Polar Voltage Space Vectors of the Six-Phase Two-Level VSI

Abstract

The paper recommends polar voltage space vectors of the six-phase and two-level inverter as a useful mathematical tool for vector control of the inverter. The inverter model is described using three mathematical tools: analytic expressions, voltage state, and space vectors. The analytic formulas allow for the determination of elementary physical inverter quantities: current and voltage. The state voltage vectors make it easy to define phase voltage distribution in every possible state of the inverter and voltage space vectors are the most important tool used for inverters’ control. The space vectors are defined using the standard voltage space vector transformation, while the state vectors are denoted by binary numbers and determine all voltage states of the inverter. The proposed notation system and vectors’ marking seem to be extremely useful in specifying the inverter states. This system certifies a deep correlation between the space and state vectors as they are described using the same digits. The properties of the system were confirmed during the simulation tests. Some examples of the inverter vector control based on polar voltage space vectors prove that the proposed solution is a useful mathematical tool and may be in fact suitable in designing inverter control algorithms. The simulation experiment described in this paper shows that the assumed control strategy allows for a significant reduction in the amount of switching compared to PWM. At the same time, the adopted vector strategy allows for the obtaining of a very favorable value of the current THD coefficient while maintaining the RMS values of the currents.