Abstract
In the last decades, there is a rapid development towards new energy sources due to the increasing demand of energy and cost of the fossil fuels. Renewable energy sources getting more popular day by day due to government support and carbon dioxide (CO2) emission reduction policy to reduce greenhouse gas emissions. Photovoltaic energy generation is the excellent example of energy generation through various serious parallel arrangement of a small voltage generating cells or modules. There are directly use of synchronous generators to transfer power to grid from hydro energy plant, geothermal energy plant, bio-fuel energy plants. However, the photovoltaic energy generation systems requires the power electronic converters system to satisfy the demand of realtime application or electric grid. Therefore, for real-time applications or before feeding energy to the grid via inverter, photovoltaic systems linked with DC-DC converters, which have high-voltage conversion ratio capability. Thus, DC-DC power converter is the paramount constituent in the photovoltaic power conversion stage. This research work carried out in focusing on hardware implementation and investigation studies of novel non-isolated unidirectional DC-DC multistage power converter configurations for renewable energy application. The comprehensive review of various unidirectional non-isolated DC-DC multistage power converters are presented and it is found that not all of them have the capability to convert low voltage into high voltage, thus not suitable for photovoltaic energy applications. It is investigated that there is a scope to design new DC-DC multistage power converter topologies configurations with high voltage conversion ratio by employing a new arrangement of reactive elements and semiconductor devices. A new breed of DC-DC multistage power converters called “X-Y converter family” proposed for photovoltaic application by utilizing the switchedinductor, the switched capacitor, the voltage lift switch capacitor and modified voltage lift switched capacitor, voltage doubler and multiplier boosting techniques. The derivation of voltage conversion ratio, advantage of each converter of X-Y family and hierarchy of X-Y family is discussed. The research work also proposed a new DC-DC multistage power converter without a magnetic component for photovoltaic application by utilizing the concept of switched capacitors. An original Transformer and Switched Capacitor (T-SC) based multistage power converter proposed for high-voltage/lowcurrent photovoltaic applications by combining the feature of the boost converter, transformer and switched capacitor. New Nx IMBC (Nx Interleaved Multilevel Boost Converter) or Cockcroft Walton (CW) Voltage Multiplier based Multistage/Multilevel Power Converter (CW-VM-MPC) converter topologies are presented to achieve maximum voltage conversion ratio by utilizing the feature of Cockcroft Walton (CW) voltage multiplier. Moreover, the proposed multistage power converter compared with each other as well as recently proposed multistage power converters in term of voltage conversion ratio, number of devices and costs.
D.Eng. (Electrical and Electronic Engineering)