Micro-grid fault recovery control method and system based on hierarchical control

Abstract

The invention provides a micro-grid fault recovery control method and system based on hierarchical control, and the method comprises the steps: building a virtual leader-following consistency control model based on a hierarchical control architecture of a micro-grid system; determining a control mode of each level based on the virtual leader-following consistency control model; wherein in the primary control link, droop control is adopted to control the frequency and voltage of the micro-grid; in the secondary control link, voltage secondary control is adopted to adjust the voltage of the micro-grid to a given reference value, and angular frequency secondary control is adopted to adjust the frequency of the micro-grid to a given reference value; and starting a secondary control link by using a set event triggering mechanism, adjusting the output voltage and frequency of the micro-grid to keep constant, and recovering the fault of the micro-grid. According to the invention, the stability of the system can be improved, the control strategy is optimized, the adaptive capacity of the system to a dynamic environment is improved, and finally efficient network and physical layer cooperative control is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrid fault recovery, and in particular to a microgrid fault recovery control method and system based on hierarchical control, as well as a corresponding computer terminal and a computer-readable storage medium. Background Art

[0002] In recent years, with the rapid development of the world economy and the significant improvement of people's living standards, the global demand for energy has risen sharply. This trend has put tremendous pressure on traditional energy supply methods, and there is an urgent need to seek new solutions. In this context, the introduction of distributed energy resources (DER) provides an effective way to solve the problems related to energy supply. DER can not only reduce the loss in the process of energy transmission and improve energy utilization efficiency, but also enhance the flexibility and reliability of the energy system. Therefore, it is regarded as an important supplement and effective support for future large-scale power grids. However, since distributed power sources are restricted by natural environmental conditions, such as the intermittent nature and instability of solar and wind energy, DER still has some defects in practical applications. These defects may affect the stability and reliability of the power grid. Therefore, DER needs to be effectively managed and controlled. To this end, the concept of microgrid came into being, aiming to integrate DER into the main power grid while weakening its negative impact on the power grid. At present, in microgrid systems, droop control is generally used to achieve plug-and-play of DER. However, under steady-state conditions, the system frequency and voltage often deviate from the reference value, and the ability to distribute reactive power is insufficient. This deviation not only affects the power quality, but may also lead to instability in the power system. Therefore, it is usually necessary to improve the droop control or introduce secondary control to form a hierarchical control structure to correct the frequency and voltage. In this way, the operating performance of the microgrid can be effectively improved, so that it can work better with the main grid and ensure the stability and efficiency of the power system.

[0003] At present, traditional secondary control adopts a centralized control structure based on a central controller, which requires collecting all the information of each DER and then sending control instructions to each DER. The communication network is complex and the communication volume is huge, which reduces the stability of the system. In recent years, distributed coordinated control strategies have been widely used in secondary control of microgrids. In distributed coordinated control, the controller of each DER only communicates with adjacent DERs, and does not require a central controller, which improves the robustness of the system, but does not consider the voltage recovery control problem, which in turn affects the quality of the voltage and frequency output by each DER, becoming a problem to be solved in this field. At present, no description or report of similar technology to the present invention has been found, and similar information at home and abroad has not yet been collected. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a microgrid fault recovery control method and system based on hierarchical control, and also relates to a corresponding computer terminal and a computer-readable storage medium.

[0005] According to one aspect of the present invention, a microgrid fault recovery control method based on hierarchical control is provided, comprising:

[0006] Based on the hierarchical control architecture of the microgrid system, a virtual leader-follower consistency control model is established;

[0007] Based on the virtual leader-follower consistency control model, the control mode of each level is determined; wherein: in the primary control link, the frequency and voltage of the microgrid are controlled by droop control; in the secondary control link, the voltage of the microgrid is adjusted to a given reference value by voltage secondary control, and the frequency of the microgrid is adjusted to a given reference value by angular frequency secondary control;

[0008] Using the set event trigger mechanism, the secondary control link is started to adjust the microgrid output voltage and frequency to remain constant and recover from microgrid faults.

[0009] Preferably, the hierarchical control architecture based on the microgrid system is used to establish a virtual leader-follower consistency control model, including:

[0010] Providing a hierarchical control architecture for microgrid restoration control;

[0011] Assume that the ith distributed power source has N adjacent power sources for communication, the communication connection graph between the ith distributed power source and the N adjacent power sources includes at least one directed spanning tree, and the virtual leader is set as a globally reachable point;

[0012] In the microgrid system, the voltage and frequency droop controllers of the i-th distributed generation are designed as follows:

[0013]

[0014] In the formula, ω i and U i are the output frequency and voltage of the distributed unit respectively; ω ref and U ref are the frequency reference value and the voltage reference value respectively; m i and n i is the droop coefficient, P i and Q i are the active power and reactive power of the distributed unit respectively;

[0015] According to the above droop controller design, the virtual leader-follower consistency control design corresponding to the i-th distributed generation is:

[0016]

[0017] In the formula, u i is the virtual leader-follower consistency control function, N i is the set of adjacent power sources of the i-th distributed power source; k xi1 and k xi2 is the undetermined gain factor; x i and x j represents the voltage or frequency of the i-th distributed power source and the j-th distributed power source; a ij is the connection relationship between the i-th distributed power source and the j-th distributed power source, b i is the connection relationship between the virtual leader and the follower. If there is a connection, then b i >0, otherwise b i =0;

[0018] The virtual leader-follower consensus protocol of the i-th distributed power source is:

[0019]

[0020] In the formula, α i , α j and α L are the failure coefficients of the i-th distributed generation, the j-th distributed generation and the virtual leader respectively; x L is the state quantity of the virtual leader;

[0021] Under the effect of formula (3), when k xi1 and k xi2 When certain conditions are met, the status of the follower and the virtual leader can always follow each other;

[0022] Assume that the state equation of the microgrid system is a first-order equation.

[0023]

[0024] in,

[0025]

[0026] Perform Laplace transform on equation (4):

[0027]

[0028] In the formula, u 1 is the first distributed power state quantity, u 2is the state quantity of the second distributed power source; X(s) is the state quantity after Laplace transformation; x 1 (t)| t＝0 and x 2 (t)| t＝0 are the initial values ​​of the output state quantities of the first distributed power source and the second distributed power source droop controller, respectively. The deviation between the output state quantity and the state quantity corresponding to the virtual leader is:

[0029]

[0030] At the same time, there are:

[0031]

[0032] When the gain coefficient meets the following conditions, the microgrid system can meet the consistency requirements:

[0033]

[0034] In the formula, c 1 =∫x 1 (t)dt| t＝0 , c 2 =∫x 2 (t)dt| t＝0 .

[0035] Preferably, the hierarchical control architecture for providing a microgrid restoration control comprises:

[0036] It is assumed that a number of distributed power sources are arranged in a microgrid, and hierarchical control is adopted for voltage stability control to construct a hierarchical control architecture; wherein: the hierarchical control architecture includes an information layer and a physical layer, the information layer includes: an event triggering link and a communication network, and the physical layer includes a primary control link, a secondary control link, a power calculation link, a voltage synthesis link, a voltage and current dual closed-loop link and a PWM signal generator.

[0037] Preferably, the voltage secondary control includes:

[0038] The voltage control strategy for droop control is written as:

[0039]

[0040] Where U di is the d-axis component of the voltage dq of the i-th distributed generation, U ref is the voltage reference value, n i is the droop coefficient, Q i is the reactive power output by the i-th distributed generation, U qi is the q-axis component of the voltage dq of the i-th distributed generation;

[0041] The goal of voltage secondary control is to make U di tends to the voltage reference value U ref , that is, to synchronize the voltage of each distributed power source to a given reference value when the control input is bounded;

[0042] Differentiate equation (11) and take the auxiliary variable as have:

[0043]

[0044] The voltage synchronization problem of multiple distributed generation integrated microgrids is converted into a synchronization tracking problem of a first-order linear multi-agent system. Combined with the consistency strategy, the voltage consistency protocol is designed as follows:

[0045]

[0046] In the formula, k Ui1 is the voltage synchronization gain of the distributed generation, k Ui2 is the voltage synchronization gain of the virtual leader, α i , α j and α L are the failure coefficients of the i-th distributed generation, the j-th distributed generation and the virtual leader, respectively, and b i is the connection relationship between the virtual leader and the follower, a ij is the connection relationship between the i-th distributed power source and the j-th distributed power source, U i (t),U j (t) are the output voltage amplitudes of the droop controllers of the i-th and j-th distributed generation in the microgrid system; U L (t) is the voltage of the virtual pilot and is related to U ref equal; under this consistency protocol, according to formula (13), it can be obtained that the output voltage amplitudes of each distributed power droop controller tend to be consistent; the voltage controller is recorded as At this time, the feedback amount to the voltage is:

[0047]

[0048] In the formula, δ is, U i is the output voltage of the distributed power supply, n is, for;

[0049] The voltage feedback is used to adjust the voltage in the microgrid system to a given reference value, so that the voltage and frequency of the microgrid system are kept synchronous and normal operation is restored.

[0050] Preferably, the angular frequency secondary control includes:

[0051] The frequency control strategy for droop control is:

[0052] ω i =ω ref -m i P i (15)

[0053] In the formula, ω i is the output frequency of the distributed power supply, ω ref Frequency reference value, m i is the droop coefficient, P i is the active power output by the i-th distributed power source;

[0054] The goal of the angular frequency secondary control is to make ω i Tends to ω ref ; Differentiate formula (15) and set an auxiliary variable to Establish the following formula:

[0055]

[0056] In the formula, u ωi is the angular frequency control function;

[0057] Combined with the consistency strategy, the angular frequency consistency protocol is designed as follows:

[0058]

[0059] In the formula, a ij is the element of the adjacency matrix; j = 1, 2, 3, ..., N, ω L (t) is the angular frequency of the virtual leader. If the virtual leader is connected to the i-th distributed power source, there is b i > 0, otherwise b i =0; k ωi1 and k ωi1 is the gain; the angular frequency controller is recorded as At this time, the angular frequency feedback amount is:

[0060]

[0061] In the formula, δ is, U i is the output voltage of the distributed power supply, m is, for;

[0062] The angular frequency feedback is used to adjust the angular frequency in the microgrid system to a given reference value, so that the voltage and frequency of the microgrid system are kept synchronous and normal operation is restored.

[0063] According to another aspect of the present invention, a microgrid fault recovery control system based on hierarchical control is provided, comprising:

[0064] A consistency mechanism building module, which builds a virtual leader-follower consistency control model based on the hierarchical control architecture of the microgrid system;

[0065] A control mode determination module, which determines the control mode of each level based on the virtual leader-follower consistency control model; wherein: in the primary control link, droop control is used to control the frequency and voltage of the microgrid; in the secondary control link, voltage secondary control is used to adjust the voltage of the microgrid to a given reference value, and angular frequency secondary control is used to adjust the frequency of the microgrid to a given reference value;

[0066] The microgrid fault recovery module uses the set event trigger mechanism to start the secondary control link, adjust the microgrid output voltage and frequency to keep constant, and recover from the microgrid fault.

[0067] According to a third aspect of the present invention, there is provided a computer terminal comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, can be used to execute any one of the methods described above in the present invention, or to run the system described above in the present invention.

[0068] According to a fourth aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can be used to execute any of the methods described above in the present invention, or to run the system described above in the present invention.

[0069] Due to the adoption of the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0070] The microgrid fault recovery control method and system based on hierarchical control provided by the present invention provide a secondary control strategy for voltage and frequency at the physical layer based on the event triggering mechanism of the information layer. The strategy can monitor the state changes of the power system in real time and respond quickly, thereby improving the stability of the system. It not only optimizes the control strategy, but also improves the system's adaptability to dynamic environments, and ultimately achieves efficient coordinated control of the network and physical layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0072] Figure 1 The present invention is a flowchart of a microgrid fault recovery control method based on hierarchical control in a preferred embodiment of the present invention.

[0073] Figure 2Schematic diagram of the topological structure of a consistency controller with a leader and two followers in a preferred embodiment of the present invention.

[0074] Figure 3 It is a schematic diagram of the component modules of a microgrid fault recovery control system based on hierarchical control in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0075] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0076] In view of the problem that the voltage recovery control is not considered in the prior art, which in turn affects the quality of the voltage and frequency output by each distributed power source (DER), an embodiment of the present invention provides a microgrid fault recovery control method based on hierarchical control. The method is based on an event trigger mechanism and adopts a secondary control strategy for voltage and frequency. It can monitor the state changes of the power system in real time and respond quickly, thereby improving the stability of the system. It not only optimizes the control strategy, but also improves the system's adaptability to dynamic environments, and ultimately achieves efficient network and physical layer collaborative control.

[0077] Specifically, Figure 1 As shown, the microgrid fault recovery control method based on hierarchical control provided in this embodiment may include the following operations:

[0078] S1, based on the hierarchical control architecture of the microgrid system, a virtual leader-follower consistency control model is established;

[0079] S2, based on the virtual leader-follower consistency control model, determines the control mode of each level; wherein: in the primary control link, droop control is used to control the frequency and voltage of the microgrid; in the secondary control link, voltage secondary control is used to adjust the voltage of the microgrid to a given reference value, and angular frequency secondary control is used to adjust the frequency of the microgrid to a given reference value;

[0080] S3, using the set event trigger mechanism, starts the secondary control link to adjust the microgrid output voltage and frequency to keep constant and recover from the microgrid fault.

[0081] In some preferred implementations, the above S1, based on the hierarchical control architecture of the microgrid system, establishes a virtual leader-follower consistency control model, and may further include the following operations:

[0082] S11, providing a hierarchical control architecture for microgrid restoration control;

[0083] S12, assuming that the i-th distributed power source has N adjacent power sources for communication, the communication connection graph between the i-th distributed power source and the N adjacent power sources contains at least one directed spanning tree, and the virtual leader is set as a globally reachable point;

[0084] S13, in the microgrid system, the voltage and frequency droop controller of the i-th distributed generation is designed as:

[0085]

[0086] In the formula, ω i and U i are the output frequency and voltage of the distributed unit respectively; ω ref and U ref are the frequency reference value and the voltage reference value respectively; m i and n i is the droop coefficient, P i and Q i are the active power and reactive power of the distributed unit respectively;

[0087] S14, according to the above droop controller design, the virtual leader-follower consistency control design corresponding to the i-th distributed power source is:

[0088]

[0089] In the formula, u i is the virtual leader-follower consistency control function, N i is the set of adjacent power sources of the i-th distributed power source; k xi1 and k xi2 is the undetermined gain factor; x i and x j represents the voltage or frequency of the i-th distributed power source and the j-th distributed power source; a ij is the connection relationship between the i-th distributed power source and the j-th distributed power source, b i is the connection relationship between the virtual leader and the follower. If there is a connection, then b i >0, otherwise b i =0;

[0090] S15, the virtual leader-follower consensus protocol of the i-th distributed power source is:

[0091]

[0092] In the formula, α i , α j and α Lare the failure coefficients of the i-th distributed generation, the j-th distributed generation and the virtual leader respectively; x L is the state quantity of the virtual leader;

[0093] Under the effect of formula (3), when k xi1 and k xi2 When certain conditions are met, the status of the follower and the virtual leader can always follow each other;

[0094] S16, assume that the state equation of the microgrid system is a first-order equation.

[0095]

[0096] in,

[0097]

[0098] Performing Laplace transform on equation (4), we have:

[0099]

[0100] In the formula, u 1 is the first distributed power state quantity, u 2 is the state quantity of the second distributed power source; X(s) is the state quantity after Laplace transformation; x 1 (t)| t＝0 and x 2 (t)| t＝0 are the initial values ​​of the output state quantities of the first distributed power source and the second distributed power source droop controller, respectively. The deviation between the output state quantity and the state quantity corresponding to the virtual leader is:

[0101]

[0102] At the same time, there are:

[0103]

[0104]

[0105] S17, when the gain coefficient meets the following conditions, the microgrid system can meet the consistency requirements:

[0106]

[0107] In the formula, c 1 =∫x 1 (t)dt| t＝0 , c 2 =∫x 2 (t)dt| t＝0 .

[0108] In some preferred implementations, the above S11 provides a hierarchical control architecture for microgrid restoration control, and may further include the following operations:

[0109] Assume that there are several distributed power sources in the microgrid, and hierarchical control is used for voltage stability control, and a hierarchical control architecture is constructed; wherein: the hierarchical control architecture includes an information layer and a physical layer, the information layer includes: event triggering link and communication network, the physical layer includes interconnected primary control link, secondary control link, power calculation link, voltage synthesis link, voltage and current double closed loop link and PWM signal generator, wherein the interconnection relationship between the various parts can adopt the existing technology, which will not be repeated here. Figure 2 As shown in Figure 1, the consistency controller topology of a leader and two followers in the information layer, the followers are composed of inverters and filters, connected to the virtual leader through actual lines. The solid lines represent physical connections, and the dotted lines represent information connections.

[0110] In some preferred embodiments, the above S2, voltage secondary control, includes:

[0111] The voltage control strategy for droop control is written as:

[0112]

[0113] Where U di is the d-axis component of the voltage dq of the i-th distributed generation, U ref is the voltage reference value, n i is the droop coefficient, Q i is the reactive power output by the i-th distributed generation, U qi is the q-axis component of the voltage dq of the i-th distributed generation;

[0114] The goal of voltage secondary control is to make U di tends to the voltage reference value U ref , that is, to synchronize the voltage of each distributed power source to a given reference value when the control input is bounded;

[0115] Differentiate equation (11) and take the auxiliary variable as have:

[0116]

[0117] The voltage synchronization problem of multiple distributed generation integrated microgrids is converted into a synchronization tracking problem of a first-order linear multi-agent system. Combined with the consistency strategy, the voltage consistency protocol is designed as follows:

[0118]

[0119] In the formula, k Ui1 is the voltage synchronization gain of the distributed generation, k Ui2 is the voltage synchronization gain of the virtual leader, α i , α j and α L are the failure coefficients of the i-th distributed generation, the j-th distributed generation and the virtual leader, respectively, and b i is the connection relationship between the virtual leader and the follower, a ij is the connection relationship between the i-th distributed power source and the j-th distributed power source, U i (t), U j (t) are the output voltage amplitudes of the droop controllers of the i-th and j-th distributed generation in the microgrid system; U L (t) is the voltage of the virtual pilot and is related to U ref equal; under this consistency protocol, according to formula (13), it can be obtained that the output voltage amplitudes of the droop controllers of each distributed power source tend to be consistent; the voltage controller (that is, the voltage control part in the droop controller, whose value is the output voltage of each DER after the consistency protocol) is recorded as At this time, the feedback amount to the voltage is:

[0120]

[0121] In the formula, δ is, U i is the output voltage of the distributed power supply, n is, for;

[0122] The voltage feedback is used to adjust the voltage in the microgrid system to a given reference value, so that the voltage and frequency of the microgrid system are kept synchronous and normal operation is restored.

[0123] In some preferred embodiments, the above S3, angular frequency secondary control, includes:

[0124] The frequency control strategy for droop control is:

[0125] ω i =ω ref -m i P i (15)

[0126] In the formula, ω i is the output frequency of the distributed power supply, ω ref Frequency reference value, m i is the droop coefficient, P i is the active power output by the i-th distributed power source;

[0127] The goal of the angular frequency secondary control is to make ω i Tends to ωref ; Differentiate formula (15) and set an auxiliary variable to Establish the following formula:

[0128]

[0129] In the formula, u ωi is the angular frequency control function;

[0130] Combined with the consistency strategy, the angular frequency consistency protocol is designed as follows:

[0131]

[0132] In the formula, a ij is the element of the adjacency matrix; j = 1, 2, 3, ..., N, ω L (t) is the angular frequency of the virtual leader. If the virtual leader is connected to the i-th distributed power source, there is b i > 0, otherwise b i =0; k ωi1 and k ωi1 is the gain; the angular frequency controller (i.e., the controller that adjusts the angular frequency of the microgrid system to a given reference value, whose value is obtained by setting the auxiliary variable, i.e., equation (16)) is recorded as At this time, the angular frequency feedback amount is:

[0133]

[0134] In the formula, δ is, U i is the output voltage of the distributed power supply, m is, for;

[0135] The angular frequency feedback amount is used to adjust the angular frequency in the microgrid system to a given reference value, so that the voltage and frequency of the microgrid system are kept synchronous and normal operation is restored.

[0136] Based on the same inventive concept, an embodiment of the present invention further provides a microgrid fault recovery control system based on hierarchical control.

[0137] Specifically, Figure 3 As shown, the embodiment provides a microgrid fault recovery control system based on hierarchical control, which may include the following modules:

[0138] A consistency mechanism building module, which builds a virtual leader-follower consistency control model based on the hierarchical control architecture of the microgrid system;

[0139] A control mode determination module, which determines the control mode of each level based on a virtual leader-follower consistency control model; wherein: in the primary control link, droop control is used to control the frequency and voltage of the microgrid; in the secondary control link, voltage secondary control is used to adjust the voltage of the microgrid to a given reference value, and angular frequency secondary control is used to adjust the frequency of the microgrid to a given reference value;

[0140] The microgrid fault recovery module uses the set event trigger mechanism to start the secondary control link, adjust the microgrid output voltage and frequency to keep constant, and recover from the microgrid fault.

[0141] It should be noted that the steps in the method provided by the present invention can be implemented by using the corresponding components in the system, and those skilled in the art can refer to the technical solution of the system to implement the step flow of the method, and can also refer to the technical solution of the method to implement the composition of the system, that is, the embodiments in the system and the embodiments in the method can be understood as preferred examples of each other, which will not be elaborated here.

[0142] An embodiment of the present invention further provides a computer terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the processor can be used to execute any method of the above-mentioned embodiments of the present invention, or to run any system of the above-mentioned embodiments of the present invention.

[0143] Optionally, the memory is used to store programs; the memory may include volatile memory (English: volatile lememory), such as random-access memory (English: random-access memory, abbreviated: RAM), such as static random-access memory (English: static random-access memory, abbreviated: SRAM), double data rate synchronous dynamic random access memory (English: Double Data Rate Synchronous Dynamic Random Access Memory, abbreviated: DDR SDRAM), etc.; the memory may also include non-volatile memory (English: non-volatile memory), such as flash memory (English: flash memory). The memory is used to store computer programs (such as applications, functional modules, etc. that implement the above method), computer instructions, etc., and the above computer programs, computer instructions, etc. can be partitioned and stored in one or more memories. And the above computer programs, computer instructions, data, etc. can be called by the processor.

[0144] The above-mentioned computer programs, computer instructions, etc. may be stored in one or more memories in partitions, and the above-mentioned computer programs, computer instructions, data, etc. may be called by a processor.

[0145] The processor is used to execute the computer program stored in the memory to implement the various steps of the method or various modules of the system involved in the above embodiments. For details, please refer to the relevant descriptions in the above method and system embodiments.

[0146] The processor and the memory may be independent structures or integrated structures. When the processor and the memory are independent structures, the memory and the processor may be coupled and connected via a bus.

[0147] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, it can be used to execute any method of the above embodiments of the present invention, or to run any system of the above embodiments of the present invention.

[0148] Among them, computer-readable media include computer storage media and communication media, wherein the communication media include any media that facilitates the transmission of computer programs from one place to another. The storage medium can be any available medium that can be accessed by a general or special-purpose computer. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and the storage medium can be located in an ASIC. In addition, the ASIC can be located in a user device. Of course, the processor and the storage medium can also be present in a communication device as discrete components.

[0149] The microgrid fault recovery control method and system based on hierarchical control provided in the above-mentioned embodiments of the present invention designs a secondary control strategy for voltage and frequency at the physical layer based on the event trigger mechanism of the information layer. The strategy can monitor the state changes of the power system in real time and respond quickly, thereby improving the stability of the system. It not only optimizes the control strategy, but also improves the system's adaptability to dynamic environments, and ultimately achieves efficient coordinated control of the network and physical layers.

[0150] All matters not covered in the above embodiments of the present invention are well known in the art.

[0151] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A microgrid fault recovery control method based on hierarchical control, characterized in that: include: Based on the hierarchical control architecture of the microgrid system, a virtual leader-follower consistency control model is established; Based on the virtual leader-follower consistency control model, the control mode of each level is determined; wherein: in the primary control link, the frequency and voltage of the microgrid are controlled by droop control; in the secondary control link, the voltage of the microgrid is adjusted to a given reference value by voltage secondary control, and the frequency of the microgrid is adjusted to a given reference value by angular frequency secondary control; Using the set event trigger mechanism, the secondary control link is started to adjust the microgrid output voltage and frequency to remain constant and recover from microgrid faults.

2. The microgrid fault recovery control method based on hierarchical control according to claim 1, characterized in that: The hierarchical control architecture based on the microgrid system establishes a virtual leader-follower consistency control model, including: Providing a hierarchical control architecture for microgrid restoration control; Assume that the ith distributed power source has N adjacent power sources for communication, the communication connection graph between the ith distributed power source and the N adjacent power sources includes at least one directed spanning tree, and the virtual leader is set as a globally reachable point; In the microgrid system, the voltage and frequency droop controllers of the i-th distributed generation are designed as follows: In the formula, ω i and U i are the output frequency and voltage of the distributed unit respectively; ω ref and U ref are the frequency reference value and the voltage reference value respectively; m i and n i is the droop coefficient, P i and Q i are the active power and reactive power of the distributed unit respectively; According to the above droop controller design, the virtual leader-follower consistency control design corresponding to the i-th distributed generation is: In the formula, u i is the virtual leader-follower consistency control function, N i is the set of adjacent power sources of the i-th distributed power source; k xi1 and k xi2 is the undetermined gain coefficient; z i and z j represents the voltage or frequency of the i-th distributed power source and the j-th distributed power source; a ij is the connection relationship between the i-th distributed power source and the j-th distributed power source, b i is the connection relationship between the virtual leader and the follower. If there is a connection, then b i >0, otherwise b i =0; The virtual leader-follower consensus protocol of the i-th distributed power source is: In the formula, α i , α j and α L are the failure coefficients of the i-th distributed generation, the j-th distributed generation and the virtual leader respectively; x L is the state quantity of the virtual leader; Under the effect of formula (3), when k xi1 and k xi2 When certain conditions are met, the status of the follower and the virtual leader can always follow each other; Assume that the state equation of the microgrid system is a first-order equation. in, Perform Laplace transform on equation (4): Where, u1 is the state quantity of the first distributed power source, u2 is the state quantity of the second distributed power source; X(s) is the state quantity after Laplace transformation; x1(t)| t＝0 and x2(t)| t＝0 are the initial values ​​of the output state quantities of the first distributed power source and the second distributed power source droop controller, respectively. The deviation between the output state quantity and the state quantity corresponding to the virtual leader is: At the same time, there are: When the gain coefficient meets the following conditions, the microgrid system can meet the consistency requirements: Where, c1=∫x1(t)dt| t＝0 , c2=∫x2(t)dt| t＝0 .

3. The microgrid fault recovery control method based on hierarchical control according to claim 2 is characterized in that: The hierarchical control architecture for providing a microgrid restoration control includes: It is assumed that a number of distributed power sources are arranged in a microgrid, and hierarchical control is adopted for voltage stability control to construct a hierarchical control architecture; wherein: the hierarchical control architecture includes an information layer and a physical layer, the information layer includes: an event triggering link and a communication network, and the physical layer includes a primary control link, a secondary control link, a power calculation link, a voltage synthesis link, a voltage and current dual closed-loop link and a PWM signal generator.

4. The microgrid fault recovery control method based on hierarchical control according to claim 1, characterized in that: The voltage secondary control comprises: The voltage control strategy for droop control is written as: Where U di is the d-axis component of the voltage dq of the i-th distributed generation, U ref is the voltage reference value, n i is the droop coefficient, Q i is the reactive power output by the i-th distributed generation, U qi is the q-axis component of the voltage dq of the i-th distributed generation; The goal of voltage secondary control is to make U di tends to the voltage reference value U ref , that is, to synchronize the voltage of each distributed power source to a given reference value when the control input is bounded; Differentiate equation (11) and take the auxiliary variable as have: The voltage synchronization problem of multiple distributed generation integrated microgrids is converted into a synchronization tracking problem of a first-order linear multi-agent system. Combined with the consistency strategy, the voltage consistency protocol is designed as follows: In the formula, k Ui1 is the voltage synchronization gain of the distributed generation, k Ui2 is the voltage synchronization gain of the virtual leader, α i , α j and α L are the failure coefficients of the i-th distributed generation, the j-th distributed generation and the virtual leader, respectively, and b i is the connection relationship between the virtual leader and the follower, a ij is the connection relationship between the i-th distributed power source and the j-th distributed power source, U i (t), U j (t) are the output voltage amplitudes of the droop controllers of the i-th and j-th distributed generation in the microgrid system; U L (t) is the voltage of the virtual pilot and is related to U ref equal; under this consistency protocol, according to formula (13), it can be obtained that the output voltage amplitudes of each distributed power droop controller tend to be consistent; the voltage controller is recorded as At this time, the feedback amount to the voltage is: In the formula, δ is, U i is the output voltage of the distributed power supply, n is, for; The voltage feedback is used to adjust the voltage in the microgrid system to a given reference value, so that the voltage and frequency of the microgrid system are kept synchronous and normal operation is restored.

5. The microgrid fault recovery control method based on hierarchical control according to claim 1, characterized in that: The angular frequency secondary control comprises: The frequency control strategy for droop control is: oh i =ω ref -m i P i (15) In the formula, ω i is the output frequency of the distributed power supply, ω ref Frequency reference value, m i is the droop coefficient, P i is the active power output by the i-th distributed power source; The goal of the angular frequency secondary control is to make ω i Tends to ω ref ; Differentiate formula (15) and set an auxiliary variable to Establish the following formula: In the formula, u ωi is the angular frequency control function; Combined with the consistency strategy, the angular frequency consistency protocol is designed as follows: In the formula, a ij is the element of the adjacency matrix; j = 1, 2, 3, ..., N, ω L (t) is the angular frequency of the virtual leader. If the virtual leader is connected to the i-th distributed power source, there is b i > 0, otherwise b i =0; k ωi1 and k ωi1 is the gain; the angular frequency controller is recorded as At this time, the angular frequency feedback amount is: In the formula, δ is, U i is the output voltage of the distributed power supply, m is, for; The angular frequency feedback amount is used to adjust the angular frequency in the microgrid system to a given reference value, so that the voltage and frequency of the microgrid system are kept synchronous and normal operation is restored.

6. A microgrid fault recovery control system based on hierarchical control, characterized in that: include: A consistency mechanism building module, which builds a virtual leader-follower consistency control model based on the hierarchical control architecture of the microgrid system; A control mode determination module, which determines the control mode of each level based on the virtual leader-follower consistency control model; wherein: in the primary control link, droop control is used to control the frequency and voltage of the microgrid; in the secondary control link, voltage secondary control is used to adjust the voltage of the microgrid to a given reference value, and angular frequency secondary control is used to adjust the frequency of the microgrid to a given reference value; The microgrid fault recovery module uses the set event trigger mechanism to start the secondary control link, adjust the microgrid output voltage and frequency to keep constant, and recover from the microgrid fault.

7. A computer terminal comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, it can be used to perform the method described in any one of claims 1 to 5, or to run the system described in claim 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, it can be used to perform the method described in any one of claims 1 to 5, or to run the system described in claim 6.

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