A frequency modulation battery energy storage system based on direct current string regulation

Abstract

The present application belongs to the technical field of electrochemical energy storage application, and particularly relates to a frequency modulation battery energy storage system based on direct current group string deployment. Under the premise of equal application and investment, the frequency modulation battery energy storage system design is adopted by selecting suitable lithium battery products and optimizing deployment, the overall frequency modulation energy storage system is divided into a charging frequency modulation energy storage subsystem and a discharging frequency modulation energy storage subsystem, the battery charging and discharging are respectively carried out independently in the two subsystems, the frequent cyclic charging and discharging in one frequency modulation energy storage system during frequency modulation operation is avoided, the number of charging and discharging back and forth conversion is reduced, the battery life is prolonged, the system efficiency is improved, and the flexible system architecture with the battery group string as the control unit for dynamic recombination not only optimizes the system configuration but also reduces the investment cost, so that the frequency modulation energy storage system efficiency can be effectively improved, the energy storage system life can be prolonged, and the investment benefit can be increased.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage application technology, specifically relating to a frequency-modulated battery energy storage system based on DC string modulation. Background Technology

[0002] The large-scale integration of distributed power sources and renewable energy into the grid poses a significant risk to grid frequency stability, directly impacting the stable and safe operation of the grid. Battery energy storage systems participating in grid frequency regulation are a viable approach, and have gained popularity and widespread application within the industry. Currently, lithium batteries are the most commonly used battery energy storage systems suitable for frequency regulation applications. Their characteristics include: lithium batteries have a limited number of deep charge-discharge cycles within their lifespan; however, battery energy storage systems used for grid (power plant) frequency regulation require frequent charging and discharging, averaging hundreds of times per day, with each cycle lasting only a few minutes. This poses a significant challenge for power-type lithium batteries with their limited charge-discharge cycles, severely impacting the efficiency and lifespan of the lithium battery energy storage system. Another characteristic of lithium batteries is that their charging and discharging current rates are generally different, with the rated maximum charging power often being half of the rated maximum discharging power. If charging and discharging are designed separately in two subsystems, configuring the system based on the discharging current rate would result in a significantly excessive charging current rate, failing to meet charging requirements. Conversely, configuring it based on the charging current rate would require increasing the energy storage capacity and investment costs. Nevertheless, the advantages of using lithium batteries include quick system deployment, mature technology, and good profit margins, making them a preferred choice.

[0003] Therefore, to build a good frequency regulation energy storage system, under the premise of the same application and investment, it is necessary to select suitable lithium battery products and optimize the design of the frequency regulation battery energy storage system. How to reduce the number of repeated charge and discharge cycles of lithium batteries, while optimizing the system configuration to reduce investment costs, are the key issues to improve the efficiency, lifespan and investment benefits of frequency regulation energy storage systems.

[0004] One effective solution is to separate battery charging and discharging into two subsystems, avoiding frequent charging and discharging cycles within a single subsystem, reducing the number of charging and discharging cycles, extending battery life, and improving system efficiency. Summary of the Invention

[0005] As is well known, frequency regulation energy storage systems mainly consist of lithium batteries, battery management systems (BMS), energy storage converters, transformers, and corresponding control and connection accessories. The cost of lithium batteries accounts for approximately half of the total cost. Because the rated current rates for charging and discharging are different, independent configurations are required for each. However, this configuration leads to inconsistent charging and discharging volumes during frequency regulation, resulting in unbalanced and unsustainable operation. To address these issues and ensure the cost-effectiveness, sustainable, and safe operation of frequency regulation energy storage systems, optimizing system structure and sharing battery configurations is the preferred approach. 1. To this end, this invention proposes a frequency-regulating battery energy storage system based on DC string dispatching, mainly comprising: a grid dispatching terminal, a power grid, power grid power lines, a power communication network, a grid AGC terminal, a frequency-regulating energy storage system control device, a frequency-regulating energy storage system communication line, a charging frequency-regulating energy storage subsystem converter, a charging energy storage system transformer, a positive terminal of the charging frequency-regulating energy storage subsystem converter, a negative terminal of the charging frequency-regulating energy storage subsystem converter, a discharging frequency-regulating energy storage subsystem converter, a discharging energy storage system transformer, a positive terminal of the discharging frequency-regulating energy storage subsystem converter, and a discharging frequency-regulating energy storage subsystem. The converter negative terminal, the charging frequency regulation energy storage subsystem converter positive DC bus, the charging frequency regulation energy storage subsystem converter negative DC bus, the discharging frequency regulation energy storage subsystem converter positive DC bus, the discharging frequency regulation energy storage subsystem converter negative DC bus, the first battery string, the first battery string positive terminal, the first battery string negative terminal, the charging controlled switch for the first battery string positive terminal, the discharging controlled switch for the first battery string positive terminal, the charging controlled switch for the first battery string negative terminal, the discharging controlled switch for the first battery string negative terminal, the second battery string, and the... The following are the components of the battery string: positive terminal of the second battery string, negative terminal of the second battery string, charging control switch of the positive terminal of the second battery string, discharging control switch of the positive terminal of the second battery string, charging control switch of the negative terminal of the second battery string, discharging control switch of the negative terminal of the second battery string, and the nth battery string.

[0006] The positive terminal of the first battery string is connected to the charging control switch of the first battery string via the positive terminal of the first battery string. The charging control switch of the positive terminal of the first battery string is then connected to the positive DC bus of the charging frequency regulation energy storage subsystem converter, and the positive DC bus of the charging frequency regulation energy storage subsystem converter is connected to the positive terminal of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the first battery string is connected to the charging control switch of the negative terminal of the first battery string via the negative terminal of the first battery string. The charging control switch of the negative terminal of the first battery string is then connected to the negative DC bus of the charging frequency regulation energy storage subsystem converter, and the negative DC bus of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter is then connected to the power grid line of the power grid through the charging energy storage system transformer, thus forming the power path of the frequency regulation energy storage system for charging the first battery string.

[0007] The positive terminal of the second battery string is connected to the charging control switch of the second battery string via the positive terminal of the second battery string. Then, the charging control switch of the positive terminal of the second battery string is connected to the positive DC bus of the charging frequency regulation energy storage subsystem converter, and the positive DC bus of the charging frequency regulation energy storage subsystem converter is connected to the positive terminal of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the second battery string is connected to the charging control switch of the negative terminal of the second battery string via the negative terminal of the second battery string. Then, the charging control switch of the negative terminal of the second battery string is connected to the negative DC bus of the charging frequency regulation energy storage subsystem converter, and the negative DC bus of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal of the charging frequency regulation energy storage subsystem converter. Finally, the charging frequency regulation energy storage subsystem converter is connected to the power grid line of the power grid through the charging energy storage system transformer, thus forming the power path of the frequency regulation energy storage system for charging the second battery string.

[0008] The positive terminal of the nth battery string is connected to the charging control switch of the nth battery string via the positive terminal of the nth battery string. The charging control switch of the positive terminal of the nth battery string is then connected to the positive DC bus of the charging frequency regulation energy storage subsystem converter, and the positive DC bus of the charging frequency regulation energy storage subsystem converter is connected to the positive terminal of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the nth battery string is connected to the charging control switch of the nth battery string via the negative terminal of the nth battery string. The charging control switch of the negative terminal of the nth battery string is then connected to the negative DC bus of the charging frequency regulation energy storage subsystem converter, and the negative DC bus of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter is then connected to the power grid line of the power grid through the charging energy storage system transformer, thus forming the power path of the frequency regulation energy storage system for charging the nth battery string.

[0009] The positive terminal of the first battery string is connected to the discharge control switch of the first battery string via the positive terminal of the first battery string. Then, the discharge control switch of the positive terminal of the first battery string is connected to the positive DC bus of the discharge frequency regulation energy storage subsystem converter, and the positive DC bus of the discharge frequency regulation energy storage subsystem converter is connected to the positive terminal of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the first battery string is connected to the discharge control switch of the negative terminal of the first battery string via the negative terminal of the first battery string. Then, the discharge control switch of the negative terminal of the first battery string is connected to the negative DC bus of the discharge frequency regulation energy storage subsystem converter, and the negative DC bus of the discharge frequency regulation energy storage subsystem converter is connected to the negative terminal of the discharge frequency regulation energy storage subsystem converter. Finally, the discharge frequency regulation energy storage subsystem converter is connected to the power grid line of the power grid through the discharge energy storage system transformer, thus forming the power path of the frequency regulation energy storage system for the discharge of the first battery string.

[0010] The positive terminal of the second battery string is connected to the discharge control switch of the second battery string via the positive terminal of the second battery string. Then, the discharge control switch of the positive terminal of the second battery string is connected to the positive DC bus of the discharge frequency regulation energy storage subsystem converter, and the positive DC bus of the discharge frequency regulation energy storage subsystem converter is connected to the positive terminal of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the second battery string is connected to the discharge control switch of the negative terminal of the second battery string via the negative terminal of the second battery string. Then, the discharge control switch of the negative terminal of the second battery string is connected to the negative DC bus of the discharge frequency regulation energy storage subsystem converter, and the negative DC bus of the discharge frequency regulation energy storage subsystem converter is connected to the negative terminal of the discharge frequency regulation energy storage subsystem converter. Finally, the discharge frequency regulation energy storage subsystem converter is connected to the power grid line of the power grid through the discharge energy storage system transformer, thus forming the power path of the frequency regulation energy storage system for the discharge of the second battery string.

[0011] The positive terminal of the nth battery string is connected to the discharge control switch of the nth battery string through the positive terminal of the nth battery string. Then, the discharge control switch of the positive terminal of the nth battery string is connected to the positive DC bus of the discharge frequency regulation energy storage subsystem converter, and the positive DC bus of the discharge frequency regulation energy storage subsystem converter is connected to the positive terminal of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the nth battery string is connected to the discharge control switch of the nth battery string through the negative terminal of the nth battery string. Then, the discharge control switch of the negative terminal of the nth battery string is connected to the negative DC bus of the discharge frequency regulation energy storage subsystem converter, and the negative DC bus of the discharge frequency regulation energy storage subsystem converter is connected to the negative terminal of the discharge frequency regulation energy storage subsystem converter. Finally, the discharge frequency regulation energy storage subsystem converter is connected to the power line of the power grid through the discharge energy storage system transformer, thus forming the power path of the frequency regulation energy storage system for the discharge of the nth battery string.

[0012] The power grid dispatching terminal is connected to the power grid AGC terminal through the power communication network, forming a communication link for issuing power grid frequency regulation dispatching control commands;

[0013] The frequency modulation energy storage system control device is connected to the charging frequency modulation energy storage subsystem converter, the discharging frequency modulation energy storage subsystem converter, the first battery string, the charging control switch of the positive terminal of the first battery string, the discharging control switch of the positive terminal of the first battery string, the charging control switch of the negative terminal of the first battery string, the discharging control switch of the negative terminal of the first battery string, the second battery string, the charging control switch of the positive terminal of the second battery string, the discharging control switch of the positive terminal of the second battery string, the charging control switch of the negative terminal of the second battery string, the discharging control switch of the negative terminal of the second battery string, the nth battery string, the charging control switch of the positive terminal of the nth battery string, the discharging control switch of the positive terminal of the nth battery string, the charging control switch of the negative terminal of the nth battery string, and the discharging control switch of the negative terminal of the nth battery string, forming a communication link for frequency modulation control of the frequency modulation energy storage system.

[0014] The frequency regulation energy storage system is also characterized by the following: the overall frequency regulation energy storage system consists of two parts: a charging frequency regulation energy storage subsystem and a discharging frequency regulation energy storage subsystem. The rated charging and discharging power of any frequency regulation energy storage subsystem is greater than or equal to the power required for grid frequency regulation. The rated energy storage capacity configured in the charging frequency regulation energy storage subsystem is N times the rated energy storage capacity configured in the discharging frequency regulation energy storage subsystem, i.e.: N = maximum allowable discharge current of the battery / maximum allowable charging current of the battery.

[0015] The rated energy storage capacity of the charging frequency regulation energy storage subsystem = the rated energy storage capacity of the discharging frequency regulation energy storage subsystem * N;

[0016] The operation control method of the frequency-modulated battery energy storage system based on DC string modulation is as follows:

[0017] When the frequency regulation energy storage system is in normal operation, the control device monitors the charge levels of the first, second, and nth battery strings in real time. Based on the amount of charge stored in each battery string, it dynamically configures the system. The battery strings with the largest stored charge (one-Nth of the total charge) are designated as the discharge frequency regulation energy storage subsystem, and connected to the positive and negative DC bus of the discharge frequency regulation energy storage subsystem converter via controlled switches. Simultaneously, the remaining battery strings with smaller stored charge are designated as the charging frequency regulation energy storage subsystem, and connected to the positive and negative DC bus of the charging frequency regulation energy storage subsystem converter via controlled switches. This constitutes and operates the frequency regulation energy storage system.

[0018] During the above process, the frequency regulation energy storage system control device monitors in real time and receives frequency regulation power commands from the grid dispatch terminal through the grid AGC terminal. If it is determined to be a positive power frequency regulation demand command, it controls the discharge frequency regulation energy storage subsystem to discharge according to the discharge power required by the grid dispatch; if it is determined to be a negative power frequency regulation demand command, it controls the charging frequency regulation energy storage subsystem to charge according to the charging power required by the grid dispatch.

[0019] The frequency regulation energy storage system control device monitors in real time and dynamically reconfigures the system when it detects that the battery strings are fully charged or fully discharged. Specifically, it dynamically configures the system based on the amount of energy stored in each battery string, designating the battery strings with the largest stored energy (Nths) as the discharging frequency regulation energy storage subsystem and the remaining battery strings with the smallest stored energy as the charging frequency regulation energy storage subsystem. This reconfigures and operates the frequency regulation energy storage system, ensuring that the rated energy storage capacity of the charging subsystem is always N times that of the discharging subsystem. During a dynamic adjustment cycle, the charging subsystem only charges, while the discharging subsystem only discharges.

[0020] The frequency-regulating battery energy storage system based on DC string distribution is characterized in that the battery strings constituting the frequency-regulating energy storage subsystem are composed of batteries, a battery management system (BMS), and accessories connected together, and the specifications, quantity, and rated capacity of the batteries in each battery string are equal.

[0021] The frequency-modulated battery energy storage system based on DC string modulation is characterized by a frequency-modulated energy storage system control device, comprising: a computer real-time monitoring and control module, a preset system program module, a data storage circuit module, a clock module, a communication management module, a power supply module, and a system control bus, wherein:

[0022] The computer real-time monitoring and control module is connected to the pre-set system program module, data storage circuit module, clock module, communication management module, and power supply module through the system control bus, forming a frequency modulation energy storage management and control system and a control and communication link;

[0023] The computer real-time monitoring and control module connects to the power communication network and the power grid AGC terminal through the communication management module to receive frequency regulation power commands issued by the power grid dispatch terminal. It also connects to the communication lines of the frequency regulation energy storage system and the equipment of the frequency regulation energy storage system through the communication management module, thus forming a control link for frequency regulation power distribution and monitoring of the frequency regulation energy storage system.

[0024] This invention discloses a frequency-regulating battery energy storage system based on DC string configuration. Under the premise of equivalent application and investment, it adopts a frequency-regulating battery energy storage system design with the selection of suitable lithium battery products and optimized configuration. The overall frequency-regulating energy storage system is divided into two parts: a charging frequency-regulating energy storage subsystem and a discharging frequency-regulating energy storage subsystem. Battery charging and discharging are carried out independently in the two subsystems, avoiding frequent cyclic charging and discharging in a single frequency-regulating energy storage system during frequency regulation operation. This reduces the number of charging and discharging conversions, extends battery life, and improves system efficiency. At the same time, it adopts a flexible system architecture with battery strings as control units for dynamic reconfiguration, which not only optimizes system configuration but also reduces investment costs. This can effectively improve the efficiency of the frequency-regulating energy storage system, extend the life of the energy storage system, and increase investment benefits. Attached Figure Description

[0025] Figure 1 This is a schematic block diagram of a frequency-modulated battery energy storage system based on DC string modulation.

[0026] Figure 2 This is a schematic diagram illustrating the structural principle of the control device for a frequency regulation energy storage system. Detailed Implementation

[0027] As an example, a frequency-modulated battery energy storage system based on DC string modulation is described in conjunction with the accompanying drawings. However, the technology and solution of the present invention are not limited to the content given in this example.

[0028] like Figure 1As shown, a frequency-regulating battery energy storage system based on DC string dispatch mainly includes: a power grid dispatch terminal (1), a power grid (2), a power grid power line (3), a power communication network (4), a power grid AGC terminal (5), a frequency-regulating energy storage system control device (6), a frequency-regulating energy storage system communication line (7), a charging frequency-regulating energy storage subsystem converter (8), a charging energy storage system transformer (8c), a positive terminal of the charging frequency-regulating energy storage subsystem converter (80), a negative terminal of the charging frequency-regulating energy storage subsystem converter (81), and a discharging frequency-regulating energy storage subsystem converter. Device (9), discharge energy storage system transformer (9c), discharge frequency regulation energy storage subsystem converter positive terminal (90), discharge frequency regulation energy storage subsystem converter negative terminal (91), charging frequency regulation energy storage subsystem converter positive DC bus (8a), charging frequency regulation energy storage subsystem converter negative DC bus (8b), discharge frequency regulation energy storage subsystem converter positive DC bus (9a), discharge frequency regulation energy storage subsystem converter negative DC bus (9b), first battery string (11), first battery string positive terminal (11a), first battery string Battery string negative terminal (11b), first battery string positive terminal charging control switch (811), first battery string positive terminal discharging control switch (812), first battery string negative terminal charging control switch (911), first battery string negative terminal discharging control switch (912), second battery string (21), second battery string positive terminal (21a), second battery string negative terminal (21b), second battery string positive terminal charging control switch (821), second battery string positive terminal discharging control switch (812), second battery string positive terminal discharging control switch (812), second battery string negative terminal charging ... 822), charging control switch (921) for the negative terminal of the second battery string, discharging control switch (922) for the negative terminal of the second battery string, the nth battery string (n1), the positive terminal (n1a) of the nth battery string, the negative terminal (n1b) of the nth battery string, charging control switch (8n1) for the positive terminal of the nth battery string, discharging control switch (8n2) for the positive terminal of the nth battery string, charging control switch (9n1) for the negative terminal of the nth battery string, and discharging control switch (9n2) for the negative terminal of the nth battery string, wherein:

[0029] The positive terminal of the first battery string (11) is connected to the charging control switch (811) of the first battery string via the positive terminal (11a) of the first battery string. The charging control switch (811) of the first battery string is then connected to the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter. The positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter is connected to the positive terminal (80) of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the first battery string (11) is connected to the first battery... The charging control switch (911) of the negative terminal of the first battery string is connected to the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter, and the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal (81) of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter (8) is then connected to the power line (3) of the power grid (2) through the charging energy storage system transformer (8c), thus forming the power path of the frequency regulation energy storage system for charging the first battery string (11).

[0030] The positive terminal (21) of the second battery string is connected to the charging control switch (821) of the second battery string via the positive terminal (21a) of the second battery string. The charging control switch (821) of the second battery string is then connected to the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter. The positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter is also connected to the positive terminal (80) of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the second battery string (21) is connected to the second battery string via the negative terminal (21b). The charging control switch (921) of the negative terminal of the second battery string is connected to the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter, and the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal (81) of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter (8) is then connected to the power line (3) of the power grid (2) through the charging energy storage system transformer (8c), thus forming the power path of the frequency regulation energy storage system for charging the second battery string (21).

[0031] The positive terminal (n1) of the nth battery string is connected to the charging control switch (8n1) of the nth battery string via the positive terminal (n1a). The charging control switch (8n1) of the nth battery string is then connected to the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter. The positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter is also connected to the positive terminal (80) of the charging frequency regulation energy storage subsystem converter. Simultaneously, the negative terminal of the nth battery string (n1) is connected to the nth battery via the negative terminal (n1b). The charging control switch (9n1) of the negative terminal of the string is connected to the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter, and the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal (81) of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter (8) is then connected to the power line (3) of the power grid (2) through the charging energy storage system transformer (8c), thus forming the power path of the frequency regulation energy storage system for charging the nth battery string (n1).

[0032] The positive terminal of the first battery string (11) is connected to the discharge control switch (812) of the first battery string through the positive terminal (11a) of the first battery string. Then, the discharge control switch (812) of the first battery string is connected to the positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter. The positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter is connected to the positive terminal (90) of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the first battery string (11) is connected to the first battery... The discharge control switch (912) of the negative terminal of the first battery string is connected to the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter, and the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter is connected to the negative terminal (91) of the frequency regulation energy storage subsystem converter. The frequency regulation energy storage subsystem converter (9) is then connected to the power line (3) of the power grid (2) through the power storage system transformer (9c), forming the frequency regulation energy storage system power path for the discharge of the first battery string (11).

[0033] The positive terminal of the second battery string (21) is connected to the discharge control switch (822) of the second battery string via the positive terminal (21a) of the second battery string. The discharge control switch (822) of the second battery string is then connected to the positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter. The positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter is also connected to the positive terminal (90) of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the second battery string (21) is connected to the second battery string via the negative terminal (21b). The discharge control switch (922) of the negative terminal of the second battery string is connected to the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter, and the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter is connected to the negative terminal (91) of the frequency regulation energy storage subsystem converter. The frequency regulation energy storage subsystem converter (9) is then connected to the power line (3) of the power grid (2) through the power storage system transformer (9c), forming the frequency regulation energy storage system power path for the discharge of the second battery string (21).

[0034] The positive terminal of the nth battery string (n1) is connected to the discharge control switch (8n2) of the nth battery string via the positive terminal (n1a). The discharge control switch (8n2) then connects to the positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter. The positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter is also connected to the positive terminal (90) of the discharge frequency regulation energy storage subsystem converter. Simultaneously, the negative terminal of the nth battery string (n1) is connected to the nth battery string via the negative terminal (n1b). The discharge control switch (9n2) of the negative terminal of the nth battery string is connected to the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter, and the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter is connected to the negative terminal (91) of the frequency regulation energy storage subsystem converter. The frequency regulation energy storage subsystem converter (9) is then connected to the power line (3) of the power grid (2) through the power storage system transformer (9c), thus forming the frequency regulation energy storage system power path for the discharge of the nth battery string (n1).

[0035] The power grid dispatch terminal (1) is connected to the power grid AGC terminal (5) through the power communication network (4) to form a communication link for issuing power grid frequency regulation dispatch control commands;

[0036] The frequency modulation energy storage system control device (6) is connected to the charging frequency modulation energy storage subsystem converter (8), the discharging frequency modulation energy storage subsystem converter (9), the first battery string (11), the charging control switch (811) of the positive terminal of the first battery string, the discharging control switch (812) of the positive terminal of the first battery string, the charging control switch (911) of the negative terminal of the first battery string, the discharging control switch (912) of the negative terminal of the first battery string, the second battery string (21), and the charging control switch of the positive terminal of the second battery string via the frequency modulation energy storage system communication line (7). (821), the discharge control switch of the positive terminal of the second battery string (822), the charging control switch of the negative terminal of the second battery string (921), the discharge control switch of the negative terminal of the second battery string (922), the nth battery string (n1), the charging control switch of the positive terminal of the nth battery string (8n1), the discharge control switch of the positive terminal of the nth battery string (8n2), the charging control switch of the negative terminal of the nth battery string (9n1), and the discharge control switch of the negative terminal of the nth battery string (9n2) constitute the communication link for frequency modulation control of the frequency modulation energy storage system;

[0037] The frequency regulation energy storage system is also characterized by the following: the overall frequency regulation energy storage system consists of two parts: a charging frequency regulation energy storage subsystem and a discharging frequency regulation energy storage subsystem. The rated charging and discharging power of any frequency regulation energy storage subsystem is greater than or equal to the power required for grid frequency regulation. The rated energy storage capacity configured in the charging frequency regulation energy storage subsystem is N times the rated energy storage capacity configured in the discharging frequency regulation energy storage subsystem, i.e.: N = maximum allowable discharge current of the battery / maximum allowable charging current of the battery.

[0038] The rated energy storage capacity of the charging frequency regulation energy storage subsystem = the rated energy storage capacity of the discharging frequency regulation energy storage subsystem * N;

[0039] The operation control method of the frequency-modulated battery energy storage system based on DC string modulation is as follows:

[0040] When the frequency regulation energy storage system is in normal operation, the frequency regulation energy storage system control device (6) monitors the power of the first battery string (11), the second battery string (21), and the nth battery string (n1) in real time, and dynamically configures the battery strings according to the amount of power stored. The battery strings with more stored power are designated as the discharge frequency regulation energy storage subsystem, and are connected to the positive DC bus (9a) and negative DC bus (9b) of the discharge frequency regulation energy storage subsystem converter through a controlled switch. At the same time, the remaining battery strings with less stored power are designated as the charging frequency regulation energy storage subsystem, and are connected to the positive DC bus (8a) and negative DC bus (8b) of the charging frequency regulation energy storage subsystem converter through a controlled switch. Thus, the frequency regulation energy storage system is formed and put into operation.

[0041] During the above process, the frequency regulation energy storage system control device (6) monitors in real time and receives the frequency regulation power command issued by the grid dispatch terminal (1) through the grid AGC terminal (5). If it is determined to be a positive power frequency regulation demand command, it controls the discharge frequency regulation energy storage subsystem to discharge according to the discharge power required by the grid dispatch; if it is determined to be a negative power frequency regulation demand command, it controls the charging frequency regulation energy storage subsystem to charge according to the charging power required by the grid dispatch.

[0042] The frequency regulation energy storage system control device (6) monitors in real time and will dynamically reconfigure when it detects that the battery string is fully charged or fully discharged. That is, it dynamically configures the battery string according to the amount of energy stored in the battery string, designating the battery string with more stored energy as the discharge frequency regulation energy storage subsystem and the remaining battery string with less stored energy as the charging frequency regulation energy storage subsystem. Thus, the frequency regulation energy storage system is reconstructed and put into operation, so that the rated energy storage capacity of the charging frequency regulation energy storage subsystem is always N times that of the discharging frequency regulation energy storage subsystem. In one dynamic adjustment cycle, the charging frequency regulation energy storage subsystem only charges, and the other discharging frequency regulation energy storage subsystem only discharges.

[0043] The frequency-regulating battery energy storage system based on DC string distribution is characterized in that the battery strings constituting the frequency-regulating energy storage subsystem are composed of batteries, a battery management system (BMS), and accessories connected together, and the specifications, quantity, and rated capacity of the batteries in each battery string are equal.

[0044] like Figure 2 As shown, a frequency-modulated battery energy storage system based on DC string modulation is characterized in that the frequency-modulated energy storage system control device (6) includes: a computer real-time monitoring and control module (601), a preset system program module (602), a data storage circuit module (603), a clock module (604), a communication management module (605), a power supply module (606), and a system control bus (607), wherein:

[0045] The computer real-time monitoring and control module (601) is connected to the preset system program module (602), data storage circuit module (603), clock module (604), communication management module (605), and power supply module (606) respectively through the system control bus (607), forming a frequency modulation energy storage management and control system and control and communication link;

[0046] The computer real-time monitoring and control module (601) connects to the power communication network (4) and the power grid AGC terminal (5) through the communication management module (605) to receive the frequency regulation power command issued by the power grid dispatch terminal (1), and connects to the communication line (7) of the frequency regulation energy storage system and the equipment of the frequency regulation energy storage system through the communication management module (605) to form a control link for frequency regulation power distribution and frequency regulation energy storage system monitoring.

[0047] This invention discloses a frequency-regulating battery energy storage system based on DC string configuration. Under the premise of equivalent application and investment, it adopts a frequency-regulating battery energy storage system design with the selection of suitable lithium battery products and optimized configuration. The overall frequency-regulating energy storage system is divided into two parts: a charging frequency-regulating energy storage subsystem and a discharging frequency-regulating energy storage subsystem. Battery charging and discharging are carried out independently in the two subsystems, avoiding frequent cyclic charging and discharging in a single frequency-regulating energy storage system during frequency regulation operation. This reduces the number of charging and discharging conversions, extends battery life, and improves system efficiency. At the same time, it adopts a flexible system architecture with battery strings as control units for dynamic reconfiguration, which not only optimizes system configuration but also reduces investment costs. This can effectively improve the efficiency of the frequency-regulating energy storage system, extend the life of the energy storage system, and increase investment benefits.

Claims

1. A frequency modulation battery energy storage system based on direct current string regulation, comprising: Power grid dispatch terminal (1), power grid (2), power grid power line (3), power communication network (4), power grid AGC terminal (5), frequency regulation energy storage system control device (6), frequency regulation energy storage system communication line (7), charging frequency regulation energy storage subsystem converter (8), charging energy storage system transformer (8c), charging frequency regulation energy storage subsystem converter positive terminal (80), charging frequency regulation energy storage subsystem converter negative terminal (81), discharging frequency regulation energy storage subsystem converter (9), discharging energy storage system transformer (9c), discharging Positive terminal (90) of the frequency modulation energy storage subsystem converter, negative terminal (91) of the discharge frequency modulation energy storage subsystem converter, positive DC bus (8a) of the charging frequency modulation energy storage subsystem converter, negative DC bus (8b) of the charging frequency modulation energy storage subsystem converter, positive DC bus (9a) of the discharge frequency modulation energy storage subsystem converter, negative DC bus (9b) of the discharge frequency modulation energy storage subsystem converter, first battery string (11), positive terminal (11a) of the first battery string, negative terminal (11b) of the first battery string The first battery string has a charging control switch (811) for the positive terminal, a discharging control switch (812) for the positive terminal, a charging control switch (911) for the negative terminal, a discharging control switch (912) for the negative terminal, a second battery string (21), a positive terminal (21a) for the second battery string, a negative terminal (21b) for the second battery string, a charging control switch (821) for the positive terminal, and a discharging control switch (822) for the positive terminal, and a second battery string... The following are controlled switches for the following battery string: charging control switch (921) for the negative terminal of the second battery string, discharging control switch (922) for the negative terminal of the nth battery string, the nth battery string (n1), the nth battery string positive terminal (n1a), the nth battery string negative terminal (n1b), charging control switch (8n1) for the positive terminal of the nth battery string, discharging control switch (8n2) for the positive terminal of the nth battery string, charging control switch (9n1) for the negative terminal of the nth battery string, and discharging control switch (9n2) for the negative terminal of the nth battery string, wherein: The positive terminal of the first battery string (11) is connected to the charging control switch (811) of the first battery string via the positive terminal (11a) of the first battery string. The charging control switch (811) of the first battery string is then connected to the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter. The positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter is connected to the positive terminal (80) of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the first battery string (11) is connected to the first battery... The charging control switch (911) of the negative terminal of the first battery string is connected to the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter, and the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal (81) of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter (8) is then connected to the power line (3) of the power grid (2) through the charging energy storage system transformer (8c), thus forming the power path of the frequency regulation energy storage system for charging the first battery string (11). The positive terminal of the second battery string (21) is connected to the controlled switch (821) of the positive DC bus of the charging converter of the second battery string via the positive terminal (21a) of the second battery string. Then, the controlled switch (821) of the positive terminal of the second battery string is connected to the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter, and the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter is connected to the positive terminal (80) of the charging frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the second battery string (21) is connected to the negative terminal (21b) of the second battery string. The charging control switch (921) is connected to the negative terminal of the second battery string, and then the charging control switch (921) is connected to the negative DC bus (8b) of the charging frequency regulation energy storage subsystem converter. The negative DC bus (8b) of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal (81) of the charging frequency regulation energy storage subsystem converter. Then the charging frequency regulation energy storage subsystem converter (8) is connected to the power line (3) of the power grid (2) through the charging energy storage system transformer (8c), thus forming the power path of the frequency regulation energy storage system for charging the second battery string (21). The positive terminal of the nth battery string (n1) is connected to the charging control switch (8n1) of the nth battery string via the positive terminal (n1a). The charging control switch (8n1) of the nth battery string is then connected to the positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter. The positive DC bus (8a) of the charging frequency regulation energy storage subsystem converter is also connected to the positive terminal (80) of the charging frequency regulation energy storage subsystem converter. Simultaneously, the negative terminal of the nth battery string (n1) is connected to the nth battery string via the negative terminal (n1b). The charging control switch (9n1) of the negative terminal of the string is connected to the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter, and the DC bus (8b) of the negative terminal of the charging frequency regulation energy storage subsystem converter is connected to the negative terminal (81) of the charging frequency regulation energy storage subsystem converter. The charging frequency regulation energy storage subsystem converter (8) is then connected to the power line (3) of the power grid (2) through the charging energy storage system transformer (8c), thus forming the power path of the frequency regulation energy storage system for charging the nth battery string (n1). The positive terminal of the first battery string (11) is connected to the discharge control switch (812) of the first battery string through the positive terminal (11a) of the first battery string. Then, the discharge control switch (812) of the first battery string is connected to the positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter. The positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter is connected to the positive terminal (90) of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the first battery string (11) is connected to the first battery... The discharge control switch (912) of the negative terminal of the first battery string is connected to the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter, and the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter is connected to the negative terminal (91) of the frequency regulation energy storage subsystem converter. The frequency regulation energy storage subsystem converter (9) is then connected to the power line (3) of the power grid (2) through the power storage system transformer (9c), forming the frequency regulation energy storage system power path for the discharge of the first battery string (11). The positive terminal of the second battery string (21) is connected to the discharge control switch (822) of the second battery string via the positive terminal (21a) of the second battery string. The discharge control switch (822) of the second battery string is then connected to the positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter. The positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter is also connected to the positive terminal (90) of the discharge frequency regulation energy storage subsystem converter. At the same time, the negative terminal of the second battery string (21) is connected to the second battery string via the negative terminal (21b). The discharge control switch (922) of the negative terminal of the second battery string is connected to the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter, and the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter is connected to the negative terminal (91) of the frequency regulation energy storage subsystem converter. The frequency regulation energy storage subsystem converter (9) is then connected to the power line (3) of the power grid (2) through the power storage system transformer (9c), forming the frequency regulation energy storage system power path for the discharge of the second battery string (21). The positive terminal of the nth battery string (n1) is connected to the discharge control switch (8n2) of the nth battery string via the positive terminal (n1a). The discharge control switch (8n2) then connects to the positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter. The positive DC bus (9a) of the discharge frequency regulation energy storage subsystem converter is also connected to the positive terminal (90) of the discharge frequency regulation energy storage subsystem converter. Simultaneously, the negative terminal of the nth battery string (n1) is connected to the nth battery string via the negative terminal (n1b). The discharge control switch (9n2) of the negative terminal of the nth battery string is connected to the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter, and the DC bus (9b) of the negative terminal of the frequency regulation energy storage subsystem converter is connected to the negative terminal (91) of the frequency regulation energy storage subsystem converter. The frequency regulation energy storage subsystem converter (9) is then connected to the power line (3) of the power grid (2) through the power storage system transformer (9c), thus forming the frequency regulation energy storage system power path for the discharge of the nth battery string (n1). The power grid dispatch terminal (1) is connected to the power grid AGC terminal (5) through the power communication network (4) to form a communication link for issuing power grid frequency regulation dispatch control commands; The frequency modulation energy storage system control device (6) is connected to the charging frequency modulation energy storage subsystem converter (8), the discharging frequency modulation energy storage subsystem converter (9), the first battery string (11), the charging control switch (811) of the positive terminal of the first battery string, the discharging control switch (812) of the positive terminal of the first battery string, the charging control switch (911) of the negative terminal of the first battery string, the discharging control switch (912) of the negative terminal of the first battery string, the second battery string (21), and the charging control switch of the positive terminal of the second battery string via the frequency modulation energy storage system communication line (7). (821), the discharge control switch of the positive terminal of the second battery string (822), the charging control switch of the negative terminal of the second battery string (921), the discharge control switch of the negative terminal of the second battery string (922), the nth battery string (n1), the charging control switch of the positive terminal of the nth battery string (8n1), the discharge control switch of the positive terminal of the nth battery string (8n2), the charging control switch of the negative terminal of the nth battery string (9n1), and the discharge control switch of the negative terminal of the nth battery string (9n2) constitute the communication link for frequency modulation control of the frequency modulation energy storage system; The frequency regulation energy storage system is also characterized by the following: the overall frequency regulation energy storage system consists of two parts: a charging frequency regulation energy storage subsystem and a discharging frequency regulation energy storage subsystem. The rated charging and discharging power of any frequency regulation energy storage subsystem is greater than or equal to the power required for grid frequency regulation. The rated energy storage capacity configured in the charging frequency regulation energy storage subsystem is N times the rated energy storage capacity configured in the discharging frequency regulation energy storage subsystem, i.e.: N = maximum allowable discharge current of the battery / maximum allowable charging current of the battery. The rated energy storage capacity of the charging frequency regulation energy storage subsystem = the rated energy storage capacity of the discharging frequency regulation energy storage subsystem * N; The operation control method of the frequency-modulated battery energy storage system based on DC string modulation is as follows: When the frequency regulation energy storage system is in normal operation, the frequency regulation energy storage system control device (6) monitors the power of the first battery string (11), the second battery string (21), and the nth battery string (n1) in real time, and dynamically configures the battery strings according to the amount of power stored. The battery strings with more stored power are designated as the discharge frequency regulation energy storage subsystem, and are connected to the positive DC bus (9a) and negative DC bus (9b) of the discharge frequency regulation energy storage subsystem converter through a controlled switch. At the same time, the remaining battery strings with less stored power are designated as the charging frequency regulation energy storage subsystem, and are connected to the positive DC bus (8a) and negative DC bus (8b) of the charging frequency regulation energy storage subsystem converter through a controlled switch. Thus, the frequency regulation energy storage system is formed and put into operation. During the above process, the frequency regulation energy storage system control device (6) monitors in real time and receives the frequency regulation power command issued by the grid dispatch terminal (1) through the grid AGC terminal (5). If it is determined to be a positive power frequency regulation demand command, it controls the discharge frequency regulation energy storage subsystem to discharge according to the discharge power required by the grid dispatch; if it is determined to be a negative power frequency regulation demand command, it controls the charging frequency regulation energy storage subsystem to charge according to the charging power required by the grid dispatch. The frequency regulation energy storage system control device (6) monitors in real time and will dynamically reconfigure when it detects that the battery string is fully charged or fully discharged. That is, it dynamically configures the battery string according to the amount of energy stored in the battery string, designating the battery string with more stored energy as the discharge frequency regulation energy storage subsystem and the remaining battery string with less stored energy as the charging frequency regulation energy storage subsystem. Thus, the frequency regulation energy storage system is reconstructed and put into operation, so that the rated energy storage capacity of the charging frequency regulation energy storage subsystem is always N times that of the discharging frequency regulation energy storage subsystem. In one dynamic adjustment cycle, the charging frequency regulation energy storage subsystem only charges, and the other discharging frequency regulation energy storage subsystem only discharges.

2. The frequency modulation battery energy storage system based on DC string regulation according to claim 1, characterized in that The battery string that makes up the frequency regulation energy storage subsystem is composed of batteries, a battery management system (BMS), and accessories connected together, and the specifications, quantity, and rated capacity of the batteries in each battery string are equal.

3. The frequency modulation battery energy storage system based on DC string regulation according to claim 1, characterized in that The frequency regulation energy storage system control device (6) includes: a computer real-time monitoring and control module (601), a preset system program module (602), a data storage circuit module (603), a clock module (604), a communication management module (605), a power supply module (606), and a system control bus (607), wherein: The computer real-time monitoring and control module (601) is connected to the preset system program module (602), data storage circuit module (603), clock module (604), communication management module (605), and power supply module (606) respectively through the system control bus (607), forming a frequency modulation energy storage management and control system and control and communication link; The computer real-time monitoring and control module (601) connects to the power communication network (4) and the power grid AGC terminal (5) through the communication management module (605) to receive the frequency regulation power command issued by the power grid dispatch terminal (1), and connects to the communication line (7) of the frequency regulation energy storage system and the equipment of the frequency regulation energy storage system through the communication management module (605) to form a control link for frequency regulation power distribution and frequency regulation energy storage system monitoring.

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