Method for controlling bidirectional virtual synchronous machine of multi-interconnection converter of alternating current and direct current hybrid micro-grid

Abstract

The invention provides an AC / DC hybrid micro-grid multi-interconnection converter bidirectional virtual synchronous machine control method, which is used for controlling three ICs connected between a DC micro-grid and an AC micro-grid in a distributed manner, and comprises the following steps: for a first IC, adopting a virtual inertia DC voltage support control strategy, when a direct-current micro power source breaks down, continuous operation of a direct-current load is effectively supported, and inertia of a micro-grid is improved by simulating mechanical characteristics of a synchronous generator. For the second IC, an AC voltage support control strategy based on a VSG is adopted, so that an AC side load is supported when an AC power supply fails and an AC load is increased, and the inertia of the micro-grid is improved by simulating the mechanical characteristics of a synchronous generator; and for the third IC, a PQ control strategy based on the VSG is adopted, so that the direct current side supports the alternating current load when the alternating current load is increased, and the alternating current side supports the direct current load when the direct current load is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel power systems, and in particular relates to a bidirectional virtual synchronous machine control method for multiple interconnected converters in an AC / DC hybrid microgrid. Background Art

[0002] The interlinking converter (IC) connects the AC and DC microgrids and maintains the stability of the AC / DC hybrid microgrid system through power exchange. PQ control is also called constant power control, which uses the output power of the IC as the input of the closed-loop control system to control the active power and reactive power output of the IC to be constant.

[0003] The general PQ mode IC control strategy is mainly used when the microgrid works in the grid-connected mode. At this time, the export voltage of the microgrid and its parallel energy storage system can be supported by the distribution network, and the energy storage system mainly exchanges power with the distribution network. However, the traditional PQ mode IC control strategy has the problem of insufficient frequency or voltage support on one side when the load on one side suddenly increases. At the same time, the traditional PQ mode IC control strategy adopts a bidirectional droop control strategy to improve the primary response caused by interference, but due to the lack of inertial response, the droop control cannot improve the voltage and frequency stability of the hybrid microgrid system. Especially for independent microgrids, the low inertia characteristics make the system stability affected by the increased penetration of distributed generators and sudden load changes. In addition, the traditional single PQ mode IC control strategy can only handle the situation of sudden load changes on one side, and cannot adapt to more complex situations, such as AC micro-source failure or DC micro-source failure.

[0004] In order to solve the above problems, people have been seeking an ideal technical solution. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies in the prior art and thereby provide a method for controlling a bidirectional virtual synchronous machine of a multi-interconnected converter in an AC / DC hybrid microgrid. By improving the control strategy of a multi-IC bidirectional virtual synchronous machine (virtual synchronous generator, VSG) in an AC / DC hybrid microgrid, the system can cope with more complex situations and improve the stability of the AC / DC hybrid microgrid.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides a method for controlling a bidirectional virtual synchronous machine of a multi-interconnected converter in an AC / DC hybrid microgrid, the method being used to control three ICs distributedly connected between a DC microgrid and an AC microgrid, comprising:

[0008] For the first IC, a virtual inertia DC voltage support control strategy is adopted to effectively support the uninterrupted operation of DC loads when the DC micro-source fails, and to improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator;

[0009] For the second IC, an AC voltage support control strategy based on VSG is adopted to support the AC side load when the AC power fails or the AC load increases, and to improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; in order to ensure the stable operation of the second IC and the AC microgrid and improve the transient performance, a synchronous control strategy is also adopted to achieve equal voltages on both sides of the AC microgrid and this IC before grid connection;

[0010] For the third IC, a VSG-based PQ control strategy is adopted to enable the DC side to support the AC load when the AC load increases and vice versa, to achieve power mutual assistance.

[0011] Based on the above, the AC microgrid is:

[0012]

[0013] Among them, ω ac and Indicates the frequency of the AC microgrid subsystem and its rated value; V ac and Represents the AC voltage of the AC microgrid subsystem and its nominal value; P ac and Indicates the actual output active power and rated active power of the AC microgrid subsystem; Q ac and Represents the actual output reactive power and rated reactive power of the AC microgrid subsystem; m ac is the active power-frequency droop coefficient; n ac is the reactive power-voltage droop coefficient;

[0014] The DC microgrid is:

[0015]

[0016] Among them, V dc and Represents the DC microgrid subsystem voltage and its nominal value; P dc and Represents the actual output active power and rated active power of the DC microgrid subsystem; m dc is the voltage-power droop coefficient.

[0017] Based on the above, the control method of the first IC is:

[0018] 3-1) Use virtual inertial control to improve inertial support and enhance system stability:

[0019]

[0020] Among them, C v The capacitance value that provides virtual inertia for the DC side, V dc,ref are the DC bus voltage reference values ​​obtained by solving the virtual inertia equation (1), V dc,nom Indicates the nominal value of the DC bus voltage, D v represents the damping coefficient, R v represents the droop coefficient of the virtual inertia ring, i set Indicates the current reference value at the connection point between the first IC and the DC bus, i o Indicates the current output by the IC to the DC bus;

[0021] 3-2) The outer loop control adopts PI control, setting i q,ref =0, the reference current values ​​of d-axis and q-axis are as follows:

[0022]

[0023] in, and They represent the proportional and integral coefficients of the outer loop control of the DC voltage support controller, Indicates the actual value of the DC bus voltage;

[0024] 3-3) The current inner loop control adopts PI control, and the d-axis and q-axis reference voltage values ​​of the first IC are as follows:

[0025]

[0026] Among them, v od and v oq are the d-axis and q-axis components of the filtered voltage value, and The d-axis and q-axis components of the current before the DC voltage support control filter are and They respectively represent the proportional and integral coefficients of the outer loop control in the DC voltage support control, and L1 represents the inductance value of the DC voltage support control filter.

[0027] Based on the above, the control method of the second IC is:

[0028] 4-1) Calculate and measure the voltage amplitude and phase angle of the AC microgrid and IC using the following formula:

[0029]

[0030] 4-2) Define the voltage amplitude, phase angle, and angular frequency errors as follows:

[0031]

[0032] 4-3) The AC microgrid and the second IC are connected to the grid through voltage synchronization, phase angle synchronization, and angular frequency synchronization. The voltage synchronization, phase angle synchronization, and angular frequency synchronization are defined as follows:

[0033]

[0034] Among them, k pv1 and k iv1 is the parameter of the voltage synchronization term PI controller, k pθ and k iθ is the phase angle synchronization term PI controller parameter, k pω and k iω is the parameter of the PI controller of the angular frequency synchronization term;

[0035] 4-4) The power loop adopts the VSG control strategy. The relationship between the active power and angular frequency and the reactive power and voltage of the second IC is as follows:

[0036]

[0037] Among them, ω and ω0 are the actual angular frequency and the nominal angular frequency, J is the moment of inertia, D is the damping factor, m ω is the proportional adjustment factor of the frequency modulation, P2 and P ref are the actual active power and active power reference value, m q is the proportional adjustment factor of the voltage regulation, V and V0 are the actual voltage amplitude and the nominal voltage amplitude, Q2 and Q ref are actual reactive power and reactive power reference value respectively;

[0038] 4-5) The voltage loop adopts PI control, and the current reference values ​​of the d-axis and q-axis are as follows:

[0039]

[0040] Among them, i gd and i gq are the d-axis and q-axis components of the filtered current, C2 is the capacitor of the LCL filter, and v gd and v gq are the d-axis and q-axis components of the filtered voltage, k pv2 and k iv2 are the proportional and integral coefficients of the voltage loop PI controller.

[0041] 4-6) The current loop adopts PI control, and the voltage reference values ​​of the d-axis and q-axis are as follows:

[0042]

[0043] Among them, i d and i q are the d-axis and q-axis components of the current before filtering, L is the capacitance of the LCL filter, k pi and k ii are the proportional and integral coefficients of the current loop PI controller.

[0044] Based on the above, the control method of the third IC is:

[0045] 5-1) Use VSG control strategy to obtain the preliminary reference value of outer loop power:

[0046]

[0047]

[0048] in, and f pu is the actual value of the normalized voltage and frequency, V and f are the actual values ​​of the measured voltage and frequency, and f max and f min is the maximum frequency and minimum frequency of the AC microgrid, V max and V min is the maximum voltage and minimum voltage of the DC microgrid, m IC is the droop control coefficient of the third IC, C0 is the DC voltage differential coefficient, and J1 is the AC frequency differential coefficient;

[0049] 5-2) The power outer loop adopts PI control, and the d-axis and q-axis reference current values ​​of the third IC are as follows:

[0050]

[0051] Among them, the reference value of the outer loop active power P ref =ΔP IC +P1, P1 is the power adjustment command issued by the upper controller, the reactive power reference value Q ref =0, P3 and Q3 are the active power and reactive power transmitted by the PQ mode interconnected converter, and are the proportional coefficient and integral coefficient of the PI controller of the active power of the power outer loop, and are the proportional coefficient and integral coefficient of the PI controller of the reactive power of the power outer loop;

[0052] 5-3) The current inner loop adopts PI control, and the voltage reference values ​​of the d-axis and q-axis are as follows:

[0053]

[0054] Among them, i d and i q are the d-axis and q-axis components of the current before filtering, L is the capacitance of the LCL filter, k pi and k ii are the proportional and integral coefficients of the current loop PI controller.

[0055] In a second aspect, the present invention provides a bidirectional virtual synchronous machine control system for a multi-interconnected converter of an AC / DC hybrid microgrid, comprising: controlling three ICs connected in a distributed manner between a DC microgrid and an AC microgrid, and:

[0056] a first controller, for controlling the first IC, configured to: adopt a virtual inertia DC voltage support control strategy to effectively support uninterrupted operation of the DC load when a DC micro power source fails, and improve the inertia of the microgrid by simulating the mechanical characteristics of a synchronous generator;

[0057] The second controller is used to control the second IC and is configured to: adopt an AC voltage support control strategy based on VSG to support the AC side load when the AC power fails and the AC load increases, and improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; in order to ensure the stable operation of the second IC and the AC microgrid and improve the transient performance, a synchronous control strategy is also adopted to achieve equal voltages on both sides of the AC microgrid and the IC before grid connection;

[0058] The third controller is used to control the third IC and is configured to: adopt a PQ control strategy based on VSG, so that the DC side supports the AC load when the AC load increases, and the AC side supports the DC load when the DC load increases, so as to achieve power mutual assistance.

[0059] In a third aspect, the present invention provides an electronic device, comprising:

[0060] at least one processor, and a memory coupled to the at least one processor;

[0061] The memory stores a computer program, and the computer program can be executed by the at least one processor to implement the bidirectional virtual synchronous machine control method of multi-interconnected converters in an AC / DC hybrid microgrid as described.

[0062] In a fourth aspect, the present invention provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed, it can implement the bidirectional virtual synchronous machine control method of multi-interconnected converters in an AC / DC hybrid microgrid as described.

[0063] In a fifth aspect, the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the bidirectional virtual synchronous machine control method for multi-interconnected converters in an AC / DC hybrid microgrid as described.

[0064] The present invention has the following beneficial effects and advantages:

[0065] 1. The three ICs improve the inertia of the system, reduce the frequency or voltage offset, and improve the stability of the AC / DC hybrid microgrid by simulating the characteristics of synchronous generators.

[0066] 2. A synchronous control strategy is adopted for the second IC to achieve equal voltages on both sides of the AC microgrid and the IC before grid connection, ensuring stable operation of the second IC after being connected in parallel with the AC microgrid and improving transient performance.

[0067] 3. Compared with the traditional three-parallel PQ mode IC control strategy, regardless of whether secondary control is considered, the method of the present invention can reduce the frequency or voltage offset of one side when the load on that side increases, thereby enhancing the stability of system operation.

[0068] 4. The designed virtual inertia DC voltage support control strategy and VSG-based AC voltage support control strategy are able to adapt to more complex situations, such as AC micro-source failure or DC micro-source failure, compared to the traditional single PQ mode control which can only handle the situation where the load on one side suddenly changes. This improves the stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is the control method structure diagram of the first IC.

[0070] Figure 2 This is the control method block diagram of the second IC.

[0071] Figure 3 This is a control method block diagram of the third IC.

[0072] Figure 4 A schematic diagram of an electronic device provided in Example 3 of the present application.

[0073] Figure 5 A schematic diagram of a computer-readable storage medium provided for Example 3 of the present application. DETAILED DESCRIPTION

[0074] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0075] Example 1

[0076] like Figure 1-Figure 3As shown, the present invention provides a method for controlling a bidirectional virtual synchronous machine of a multi-interconnected converter in an AC / DC hybrid microgrid, the method being used to control three ICs distributedly connected between a DC microgrid and an AC microgrid, comprising:

[0077] For the first IC, a virtual inertia DC voltage support control strategy is adopted to effectively support the uninterrupted operation of DC loads when the DC micro-source fails, and to improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator;

[0078] For the second IC, an AC voltage support control strategy based on VSG is adopted to support the AC side load when the AC power fails or the AC load increases, and to improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; in order to ensure the stable operation of the second IC and the AC microgrid and improve the transient performance, a synchronous control strategy is also adopted to achieve equal voltages on both sides of the AC microgrid and this IC before grid connection;

[0079] For the third IC, a VSG-based PQ control strategy is adopted to enable the DC side to support the AC load when the AC load increases and vice versa, to achieve power mutual assistance.

[0080] The specific control method of bidirectional virtual synchronous machine of multi-interconnected converters in AC / DC hybrid microgrid is as follows:

[0081] The AC microgrid is:

[0082]

[0083] Among them, ω ac and Indicates the frequency of the AC microgrid subsystem and its rated value; V ac and Represents the AC voltage of the AC microgrid subsystem and its nominal value; P ac and Indicates the actual output active power and rated active power of the AC microgrid subsystem; Q ac and Represents the actual output reactive power and rated reactive power of the AC microgrid subsystem; m ac is the active power-frequency droop coefficient; n ac is the reactive power-voltage droop coefficient;

[0084] The DC microgrid is:

[0085]

[0086] Among them, V dc and Represents the DC microgrid subsystem voltage and its nominal value; Pdc and Represents the actual output active power and rated active power of the DC microgrid subsystem; m dc is the voltage-power droop coefficient.

[0087] The control method of the first IC is:

[0088] 3-1) Use virtual inertial control to improve inertial support and enhance system stability:

[0089]

[0090] Among them, C v The capacitance value that provides virtual inertia for the DC side, V dc,ref are the DC bus voltage reference values ​​obtained by solving the virtual inertia equation (1), V dc,nom Indicates the nominal value of the DC bus voltage, D v represents the damping coefficient, R v represents the droop coefficient of the virtual inertia ring, i set Indicates the current reference value at the connection point between the first IC and the DC bus, i o Indicates the current output by the IC to the DC bus;

[0091] 3-2) The outer loop control adopts PI control, setting i q,ref =0, the reference current values ​​of d-axis and q-axis are as follows:

[0092]

[0093] in, and They represent the proportional and integral coefficients of the outer loop control of the DC voltage support controller, Indicates the actual value of the DC bus voltage;

[0094] 3-3) The current inner loop control adopts PI control, and the d-axis and q-axis reference voltage values ​​of the first IC are as follows:

[0095]

[0096] Among them, v od and v oq are the d-axis and q-axis components of the filtered voltage value, and The d-axis and q-axis components of the current before the DC voltage support control filter are and They respectively represent the proportional and integral coefficients of the outer loop control in the DC voltage support control, and L1 represents the inductance value of the DC voltage support control filter.

[0097] The control method of the second IC is:

[0098] 4-1) Calculate and measure the voltage amplitude and phase angle of the AC microgrid and IC using the following formula:

[0099]

[0100] 4-2) Define the voltage amplitude, phase angle, and angular frequency errors as follows:

[0101]

[0102] 4-3) The AC microgrid and the second IC are connected to the grid through voltage synchronization, phase angle synchronization, and angular frequency synchronization. The voltage synchronization, phase angle synchronization, and angular frequency synchronization are defined as follows:

[0103]

[0104] Among them, k pv1 and k iv1 is the parameter of the voltage synchronization term PI controller, k pθ and k iθ is the phase angle synchronization term PI controller parameter, k pω and k iω is the parameter of the PI controller of the angular frequency synchronization term;

[0105] 4-4) The power loop adopts the VSG control strategy. The relationship between the active power and angular frequency and the reactive power and voltage of the second IC is as follows:

[0106]

[0107] Among them, ω and ω0 are the actual angular frequency and the nominal angular frequency, J is the moment of inertia, D is the damping factor, m ω is the proportional adjustment factor of the frequency modulation, P2 and P ref are the actual active power and active power reference value, m q is the proportional adjustment factor of the voltage regulation, V and V0 are the actual voltage amplitude and the nominal voltage amplitude, Q2 and Q ref are actual reactive power and reactive power reference value respectively;

[0108] 4-5) The voltage loop adopts PI control, and the current reference values ​​of the d-axis and q-axis are as follows:

[0109]

[0110] Among them, i gd and i gq are the d-axis and q-axis components of the filtered current, C2 is the capacitor of the LCL filter, and v gd and vgq are the d-axis and q-axis components of the filtered voltage, k pv2 and k iv2 are the proportional and integral coefficients of the voltage loop PI controller.

[0111] 4-6) The current loop adopts PI control, and the voltage reference values ​​of the d-axis and q-axis are as follows:

[0112]

[0113] Among them, i d and i q are the d-axis and q-axis components of the current before filtering, L is the capacitance of the LCL filter, k pi and k ii are the proportional and integral coefficients of the current loop PI controller.

[0114] The control method of the third IC is:

[0115] 5-1) Use VSG control strategy to obtain the preliminary reference value of outer loop power:

[0116]

[0117] in, and f pu is the actual value of the normalized voltage and frequency, V and f are the actual values ​​of the measured voltage and frequency, and f max and f min is the maximum frequency and minimum frequency of the AC microgrid, V max and V min is the maximum voltage and minimum voltage of the DC microgrid, m IC is the droop control coefficient of the third IC, C0 is the DC voltage differential coefficient, and J1 is the AC frequency differential coefficient;

[0118] 5-2) The power outer loop adopts PI control, and the d-axis and q-axis reference current values ​​of the third IC are as follows:

[0119]

[0120] Among them, the reference value of the outer loop active power P ref =ΔP IC +P1, P1 is the power adjustment command issued by the upper controller, the reactive power reference value Q ref =0, P3 and Q3 are the active power and reactive power transmitted by the PQ mode interconnected converter, and are the proportional coefficient and integral coefficient of the PI controller of the active power of the power outer loop, and are the proportional coefficient and integral coefficient of the PI controller of the reactive power of the power outer loop;

[0121] 5-3) The current inner loop adopts PI control, and the voltage reference values ​​of the d-axis and q-axis are as follows:

[0122]

[0123] Among them, i d and i q are the d-axis and q-axis components of the current before filtering, L is the capacitance of the LCL filter, k pi and k ii are the proportional and integral coefficients of the current loop PI controller.

[0124] Example 2

[0125] This embodiment provides a bidirectional virtual synchronous machine control system for multiple interconnected converters of an AC / DC hybrid microgrid, including: controlling three ICs distributedly connected between a DC microgrid and an AC microgrid, and:

[0126] a first controller, for controlling the first IC, configured to: adopt a virtual inertia DC voltage support control strategy to effectively support uninterrupted operation of the DC load when a DC micro power source fails, and improve the inertia of the microgrid by simulating the mechanical characteristics of a synchronous generator;

[0127] The second controller is used to control the second IC and is configured to: adopt an AC voltage support control strategy based on VSG to support the AC side load when the AC power fails and the AC load increases, and improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; in order to ensure the stable operation of the second IC and the AC microgrid and improve the transient performance, a synchronous control strategy is also adopted to achieve equal voltages on both sides of the AC microgrid and the IC before grid connection;

[0128] The third controller is used to control the third IC and is configured to: adopt a PQ control strategy based on VSG, so that the DC side supports the AC load when the AC load increases, and the AC side supports the DC load when the DC load increases, so as to achieve power mutual assistance.

[0129] It should be noted that the system embodiment of this embodiment is similar to the method embodiment of Embodiment 1, so the description is relatively simple, and the relevant parts can refer to the method of Embodiment 1.

[0130] Example 3

[0131] The present application also provides an electronic device, referring to Figure 4 , Figure 4 Schematic diagram of an electronic device proposed in an embodiment of the present application. Figure 4As shown, the electronic device includes: a memory and a processor, the memory and the processor are connected via a bus communication, the memory stores a computer program, and the computer program can be run on the processor, thereby implementing the steps in the AC / DC hybrid microgrid multi-interconnected converter bidirectional virtual synchronous machine control method disclosed in Example 1 of the present application.

[0132] The present application also provides a computer-readable storage medium. Figure 5 , Figure 5 Schematic diagram of a computer-readable storage medium proposed in an embodiment of the present application. Figure 5 As shown, a computer program / instruction is stored on a computer-readable storage medium, and when the computer program / instruction is executed by a processor, the steps in the method for controlling a bidirectional virtual synchronous machine of a multi-interconnected converter of an AC / DC hybrid microgrid as disclosed in Example 1 of the present application are implemented.

[0133] An embodiment of the present application also provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps in the method for controlling bidirectional virtual synchronous machines of multi-interconnected converters in an AC / DC hybrid microgrid as disclosed in Example 1 of the present application.

[0134] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0135] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, devices or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0136] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, systems, devices, storage media, and program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1A device that provides the functions specified in a block or multiple blocks.

[0137] The methods, systems, devices, media and products provided by the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the methods and core ideas of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for controlling bidirectional virtual synchronous machines of multiple interconnected converters in an AC / DC hybrid microgrid, characterized in that: The method is used to control three ICs distributedly connected between a DC microgrid and an AC microgrid, including: For the first IC, a virtual inertia DC voltage support control strategy is adopted to effectively support the uninterrupted operation of DC loads when the DC micro-source fails, and to improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; For the second IC, an AC voltage support control strategy based on VSG is adopted to support the AC side load when the AC power fails or the AC load increases, and to improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; in order to ensure the stable operation of the second IC and the AC microgrid and improve the transient performance, a synchronous control strategy is also adopted to achieve equal voltages on both sides of the AC microgrid and this IC before grid connection; For the third IC, a VSG-based PQ control strategy is adopted to enable the DC side to support the AC load when the AC load increases and vice versa, to achieve power mutual assistance.

2. The method for controlling bidirectional virtual synchronous machines of multiple interconnected converters in an AC / DC hybrid microgrid according to claim 1, characterized in that: The AC microgrid is: Among them, ω ac and Indicates the frequency of the AC microgrid subsystem and its rated value; V ac and Represents the AC voltage of the AC microgrid subsystem and its nominal value; P ac and Indicates the actual output active power and rated active power of the AC microgrid subsystem; Q ac and Represents the actual output reactive power and rated reactive power of the AC microgrid subsystem; m ac is the active power-frequency droop coefficient; n ac is the reactive power-voltage droop coefficient; The DC microgrid is: Among them, V dc and Represents the DC microgrid subsystem voltage and its nominal value; P dc and Represents the actual output active power and rated active power of the DC microgrid subsystem; m dc is the voltage-power droop coefficient.

3. The method for controlling bidirectional virtual synchronous machines of multiple interconnected converters in an AC / DC hybrid microgrid according to claim 2, characterized in that: The control method of the first IC is: 3-1) Use virtual inertial control to improve inertial support and enhance system stability: Among them, C v The capacitance value that provides virtual inertia for the DC side, V dc,ref are the DC bus voltage reference values ​​obtained by solving the virtual inertia equation (1), V dc,nom Indicates the nominal value of the DC bus voltage, D v represents the damping coefficient, R v represents the droop coefficient of the virtual inertia ring, i set Indicates the current reference value at the connection point between the first IC and the DC bus, i o Indicates the current output by the IC to the DC bus; 3-2) The outer loop control adopts PI control, setting i q,ref =0, the reference current values ​​of d-axis and q-axis are as follows: in, and They represent the proportional and integral coefficients of the outer loop control of the DC voltage support controller, Indicates the actual value of the DC bus voltage; 3-3) The current inner loop control adopts PI control, and the d-axis and q-axis reference voltage values ​​of the first IC are as follows: Among them, v od and v oq are the d-axis and q-axis components of the filtered voltage value, and The d-axis and q-axis components of the current before the DC voltage support control filter are and They respectively represent the proportional and integral coefficients of the outer loop control in the DC voltage support control, and L1 represents the inductance value of the DC voltage support control filter.

4. The method for controlling bidirectional virtual synchronous machines of multiple interconnected converters of an AC / DC hybrid microgrid according to claim 2 is characterized in that: The control method of the second IC is: 4-1) Calculate and measure the voltage amplitude and phase angle of the AC microgrid and IC using the following formula: 4-2) Define the voltage amplitude, phase angle, and angular frequency errors as follows: 4-3) The AC microgrid and the second IC are connected to the grid through voltage synchronization, phase angle synchronization, and angular frequency synchronization. The voltage synchronization, phase angle synchronization, and angular frequency synchronization are defined as follows: Among them, k pv1 and k iv1 is the parameter of the voltage synchronization term PI controller, k pθ and k iθ is the phase angle synchronization term PI controller parameter, k pω and k iω is the parameter of the PI controller of the angular frequency synchronization term; 4-4) The power loop adopts the VSG control strategy. The relationship between the active power and angular frequency and the reactive power and voltage of the second IC is as follows: Among them, ω and ω0 are the actual angular frequency and the nominal angular frequency, J is the moment of inertia, D is the damping factor, m ω is the proportional adjustment factor of the frequency modulation, P2 and P ref are the actual active power and active power reference value, m q is the proportional adjustment factor of the voltage regulation, V and V0 are the actual voltage amplitude and the nominal voltage amplitude, Q2 and Q ref are actual reactive power and reactive power reference value respectively; 4-5) The voltage loop adopts PI control, and the current reference values ​​of the d-axis and q-axis are as follows: Among them, i gd and i gq are the d-axis and q-axis components of the filtered current, C2 is the capacitor of the LCL filter, and v gd and v gq are the d-axis and q-axis components of the filtered voltage, k pv2 and k iv2 are the proportional and integral coefficients of the voltage loop PI controller. 4-6) The current loop adopts PI control, and the voltage reference values ​​of the d-axis and q-axis are as follows: Among them, i d and i q are the d-axis and q-axis components of the current before filtering, L is the capacitance of the LCL filter, k pi and k ii are the proportional and integral coefficients of the current loop PI controller.

5. The method for controlling bidirectional virtual synchronous machines of multiple interconnected converters in an AC / DC hybrid microgrid according to claim 2, characterized in that: The control method of the third IC is: 5-1) Use VSG control strategy to obtain the preliminary reference value of outer loop power: in, and f pu is the actual value of the normalized voltage and frequency, V and f are the actual values ​​of the measured voltage and frequency, and f max and f min is the maximum frequency and minimum frequency of the AC microgrid, V max and V min is the maximum voltage and minimum voltage of the DC microgrid, m IC is the droop control coefficient of the third IC, C0 is the DC voltage differential coefficient, and J1 is the AC frequency differential coefficient; 5-2) The power outer loop adopts PI control, and the d-axis and q-axis reference current values ​​of the third IC are as follows: Among them, the reference value of the outer loop active power P ref =ΔP IC +P1, P1 is the power adjustment command issued by the upper controller, the reactive power reference value Q ref =0, P3 and Q3 are the active power and reactive power transmitted by the PQ mode interconnected converter, and are the proportional coefficient and integral coefficient of the PI controller of the active power of the power outer loop, and are the proportional coefficient and integral coefficient of the PI controller of the reactive power of the power outer loop; 5-3) The current inner loop adopts PI control, and the voltage reference values ​​of the d-axis and q-axis are as follows: Among them, i d and i q are the d-axis and q-axis components of the current before filtering, L is the capacitance of the LCL filter, k pi and k ii are the proportional and integral coefficients of the current loop PI controller.

6. A bidirectional virtual synchronous machine control system for multiple interconnected converters in an AC / DC hybrid microgrid, characterized in that: include: Control three ICs distributedly connected between the DC microgrid and the AC microgrid, and: A first controller, for controlling the first IC, is configured to: adopt a virtual inertia DC voltage support control strategy to effectively support uninterrupted operation of the DC load when a DC micro power source fails, and improve the inertia of the microgrid by simulating the mechanical characteristics of a synchronous generator; The second controller is used to control the second IC and is configured to: adopt an AC voltage support control strategy based on VSG to support the AC side load when the AC power fails and the AC load increases, and improve the inertia of the microgrid by simulating the mechanical characteristics of the synchronous generator; in order to ensure the stable operation of the second IC and the AC microgrid and improve the transient performance, a synchronous control strategy is also adopted to achieve equal voltages on both sides of the AC microgrid and the IC before grid connection; The third controller is used to control the third IC and is configured to: adopt a PQ control strategy based on VSG, so that the DC side supports the AC load when the AC load increases, and the AC side supports the DC load when the DC load increases, so as to achieve power mutual assistance.

7. An electronic device, characterized in that: include: at least one processor, and a memory coupled to the at least one processor; The memory stores a computer program, and the computer program can be executed by the at least one processor to implement the bidirectional virtual synchronous machine control method for multi-interconnected converters of an AC / DC hybrid microgrid as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed, it can implement the method for controlling bidirectional virtual synchronous machines of multi-interconnected converters in an AC / DC hybrid microgrid as described in any one of claims 1 to 5.

9. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, the method for controlling a bidirectional virtual synchronous machine of a multi-interconnected converter in an AC / DC hybrid microgrid is implemented as claimed in any one of claims 1 to 5.

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