微网逆变器的改进鲁棒下垂多环控制

Improved Robust Droop Multiple Loop Control for Parallel Inverters in Microgrid

对于孤岛模式下的逆变器,其等效输出阻抗和连线阻抗差异对功率分配和环流抑制的影响较大。鲁棒下垂控制虽然可以减小阻抗差异对功率精确分配的影响,但在逆变器投入并联运行过程,存在冲击电流大、过渡时间长的不足,影响鲁棒下垂控制的实用化。为此,以阻性线路阻抗为例,提出一种改进的鲁棒下垂多环控制方法,其由功率外环和电压、电流双环构成。电压、电流双环设计中,采用考虑负载影响的控制器参数设计方法,抑制负载变化对电容电流内环跟踪性能的不利影响。功率外环通过引入阻性虚拟阻抗将逆变器的等效输出阻抗设计成阻性,提出一种改进的鲁棒下垂控制方法,与常规鲁棒下垂控制相比,可以改善逆变器的并机过程,减小并机冲击电流,加快并机过渡过程,实现平滑快速并机过渡。仿真与实验结果表明了所提理论的正确性和有效性。

For parallel multi-inverters in island microgrid, the difference of equivalent output impedance and line impedance effects greatly on power sharing and circulating current restraining greatly. Robust droop control can reduce the impacts on accurate power sharing due to the impedance difference. But there are large impact current and long transition time in the start transition process, which hinder the actual engineering application. Thus, in the case of resistive line impedance, an improved robust droop multiple loop control method is proposed, which includes the outer power loop and the double loop of inner voltage and current. In the voltage and current loop, the controller parameter design method considering the influences of load is applied, to suppress the adverse impact of load change. In the outer power loop, the equivalent output impedance of inverters is redesigned as resistance by virtual resistive impedance. An improved robust droop control strategy is proposed. Compared with the conventional robust droop control, the improved robust droop can improve start transition process, reduce the impact current, speed up the transition process and realize rapid smooth transition. Simulation and experimental results verify the control strategy.