【作者】 陈博；

【导师】 王萍； 王议锋；

【作者基本信息】 天津大学 ， 电力电子与电力传动， 2019， 博士

【摘要】 近年来,随着储能技术进步和成本降低以及需求侧的演化发展,分布式储能在电力系统中的广泛应用是未来电网发展的必然趋势。同时,随着蓄电池的低压化,相关电力电子变换器拓扑的多样化和系统控制策略的复杂化,分布式储能系统正朝着高频化、高效化、小型化和可控化的方向发展。这就要求作为分布式储能系统核心设备的隔离型双向直流变换器具备高频、高增益、高功率密度、高效率和宽电压增益范围等特点。如何提升双向隔离型变换器功率密度、拓宽变换器的电压变换范围并同时保证变换器的全负载范围内的高效率功率变换具有重要的研究意义。为此,本文围绕“隔离谐振型双向功率变换技术”的课题,从变换器的高效、电压宽范围实现和高频、高效、高功率密度实现两方面开展研究,按照拓扑设计、数学建模、特性分析、参数优化和实验验证的顺序进行详细论述。本文的主要工作包括:(1)提出了新型的具有双变压器结构的高增益双向CLTC和CDT-LC谐振型直流变换器电路拓扑。两种电路拓扑可在全负载范围内实现零电压开通(Zero Voltage Switching,ZVS)和零电流关断(Zero Current Switching,ZCS),从而保证变换器高效率运行。介绍了两种拓扑的运行模态和工作特性。并针对拓扑中特有的双变压器结构提出了受控源等效的化简分析方法,定性的分析了CDT-LC拓扑所具有的增益特性优势。基于时域分析方法建立了对应的数学模型,研究了变换器的增益特性及软开关特性,验证了变换器在较窄的频率范围内实现双向0.8～1.2的宽范围电压增益,其特性十分适用于低压、大电流的分布式储能双向充放电场景中。同时,本文以谐振点效率最优为目标进行了合理的参数设计,获得了最优的谐振腔参数。(2)提出了谐振变换器的高频损耗模型,并基于CDT-LC的理论参数和仿真结果进行了对应的损耗分析。研究了采用Si C器件代替传统Si器件对变换器损耗的影响。通过建立2.5k W CDT-LC样机,进行实验验证理论分析的正确性与准确性。同时,通过与其他变换器的对比试验证实了CDT-LC变换器在工作频率范围、效率和增益调节范围等方面存在的显著优势。(3)提出了应用于高频高增益环境的改进型Multi-CLLC结构。介绍了拓扑的工作模态,并根据拓扑等效电路建立了具有普适性的数学模型。给出了详细高频软开关实现条件与变换器参数设计过程。此外,深入探讨了高频磁性元件集成设计方法,并提出了应用于PCB绕组的多线圈优化布线方法。最终,通过损耗分析计算验证了该方法对提高效率具有显著的作用。(4)搭建了一台400W额定工作频率1MHz的Multi-CLLC实验样机进行实验,验证了理论分析,实现了变换器的高效高功率密度。此外,通过对比试验,分析了Ga N开关器件对变换器效率提升的影响。同时,针对试验样机在高频情况下所遇到的问题进行了分析总结,并提出了对应的改进方案。证明了隔离谐振型双向直流变换器在高频场景中的应用仍然具有广阔的研究潜力和探索空间。更多还原

【Abstract】 In recent years,with the improved of energy storage technology and cost reduction,as well as the development of demand side,distributed energy storage is widely used as the inevitable trend of future power grid development.At the same time,with the low voltage storage battery,the diversification of power electronic converter topology and the complexity of system control strategy,distributed energy storage system is developing towards high frequency,high efficiency,miniaturization and controllability.This requires isolated bidirectional DC converter as the core equipment of distributed energy storage system to have the characteristics of high frequency,high gain,high power density,high efficiency and wide voltage gain range.How to improve the power density of bi-directional isolation converter,widen the voltage conversion range of converter and ensure high efficiency power conversion in the full load range of converter has important research significance.For this reason,this paper focuses on the subject of "Isolated Resonance Bidirectional Power Conversion Technology".The research is carried out from two aspects: the wide gain range with high efficiency and realization of high frequency,high efficiency and high power density for converter.It is discussed in detail according to the order of topology design,mathematical modeling,characteristic analysis,parameter optimization and experimental verification.The major works are organized as below:(1)Two novel circuit topologies of high gain bidirectional CLTC and CDT-LC resonant DC-DC converter with dual transformer structure are proposed.The two circuit topologies can realize ZVS and ZCS in full load range to harvest high efficiency.The operating modes and working characteristics of two topologies are introduced.A simplified equivalent analysis method is proposed to simplify the dual transformer structure by using controlled source,and the advantages of CDT-LC in gain feature are qualitatively analyzed.Based on the time-domain analysis method,the corresponding mathematical model is established to discusse the gain feature and soft-switching characteristics for the CDT-LC converter.It is verified that the converter achieves a bi-directional normalized voltage gain of 0.8-1.2 within a narrow frequency range.Its characteristics are very suitable for the bi-directional charging and discharging scenarios distributed energy storage with low-voltage and high-current.Besides,the parameters are designed reasonably to optimize the efficiency at the resonant point,and the optimal parameters are obtained.(2)The high frequency loss model is proposed,and the corresponding loss analysis for CDT-LC is carried out based on parameters and simulation results.The influence of replacing traditional Si devices with Si C devices on the loss of converter is studied.A 2.5k W CDT-LC prototype was established to verify the correctness and accuracy of theoretical analysis.At the same time,compared with other converters,the obvious advantages of CDT-LC converter in operating frequency range,efficiency and gain regulation range are confirmed.(3)An improved multi-CLLC structure for high frequency and high gain environment is proposed.The working mode of the topology is introduced,and a universal mathematical model is established.Detailed implementation conditions of high frequency soft switching and design process of converter parameters are given.In addition,an integrated design method of high-frequency magnetic components is discussed in depth,and a multi-coil optimal wiring method applied to PCB windings is proposed.Finally,the loss analysis and calculation show that the transformer design method has significant effect on improving efficiency.(4)A 400 W Multi-CLLC experimental prototype with rated operating frequency of 1 MHz was established to verify the theoretical analysis.It has achieved high efficiency and high power density.Besides,the influence of Ga N devices on the efficiency improving for converter is analyzed based on the comparative experiments.Also,the problems encountered in the high frequency experiments are analyzed and summarized.And some corresponding improvement methods are put forward.At last,it has proved that the application of isolated resonant bidirectional DC converter in high frequency scenario still has broad research potential and exploration space.更多还原