Techno-economic evaluation of alternative configurations for very large scale PV power systems including energy storage

PV systems are already mature, especially for small and medium size applications. However, in the last couple of years larger PV power plants in the range of 100MW have been installed and set in operation. An important question that arises for very large scale PV power systems is the optimization of the overall system configuration, especially due to the very high initial costs and the financing of such projects. Several concepts in the literature have been investigated regarding efficiency and technical feasibility; however it is also important to evaluate their economic feasibility, using commonly accepted metrics. In this paper four different system configurations are presented, with the typical system configuration of central inverters and medium voltage transformers used as a reference. The other three alternatives include high power DC-DC converters connected in series or in parallel, as well as cascaded DCAC inverters. In addition, taking into account current developments in energy storage, new possibilities for combining PV with energy storage for large scale plants are rising, in order to deal with the grid integration of ever increasing PV installations. Therefore, a comparison is performed among a PV power plant with and without energy storage for different operation scenarios. The results show clearly the increase of cost and indicate the need for new evaluation metrics to include the expected benefits from the integration of energy storage to PV power systems.