直流微电网多源并联自主均流控制策略

Autonomous Current Sharing Control Strategy for Parallel Micro-sources in DC Microgrids

实现微源间负荷电流的精确分配及母线电压的无差调节是直流微电网重要的控制目标,但由于线路阻抗及低速通信的存在,传统下垂控制很难同时满足均流及稳定性的要求。提出一种基于低频低幅值交流信号注入的多源并联自主均流控制策略,在各变流器直流输出上注入交流小信号,并使其频率与输出直流电流产生频率–电流下垂特性,利用产生的无功功率环流调节各变流器输出直流电压,进而在反馈机制下,实现多变流器间的并联控制及负荷电流的精确分配;在此基础上,利用限幅及负阻抗环节,提出一种改进的母线电压补偿方法,进一步降低了由于线路阻抗造成的电压跌落,该方法无需互联通信线,无需改变硬件结构,易于实现;最后利用小信号建模,分析了控制策略的稳定性和动态性能。仿真和实验验证了所提方法的可行性和有效性。

Accurate current sharing between micro-sources and no-deviation regulation for bus voltage are two important control objectives in DC microgrids.Due to existence of line impedance and low-speed communication,traditional droop control is difficult to meet the requirements of current sharing and voltage stability at the same time.This paper proposes a new power sharing control strategy for parallel micro-sources based on injected small AC voltage with low frequency and low amplitude.A small AC voltage is superimposed onto the output DC voltage of each converter.Through the droop characteristics between injected frequency and output DC current,reactive circulating power would be generated and then used to regulate the output DC voltage of each converter,so as to achieve accurate load current sharing under feedback mechanism.On this basis,an autonomous bus voltage regulation strategy is proposed to compensate voltage drop due to limiter link and virtual negative impedance.This method is easy to implement without need of any communication and change of hardware structure.Finally,the stability and dynamic performance of the control strategy are analyzed using small signal modeling.Simulation and experiment results validate feasibility and effectiveness of the proposed control strategy.