Adaptive Dual-MAF Weighted SRF-PLL with Online Self-Tuning PI Control for DSTATCOM Power Quality Enhancement

Abstract

This paper proposes an Adaptive Dual-Moving-Average-Filter Weighted Synchronous Reference Frame Phase-Locked Loop (Adaptive Dual-MAF Weighted SRF-PLL) with online self-tuning proportional–integral (PI) control for power-quality enhancement using a three-phase Distribution Static Compensator (DSTATCOM). The proposed synchronization scheme processes the quadrature-axis phase-error signal through parallel short- and long-window moving-average filters to combine fast tracking with improved disturbance attenuation. Unlike fixed-weight structures, the relative contribution of the two MAF outputs is adjusted online using a normalized-gradient adaptation law with projection and complementary-weight constraints. A bounded disturbance index is additionally employed to regulate the adaptation rate and PLL dynamics according to the instantaneous synchronization condition. Online adaptive self-tuning PI regulators are incorporated into the DC-link and PCC-voltage control loops to accommodate variations in operating conditions while maintaining bounded controller gains. The complete control scheme is implemented on a SPARTAN-6 FPGA-based DSTATCOM prototype and experimentally evaluated under nonlinear, unbalanced, and dynamic load conditions. The measured RMS source currents are 6.98A, 6.93A, and 7.00A for phases a, b, and c, respectively, with corresponding current THDs of 3.52%, 3.49%, and 3.91%. The experimental results further demonstrate balanced source currents during load asymmetry, effective reactive-current compensation, and stable regulation of the 220-V DC link during load transitions. These results confirm the suitability of the proposed adaptive synchronization and control structure for real-time DSTATCOM-based power-quality compensation.