三相变流器LCL滤波器参数优化新方法

A New Parameter Optimization Method of LCL Filters in Three-phase Converters

LCL滤波器体积较小,对高频电流谐波有着显著的抑制作用,广泛应用于大功率三相AC/DC变流器中。LCL滤波器的参数设计大多考虑开关频率处的谐波,以LCL滤波器输入输出端的谐波电流衰减作为优化目标,往往会导致参数设计大于实际要求,增大滤波器体积与成本,且不易理论验证是否满足总谐波失真(total harmonic distortion,THD)要求。提出一种基于THD估算的LCL滤波器设计优化方法,将THD估算模型代替实际LCL滤波器模型进行试验设计,以IEEE Std 1547.2-2008规定的并网标准中总谐波畸变率为优化目标,滤波器谐振频率为约束条件,单次谐波畸变率为修正因子,通过简化梯度算法进行LCL滤波器参数的优化,并讨论闭环系统的稳定性和电流环PI控制器的影响。最后通过仿真和实验验证了设计的合理性。

LCL filters are widely used in high power three-phase AC/DC converters for its advantages of small volume and inhibition of high frequency current harmonic. The parameter design of LCL filters mostly considers switching frequency harmonic with the input and output harmonic current attenuation as the optimization target. The designed parameters may larger than the actual demand. It would lead to the increase of size and cost, and is not easy to verify the Total Harmonic Distortion （THD） requirements. This paper proposes a method of LCL filter design based on the THD estimation. It uses the THD estimation model instead of the real LCL filter model for Design of Experiments with IEEE Std1547.2-2008 interconnection standards. Total harmonic distortion rate is used as the optimization objective, the filter resonance frequency as the constraint conditions, and a single harmonic distortion rate as the correction factor. Predigesting Grads Algorithm is adopted for LCL filter parameters optimization. The stability of the closed-loop system and the current-loop PI controller influence are discussed. Finally, simulation and experimental results verify the rationality of the design.