Negative Sequence Virtual Admittance Based Unbalance Control Strategy in Islanded Mode Microgrid
Wu Xuezhi1, Liu Haichen1, Tang Fen2, Liu Jingdou1, Wu Liangliang1
1.National Active Distribution Network Technology Research Center Beijing Jiaotong University Beijing 100044 China; 2.Collaborative Innovation Center of Electric Vehicles in Beijing Beijing 100044 China
Abstract：The parallel negative equivalent circuit of the voltage control mode converters and the current control mode converter are analyzed. It is pointed out that the method using voltage control mode converter with negative sequence virtual impedance to compensate the negative sequence current will introduce the negative sequence voltage at the point of common coupling. Based on the traditional control method of current control mode converter in microgrid, a method of utilizing current control mode converter with negative sequence virtual admittance is proposed. The negative sequence current reference which is obtained by multiplying the negative sequence virtual admittance and the negative sequence voltage of the AC bus is added to the positive current reference to control the output current of the converter. A method for calculating the negative sequence virtual admittance based on voltage unbalance factor is proposed, which reduces the voltage unbalance factor at the point of common coupling. Compared with the existing calculation method using the proportional integral controller, it is shown that the proposed calculation method is more in line with the “plug and play” rule of the microgrid.
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2019, Vol. 34 
