Energy storage system, filter parameter acquisition method and apparatus, and electronic device

Abstract

The application relates to an energy storage system, a filter parameter acquisition method and apparatus, and an electronic device, and relates to the field of power systems. The method comprises: acquiring relevant parameters of an energy storage system, the relevant parameters comprising: the working frequency of a power grid connected to the energy storage system, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage of sub-modules in the energy storage system, the current pulsation rate, and the voltage pulsation rate; and, on the basis of the relevant parameters and the corresponding relationship between filter parameters in the sub-modules and the relevant parameters, determining the filter parameters in the corresponding relationship. In the present application, a passive method of a passive filter is used to suppress a pulsating current in the energy storage system, the pulsating current being suppressed by means of the arrangement of an LC filter in the sub-modules; the parameters of the LC filter in each sub-module are all determined on the basis of relevant parameters of the energy storage system and the correlation between filter parameters in the sub-module and the relevant parameters; thus, accurate passive filter parameters can be obtained, to thereby accurately suppress a current pulsating current in the energy storage system.

Description

Energy storage system, filter parameter acquisition method, device and electronic equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311259096.9, filed on September 26, 2023, entitled “A method, device and electronic device for obtaining energy storage system, filter parameters”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of power systems, and specifically to an energy storage system, a filter parameter acquisition method, a device, and an electronic device. Background Art

[0004] With the development of power systems, modular multi-level energy storage systems are gradually entering the demonstration application stage. Modular multi-level energy storage systems include multiple sub-modules, each of which can be connected in series and / or in parallel. The sub-modules generally integrate power electronic components such as electrochemical devices. In AC systems, each sub-module has the inherent problem of single-phase inverter power pulsation. Power pulsation causes pulsating current in the charge and discharge current of the electrochemical device. Due to the large amplitude of the pulsating current, the peak current of the electrochemical device will exceed the rated current of the electrochemical device, thereby reducing the service life of the electrochemical device.

[0005] Summary of the Invention

[0006] In view of this, the purpose of this application is to provide an energy storage system, a filter parameter acquisition method, a device and an electronic device to improve the problem in the related art that the pulsating current in the current energy storage system cannot be accurately suppressed, thereby reducing the service life of the electrochemical device.

[0007] The embodiment of the present application is implemented as follows:

[0008] In a first aspect, an embodiment of the present application provides an energy storage system, comprising: a submodule, the submodule comprising: an LC filter and an electrochemical device, the electrochemical device being connected in parallel with the filter capacitor in the LC filter and in series with the filter inductor in the LC filter, the filter inductor being located between the electrochemical device and the filter capacitor; wherein the parameters of the LC filter are determined according to relevant parameters of the energy storage system and the correlation between the filter parameters and the relevant parameters, wherein the relevant parameters include the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current ripple rate, and voltage ripple rate of the submodule; the correlation is determined according to an AC / DC network, the AC / DC network being an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule, and when equivalent, the current flowing through the DC side circuit is equivalent to the superposition of DC current, base frequency AC, and double frequency AC.

[0009] The present application adopts a passive method of a passive LC filter to suppress the pulsating current in the energy storage system, and suppresses the pulsating current by setting an LC filter in the sub-module. At the same time, the parameters of the LC filter in each sub-module in the present application are determined based on the above-mentioned relevant parameters of the energy storage system and the correlation between the filter parameters and the relevant parameters, and the correlation is determined based on the equivalent AC-DC network of the DC side circuit connected to the half-bridge circuit in the sub-module. When equivalent, the current flowing through the DC side circuit is equivalent to the superposition of DC current, base frequency AC and double frequency AC, so that accurate passive filter parameters can be obtained, and then the pulsating current in the current energy storage system can be accurately suppressed, thereby improving the problem of shortened service life of the electrochemical device due to the influence of pulsating current.

[0010] In combination with a possible implementation manner of the embodiment of the first aspect, the relevant parameters further include: the internal resistance of the electrochemical device.

[0011] In the embodiment of the present application, when designing the filter parameters in the submodule, the internal resistance of the electrochemical device is also taken into account, so that the designed filter parameters are more accurate and can better suppress the pulsating current in the current energy storage system.

[0012] In combination with a possible implementation manner of the embodiment of the first aspect, the correlation includes: a first correlation between the filter parameters and the first related parameters, and a second correlation between the filter parameters and the second related parameters, wherein the first correlation is determined according to the DC network, the baseband AC network and the doubled frequency AC network decomposed from the AC / DC network; the second correlation is determined according to the baseband AC network and the doubled frequency AC network; the parameters of the LC filter are obtained according to the first equation and the second equation, wherein the first equation is obtained according to the first related parameter in the related parameters and the first correlation, and the second equation is obtained according to the second related parameter in the related parameters and the second correlation; wherein the first related parameters include: the operating frequency of the power grid, the current pulsation rate, and the internal resistance of the electrochemical device; wherein the second related parameters include: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the internal resistance of the electrochemical device, the voltage pulsation rate, and the voltage.

[0013] In the embodiment of the present application, it is only necessary to substitute the first relevant parameter into the first correlation to obtain the first equation, and substitute the second relevant parameter into the second correlation to obtain the second equation. By solving the first equation and the second equation, the parameters of the LC filter can be obtained quickly and accurately.

[0014] In a second aspect, an embodiment of the present application further provides a filter parameter acquisition method, comprising:

[0015] Obtain relevant parameters of the energy storage system, wherein the relevant parameters include: the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current ripple rate, and voltage ripple rate of the submodule in the energy storage system; determine the filter parameters in the correlation based on the relevant parameters and the correlation between the filter parameters in the submodule and the relevant parameters, wherein the filter parameters are used to design the LC filter in the submodule, the electrochemical device in the submodule is connected in parallel with the filter capacitor in the LC filter and in series with the filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor; the correlation is determined based on an AC / DC network, which is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule. When equivalent, the current flowing through the DC side circuit is equivalent to the superposition of DC current, baseband AC, and doubled frequency AC.

[0016] In combination with a possible implementation manner of the embodiment of the second aspect, the relevant parameters also include: the internal resistance of the electrochemical device.

[0017] In combination with a possible implementation manner of the second aspect embodiment, the correlation includes: a first correlation between the filter parameter and a first related parameter, and a second correlation between the filter parameter and a second related parameter, wherein the first correlation is determined according to the DC network, the baseband AC network and the doubled frequency AC network decomposed from the AC / DC network; the second correlation is determined according to the baseband AC network and the doubled frequency AC network; determining the filter parameters in the correlation according to the related parameters and the correlation between the filter parameters and the related parameters includes: obtaining a first equation according to the first related parameter in the related parameters and the first correlation, wherein the first related parameter includes: the operating frequency of the power grid, the current pulsation rate, and the internal resistance of the electrochemical device; obtaining a second equation according to the second related parameter in the related parameters and the second correlation, wherein the second related parameter includes: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the internal resistance of the electrochemical device, the voltage pulsation rate, and the voltage; determining the filter parameters in the correlation according to the first equation and the second equation.

[0018] In conjunction with a possible implementation of the embodiment of the second aspect, the expression of the first equation is: Wherein, α is the current ripple rate, ω1 is 1 times the working frequency of the power grid, ω2 is 2 times the working frequency of the power grid, R b is the internal resistance of the electrochemical device, L is the inductance value in the filter parameters, and C is the capacitance value in the filter parameters.

[0019] In the embodiment of the present application, the range of the parameters of the LC filter can be quickly and accurately obtained based on the above expression.

[0020] In conjunction with a possible implementation of the embodiment of the second aspect, the expression of the second equation is: Wherein, β is the voltage ripple rate, ω1 is 1 times the operating frequency of the power grid, ω2 is 2 times the operating frequency of the power grid, R b is the internal resistance of the electrochemical device, L is the inductance value in the filter parameters, C is the capacitance value in the filter parameters, V bat is the voltage, M is the modulation ratio of the grid, I m is the current amplitude of the power grid.

[0021] In the embodiment of the present application, the range of the parameters of the LC filter can be quickly and accurately obtained based on the above expression.

[0022] In combination with a possible implementation manner of the embodiment of the second aspect, before determining the filter parameters in the correlation based on the relevant parameters and the correlation between the filter parameters and the relevant parameters in the sub-module, the method also includes: obtaining the current component of the electrochemical device branch in the sub-module, the current component including the DC component of the electrochemical device branch, the fundamental frequency current component of the electrochemical device branch, and the double frequency current component of the electrochemical device branch; obtaining the voltage component of the capacitor branch in the sub-module, the voltage component including the first voltage pulsation generated by the fundamental frequency current in the capacitor branch, and the second voltage pulsation generated by the double frequency current in the capacitor branch; obtaining a first correlation based on the current component of the electrochemical device branch in the sub-module; obtaining a second correlation based on the voltage component of the capacitor branch in the sub-module and the voltage, wherein the correlation includes the first correlation and the second correlation.

[0023] In an embodiment of the present application, by obtaining the current component of the electrochemical device branch in the sub-module, the first correlation can be accurately obtained, such as the first correlation is the ratio of the sum of the fundamental frequency current component and the double frequency current component to the DC component; by obtaining the voltage component of the capacitor branch in the sub-module, the second correlation can be accurately obtained, such as the second correlation is the ratio of the sum of the first voltage pulsation and the second voltage pulsation to the voltage of the sub-module.

[0024] In combination with a possible implementation method of the second aspect of the embodiment, obtaining the current component of the electrochemical device branch in the sub-module includes: decomposing the AC / DC network into a DC network, a baseband AC network, and a doubled frequency AC network; obtaining the DC component of the electrochemical device branch based on the DC network; obtaining the baseband current component of the electrochemical device branch based on the baseband AC network; and obtaining the doubled frequency current component of the electrochemical device branch based on the doubled frequency AC network.

[0025] In an embodiment of the present application, by decomposing the equivalent circuit of the DC side circuit connected to the half-bridge circuit in the sub-module (i.e., the AC / DC network) into a superposition of a DC network, a baseband AC network, and a double-frequency AC network, the DC component, the baseband current component, and the double-frequency current component of the electrochemical device branch can be accurately determined.

[0026] In combination with a possible implementation method of the second aspect of the embodiment, obtaining the voltage component of the capacitor branch in the sub-module includes: decomposing the AC / DC network to obtain a baseband AC network and a doubled frequency AC network; based on the baseband AC network, determining the first voltage pulsation generated by the baseband current in the capacitor branch; based on the doubled frequency AC network, determining the second voltage pulsation generated by the doubled frequency current in the capacitor branch.

[0027] In an embodiment of the present application, by decomposing the equivalent circuit of the DC side circuit connected to the half-bridge circuit in the sub-module (i.e., the AC / DC network) into the superposition of the DC network, the baseband AC network, and the doubled-frequency AC network, the first voltage pulsation generated by the baseband current in the capacitor branch and the second voltage pulsation generated by the doubled-frequency current in the capacitor branch can be accurately determined.

[0028] In a third aspect, an embodiment of the present application further provides a filter parameter acquisition device, comprising: an acquisition module and a determination module; the acquisition module is used to acquire relevant parameters of the energy storage system, the relevant parameters including: the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current pulsation rate, and voltage pulsation rate of the sub-module in the energy storage system; the determination module is used to determine the filter parameters in the correlation based on the relevant parameters and the correlation between the filter parameters in the sub-module and the relevant parameters, wherein the filter parameters are used to design an LC filter, the electrochemical device in the sub-module is connected in parallel with the filter capacitor in the LC filter, and in series with the filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor; the correlation is determined according to an AC / DC network, and the AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the sub-module. When equivalent, the current flowing through the DC side circuit is equivalent to the superposition of DC current, baseband AC, and double-frequency AC.

[0029] In a fourth aspect, an embodiment of the present application further provides an electronic device, comprising: a memory and a processor, the processor being connected to the memory; the memory being used to store programs; and the processor being used to call the programs stored in the memory to execute a method provided in the above-mentioned second aspect embodiment and / or any possible implementation method in combination with the second aspect embodiment.

[0030] Other features and advantages of the present application will be described in the following description. The purpose and other advantages of the present application can be realized and obtained through the structures specifically pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can also obtain other drawings based on these drawings. The above and other purposes, features, and advantages of the present application will be more clearly illustrated through the drawings.

[0032] FIG1 shows a circuit diagram of an energy storage system provided in an embodiment of the present application.

[0033] FIG2 shows a circuit diagram of a submodule provided in an embodiment of the present application.

[0034] FIG3 shows an equivalent schematic diagram of a DC side circuit provided in an embodiment of the present application.

[0035] FIG4 shows a schematic diagram of decomposing an AC / DC network into a superposition of a DC network, a baseband AC network, and a doubled-frequency AC network, provided by an embodiment of the present application.

[0036] FIG5 shows a flow chart of a filter parameter acquisition method provided in an embodiment of the present application.

[0037] FIG6 shows a module diagram of a filter parameter acquisition device provided in an embodiment of the present application.

[0038] FIG7 shows a schematic structural diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following embodiments can be used as examples to more clearly illustrate the technical solutions of the present application, and are not intended to limit the scope of protection of the present application. It will be understood by those skilled in the art that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other.

[0040] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in the subsequent figures. At the same time, in the description of this application, relational terms such as "first", "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements that are not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "comprise a..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0041] Furthermore, the term "and / or" in this application is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0042] In the description of the embodiments of the present application, unless otherwise clearly specified or limited, the technical term "connection" may refer to a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0043] In view of the fact that the relevant technologies cannot accurately suppress the pulsating current in the current energy storage system, the current peak of the electrochemical device will exceed the rated current of the electrochemical device, thereby reducing the service life of the electrochemical device. In order to accurately suppress the pulsating current in the current energy storage system, the present application adopts a passive method of a passive filter to suppress the pulsating current in the energy storage system, and suppresses the pulsating current by setting an LC filter in the submodule. Specifically, the electrochemical device in the submodule is connected in parallel with the DC side capacitor through a filter inductor, and the inductor and the capacitor form an LC filter, so that the amplitude of the base frequency pulsating current and the double frequency pulsating current in the electrochemical device is greatly attenuated. However, the design of the passive filter is closely related to the efficiency and cost of the submodule, and accurate passive filter parameters need to be obtained.

[0044] In order to obtain accurate passive filter parameters, the embodiment of the present application targets a modular multi-level energy storage system using a passive filter, and performs theoretical modeling and analysis on the pulsating current in the sub-module, and concludes that its pulsating current is composed of DC current, base-frequency AC and double-frequency AC. Therefore, when the DC side circuit connected to the half-bridge circuit in the sub-module is equivalent, the current flowing through the DC side circuit will be equivalent to the superposition of DC current, base-frequency AC and double-frequency AC. Then, based on the equivalent AC / DC network, the correlation between the filter parameters and related parameters is obtained, thereby accurately guiding the filter parameter design, and further improving the problem of shortened service life of the electrochemical device due to the influence of pulsating current.

[0045] The electrochemical device is a device or apparatus that realizes an electrochemical reaction and is used to provide electrical energy, and can be, for example, a battery or other product. The battery can be a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0046] In one embodiment, a schematic diagram of an energy storage system provided in an embodiment of the present application is shown in Figure 1. It should be understood that the example diagram shown in Figure 1 only represents a portion of the energy storage system, illustrating only the portion related to the bridge arm. The energy storage system includes multiple bridge arms, each of which includes multiple submodules (SMs) connected in series, and each bridge arm is connected to one phase of a three-phase AC power grid.

[0047] The filter parameters in each submodule of the energy storage system provided in the embodiments of the present application are determined based on the relevant parameters of the energy storage system and the correlation between the filter parameters and the relevant parameters, thereby obtaining accurate passive filter parameters. The correlation is determined based on an AC / DC network, which is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule. During the equivalent process, the current flowing through the DC side circuit is equivalent to the superposition of DC current, baseband AC, and doubled-frequency AC, thereby accurately guiding the design of the filter parameters.

[0048] Among them, the relevant parameters include the operating frequency ω of the power grid to which the energy storage system is connected, the current amplitude I m , the modulation ratio of the grid M, the voltage of the submodule V bat , the current ripple rate α of the submodule, and the voltage ripple rate β of the submodule.

[0049] The grid to which the energy storage system is connected can be a three-phase (A, B, C) AC grid, a two-phase AC grid, or a single-phase AC grid. Different AC grids correspond to different operating frequencies, current amplitudes, and modulation ratios.

[0050] Among the above-mentioned related parameters, the operating frequency of the power grid ω, the current amplitude of the power grid I m The value of the grid modulation ratio M depends on the grid to which the energy storage system is connected. The voltage V bat Depends on the output voltage of the electrochemical device in the submodule. The submodule's current ripple rate α and voltage ripple rate β can be set according to design requirements. Typically, the current ripple rate α is no greater than a first threshold, and the voltage ripple rate β is no greater than a second threshold. Both the first and second thresholds are greater than 0 and typically no greater than 1.

[0051] The correlation may include: a first correlation between a filter parameter and a first related parameter, and a second correlation between a filter parameter and a second related parameter, wherein the first correlation is determined based on a DC network, a baseband AC network, and a double-frequency AC network decomposed from an AC / DC network; and the second correlation is determined based on the baseband AC network and the double-frequency AC network. The filter parameters in each submodule are determined based on the relevant parameters of the energy storage system, the first correlation, and the second correlation.

[0052] Among them, the first equation can be obtained according to the first related parameter and the first correlation among the related parameters, and the second equation can be obtained according to the second related parameter and the second correlation among the related parameters. Then, the filter parameters in the submodule can be obtained according to the first equation and the second equation. In an optional implementation manner, the first related parameter includes: the operating frequency of the power grid, the current pulsation rate of the submodule. The second related parameter includes: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage pulsation rate of the submodule, and the voltage of the submodule. In the embodiment of the present application, it is only necessary to substitute the first related parameter into the first correlation to obtain the first equation, and substitute the second related parameter into the second correlation to obtain the second equation. By solving the first equation and the second equation, the parameters of the LC filter can be quickly and accurately obtained.

[0053] The first related parameters include: the operating frequency of the power grid and the current ripple rate of the submodule. The expression of the first equation is:

[0054] Among them, α is the current ripple rate of the submodule, ω1 is 1 times the operating frequency of the grid, ω2 is 2 times the operating frequency of the grid, L is the inductance value in the filter parameters, and C is the capacitance value in the filter parameters.

[0055] The first correlation is similar to the first equation, and the expression obtained by substituting the value of the first correlation parameter into the first correlation is the first equation.

[0056] The second related parameters include: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage ripple rate of the submodule, and the voltage of the submodule. The expression of the second equation is:

[0057] Among them, β is the voltage ripple rate of the submodule, ω1 is 1 times the working frequency of the grid, ω2 is 2 times the working frequency of the grid, L is the inductance value in the filter parameters, C is the capacitance value in the filter parameters, V bat is the voltage of the submodule, M is the modulation ratio of the grid, I m is the current amplitude of the power grid.

[0058] The second correlation is similar to the second equation, and the expression obtained by substituting the value of the second correlation parameter into the second correlation is the second equation.

[0059] The filter parameters in this application include: inductance value L and capacitance value C. In the above first equation and second equation, only L and C are unknowns, and the remaining parameters are all known values. By solving the set of equations, the filter parameters can be determined.

[0060] In one embodiment, since the internal resistance of the electrochemical device is large, the internal resistance of the electrochemical device should also be taken into account when designing the filter parameters in the submodule. In this case, the relevant parameters also include the internal resistance of the electrochemical device, such as R b In this application, by taking the internal resistance of the electrochemical device into consideration, the designed filter parameters are made more accurate, which can better suppress the pulsating current in the current energy storage system.

[0061] When the relevant parameters also include the internal resistance of the electrochemical device, the first relevant parameters include: the operating frequency of the power grid, the current ripple rate of the submodule, and the internal resistance of the electrochemical device. The second relevant parameters include: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage ripple rate of the submodule, the voltage of the submodule, and the internal resistance of the electrochemical device.

[0062] The first related parameter also includes: the internal resistance of the electrochemical device, and the expression of the first equation is:

[0063] Among them, α is the current ripple rate of the submodule, ω1 is 1 times the working frequency of the grid, ω2 is 2 times the working frequency of the grid, R b is the internal resistance of the electrochemical device, L is the inductance value in the filter parameters, and C is the capacitance value in the filter parameters.

[0064] The second related parameter also includes: the internal resistance of the electrochemical device. The expression of the second equation is:

[0065] Among them, β is the voltage ripple rate of the submodule, ω1 is 1 times the working frequency of the grid, ω2 is 2 times the working frequency of the grid, R b is the internal resistance of the electrochemical device, L is the inductance value in the filter parameters, C is the capacitance value in the filter parameters, V bat is the voltage of the submodule, M is the modulation ratio of the grid, I m is the current amplitude of the power grid.

[0066] In an optional implementation manner, the correlation relationship including the first correlation relationship and the second correlation relationship may be obtained in the following manner:

[0067] Obtain the current component of the electrochemical device branch in the submodule, and obtain a first correlation based on the current component of the electrochemical device branch in the submodule, wherein the current component includes a DC component of the electrochemical device branch, a fundamental frequency current component of the electrochemical device branch, and a double frequency current component of the electrochemical device branch; obtain the voltage component of the capacitor branch in the submodule, and obtain a second correlation based on the voltage component of the capacitor branch in the submodule and the voltage of the submodule, wherein the voltage component includes a first voltage pulsation generated in the capacitor branch by the fundamental frequency current, and a second voltage pulsation generated in the capacitor branch by the double frequency current.

[0068] In order to better understand the above process, Idc is used to represent the DC component of the electrochemical device branch, ibat1 is used to represent the fundamental frequency current component of the electrochemical device branch, ibat2 is used to represent the double frequency current component of the electrochemical device branch, and v is used to represent the DC component of the electrochemical device branch. C1 Indicates the first voltage ripple, with v C2 Indicates the second voltage pulsation, then

[0069] in, Considering the internal resistance R b In case of:

[0070] Among them, I dc1m is the current amplitude of the fundamental frequency AC network, I dc2m is the current amplitude of the double frequency AC network, Z C1 is the capacitive impedance in the fundamental frequency AC network, Z b1 is the inductance and internal resistance R in the fundamental frequency AC network b The impedance, Z C2 is the capacitance impedance in the double frequency AC network, Z b2 is the inductance and internal resistance R in the double frequency AC network b impedance.

[0071] Without considering the internal resistance R b In the case of Z b1 is the impedance of the inductor in the fundamental frequency AC network, Z b2 is the impedance of the inductor in the double frequency AC network. At this time, directly change the above ibat1, ibat2, v C1 、v C2 The internal resistance R in the expression b Remove it and you can get the result without considering the internal resistance R b In the case of ibat1, ibat2, vC1 、v C2 expression.

[0072] In one possible embodiment, the process for obtaining the current components of the electrochemical device branch in the submodule may include: decomposing the AC / DC network into a DC network, a baseband AC network, and a double-frequency AC network; obtaining the DC component of the electrochemical device branch based on the DC network; obtaining the baseband current component of the electrochemical device branch based on the baseband AC network; and obtaining the double-frequency current component of the electrochemical device branch based on the double-frequency AC network. The AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule.

[0073] For a better understanding, the following is an explanation of the circuit schematic of the submodule shown in Figure 2. In addition to the LC filter, each submodule also includes an electrochemical device and a half-bridge circuit. One side of the half-bridge circuit is connected to the AC network, and the other side of the half-bridge circuit is connected to the LC filter. The LC filter is connected to the electrochemical device. Specifically, the electrochemical device is connected in series with the filter inductor in the LC filter and in parallel with the filter capacitor in the LC filter. The filter inductor is located between the electrochemical device and the filter capacitor. The electrochemical device and LC filter in Figure 2 are located as the DC side circuit connected to the half-bridge circuit in the submodule.

[0074] Figure 3 shows an equivalent schematic diagram of the DC side circuit. The left side of Figure 3 can be equated to the right side, resulting in an AC / DC network. In this equivalence, the current flowing through the DC side circuit is considered to be a superposition of DC current, fundamental frequency AC, and double frequency AC. Ignoring the influence of high-frequency components, the AC / DC network on the right side of Figure 3 can be further decomposed into the superposition of the DC network, fundamental frequency AC network, and double frequency AC network, as shown in Figure 4.

[0075] After decomposing the equivalent AC / DC network into the network model shown in Figure 4, the DC component of the electrochemical device branch can be obtained based on the DC network, the fundamental frequency current component of the electrochemical device branch can be obtained based on the fundamental frequency AC network, and the double frequency current component of the electrochemical device branch can be obtained based on the double frequency AC network. For example, by solving the DC network, the DC component of the current I b =I dc By solving the fundamental frequency AC network, we can get the fundamental frequency current component ibat1, and by solving the double frequency AC network, we can get the double frequency current component ibat2.

[0076] In some possible implementations, the process of obtaining the voltage component of the capacitor branch in the submodule may be: directly obtaining from a database, where the voltage component of the capacitor branch in the submodule is pre-stored.

[0077] In some possible implementations, the process of obtaining the voltage component of the capacitor branch in the submodule may include: decomposing the AC / DC network to obtain a baseband AC network and a doubled-frequency AC network; determining a first voltage ripple generated in the capacitor branch by the baseband current based on the baseband AC network; and determining a second voltage ripple generated in the capacitor branch by the doubled-frequency current based on the doubled-frequency AC network. The AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule.

[0078] For ease of understanding, the schematic diagrams shown in Figures 3 and 4 are used for illustration. Ignoring the influence of high-frequency components, the AC / DC network on the right side of Figure 3 can be further decomposed into the superposition of the DC network, the baseband AC network, and the double-frequency AC network shown in Figure 4. Afterwards, the first voltage pulsation generated by the baseband current in the capacitor branch can be determined based on the baseband AC network in Figure 4, and the second voltage pulsation generated by the double-frequency current in the capacitor branch can be determined based on the double-frequency AC network in Figure 4. For example, the phasor method can be applied to calculate the first voltage pulsation v generated by the baseband current in the baseband AC network. C1 , use the phasor method to calculate the second voltage ripple v generated by the double frequency current in the double frequency AC network C2 .

[0079] In the above embodiment, because the pulsating current in the sub-module is theoretically modeled and analyzed, its components include DC component, fundamental frequency component, and double frequency component, the above AC / DC network is decomposed into the superposition of DC network, fundamental frequency AC network and double frequency AC network.

[0080] For a better understanding, the following is an explanation of the energy storage system shown in Figure 1. When only the fundamental frequency component is considered, taking phase A as an example, the switching function S of the upper bridge arm ap It can be expressed as follows:

[0081] S ap =M dc -Msinωt, where U dc is the DC component of the upper arm voltage, U mj is the voltage amplitude of phase j of the power grid. Taking phase A as an example, phase j = phase A, N is the number of bridge arms, and I m is the current amplitude of the power grid, U c The average value of the capacitor voltage of each submodule is usually equal to the voltage V bat Without considering the circulating current, the currents flowing through the upper and lower bridge arms of phase A are and Then we have:

[0082] in, φ is the phase angle difference between voltage and current. When φ=90°, It can be seen that the current flowing through the submodule includes a DC component, a fundamental frequency component, and a double frequency component. At the same time, the AC component accounts for a large proportion. If no suppression measures are taken, the current will flow through a large pulsating current, affecting the battery life.

[0083] In the embodiment of the present application, in order to analyze the harmonic components of the electrochemical device current when the energy storage system shown in FIG1 is operating in four quadrants, an analytical expression of the DC side ripple current in the submodule is derived based on the switching function.

[0084] The AC side output voltage and current of a submodule in the upper arm of phase A are:

[0085] v apj =V mapj (1+cosωt);

[0086] Among them, V mapj is the output voltage amplitude of the submodule, generally Ignoring the effect of filter inductance, it can be approximately considered to be in phase with the grid voltage. Ignoring high-frequency components, the DC side ripple current i is derived based on the switching function. DC The analytical expression is:

[0087] in, Usually V bat =U c Decompose the DC side ripple current analytical expression to obtain the DC component of the DC side current I dc , fundamental frequency component i dc_1 (t), double frequency component i dc_2 (t) are:

[0088] Based on the analytical expression of the DC side ripple current, we can know that

[0089] The present application also provides a filter parameter acquisition method that can quickly and accurately determine the parameters of the LC filter in the submodule, thereby accurately guiding the design of the LC filter. In one possible embodiment, the electrochemical device in the submodule is connected in parallel with the filter capacitor in the LC filter and in series with the filter inductor in the LC filter, with the filter inductor located between the electrochemical device and the filter capacitor. The filter parameter acquisition method provided in the present application is described below in conjunction with the process shown in Figure 5.

[0090] S1: Obtain relevant parameters of the energy storage system, including: the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current ripple rate, and voltage ripple rate of the submodules in the energy storage system.

[0091] In one optional implementation, the relevant parameters of the energy storage system may be obtained from a local database and / or a third party, or the relevant parameters may be prepared in advance for subsequent use. In some possible implementations, the relevant parameters of the energy storage system may also be obtained in real time, such as by obtaining relevant parameters of the energy storage system input by a user in real time.

[0092] In some possible implementations, when designing the filter parameters in the submodule, the internal resistance of the electrochemical device should also be taken into account. In this case, the relevant parameters also include the internal resistance of the electrochemical device, such as R b express.

[0093] S2: Determine the filter parameters in the correlation according to the correlation parameters and the correlation between the filter parameters in the submodule and the correlation parameters.

[0094] After obtaining the relevant parameters, the filter parameters can be determined based on the obtained relevant parameters and the predetermined correlation between the filter parameters and the relevant parameters in the submodule. The LC filter can then be designed based on the determined filter parameters. The filter parameters are used to design the LC filter. The correlation is determined based on the AC / DC network, which is the equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule. During the equivalent circuit, the current flowing through the DC side circuit is equivalent to the superposition of DC current, baseband AC current, and doubled frequency AC current.

[0095] The correlation relationship represents the relationship between the filter parameters and the related parameters, and may be an expression including the filter parameters and the related parameters.

[0096] In one embodiment, the correlation may include: a first correlation between a filter parameter and a first related parameter, and a second correlation between the filter parameter and a second related parameter, wherein the first correlation is determined based on the DC network, the baseband AC network, and the doubled-frequency AC network decomposed from the AC / DC network; and the second correlation is determined based on the baseband AC network and the doubled-frequency AC network. The first related parameter includes: the operating frequency of the power grid and the current ripple rate of the submodule. The second related parameter includes: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage ripple rate of the submodule, and the voltage of the submodule.

[0097] The first correlation relationship represents the correlation relationship between the first correlation parameter and the filter parameter, which can be an expression including the filter parameter and the first correlation parameter. Similarly, the second correlation relationship represents the correlation relationship between the second correlation parameter and the filter parameter, which can be an expression including the filter parameter and the second correlation parameter.

[0098] When the relevant parameters include a first correlation relationship and a second correlation relationship, the implementation process of S2 can be: obtaining a first equation based on the first relevant parameters and the first correlation relationship in the relevant parameters, obtaining a second equation based on the second relevant parameters and the second correlation relationship in the relevant parameters, and determining the filter parameters in the correlation relationship based on the first equation and the second equation.

[0099] When the relevant parameters also include the internal resistance of the electrochemical device, the first and second relevant parameters also include the internal resistance of the electrochemical device. In this case, the first relevant parameters include: the operating frequency of the power grid, the current ripple rate of the submodule, and the internal resistance of the electrochemical device; the second relevant parameters include: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the internal resistance of the electrochemical device, the voltage ripple rate of the submodule, and the voltage of the submodule.

[0100] In an optional embodiment, when the first related parameter also includes the internal resistance of the electrochemical device, the expression of the first equation is:

[0101] When the second related parameter also includes the internal resistance of the electrochemical device, the expression of the second equation is:

[0102] In an optional embodiment, before S2, the filter parameter acquisition method also includes: acquiring the current component of the electrochemical device branch in the sub-module, wherein the current component includes the DC component of the electrochemical device branch, the fundamental frequency current component of the electrochemical device branch, and the double frequency current component of the electrochemical device branch; obtaining a first correlation based on the current component of the electrochemical device branch in the sub-module; and acquiring the voltage component of the capacitor branch in the sub-module, wherein the voltage component includes a first voltage pulsation generated by the fundamental frequency current in the capacitor branch, and a second voltage pulsation generated by the double frequency current in the capacitor branch; obtaining a second correlation based on the voltage component and voltage of the capacitor branch in the sub-module.

[0103] In one embodiment, the process of obtaining the current component of the electrochemical device branch in the submodule can be: decomposing the AC / DC network into a DC network, a baseband AC network, and a doubled-frequency AC network, wherein the AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule; based on the DC network, obtaining the DC component of the electrochemical device branch; based on the baseband AC network, obtaining the baseband current component of the electrochemical device branch; based on the doubled-frequency AC network, obtaining the doubled-frequency current component of the electrochemical device branch.

[0104] In one embodiment, the process of obtaining the voltage component of the capacitor branch in the sub-module can be: decomposing the AC / DC network to obtain a baseband AC network and a doubled-frequency AC network, wherein the AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the sub-module; based on the baseband AC network, determining the first voltage pulsation generated by the baseband current in the capacitor branch; based on the doubled-frequency AC network, determining the second voltage pulsation generated by the doubled-frequency current in the capacitor branch.

[0105] The filter parameter acquisition method provided in the embodiment of the present application has the same implementation principle and technical effects as those in the aforementioned energy storage system embodiment. For the sake of brief description, for matters not mentioned in the method embodiment, reference can be made to the corresponding content in the aforementioned energy storage system embodiment.

[0106] The embodiment of the present application further provides a filter parameter acquisition device 100 , as shown in FIG6 . The filter parameter acquisition device 100 includes: an acquisition module 110 and a determination module 120 .

[0107] The acquisition module 110 is used to obtain relevant parameters of the energy storage system, including: the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current pulsation rate, and voltage pulsation rate of the submodules in the energy storage system.

[0108] The determination module 120 is configured to determine the filter parameters in the correlation according to the correlation parameters and the correlation between the filter parameters in the submodules and the correlation parameters, wherein the filter parameters are used to design an LC filter.

[0109] The correlation includes: a first correlation between the filter parameter and a first correlation parameter, and a second correlation between the filter parameter and a second correlation parameter; a determination module 120 is used to obtain a first equation based on a first correlation parameter among the correlation parameters and the first correlation, wherein the first correlation parameter includes: the operating frequency of the power grid, the current pulsation rate, and the internal resistance of the electrochemical device; a second equation is obtained based on a second correlation parameter among the correlation parameters and the second correlation, wherein the second correlation parameter includes: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the internal resistance of the electrochemical device, the voltage pulsation rate, and the voltage; and the filter parameters in the correlation are determined based on the first equation and the second equation.

[0110] Optionally, the acquisition module 110 is further used to acquire the current component of the electrochemical device branch in the sub-module, the current component including the DC component of the electrochemical device branch, the fundamental frequency current component of the electrochemical device branch, and the double frequency current component of the electrochemical device branch; acquire the voltage component of the capacitor branch in the sub-module, the voltage component including the first voltage pulsation generated by the fundamental frequency current in the capacitor branch, and the second voltage pulsation generated by the double frequency current in the capacitor branch; obtain a first correlation based on the current component of the electrochemical device branch in the sub-module; obtain a second correlation based on the voltage component of the capacitor branch in the sub-module and the voltage, wherein the correlation includes the first correlation and the second correlation.

[0111] Optionally, the acquisition module 110 is further used to decompose the AC / DC network into a DC network, a baseband AC network, and a doubled-frequency AC network, wherein the AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the sub-module; based on the DC network, the DC component of the electrochemical device branch is obtained; based on the baseband AC network, the baseband current component of the electrochemical device branch is obtained; based on the doubled-frequency AC network, the doubled-frequency current component of the electrochemical device branch is obtained.

[0112] Optionally, the acquisition module 110 is also used to decompose the AC / DC network to obtain a baseband AC network and a doubled frequency AC network, wherein the AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the sub-module; based on the baseband AC network, determine the first voltage pulsation generated by the baseband current in the capacitor branch; based on the doubled frequency AC network, determine the second voltage pulsation generated by the doubled frequency current in the capacitor branch.

[0113] The filter parameter acquisition device 100 provided in the embodiment of the present application has the same implementation principle and technical effects as those of the aforementioned method embodiment. For the sake of brief description, for matters not mentioned in the device embodiment, reference may be made to the corresponding content in the aforementioned method embodiment.

[0114] As shown in FIG7 , FIG7 shows a structural block diagram of an electronic device 200 provided in an embodiment of the present application. The electronic device 200 includes: a transceiver 210 , a memory 220 , a communication bus 230 and a processor 240 .

[0115] The transceiver 210, the memory 220, and the processor 240 are electrically connected to each other directly or indirectly to achieve data transmission or interaction. For example, these components can be electrically connected to each other via one or more communication buses 230 or signal lines. The transceiver 210 is used to send and receive data. The memory 220 is used to store computer programs, such as the software function module shown in Figure 6, i.e., the filter parameter acquisition device 100. The filter parameter acquisition device 100 includes at least one software function module that can be stored in the memory 220 in the form of software or firmware or solidified in the operating system (OS) of the electronic device 200. The processor 240 is used to execute the executable module stored in the memory 220, such as the software function module or computer program included in the filter parameter acquisition device 100. For example, the processor 240 is used to execute the above-mentioned filter parameter acquisition method.

[0116] The memory 220 may be, but is not limited to, a random access memory (RAM), a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), etc.

[0117] The processor 240 may be an integrated circuit chip with signal processing capabilities. The above-mentioned processor may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), a microprocessor, etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. The various methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. Alternatively, the processor 240 may also be any conventional processor, etc.

[0118] The electronic devices 200 mentioned above include, but are not limited to, mobile phones, tablets, computers, servers, etc.

[0119] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0120] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A filter parameter acquisition method, comprising: Acquire relevant parameters of the energy storage system, the relevant parameters including: the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current pulsation rate, and voltage pulsation rate of the submodules in the energy storage system; According to the relevant parameters and the correlation between the filter parameters and the relevant parameters in the submodule, the filter parameters in the correlation are determined, wherein the filter parameters are used to design the LC filter in the submodule, the electrochemical device in the submodule is connected in parallel with the filter capacitor in the LC filter, and in series with the filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor; the relevant relationship is determined according to the AC / DC network, and the AC / DC network is an equivalent circuit of the DC side circuit connected to the half-bridge circuit in the submodule, and when equivalent, the current flowing through the DC side circuit is equivalent to the superposition of DC current, base frequency AC and double frequency AC.

2. The method according to claim 1, wherein: The related parameters also include: the internal resistance of the electrochemical device.

3. The method according to claim 2, wherein: The correlation relationship includes: a first correlation relationship between the filter parameter and a first correlation parameter, and a second correlation relationship between the filter parameter and a second correlation parameter, wherein the first correlation relationship is determined according to a DC network, a baseband AC network, and a double frequency AC network decomposed from the AC / DC network; and the second correlation relationship is determined according to the baseband AC network and the double frequency AC network; The determining the filter parameters in the correlation according to the correlation parameters and the correlation between the filter parameters and the correlation parameters comprises: According to a first related parameter among the related parameters and the first related relationship, a first equation is obtained, wherein the first related parameter includes: an operating frequency of the power grid, the current pulsation rate, and an internal resistance of the electrochemical device; According to the second related parameter in the related parameters and the second related relationship, a second equation is obtained, wherein the second related parameter includes: the operating frequency of the power grid, the current amplitude of the power grid, the modulation ratio of the power grid, the internal resistance of the electrochemical device, the voltage pulsation rate, and the voltage; According to the first equation and the second equation, filter parameters in the correlation relationship are determined.

4. The method according to claim 3, wherein: The expression of the first equation is: Wherein, α is the current pulsation rate, ω1 is 1 times the working frequency of the power grid, ω2 is 2 times the working frequency of the power grid, R b is the internal resistance of the electrochemical device, L is the inductance value in the filter parameters, and C is the capacitance value in the filter parameters.

5. The method according to claim 3, wherein: The expression of the second equation is: Wherein, β is the voltage pulsation rate, ω1 is 1 times the working frequency of the power grid, ω2 is 2 times the working frequency of the power grid, R b is the internal resistance of the electrochemical device, L is the inductance value in the filter parameter, C is the capacitance value in the filter parameters, V bat is the voltage, M is the modulation ratio of the power grid, and Im is the current amplitude of the power grid.

6. The method according to any one of claims 1 to 5, wherein: Before determining the filter parameters in the correlation according to the correlation parameters and the correlation between the filter parameters in the submodule and the correlation parameters, the method further includes: Acquire current components of the electrochemical device branch in the submodule, wherein the current components include a direct current component of the electrochemical device branch, a fundamental frequency current component of the electrochemical device branch, and a double frequency current component of the electrochemical device branch; Obtaining a first correlation according to a current component of a branch of an electrochemical device in the submodule; Acquire a voltage component of the capacitor branch in the submodule, wherein the voltage component includes a first voltage pulsation generated by a base frequency current in the capacitor branch and a second voltage pulsation generated by a double frequency current in the capacitor branch; A second correlation is obtained according to the voltage component of the capacitor branch in the submodule and the voltage, wherein the correlation includes the first correlation and the second correlation.

7. The method according to claim 6, wherein: Obtaining the current component of the electrochemical device branch in the submodule includes: Decomposing the AC / DC network into a DC network, a baseband AC network and a double frequency AC network; Based on the DC network, obtaining a DC component of the electrochemical device branch; Based on the fundamental frequency AC network, obtaining the fundamental frequency current component of the electrochemical device branch; Based on the double frequency AC network, a double frequency current component of the electrochemical device branch is obtained.

8. The method according to claim 6, wherein: Obtaining a voltage component of a capacitor branch in the submodule includes: Decomposing the AC / DC network to obtain the baseband AC network and the doubled frequency AC network; Based on the baseband AC network, determining a first voltage pulsation generated by the baseband current in the capacitor branch; Based on the double frequency AC network, a second voltage pulsation generated by the double frequency current in the capacitor branch is determined.

9. An energy storage system, comprising: a submodule, The submodule comprises: an LC filter and an electrochemical device, wherein the electrochemical device is connected in parallel with the filter capacitor in the LC filter and in series with the filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor; Wherein, the parameters of the LC filter are determined according to the method according to any one of claims 1-8.

10. A filter parameter acquisition device, comprising: An acquisition module is used to acquire relevant parameters of the energy storage system, wherein the relevant parameters include: the operating frequency of the power grid to which the energy storage system is connected, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, current pulsation rate, and voltage pulsation rate of the submodules in the energy storage system; A determination module is used to determine the filter parameters in the correlation according to the relevant parameters and the correlation between the filter parameters in the submodule and the relevant parameters, wherein the filter parameters are used to design an LC filter, the electrochemical device in the submodule is connected in parallel with the filter capacitor in the LC filter, and is connected in series with the filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor; the correlation is determined according to an AC / DC network, and the AC / DC network is an equivalent circuit of a DC side circuit connected to a half-bridge circuit in the submodule, and when equivalent, the current flowing through the DC side circuit is equivalent to the superposition of a DC current, a base frequency AC, and a double frequency AC.

11. An electronic device, comprising: A memory and a processor, wherein the processor is connected to the memory; The memory is used to store programs; The processor is used to call the program stored in the memory to execute the method according to any one of claims 1 to 9.

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