Mitigating the effect of load shedding in electrical grid using hybrid renewable energy system approach

Abstract

Load shedding is an operating condition whereby the electrical grid is temporarily disconnected or suspended from the load. The idea is to minimize the deficit between generation capacity and load demand, while ensuring a fair level of supply availability for all consumers. Load shedding is a prominent problem for many developing countries and thus, this thesis investigates the prospects of hybrid renewable energy system (HRES) to mitigate its effect at the distribution level. The proposed HRES in this work is configured using the photovoltaic (PV) array, wind turbine (WT), energy storage unit (ESU) and diesel generator (Gen). Despite the substantial amount of literatures on HRES, limited work is directly related to load shedding mitigation in grid-connected system. Furthermore, it is unclear what would be the cost of installing HRES and under what operating conditions the system would perform optimally. Thus, the main design objective of the proposed system is to ensure supply availability with minimum levelized cost of electricity (LCOE) and payback period (PBP). A small residential locality in Quetta, Pakistan is selected as a case study to test the system. The proposed HRES is equipped with the energy management scheme (EMS), which is designed in MATLAB/Stateflow. The sizes of HRES components (i.e., PV, WT and ESU) are optimized by the grasshopper optimization algorithm (GOA) and the results are verified with particle swarm optimization algorithm (PSO). The objective function of the optimization is characterized by three variables: LCOE, PBP and the loss of power supply probability (LPSP). Scenario-based simulations are performed in MATLAB to validate the functionality of the EMS and the behaviour of optimized HRES for various load shedding and meteorological conditions. In addition, it is compared with the conventional solutions for load shedding, namely the diesel generator (only), uninterruptable power supply (UPS), and the combination of both. The results based on one-year climatic data shows that the LCOE for the HRES is 6.64 cents/kWh, with PBP of 7.4 years. The LCOE of HRES is 77.6% cheaper than the LCOE for generator (only), 49.8% for the UPS, and 66.7% for the combined solution. Accordingly, the PBP is also shorter compared to diesel generator (12.9 years), UPS (9.8 years) and the combined system (11.3 years). Furthermore, the integration of HRES alleviates the annual grid burden by 32.9, 47.2 and 42.3%, respectively. These results confirm the superiority of the HRES over the conventional solutions. Finally, sensitivity analysis is performed to observe the changes in the LCOE and PBP with respect to the variation in the components prices, feed-in-tariff rate, metrological conditions and load demand. It can be concluded that a well-designed and optimized HRES has the potential to effectively mitigate the problem of load shedding with reasonable cost.