Performance Improvement of Five Phase Induction Motor Drive System with Different Converter Configurations

Abstract

The environment friendly transportation system has been drawing great attention worldwide, with a prospect of keeping climatic changes in check and minimizing the air pollution to an acceptable extent. Thus, advancement in electric based technologies for machineries used for propulsion has been a topic of great interest in variety of conveyance system, which includes hybrid vehicles, aircrafts and ships. Also, this progression is applicable to machineries to generators for power generation using renewable sources.
These types of applications are not well suited for the conventional machineries, which are based on three-phase suitability. Besides, due to the scenario of source and load system being isolated from the main power network in such applications, it is not a regulation anymore to restrict the number of phases in such machineries to only three. Moreover, the multi-phase machines propose a number of advantages as compared to the conventional three-phase type. The merits majorly include multi-phase drive’s power converter switch rating requirement is now reduced. Also, with higher number of phases its fault tolerant capability is highly increased.
The research on multi-phase drives and their application in real-world has developed at a good pace from past two decades. From all the old as well as modern machine drives available, the application of induction motor drives is still way long ahead from its competitors. Thus, research on multi-phase induction motor drives have been in the limelight in recent years. Specially, the five-phase induction motor drive system has drawn great attention and interest.
The converter arena in machine drives section is a major component to be dealt with. The conventional converter configurations used for three-phase drives can also be implemented for higher phase configuration with necessary modifications. However, since topological advancement in converter design sector has gone to a higher level, different advanced configuration with specific suitability to such multi-phase drive application is also a topic to be looked upon. Thus, two different converter configurations have been dealt with, in this thesis, i.e. Multi-level inverter (MLI) and Z-source inverter (ZSI), with more emphasis on the latter one. The MLI configuration obviously provides greater flexibility in supplying individual phases of multi-phase drive, however, their controlling complexity also increases with it. Also, the cost of using such configurations is on a higher side. The ZSI, nevertheless, iv
is more useful in voltage sensitive applications where there are high chances of voltage disturbances from the supply side. The additional control function of voltage control for ZSI can also be integrated with control structure of machine in drive system.
With the advent of modern and sophisticated processors, the control structure for multi-phase drive is now easier to design and implement. Out of different control techniques already in use for conventional three-phase induction motor system, such as scalar control, FOC (field oriented control), DTC (direct torque control), adaptive control technique, etc., DTC as such or in modified structure is still in large a highly preferable choice. Henceforth, DTC is primarily used in this work for designing the inherent control structure of five-phase induction motor. Furthermore, for voltage control of quasi Z-Source Inverter (qZSI), a duty cycle generation method is devised using a non-linear control function technique, known as dynamic evolution control (DEC). This duty cycle is further integrated with DTC for designing the complete control algorithm for qZSI fed five-phase induction motor drive system operating under conditions of supply voltage disturbance in the form of sag and voltage interruption.
In this work, along with voltage control function of DEC method, it’s another controlling aspect is also explored, which is in respect to the source current. An attempt is made to counteract the THD content of source current along with voltage control by adapting to a proposed current controlled DEC method for qZSI fed five-phase induction motor drive system.
The proposed work for five-phase induction motor drive system, which includes analysis based on different converters at front-end such as MLI and qZSI, and also the proposed controllers are precisely described by mathematical and diagrammatic descriptions. The practicality of the proposed configurations is authenticated by their simulation and real-time results.