Static voltage stability index analysis method and system during fault of multi-new energy field

Abstract

The application provides a multi-new energy field fault period static voltage stability index analysis method and system, the method comprises the following steps: according to the fault type and fault position of the multi-new energy field station connected to the power grid system, the power grid node voltage equation including the generator node, the new energy node to be evaluated, the remaining new energy node, the tie node and the fault node is established; according to the power grid node voltage equation, the equivalent single-machine equivalent circuit of each new energy access node is obtained by analyzing the equivalent single-machine grid-connected system equivalent potential and equivalent impedance of the corresponding power grid of the new energy node to be evaluated; the voltage stability weak node of the multi-new energy grid-connected system during low voltage ride through is calculated and obtained according to the equivalent single-machine grid-connected system equivalent circuit; the corresponding optimization processing is carried out according to the voltage stability weak node of the multi-new energy grid-connected system during low voltage ride through.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system analysis, and particularly to a method and system for analyzing static voltage stability indicators during fault of multiple new energy fields. BACKGROUND

[0002] In today's society, renewable energy is being developed vigorously, and a new energy-based power system is being constructed. With the increasing proportion of distributed new energy connected to the power grid, the fault characteristics of the power grid will be determined by new energy sources. Due to the large number of new energy sources and the dispersed access locations, the output fault current is affected by the short-circuit fault low-voltage ride-through control strategy, which brings difficulties to the analysis of short-circuit fault of new energy power grid. At the same time, there is a static voltage stability problem during the low-voltage ride-through of high-proportion new energy connected to the power grid. Once the static voltage instability occurs, it will lead to unsuccessful low-voltage ride-through and system oscillation. Therefore, it is very important to study the static voltage stability evaluation method of high-proportion new energy connected to the power grid. At present, there is little research on the static voltage stability problem of high-proportion new energy connected to the power grid during short-circuit fault low-voltage ride-through. Most of the literature studies the static voltage stability problem of new energy connected to the power grid in normal steady-state operation, and proposes impedance modulus margin index, short-circuit ratio index, etc. However, the power grid is different during short-circuit fault and normal steady-state operation. During short-circuit fault, new energy sources output controlled reactive current component and active current component according to the regulations, showing nonlinear controlled current source characteristics, while during normal steady-state operation, new energy sources are constant active and constant reactive, i.e. PQ nodes, which are completely different. Therefore, it is necessary to study the static voltage stability problem of high-proportion new energy connected to the power grid during short-circuit fault.

[0003] The prior art mainly adopts impedance modulus margin index, short circuit ratio index and the like for static voltage stability evaluation under normal operation state of a power system. For these indexes, the prior art mainly adopts the following methods for analysis: 1) a static voltage stability critical point calculation method based on short circuit ratio. The short circuit ratio defines the strength of an external alternating current power grid relative to the access of new energy, reflects the relative strength between voltage support provided by the alternating current system and voltage change caused by the grid connection of new energy, and a critical short circuit ratio is derived according to the concept of static voltage stability, which is used to judge the strength of the system to which new energy is connected and the static voltage stability of the system. 2) a construction method of static voltage stability index and static voltage stability domain of a power system: all new energy, loads and direct current nodes with similar PQ node properties in the power grid are selected, an impedance matrix of the selected nodes is calculated, and the voltage amplitude, active power and reactive power of each node are obtained through power flow calculation; then, the static voltage stability index under the current operation state is derived by substituting into the static voltage stability criterion; finally, the boundary of the static voltage stability domain is depicted by the critical value of the static voltage stability index, and the stability margin of each node and the node close to the voltage stability limit are observed. 3) application of impedance modulus margin of new energy access power grid under normal operation in static voltage stability. The static voltage stability limit of the access system is given based on the impedance modulus margin, and the calculation method of the impedance modulus margin index of a single new energy and a multi-machine system is given.

[0004] The prior art mainly aims at static voltage stability evaluation of new energy access power grid under normal steady state operation, and there is a difference between static voltage stability evaluation under steady state during fault low voltage ride through of new energy access power grid and normal steady state. SUMMARY

[0005] The present application aims to provide a multi-new energy field fault period static voltage stability index analysis method and system, establish a short circuit fault period static voltage stability index based on phase margin for new energy power source access power grid, and propose a low penetration control optimization strategy to improve static voltage stability, thereby solving the problem of static voltage stability evaluation during fault low voltage ride through of high proportion of new energy access power grid.

[0006] To achieve the above-mentioned purpose, the static voltage stability index analysis method during multi-renewable energy field faults provided in the present application specifically includes: establishing a grid node voltage equation including a generator node, a new energy node to be evaluated, a remaining new energy node, a connection node and a fault node according to the fault type and fault location of the multi-renewable energy field access power grid system; analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the new energy node to be evaluated according to the grid node voltage equation to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated; calculating the voltage stability weak nodes during low voltage crossing of the multi-renewable energy grid-connected system according to the equivalent single-machine grid-connected system equivalent circuit; and performing corresponding optimization processing according to the voltage stability weak nodes during low voltage crossing of the multi-renewable energy grid-connected system.

[0007] In the above-mentioned method for analyzing static voltage stability indicators during multi-renewable energy field faults, optionally, analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the grid corresponding to the new energy node to be evaluated according to the grid node voltage equation to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated includes: according to the grid node voltage equation, obtaining the node impedance matrix by equating the remaining new energy nodes to admittances and adding them into the composite sequence network admittance matrix; analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the grid corresponding to the new energy node to be evaluated through the node impedance matrix to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated.

[0008] In the above-mentioned method for analyzing static voltage stability indicators during multi-renewable energy field faults, optionally, obtaining voltage stability weak nodes during low voltage ride-through of the multi-renewable energy grid-connected system according to the equivalent circuit calculation of the equivalent single-machine grid-connected system includes: obtaining static voltage stability phase deviation and short-circuit fault static voltage stability phase margin indicators of each new energy access node during the low voltage ride-through of the new energy fault according to the equivalent circuit calculation of the equivalent single-machine grid-connected system; and obtaining voltage stability weak nodes during low voltage ride-through of the multi-renewable energy grid-connected system by analyzing the static voltage stability phase deviation and short-circuit fault static voltage stability phase margin indicators of each new energy access node.

[0009] In the above-mentioned method for analyzing static voltage stability indicators during multi-renewable energy field faults, optionally, corresponding optimization processing is performed according to the voltage stability weak nodes during the low voltage ride through of the multi-renewable energy grid-connected system, including: improving the static voltage stability based on the static voltage stability phase margin indicator calculation principle during the low voltage ride through of a short circuit fault of the multi-renewable energy field access grid system according to the voltage stability weak nodes during the low voltage ride through of the multi-renewable energy grid-connected system.

[0010] In the static voltage stability index analysis method during the fault period of the multi-new energy field, optionally, the static voltage stability phase margin index calculation principle based on the low voltage ride through period of the multi-new energy field station accessing the power grid system short circuit fault is used to improve the static voltage stability, which includes: based on the static voltage stability phase margin index calculation principle during the low voltage ride through period of the multi-new energy field station accessing the power grid system short circuit fault, the phase deviation between the equivalent potential in the equivalent single machine grid-connected system equivalent circuit and the node voltage of the new energy field station is reduced to a preset value, so as to improve the static voltage stability.

[0011] In the static voltage stability index analysis method during the fault period of the multi-new energy field, optionally, the phase deviation between the equivalent potential in the equivalent single machine grid-connected system equivalent circuit and the node voltage of the new energy field station is reduced to a preset value, which further includes: obtaining a first ratio according to the ratio between the active component and the reactive component of the new energy field injection current; obtaining a second ratio according to the ratio between the resistance component and the reactance component of the equivalent single machine grid-connected system equivalent impedance; when the first ratio and the second ratio are the same, the preset value is met.

[0012] In the static voltage stability index analysis method during the fault period of the multi-new energy field, optionally, the weak voltage stability node during the low voltage ride through period of the multi-new energy grid-connected system is obtained by analyzing the short circuit fault static voltage stability phase margin index of each new energy access node, which includes: obtaining the weak voltage stability node during the low voltage ride through period of the multi-new energy grid-connected system according to the node with the minimum short circuit fault static voltage stability phase margin index.

[0013] In the static voltage stability index analysis method during the fault period of the multi-new energy field, optionally, the static voltage stability phase margin index calculation of the multi-new energy field station accessing the power grid system short circuit fault low voltage ride through period includes: obtaining the positive sequence node voltage equation of the multi-new energy field dispersedly accessing the power grid, obtaining the corresponding fault additional impedance according to the fault type; obtaining the voltage expression of the new energy node to be evaluated by converting the fault additional impedance and the positive sequence node voltage equation, obtaining the equivalent single machine grid-connected system equivalent parameter of the new energy node to be evaluated by the voltage expression; calculating the short circuit fault static voltage stability phase margin index by the equivalent single machine grid-connected system equivalent potential and the node voltage of each new energy access node.

[0014] In the static voltage stability index analysis method during the fault of the multi-new energy field, optionally, the voltage expression of the new energy node to be evaluated is obtained by conversion of the fault additional impedance and the positive sequence node voltage equation, and the voltage expression of the new energy node to be evaluated is obtained by eliminating the fault node and the tie node in the positive sequence node voltage equation through the fault additional impedance to obtain a first node voltage equation containing only the generator node, the new energy node to be evaluated, and the remaining new energy node; the remaining new energy node in the first node voltage equation is equivalent to an admittance to obtain a second node voltage equation by adding the admittance to a composite sequence network admittance matrix; and the voltage expression of the new energy node to be evaluated is obtained by eliminating the remaining new energy node in the second node voltage equation.

[0015] The application further provides a static voltage stability index analysis system during the fault of a multi-new energy field, and the system comprises: an establishment module configured to establish a power grid node voltage equation comprising a generator node, a new energy node to be evaluated, a remaining new energy node, a tie node, and a fault node according to a fault type and a fault position of the multi-new energy field station connected to a power grid system; an analysis module configured to analyze equivalent single-machine equivalent potential and equivalent impedance of an equivalent single-machine grid-connected system corresponding to the new energy node to be evaluated according to the power grid node voltage equation to obtain an equivalent single-machine grid-connected system equivalent circuit of each new energy node to be evaluated; a screening module configured to calculate voltage stability weak nodes during low-voltage ride-through of a multi-new energy grid-connected system according to the equivalent single-machine grid-connected system equivalent circuit; and an optimization module configured to perform corresponding optimization processing according to the voltage stability weak nodes during low-voltage ride-through of the multi-new energy grid-connected system.

[0016] The application further provides an electronic device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the above method when executing the computer program.

[0017] The application further provides a computer readable storage medium, which stores a computer program for executing the above method.

[0018] The application further provides a computer program product, which comprises computer programs / instructions, and the computer programs / instructions implement the steps of the above method when executed by a processor.

[0019] The beneficial technical effect of the present application is that: a static voltage stability assessment method and index are proposed during the low-voltage ride-through period of a short-circuit fault when a high proportion of new energy is connected to the power grid, including two parts: static voltage stability assessment during the low-voltage ride-through period of a short-circuit fault when a high proportion of multiple new energy stations are connected to the power grid, and an optimal control strategy for static voltage stability during the low-voltage ride-through period of a new energy station fault. Furthermore, the voltage stability levels during the low-voltage ride-through period of a new energy access node fault in the system can be ranked by calculating the index, and the weak nodes of voltage stability during the low-voltage ride-through period of a new energy power grid fault can be understood without the need for simulation, which is of great significance for guiding the safety and stability analysis of the power grid in terms of voltage stability. The proposed optimal control strategy for static voltage stability during the low-voltage ride-through period can effectively improve the static voltage stability during the low-voltage ride-through period of a new energy station fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application, constitute a part of the present application, and do not constitute a limitation of the present application. In the drawings:

[0021] Figure 1 A flow chart of a method for analyzing static voltage stability indicators during a multi-energy power plant fault period provided by an embodiment of the present application;

[0022] Figure 2 A schematic diagram of a fault circuit provided in one embodiment of the present application;

[0023] Figure 3 A schematic diagram of a flow chart for obtaining an equivalent circuit according to an embodiment of the present application;

[0024] Figure 4 A schematic diagram of a weak node analysis process provided in one embodiment of the present application;

[0025] Figure 5 This is a schematic diagram of an optimization strategy analysis provided by an embodiment of the present application;

[0026] Figure 6 A schematic diagram of a process for obtaining a short-circuit fault static voltage stability phase margin indicator according to an embodiment of the present application;

[0027] Figure 7 A schematic diagram of a flow chart for obtaining a voltage expression according to an embodiment of the present application;

[0028] Figure 8 This is a schematic diagram of an equivalent circuit of a single-machine grid-connected system of a node c to be evaluated provided in one embodiment of the present application;

[0029] Figure 9 This is a schematic diagram of the voltage phasor of the equivalent single-machine grid-connected system of the node c to be evaluated provided in one embodiment of the present application;

[0030] Figure 10 An application flowchart of the multi-new energy field fault period static voltage stability index analysis system provided by an embodiment of the present application is shown in the figure.

[0031] Figure 11 A structural diagram of an electronic device provided by an embodiment of the present application is shown in the figure.

[0032] Figure 12 A structural diagram of a multi-new energy access IEEE 33-node distribution network provided by an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in detail below with reference to the accompanying drawings and embodiments, so that how the present application applies technical means to solve technical problems and achieves technical effects can be fully understood and implemented. It should be noted that, unless there is a conflict, each embodiment in the present application and each feature in each embodiment can be combined with each other, and the technical solutions formed thereby are all within the protection scope of the present application.

[0034] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a group of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown.

[0035] Please refer to Figure 1 The multi-new energy field fault period static voltage stability index analysis method provided by the present application specifically includes:

[0036] S101: According to the fault type and fault location of the multi-new energy field station access power grid system, the power grid node voltage equation including the generator node, the to-be-evaluated new energy node, the remaining new energy node, the tie node and the fault node is established;

[0037] S102: According to the power grid node voltage equation, the equivalent single-machine equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system corresponding to the to-be-evaluated new energy node are analyzed to obtain the equivalent single-machine grid-connected system equivalent circuit of each to-be-evaluated new energy access node;

[0038] S103: According to the equivalent single-machine grid-connected system equivalent circuit, the voltage stability weak node during the low voltage ride through of the multi-new energy grid-connected system is calculated and obtained;

[0039] S104: According to the voltage stability weak node during the low voltage ride through of the multi-new energy grid-connected system, the corresponding optimization processing is performed.

[0040] Specifically, the multi-new energy field fault period static voltage stability index analysis method provided in the application mainly contains two links, specifically as follows:

[0041] (1) Static voltage stability phase margin index calculation of multi-new energy field station during low voltage ride through of short circuit fault of power grid system.

[0042] (2) Optimal control strategy of static voltage stability during low voltage ride through of new energy field station access to power grid fault.

[0043] In actual work, the static voltage stability phase margin index calculation link of multi-new energy field station during low voltage ride through of short circuit fault of power grid system mainly contains the following processes:

[0044] The power grid node voltage equation including generator node, to-be-evaluated new energy node c, remaining new energy node, tie node and fault node is established; the equivalent single-machine grid-connected system equivalent circuit of each to-be-evaluated new energy access node is obtained; on this basis, the new energy fault low voltage ride through period static voltage stability phase deviation and short circuit fault static voltage stability phase margin index of each new energy access node are calculated, so as to evaluate the system voltage stability during fault low voltage ride through. The specific fault circuit schematic diagram is shown in Figure 2 ; the specific implementation mode of each step will be described in detail in subsequent embodiments, which will not be exemplified one by one here.

[0045] Please refer to Figure 3 , in an embodiment of the application, obtaining the equivalent single-machine grid-connected system equivalent circuit of each to-be-evaluated new energy access node according to the equivalent single-machine grid-connected system equivalent potential and equivalent impedance of the power grid corresponding to the to-be-evaluated new energy node based on the power grid node voltage equation contains:

[0046] S301: According to the power grid node voltage equation, the node impedance matrix is obtained by adding the admittance of the remaining new energy node to the composite sequence network admittance matrix;

[0047] S302: The equivalent single-machine grid-connected system equivalent circuit of each to-be-evaluated new energy access node is obtained by analyzing the equivalent single-machine grid-connected system equivalent potential and equivalent impedance of the power grid corresponding to the to-be-evaluated new energy node based on the node impedance matrix.

[0048] Further, please refer to Figure 4 , in an embodiment of the application, the weak voltage node of multi-new energy grid-connected system during low voltage ride through is calculated and obtained according to the equivalent single-machine grid-connected system equivalent circuit, which contains:

[0049] S401: Calculate the static voltage stability phase deviation and short-circuit fault static voltage stability phase margin index of each new energy access node during the new energy fault low voltage ride through period according to the equivalent circuit of the equivalent single machine grid-connected system;

[0050] S402: Obtain the voltage stability weak node of the multi-new energy grid-connected system during the low voltage ride through period through the static voltage stability phase deviation and short-circuit fault static voltage stability phase margin index analysis of each new energy access node.

[0051] Specifically, in actual work, reference can be made to Figure 2 The specific implementation process of the above embodiment is as follows:

[0052] 1) For the specific fault type and fault location of the multi-new energy station access grid system, the grid node voltage equation including the generator node, the new energy node to be evaluated c, the remaining new energy nodes, the tie node and the fault node is established.

[0053] 2) Keep the new energy at the key node c to be evaluated, and equivalent the new energy of the remaining nodes to admittance to join the composite sequence network admittance matrix, and further obtain the node impedance matrix, and obtain the equivalent single machine grid-connected system equivalent potential of the key node c to be evaluated looking at the grid And equivalent impedance Obtain the equivalent single machine grid-connected system equivalent circuit of each new energy access node of the multi-new energy grid-connected system during the fault.

[0054] 3) For the equivalent single machine grid-connected system equivalent circuit of the key node c to be evaluated, calculate the static voltage stability phase deviation and short-circuit fault static voltage stability phase margin index during the new energy fault low voltage ride through period, and take the minimum node of the short-circuit fault static voltage stability phase margin index as the voltage stability weak node of the multi-new energy grid-connected system during the low voltage ride through period.

[0055] In an embodiment of the present application, the corresponding optimization processing according to the voltage stability weak node of the multi-new energy grid-connected system during the low voltage ride through period comprises: improving the static voltage stability based on the static voltage stability phase margin index calculation principle of the multi-new energy station access grid system during the short-circuit fault low voltage ride through period according to the voltage stability weak node of the multi-new energy grid-connected system during the low voltage ride through period.

[0056] The static voltage stability phase margin index calculation principle based on the short-circuit fault low voltage ride-through of the multi-new energy station access power grid system can comprise: reducing the phase deviation between the equivalent potential in the equivalent circuit of the equivalent single-machine grid-connected system and the node voltage of the new energy station to a preset value to improve the static voltage stability. The weak voltage stability node during the low voltage ride-through of the multi-new energy grid-connected system can be obtained through the short-circuit fault static voltage stability phase margin index analysis of each new energy access node, which can comprise: obtaining the weak voltage stability node during the low voltage ride-through of the multi-new energy grid-connected system according to the node with the minimum short-circuit fault static voltage stability phase margin index.

[0057] Specifically, the static voltage stability optimal control strategy during the short-circuit fault low voltage ride-through of the new energy station access power grid is proposed in the present application; the ratio of the active component to the reactive component of the current injected by the new energy station is the same as the ratio of the resistance component to the reactance component of the equivalent impedance of the equivalent single-machine grid-connected system, at which time the static voltage stability level of the power grid can be improved. The static voltage stability optimal control strategy during the short-circuit fault low voltage ride-through of the new energy station access power grid; through the static voltage stability phase margin index calculation principle during the short-circuit fault low voltage ride-through of the multi-new energy station access power grid system, the phase deviation between the equivalent potential in the equivalent circuit of the equivalent single-machine grid-connected system and the node voltage of the new energy station is reduced, that is, the static voltage stability can be improved.

[0058] Further, please refer to Figure 5 In an embodiment of the present application, reducing the phase deviation between the equivalent potential in the equivalent circuit of the equivalent single-machine grid-connected system and the node voltage of the new energy station to a preset value further comprises:

[0059] S501: obtaining a first ratio according to the ratio between the active component and the reactive component of the current injected by the new energy station;

[0060] S502: obtaining a second ratio according to the ratio between the resistance component and the reactance component of the equivalent impedance of the equivalent single-machine grid-connected system;

[0061] S503: when the first ratio is the same as the second ratio, a preset value is met.

[0062] Specifically, for the new energy station access power grid system, the equivalent single-machine grid-connected system equivalent impedance of the new energy station looking towards the power grid is obtained by using the node impedance matrix The ratio of the active component to the reactive component of the current injected by the new energy station is the same as the ratio of the resistance component to the reactance component of the equivalent impedance of the equivalent single-machine grid-connected system.

[0063] Please refer to​Figure 6 As shown in the embodiment of the present application, the calculation of the static voltage stability phase margin index of the multi-new energy field station during the short-circuit fault low voltage ride through of the grid system includes:

[0064] S601: Obtain the positive sequence node voltage equation of the multi-new energy field distributed access grid, and obtain the corresponding fault additional impedance according to the fault type;

[0065] S602: Convert the voltage expression of the new energy node to be evaluated through the fault additional impedance and the positive sequence node voltage equation, and obtain the equivalent single-machine grid system equivalent parameter of the new energy node to be evaluated through the voltage expression;

[0066] S603: Calculate the short-circuit fault static voltage stability phase margin index through the equivalent single-machine grid system equivalent potential and node voltage of each new energy access node.

[0067] Further reference is made to Figure 7 As shown, the voltage expression of the new energy node to be evaluated is obtained through the conversion of the fault additional impedance and the positive sequence node voltage equation, which includes:

[0068] S701: Eliminate the fault node and the tie node in the positive sequence node voltage equation through the fault additional impedance to obtain a first node voltage equation containing only the generator node, the new energy node to be evaluated and the remaining new energy nodes;

[0069] S702: Equivalent the remaining new energy nodes in the first node voltage equation to admittance to obtain a second node voltage equation by adding the admittance to the composite sequence network admittance matrix;

[0070] S703: Eliminate the remaining new energy nodes in the second node voltage equation to obtain the voltage expression of the new energy node to be evaluated.

[0071] In order to more clearly understand the specific implementation process and method of the multi-new energy field fault period static voltage stability index analysis method provided by the present application, the above multi-new energy field fault period static voltage stability index analysis method will be described as a whole. Those skilled in the art can know that this example is only a use example of the multi-new energy field fault period static voltage stability index analysis method provided by the present application, and does not limit it in any way.

[0072] (1) Static voltage stability phase margin index calculation of multi-new energy field station access grid system during short-circuit fault low voltage ride through.

[0073] For new energy stations concentrated access to the same bus or node, multiple new energy should be combined into one new energy station. From the perspective of short-circuit current calculation, multiple currents injected into the same node need to be combined into one current, and then the short-circuit fault static voltage stability phase margin index calculation and analysis are carried out.

[0074] For the static voltage stability evaluation of multi-new energy station dispersed access to the power grid system during short-circuit fault, the equivalent circuit of the equivalent single machine grid-connected system of each new energy access node needs to be obtained, and the equivalent impedance of the remaining nodes of new energy is added to the node admittance matrix.

[0075] Firstly, the positive sequence node voltage equation of multi-new energy station dispersed access to the power grid needs to be obtained, Figure 2 The positive sequence node voltage equation is:

[0076]

[0077] In the formula, the subscripts G, c, R, Q and f are the generator node, the new energy node to be evaluated, the remaining new energy nodes, the tie node and the fault node, is the system admittance matrix, and are the node voltage and node injected current vectors respectively.

[0078] When a three-phase fault occurs, the fault additional impedance is 0, the positive sequence node admittance matrix is removed from the corresponding row and column, and the node voltage equation can be obtained:

[0079]

[0080] After removing the tie node, we get:

[0081]

[0082] When an asymmetric fault occurs, the fault additional impedance is determined by the specific fault type, and the positive sequence node admittance matrix is removed from the fault node to obtain:

[0083]

[0084] After removing the tie node, we get:

[0085]

[0086] After obtaining the node voltage equation containing only the new energy node to be evaluated, the remaining new energy nodes and the generator node, the remaining new energy nodes are equivalent to the admittance and added to the composite sequence network admittance matrix to obtain:

[0087]

[0088] After removing the remaining new energy nodes, we get:

[0089]

[0090] Let

[0091]

[0092] The voltage expression of the node c to be evaluated is obtained as:

[0093]

[0094] Therefore, the equivalent single-machine grid-connected system equivalent parameter of the node c to be evaluated is:

[0095]

[0096] The equivalent circuit is shown in Figure 8 .

[0097] By the equivalent single-machine grid-connected system equivalent potential and node voltage of each new energy access node, the short-circuit fault static voltage stability phase margin index is calculated, and the node with the minimum short-circuit fault static voltage stability phase margin index is taken as the weak node of voltage stability during the fault low voltage ride through of the multi-new energy grid-connected system. The calculation formula of the static voltage stability phase deviation Dq of the new energy node c during the fault low voltage ride through is:

[0098]

[0099] The static voltage stability phase deviation Dq of the new energy node c during the current fault low voltage ride through is calculated as c , and the Dq cmax of the new energy node c at the stability limit is 90°. The calculation of the short-circuit fault static voltage stability phase margin index of the new energy node c is defined as:

[0100]

[0101] K c is greater than 0, the voltage stability of the new energy node c during the fault low voltage ride through. After calculating the short-circuit fault static voltage stability phase margin index of all new energy access nodes, the minimum value of the short-circuit fault static voltage stability phase margin index is taken as the stability index of the multi-new energy grid-connected system:

[0102] K min = min(K c1 ,…,K ck )

[0103] K min corresponding to the new energy node is the weak node of voltage stability during the fault low voltage ride through of the multi-new energy grid-connected system. The voltage stability of the multi-new energy grid-connected system during the fault low voltage ride through, then Kmin Should be greater than or equal to 0. When K min Very close to 0, for example, K min The range is between [0,0.05]. It can be considered that the multi-renewable energy grid-connected system is in a critical voltage stable state during the low voltage ride-through period. If K min Less than 0, the static voltage stability is lost during the low voltage ride-through period of the new energy grid-connected system fault.

[0104] (2) Optimal control strategy for static voltage stability during low voltage ride-through when new energy stations are connected to the grid.

[0105] The voltage at the node of the new energy station in the equivalent circuit of the equivalent single-machine grid-connected system Thevenin equivalent potential The product of the current injected into the grid during low voltage ride-through of the new energy station and the impedance Synthesis, such as Figure 9 shown.

[0106] The ratio of the active component to the reactive component of the current injected by the new energy station and the equivalent impedance of the equivalent single-machine grid-connected system The resistance component Z r and the reactance component Z x The ratio is the same:

[0107]

[0108] At this time, the voltage at the new energy station Thevenin equivalent potential Static voltage stability phase deviation Dq during fault low voltage ride-through c Equal to 0°, K c Equal to 1, the voltage stability is good.

[0109] The present application also provides a static voltage stability index analysis system during faults of multiple renewable energy sites, the system comprising: an establishment module for establishing a grid node voltage equation including a generator node, a new energy node to be evaluated, remaining new energy nodes, a connection node and a fault node according to the fault type and fault location of the multiple renewable energy sites connected to the power grid system; an analysis module for analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated according to the grid node voltage equation to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated; a screening module for calculating the voltage stability weak nodes during low voltage crossing of the multiple renewable energy grid-connected system according to the equivalent single-machine grid-connected system equivalent circuit; and an optimization module for performing corresponding optimization processing according to the voltage stability weak nodes during low voltage crossing of the multiple renewable energy grid-connected system.

[0110] Specifically, taking the static voltage stability problem of multiple new energy station dispersedly accessing the power grid system during short-circuit fault low voltage ride through as an example for analysis, the static voltage stability margin index evaluation calculation is explained in detail, and the difference of static voltage stability margin before and after the implementation of the optimal control strategy of new energy station during fault low voltage ride through is compared. The evaluation implementation process is shown in Figure 10

[0111] Step one: establish a multiple new energy station access power grid circuit, set the basic parameters of new energy power supply, low-pass control strategy and power grid fault;

[0112] Specifically, Figure 12 The IEEE33 node distribution network shown in has 8 nodes accessing distributed new energy, node 1 is connected with external power supply, the internal impedance of external power supply is 2 ohms. The reference voltage is 12.66kV, the reference capacity is 10MW, the capacity of distributed new energy is 3.8MW, and it is considered that the distributed new energy fully generates reactive power according to the rated current during fault low voltage ride through. It is assumed that the symmetrical fault of the power grid causes the voltage of the external power supply to drop from 1.05p.u. to 0.2p.u.

[0113] Step two: calculate the short-circuit current of the new energy access power grid;

[0114] Specifically, the amplitude of the current injected by each distributed new energy is 0.1p.u., and the power factor angle is 0°. The short-circuit iteration calculation obtains the output current of each distributed new energy as shown in Table 1.

[0115] Table 1

[0116] Node New energy output current / p.u. Node New energy output current / p.u. 4 -0.3797+0.0148i 22 -0.3719+0.0778i 10 -0.1982+0.3242i 23 -0.3798-0.0110i 15 0.3781-0.0375i 27 -0.2965+0.2377i 20 -0.3778+0.0412i 33 -0.0764+0.3722i

[0117] Step three: for each new energy power supply access node, the equivalent potential of the node looking into the power grid during fault low voltage ride through is obtained by using the equivalent principle of equivalent single machine grid-connected system;

[0118] Specifically, the equivalent potential of each distributed new energy node looking into the power grid and the node voltage are shown in Table 2.

[0119] Table 2

[0120]

[0121] Step four: according to the static voltage stability phase deviation calculation formula during new energy fault low voltage ride through, the static voltage stability phase deviation of each new energy access node during new energy fault low voltage ride through is calculated.

[0122] Specifically, the static voltage stability phase deviation of each distributed new energy node during new energy fault low voltage ride through is calculated as shown in Table 3. ​

[0123] Table 3

[0124] Node Phase deviation / ° Node Phase deviation / ° 4 17.1236 22 33.9507 10 34.2297 23 18.8809 15 89.6684 27 21.3196 20 27.5711 33 46.5014

[0125] Step 5: Calculate the short-circuit fault static voltage stability phase margin index of each new energy access node based on the static voltage stability phase deviation during the low voltage ride-through period of the new energy fault.

[0126] Specifically, the short-circuit fault static voltage stability phase margin index calculated for each distributed new energy node is shown in Table 4 below.

[0127] Table 4

[0128] Node K c ]]> Node K c ]]> 4 0.8097 22 0.6228 10 0.6197 23 0.7902 15 0.0037 27 0.7631 20 0.6937 33 0.4833

[0129] Step 6: Based on the indicator results of each node, the new energy access node with the smallest indicator is selected as the voltage stability weak node during the low voltage ride-through period of the new energy grid fault.

[0130] Specifically, according to the table above, it is easy to know that node 15 is a node with weak voltage stability during the low voltage ride-through period of the new energy grid fault. 15 The indicator is 0.0037, close to 0. Therefore, it can be considered that the voltage stability margin of the new energy fault system during the low voltage ride-through period is very low, and the system voltage is critically stable. If the new energy capacity increases or the system voltage drop increases, the system will become unstable.

[0131] Step 7: Change the new energy low voltage ride-through control strategy for nodes with larger indicators to the optimal control strategy proposed in this application, and calculate the indicators again.

[0132] Specifically, the low voltage ride-through control strategy of node 15 with the largest phase margin index and node 33 with the largest phase margin index is changed to the optimal control strategy, and the short-circuit fault static voltage stability phase margin index calculated for each distributed new energy node is shown in Table 5 below.

[0133] Table 5

[0134] Node K c ]]> Node K c ]]> 4 0.8985 22 0.8568 10 0.7310 23 0.9107 15 0.8994 27 0.8126 20 0.8900 33 0.9318

[0135] It can be seen that when the new energy station with larger indicators adopts the static voltage stability optimal control strategy during the fault low voltage ride-through period, the phase margin indicators of all new energy nodes increase and the voltage stability is greatly improved, indicating the effectiveness of the static voltage stability optimal control strategy.

[0136] According to the above embodiments, it can be seen that the indicators provided by this application can accurately calculate the static stability margin of the new energy station during the low voltage ride-through period of the short-circuit fault of the power grid. The calculation method is simple and practical. The static voltage stability optimal control strategy during the low voltage ride-through period can effectively improve the static voltage stability during the low voltage ride-through period. By calculating the indicators, the voltage stability of the new energy access node in the system during the low voltage ride-through period can be ranked. Without the need for simulation, the voltage stability weak nodes during the low voltage ride-through period of the new energy grid fault can be understood. The optimal control strategy for the static voltage stability during the low voltage ride-through period of the new energy station fault is proposed based on the indicator principle.

[0137] The beneficial technical effect of the present application is that: a static voltage stability assessment method and index are proposed during the low-voltage ride-through period of a short-circuit fault when a high proportion of new energy is connected to the power grid, including two parts: static voltage stability assessment during the low-voltage ride-through period of a short-circuit fault when a high proportion of multiple new energy stations are connected to the power grid, and an optimal control strategy for static voltage stability during the low-voltage ride-through period of a new energy station fault. Furthermore, the voltage stability levels during the low-voltage ride-through period of a new energy access node fault in the system can be ranked by calculating the index, and the weak nodes of voltage stability during the low-voltage ride-through period of a new energy power grid fault can be understood without the need for simulation, which is of great significance for guiding the safety and stability analysis of the power grid in terms of voltage stability. The proposed optimal control strategy for static voltage stability during the low-voltage ride-through period can effectively improve the static voltage stability during the low-voltage ride-through period of a new energy station fault.

[0138] Figure 11 A schematic diagram of the physical structure of an electronic device provided in an embodiment of the present invention, such as Figure 11 As shown, the electronic device includes: a processor (processor) 501, a memory (memory) 502 and a bus 503.

[0139] The processor 501 and the memory 502 communicate with each other via a bus 503 .

[0140] The processor 501 is configured to call program instructions in the memory 502 to execute the methods provided by the above method embodiments.

[0141] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the method for analyzing static voltage stability indicators during a multi-energy power plant fault is implemented.

[0142] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the above-mentioned method for analyzing static voltage stability indicators during a multi-energy power plant fault.

[0143] Those skilled in the art will appreciate that embodiments of the application can be readily used as software, hardware, or a combination of software and hardware. In a software embodiment, the methods can be tangibly embodied in a machine-readable storage medium having stored thereon instructions that can be used to program a computer to perform any of the operations described herein. The software implementation can be for example, in the form of a computer program product. The software implementation can be implemented in a centralized fashion in one computer system or processor, or in a distributed fashion where different elements are spread across several interconnected computer systems or processors.

[0144] The present application is described in relation to flow diagrams and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It is understood that each block of the flow diagrams and / or block diagrams, and combinations of blocks in the flow diagrams and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks. Figure 1 one or more functions specified in one or more of the flow diagrams and / or block diagrams. Figure 1 means for performing each of the functions specified in the flow diagrams and / or block diagrams block or blocks.

[0145] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flow diagrams and / or block diagrams flow or flows and / or block or blocks. Figure 1 one or more functions specified in one or more of the flow diagrams and / or block diagrams. Figure 1 means for performing each of the functions specified in the flow diagrams and / or block diagrams block or blocks.

[0146] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flow diagrams and / or block diagrams flow or flows and / or block or blocks. Figure 1 one or more functions specified in one or more of the flow diagrams and / or block diagrams. Figure 1 means for performing each of the functions specified in the flow diagrams and / or block diagrams block or blocks.

[0147] The specific embodiments described hereinabove are presented by way of example to teach the best application of the application. However, various modifications and changes can be made within the scope of the present application which should be understood to be limited only by the claims.

Claims

1. A method for analyzing static voltage stability indicators during a multi-energy power plant fault, characterized in that: The method comprises: According to the fault type and location of the multiple renewable energy stations connected to the power grid system, the grid node voltage equations including the generator node, the renewable energy node to be evaluated, the remaining renewable energy nodes, the contact node and the fault node are established; Analyze the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated according to the grid node voltage equation to obtain the equivalent circuit of the equivalent single-machine grid-connected system of each new energy access node to be evaluated; According to the equivalent circuit of the equivalent single-machine grid-connected system, the voltage stability weak nodes of the multi-renewable energy grid-connected system during the low voltage ride-through period are obtained; Perform corresponding optimization processing according to the voltage stability weak nodes during the low voltage ride-through period of the multi-renewable energy grid-connected system; Analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated according to the grid node voltage equation to obtain the equivalent circuit of the equivalent single-machine grid-connected system of each new energy access node to be evaluated includes: According to the grid node voltage equation, the node impedance matrix is ​​obtained by equating the remaining new energy nodes to admittances and adding them into the composite sequence network admittance matrix; Analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated through the node impedance matrix to obtain the equivalent circuit of the equivalent single-machine grid-connected system of each new energy access node to be evaluated; The weak nodes of voltage stability during low voltage ride-through of the multi-renewable energy grid-connected system obtained by calculating the equivalent circuit of the equivalent single-machine grid-connected system include: According to the equivalent circuit of the equivalent single-machine grid-connected system, the static voltage stability phase deviation during the low voltage ride-through period of the new energy fault and the static voltage stability phase margin index of the short circuit fault of each new energy access node are calculated; The voltage stability weak nodes of the multi-renewable energy grid-connected system during low voltage ride-through are obtained by analyzing the static voltage stability phase deviation and short-circuit fault static voltage stability phase margin indicators of each renewable energy access node.

2. The method for analyzing static voltage stability index during a multi-energy power plant fault according to claim 1, characterized in that: The corresponding optimization processing according to the voltage stability weak nodes during the low voltage ride-through period of the multi-renewable energy grid-connected system includes: According to the voltage stability weak nodes during the low voltage ride-through period of the multi-renewable energy grid-connected system, the static voltage stability is improved based on the static voltage stability phase margin index calculation principle during the low voltage ride-through period of a short circuit fault of the multi-renewable energy station access power grid system.

3. The method for analyzing static voltage stability index during a multi-energy power plant fault according to claim 2, characterized in that: The calculation principle of the static voltage stability phase margin index during the low voltage ride-through period of a short-circuit fault in a power grid system with multiple renewable energy stations is used to improve the static voltage stability. Based on the calculation principle of the static voltage stability phase margin index during the low voltage ride-through period of a short-circuit fault in a power grid system with multiple renewable energy stations connected, the static voltage stability is improved by reducing the phase deviation between the equivalent potential in the equivalent circuit of the equivalent single-machine grid-connected system and the node voltage of the renewable energy station to a preset value.

4. The method for analyzing static voltage stability index during a multi-energy power plant fault according to claim 3 is characterized in that: Reducing the phase deviation between the equivalent potential in the equivalent circuit of the equivalent single-machine grid-connected system and the node voltage of the new energy station to a preset value also includes: Obtaining a first ratio according to a ratio between an active component and a reactive component of a current injected by the new energy field; obtaining a second ratio according to a ratio between a resistance component and a reactance component of an equivalent impedance of an equivalent single-machine grid-connected system; When the first ratio is the same as the second ratio, it meets the preset value.

5. The method for analyzing static voltage stability index during a multi-energy power plant fault according to claim 1, characterized in that: By analyzing the short-circuit fault static voltage stability phase margin index of each renewable energy access node, it is found that the weak voltage stability nodes of the multi-renewable energy grid-connected system during the low voltage ride-through period include: The voltage stability weak node of the renewable energy grid-connected system during low voltage ride-through is obtained according to the node with the smallest short-circuit fault static voltage stability phase margin index.

6. The method for analyzing static voltage stability index during a multi-energy power plant fault according to claim 2, characterized in that: The calculation of the static voltage stability phase margin index during the low voltage ride-through period of a short-circuit fault in a power grid system with multiple renewable energy stations connected includes: Obtain the positive-sequence node voltage equation for decentralized access of multiple renewable energy fields to the power grid, and obtain the corresponding additional fault impedance based on the type of fault. A voltage expression of the new energy node to be evaluated is obtained by converting the fault additional impedance and the positive sequence node voltage equation, and an equivalent single-machine grid-connected system equivalent parameter of the new energy node to be evaluated is obtained by the voltage expression; The short-circuit fault static voltage stability phase margin index is calculated based on the equivalent single-machine grid-connected system equivalent potential and node voltage of each renewable energy access node.

7. The method for analyzing static voltage stability indicators during a multi-energy power plant fault according to claim 6, characterized in that: The voltage expression of the new energy node to be evaluated is obtained by converting the fault additional impedance and the positive sequence node voltage equation, including: Eliminating the fault node and the tie node in the positive sequence node voltage equation by using the fault additional impedance to obtain a first node voltage equation containing only the generator node, the new energy node to be evaluated and the remaining new energy nodes; The remaining new energy nodes in the first node voltage equation are equivalent to admittances and added into the composite sequence network admittance matrix to obtain the second node voltage equation; Eliminate the remaining new energy nodes in the second node voltage equation to obtain a voltage expression for the new energy node to be evaluated.

8. A static voltage stability index analysis system during a multi-energy power plant fault, characterized in that: The system comprises: Establish a module for establishing grid node voltage equations including generator nodes, new energy nodes to be evaluated, remaining new energy nodes, tie nodes, and fault nodes based on the fault type and location of the fault occurring when multiple new energy stations are connected to the grid system; An analysis module is configured to analyze the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated according to the power grid node voltage equation to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated; analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated according to the power grid node voltage equation to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated comprises: according to the power grid node voltage equation, obtaining a node impedance matrix by equating the remaining new energy nodes to admittances and adding them into the composite sequence network admittance matrix; analyzing the equivalent potential and equivalent impedance of the equivalent single-machine grid-connected system of the power grid corresponding to the new energy node to be evaluated according to the node impedance matrix to obtain the equivalent single-machine grid-connected system equivalent circuit of each new energy access node to be evaluated; A screening module is configured to obtain voltage stability weak nodes of a multi-renewable energy grid-connected system during a low voltage ride-through period based on the equivalent circuit calculation of the equivalent single-machine grid-connected system; obtaining voltage stability weak nodes of a multi-renewable energy grid-connected system during a low voltage ride-through period based on the equivalent circuit calculation of the equivalent single-machine grid-connected system comprises: obtaining static voltage stability phase deviation and short-circuit fault static voltage stability phase margin indicators of each new energy access node during a new energy fault low voltage ride-through period based on the equivalent circuit calculation of the equivalent single-machine grid-connected system; obtaining voltage stability weak nodes of a multi-renewable energy grid-connected system during a low voltage ride-through period through analysis of the static voltage stability phase deviation and short-circuit fault static voltage stability phase margin indicators of each new energy access node; The optimization module is used to perform corresponding optimization processing according to the voltage stability weak nodes during the low voltage ride-through period of the multi-new energy grid-connected system.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

11. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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