DSP Based Filter Design to Improve Power Quality for Industrial Customers

Abstract

Nowadays power quality phenomena has become a vital issue that is attracting many researchers due to advances in power semiconductor industries and its interfaces with existing power system networks. Various adjustable and non-linear loads at consumers premises derive current from the supply network which is never maintained to harmonics of the fundamental. The main focus of this paper is to identify the interharmonic content in a real time situation, improving the accuracy of the varying parameter based analysis and subsequently deriving the inputs to the proposed numerical filter. The frequency spectrum analysis is performed using digital signal processing algorithm to locate and identify the interharmonic content that will ultimately lead to find solution strategy in a real time environment. The validation and implementation of the above issue is carried out using matlab software. Mathematical models are formulated considering important non-linear sources such as ac voltage controllers, arc furnace loads, cycloconverters and loads that cause flickers. The concept is justified numerically and experimentally to address the random and non-linear behaviour of the overall system. Interharmonics which is considered to be one of the major cause for producing flicker is mathematically modelled. Modern adjustable drives also generate a wide spectrum of interharmonic components which affect the quality of the delivered energy, increase the energy losses, as well as decrease the reliability of a power system. This paper explores the application of digital low pass equiripple filter to the estimation of interharmonics and mitigate the undesired components accurately. The proposed digital filter algorithm with required specification is applied to the windowed version of original waveform to determine the coefficients of the filter to realize its effectiveness through hardware structure. Consequently, the spectral information obtained after processing is found to be the faithful representation of the fundamental component eliminating all interharmonics. The methodology used in this paper thoroughly investigates the effects of poor quality of power for consumers and suppliers. The proposed mitigation strategy for improving power quality can gain significant importance along with the issue of power quantity improvement.

Keywords: Arc furnace loads, Cycloconverter, Digital filter, Equiripple filter, Flicker, Interharmonics, Modern adjustable drives, Power Quality.

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