Browsing by Author "Silva, J. Fernando A."
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- Dual resonant voltage droop compensation for bipolar solid-state Marx generator topologiesPublication . Canacsinh, Hiren; Silva, J. Fernando A.; Redondo, Luís Manuel dos SantosThis paper discusses a novel methodology to increase the voltage droop compensation range in generalized solid-state bipolar high-voltage Marx modulators with one resonant stage. To maintain the modularity characteristic of bipolar Marx modulators, the imbedding of additional resonant stages is not straightforward. Nevertheless, this paper proposes to add a second resonant stage to the already existing resonant-type voltage droop compensation stage. This second stage increases the voltage droop compensation percentage of a generalized solid-state bipolar Marx generator. The compensation of the bipolar pulse voltage droop is now achieved by adding two auxiliary synchronous compensation resonant voltages, to the output capacitive decaying voltage. Simulation and experimental results are presented for six Marx plus two resonant stages, 16% voltage droop, with 3-kV pulse amplitude, 100-μs pulsewidth, 40-ms relaxation time, and 10-Hz pulse repetition rate.
- Multilevel inverter based on a dual two-level nine-switch converter for a dual three-phase or six-phase motor drive systemPublication . Pires, V. Fernão; Cordeiro, Armando; Foito, Daniel; Pires, A. J.; Silva, J. Fernando A.; Chen, HaoThe nine-switch inverter is considered as a very interesting solution for three-phase dual output applications, such as dual three-phase or six-phase motor drive systems. The main advantage of this approach is a converter topology with a reduced number of power semiconductors. However, the AC output voltages are limited to only two levels. This work proposes a new inverter topology for dual three-phase or six-phase motor drive systems with multilevel output characteristics. The proposed topology is based on two isolated inverters, but the number of legs is reduced from six to three. This structure creates a modular multilevel inverter with a high number of voltage levels while using a comparatively smaller number of power semiconductors. A modulation strategy, associated with the proposed topology, is presented to ensure multilevel operation. The proposed topology and modulation strategy will be tested first through a simulation in Matlab/Simulink and then by laboratory tests using an experimental prototype. The obtained results show a good agreement between simulations and experiments, both confirming the theoretical studies.
- New backstepping controllers with enhanced stability for neutral point clamped converters interfacing photovoltaics and AC microgridsPublication . Barros, J. Dionísio; Silva, J. Fernando A.; Rocha, Luis LamyThis work presents a new approach to obtain pulse width modulation (PWM) backstepping controllers with enhanced stability for neutral point clamped (NPC) multilevel converters to deliver energy from photovoltaic (PV) panels into AC microgrids. Stability enhanced backstepping non-linear controllers are obtained from the equations of the dq frame converter model to regulate the PV voltage to track the power point, and to balance the capacitor voltages through DC biasing of the PWM carriers, using a novel dynamic equation of the capacitors incremental unbalance voltage, while controlling the grid injected AC currents. Besides, the proposed controllers can change the PV panels operating point to curtail inject power for AC voltage / frequency regulation. The NPC converter and AC microgrid are simulated in MATLAB / Simulink and implemented in the laboratory to evaluate the performance of the PV energy conversion using the new stability enhanced backstepping PWM control. Simulation and experimental results show that, regarding predictive controllers, the novel stability enhanced backstepping requires lower microprocessor power than predictive controllers while presenting a similar behavior in PV voltage and power point tracking regulation, or for voltage / frequency regulation of the microgrid. AC injected currents show low levels of total harmonic distortion similar to predictive controllers and can operate at near unity power factor.