Performance Evaluation of Current Control Algorithms Used for Active Power Filters

Hysteresis band instantaneous current control PWM technique is becoming popular due to its simplicity in implementation, fast current control response, and inherent peak current limiting capability. However, a current controller with a fixed hysteresis band leads to varying switching frequency and, thereby, non-optimum (unwanted) current ripples are generated in the load. This paper compares the performance of three hysteresis band current control algorithms used for shunt active power filters (APF). Each algorithm utilizes adaptive hysteresis band current controller, where hysteresis band is programmed as a function of supply voltage, capacitor dc voltage and the slope of reference compensator current wave. The algorithms are analytically derived to maintain the switching frequency constant. The APF is realized using three-phase IGBT based PWM voltage source inverter bridges with a common dc bus capacitor. A 3-phase diode rectifier with resistive-capacitive loading is used as the non-linear load. Comparisons of controllers are done based on various performance criteria such as total harmonic distortion (THD), current spectrum, rms of current error and dc bus voltage regulation with change in loading.