Switched reluctance generator drive in the low and medium speed operation : modelling and analysis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering at Massey University, Manawatu, New Zealand
Wind is a natural source of energy related to the low and medium speed range. Electricity
can be generated from the wind by using a variable speed machine. Among the common
types of machines available are: double fed induction generator (DFIG), induction
generator and also synchronous generator. However, the latest addition to the group is the
Switched Reluctance Generator (SRG), which has attractive features such as simple in
construction, inexpensive, robust and reliable. Current research on the SRG has been
focusing on optimizing its performance individually in terms of structure, control and also
reducing the components of power electronic devices. Despite the extensive research on
the individual component of the machine, the comprehensive performance of the SRG has
not yet been published. The main contribution of this thesis is the proposed modelling
framework of the SRG. Based on the framework, extensive and in depth comparative
analysis can be conducted.
Firstly, the design of the existing machine including the winding configuration and rotor
structure using finite element method is investigated. Secondly, based on the principle of
electromagnetism, a simulation framework that adopts a heuristic method to perform
comparative analysis between different types of SRG has been proposed. This framework
serves as a platform to the development of the SRG in the low and medium speed
operation. It can be used to predict the performance of the machine before it can be
implemented on a prototype, thus, saving time and costs.
Thirdly, the procedure to determine the optimal control variables is proposed. Basically,
the controller plays an important role to determine the placement of the firing angles
along the inductance profile. The most influential parameter that affects the percentage of
power generated which are the firing angles and voltage level has been identified. A
polynomial function relating the percentage of power generated in terms of the optimal
control variables has also been developed.
Lastly, a novel control method is proposed to operate the machine in single pulse mode as
opposed to the current chopping mode during the low speed range. The proposed control
scheme provides the highest percentage of power generated during the low speed range.
Overall, the research will aid in the development of the SRG by allowing user to choose
the best generating operation within any speed range.