Dionisis Voglitsis

Incorporation of Harmonic Injection in an Interleaved Flyback Inverter for the Implementation of an Active Anti-Islanding Technique

Over recent years, the output power of micro-inverters [module-incorporated inverter (MIC)] is progressively pushed to higher levels, following the current photovoltaic (PV) modules market trends. The interleaved Flyback inverter—under discontinuous conduction mode of operation (DCM)—is an appealing solution for PV applications which are based on MIC technology. This topology provides increased power level for distributed PV generation exploitation with simple control configuration, high efficiency, and reduced filter size. In this paper, the harmonic injection capability is incorporated into the interleaved Flyback inverter for the implementation of an active anti-islanding scheme. A suitable technical solution is proposed that bypasses the unfolding H-bridge, without affecting the active power generation of the inverter and without requiring any hardware modification. In addition, a mathematical model based on the instantaneous power balance theory is presented, being a powerful analysis tool for inverters operating under complete magnetic discharge such as the Flyback inverter (either conventional or interleaved) under DCM or boundary conduction mode of operation. The proposed model predicts accurately the steady-state operational behavior of the Flyback inverter under current harmonic injection, either in grid-tied or islanding operation. The proposed technical implementation method and mathematical model are verified through simulation and experimental results. Finally, an anti-islanding set-up based on the proposed harmonic injection technique is presented and implemented into the Flyback micro-inverter. The proposed set-up is verified through experimental results on various quality factor values, as well as for weak grid conditions.

Active Thermoelectric Cooling Solutions for Airspace Applications: the THERMICOOL Project

To increase the reliability of aerospace electronics and reduce their overall power consumption, we investigated the possibility of incorporating active thermoelectric cooling (TEC) solutions. The harsh avionic environment demands sophisticated active control schemes that enable the achievement of high coefficient of performance. The positive effect of active PWM control has been validated both in simulation and on a working laboratory prototype that allowed us to clarify the pros and cons of the incorporation of TEC techniques in avionics applications. This paper has been performed under the framework of CLEAN SKY—THERMICOOL project.

Investigation of a Waste Heat Recovery System for a more electric ship

Several types of energy recovery systems (i.e. shaft generators etc.) have been installed in marine vessels, in order to reduce the fuel consumption and ultimately improve the efficiency of the vessels. In this paper, an energy recovery system utilizing the thermal losses of a real ship is investigated. The main goal of this work is to improve the overall efficiency of the ship. Therefore, a theoretical study and apparatus selection is conducted for every part of a proposed Waste Heat Recovery System. Moreover, simulation results of each part, as well as of the whole system, are presented in this paper.

Sensitivity Analysis for the Power Quality Indices of Standalone PV Systems

Standalone photovoltaic systems is a key technology for the increase of renewable energy sources share in electricity production worldwide. The power quality of those systems plays a fundamental role in avoiding volatile power supply. This calls for a concrete design in order to meet power quality specifications. In this context, a methodology has been developed in a previous work, in order to set the values of the parameters that optimize the power quality indices of the system. In this paper, an extensive sensitivity analysis is performed regarding the influence of the optimized parameters variation on the power quality indices. Throughout the outcomes of the sensitivity analysis a more insightful view of the system performance under the deviations of system parameters is revealed, which in combination with the aforementioned optimal design strategy becomes an essential tool that ensures high power quality level. The theoretical outcomes are validated by experimental results, highlighting the effectiveness of the proposed design strategy.