Study On Control Approaches For Three Phase Shunt Active Power Filters

As harmonic interference problems generated by bulk thyristor converters become increasingly serious as they are widely used in industrial applications and transmission/distribution systems, compensation for harmonic and reactive currents becomes important. Traditionally, passive LC filters have been used to eliminate line current harmonics and to increase the power factor. However, in practical applications these passive filters present many disadvantages, such as aging and tuning problems, series and parallel resonances and others. In order to overcome these problems, many compensated methods based on the technique of power electronics have been researched and developed recently, one of them is active power filters, which have gradually been recognized as a feasible solution to the problems created by nonlinear loads.Firstly the background, development and future prospect of active power filter are described in detail, and it comes to the conclusion that active power filter has many merits and functions including harmonic compensation, reactive power compensation, voltage regulation and flicker suppression. Different control approaches for active power filters are analyzed, and space vector based hysteresis control and one cycle control are discussed extensively.Compared with traditional SPWM control, SVPWM control is more superior in improving wave quality, reducing switching frequency, enhancing utilization of DC voltage. In this thesis a novel simple space vector current control strategy is presented, and it is based on three-level hysteresis comparators which select appropriate inverter voltage vectors via switching table. This guarantee a precise zero voltage vector selection and therefore leads to decreasing of inverter -switching frequency. The regulator works with the current components represented in a stationary coordinate system α-β , and it is able to suppress the high harmonic current in steady-state and give the quick...