A Study of Active Power Filters Applying Space Vectors and their Compensation Algorithm

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In recent years, active power filters have been studied and developed to suppress harmonics generated by static power converters. Notably, attention has been paid to the active power filter using switching devices such as power transistors and gate-turn-off thyristors, which have made remarkable progress in capacity and switching performance.In this study, the compensation algorithm of the active power filter is proposed on the basis of the instantaneous reactive power applying space vector theory. This is quite different in principle from the conventional compensation algorithm, thus giving better compensation characteristics in transient states. An experimental active power filter was constructed, of rating 7kVA. The power circuit consisted of quad-series voltage source PWM converters using 24 power transistors. The main purpose of the mutiple converters was to suppress the harmonics caused by the switching operation without increasing the switching frequency.The validity of the active power filter was comfirmed experimentally. A three-phase thyristor bridge converter of rating 20kVA was used as an example of harmonic current generators. It was verified that the harmonic current can be fully eliminated not only in steady state but also in transient states, applying the compensation algorithm developed in this theory. The total efficiency of the active power filter was 90-92 percent, including the loss of the multiple converters.