The levelized cost of electricity production is highly dependent on the cost of fuel oil on the world market. In order to reduce the dependency on the fuel oil, many countries are adopting an energy transition towards distributed generation. Distributed generation can be described as various means of generating electricity at or near where it will be used. Such generating mode can be a solar PV system, wind turbine generator and other renewable energy sources. However, it entails lots of challenges as it uses power electronics devices as the power grid interface, which causes a reduction in the system inertia and at the same time affecting the frequency, thereby affecting the stability. To enhance this stability, appropriate control measures need to be adopted. This paper brings forward a novel approach for frequency control support of a wind turbine generator (WTG) in a diesel generation mix. The novelty of this research paper explained on the concurrent application of a Proportional derivative (PD) and a Proportional Integral Derivative (PID) for speed and frequency control in a WTG. The analysis of this experimental research was carried out through the modelling of the rate of change of frequency (RoCoF) using MATLAB / Simulink software. The results showed that the use of these controllers in presence of WTG provide frequency support to the system as the frequency varied within the acceptable limit of ±0.5Hz. Additionally, this experimental research work also proved that the use of speed / governor control in form of the PID improved the RoCoF and provided an enhancement in the stability of the test system. Finally, this paper confirmed that the integration of WTG to the grid required the use of appropriate control algorithm for an efficient exploitation of this kind of renewable energy source.

The impact of previous energy crisis gives an insight into what happens when the oil price crashes. Μany countries were affected due the slow reaction in boosting the economic growth in key sectors such as oil-importing activities and the economic restructuring progress to face the challenges. But the present energy crisis resulting from the COVID-19 pandemic period and closure of many borders, has encouraged power distributors and generators to have recourse to renewable energy for grid integration. Countries such as USA, Germany, Italy, Spain and India are moving towards increasing the share of renewable energy on the grid. The increasing use of solar power systems over the past few years is being favoured for the decarbonization process. The percentage growth in integrating solar PV energy is forecasted to reach 23% in the future. This widespread application of renewable power energy sources (RES) such as wind and solar power comprise of many challenges namely power quality and stability. With this consequent increase in RES, synchronous generators are being displaced and replaced by power electronics grid interface, which reduces the overall rotating masses, hence the system inertia. Stability study in the presence of renewable energy is therefore an important aspect to be considered to meet the required power quality of the grid. This paper brings forward the use of equal area criterion (EAC) method for assessing the stability of the power system network with presence of renewable energy such as solar energy system in the generation portfolio. EAC provides an effective visual and analytical approach for transient stability analysis. The investigations have been performed within the steady and transient conditions in form of a 3-phase fault. The modelling and analysis were carried out using MATLAB/Simulink. Calculation of the critical clearing time (CCT) for stability assessment is the main contribution to knowledge. The increase in the CCT confirms that the Solar PV penetration to the grid will improve the transient characteristics of the national grid network.

The increased penetration of renewable energy sources in the distribution system affects the stability and efficiency of the system. To account for the intermittent nature of these sources, distribution network reconfiguration and the integration of custom power devices are important. This paper aims to identify the optimum location of photovoltaic systems and unified power quality conditioners in the distribution system considering economic and technical aspects. Three metaheuristic algorithms namely nondominated sorting genetic algorithm-II (NSGA-II), strength pareto evolutionary algorithm-2 (SPEA2) and multi-objective evolutionary algorithm based on decomposition (MOEA/D) were employed. Furthermore, three hybrid algorithms were developed by dividing the population into two parts. Multi-objective particle swarm optimisation (MOPSO) was applied in the upper part while NSGA-II, SPEA2 or MOEA/D was used in the lower part of the population resulting in three hybrid algorithms: MOPSO-NSGA II, MOPSO-SPEA2, MOPSO-MOEA/D. The simulation was performed on the IEEE-123 Node Test Feeder system using the OpenDSS and MATLAB environment. The performance of the proposed algorithms was compared according to their computation time and performance metrics such as pure diversity, generational distance and spacing. It was found that the hybrid algorithms enhance the convergence of the solutions to the true Pareto front. Combining SPEA2 or MOEA/D with MOPSO also reduced the complexity of the algorithms resulting in a lower simulation time.