新能源并网逆变器用复合型输出LLCL型滤波器的改进

摘要

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.%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。