Selective Harmonic Mitigation Based on Closest Level Modulation Scheme for Cascaded H-Bridge Multilevel Inverter

Abstract

Multi-inverters have higher quality output waveform as they have lower total harmonic distortion (THD) but the individual harmonics do not satisfy the Grid Code EN 50160 and CIGRE Code WG 36-05. Therefore, mitigation of these individual harmonics is necessary to satisfy the mentioned codes. In this paper, a novel solution for mitigating individual harmonics has been proposed. The proposed harmonic mitigation technique uses nearest level control (NLC) for reducing individual harmonics in a grid-cascaded H-bridge multilevel inverter (CBH-MLI). The proposed technique involves solving simultaneous non-linear equations in real-time. For this, first non-linear equations have been derived and then proposed individual harmonics mitigation techniques are digitally applied for 7-level and 9-level CHB-MLI. The main advantage of the proposed novel technique is that it is easy to implement in real time due to less computational burden and lower complexity. Further, an experimental setup has been developed to validate the simulation results. From the results it is obtained that individual harmonics has been reduced for 7-level and 9-level CHB-MLI.