Active power filter system for compensation of reactive power and harmonics of high power three-phase load

Abstract

General active power filter system is divided as the following three branches, that is, FACTS (Flexible AC Transmission System) for terminal voltage stabilization of transmission line, SVC (Static Var Compensator) for reactive power compensation of load and active power filter for load harmonic compensation.AB In this thesis, three active power filter systems are presented for compensation of reactive power and harmonics of high power three-phase load. From this, it results in more accurate phase angle synchronization with ac source in high power SVC (Static Var Compensator), active filters of both simple structure without tuned filter and low cost with low DC voltage. At first, a control for high power SVC using novel software vector product phase locked loop (VP-PLL) is introduced for synchronizing its phase angle more accurately. in the meantime, the presented VP-PLL has much better performance than the conventional hardware PLL in higher power application because maximum controllable phase angle becomes smaller in that case. Thus, the overall controller has dual loop structure composed of inner VP-PLL for phase angle synchronization and outer Q-loop for reactive power compensation of load. Its performance is verified through experiments of 100 kVAR power capacity in case of stand-alone and load linked system operation. Secondly, a new active filter composed of filter capacitor without tuned filter is proposed for harmonic compensation of load, from which there exist no shift of resonant frequencies caused by aging of devices, no bulky inductors. Size of filter capacitance is selected considering minimum power rating of the converter. Also, frequency analyses in terms of open and closed loop are achieved for design of controller, from which harmonic load current is compensated by a simple current control using instantaneous pq-theory. Finally, the usability of the presented topology is confirmed through 10kVA simulation and 1kVA experiment with 6-pulse diode...