Modulated Predictive Current Control of Back-to-Back NPC Converter in PMSG Wind Energy System with Reduced Computational Burden

This paper proposes a novel modulated predictive current control with a reduced computational burden for a three-phase back-to-back connected neutral-point clamped (NPC) converter in a permanent magnet synchronous generator (PMSG) based wind energy system. An algorithm has been developed to determine the optimal sector number based on measured generator- and grid-side voltages and currents. The eight voltage vectors in the optimal sector are then used to determine the optimal triangular region (among 6) that produces the minimum cost function value for NPC rectifier and inverter. The three voltage vectors in the optimal triangular region are selected and applied to the rectifier and inverter via seven segment switching scheme. The dwell times of medium voltage vectors in the switching sequence are adjusted dynamically to balance the DC capacitor voltages. The proposed approach produces constant switching frequency, minimal steady-state errors, and fast transient response. The developed control scheme is tested on a 3 MW, 3 kV PMSG wind energy system through MATLAB simulations.