Estimation of Interharmonics Using Exponential Wave Fitting Algorithm

In this paper, exponential wave fitting algorithm is proposed for the estimation of harmonics and interharmonics in power system. A appropriate control approach must be provided to ease the harmonics. To obtain suitable control parameter, the harmonics present in the system is to be estimated. In this work, the estimation of interharmonics was done with and without noise. Interharmonics can be thought of as the inter-modulation of the fundamental and harmonic components of the system with any other frequency components and can be perceived in an increasing number of loads. These loads include static frequency converters, cycloconverters, sub-synchronous converter cascades, induction motors, arc furnaces and all loads not pulsating synchronously with the fundamental power system frequency. International Electro technical Commission (IEC) which is the international body recognized as the curator of electric power quality standards (IEC-1000-2-1) officially defined this terminology as ‘Between the harmonics of the power frequency voltage and current, further frequencies can be observed which are not an integer of the fundamental, They can appear as discrete frequencies or as a wide- band spectrum’. A recent IEC-61000-2-2 draft redefines interharmonic as ‘Any frequency which is not an integer multiple of the fundamental frequency’. IEEE Interharmonic Task Force adopted this definition. As harmonics and interharmonics have much adverse effects on the equipment, a proper control strategy must be provided to alleviate the harmonics.