【作者】 王小方；

【导师】 吴敏； 黄志武；

【作者基本信息】 中南大学 ， 控制科学与工程， 2011， 博士

【摘要】 电力机车辅助变流器是为机车牵引及制动系统提供保障的一种重要设备,它的性能将直接影响机车的正常运行。由于这类变流器的单台容量较大,因此早期的辅助变流器往往存在体积大、噪声大和损耗大等缺点。为了实现大功率变流器装置的小型化、低耗化和高效化,目前有效并被广泛采用的设计方法是提高变流器的工作频率,达到增大功率密度、提高瞬时响应速度、抑制音频噪声等目的。在进行高频化设计时,需要面对和解决一系列问题,包括如何有效地解决由于变流器开关频繁动作而产生的如开关损耗、二极管反向恢复电流和电源电磁干扰等,而软开关技术能够有效解决这些问题。本文研究一种基于无源软开关技术的大功率高频辅助变流器,其功率为260kVA,开关工作频率为15kHz。论文首先提出一种新型的辅助变流器拓扑结构,分析了关键电路的工作原理；然后,利用状态空间平均法和智能控制方法对变流器进行建模和控制；最后,根据给定的技术指标,计算电路参数,开发系统样机,并通过对关键模块的测试验证辅助变流器的正确性和实用性。(1)基于无源软开关技术的辅助变流器拓扑结构结合260kVA无源软开关辅助变流器的面向对象和工作环境,基于无源软开关技术和直-(交)-直-交(DC-(AC)-DC-AC)变流技术,提出了一种新型的大功率高频辅助变流器系统拓扑结构。变流器的前端(DC-(AC)-DC部分)由三个采用输入串联输出并联方式连接的高频DC/DC变换器组成,这种模块化系统结构的设计可以降低开关器件的电压等级,而且该配置方式的自动平衡机制可以保证系统的稳定性；变流器的后端(DC-AC部分)为将直流转化为交流的DC/AC逆变器,其中无源软开关箝位电路技术的使用可以有效地降低变流器的体积和重量。同时,对主电路中的缓冲型无源软开关电路、能量恢复电路、RCD箝位电路等几个关键电路的工作原理进行分析,在此基础上,提出一种基于能量恢复的新型RCD位电路,进一步提高了辅助变流器的工作效率。(2)基于状态空间平均法的辅助变流器模型分析对于辅助变流器中的高频DC/DC变换器,应用状态空间平均法,建立了变换器的数学模型。针对变换器的强非线性特点,为了获得良好的稳态、瞬态、动态等特性,在考虑变压器漏感、输出滤波电感、以及电容等效短路电阻的情况下,建立了变换器的等效电路。通过分析一个周期内变换器关键部件的电压和电流理想波形的变化趋势,得到了不同状态下的变换器等效电路和对应的状态变量方程描述。在此基础上,通过平均化和线性化处理,获得了变换器在连续工作模式下的状态平均方程和小信号传递函数。(3)基于遗传算法的辅助变流器智能控制方法为了降低辅助变流器中电气设置参数的不确定性,负载性质的多变性等因素对系统的负面影响,对变流器的控制策略进行研究,提出了一种基于遗传算法的智能控制方法。针对DC/DC变换器,首先,选择合适的PWM控制方式,构建双闭环控制结构,即利用电流内环反馈获得优异的动态响应,电压外环反馈获得期望的穿越频率和相位裕度。然后,采用传统PID控制方法对DC/DC变换器实施控制,依据一定原则选取合适的PID参数,通过仿真验证了控制效果。最后,针对现有DC/DC转换器采用传统的PID控制方法难以获得最优控制参数的问题,提出一种基于遗传算法的智能PID控制策略,在双闭环控制结构中,采用遗传算法对电压外环中PID控制器的参数进行自寻优,电流内环仍采用PI控制算法实现电流反馈控制。仿真结果表明,相比于传统PID控制,基于遗传算法的PID控制策略能够获得更好的动态响应和稳定裕度。针对DC/AC逆变器,采用遗传算法对空间矢量调制进行控制,实现了三相输出电压波形地有效控制。(4)辅助变流器样机的实现与测试结合本文的理论研究,完成了260kVA无源软开关辅助变流器的软硬件设计,开发了系统样机,对相关模块进行了测试。针对辅助变流器的工作环境和各项技术指标,基于前面章节的理论分析,完成了辅助变流器主电路中关键器件的参数设计和选型,研制出了260kVA无源软开关辅助变流器装置。然后,利用该实验装置进行了实验测试,重点对DC/DC模块和DC/AC模块进行测试、分析和评估,验证所设计的辅助变流器在实际运行条件下的正确性和实用性。更多还原

【Abstract】 Electric locomotive auxiliary converter provides protection for locomotive traction and braking system, and its performance directly affects the normal operation of locomotive. Because of the large capacity of this kind of auxiliary converter, the early auxiliary converters usually exist a series of defects, such as bulky, noisy, big loss, and so on. In order to realize miniaturization, low loss and high efficiency, increasing the frequency of the converter has been applied widely and it increases system power density, improves transient response speed, and suppresses radio noise. Some problems such as switching power loss, diode reverse recover current, and electromagnetic interference caused by high-frequency operation of switches should be considered for the high-frequency design.This dissertation studies a high-frequency and high power auxiliary converter based on the passive soft-switching technology, and the power and operating frequency of the converter is 260kVA and 15kHz, respectively. Firstly, a new topology of the converter is proposed and the working principles of key circuits are analyzed. Then, the state space averaging method and intelligent control are used for the modeling and control of the converter. Finally, based on the given qualifications, the parameters of main circuits are calculated and a model machine is developed, and then experiment tests of key models are implemented to verify the correctness and practicality of auxiliary converter.(1) Topology of auxiliary converter based on the passive soft-switching technologyConsidering the oriented object and working environment of the auxiliary converter, a new topology of a high-power and high-frequency auxiliary converter is proposed by applying the passive soft-switching and DC-(AC)-DC-AC converting technique. The front-end of the auxiliary converter is composed of three DC/DC converters connected with each other with the input-series-output-parallel style, and such modular architecture reduces switching voltage level and guarantees system stability. The back-end of the auxiliary converter is composed of a DC/AC inverter which transforms DC into AC, and the usage of the passive soft-switching clamp circuit technology reduces the weight and volume of the converter. Moreover, the operation principles of main circuits, such as passive soft-switching circuit, energy recovery circuit, and clamp circuit, are descried, and an improved RCD clamp circuit is proposed to improve the efficiency of the auxiliary converter.(2) Modeling and analysis of auxiliary converter based on state space averaging methodFor the high-frequencyDC/DC converter in the auxiliary converter, modeling and analysis of the auxiliary converter is presented applying the state space averaging method. Considering the strong nonlinearity of the converter, in order to obtain satisfying steady state, transient and dynamic characteristics, equivalent circuit of the converter is established on the condition of considering the transformer leakage inductance, output filter inductor and equivalent short-circuit resistance of the capacitor. Then the key voltage and current waves in a cycle is analyzed, and the corresponding equivalent circuits and state space equations under different states are derived. Finally, throug the averaging process and linearization process, the small-signal transfer function and state space model of the converter are obtained in continuous operating mode.(3) Intelligent control of auxiliary converter based on genetic algorithmIn order to ensure the performance of the auxiliary converter against the negative effects caused by the uncertainties of electrical parameters, variability of load and any other factors, a genetic algorithm based control method for the auxiliary converter is proposed. For the DC/DC converter, an appropriate PWM control scheme is selected, and then the double closed-loop control structure of the DC/DC converter is built, where good dynamic response is obtained by current feedback, i.e. inner loop and desired crossover frequency and phase margin are achieved by voltage feedback, i.e. outer loop. Then, traditional PID technology is used, and the simulation results verify the control effect after selecting the PID parameters according to certain principles. However, since the traditional PID control method is difficult to obtain the optimal parameters of the controller, a PID tuning algorithm based on genetic algorithm is proposed to optimize the performance of DC/DC converter. Under the double closed-loop control structure, the genetic algorithm is employed to optimize the parameters of PID controller for the voltage loop, and PI controller is used to achieve current feedback control. The simulation results show that the PID controller based on genetic algorithm can get better dynamic response and stability margin. For the DC/AC inverter, the genetic algorithm is employed to control the space vector modulation, which achieve effective control of three-phase output voltage waveform.(4) Design, implementation and test of auxiliary converterBased on the theoretical study, the hardware and software of the 260kVA passive soft-switching auxiliary converter is designed, the model machine is developed, and some experiments for key models are carried out on the model machine. According to the working condition and various technical indicators, the parameters of the main circuit are determined, and the auxiliary converter is established. Moreover, experimental tests and analysis of the established device are performed, the results verify that the designed auxiliary converter is correct and practical under actual operating conditions.更多还原