Resumen de Distributed power electronics for extended efficiency and lifetime of utility-scale photovoltaic systems
This research focuses on the measurement and the modeling of submodule-level ageing effects. The paper reports measurements in a population of 42 submodules, with emphasis on the differences with respect to previously reported module level measurements. Although the degradation rate should remain unaffected by the granularity level, it is expected that submodule level models will exhibit a higher coefficient of variation with respect to the module level. Attention is paid to differences between short-circuit and maximum power currents, as the number of results showing both measurements is scarce.
Since there is potential for unmeasured energy yield penalty due to submodule-level mismatch, the research also aims to quantify the recoverable power loss. First, we evaluates the skewness of the distributions and explores non-gaussian statistical models in PV parameter modeling. It is shown that previously reported negative skewness in the power and current distributions of PV systems impacts on long-term forecasts. Then, the efficiency and the 25 years energy yield of several PV systems is assessed by means of Monte Carlo simulations and compared with the previous results mentioned above.
After having all the measured submodule level data, in this research, a converter for submodules based on resonant conversion topology has been analyzed and designed. First, power rating of the converter determined by comparing the required power processing by different DPP architectures. The topology of the converter has been selected based on the requirement of this specific application. Detailed design procedure and experimental realization of the converter has also been presented. The performance of the converter is evaluated in two steps as follows.
1) Steady-state performance of the converter has been verified. The experimental results show an efficiency of 89 % in case of 500 mW load using the burst-mode and maximum efficiency close to 93 % at 3 W. With a load of 8 W, the converter is always on and the efficiency drops to 90 %.
2) The performance of the converter for mitigation of mismatch has been verified by connecting three converter to a PV module. It has been observed that these converter can extract the maximum power from in presence of mismatch among the submodule currents.
Brief discussion about how this research can improve the levelized cost of energy (LCOE) has been done. It is shown that, with a cost of 6 euro per PV module, these converters can reduce the LCOE in a range between 2.44 and 3.88 % of current PV energy costs, depending on the size of the system and the available irradiance.
