Distributed control of PV strings with module integrated converters in presence of a central MPPT

In some cases it is unavoidable that part of the rooftop PV array is periodically shadowed by an adjacent object, greatly reducing yield. Usually, the time and amount of shadowing is known, and is considered as extra loss due to the location. Module Integrated Converter (MIC) systems are known to be a good solution for such cases, having the potential to increase the yield with as high as 25%, although there is the added cost of the MICs. A cost-effective solution could be to limit the installation of MICs only to the affected modules. However, this solution carries some new challenges in that the MIC should ensure the string voltage stability and MPP operation in presence of other MICs and `plain´ panels. It must also be transparent to the main inverters´ MPPT, so that it can track during normal operation. In this paper, a system layout with local MPPT without voltage control is proposed, which is able to ensure string voltage stability and MPP tracking in presence of a central MPPT.