【作者】 方堃；

【导师】 周林；

【作者基本信息】 重庆大学 ， 电气工程， 2010， 硕士

【摘要】 随着作为能源主流的一次能源的日渐减少和能源需求的日益增长,新能源发电将在未来能源结构中占据越来越高的比例,新能源发电技术的研究和应用具有重要的战略地位,其中光伏发电是最具潜力的战略替代发电技术。高频化是变换器的发展趋势,能提高系统响应速度和功率密度,但高频化所造成的开关损耗加剧,致使变换器效率严重下降,电磁干扰增大。双频变换理念兼顾“高频”和“效率”,目前已发展设计出多种双频变换器,而且拓扑结构灵活,可控性高,特别适合中型、大型功率场合的应用。本文对双频变换器在光伏发电系统中的应用进行理论分析和仿真,提高光伏并网发电系统的功率密度、转换效率、动态响应速度和稳态精度。首先确定双频单相光伏发电系统的两级式系统结构,前级为Boost升压变换器保证稳定的直流链输出,后级为三桥臂双频Buck逆变器将光伏阵列输出电能并入电网,然后对光伏发电系统各环节进行分析研究。选用工程用单指数模型对光伏阵列建模,模型输出随光照强度和温度变化,能够模拟实际光伏阵列的输出情况。对Boost变换器的工作状态进行分析,确定参数设计各原则,并建立Boost变换器小信号模型,对该非最小相位系统采用电压反馈外环和峰值电流内环的双环控制策略,能够确保稳定的直流链电压输出。根据光伏并网发电系统要求,采用三桥臂双频Buck逆变器,分析其工作模式,并设计逆变器参数,针对高频单元和低频单元的不同职能,区别性的分别采用瞬时电流反馈控制和电流滞环控制策略。基于双频光伏发电系统,针对光伏发电系统输出变化范围较大的特殊性,设计可实现变拓扑的光伏发电系统。前级采用四开关新型Buck-Boost变换器,针对不同的光伏阵列输出电压实现升压、降压、直接输出三种模式的灵活控制;后级采用基于双频逆变器的变拓扑逆变器,根据输送功率的大小变化,改变工作单元、工作频率和滤波电感值,提高系统控制和功率转换的灵活性。更多还原

【Abstract】 Accompany with reduction and growing desire of first energy which is the main power currently, new energy power generation will stand a more important way in the future energy structure, which make its research and application more strategically vital. In all kinds of new energies, photovoltaic (PV) power generation is the most potential substitute.High-frequency operation could improve system responding speed and power density, so it is a trend of converter development. In the same while, it brings more switch wastage that takes down efficiency and increase electromagnetic interference. Double-frequency converting theory gives attention to both high-frequency and efficiency, and derives series of double-frequency converters which have flexible topology and high control performance, suitable in application for middle and high power transform.The thesis researches on application of double-frequency converter in PV power generation system, analyses double-frequency theory and do simulation for test, finally proves it could improve the system power density, converting efficiency, dynamic responding speed and steady precision.Firstly, the double-frequency single-phase PV system construction is confirmed and designed as two-stage system. The front stage applies Boost converter to make a steady DC voltage output; while the latter stage design a three-bridge double-frequency Buck inverter to transform power to the grid. Then, the paper researches on every part of the PV generation system. Simulation of PV cells are based on engineering model, which is capable to simulate real PV cell output under changing light intensity and temperature. The paper analyses the working state of Boost converter, supplies the design method of parameters, founds small-signal model, design double-circle control strategy to maintain a steady DC voltage output. According to requirement of PV grid-connected generation system, three-bridge double-frequency Buck inverter is chosen. After operating mode analysis and parameters design, controlling strategies are respectively run on high-frequency unit and low-frequency unit, instantaneous current feedback for former, hysteresis current control for latter.PV power generation system outputs energy in a huge variable range caused by environment change, the paper designs variable topology of PV system based on the designed double-frequency PV grid-connected generation system. For front stage, a new Buck-Boost converter with four switches is designed to implement voltage increase, decrease or direct transmission due to different PV cell output voltage, which makes the control more flexible. For the latter stage, variable inverter topology is developed based on double-frequency inverter, which could change working unit, switch frequency and filter inductance to fulfill transformed power variety, that also improve flexibility of system control and power transform.更多还原