CN117335476A - SOC balance method, device and system for network-structured energy storage - Google Patents

Abstract

The invention relates to a SOC balance method, a device and a system for net-structured energy storage, wherein the method is applied to a net-structured energy storage system, the net-structured energy storage system comprises a plurality of net-structured converters and energy storage equipment connected with the net-structured converters, and the method comprises the following steps: acquiring the real-time SOC of each energy storage device, and calculating to acquire an average SOC; and generating an active power compensation signal for each grid-connected converter based on the difference value between the average SOC and the real-time SOC of the corresponding energy storage device, and controlling the output active power of the grid-connected converter based on the active power compensation signal. Compared with the prior art, the system and the method can realize SOC balance among multiple energy storage devices on the premise of not influencing the supporting capacity of the system power grid, and have the advantages of high reliability and the like.

Description

SOC balancing method, device and system for networked energy storage

Technical field

The invention belongs to the field of power electronics technology, and specifically relates to a SOC (state of charge, state of charge) balancing method, device and system for networked energy storage.

Background technique

In the existing power system, the proportion of new energy sources such as wind power and photovoltaic power generation continues to increase. However, these new energy sources are intermittent and unpredictable, making it difficult to meet the stable supply of power loads. At the same time, with the rapid growth of power load, the peak and valley differences in power demand have become increasingly obvious. By storing and releasing new energy, energy storage converters can effectively buffer the intermittency of new energy, promote large-scale integration of new energy into the grid, and achieve flat-top filling of power loads, thereby improving the reliability and flexibility of the power grid. . In addition, early energy storage systems mainly used grid-following converters, which were only used to provide power output to the grid. However, as the proportion of converters in the power grid increases, the requirements for converters also increase. In addition to power output, converters also need to provide grid support for the grid. In order to meet this demand, a grid-type converter is proposed. By simulating the port characteristics of a traditional synchronous machine, the grid-type converter not only achieves power output, but also achieves active support for the power grid.

The invention patent CN116316768B proposes a network-type distributed energy storage system. The system includes: a battery module, a network-type power conversion module, an integrated energy storage management module and a medium-voltage transformer. By setting sub-systems corresponding to the batteries one-to-one The power conversion unit can prevent inter-cluster voltage unevenness caused by battery cluster inconsistency, automatically adjust the power distribution of each battery cluster, and fully utilize the flexibility of distributed energy storage to realize battery energy storage while actively supporting the power grid. Maximize utilization. This patent only considers the power balance between each power conversion unit and does not consider the impact of power distribution on battery SOC. If the SOC of the energy storage device is too low, it will reduce the life of the energy storage device and affect the efficiency of the system.

Invention patent CN115276069B discloses a virtual network coordination control method and device for large-scale energy storage power stations. Each battery pack PCS in the energy storage system controls the supporting grid frequency based on the virtual synchronous generator (VSG). According to the SOC status of each battery pack in the energy storage system, the virtual inertia parameters of each VSG unit are adjusted based on the proposed control coefficient correction algorithm. Correction, thereby adjusting the power output of the energy storage unit. However, this control strategy modifies control parameters such as virtual inertia, which will affect the inertia characteristics and the ability of the energy storage system to support the power grid.

In order to ensure the good operation of the power grid, two requirements are put forward for the energy storage grid-connected system: first, to improve the support capacity of the energy storage grid-connected system to the power grid, which can be achieved by using grid-type converters; second, to realize multiple storage grid-connected systems. SOC balance between energy devices. If the SOC of the energy storage device is too low, it will reduce the life of the energy storage device. SOC balance can avoid this situation. However, it is difficult for the current method to achieve these two requirements at the same time. Some methods ensure the grid support capability of the energy storage grid-connected system, but do not consider SOC balance. Another part of the method ensures SOC balance, but changes the grid support capacity of the energy storage grid-connected system. Therefore, it is necessary to develop a new energy storage grid-connected system control method to achieve SOC balance among multiple energy storage devices without affecting the system grid support capacity.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a highly reliable SOC balancing method, device and system for network-type energy storage, which can achieve multiple functions without affecting the system power grid support capacity. SOC balance between energy storage devices.

The object of the present invention can be achieved through the following technical solutions:

A SOC balancing method for network-type energy storage, applied to a network-type energy storage system. The network-type energy storage system includes multiple network-type converters and energy storage equipment connected to them, including the following steps:

Obtain the real-time SOC of each energy storage device and calculate an average SOC;

For each grid-type converter, an active power compensation signal is generated based on the difference between the average SOC and the real-time SOC of the corresponding energy storage device, and based on the active power compensation signal, the output of the grid-type converter is controlled. Active power.

Further, the active power compensation signal is obtained based on a PI controller, a repetitive controller or a model predictive controller.

Further, the calculation formula of the active power compensation signal is:

Among them, ΔP is the active power compensation signal, K _p,SOC and K _i,SOC are the proportional coefficient and integral coefficient of the PI controller respectively, SOC _ave is the average SOC, and SOC _i is the real-time SOC of the i-th energy storage device.

Further, the active power compensation signals of each of the grid-type converters are generated independently.

Further, the output active power of the control grid-type converter specifically includes:

Collect voltage and current information at the public connection point of the grid-type converter in real time, and calculate and obtain the corresponding real-time active power based on the voltage and current information;

Generate a voltage phase control signal based on the real-time active power and the active power compensation signal;

A control instruction is generated based on the voltage phase control signal to control the output active power of the grid-type converter.

Further, after collecting the voltage and current information, the corresponding real-time reactive power is calculated based on the voltage and current information, a voltage amplitude control signal is generated, and a control instruction is generated based on the voltage amplitude control signal to control the network construction. The output reactive power of the converter.

The invention also provides a SOC balancing device for network-type energy storage, which is applied to a network-type energy storage system. The network-type energy storage system includes a plurality of network-type converters and energy storage equipment connected thereto, including :

The acquisition and processing module is connected to each energy storage device to obtain the real-time SOC of the energy storage device and calculate an average SOC;

Multiple single converter control modules are respectively connected to each network-type converter and connected to the acquisition and processing module. Based on the difference between the average SOC and the real-time SOC of the corresponding energy storage device, an active power compensation signal is generated. , based on the active power compensation signal, control the output active power of the corresponding grid-type converter.

Further, the single converter control module includes:

SOC balance control unit, used to generate the active power compensation signal;

A grid-type control unit is used to generate control instructions for controlling the output power of a corresponding grid-type converter through active power control and reactive power control, and in active power control, compensation is performed based on the active power compensation signal. deal with.

Further, the active power compensation signal is obtained based on a PI controller, a repetitive controller or a model predictive controller.

Further, the calculation formula of the active power compensation signal is:

Among them, ΔP is the active power compensation signal, K _{p, SOC} and K _{i, SOC} are the proportional coefficient and integral coefficient of the PI controller respectively, SOC _ave is the average SOC, and SOC _i is the i-th network-type converter connected The real-time SOC value of the energy storage device.

Further, in the network-type control unit, the active power control specifically includes:

Collect voltage and current information at the common connection point of the grid-type converter in real time, and calculate and obtain the corresponding real-time active power based on the voltage and current information;

Generate a voltage phase control signal based on the real-time active power and the active power compensation signal;

A control instruction is generated based on the voltage phase control signal to control the output power of the corresponding grid-type converter.

Further, in the network-type control unit, the reactive power control specifically includes:

The corresponding real-time reactive power is calculated based on the voltage and current information, a voltage amplitude control signal is generated, and a control instruction is generated based on the voltage amplitude control signal to control the output reactive power of the grid-type converter.

The present invention also provides a network-type energy storage system, including the above-mentioned SOC balancing device for network-type energy storage.

Compared with the prior art, the present invention has the following beneficial effects:

1. On the premise of ensuring the grid support capability of the grid-type converter, the present invention generates an active power compensation signal according to the real-time SOC, and dynamically adjusts the grid control parameters, thereby adjusting the output power of the grid-type converter to achieve The SOC balance between multiple energy storage devices is ensured to ensure that the SOC of some energy storage devices will not be too low, which increases the life of the energy storage system and ensures the good operation of the system.

2. The control strategy of the present invention does not modify the original control parameters and ensures the same inertia characteristics.

3. The present invention performs independent control on each network-type converter, and can be realized by local control of each network-type converter, thereby improving the reliability of the system.

Description of drawings

Figure 1 is a schematic structural diagram of the network energy storage system applied in the present invention;

Figure 2 is a schematic diagram of the SOC balancing strategy architecture of the present invention;

Figure 3 is a schematic diagram of the DC voltage controller of the DC-DC converter;

Figure 4 shows the active power and SOC simulation results of the same starting SOC under the control of the present invention, where (4a) is the active power and (4b) is the SOC;

Figure 5 shows the active power and SOC simulation results of different starting SOCs under the control of the present invention, where (5a) is the active power and (5b) is the SOC.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention and provides detailed implementation modes and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

Example 1

This embodiment provides a SOC balancing method for network-type energy storage, which is applied to a network-type energy storage system. As shown in Figure 1, the network-type energy storage system includes multiple network-type converters and connected to them. Energy storage equipment, the SOC balancing method includes the following steps: obtain the real-time SOC value of the energy storage equipment connected to each network-type converter, and calculate an average SOC; for a certain network-type converter, based on The difference between the average SOC and the real-time SOC value of the grid-type converter generates an active power compensation signal. Based on the active power compensation signal, the output active power of the corresponding grid-type converter is controlled. This SOC balancing method can perform SOC balancing control on multiple energy storage grid-connected converters using network-type control, ensuring that the SOC of some energy storage devices will not be too low, extending the life of the energy storage system, and ensuring the system's Running well.

In a specific implementation, the active power compensation signal can be obtained based on a PI controller, a repetitive controller, a model predictive controller, or the like. This embodiment uses a PI controller, and the calculation formula of the active power compensation signal is:

Among them, ΔP is the active power compensation signal, K _{p, SOC} and K _{i, SOC} are the proportional coefficient and integral coefficient of the PI controller respectively, SOC _ave is the average SOC, and SOC _i is the i-th network-type converter connected The real-time SOC value of the energy storage device.

Through the above PI controller, the active power compensation signal can be easily obtained, and then the output power of the grid-type converter can be controlled to ensure the SOC balance between multiple grid-type converters.

This embodiment verifies the effectiveness of the above solution through the following two simulation experiments, and uses a simulation platform to build a system simulation model. The model includes energy storage batteries, grid-type converters, line impedance, large power grid models, etc.

Simulation experiment 1:

Two mesh-type converters are used. The control parameters of the two mesh-type converters, such as virtual inertia and virtual damping, are different. Two grid-type converters are connected to two sets of batteries respectively, and the two sets of batteries have the same capacity.

The initial capacities of the two groups of batteries here are the same, and the SOC balance strategy and network control are working normally. The output active power and SOC status of the two converters are shown in Figure 4. It can be seen that because the grid control parameters of the two grid-type converters are different, in the initial state, the output active power of the two grid-type converters is significantly different. But after entering the steady state, the SOC balance strategy keeps the output active power of the two converters the same. Because both sets of batteries have the same capacity, all the same active power output keeps the SOC of both sets of batteries always the same.

Simulation experiment 2:

Two mesh-type converters are used. The control parameters of the two mesh-type converters, such as virtual inertia and virtual damping, are different. Two grid-type converters are connected to two sets of batteries respectively, and the two sets of batteries have the same capacity.

The initial capacities of the two groups of batteries here are different, the network control is always working, and the SOC balancing strategy only starts to work after 7 seconds. The output active power and SOC status of the two converters are shown in Figure 5. It can be seen that because the network control parameters of the two network-type converters are different, the output active power of the two network-type converters is significantly different before 7s, and the initial SOC of the two groups of batteries is different, so The SOC of the two sets of batteries is also always different. After 7 seconds, the SOC balancing strategy starts to work, and the output active power of the two converters changes, so the SOC corresponding to the two sets of batteries also changes. It can be seen that the output active power of the two converters tends to be the same, and the SOC of the two sets of batteries also changed from different values to the same value.

If the above method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention essentially or the part that contributes to the existing technology or the part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program code. .

Example 2

This embodiment provides a SOC balancing device for network-type energy storage, which can be applied to a network-type energy storage system as shown in Figure 1. The network-type energy storage system includes multiple energy storage devices and corresponding Network type converter. The energy storage device is connected to the grid-type converter through a DC-DC converter, and the DC-DC converter is used to adjust the DC voltage of the grid-type converter. The DC-DC converter uses a typical BOOST converter. The grid-type converter topology adopts a typical two-level topology, and the filter structure adopts an LCL filter, which is connected to the AC power grid through lines, and the line impedance cannot be ignored.

Referring to Figure 2, the SOC balancing device provided in this embodiment includes an acquisition and processing module and multiple single converter control modules. The acquisition and processing module is connected to the energy storage equipment connected to each network-type converter. In order to obtain the real-time SOC value of the energy storage device, an average SOC is calculated; multiple single converter control modules are connected to each network-type converter respectively, and are connected to the acquisition and processing module. Based on the average SOC of the energy storage device and The difference between the real-time SOC values of the connected grid-type converters generates an active power compensation signal. Based on the active power compensation signal of the energy storage device, the output active power of the corresponding grid-type converter is controlled. The single converter control module independently controls a grid-type converter.

In the specific implementation, as shown in Figure 2, the single converter control modules adopt a control architecture of SOC balance + network control, in which the SOC balance strategy is responsible for achieving SOC balance among multiple converters. The grid control strategy is responsible for achieving grid support. Specifically, the single converter control module includes an SOC balance control unit and a network-type control unit, where the SOC balance control unit is used to generate the active power compensation signal; the network-type control unit is used to control the active power and the network-type control unit. Active power control generates control instructions for controlling the output power of the corresponding grid-type converter, and in active power control, compensation processing is performed based on the active power compensation signal.

In this embodiment, the network-type control unit can implement active power control, reactive power control and voltage control. The active power control system is used to adjust the phase of the output voltage, and the reactive power control system is used to adjust the amplitude of the output voltage. In general, active power control and reactive power control are as shown in (2) and (3).

V＝V ₀ -K _Q (Q _g -Q ₀ ) (3)

Among them, J and D _p are the simulated inertia and stator damping, P ₀ , ω ₀ , Q ₀ , V ₀ are the reference values of active power, frequency, reactive power and voltage amplitude respectively.

There are multiple network-type converters with different control parameters in the system, and these control parameters will affect the output power of the converter. The state of charge (SOC) of the energy storage device depends on the output active power of the grid-type converter. Therefore, the SOC of the battery can be adjusted only by changing the output active power of the grid-type converter.

In order to improve the SOC balance of multiple network-type converters without changing the control parameters, this embodiment adds an SOC balance control unit based on the network-type control unit. Assume that the number of grid-type converters connected to the battery is n, and each grid-type converter adopts SOC balance control to keep the SOC of each battery the same. In this embodiment, the energy storage device used is a battery, and all network-type converters communicate with each other through the acquisition and processing module to obtain SOC information of all batteries. The acquisition and processing module is also used to calculate the average SOC (SOC _ave ) of all batteries and transmit the SOC _ave to all network-type converters. To achieve SOC balance, the SOC of a single networked converter should be equal to the average SOC. In this case, this embodiment obtains the active power compensation signal through the PI controller to achieve SOC balance control, thereby achieving zero static error. The expression of the active power compensation signal is:

Among them, K _p,SOC and K _i,SOC are the proportional coefficient and integral coefficient of the PI controller respectively.

The PI controller output ΔP is sent to the active power control of the network control unit as compensation. The active power control scheme with compensation is rewritten as:

Among them, ΔP is the power given compensation signal calculated by the SOC balance strategy.

In this embodiment, the control system of the DC-DC converter is shown in Figure 3 and is used to adjust the output voltage of the DC-DC converter, that is, the DC voltage of the grid-type converter. A proportional-integral (PI) controller is used to achieve zero steady-state error. The calculation expression is:

Among them, V _{dc, ref} is the DC voltage given, V _dc is the actual DC voltage value, K _{p, dc} , K _{i, dc} are the proportional coefficient and integral coefficient of the PI controller respectively.

Example 3

This embodiment provides a network-type energy storage system, including a plurality of network-type converters, energy storage equipment connected thereto, and a SOC balancing device for network-type energy storage as described in Embodiment 2, wherein, SOC The balancing device is set corresponding to each network-type converter and each energy storage device, and independently controls each network-type converter to achieve SOC balance among the energy storage devices of the entire network-type energy storage system. .

The preferred embodiments of the present invention are described in detail above. It should be understood that those skilled in the art can make many modifications and changes based on the concept of the present invention without creative efforts. Therefore, any technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention and on the basis of the prior art should be within the scope of protection determined by the claims.

Claims (13)

1. A SOC balancing method for network-type energy storage, applied to a network-type energy storage system. The network-type energy storage system includes multiple network-type converters and energy storage equipment connected to them. It is characterized by: , including the following steps: Obtain the real-time SOC of each energy storage device and calculate an average SOC; For each grid-type converter, an active power compensation signal is generated based on the difference between the average SOC and the real-time SOC of the corresponding energy storage device, and based on the active power compensation signal, the output of the grid-type converter is controlled. Active power. 2. The SOC balancing method for networked energy storage according to claim 1, characterized in that the active power compensation signal is obtained based on a PI controller, a repetitive controller or a model prediction controller. 3. The SOC balancing method for networked energy storage according to claim 2, characterized in that the calculation formula of the active power compensation signal is: Among them, ΔP is the active power compensation signal, K _p,SOC and K _i,SOC are the proportional coefficient and integral coefficient of the PI controller respectively, SOC _ave is the average SOC, and SOC _i is the real-time SOC of the i-th energy storage device. 4. The SOC balancing method for grid-type energy storage according to claim 1, characterized in that the active power compensation signals of each grid-type converter are generated independently. 5. The SOC balancing method of grid-type energy storage according to claim 1, characterized in that the control of the output active power of the grid-type converter specifically includes: Collect voltage and current information at the public connection point of the grid-type converter in real time, and calculate and obtain the corresponding real-time active power based on the voltage and current information; Generate a voltage phase control signal based on the real-time active power and the active power compensation signal; A control instruction is generated based on the voltage phase control signal to control the output active power of the grid-type converter. 6. The SOC balancing method of network-type energy storage according to claim 5, characterized in that, after collecting the voltage and current information, the corresponding real-time reactive power is also calculated based on the voltage and current information to generate a voltage amplitude. The voltage amplitude control signal generates a control instruction based on the voltage amplitude control signal to control the output reactive power of the grid-type converter. 7. A SOC balancing device for network-type energy storage, applied to a network-type energy storage system. The network-type energy storage system includes a plurality of network-type converters and energy storage equipment connected thereto, and is characterized by: ,include: The acquisition and processing module is connected to each energy storage device to obtain the real-time SOC of the energy storage device and calculate an average SOC; Multiple single converter control modules are respectively connected to each network-type converter and connected to the acquisition and processing module. Based on the difference between the average SOC and the real-time SOC of the corresponding energy storage device, an active power compensation signal is generated. , based on the active power compensation signal, control the output active power of the corresponding grid-type converter. 8. The SOC balancing device for network-type energy storage according to claim 7, characterized in that the single converter control module includes: SOC balance control unit, used to generate the active power compensation signal; A grid-type control unit is used to generate control instructions for controlling the output power of a corresponding grid-type converter through active power control and reactive power control, and in active power control, compensation is performed based on the active power compensation signal. deal with. 9. The SOC balancing device for networked energy storage according to claim 7 or 8, characterized in that the active power compensation signal is obtained based on a PI controller, a repetitive controller or a model prediction controller. 10. The SOC balancing device for networked energy storage according to claim 9, characterized in that the calculation formula of the active power compensation signal is: Among them, ΔP is the active power compensation signal, K _{p, SOC} and K _{i, SOC} are the proportional coefficient and integral coefficient of the PI controller respectively, SOC _ave is the average SOC, and SOC _i is the i-th network-type converter connected The real-time SOC value of the energy storage device. 11. The SOC balancing device for network-type energy storage according to claim 8, characterized in that in the network-type control unit, the active power control specifically includes: Collect voltage and current information at the common connection point of the grid-type converter in real time, and calculate and obtain the corresponding real-time active power based on the voltage and current information; Generate a voltage phase control signal based on the real-time active power and the active power compensation signal; A control instruction is generated based on the voltage phase control signal to control the output power of the corresponding grid-type converter. 12. The SOC balancing device for network-type energy storage according to claim 11, characterized in that in the network-type control unit, the reactive power control specifically includes: The corresponding real-time reactive power is calculated based on the voltage and current information, a voltage amplitude control signal is generated, and a control instruction is generated based on the voltage amplitude control signal to control the output reactive power of the grid-type converter. 13. A network-type energy storage system, characterized by comprising the SOC balancing device for network-type energy storage according to any one of claims 7-12.