Decoupled Continuous Control Set Model Predictive Control for T-Type Three-Phase Four-Leg Three-Level Inverters Driving Constant Power Loads

The control coupling and stability of three-phase photovoltaic systems with constant power loads (CPLs) are two key technical issues that urgently need to be addressed. However, current methods are difficult to solve both technical challenges simultaneously. To address these issues, this article proposes a novel decoupled continuous control set model predictive control (CCS-MPC) strategy for LC-filter T-type three-phase four-leg three-level voltage source inverters (3P4L-3L-VSIs) driving CPLs. The control strategy is developed in αβγ frame. The model of 3P4L-3L-VSIs is first transformed from abc frame to the αβγ frame to remove the coupling effects in the abc frame. Then based on the decoupled model in the αβγ frame, a novel CCS-MPC strategy is proposed to provide balanced sinusoidal voltages. The α and β components are regulated by the A, B, and C legs, while the zero-sequence component is regulated by the N leg. To confirm the effectiveness of the proposed strategy, both simulation and experimental results are presented to verify the proposed decoupled CCS-MPC strategy. The results show that the proposed control achieves low computational burden and total harmonic distortion and can increase the stability margin especially for CPLs compared with the commonly used PI-based control, PR-based control, and deadbeat control.