Output Voltage Harmonics Mitigation in Static Frequency Converter for Shore to Ship Power Connection Supplying Nonlinear Loads using Multi-frequency Quasi Resonant Controller

Abstract

Static frequency converter (SFC) is considered one of the main parts of the shore to ship power connection to match the frequency between the utility grid and ships docked at berth. Onboard nonlinear loads such as diode rectifiers and LED lamps distort the SFC output voltages with 3rd, 5th and 7th harmonics. Passive and active filters are usually used to mitigate these harmonics which increase the overall size and cost and reduce the system reliability. This paper proposes a multi-frequency quasi resonant harmonic compensator (MFQR-HC) for compensating these harmonics. The SFC mathematical model is presented, and the corresponding transfer functions are obtained. The proposed control system is designed in the stationary reference frame and analyzed in frequency domain considering reference tracking and disturbance rejection capabilities. The system has been tested in simulation using MATLAB/SIMULINK with linear and standard nonlinear load. An experimental setup is implemented to validate the simulation results. The experimental results confirm the satisfactory operation of the SFC with the proposed controller to achieve perfect tracking of 60 Hz reference signals and rejecting 3rd, 5th and 7th harmonics successfully. Eventually, Total Harmonic Distortion (THD) under nonlinear loads is reduced to meet the international standards.