Converter-side inductor design for a grid-connected converter equipped with an LCL filter

Abstract

An LCL filter is used between the grid and the grid converter to attenuate the switching harmonics. The LCL filter is one of the bulkiest and heaviest components in the grid-connected converter. The size of the LCL filter can be decreased significantly using higher switching frequencies enabled by next generation semiconductors. Further size reduction can be achieved using air-forced cooling conditions. This thesis presents the compact design of a converter-side inductor of an LCL filter. The design is implemented using the area product approach. The core material of the inductor is selected based on the highest peak flux density within saturation and core-loss density limits. Both the fundamental and the high frequency effects are considered to calculate the peak flux density. The winding wire is selected based on the rms current density. The gapped core is considered for the design and the effect of fringing flux on the inductance is studied. The thermal modeling of the inductor is included in the design. The design method is implemented on three different designs. The natural and the air-forced cooling conditions are considered. The effects of the peak flux density of the material and the effects of the cooling conditions on the size of the inductors are studied. A prototype inductor of 350 uH is manufactured to verify the design algorithm. The 2605SA1 core material is used in the prototype inductor under air-forced cooling condition. Analytical and experimental results are presented.