European Journal of Scientific Research - EuroJournals

901 K. G. Firouzjah, H. Eshaghtabar, A. Sheikholeslami and S. Lesan
Figure 10: Simulation results under load increasing with backup existence
5.5. Fuel Cell's Output Voltage Drops, Load Increases and Backup Battery Exists
The worst state of illustrated system in Fig. 1 is increment of load during fuel cell's failure. The main
objective of this research is improved FC based system in this condition. As a mater of fact, backup
battery has two tasks:
1. DC link capacitor's voltage regulation in desired level.
2. Transient states of system variation reduction.
According to Fig. 11, the output parameters (i.e. DC link capacitor voltage, load voltage and
current) have the desired value and minimum transient state together. However a fail occurs during 0.2-
1 second for the fuel cell, and furthermore the three phase load increases at 0.45 second, backup battery
is capable to reach the above goals.
Figure 11: Simulation results under fuel cell's failure, load increasing and backup existence.
Note that the back up battery operates when fuel cell is not capable to do its task so well. As
shown in Fig. 12, backup battery operates during fuel cell's failure and load increment (0.2-1 second)
whereas SB=1. On the other hand, when fuel cell be able to feed load and DC link capacitor lonely, SB
is set to zero and backup battery will be in charging mode.