This paper introduces a novel methodology for determining critical switching angles in a five-level, three-phase inverter, significantly improving the harmonic mitigation range to effectively mitigate the fifth and seventh harmonics. This method adheres to stringent grid codes over a wide range of modulation indices, as confirmed through detailed simulations. Analyzing five unique cases, the research expands the modulation index spectrum for mitigating fifth and seventh harmonics to 91.5%, a 30% increase over previous limits, without altering inverter switching frequency, number of angles, or fundamental voltage. This novel approach not only broadens operational ranges but also sets a new standard in harmonic suppression, as demonstrated by extensive graphical and MATLAB/Simulink-based simulation evidence.

In power electronic systems, the management of harmonic distortion is paramount for ensuring both efficiency and reliability. This study introduces a methodology involving three switching events per quarter cycle in a three-phase, two-level voltage source inverter (VSI) to eliminate three specific harmonics, while also attenuating several others. By strategically implementing three switches per quarter cycle, lower-order harmonics are effectively targeted for elimination and mitigation in accordance with grid codes, thereby contributing to the reduction of Total Harmonic Distortion (THD). MATLAB simulations are employed to graphically derive and validate the optimal switching angles, demonstrating the efficacy of the proposed method across various modulation indices. The results indicate that maintaining a band gap of (±5%) can attenuate harmonics up to the 23rdorder, thereby enhancing overall power quality and ensuring compliance with harmonic standards.

The selective harmonic elimination technique allows us to eliminate completely N number of harmonics with (N+1) number of switchings per quarter. However, instead of completely removing grid regulations demand that harmonics be kept to less than 5%. Therefore, there exists a possibility of bringing more harmonics within the 5% band while keeping the number of switchings fixed. This degree of freedom is explored in this paper wherein many harmonics are mitigated while keeping only two switchings per quarter. The analysis is tested in simulation for various operating conditions using MATLAB/Simulink software. It is shown that up to 17 th harmonic can be mitigated to less than 5% with two switchings per quarter.

A simple and efficient graphical selective harmonic elimination method has been developed in this paper using which multiple harmonics can be simultaneously reduced even with two switchings per quarter. The method is also extended to reduce overall THD with the help of a cost function. The boundary conditions of the switching angles have been analytically derived, after which the switching angles are obtained graphically for simultaneous removal of lower-order harmonics. The proposed technique has been extensively simulated at various modulation indices using MATLAB/Simulink to validate the proposed graphical analysis.

In this paper, islanded mode microgrid system using biogas and solar PV is discussed for small power applications (upto 250 W) in remote locations. Biogas generation is done using stirling engine coupled with DC generator which directly converts biogas to electrical power. Solar PV system with double sliding integral control based MPPT tracking is connected in parallel with the biogas system. These two sources are connected in parallel to a flyback converter for stepping up the voltage. This is fed to a single phase inverter which is controlled to give constant 220 V, 50 Hz AC to form a hybrid microgrid. The proposed system and the control scheme is modeled in MATLAB/Simulink and tested at different conditions of solar and biogas availability and the results are presented. The proposed system could produce 220 V supply with ≈ 1.5% THD.