Instantaneous Reactive Power Control Based on Five-Level Inverter for Grid Connected PV System Improvement

Abstract

Grid-connected photovoltaic systems have become the most important and popular use of the solar energy. In this paper, a photovoltaic system connected to a three-phase network is presented. The system is connected in a single step using a five-stage voltage source inverter to improve the quality of the power in the distribution system. The control strategy applied for the optimal operation of the photovoltaic system is based on the theory of instantaneous reactive power. This strategy is simple and has the advantage of running the system all day without using Phase-Locked Loop (PLL). The multilevel inverter switching signals are derived from the Pulse Width Modulated Current Controller, which provides good dynamic performance in both steady state and transient conditions. The voltage of the continuous bus capacitors is controlled using the PI controller. The validation of this proposed system is carried out through simulation with different levels of irradiations and by a comparison with the performance of a two-level inverter used in the original configuration. This specific configuration shows good results regarding the waveforms of the voltages and the output currents as well as the level of the quality of the energy represented in this paper by the THD parameter that has been studied in comparison with the two-level converter.