Micro-grid group electric energy quality problem suppression system and method based on adaptive virtual impedance

Abstract

The invention relates to the technical field of micro-grid group control, and discloses a micro-grid group electric energy quality problem suppression system and method based on adaptive virtual impedance, and the system comprises an adaptive virtual impedance generation unit, n micro-grid group electric energy quality monitoring units, and a plurality of connection impedance control units. The micro-grid group electric energy quality monitoring units are connected with the micro-grid subnets in a one-to-one correspondence mode, the output ends of the n micro-grid group electric energy quality monitoring units are all connected with the input end of the self-adaptive virtual impedance generation unit, and one connection impedance control unit is connected between any two micro-grid subnets which are connected. The output end of the adaptive virtual impedance generation unit is connected with the input ends of the plurality of connection impedance control units. According to the method, the electric energy quality problem in the micro-grid group is solved, the distribution condition of the electric energy quality problem of the micro-grid group is researched, and the electric energy quality problem is restrained within a certain range in combination with a corresponding electric energy quality restraining method.

Description

Technical Field

[0001] The present invention relates to the field of microgrid control technology, and in particular to a microgrid power quality problem suppression system and method based on adaptive virtual impedance. Background Art

[0002] A microgrid group is a large-scale distributed power supply and utilization network that connects multiple microgrids together. Each microgrid in the group is called a microgrid subgrid. Each microgrid subgrid in the microgrid group can be directly connected to the connection impedance using a switch, or it can be flexibly interconnected using power electronic converters. These converters are called connection converters. When flexible interconnection using connection converters is used, power scheduling and power quality management within the microgrid group can be effectively controlled by setting corresponding control strategies in the connection converters. Compared with a single microgrid, the structure of a microgrid group is more complex. When power quality problems occur in one or more nodes, such as harmonics and single-phase imbalance, these power quality problems will be transmitted within the microgrid group. Harmonic currents and negative sequence currents cause harmonic voltage problems and negative sequence voltage problems in each node of the microgrid group. Summary of the invention

[0003] The purpose of the present invention is to solve the power quality problem within the microgrid group, study the distribution of power quality problems in the microgrid group, suppress the power quality problems within a certain range by combining corresponding power quality suppression methods, and provide a microgrid group power quality problem suppression system based on adaptive virtual impedance.

[0004] In order to achieve the above-mentioned object of the invention, the embodiment of the present invention provides the following technical solutions:

[0005] A microgrid group power quality problem suppression system based on adaptive virtual impedance, wherein the microgrid group includes n microgrid subnets, and any two microgrid subnets can be connected to each other, and the system includes an adaptive virtual impedance generation unit, n microgrid group power quality monitoring units, and a plurality of connection impedance control units;

[0006] The input ends of the n microgrid subnets are connected to the distribution network busbar, the microgrid group power quality monitoring units are connected to the microgrid subnets in a one-to-one correspondence, and the microgrid group power quality monitoring units are used to obtain power quality information of the microgrid subnets;

[0007] The output ends of the n microgrid power quality monitoring units are all connected to the input end of the adaptive virtual impedance generation unit, and the adaptive virtual impedance generation unit is used to determine whether the power quality information of the microgrid subnet exceeds a set threshold and give a virtual impedance instruction;

[0008] One of the connection impedance control units is connected between any two connected microgrid subnets, the output end of the adaptive virtual impedance generation unit is respectively connected to the input ends of several connection impedance control units, and the connection impedance control unit is used to adjust the equivalent impedance of the microgrid subnet connection line according to the virtual impedance instruction.

[0009] Furthermore, the microgrid group power quality monitoring unit includes a voltage sensor, a current sensor, and a data analysis unit; the voltage sensor and the current sensor are used to obtain the voltage signal and the current signal of the corresponding connected microgrid subnet, and transmit them to the data analysis unit; the data analysis unit analyzes the voltage signal and the current signal to obtain the power quality information of the microgrid subnet.

[0010] Furthermore, the power quality information includes harmonic signals and three-phase imbalance.

[0011] Furthermore, the adaptive virtual impedance generation unit constructs an adaptive law according to the power quality information and the microgrid group parameters, and determines whether the harmonic signal or three-phase imbalance of the microgrid subnet exceeds a set threshold through the adaptive law. If it exceeds the set threshold, a virtual impedance instruction required for suppressing the power quality problem is generated, and the virtual impedance instruction is transmitted to each connected impedance control unit.

[0012] Furthermore, the virtual impedance instruction includes harmonic virtual impedance and negative sequence virtual impedance.

[0013] Furthermore, the connection impedance control unit includes a connection converter and a control unit; the control unit receives a virtual impedance instruction and controls the action of the connection converter to adjust the equivalent impedance of the microgrid subnet connection line, thereby suppressing the power quality problem of the microgrid group.

[0014] The method for suppressing power quality problems of microgrids based on adaptive virtual impedance includes the following steps:

[0015] Step 1, each microgrid group power quality monitoring unit obtains power quality information of the corresponding connected microgrid subnet;

[0016] Step 2, the adaptive virtual impedance generation unit constructs an adaptive law according to the power quality information of all microgrid subnets and microgrid group parameters to determine whether the power quality information exceeds a set threshold;

[0017] Step 3: If the power quality information exceeds the set threshold, the adaptive virtual impedance generation unit generates a virtual impedance instruction required for power quality problem suppression, and transmits the virtual impedance instruction to each connection impedance control unit to adjust the equivalent impedance of the microgrid subnet connection line.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention connects the impedance control unit to suppress the power quality problems in the microgrid according to the virtual impedance instruction, which has strong feasibility.

[0020] (2) The present invention implements the adaptive control method in combination with the connection impedance control unit between microgrid subgrids, eliminating the need to set up multiple dedicated power quality suppression devices in the microgrid group and reducing system costs.

[0021] (3) The method for suppressing power quality problems proposed in the present invention suppresses the power quality problems of each node in the microgrid group from the perspective of the microgrid subgrid connection impedance, thereby making the power quality management of the microgrid group systematic and holistic. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 It is a block diagram of the system unit of the present invention;

[0024] Figure 2 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0026] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance, or implying any such actual relationship or order between these entities or operations. In addition, the terms "connected", "connected", etc. can be directly connected between elements, or indirectly connected via other elements.

[0027] Embodiment 1:

[0028] The present invention is achieved through the following technical solutions: Figure 1 As shown, a microgrid group power quality problem suppression system based on adaptive virtual impedance, the microgrid group includes n microgrid subnets, and any two microgrid subnets can be connected to each other. The system includes: an adaptive virtual impedance generation unit, n microgrid group power quality monitoring units, and a plurality of connection impedance control units. The input ends of the n microgrid subnets are connected to the distribution network bus, the microgrid group power quality monitoring units are connected to the microgrid subnets in a one-to-one correspondence, the output ends of the n microgrid group power quality monitoring units are all connected to the input end of the adaptive virtual impedance generation unit, one connection impedance control unit is connected between any two microgrid subnets that have a connection relationship, and the output end of the adaptive virtual impedance generation unit is respectively connected to the input end of a plurality of connection impedance control units.

[0029] Each of the microgrid group power quality monitoring units includes a voltage sensor, a current sensor, and a data analysis unit. The voltage sensor and the current sensor are used to obtain the voltage signal and the current signal of the corresponding connected microgrid subnet, and transmit them to the data analysis unit; the data analysis unit analyzes the voltage signal and the current signal to obtain the power quality information of the microgrid subnet, and the power quality information includes harmonic signals and three-phase imbalance.

[0030] The adaptive virtual impedance generation unit receives the power quality information of the microgrid subnet sent by the microgrid power quality monitoring unit, and constructs an adaptive law according to the power quality information and the microgrid group parameters, that is, it is constructed by using the gradient descent method according to the power quality information and the initial impedance parameters of the microgrid group. The adaptive law construction method includes but is not limited to the MIT method, the Lyapunov method, etc.

[0031] When the harmonic signals and three-phase imbalance of all microgrid subgrids in the microgrid group do not exceed the set threshold, the signal generated by the adaptive virtual impedance generation unit remains unchanged. It should be noted that the harmonic signal and three-phase imbalance are indicators of power quality information. The corresponding values ​​can be calculated according to the power quality standard, and the corresponding thresholds can be set by the management personnel of the microgrid group. The specific setting can refer to the power quality standard and the actual operation requirements of the microgrid group.

[0032] When the harmonic signal or three-phase imbalance of any microgrid subgrid in the microgrid group exceeds the set threshold, the harmonic signal and three-phase imbalance at this time are substituted into the calculation of the adaptive virtual impedance generation unit. The adaptive virtual impedance generation unit generates the virtual impedance instruction required for suppressing power quality problems. The virtual impedance instruction includes harmonic virtual impedance and negative sequence virtual impedance, and transmits the virtual impedance instruction to each connected impedance control unit.

[0033] The connection impedance control unit includes a connection converter and a control unit. The control unit receives a virtual impedance instruction and controls the action of the connection converter to adjust the equivalent impedance of the microgrid subgrid connection line, that is, to change the connection impedance between the microgrid subgrids in the microgrid group, thereby suppressing the power quality problems of the microgrid group.

[0034] It should be noted that any two microgrid subnets in a microgrid group can be connected, depending on the actual operation of the microgrid, such as Figure 1 As shown, assuming that there are 4 microgrid subnets (i.e., n=4), microgrid subnet 1 can be connected to microgrid subnet 2, and can also be connected to microgrid subnet 3 at the same time. Similarly, microgrid subnet 2 can also be connected to microgrid subnet 3 and microgrid subnet 4. The connection impedance control unit is only connected between two microgrid subnets that have a direct connection relationship. Figure 1 The virtual impedance instruction 12 generated by the adaptive virtual impedance generating unit is sent to the connection impedance control unit connected between microgrid subnet 1 and microgrid subnet 2.

[0035] The virtual impedance instructions sent by the adaptive virtual impedance generation unit to each connection impedance control unit may be different, because the adaptive virtual impedance generation unit needs to calculate the corresponding virtual impedance instructions based on the actual power quality information and impedance parameters of all microgrid subnets, obtain distributed power quality information for integrated and coordinated calculation, and then suppress the overall power quality problems of the microgrid group, thereby achieving control from distribution to global. After the adaptive virtual impedance generation unit generates a virtual impedance instruction, each connection impedance control unit adjusts the equivalent impedance of the connection line according to the received virtual impedance instruction, so the next time the adaptive virtual impedance generation unit obtains new power quality information and adjusted impedance parameters.

[0036] Based on the above system, the present invention also proposes a method for suppressing power quality problems of microgrid groups based on adaptive virtual impedance, such as Figure 2 As shown, the following steps are included:

[0037] Step 1: Each microgrid power quality monitoring unit obtains power quality information of the corresponding connected microgrid subnet.

[0038] The voltage sensor and current sensor in the microgrid power quality monitoring unit obtain the voltage signal and current signal of the corresponding microgrid subnet. The data analysis unit in the microgrid power quality monitoring unit analyzes the voltage signal and current signal to obtain the power quality information of the microgrid subnet, including harmonic signals and three-phase imbalance.

[0039] Step 2: The adaptive virtual impedance generation unit constructs an adaptive law according to the power quality information of all microgrid subnets and microgrid group parameters to determine whether the power quality information exceeds a set threshold.

[0040] The adaptive virtual impedance generation unit receives the power quality information of the microgrid subnet sent by the microgrid power quality monitoring unit, and constructs an adaptive law according to the power quality information and the microgrid group parameters, that is, it is constructed by using the gradient descent method according to the power quality information and the initial impedance parameters of the microgrid group. The adaptive law construction method includes but is not limited to the MIT method, the Lyapunov method, etc.

[0041] Step 3: If the power quality information exceeds the set threshold, the adaptive virtual impedance generation unit generates a virtual impedance instruction required for power quality problem suppression, and transmits the virtual impedance instruction to each connection impedance control unit to adjust the equivalent impedance of the microgrid subnet connection line.

[0042] When the harmonic signals and three-phase imbalance of all microgrid subgrids in the microgrid group do not exceed the set threshold, the signal generated by the adaptive virtual impedance generation unit remains unchanged.

[0043] When the harmonic signal or three-phase imbalance of any microgrid subgrid in the microgrid group exceeds the set threshold, the harmonic signal and three-phase imbalance at this time are substituted into the calculation of the adaptive virtual impedance generation unit. The adaptive virtual impedance generation unit generates the virtual impedance instruction required for power quality problem suppression. The virtual impedance instruction consists of harmonic virtual impedance and negative sequence virtual impedance, and transmits the virtual impedance instruction to each connected impedance control unit.

[0044] The connection impedance control unit includes a connection converter and a control unit. The control unit receives a virtual impedance instruction and controls the connection converter to adjust the equivalent impedance of the microgrid subnet connection line, that is, to change the connection impedance between the microgrid subnets in the microgrid group, thereby suppressing the power quality problem between the microgrid groups. The next time the adaptive virtual impedance generation unit obtains new power quality information and the adjusted impedance parameters.

[0045] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A microgrid group power quality problem suppression system based on adaptive virtual impedance, wherein the microgrid group includes n microgrid subgrids, and any two microgrid subgrids can be interconnected, characterized in that: The system comprises an adaptive virtual impedance generation unit, n microgrid power quality monitoring units, and a plurality of connection impedance control units; The input ends of the n microgrid subnets are connected to the distribution network busbar, the microgrid group power quality monitoring units are connected to the microgrid subnets in a one-to-one correspondence, and the microgrid group power quality monitoring units are used to obtain power quality information of the microgrid subnets; The output ends of the n microgrid power quality monitoring units are all connected to the input end of the adaptive virtual impedance generation unit, and the adaptive virtual impedance generation unit is used to determine whether the power quality information of the microgrid subnet exceeds a set threshold and give a virtual impedance instruction; One of the connection impedance control units is connected between any two connected microgrid subnets, the output end of the adaptive virtual impedance generation unit is respectively connected to the input ends of several connection impedance control units, and the connection impedance control unit is used to adjust the equivalent impedance of the microgrid subnet connection line according to the virtual impedance instruction.

2. The microgrid power quality problem suppression system based on adaptive virtual impedance according to claim 1 is characterized in that: The microgrid power quality monitoring unit includes a voltage sensor, a current sensor, and a data analysis unit; the voltage sensor and the current sensor are used to obtain the voltage signal and the current signal of the corresponding connected microgrid subnet, and transmit them to the data analysis unit; the data analysis unit analyzes the voltage signal and the current signal to obtain the power quality information of the microgrid subnet.

3. The microgrid power quality problem suppression system based on adaptive virtual impedance according to claim 1 or 2, characterized in that: The power quality information includes harmonic signals and three-phase imbalance.

4. The microgrid power quality problem suppression system based on adaptive virtual impedance according to claim 3 is characterized in that: The adaptive virtual impedance generation unit constructs an adaptive law according to the power quality information and the microgrid group parameters, and determines whether the harmonic signal or three-phase imbalance of the microgrid subnet exceeds the set threshold through the adaptive law. If it exceeds the set threshold, a virtual impedance instruction required for suppressing the power quality problem is generated, and the virtual impedance instruction is transmitted to each connected impedance control unit.

5. The microgrid power quality problem suppression system based on adaptive virtual impedance according to claim 4 is characterized in that: The virtual impedance instruction includes harmonic virtual impedance and negative sequence virtual impedance.

6. The microgrid power quality problem suppression system based on adaptive virtual impedance according to claim 1 is characterized by: The connection impedance control unit includes a connection converter and a control unit; the control unit receives a virtual impedance instruction, controls the action of the connection converter, adjusts the equivalent impedance of the microgrid subnet connection line, and thus suppresses the power quality problem of the microgrid group.

7. A method for suppressing power quality problems of a microgrid group based on adaptive virtual impedance, which is implemented based on the system for suppressing power quality problems of a microgrid group based on adaptive virtual impedance according to any one of claims 1 to 6, and is characterized in that: The following steps are involved: Step 1, each microgrid group power quality monitoring unit obtains power quality information of the corresponding connected microgrid subnet; Step 2, the adaptive virtual impedance generation unit constructs an adaptive law according to the power quality information of all microgrid subnets and microgrid group parameters to determine whether the power quality information exceeds a set threshold; Step 3: If the power quality information exceeds the set threshold, the adaptive virtual impedance generation unit generates a virtual impedance instruction required for power quality problem suppression, and transmits the virtual impedance instruction to each connection impedance control unit to adjust the equivalent impedance of the microgrid subnet connection line.

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