交直流混合微电网中AC/DC双向功率变流器的新控制策略

One novel control strategy of the AC / DC bi-directional power converter in micro-grid

交直流混合微电网中的AC/DC双向变流器,对系统的稳定运行和功率的协调分配有着重要作用。为了使直流微电网部分作为一个电压功率可控的单元接入交流母线,提出了一种新的AC/DC双向变流器控制策略,用于平衡交直流微电网间的功率流动并提高系统联网和孤岛运行的稳定性及可控性。在联网模式时,新方法基于dq坐标系,通过直流侧电压外环给定内环直轴电流参考值,进而控制功率流动和联网运行。孤岛模式时,新方法以交直流母线的电压差值作为外环,控制功率在交直流母线间的流动,使其互为支撑,提高系统稳定性。与传统的并网控制不同,新方法在电压控制的基础上引入有功功率控制项,很好地解决了并网时功率流动的问题。通过对双向变流器及其控制策略的分析研究,给出新方法的状态方程及控制框图。仿真结果证明了该方法的可行性和有效性。

The bidirectional converter of AC/DC hybrid microgrid plays a crucial role in the stable operation and power allocation of power system. In order to improve the stability of microgrid, this paper proposes a novel AC/DC bidirectional converter control strategy to keep the power balance of AC/DC microgrid. The new control strategy of microgrid is different in grid-connected mode and islanding mode. In the dq coordinate system, the bidirectional converter is able to control the power flow of microgrid in grid-connected mode through the direct axis current value which is calculated by the outer loop control of DC voltage. When it operates in islanding mode, the bidirectional converter controls the power flow between AC and DC through the voltage difference between AC and DC buses. Unlike the traditional control strategy, the active power control loop is introduced in the new algorithm. Then the DC microgrid becomes a controllable unit to incorporate into the AC bus which can improve the stability and controllability of microgrid. After the analysis of the bidirectional converter, the control block diagram of the new control strategy is given. Comprehensive simulation results indicate that the system based on new control method is stable and effective.