Gradient-Based Predictive Pulse Pattern Control with Optimal Active Neutral Point Potential Balancing for Five-Level Medium-Voltage Drives

Abstract

This paper presents a control algorithm for five-level neutral-point-clamped (NPC) H-bridge medium-voltage (MV) drives. Specifically, a model predictive control (MPC) method is developed to directly manipulate optimized pulse patterns (OPPs) in real time. This enables accurate tracking of the optimal reference trajectory while achieving excellent transient performance. Moreover, owing to the multiple-input multiple-output nature of the proposed controller, the neutral point (NP) potential balancing problem is addressed within the same control loop. To achieve this, the proposed method includes an optimal active NP potential balancing mechanism that ensures minimal NP potential ripple and equal utilization of the switching devices. The effectiveness of the proposed control method is demonstrated on the target MV drive system, and its superior performance is demonstrated through comparisons to existing approaches.