Harmonic mitigation for a megawatt grid-tied fuel cell system

This research deals with the design of an LCL filter for a grid tied megawatt fuel cell stack. In the adopted configuration, the LCL filter links a three-level neutral clamped point inverter with the grid. A typical inverter is a source of harmonics as in general its output is not a pure sinewave. Standards such each IEEE 519 and IEC 61000-3-6 define the allowable harmonics distortion for both the current and the voltage in a power system based on the current level and the voltage level respectively. This paper aims to design an LCL filter to reduce harmonics produced by a three-level inverter serving as interface between a fuel cell stack and a grid and meet the abovementioned standards. The input of the grid tied inverter is connected to a 1.4 MW solid oxide fuel cell stack at 1400 V. The inverter is modelled and controlled to deliver 1.2 MW at 600 V between phases. To evaluate the performance of the designed filter, the system including the 1.4 MW fuel cell stack, the inverter, the LCL filter, a grid and a load is simulated using Matlab/Simulink environment. The results show that the designed filter reduces the total harmonics distortion to 0.46 % and 24.87 % for the voltage and the current, respectively.