Inverters for distributed energy systems with a seamless transfer between utility interactive and stand alone modes

In recent years, there has been an increase in the use of renewable energy due to the growing concern for the pollution caused by fossil-fuel-based energy. On-site power generation using sources like photovoltaic (PV) arrays and fuel cells can be used to reduce the dependence on energy from the grid as well as provide back up power for critical systems during grid outages.; This thesis proposes an inverter topology that can be used with fuel cells, to convert the DC power output of the fuel cells to the more useful 120/240V AC. The operation and design of the various stages of the system are discussed. Controller design of the DC-DC converter with an aim to reduce the 120Hz ripple in the input current is also presented.; In order to extract the maximum utility of these systems, the inverter has to be able to operate in both the grid-tied and off-grid modes. Although existing systems can operate in both these modes, they are not able to carry out a real-time transfer from one mode to the other without any interruption to the load. An algorithm has been developed which can effect a seamless transfer between the two modes of operation with minimum interruption to the load. The algorithm has been described in detail and simulation and experimental results are presented to verify the performance of the proposed algorithm.