孤岛下基于负序虚拟导纳的微网不平衡控制策略

Negative Sequence Virtual Admittance Based Unbalance Control Strategy in Islanded Mode Microgrid

分析了微网中电压控制模式变流器和电流控制模式变流器的并联负序等效电路,指出使用电压控制模式变流器加负序虚拟阻抗的方法来补偿负序电流会在公共耦合点引入负序电压。基于微网中电流控制模式变流器的传统控制方法,提出了使用负序虚拟导纳的方法使用电流控制模式变流器来补偿负序电流的方法,将负序虚拟导纳与交流母线电压的负序分量相乘作为负序电流补偿指令并与正序电流指令叠加控制变流器输出。给出了一种基于电压不平衡度的动态调节负序虚拟电导的方法,降低了公共耦合点的电压不平衡度。与已有的使用比例积分控制器的计算方法对比,说明了该方法更符合微网“即插即用”的特点。通过仿真和实验证明了补偿策略的有效性。

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.