Study On Instantaneous Comparison Control Strategy For Active Power Filter

The widespread use of nonlinear loads is leading to harmonic problem becoming increasingly serious in power system, so it is in urgent need of compensation for the harmonics. Recently active power filters (APF) is a viable equipment to eliminate the harmonics and its performance depends on the method and the control techniques. This paper studies control methods of APF and the main contents are as follows:At the beginning, several one-cycle control (OCC) strategies in single-phase APF are illustrated and their principles are presented in the paper, the stability of OCC approaches is analyzed and compared. The analysis results show that under same circuit parameters double-direction compensation control strategy is most stable, besides, by means of double-direction compensation control strategy the global stability can be realized.Because the time-control instantaneous comparison method has a problem of localized instability when it is used in APF, this paper presents an improved method based on double-direction compensation control strategy and researches its simulation. Simulation results verify that, compared with the typical time-control instantaneous comparison method, the stability region is enlarged and the error between compensating current and referenced signal is reduced by the double-direction compensation instantaneous comparison controlled APF in single-phase and three-phase system.Furthermore, double-direction compensation instantaneous comparison controlled APF without current-detection circuit is presented. The novel APF consults the OCC APF to let input current follow input voltage change and needn't detect current, thus the system circuit simplification. In contrast with double-direction compensation OCC controlled APF, the double-direction compensation instantaneous comparison controlled APF without current-detection circuit has a simple circuit, an easy control and a good compensation performance. Simulation results prove that the harmonic and reactive current is eliminated by the proposed scheme not only in single-phase but also in three-phase system. Finally, the experimental research of single-phase APF with double-direction compensation instantaneous comparison control is built based on the simulation and experiment sample is obtained. The experimental results confirm the feasibility of this scheme.