230 VDC elementary block in off-grid PV systems

This paper reports on a new development approach of off-grid systems based on PV and batteries, representing, among other things, a great interest for rural electrification in developing countries. A renewable energy production elementary block is proposed and analyzed. This block can work autonomously or as a basic element of a high power production cluster dedicated to rural areas. Replacement of AC bus by DC power bus is shown to be more advantageous thanks to better energy efficiency. The proposed approach also allows new architectures in the field of storage, and the systematic use of typical batteries associations, cause of their accelerated ageing, can thus be avoided. Each low voltage battery is found to be able to separately supply a high power standalone inverter or even a grid reinjection inverter following the retained boost ratio. The proposed architecture could be considered as a basis for solar DC micro-grids, gathering several individual producers on the same network, minimizing instabilities due to phase and frequency mismatches in case of AC grids. With even a high elevation ratio, the proposed block can be integrated in long-distances DC or HVDC power transport, thus, contributing to the improvement of wider spread of renewable energy.