新能源并网逆变器用复合型输出LLCL型滤波器的改进

程超，汪飞，许德志，阮毅

(上海大学 机电工程与自动化学院，上海200072)

摘要：通过对单相并网逆变器输出侧电流谐波的分析表明，在逆变器输出侧的电流谐波主要集中在开关频率和开关频率的整数倍处，其中开关频率处的谐波含量最大。为了更大程度地对开关频率处的谐波进行抑制而选择LLCL滤波器。由于系统谐振尖峰的存在，考虑成本低和简单的特点，所以选择无源阻尼法来抑制系统谐振尖峰。为了减小阻尼损耗而选择了电感和电阻并联方式。根据LCL滤波器能够在大于2倍开关频率区间表现的良好滤波能力以及LLCL滤波器在开关频率处能够更大程度地抑制电流谐波的特征，将二者结合产生了复合型LLCL滤波器。最后用仿真和试验证明： 复合型LLCL滤波器在滤波效果以及阻尼损耗方面表现出的相对优越性。

关键词：逆变器; LLCL滤波器; 串联谐振; 开关频率

通讯作者：程超

中图分类号：TM 464文献标志码： A

收稿日期:2014-12-09

A Composite LLCL Filters of Grid-Connected Inverters for

Renewable Energy Application

CHENGChao,WANGFei,XUDezhi,RUANYi

(School of Mechatronics Engineering and Automation, Shanghai University， Shanghai 200072, China)

Abstract：Based on harmonic analysis of the output current of a single-phase grid-connected inverter, the output current harmonics mainly concentrate at the switching frequency and its integer multiple harmonics. And the harmonics at switching frequency is the most. To damp the harmonics at switching frequency greatly, LLCL filter was chosen. Due to the resonance peak, considering the low cost and simplicity, passive damping methods were selected to suppress the resonance peak. In order to reduce the losses on the damping components, an inductor and a resistor in parallel were adopted. According to the good filtering performance above twice the switch frequency of LCL filters and the better filtering characteristics of current harmonics at the switching frequency of an LLCL filter, a composite LLCL filter was investigated. Simulations and experimental results proved that the composite LLCL filter had better filtering effect and less damping losses by combining the two types of filters.

Key words： inverter; LLCL filter; series resonant; switching frequency

0引言

在国际不可再生能源日益匮乏的背景下，以风力发电和太阳能发电等为代表的新能源并网发电技术显得越来越重要[1-2]。作为新能源并网发电的核心部分——并网逆变器，需要通过滤波器与电网连接，达到阻止电流谐波进入电网而造成电网的不稳定和损坏。因此如何设计更有效的滤波器来获得高质量的进网电流显得格外重要。

并网电流高次谐波主要集中在逆变器开关频率及其整数倍频率处。……