RESUMO
The Multilevel inverter (MLI) plays a pivotal role in Renewable Energy (RE) systems by offering a cost-effective and highly efficient solution for converting DC from Photovoltaic (PV) sources into AC at high voltages. In addition, an innovative technology holds immense significance as it not only enables the seamless integration of PV systems into the grid but also ensures optimal power generation, thereby contributing to the widespread adoption of RE and fostering a sustainable future. This paper presents a modified sinusoidal pulse width modulation (SPWM) control scheme for a three-phase half-bridge cascaded MLI-powered PV sources. The selection of the MLI configuration is motivated by its reduced number of switching components, which enhances system reliability and simplifies experimental implementation. Compared to the SPWM schemes which require (m-1) carriers that make the generation of the pulse circuit very complex, the proposed control scheme requires only three signals: a carrier signal, a triangular waveform, and a modulating signal. This approach significantly reduces the complexity of control and facilitates practical implementation. The proposed control scheme simulation is verified using MATLAB/SIMULINK Software. The grey wolf optimization (GWO) algorithm is implemented to determine the optimal switching angles of the proposed control scheme. The Total Harmonic Distortion (THD) objective is selected to be the fitness function to be minimized for improving the quality of the output waveforms. For verification, the results of the proposed GWO-based modified SPWM control scheme are compared with those obtained using both the Particle swarm Optimization (PSO) and Genetic algorithm (GA) used in the literature. Simulation results declared that the proposed control scheme improves performance, especially THD which is minimized to 6.8%. Experimental validation has been conducted by building a laboratory prototype of the proposed system. The experimental and simulation results gave acceptable and limited convergent results considering the experimental difficulties.
RESUMO
Although integrating a distributed generation (DG) into a distribution system (DS) has several benefits, it may be accompanied by some issues, such as ferroresonance. Therefore, ferroresonance investigations in an integrated DS with multi-DGs have been identified as a research gap. To this end, this paper presents a new method to mitigate ferroresonance in distribution networks, after which ferroresonance in an IEEE-33 bus radial DS integrated with multi-DGs was investigated. Here the RLC shunt limiter is introduced as a method for mitigating ferroresonance, including a design approach for adjusting its dimensions to fit the system. Investigations revealed that this shunt relied on the negative sequence detector to connect it to the system during ferroresonance. Finally, the effectiveness and superiority of the proposed method have been demonstrated by comparing its result with those obtained using other existing ferroresonance mitigation methods used in the literature.
