| As a stable,environmentally friendly and efficient power plant,micro turbine is a widely used distributed power source.Micro turbines have high rotational speeds,which usually require permanent magnet synchronous generators to operate in coaxial with them to produce intermediate frequency AC.Because the intermediate frequency AC generated by permanent magnet synchronous generator driven by micro turbine can not be directly used for load,it is necessary to convert the output power of generator.Based on the above requirement,a converter for micro turbine power generation system is designed,which converts the intermediate frequency AC generated by permanent magnet synchronous generator driven by micro turbine to generate three-phase AC power frequency which can meet the demand of load operation and ensure the stable operation of micro turbine power generation system and its loadThe converter designed in this thesis is mainly composed of VIENNA rectifier and three-phase bridge inverter.VIENNA rectifier mainly converts the intermediate frequency AC output of permanent magnet synchronous generator into DC which satisfies the requirement of voltage level and provides stable input for the inverter.Inverter mainly converts the input provided by VIENNA rectifier into three-phase AC power frequency which meets the requirement of load.In order to ensure the stable operation of the micro turbine power generation system,this thesis mainly focuses on two aspects:firstly,the topology and mathematical model of the converter used in the micro turbine power generation system are established,and the control strategies of the VIENNA rectifier and three-phase bridge inverter are designed.By decomposing the input current of the VIENNA rectifier in the dq rotating coordinate system,the control strategy of the three-phase bridge inverter is designed.The decomposition of the input three-phase current of the rectifier on the quadrature axis is the control objective Combined with the voltage and current double closed-loop control,the VIENNA rectifier works in the unit power factor state and improves the efficiency of the rectifier while providing stable DC output.The control part of the inverter improves the traditional droop control on the premise of considering the influence of the line impedance on the control effect The virtual impedance compensation link is introduced to ensure that the external parameters of the inverters are consistent in different line lengths and access modes,which reduces the influence of the impedance parameters and line impedance parameters on the control effect Combining with the voltage and current double closed-loop control strategy,the amplitude and frequency of the three-phase AC voltage output of the inverters are stable and do not fluctuate greatly with the change of load.At the same time,the response speed of the system is improved.Secondly,aiming at the problem that the power output of micro turbine power generation system does not meet the demand of load power,the stability of output voltage and the average distribution of power in parallel operation of inverters are studied in order to reduce the switching stress and system volume,satisfy the plug-and-play requirements of distributed power generation system,and improve the power supply reliability and redundant power supply capability of the system when a single distributed power supply failsThe above topology and control strategy are simulated under the environment of Matlab/Simulink,and the reliability of the control strategy is verified.An experimental platform of converter for micro turbine power generation system is built,and the above design is further verified by experiments. |
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