Stability Analysis of a Five-Phase Series Connected Two-Motor Drive System

Vol.2 No.2

Year: 2008

Issue: Oct-Dec

Title: Stability Analysis of a Five-Phase Series Connected Two-Motor Drive System   

Author Name: Sk. Moin Ahmed, Atif Iqbal   

Synopsis:   

Multi-phase machines in adjustable speed drives is nowadays extensively considered for various applications such as electric ship propulsion, ‘more-electric aircraft’ and traction applications, including EVs and EHVs. In addition to well-known advantages, use of multi-phase machines enables independent vector control of a certain number of machines whose stator windings are connected in series in an appropriate manner, with the supply coming from a single voltage source inverter (VSI). The concept was initially proposed for a five-phase series-connected two-motor drive, but is applicable to any system phase number greater than or equal to five. The stability analysis is an important aspect of a drive system since the motor operates in wide range of frequencies with these types of control strategies. This paper is aimed at the evaluation of the stability of a five-phase series-connected two-motor drive system. The model of a five-phase series-connected machine is at first linearised using small signal modelling approach and is then represented in state space form. The state-space model thus obtained is then used to determine the transfer functions using the developed Matlab code. The classical stability tools are used to evaluate the control characteristics. Analytical, simulation and experimental results are provided to support the findings.