Reactive Voltage Partitioning And Coordinated Control Method Of Active Distribution Network

With the rapid development of smart grids,distributed generation with clean energy as the core has been more and more widely used.In recent years,distributed generation has played an increasingly active role in the distribution network.By using the reactive voltage control ability of distributed generation,the voltage regulation of the distribution network can be realized,so that the power grid can operate stably and greatly improve the reliability of the power grid.Faced with the problems of low voltage or voltage limit during the actual grid operation,combined with the available reactive power capacity of the distributed power supply itself,adjusting its corresponding inductive or capacitive reactive power output can optimize the reactive voltage of distribution network and various voltage problems can be alleviated.This paper mainly studies the voltage control of photovoltaic based distributed generation connected to distribution network.First,the mathematical model of photovoltaic cells and grid-connected inverters are described.Then,according to the basic structure of the photovoltaic grid-connected system,the photovoltaic grid-connected equivalent model is constructed and the relevant parameter settings are given.The selection of the inverter control mode of the photovoltaic equivalent model is very important to support grid voltage.In this paper,the PQ-PV switchable control mode is proposed by adding a selector based on the voltage change,so that the inverter can reasonably select the PQ control mode or the PV control mode,so as to provide support when voltage drop occurs in distribution network buses.Then,considering that the output of active power and reactive power will affect the voltage of each bus in the network when the distributed power is connected to the distribution network,a voltage control zone division method based on reactive voltage sensitivity is proposed.On the basis of reactive voltage sensitivity,the corresponding voltage change matrix is constructed,so that the reactive voltage control zone of the active distribution network is divided by using the clustering analysis method.It is worth mentioning that all buses within the controllable zone can be compensated by the distributed generation,and the distributed generation has a great influence on the voltage of the buses within the controllable zone,and has little effect on the voltage of the buses outside the controllable zone.Finally,based on the active distribution network voltage coordination control strategy of reactive voltage partition,the IEEE 33-bus distribution system model is built in the power system simulation software DIg SILENT Power Factory.Then,based on the voltage variation,the special situations such as the network topology changes and overlapping of buses in the controllable zone are analyzed,and the specific partition results are given.The partition of the controllable zone is related to the access location、quantity and size of distributed generation.In order to obtain better voltage compensation effect and maintain the stable operation of the system,the inverter control mode is selected according to the voltage sags of the corresponding buses by changing the network structure condition under the fault condition of the distribution network,and several distributed power sources are coordinated to participate in the regulation and control.