二极管电容电感网络高增益变换器软开关及动态性能优化

DC-DC converters with high voltage gain usually lack features like high efficiency and fast dynamic performance. It has been one of the key scientific and technical issues urged to be solved in the field of renewable energy generation and storage system. Compared with other existing high step-up DC-DC conversion technologies, Diode-Capacitor-Inductor (DCL) network voltage boost cell has the potential advantages of low cost, high efficiency, and modularized design. However, converters based on this technology have the inherent deficiencies of large switching loss, series EMI issue and poor dynamic performance, which has been the major bottleneck problem limiting its practical application. This research program focus on a family of typical high voltage gain DC-DC converter with DCL network. Firstly, a high-frequency resonant converter with soft switching capability is proposed by combining its passive components and parasitic capacitors of switching devices. Consequently, efficiency and power density of the converter can be considerably improved and the cost of passive components could be reduced at the same time. Then the modeling simplification principle of multi-cell high-order nonlinear circuit is investigated. The reduced-order model with the consideration of inner damping can be established by utilizing the difference of time constants between DCL network and the external circuit. So the accurate system characteristics can be well obtained. Finally, the dynamic response process of the converter is studied based on the system’s time-domain characteristics. A nonlinear predictive control algorithm of minimum transient time will be proposed to improve the dynamic performance of the output voltage. Research results will provide the sound theoretical foundation and technical support for the practical application of DCL network based high voltage gain DC-DC converters, which will bring the direct economic and social benefit.

直流变换器的高增益与高效率、快速动态响应之间的矛盾，是新能源发电和储能系统等领域亟待解决的关键科学技术问题之一。综合现有高增益直流变换技术，二极管电容电感(DCL)网络升压单元具有低成本、模块化的潜在优势。但是该类变换器开关损耗大、噪声大、动态性能差，这些固有缺陷成为限制其实际应用的主要瓶颈。本项目以一类典型的DCL网络直流变换器为对象，研究利用其自身无源器件与开关管寄生电容的谐振，实现具有软开关的高频电路，提高效率和功率密度，降低无源器件成本；进一步研究多单元高阶非线性电路的简化建模原理，利用DCL网络与外部电路时间常数的差异，建立考虑系统阻尼的统一降阶模型，以获得精确的时域、频域特性；最后，基于时域特性，研究其最优的动态响应过程，提出调节时间最小的非线性预测控制算法，提高输出动态性能。研究成果将为DCL网络高增益直流变换器的实际应用提供系统的理论和技术支持，产生直接的经济和社会效益。

直流变换器的高增益与低成本、高效率、小型轻量化、快速动态响应之间的矛盾，是中小功率便携电源和户用光储发电系统面临的关键技术瓶颈之一。其背后的核心科学问题概括为：1）高增益意味着电力半导体器件和无源元件同时承受低压侧大电流和输出侧高电压，元件成本高且损耗大；2）电感电流、电容电压均为直流量，无自然过零点，软开关设计复杂且难度大；3）高增益场合，电压增益的强非线性和非最小相位系统特性明显，动态性能差。本项目从电压增益、元器件应力、成本、功率密度和效率五个维度量化比较包括级联（堆叠）型、多电平型、交错型、阻抗源网络型、开关电容（电感）型、磁耦合型等典型升压技术，揭示出多相交错多二极管电容网络升压结构兼有器件应力低和升压能力强的综合性能优势；进一步结合相邻二极管工作状态互补且动作时刻仅受开关器件控制的特性，优选公共电流支路，按照共用谐振元件最小化器件需求且能量尽量回馈高压侧的基本原则，提出适用的通用准谐振零电压（ZVS）、零电压转换（ZVT）软开关拓扑构造机理及参数优化设计方法，提高全电压范围电能转换效率不低于3%。针对一类开关电容倍压的双向直流变换器，提出了零器件成本的ZVS软开关拓扑构造理论和集成单电源驱动设计方法，显著减小功率板尺寸25%，降低驱动成本50%。基于无源元件时间常数差异，提出适用于多单元复杂结构高增益直流变换器降阶建模理论和方法，建立统一的二阶/三阶模型，精确刻画时域和频域特性；针对高增益升压型直流变换器强非线性和非最小相位系统特性，提出无源和有源阻尼设计理论，消除右半平面零点，将电压环带宽扩大10倍，有效满足高精度电源动态响应要求。研究成果为高增益直流变换器的综合优化设计提供科学理论指导，发表高水平SCI、EI检索学术论文10余篇，授权发明专利9项。部分高增益直流变换拓扑构造理论及软开关设计方法成功应用于集成中小功率电源模块和单兵作战便携电源设备，产生直接的经济和社会效益。