A steady-state modeling method for distribution network containing electric springs based on equivalent circuit

Abstract

The present invention relates to the field of power electronics technology, and in particular to a method for steady-state modeling of a distribution network containing electric springs based on an equivalent circuit, comprising: establishing a topological structure of a corresponding electric spring; analyzing a working mode of the corresponding electric spring based on the topological structure of the corresponding electric spring; establishing an equivalent circuit model of the corresponding electric spring based on the working mode of the corresponding electric spring; substituting the equivalent circuit model of the corresponding electric spring into a steady-state equation of the distribution network to construct a corresponding steady-state model of the distribution network containing electric springs. The method for steady-state modeling of a distribution network containing electric springs based on an equivalent circuit of the present invention can perform equivalent processing on a steady-state model of an electric spring, thereby effectively constructing a steady-state model of a distribution network containing electric springs, to assist in analyzing the influence of electric springs on the distribution network.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a steady-state modeling method for a power spring-containing distribution network based on an equivalent circuit. Background Art

[0002] In response to the global climate change, countries around the world have formulated energy transformation strategies to seek the commanding heights of the new round of scientific and technological revolution and industrial transformation competition and achieve efficient, intelligent and safe use of new energy. The proportion of domestic renewable energy continues to increase, but with the large-scale grid connection of renewable energy power generation, a series of problems will arise. Due to the intermittent and unstable characteristics of renewable energy, the imbalance between power generation and load demand is becoming increasingly prominent, affecting the operational safety and power quality of the power system.

[0003] The electric spring can change the operation mode of the traditional power system in which the power generation follows the load changes, realizes a new operation mode in which the demand side load follows the power generation changes, and can effectively solve the problems caused by the power generation of new energy. Among them, the Chinese patent with the publication number CN113872242A discloses "A method and device for energy optimization of active distribution network using electric springs", and the method includes: obtaining the input data of the active distribution network; the input data of the active distribution network includes the power factor of non-critical loads; according to the power factor of non-critical loads, determining the active power regulation range based on the flexible load of the electric spring; inputting the input data of the active distribution network and the active power regulation range based on the flexible load of the electric spring into the preset active distribution network energy optimization model to generate the optimization output result; the preset active distribution network energy optimization model includes the constraint conditions based on the flexible load of the electric spring.

[0004] The above existing schemes use electric springs as the regulating medium of the load distribution network, which can improve the voltage quality of the active distribution network. The electric spring is a compensator that is connected in series with non-critical loads and in parallel with critical loads, so that non-critical voltages can be flexibly adjusted to ensure the quality of critical voltages. The research on electric springs in existing schemes mainly focuses on the local control strategies of electric springs, such as alleviating voltage and frequency fluctuations, improving three-phase imbalance, suppressing harmonics and maintaining voltage stability. However, the existing schemes do not analyze the impact of electric springs on the distribution network from a macro perspective. At the same time, the steady-state model of the electric spring is a complex nonlinear equation with trigonometric functions. It is difficult to ensure the efficiency and convergence of the problem solving using a nonlinear programming model, which makes it difficult to substitute it into the steady-state model of the distribution network for analysis. Therefore, how to design a method that can effectively construct a steady-state model of a distribution network containing electric springs is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a steady-state modeling method for a distribution network containing electric springs based on an equivalent circuit, which can perform equivalent processing on the steady-state model of the electric spring, thereby effectively constructing a steady-state model of the distribution network containing electric springs, so as to assist in analyzing the impact of the electric springs on the distribution network.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A steady-state modeling method for a power distribution network containing electric springs based on an equivalent circuit comprises the following steps:

[0008] S1: Establish the topological structure corresponding to the electric spring;

[0009] S2: Analyze the working mode of the corresponding electric spring based on the topological structure of the corresponding electric spring;

[0010] S3: establishing an equivalent circuit model of the corresponding electric spring based on the working mode of the corresponding electric spring;

[0011] S4: Substitute the equivalent circuit model of the corresponding power spring into the steady-state equation of the distribution network to construct the corresponding steady-state model of the distribution network containing the power spring.

[0012] Preferably, in step S2, based on the topological structure of the corresponding power spring and the state of the distribution network absorbing or injecting reactive power, the working mode of the corresponding power spring is divided into an inductive mode and a capacitive mode.

[0013] Preferably, in step S2, the working mode of the electric spring is analyzed by the following steps:

[0014] S201: When the distribution network is in the state of reactive power absorption, the working mode of the corresponding power spring is the inductive mode, and the AC side voltage V l,ES <θ l,ES Ratio of non-critical load current I l,NL <θ l,N 90 degrees ahead;

[0015] S202: When the distribution network is in a state of reactive power injection, the working mode of the corresponding power spring is the capacitor mode, and the AC side voltage V l,ES <θ l,ES Ratio of non-critical load current I l,NL <θ l,N Lag 90 degrees.

[0016] Preferably, in step S202, the capacitance mode includes capacitance mode I and capacitance mode II;

[0017] When the working mode of the corresponding power spring is capacitor mode I, a small amount of reactive power is injected into the distribution network, and the non-critical load voltage V l,NL <θ l,NL Greater than bus voltage V l <θ i ;

[0018] When the working mode of the corresponding power spring is capacitor mode II, a large amount of reactive power is injected into the distribution network, and the non-critical load voltage V l,NL <θ l,NL Gradually reduce the non-critical load voltage V l,NL ∠θ l,NL Less than bus voltage V l ∠θ i .

[0019] Preferably, in step S3, a corresponding virtual node and two opposite branch impedances are added based on the topological structure and working mode of the corresponding power spring, and a corresponding node admittance matrix is ​​constructed.

[0020] Preferably, in step S3, the equivalent circuit model of the electric spring is expressed as:

[0021]

[0022]

[0023] Where: P i t and They represent the active power and reactive power injected into the busbar during period t respectively; and Bus voltage V i t The real and imaginary parts of G ij and B ij represent the real and imaginary parts of the admittance matrix of node ij respectively.

[0024] Preferably, in step S4, the steady-state model of the power spring distribution network includes:

[0025] 1) Equivalent circuit model of electric spring:

[0026]

[0027]

[0028] Where: P i t and They represent the active power and reactive power injected into the busbar during period t respectively; and Bus voltage Vi t The real and imaginary parts of G ij and B ij Respectively represent the real and imaginary parts of the node ij admittance matrix;

[0029] 2) Power balance equation:

[0030]

[0031]

[0032] Where: P i t and They represent the active power and reactive power injected into the busbar during period t respectively; It represents the active power output of distributed generation in the distribution network; and denote the reactive power output of the power spring and the distribution network capacitor respectively; and They represent the active power and reactive power of the key load in period t respectively; and Respectively represent the active power and reactive power of non-critical loads in period t

[0033] 3) Active power and reactive power of non-critical loads:

[0034]

[0035]

[0036] Where: and Respectively represent the active power and reactive power of non-critical loads; and Represents non-critical load voltage The real and imaginary parts of and Respectively represent the real and imaginary parts of the injected bus current;

[0037] in,

[0038]

[0039] Where: and Respectively represent the bus voltage V i t The real and imaginary parts of G hj and B hj represent the real and imaginary parts of the admittance matrix of node hj respectively.

[0040] Compared with the prior art, the steady-state modeling method of the power distribution network containing power springs in the present invention has the following beneficial effects:

[0041] The present invention analyzes the working mode by constructing the topological structure of the electric spring, and then establishes the corresponding equivalent circuit model in combination with the working mode of the electric spring, that is, the electric spring steady-state model can be equivalently processed to reduce the complexity of the electric spring steady-state model, so that the steady-state model of the distribution network containing the electric spring can be effectively constructed; and the constructed steady-state model of the distribution network containing the electric spring can improve the speed and efficiency of solving the optimized operation of the distribution network, so as to assist in analyzing the influence of the electric spring on the distribution network. At the same time, the present invention improves the voltage of the distribution network through the electric spring, so that the electric spring can change the operating mode of the traditional power system in which the power generation follows the load changes, and realizes a new operating mode in which the demand-side load follows the power generation changes, so that the problems caused by the power generation of new energy can be effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to make the purpose, technical solution and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0043] Figure 1 It is the logic block diagram of the steady-state modeling method of the distribution network containing power springs based on equivalent circuit;

[0044] Figure 2 A schematic diagram of the circuit structure of the topological structure of the electric spring;

[0045] Figure 3 (a) is the voltage vector diagram of the inductive mode;

[0046] Figure 3 (b) is a schematic diagram of the voltage vector of capacitance mode I;

[0047] Figure 3 (c) is a voltage vector diagram of capacitance mode II;

[0048] Figure 4 Schematic diagram of constructing the node admittance matrix. DETAILED DESCRIPTION

[0049] The following is a further detailed description through specific implementation methods:

[0050] Example:

[0051] This embodiment discloses a steady-state modeling method for a power distribution network containing electric springs based on an equivalent circuit.

[0052] like Figure 1 As shown, a steady-state modeling method of a power distribution network containing electric springs based on an equivalent circuit comprises the following steps:

[0053] S1: Establish the topological structure corresponding to the electric spring;

[0054] S2: Analyze the working mode of the corresponding electric spring based on the topological structure of the corresponding electric spring;

[0055] S3: establishing an equivalent circuit model of the corresponding electric spring based on the working mode of the corresponding electric spring;

[0056] S4: Substitute the equivalent circuit model of the corresponding power spring into the steady-state equation of the distribution network to construct the corresponding steady-state model of the distribution network containing the power spring.

[0057] The present invention analyzes the working mode by constructing the topological structure of the electric spring, and then establishes the corresponding equivalent circuit model in combination with the working mode of the electric spring, that is, the electric spring steady-state model can be equivalently processed to reduce the complexity of the electric spring steady-state model, so that the steady-state model of the distribution network containing the electric spring can be effectively constructed; and the constructed steady-state model of the distribution network containing the electric spring can improve the speed and efficiency of solving the optimized operation of the distribution network, so as to assist in analyzing the influence of the electric spring on the distribution network. At the same time, the present invention improves the voltage of the distribution network through the electric spring, so that the electric spring can change the operating mode of the traditional power system in which the power generation follows the load changes, and realizes a new operating mode in which the demand-side load follows the power generation changes, so that the problems caused by the power generation of new energy can be effectively solved.

[0058] In the specific implementation process, the construction Figure 2 The topology of the power spring is shown in Figure 1. The power spring consists of a voltage source inverter, a bidirectional DC power supply, and a low-pass filter.

[0059] The AC side of the power spring is connected in series with the non-critical load, and the DC side is a voltage-stabilizing capacitor. The power spring and the critical load are connected in parallel on the same bus. The power spring transfers voltage or active power fluctuations to the non-critical load through reactive power compensation, ensuring the voltage stability of the critical load and achieving supply and demand balance. l <θ i , I l,NL <φ l,N and V l,ES <θ l,ES They are bus voltage, non-critical load voltage and (power spring) AC side voltage respectively.

[0060] The present invention establishes the topological structure of the electric spring, so that the working mode of the electric spring can be effectively analyzed, and then the equivalent circuit model of the electric spring can be established to reduce the complexity of the steady-state model of the electric spring, thereby assisting in constructing a steady-state model of the power distribution network containing the electric spring.

[0061] In the specific implementation process, based on the topological structure of the corresponding power spring and the relationship between the reactive power injection amount and the voltage of the distribution network, the working mode of the corresponding power spring is divided into inductive mode and capacitive mode. Figure 3 shown.

[0062] The working mode of the electric spring is analyzed through the following steps:

[0063] S201: When the distribution network is in the state of reactive power absorption, the working mode of the corresponding power spring is the inductive mode, and the AC side voltage V l,ES <θ l,ES Ratio of non-critical load current I l,NL <θ l,N Lead 90 degrees, such as Figure 3 (a) shown.

[0064] At this time, if the bus voltage is too high, the power spring can absorb reactive power to maintain voltage stability of critical loads.

[0065] S202: When the distribution network is in a state of reactive power injection, the working mode of the corresponding power spring is the capacitor mode, and the AC side voltage V l,ES <θ l,ES Ratio of non-critical load current I l,NL <φ l,N Lag 90 degrees, such as Figure 3 As shown in (b) and (c).

[0066] According to the amount of reactive power injected, the capacitance mode of the power spring includes capacitance mode I and capacitance mode II;

[0067] like Figure 3 As shown in (b), when the working mode of the corresponding power spring is capacitor mode I, a small amount of reactive power is injected into the distribution network, and the non-critical load voltage V l,NL <θ l,NL Greater than bus voltage V l <θ l ;

[0068] like Figure 3 As shown in (c), when the working mode of the corresponding power spring is capacitor mode II, a large amount of reactive power is injected into the distribution network, and the non-critical load voltage V l,NL <θ l,NL Gradually reduce the non-critical load voltage V l,NL <θ l,NL Less than bus voltage V l <θ l .

[0069] Through analysis, the reactive output of the power spring can be controlled to make the power spring work in inductive mode or capacitive mode II, which can not only ensure the voltage stability of the active distribution network bus, but also reduce non-critical voltage and achieve energy saving.

[0070] The present invention analyzes the working mode of the electric spring based on the topological structure of the electric spring and the relationship between the reactive power injection amount and the voltage of the distribution network, so that an equivalent circuit model can be effectively established, that is, the electric spring steady-state model can be equivalently processed to reduce the complexity of the electric spring steady-state model, thereby effectively constructing a steady-state model of the distribution network containing the electric spring.

[0071] In the specific implementation process, the steady-state model of the electric spring is a complex model, which contains trigonometric functions, square roots and other nonlinear terms. In order to reduce the complexity of the steady-state model of the electric spring, the corresponding virtual nodes and two opposite branch impedances are added based on the topological structure and working mode of the corresponding electric spring, and the corresponding node admittance matrix is ​​constructed.

[0072] Regarding the construction of the node admittance matrix, this embodiment is based on Figure 4 Take the example to illustrate: the busbar l of the power spring is equivalent to the busbars h, m and k. The busbars h and k are the busbars of non-critical loads and critical loads respectively. The branch hk is a zero impedance branch. Therefore, a virtual node m and two opposite branch impedances z hm and z mk It can construct the admittance matrix of a node hk.

[0073] The equivalent circuit model of the electric spring is expressed as:

[0074]

[0075]

[0076] Where: P i t and They represent the active power and reactive power injected into the busbar during period t respectively; and Bus voltage V i t The real and imaginary parts of G ij and B ij represent the real and imaginary parts of the node admittance matrix respectively.

[0077] In the specific implementation process, the steady-state model of the power distribution network with power springs includes:

[0078] 1) Equivalent circuit model of electric spring (relationship between busbar power injection and voltage in rectangular coordinates):

[0079]

[0080]

[0081] Where: P i t and They represent the active power and reactive power injected into the busbar during period t respectively; and Bus voltage V i t The real and imaginary parts of G ij and B ij Respectively represent the real and imaginary parts of the node ij admittance matrix;

[0082] 2) Power balance equation:

[0083]

[0084]

[0085] Where: P i t and They represent the active power and reactive power injected into the busbar during period t respectively; It represents the active power output of distributed generation in the distribution network; and denote the reactive power output of the power spring and the distribution network capacitor respectively; and They represent the active power and reactive power of the key load in period t respectively; and They represent the active power and reactive power of non-critical loads in period t respectively;

[0086] 3) Active power and reactive power of non-critical loads:

[0087]

[0088]

[0089] Where: and Respectively represent the active power and reactive power of non-critical loads; and Represents non-critical load voltage The real and imaginary parts of and Respectively represent the real and imaginary parts of the injected bus current;

[0090] in,

[0091]

[0092] Where: and Respectively represent the bus voltage V i t The real and imaginary parts of G hj and B hj represent the real and imaginary parts of the admittance matrix of node hj respectively.

[0093] The steady-state model of the power distribution network containing the electric spring constructed by the present invention can improve the solution speed and efficiency of the optimized operation of the distribution network, thereby facilitating the auxiliary analysis of the influence of the electric spring on the distribution network.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A steady-state modeling method for a power distribution network containing power springs based on an equivalent circuit, characterized in that: The following steps are involved: S1: Establish the topological structure corresponding to the electric spring; S2: Analyze the working mode of the corresponding electric spring based on the topological structure of the corresponding electric spring; In step S2, based on the topological structure of the corresponding power spring and the state of the distribution network absorbing or injecting reactive power, the working mode of the corresponding power spring is divided into an inductive mode and a capacitive mode; S3: establishing an equivalent circuit model of the corresponding electric spring based on the working mode of the corresponding electric spring; In step S3, a corresponding virtual node and two opposite branch impedances are added based on the topological structure and working mode of the corresponding power spring, and a corresponding node admittance matrix is ​​constructed; In step S3, the equivalent circuit model of the electric spring is expressed as: Where: and They represent the active power and reactive power injected into the busbar during period t respectively; and Bus voltage The real and imaginary parts of G ij and B ij Respectively represent the real and imaginary parts of the node ij admittance matrix; S4: Substitute the equivalent circuit model of the corresponding power spring into the steady-state equation of the distribution network to construct the corresponding steady-state model of the distribution network containing the power spring; In step S4, the steady-state model of the power spring distribution network includes: 1) Equivalent circuit model of electric spring: Where: and They represent the active power and reactive power injected into the busbar during period t respectively; and Bus voltage The real and imaginary parts of G ij and B ij Respectively represent the real and imaginary parts of the node ij admittance matrix; 2) Power balance equation: Where: and They represent the active power and reactive power injected into the busbar during period t respectively; It represents the active power output of distributed generation in the distribution network; and denote the reactive power output of the power spring and the distribution network capacitor respectively; and They represent the active power and reactive power of the key load in period t respectively; and They represent the active power and reactive power of non-critical loads in period t respectively; 3) Active power and reactive power of non-critical loads: Where: and Respectively represent the active power and reactive power of non-critical loads; and Represents non-critical load voltage The real and imaginary parts of and Respectively represent the real and imaginary parts of the injected bus current; in, Where: and Respectively represent bus voltage The real and imaginary parts of G hj and B hj represent the real and imaginary parts of the admittance matrix of node hj respectively.

2. The method for steady-state modeling of a power distribution network containing power springs based on an equivalent circuit as claimed in claim 1, characterized in that: In step S2, the working mode of the electric spring is analyzed by the following steps: S201: When the distribution network is in the state of reactive power absorption, the working mode of the corresponding power spring is the inductive mode, and the AC side voltage V l,ES ∠θ l,ES Ratio of non-critical load current I l,NL ∠φ l,N 90 degrees ahead; S202: When the distribution network is in a state of reactive power injection, the working mode of the corresponding power spring is the capacitor mode, and the AC side voltage V l,ES ∠θ l,ES Ratio of non-critical load current I l,NL ∠φ l,N Lag 90 degrees.

3. The steady-state modeling method of a power distribution network containing electric springs based on an equivalent circuit as claimed in claim 2, characterized in that: In step S202, the capacitance mode includes capacitance mode I and capacitance mode II; When the working mode of the corresponding power spring is capacitor mode I, a small amount of reactive power is injected into the distribution network, and the non-critical load voltage V l,NL ∠θ l,NL Greater than bus voltage V l ∠θ i ; When the working mode of the corresponding power spring is capacitor mode II, a large amount of reactive power is injected into the distribution network, and the non-critical load voltage V l,NL ∠θ l,NL Gradually reduce the non-critical load voltage V l,NL ∠θ l,NL Less than bus voltage V l ∠θ i .

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