三相不平衡负载下静止同步补偿器控制策略研究

低压配电网中不平衡负载会导致设备不正常运行、降低电能质量。对此,提出了一种新型控制策略,该策略通过瞬时对称分量法和信号延迟对消法(DSC)计算出负载电流、配电静止同步补偿器(DSTATCOM)输出电流的正序、负序分量,然后分别在正、负序同步旋转坐标控制正、负序分量,对正序分量的控制使DSTATCOM补偿负载无功电流,对负序分量的控制使DSTATCOM补偿不平衡负载导致的负序电流。搭建了DSTATCOM试验平台,试验结果表明,该策略在不平衡负载下,使得DSTATCOM能有效补偿负载无功电流和负序电流,实现了电网单位功率因数,电网电流平衡度达到了国标要求,总谐波失真(THD)小于5%。研究成果可为不平衡负载情况下的DSTATCOM控制提供参考。

Control Method of DSTATCOM under Three-phase Unbalanced Load

In this paper, a new control strategy was proposed, which is based on the fact that the unbalanced load in the low voltage distribution network will cause the equipment to run abnormally and reduce the power quality. Usually, the static synchronous compensator was used to compensate the negative current caused by reactive current and unbalanced load. The positive and negative sequence components of the DSTATCOM output current were calculated by the instantaneous symmetric component method and the signal delay cancellation method (DSC). Then, the positive and negative sequence components were controlled in the positive and negative sequence synchronous rotation coordinates respectively. The control of the positive sequence component allowed the DSTATCOM to compensate for the reactive current of the load, and the control of the negative sequence component made DSTATCOM to compensate for the negative sequence current caused by the unbalanced load. The experimental results show that the proposed control strategy can make the DSTATCOM effectively compensate the load reactive current and negative sequence current under the unbalanced load. The THD of supply current is obtained below 5% with unity power factor under different load conditions, and the grid side current is balanced which meet the requirements of National Standard.