A Robust LQG Servo Control Strategy of Shunt-Active Power Filter for Power Quality Enhancement

This paper proposes a linear quadratic Gaussian (LQG) servo controller for the current control of shunt-active power filter (SAPF) operating under balanced and unbalanced supply voltages. This LQG controller is comprised of a LQ regulator and a Kalman filter (KF) that minimizes the error between the output currents and their variations. A feedback compensator is used in LQG servo controller that benefits an SAPF system by increasing tracking error reduction, gain stability, reducing amplitude distortion and sensitivity to external disturbances. A KF-based new reference current generation scheme is developed here to resolve the difficulty of tuning gains of a proportional integral controller and for avoiding the use of voltage sensors making it cost effective. Consequently, this reference scheme has self-capability of dc-link voltage regulation by adaptively estimating the peak value of source reference current with changing load conditions. The control algorithm is embedded in SAPF using a MATLAB/Simulink software environment. The effectiveness of the proposed LQG ServoKF algorithm is evaluated through comparison with an existing LQRKFalgorithm and then validated with experimental studies pursued using a dSPACE1104 computing platform. From the obtained experimental and simulation results, it is observed that the proposed control strategy exhibits superior performance in terms of robustness improvement and current harmonics mitigation under steady-state and dynamic load conditions, thus making it more effective for practical applications.