An Advanced Modular Multilevel Inverters for Grid-connected PV Optimization by Maximum Power Point Tracking

Modular multilevel inverters (MMLIs), acknowledged not only for its modular structure, scalability and low harmonic distortion but also offers an efficient solution, for managing high-power renewable-energy applications. However, these often depends on conventional centralized control methods, which are insufficient in addressing critical challenges like scalability and hardware delays in distributed control systems. This paper emphases on the design and implementationof an advanced 3-Ph. MMLI for a 400-kW solar plant connected to a 25 kV grid. The study examines the system's performance, control strategies and operational challenges encountered during the integration with grid. To optimize energy extraction from the PV array, incorporate a DC/DC, converter featuring MPPT, through ‘Perturb and Observe’ (P & D) technique. The extracted energy is then stepped up and converted into 3-Ph. AC voltage through MMLI. The output from these, feed into a common 500V DC bus, enabling the overall system integration. Unlike earlier methods which are used open-loop control to address power imbalances among legs, this study employs closed-loop control using to correct mismatched DC loop currents. This allows, dynamic adjustment the voltage across PV array to optimize output efficiency. The efficacy of the proposed control-strategy has been validated through Mat lab/Simulink simulations, demonstrating its potential.