Minimizing energy storage utilization in a stand-alone dc microgrid using photovoltaic flexible power control

DC microgrids with photovoltaic (PV) systems often incorporate a battery energy storage system (BESS) to regulate the dc bus voltage fluctuations due to the intermittent irradiance changes and load transients. Traditional control schemes do not consider the battery charging rate, leading to high current stress and shortening the battery lifetime. In this paper, a coordinated control for a PV system and the BESS is proposed, which implements a deterministic rule-based control strategy that regulates the battery charging rate depending on the available PV power reserve and the battery state-of-charge. Furthermore, the proposed control considers the PV system as the primary dc voltage regulator and treats the BESS as a secondary voltage regulating resource. The performance of the proposed control is investigated via simulation results.Index terms-Battery energy storage system (BESS), dc microgrid (dcMG), photovoltaic (PV) system, rule-based control.

Reduced battery usage in a hybrid battery and photovoltaic stand-alone DC microgrid with flexible power point tracking. IEEE Energy Conversion Congress and Exposition (ECCE), 3894-3899.

Conventionally, a flexible photovoltaic (PV) power control strategy is used to reduce battery utilization in stand-alone dc microgrids (dcMGs). However, conventional control schemes deploy multiple voltage controllers to regulate the dc-link voltage, causing mode transitions during the transients and complicating the controller design. This paper proposes a simplified control strategy for the PV system and the battery energy storage system in a standalone dcMG with a single voltage controller to regulate the dc-link voltage. The proposed control strategy enhances the transient response of the system by eliminating the mode transitions between voltage controllers and simplifying the hybrid control scheme while reducing the battery utilization. Additionally, the proposed solution does not require the knowledge of the load, which facilitates its application. The effectiveness of the proposed control strategy is validated with simulation results.Index terms-Battery energy storage system (BESS), battery state-of-charge (SoC), dc microgrid (dcMG), flexible power point tracking (FPPT), photovoltaic (PV) systems.

In stand-alone dc microgrids, battery energy storage systems (BESSs) are conventionally used for regulating the dclink voltage, causing a continuous battery operation. Though operating the photovoltaic (PV) system at its maximum power point yields minimum battery discharge current, the opposite is true for battery charging current. Therefore, reducing the battery charging current based on its state-of-charge (SoC) and the amount of available PV surplus power (which can be treated as virtually stored energy) is an opportunity for improving the battery life. The main objective of the control strategy proposed in this paper is to prolong the battery lifetime by reducing the charging current and keeping the battery SoC at lower values if the PV power is enough to supply the loads. Additionally, the PV system is used as the primary asset to regulate the microgrid voltage. The dynamic performance of the proposed control strategy is validated with experimental tests under various operating conditions. Furthermore, its effectiveness in prolonging the battery lifetime is evaluated using an aging model of a Li-ion battery (without loss of generality) by simulated case studies.