Abstract
Auxiliary services are vital for the operation of a substation. If a contingency affects the distribution feeder that provides energy for the auxiliary services, it could lead to the unavailability of the substation’s service. Therefore, backup systems such as diesel generators are used. Another alternative is the adoption of a microgrid with batteries and photovoltaic generation to supply substation auxiliary services during a contingency. Nevertheless, high battery costs and the intermittence of photovoltaic generation requires a careful analysis so the microgrid capacity is defined in a compromise between the investment and the unavailability reduction of auxiliary services. This paper proposes a method for the capacity sizing of a microgrid with batteries, photovoltaic generation, and bidirectional inverters to supply auxiliary services in substations under a contingency. A set of alternatives is assessed through exhaustive search and Monte Carlo simulations to cater for uncertainties of contingencies and variation of solar irradiation. An unavailability index is proposed to measure the contribution of the integrated hybrid microgrid to reduce the time that the substation is not in operation. Simulations carried out showed that the proposed method identifies the microgrid capacity with the lowest investment that satisfies a goal for the unavailability of the substation service.
Highlights
Substations are one of the main components of electrical power systems
13, 6037 the unavailability time in each interruption it is important to know both the energy requested by the Auxiliary services in substations (ASS) loads and the total energy available from the microgrid, which depends on the energy in the battery system and the energy generated by the photovoltaic panels during the Generalizing the calculation above, the general load factor can be written as shown in Equation (7): contingency
This paper addresses the optimal sizing of a microgrid for the reserve supply of the substation’s auxiliary services intending to reduce the time of unavailability of these loads when the main supply is under contingency
Summary
Substations are one of the main components of electrical power systems. They serve to modify the voltage level and allow basic maneuvering of power flow within the system. Hybrid microgrids are combinations of alternative energy sources and energy storage systems to provide energy for a particular purpose Both resources can be directly connected to the DC bus of the substation, but DC-AC inverters are necessary to power the AC bus; bidirectional inverters are capable of convert AC to DC, which is convenient in cases where the energy storage system requires to be charged by the AC supply instead of the photovoltaic generation. A two-part work makes first a critical analysis of the different types of fuel-cells for energy supply that can be a backup or main source [1]; they can be combined with other technologies such as a photovoltaic generation to support an electrolysis system and produce hot water for other uses; the second part discusses a case study of the use of fuel-cells in a real substation in Romania, bringing economic information of three possible uses for the fuel-cells [25].
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