Synthesis of Microgrid Model for Scalable Hybrid Renewable Energy Power Generation

Renewable Energy Sources (RESs) such as solar, wind, and biodiesel are considered clean energy sources for power stations. However, the difficulty in extracting power from these RESs is due to dynamic fluctuations in weather parameters, especially in wind and solar PV systems. Besides, using solar PV-wind power generation in stand-alone mode would require larger storage devices to compensate for the fluctuating nature, which would make the overall system more expensive. Hence, a proposed hybrid system of solar PV, wind, and biodiesel is suitable to enhance reliability and reduce the Battery Energy Storage System (BESS) requirements. In the proposed system, power generated from solar PV and wind was controlled using a modified Maximum Power Point Tracking (MPPT) controller due to the stochastic nature of these sources. The former direct MPPT controller using the Perturb and Observe (P&O) algorithm provide duty cycle that is compared with the carrier signal to control the boost converter. Therefore, it cannot regulate the DC bus voltage to the desired value. In order to regulate the DC bus voltage, the duty cycle of the direct MPPT controller is corrected through Proportional-Integral (PI) controllers. The biodiesel source was controlled by using a PI controller due to the production of a constant generated output voltage. The output voltages from the three sources were integrated at a common DC link with the BESS to control the voltage variation of the DC bus for dynamic DC loads. Thereafter, the DC bus was connected to the voltage source converter (VSC) operated as an inverter using voltage and frequency control at the Point of Common Coupling (PCC), where the AC loads are connected. The proposed design of a hybrid Solar PV-wind and biodiesel system was modelled and simulated using MATLAB/Simulink software. On testing the performance of the system, it was observed that the voltage and frequency at the AC load were maintained constant at 1 pu and 50 Hz, respectively. This type of energy source is feasible for use in rural areas of most Sub-Saharan African countries, including Tanzania, either under isolated or as grid-connected.