Comparison of active and passive damping methods for application in high power active power filter with LCL-filter

LCL-type filter possessing sufficient attenuation ratio for switching ripple with small LC parameters is appropriate to be used as output filter to get high slew rate of compensation current. However, LCL-filter, as a three order resonant circuit itself, is difficult to be stable. This paper compares active and passive methods for LCL filter resonance damping; assesses their suitability for the high power active power filter application and presents their benefits and drawbacks. The results presented show that both methods compensate harmonics effectively and attenuate switching ripple sufficiently. However, there are still some differences both in the filtering performance and the power losses in the high power application. The active methods require more sensors and increase algorithm complexity, while additional damping resistors are needed in the passive methods and result in large losses. Simulation validates the feasibility of the method proposed by this paper.