【作者】 刘庆丰；

【导师】 刘丁； 王华民；

【作者基本信息】 西安理工大学 ， 电力电子与电力传动， 2008， 博士

【摘要】 感应加热电源在冶金、金属热处理等行业中有着广泛的应用,对国民经济发展有很大的推动作用,随着电力电子技术的不断发展,目前对感应加热电源的研究,尤其对高频电源的研究日益受到重视。为发展高频感应加热电源技术,同时促进多电平逆变器在高频领域的应用,文中对基于多电平变换技术的高频感应加热电源进行了研究。分析了感应加热电源应用中,两模块级联的多电平逆变器在传统触发方式下的工作过程,得出了以下的结论：在导通时间短的逆变模块中,存在二极管反向恢复电流的不良影响；逆变器的输出电压存在电位不对称现象,增加了逆变器输出电压谐波调节工作的复杂度。提出了感应加热电源级联型多电平逆变器新型的工作方式。通过对功率开关器件触发信号的设置研究,解决了多电平逆变器输出电压波形的调整问题；通过分析负载电流换向点与触发信号死区的关系,研究了负载电压的二次换向问题,给出了避免负载电压在死区工作期发生二次换向的工作条件；详细分析了多电平逆变器在新型工作方式下的工作过程。设计了一套无源无损吸收电路,抑制多电平逆变器工作过程中二极管的反向恢复电流,改善功率器件的开关条件。详细分析了无源无损吸收电路的工作过程,并给出了吸收电路的参数设计方法。为发展级联型多电平逆变器在单相高频大功率系统中的应用,对多电平逆变器在高频运用中的谐波控制问题进行了研究。采用阶梯波PWM法消除低次谐波时,通过求解功率器件开关角方程组,给出了级联模块电源电压比值不同时开关角的选择范围及输出电压基波幅值的调节范围,并依据输出电压谐波畸变率与基波幅值的关系,得出了级联模块电源电压比值的选择原则。提出了一种基于波形合成消除多电平逆变器输出电压特定谐波的方法。当级联模块数增加或待消除谐波次数增加时,避免了采用阶梯波PWM法中对高次多变量方程组的求解,利用此方法可通过简单的三角公式递推计算获得实现多个特定谐波消除的开关角。详细论述了该方法的基本原理和数学递推过程。提出了高频感应加热电源级联型多电平逆变器输出电压的谐波控制方法。通过对感应加热电源输出功率特性的分析,为提高逆变电源容量的利用率,应尽可能提高感应加热电源逆变器输出电压中的基波含量,减小输出电压的谐波畸变率。利用多电平逆变器谐波控制方法及感应加热电源多电平逆变器输出电压的特点,对两模块级联多电平逆变器输出电压的特定谐波消除方法进行了数学推导,给出了功率器件开关角的取值建议。通过仿真与实验研究,验证了文中的理论分析结果及设计方法的正确性。更多还原

【Abstract】 Induction heating power supply is widely used in metallurgy, metal heating treatment field and has a powerful pushing force for national economy. With power electronics technology improving, research on the induction heating power supply especially on high frequency application is emphasis more than ever. For developing the technology of high frequency induction heating power supply and promoting the high frequency application of multilevel inverter, high frequency induction heating power supply based on multilevel technology is studied in this paper.It is analyzed that the work process of two H-bridges cascaded multilevel inverter in induction heating power supply with traditional driving signal. The conclusion is that reverse recovery current in diode could cause ill effect in inverter module in case of short turn-on time, and an asymmetry output voltage level of inverter could increase the complexity of harmonics control.A novel working mode of multilevel inverter in induction heating power supply is presented. The output voltage of multilevel inverter could be adjusted by setting driving signal of power switch; the relationships between the dead region of driving signals and the phase commutating points of load current are investigated to analyze the problem of load voltage commutating, the working conditions are given to avoid repetitious commutation of load voltage polarity in dead region; the operation process of multilevel inverter with novel working mode is analyzed in detail.A passive lossless snubber circuit is designed for restraining the reverse recovery current in diode and improving the turn-on condition of power switch. The operation process of snubber circuit is investigated in detail and corresponding method of parameters designing is given.The harmonics controlling means of cascaded multilevel inverter applicable to high frequency field are discussed for developing high frequency application of multilevel inverter in single-phase power system. In order to eliminate lower order harmonic in the multilevel inverter with different DC source ratio, the range of switching angles and fundamental voltage amplitude are given by solving the switching angles equation system. According to the relationship between the total harmonic distortion and fundamental voltage amplitude, the method of selecting module source ratio is presented.A method of eliminating specified harmonics based waveform resultant principle in cascaded multilevel inverter is given to avoid solution of the multi-variable high-order equation system, when the number of modules cascaded in inverter or the order of the harmonics to be eliminated increase. The switching angles can be easily obtained by simple trigonometry formula deduction for eliminating specified multi-harmonics. Basic principle and deduction procedure are explained.A harmonics control way of output voltage of cascaded multilevel inverter in high frequency induction hearting power supply is presented. According to the characteristic of output power in induction hearting power supply, the fundamental voltage content in output waveform of inverter should be increased as high as possible, which decreases total harmonic distortion ratio of output voltage, for improving the utilization ratio of inverter power supply. Based on the harmonics control way of multilevel inverter and the characteristic of output voltage of multilevel inverter in induction hearting power supply, basic procedure of eliminating specified harmonics in two modules cascaded multilevel inverter is deduced and the reasonable values of switching angles are advised.The results of simulation and experiment have verified the validity of design methods and the conclusions given by theoretically analyzing in this paper.更多还原