Xu Xiaogang

Repetitive control implementation with frequency adaptive algorithm for shunt active power filter

Shunt active power filter (APF), as parallel part of unified power quality modulation (UPQC), has been proved as a flexible solution for compensating the harmonic distortion caused by nonlinear loads in power distribution power systems. Digital repetitive control can achieve zero steady-state tracking error of any periodic signal under the sampling points within one repetitive cycle that must be a specific integer. However, the compensation performances of the APF would be degradation when the grid frequency varies. In this paper, an improved repetitive control scheme with frequency adaptive capability is presented to track any periodic signal with variable grid frequency, and then the variable delay items caused by time-varying grid frequency are approximated with Pade approximants. Additionally, the stability criterion of proposed repetitive control scheme is given. A three-phase shunt APF experimental platform with proposed repetitive control scheme is built in our laboratory. Simulation and experimental results demonstrate the effectiveness of the proposed repetitive control scheme.

Research on an improved fuzzy detecting algorithm of harmonic and reactive-power signals for the shunt APF

The harmonic and reactive current detection and analysis is a prerequisite to achieve the control of power quality, the accurate detection of harmonic and reactive current can provide a good basis for harmonic control. this paper proposes an improved harmonic and reactive-power current detection technique based on the fuzzy controller method combined with particle swarm optimization (PSO) for the APF, the PSO can enlarge the value range of the adjustment factor of signal parameters in the Fuzzy algorithm, the harmonic and reactive-power components can be detected fast and accurately. The proposed method has some advantages such as: This method omits the vector transform and low-pass filter, and the hardware cost of this method is low for no PLL circuit. Simulation and experimental results are utilized to prove that the proposed algorithm is simple and effective.