微网储能多逆变器并联负载不平衡下的均衡控制

BALANCED CONTROL STRATEGY FOR MULTI-ENERGY STORAGE INVERTERS IN MICROGRID IN PARALLELED WITH UNBALANCED LOAD

为了满足三相储能逆变器并联带不平衡负载运行时的环流及不平衡电压控制要求,在单同步旋转坐标系(single synchronous reference frame,SSRF)控制系统模型的正、负序变换的基础上,推导储能逆变器的正、负序输出阻抗特性,分析输出阻抗与环流及电压控制间的不均衡性,即增大阻抗有利于抑制环流,而减小阻抗有利于抑制不平衡。针对上述不均衡控制问题,在SSRF控制的基础上,一方面通过引入负序补偿器适当减小负序输出阻抗,从而可有效抑制输出电压不平衡;另一方面,通过引入虚拟阻抗来增强环流抑制能力,实现环流与电压的均衡控制,具有较高的稳定性。实验结果表明理论分析和控制方案的有效性。

In order to satisfy the circulating current and unbalanced voltage control requirement of the three-phase energy storage inverter in paralleled with unbalanced load operation, on the basis of positive and negative sequence transformation of single synchronous reference frame （SSRF） control system model, the positive and negative sequence output impedance of energy storage inverter was derived, the imbalance between output impedance, circulating current and voltage control was analyzed, i.e., increasing impedance could restrain circulating current while decreasing impedance could suppress unbalance. To solve the problem, a negative sequence compensation controller with reducing negative sequence output impedance appropriately was developed to suppress unbalance of output voltage based on SSRF control; on the other hand, the virtual impedance was introduced to promote control ability of circulation current, and realize proportion control of circulation current and voltage which had higher stability. The experiment results verify the validity of theoretical analysis and proposed control strategy.