Enhancing the stability of AHF

Abstract

Active harmonic filters (AHFs) have a problem of losing their stability when they are installed in a distribution network having power factor correction (PFC) capacitors. This study has made an effort to assess the stability margin of an AHF installed in a distribution network along with PFC capacitors. After establishing the underlying cause of instability, an attempt has been made in this study to propose a control algorithm, so that the problem of instability is overcome when these AHFs are made to operate in tandem with PFC capacitors. The effectiveness of the proposed control algorithm is established by carrying out detailed simulation studies of the system. A 30 kVA laboratory prototype of the AHF has been fabricated. Detailed experimental validations have been carried out utilising the aforesaid prototype to confirm the viability of the proposed scheme. Nomenclature List of symbols K P proportional gain of the controller K R resonant gain of the controller ω n resonant frequency of the controller ω b bandwidth around the resonant frequency T one switching period of the inverter ϕ phase angle of the network at the nth harmonic frequency ϕ L phase angle of the nth harmonic load current component ϕ T phase angle of the test current generated by the active filter

Enhancing the stability of active harmonic filter using artificial neural network‐based current control scheme

“…A critical survey of the schemes reported in the literature indicates that there exists a need to dynamically adjust the controller gain by continuously monitoring the variations in the network so that the SAHF achieves stable operation under all operating conditions of the network. One such scheme is reported in [33], wherein a current perturbation technique is employed. The prevailing values of network parameters are estimated by monitoring the change in the supply current before, and after the perturbation.…”

“…However, this scheme becomes ineffective when the operating condition of the network changes significantly compared to the instant when the network impedance estimation process was executed. In order to address this issue, it has been recommended in [33] to perturb the network more frequently, and thereby assess the changes in network parameters on a periodic basis. This in turn requires frequent stoppage of the harmonic compensation process, and hence it may not be an acceptable solution.…”