Rooftop Photovoltaic System with Battery Storage to Supply Power in a Sewage Water Pumping Station based Industrial Microgrid with Zero Grid Power

Abstract

Achieving zero grid power in systems that utilize solar photovoltaic (PV) energy is a challenging task. This is because of the varying power output of solar PV due to the changing weather conditions and the controls required for a three-phase system. A system that operates induction motor loads, such as in the water pumping plant, increases this difficulty due to their high starting currents and power requirements, which can cause large voltage dips in a grid-connected system, and can have an even larger impact on isolated ones. A battery energy storage system (BESS), consisting of a large lithium-ion battery, a bi-directional dc-dc converter and a bi-directional dc-ac converter is considered in this paper to normalize the output power. A model is developed to accurately simulate the motor loads and the control strategies to operate the system to consume zero grid power at all times. These strategies are designed to limit the transients in the system, as well as to mitigate voltage dips and swells to create a more robust micro-grid. The proposed strategies are then applied for use in a water pumping plant equipped with solar PV and BESS and the simulation results show that the proposed strategy is effective in ensuring that the plant can maintain a zero grid power consumption when sufficient capacities of the solar PV and BESS are available that can be allocated to generate and store the required energy to meet the varying load.