Development of a robust antiislanding algorithm for utility interconnection of distributed fuel cell powered generation

In this paper, a robust antiislanding algorithm for distributed fuel cell powered generation (DFPG) is proposed. Three different islanding scenarios are explored and presented based on analysis of real and reactive power mismatch. It is shown via analysis that islanding voltage is a function of real power alone, where as its frequency is a function of both real and reactive power. Following this analysis, a robust antiislanding algorithm is developed. The proposed algorithm continuously perturbs (±5%) the reactive power supplied by DFPG while simultaneously monitoring the utility voltage and frequency. If islanding were to occur, a measurable frequency deviation takes place, upon which the real power of DFPG is further reduced to 80%, now a drop in voltage positively confirms islanding and the DFPG is safely disconnected. This method of control is shown to be robust: able to detect islanding under resonant loads, fast acting (operable in one cycle). Possible islanding conditions are simulated and verified with analysis. Experimental results on a 0.5 kW fuel cell system connected to 120 V, 60 Hz utility are discussed.