Performance Analysis of Multilevel Inverters in Fuel Cell Applications

As the world's energy use continues to grow, the development of clean distributed generation becomes increasingly important. Fuel cells are an environmentally friendly renewable energy source that can be used in a wide range of applications and are ideal for distributed power applications. A Fuel Cell is a device that electrochemically converts fuel into electricity. The fuel cell uses an electrochemical process which converts the fuel directly into electricity with little energy loss in the form of heat. The static (V-I) characteristics of fuel cells show more than a 30% difference in the output voltage between no-load to full-load conditions. This inevitable decrease, which is caused by internal losses, reduces the utilization factor of the fuel cells at low loads. Additionally, the converters fed by these fuel cells have to be derated to accommodate higher input voltages at low currents. When one of these fuel cells is connected to an inverter, they will not be able to produce ac grid level voltages. A dc-dc boost converter is generally required to boost the voltage level for the inverter. This boost converter, in addition to boosting the fuel cell voltage, also regulates the inverter input voltage and isolates the low and high voltage circuits. In this paper Analysis of cascaded bridge multilevel inverter have with & without pwm techniques have been done & results are also compared based on the harmonics available.