基于线路阻抗补偿的直流微源并联均流控制策略

Current Sharing Control Strategy of Parallel DC Micro-sources Based on Line Impedance Compensation

针对直流微电网内微源变流器间的自主均流控制及母线电压的二次跌落问题,提出一种基于线路阻抗补偿的多源均流控制策略,利用改进频率注入法的反馈机制使各变流器总等效下垂系数相等且为最小线路阻抗值,进而获得各变流器线路阻抗的补偿信息;再将主动频率注入法切换至传统下垂控制,利用所得线路阻抗补偿值刷新各变流器下垂系数,从而满足功率精确分配的要求。该方法仅利用变流器本地信息,在保证负荷功率分配精度的同时,有效改善了由频率注入法带来的电能质量问题,同时避免了传统下垂控制造成的母线电压二次跌落问题。利用小信号建模分析了系统的稳定性,同时为验证该策略的控制效果,搭建了相应的直流微电网仿真模型和HIL StarSim实验平台,结果表明所提策略能够有效完成母线电压稳定和负荷功率精确分配的控制目标。

In order to solve the problems of autonomous current sharing between micro-source converters and the bus voltage secondary drop in DC microgrid,a current sharing control strategy based on line impedance compensation is proposed in this paper.Through the feedback mechanism of the improved frequency injection method,the total equivalent droop coefficients of every converter are equal and they are the minimum line impedance value,thus the compensation information of each converter line impedance is obtained.On this basis,the active frequency injection method is switched to the traditional droop control,and the droop coefficient of each converter is refreshed by using the obtained line impedance compensation value to meet the requirements of the accurate power sharing.Only with the local information of the converters,this method effectively improves the power quality caused by frequency injection while ensures the load power sharing accuracy,and the secondary voltage drop caused by the traditional droop control is avoided.The system stability is analyzed by small signal modeling.In order to verify the control effect of the proposed strategy,the corresponding model and the HIL StarSim experimental platform are built.The results show that the method can effectively achieve the stability of the bus voltage and the accurate sharing of the load power.