An Adaptive Fuzzy Based Grid Forming Inverter Integrated with Hybrid Renewable Source and Storage Unit for Grid Support
Abstract
In the modern electrical power systems, the incorporation of renewable energy sources into weak grids has led to power fluctuations, voltage instability, frequency deviations and harmonic distortion. The Grid Forming (GFM) inverters place vital role in a weak grid with low rating and disruptive voltages. The GFM inverter ensures stable voltages magnitudes and frequency of the grid system, which stabilizes the loads connected to the system and injects the required power by the grid, compensating the loads requirement when the grid fails. In this paper, an HRS (Hybrid Renewable Source) and storage unit based GFM inverter is designed for power sharing to the grid. The GFM inverter control includes PQ droop control modules, which define the required voltage magnitude, frequency and phase in synchronization to the grid. The conventional GFM inverter control comprises of PI voltage and current regulators generating the reference signals for the SPWM technique. Due to low damping of the PI regulator, the oscillations and ripple in the signals are increased during initial and transient conditions. This increases the ripple in the DC voltage and injected powers of the renewable source modules. In order to suppress these issues, the PI regulator is replaced with the AFPIC (Adaptive Fuzzy - PI Control) regulator, which ensures increased damping, reducing the ripple. The AFPIC regulator varies the Kp and Ki gains of the PI regulator during the initial and transient states, reducing the disturbances in the reference signals. A relative analysis is presented in this paper with PI and AFPIC regulators integrated into the GFM inverter controller under faulty and transient conditions with the help of MATLAB Simulink software. The results show a significant drop in ripple of DC voltage and renewable injected active powers, THD of the inverter current with the AFPIC regulator, ensuring the robustness of the proposed controller.