无锁相环i_p-i_q检测任意次谐波电流的新方法

New Algorithm for Random Harmonic Current Detection Using i_p-i_q Without Phase Lock Loop

电力有源滤波器是补偿电力系统谐波及无功功率的重要装置,其关键的环节是实时准确地检测出谐波电流。为了检测出任意次谐波电流,消除其对电网的危害,提出了基于瞬时无功理论的无锁相环ip-iq检测方法,该法可检测三相三线制不对称系统任意次谐波的正、负序分量,并将其相加得到任意次谐波电流,而无锁相环ip-iq检测法中的变换矩阵中的频率换为一个固定值可省去传统ip-iq检测方法中锁相环,简化了电路。理论分析表明,ip-iq变换过程中频率偏差不影响检测结果,且可通过设置变换矩阵频率实现对任意次谐波的检测。仿真结果证实了本文所提出新方法的准确性。

In order to detect the random harmonic and eliminate the harm of harmonic to the power system, this paper put forward a new detection method based on the instantaneous reactive power theory without phase lock loop （PLL）. This new method can detect positive and negative sequence components of random harmonic current respectively under three-phase asymmetrical system which is not influenced by voltage and can be applied to unbalanced load current, then the detected positive, negative phase sequences can be summed up to obtain the random harmonic current. In the new method, the transfer matrix is replaced by a fixed value because of the error will be eliminated. The new detecting harmonic current method gets rid of the PLL circuit, the benefit of the new method without PLL circuit is apparent. It not only saves the cost but also gives the more precision results. Theoretical analysis show that in the ip-iq transformation processes the detection results will not be influenced by frequency offset. This paper gives the principle of the arithmetic. The method is simulated by the Matlab software. The results from the simulation prove the correctness of the algorithm. At last, the paper points out that the new method can be applied to the single-phase circuit, so this method is available.