Real-Time Solar–Diesel Generator Power Coordination for Industrial Loads Under Grid Outage Conditions

Abstract

There is a growing interest from opinion-making bodies and the government to promote the use of solar photovoltaic (PV) systems in the industrial sector. But most grid-connected solar PV plants are equipped with anti-islanding protection that causes the solar inverter to disconnect immediately when the utility grid is down. While this protection helps ensure the safety of utility employees and equipment, it also means that solar energy cannot be used during outages. As such, the industry relies almost entirely on diesel generators (DGs) for power supply, even during the day when solar power is available. The SABIC Research and Technology Centre in Bangalore has a 540-kW grid-connected rooftop solar photovoltaic system. The site consumes about 2,160 kWh of electricity per day. The solar plant indeed makes a noticeable contribution to the load under normal conditions. However, the PV system shuts down during grid power outages due to anti–islanding protection, and the facility runs on DG power only, even though solar power is available. This bottleneck has cost the facility nearly 2.4 lakh kWh of potential solar energy generation over the last two years alone, leading to increased diesel use, higher operating expenses, and higher carbon emissions. This study presents a real-time solar–diesel generator coordination control strategy that enables high penetration and controlled use of solar power during grid outages. The proposed controller adaptively adjusts the output of the solar inverter based on the load demand, the diesel generator's operating limits, and the system voltage and frequency. It also prevents reverse power flow to the diesel generator and maintains a minimum spinning reserve for stable operation. The discussed system is simulated and modelled in MATLAB/Simulink. Simulation results demonstrate that different scenarios were analysed, including grid outage, load variation, and solar generation fluctuation. The simulation results show that the presented scheme can maintain stable system voltage and frequency and maximise solar power utilisation. The system significantly reduces the diesel generator load and fuel consumption, improving energy efficiency and environmental friendliness for the industrial plant.