Voltage-behind-reactance model of six-phase synchronous machines considering stator mutual leakage inductance and main flux saturation

•A voltage behind reactance model of a six-phase synchronous machine is proposed.•The effect of mutual leakage inductance between three-phase sets is analyzed.•The effect of main flux saturation is considered and analyzed.

Six-phase synchronous machines have been used in special-purpose applications such naval and aircraft power systems, and are now being considered in renewable energy systems due to their advantages such as lower power per phase, less mechanical stress, and higher reliability compared to three-phase machines. This paper is focused on techniques for modeling six-phase synchronous machines in transient simulation programs. Firstly, the qd0 model is presented, and a method for incorporating the main flux saturation is proposed. However, since in simulation programs, the qd0 model is interfaced as a current source, it creates interfacing challenges with power electronics devices and inductive networks. To alleviate the interfacing challenge, the already available coupled-circuit phase domain (CCPD) model is also considered. This paper presents a new voltage-behind-reactance (VBR) formulation that includes the stator mutual inductances and main flux saturation, while achieving direct interface with external circuit. The presented VBR model is verified in a single-phase to ground fault scenario while connected to an arbitrary six-phase network. The computer studies demonstrate the numerical advantages of the new model including simulation time and accuracy over the CCPD and the conventional qd0 models.