Power Quality Improvement Through a Model Predictive Droop-based Grid-forming Inverter Control

Grid-forming (GFM) inverter technology is taking center stage in grid dynamics and control strategies as inverter-based resources (IBRs) penetrations experience significant advances. This work presents the need for continuous modification in GFM inverter controls regarding power quality by comparing a shunt-compensated droop-based GFM inverter control technique with its improved version by modifying the secondary control. The proposed approach uses a mathematical model of power converters without pulse width modulated signals to predict the AC load voltage and frequency response. Both voltage and frequency are regulated under balanced and unbalanced loads in transient and steady-state analysis while maintaining active and reactive power sharing in a cluster of IBRs. The cost function of the predictive control can additionally be designed to regulate load current under fault conditions. The performance of the control strategies is demonstrated with MATLAB/Simulink simulation studies. Total harmonic distortion (THD) for the various loads is illustrated and compared to related works to verify the superiority of the proposed secondary control modification.