Pq Open-Loop Control of a Grid-Tied Inverter Interfacing a Large-Scale Fuel Cell Stack

Abstract

A fuel cell output voltage varies significantly with the variation of the output current. To maintain a stable voltage of a grid-connected fuel cell stack and converts its output voltage into AC, an inverter is required. Generally, the power quality, and grid stability and performance can be significantly affected bythe extensive use of large-scale power converters. Proper control settings of these power converters are essential to eliminate such issues and ensure that the system complies with the grid voltage, frequency,and phase. This paper deals with the control of a grid-connected diode clamped three-phase inverter interfacing a1.2 MW fuel cell stack. The aim is to model and to simulate a grid-connected fuel cell inverter. The adopted control strategy is based on active and reactive power open-loop control scheme. The frequency and phase of the inverter are synchronised with the grid frequency using a phase-locked-loop. An LCL filter serving as an interface between the inverter and the grid is used to mitigate the effect of harmonics. The modelling and simulation are carried out using Matlab/Simulink environment. Results show that the grid-connected fuel cell inverter complies with the grid voltage, frequency, and phase with both total harmonic distortions of voltage and current around 0.09%.