Research On Novel Power Conversion Techniques Of Switched Reluctance Drive

Switched reluctance drive (called SRD for short) is made up of switched reluctance motor (called SRM for short), power converter and controller, of which power converter is the key factor that affects the performance and the cost of SRD. In the troditional hard-switching mode, there exist switching losses, electric stress and electromagnetic interference in the SRD power converter. In order to decrease the switching losses of the power devices, reduce the switch electrical stress and restrain the electromagnetic interference generated in the the switching process, this paper puts forward two new soft-switching SRD power converter topologies: parallel quasi-resonant DC link-based SRD power converter and capacitor divider quasi-resonant DC link-based SRD power converter. In this paper, first, it introduced the structures and features of the two power converters. Then, by dividing the operating mode of the circuits and finding the equivalent circuits under each operating mode, the paper analysed their soft-switching mechanisms, calculated the time that each mode takes and ensures the basic requirements that normal resonance has to meet, and gave the reasonable time sequence for control. Finally, using PSPICE software, digital simulations to the proposed soft-switching power circuits were conducted. By means of simulating, the influences to the resonance properties by various factors were studied, which include the changes of time when the phase switch opening, the length of the inductive energy storage, the zero voltage period width of the bus and the size of the SRM winding inductance. At the same time, the soft-switching performance of all devices was validated by simulating.As energy issues become increasingly prominent, it is expected that some of the original drive system, whose producing technics do not require the speed of motor, can achieve their purposes of energy-saving by speed governing. Particularly, the drive systems of high-voltage high-power fans, pumps and other machines, which have huge power consumption, can save a lot of power by speed governing. But because of having no high voltage power electronic devices, and voltage equalization among devices in series is still hard to realize by connecting devices in series directly, the field of high voltage SRD is blank so far. Therefore, this paper proposed a new type of high voltage SRD power converter by combining a special transformer and low voltage cell circuits ingeniously. The paper introduced the composition and the theory of the new type of high-voltage SRD, explaind the voltage regulating principles of the power converter. As well, it demonstrated that the power converter almost has no harmonic pollution to the power source and has a high net-side power factor from three aspects: mathematical analysis, computer simulation and experiment.Furthermore, the paper also brought the quasi-resonant soft switching scheme into the new high-voltage SRD power converter, makes it easier for the power electronic devices to switch in zero voltage condition. So, the reliability of the power converter is improved from one side. It also gives the control strategy of the soft-switching high-voltage SRD power converter, which is verified by MATLAB simulation.