Gradient-Based Predictive Pulse Pattern Control of Five-Level Medium-Voltage Drives with Dc-Link Voltage Ripple Minimization

Abstract

This paper presents a control and modulation strategy for medium-voltage (MV) five-level neutral-point-clamped (NPC) H-bridge drive systems. The proposed method combines system-specific optimized pulse patterns (OPPs) and a gradient-based model predictive control (MPC) scheme. Specifically, the OPPs are designed to reduce the significant dc-link voltage ripple, which is an inherent drawback of the topology at hand, while simultaneously enabling very low stator current total demand distortion (TDD). To achieve high-bandwidth closed-loop operation, the developed MPC scheme individually manipulates the OPP switching time instants at the single-phase level. As a result, the combination of optimal control with optimal modulation ensures both excellent steady-state performance and fast dynamic responses. The proposed approach is validated in real time using a hardware-in-the-loop (HIL) environment, demonstrating its effectiveness and superior performance compared to conventional methods such as field-oriented control (FOC) with space vector modulation (SVM), direct torque control (DTC), and finite control set MPC (FCS-MPC).