Browsing by Author "Silva, J. F."
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- Electric vehicle integrated battery charger for an AC drive with open windingsPublication . Fernão Pires, V.; Cordeiro, Armando; Foito, Daniel; Silva, J. F.Merging of electric vehicle (EV) charging converter within the EV motor drive allows to minimize the charging system regarding volume, weight, and cost. Thus, several integrated battery charger topologies have been presented for well known drives. However, very few works have been addressed for open windings motor drives. This work is focused on open windings motor drives and battery charger types, proposing a new integrated charger topology. The proposed solution avoids the extra three-phase power factor corrector (PFC) and provides bidirectional power flow, allowing the vehicle batteries to operate also as a grid storage system. Some terminals of the motor open windings are connected to a three-phase inverter supplied by the batteries while the remaining terminals are connected to a three-phase inverter with a floating capacitor. The proposed EV battery charger will be verified and tested by several simulation results.
- Fast optimum-predictive control and capacitor voltage balancing strategy for bipolar back-to-back NPC converters in high-voltage direct current transmission systemsPublication . Chaves, Miguel; Margato, Elmano; Silva, J. F.; Pinto, S. F.; Santana, J.Multilevel power converters have been introduced as the solution for high-power high-voltage switching applications where they have well-known advantages. Recently, full back-to-back connected multilevel neutral point diode clamped converters (NPC converter) have been used inhigh-voltage direct current (HVDC) transmission systems. Bipolar-connected back-to-back NPC converters have advantages in long-distance HVDCtransmission systems over the full back-to-back connection, but greater difficulty to balance the dc capacitor voltage divider on both sending and receiving end NPC converters. This study shows that power flow control and dc capacitor voltage balancing are feasible using fast optimum-predictive-based controllers in HVDC systems using bipolar back-to-back-connected five-level NPC multilevel converters. For both converter sides, the control strategytakes in account active and reactive power, which establishes ac grid currents in both ends, and guarantees the balancing of dc bus capacitor voltages inboth NPC converters. Additionally, the semiconductor switching frequency is minimised to reduce switching losses. The performance and robustness of the new fast predictive control strategy, and its capability to solve the DC capacitor voltage balancing problem of bipolar-connected back-to-back NPCconverters are evaluated.
- Fault tolerant operation of three-phase 3 level T-Type qZS inverters using sliding mode current controllersPublication . Fernao Pires, Vitor; Foito, Daniel; Santos, Natalia; Cordeiro, Armando; Roncero Clemente, Carlos; Silva, J. F.Due to the boost characteristic and the several possible outputs of quasi-Z-source inverters (qZSI), these topologies can be valuable options to operate under fault conditions, provided the controller is able to take advantage of the available output states. Thus, the development of control systems to take advantage of the available outputs is needed. Hence, this paper focuses on the development of a control system to operate a three-phase three-level T-Type qZSI under fault tolerant conditions. The controller is based on a sliding mode current controller associated to a vectorial modulator selecting the available outputs. The proposed strategy for the controller and modulator is presented taking into consideration the normal and fault-tolerant requirements. The strategy also considers the balance of the capacitors under fault tolerant condition. The converter operating in both modes is tested through several simulation studies.
- A single-switch DC-DC converter with a high voltage gain capability and reduced voltage stress of the switch for renewable energy applicationsPublication . Fernao Pires, Vitor; Cordeiro, Armando; Foito, Daniel; Monteiro, Joaquim; Silva, J. F.The growing trend toward high-efficiency, high gain converters that minimize component count, has spurred the development of many new step-up topologies. In this context introduces a new single-switch, non-isolated DC-DC step-up converter topology specifically designed for renewable energy applications. Key advantages of this topology include a high boost factor, continuous input current, reduced voltage stress on the switch, and a suitable number of elements relative to the achieved boost factor. These features address many of the critical design objectives. The steady-state analysis of the proposed converter is presented and discussed. Simulation and experimental results are presented to verify the theory and performance of the converter.