https://researchid.co/luislamyrocha
@isel.pt
Instituto Superior de Engenharia de Lisboa
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Scopus Publications
J. Dionísio Barros, J. Fernando A. Silva, and Luis Rocha
Elsevier BV
J. Dionísio Barros, Luis Rocha, and J. Fernando Silva
MDPI AG
This work introduces modified backstepping methods to design controllers for neutral point clamped (NPC) converters interfacing a DC/AC microgrid. The modified backstepping controllers are derived from a proper converter model, represented in dq coordinates, and are designed to regulate the DC voltage and to balance the two NPC converter DC capacitor voltages through a DC offset in the sinusoidal pulse width modulation (SPWM) carriers. The averaged and separated dynamics backstepping controllers also enforce nearly sinusoidal AC currents at a given power factor. The two proposed NPC converter controllers are evaluated through MATLAB/Simulink simulations and experimental implementation using a laboratory prototype. Simulations and experimental results show that the two modified backstepping controllers regulate the microgrid DC voltage in steady state and in transient operation, even with load disturbances or DC voltage reference changes, while enforcing nearly AC sinusoidal currents at a given power factor or injected reactive power. The modified backstepping-controlled NPC converter is bidirectional, converting energy from DC renewable energy sources or storage systems to AC or charging storage systems from AC. The results also highlight the effective balancing of the NPC DC capacitor voltages.
J. Dionísio Barros, Luis Rocha, and J. Fernando Silva
MDPI AG
In this work, DC and AC parts of hybrid microgrids are interconnected by a neutral point clamped—NPC converter controlled using a new backstepping predictive (BP) method. The NPC converter is controlled to operate in the DC microgrid voltage control mode or in the AC microgrid power control mode. The novel backstepping predictive controller is designed using the dq state space dynamic model of the NPC converter connected to the hybrid microgrid. The designed BP controller regulates the DC voltage or AC injected power, balances the capacitor voltages, controls the AC currents, and enforces the near unity power factor. Simulation (MATLAB/Simulink) and experimental (laboratory prototype) results show that the converter can regulate the DC voltage in the DC microgrid interconnection point, by adjusting the AC power conversion to compensate variations on the loads or on the distributed renewable energy sources in the DC microgrid. AC currents are sinusoidal with low harmonic distortion. The obtained BP controller is faster at balancing capacitor voltages than PWM (pulse width modulation) control with carrier offset. The fast AC power response allows the converter to be used as a primary frequency regulator of the AC microgrid. This research is appropriate for power and voltage control in hybrid microgrids with renewable energy.
H. Canacsinh, F. A. Silva, L. M. Redondo, L. Rocha, V. Silva, J. Mendes, H. Bermaki, and A. Semmak
IEEE
In this paper a voltage droop compensation based on a resonant circuit is proposed for the optimized solid-state bipolar Marx modulator. Keeping the modularity characteristics and the circuit topology, one auxiliary resonant stage was added to the existing Marx stages. The compensation concept consists of adding the auxiliary voltage to the output positive or negative pulse for voltage droop compensation. Simulation results are presented for five stages Marx circuit, 10% voltage droop, using 800 V per stage, 100 ps pulse duration at 50Hz frequency.
L. Lamy Rocha, Hiren Canacsinh, J. Fernando Silva, L. M. Redondo, and T. Luciano
IEEE
This paper presents a generalized n stage dynamic model for unipolar semiconductor based Marx generators. The model is tailored for the capacitors charging mode to enable the estimation of the maximum pulse repetition rate of the n stage generator. The maximum pulse repetition rate for the n stage Marx generator can be calculated as a function of the number n of stages, and of the voltage decay allowed in each capacitor (usually less than 10%). Furthermore, given a needed pulse repetition rate the model can estimate the optimum number of stages (n) so that the working voltage of each stage can be selected. Simulation results for a ten-stage (n=10) positive output Marx generators are presented and discussed.
L. Lamy Rocha, J. Fernando Silva, and L. M. Redondo
Institute of Electrical and Electronics Engineers (IEEE)
This paper presents generalized dynamic models for Marx derived multilevel half-bridge bipolar modulators. This high-voltage topology uses modular Marx multilevel converter diode (<inline-formula> <tex-math notation="LaTeX">$\\text{M}^{\\mathrm {{3}}}$ </tex-math></inline-formula>CD) cells to generate positive and negative (bipolar) pulses or unipolar (positive or negative voltage pulses). The developed models are tested in transient studies of pulse voltages and currents in the load. Simulation and experimental results are presented and compared.
L. Lamy Rocha, J. Fernando Silva, and L. M. Redondo
Institute of Electrical and Electronics Engineers (IEEE)
This paper shows how to use modular Marx multilevel converter diode (M3CD) modules to apply unipolar or bipolar high-voltage pulses for pulsed power applications. The M3CD cells allow the assembly of a multilevel converter without needing complex algorithms and parameter measurement to balance the capacitor voltages. This paper also explains how to supply all the modular cells in order to ensure galvanic isolation between control circuits and power circuits. The experimental results for a generator with seven levels, and unipolar and bipolar pulses into resistive, inductive, and capacitive loads are presented.
Luis Lamy Rocha, Jose Fernando Silva, and Luis M. Redondo
Institute of Electrical and Electronics Engineers (IEEE)
This paper describes a modular solid-state switching cell derived from the Marx generator concept to be used in topologies for generating multilevel unipolar and bipolar high-voltage (HV) pulses into resistive loads. The switching modular cell comprises two ON/OFF semiconductors, a diode, and a capacitor. This cell can be stacked, being the capacitors charged in series and their voltages balanced in parallel. To balance each capacitor voltage without needing any parameter measurement, a vector decision diode algorithm is used in each cell to drive the two switches. Simulation and experimental results, for generating multilevel unipolar and bipolar HV pulses into resistive loads are presented.