中文摘要：

三电平逆变器因为电压应力只有两电平逆变器的一半,并且具有损耗小、谐波含量低的特点,所以在风能、太阳能等新能源发电系统中得到了越来越多的应用和研究。文中从新能源的功率随机波动特点出发,首先,评估了应用于新能源系统的传统三电平逆变器拓扑的损耗特点,然后,针对应用于光伏发电系统的三电平并网逆变器提出了硬件和控制策略上的改进,最后,利用一台样机验证了所提出的改进措施。试验证明,所提改进措施能够有效改善和提高三电平逆变器的效率,尤其是在中低功率范围内的效率。

英文摘要：

By virtue of its remarkably low voltage stress,low harmonics and low power loss,the three-level inverter is increasingly applied in renewable energy systems such as the solar and wind power system.Anyway,the manifest feature of the new energy generating system is power fluctuation.Proceeding from the stochastic power fluctuation,the conventional three- level inverter is evaluated in terms of its topological power loss first.Then,some new schemes of hardware and control strategies are proposed for a three-level inverter applied in a solar inverter.Finally,aprototype is built to verify the improvement.Test results show the proposed schemes can improve the efficiency of the three-level inverter,especially the efficiency in the low and medium power range.