【作者】 王国君；

【导师】 孙力；

【作者基本信息】 哈尔滨工业大学 ， 电气工程及其自动化， 2008， 硕士

【摘要】 随着能源短缺问题的日益突显,新能源与再生制动能量的利用成为人们的关注的焦点。并网逆变器因此在新能源发电及再生制动能量回馈领域得到广泛的应用。但是,目前应用的并网逆变器大多存在着逆变电流谐波污染大、功率因数低,抗干扰能力差,所需传感器数量较多等缺点。本文将基于虚拟磁链(Virtual Flux, VF)的直接功率控制(Direct Power Control, DPC)策略应用到并网逆变器中,并提出了虚拟磁链观测器的改进方法,解决传统方法存在的问题,在省去交流电压传感器的后,能保证系统的可靠高效运行。首先,本文分析三相电压型并网逆变器的拓扑结构及其工作原理,建立并网逆变器系统在三相静止坐标系,两相静止坐标系及两相旋转坐标系下的数学模型,为深入分析并网逆变器的直接功率控制策略奠定了理论基础。其次,在并网逆变器中引入虚拟磁链的概念,用于无交流电压传感器的瞬时功率计算。为解决因初始值选取不当造成的观测结果存在直流偏差等问题,本文设计了改进虚拟磁链(Improved Virtual Flux, IVF)观测器,进一步改善了系统控制性能,并在Matlab/Simulink仿真环境下对所提出改进方法进行仿真验证。在此基础上,本文研究了并网逆变器系统的滞环和定频两种SVPWM调制方式的原理,给出了两种调制方式的电压矢量的选取方法,分析了滞环SVPWM调制中的功率滞环宽度与开关频率的关系,分别建立了采用两种调制方式的IVF-DPC并网逆变器系统仿真模型,对其控制性能进行对比分析。最后,采用以数字信号处理器TMS320F2812为控制单元,搭建了定频SVPWM调制的IVF-DPC并网逆变器系统实验平台。通过实验研究验证了本文所提出的并网逆变器及其控制方法的正确性和实用性。更多还原

【Abstract】 With the lack of the energy becoming more and more serious, it is going to focus on the utilization of the renewable energy and the regenerative braking energy. Therefore the grid-connected three-phase voltage source inverter is widely applied in these fields. However, most of the inverters have the problems of high harmonic pollution in invert current, low power factor, and too many sensors. This paper proposes a novel control strategy, which based on direct power control with virtual flux, for grid-connected inverter to solve these problems. The improved method for the virtual flux observer is illustrated to improve the stabilization of the voltage-sensorless inverter in the paper.Firstly, it is analyzed the structure and theory of the grid-connected three-phase voltage source inverter, and established the mathematical model in the three-phase static coordinate, two-phase static coordinate and two-phase rotating coordinate. It provides the foundation for analyzing the theory of direct power control.Secondly, based on the analysis of the theory of direct power control, the conception of virtual flux is utilized in the grid-connected three-phase voltage source inverter to estimate the transient active and reactive power. The virtual flux observer is improved to solve the problems of the direct current offset and improve the system stabilization. The improved virtual flux observing method is simulated in the Matlab/Simulink environment.After the analysis above, the theory of the hysteresis and the fixed frequency SVPWM modulation for IVF-DPC inverter is studied. The relationship between the switch frequency and hysteresis band is researched in order to compare the performance of two modulations. The principle is explained for the voltage vector choice. The system simulation models of two modulations are founded to compare the control capability.Finally, Using the TMS320F3812 digital signal processor as the control unit, the experiment system of grid-connected three-phase voltage source inverter is designed which is based on IVF-DPC in fixed frequency modulation. The experimental results prove the correctness and practicability of the grid connected inverter with the control strategy.更多还原