A Wavelet Inspired 2nd Order LPF Based Control Technique for Active Power Filters

  • Isaac OTCHERE

Student thesis: Master's Thesis


Recent developments in solid state power electronic devices such as converters, diode bridge rectifiers etc. have played a significant role by supplying electric controlled power not only to industrial loads but residential buildings as well. This is due to the flexibility and reliability in their solid state operations. However, these devices which are mostly nonlinear loads contribute to power quality (PQ) related concern. Thus, polluting the power grid with more harmonics and also increase the reactive power demand. These actions consequently deteriorate the overall efficiency of the power system. But with advanced innovation in the semiconductor industry, Active Power Filters (APFs) are considered to be one of the strongest contenders deployed to compensate these PQ related obstacles. But the steady state and dynamic performance of APFs for effective compensation largely depend on the control technique deployed which is considered as the brain of APF. Therefore, a novel wavelet inspired 2nd order Low Pass Filter (LPF) control technique for online Shunt APF application is proposed in this thesis. The proposed controller stems from the concept of Discrete Wavelet Transform (DWT) based Multiresolution Analysis (MRA) to extract the fundamental frequency component of a distorted and unbalanced load current. The extracted signal is deployed to formulate the reference current generation signal needed to drive the Shunt APF. But to improve the accuracy of the fundamental frequency extraction, only one level of the 2nd order LPF pyramid tree is utilized. Also, no external compensation strategy was used in compensating the extraction error. The proposed online 2nd order LPF based controller is simulated in a Simulink environment and the dynamic performance is tested under unbalanced and distorted conditions. To further validate the performance of the proposed controller, the famous Synchronous Reference Frame theory have been used as bench mark.
Date of AwardMay 2015
Original languageAmerican English
SupervisorVinod Khadkikar (Supervisor)


  • Solid State Power Electronic Devices
  • Power Quality
  • Power System
  • Active Power Filters
  • Low Pass Filter
  • Discrete Wavelet Transform.

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