Research On Voltage/var Optimization Of Distributed Network With High PV Penetration

Photovoltaic(PV)has become the main form of distributed generator in distribution networks because of its cleanliness,durability,and abundance.However,owing to the continuous growth of renewable energy demand,the high penetration of PV has changed the reactive power-voltage characteristics of traditional distributio n networks,causing safe and economic problems.Therefore,it is necessary to do researches on voltage/var optimization control strategy for distribution networks with high PV penetration,which aims to eliminate the problems by making full use of the reactive power adjusting ability of multiple adjustable resources.From the perspective of ful y exploiting PV reactive power adjusting ability and mobilizing PV to actively participate in distribution network regulation,the studies which focus on multi-device coordination reactive power optimization and multi-le ve l voltage control are carried out as follows:Firstly,as the basis of reactive power optimization model,the reactive power regulation models of adjustable resources are established,such as PV,static var compensators,on-load tap-changers and shunt capacitors.Meanwhile,a load model which describes the complexity and diversity of distribution network load,and a distribution network model which describes balanced power are constructed.Then,two kinds of voltage/var optimization control strategies are proposed.(1)As to the problem of multi-device coordination reactive power optimizatio n,by comprehensively considering the different reactive power regulation characteristics of adjustable resources and the stochasticity of PV,A dual-time reactive power optimization scheduling strategy is proposed based on the optimal power flow(OPF),which includes day-ahead plan and intraday short-term scheduling.Day-ahead plan is planned to coordinate discrete equipment and continuous equipment by constructing a dynamic reactive power optimization model,which can achieve the goal of solving economic problems.In addition,with the constraints on the number of movements of discrete equipment at adjacent moments,large-scale actions can be avoided.While,Intraday short-term scheduling deals with forecasting errors and power fluctuatio ns,and can effectively solve the safe problems.(2)As to the problem of multi-level voltage coordination control,based on model predictive control(MPC),a multi-level voltage interactive control problem is proposed.A interactive model between high-voltage(HV)distribution network and mediumvoltage(MV)distribution network is established by considering the account the sequence of actions of discrete devices in the future time period,which is defined by AVC strategy.Meanwhile,another interactive model between MV distribution network and low-voltage(LV)distribution network is established by considering LV control strategy and operation status,which includes uncertainty exchange power model and interaction node voltage.Thus,taking the different types of PV as objects,multi-le ve l voltage control can be implemented by rolling optimization.In addition,a feedback correction is constructed to improve the accuracy due to prediction errors.Simulations are presented on IEEE 33-bus distribution system to ilustrate the correctness and effectiveness of the proposed strategies.