复合三电平直流变换器及其高电压增益运行优化控制

Among the shipbord integrated power system, photovoltaic system and electric vehicle driving system, there is a common problem, namely different voltage levels, which exist between the high-voltage DC bus and the low-voltage electrical equipments, PV arrays, and batteries. Therefore, the future research on a family of hybrid three-level DC-DC converters with high voltage-gain will be carried out in this project. There are two key scientific problems, such as the uniform establishment of the hybrid three-level DC-DC converters and the optimal control of the converters operation. As to the research ways, the methods of theory analysis and deduction, numerical simulation analysis, and the verification of prototype experiments are adopted. Firstly, the combined forms between the power switch and diode are extended, and the minimal three-port power cells are established, then the principle of high power-density and operation with high voltage-gain is revealed. Secondly, according to the proposed PWM control method with double-wave, the optimal control method is developed based on the fuzzy control theory and perturbation method. In addition to the optimized duty cycles, both the efficiency and the capacitor voltages balancing of the converters are improved. Finally, the validity of the proposed topology family and the optimal control method is verified by the prototype. In a word, the research results will have the active impact on the improving performance of the DC-DC conversions among the shipboard power distributed system, photovoltaic system, and electric vehicle driving system.

舰船综合电力系统、光伏发电系统和电动汽车驱动系统中，高压直流母线与低压用电设备、低压光伏阵列、低压蓄电池之间，存在着电压等级匹配悬殊的共性问题。为此，本项目拟开展一族高电压增益用复合三电平直流变换器的研究工作。围绕变换器拓扑族的统一构建和高电压增益运行优化控制两个要点，采用理论分析推导、数值仿真分析和平台实验等方法进行研究。首先，拓展功率开关和二极管的组合形式，建立最小三端口功率单元，根据拓扑合成约束条件，探索统一构成复合拓扑族的功率单元组成规律，进而揭示其高功率密度、高电压增益运行机理。其次，在双调制波PWM控制方法基础上，发展一种基于模糊控制理论和扰动法的优化控制方法，使得变换器功率开关消除极端占空比的同时，提高变换器的效率和电容电压平衡特性。最后，搭建实验平台验证拓扑族和优化控制方法的有效性。研究成果将对舰船配电、光伏发电和电动汽车驱动系统等直流变换环节性能的改善产生积极影响。

本项目针对光伏发电系统中，不受“阴影遮蔽”等因素影响的“并联低压光伏电池与电网电压等级不匹配问题”，研究了一种具有高电压增益的直流变换器，将并联光伏电池的低压直流电变换到直流母线所需的高压直流电，供并网逆变器并网发电。提出了一种将两个准Boost三电平直流变换器“输入端串联-输出端并联”的拓扑合成方法，创新性地构建了一种新型的复合Boost三电平直流变换器拓扑，无需变压器便可实现高电压增益、非极端占空比运行。该研究新成果有望实际应用于产业化光伏发电系统中；针对舰船综合电力系统中，将舰船发电与电力推进、舰载设备用电集成，并以高压直流母线作为电能的主要传输和分配形式，构成舰船的直流区域配电系统。研究了一种能够将舰船的850~1250V的高压直流母线电压降压为68V的低压直流电的大比例降压直流变换器，作为二次直流电源为舰载重要直流设备供电。创新性地提出了一种无变压器式大比例降压三电平直流变换器，可采用易于集成封装的低耐压功率器件，构成高功率密度、高效率的舰载二次直流电源，既实现大比例降压，又能够避免功率开关的极端占空比运行。该研究成果有望实际应用于舰船直流区域配电系统中的舰载二次直流电源；大比例降压三电平直流变换器的拓扑结构决定其对占空比的控制具有一定的冗余度。研究了在功率开关占空比允许范围内最大限度地减小电感电流纹波的方法。根据所选功率开关所允许的占空比范围、电压增益范围，构建了拓扑双调制度的约束方程，确定了两种类型的协调控制系数，提出了功率开关非极端占空比与电感电流纹波协调控制的方法。该研究成果有望实际应用于舰船直流区域配电系统中的舰载二次直流电源中。