CN111767622A - Equivalent method for power system - Google Patents
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Abstract
The invention provides an equivalent method of a power system, which comprises the steps of S1, dividing the power system into an internal system, an external system and a buffer system; s2, establishing an equivalent model of a cluster of the generator set in the external system, and establishing an equivalent load model of loads of all load nodes in the external system; s3, eliminating all nodes of the external system, and adding the loads on all the load nodes to obtain an equivalent load model initial parameter; s4, constructing a target function with minimum injected power deviation of boundary nodes before and after equivalence of an external system, setting a particle swarm solution space according to initial parameters of an equivalence load model, and iteratively adjusting equivalence load parameters to enable the load flow of the boundary nodes before and after equivalence to be consistent, so as to obtain optimal parameters of the equivalence load model; s5, identifying model parameters of the generator set by using a parallel particle swarm algorithm; s6, evaluating the equivalence result, and optimizing the equivalence model and parameters according to the evaluation result; and a method for simplifying a buffer system and a core unit is adopted, so that equivalent difficulty is reduced.
Description
Technical Field
The invention belongs to the technical field of power systems, and particularly relates to an equivalence method for a power system.
Background
With the continuous development of urban economy and the continuous development of power distribution network structures, the trend of lines in an urban power distribution network and the distribution of power distribution facilities and users have obvious geographic characteristics. Because the regions and the power distribution facilities are centralized, the urban power distribution network has more cross spans with other ground features. In order to improve the power supply reliability, besides building reliable power supply points, the common structure of the power distribution network adopts a ring-type network of a graph, or a double-end power supply chain network of the graph and a multi-power supply network of the graph, namely, the original independent radiation type power distribution network is changed into a chain-type power distribution network with flexible operation.
The electromagnetic ring network is generated in the process of power development, and the purpose of the electromagnetic ring network is to increase the reliability of the operation of a power grid. With the continuous input of a 500kV power grid, in order to limit short-circuit current, a 220kV electromagnetic ring network is required to operate in an open loop mode. This causes the problem of loop closing in power networks of 110kV and below. Since loop closure is usually performed between two busbars or feeders, this will involve both the transmission network and the distribution network. For the judgment of the closed loop operation of the power distribution network, two main current views exist in China at present: 1) by means of operation management experience, a general conclusion whether the distribution network can be closed is given according to the load level, the distribution condition and the operation mode of the distribution network; 2) before the power distribution network is closed, calculation analysis or simulation is carried out, and whether the power distribution network can be closed is judged according to the result. In the first view, due to the lack of strict mathematical models and theoretical derivation, the obtained conclusions are mostly directed to specific networks and are not universal or representative. The second view has wide representativeness, and basically adopts the establishment of a unified mathematical model to perform steady-state analysis or transient analysis on the network before and after loop closing so as to evaluate the operation condition of the network after loop closing. Therefore, the topology information of the relevant power transmission network part is obtained, and the unified network model is established, so that the calculation accuracy of the closed loop current can be guaranteed.
When the closed loop calculation of the power distribution network is carried out, all real-time information of the whole system is often difficult to obtain at a local dispatching center, and the scale of a system mathematical model must be consistent with the obtained real-time information, so that parts with small influence on closed loop current or some parts which are not observable in the system have to be processed by an equivalence method.
Disclosure of Invention
The invention aims to provide an equivalent method of a power system, which is characterized in that a reliable power grid model and an equipment model are established according to the characteristics and conditions of a power grid, the equivalence is reasonable, and an external grid equivalent model is established to provide model support for closed-loop power-transfer calculation.
The invention provides the following technical scheme:
an electrical power system equivalence method comprising the steps of:
s1, dividing the power system into an internal system, an external system and a buffer system, wherein the internal system and the buffer system form a research system; s2, establishing an equivalent model of a cluster of the generator set in the external system, and establishing an equivalent load model of loads of all load nodes in the external system; s3, eliminating all nodes of the external system, and adding the loads on all the load nodes to obtain an equivalent load model initial parameter; s4, constructing a target function with minimum injected power deviation of boundary nodes before and after equivalence of an external system, setting a particle swarm solution space according to initial parameters of an equivalence load model, and iteratively adjusting equivalence load parameters to enable the load flow of the boundary nodes before and after equivalence to be consistent, so as to obtain optimal parameters of the equivalence load model; s5, identifying model parameters of the generator set by using a parallel particle swarm algorithm; and S6, evaluating the equivalence result, and optimizing the equivalence model and the parameters according to the evaluation result.
Preferably, the power system is divided into an internal system and an external system according to the application purpose of the equivalent network, and boundary nodes between the internal system and the external system form a boundary node set; the boundary node sets a short-circuit point in an internal system, and whether the short-circuit current is attenuated or not is examined from an external branch of the internal system; if attenuation occurs, continuously investigating the adjacent external branch until the short-circuit current of the investigated branch is not attenuated, wherein the end point of the branch is the boundary node of the external system; from the internal system border node to the external system border node is a buffer system.
Preferably, the establishing an equivalent model of the cluster of the generator set in the external system includes: clustering generator nodes in the external system by using a k-means algorithm to obtain a clustering result; and acquiring the sum of transfer functions of excitation system models of generator nodes in a clustering center in the clustering result, and taking the sum of transfer functions of the excitation system models of the generator nodes in the clustering center as the transfer function of an equivalent generator node of the research system.
Preferably, the establishing an equivalent model of the cluster of the generator set in the external system includes: dividing all the units into a plurality of coherent machine groups, determining a core unit in the coherent machine groups, determining an equivalent generator model based on the core unit, respectively aggregating the capacity and the kinetic energy of the rest units in the coherent machine groups according to the equivalent machine model, and determining equivalent step-up transformers and load parameters by adopting parameters of the core unit except the capacity and the kinetic energy.
Preferably, the identifying the parameters of the generator set model by using the parallel particle swarm algorithm comprises: before external systems are equivalent, transient response data of a research system under the excitation of disturbance signals are measured, wherein the transient response data comprise tie line power, bus frequency of the research system and active power of a generator; constructing a target function according to the minimum deviation of a certain bus frequency and the active power of a generator in a research system; initializing parameters to be identified and parallel particle swarm algorithm parameters of a power generation unit model, dividing a seed group into a plurality of sub-groups through a distribution sub-thread, distributing the number of particles to the plurality of sub-groups, and calculating an adaptive value of each sub-group; inputting an excitation signal, calculating a target variable value of a generator set model, and calculating the bus frequency and the active power of a generator at the corresponding position of a research system under the excitation signal; and calculating the value of the target function constructed in the step, and updating the speed and the position of the particles in the plurality of sub-populations in the sub-thread according to the evolution rule of the particle swarm to obtain the current optimal solution of the population, namely the model parameter of the generator set.
The invention has the beneficial effects that:
according to the equivalent method of the power system, a buffer system is added during the division of an internal system and an external system, a decoupling layer and the internal system are combined to form an expanded internal system, and the decoupling and access design of a subsequent external subsystem is realized; in the equivalence of an external system, an equivalent generator model is formed by adopting a core unit concept, so that the equivalence calculation steps are simplified while the characteristics of a coherent cluster are highlighted. The cluster modeling is combined with the identification equivalence method, so that the problems that generator parameters are difficult to obtain and complex to aggregate in the homodyne equivalence method are solved. Meanwhile, equivalent refined model parameters are dynamically identified through the proposed parallel optimization technology, and the equivalent precision and the equivalent efficiency are obviously improved; in the parallel identification equivalence stage, an identification model taking the minimum deviation of the bus voltage frequency and the generator active power in the research system before and after equivalence as a target function is constructed, an equivalence model parameter identification method based on a parallel particle swarm algorithm is provided, and the problem of long time consumption of the traditional identification method is solved.
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The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic flow diagram of the process of the present invention.
Detailed Description
As shown in fig. 1, an equivalent method of a power system includes the following steps:
s1, dividing the power system into an internal system, an external system and a buffer system, wherein the internal system and the buffer system form a research system; dividing a power system into an internal system and an external system according to the application purpose of the equivalent network, and forming boundary nodes between the internal system and the external system into a boundary node set; setting a short-circuit point in an internal system by the boundary node, and inspecting whether short-circuit current is attenuated or not from an external branch of the internal system; if attenuation occurs, continuously investigating the adjacent external branch until the short-circuit current of the investigated branch is not attenuated, wherein the end point of the branch is the boundary node of the external system; from the internal system border node to the external system border node is a buffer system.
S2, establishing an equivalent model of a cluster of the generator set in the external system, and establishing an equivalent load model of loads of all load nodes in the external system;
the method for establishing the equivalent model of the cluster of the generator set in the external system comprises the following steps: dividing all the units into a plurality of coherent machine groups, determining a core unit in the coherent machine groups, determining an equivalent generator model based on the core unit, respectively aggregating the capacity and the kinetic energy of the rest units in the coherent machine groups according to the equivalent machine model, and determining equivalent step-up transformers and load parameters by adopting parameters of the core unit except the capacity and the kinetic energy.
The method for establishing the equivalent model of the cluster of the generator set in the external system comprises the following steps: clustering generator nodes in an external system by using a k-means algorithm to obtain a clustering result; and acquiring the sum of transfer functions of excitation system models of generator nodes in a clustering center in the clustering result, and taking the sum of transfer functions of the excitation system models of the generator nodes in the clustering center as the transfer function of an equivalent generator node of the research system.
S3, eliminating all nodes of the external system, and adding the loads on all the load nodes to obtain an equivalent load model initial parameter;
s4, constructing a target function with minimum injected power deviation of boundary nodes before and after equivalence of an external system, setting a particle swarm solution space according to initial parameters of an equivalence load model, and iteratively adjusting equivalence load parameters to enable the load flow of the boundary nodes before and after equivalence to be consistent, so as to obtain optimal parameters of the equivalence load model;
s5, identifying model parameters of the generator set by using a parallel particle swarm algorithm; identifying the generator set model parameters using a parallel particle swarm algorithm comprises: before external systems are equivalent, transient response data of a research system under the excitation of disturbance signals are measured, wherein the transient response data comprise tie line power, bus frequency of the research system and active power of a generator; constructing a target function according to the minimum deviation of a certain bus frequency and the active power of a generator in a research system; initializing parameters to be identified and parallel particle swarm algorithm parameters of a power generation unit model, dividing a seed group into a plurality of sub-groups through a distribution sub-thread, distributing the number of particles to the plurality of sub-groups, and calculating an adaptive value of each sub-group; inputting an excitation signal, calculating a target variable value of a generator set model, and calculating the bus frequency and the active power of a generator at the corresponding position of a research system under the excitation signal; and calculating the value of the target function constructed in the step, and updating the speed and the position of the particles in the plurality of sub-populations in the sub-thread according to the evolution rule of the particle swarm to obtain the current optimal solution of the population, namely the model parameter of the generator set.
And S6, evaluating the equivalence result, and optimizing the equivalence model and the parameters according to the evaluation result.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. An electrical power system equivalence method, characterized by comprising the steps of:
s1, dividing the power system into an internal system, an external system and a buffer system, wherein the internal system and the buffer system form a research system;
s2, establishing an equivalent model of a cluster of the generator set in the external system, and establishing an equivalent load model of loads of all load nodes in the external system;
s3, eliminating all nodes of the external system, and adding the loads on all the load nodes to obtain an equivalent load model initial parameter;
s4, constructing a target function with minimum injected power deviation of boundary nodes before and after equivalence of an external system, setting a particle swarm solution space according to initial parameters of an equivalence load model, and iteratively adjusting equivalence load parameters to enable the load flow of the boundary nodes before and after equivalence to be consistent, so as to obtain optimal parameters of the equivalence load model;
s5, identifying model parameters of the generator set by using a parallel particle swarm algorithm;
and S6, evaluating the equivalence result, and optimizing the equivalence model and the parameters according to the evaluation result.
2. The power system equivalence method according to claim 1, characterized in that the power system is divided into an internal system and an external system according to an equivalence network application purpose, and boundary nodes between the internal system and the external system form a boundary node set; the boundary node sets a short-circuit point in an internal system, and whether the short-circuit current is attenuated or not is examined from an external branch of the internal system; if attenuation occurs, continuously investigating the adjacent external branch until the short-circuit current of the investigated branch is not attenuated, wherein the end point of the branch is the boundary node of the external system; from the internal system border node to the external system border node is a buffer system.
3. The power system equivalence method of claim 1, wherein the establishing an equivalence model of a fleet of generator sets in an external system comprises: clustering generator nodes in the external system by using a k-means algorithm to obtain a clustering result; and acquiring the sum of transfer functions of excitation system models of generator nodes in a clustering center in the clustering result, and taking the sum of transfer functions of the excitation system models of the generator nodes in the clustering center as the transfer function of an equivalent generator node of the research system.
4. The power system equivalence method of claim 1, wherein the establishing an equivalence model of a fleet of generator sets in an external system comprises: dividing all the units into a plurality of coherent machine groups, determining a core unit in the coherent machine groups, determining an equivalent generator model based on the core unit, respectively aggregating the capacity and the kinetic energy of the rest units in the coherent machine groups according to the equivalent machine model, and determining equivalent step-up transformers and load parameters by adopting parameters of the core unit except the capacity and the kinetic energy.
5. The power system equivalence method of claim 1, wherein the identifying genset model parameters using parallel particle swarm optimization comprises:
before external systems are equivalent, transient response data of a research system under the excitation of disturbance signals are measured, wherein the transient response data comprise tie line power, bus frequency of the research system and active power of a generator;
constructing a target function according to the minimum deviation of a certain bus frequency and the active power of a generator in a research system;
initializing parameters to be identified and parallel particle swarm algorithm parameters of a power generation unit model, dividing a seed group into a plurality of sub-groups through a distribution sub-thread, distributing the number of particles to the plurality of sub-groups, and calculating an adaptive value of each sub-group;
inputting an excitation signal, calculating a target variable value of a generator set model, and calculating the bus frequency and the active power of a generator at the corresponding position of a research system under the excitation signal;
and calculating the value of the target function constructed in the step, and updating the speed and the position of the particles in the plurality of sub-populations in the sub-thread according to the evolution rule of the particle swarm to obtain the current optimal solution of the population, namely the model parameter of the generator set.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103955594A (en) * | 2014-01-07 | 2014-07-30 | 云南电网公司西双版纳供电局 | Dynamic equivalence method of electric power system |
| CN104600756A (en) * | 2015-01-29 | 2015-05-06 | 华中科技大学 | Cluster equivalent modeling method for small and medium size hydroelectric generating sets |
| WO2017035964A1 (en) * | 2015-08-31 | 2017-03-09 | 中车大连电力牵引研发中心有限公司 | Method and system for determining load characteristics of electric power system |
| CN108539737A (en) * | 2018-05-09 | 2018-09-14 | 国网上海市电力公司 | A kind of power system dynamic equivalence optimization method of Practical |
| CN111291464A (en) * | 2018-12-07 | 2020-06-16 | 中国电力科学研究院有限公司 | Dynamic equivalence method and device for power system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103955594A (en) * | 2014-01-07 | 2014-07-30 | 云南电网公司西双版纳供电局 | Dynamic equivalence method of electric power system |
| CN104600756A (en) * | 2015-01-29 | 2015-05-06 | 华中科技大学 | Cluster equivalent modeling method for small and medium size hydroelectric generating sets |
| WO2017035964A1 (en) * | 2015-08-31 | 2017-03-09 | 中车大连电力牵引研发中心有限公司 | Method and system for determining load characteristics of electric power system |
| CN108539737A (en) * | 2018-05-09 | 2018-09-14 | 国网上海市电力公司 | A kind of power system dynamic equivalence optimization method of Practical |
| CN111291464A (en) * | 2018-12-07 | 2020-06-16 | 中国电力科学研究院有限公司 | Dynamic equivalence method and device for power system |
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