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- Novel design of the converter for an active UPS application based on Marx modulator concept with supercapacitorsPublication . Pestana, Celso; Canacsinh, Hiren; Chaves, Miguel; Gamboa, Paulo; Cordeiro, Armando; Luís, Ricardo; Martins, Ana Alexandra; Encarnação, Luís; Pereira, Fernando; Silva, José Fernando; Santos, NunoA new Marx modulator 4-leg multilevel converter is proposed to replace the well-known 4-leg inverter fed from batteries in Uninterruptible Power Supply (UPS) applications. The novel design concept for the Marx modulator based multilevel converter is presented and described. Each leg uses 2 Marx modulator modules, each one using an Electrochemical Double-Layer Capacitor (EDLC) (also known as supercapacitor (SC)) energy storage bank. The new topology concept enables multilevel operation with five voltage level per phase, allowing high quality voltage and current waveforms, distributed supercapacitor storage and reduction of supercapacitor bank voltage. The proposed converter can operate as UPS or as Active Power Filter (APF), powering non-linear or/and unbalanced loads, while balancing each leg supercapacitor voltage. A control strategy to choose the redundant vector configuration to balance the supercapacitor voltages is explained. Simulation results are presented for a Marx modulator based interactive 40 kVA UPS.
- Transformerless ultra-high gain buck-boost DC-DC converter with single-switch of reduced voltage stressPublication . Cordeiro, Armando; Gamboa, Paulo; Luís, Ricardo; Fonte, Pedro M; Monteiro, Joaquim; Martins, João F.; Silva, J. Fernando; Foito, Daniel; Fernao Pires, VitorThis paper introduces a new DC-DC power converter topology capable of both step-up and step-down voltage conversion, with an exceptionally high voltage gain ratio.. Besides the high extension of the voltage gain range, the converter is also characterized by the use of a single switch. Moreover, the stress imposed on the switch's voltage is minimized, enabling the utilization of low-voltage, low RDS-ON MOSFETs. Consequently, this modification leads to reduced costs and losses associated with switch conduction and turn ON. Another aspect concerning the proposed converter is that the input current exhibits a continuous behavior, which can be significant for various applications. The paper provides insights into the operational performance, steady state behavior, and mathematical underpinnings of the proposed dc-dc converter. Comparative evaluation of the static voltage gain of the proposed converter and other topologies with comparable characteristics will also be shown. Verification of the presented converter's key features are conducted through both simulation and experimental assessments using a 440-W laboratory prototype. Through these analyses, the efficacy and viability of the modified coupled-inductor SEPIC converter with enhanced voltage gain capability are confirmed.
- ESS design and management considering solar PV to fed off-grid EV chargerPublication . Santos, Diogo; Fonte, Pedro M; Pereira, Rita; Barata, Filipe; Almeida, Paulo; Cordeiro, Armando; Luís, Ricardo; Fernao Pires, VitorThe increase of electric vehicles creates several challenges to the electric grid, mainly in those with weak power or off-grid. DC microgrids are becoming more and more important in the context of renewable energy sources, where solar PV systems are dominant. In this paper is proposed the design of a DC system to charge electric vehicles using PV generation and a battery storage system. A single DC-DC converter is used to operate the solar PV array with maximum power point tracking method and controls power flow from PV to storage battery and to the EV, operating as DC EV charger. The operation under various loading conditions is discussed. The performance of the proposed solution was simulated using MATLAB/Simulink software.