Distributed power generation systems (DPGSs) integrate power sources that tend to be smaller than the typical utility scale, such as for renewable energy sources and other applications. Storage systems that incorporate supercapacitors (SCs) have been proposed to extend the life of batteries and to increase the power capacity of the DPGSs, guaranteeing maximum efficiency. The extraction of energy in SCs is more demanding than in the case of batteries; when SCs have delivered only 75% of their energy, their voltage has already decreased to 50%. Beyond this value, the banks fail to meet the requirements demanded by loads that require a minimum voltage to operate correctly, leaving 25% of the energy unused, thereby limiting the deep charge/discharge cycles that occur. This paper presents a model of a switching matrix applied in a bank of SCs. The model allows the use of a simpler circuit to achieve a large number of serial/parallel-configuration connections (levels), improving the utilization of energy to obtain deep discharge cycles in each SC; therefore, by increasing the average energy extracted from each SC, it extends the power delivery time in the storage bank. The efficiency was verified by experimental results obtained using a bank of six SCs.

Grid-connected photovoltaic (PV) systems require an inverter that allows an efficient integration between the panels and the grid; however, the operation of conventional inverters is limited to the periods of power generation by the panels. This paper proposes a control scheme based on the theory of passivity to provide additional functions to the inverter of a PV system. These additional functions improve the power quality; for example, when loads demand inductive currents be connected, the power factor is improved independently of the intermittency of the solar energy source. The performance of the system with the passivity-based control is verified by simulation and experimentation using MATLAB/Simulink^® (2017a, MathWorks, Natick, MA, USA).