不平衡负载条件下三相四桥臂变流器的改进分序控制

Improved Sequence Decomposition Control Strategy for Three-phase Four-leg Inverter with Unbalanced Load

为改善独立供电系统中负载不平衡带来的电能质量问题,提出了一种适用于三相四桥臂变流器的改进正序、负序及零序独立控制策略。该方法包括基于降阶广义积分器的快速正负序分离,以及正序与负序双同步旋转坐标系下的闭环控制算法。针对零序分量的基波频率脉动特性,采用比例谐振调节器对零序电压、电流进行控制,简化了原有的分序控制算法。仿真与实验结果表明,该控制方案能有效抑制负载不平衡带来的扰动,保持负载电压平衡。所采用的零轴控制可有效降低零序输出阻抗。且该方案较易实现,显著提高了独立供电系统的供电质量。

In order to improve the power quality caused by unbalanced load in standalone power systems, we proposed a control strategy, which could be suitable for the positive, negative and zero sequence independently, and could be used in three-phase four-leg inverter. The strategy included rapid separation of sequence components based on reduced order ge- neralized integrator, and closed-loop controller in both positive and negative synchronous rotating reference frame. Furthermore, analyzing the fundamental wave pulse characteristics of zero sequence component, we simplified the exist- ing sequence decomposition control algorithm by using the proportional resonant regulators to control zero sequence voltage and current. The simulation and experimental results show that the proposed method is capable of mitigating the disturbance due to the unbalanced load and maintaining the load voltage balanced. The zero-axis control can effectively reduce zero sequence output impedance. Moreover, the method is easy to implement and it enhances the voltage quality in standalone power systems obviously.