Improved harmonic current detection for three-phase four-wire active power filter

Accurate and fast harmonic current detection plays an important role in determining the compensation performance of active power filters. In this paper, an improved three-phase four-wire harmonic current detection method is proposed by combining the traditional instantaneous reactive power theory with the FBD method. In this method, the algorithm complexity is reduced by cutting the unnecessary separation link of the zero-sequence current, and the matrix operations caused by the coordinate transformation in the traditional instantaneous reactive power method are also reduced, thus improving the real-time and dynamic performance of the harmonic current detection. Moreover, the zero-axiscurrent is compensated separately and the balance control of upper and lower capacitor voltages is conducted, so as to ensure the applicability of the active power filter of three-phase four-wire capacitors. In order to reduce the hysteresis error caused by the low-pass filter during the sampling and calculation and to improve the harmonic detection accuracy, an improved moving average algorithm is adopted to replace the low-pass filter. Finally, the feasibility and superiority of the proposed method are verified through the simulation and experiment in a three-phase four-wire active power filter. ©, 2014, South China University of Technology. All right reserved.