Enhanced UPQC Control System for Power Quality Improvement in Wave Energy-Driven PMSG Systems

This study pioneered the use of UPQC in a wave energy-driven PMSG system for power quality improvements. Various fault sand harmonics cause PQ issues in the proposed system. An enhanced control scheme of the UPQC is proposed to mitigate the PQ issues. A three-phase FFSOGI-QT1-PLL is proposed to fast and accurately extract the fundamental frequency component of the load current for use in the control of parallel converter while single-phase FFSOGI-QT1-PLL has been utilized to identify voltage faults with the series converter control at the generator side. The test results of this method compared to the methods in the literature show that the proposed method stands out better against source voltage faults, unbalanced and highly inductive non-linear various load conditions. In comparison to traditional PI, a new N-PI for the DC-bus voltage control is adopted to provide better tracking performance with lower voltage errors/oscillations, to suppress voltage overshoot and to accelerate the start-up process of the system dynamics. With the proposed control method of the parallel compensator, the DC-bus voltage deviation is kept with 0.2 V ∼0.5 V , the THD of the source current in all cases is kept around 1.5 ∼2.0%, and the THD of the load voltage is less than 1.0% complying with the IEEE standard. Control system presented in this work enhance the dynamic performance of the system under voltage conditions at the generator side and sudden load change. Comprehensive validation results are provided to demonstrate the advantages of the proposed approach over the conventional counterpart.

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