The Study Of Distributed Power Control Of Island Microgrid

In islanded micro-grid,droop control is a method widely used to achieve proportional distribution of load power in distributed generation,but because of low voltage micro-grid is resistive and the distributed generation output impedance and line impedance is mismatch,the load reactive power is difficult to achieve proportional distribution.In addition,droop control is a differential control so that voltage and frequency will be error after the load changes.In order to solve the above two problems,this paper carries on the related research.This paper studies the island micro-grid distributedprimary control,control methods of free inverter interfaceddistributed power and inverter interfaced distributed power in the micro-grid are given,discusses the basic theory of distributed secondary control,introduces the communication directed graph,the first-order consensus control and the consensus with leader node.On the basis of distributed primary control and secondary control,this paper constructed a distributed hierarchical control that the primary droop control is mainly used to control the distribution of load power,the secondary control is used to compensate for the voltage and frequency deviation brought by the droop control.Then,accordingto the traditional droop control can't proportional distribute load reactive power,this paper proposes an improved droop control method based on coordinate transformation,designs an improved droop controller,analyzes the power allocation mechanism of islanded micro-grid,and three kinds of simulation examplesare designed to verifythe method according to different line parameters.Finally,in order to solve the problem of voltage and frequency deviation caused by improved droop control method,this paper presents a distributed secondary control method and an improved distributed secondary control method,and designs the virtual reactive power-voltage controller and virtual power-frequency controller respectively.To verify the efficiency of the two methods,this paper builds a simulation of a simple network and a mesh network as an example,which is validated by simulation.The simulation results indicate that the proposed distributed primary improved droop control method can not only realize the reactive power proportional distribution of the load in low voltage resistive micro-grid,but also can be used for medium voltage resistive-inductive micro-grid network;This distributed secondary control method and the improvement of its method can better improve the voltage and frequency quality compared to the improved droop control method and centralized secondary control method.