R0_1 = 10mΩ, and R0_2 = 10mΩ. If the parallel relays RY1 and RY3 are turned on as they are, a very large inrush current flows as calculated by the following equation, and the reliability of the contacts of the relays RY1 and RY3 is significantly deteriorated.
(410V-390V) / (10mΩ + 10mΩ) = 1000A

[Operation of power converter]
For example, assume that the voltage of the battery BT1 is higher than the voltage of the battery BT2. The power storage system of the present embodiment uses a power converter connected to the batteries BT1 and BT2 to return electric power from the battery BT1 having a relatively high voltage to the battery BT2 having a relatively low voltage. At this time, a discharge current flows through the battery BT1 and a charge current flows through the battery BT2. This current causes a voltage drop in the series equivalent resistance R0 and the polarization Rn / Cn, and the deviation of the open circuit voltage Vo approaches zero. Therefore, the voltage applied to the parallel relays RY1 and RY3 becomes small.

As described above, in the present embodiment, a power converter is used to pass a current so that the potential difference between the batteries BT1 and BT2 becomes small, and the parallel relays RY1 and RY3 are turned on in a state where the potential difference is equal to or less than the threshold value. As a result, the inrush current can be suppressed, and the reliability of the relays RY1, RY3, and the power storage system 401 as a whole can be improved.

[About voltage balancing]
In the voltage balancing process, it is not necessary to charge and discharge until the open circuit voltage Vo becomes exactly equal. By causing a voltage drop in the internal resistance R0 and the polarization Rn / Cn of the battery, the inrush current when closing the parallel relays RY1 and RY3 may be reduced. This is because the effect on relay reliability is dominated by the open / close current rather than the allowable current during continuous energization of the relay.

In short, the potential difference between the batteries BT1 and BT2 at the moment when the relays RY1 and RY3 are turned on may be equal to or less than a predetermined threshold value, and the power converter can be operated only for a limited short time before and after the on operation. Therefore, it is possible to carry out an operation of energizing a current larger than the continuous rated current of the power converter for a short time. As a result, the parallelization of the batteries BT1 and BT2 can be completed in a shorter time.

As shown in FIG. 7, even after parallel connection, a reflux current flows until the open circuit voltage Vo is balanced. However, as described above, since the permissible continuous energization current of a relay is generally sufficiently large with respect to the switching current, it does not affect the reliability of the battery or the relay.

[About power converter]
The power converter for the voltage balancing process does not need to be dedicated. For example, by using an in-vehicle charger mounted on an electric vehicle, a DC / DC converter for an auxiliary battery, an electric air conditioner compressor, or a combination thereof, a current may flow so as to reduce the potential difference between the batteries. The configuration using these power converters will be sequentially described in each embodiment. By utilizing these power converters, which are mainly used continuously for functions other than voltage balancing, for voltage balancing processing only before and after parallel connection of batteries, the number of devices can be reduced, and the number of devices can be reduced. Utilization efficiency can be improved.

Next, the parallelization process and the parallel release process, which are the basic operations in the series-parallel switching, will be described with reference to the flowcharts of FIGS. 8 and 9. The parallelization process and the parallelization process are referred to as predefined steps S30 and S40 in the flowcharts of FIGS. 13 and 16. In the following flowchart description, the symbol "S" indicates a step.

In the parallelization process shown in FIG. 8, when it is first determined in S31 that there is a parallel connection request, the process proceeds to S32. In S32, it is determined whether or not the potential difference between the batteries BT1 and BT2 is equal to or less than the threshold value. If the potential difference is equal to or less than the threshold value and YES is determined in S32, the process proceeds to S35. If the potential difference exceeds the threshold value and is determined to be NO in S32, the process proceeds to S33. In S33, the control circuit 45 starts a voltage balancing operation by the power converter. This operation is continued until it is determined in S34 that the potential difference is equal to or less than the threshold value. When it is determined in S32 or S34 that the potential difference is equal to or less than the threshold value, the process shifts to S35, and the control circuit 45 turns on the parallel relays RY1 and RY3. Then, the control circuit 45 stops the operation of the power converter in S36.

In the parallel release process shown in FIG. 9, when it is first determined in S41 that there is a parallel release request, the process proceeds to S42. In S42, it is determined whether or not the relay current flowing through the relays RY1 and RY3 is equal to or less than the threshold value. If the relay current is equal to or less than the threshold value and YES is determined in S42, the process proceeds to S45. If the relay current exceeds the threshold value and is determined to be NO in S42, the process proceeds to S43. In S43, the control circuit 45 starts the voltage balancing operation by the power converter. This operation is continued until it is determined in S44 that the relay current is equal to or less than the threshold value. When it is determined in S42 or S44 that the relay current is equal to or less than the threshold value, the process shifts to S45, and the control circuit 45 turns off the parallel relays RY1 and RY3. Then, the control circuit 45 stops the operation of the power converter in S46.

Here, the significance of executing the parallel disconnection process when the parallel connection is disconnected again immediately after the parallel connection will be described. Immediately after the potential difference between the batteries BT1 and BT2 is eliminated by the power converter and parallelized, a reflux current flows between the batteries BT1 and BT2 until the battery open-circuit voltages Vo_1 and Vo_2 are balanced. If the internal resistance of the batteries BT1 and BT2 and the time constant of polarization are large, it may take time. When reconnecting in series with the return current flowing, or when turning off all relays to stop the system, if the relays RY1 and RY3 are cut off as they are, the return current will be cut off, and the contacts of the relays RY1 and RY3 will be cut off. May reduce the reliability of the. Therefore, it cannot be shut off immediately as it is.

Therefore, in response to this problem, when a recirculation current is flowing through the relays RY1 and RY3, a recirculation current is passed through a power converter before the relays RY1 and RY3 are turned off, and the current flowing through the relays RY1 and RY3 is below the threshold value. It shuts off in the state of. As a result, even when there is a parallel release request and a recirculation current is flowing between the batteries BT1 and BT2, the relays RY1 and RY3 can be cut off without waiting for the attenuation of the balanced current.

Next, two embodiments of the specific configuration of the vehicle-mounted charger 20 are shown in FIGS. 10 and 11 as the first embodiment and the second embodiment. Here, the reference numerals of the vehicle-mounted chargers of the first and second embodiments are "201" and "202", respectively.

The vehicle-mounted charger 201 of the first embodiment shown in FIG. 10 includes, for example, an AC / DC conversion circuit 21 configured as a PFC, and a plurality of DC / DC converters 301 and 302 as internal circuits. The input end of the AC / DC conversion circuit 21 is connected to the commercial power supply 15 via the AC power supply connection units 16 and 17. The DC / DC converters 301 and 302 are connected in parallel to a common DC bus which is an output end of the AC / DC conversion circuit 21.

The DC / DC converters 301 and 302 are transformer type bidirectional DC / DC converters, and a circuit type such as a dual active bridge type is applied. The first DC / DC converter 301 includes a core 331, a primary winding 311 and a secondary winding 321 as well as a primary side switching circuit 341 and a secondary side switching circuit 351. Each one primary winding 311 and secondary winding 321 is wound around one core 331. The switching circuits 341 and 351 periodically alternate the direction of the current flowing through the windings 311 and 321.

Similarly, the second DC / DC converter 302 includes a core 332, a primary winding 312 and a secondary winding 322, and a primary side switching circuit 342 and a secondary side switching circuit 352. Each one primary winding 312 and secondary winding 322 is wound around one core 332. The switching circuits 342 and 352 periodically change the direction of the current flowing through the windings 312 and 322. The first DC / DC converter 301 and the second DC / DC converter 302 have the same specifications, or at least the winding ratios of the primary windings 311 and 312 and the secondary windings 321 and 322 are set to be the same.

In the voltage balancing process, the batteries BT1 and BT2 are connected to the secondary output ports P1 and P2 of the DC / DC converters 301 and 302, respectively. Then, as shown by the thick arrow, the route passes from the secondary side to the primary side of the first DC / DC converter 301, passes through the common DC bus, and passes from the primary side to the secondary side of the second DC / DC converter 302. , The electric power between the batteries BT1 and BT2 is returned.

The vehicle-mounted charger 202 of the second embodiment shown in FIG. 11 includes, for example, an AC / DC conversion circuit 21 configured as a PFC and a multi-port type DC / DC converter 303 as an internal circuit. The input end of the AC / DC conversion circuit 21 is connected to the commercial power supply 15 via the AC power supply connection units 16 and 17. The DC / DC converter 303 is connected to the DC bus which is the output end of the AC / DC conversion circuit 21.

The DC / DC converter 303 is a transformer type bidirectional DC / DC converter, and a circuit type such as a triple active bridge type is applied. The DC / DC converter 303 includes a core 33, a primary winding 31, and two secondary windings 321 and 322, as well as a primary side switching circuit 34 and a secondary side switching circuits 351 and 352. One primary winding 31 and two secondary windings 321 and 322 are wound around one core 33. The switching circuits 34, 351 and 352 periodically change the direction of the current flowing through the windings 31, 321 and 322.

In the voltage balancing process, the batteries BT1 and BT2 are connected to the two secondary output ports P1 and P2 of the DC / DC converter 303, respectively. Then, as shown by the thick arrow, the electric power between the batteries BT1 and BT2 is returned through the path from the secondary side of the first DC / DC converter 301 to the secondary side of the second DC / DC converter 302. In this configuration, the power recirculation path is shortened and the loss is reduced as compared with the vehicle-mounted charger 201 of the first embodiment. Further, since the number of primary windings is reduced, the size of the DC / DC converter can be reduced.

(Third Embodiment)
In the third and fourth embodiments, a configuration in which two batteries BT1 and BT2 connected in series or in parallel are charged with DC power from the external charger 10 will be described. For example, assume a situation where power is supplied to an electric vehicle or a plug-in hybrid vehicle at a charging station. It is required to externally charge a DC voltage of, for example, 800V in the series connection state of the two batteries BT1 and BT2, and 400V, for example, in the parallel connection state. However, since the charging capacity of the external charger 10 is not always sufficient, it is necessary to check before starting the external charging.

The third embodiment will be described with reference to FIGS. 12 to 14. As shown in FIG. 12, the power storage system 401 in the vehicle includes a positive electrode terminal 11 and a negative electrode terminal 12 as an external charging connection portion. At the time of performing external charging, the external charger 10 is connected to the external charging connection portions 11 and 12 via a power line. Further, the information on the outputable voltage of the external charger 10 is transmitted to the control circuit 45 by wired or wireless communication.

Although not the subject of the third embodiment, FIG. 12 also shows the external charging of the in-vehicle charger 20. The commercial power supply device 15 is connected to the AC power supply connection units 16 and 17, and can charge an AC voltage of 100 V or 200 V to the vehicle-mounted charger 20 of the power storage system 401. Even in this configuration, if the commercial power supply device 15 has an output capacity management and communication function, information communication may be performed with the control circuit 45 at the time of charging.

The series-parallel selection process at the time of external charging according to the third embodiment is shown in the flowcharts of FIGS. 13 and 14. The two flowcharts are connected at points A, B, and C. Details of the parallelization process of S30 and the parallelization process of S40 are shown in FIGS. 8 and 9. The external charging start process of S50 is a general process such as turning on the connection relays RY6 and RY7 with the external charger 10 based on communication or the like and passing the output current of the external charger 10 based on the command. The description is omitted.

First, in S11, the control circuit 45 determines whether the batteries BT1 and BT2 are abnormal based on the voltage information from the battery voltage monitoring unit 43, the temperature information from the battery temperature monitoring unit 44, and the like. If it is abnormal, charging is not possible, so the process ends. However, when either one of the batteries BT1 and BT2 is normal and the other is abnormal, the control circuit 45 uses, for example, a matrix-shaped relay to connect only the normal battery to the charger or load to charge or discharge the battery. It is possible to make it. That is, it is possible to disconnect only the battery determined to be abnormal. If it is determined that the batteries BT1 and BT2 are not abnormal and there is an external charge request in S12, the process proceeds to S13.

Based on the information from the external charger 10, the control circuit 45 determines in S13 whether the maximum voltage of the external charger 10 exceeds the maximum voltage (for example, 400V) when the batteries are in parallel. If NO, it is determined that external charging is not possible and the process is terminated. If YES in S13, the control circuit 45 determines in S14 whether the maximum voltage of the external charger 10 exceeds the calculated value of the current battery series voltage, that is, the voltage corresponding to the current battery series connection. In this case, the sum of the voltages of the batteries BT1 and BT2 may be simply calculated, or the sum value may be corrected. If YES in S14, series charging is determined, and the process proceeds to S15. If NO in S14, parallel charging is determined and the process proceeds to S25.

When the series charge is determined, the control circuit 45 determines in S15 that it is currently in a parallel state, and performs a parallel release process in S40. After the parallel release process or when it is determined in S15 that the parallel state is not currently present, the control circuit 45 turns on the serialization relay RY2 in S16 and performs an external charge start process in S50.

When series charging is performed, the voltage in series of the batteries BT1 and BT2 gradually increases. Therefore, the control circuit 45 repeatedly determines in S18 whether the current battery series voltage has reached the maximum voltage of the external charger 10 during external charging. If the current battery series voltage exceeds the maximum voltage of the external charger 10, it is determined as NO in S18. Then, the process proceeds to S30 via the NO determination of S25, and after the parallelization process, external charging in parallel is continued. In this case, it is possible to start charging in series and switch to parallel charging from the middle as the battery voltage rises. After the series charging is performed, if it is determined in S19 that the external charging end condition is satisfied, the control circuit 45 performs the parallel processing of S30 and then ends the processing.

When the parallel charge is determined, the control circuit 45 determines in S25 that it is not currently in the parallel state, and performs the parallelization process in S30. After the parallelization process, or when it is determined in S25 that the state is not currently in parallel, the control circuit 45 performs the external charge start process in S50. It should be noted that the step of monitoring that the current battery parallel voltage does not reach the maximum voltage of the external charger 10 during the external charging in parallel is omitted. If the same steps as in S18 are performed and the current battery parallel voltage exceeds the maximum voltage of the external charger 10, charging at a constant voltage (CV charging) is continued, or the process is terminated because charging cannot be continued. You may. After that, when it is determined in S29 that the external charge end condition is satisfied, the control circuit 45 ends the process.

As described above, in the third embodiment, the control circuit 45 switches between series charging and parallel charging based on the information of the outputable voltage communicated from the external charger 10. If the outputable voltage of the external charger 10 is at a level that allows series charging, the control circuit 45 selects series charging to enable quick charging. On the other hand, if the outputable voltage of the external charger 10 is insufficient for series charging but at a level capable of parallel charging, the control circuit 45 can respond to the external charging request by selecting parallel charging. Therefore, appropriate external charging can be performed according to the situation of the external charger 10.

(Fourth Embodiment)
Next, a fourth embodiment to which the third embodiment is applied will be described with reference to FIGS. 15 and 16. FIG. 15 shows a state in which the relays RY2, RY6, and RY7 of FIG. 12, that is, the serialized relay is turned on. In the fourth embodiment, the voltage balancing process is performed by the power return between the batteries BT1 and BT2 during series charging.

When the internal resistance of the batteries BT1 and BT2 is large, the current rating of the power converter used for the voltage balancing process is low, and the voltage deviation between the batteries BT1 and BT2 is large, the parallelization relay is turned on in the voltage balancing process. It takes time to do. Therefore, in the fourth embodiment, the voltage balancing process between the batteries BT1 and BT2 is performed by the power converter in the vehicle in parallel during the external charging in series by the external charger 10. In the example of the power storage system 401 shown in FIG. 15, an in-vehicle charger 20 is used as the power converter.

The voltage balancing process during external charging according to the fourth embodiment is shown in the flowchart of FIG. In FIG. 16, the steps other than S17 are substantially the same as those in FIGS. 13 and 14, and thus the description thereof will be omitted. Further, the description of S11, S13, and S18 in FIG. 13 will be omitted. If YES is determined in S14 and serial charging is determined, external charging is started in S50 after the serialization relay of S16 is turned on, and then voltage balancing operation by the power converter is started in S17. After that, when it is determined in S19 that the external charge end condition is satisfied, the control circuit 45 performs the parallelization process of S30 and then ends the process.

In the fourth embodiment, the voltage deviation caused by the difference in the capacity, internal resistance, etc. of the batteries BT1 and BT2 can be reduced prior to the parallel operation during the execution of external charging. Therefore, it is possible to shorten the time required for voltage balancing until the operation of switching to parallel is performed after the completion of external charging in series, or it is possible to switch to parallel immediately after the completion of charging.

(Fifth Embodiment)
In the fifth and sixth embodiments, a power converter other than the in-vehicle charger 20 is used for the voltage balancing process with respect to the above embodiment. The fifth embodiment will be described with reference to FIGS. 17 and 18. In the power storage system 405 of the fifth embodiment, the DC / DC converter 50 for the auxiliary battery is used as the power converter for the voltage balancing process. The DC / DC converter 50 for the auxiliary battery lowers the high voltage of the batteries BT1 and BT2 to a low voltage such as 12V or 48V, and supplies the auxiliary battery 55. The output end of the DC / DC converter 50 for the auxiliary battery on the auxiliary battery 55 side is "one or more connected to a target other than the power storage module, which is different from the plurality of input / output ends connected to the plurality of power storage modules. Corresponds to the input / output end of.

As shown in FIG. 17, the batteries BT1 and BT2 are connected to the input / output ports P1 and P2 of the auxiliary battery DC / DC converter 50, respectively. The opening / closing patterns of the relays RY1-RY7 during charging and discharging are the same as those in the first and second embodiments. The in-vehicle charger 20 is treated as a kind of load 80.

As shown in FIG. 18, the auxiliary battery DC / DC converter 50 has, for example, the same configuration as the second embodiment of the multi-port DC / DC converter 303. Power is returned between the secondary winding 341 connected to the battery BT1 and the secondary winding 342 connected to the battery BT2. The DC / DC converter 50 for the auxiliary battery may be configured such that a plurality of DC / DC converters 301 and 302 are arranged in parallel as in the first embodiment.

Here, the auxiliary battery 55, unlike the batteries BT1 and BT2, corresponds to a power storage module in which the series-parallel connection cannot be switched, that is, "another power storage module having a series connection or a fixed parallel connection". The DC / DC converter 50 for an auxiliary battery has an auxiliary battery in which one end opposite to the input / output ends connected to the batteries BT1 and BT2 is "another power storage module having a fixed series connection or parallel connection". Connected to 55. As a result, the voltage balancing process can be carried out by effectively utilizing the in-vehicle device.

(Sixth Embodiment)
The sixth embodiment will be described with reference to FIGS. 19 and 20. In the power storage system 406 of the sixth embodiment, a plurality of inverters 61 and 62 of the electric air conditioner compressor 60 are used as the power converter for the voltage balancing process. The inverters 61 and 62 convert the DC power of the batteries BT1 and BT2 into, for example, three-phase AC power, and supply the DC power to the plurality of winding sets 63 and 64 of the AC motor 65. The AC output ends of the inverters 61 and 62 correspond to "one or more input / output ends connected to an object other than the power storage module, which is different from the plurality of input / output ends connected to the plurality of power storage modules".

As shown in FIG. 19, the batteries BT1 and BT2 are connected to the input / output ports P1 and P2 of the electric air conditioner compressor 60, that is, the input terminals of the inverters 61 and 62, respectively. As shown by the broken line G, the negative side connection destination of the balanced current path may be the load 80 side, and the relay may be shared. Further, the relay 68 that opens and closes the path between the batteries BT1 and BT2 and the electric air conditioner compressor 60 may not be provided. The opening / closing patterns of the relays RY1-RY7 during charging and discharging are the same as those in the first and second embodiments. The in-vehicle charger 20 is treated as a kind of load 80.

In the AC motor 65 shown in FIG. 20, two sets of three-phase winding sets 63 and 64 are wound around a common stator core. The AC motor 65 rotates a common output shaft by energizing the winding sets 63 and 64 to generate a single mechanical output. The output end of the first inverter 61 is connected to one winding set 63, and the output end of the second inverter 62 is connected to the other winding set 64. That is, the output ends of the inverters 61 and 62 are connected to different winding sets 63 and 64. One battery BT1 is connected to the input end of the first inverter 61 that supplies electric power to the first winding set 63. The other battery BT2 is connected to the input end of the second inverter 62 that supplies power to the second winding set 64.

For example, when the voltage of the battery BT1 is higher than the voltage of the battery BT2, the control circuit 45 controls the phase so that the first inverter 61 is driven and the second inverter 61 is regenerated. Therefore, the first inverter 61 consumes the electric power of the battery BT1 to supply energy to the AC motor 65, and powers and operates so as to generate torque in the output shaft. The second inverter 62 regeneratively operates so as to return the energy of the counter electromotive force due to the rotation of the output shaft of the AC motor 65 to the battery BT2.

In this way, the return of electric power is realized between the two inverters 61 and 62. As described above, in the sixth embodiment, the voltage balancing process can be carried out by effectively utilizing the existing electric air conditioner compressor 60 in the vehicle.

It should be noted that the configuration in which one of the plurality of inverters is driven and the other is regenerated to recirculate the electric power is not limited to the configuration of the AC motor that generates a single mechanical output as described above. For example, the mechanical output generated by the power running operation of one inverter may be converted into gas pressure, and the other inverter may be regenerated by the mechanical input obtained by reconverting the gas pressure.

(7th Embodiment)
Next, the seventh embodiment will be described with reference to FIG. The power storage system 407 of the seventh embodiment uses the vehicle-mounted charger 20 as the power converter and switches the series-parallel of the three batteries BT1, BT2, and BT3. A battery BT3 and a relay RY8-RY10 are added to the power storage system 401 of FIG. Similar to the power storage system 401, the negative side connection destination of the balanced current path may be the load 80 side, and the relay may be shared. Further, the relay 28 that opens and closes the path between the batteries BT1 and BT2 and the in-vehicle charger 20 may not be provided.

Regarding the relay opening / closing pattern, the relays RY2, RY9, RY6, and RY7 are turned on during the three-series charging. At the time of three parallel charging, the relays RY1, RY3, RY8, RY10, RY6, and RY7 are turned on. At the time of three parallel discharges, the relays RY1, RY3, RY8, RY10, RY4, and RY5 are turned on.

As described above, even in a power storage system including three or more power storage modules, the same effect can be obtained by the same voltage balancing process as in the above embodiment. Here, in the voltage balancing process of a plurality of power storage modules, it is basically assumed that the plurality of power storage modules are connected to the power converter at the same time.

However, it is theoretically possible to connect each power storage module to the power converter in a time-division manner by using, for example, a matrix-shaped relay. Therefore, in a power storage system including three or more power storage modules, the power converter does not have to be connected to all the power storage modules at the same time. That is, any two or more power storage modules among the plurality of power storage modules may be configured to be connectable to the power converter.

(Other embodiments)
The control circuit 45 is not limited to the configuration in which the power converter is feedback-controlled based on the voltage detection value detected by the battery voltage monitoring unit 43, and for example, the power converter is fed forward from the initial voltage and the operation time at the start of operation. You may control it. Further, instead of using the detected value of the battery voltage, the power converter may be controlled based on the voltage estimated value estimated from other parameters.

In FIG. 3, the charging infrastructure and the load drive voltage are roughly classified into two types, 400V class and 800V class, but the present invention is not limited to this, and the present invention can be applied to, for example, a system having a load voltage of 200V class. .. More specifically, when the load is driven, the power storage modules may be connected in parallel and used in the 200 V class, and when charging, the power storage modules may be connected in series and charged by the 400 V class charging infrastructure.

The power storage system of the present invention is not limited to those mounted on electric vehicles and plug-in hybrid vehicles, and can be applied to any system that can switch the series-parallel connection state of a plurality of power storage modules. As described above, the power storage module is not limited to the battery module, and a capacitor or the like may be used. Further, for example, when used in a vehicle other than an electric vehicle, there is not always a device that can be used as a power converter for voltage balancing processing, so a power converter dedicated to voltage balancing processing may be installed.

As described above, the present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the invention.

10 ... External charger (charger),
20 (201, 202) ... In-vehicle charger (charger),
401, 405, 406, 407 ... Power storage system,
45 ... Control circuit,
50 ... DC / DC converter (power converter) for auxiliary battery,
61, 62 ... Inverter (power converter),
BT1-BT3 ... Battery (power storage module),
RY1-RY10 ... Relay (series-parallel switch).

Claims (12)

Multiple storage modules (BT1, BT2, BT3), each containing one or more storage cells,
A series-parallel switch (RY1-RY10) capable of switching the connection state of the plurality of power storage modules in series and in parallel, and
A power converter (201, 50) for transferring power between any two or more of the power storage modules, and a power converter (201, 50).
The control circuit (45) that controls the series-parallel switch and the power converter,
Equipped with
Prior to the parallel switching of the plurality of power storage modules, the control circuit performs a voltage balancing process for operating the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the control circuit performs the voltage balancing process. A power storage system that switches between series and parallel switches.
The power converter has one or more input / output ends connected to an object other than the power storage module, in addition to the plurality of input / output ends connected to the plurality of power storage modules.
The power converter
A power storage system including a plurality of DC / DC converters (301, 302) having an input / output port connected to each of the plurality of power storage modules at one end and capable of bidirectionally energizing power between the input / output ports . The power converter includes an AC / DC conversion circuit (21) that converts AC power supplied from an external AC power supply (15) into DC power, and stores DC power output by the AC / DC conversion circuit. A charger (201) that can charge the module.
The first aspect of claim 1 , wherein one end of one or more DC / DC converters opposite to the input / output end connected to the power storage module is connected to a DC bus which is an output of the AC / DC conversion circuit. Power storage system. In the power converter (50), one end of one or more DC / DC converters opposite to the input / output end connected to the power storage module is connected in series or in parallel to the power storage module. The power storage system according to claim 1 , wherein is connected to another power storage module to which is fixed. Multiple storage modules (BT1, BT2, BT3), each containing one or more storage cells,
A series-parallel switch (RY1-RY10) capable of switching the connection state of the plurality of power storage modules in series and in parallel, and
A power converter (202) for transferring power between any two or more of the power storage modules, and a power converter (202).
The control circuit (45) that controls the series-parallel switch and the power converter,
Equipped with
Prior to the parallel switching of the plurality of power storage modules, the control circuit performs a voltage balancing process for operating the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the control circuit performs the voltage balancing process. A power storage system that switches between series and parallel switches.
The power converter has one or more input / output ends connected to an object other than the power storage module, in addition to the plurality of input / output ends connected to the plurality of power storage modules.
The power converter
Charging that includes an AC / DC conversion circuit (21) that converts AC power supplied from an external AC power supply (15) into DC power, and the DC power output by the AC / DC conversion circuit can be charged to the power storage module. It is a vessel (202),
The transformer has a transformer in which one primary winding (31) and a plurality of secondary windings (321, 322) to which the plurality of power storage modules are connected are wound around one core (33). Includes a DC / DC converter (303) capable of bidirectionally energizing power between input and output ports of multiple secondary windings.
A power storage system in which one end of one or more DC / DC converters opposite to the input / output end connected to the power storage module is connected to a DC bus which is an output of the AC / DC conversion circuit . Multiple storage modules (BT1, BT2, BT3), each containing one or more storage cells,
A series-parallel switch (RY1-RY10) capable of switching the connection state of the plurality of power storage modules in series and in parallel, and
A power converter (50) for transferring power between any two or more of the power storage modules, and a power converter (50).
The control circuit (45) that controls the series-parallel switch and the power converter,
Equipped with
Prior to the parallel switching of the plurality of power storage modules, the control circuit performs a voltage balancing process for operating the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the control circuit performs the voltage balancing process. A power storage system that switches between series and parallel switches.
The power converter has one or more input / output ends connected to an object other than the power storage module, in addition to the plurality of input / output ends connected to the plurality of power storage modules.
The power converter
The transformer has a transformer in which one primary winding (31) and a plurality of secondary windings (321, 322) to which the plurality of power storage modules are connected are wound around one core (33). Includes a DC / DC converter (303) capable of bidirectionally energizing power between input and output ports of multiple secondary windings.
One end of one or more DC / DC converters opposite to the input / output end connected to the power storage module is another power storage module having a fixed series connection or parallel connection different from the power storage module. A power storage system connected to 55) . Multiple storage modules (BT1, BT2, BT3), each containing one or more storage cells,
A series-parallel switch (RY1-RY10) capable of switching the connection state of the plurality of power storage modules in series and in parallel, and
A power converter (61, 62) for transferring power between any two or more of the power storage modules, and a power converter (61, 62).
The control circuit (45) that controls the series-parallel switch and the power converter,
Equipped with
Prior to the parallel switching of the plurality of power storage modules, the control circuit performs a voltage balancing process for operating the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the control circuit performs the voltage balancing process. A power storage system that switches between series and parallel switches.
The power converter has one or more input / output ends connected to an object other than the power storage module, in addition to the plurality of input / output ends connected to the plurality of power storage modules.
The power converter is composed of a plurality of inverters (61, 62) that convert input DC power into AC power and output it to a load (65).
The power storage module is connected to the input end of the corresponding inverter and is connected to each other.
Some of the inverters operate in a power manner so as to consume the DC power of the connected power storage module and supply energy to the load.
The other inverter among the plurality is a power storage system that regeneratively operates so as to return the energy of the load to the connected power storage module . The common load of the plurality of inverters is an AC motor (65) that generates a single mechanical output by energizing a plurality of winding sets (63, 64), and the output ends of the respective inverters are mutual. The power storage system according to claim 6 , which is connected to different winding sets. Multiple storage modules (BT1, BT2, BT3), each containing one or more storage cells,
A series-parallel switch (RY1-RY10) capable of switching the connection state of the plurality of power storage modules in series and in parallel, and
A power converter (201, 202, 50, 61, 62) that transfers power between any two or more of the power storage modules.
The control circuit (45) that controls the series-parallel switch and the power converter,
Equipped with
Prior to the parallel switching of the plurality of power storage modules, the control circuit performs a voltage balancing process for operating the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the control circuit performs the voltage balancing process. A power storage system that switches between series and parallel switches.
The power storage module is further provided with an external charging connection unit (11, 12) connected to an external charger (10) capable of charging DC power.
The control circuit determines switching of the power storage module in series or in parallel based on the information of the outputable voltage of the external charger communicated from the external charger when there is an external charging request by the external charger. Power storage system. Multiple storage modules (BT1, BT2, BT3), each containing one or more storage cells,
A series-parallel switch (RY1-RY10) capable of switching the connection state of the plurality of power storage modules in series and in parallel, and
A power converter (201, 202, 50, 61, 62) that transfers power between any two or more of the power storage modules.
The control circuit (45) that controls the series-parallel switch and the power converter,
Equipped with
Prior to the parallel switching of the plurality of power storage modules, the control circuit performs a voltage balancing process for operating the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then the control circuit performs the voltage balancing process. A power storage system that switches between series and parallel switches.
The power storage module is further provided with an external charging connection unit (11, 12) connected to an external charger (10) capable of charging DC power.
The control circuit is a power storage system that performs the voltage balancing process during external charging in a state where a plurality of the power storage modules are connected in series . The eighth or nine claim, wherein the power converter has one or more input / output ends connected to an object other than the power storage module, in addition to the plurality of input / output ends connected to the plurality of power storage modules. Power storage system. Further, a module voltage monitoring unit (43) for monitoring the voltage of the power storage module is provided.
The power storage system according to any one of claims 1 to 10, wherein the control circuit controls the power converter based on a voltage detection value detected by the module voltage monitoring unit. An abnormality detection unit (43, 44) for detecting an abnormality in the power storage module is further provided.
When an abnormality in the power storage module is detected by the abnormality detection unit,
The power storage system according to any one of claims 1 to 11, wherein the control circuit cuts off the connection between the power storage module in which an abnormality is detected and the charger, load, or power converter.

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