Design of third order L-C-L filter for diode-clamped multi-level inverter

The demand for three-phase pulse width modulation (PWM) inverters in applications such as power control or grid connecting has increased in recent years. The use of power converters is very important in maximizing the power transfer from renewable energy sources such as wind, solar, or even a hydrogen-based fuel cell to the utility grid. The inverters are connected to the grid via various topologies of filters such as L, L-C or L-C-L. This paper proposes filter design guideline for L-C-L topology. The harmonics which is induced by the low switching frequency is reduced by such L-C-L filter and generates a satisfactory level of grid-side current using a relatively low inductance. L-C-L filters offer a better choice of attenuating switching frequency harmonics. The filter requirements are driven by tight filtering tolerances of standards such as IEEE 519-1992 and IEEE P1547.2-2003. Higher order L-C-L filters are essential to achieve these regulatory standard requirements at compact size and weight. The effectiveness of the proposed algorithm is verified by simulations in matlab-simulink.