An energy storage system, a method, apparatus, and electronic device for obtaining filter parameters.

Abstract

This application relates to an energy storage system, a method, apparatus, and electronic equipment for obtaining filter parameters, belonging to the field of power systems. The method includes: obtaining relevant parameters of the energy storage system, including: the operating frequency of the power grid connected to the energy storage system, the current amplitude of the power grid, the modulation ratio of the power grid, and the voltage, current ripple rate, and voltage ripple rate of the sub-modules in the energy storage system; and determining the filter parameters in the correlation relationship based on the relevant parameters and the correlation between the filter parameters in the sub-modules and the relevant parameters. This application employs a passive method using passive filters to suppress ripple current in the energy storage system. Ripple current is suppressed by setting LC filters in the sub-modules, and the parameters of the LC filters in each sub-module are determined based on the relevant parameters of the energy storage system and the correlation relationship between the filter parameters and the relevant parameters. This allows for accurate passive filter parameters to be obtained, thereby accurately suppressing the ripple current in the current energy storage system.

Description

Technical Field

[0001] This application belongs to the field of power systems, specifically relating to an energy storage system, a method for obtaining filter parameters, a device, and electronic equipment. Background Technology

[0002] With the development of power systems, modular multilevel energy storage systems are gradually entering the demonstration application stage. A modular multilevel energy storage system comprises multiple sub-modules, which can be connected in series and / or parallel. These sub-modules typically integrate power electronic components such as electrochemical devices. In AC systems, each sub-module suffers from the inherent problem of power ripple in the single-phase inverter. This power ripple causes pulsating current in the charging and discharging current of the electrochemical device. Due to the large amplitude of this pulsating current, the peak current of the electrochemical device can exceed its rated current, thus reducing its lifespan. Summary of the Invention

[0003] Therefore, the purpose of this application is to provide an energy storage system, a method for obtaining filter parameters, an apparatus, and an electronic device to improve the problem in the related art that it is impossible to accurately suppress pulsating current in the current energy storage system, thereby reducing the service life of the electrochemical device.

[0004] The embodiments of this application are implemented as follows:

[0005] In a first aspect, embodiments of this application provide an energy storage system, comprising: a submodule, the submodule including: an LC filter and an electrochemical device, the electrochemical device being connected in parallel with a filter capacitor in the LC filter and in series with a 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 based on 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 based on an AC / DC network, the AC / DC network being the equivalent circuit of the DC side circuit of the half-bridge circuit connected in the submodule, in which the current flowing through the DC side circuit is equivalent to the superposition of DC current, fundamental frequency AC, and second harmonic AC.

[0006] This application employs a passive method using passive LC filters to suppress pulsating current in the energy storage system. Pulsating current is suppressed by setting LC filters in sub-modules. Furthermore, the parameters of the LC filters in each sub-module are determined based on the aforementioned relevant parameters of the energy storage system and the correlation between the filter parameters and these relevant parameters. This correlation is determined based on the equivalent AC / DC network of the DC-side circuit connecting the half-bridge circuit in the sub-module. In this equivalent process, the current flowing through the DC-side circuit is equivalent to the superposition of DC current, fundamental frequency AC, and second harmonic AC. Therefore, accurate passive filter parameters can be obtained, thereby accurately suppressing the pulsating current in the current energy storage system and improving the problem of shortened lifespan of electrochemical devices caused by pulsating current.

[0007] In one possible implementation of the first aspect embodiment, the relevant parameters further include: the internal resistance of the electrochemical device.

[0008] In this embodiment, the internal resistance of the electrochemical device is also taken into account when designing the filter parameters in the submodule, so that the designed filter parameters are more accurate and can better suppress the pulsating current in the current energy storage system.

[0009] In one possible implementation of the first aspect embodiment, the correlation relationship includes: a first correlation relationship between the filter parameters and a first correlation parameter, and a second correlation relationship between the filter parameters and a second correlation parameter, wherein the first correlation relationship is determined based on the DC network, fundamental frequency AC network, and second harmonic AC network decomposed from the AC / DC network; the second correlation relationship is determined based on the fundamental frequency AC network and the second harmonic AC network; the parameters of the LC filter are obtained according to a first equation and a second equation, wherein the first equation is obtained based on the first correlation parameter and the first correlation relationship among the correlation parameters, and the second equation is obtained based on the second correlation parameter and the second correlation relationship among the correlation parameters; wherein the first correlation parameter includes: the operating frequency of the power grid, the current ripple rate, and the internal resistance of the electrochemical device; 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 ripple rate, and the voltage.

[0010] In this embodiment, it is only necessary to substitute the first correlation parameter into the first correlation relationship to obtain the first equation, and substitute the second correlation parameter into the second correlation relationship 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.

[0011] Secondly, embodiments of this application also provide a method for obtaining filter parameters, including:

[0012] Obtain relevant parameters of the energy storage system, including: the operating frequency of the power grid connected to the energy storage system, the current amplitude of the power grid, the modulation ratio of the power grid, and the voltage, current ripple rate, and voltage ripple rate of the sub-modules in the energy storage system. Based on the relevant parameters and the correlation between the filter parameters in the sub-modules and the relevant parameters, determine the filter parameters in the correlation relationship. The filter parameters are used to design the LC filter in the sub-module. 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. The filter inductor is located between the electrochemical device and the filter capacitor. The correlation relationship is determined based on an AC / DC network, which is the equivalent circuit of the DC-side circuit connecting the half-bridge circuit in the sub-module. In the equivalent circuit, the current flowing through the DC-side circuit is equivalent to the superposition of DC current, fundamental frequency AC, and second harmonic AC.

[0013] In one possible implementation of the second aspect embodiment, the relevant parameters further include: the internal resistance of the electrochemical device.

[0014] In one possible implementation of the second aspect embodiment, the correlation relationship includes: a first correlation relationship between the filter parameters and a first correlation parameter, and a second correlation relationship between the filter parameters and a second correlation parameter, wherein the first correlation relationship is determined based on the DC network, fundamental frequency AC network, and second harmonic AC network decomposed from the AC / DC network; the second correlation relationship is determined based on the fundamental frequency AC network and the second harmonic AC network; determining the filter parameters in the correlation relationship based on the correlation parameters and the correlation relationship between the filter parameters and the correlation parameters includes: obtaining a first equation based on the first correlation parameter and the first correlation relationship, wherein the first correlation parameter includes: the operating frequency of the power grid, the current ripple rate, and the internal resistance of the electrochemical device; obtaining a second equation based on the second correlation parameter and the second correlation relationship, 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 ripple rate, and the voltage; and determining the filter parameters in the correlation relationship based on the first equation and the second equation.

[0015] In conjunction with one possible implementation of the second aspect embodiment, the expression for the first equation is: Wherein, α is the current ripple rate, ω1 is 1 times the operating frequency of the power grid, ω2 is 2 times the operating frequency of the power grid, and R... b L is the internal resistance of the electrochemical device, C is the inductance value in the filter parameters, and C is the capacitance value in the filter parameters.

[0016] In the embodiments of this application, the range of parameters of the LC filter can be obtained quickly and accurately based on the above expression.

[0017] In conjunction with one possible implementation of the second aspect embodiment, the expression for 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, and R... b V 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, and V bat Let M be the voltage, M be the modulation ratio of the power grid, and I be the voltage. m The value is the current amplitude of the power grid.

[0018] In the embodiments of this application, the range of parameters of the LC filter can be obtained quickly and accurately based on the above expression.

[0019] In a possible implementation of the second aspect embodiment, before determining the filter parameters in the correlation relationship based on the correlation parameters and the correlation relationship between the filter parameters and the correlation parameters in the submodule, the method further includes: obtaining the current component of the electrochemical device branch in the submodule, the current component including the DC component of the electrochemical device branch, the fundamental frequency current component of the electrochemical device branch, and the second harmonic current component of the electrochemical device branch; obtaining the voltage component of the capacitor branch in the submodule, the voltage component including a first voltage pulsation generated by the fundamental frequency current in the capacitor branch and a second voltage pulsation generated by the second harmonic current in the capacitor branch; obtaining a first correlation relationship based on the current component of the electrochemical device branch in the submodule; obtaining a second correlation relationship based on the voltage component of the capacitor branch in the submodule and the voltage, wherein the correlation relationship includes the first correlation relationship and the second correlation relationship.

[0020] In this embodiment, by obtaining the current component of the electrochemical device branch in the submodule, the first correlation can be accurately obtained, such as the ratio of the sum of the fundamental frequency current component and the second harmonic current component to the DC component; by obtaining the voltage component of the capacitor branch in the submodule, the second correlation can be accurately obtained, such as the ratio of the sum of the first voltage pulsation and the second voltage pulsation to the voltage of the submodule.

[0021] In one possible implementation of the second aspect embodiment, obtaining the current component of the electrochemical device branch in the submodule includes: decomposing the AC / DC network into a DC network, a fundamental frequency AC network, and a second harmonic AC network; obtaining the DC component of the electrochemical device branch based on the DC network; obtaining the fundamental frequency current component of the electrochemical device branch based on the fundamental frequency AC network; and obtaining the second harmonic current component of the electrochemical device branch based on the second harmonic AC network.

[0022] In this embodiment, by decomposing the equivalent circuit (i.e., AC / DC network) of the DC side circuit connected to the half-bridge circuit in the submodule into a superposition of a DC network, a fundamental frequency AC network, and a second harmonic AC network, the DC component, fundamental frequency current component, and second harmonic current component of the electrochemical device branch can be accurately determined.

[0023] In one possible implementation of the second aspect embodiment, obtaining the voltage component of the capacitor branch in the submodule includes: decomposing the AC / DC network to obtain a fundamental frequency AC network and a second harmonic AC network; determining a first voltage ripple generated by the fundamental frequency current in the capacitor branch based on the fundamental frequency AC network; and determining a second voltage ripple generated by the second harmonic current in the capacitor branch based on the second harmonic AC network.

[0024] In this embodiment of the application, by decomposing the equivalent circuit (i.e., AC / DC network) of the DC side circuit connected to the half-bridge circuit in the submodule into the superposition of the DC network, the fundamental frequency AC network and the second harmonic AC network, the first voltage ripple generated by the fundamental frequency current in the capacitor branch and the second voltage ripple generated by the second harmonic current in the capacitor branch can be accurately determined.

[0025] Thirdly, this application embodiment also provides a filter parameter acquisition device, including: 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 connected to the energy storage system, 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 sub-modules in the energy storage system; the determination module is used to determine the filter parameters in the relevant relationship 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, the filter inductor is located between the electrochemical device and the filter capacitor; the correlation relationship is determined based on an AC / DC network, the AC / DC network is the equivalent circuit of the DC side circuit of the half-bridge circuit in the sub-module, in which the current flowing through the DC side circuit is equivalent to the superposition of DC current, fundamental frequency AC and second harmonic AC.

[0026] Fourthly, embodiments of this application also provide an electronic device, including: a memory and a processor, the processor being connected to the memory; the memory being used to store a program; the processor being used to invoke the program stored in the memory to perform a method provided as described in the second aspect embodiments and / or in combination with any possible implementation of the second aspect embodiments.

[0027] Other features and advantages of this application will be set forth in the following description. The objectives and other advantages of this application can be realized and obtained through the structures specifically pointed out in the written description and the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings. The above and other objects, features, and advantages of this application will become clearer through the accompanying drawings.

[0029] Figure 1 A circuit diagram of an energy storage system provided in an embodiment of this application is shown.

[0030] Figure 2 A circuit diagram of a submodule provided in an embodiment of this application is shown.

[0031] Figure 3 An equivalent schematic diagram of a DC-side circuit provided in an embodiment of this application is shown.

[0032] Figure 4 This illustration shows a schematic diagram of an AC / DC network decomposed into a superposition of a DC network, a fundamental frequency AC network, and a second harmonic AC network, according to an embodiment of this application.

[0033] Figure 5 A flowchart illustrating a filter parameter acquisition method provided in an embodiment of this application is shown.

[0034] Figure 6 A schematic diagram of a filter parameter acquisition device provided in an embodiment of this application is shown.

[0035] Figure 7 A schematic diagram of the structure of an electronic device provided in an embodiment of this application is shown. Detailed Implementation

[0036] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following embodiments are provided as examples to more clearly illustrate the technical solutions of this application, and should not be used to limit the scope of protection of this application. Those skilled in the art will understand that, without conflict, the following embodiments and features can be combined with each other.

[0037] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, relational terms such as "first," "second," etc., in the description of this application are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one…" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0038] Furthermore, the term "and / or" in this application is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0039] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical term "connection" can refer to a direct electrical connection or an indirect electrical connection through an intermediate medium.

[0040] Given that current technologies cannot accurately suppress pulsating current in energy storage systems, resulting in current peak values ​​exceeding the rated current of the electrochemical device and thus reducing its lifespan, this application employs a passive filter method to suppress pulsating current in energy storage systems. Specifically, an LC filter is set in the submodule to suppress pulsating current. The electrochemical device in the submodule is connected in parallel with a DC-side capacitor via a filter inductor. The inductor and capacitor form an LC filter, which significantly attenuates the amplitude of the fundamental frequency and second harmonic frequency pulsating current in the electrochemical device. However, the design of the passive filter is closely related to the efficiency and cost of the submodule, requiring accurate passive filter parameters.

[0041] To obtain accurate passive filter parameters, this application embodiment focuses on a modular multilevel energy storage system employing passive filters. It theoretically models and analyzes the pulsating current in the sub-modules, determining that the pulsating current consists of DC current, fundamental frequency AC, and second harmonic AC. Therefore, when equivalencing the DC-side circuit connected to the half-bridge circuit in the sub-module, the current flowing through the DC-side circuit is equivalent to the superposition of DC current, fundamental frequency AC, and second harmonic AC. Then, based on the equivalent AC / DC network, the correlation between filter parameters and related parameters is obtained, thereby accurately guiding filter parameter design and improving the problem of shortened lifespan of electrochemical devices caused by pulsating current.

[0042] An electrochemical device is a device or apparatus that performs an electrochemical reaction to provide electrical energy; for example, it can be a battery. This battery can be a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, etc.

[0043] In one embodiment, a schematic diagram of the energy storage system provided in this application is shown below. Figure 1 As shown. It is understandable that... Figure 1 The example diagram shown represents only a portion of the energy storage system, illustrating only the parts related to the bridge arms. The energy storage system comprises multiple bridge arms, each including multiple sub-modules (SMs) connected in series, and each bridge arm is connected to one phase of a three-phase AC power grid.

[0044] The filter parameters in each submodule of the energy storage system provided in this application embodiment 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. Specifically, this correlation is determined based on the AC / DC network, which is the equivalent circuit of the DC-side circuit connecting the half-bridge circuit in the submodule. In this equivalent circuit, the current flowing through the DC-side circuit is equivalent to the superposition of DC current, fundamental frequency AC, and second harmonic AC, thus providing precise guidance for filter parameter design.

[0045] The relevant parameters include the operating frequency ω of the power grid to which the energy storage system is connected and the current amplitude I of the power grid. m The modulation ratio M of the power grid, and the voltage V of the submodule. bat The current ripple rate α of the submodule and the voltage ripple rate β of the submodule.

[0046] The power grid connected to the energy storage system 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.

[0047] Among the aforementioned relevant parameters, the operating frequency ω of the power grid and the current amplitude I of the power grid are... m The modulation ratio M of the power grid depends on the power grid to which the energy storage system is connected. The voltage V of the submodule... bat This depends on the output voltage of the electrochemical device in the submodule. The current ripple rate α and voltage ripple rate β of the submodule can be set according to design requirements. Typically, the current ripple rate α is not greater than a first threshold, and the voltage ripple rate β is not greater than a second threshold. The first and second thresholds are greater than 0, but typically not greater than 1.

[0048] The correlation relationships can include: a first correlation relationship between the filter parameters and a first correlation parameter, and a second correlation relationship between the filter parameters and a second correlation parameter. The first correlation relationship is determined based on the DC network, the fundamental frequency AC network, and the second harmonic AC network decomposed from the AC / DC network; the second correlation relationship is determined based on the fundamental frequency AC network and the second harmonic AC network. The filter parameters in each submodule are determined based on the correlation parameters of the energy storage system, the first correlation relationship, and the second correlation relationship.

[0049] In this process, a first equation can be obtained based on the first relevant parameter and the first correlation relationship among the relevant parameters. A second equation can then be obtained based on the second relevant parameter and the second correlation relationship among the relevant parameters. Finally, the filter parameters in the submodule can be obtained based on the first equation and the second equation. In one optional implementation, the first relevant parameters include: the operating frequency of the power grid and the current ripple rate of the submodule. 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, and the voltage of the submodule. In this embodiment, simply substituting the first relevant parameter into the first correlation relationship yields the first equation, and substituting the second relevant parameter into the second correlation relationship yields the second equation. By solving the first and second equations, the parameters of the LC filter can be obtained quickly and accurately.

[0050] The first relevant parameters include: the operating frequency of the power grid and the current ripple rate of the submodule. The expression for the first equation is:

[0051]

[0052] Where α is the current ripple rate of the submodule, ω1 is 1 times the operating frequency of the power grid, ω2 is 2 times the operating frequency of the power grid, L is the inductance value in the filter parameters, and C is the capacitance value in the filter parameters.

[0053] The first correlation is similar to the first equation. Substituting the values ​​of the first correlation parameters into the expression obtained by the first correlation is the first equation.

[0054] The second set of relevant parameters 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. The expression for the second equation is:

[0055]

[0056] Where β is the voltage ripple rate of the submodule, ω1 is 1 times the operating frequency of the mains grid, ω2 is 2 times the operating frequency of the mains grid, L is the inductance value in the filter parameters, C is the capacitance value in the filter parameters, and V bat The voltage of the submodule is M, the modulation ratio of the power grid is I. m This represents the current amplitude of the power grid.

[0057] The second correlation is similar to the second equation. Substituting the values ​​of the second correlation parameters into the expression obtained from the second correlation gives us the second equation.

[0058] The filter parameters in this application include: inductance value L and capacitance value C. In the first and second equations mentioned above, only L and C are unknowns, while the other parameters are known values. By solving the system of equations, the filter parameters can be determined.

[0059] In one implementation, because the internal resistance of the electrochemical device is relatively 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 This application demonstrates that by taking into account the internal resistance of the electrochemical device, the designed filter parameters are more accurate and can better suppress pulsating currents in current energy storage systems.

[0060] 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.

[0061] The first relevant parameter also includes: the internal resistance of the electrochemical device, and the expression for the first equation is:

[0062]

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

[0064] The second relevant parameter also includes: the internal resistance of the electrochemical device, and the expression for the second equation is:

[0065]

[0066] Where β is the voltage ripple rate of the submodule, ω1 is 1 times the operating frequency of the power grid, ω2 is 2 times the operating frequency of the power grid, and R b V 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, and V is the capacitance value. bat The voltage of the submodule is M, the modulation ratio of the power grid is I. m This represents the current amplitude of the power grid.

[0067] In one alternative implementation, the correlation relationship, which includes the first correlation relationship and the second correlation relationship, can be obtained in the following manner:

[0068] 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 the DC component of the electrochemical device branch, the fundamental frequency current component of the electrochemical device branch, and the second harmonic 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 the first voltage pulsation generated by the fundamental frequency current in the capacitor branch and the second voltage pulsation generated by the second harmonic current in the capacitor branch.

[0069] To better understand the above process, let Idc represent the DC component of the electrochemical device branch, ibat1 represent the fundamental frequency current component of the electrochemical device branch, ibat2 represent the second harmonic current component of the electrochemical device branch, and v C1 The first voltage pulsation is represented by v. C2 Indicating the second voltage pulsation, then

[0070]

[0071] in, Considering the internal resistance R of the electrochemical device b In the following circumstances:

[0072]

[0073]

[0074]

[0075]

[0076] Among them, I dc1mThis represents the current amplitude of the fundamental frequency AC network. I dc2m This represents the current amplitude of the second-harmonic AC network. Z C1 Z represents the capacitance impedance in the fundamental frequency AC network. b1 The inductance and internal resistance R in the baseband AC network b The impedance, Z C2 Z represents the capacitance impedance in a second-harmonic AC network. b2 The inductance and internal resistance R in a frequency-doubled AC network b The impedance.

[0077] Without considering the internal resistance R b In the case of Z b1 Z represents the impedance of the inductor in the fundamental frequency AC network. b2 This represents the impedance of the inductor in a double-frequency AC network. At this point, directly connect the aforementioned ibat1, ibat2, and v... C1 v C2 The internal resistance R in the expression b By removing this, we can obtain the result without considering the internal resistance R. b ibat1, ibat2, v C1 v C2 The expression.

[0078] In one possible implementation, the process of obtaining the current component of the electrochemical device branch in the submodule can be as follows: decomposing the AC / DC network into a DC network, a fundamental frequency AC network, and a second harmonic AC network; obtaining the DC component of the electrochemical device branch based on the DC network; obtaining the fundamental frequency current component of the electrochemical device branch based on the fundamental frequency AC network; and obtaining the second harmonic current component of the electrochemical device branch based on the second harmonic AC network. Here, the AC / DC network is the equivalent circuit of the DC side circuit connecting the half-bridge circuit in the submodule.

[0079] To better understand, let's combine the following... Figure 2 The circuit diagrams of the sub-modules are illustrated below. Each sub-module, in addition to containing an LC filter, 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 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. Figure 2 The part containing the electrochemical device and LC filter is the DC side circuit of the half-bridge circuit in the submodule.

[0080] The equivalent schematic diagram of the DC side circuit is as follows: Figure 3 As shown, it can be Figure 3 The left part of the middle part is equivalent to Figure 3 The right side of the circuit is then used to obtain the AC / DC network. In the equivalent circuit, the current flowing through the DC side is represented as a superposition of DC current, fundamental frequency AC current, and second harmonic AC current. Ignoring the influence of high-frequency components, the circuit can be further... Figure 3 The AC / DC network on the right side is decomposed into Figure 4 The superposition of the DC network, the fundamental frequency AC network, and the second harmonic AC network is shown.

[0081] Decomposing the equivalent AC / DC network into Figure 4 After obtaining the network model shown, 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 second harmonic current component of the electrochemical device branch can be obtained based on the second harmonic AC network. For example, by solving the DC network, the DC component I of the current can be obtained. b =I dc Solving the fundamental frequency AC network yields the fundamental frequency current component ibat1, and solving the second harmonic AC network yields the second harmonic current component ibat2.

[0082] In some possible implementations, the process of obtaining the voltage components of the capacitor branches in the submodule can be: directly obtaining them from the database, where the voltage components of the capacitor branches in the submodule are pre-stored.

[0083] In some possible implementations, the process of obtaining the voltage component of the capacitor branch in the submodule may involve: decomposing the AC / DC network to obtain a fundamental frequency AC network and a second harmonic AC network; determining the first voltage ripple generated by the fundamental frequency current in the capacitor branch based on the fundamental frequency AC network; and determining the second voltage ripple generated by the second harmonic current in the capacitor branch based on the second harmonic AC network. Here, the AC / DC network is the equivalent circuit of the DC-side circuit connecting the half-bridge circuit in the submodule.

[0084] For ease of understanding, combined with Figure 3 , Figure 4 The schematic diagram shown illustrates this. Ignoring the influence of high-frequency components, we can further... Figure 3 The AC / DC network on the right side is decomposed into Figure 4 The superposition of the DC network, the fundamental frequency AC network, and the second harmonic AC network shown can then be used as a basis for... Figure 4 The fundamental frequency AC network in the figure determines the first voltage ripple generated by the fundamental frequency current in the capacitor branch, based on Figure 4 In a second-harmonic AC network, the second voltage ripple generated by the second-harmonic current in the capacitor branch is determined. For example, the phasor method can be used to calculate the first voltage ripple v generated by the fundamental frequency current in the fundamental frequency AC network. C1The phasor method is applied to calculate the second voltage ripple v generated by the second harmonic current in the second harmonic AC network. C2 .

[0085] In the above implementation, because the pulsating current in the submodule is theoretically modeled and analyzed, it is found that its components include DC component, fundamental frequency component, and second harmonic component. Therefore, the above AC / DC network is decomposed into a superposition of DC network, fundamental frequency AC network, and second harmonic AC network.

[0086] To better understand, let's combine the following... Figure 1 The energy storage system shown is explained below. Considering only the fundamental frequency component, taking phase A as an example, the switching function S of the upper bridge arm is... ap It can be represented as follows:

[0087] S ap =M dc -Msinωt, where U dc U is the DC component of the upper bridge arm voltage. mj Let j be the voltage amplitude of the grid phase. Taking phase A as an example, j = phase A at this time. N is the number of bridge arms, and I... m U represents the current amplitude of the power grid. c This is the average value of the capacitor voltages of each submodule, typically equal to the submodule voltage V. bat Without considering circulating current, the currents flowing through the upper and lower arms of phase A are respectively... and Then we have:

[0088]

[0089] in, The phase angle difference between voltage and current, when hour, It can be seen that the current flowing through the submodule includes DC components, fundamental frequency components, and second harmonic components. Meanwhile, the AC component accounts for a relatively large proportion. If no suppression measures are taken, a large pulsating current will flow through the current, affecting the battery's lifespan.

[0090] In this embodiment of the application, in order to analyze Figure 1 The harmonic components of the current of the electrochemical device during the four-quadrant operation of the energy storage system are shown. The analytical expression of the DC-side ripple current in the submodule is derived based on the switching function.

[0091] The AC output voltage and current of a certain submodule in phase A upper arm are:

[0092] v apj =V mapj (1+cosωt);

[0093] Among them, V mapj The output voltage amplitude of the submodule is generally... Neglecting the effect of the filter inductor, it can be approximated as being 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 parsing expression is:

[0094]

[0095]

[0096] in, Typically V bat =U c The DC component I of the DC-side current is obtained by decomposing the analytical expression of the DC-side ripple current. dc Fundamental frequency component i dc_1 (t), second harmonic component i dc_2 (t) are respectively:

[0097]

[0098]

[0099]

[0100] Based on the analytical expression of DC-side ripple current, it can be seen that...

[0101] This application also provides a method for obtaining filter parameters. This method can quickly and accurately determine the parameters of the LC filter in the submodule, thereby precisely guiding the design of the LC filter. In one possible implementation, the electrochemical device in the submodule is connected in parallel with the filter capacitor in the LC filter, and connected in series with the filter inductor in the LC filter. The filter inductor is located between the electrochemical device and the filter capacitor. The following describes the method in conjunction with... Figure 5 The flowchart shown illustrates the filter parameter acquisition method provided in the embodiments of this application.

[0102] 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, and the voltage, current ripple rate, and voltage ripple rate of the sub-modules in the energy storage system.

[0103] In one optional implementation, the relevant parameters of the energy storage system can be obtained from a local database and / or a third party, or the relevant parameters can be prepared in advance for later use. In some possible implementations, the relevant parameters of the energy storage system can also be obtained in real time, such as obtaining the relevant parameters of the energy storage system input by the user in real time.

[0104] 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.

[0105] S2: Determine the filter parameters in the correlation relationship based on the relevant parameters and the correlation relationship between the filter parameters and the relevant parameters in the submodule.

[0106] After obtaining the relevant parameters, the filter parameters can be determined based on these parameters and the pre-determined correlation between the filter parameters and the relevant parameters in the submodule. Then, an LC filter can 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 connecting the half-bridge circuit in the submodule. In the equivalent circuit, the current flowing through the DC-side circuit is equivalent to the superposition of DC current, fundamental frequency AC, and second harmonic AC.

[0107] This correlation characterizes the relationship between filter parameters and correlation parameters, and it can be an expression that includes both filter parameters and correlation parameters.

[0108] In one implementation, the correlation may include: a first correlation between filter parameters and a first correlation parameter, and a second correlation between filter parameters and a second correlation parameter. The first correlation is determined based on the DC network, fundamental frequency AC network, and second harmonic AC network decomposed from the AC / DC network; the second correlation is determined based on the fundamental frequency AC network and the second harmonic AC network. The first correlation parameter includes: the operating frequency of the power grid and the current ripple rate of the submodule. 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 voltage ripple rate of the submodule, and the voltage of the submodule.

[0109] The first correlation relationship characterizes the correlation between the first correlation parameter and the filter parameters; it can be an expression that includes both the filter parameters and the first correlation parameter. Similarly, the second correlation relationship characterizes the correlation between the second correlation parameter and the filter parameters; it can be an expression that includes both the filter parameters and the second correlation parameter.

[0110] When the relevant parameters include a first correlation and a second correlation, the implementation process of S2 can be as follows: based on the first correlation parameter and the first correlation relationship in the relevant parameters, obtain the first equation; based on the second correlation parameter and the second correlation relationship in the relevant parameters, obtain the second equation; and based on the first equation and the second equation, determine the filter parameters in the correlation relationship.

[0111] Where the relevant parameters also include the internal resistance of the electrochemical device, then the first and second relevant parameters also include the internal resistance of the electrochemical device. In this case, the first relevant parameter includes: 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 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 ripple rate of the submodule, and the voltage of the submodule.

[0112] In one optional implementation, when the first relevant parameter further includes the internal resistance of the electrochemical device, the expression for the first equation is:

[0113]

[0114] When the second relevant parameter also includes the internal resistance of the electrochemical device, the expression for the second equation is:

[0115]

[0116] In one optional implementation, before S2, the filter parameter acquisition method further includes: acquiring the current component of the electrochemical device branch in the submodule, 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 second harmonic current component of the electrochemical device branch; obtaining a first correlation relationship based on the current component of the electrochemical device branch in the submodule; and acquiring the voltage component of the capacitor branch in the submodule, 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 second harmonic current in the capacitor branch; obtaining a second correlation relationship based on the voltage component and voltage of the capacitor branch in the submodule.

[0117] In one implementation, the process of obtaining the current component of the electrochemical device branch in the submodule may be as follows: decomposing the AC / DC network into a DC network, a fundamental frequency AC network, and a second harmonic AC network, wherein the AC / DC network is the equivalent circuit of the DC side circuit connecting the half-bridge circuit in the submodule; obtaining the DC component of the electrochemical device branch based on the DC network; obtaining the fundamental frequency current component of the electrochemical device branch based on the fundamental frequency AC network; and obtaining the second harmonic current component of the electrochemical device branch based on the second harmonic AC network.

[0118] In one implementation, the process of obtaining the voltage component of the capacitor branch in the submodule may be as follows: decompose the AC / DC network to obtain the fundamental frequency AC network and the second harmonic AC network, wherein the AC / DC network is the equivalent circuit of the DC side circuit of the half-bridge circuit in the submodule; based on the fundamental frequency AC network, determine the first voltage ripple generated by the fundamental frequency current in the capacitor branch; based on the second harmonic AC network, determine the second voltage ripple generated by the second harmonic current in the capacitor branch.

[0119] The filter parameter acquisition method provided in this application embodiment has the same implementation principle and technical effect as the aforementioned energy storage system embodiment. For the sake of brevity, any parts not mentioned in the method embodiment can be referred to the corresponding content in the aforementioned energy storage system embodiment.

[0120] This application embodiment also provides a filter parameter acquisition device 100, such as... Figure 6 As shown. The filter parameter acquisition device 100 includes: an acquisition module 110 and a determination module 120.

[0121] The acquisition module 110 is used to acquire 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, and the voltage, current ripple rate, and voltage ripple rate of the sub-modules in the energy storage system.

[0122] The determining module 120 is used to determine the filter parameters in the correlation relationship based on the correlation parameters and the correlation relationship between the filter parameters and the correlation parameters in the sub-module, wherein the filter parameters are used to design the LC filter.

[0123] The correlation relationships include: a first correlation relationship between the filter parameters and a first correlation parameter, and a second correlation relationship between the filter parameters and a second correlation parameter; the determining module 120 is used to obtain a first equation based on the first correlation parameter and the first correlation relationship among the correlation parameters, wherein the first correlation parameter includes: the operating frequency of the power grid, the current ripple rate, and the internal resistance of the electrochemical device; to obtain a second equation based on the second correlation parameter and the second correlation relationship among the correlation parameters, 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 ripple rate, and the voltage; and to determine the filter parameters in the correlation relationships based on the first equation and the second equation.

[0124] Optionally, the acquisition module 110 is further configured to acquire the current component of the electrochemical device branch in the submodule, the current component including the DC component of the electrochemical device branch, the fundamental frequency current component of the electrochemical device branch, and the second harmonic current component of the electrochemical device branch; acquire the voltage component of the capacitor branch in the submodule, the voltage component including a first voltage pulsation generated by the fundamental frequency current in the capacitor branch and a second voltage pulsation generated by the second harmonic current in the capacitor branch; obtain a first correlation relationship based on the current component of the electrochemical device branch in the submodule; and obtain a second correlation relationship based on the voltage component of the capacitor branch in the submodule and the voltage, wherein the correlation relationship includes the first correlation relationship and the second correlation relationship.

[0125] Optionally, the acquisition module 110 is further configured to decompose the AC / DC network into a DC network, a fundamental frequency AC network, and a second harmonic AC network, wherein the AC / DC network is the equivalent circuit of the DC side circuit of 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 fundamental frequency AC network, the fundamental frequency current component of the electrochemical device branch is obtained; and based on the second harmonic AC network, the second harmonic current component of the electrochemical device branch is obtained.

[0126] Optionally, the acquisition module 110 is further configured to decompose the AC / DC network to obtain a fundamental frequency AC network and a second harmonic AC network, wherein the AC / DC network is the equivalent circuit of the DC side circuit of the half-bridge circuit in the sub-module; based on the fundamental frequency AC network, determine the first voltage ripple generated by the fundamental frequency current in the capacitor branch; and based on the second harmonic AC network, determine the second voltage ripple generated by the second harmonic current in the capacitor branch.

[0127] The filter parameter acquisition device 100 provided in this application embodiment has the same implementation principle and technical effect as the aforementioned method embodiment. For the sake of brevity, any parts not mentioned in the device embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0128] like Figure 7 As shown, Figure 7 This diagram illustrates a structural block diagram of an electronic device 200 provided in an embodiment of this application. The electronic device 200 includes: a transceiver 210, a memory 220, a communication bus 230, and a processor 240.

[0129] The transceiver 210, memory 220, and processor 240 are electrically connected directly or indirectly to achieve data transmission or interaction. For example, these components can be electrically connected to each other through 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... Figure 6 The software functional module shown is the filter parameter acquisition device 100. The filter parameter acquisition device 100 includes at least one software functional module that can be stored as software or firmware in the memory 220 or embedded in the operating system (OS) of the electronic device 200. The processor 240 is used to execute executable modules stored in the memory 220, such as the software functional module or computer program included in the filter parameter acquisition device 100. For example, the processor 240 is used to execute the filter parameter acquisition method described above.

[0130] The memory 220 may be, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0131] Processor 240 may be an integrated circuit chip with signal processing capabilities. The aforementioned processor can be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), a microprocessor, etc.; it can 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, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. Alternatively, processor 240 can also be any conventional processor.

[0132] Among them, the aforementioned electronic devices 200 include, but are not limited to, mobile phones, tablets, computers, servers, etc.

[0133] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0134] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A filter parameter acquisition method characterized by comprising: The method comprises: obtaining relevant parameters of an energy storage system, the relevant parameters comprising: an operating frequency of a power grid connected to the energy storage system, a current amplitude of the power grid, a modulation ratio of the power grid, a voltage of a sub-module in the energy storage system, a current ripple rate, a voltage ripple rate; determining filter parameters in the relevant relationship according to the relevant parameters and a correlation between the filter parameters and the relevant parameters, wherein the filter parameters are used to design an LC filter in the sub-module, an electrochemical device in the sub-module is connected in parallel with a filter capacitor in the LC filter and in series with a filter inductor in the LC filter, the filter inductor is located between the electrochemical device and the filter capacitor; the correlation is determined according to an AC / DC network, which is an equivalent circuit of a DC side circuit of a half-bridge circuit connected to the sub-module; in the equivalent state, a current flowing through the DC side circuit is equivalent to a superposition of a direct current, a fundamental frequency alternating current and a double-frequency alternating current.

2. The method of claim 1, wherein, The relevant parameters further comprise: an internal resistance of the electrochemical device.

3. The method of claim 2, wherein, The relevant relationship comprises: a first correlation between the filter parameters and a first relevant parameter, and a second correlation between the filter parameters and a second relevant parameter, wherein the first correlation is determined according to a direct current network, a fundamental frequency alternating current network and a double-frequency alternating current network decomposed from the AC / DC network; the second correlation is determined according to the fundamental frequency alternating current network and the double-frequency alternating current network; The determining of the filter parameters in the relevant relationship according to the relevant parameters and the correlation between the filter parameters and the relevant parameters comprises: obtaining a first equation according to a first relevant parameter in the relevant parameters and the first correlation, wherein the first relevant parameter comprises: the operating frequency of the power grid, the current ripple rate, the internal resistance of the electrochemical device; obtaining a second equation according to a second relevant parameter in the relevant parameters and the second correlation, wherein the second relevant parameter comprises: 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, the voltage; determining the filter parameters in the relevant relationship according to the first equation and the second equation.

4. The method of claim 3, wherein, The expression of the first equation is: ， wherein, is the current ripple rate, is the operating frequency of the power grid, is the operating frequency of the power grid, is the internal resistance of the electrochemical device, L is the inductance value in the filter parameter, and C is the capacitance value in the filter parameter.

5. The method of claim 3, wherein, The expression of the second equation is: ， wherein is the voltage ripple rate, is the operating frequency of the power grid, is the operating frequency of the power grid, 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 parameter, is the voltage, M is the modulation ratio of the power grid, is the current amplitude of the power grid.

6. The method according to any one of claims 3-5, characterized in that, Before the determining of the filter parameters in the relevant relationship according to the relevant parameters and the correlation between the filter parameters and the relevant parameters, the method further comprises: obtaining current components of an electrochemical device branch in the sub-module, the current components comprising: a direct current component of the electrochemical device branch, a fundamental frequency current component of the electrochemical device branch, a double-frequency current component of the electrochemical device branch; obtaining a first correlation according to the current components of the electrochemical device branch in the sub-module; obtaining voltage components of a capacitor branch in the sub-module, the voltage components comprising: a first voltage ripple generated by a fundamental frequency current in the capacitor branch, and a second voltage ripple generated by a double-frequency current in the capacitor branch; A second correlation relationship is obtained according to the voltage component of the capacitor branch in the sub-module and the voltage, wherein the correlation relationship includes the first correlation relationship and the second correlation relationship.

7. The method of claim 6, wherein, The current component of the electrochemical device branch in the sub-module is obtained, including: The AC-DC network is decomposed into a DC network, a fundamental frequency AC network and a double frequency AC network; The DC component of the electrochemical device branch is obtained based on the DC network; The fundamental frequency current component of the electrochemical device branch is obtained based on the fundamental frequency AC network; The double frequency current component of the electrochemical device branch is obtained based on the double frequency AC network.

8. The method of claim 6, wherein, The voltage component of the capacitor branch in the sub-module is obtained, including: The AC-DC network is decomposed to obtain the fundamental frequency AC network and the double frequency AC network; The first voltage fluctuation of the fundamental frequency current in the capacitor branch is determined based on the fundamental frequency AC network; The second voltage fluctuation of the double frequency current in the capacitor branch is determined based on the double frequency AC network.

9. An energy storage system characterized by, The sub-module includes an LC filter and an electrochemical device, the electrochemical device is connected in parallel with a filter capacitor in the LC filter and connected in series with a filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor. The parameters of the LC filter are determined according to the method of any one of claims 1-8.

10. A filter parameter acquisition apparatus characterized by comprising: The method includes: The obtaining module is used to obtain the related parameters of the energy storage system, including the working frequency of the power grid connected to the energy storage system, the current amplitude of the power grid, the modulation ratio of the power grid, the voltage, the current fluctuation rate and the voltage fluctuation rate of the sub-module in the energy storage system; The determining module is used to determine the filter parameters in the correlation relationship according to the related parameters and the correlation relationship between the filter parameters and the related parameters in the sub-module, wherein the filter parameters are used to design an LC filter, the electrochemical device in the sub-module is connected in parallel with a filter capacitor in the LC filter and connected in series with a filter inductor in the LC filter, and the filter inductor is located between the electrochemical device and the filter capacitor; the correlation relationship is determined according to an AC-DC network, which is an equivalent circuit of a DC side circuit of a half-bridge circuit connected in the sub-module, and in the equivalent state, the current flowing through the DC side circuit is equivalent to the superposition of the DC current, the fundamental frequency AC and the double frequency AC.

11. An electronic device, comprising: The method includes: The memory and the processor are connected; The memory is used to store programs; The processor is used to call the programs stored in the memory to execute the method of any one of claims 1-8.

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