电容自均压带辅助二极管多电平变换器拓扑及控制研究

Multilevel converter is an important development direction of high voltage power converters with lager capacity,and the capacitor voltage unbalance issue is a key problem for the application of multilevel power converters.A novel capacitor voltage self-balance multilevel converter with clamping diode (CVS-MC) is proposed and the mathematic model based on S-Function is built. The pulse width modulation and system controlfor CVS-MC is discused and developed. The power of a unit in the converter is calculated and analysised by using the model of the converter and the rule of influence on the power and the capacitor voltage of the converter which is composed by nonideal parts (time delay, nonideal driving pulse and so on.) is studied and analysised. Besides, the working condition of the clamping diode and the influence on capacitor voltage banlance is analysised. Finally，a prototype of CVS-MC will be built. The proposed multilevel converter topology and control method will be validated by experiments.

多电平变换器是高压大容量电力电子变换器的重要发展方向，电容电压不平衡是影响多电平变换器应用的关键难题，本项目通过拓扑推演，提出一种电容电压自均衡带辅助二极管多电平变换器拓扑，得出构成规则；同时基于开关函数建立带辅助二极管多电平变换器的数学模型，研究变换器脉宽调制方法与控制方法；利用所建数学模型对该变换器的单元功率、电容电压等进行分析；同时，对该变换器中辅助二极管工作特性进行分析，并且对变换器单元电容电压平衡的影响因素进行分析；搭建实验样机进行实验研究。

电容电压不平衡是目前多电平变换器技术的重要问题之一，也是研究热点。本课题完成了计划研究内容，提出了带辅助二极管电容电压双向均衡的电路拓扑，通过在半桥拓扑增加辅助二极管，实现邻近单元电容电压的箝位控制，同时采用左右箝位支路构成闭环的箝位通道，使得整个变换器的电容电压得到均衡，大大简化了电容电压的控制复杂度，只需很少电容电压检测电路，使变换器电容电压检测控制接近于两电平变换器的水平；研究了带辅助二极管电容电压自均压的变换器的脉宽调制方法和控制方法，提出了基于分时复用思想的直流电压控制；同时提出一种灵活直流电容电压控制方法，实现变换器驱动电机时的下部分阀体电容电压灵活控制，提高其效率和调制比；分析了带辅助二极管电容电压自均衡变换器中二极管箝位特性和影响因素，改进了拓扑结构，提高了拓扑实用性。