Unipolar SHEPWM for Pure Sine Wave Single-Phase Inverter

Modern power systems, such as DC-AC inverters, have improved in efficiency. They employ simple control methods. During the switching process, however, they cause harmonic difficulties. This has an effect on the overall system's performances. To reduce these undesired harmonic distortions, unipolar Selective Harmonic Elimination SHEPWM was used in this work. At optimal switching angles, it cancels out odd harmonics. Its goal is to get rid of the first 100 low-order harmonics. By solving non-linear transcendental equations in MATLAB, the fsolve function was utilized to calculate the optimal 50 angles for the SHEPWM. The resulting SHEPWM control signal is implemented in LTspice. It operates a single-phase pure sine wave inverter. Finally, at the inverter output, an LC low-pass filter is used to improve the response and obtain a better sinusoidal AC waveform with lower THD.