Efficient multiple-reference-frame controller for harmonic suppression in active power filters

Abstract

Active power filters are often proposed as flexible solutions to tackle power quality problems in electric distribution systems. The need of tracking harmonic currents and voltages with these electronic devices exceeds the capabilities of conventional Proportional%2BIntegral controllers and more sophisticated algorithms are sought. This paper presents a control method based on multiple reference frames for tracking or rejecting periodic signals in this context. The proposed scheme allows recursive calculation when referring signals to reference frames rotating synchronously with harmonic equivalent space vectors whilst only a very small number of trigonometricfunction evaluations are required. This gives an accurate, efficient and intuitive harmonic controller. Furthermore, using the proposed approach, the control of each harmonic can be dealt with using simple Integral controllers. This paper explains the algorithm implementation and investigates its performance when tackling current harmonics of non-linear loads in power systems. In addition, a rigorous closed-loopstability analysis is carried out. The same controller is easily designed for all harmonics with the help of the compensation of the plant frequency response at the targeted frequencies. Detailed simulation of a shunt active power filter is provided to validate the main contributions of the paper. A scenario with grid-frequency variations is considered to evaluate the adaptation capability of the proposed controller.