The Compensation Control Of Unbalanced Voltage In Microgrid Based On STATCOM

In the low voltage microgrid, single-phase load, three-phase unbalanced load, the load between the two phases can cause the imbalance of three-phase voltage. Voltage imbalance leads to output power fluctuation of DG and the device overheating,even sensitive equipment in fault. So it needs the system with fast reactive power support. STATCOM because of its fast dynamic characteristics is suitable the compensation control of unbalanced voltage in microgrid.The voltage unbalance of point of common coupling in microgrid is changed due to the variable unbalanced load. This paper presents a control method for static synchronous compensator(STATCOM) based on the positive and negative sequence virtual admittance control in response to load changes. The STATCOM simultaneously operates as fundamental positive-sequence admittance and fundamental negative-sequence conductance to restore the positivese quence voltage to the nominal value as well as reduce the negative-sequence voltage to an allowable level. Because of the existence of the transmission line impedance,when the power flows on the adjacent line is larger, the STATCOM control voltage only by local information, which may cause the voltage of adjacent point of common coupling beyond allowable level. Therefore, this paper analyzes the Voltage variation of local PCC for the near line power flow.STATCOM compensates the voltage with local information and the power flows of adjacent lines to achieve the goal of regional voltage adjustment.The experimental platform of Microgrid with STATCOM was built based on MATLAB / Simulink simulation and analysis. The experiment of Pf/QV droop control for the dual micro source and unbalanced voltage compensation control of STATCOM with the single micro source was completed.The results of simulation and experiment show that the virtual admittance control method of STATCOM can be used to reduce the three-phase unbalance voltage of microgrid.