Dynamic Var/Harmonic Compensation with Inverter-Less Active Filters

Industrial plants are faced with stringent requirements enforced by the utility to meet power factor and power quality requirements. These plants, in order to avoid very costly penalties, have traditionally utilized switchable shunt capacitor banks with detuning reactors for power factor correction, along with a separate active harmonic filter in cases where harmonic currents are an issue as well. Alternate solutions such as SVCs and STATCOMs have been considered to be too expensive for use in industrial power conditioning applications. This paper proposes a dynamic capacitor (D-CAP) based on the family of inverter-less active filters (ILAF) that is able to provide a dynamically controllable capacitance with active harmonic compensation integrated onto the same unit. This new device is seen to be compact, and is likely to be cost competitive against simple switched shunt capacitors. It can maintain power factor close to unity, offering dynamic capabilities better than switched capacitors or SVCs, possibly lending itself for arc-furnace type of loads.