Energy storage converter multi-machine parallel control method, device and equipment and storage medium

Abstract

The invention provides an energy storage converter multi-machine parallel control method, device and equipment and a storage medium, and the method comprises the steps: firstly, disassembling a grid-connected system in which energy storage converters are connected in parallel into a plurality of equivalent circuits under independent excitation, and building a transfer function between the response current of each equivalent circuit and an excitation source; then, determining a Bode diagram of a transfer function changing along with the parallel connection number, and obtaining a frequency response closed-loop transfer function of each energy storage converter according to the transfer function and a power expression of the energy storage converter to the common bus voltage; finally, control parameters are determined by combining the Bod e graph and the closed-loop transfer function, and multi-machine parallel control is achieved. The method disclosed by the invention reveals the interaction of frequency responses among the energy storage converters, and provides a theoretical basis for system control parameter selection and frequency optimization control.

Description

Technical Field

[0001] The present application relates to the field of power grid peak regulation, and in particular to a method, device, equipment and storage medium for parallel control of multiple energy storage converters. Background Art

[0002] As the interface between the energy storage system and the power grid, the performance of the energy storage converter has an important impact on the stability of the power system. As new energy gradually becomes the main body of power system electricity, more energy storage and other equipment with active support capabilities are needed to take the responsibility of voltage and frequency adjustment. Active support energy storage systems not only have the ability to support the stability of the power grid, but also have multiple functions such as conventional energy storage and reactive power compensation. They are the key to ensuring the stable operation of high-proportion new energy systems.

[0003] In the scenario of new energy grid connection, it is often necessary to operate multiple energy storage VSCs in parallel to provide greater capacity and more flexible control strategies. There are complex interactions between the power sources in the energy storage VSC multi-machine parallel system, including the characteristics of the energy storage VSC itself, between energy storage VSCs, and between energy storage VSCs and grid power sources. These complex interactions can lead to system stability problems, especially when the number of parallel connections increases. Summary of the invention

[0004] The purpose of the present application is to overcome the above-mentioned prior art and provide a method, device, equipment and storage medium for parallel control of multiple energy storage converters.

[0005] The present application provides a method for controlling multiple energy storage converters in parallel, comprising:

[0006] Decompose the grid-connected system with energy storage converters in parallel into multiple equivalent circuits under separate excitation;

[0007] Establishing the transfer function between the response current and the excitation source when each of the equivalent circuits acts alone;

[0008] Determine a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes;

[0009] Determine the frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and the power expression transmitted from the i-th energy storage converter to the common bus voltage;

[0010] The control parameters of the energy storage converter are determined according to the Bode diagram and the frequency response closed-loop transfer function, and multi-machine parallel control is performed.

[0011] Optionally, the grid-connected system in which the energy storage converters are connected in parallel is decomposed into a plurality of equivalent circuits under separate excitations, including:

[0012] According to the voltage source form, the grid-connected system in which multiple energy storage converters are connected in parallel is equivalent to an equivalent circuit under the excitation of multiple independent voltage sources.

[0013] Optionally, the transfer function between the response current and the excitation source includes transfer functions G1, G2, and G3 under the action of Us1 alone, Usk alone, and Ug alone.

[0014] Optionally, determining a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes includes:

[0015] According to the changes of transfer functions G1, G2, and G3 as the number of parallel energy storage converters increases, the Bode diagrams under different excitation sources are obtained.

[0016] Optionally, in the step of determining the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function,

[0017] By analyzing the influence of the inertia and damping parameter changes of each energy storage converter in the grid-connected system with energy storage converters connected in parallel on the frequency response characteristics of other energy storage converters, the optimized control parameters are determined.

[0018] Optionally, the control parameters include virtual inertia and virtual damping.

[0019] Optionally, it also includes:

[0020] The energy storage converter simulation model was built using MATLAB / Simulink software.

[0021] The present application also provides a multi-machine parallel control device for energy storage converters, comprising:

[0022] A decomposition module decomposes the grid-connected system of energy storage converters in parallel into multiple equivalent circuits under separate excitation;

[0023] A transfer module, for establishing a transfer function between a response current and an excitation source when each of the equivalent circuits acts alone;

[0024] A mapping module is used to determine a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes;

[0025] A closed-loop module, determining a frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and an expression of power transmitted from the i-th energy storage converter to the common bus voltage;

[0026] The control module determines the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performs multi-machine parallel control.

[0027] The present application also provides a multi-machine parallel control device for energy storage converters, comprising:

[0028] Memory;

[0029] A processor is used to retrieve the computer executable program of the above-mentioned energy storage converter multi-machine parallel control method from the memory, and execute: decomposing the grid-connected system of the energy storage converters in parallel into multiple equivalent circuits under separate excitations; establishing the transfer function between the response current and the excitation source when each of the equivalent circuits acts alone; determining the Bode diagram of the transfer function between the response current and the excitation source as the number of parallel energy storage converters changes; determining the frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and the power expression transmitted by the i-th energy storage converter to the common bus voltage; determining the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performing multi-machine parallel control.

[0030] The present application also provides a storage medium, comprising: storing a computer executable program, wherein the computer executable program is used to be called by a processor to execute the steps of the above-mentioned energy storage converter multi-machine parallel control method.

[0031] The beneficial effects of this application are:

[0032] The present application provides a method for controlling multiple energy storage converters in parallel, including: decomposing a grid-connected system of energy storage converters in parallel into multiple equivalent circuits under separate excitations; establishing the transfer function between the response current and the excitation source when each of the equivalent circuits acts alone; determining the Bode diagram of the transfer function between the response current and the excitation source as the number of energy storage converters in parallel changes; determining the frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and the power expression of the i-th energy storage converter transmitted to the common bus voltage; determining the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performing multi-machine parallel control. The present application discloses the interaction between the change of the control parameters of one energy storage converter in the system and the frequency response of another energy storage converter, and provides a theoretical basis for the selection of control parameters and the optimal control of the system frequency of a multi-machine parallel grid-connected system of energy storage converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the multi-machine parallel control process of the energy storage converter in this application;

[0034] Figure 2 It is a schematic diagram of the typical control structure of the energy storage VSC in this application;

[0035] Figure 3 is a schematic diagram of an equivalent circuit under the interaction of various excitation sources in this application;

[0036] FIG. 4( a) is a diagram of the U s1 Bode diagram under the action of excitation source;

[0037] FIG. 4( b ) is a diagram of the U sk Bode diagram under the action of excitation source;

[0038] FIG. 4( c ) is a diagram of the U g Bode diagram under the action of excitation source;

[0039] FIG5( a ) is a bode diagram motion trajectory diagram of J2 increase in this application;

[0040] FIG5( b ) is a bode diagram motion trajectory diagram of D2 increase in this application;

[0041] FIG5( c ) is a root locus diagram when J2 and D2 increase in the present application;

[0042] FIG6( a ) is a harmonic analysis diagram of the output current when the number of parallel connection of two energy storage VSCs in the present application increases;

[0043] FIG6( b ) is a harmonic analysis diagram of the output current when the number of parallel connections of three energy storage VSCs in the present application increases;

[0044] FIG. 7( a ) is a waveform diagram of the PCS-VSC1 frequency when J2 changes in the present application;

[0045] FIG7( b ) is a waveform diagram of the active power of PCS-VSC1 when J2 changes in the present application;

[0046] FIG7( c ) is a waveform diagram of the PCS-VSC1 frequency when D2 changes in the present application;

[0047] FIG7( d ) is a waveform diagram of the active power of PCS-VSC1 when D2 changes in the present application. DETAILED DESCRIPTION

[0048] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0049] Please refer to Figure 1As shown, the present application provides a method for controlling multiple energy storage converters in parallel, comprising:

[0050] S101. Decompose the grid-connected system in which energy storage converters are connected in parallel into a plurality of equivalent circuits under separate excitation.

[0051] like Figure 2 As shown, the energy storage converter (energy storage VSC) grid-connected architecture.

[0052] In the main circuit structure, L, R L , C are the filter inductance, resistance and capacitance of the inverter respectively; L g and R g are the line inductance and resistance respectively.

[0053] DC side V dc is the voltage of the energy storage system.

[0054] e ck (k=a, b, c) means that the AC filter capacitor voltage is equal to the AC output voltage of the energy storage VSC.

[0055] e cd 、e cq It is the corresponding dq axis component after coordinate transformation.

[0056] i Lk and i k (k=a, b, c) are the AC filter inductor current and the energy storage VSC AC output current respectively.

[0057] i Ld 、i Lq and i d 、i q is i Lk and i k The dq-axis components of .

[0058] uk is the grid voltage at the grid connection point.

[0059] u od and u oq They are the dq axis components of the VSC control voltage respectively.

[0060] Virtual synchronous machine control mainly consists of two parts:

[0061] (1) Active power-frequency control introduces the rotor mechanical equation model in the mathematical model of the synchronous machine and the inertia damping characteristics of the synchronous machine.

[0062] (2) Reactive power-voltage control simulates the excitation characteristics of synchronous machines, allowing the energy storage VSC to have voltage regulation capabilities, as shown in the following formula;

[0063]

[0064] Where J and D are virtual inertia and virtual damping, respectively; ω, ω0 and Δω are the VSC output angular frequency, rated frequency and the difference between the two, respectively; ω bus AC bus angular frequency; P ref is the active power reference value; P out is the output active power of VSC; δ is the output voltage phase of the converter, i.e., the reference phase.

[0065]

[0066] In the formula, K q is the integral coefficient; Q ref is the reactive power reference value; Q0 is the VSC output reactive power; D q is the reactive voltage regulation coefficient; e cn is the voltage amplitude reference value; E is the potential inside the energy storage VSC.

[0067] like Figure 3 As shown in the figure, the energy storage VSC multi-machine parallel grid-connected system is mainly composed of the energy storage VSC equivalent power supply Us, the LCL filter circuit equivalent impedance, the line equivalent impedance and the grid power supply.

[0068] This application is built using MATLAB / Simulink software Figure 2 The energy storage VSC simulation model shown in the figure and the main simulation parameters are shown in Table 1.

[0069] Table 1 Main control parameters of voltage source energy storage parallel system

[0070]

[0071]

[0072] S102, respectively establishing a transfer function between the response current and the excitation source when each of the equivalent circuits acts alone.

[0073] According to the equivalent circuit, U s1 , U sk , U g When acting alone, it corresponds to I r1 The transfer functions G1, G2, and G3 between the response current and the three excitation sources are expressed as follows:

[0074]

[0075] in:

[0076]

[0077] S103, determining a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes.

[0078] like Figure 4(a) , 4(b) ,4(c) shows the Bode diagram of the transfer functions G1, G2, and G3 as the number of energy storage VSCs in parallel changes.

[0079] WhenU s1 Under its own excitation, as the number of parallel connections increases, the resonance peak point moves toward the low-frequency direction. Therefore, the possibility of low-frequency resonance in the energy storage VSC parallel system will increase under the excitation of the converter itself.

[0080] WhenU sk Under excitation, as the number of parallel connections increases, the resonance point at low frequency remains unchanged, and the resonance point at high frequency moves toward low frequency. Although the amplitude decreases, the possibility of resonance still exists.

[0081] When the grid power supply U g Under excitation, as the number of parallel connections increases, the high-frequency resonance peak shifts toward the low-frequency direction, while the low-frequency resonance peak does not shift, and the amplitude changes of the two are small; under the excitation of the corresponding grid power supply, the possibility of low-frequency resonance of the grid-connected current of the first energy storage VSC increases.

[0082] From the above analysis, it can be seen that when the number of energy storage VSCs in parallel gradually increases, under the excitation of different voltage sources, the entire energy storage VSC parallel system is in different resonant characteristics. The overall performance is that with the increase in the number of parallel units, the possibility of resonance in the energy storage VSC parallel system increases.

[0083] S104. Determine the frequency response closed-loop transfer function of the ith energy storage converter according to the transfer function between the response current and the excitation source and the expression of the power transmitted by the ith energy storage converter to the common bus voltage.

[0084] The power delivered to the common bus voltage by the i-th energy storage VSC can be expressed as:

[0085]

[0086] Where: e ci is the output voltage amplitude; K i =1.5eciUg / Xg, Xg is the equivalent line inductance; P outi is the active power output by the i-th energy storage VSC.

[0087] Combining the transfer function, the power delivered by the i-th energy storage VSC to the common bus voltage can be obtained:

[0088]

[0089] From the above formula, the closed-loop transfer function of the frequency response of the i-th energy storage VSC is:

[0090]

[0091] For example:

[0092] When the parameters of J2 and D2 of the parallel PCS-VSC2 change, its Δω1(s) / ΔP load The amplitude-frequency characteristic curve of (s) is shown in the Bode diagram. Figure 5(a) , 5(b) shown.

[0093] Figures 5(a) and 5(b) show the influence of the control parameters J2 and D2 of PCS-VSC2 on the frequency response of PCS-VSC1 in a system with two energy storage VSCs in parallel. When J2 of PCS-VSC2 increases, the low-frequency resonance point of PCS-VSC1 moves to the lower left corner of the bode diagram. It can be seen that for the same load fluctuation, the increase of J2 will affect the stability of the frequency response of PCS-VSC1, but has no obvious effect in the high-frequency region, that is, it has no obvious effect on the maximum frequency deviation rate (RoCoF) of Δω1. When D2 of PCS-VSC2 increases, the low-frequency resonance point of PCS-VSC1 is weakened, and the amplitude-frequency characteristic curve in the high-frequency region has no obvious change. It can be seen that the D2 value has a small effect on the RoCoF of the PCS-VSC1 frequency response, but as D2 increases, the amplitude of the low-frequency band (<1HZ) decreases. It can be seen that the increase of D2 can improve the frequency response stability of PCS-VSC1.

[0094] Figure 5(c) shows the relationship between Δω1(s) / ΔP when J2 and D2 increase. load From the root locus diagram of (s), we can see that there are 5 characteristic roots, among which S 11 , S 12 is a pair of invariant conjugate complex roots, S 21 , S 22 is a pair of conjugate complex roots, and its changing direction is shown by the arrow in the figure. S3 is located on the real axis, and its changing direction is as shown by the arrow. When J2 increases, S 21 , S 22 When it moves closer to the left side of the complex plane, the stability of PCS-VSC1 is improved, but when J2 is too large, S3 moves closer to the right side of the complex plane and the stability margin is reduced; when D2 increases, S21, S22, and S3 all move closer to the left side of the complex plane. It can be seen that the increase of D2 will improve the frequency modulation stability of PCS-VSC1 to a greater extent.

[0095] Here is another example:

[0096] Figure 6(a) and Figure 6(b) are the PCC current harmonic analysis diagrams of two and three energy storage VSCs in parallel. PCS-VSC2 and PCS-VSC3 have the same configuration. As the number of energy storage VSCs in parallel increases, the THD value of the output current of the energy storage VSC parallel system increases. It can be seen that for energy storage VSCs with the same configuration, the stability will deteriorate as the number of parallel connections increases.

[0097] Taking the parallel connection of two energy storage VSCs as an example, the influence of the changes in the inertia and damping parameters of PCS-VSC2 on the frequency characteristics of PCS-VSC1 is analyzed.

[0098] Please refer to Figures 7(a), 7(b), 7(c) and 7(d), which show the changes in PCS-VSC2 inertia and damping parameters, PCS-VSC1 frequency changes and active output waveforms under grid frequency disturbance;

[0099] Figure 7(a) and Figure 7(b) show that when the grid frequency fluctuates at 2.5s, PCS-VSC1 performs frequency modulation, and the inertia of PCS-VSC2 increases, the overshoot of the output frequency of PCS-VSC1 decreases, and the overshoot of the output power also decreases, but the maximum RoCoF does not change significantly, and the frequency response stabilization time is prolonged.

[0100] Figure 7(c) and Figure 7(d) show that when the damping of PCS-VSC2 increases, the overshoot of the output frequency and output power of PCS-VSC1 decreases, the frequency response stabilization time shortens, and the maximum RoCoF does not change significantly.

[0101] S105, determining control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performing multi-machine parallel control.

[0102] First, the resonance characteristics of the energy storage VSC parallel system under different excitation sources can be observed through the Bode plot. As the number of parallel connections increases, the possibility of low-frequency resonance in the system increases. This information is crucial for determining control parameters to suppress resonance and improve system stability.

[0103] Secondly, the frequency response closed-loop transfer function can be used to analyze the impact of changes in control parameters (such as virtual inertia J and virtual damping D) on the frequency response characteristics of other energy storage VSCs. For example, when the inertia or damping parameters of a parallel energy storage VSC change, it will have a significant impact on the frequency response of other energy storage VSCs. By adjusting these control parameters, the frequency response characteristics of the system can be optimized, such as reducing frequency overshoot and shortening stabilization time.

[0104] Specifically, when determining the control parameters, factors such as system stability, frequency response speed and accuracy are comprehensively considered. The system performance under different control parameter combinations can be verified through simulation or experiments, and the optimal parameter combination can be selected for multi-machine parallel control.

[0105] Finally, when implementing multi-machine parallel control, it is necessary to ensure the coordinated operation of each energy storage VSC. This can be achieved through advanced control strategies and algorithms, such as distributed control, centralized control or hybrid control. These control strategies can be selected and optimized according to the actual situation and needs of the system.

[0106] The present application also provides a multi-machine parallel control device for energy storage converters, comprising:

[0107] A decomposition module decomposes the grid-connected system of energy storage converters in parallel into multiple equivalent circuits under separate excitation;

[0108] A transfer module, for establishing a transfer function between a response current and an excitation source when each of the equivalent circuits acts alone;

[0109] A mapping module is used to determine a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes;

[0110] A closed-loop module, determining a frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and an expression of power transmitted from the i-th energy storage converter to the common bus voltage;

[0111] The control module determines the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performs multi-machine parallel control.

[0112] The present application also provides a multi-machine parallel control device for energy storage converters, comprising:

[0113] Memory;

[0114] A processor is used to retrieve the computer executable program of the above-mentioned energy storage converter multi-machine parallel control method from the memory, and execute: decomposing the grid-connected system of the energy storage converters in parallel into multiple equivalent circuits under separate excitations; establishing the transfer function between the response current and the excitation source when each of the equivalent circuits acts alone; determining the Bode diagram of the transfer function between the response current and the excitation source as the number of parallel energy storage converters changes; determining the frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and the power expression transmitted by the i-th energy storage converter to the common bus voltage; determining the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performing multi-machine parallel control.

[0115] The present application also provides a storage medium, comprising: storing a computer executable program, wherein the computer executable program is used to be called by a processor to execute the steps of the above-mentioned energy storage converter multi-machine parallel control method.

Claims

1. A method for controlling multiple energy storage converters in parallel, characterized in that: include: Decompose the grid-connected system with energy storage converters in parallel into multiple equivalent circuits under separate excitation; Establishing the transfer function between the response current and the excitation source when each of the equivalent circuits acts alone; Determine a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes; Determine the frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and the power expression transmitted from the i-th energy storage converter to the common bus voltage; The control parameters of the energy storage converter are determined according to the Bode diagram and the frequency response closed-loop transfer function, and multi-machine parallel control is performed.

2. The energy storage converter multi-machine parallel control method according to claim 1, characterized in that: The grid-connected system with parallel energy storage converters is decomposed into multiple equivalent circuits under separate excitation, including: According to the voltage source form, the grid-connected system in which multiple energy storage converters are connected in parallel is equivalent to an equivalent circuit under the excitation of multiple independent voltage sources.

3. The energy storage converter multi-machine parallel control method according to claim 1, characterized in that: The transfer function between the response current and the excitation source includes transfer functions G1, G2, and G3 under the action of Us1 alone, Usk alone, and Ug alone.

4. The energy storage converter multi-machine parallel control method according to claim 3 is characterized in that: Determining a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes, comprising: According to the changes of transfer functions G1, G2, and G3 as the number of parallel energy storage converters increases, the Bode diagrams under different excitation sources are obtained.

5. The energy storage converter multi-machine parallel control method according to claim 1, characterized in that: In the step of determining the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, The control parameters are determined by analyzing the influence of the inertia and damping parameter changes of each energy storage converter in the grid-connected system in which energy storage converters are connected in parallel on the frequency response characteristics of other energy storage converters.

6. The energy storage converter multi-machine parallel control method according to claim 1, characterized in that: The control parameters include virtual inertia and virtual damping.

7. The energy storage converter multi-machine parallel control method according to claim 1, characterized in that: Also includes: Use MATLAB / Simulink software to build a simulation model of the energy storage converter.

8. A multi-machine parallel control device for energy storage converters, characterized in that: include: A decomposition module decomposes the grid-connected system of energy storage converters in parallel into multiple equivalent circuits under separate excitation; A transfer module, for establishing a transfer function between a response current and an excitation source when each of the equivalent circuits acts alone; A mapping module is used to determine a Bode diagram of the transfer function between the response current and the excitation source as the number of parallel-connected energy storage converters changes; A closed-loop module, determining a frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and an expression of power transmitted from the i-th energy storage converter to the common bus voltage; The control module determines the control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performs multi-machine parallel control.

9. A multi-machine parallel control device for energy storage converters, characterized in that: include: Memory; A processor, used to retrieve from the memory a computer executable program of the method for controlling multiple energy storage converters in parallel according to any one of claims 1 to 7, and execute: decomposing a grid-connected system in which energy storage converters are connected in parallel into a plurality of equivalent circuits under separate excitations; establishing a transfer function between a response current and an excitation source when each of the equivalent circuits acts alone; determining a Bode diagram of the transfer function between the response current and the excitation source as the number of energy storage converters connected in parallel changes; determining a frequency response closed-loop transfer function of the i-th energy storage converter according to the transfer function between the response current and the excitation source and an expression of the power transmitted from the i-th energy storage converter to the common bus voltage; determining control parameters of the energy storage converter according to the Bode diagram and the frequency response closed-loop transfer function, and performing multi-machine parallel control.

10. A storage medium, characterized in that: include: A computer executable program is stored, and the computer executable program is used to be called by a processor to execute the steps of the energy storage converter multi-machine parallel control method according to any one of claims 1 to 7.

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