KR102536488B1 - Method for balancing and charging in energy storage system stacking multiple battery modules - Google Patents

Abstract

The present invention relates to a method for balancing and charging an energy storage device composed of parallelly stacking battery modules having different number of charge/discharge cycles or usage conditions, the steps of connecting the master unit and the slave units in a state in which they can communicate with each other ; collecting, by the master unit, battery module information about an open-circuit voltage (OCV), a state of charge (SOC), and a state of aging (SOH) of a battery module included in each of the slave units; performing balancing of the battery modules according to control of the master unit based on the collected battery module information; and connecting the slave units to a DC bus.

Description

Balancing and charging method of energy storage device in which multiple battery modules are stacked in parallel

The present invention relates to a method for balancing and charging an energy storage device, and more particularly, to a method for balancing and charging battery modules in an energy storage device configured by stacking battery modules in parallel with different number of charge/discharge cycles or usage conditions. It is about.

An energy storage system (ESS) collectively refers to an overall system that stores energy through various storage devices and enables it to be reused. Such an energy storage device is generally composed of a tray or rack by binding a certain number of battery modules according to an installed capacity, and the number is fixed without adding or replacing battery modules.

However, in the case of an energy storage device for home or camping use, it is necessary to detach and use a battery module as much as necessary for the convenience of movement or use, and the market demand for this is gradually increasing.

However, when the number of battery modules is configured with a variable number in this way, each battery module has an open circuit voltage (OCV), state of charge (SOC) and Since the state of health (SOH) may be different from each other, safety may be a problem in charging and discharging the energy storage device.

In other words, in an energy storage device in which a number of battery modules are stacked in parallel, balancing by connecting all battery modules in parallel may take less time, but overcurrent may occur or sparks may occur due to voltage mismatch of the battery modules or the module may be damaged. They can explode and cause serious safety problems. In addition, in charging the entire battery module, a plurality of chargers are required to charge individual battery modules, and if all battery modules are connected in parallel and charged at the same time, overcurrent may flow, which may also cause a serious safety problem. Therefore, there is a need for a method for balancing and charging the module in the fastest possible time without using a high current in such an energy storage device.

Publication No. 10-2019-0127060

An object of the present invention is to provide a stable and efficient balancing and charging method in an energy storage device configured by stacking battery modules having different charging/discharging cycles or usage conditions in parallel.

The present invention for solving the above technical problem is a method for balancing and charging an energy storage device configured by stacking a master unit and a plurality of slave units in parallel, wherein the master unit and the slave units are connected in a state in which they can communicate with each other doing; collecting, by the master unit, battery module information about an open-circuit voltage (OCV), a state of charge (SOC), and a state of aging (SOH) of a battery module included in each of the slave units; performing balancing of the battery modules according to control of the master unit based on the collected battery module information; and connecting the slave units to a DC bus.

In addition, the performing of the balancing may include calculating an average value of the state of charge of the battery modules; performing first balancing by pairing and connecting two adjacent battery modules in the middle of the battery modules, and then performing second balancing by pairing adjacent battery modules together so as not to overlap each other; determining whether a state of charge of each of the battery modules is within a predetermined range based on the average value of the state of charge; and terminating the balancing of the battery module according to the determination result.

Prior to the balancing, the method may further include determining whether the open-circuit voltages of the battery modules are in a flat section in a stable state.

The method may further include determining whether the state of charge of the battery modules is at a usable level after performing the balancing, and simultaneously charging and balancing the battery modules according to the determination result.

In addition, the performing of the charging and balancing may include charging an Nth battery module; Connecting the charged N-th battery module and the (N-1)-th battery module to perform balancing, and simultaneously charging the (N-2)-th battery module.

The method further includes determining whether the state of charge of the battery modules has reached a maximum state of charge and terminating the charging according to the determination result, wherein the maximum state of charge is set in advance based on the aging state information of the battery modules. It can be.

According to the present invention, a large-capacity energy storage device can be configured by stacking battery modules in parallel in different charge/discharge states, usage times, and aging states.

In addition, through module balancing, sparks or overcurrent due to differences in open-circuit voltage can be prevented, and multiple battery modules stacked with one charging device can be effectively charged without having to have a charging device for each battery module. there is

1 is a conceptual diagram showing the main configuration of an energy storage device according to an embodiment of the present invention.
2 is a block diagram schematically showing the internal configuration of an energy storage device according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating an embodiment of a detailed configuration of the power conversion system of FIG. 2 .
FIG. 4 is a circuit diagram illustrating an embodiment of a detailed configuration of the bidirectional DC/DC converter of FIG. 3 .
5 is a flowchart illustrating a charging and discharging process of an energy storage device according to an embodiment of the present invention.
6 is a flowchart illustrating a balancing process of a battery module according to an embodiment of the present invention.
7 is a conceptual diagram for explaining a balancing process of a battery module according to an embodiment of the present invention.
8 is a flowchart illustrating a charging process of a battery module according to an embodiment of the present invention.
9 is a conceptual diagram for explaining a charging process of a battery module according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram showing the main configuration of an energy storage device according to an embodiment of the present invention.

Referring to FIG. 1 , an energy storage device 10 may include a master unit 100 and a plurality of slave units 200 .

Depending on the embodiment, the master unit 100 and the slave unit 200 may be stacked in a vertical direction as shown in Fig. 1. The number of stacked slave units 200 is not limited, and the slave unit is required as needed. The total battery capacity can be easily adjusted by adding or removing (200).

A (+) terminal connected to a DC bus and a (-) terminal connected to a DC bus, and a communication (com) terminal connected to a communication line may be provided on the top and/or bottom of the master unit 100 and the slave unit 200. Each of the terminals may be fastened in a sliding and fitting manner, and thus the master unit 100, the slave unit 200, and the slave units 200 may be connected in parallel.

2 is a block diagram schematically showing the internal configuration of an energy storage device according to an embodiment of the present invention, FIG. 3 is a block diagram showing an embodiment of the detailed configuration of the power conversion system of FIG. 2, and FIG. 3 is a circuit diagram showing an embodiment of the detailed configuration of the bidirectional DC/DC converter.

Referring to FIG. 2 , the master unit 100 may include a module control system 110 , a power conversion system 120 and a main switch 130 .

The module control system 110 may be connected to the slave units 200 through a communication line (COM). The module control system 110 may collect and store information about the battery modules 210 included in each slave unit 200, and use this to perform balancing, charging, and discharging of the battery modules 210. You can have the overall control you need.

The power conversion system 120 is connected to the DC bus (+), and provides electrical energy provided from the battery modules 210 to various loads connected to the outside through bi-directional power conversion, or the power of the battery modules 210. Power for charging and balancing can be provided through the DC bus (+).

The main switch 130 may be turned on or off according to the control of the module control system 110, and may connect or block the connection of the entire slave unit 200 to the DC bus (+).

The slave unit 200 may include a battery module 210, a battery management system 220, a power conversion system 230, a communication unit 240, a sub switch 250, and a module connection switch.

The battery module 210 may refer to a battery assembly in which a certain number of battery cells, which are basic units of a secondary battery that can be used by charging and discharging electrical energy, are bundled and put into a frame.

In an embodiment of the present invention, each battery module 210 may be configured to have the same initial specifications as performance, charge capacity, and nominal voltage. However, as the energy storage device 10 according to the present invention can configure the battery capacity variably, the number of uses or the period of use of each battery module 210 may be different from each other, and accordingly, the state of each battery module 210 There may also be differences in information such as state of charge (SOC), state of health (SOH), open circuit voltage (OCV), and the like.

In particular, if the slave unit 200 is newly added or replaced and the battery modules are directly connected in parallel in a state where there is a difference in open-circuit voltage between the battery modules, a spark or a high current is generated between the battery modules, which may affect the safety of the energy storage device. Since it can cause a serious problem, it is necessary to first balance the battery modules to ensure safety. A detailed description of this will be described later with reference to FIGS. 5 to 7 .

The battery management system 220 manages stable and efficient charging and discharging through voltage balancing of battery cells, and detects the current, voltage, temperature, etc. of the battery module to determine the state of charge (SOC) and state of aging (SOH) It can perform predictive and monitoring functions.

The power conversion system 230 may be connected between the battery module 210 and the DC bus (+), and may perform various functions other than power conversion required for balancing and charging and discharging the battery module.

Referring to FIGS. 3 and 4 , the power conversion system 230 may include a bidirectional DC/DC converter 231 , a mode controller 232 and a voltage detector 233 .

The bi-directional DC/DC converter 231 boosts or steps down the DC voltage on the battery module 210 side and transfers it to the DC bus (+) side, or boosts or steps down the DC voltage on the DC bus (+) side to the battery module 210. can be provided with In addition, the bidirectional DC / DC converter 231 transfers the DC voltage on the battery module 210 side to the DC bus (+) without power conversion or active balancing between the battery modules 210 connected through the sub switch 250 It may include a circuit configuration for performing.

The mode control unit 232 controls on/off of the switching elements S1 to S5 in the bidirectional DC/DC converter 231, so that the bidirectional DC/DC converter 231 is in a buck mode, boost mode mode, bypass mode, balancing mode, and open mode. For example, the mode controller 232 may operate the DC/DC converter 231 in a buck mode during module balancing and charging, and may operate the DC/DC converter 231 in a boost mode during discharging.

On the other hand, in determining the mode of the bidirectional DC / DC converter 231, the mode control unit 232 according to the command (CMD) transmitted from the module control system 110 or the battery module 210 side voltage (Vb) and The result of comparing the DC bus (+) side voltage (Vd) can be used. In this case, the battery module 210 side voltage Vb may be provided from the battery management system 220 , and the DC bus (+) side voltage Vd may be provided through the voltage detector 233 .

Referring back to FIG. 2 , the communication unit 240 is connected to the module control system 110 through a communication line (COM), and data collected by the battery management system 220 and the power conversion system 230 is transmitted to the module control system. Commands and data provided to 110 or transmitted by the module control system 110 may be provided to the battery management system 220 or the power conversion system 230 . Communication between the master unit 100 and the slave unit 200 may use a CAN (Controller Area Network) or TCP/IP method.

The sub switch 250 serves to connect or block the connection of the slave unit 200 to the DC bus (+) under the control of the power conversion system 230, and when the main switch 130 is turned off, the slave unit 200 It serves to enable parallel connection of (200).

The sub switch 250 may be installed between the power conversion system 230 and the DC bus (+), and the power conversion system 230 switches the DC/DC converter 241 to an open mode or a bypass mode according to an embodiment. It can be replaced by operating with

The module connection switch 260 serves to connect adjacent slave units 200 and can be controlled by the power conversion system 230 of the slave units 200 . For example, the first module connection switch 260-1 may connect or disconnect the first slave unit 200-1 and the second slave unit 200-2 on a DC bus.

5 is a flow chart showing a charging/discharging process of an energy storage device according to an embodiment of the present invention, FIG. 6 is a flowchart showing a balancing process of a battery module according to an embodiment of the present invention, and FIG. 7 is an embodiment of the present invention. It is a conceptual diagram for explaining the balancing process of the battery module according to.

Referring to FIG. 5 , a user may stack an appropriate number of slave units 200 and connect them to the master unit 100 in order to configure a required battery capacity. Then, when power is supplied to the energy storage device 10, the master unit 100 and the slave unit 200 become communicable with each other through the communication line COM (S100).

At this time, the connection through the DC bus (+) of the master unit 100 and the slave unit 200 is cut off. That is, both the main switch 130 and the sub switch 250 are in an off state. This is to prevent the energy storage device from being damaged due to a high current flowing between the battery modules or spark generation when battery modules having different open-circuit voltages are directly connected in parallel.

Thereafter, the module control system 110 of the master unit 100 may collect and store battery module information provided from the battery management system 220 of each slave unit 200 (S110). Here, the battery module information may include an open-circuit voltage (OCV), state of charge (SOC), and state of aging (SOH) of the battery module 210 .

On the other hand, since the measured value of the open-circuit voltage of the battery module 200 may vary depending on the measurement environment or the state of the battery module, it is necessary to additionally check whether the measured value is in the flat section by repeatedly measuring it in consideration of the idle time ( S120).

After the collection of battery module information is completed, the module control system 110 may perform balancing of the battery modules 210 based on the collected battery module information. Here, battery module balancing may refer to a process of adjusting the voltage or state of charge of battery modules to the same or similar level in order to secure the safety of the energy storage device prior to using or charging the battery modules by connecting them in parallel.

Referring to FIGS. 6 and 7 , the module control system 110 may calculate an average value by summing the state of charge of each battery module (S131).

Thereafter, the module control system 110 may perform battery module balancing by controlling the power conversion system 230, the sub switch 250, and the module connection switch 260 of each slave unit 200 (S130). Specifically, the module control system 110 connects two adjacent battery modules in pairs to perform first balancing (Stage 1), and then pairs and connects adjacent battery modules again so as not to overlap to perform second balancing ( Stage 2) can be performed (S132). For example, as shown in FIG. 7 , in the first balancing process, the first battery module 210-1, the second battery module 210-2, the third battery module 210-3, and the fourth battery module (210-4) can perform balancing in pairs. Also, in the second balancing process, the second battery module 210-2 and the third battery module 210-3, and the fourth battery module 210-4 and the fifth battery module 210-5 are paired. Balancing can be performed simultaneously. As mentioned above, the simultaneous balancing of adjacent battery modules in pairs is to minimize the time required for module balancing.

The module control system 110 may check the state of charge of each of the battery modules after the first balancing and the second balancing process, and determine whether the states of charge of the battery modules are all within a target range (S133). For example, the module control system 110 may calculate the difference between the SOC value of the battery module and the previously calculated overall average value, and compare the difference value with a preset value.

According to the determination result of step S133, the module control system 110 may repeatedly perform the first balancing process and the second balancing process or terminate the battery module balancing process (S134).

Referring back to FIG. 5 , after the battery module balancing is finished, the module control system 110 controls the main switch 130 and the sub switch 250 and/or the module connection switch 260 to be in an on state to turn on the battery module s 200 can be connected to the DC bus (+) (S140). Accordingly, the battery modules 200 are placed in a state in which charging and discharging are possible.

Thereafter, the module control system 110 may determine whether the state of charge of the balanced battery module is at a discharging level (S150), and may perform a battery charging process according to the determination result (S160).

8 is a flowchart illustrating a battery module charging process according to an embodiment of the present invention, and FIG. 9 is a conceptual diagram illustrating a battery module charging process according to an embodiment of the present invention.

Referring to FIGS. 8 and 9 , the battery charging process according to an embodiment of the present invention sequentially charges the battery modules one by one, rather than performing all of the battery modules connected in parallel at once, and at the same time, module balancing is performed in parallel. Suggest how to do it.

Specifically, assuming that five battery modules are connected in parallel as shown in FIG. 9, the module control system 110 first charges the fifth battery module 210-5 farthest from the master unit 100. It can (S161). That is, in the present invention, since charging and balancing must be performed simultaneously as will be described later, the sub switch 250-N of the Nth battery module 200-N located farthest from the state in which all module connection switches 260 are connected Connect and start charging for the first time. At this time, the remaining sub switches 250-1 to 250-(N-1) are in an off state.

After charging of the fifth battery module 210-5 is completed, the module control system 110 performs balancing of the fifth battery module 210-5 and the fourth battery module 210-4 (S162), At the same time, the third battery module 210-3 may be charged (S162).

That is, the third module connection switch 260-3 is turned off, and the first module connection switch 260-1, the second module connection switch 260-2, and the third sub switch 250-3 is turned on to charge the third battery module 200-3, and at the same time, the fourth module connection switch 260-4, the fourth sub switch 250-4 and the fifth sub switch 250-5 ) may be controlled to be in an on state to balance the fourth battery module 200-4 and the fifth battery module 200-5.

Similarly, after charging of the third battery module 210-3 is completed, the module control system 110 performs balancing of the third battery module 210-3 and the second battery module 210-2 (S163 ), and at the same time, the first battery module 210-1 can be charged (S163).

That is, the first module connection switch 260-1 is turned off and the first sub-switch 250-1 is controlled to be turned on to charge the first battery module 200-1, and at the same time, the second The second battery module 200-2 and the third battery module 200 are controlled to turn on the module connection switch 260-2, the second sub switch 250-2, and the third sub switch 250-3. -3) can be balanced.

In this way, the module control system 110, after completing the charging of the n-th battery module, while charging the next (n-2)-th battery module, the previously charged n-th battery module and (n-1) All battery modules may be charged and balanced by simultaneously balancing the first battery module.

Meanwhile, the module control system 110 may periodically check the state of charge of the battery modules during the charging process to determine whether the state of charge of all battery modules has reached the maximum state of charge, and according to the determination result, the state of charge of the battery module may be determined. can end (S164, S165). Here, the maximum state of charge may be preset or calculated based on aging state information of the battery modules.

Since this charging method is performed in a state where several battery modules are stacked with one charging device, there is no need to have a charging device for each battery module, and there is no risk of high current even if the number of battery modules stacked is large, so the entire system safety and efficiency can be maximized. In addition, when charging the battery module, the time required to charge the entire battery module can be minimized by concurrently performing charging and module balancing.

In the above, the present invention has been described with reference to the embodiments shown in the drawings, but this is only exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. will be. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

10: energy storage device 100: master unit
110: module control system 120: power conversion system
200: slave unit 210: battery module
220: battery management system 230: power conversion system
231: bi-directional DC/DC converter 232: mode controller
233; Voltage detection unit 240: communication unit
250: sub switch

Claims (6)

In the balancing and charging method of an energy storage device configured by stacking a master unit and a plurality of slave units in parallel,
connecting the master unit and the slave units in a communicable state;
collecting, by the master unit, battery module information about an open-circuit voltage (OCV), a state of charge (SOC), and a state of aging (SOH) of a battery module included in each of the slave units;
performing balancing of the battery modules according to control of the master unit based on the collected battery module information; and
Connecting the slave units with a DC bus,
The step of performing the balancing is,
Calculating an average value of the state of charge of the battery modules;
performing first balancing simultaneously by pairing and connecting two adjacent battery modules in the middle of the battery modules, and then pairing two adjacent battery modules together so as not to overlap and simultaneously performing second balancing;
determining whether a state of charge of each of the battery modules is within a predetermined range based on the average value of the state of charge; and
A balancing and charging method for an energy storage device comprising the step of terminating the balancing of the battery module according to the determination result. delete According to claim 1,
Prior to the balancing, the method of balancing and charging an energy storage device further comprising determining whether the open-circuit voltages of the battery modules are in a flat section in a stable state. According to claim 1,
After performing the balancing, determining whether the state of charge of the battery modules is at a usable level, and according to the determination result, further comprising the step of simultaneously charging and balancing the battery modules in parallel,
The step of simultaneously performing the charging and balancing in parallel,
charging an Nth battery module; and
Connecting the charged N-th battery module and the (N-1)-th battery module to perform balancing, and simultaneously charging the (N-2)-th battery module. How to balance and charge your device. delete According to claim 4,
Determining whether the state of charge of the battery modules has reached a maximum state of charge, and terminating charging according to the determination result;
The maximum state of charge is a balancing and charging method of an energy storage device, characterized in that preset based on the aging state information of the battery modules.

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