一种新型单相三开关光伏并网逆变器研究

摘要

光伏逆变器由于受外界因素以及逆变器的一些内在因素的影响，导致逆变器对输入电压的要求很严格。传统的逆变器加变压器的方法和多级级联的方法不能够妥善解决输入电压适应性的问题。为满足对大范围直流电压输入变化的适应性要求，同时实现光伏并网逆变器逆变与升压两个功能，提出了一种新型的单相三开关光伏并网逆变器拓扑。采用高频开关器件和反激变换器，替换了传统笨重的工频升压变压器，使得逆变器的体积、重量及成本降低，易于集成，且提高了变换效率。实时波形反馈技术的闭环SPWM（sinusoidal pulse width modulation）控制方法，可提供快速响应。通过一个小的交流滤波器可获得低谐波失真的正弦输出。对理论分析结果进行仿真验证，结果表明该新型单相三开关光伏并网逆变器具有拓扑简单，适应大范围直流输入电压变化，可靠性高等优点。%There are strict requirements of input voltage for a photovoltaic inverter due to some external effects and internal factors, and it is difficult to solve the problem of tolerance to varied input DC voltage properly through the traditional method of an inverter plus a transformer and multi-stage cascading. In order to meet the need of tole-rance to a widely varied input DC voltage and realize the function of inversion and step-up in photovoltaic grid-connected inverter, this paper puts forward a novel single-phase photovoltaic grid-connected inverter topology with three switches. High-frequency switches and fly-back converter were adopted to substitute the traditional bulky line frequency step-up transformer, which made the system easy to integrate with small volume, low weight and cost, and higher efficiency. The closed-loop sinusoidal PWM control method with real-time waveform feed-back technique can provide fast dynamic response. Through a small ac filter, the inverter achieved low-THD sinu-soidal output. Simulation results verify that the novel single-phase photovoltaic grid-connected inverter is fea-tured by simple structure and control, tolerance to a widely varied input DC voltage with high reliability.