摘要
三电平逆变器并网系统适应于高压大功率场合,宜采用LCL滤波器。相比L滤波器,LCL滤波器采用的滤波电感较小,能有效减小系统体积并降低损耗等。该文首先对基于正弦脉宽调制SPWM(sinusoidal pulse width modulation)的三电平并网逆变器进行了详细的纹波分析。在保持同传统定义的三电平开关函数不变的基础上,将一个调制周期分4个时段,并对4个时段的纹波变化规律做具体分析,在忽略高频分量的开关模型下详细计算出桥臂侧电感与纹波电流幅值之间的关系;然后考虑网侧电感参数和电流衰减率之间的关系以及滤波电容参数的限制范围,计算网侧电感和滤波电容参数值;同时为抑制LCL谐振峰并兼顾系统损耗,采用无源阻尼法对电容串联电阻阻值进行选取。最后,通过仿真和试验证明了该方法的可行性。
With the increasing penetration of renewable energy in the utility grid and the emerging concept of micro grid system with renewable energy, there is a high demand for the three-level grid-connected power inverter. The grid interface inverter plays a critical role as the energy control center in the renewable energy micro-grid. Compared with L filter, the LCL filter has been concerned for the advantages of smaller filter inductance, effectively reducing the system size and loss. The aim of the paper is to propose a design procedure for an LCL filter in a grid-connected three-level inverter. The main goal is to ensure a reduction of the ripple current at a reasonable cost, and at the same time obtain a high performance rectifier. In this paper a step-by-step procedure for designing an LCL filter is proposed and verified by simulations and experiments. Firstly, the paper provides a detailed analysis of the ripple current based on a three-level inverter with the strategy of SPWM(sinusoidal pulse width modulation). A power frequency cycle is divided into 4 periods to be specifically analyzed and the relationship between inverter-side inductor and ripple current amplitude is calculated based on the switch model that ignores the component of high frequency. Maximum inverter-side current ripple is shown in the figures both around summit and zero of fundamental current. As a result, current ripple wave around summit has mare representative. In this way, the method can be easily extended to three-level inverter topology and SPWM strategy. Then the result is used to narrow range of inverter-side inductance. Considering the higher the inductance, the more the losses, inductance should be smaller in order that it will not affect the filtering. Secondly, the parameter of grid-side inductor is designed considering the effect of the ratio of grid-side inductor to inverter-side inductor on the decay rate of harmonic current. And the parameter of filter capacitor is determined by the power limitation. Then, resistor has been know
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第22期199-206,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
广东省引进创新科研团队计划资助(2011N015)
国家863高技术基金项目(2015AA050104)
关键词
滤波器
逆变器
脉宽调制
三电平并网逆变器
纹波电流
electric filters
electric inverters
pulse width modulation
three-level grid-connected inverter
ripple current
