混合可再生能源并网发电中变结构多输入直流变换器的研究

The exploitation and utilization of renewable resources have attracted a great deal of attention. However, solar energy and wind energy are affected by some factors such as climatic conditions and they are unstable and discontinuous. So it is necessary to integrate the renewable energy resources to form a hybrid power system to provide continuous and stable electric power. In order to simplify the configuration and lower the cost, multiple-input converter (MIC) will be the development tendency replacing the several single-input converters in the hybrid renewable energy power system. Because the voltage level of the renewable resources is quite different, for instance,the PV output voltage is relatively low to about 45V, the multiple-input DC/DC converter should achieve high voltage gain to meet the requirement of DC bus when the renewable resource with lower output voltage worked individually. Unfortunately, the existing multiple-input DC/DC converter cannot meet this requirement. To overcome this problem, the concept of Variable-Structure Multiple-Input DC/DC Converter (VS-MIC) is proposed in this proposal. The VS-MIC can transform to two sub-topologies by controlling the changing circuit to be suitable for the combination mode with several input sources and the individual mode with high voltage gain at lower input voltage. The research emphases of this project are the structure of the VS-MIC, control strategies and stability analysis, which researched successfully would help to improve the reliability and flexibility and reduce the cost of the hybrid renewable energy power system, and provide a new modularized method for the development of renewable energy. Therefore, it has important theoretical value and practical significance.

鉴于新能源发电的不稳定和不连续性，多种新能源混合的分布式并网发电系统显示出广阔的发展空间和应用前景。为简化混合可再生能源发电系统的结构和降低成本，多输入直流变换器逐步取代多个单输入直流变换器成为未来的发展趋势。由于各种新能源端电压等级有高有低，在低电压等级输入源单独工作时，为满足直流母线电压的要求，直流变换器必须具有高增益性，而现有的多输入直流变换系统并不能满足该要求。为解决上述问题，本项目提出研究变结构多输入直流变换器的思路，用同一套电路元件，通过简单的切换控制，改变变换器的结构，使其既能实现多输入时的联合供电，又能满足低电压输入源单独工作时的高增益性。本申请项目以变结构多输入变换器的构成、控制方案和系统稳定性分析为研究重点，项目的研究成功将有助于提升混合可再生能源并网发电系统的可靠性和灵活性，降低成本，为新能源发电的推广应用提供一种新的模块化的解决思路，具有较好的理论价值和实用意义。

本项目研究混合分布式并网发电系统中变结构多输入直流变换器系统，用同一套电路元件，通过简单的切换控制，既能实现多输入时的联合供电，又能满足低电压输入时的高增益工作。项目的研究目标在于简化混合可再生能源发电系统的结构和成本。项目主要完成了以下几方面的工作：（1）高效率变结构多输入直流变换器拓扑：项目主要从变结构电路拓扑构成及提高效率两个方面进行了研究。其一从开关电感三端网络出发，提出了基于拓扑组合和基于倍压单元的两类变结构多输入直流变换器，进行了相关理论分析和实验验证，取得了较好的效果；其二从提高效率的角度，研究了基于耦合电感的有源钳位型和低输入纹波的高增益软开关直流变换器，并进行了实验验证，为变结构多输入直流变换器效率的提高奠定了基础。（2）变结构多输入直流变换器的数学模型：分别对单输入高增益直流变换器和两输入直流变换器进行了小信号建模分析，建立了其平均小信号模型并进行了相关的实验研究，为下一步实际应用提供了支撑。（3）变结构多输入直流变换器的能量管理控制策略：研究了实际工况下各输入源的能量分配策略，分析了变换器结构切换时的控制方案，并进行了相关的实验研究，结果表明变换器能够实现结构的自动切换，且切换后能快速恢复稳定；研究了基于粒子群算法的多端口变换器的最大功率跟踪策略和基于竞争策略的多端口变换器能量管理策略，能满足不同应用场合的需求。