Research On Solving Strategy For Dynamic Reactive Power Optimization Of Active Distribution Network

Reactive power optimization is an important means to improve the voltage quality and reduce network loss of distribution network.At present,large-scale distributed generator is connected to the distribution network,which brings new difficulties for reactive power optimization.Compared with the traditional distribution network,the dynamic reactive power optimization of the active distribution network is more complex.On the one hand,the reactive power control equipment of the active distribution network includes both discrete control devices such as capacitors and continuous control devices such as DG.The characteristic of non-frequent switching of discrete control equipment leads to the coupling of each optimization period,which makes the dynamic reactive power optimization problem become a mix-integer non-linear and strong time-space coupling programming.At present,there is no fast direct method to solve it.On the other hand,each reactive power control equipment has different reactive power output characteristics.In order to obtain better reactive power optimization results,it is necessary to effectively coordinate the reactive power output of DG and traditional reactive power compensation devices.This thesis studies the above problems,and the specific work is as follows:(1)The first part studies the characteristics of active distribution network compared with traditional distribution network,deduces the relationship between reactive power and voltage,reactive power and network loss,and summarizes the characteristics of all kinds of reactive power compensation devices.This provides a theoretical basis for the modeling and simulation of follow-up problems.(2)Aiming at the dynamic reactive power optimization problem of active distribution network with uncoupled characteristics,taking the network loss,voltage deviation and the minimum capacity of reactive power compensation device as the objective function,the mathematical model is established under the constraints of power flow constraint,reactive power output constraint and node voltage amplitude constraint,and the corresponding solving strategy is designed and solved by particle swarm optimization algorithm.The research on dynamic reactive power optimization of active distribution network with uncoupled characteristics lays a foundation for the follow-up study of dynamic reactive power optimization of active distribution network with strong time-space coupling.(3)Aiming at the dynamic reactive power optimization problem of active distribution network with strong time-space coupling,a decoupling strategy called relaxation-clustering is proposed.Firstly,the 24-hour optimal reactive power compensation value of capacitor bank obtained by relaxing discrete variables and switching operation constraints of the capacitor bank.Secondly,division of time periods and the actual compensation capacity of capacitor banks is determined based on K-Means clustering.Finally,the dynamic reactive power optimization results are determined by correcting continuous variables.The strategy only needs to solve the nonlinear programming model,which can reduce the solution scale and obtain scheduling results with high satisfaction.