微网储能两级式双向变流器稳定性机理研究

Energy storage based bidirectional converting is one of the key techniques to promote the efficiency and stability of new energy powered microgrid system. This project mainly concentrates on a non-isolated bidirectional two-stage DC/AC converter designed for energy storage system of microgrid and deal with its stability issues such as dynamic instabilities and relative control strategies. The main concerns including: (1) hierarchically define system aggregation and decomposition level, derivate the equivalent analytical mathematic model for single-phase and three-phase two-stage inverter; (2) investigate the relation between filter parameters and system stability boundaries synthetically in terms of two operation directions; (3) analyze the influence from battery inherent impedance on the system stability by concerning simplified equivalent circuit static model and nonlinear dynamic model respectively; (4) by extracting instability characteristics,, design instability suppressing algorithm with self-adaptive regulation abilities. Via researching the instable behaviors and its suppressing strategies, to improve the operation efficiency and stability is the starting point of this project. Analysis of influence from batteries and filters on stability of bidirectional two-stage converter system is the main research innovation. The research achievement could promote the mutual knowledge penetration between control theory, power electronics and information processing, and provide further theoretical support for popularization of energy converting techniques.

储能型双向变流是提高新能源发电微网运行效率与可靠性的关键技术之一。本项目以微网储能系统中非隔离型两级式双向DC/AC变流器为研究对象，针对系统失稳机理及抑制算法展开研究，主要包括：（1）分级确定系统的集结和分解程度，建立单相、三相两级式系统的等效解析数学模型；（2）剖析交流侧LC滤波器参数与系统失稳机理及双向运行模式稳定边界的关系；（3）分别建立储能电池静态等效电路模型和非线性动态模型，研究储能电池对系统失稳特性的影响；（4）分析失稳特征量，设计具有自适应能力的失稳抑制算法。探讨微网双向变流器的失稳行为，设计抑制策略以提高其运行可靠性是本课题的出发点。从机理上研究储能电池、交流侧滤波器对双向两级式变流器稳定性的影响是主要创新点。研究成果能促进控制理论、电力电子、信息处理等学科的交叉融合，为新能源发电微网储能变流技术的进一步推广提供理论支撑。

本项目主要研究了微网系统中非隔离型双向DC/AC并网以及DC/DC储能变流器的不稳定性及控制问题。主要工作包括：（1）以稳定裕度为指标量，对双向DC/AC并网型变流器LCL滤波器参数进行了优化设计；（2）基于小信号模型和阻抗判据分析了风光互补直流微网稳定性问题，并设计了直流母线电压控制方法；（3）设计了单开关双耦合高电压增益变流器和新型PT控制变流器并将其应用于光伏发电单元；（4）提出了浮地型忆阻与忆容器模拟电路，并将其应用于设计张弛振荡器以及新型控制器，以期实现对微网变流器失稳行为的控制。相关研究工作还在进行当中，将在后续工作中逐步完善对微网系统储能双向变流器的稳定性问题分析。