Voltage stability and PQ analysis of a PV solar grid-connected system under varying weather conditions in Oman

Abstract

This paper studies the voltage stability and power quality (PQ) of a 128 kW grid-connected photovoltaic (PV) system installed at a school in Al-Hamra, Oman, by using a MATLAB/Simulink model. An incremental conductance maximum power point tracking (MPPT) algorithm is used to control the duty cycle of a DC/DC boost converter and to keep the DC-link voltage almost constant at about 498 V for different solar irradiance levels. A rotating d-q control strategy is applied to the voltage source converter (VSC) to generate balanced three-phase currents with a high power factor while the PV system partly supplies an average 400 kW school load and the remaining power is taken from the local distribution network. Steady-state and transient simulations with real irradiance and temperature data are carried out to examine the system performance during sudden changes in irradiance, load, and grid conditions such as voltage sags. The results show that the proposed control scheme keeps the DC-link voltage stable, reduces overshoot during disturbances, and achieves good power quality at the point of common coupling, with THDi of about 1.45%. Although this work is based only on simulations, it confirms that the controller can operate robustly under different weather and operating conditions and can help the integration of solar PV into the Omani distribution network.