Improve power quality and stability of grid - Connected PV system by using series filter

As the world increasingly focuses on renewable energy sources, grid-connected PV systems will continue to play a critical role in meeting our energy needs. This integration has brought many benefits, but has also created various problems related to power quality and stability at the connection points. Various techniques are used to improve the power quality, such as passive filters, tuned passive harmonic filters, and active filters. This paper presents the use of a series active filter on the DC side of grid-connected PV systems to improve their power quality, stability, and dynamic performance. The proposed filter consists of an inductor, two capacitors, and four transistor-diode pairs, the operation of which is controlled by a sinusoidal pulse width modulation (SPWM) scheme. The MATLAB/Simulink is used to build and validate a comprehensive mathematical model of the studied system. The transfer function of the system is identified and its transient response is studied under various test input signals. A Bode plot is also generated to assess the impact of the integration of this component on the stability of the system. The results showed that incorporating the filter resulted in a significant reduction in the total harmonic distortion factor (Thd%) for both the voltage and current waves at the inverter output. Moreover, it improved the transient response characteristics of the system by significantly reducing the maximum overshoot value of the system response with respect to the test input signals. The results indicate that the stability of the system is improved after the filter addition, as evidenced by the increased gain margin and phase margin in the system Bode plot.