WO2019082776A1

WO2019082776A1 - Power storage system

Info

Publication number: WO2019082776A1
Application number: PCT/JP2018/038765
Authority: WO
Inventors: 宜久山口; 耕司間崎; 将也 ▲高▼橋; 拓也木口; 晋平瀧田
Original assignee: 株式会社デンソー
Priority date: 2017-10-27
Filing date: 2018-10-18
Publication date: 2019-05-02
Also published as: JP7073669B2; CN111264014B; JP2019080473A; CN111264014A

Abstract

A power storage system (401) is provided with: batteries (BT1, BT2) as "a plurality of power storage modules each including at least one power storage cell"; relays (RY1-RY7); an on-vehicle charger (20) as a power converter; and a control circuit (45). The relays (RY1-RY3) are capable of switching the connection state of the batteries (BT1, BT2) between series connection and parallel connection. The on-vehicle charger (20) causes power to be exchanged between the batteries (BT1, BT2). The control circuit (45) controls the relays (RY1-RY7) and the on-vehicle charger (20). The control circuit (45) performs, prior to switching of the batteries (BT1, BT2) to the parallel connection, a voltage balancing process of causing the on-vehicle charger (20) to operate so that the potential difference between the batteries (BT1, BT2) becomes not more than a predetermined threshold value, and then turns on the relays (RY1, RY3).

Description

Power storage system

Cross-reference to related applications

This application is based on patent application number 2017-207925 filed on October 27, 2017, the contents of which are incorporated herein by reference.

The present invention relates to a storage system.

BACKGROUND Conventionally, a storage system in which a plurality of storage modules can be switched in series and in parallel is known. For example, the battery system for an industrial machine disclosed in Patent Document 1 aims to enable quick charging under high voltage and to use low voltage components. In this system, charge / discharge switching means for selectively switching the connection state between the battery unit and the charge input unit or the power load, and alternatively or alternatively, electrically connecting the plurality of battery units in parallel or in series. And / or a parallel / serial switching unit or the like.

In the discharge control flow of this system, in a state where a plurality of battery units are connected in parallel, discharge from the plurality of battery units to the power load is performed. In addition, in the charge control flow, in a state in which a plurality of battery units are connected in series, the rapid charger charges the plurality of battery units via the charge input unit. After completion of charging, if the voltage difference between the plurality of battery units is equal to or greater than the threshold value, voltage unit balance processing is performed to eliminate the voltage difference.

Patent No. 5611400

In the voltage unit balancing process of Patent Document 1, a current is caused to flow between the two battery units through a path provided with a resistance, so that a loss due to the resistance occurs. In addition, since the current can be suppressed by the resistance, it takes time for balancing. In addition, in the system of patent document 1, after completion of the balance process between voltage units, it is set as a standby state, and it is estimated that the time which balancing takes is not a problem.

Hereinafter, in the present specification, a “storage module” is used as a term of the upper concept including the battery unit of Patent Document 1. When the technology of Patent Document 1 is applied to the external charging of an electric car or a plug-in hybrid car, a situation in which a plurality of storage modules are switched to parallel connection after charging in series is completed, and the main machine motor as a load discharges and runs 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 reduced due to the arc of the contact or the short circuit current.

An object of the present disclosure is to provide a storage system that balances voltages of a plurality of storage modules while avoiding generation of a loss and a decrease in contact life when switching a plurality of storage modules from series to parallel. .

The storage system of the present disclosure includes a plurality of storage modules, a series-parallel switch, a power converter, and a control circuit. Each of the plurality of storage modules includes one or more storage cells. The series-parallel switch can switch connection states of a plurality of storage modules in series and in parallel. The power converter transfers power between any two or more storage modules of the plurality of storage modules. The control circuit controls the series-parallel switch and the power converter.

The control circuit performs “voltage balancing processing” to operate the power converter so that the potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold prior to parallel switching of the plurality of power storage modules, and then performs serial / parallel switching Switch the

In the present disclosure, the voltage of the storage module is balanced by causing energy to flow back and forth between arbitrary storage modules via the power converter. As a result, since the inrush current can be suppressed when the contacts of the series-parallel switch such as a relay are connected, the reliability and the life of the series-parallel switch can be improved. Further, the loss can be reduced as compared with the prior art in which the current flows between the storage modules via the resistor.

Preferably, the power converter has one or more input / output terminals connected to a target other than the power storage module separately from the plurality of input / output terminals connected to the plurality of power storage modules.

For example, in a storage system mounted on an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle, a main unit battery corresponds to a storage module. For electric vehicles, a DC / DC converter used as an internal circuit of a charger that charges AC power supplied from an AC power source to a main unit battery, a DC / DC converter for auxiliary battery, an inverter that drives a main unit motor and an air conditioner Power converters are already mounted. By utilizing these power converters for voltage balancing processing, the number of devices can be reduced and the utilization efficiency of the devices can be improved.

The above object and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the attached drawings. The drawing is
FIG. 1 is a block diagram of the storage system of the first and second embodiments, FIG. 2 is a configuration diagram showing a battery voltage monitoring configuration of the storage module, Figure 3 shows the relationship between charging infrastructure and load drive voltage, FIG. 4 is a diagram for explaining an event at the time of switching from serial to parallel; Fig. 5 is a diagram showing an example of characteristics of relay contact life with respect to switching current, FIG. 6 is a diagram (1) for explaining the principle of the voltage balancing process, FIG. 7 is a diagram (2) illustrating the principle of the voltage balancing process, FIG. 8 is a flowchart of parallel connection processing; FIG. 9 is a flowchart of parallel cancellation processing; FIG. 10 is a block diagram of an on-vehicle charger in which a plurality of DC / DC converters are arranged in parallel, which is the power converter of the first embodiment; FIG. 11 is a block diagram of an on-board charger using a multiport DC / DC converter, which is a power converter of the second embodiment; FIG. 12 is a block diagram of the storage system of the third embodiment, FIG. 13 is a flowchart of series-parallel selection processing during external charging according to the third embodiment, FIG. 14 is a continuation of the flowchart of FIG. FIG. 15 is a block diagram of the storage system of the fourth embodiment, FIG. 16 is a flowchart of a voltage balancing process during external charging according to the fourth embodiment, FIG. 17 is a block diagram of the storage system of the fifth embodiment, FIG. 18 is a block diagram of a DC / DC converter for an accessory battery which is a power converter of a fifth embodiment, FIG. 19 is a configuration diagram of a power storage system according to a sixth embodiment, FIG. 20 is a block diagram of an inverter for an air conditioner compressor which is a power converter of a sixth embodiment, FIG. 21 is a block diagram of a power storage system of the seventh embodiment.

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

The connection states of the plurality of storage modules are switched in series and in parallel by the series-parallel switch. The series-parallel switch is typically a relay composed of a mechanical relay or a semiconductor switch. Furthermore, the storage system of the present embodiment includes a power converter for transferring power between any two or more storage modules among a plurality of storage modules, and a control circuit for controlling a series-parallel switch and the power converter. Prepare. The following embodiments differ in the configuration of the power converter and the configuration relating to charging and discharging of the storage module.

First and second embodiments
First, the configuration of a power storage system 401 common to the first and second embodiments will be described with reference to FIG. The storage system 401 includes two batteries BT1 and BT2 as "a plurality of storage modules", relays RY1-RY7 as a "serial / parallel switch", an on-vehicle charger 20 as a "power converter", and a control circuit 45. Equipped with The batteries BT1 and BT2 are high-voltage battery modules, such as 400 V, which can be charged and discharged, such as lithium ion batteries. Hereinafter, the "battery module" is omitted and referred to as "battery". Moreover, although the low voltage (for example, 12V) "auxiliary battery" is mentioned in below-mentioned 5th Embodiment, all "battery" is used in the meaning of a high voltage battery.

In the storage system 401, the batteries BT1 and BT2 are provided between the external

charge connection units

11 and 12 and the load 80. The load 80 is exemplified by devices generally used in electric vehicles and plug-in hybrid vehicles. Relays RY1 and RY3 respectively open and close a path between positive electrodes of batteries BT1 and BT2 and between negative electrodes. Relay RY2 opens and closes the path between the negative electrode of battery BT1 and the positive electrode of battery BT2. Relays RY4 and RY5 open and close the path between the positive and negative electrodes of battery BT2 and 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. 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.

An external charger described in the third and fourth embodiments is connected to the external

charging connection units

11 and 12. In the case of using an external charger compatible with 800 V in external charging via the external

charging connection portions

11 and 12, serial charging is performed in a state in which the batteries BT1 and BT2 are connected in series. On the other hand, when an external charger compatible with 400 V is used, parallel charging is performed in a state where the batteries BT1 and BT2 are connected in parallel.

In the following description of the relay switching pattern, when “one relay is on” in RY1-RY7, it is assumed that “other relays are off”. During two series charging, the relays RY2, RY6 and RY7 are turned on. During two parallel charging, the relays RY1, RY3, RY6 and RY7 are turned on. The relays RY1, RY3, RY4 and RY5 are turned on at the time of two parallel discharges in which the power of 400 V is supplied from the batteries BT1 and BT2 to the load 80. The relay switching is operated by the command of the control circuit 45.

As a general function, the on-vehicle charger 20 converts AC power supplied from an external commercial power source through the AC power

supply connection units

16 and 17 into DC power and charges the batteries BT1 and BT2. In the storage system 401 of the first and second embodiments, the positive and negative terminals of the battery BT1 are connected to the input / output port P1 of the on-vehicle charger 20, and the positive and negative terminals of the battery BT2 are connected to the input / output port P2. Ru. The path between the batteries BT1 and BT2 and the input / output ports P1 and P2 of the on-vehicle charger 20 is referred to as a balanced current path. As indicated by the broken line G, the negative connection destination of the balanced current path may be the load 80 side, and the relay may be shared. Further, the relay 28 for opening and closing the path between the batteries BT1 and BT2 and the on-vehicle charger 20 may not be provided.

Here, the input end of the on-vehicle charger 20 connected to the AC power

supply connection portions

16 and 17 is “connected to a target other than the storage module different from the plurality of input / output ends connected to the plurality of storage modules. Equivalent to one or more input / output terminals. Also, the operation of the on-vehicle charger 20 is controlled by the control circuit 45. Details of the operation of the on-vehicle charger 20 will be described later.

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

The battery voltage monitoring unit 43 may detect the inter-terminal voltages Vb1 and Vb2 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 with a current sensor. The battery voltages Vb1 and Vb2 are voltages including the loss due to the internal resistance at the time of energization. Therefore, symbols different from the open circuit voltages Vo_1 and Vo_2 in FIGS. 6 and 7 are used.

Further, the battery voltage monitoring unit 43 detects an abnormality when the voltage of the batteries BT1 and BT2 is 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 which 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, the load, or the power converter. That is, the battery voltage monitoring unit 43 and the battery temperature monitoring unit 44 function as an "abnormality detection unit".

Subsequently, the background of the present embodiment will be described with reference to FIGS. 3 to 5 before the description of the specific configuration and effects of the embodiments. FIG. 3 shows the relationship between the charging infrastructure for the storage module and the load drive voltage. Here, it is assumed that the voltage of the storage module is typically 400V class. In addition, it is assumed that there are two types of charging infrastructures, such as a charging station, compatible with 400V and 800V, and there are two types of loads used: one driven by 400V and one driven by 800V. Do. There is no problem when charging a storage module that drives a load with a 400V class with a 400V charging infrastructure or charging an storage module that drives a load with a 800V class with a 800V charging infrastructure.

On the other hand, consider a case where the storage module is charged with a charging infrastructure of a voltage different from the load drive voltage. Then, if two storage modules for driving a 400V class load are connected in series at the time of charging, charging can be performed with a 800V class charging infrastructure. And it can switch to parallel connection at the time of load drive, ie, discharge, and can be used by 400V class. Conversely, if the storage module charged in the 400V class charging infrastructure in the parallel connection state is switched to two series connection at the time of load driving, it can be used in the 800V class. As described above, by making it possible to switch the connection state of a plurality of power storage modules in series and in parallel, it is possible to cope with many charging infrastructures.

Specifically, vehicle equipment such as main motors and accessories of electric vehicles and plug-in hybrid vehicles and charging infrastructure are expected to shift from the current 400 V class to the 800 V class in the future, for shortening charging time and the like. Then, a situation may occur where the vehicle specifications and the charging infrastructure specifications do not match, especially during the transition period of the transition. Therefore, it is required to make it possible to switch between series and parallel battery modules between charging and driving a load, that is, driving in the case of driving a main unit motor. To that end, a series-parallel switch such as a mechanical relay or a relay composed of a semiconductor switch is necessarily provided in the circuit.

Referring to FIG. 4, it is assumed that there is a potential difference between the two batteries BT1 and BT2 due to the variation 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%. Note that thick arrows indicate that the voltage is higher than thin arrows. When the relay is turned on and switched to parallel connection after DC charging in the external charger, a short circuit current due to the potential difference between the batteries BT1 and BT2 flows, and an arc occurs at the relay contact.

FIG. 5 shows the relationship between the switching current and the switching endurance number of the relay, in other words, the relay contact life. The horizontal and vertical axes are on a logarithmic scale. As can be seen from FIG. 5, the larger the switching current, the smaller the number of switching endurance times. Therefore, in consideration of the design life of the device, it is necessary to suppress the switching current to a certain safe value or less based on the predetermined number of times of endurance and the characteristics of the relay. For this purpose, it is necessary to balance the voltages of the batteries BT1 and BT2 and eliminate the potential difference and then parallelize the voltages before the parallel connection.

Here, in the prior art disclosed in Patent Document 1 (Japanese Patent No. 5611400), a current is caused to flow between two battery units through a path provided with a resistance, so that a loss due to the resistance occurs. In addition, since the current can be suppressed by the resistance, there is a problem that it takes time for balancing. Further, the method of adjusting a battery pack disclosed in Japanese Patent Laid-Open No. 2005-151679 also applies a current between modules via a resistor, and has the same problem as that of the technology of Patent Document 1. Therefore, in the present embodiment, the potential difference between the storage modules is balanced in a short time while avoiding the occurrence of loss and the decrease in the life of the contact.

Therefore, 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, the power converter is operated to exchange power between batteries having different terminal voltages. That is, energy is returned between the plurality of batteries by the power converter, and the voltage drop between the terminals and the voltage rise are caused to make the potential difference between the terminals of the plurality of batteries equal to or less than a predetermined threshold. 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, by the voltage balancing process, the contacts of the parallel connection relay can be turned on without generating an excessive inrush current, and hence the reliability and the life of the relay can be improved. In addition, since the current is not supplied through the resistor as in the prior art, the loss can be reduced and the voltages among 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 balancing current is caused to flow between the batteries BT1 and BT2 using the power converter when the paralleling relays RY1 and RY3 are off. FIG. 7 shows that the paralleling relays RY1 and RY3 are turned on. Shows the state after parallel connection. The rush current shown by a long broken line in FIG. 6 and the return current shown by a short broken line in FIG. 7 flow from the high voltage side to the low voltage side.

[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, that each battery was used for different loads before parallel connection, and the like are considered as 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 capacitors Cn (n = 1 to N). The value of N is selected according to the model reproduction level, but is illustrated here as n = 1,2. For the battery BT1, the end of each symbol is denoted as “_1”, and for the battery BT2, the end of each symbol is denoted as “_2”.

For example, it is assumed that open circuit voltage Vo_1 = 410V, Vo_2 = 390V, equivalent series resistance R0_1 = 10 mΩ, and R0_2 = 10 mΩ. If the paralleling relays RY1 and RY3 are turned on as it is, 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.
(410 V-390 V) / (10 mΩ + 10 mΩ) = 1000 A

[Power converter operation]
For example, it is assumed that the voltage of the battery BT1 is higher than the voltage of the battery BT2. The storage system of this embodiment uses a power converter connected to the batteries BT1 and BT2 to return 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 in the battery BT1, and a charge current flows in the battery BT2. In addition to the voltage drop occurring in the series equivalent resistance R0 and the polarization Rn / Cn due to this current, the deviation of the open circuit voltage Vo approaches zero. Therefore, the voltage applied to the parallelization relays RY1 and RY3 decreases.

As described above, in the present embodiment, a current is supplied using the power converter so that the potential difference between the batteries BT1 and BT2 is reduced, and the parallelization relays RY1 and RY3 are turned on in the state where the potential difference is less than the threshold. Thus, the rush current can be suppressed, and the reliability of the relays RY1 and RY3 and the entire storage system 401 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 at the time of closing the paralleling relays RY1 and RY3 may be reduced to the last. This is because the relay reliability is affected by the switching 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, and the power converter can be operated only for a limited short time before and after the on operation. Therefore, an operation of supplying a current larger than the continuous rated current of the power converter for a short time is also possible. Thus, parallelization of the batteries BT1 and BT2 can be completed in a shorter time.

As shown in FIG. 7, even after the parallel connection, the return current flows until the open circuit voltage Vo is balanced. However, as described above, in general, the continuous conduction allowable current of the relay is sufficiently large with respect to the switching current, so 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 have to be dedicated. For example, by using an on-board charger mounted on an electric vehicle, a DC / DC converter for 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 using these power converters, which are continuously used mainly 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 Utilization efficiency can be improved.

Next, parallelization processing and parallel cancellation processing, which are basic operations in the series-parallel switching, will be described with reference to the flowcharts of FIGS. The parallelization processing and the parallel cancellation processing are referred to as defined steps S30 and S40 in the flowcharts of FIGS. 13 and 16. In the following description of the flow chart, the symbol "S" indicates a step.

In the parallelization process shown in FIG. 8, if it is determined that there is a parallel connection request in S31, the process proceeds to S32. In S32, it is determined whether the potential difference between the batteries BT1 and BT2 is equal to or less than a threshold. If the potential difference is equal to or less than the threshold value and it is determined as YES in S32, the process proceeds to S35. If the potential difference exceeds the threshold and it is determined as NO in S32, the process proceeds to S33. At S33, the control circuit 45 starts the voltage balancing operation by the power converter. This operation is continued until it is determined in S34 that the potential difference is less than or equal to the threshold. If it is determined in S32 or S34 that the potential difference is equal to or less than the threshold value, the process proceeds to S35, and the control circuit 45 turns on the parallelization relays RY1 and RY3. Then, the control circuit 45 stops the operation of the power converter at S36.

In the parallel release process shown in FIG. 9, when it is determined that there is a parallel release request in S41, the process proceeds to S42. In S42, it is determined whether the relay current flowing through the relays RY1 and RY3 is equal to or less than a threshold. If the relay current is equal to or less than the threshold value and it is determined YES in S42, the process proceeds to S45. If the relay current exceeds the threshold value and it is determined as NO in S42, the process proceeds to S43. At 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 less than or equal to the threshold. If it is determined in S42 or S44 that the relay current is equal to or less than the threshold value, the process proceeds to S45, and the control circuit 45 turns off the parallelization relays RY1 and RY3. Then, the control circuit 45 stops the operation of the power converter in S46.

Here, the meaning of executing the parallel cancellation processing when the parallel connection is canceled 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 parallelization is performed, a return current flows between the batteries BT1 and BT2 until the battery open 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 connecting in series again while the return current is flowing, or when all relays are turned off to stop the system, if relays RY1 and RY3 are shut off as they are, the return current will be cut off, and the contacts of relays RY1 and RY3 May reduce the reliability of the Therefore, as it is, it can not cut off immediately.

In order to solve this problem, when the return current is flowing to the relays RY1 and RY3, the return current is made to flow in the power converter before turning off the relays RY1 and RY3, and the current flowing through the relays RY1 and RY3 is below the threshold Shut off in the state of This makes it possible to shut off the relays RY1 and RY3 without waiting for the attenuation of the balancing current even when there is a parallel cancellation request and a reflux current flows between the batteries BT1 and BT2.

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

The on-vehicle 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 AC / DC conversion circuit 21 has an input end connected to the commercial power supply 15 via the AC

power supply connections

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 dual active bridge type is applied, for example. The first DC / DC converter 301 includes a core 331, a primary winding 311 and a secondary winding 321, and a switching circuit 341 on the primary side and a switching circuit 351 on the secondary side. Each one primary winding 311 and one secondary winding 321 are wound around one core 331. The switching

circuits

341, 351 periodically alternate the direction of the current flowing through the

windings

311, 321.

Similarly, the second DC / DC converter 302 includes a core 332, a primary winding 312 and a secondary winding 322, and a switching circuit 342 on the primary side and a switching circuit 352 on the secondary side. Each one primary winding 312 and one secondary winding 322 are wound around one core 332. The switching

circuits

342 and 352 periodically alternate the direction of the current flowing in the

windings

312 and 322. In the first DC / DC converter 301 and the second DC / DC converter 302, the same specifications or the winding ratios of at least 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 side output ports P1 and P2 of the DC /

DC converters

301 and 302, respectively. Then, as indicated by thick arrows, a path from the secondary side of the first DC / DC converter 301 to the primary side, and a path from the primary side to the secondary side of the second DC / DC converter 302 via the common DC bus. , And the power between the batteries BT1 and BT2 is returned.

The vehicle-mounted charger 202 of 2nd Embodiment shown in FIG. 11 contains the AC / DC conversion circuit 21 comprised as PFC, for example, and one multiport DC / DC converter 303 as an internal circuit. The AC / DC conversion circuit 21 has an input end connected to the commercial power supply 15 via the AC

power supply connections

16 and 17. The DC / DC converter 303 is connected to a DC bus which is an 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, for example. The DC / DC converter 303 includes a core 33, a primary winding 31, two

secondary windings

321 and 322, a switching circuit 34 on the primary side, and switching

circuits

351 and 352 on the secondary side. One primary winding 31 and two

secondary windings

321 and 322 are wound around one core 33. The switching

circuits

34, 351, 352 periodically alternate the direction of the current flowing through the

windings

31, 321, 322.

In the voltage balancing process, the batteries BT1 and BT2 are connected to the two secondary side output ports P1 and P2 of the DC / DC converter 303, respectively. Then, as indicated by a thick arrow, power between the batteries BT1 and BT2 is returned along a path passing 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 return path is shortened and the loss is reduced as compared with the on-vehicle charger 201 of the first embodiment. In addition, 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 will be described in which direct current power is charged from the external charger 10 to two batteries BT1 and BT2 connected in series or in parallel. For example, it is assumed that power is supplied to an electric car or a plug-in hybrid car at a charging station. It is required that a DC voltage of, for example, 800 V in the series connection state of the two batteries BT1, BT2 be externally charged in the parallel connection state, for example, 400 V. However, since the charging capability of the external charger 10 is not always sufficient, it is necessary to confirm it before starting the external charging.

A third embodiment will be described with reference to FIGS. 12 to 14. As shown in FIG. 12, a storage system 401 in a vehicle includes a positive electrode terminal 11 and a negative electrode terminal 12 as external charging connection parts. When performing external charging, the external charger 10 is connected to the

external charging connections

11 and 12 via a power line. Also, information on the possible output 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 on-vehicle charger 20. The commercial power supply device 15 is connected to the AC

power connection portions

16 and 17 and can charge the on-vehicle charger 20 of the storage system 401 with an alternating voltage of 100 V or 200 V. Also in this configuration, when the commercial power supply device 15 has the management and communication function of the output capability, the information may be communicated to the control circuit 45 at the time of charging.

The series-parallel selection processing during 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, C. The parallelization process of S30 and the parallel cancellation process of S40 are shown in detail in FIG. 8 and FIG. The external charge 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 etc. and supplying the output current of the external charger 10 based on the command, etc. Details The description is omitted.

First, in S11, the control circuit 45 determines whether the batteries BT1 and BT2 are abnormal based on voltage information from the battery voltage monitoring unit 43, temperature information from the battery temperature monitoring unit 44, and the like. In the case of abnormality, the processing is ended because charging is impossible. However, when one of the batteries BT1 and BT2 is normal and the other is abnormal, the control circuit 45 connects only the normal battery to the charger or load to charge or discharge, for example, by using a matrix-like relay. It is possible to That is, it is also 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, 400 V) in paralleling the batteries. In the case of NO, it is determined that external charging is not possible, and the process is ended. 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 a correction may be added to the value of the sum. 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 serial charging is determined, if the control circuit 45 determines that the current state is the parallel state in S15, the control circuit 45 performs the parallel cancellation process in S40. After the parallel cancellation processing, or when it is determined that the current state is not the parallel state in S15, the control circuit 45 turns on the serialization relay RY2 in S16 and performs the external charge start processing 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 whether the present battery series voltage has reached the maximum voltage of the external charger 10 at S18 during external charging. If the current battery series voltage exceeds the maximum voltage of the external charger 10, S18 is determined to be NO. And after NO determination of S25, it transfers to S30, and the parallel external charge is continued after parallelization processing. In this case, charging can be started in series, and switching to parallel charging can be performed halfway along with the rise in battery voltage. If it is determined that the external charge termination condition is satisfied in S19 after the serial charge is performed, the control circuit 45 performs the parallelization process in S30 and then ends the process.

When the parallel charging is determined, if the control circuit 45 determines that the current state is not the parallel state at S25, the control circuit 45 performs the parallelization process at S30. After the parallelization processing, or when it is determined that the current state is not the parallel state at S25, the control circuit 45 performs the external charge start processing at S50. The step of monitoring that the current battery parallel voltage has not reached the maximum voltage of the external charger 10 during the external charging in parallel is omitted. In addition, if the current battery parallel voltage exceeds the maximum voltage of the external charger 10 by performing the same steps as S18, charging with a constant voltage (CV charging) may be continued, or the processing may be terminated due to a charge continuation failure. You may Thereafter, when it is determined in S29 that the external charge termination condition is satisfied, the control circuit 45 terminates the process.

As described above, in the third embodiment, the control circuit 45 switches between serial charging and parallel charging based on the information of the possible output voltage communicated from the external charger 10. If the possible output voltage of the external charger 10 is a level capable of series charging, the control circuit 45 can select the series charging to enable rapid charging. On the other hand, if the possible output voltage of the external charger 10 is insufficient for series charging but parallel charging is possible, the control circuit 45 can meet the external charging request by selecting parallel charging. Therefore, appropriate external charging can be performed according to the condition of the external charger 10.

Fourth Embodiment
Next, a fourth embodiment to which the third embodiment is applied will be described with reference to FIG. 15 and FIG. FIG. 15 shows the relays RY2, RY6 and RY7 of FIG. 12, that is, the state in which the serialization 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.

If the voltage deviation between the batteries BT1 and BT2 is large when the internal resistance of the batteries BT1 and BT2 is large or the current rating of the power converter used for voltage balancing is low, the paralleling relays are turned on in the voltage balancing processing. It takes time to do it. Therefore, in the fourth embodiment, during external charging in series by the external charger 10, voltage balancing processing between the batteries BT1 and BT2 by the power converter in the vehicle is performed in parallel. In the example of the storage system 401 shown in FIG. 15, the on-vehicle charger 20 is used as a power converter.

The voltage balancing process during external charging according to the fourth embodiment is shown in the flowchart of FIG. Steps in FIG. 16 other than step S17 are substantially the same as in FIG. 13 and FIG. Moreover, description is abbreviate | omitted about S11, S13, S18 in FIG. If it is determined as YES in S14 that DC charging is determined and external charging is started in S50 after the serialization relay of S16 is turned on, then in S17, voltage balancing operation by the power converter is started. Thereafter, when it is determined in S19 that the external charge termination condition is satisfied, the control circuit 45 performs the parallelization process of S30 and then terminates the process.

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

Fifth Embodiment
In the fifth and sixth embodiments, a power converter other than the on-vehicle charger 20 is used for the voltage balancing process, as compared with the above embodiment. The fifth embodiment will be described with reference to FIGS. 17 and 18. In the storage system 405 of the fifth embodiment, the auxiliary battery DC / DC converter 50 is used as a power converter for voltage balancing processing. The auxiliary battery DC / DC converter 50 steps down the high voltage of the batteries BT1 and BT2 to a low voltage such as 12 V or 48 V and supplies it to the auxiliary battery 55. The output terminal on the accessory battery 55 side of the accessory battery DC / DC converter 50 “One or more connected to a target other than the storage module other than the plurality of input / output terminals connected to the plurality of storage modules Corresponds to the input / output end of

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

As shown in FIG. 18, the auxiliary battery DC / DC converter 50 has a configuration of a multiport DC / DC converter 303 similar to that of the second embodiment, for example. Power is returned between the secondary winding 341 connected to the battery BT1 and the secondary winding 342 connected to the battery BT2. The auxiliary battery DC / DC converter 50 may have a configuration in which a plurality of DC /

DC converters

301 and 302 are arranged in parallel, as in the first embodiment.

Here, the auxiliary battery 55 is different from the batteries BT1 and BT2 and corresponds to a storage module whose serial-parallel connection can not be switched, that is, "another storage module to which serial connection or parallel connection is fixed". The auxiliary battery DC / DC converter 50 has an auxiliary battery whose one end opposite to the input / output terminal connected to the batteries BT1 and BT2 is "another storage module in which serial connection or parallel connection is fixed". Connected to 55. Thus, the voltage balancing process can be performed by effectively utilizing the on-vehicle device.

Sixth Embodiment
A sixth embodiment will be described with reference to FIGS. 19 and 20. In the storage system 406 of the sixth embodiment, a plurality of

inverters

61 and 62 of the electric air conditioning compressor 60 is used as a power converter for voltage balancing processing. The

inverters

61 and 62 convert direct current power of the batteries BT1 and BT2 into, for example, three-phase alternating current power, and supply them to the plurality of winding

sets

63 and 64 of the alternating current motor 65. The AC output terminals of the

inverters

61 and 62 correspond to “one or more input / output terminals connected to a target other than the plurality of storage modules connected to a target other than the plurality of storage modules”.

As shown in FIG. 19, the batteries BT1 and BT2 are connected to input / output ports P1 and P2 of the electric air-conditioner compressor 60, that is, input ends of the

inverters

61 and 62. As indicated by the broken line G, the negative connection destination of the balanced current path may be the load 80 side, and the relay may be shared. Further, the relay 68 for opening and closing the path between the batteries BT1 and BT2 and the electric air conditioner compressor 60 may not be provided. The open / close patterns of the relays RY1-RY7 during charging and discharging are the same as in the first and second embodiments. The on-vehicle charger 20 is treated as a type 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 to generate a single mechanical output by energizing each of the winding

sets

63, 64. 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, respectively. One battery BT1 is connected to the input end of a first inverter 61 for supplying power to the first winding set 63. The other battery BT2 is connected to the input end of a 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 causes the first inverter 61 to perform a powering operation and controls the phase so as to cause the second inverter 61 to perform a regenerative operation. Therefore, the first inverter 61 consumes the power of the battery BT1, supplies energy to the AC motor 65, and performs a power running operation to generate torque on the output shaft. The second inverter 62 performs a regenerative operation so as to return the energy of the back electromotive force due to the rotation of the output shaft of the AC motor 65 to the battery BT2.

Thus, the return of power is realized between the two

inverters

61 and 62. As described above, in the sixth embodiment, the voltage balancing process can be performed by effectively using the electric air conditioning compressor 60 already installed in the vehicle.

Note that the configuration in which one of the plurality of inverters is in a powering operation and the other is in a regenerative operation to return electric power is not limited to the configuration of an AC motor that generates a single mechanical output as described above. For example, the mechanical output generated by the power running operation of one of the inverters may be converted into a gas pressure, and the mechanical input in which the gas pressure is reconverted may cause the other inverter to perform a regenerative operation.

Seventh Embodiment
A seventh embodiment will now be described with reference to FIG. The storage system 407 of the seventh embodiment uses the on-vehicle charger 20 as a power converter to switch between series-parallel connection of three batteries BT1, BT2, and BT3. A battery BT3 and relays RY8 to RY10 are added to the storage system 401 of FIG. Similar to the storage system 401, the negative connection destination of the balancing current path may be the load 80 side, and the relay may be shared. Further, the relay 28 for opening and closing the path between the batteries BT1 and BT2 and the on-vehicle charger 20 may not be provided.

With regard to the relay open / close pattern, the relays RY2, RY9, RY6, RY7 are turned on during three-series charging. During three parallel charging, the relays RY1, RY3, RY8, RY10, RY6, RY7 are turned on. During three parallel discharges, the relays RY1, RY3, RY8, RY10, RY4, RY5 are turned on.

As described above, also in the storage system including three or more storage modules, the same operation and effect can be obtained by the voltage balancing process similar to that of the above embodiment. Here, in the voltage balancing process of the plurality of storage modules, basically, it is assumed that the plurality of storage modules are simultaneously connected to the power converter.

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

(Other embodiments)
The control circuit 45 is not limited to feedback control of the power converter based on the voltage detection value detected by the battery voltage monitoring unit 43. For example, the power converter is feed-forwarded from the initial voltage at the start of operation and the operation time. You may control. Also, the power converter may be controlled based on a voltage estimated value estimated from other parameters, instead of using the detected value of the battery voltage.

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

The storage system of the present disclosure is not limited to one mounted on an electric vehicle or a plug-in hybrid vehicle, and can be applied to any system capable of switching the connection state of multiple storage modules in series and parallel. As described above, the storage module is not limited to the battery module, and a capacitor or the like may be used. Further, for example, when used other than the electric vehicle, there is not necessarily an apparatus that can be used as a power converter for the voltage balancing process, so a power converter dedicated to the voltage balancing process may be installed.

As mentioned above, this indication is not limited at all to the above-mentioned embodiment, and can be carried out in various forms in the range which does not deviate from the meaning.

The present disclosure has been described in accordance with the embodiments. However, the present disclosure is not limited to the embodiments and structures. The present disclosure also includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, and further, other combinations and forms including one element or more, or less or less, are also within the scope and the scope of the present disclosure.

Claims

A plurality of storage modules (BT1, BT2, BT3) each including one or more storage cells;
A series / parallel switch (RY1-RY10) capable of switching the connection states of the plurality of storage modules in series and in parallel;
A power converter (201, 202, 50, 61, 62) for transferring power between any two or more of the plurality of storage modules;
A control circuit (45) for controlling the series-parallel switch and the power converter;
Equipped with
The control circuit performs, prior to parallel switching of the plurality of storage modules, a voltage balancing process for operating the power converter such that a potential difference between the plurality of storage modules is equal to or less than a predetermined threshold value. A storage system that switches between series and parallel switches.
The power storage device according to claim 1, further comprising: at least one input / output terminal connected to an object other than the storage module in addition to the plurality of input / output terminals connected to the plurality of storage modules. system.
The power converter (201)
A plurality of DC / DC converters (301, 302) each having an input / output port connected to each of the plurality of storage modules at one end, and capable of bi-directionally supplying power between the input / output ports Storage system as described.
The power converter (202, 50)
It has a transformer in which one primary winding (31) and a plurality of secondary windings (321, 322) to which the plurality of storage modules are respectively connected are wound around one core (33), The storage system according to claim 2, further comprising a DC / DC converter (303) capable of bi-directionally supplying power between input and output ports of the plurality of secondary windings.
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 from the AC / DC conversion circuit. It is a charger (201, 202) that can charge the module,
The one end on the opposite side to the input / output terminal connected to the said electrical storage module in one or more said DC / DC converters is connected to DC bus which is an output of said AC / DC conversion circuit. Storage system as described.
In the power converter (50), one end opposite to the input / output terminal connected to the storage module in one or more of the DC / DC converters is connected in series or in parallel, which is different from the storage module The storage system according to claim 3 or 4, wherein the storage module is connected to another storage module fixed.
The power converter is constituted by a plurality of inverters (61, 62) which convert the input DC power into AC power and outputs the AC power to a load (65).
The storage modules are connected to the input ends of the corresponding inverters, respectively.
Among the plurality of inverters, a part of the plurality of inverters consumes DC power of the connected storage modules and performs a powering operation to supply energy to the load;
The storage system according to claim 2, wherein among the plurality of inverters, the inverter performs a regenerative operation so as to return the energy of the load to the connected storage module.
The common load of the plurality of inverters is an AC motor (65) that generates a single mechanical output by energizing the plurality of winding sets (63, 64), and the output ends of the respective inverters are mutually connected The storage system according to claim 7, wherein the storage system is connected to different winding sets.
It further comprises external charging connections (11, 12) connected to an external charger (10) capable of charging the storage module with DC power,
The control circuit determines serial or parallel switching of the storage module based on information of an outputtable voltage of the external charger communicated from the external charger when there is an external charging request by the external charger. A storage system according to any one of claims 1 to 8.
It further comprises external charging connections (11, 12) connected to an external charger (10) capable of charging the storage module with DC power,
The storage system according to any one of claims 1 to 9, wherein the control circuit performs the voltage balancing process during external charging in a state in which a plurality of storage modules are connected in series.
And a module voltage monitoring unit (43) for monitoring the voltage of the storage module.
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.
It further comprises an abnormality detection unit (43, 44) that detects an abnormality of the storage module,
When an abnormality of the storage module is detected by the abnormality detection unit,
The storage system according to any one of claims 1 to 11, wherein the control circuit shuts off the connection between the storage module in which an abnormality is detected and a charger, a load, or the power converter.