Transformerless Hybrid Power Filter Based On a Six-Switch Two-Leg Inverter for Improved Harmonic Compensation Performance

One of the most important issues is related to current harmonics generated by the increasing number of nonlinear loads connected to the power grid, such as diode and thyristor front-end rectifiers. As a consequence, these harmonics can cause voltage distortions, additional losses in the power system, and malfunction of sensitive electronic equipment. For this reason, harmonic restriction standards, such as IEEE 519, have been recommended to limit the harmonic currents injected into the grid by nonlinear loads. Shunt passive filters, consisting of tuned LC filters and high pass filters, have been traditionally used as a simple and low cost solution to compensate current harmonics. Nevertheless, their performance strongly depends on the grid impedance and can possibly cause the unwanted parallel resonance phenomena with the grid.