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Perfect power system voltage stability is not possible in practice. Generally, the power grid is continually exposed to changes in its load and operating conditions. Therefore, dynamic stability analysis is one the most important and effective elements for greater security, stability and reliability of planning, design, operation and economic aspects of electric power networks. This study investigates and reports on the dynamic stability of the power system with a large‐scale photovoltaic system (L‐S PV). Two different scenarios with centralised PV power plants are considered in the medium voltage level without voltage regulation capabilities. Simulation results with these scenarios will show how the voltage instability decreases with the L‐S PV based on the bus status, disturbance location, and disturbance duration. In addition, the study discusses network terminal voltage, generator's rotor angle, generator's terminal current, generator's reactive power and electrical power output. This study is an extension of the earlier published conference paper. [ABSTRACT FROM AUTHOR]

Partial shading of a photovoltaic (PV) installation has an inconsistent impact on power production. This study investigates the effect of partial shading on PV performance. The experiments were carried out with a 90‐W PV module under both variable and constant irradiations with shaded area increased from 0 to 80% to observe the effect of variable solar radiation at certain shading points. The effect of shading under irradiation levels from 300 to 800 W/m2 was investigated. At a 600 W/m2 irradiation level, the shading impact factor was 1.25 with a 25% shading, while at 75% shading the impact factor decreased to 0.86. Results also show that for every 100 W/m2 increase in irradiation level, the electrical power output was enhanced by 3.89, 3.37, 2.27, and 2.02 W at 0, 25, 50, and 75% shading, respectively. The efficiency level was increased by 0.29, 0.27, 0.25, and 0.22% at 0, 25, 50, and 75% shading, respectively. Increasing the shaded area by 10% causes a 12.41 W drop in power output and a 2.3% drop in electrical efficiency. Partial shading not only deteriorates the PV performance, but also causes long‐term degradation of the module. [ABSTRACT FROM AUTHOR]