微网逆变器不平衡负载控制技术研究

Research on Unbalanced Control Technology of Micro Inverter

微电网逆变器的一个重要性能是离网时在三相负载不平衡情况下仍能维持三相输出电压的对称性。传统对称分量法与叠加原理虽然能在三相逆变器带不平衡负载时通过对输出电压正、负、零序分量的不同补偿来维持三相电压的平衡,但该方法运算量大,不宜控制。针对微网逆变器接不平衡负载的情况,提出一种简单有效的系统控制策略,即谐振控制器的控制方法。该控制策略免去常规控制中所需电压/电流正负序分离及环路单独控制,极大简化了系统控制结构。仿真和实验结果验证了该方法能有效抑制由不平衡负载引起的输出电压畸变,获得高质量输出电压波形。

One of the important functions of micro-grid inverter is to maintain the symmetric three-phase output voltage when the three-phase loads are unbalanced.Although the traditional symmetrical component decomposing and superimpose theory can keep the voltage balance through compensating the positive-sequence,negative-sequence and zero-sequence components of output voltage,however,this method is time-consuming and not suitable for control.Aiming at micro-grid inverter with unbalanced loads, a simple and feasible resonant controller is proposed, avoiding the separation of positive and negative sequence of output voltage.The effectiveness of the proposed control strategy to reduce the voltage distortion under the unbalanced loads is verified by simulation and experimental results.