PHOTOVOLTAIC UNITS, METHODS OF OPERATING PHOTOVOLTAIC UNITS AND CONTROLLERS THEREFOR

摘要

The present invention relates to the field of photovoltaic systems with solar cell (s) or modules having insolation differences or mismatch. Each solar module is formed by placing a large number of solar cells in series. The PV system is then formed by placing a number of solar modules in series in a string and sometimes by placing multiple strings of series-connected solar modules in parallel, depending on the desired output voltage and power range of the PV system. In practical cases, differences will exist between output powers of the solar cells in the various modules, e.g. due to (part of) the modules being temporarily shaded, pollution on one or more solar cells, or even spread in solar-cell behaviour that may become worse during aging. Due to the current-source-type behaviour of solar cells and their series connection these differences will lead to a relatively large drop in output power coming from the PV system. This invention addresses this problem by adding DC-DC converters (803) on a single or multiple solar-cell level that source or sink difference currents thereby increasing the output power of the complete PV system. In embodiments, the efficiency of photovoltaic systems with solar cell (s) or modules is improved by compensating for output-power loss caused by insolation difference and mismatch.