The paper investigates the system efficiency for power distribution in residential localities considering daily load variations. Relevant system modeling is presented. A mathematical model is devised, which is based on the data from the Energy Information Administration (EIA), USA, for analysis. The results reveal that the DC distribution system can present an equivalent or even better efficiency compared to the AC distribution network with an efficiency advantage of 2.3%, averaged over a day. Furthermore, the distribution systems are compared under various capacities of solar PV accounting for the effect of variation in solar irradiation over time.

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This paper presents the modeling, simulation and control of a grid connected doubly fed induction generator (DFIG) coupled with the wind turbine. Among all the renewable energy resources, wind energy is rapidly gaining interest of developed as well as underdeveloped countries. Due to the increase in demand of electrical energy and increase in environmental pollution the use of wind energy to meet the domestic and industrial power demands is essential and inevitable. The main benefit is the production of economically justified and ecofriendly energy in bulk quantity. Because of the irregularity of wind speed, the output of wind turbine varies and that is why, variable speed wind turbines are more practical these days. In order to integrate the variable output of the wind turbine with the power grid, doubly fed induction generators are used due to their inherent advantages like active and reactive power control, absence of large capacitive banks and improved power quality. A DFIG is modeled using the electric equivalent circuit and dq 0 transformation along with the stator flux oriented vector control approach is used to decouple active and reactive power. Back to back power converters serve the purpose of controlling active and reactive powers at sub/super synchronous speeds. So the implementation of the proposed scheme ensures the constant output frequency and voltages with the control of active and reactive power and is highly suitable for grid integration in Distributed Generation (DG) Applications. The proposed scheme is implemented in SIMULINK / MATLAB environment and the simulation results validate the efficacy of the proposed scheme.

Summary Many countries in the developing world undergo regular power outages (scheduled and nonscheduled) due to lack of sufficient generation capability or transmission and distribution bottlenecks. Therefore, uninterruptible power supply (UPS) systems are commonly installed to critical power loads during daily power outages. While the integration of solar photovoltaic (PV) with these UPSs has seen rapid growth in recent years, their incorporation in conventional topologies is highly suboptimal. Therefore, in this work, we formulate a mathematical framework for optimal solar PV integration with domestic UPS systems for minimum cost solution incorporating all relevant system constraints and requisite system losses. We also propose and develop a retrofitting technological solution to integrate solar PV with typical UPS systems for optimal system operation. Results show that the proposed methodology and system implementation can achieve cost savings of up to 40.6% compared with conventional UPS system (without solar) in typical scenarios. In addition, with the proposed optimized utilization of PV, the grid utilization is decreased by 75% compared with the conventional case where UPS is integrated with solar using standard maximum power point charge controllers. This work is therefore highly useful for many developing regions with intermittent grids.

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