Research On Voltage Unbalance Control Of Microgrid In Island Operation Mode

The control of unbalanced voltage is one of the key technologies,which is to ensure the quality of the power supply and the stability of the system in the microgrid.This paper plans to carry out research from the aspects,including the control of unbalanced voltage of inverter port and PCC point in the microgrid,the coordinated control of multi-node voltage imbalance of the microgrid system and the optimization algorithm of coordinated control of multi-node voltage imbalance of the microgrid system.The main research contents of this paper are as follows:Research on single node voltage unbalance control strategy of microgrid inverter.As the three-phase unbalanced load is very easy to occur in an isolated microgrid,it is essential to select an appropriate control strategy to ensure the stable operation of the inverter under unbalanced conditions.Therefore,the steady state and dynamic characteristics of virtual synchronous machine(VSG)is analyzed based on the VSG control method,then the control parameters of VSG are designed.Considering the influence of unbalanced load,a single-station control strategy is proposed to solve the microgrid voltage imbalance of inverter port and PCC,which can control the voltage imbalance degree of single node within the limited range of adjustable coefficient.Research on multi-node voltage unbalance coordinated control strategy of microgrid system.In the microgrid system,if it controls the voltage unbalance degree of one node only,the voltage unbalance degree of other nodes will be uncontrollable.Therefore,oriented on the microgrid layered control strategy and the analysis of the negative sequence voltage imbalance coordination compensation principle,combined with the advantages of artificial fish swarm algorithm in solving multi-objective optimization problems,the objective function of imbalance control was established by comprehensively considering the voltage imbalance of inverter port and PCC as constraint conditions.An adaptive coordinated compensation control strategy is proposed,which is for multi-node voltage unbalance in microgrid system.The strategy can realize adaptive adjustment and the coordinated control of multi-node voltage unbalance in micro-grid system.Research on optimization algorithm of coordinated control of multi-node voltage imbalance of the microgrid system.Due to the randomness of the artificial fish swarm algorithm when searching for results,the search direction of the artificial fish cannot be planned,and the voltage imbalance level of each node in the system may not reach the optimal configuration.In order to solve this problem,the influence of the behavior operator and parameters of the fish swarm algorithm on the search process of the algorithm is analyzed and discussed,and an adaptive coordinated control optimization algorithm for multi-node voltage unbalance degree of microgrid is proposed.By comparing the simulation results,it is proved that the proposed algorithm converges quickly and the search results are concentrated in the desired region.The optimized coordinated compensation control strategy ensures that the voltage unbalance degree of the inverter port and PCC meets the requirements,and the voltage balance degree is improved.Experimental verification of microgrid inverter port and PCC voltage unbalance compensation algorithm.Based on TMS320F28335 minimum system,Starsim real-time simulator and the central controller of the upper computer,the hardware platform of the hardware-in-the-loop simulation of the microgrid system is built,the microgrid inverter program and the upper computer software are written,and the control strategies of singlenode voltage unbalance control and multi-node voltage unbalance coordinated control of the microgrid are verified by detailed experiments.