A Near-State Three-Dimensional Space Vector Modulation for a Three-Phase Four-Leg Voltage Source Inverter

A near-state three-dimensional space-vector modulation (NS 3-D SVM) switching scheme, which aims to reduce the common-mode noise in a three-phase four-leg voltage source inverter, is proposed. The impact of common-mode noise, which is related to electromagnetic interference issues for a high-voltage level four-leg system, is investigated first. Identification of the section in a 3-D space, selection of the near-state switching vectors, and sequence of the selected switching vectors are then introduced in steps to describe the proposed switching scheme. The proposed switching scheme is based on classical 3-D SVM, producing higher dc-link utilization, less harmonic content, and reduced switching loss compared to sinusoidal PWM. Theory, simulation, and experimental results show that the near-state 3-D SVM can work under both balanced and unbalanced load conditions.