Novel Harmonic Current Detecting Algorithm

Real time and accurate reference current signal is vital for active power filter(APF).So, a lot of method for harmonic current detecting have been proposed to improve the performance of active power filter. To avoid some shortages which exist in the harmonic current detecting methods now, such as time delay, large computation, and so on, an improved ip-iq algorithm based on instantaneous reactive power theory is presented. At first, this algorithm can simplifier the computation by omitting the process of changing between three phase and two phase. At second, this algorithm can detect the harmonic current effectively not only under the balanced power system, but also under the unbalanced power system too. At last, this algorithm can obtain the synchronous rotary angle used in the ip-iq transformation algorithm by using the single phase voltage, so eliminates the influence brought by the time delay of PLL when using traditional ip-iq transformation algorithm. Simulation and experiment results validate that the proposed algorithm can enhance not only the real time response of active power filter, but also its current tracking effect, and suits to the APF’s engineering application more.