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Model And Algorithm On Optimal Allocation Of Dynamic VAR Compensation In Bulk Power Systems

Posted on:2020-06-06Degree:MasterType:Thesis
Country:ChinaCandidate:L WuFull Text:PDF
GTID:2392330590484546Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
The rapid development of modern power systems has provided sufficient power supply to the society.Meanwhile,its safe and stable operation is also facing important challenges.The wide applications of HVDC,induction motor loads and various power electronic devices bring great threats in the aspect of transient voltage stability.Dynamic VAR compensation(DVC)is a feasible solution the the transient voltage issues.However,the investment of DVC is so high that it requires rational planning methods.This thesis focuses on the allocation of DVC in bulk power systems in the aspect of model and algorithms.A two-stage planning method using zoning approach and a full-optimization based method using linear approximation are proposed,respectively.The main contents are as follows.1)Based on the transient voltage behavior characteristics of nodes,the transient voltage fluctuation characteristics and risk indexes of nodes are defined.The former is used to describe the dynamic voltage behavior of nodes,and the latter is used to describe the risk of voltage instability.Furthermore,vector typed indexes for describing fault characteristics are constructed based on the aforementioned indexes.The AP clustering algorithm is introduced,and the continegncies clustering analysis is carried out by considering the correlation degree of fault features.the NE 39-bus system is used to validate the proposed algorithms.Finally,a method of extracting the main fault sets in the case of large fault sets is proposed,which provides a fault reduction method for application scenarios such as dynamic reactive power compensation which need to consider a large number of faults.2)For the purpose of transient voltage control,two power system partitioning methods based on transient voltage information are proposed.The first method establishes a vector typed index to describe the characteristics of node voltage fluctuation.Based on the sparse feature of the vector,DS and CS indexes are difined to evaluate the similarity.Then,AP clustering algorithm is applied to cluster nodes.The second method is based on a large number of transient simulation data,using data mining approach to achieve partitioning.The second method requires abundant information and is of strong applicability when the system model accuracy is high.At the same time,the similarities and differences between the two methods are compared,and compared with the traditional zoning method based on steady-state information as well.The applicability of the proposed method in the field of transient voltage control is demonstrated.3)A two-stage allocation method for DVC planning is proposed.Based on the results of power system partitioning,installation sites are selected by zones and then the capacity is optimized.The indexes constructed according to the transient voltage information of the system can describe the similarity of the transient voltage behavior of the system nodes,so the partitioning results based on the indexes are more suitable for the purpose of the transient voltage control.According to the principle of siting by zones,the node with the strongest transient voltage control ability in each zone is selected as compensation sites,and particle swarm optimization is introduced to realize capacity optimization.The proposed method effectively reduces the dimension of the problem,the amount of calculation,and is convenient for application in engineering practice.It has strong applicability for large-scale systems.4)From another point of view,a full-optimization model which can simultaneously optimize sites and sizes is proposed.Firstly,based on the characteristics of transient voltage fluctuation,the electrical connection between nodes is established.With this,the quadratic penalty term of the optimization objective function is constructed.Then,according to the idea of sensitivity analysis,the linear constraints for solving the feasible region of allocation capacity increment are proposed based on the control effect of dynamic reactive power compensation.Finally,the linear approximation is modified by iteration process to eliminate the error.The proposed optimization model overcomes the combinatorial explosion problem caused by random search algorithm.It linearly transforms differential-algebraic equations to realize the whole-space search in feasible region,and improves the optimality of the search results.At the same time,the relevant accelerated search strategy and linear programming relaxation method are proposed,and the validity of the model is verified by 39-bus system and a real transmission system.The research results of this paper provide an effective analysis tool and theoretical guidance for evaluating transient voltage risk and dynamic reactive power compensation planning.
Keywords/Search Tags:Dynamic VAR compensation planning, transient voltage control index system, two-stage allocation method, linear approximation, full-optimization method
PDF Full Text Request
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