Research on DC-Link Ripple Voltage Compensation for Single-Phase Photovoltaic System by Frequency Analysis

Photovoltaic systems are generating interest as efficient renewable energy sources owing to the lowering of the price and cost of power generation with the progress of research and development. In a single-phase photovoltaic power generation system, a 120 Hz ripple voltage occurs in the DC-link capacitor due to the use of a full-bridge inverter. The ripple voltage affects the inverter controller and generates harmonics in the inverter current, thereby increasing the current distortion. By compensating for the 120 Hz ripple voltage, the influence of the ripple can be reduced, and thereby the current distortion can be decreased. However, conventional compensation methods increase the number of calculations, and errors occur because the parameters of the passive element in the inverter are used for the calculation. In addition, errors are caused by the phase delay and gain reduction of the low-pass filter used in the inverter. The proposed ripple compensation method was developed that reduced the computation time using the Goertzel algorithm and reduced errors by reflecting the phase delay and gain reduction of the filter. Simulations were performed using PSIM software to confirm the proposed method. The proposed methods were confirmed using the same hardware as in the simulations.