Abstract
Stand-alone Electrical microgrids (MGs) require power management strategies to extend the life-time of their devices and to guarantee the global power balance of non-critical loads such as lighting of small sections of an university campus or individual air conditioning systems. This paper proposes an energy management strategy (EMS) for an isolated DC microgrid formed by a photovoltaic system (PVS), an energy storage system (battery), and a noncritical load. This configuration enables the photovoltaic system to control the power generation and ensures that the storage element does not exceed the safe limits of the state of charge. To control the generation of the photovoltaic system, two operating modes based on the perturb and observe (P&O) algorithm are implemented. The first one performs a maximum power point tracking (MPPT) action, while the second one regulates the power generated by the PVS to match the load requirement (power demand tracking, PDT). The management strategy also considers different operating states for ensuring the battery safety: normal operation, overcharge (at the maximum state of charge), and bulk charge (at the minimum state of charge); in those states the disconnection/connection of both the battery and the load is also considered. The main contribution of this work is to design and test a control strategy for an EMS aimed at regulating a standalone microgrid based on a PV system and an energy storage device. This solution is validated using detailed MG circuital simulations, which includes the PV source model (single-diode model), lithium-ion battery model, constant power load model and the DC/DC converters equations; moreover, realistic power generation and demand from Universidad Nacional de Colombia, located at Medellín-Colombia, are considered. The results obtained demonstrate the effectiveness of the energy management strategy, and in this way, enable to extend the battery lifetime and reduce the costs associated to the maintenance and disconnection of the microgrid in educational buildings or other applications focused on this type of DC microgrid.
Highlights
The integration of renewable energy sources (RES) into electrical power systems has been an active field of study for more than ten years, which is usually oriented to reduce the environmental impact of energy generation and to increase the coverage of electrical networks [1,2]
In order to simulate the components of the stand-alone photovoltaic system (SPVS) and the control strategies, it was employed the specialized software PSIM
This work proposes an energy management strategy applied to a stand-alone DC microgrid formed by a photovoltaic system (PVS), a battery, a not-critical DC load, and a capacitor as a backup storage element
Summary
The integration of renewable energy sources (RES) into electrical power systems has been an active field of study for more than ten years, which is usually oriented to reduce the environmental impact of energy generation and to increase the coverage of electrical networks [1,2]. Photovoltaic systems (PVSs) are commonly included in DC MGs as DGs due to the wide availability of solar energy [12]; and the integration of a PVS, an ESS, and loads is known as a stand-alone photovoltaic system (SPVS) [13]. Such microgrid structure is commonly used in several applications that require a global power balance [39,40,41].
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