一种精确检测三相不对称系统中各次谐波的新方法

本文提出一种精确检测不对称系统中各次谐波正负零序分量的新方法。该方法不直接采用对称分量法,而通过广义d_k-q_k旋转坐标变换,分别对三相电流按照相序a-b-c和a-c-b进行两次低通滤波得到三相电流的正、负序分量,同时分解零序分量,并通过低通滤波得到任意次谐波电流的零序分量。最终将对应分量求和得到检测结果。仿真分析表明,该方法无论三相电路电压是否畸变,都能够得到精确的检测结果。对于三相不对称系统(包括缺相),仍然可以精确检测出任意次谐波电流,并可用于基波有功和无功电流的检测。因此,它可应用于电力系统故障检测、保护和电力有源滤波器谐波电流检测中。

New Method of Harmonic Current Detection for Threephase Unbalanced System

The paper proposes a novel method of harmonic current detection for three-phase unbalanced system,which can detect the positive,negative and zero-sequence components of any term harmonic current precisely.While not adopting the symmetrical compo- nents method directly,the three-phase current is transformed to generalized d_k-q_k coordinate firstly,then filtered by low pass filter and inverse transformation,therefore the positive sequence component is detected.Only change the phase sequence from a-b-c to a-c-b,the negative component can be detected similarly.Meanwhile,the zero-sequence component is decomposed and filtered by low pass filter to obtain the zero-sequence component of any term harmonic current.Finally,sum the three components correspondingly to obtain the de- tect result.The simulation result shows that this method can detect any term harmonic current effectively and precisely nevertheless the distortion and asymmetry of three-phase system.It can also be used as the detection of active and reactive components of fundamental current It can be widely applied to fault detection,protection for power system and active power filter.