A market review on Hybrid Inverters with Back-Up (HIBU) is presented, selecting products from eleven global inverter manufacturers. A systemic review of all the productsis performed, along with a general comparison of their main features. Trends in power ranges, battery voltages, back-up connection scheme and switching times are then highlighted and other more peculiar characteristics are assessed. A focus on potential applications in the Swedish market is put, considering an average Swedish household consumption profile. Ten from the available software for modeling photovoltaics applications are then reviewed finding PVsyst, Homer and SAM the most suitable tools for computing systems with HIBU. Finally, a case study is simulated on PVsyst showing the influence of the battery size on the percentage of covered load for different values of grid availability. The influence of different locations and different battery discharging strategies is also assessed, critically evaluating the reliability of the model used on PVsyst and stating the main shortcomings.

The diploma thesis is dealing with possible approaches to control distributed energy resources and storage systems. One of these approaches is a virtual power plant and its concept is described in the first part of the thesis. The virtual power plant is a controlled system of distributed energy resources, storage systems and controllable loads interconnected via communication network, that can act as a conventional power plant. The theoretical part contains a survey of control system's topologies, a brief summary of available communication infrastructures and standards. The second part of the thesis is focused on the description of operation and control of hybrid system that represents an inseparable component of virtual power plant. A Matlab Simulink model was created for this purpose. A simulation of hybrid inverter's step response is realised to test the operation of the hybrid system and it is compared with the real measurements in the laboratory. A comparison of control approaches of hybrid system implemented on the basis of measurements is also included in this thesis and was published in the scientific paper attached in the appendix.