直接计算法的本质及其检测性能

为了研究直接计算法这种检测有源电力滤波器谐波电流的检测性能,首先根据非线性负载电流的傅立叶级数表达导出基于离散傅立叶级数的谐波电流检测方法;然后证明直接计算法和基于离散傅立叶级数的谐波电流检测方法的计算公式相同,从而证明直接计算法和基于离散傅立叶级数的谐波电流检测方法在本质上完全一致;最后以直接计算法的本质和非线性负载电流的傅立叶级数表达为依据,阐释了直接计算法检测性能的结果,即:当负载电流在一个周期内的采样个数足够大并且负载电流处于稳定状态时,由直接计算法计算的基波有功电流幅值准确;当负载电流处于变化状态时,由直接计算法计算的基波有功电流幅值能够缓慢平滑跟踪基波有功电流真实幅值;若使用一个周期内的采样数据进行计算,则直接计算法的动态响应时间为1个周期;若使用0.5个周期内的采样数据进行计算,则直接计算法的动态响应时间为0.5个周期。

Essence and Detection Performance of Direct Computation Method

To study its detection performance of direct computation method,which is a detection method of harmonic current for active power filter,according to the Fourier series' expression of non-linear load current,the harmonic current detection method based on discrete Fourier series is educed.Thereafter,it is proved that the computation formulae of direct computation method and the harmonic current detection method based on the discrete Fourier series are the same.These explain that direct computation method is essentially consistent with the harmonic current detection method based on the discrete Fourier series.Finally,according to essence of the direct computation method and Fourier series'expression of non-linear load current,the detection performance of direct computation method is explained as follows.When the sampling number in a cycle is adequately large and load current is placed in stable state,the amplitude of fundamental active current calculated by the direct computation method is exact;when load current is placed in varying state,the amplitude of fundamental active current calculated by the direct computation method can slowly and smoothly track the true amplitude of fundamental active current;if the sampling data in a cycle are used to calculate,the dynamic responding time of direct computation method is a cycle;if the sampling data in half a cycle are used to calculate,the dynamic responding time of the direct computation method is half a cycle.