CN111264013A

CN111264013A - Electricity storage system

Info

Publication number: CN111264013A
Application number: CN201880069394.2A
Authority: CN
Inventors: 木口拓也; 山口宜久; 间崎耕司; 高桥将也; 瀧田晋平
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2017-10-27
Filing date: 2018-10-18
Publication date: 2020-06-09
Also published as: JP7009915B2; WO2019082778A1; JP2019080474A

Abstract

Batteries (BT1, BT2) as a plurality of power storage modules each including one or more power storage units can be connected to at least one of the chargers (10, 20) or the load (80). The relays (RY1-RY9) can switch the connection states of the batteries (BT1, BT2) to be in series and parallel. A control circuit (45) controls at least one of the chargers (10, 20) or the load (80) to which the battery is connected, and the relay (RY1-RY 9). The control circuit (45) performs a voltage equalization process in which at least one battery is charged and discharged with at least one of the chargers (10, 20) or the loads (80) before parallel switching of the batteries (BT1, BT2) so that a potential difference between the batteries (BT1, BT2) is equal to or less than a predetermined threshold value.

Description

Electricity storage system

Citation of related applications

The present application is based on the application of japanese patent application No. 2017-207926, which was filed on 27/10/2017, the contents of which are incorporated herein by reference.

Technical Field

The present invention relates to an electrical storage system.

Background

Conventionally, a power storage system capable of switching a plurality of power storage modules between series connection and parallel connection is known. For example, an industrial machine battery system disclosed in patent document 1 aims to enable rapid charging at a high voltage and to use a low-voltage system. The system comprises: a charge-discharge switching mechanism for alternatively switching a connection state of the battery unit with the charge input unit or the electric load; and a parallel/series switching mechanism for alternatively switching the electrical connection between the plurality of battery cells to be parallel or series, and the like.

In the discharge control flow of this system, discharge from the plurality of battery cells to the power load is performed in a state where the plurality of battery cells are connected in parallel. In the charge control routine, the plurality of battery cells are charged from the rapid charger via the charge input unit in a state where the plurality of battery cells are connected in series. After the charging is completed, when the voltage difference between the plurality of battery cells is equal to or greater than the threshold value, voltage cell balancing processing for eliminating the voltage difference is performed.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5611400

Disclosure of Invention

In the voltage cell balancing process of patent document 1, since a current flows between the two battery cells through a path provided with a resistor, a loss due to the resistor occurs. In addition, since the resistance suppresses the current, it takes time to balance. In the system of patent document 1, it is estimated that the time required for balancing is not a problem because the system is in a standby state after the inter-voltage-cell balancing process is completed.

Hereinafter, in the present specification, the term "power storage module" is used as a generic term including the battery cell of patent document 1. When the technique of patent document 1 is applied to external charging of an electric vehicle or a plug-in hybrid vehicle, it is assumed that after the series charging is completed, a plurality of power storage modules are switched to be connected in parallel, and the vehicle travels by discharging the power to a main machine motor as a load. If, for example, a relay is operated to switch connection in a state where the potential difference between a plurality of power storage modules is large, the life of the relay may be reduced by an arc at a contact or a short-circuit current.

The invention aims to provide an electric storage system which can avoid the generation of loss and the reduction of the service life of a contact when a plurality of electric storage modules are switched from series connection to parallel connection and can equalize the voltages of the plurality of electric storage modules.

An electrical storage system of the present invention includes a plurality of electrical storage modules, a series-parallel switch, and a control circuit. Each power storage module includes one or more power storage cells and is connectable to at least one of a charger and a load. The series-parallel switch is capable of switching the connection state of the plurality of power storage modules between series connection and parallel connection. The control circuit controls at least one of a charger and a load to which the power storage module is connected, and the series-parallel switch.

The control circuit performs "voltage equalization processing" for performing charge and discharge between one or more power storage modules and at least one of a charger and a load so that a potential difference between the plurality of power storage modules becomes equal to or less than a predetermined threshold value before switching the plurality of power storage modules in parallel, and then switches the series-parallel switch to parallel.

In the present invention, the voltage of the power storage modules is equalized by performing charge and discharge between one or more power storage modules and at least one of the charger and the load. As a result, the inrush current can be suppressed when the contacts of the series-parallel switch such as a relay are connected, and therefore, the reliability and the lifetime of the series-parallel switch can be improved. Further, the loss can be reduced as compared with the conventional technique in which current flows between the power storage modules via the resistor.

The modes of charge and discharge in the voltage equalization process are classified into the following three types.

(1) Discharging from the electrical storage module having a relatively high voltage to the load.

(2) The power storage module having a relatively low voltage is charged from the charger.

(3) A combination of discharging from the power storage module with a relatively high voltage to the load and charging from the charger to the power storage module with a relatively low voltage.

For example, in a power storage system mounted on an electrically powered vehicle such as an electric vehicle or a plug-in hybrid vehicle, a main battery corresponds to a power storage module. In this case, the charger includes: an external charger that externally charges the electric storage module with direct-current power; and an in-vehicle charger that converts alternating-current power supplied from an external AC power supply into direct-current power and charges the power storage module. The load includes a motor as a power source of the vehicle, and an inverter that converts dc power into ac power and supplies the ac power to the motor. The load includes an air conditioner for cooling and heating a vehicle interior, a DC/DC converter for supplying electric power to an auxiliary battery, and the like.

Drawings

The above objects, other objects, features and advantages of the present invention will become more apparent with reference to the accompanying drawings and the following detailed description. The drawings are as follows.

Fig. 1 is a configuration diagram of a power storage system including each embodiment.

Fig. 2 is a configuration diagram showing a battery voltage monitoring structure of the power storage module.

Fig. 3 is a diagram showing a relationship between a charging infrastructure and a load driving voltage.

Fig. 4 is a diagram illustrating a phenomenon when switching from series connection to parallel connection.

Fig. 5 is a diagram showing an example of characteristics of the relay contact life with respect to the current at the time of opening and closing.

Fig. 6 is a configuration diagram of the power storage system of the first embodiment.

Fig. 7 is a timing chart showing the change in the battery voltage according to the first embodiment.

Fig. 8 is a flowchart of a discharge process for the inverter and the motor according to the first embodiment.

Fig. 9 is a timing chart showing changes in battery voltage when the amount of power consumption of the motor is large in the first embodiment.

Fig. 10 is a configuration diagram of the power storage system according to the second embodiment.

Fig. 11 is a timing chart showing a change in battery voltage according to the second embodiment.

Fig. 12 is a flowchart of the charging process according to the second embodiment.

Fig. 13 is a timing chart showing a change in battery voltage according to a modification of the second embodiment.

Fig. 14 is a flowchart of the parallel switching process performed after the end of traveling with the series-connected batteries according to the modified example of the second embodiment.

Fig. 15 is a configuration diagram of a power storage system according to a third embodiment.

Fig. 16 is a flowchart of the discharge process to the air conditioner according to the third embodiment.

Fig. 17 is a configuration diagram of a power storage system according to a fourth embodiment.

Fig. 18 is a timing chart showing a change in battery voltage according to the fourth embodiment.

Fig. 19 is a flowchart of the discharging and charging process according to the fourth embodiment.

Detailed Description

Hereinafter, an embodiment of a power storage system including a plurality of power storage modules will be described with reference to the drawings. In the following, substantially the same components in the embodiments are denoted by the same reference numerals, and the description thereof is omitted. The first to fourth 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 serving as a vehicle power source in an electric vehicle or a plug-in hybrid vehicle is assumed. In other embodiments, a capacitor or the like may be used as the power storage module.

The plurality of power storage modules are configured to be connected in series and in parallel by a series-parallel switch. The series-parallel switch is typically a relay composed of a mechanical relay or a semiconductor switch. In the power storage system according to the present embodiment, the plurality of power storage modules may be connected to at least one of a load and a charger. The power storage system according to the present embodiment includes a control circuit that controls at least one of a charger and a load to which the power storage module is connected, and the series/parallel switch.

First, referring to fig. 1, a configuration including a power storage system 400 according to each embodiment will be described. The electric storage system 400 includes two batteries BT1, BT2 as "a plurality of electric storage modules", relays RY1-RY9 as "series-parallel switches", and a control circuit 45. Here, the module section including the two batteries BT1, BT2 and relay RY2 is a common part of all the embodiments. The module portion can be connected to at least one of the load 80 and the

chargers

10 and 20. The following embodiments are different in the configuration in which the module portion can be connected only to the load 80, the

charger

10, 20, or both the load 80 and the

charger

10, 20.

The batteries BT1 and BT2 are high-voltage battery modules such as lithium ion batteries that can be charged and discharged, for example, at 400V. Hereinafter, the "battery module" is omitted and referred to as a "battery". In this specification, basically "battery" is used in the meaning of high voltage battery, except to refer to a low voltage (e.g. 12V) auxiliary equipment battery.

As the load 80 generally used in an electric vehicle or a plug-in hybrid vehicle, a combination of a main machine motor as a power source and an inverter that converts dc power into ac power and supplies the ac power to the main machine motor is first mentioned. In the present specification, a "motor" refers to a main machine motor of a vehicle, without referring to a motor other than the main machine motor. Further, the load 80 used in the vehicle includes an air conditioner for cooling and heating a vehicle interior, a DC/DC converter for boosting and stepping down a DC voltage of the batteries BT1 and BT2 and supplying electric power to an auxiliary battery or the like. In accordance with the applied load 80, information such as a travel request, accelerator information, a request for cooling and heating, an air-conditioning set temperature, and a vehicle interior temperature is input to the control circuit 45.

The charger includes an external charger 10 and an in-vehicle charger 20. An external charger 10 provided at a charging station or the like is connected to the vehicle via a power supply cable, and charges dc power to the batteries BT1, BT 2. In the case of using an external charger supporting 800V, the series charging is performed in a state where two batteries BT1, BT2 are connected in series. On the other hand, when an external charger supporting 400V is used, parallel charging is performed in a state where the two batteries BT1 and BT2 are connected in parallel. The in-vehicle charger 20 is mounted in the vehicle, converts AC power supplied from an external AC power supply 15 into dc power, and charges the batteries BT1 and BT 2.

Relay RY2 opens and closes a path between the positive electrode of battery BT1 and the negative electrode of battery BT 2. Relays RY4, RY1 open and close paths between the positive electrodes of batteries BT1, BT2 and load 80, respectively. Relays RY5, RY3 open and close paths between the negative electrodes of batteries BT1, BT2 and load 80, respectively. Relays RY6, RY8 open and close paths between the positive electrodes of batteries BT1, BT2 and

chargers

10, 20, respectively. Relays RY7, RY9 open and close paths between the negative electrodes of batteries BT1, BT2 and

chargers

10, 20, respectively.

The control circuit 45 controls the opening and closing of the relays RY1-RY 9. In the following description of the relay opening/closing mode, when "one relay is on" of RY1-RY9, "the other relays are off". When electric discharge is made from the two batteries BT1, BT2 connected in series to the load 80, the relays RY2, RY1, RY5 are turned on. When the batteries BT1, BT2 are charged from the two

chargers

10, 20 connected in series, the relays RY2, RY8, RY7 are turned on. When electric discharge is made from the two batteries BT1, BT2 connected in parallel to the load 80, the relays RY1, RY3, RY4, RY5 are turned on. When the batteries BT1, BT2 are charged from the two

chargers

10, 20 connected in parallel, the relays RY6, RY7, RY8, RY9 are turned on.

Next, a supplementary description will be given of a configuration related to information input of the control circuit 45 common to the respective embodiments, with reference to fig. 2. The control circuit 45 acquires information of a battery voltage deviation (hereinafter also referred to as "potential difference") Δ Vb (═ 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 section 43. The battery voltage monitoring unit 43 corresponds to a "module voltage monitoring unit". The control circuit 45 controls charging and discharging between the batteries BT1, BT2 and the load 80 or the

chargers

10, 20 based on the voltage detection value detected by the battery voltage monitoring section 43, that is, by feeding back the current voltage deviation.

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 Δ Vb that is an absolute value of the difference. Alternatively, the battery voltage monitoring unit 43 may detect the voltage across the relays RY8, RY6 (or relays RY1, RY4) as the potential difference Δ Vb by the voltage sensor 73.

When the voltage of each of the batteries BT1 and BT2 is out of the normal range, the battery voltage monitoring unit 43 detects an abnormality and transmits the abnormality to the control circuit 45. Further, a battery temperature monitoring unit 44 may be provided, and the battery temperature monitoring unit 44 may detect a temperature abnormality based on the temperatures Tb1 and Tb2 of the batteries BT1 and BT2 and transmit the temperature abnormality to the control circuit 45. The control circuit 45 disconnects the battery, in which the abnormality is detected, from the load 80 or the

chargers

10 and 20. That is, the battery voltage monitoring unit 43 and the battery temperature monitoring unit 44 function as "abnormality detection units".

Next, before shifting to the description of the specific configuration and operation and effects of each embodiment, the background of the present embodiment will be described with reference to fig. 3 to 5. Fig. 3 shows a relationship between a charging infrastructure for a power storage module and a load drive voltage. Here, it is assumed that the voltage of the power storage module is normally in the order of 400V. Further, it is assumed that there are two types of charging infrastructure such as a charging station corresponding to a 400V class and a 800V class, and there are two types of loads driven by a 400V class and a 800V class as loads to be used. There is no problem in the case where the power storage module that drives the load in the 400V class is charged using the charging infrastructure in the 400V class, or in the case where the power storage module that drives the load in the 800V class is charged using the charging infrastructure in the 800V class.

On the other hand, a case where the power storage module is charged by a charging infrastructure having a voltage different from the load driving voltage is considered. Therefore, when two power storage modules that drive a load of 400V class are connected in series during charging, charging can be performed using a charging infrastructure of 800V class. When the load is driven, that is, discharged, the parallel connection is switched, and the device can be used at 400V. On the contrary, if the power storage modules charged by the 400V class charging infrastructure in the parallel connection state are switched to two series connections during load driving, the power storage modules can be used at 800V class. By switching the connection state of the plurality of power storage modules between series connection and parallel connection in this manner, it is possible to support a large number of charging infrastructures

Specifically, it is predicted that vehicle devices and charging infrastructures such as main machine motors and auxiliary devices of electric vehicles and plug-in hybrid vehicles will shift from the current 400V class to the 800V class in the future in order to shorten the charging time and the like. Thus, particularly in the transition period of the transition, a situation may occur in which the vehicle specifications do not match the specifications of the charging infrastructure. Therefore, it is required to be able to switch between series and parallel connection of the battery modules during charging and load driving, that is, during driving when the main unit motor is driven. Therefore, the circuit is inevitably provided with a series-parallel switch such as a relay including a mechanical relay or a semiconductor switch.

Referring to fig. 4, a situation is assumed in which a potential difference occurs between the two batteries BT1, BT2 due to variations in internal resistance and the like. When the voltage when the two batteries BT1, 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%. In addition, the arrow of the thick line indicates that the voltage is higher than that of the arrow of the thin line. When the relay is turned on after dc charging by an external charger and the batteries are switched to the parallel connection, a short-circuit current flows due to a potential difference between the batteries BT1 and BT2, and an arc is generated at the relay contact.

Fig. 5 shows a relationship between the current at the time of opening and closing of the relay and the number of times of opening and closing durability, in other words, the life of the relay contact. The horizontal and vertical axes are logarithmic scales. As is clear from fig. 5, the larger the current during opening and closing, the smaller the number of times of opening and closing endurance. Therefore, in consideration of the design life of the device, it is necessary to suppress the current at the time of opening and closing to a certain safe value or less in accordance with the predetermined number of times of durability and the characteristics of the relay. Therefore, it is necessary to equalize the voltages of the batteries BT1 and BT2 before parallel connection, and to perform parallel connection after eliminating the potential difference.

Here, in the conventional technique disclosed in patent document 1 (japanese patent No. 5611400), since a current flows between the two battery cells through a path provided with a resistor, a loss is caused by the resistor. Further, since the current is suppressed by the resistance, there is a problem that it takes time to equalize. In addition, the method of adjusting the battery pack disclosed in japanese patent application laid-open No. 2005-151669 also causes a current to flow between the modules via the resistors, and has the same problem as the technique of patent document 1. Therefore, the present embodiment equalizes the potential difference between the power storage modules in a short time while avoiding the occurrence of loss and the reduction in the life of the contacts.

Therefore, in the present embodiment, a plurality of batteries connected in parallel, for example, in the example of fig. 1, the battery BT1 and the battery BT2 can be connected to the load 80 or the

chargers

10, 20. Before switching from series connection to parallel connection, charging and discharging are performed between one or more batteries and at least one of load 80 and

chargers

10 and 20, so that the potential difference between batteries BT1 and BT2 becomes equal to or less than a predetermined threshold value. Then, the parallel connection relay is turned on in a state where the potential difference is equal to or less than the threshold value. Hereinafter, this process of the present embodiment is referred to as a "voltage equalization process".

In the present embodiment, the voltage equalization process allows the contacts of the parallel connection relay to be closed without generating an excessive inrush current, and the reliability and the life of the relay can be improved. Further, since the current does not flow through the resistor as in the conventional technique, the loss can be reduced, and the voltage can be equalized between the plurality of cells in a short time. Here, in the voltage equalization process, it is not necessary to charge and discharge until the battery voltages Vb1 and Vb2 are exactly equal, and it is sufficient to reduce the inrush current when the parallel relay is closed. This is because the influence of the current on the reliability of the relay during opening and closing is dominant over the allowable current during continuous energization of the relay.

(first embodiment)

Next, a specific configuration and operational effects of the voltage equalization process according to each embodiment will be described. The first embodiment will be described with reference to fig. 6 to 9. As shown in fig. 6, a power storage system 401 according to the first embodiment is configured such that a module unit can be connected to an inverter 81 and a motor 82 as a load 80 in the power storage system 400 of fig. 1. That is, at least in the stage of the parallel connection process, the module unit may not be connected to the

chargers

10 and 20. The control circuit 45 acquires, for example, the presence or absence of a travel request, accelerator information, and the like from the vehicle control circuit.

In the first embodiment, when the battery voltages Vb1 and Vb2 are unbalanced, the voltage equalization process is performed by discharging the battery with a relatively high voltage to the inverter 81 and driving the electric motor 82 to run the vehicle before the parallel switching.

In fig. 7, at the start of the process t0, the first battery voltage Vb1 is higher than the second battery voltage Vb 2. Therefore, the control circuit 45 discharges the first battery BT1 to the inverter 81, drives the motor 82, and starts the running of the vehicle. At this time, the power is discharged from a battery BT1Electrically, therefore, the decrease gradient of the first battery voltage Vb1 is relatively large. Then, at the time of equalization t when the potential difference is equal to or less than threshold value Δ Vth_BLThe control circuit 45 turns on the parallel relay. Thereafter, the electric power is discharged from the two batteries BT1 and BT2 to the inverter 81, and the motor 82 is driven to continue the running of the vehicle. Since the batteries BT1 and BT2 discharge about half of each other, the gradient of decrease in the battery voltages Vb1 and Vb2 is small. While being connected in parallel, the battery voltages Vb1, Vb2 converge to their intermediate values and thereafter shift by the same value. The same applies to the following timing chart.

Fig. 8 is a flowchart showing the parallelization process according to the first embodiment. In the following description of the flowcharts, the reference numeral "S" denotes a step. Steps substantially the same as those in the above embodiments are assigned the same step numbers, and a part of the description is omitted.

The first "1" and "6" of the two-digit step number indicate a step group common to the parallel processing in each embodiment, and the first "7", "8", and "9" indicate step groups unique to the parallel processing in each embodiment. Specifically, "7" indicates discharging to the load, "8" indicates charging from the charger, and "9" indicates a combination of discharging to the load and charging from the charger. Therefore, for example, a step with the first bit "6" may be continued after a step with the first bit "7". In the step with the first digit "7", the end of the step specific to the first embodiment in which the inverter 81 and the motor 82 are used as the load is denoted by "a".

First, in S11, control circuit 45 determines whether or not batteries BT1 and BT2 are abnormal based on the voltage information from battery voltage monitoring unit 43, the temperature information from battery temperature monitoring unit 44, and the like. In the case of an abnormality, the control circuit 45 disconnects the abnormal battery from the load 80 in S71, and ends the processing. When there is no abnormality in the batteries BT1 and BT2, the control circuit 45 determines in S72A whether or not there is a travel request, that is, whether or not there is a drive request for the inverter 81 and the motor 82. If yes in S72A, the process proceeds to S62. That is, the voltage equalization process according to the first embodiment is executed on the assumption that there is a travel request of the vehicle.

At S62, it is determined whether or not the potential difference between batteries BT1 and BT2 is equal to or less than a threshold value. When the potential difference is equal to or less than the threshold value and the determination in S62 is yes, the process proceeds to S63, and the control circuit 45 turns on the parallel relays RY1, RY3, RY4, and RY 5. When the potential difference exceeds the threshold value and it is determined as "no" in S62, it is determined in S64 which of the first battery voltage Vb1 and the second battery voltage Vb2 is higher.

When the first battery voltage Vb1 is higher than the second battery voltage Vb2 and it is determined as yes in S64, the control circuit 45 turns on the relays RY4, RY5 in S73 and connects the first battery BT1 to the load 80. When the second battery voltage Vb2 is higher than the first battery voltage Vb1 and determined as no in S64, the control circuit 45 turns on the relays RY1, RY3 in S74 and connects the second battery BT2 to the load 80. In S75A, the vehicle runs on the battery connected to load 80. This running state is continued until it is determined at S65 that the potential difference is equal to or less than the threshold value. The above steps from S64 to S65 correspond to the voltage equalization process.

When it is determined at S65 that the potential difference is equal to or less than the threshold, the process proceeds to S66, and the control circuit 45 turns on the battery-side relay not connected at S73 or S74 among the parallel relays. In S63 or S66, the parallel relay is turned on, and the parallel processing is completed. In S78A, the vehicle runs using two batteries BT1, BT2 connected in parallel.

In the first embodiment, when the potential difference between the batteries BT1 and BT2 exceeds the threshold value at the start of the process, the voltage equalization process is performed while the vehicle is running. Therefore, it is not necessary to wait for the end of the processing in a state of parking, and therefore, the convenience of the driver is improved.

Further, as shown in fig. 9, the control circuit 45 increases the amount of discharge from the first battery BT1 as the amount of power consumption of the electric motor 82 estimated from the accelerator information and the like increases compared to the normal running time at the time of acceleration or climbing of the vehicle. This increases the voltage drop gradient, and the discharge amount becomes larger than t at the time of equilibrium in the normal case_{BL_n}Early arrival at equilibrium t_{BL_q}. That is, the control circuit 45 can shorten the time of the voltage equalization process by increasing the discharge amount. As a result, since high-speed switching is required, semiconductor switches are preferably used as the relays RY1, RY3, RY4, RY 5.

(second embodiment)

A second embodiment will be described with reference to fig. 10 to 12. As shown in fig. 10, a power storage system 402 according to the second embodiment is configured such that a module unit can be connected to an external charger 10 or an in-vehicle charger 20 in the power storage system 400 of fig. 1. That is, at least in the stage of the parallel connection process, the module unit may not be connected to the load 80.

In the second embodiment, when the battery voltages Vb1, Vb2 are unbalanced after the series charging is completed, the

battery chargers

10, 20 charge the battery having a relatively low voltage before the parallel switching, thereby performing the voltage equalization process.

In fig. 11, at the time t0 when the processing after the end of the series charging is started, the first battery voltage Vb1 is higher than the second battery voltage Vb 2. Therefore, the control circuit 45 operates the

chargers

10 and 20 to charge the second battery BT2, thereby increasing the second battery voltage Vb 2. Then, at the time of equalization t when the potential difference is equal to or less than threshold value Δ Vth_BLThe control circuit 45 turns on the parallel relay. After the voltage equalization, the operation of the

chargers

10 and 20 is stopped, and therefore, the battery voltages Vb1 and Vb2 become constant.

In fact, if a situation after series charging using the external charger 10 is assumed, it is considered that the possibility of charging by voltage equalization processing directly using the external charger 10 is high. However, when the external charger 10 and the AC power supply 15 are provided at the same time in the charging station, the AC power supply 15 may be reconnected to the in-vehicle charger 20, and the voltage equalization process may be performed using the in-vehicle charger 20. Therefore, the voltage equalization process can be performed using the external charger 10 or the in-vehicle charger 20, and will be described as "

chargers

10 and 20".

Fig. 12 is a flowchart showing a parallelization process according to the second embodiment. First, the control circuit 45 determines whether or not the batteries BT1 and BT2 are abnormal, and if abnormal, disconnects the abnormal battery from the

chargers

10 and 20 in S81, and ends the process. When there is no abnormality in the batteries BT1 and BT2, the control circuit 45 determines whether or not the series charging is completed in S61. When the series charging is completed, the control circuit 45 further determines whether or not there is a travel request in S72A. If no in S72A, the process proceeds to S62. That is, the voltage equalization process according to the second embodiment is executed on the premise that the series charging is completed and there is no travel request from the vehicle.

S62, S63, S64 are the same as in the first embodiment. When the first battery voltage Vb1 is higher than the second battery voltage Vb2 and it is determined as yes in S64, the control circuit 45 turns on the relays RY8, RY9 in S83 and connects the second battery BT2 to the

chargers

10, 20. When the second battery voltage Vb2 is higher than the first battery voltage Vb1 and is determined as no in S64, the control circuit 45 turns on the relays RY6, RY7 in S84 and connects the first battery BT1 to the

chargers

10, 20. In S85, the charger operation is started for the battery connected to the

charger

10 or 20. This charger operation is continued until it is determined at S65 that the potential difference is equal to or less than the threshold value. The above steps from S64 to S65 correspond to the voltage equalization process.

When it is determined at S65 that the potential difference is equal to or less than the threshold, the process proceeds to S66, and the control circuit 45 turns on the battery-side relay not connected at S83 or S84 among the parallel relays. This completes the parallel connection process, and enables parallel charging. However, in fig. 12, no further charging is necessary, and the control circuit 45 stops the charger operation in S87.

(modification of the second embodiment)

A modification of the second embodiment will be described with reference to fig. 13 and 14. The configuration of the power storage system 402 of this modification is similar to that of fig. 10, and the batteries BT1 and BT2 are charged in parallel and used in series. Then, a scene is assumed in which after the end of traveling by the series-connected batteries BT1 and BT2, the connection is switched to parallel connection and parallel charging is performed.

In the figureAt time t0 when the processing after the end of the series-connected traveling starts, the first battery voltage Vb1 is higher than the second battery voltage Vb2 in fig. 13. Therefore, the second battery BT2 is charged at the time of equalization t when the potential difference is equal to or less than the threshold value Δ Vth_BLAnd the parallel relay is switched on. So far as it is the same as in fig. 11. Thereafter, in fig. 11, the battery voltages Vb1 and Vb2 are constant, whereas in fig. 13, the battery voltages Vb1 and Vb2 increase simultaneously due to parallel charging.

In the flowchart of fig. 14, with respect to fig. 12, the portion before S62 and the portion after S66 are different, and the middle portion is the same. S11 for battery abnormality determination at this stage and S81 for abnormal state are not taken into consideration. At S82, the control circuit 45 determines whether or not the traveling using the series-connected batteries is completed, and if it is determined to be yes, the process proceeds to S62. When the parallel connection relay is turned on in S63 or S66, the parallel connection process ends, and parallel charging is performed in S88. This enables the batteries BT1 and BT2, which consume electric power due to the series-connected traveling, to be charged in a well-balanced manner.

(third embodiment)

A third embodiment will be described with reference to fig. 15 and 16. As shown in fig. 15, a power storage system 403 according to the third embodiment is configured such that a module unit is connectable to a cooling/heating air conditioner 83 as a load 80 in the power storage system 400 of fig. 1. That is, at least in the stage of the parallel connection process, the module unit may not be connected to the

chargers

10 and 20. The control circuit 45 acquires information such as the presence or absence of a cooling/heating request, an air-conditioning set temperature, and a current vehicle interior temperature from the air-conditioning control circuit, for example.

In the third embodiment, when the battery voltages Vb1, Vb2 are unbalanced, the air conditioner 83 is discharged from the battery having a relatively high voltage before the parallel switching, thereby performing the voltage equalization process. The timing chart showing the transition of the battery voltages Vb1, Vb2 during the normal temperature adjustment is the same as that in fig. 7 of the first embodiment. Further, when the difference between the air-conditioning set temperature and the vehicle interior temperature is large and the amount of power consumption of the air conditioner 83 is large as compared with the case of normal temperature adjustment, the control circuit 45 increases the amount of discharge as the amount of power consumption increases, and the time for the voltage equalization process can be shortened.

Fig. 16 is a flowchart showing a parallelization process according to the third embodiment. In the step with the first digit "7", the end is labeled "B" in the step specific to the third embodiment in which the air conditioner 83 is used as the load. The flowchart of fig. 16 is obtained by replacing S72A, S75A, and S78A in the flowchart of fig. 8 of the first embodiment with S72B, S75B, and S78B, respectively, and adding S77B. The steps other than this are the same as those in fig. 8, and therefore, the description thereof is omitted.

If there is no abnormality in the batteries BT1 and BT2 at S11, the control circuit 45 determines whether there is a cooling/heating request, that is, whether there is a driving request of the air conditioner 83 at S72B. If yes in S72B, the process proceeds to S62. That is, the voltage equalization process according to the first embodiment is executed on the premise that a request for cooling or heating is made.

In S75B, the air conditioner 83 is started by one of the batteries connected to the load 80. This operation state is continued until it is determined at S65 that the potential difference is equal to or less than the threshold value. In S63 or S66, the parallel relay is turned on, and the parallel processing is completed. In S77B, which is shifted from S63, the air conditioner 83 is started by the two batteries BT1, BT2 connected in parallel. In S78B shifted from S66, the air conditioner 83 is continuously operated by the two batteries BT1, BT2 connected in parallel.

In the third embodiment, when the potential difference between the batteries BT1 and BT2 exceeds the threshold value at the start of the process, the voltage equalization process can be performed while cooling and heating the vehicle interior during the stop of the vehicle. Therefore, especially in summer and winter where the cooling and heating demand is high, the comfort of the passengers is ensured. In addition, in the system using the DC/DC converter that supplies low-voltage power to the auxiliary battery, the load 80 to be discharged can perform the voltage equalization process while using various auxiliary devices during parking.

(fourth embodiment)

A fourth embodiment will be described with reference to fig. 17 to 19. As shown in fig. 17, the power storage system 404 of the fourth embodiment is a configuration in which, in the power storage system 400 of fig. 1, a module portion is connectable to the external charger 10, and the module portion is connectable to the air conditioner 83 as the load 80.

In the fourth embodiment, when the battery voltages Vb1, Vb2 are unbalanced after the series charging is completed, the voltage equalization process is performed by a combination of discharging the battery having a relatively high voltage to the air conditioner 83 and charging the battery having a relatively low voltage from the external charger 10 before the parallel switching. For example, it is conceivable that the vehicle is stopped at a charging station, series-charged by the external charger 10, and then cooled and heated before the start of traveling. Although not shown, as described in the second embodiment, after series charging is performed using the external charger 10, the AC power supply 15 may be reconnected to the in-vehicle charger 20 and charging may be performed using the in-vehicle charger 20.

In fig. 18, at the time t0 when the processing after the end of the series charging is started, the first battery voltage Vb1 is higher than the second battery voltage Vb 2. Therefore, the control circuit 45 discharges the electric power from the first battery BT1 to the air conditioner 83, and lowers the first battery voltage Vb 1. At the same time, the control circuit 45 operates the external charger 10 to charge the second battery BT2, thereby increasing the second battery voltage Vb 2. Then, at the time of equalization t when the potential difference is equal to or less than threshold value Δ Vth_BLThe control circuit 45 turns on the parallel relay.

Further, as in the third embodiment, when the difference between the air conditioning set temperature and the vehicle interior temperature is large and the amount of power consumption of the air conditioner 83 is large as compared with the case of normal temperature adjustment, the control circuit 45 increases the amount of discharge as the amount of power consumption increases, and the time for the voltage equalization process can be shortened.

Here, when the air conditioner 83 is continuously used even after the voltage equalization and the charging is stopped, the battery voltages Vb1 and Vb2 gradually decrease. Therefore, by supplementing the charging of the external charger 10 according to the power consumption of the air conditioner 83, the time t of the balance can be adjusted_BLThe battery voltages Vb1 and Vb2 are maintained until the start of traveling.

Fig. 19 is a flowchart showing a parallelization process according to the fourth embodiment. The parallel connection processing of the fourth embodiment is basically a combination of the charging processing of the second embodiment and the discharging processing to the air conditioner 83 of the third embodiment. In fig. 19, S11 of the battery abnormality determination and S71 and S81 of the abnormality treatment are not described. Further, it is assumed that there is no travel request and there is a request for cooling and heating while the vehicle is being externally charged. In S61, the control circuit 45 determines whether or not the series charging is completed. When the series charging is completed, the process proceeds to S62. After the series charging is completed, there is a possibility that the battery voltages Vb1, Vb2 are unbalanced.

S62, S63, S64 are the same as the embodiments. When the first battery voltage Vb1 is higher than the second battery voltage Vb2 and it is determined as yes in S64, the control circuit 45 turns on relays RY4, RY5, RY8, RY9 in S93, connects the first battery BT1 to the load 80, and connects the second battery BT2 to the external charger 10. When the second battery voltage Vb2 is higher than the first battery voltage Vb1 and it is determined as no in S64, the control circuit 45 turns on relays RY1, RY3, RY6, RY7 in S94, connects the second battery BT2 to the load 80, and connects the first battery BT1 to the external charger 10.

At S95, air conditioner 83 is started by one of the batteries connected to load 80. Further, the operation of the external charger 10 is started for the other battery connected to the charger 10. This state is continued until it is determined at S65 that the potential difference is equal to or less than the threshold value. The above steps from S64 to S65 correspond to the voltage equalization process.

When it is determined at S65 that the potential difference is equal to or less than the threshold, the process proceeds to S66, and the control circuit 45 turns on the battery-side relay not connected at S93 or S94 among the parallel relays. In S63 or S66, the parallel relay is turned on, and the parallel processing is completed. In S97 shifted from S63, the air conditioner 83 is started with the two batteries BT1, BT2 connected in parallel, and in order to replenish the electric power consumed by the air conditioner 83, parallel charging of the external charger 10 is started. In S98 shifted from S66, the air conditioner 83 continues the operation with the two batteries BT1, BT2 connected in parallel, and in order to replenish the electric power consumed by the air conditioner 83, the parallel charging by the external charger 10 is continued.

In this wayIn the fourth embodiment of (3), when the potential difference between the batteries BT1 and BT2 exceeds the threshold value at the time of completion of external charging in series, the voltage equalization process can be performed while cooling and heating the vehicle interior during parking. In this case, by combining the charging and discharging, the time of the voltage equalization process can be shortened. In addition, t is equalized_BLSince charging is continued to supplement the power consumed by the air conditioner 83, battery voltages Vb1 and Vb2 during traveling can be appropriately ensured while maintaining the comfort of the passenger.

(other embodiments)

The control circuit 45 is not limited to a configuration for controlling charging and discharging between the batteries BT1 and BT2 and the

chargers

10 and 20 or the load 80 based on the voltage detection value detected by the battery voltage monitoring unit 43, and may perform feed-forward control of charging and discharging in accordance with the initial voltage and the charging and discharging time, for example. Further, the charge and discharge may be controlled based on a voltage estimation value estimated from another parameter without using the detected value of the battery voltage.

In fig. 3, the charging infrastructure and the load driving voltage are roughly illustrated as two types of 400V class and 800V class, but the present invention is not limited thereto, and can be applied to a system having a load voltage of 200V class, for example. More specifically, the power storage modules may be connected in parallel to be used in a 200V class during load driving, and may be connected in series to be charged using a 400V class charging infrastructure during charging.

The power storage system of the present invention is not limited to being mounted on an electric vehicle or a plug-in hybrid vehicle, and can be applied to any system that can switch the connection state of a plurality of power storage modules in series and parallel. As described above, the power storage module is not limited to the battery module, and a capacitor or the like may be used. In the above embodiment, the case where two batteries are switched in series-parallel connection is shown, but a configuration may be adopted in which three or more storage modules are switched in series-parallel connection.

As described above, the present invention is not limited to the above embodiments, and can be implemented in various ways without departing from the scope of the present invention.

The present invention has been described with reference to the embodiments. However, the present invention is not limited to the embodiments and structures. The present invention also includes various modifications and modifications within an equivalent range. In addition, various combinations and modes including only one element and one or more or less other combinations and modes also belong to the scope and the idea of the present invention.

Claims

1. An electrical storage system comprising:

a plurality of power storage modules (BT1, BT2) which respectively include one or more power storage cells and are connectable to at least one of the chargers (10, 20) and the load (80);

a series-parallel switch (RY1-RY9) that can switch the connection state of the plurality of power storage modules between series and parallel; and

a control circuit (45), wherein the control circuit (45) controls the series-parallel switch and at least one of the charger and the load to which the power storage module is connected,

the control circuit performs a voltage equalization process in which charging and discharging are performed between one or more of the power storage modules and at least one of the charger and the load before switching the plurality of power storage modules to be connected in parallel so that a potential difference between the plurality of power storage modules is equal to or less than a predetermined threshold value, and then switches the series/parallel switch to be connected in parallel.

2. The power storage system according to claim 1,

further comprises a module voltage monitoring unit (43) for monitoring the voltage of the power storage module,

the control circuit controls charging and discharging between the power storage module and the charger or the load based on a voltage detection value detected by the module voltage monitoring unit.

3. The power storage system according to claim 1 or 2,

the control circuit performs the voltage equalization process by discharging electricity from the power storage module having a relatively high voltage to the load before switching the plurality of power storage modules to be connected in parallel, and then switches the series/parallel switch to be connected in parallel.

4. The power storage system according to claim 3,

the control circuit may continue the operation of the load after the plurality of power storage modules are switched to be connected in parallel.

5. The power storage system according to claim 3 or 4,

the electric storage system is an electric storage system mounted on a vehicle using an electric motor as a power source,

the load is the motor (82) and an inverter (81) that converts direct-current power into alternating-current power and supplies the alternating-current power to the motor.

6. The power storage system according to claim 1 or 2,

the control circuit performs the voltage equalization process by charging the electric storage modules having a relatively low voltage from the charger before switching the electric storage modules to be connected in parallel, and then switches the series-parallel switch to be connected in parallel.

7. The power storage system according to claim 6,

the control circuit stops the operation of the charger after the plurality of power storage modules are switched to be connected in parallel.

8. The power storage system according to claim 1 or 2,

the control circuit performs the voltage equalization processing by a combination of discharging the power storage modules having a relatively high voltage to the load and charging the power storage modules having a relatively low voltage from the charger before switching the power storage modules to be connected in parallel, and then switches the series/parallel switch to be connected in parallel.

9. The power storage system according to claim 8,

after the plurality of power storage modules are switched to be connected in parallel, the control circuit causes the load to continue to operate and causes the charger to operate so as to replenish the power of the power storage modules consumed by the load.

10. The power storage system according to claim 9,

the electric storage system is mounted on a vehicle, the load is an air conditioner (83) for cooling and heating a vehicle interior,

the charger is an external charger (10) capable of charging the storage module with DC power.

11. The power storage system according to any one of claims 3, 4, 5, 8, 9, and 10,

in the case where the discharge from the power storage module to the load is performed, the control circuit increases the amount of discharge from the power storage module as the amount of power consumption of the load increases, thereby shortening the time of the voltage equalization process.

12. The electric power storage system according to any one of claims 1 to 11,

further comprises abnormality detection units (43, 44) for detecting an abnormality in the power storage module,

when the abnormality of the power storage module is detected by the abnormality detection unit,

the control circuit cuts off the connection between the power storage module in which the abnormality is detected and a load or a charger.