Energy storage system and method of controlling the same

Abstract

An energy storage system can include a plurality of power converters configured to perform DC / DC conversion in relation to respective battery racks, a power conversion system (PCS) configured to perform power conversion between the power converters and a power grid, and a battery section controller interworking with the plurality of power converters and the power conversion system, wherein the battery section controller is configured to control a first power converter among the plurality of power converters to perform constant voltage (CV) mode control for maintaining a voltage of a DC link at a constant level, check a state of a first battery rack to which the first power converter is connected, and change a subject performing the CV mode control for the DC link according to the state of the first battery rack.

Description

Technical Field

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2021-0097480, filed on July 26, 2021, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an energy storage system and a method for controlling the energy storage system, and more specifically, to an energy storage system comprising a plurality of power converters and a method for controlling the energy storage system. Background Technology

[0003] Energy storage systems involve renewable energy, batteries for storing electricity, and grid power. In recent years, with the expansion of smart grids and renewable energy, and the increasing emphasis on power system efficiency and stability, the demand for energy storage systems for power supply and demand control and power quality improvement is growing. Depending on their intended use, energy storage systems can have different outputs and capacities. To configure large-capacity energy storage systems, multiple battery systems can be connected. These energy storage systems are evolving towards DC-coupled energy storage systems.

[0004] Energy storage systems may include a battery compartment with multiple batteries, a battery management system (BMS), a power conversion system (PCS), and an energy management system (EMS). DC-coupled energy storage systems may also require a DC / DC converter.

[0005] Meanwhile, in ESS systems that use a separate DC / DC converter for each battery, the common approach is to calculate the output value of each battery at each moment through a central controller and transmit that value as a command to each battery. However, in this case, no suitable solution is provided for how to maintain the system voltage. Summary of the Invention

[0006] [Technical Issues]

[0007] To address the aforementioned technical problems, one objective of this disclosure is to provide a control method for an energy storage system.

[0008] In order to solve the above-mentioned technical problems, another object of this disclosure is to provide an energy storage system.

[0009] In order to solve the above-mentioned technical problems, another object of this disclosure is to provide a battery section control device.

[0010] [Technical Solution]

[0011] According to one embodiment of this disclosure, a control method for an energy storage system includes a plurality of battery racks and a plurality of power converters respectively connected to the plurality of battery racks. The method includes: controlling a first power converter among the plurality of power converters to perform constant voltage (CV) mode control for maintaining the voltage of a DC link at a constant level; checking the state of a first battery rack to which the first power converter is connected; and changing the subject performing the CV mode control for the DC link according to the state of the first battery rack.

[0012] Here, a DC link is a link between multiple power converters and a power conversion system (PCS), which is configured to perform AC / DC conversion between the multiple power converters and the power grid.

[0013] The control method may further include controlling other power converters among a plurality of power converters, excluding the first power converter, to perform constant power (CP) mode control or constant current (CC) mode control.

[0014] Changing the entity performing CV mode control for the DC link may include: stopping the first power converter from performing DC link control, and controlling a second power converter among a plurality of power converters to perform DC link control based on the state of charge (SOC) of the first battery rack.

[0015] The entity that changes the execution of CV mode control for the DC link may also include: temporarily executing both the DC link control via the first power converter and the DC link control via the second power converter before the DC link control begins solely via the second power converter.

[0016] Here, one of the multiple power converters, other than the first power converter, can be selected as the second power converter to perform DC link control in place of the first power converter, wherein the second power converter corresponds to the battery rack with an intermediate value in terms of the charging state of the battery rack.

[0017] Checking the status of the first battery rack may include determining whether the charging status of the first battery rack has reached the upper or lower limit of a preset range of charging status.

[0018] To achieve the objectives of this disclosure, an energy storage system may include: a plurality of power converters configured to perform DC / DC conversion in relation to a respective battery rack; a power conversion system (PCS) configured to perform power conversion between the power converters and the power grid; and a battery controller that interacts with the plurality of power converters and the power conversion system, wherein the battery controller is configured to control a first power converter among the plurality of power converters to perform constant voltage (CV) mode control for maintaining the voltage of the DC link at a constant level; check the state of a first battery rack to which the first power converter is connected; and change the entity performing CV mode control for the DC link according to the state of the first battery rack.

[0019] Here, the battery controller can be configured to control other power converters among a plurality of power converters, except for the first power converter, to perform constant power (CP) mode control or constant current (CC) mode control.

[0020] The battery controller can be configured to stop the first power converter performing DC link control and control the second power converter among a plurality of power converters to perform DC link control based on the state of charge (SOC) of the first battery rack.

[0021] Furthermore, the battery controller can be configured to temporarily execute both the DC link control via the first power converter and the DC link control via the second power converter simultaneously before DC link control via the second power converter begins.

[0022] The battery controller can also be configured to select one of a plurality of power converters, other than the first power converter, as the second power converter to perform DC link control in place of the first power converter, wherein the second power converter corresponds to the battery rack having an intermediate value in terms of the charging state of the battery rack.

[0023] The battery controller can also be configured to determine whether the charging state of the first battery rack has reached the upper or lower limit of the preset range of SOC, and decide whether to change the subject that performs CV mode control for the DC link.

[0024] According to another embodiment of this disclosure, a battery section controller is provided in an energy storage system. The energy storage system includes a plurality of battery racks and a plurality of power converters respectively connected to the plurality of battery racks. The battery section controller is associated with the plurality of power converters and includes: at least one processor; and a memory configured to store at least one instruction executed by the at least one processor. The at least one instruction includes: an instruction for controlling a first power converter among the plurality of power converters to perform constant voltage (CV) mode control for maintaining the voltage of a DC link at a constant level; an instruction for checking the state of a first battery rack to which the first power converter is connected; and an instruction for changing the subject of performing CV mode control for the DC link according to the state of the first battery rack.

[0025] Here, at least one instruction may also include: controlling one of the multiple power converters, other than the first power converter, to perform constant power (CP) mode control or constant current (CC) mode control.

[0026] [Beneficial Effects]

[0027] According to the embodiments of the present invention described above, multiple DC / DC converters can be used to stably control the DC link voltage in an energy storage system.

[0028] Furthermore, since the DC / DC converters other than the one that performs CV control use CP control or CC control, the battery controller can actively calculate the output reference for each battery by taking into account the state of each battery.

[0029] In addition, the power control system can perform CP control in the existing manner without additional procedures such as software changes, thus smoothly performing grid-connected control. Attached Figure Description

[0030] Figure 1 This is a block diagram of an energy storage system to which the present invention can be applied.

[0031] Figure 2 This is a conceptual diagram of a control method for an energy storage system according to an embodiment of the present invention.

[0032] Figure 3 This is an operational flowchart of a method for controlling an energy storage system according to an embodiment of the present invention. Detailed Implementation

[0033] This invention can be modified in various forms and has various embodiments, and specific embodiments thereof are shown by way of example in the accompanying drawings, which will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the specific forms disclosed; rather, the invention is intended to cover all modifications, equivalents, and substitutions falling within the spirit and scope of the invention. Throughout the description of the drawings, the same reference numerals refer to the same elements.

[0034] It should be understood that although the terms first, second, A, B, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element without departing from the scope of the invention, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more associated listed items.

[0035] It should be understood that when an element is referred to as "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In contrast, when an element is referred to as "directly connected" or "directly coupled" to another element, there are no intermediate elements. The terminology used herein is intended to describe particular embodiments only and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are also intended to include the plural forms unless the context clearly specifies otherwise. Furthermore, it should be understood that when used herein, the terms "comprising" and / or "including" specify the presence of the stated feature, integer, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0036] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant field, and should not be construed as having an idealized or overly formal meaning unless explicitly defined herein.

[0037] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0038] This invention proposes a solution for maintaining system voltage in an energy storage system that includes a DC / DC converter. Specifically, it proposes a control method for the energy storage system.

[0039] Figure 1 This is a block diagram of an energy storage system to which the present invention can be applied.

[0040] In an energy storage system (ESS), batteries are used to store energy or electricity. Typically, multiple battery modules can form a battery rack, and multiple battery racks form a battery bank. Here, depending on the device or system using the batteries, the battery rack can be referred to as a battery pack. Figure 1 The batteries shown, #1, #2, ..., and #N, can be battery packs or battery racks.

[0041] Reference Figure 1 For each battery, a battery management system (BMS) 100 can be installed. The BMS 100 can monitor the current, voltage, and temperature of each battery pack (or battery rack) to be managed, and calculate the state of charge (SOC) of the battery based on the monitoring results to control charging and discharging.

[0042] The Battery Section Controller (BSC) 200 can be located in each battery section, which includes multiple batteries, peripheral circuitry, devices for monitoring and controlling objects such as voltage, current, and temperature, and circuit breakers. Furthermore, the BSC 200 can calculate the output of each DC / DC converter based on the monitored state information of the batteries and transmit the calculated output of the DC / DC converter to the DC / DC converter.

[0043] According to embodiments of the present invention, the battery module controller can interact with multiple power converters in an energy storage system, the energy storage system including multiple battery racks and multiple power converters respectively connected to the multiple battery racks. The battery module controller may include at least one processor; and a memory configured to store at least one instruction executed by the at least one processor.

[0044] At least one instruction includes: an instruction for controlling a first power converter among a plurality of power converters to perform constant voltage (CV) mode control for maintaining the voltage of the DC link at a constant level; an instruction for checking the state of a first battery rack to which the first power converter is connected; and an instruction for a body to perform CV mode control for the DC link according to the state of the first battery rack.

[0045] In addition, at least one instruction may include controlling one of the multiple power converters, other than the first power converter, to perform constant power (CP) mode control or constant current (CC) mode control.

[0046] The power conversion system (PCS) 400 installed in each battery compartment can control the power supplied from the outside and the power supplied from the battery compartment to the outside, thereby controlling the charging and discharging of the battery. The power conversion system may include a DC / AC inverter. In other words, the power conversion system can convert the battery's output (i.e., DC power) into AC power and transmit it to the power grid (during discharge), or conversely, convert AC power from the power grid into DC power and transmit it to the battery (during charging).

[0047] The output of the DC-DC converter 500 can be connected to the PCS 400, and the PCS 400 can be connected to the power grid 600. Here, the PCS 400 typically operates in constant power mode. The power management system (PMS) 300 connected to the PCS can control the output of the PCS based on the monitoring and control results of the battery management system or battery module controller.

[0048] exist Figure 1 In the energy storage system, battery #1 is connected to DC-DC converter #1, battery #2 is connected to DC-DC converter #2, and battery #N is connected to DC-DC converter #N. The output of the DC-DC converter corresponding to each battery is connected to PCS 400 via a DC link.

[0049] A DC-DC converter can be a bidirectional converter, where, when performing a conversion from battery to load direction, the input of the DC-DC converter is connected to the battery (battery cell, battery rack, or battery pack), and the output of the DC-DC converter can be connected to the load. As examples of DC-DC converters, various types of converters can be used, such as full-bridge converters, half-bridge converters, and flyback converters.

[0050] Simultaneously, it can be achieved via Controller Area Network (CAN) or Ethernet (via... Figure 1 The dashed lines in the diagram indicate how communication is achieved in BMS100, BSC200, PMS300, and PCS400.

[0051] In an ESS system as described above, the central controller typically calculates the battery's output value at each moment and transmits the calculated value as a command to each battery (high-level control). However, high-level control is only possible when the system voltage of the energy system is maintained; that is, low-level control is required later.

[0052] refer to Figure 1 The DC link, which serves as the area between the DC / DC converter and the PCS, has a DC voltage, which is often referred to as the system voltage. For the stability of the entire energy storage system, the system voltage needs to be maintained at a constant level.

[0053] Figure 2 This is a conceptual diagram of a control method for an energy storage system according to an embodiment of the present invention.

[0054] Various control methods can be used to maintain the voltage of the DC link (i.e., the system voltage) at a constant state. In other words, a DC / DC converter and PCS are power conversion devices capable of performing constant voltage (CV) control, constant power (CP) control, constant current (CC) control, and droop control. Here, droop control can refer to control using a droop curve, which indicates the relationship between the DC link voltage and the output power of the DC / DC converter.

[0055] Typically, the power converter (PCS) performs constant voltage (CV) control or constant power (CP) control. For example, assuming the PCS performs CP control, the power management system (PMS) calculates the PCS's output reference (the power value the PCS will output) and transmits it as a command to the PCS. In this case, when the PCS receives the command and performs charging and discharging according to CP control, the voltage at the DC link will fluctuate due to the PCS's charging and discharging. Therefore, for stable system control, CV control must be implemented, where the power converter maintains the voltage at a constant level in the DC link.

[0056] However, as Figure 2 As shown, when a separate DC / DC converter is used for each battery pack, multiple DC / DC converters can exist that interact with the DC link. When two or more DC / DC converters continuously perform DC link voltage control, circulating current may occur, for example, due to voltage sensing errors. In other words, because it is practically impossible for two or more power converters to be exactly the same, the problem of sensing the same voltage as different values ​​can occur, and therefore, circulating current or control divergence arises.

[0057] Therefore, as Figure 2 As shown, according to an embodiment of the present invention, a DC / DC converter performs CV control. Figure 2 In step 1, the power converter used to perform CV control is DC / DC converter 1, and all other DC / DC converters perform CP control.

[0058] Meanwhile, if the SOC of the corresponding battery is within the appropriate limits, the CV control of the DC / DC converter can be performed without any problems. However, when the SOC of the corresponding battery reaches a certain upper or lower limit, the output of the DC / DC converter is also limited by the output limiting characteristics of the battery itself, and therefore, it may be difficult to perform normal CV control.

[0059] Therefore, according to an embodiment of the present invention, when the battery of the DC / DC converter performing CV control reaches the upper limit or lower limit of the SOC region, the DC / DC converter connected to another battery can perform CV control.

[0060] Here, when the CV control is transferred from DC / DC converter 1 to DC / DC converter 2, in step 2, both DC / DC converters temporarily perform CV control to maintain control over the DC link voltage. In step 3, following step 2, control is completely transferred to DC / DC converter 2, and only DC / DC converter 2 performs CV control, while DC / DC converter 1 performs CP mode control.

[0061] Figure 3 This is an operational flowchart of a method for controlling an energy storage system according to an embodiment of the present invention.

[0062] Figure 3 The control methods shown describe how the control method of a DC / DC converter can be changed from CV control to CP mode or CC mode control, or vice versa. Figure 3 The control method shown can be executed by the battery section controller. In other words, the main entity determining the control mode of the DC / DC converter is the battery section controller.

[0063] When the DC / DC converter performs CP mode or CC mode control, the BSC considers the battery's state of charge (SOC) to calculate the DC / DC converter's output reference and transmits it to the DC / DC converter. The DC / DC converter can then determine its output value based on this output reference. In other words, according to the present invention, proactive control that automatically determines the output based on the battery state is possible.

[0064] refer to Figure 3 In the power control method according to the present invention, one of the multiple DC / DC converters performs CV control on the DC link. Therefore, for example, if n DC / DC converters are arranged in the system and the first converter performs CV control, then all the remaining DC / DC converters perform CP mode control or CC mode control (S310).

[0065] In this state, the SOC measurement of the first DC / DC converter performing CV mode control can be performed periodically (S320). When the measured SOC of the first DC / DC converter is within an appropriate range ("No" in S330), the CV mode control of the first converter is continuously performed.

[0066] However, when the SOC of the first DC / DC converter is outside the appropriate range—that is, when the SOC of the first DC / DC converter is greater than the upper limit (SOC_high) or less than the lower limit (SOC_low) of the preset SOC range (S330 "Yes")—the main body of CV control must be changed. Specifically, among all n converters, except for the first converter performing CV mode control, the BSC can measure the SOC of the battery associated with (n-1) converters under CP / CC control (S340). Then, the BSC can select a second converter among the (n-1) converters to perform CV mode control based on the measured SOC (S350).

[0067] Here, the following equations 1 and 2 can be used to perform the process of selecting a new converter to perform CV mode control.

[0068] [Equation 1]

[0069] Diff_n=max{(x-SOC_low), (SOC_hight-x)}

[0070] In Equation 1, x is the SOC of the corresponding battery, SOC_high is the upper limit of the preset SOC range, and SOC_low is the lower limit of the preset SOC range. For a battery with a typical SOC, x will be a value greater than or equal to SOC_low and less than or equal to SOC_high (i.e., 0). <SOC_low<x<SOC_high<100)。

[0071] [Equation 2]

[0072] Next_CV_converter=a DC / DC converter with min{Diff_1, Diff_2,...,Diff_n-1)

[0073] Equation 1 allows calculation of the SOC deviation (Diff) for each battery, which is the larger of the difference between the current SOC of the corresponding battery and either the upper or lower limit. Furthermore, Equation 2 allows selection of the next DC / DC converter (Next_CV_converter) to perform CV control. According to Equation 2, the converter with the minimum SOC deviation—that is, the converter with a value at the midpoint within a preset SOC range—can be selected as the suitable converter for performing the next CV control. Therefore, when a converter with a value at the midpoint within the preset SOC range performs CV control, the CV control can be maintained for the longest possible duration, thus preventing frequent control mode switching.

[0074] The converter selection process using Equations 1 and 2 can be used not only when changing the entity performing CV control during system operation, but also when selecting the DC / DC converter performing initial CV mode control during initial system operation. In other words, Equations 1 and 2 can be used even when selecting the first converter in step S310, and in this case, SOC measurement can be performed on all DC / DC converters in the system.

[0075] Meanwhile, when the second converter is selected to perform CV control, the first converter and the second converter temporarily perform CV control simultaneously (S360) in order to maintain the voltage of the DC link stably as described above.

[0076] After a certain short period of time, only the second converter performs CV control, while all other converters, including the first converter, perform CP mode or CC mode control (S370).

[0077] According to the embodiments of the present invention described above, multiple DC / DC converters can be used to stably control the DC link voltage in an energy storage system.

[0078] In addition to the DC / DC converter that performs CV control, the DC / DC converter performs CP control or CC control, allowing the BSC to actively calculate the output reference for each battery based on the state of each battery.

[0079] In another aspect, power conversion systems in existing energy storage systems that typically do not include DC / DC converters are usually driven by CP or CC control methods. When the control method according to embodiments of the invention is applied to a battery system that uses a DC / DC converter, the power conversion system in the ESS can operate in the same manner as the method used in the existing system. In other words, according to embodiments of the invention, even if a DC / DC converter is used in the battery system, there is no need to change the software of the power conversion system, and therefore, the power conversion system can be used in the manner previously used.

[0080] Embodiments of this disclosure can be implemented as program instructions executable by various computers and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, or combinations thereof. The program instructions recorded on the computer-readable medium may be specifically designed and configured for this disclosure, or may be known and available to those skilled in the art of computer software.

[0081] Examples of computer-readable media may include hardware devices, such as ROM, RAM, and flash memory, specifically configured to store and execute program instructions. Examples of program instructions include, for example, machine code generated by a compiler and high-level language code executable by a computer using an interpreter. The exemplary hardware devices described above may be configured to operate as at least one software module to perform embodiments of this disclosure, or vice versa.

[0082] Some aspects of the invention have already been described in the context of apparatus, but can be described using corresponding methods. Here, a module or apparatus corresponds to an operation or feature of a method. Similarly, aspects of the invention already described in the context of a method can be described using corresponding modules or items or features of corresponding apparatus. For example, some or all of the operations of the method can be performed by (or using) hardware devices such as microprocessors, programmable computers, or electronic circuits. In some embodiments, one or more of the most important operations of the method can be performed by such a device.

[0083] While exemplary embodiments of the invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications may be made therein without departing from the scope of the invention.

Claims

1. An energy storage system, comprising: Multiple power converters, the multiple power converters being configured to perform DC / DC conversion in association with a corresponding battery rack; A power conversion system configured to perform power conversion between the power converter and the power grid; as well as A battery controller interacts with the plurality of power converters and the power conversion system. The battery controller is configured to control a first power converter among the plurality of power converters to perform constant voltage mode control for maintaining the voltage of the DC link at a constant level; check the state of a first battery rack connected to the first power converter; and change the main body executing the constant voltage mode control for the DC link based on the state of the first battery rack. The battery controller is configured to stop the first power converter from performing DC link control based on the charging state of the first battery rack, and to control the second power converter among the plurality of power converters to perform DC link control. The battery controller is configured to temporarily execute both the DC link control via the first power converter and the DC link control via the second power converter simultaneously before the DC link control begins solely via the second power converter.

2. The energy storage system according to claim 1, wherein, The battery controller is configured to control the other power converters among the plurality of power converters besides the first power converter to perform constant power mode control or constant current mode control.

3. The energy storage system according to claim 1, wherein, The battery controller is configured to select one of the plurality of power converters, other than the first power converter, as the second power converter to perform DC link control in place of the first power converter, wherein the second power converter corresponds to a battery rack having an intermediate value in terms of the charging state of the battery rack.

4. The energy storage system according to claim 1, wherein, The battery controller is configured to determine whether the charging state of the first battery rack has reached the upper or lower limit of a preset range of charging states, and to decide whether to change the main body that performs constant voltage mode control for the DC link.

5. The energy storage system according to claim 1, wherein, The DC link is the link between the plurality of power converters and the power conversion system.

6. A control method for an energy storage system, the energy storage system comprising a plurality of battery racks and a plurality of power converters respectively connected to the plurality of battery racks, the method comprising: Control the first of the plurality of power converters to perform constant voltage mode control for maintaining the voltage of the DC link at a constant level; Check the status of the first battery rack connected to the first power converter; as well as The main body that performs constant voltage mode control for the DC link based on the state change of the first battery rack. The entity that changes the constant voltage mode control for the DC link includes: stopping the first power converter from performing DC link control based on the charging state of the first battery rack, and controlling a second power converter among the plurality of power converters to perform DC link control. The modification of the entity performing constant voltage mode control for the DC link further includes: before the DC link control is started solely through the second power converter, temporarily executing both the DC link control via the first power converter and the DC link control via the second power converter simultaneously.

7. The control method according to claim 6 further includes controlling other power converters among the plurality of power converters besides the first power converter to perform constant power mode control or constant current mode control.

8. The control method according to claim 6, wherein, Select one of the plurality of power converters, other than the first power converter, as the second power converter to perform DC link control in place of the first power converter, wherein the second power converter corresponds to a battery rack having an intermediate value in terms of the charging state of the battery rack.

9. The control method according to claim 6, wherein, Checking the status of the first battery rack includes determining whether the charging status of the first battery rack has reached the upper or lower limit of a preset range of charging status.

10. The control method according to claim 6, wherein, The DC link is a link between the plurality of power converters and the power conversion system, which is configured to perform AC / DC conversion between the plurality of power converters and the power grid.

11. A battery section controller in an energy storage system, the energy storage system comprising a plurality of battery racks and a plurality of power converters respectively connected to the plurality of battery racks, wherein, The battery module controller is associated with the plurality of power converters, and the battery module controller includes: At least one processor; and A memory configured to store at least one instruction executed by the at least one processor; Wherein, the at least one instruction includes: Instructions for controlling the first power converter among the plurality of power converters to execute constant voltage mode control for maintaining the voltage of the DC link at a constant level; Instructions for checking the status of the first battery rack to which the first power converter is connected; and Instructions for the main body to execute constant voltage mode control for the DC link based on changes in the state of the first battery rack. The instructions for the main body to perform constant voltage mode control for the DC link based on the state change of the first battery rack include: stopping the execution of DC link control by the first power converter based on the charging state of the first battery rack, and controlling a second power converter among the plurality of power converters to perform DC link control. The instruction for the main body to perform constant voltage mode control for the DC link according to the state change of the first battery rack further includes: before the DC link control is started solely through the second power converter, controlling the DC link control performed through the first power converter and the DC link control performed through the second power converter to be performed temporarily simultaneously.

12. The battery controller according to claim 11, wherein, The at least one instruction further includes: controlling the other power converters among the plurality of power converters, excluding the first power converter, to perform constant power mode control or constant current mode control.

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