In this paper, a systematic and analytical study of non-isolated topologies belonging to the family of Reduced Redundant Power Processing (R2P2) converters is presented. Based on this study, all the non-isolated R2P2 topologies that can be implemented in reality are derived. Detailed examples clarify all possible cases of this analysis. In addition to this, the voltage ratio and the efficiency for each one of the R2P2 configurations are calculated, being further illustrated with examples. A comparison is also discussed among configurations with criteria the high step-up voltage gain and efficiency dedicated for high power applications and one of them is selected for further examination. The theoretical analysis, as well as the calculations of the step-up voltage ratio and efficiency of the selected converter are compared to experimental results conducted on a 2kW laboratory prototype designed to operate in various step-up voltage ratios and in a high-power range, proving the effectiveness of the proposed investigation.

This paper proposes goal-function-based decentralized control of microgrids. In addition to being an instrument for maintaining the grid voltage and frequency stability, each grid-tie inverter generates a current component with the aim of compensating for voltage distortion in the node where it is connected. The designed goal-function does not need to rely on the assumption that a microgrid is dominantly inductive or resistive to derive its control law, as is mostly the case with the droop-based approach. The priorities of the proposed scheme can be adjusted according to user preferences. In addition, the control algorithm is independent of network topology, can be applied in both islanded and non-islanded microgrids, and secure system scalability. The proposed method is verified by detailed simulations.

This paper proposes a novel primary level controller and coupling LCL filter design methodology for microgrid prosumer units The so-called decentralized peer-to-peer-based power flow control algorithm introduces a power exchange communication link between two contractees, namely a prosumer unit and any other unit, on the time scales of primary power flow controller. This can be regarded as feed-forwarding of power flow information between the units in close to real-time in order to attain almost instant power balancing within the system. When coupled with the conventional voltage and frequency droop primary control, as presented in the paper, and tested on a simulation model of one radial microgrid in the off-grid mode of operation, it showed enhanced static and dynamic performance. The study also investigated adverse influence of the communication link time delay. The paper addressed prosumer units microgrid voltage-forming role by proposing design and control methodology for the prosumer units’ LCL coupling filter. To that aim, thorough voltage and current harmonic emission analysis has been conducted, taking into account realistic span of a microgrid parameters’ values and presence of other units. The study and the simulation model tests revealed that the limited total voltage harmonic distortion becomes critical requirement in the off-grid model of operation.