开绕组电机双端级联式五电平逆变器调制策略研究

发布时间：2018-05-03 17:44

本文选题：开绕组异步电机 + 多电平　；参考：《中国矿业大学》2017年硕士论文

【摘要】：开绕组电机双端级联式五电平逆变器作为一种新型拓扑,利用两台二极管钳位型三电平逆变器连接在开绕组电机两端实现五电平逆变器的输出特性,并且相较于传统五电平逆变器,具有直流电压低、容错性好、控制灵活等优点,在高压大功率场合具有广阔的应用前景,本文首先分析双逆变器系统的换流过程,归纳出逆变器五种电压输出状态。重新建立开绕组异步电机在三相静止坐标系下、两相静止坐标系下及两相旋转坐标系下数学模型,并利用理想线性变压器实现电气流到信号流的转换,以此搭建出MATLAB中两相静止坐标系下开绕组异步电机的数学模型,同时进行仿真测试,验证模型的正确性。针对共母线结构开绕组电机双端级联式五电平逆变器系统,研究了传统SVPWM调制下的180°矢量分解调制策略,兼顾考虑零序电压抑制的问题。首先详细地分析了180°矢量分解调制策略的原理,通过180°矢量分解,参考电压矢量分解为两个大小相等、方向相反的等效矢量,从而将五电平调制问题简化为三电平调制问题。并在此调制策略的基础上,分析了系统中零序电压的危害,通过调整小矢量作用时间的方法抑制了系统中的零序电压。针对传统SVPWM调制输出电压频谱波形中存在明显谐波尖峰的问题,提出一种基于Sigma-Delta调制器的调制策略来优化输出电压频谱波形。然而由于新调制策略开关状态的不固定,传统的改变小矢量作用时间抑制零序电压的方法无法使用,因此提出一种120°矢量分解的方法来完全消除系统中的零序电压。新型调制策略利用Sigma-Delta调制器过采样及噪声压缩技术,优化逆变器输出电压频谱;同时利用三电平空间矢量图中两个大小相等、互差120°的基本矢量共模电压之差为零的原理,采用120°矢量分解,将参考电压分解为两个大小相等、角度互差120°的参考电压矢量,并由两台逆变器分别产生,从而完全消除系统中的零序电压。为了验证理论的有效性,搭建并调试开绕组电机双端级联式五电平逆变器实验平台,完成了传统180°矢量分解调制及其零序电压抑制、Sigm-Delta调制及其零序电压消除的实验。实验结果验证了本文理论研究内容的正确性和有效性。
[Abstract]:As a new topology, two-terminal cascaded five-level inverter of open-winding motor is connected by two diode-clamped three-level inverters to realize the output characteristics of the five-level inverter at both ends of the open-winding motor. Compared with the traditional five-level inverter, it has the advantages of low DC voltage, good fault tolerance, flexible control and so on. It has a broad application prospect in high-voltage and high-power situations. Firstly, this paper analyzes the commutation process of the dual-inverter system. Five voltage output states of inverter are summarized. The mathematical models of open-winding asynchronous motor in three-phase static coordinate system, two-phase stationary coordinate system and two-phase rotating coordinate system are re-established, and the conversion from electrical flow to signal flow is realized by using ideal linear transformer. The mathematical model of open-winding asynchronous motor in two-phase stationary coordinate system in MATLAB is built, and the simulation test is carried out to verify the correctness of the model. For the open winding motor two-terminal cascaded five-level inverter system with common bus structure, the 180 掳vector decomposition modulation strategy under traditional SVPWM modulation is studied, taking into account the problem of zero-sequence voltage suppression. Firstly, the principle of 180 掳vector decomposition modulation strategy is analyzed in detail. By 180 掳vector decomposition, the reference voltage vector is decomposed into two equivalent vectors of equal size and opposite direction, thus the five-level modulation problem is simplified as a three-level modulation problem. On the basis of this modulation strategy, the harm of zero-sequence voltage in the system is analyzed, and the zero-sequence voltage in the system is restrained by adjusting the action time of small vector. Aiming at the problem of obvious harmonic spike in the traditional SVPWM modulation output voltage spectrum waveform, a modulation strategy based on Sigma-Delta modulator is proposed to optimize the output voltage spectrum waveform. However, because the switching state of the new modulation strategy is not fixed, the traditional method of changing the action time of small vector to suppress the zero-sequence voltage is not available. Therefore, a 120 掳vector decomposition method is proposed to eliminate the zero-sequence voltage in the system. The new modulation strategy uses Sigma-Delta modulator over-sampling and noise compression techniques to optimize the output voltage spectrum of the inverter, and uses the principle of zero common mode voltage difference between two basic vectors of equal size and 120 掳difference in three-level space vector diagram. By using 120 掳vector decomposition, the reference voltage is decomposed into two reference voltage vectors of equal size and 120 掳angle difference, which are generated by two inverters respectively, thus eliminating the zero sequence voltage in the system. In order to verify the validity of the theory, an experimental platform of two-terminal cascaded five-level inverter for open-winding motor is built and debugged. The experiments of traditional 180 掳vector decomposition modulation and zero-sequence voltage suppression Sigm-Delta modulation and zero-sequence voltage elimination are carried out. The experimental results verify the correctness and validity of the theoretical research in this paper.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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