A Modified Modulation Strategy for a Five-Level Inverter Based Open-End Winding PMSM With Floating Capacitor

This paper describes a modified modulation strategy for open-end winding permenant magnet synchoronous machine (OW-PMSM) using multilevel inverter. It is drived by a dc source with three-level neutral point clamped (NPC) inverter from the primary side, and the secondary side consists of a floating capacitor with two-level inverter. The particular voltage ratio (4:1) of the dc link to the capacitor is maintained by the proposed modulation strategy, to create an output voltage waveform with five-level. Additionally, the proposed strategy can simplify algorithm complexity, making it suitable for the control of high-speed motors with high switching frequencies. The simulation based on a high-speed motor and field-orientation control (FOC) proves the effectiveness of the strategy.