Influence of reactors on input harmonics of variable frequency drives

AC line reactors and DC link reactors are widely used in variable frequency drives (VFDs) to improve the drive performance such as reducing input harmonics, improving the input power factor, and protecting the drives from surges etc. The effectiveness of both types of reactors in reducing input harmonics is affected by many factors, including the loading of the drives and the system source impedance. In this paper, a simulation is conducted to investigate the influence of such factors. An onshore and offshore power distribution systems with VFDs as the dominant loads are used as the case studies. The rules to evaluate needs for AC line or DC link reactors are proposed for practical applications.