【中文摘要】同步电动机以其可调的功率因数和输出转矩对电网电压波动不敏感等良好的运行性能,在大功率电气传动领域独占螯头。同步电机固然有很多优点,但它的最大缺点是起动困难。目前,大功率同步电机的软起动大多采用静止变频器起动方式,但由于变频器多采用晶闸管作为功率器件从而要依靠电动机产生的反电势才能自行关断并且辅助设备较多。而一旦逆变器换流失败就会导致电动机起动失败。针对晶闸管不能自行关断的缺点,本文研究了一种以IGBT做为变频器功率器件的转速开环恒压频比控制的起动方法。首先,根据同步电动机的工作原理对同步电动机的起动特性进行了具体分析,并对全压异步起动方法进行了仿真研究,得出了起动过程中电动机相电流、电磁转矩等参数的变化曲线。针对异步起动过程中定子绕组产生过大冲击电流的题目,提出了逐级变频的转速开环恒压频比控制同步电动机软起动方法。阐述了逐级变频开环控制同步电动机软起动的原理,即通过逐级改变变频器输出频率使转子转速跟随定子旋转磁场转速逐级升高至额定值。推导出起动过:程中变频器逐级变化的频率与电动机转动惯量、电磁转矩等参数的关系式。通过对一台同步电动机做工频起动和低频起动的仿真研究,证实了同步电动机在低频下依靠同步电磁转矩自行起动的可行性。通过计算转子转速达到相应同步转速的时间来确定变频器逐级升高的电压频率随时间的变化规律。然后,在采用电压型交直交变频器作为同步电机变频电源的基础上,设计了恒压频比逐级变频软起动的控制方案,利用MATLAB/SIMULINK构建了转速开环恒压频比控制同步电动机软起动的数学模型,对同步电动机的起动过程进行仿真试验,并且分别对空载起动和负载起动过程进行了分析。仿真结果验证了转速开环控制同步电动机软起动的可行性。针对同步电动机起动后的并网题目进行了理论分析,并研究了相应的并网控制方案。应用MATLAB/SIMULINK对并网过程进行仿真试验,给出并网瞬间电网电压、同步电机相电流等参数变化曲线,从而验证了并网方案的可行性。最后,对所做工作进行了总结,并展看了大功率同步电动机的软起动技术。');
【Abstract】 Synchronous motor is popular in high-power electric drive because its power factor is adjustable and output torque is not sensitive to the power grid voltage fluctuation. Although synchronous motors have many advantages, its biggest drawback is difficult to start. Large and medium-sized high-voltage synchronous motor uses asynchronous start-up method, which causes a great impulse current in the system. On the one hand, the impact current is harmful for motor itself; on the other hand, it drops voltage of power grids, accompanying with causing other equipment in power grids to work abnormally. In recent years, due to the development of power electronics technology, the soft-start technology of synchronous motor has the rapid development.At present, the soft-start of high-power synchronous motor is using static frequency converter method mostly. In this method, the control system is complex because it uses the thyristor as power devices in inverse Converter, and the thyristor\'s automatic cutting off have to rely on the back-EMF of the synchronous motor. If the inverse converter fails in commutating, motor starting fails. For the thyristor can not turn off on its own, this *** presents a synchronous motor start-up method which is called the speed open-loop constant proportion of voltage to frequency control method using IGBT inverter as power devices.Firstly, a detailed analysis of the starting characteristics of synchronous motor is given, in accordance with its work principle. The curve of motor phase current and electromagnetic torque during the start-up is obtained stemming form the simulation research on asynchronous motor starting methods. For the problem that asynchronous motor starting generates a great current impact, this *** presents speed open-loop constant proportion of voltage to frequency control method. Secondly, based on the study of open-loop control synchronous motor soft start principle, the relationship between stator rotating magnetic field speed and rotor speed is deduced under the condition that synchronous motor can start itself just relying on synchronous electromagnetic torque. By doing power frequency and low-frequency start-up simulation on the same motor, the conclusion that synchronous motor can start is proved that the synchronous motor can start itself just relying on synchronous electromagnetic torque under the low-frequency. And the rule stator voltage frequency changing with time is confirmed through computing the time rotor cost on achieving corresponding synchronous speed. Then, based on the use of voltage-type AC-DC-AC inverter as synchronous motor variable frequency power, the *** designs a constant voltage frequency ratio soft-start control method, which is realized through changing the inverter output frequency and voltage step by step to make the rotor speed to follow the stator rotating magnetic field speed and to increase to rating value. The synchronous motor starting simulation is processed on the MATLAB / SIMULINK after building the mathematic model of open-loop constant voltage frequency ratio soft-start control, which analyzes both no-load start-up and load on start-up process. The simulation results show the feasibility of constant voltage frequency ratio soft-start control method.This article also gives a theoretical analysis on conditions of synchronous motor parallel in power grid after successful start-up and introduces the appropriate parallel in project. The parallel in process simulation on MATLAB / SIMULINK for the synchronous motor reveals the change curves of the power grid instantaneous voltage, synchronous motor phase current etc. and verifies the feasibility of parallel in project.In conclusion, the dissertation concludes the whole work, analyses the findings and achievements, and brings forward further research on high-power synchronous motor.
付费硕士论文：文章格式正规，摘要、关键词、图表、代码、参考文献齐全 如需全文请联系QQ:271245358
注：此文严禁擅自转载，客户付费购买后永久清除，本站保证购买者的唯一性。
本文TAGS：[标签:文章关键词]
