This paper presents the use of Modified Exact Model Order (MEMO) estimation technique for detecting number of modes present in a mixture of sinusoid and ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique) i.e. harmonic/Interharmonics frequency components present in a signal. With increase in number of semiconductor power electronic devices, a large increase in the harmonics/interharmonics injections has witnessed in the system. Accurate estimation of these harmonic/interharmonics components are very important for their mitigation as these can create a lot of problems. This paper shows the signals with harmonic as well as interharmonic components which can be generated from arcing loads, variable frequency drives, cycloconverters etc. and their accurate estimation using MEMO-ESPRIT method. The algorithm was modelled and analyzed in MATLAB and Python platforms. The results show that the harmonics/interharmonics could be detected accurately using this method.