Hardware realization of proportional-resonant regulator based advanced current control strategy for cascaded H-bridge inverter based shunt active power filter

Multilevel inverter based shunt active power filter is cost-effective and decisive solution for mitigating numerous power quality problems in case of medium-voltage distribution sector. Performance of the filtering unit and nature of source current mainly depends on current control loop of control algorithm. Conventionally, proportional-integral controllers are used in current control loop for AC current controllability, but it suffers from severe problems, namely, magnitude and phase error in steady-state conditions. This paper presents an advanced current control loop that consists of a new breed of compensator called proportional-resonant compensator for cascaded H-bridge multilevel inverter based shunt active power filter in order to maintain zero steady-state current error. Stability of proposed current control loop and closed-loop control mechanism is extensively checked and analyzed using transfer function approach and root-locus criteria. A complete mathematical analysis of the proposed control system has been presented, and parameters of proportional-resonant regulator are finely tuned using bode plot technique. The performance of proposed control mechanism is tested using MATLAB/Simulink. A detailed experimental analysis has been carried out to verify effectiveness of the proposed controller over conventional one. Source current waveform becomes sinusoidal, and harmonic limits are in compliance with IEEE-519 standard after successful operation of filtering unit.