Distributed power electronics for extended efficiency and lifetime of utility-scale photovoltaic systems

Identificador:  TDX:2944

Handle: https://hdl.handle.net/20.500.11797/TDX2944

Autors:  Hasan, MD Nazmul

Resum:
This thesis focused on mitigation of mismatch due to ageing in PV systems. Degradation of short circuit current has been considered the principle factor that affects the energy production of PV systems due to ageing. Although, dispersion in short circuit current and maximum power current has been reported in the past, the energy loss due to dispersion has been underestimated. Moreover, dispersion of voltage-current parameters at module level have been considered for mismatch mitigation at submodule level whereas the recoverable power at submodule level may higher than that has been estimated. In order verify the accordance of submodule level data to module level data, in this research, measurements have been done at submodule level. It is shown that estimation of energy loss due to ageing based on module level dispersion data has been underrated and considering submodule level mismatch data life time energy improvement an be possible up to 4-6 %. In order to mitigate the ageing mismatch in PV system, a dc-dc bidirectional isolated low power unity gain converter is proposed. Design procedure and experimental realization of the converter is presented. A control scheme that allows bidirectional power flow is also presented. High frequency ferrite ore transformer provides the galvanic isolation between primary and secondary. In addition, resonant inductors have been integrated in the transformer, which reduces the size and cost of the converter. Experimental results show power transfer efficiencies more than 90 % for loads between 1 W to 8 W. The performance of the converter for mismatch mitigation is verified. In the laboratory, three prototype converters are attached with a PV module following the DPP PV-IP architecture approach. It is observed that these three converters an fully mitigate mismatch among three submodules and provide maximum possible power. The impact of mitigation of ageing mismatch on levelized cost of energy (LCOE) is also discussed.