Research On Semi-self-excited Power Converter For Switched Reluctance Generator

Switched reluctance generator(SRG)has a wide range of application prospects in the field of power generation due to its simple structure,wide rotational speed range,and no permanent magnets.However,the output power and power generation efficiency of SRG need to be improved.As the channel of energy conversion in the SRG power generation system,the power converter is of great significance to the performance improvement of the entire power generation system.The purpose of improving SRG output power and power generation efficiency can be achieved by designing the power converter.Self-excited asymmetrical half-bridge power converter has simple structure and strong fault tolerance,so it is widely used in SRG power generation system.However,when the power generation system is stable,its excitation voltage and generation voltage will be coupled to the same voltage,which is not easy to improve the excitation voltage,limiting the improvement of SRG output power and generation efficiency.From the view of decoupling excitation voltage and generation voltage,a semi-self-excited power converter and its control strategy are proposed in this thesis to improve the excitation voltage and make the generation voltage lower than the excitation voltage.Thus,the SRG output power and power generation efficiency can be improved.At the same time,the energy storage capacitor can be prevented from overcharging,which adds protection measures for the safe and stable operation of the system.The main research contents of this thesis are as follows:First,in order to improve the output power and generation efficiency of SRG,a semi-self-excited power converter and its control strategy are proposed to increase the excitation voltage and make the generation voltage lower than the excitation voltage from the perspective of decoupling excitation voltage and generation voltage.In the preliminary design of the semi-self-excited power converter,it is found that the energy storage capacitor will be overcharged.By adding the power generation mode to improve it,the semi-self-excited power converter structure is finally determined.The control strategy of the semi-self-excited power converter is designed.And the structure,working mode and control strategy of the semi-self-excited power converter are compared with the self-excited asymmetric half-bridge power converter.Secondly,the SRG power generation system simulation models of the semi-self-excited power converter is established to verify the effectiveness of the semi-self-excited power converter.The influence of the energy storage capacitor on the generation performance is studied,and the optimal current chopping limit is determined with the output power as the optimization goal.The operating characteristics of the semi-self-excited power converter are analyzed through starting,steady state,variable speed,variable load and single-phase fault simulations to verify its feasibility,advantages in preventing overcharging of energy storage capacitors,and strong fault tolerance.The semi-self-excited power converter and the self-excited asymmetric half-bridge power converter are simulated and compared under different circumstances.It is found that the excitation voltage and generation voltage of the phase winding under the semi-self-excited power converter are increased,and the phase current excitation time is shortened.It can improve the output power of SRG,especially at low speed.Finally,the SRG power generation system experimental platform of the semi-self-excited power converter and the self-excited asymmetric half-bridge power converter is built to verify the effectiveness of the semi-self-excited power converter.The excitation voltage and generation voltage of the phase winding and the phase current waveforms under the semi-self-excited power converter and the self-excited asymmetric half-bridge power converter are tested,and the output power and power generation efficiency of the SRG are calculated,and these parameters are compared and analyzed.The correctness of theoretical analysis and simulation,and the effectiveness of the proposed semi-self-excited power converter and its control strategy are verified by experiments.