PESC Research Papers - Academia.edu (original) (raw)

This paper proposes a multilevel power conversion concept based on the combination of neutral-point-clamped (NPC) and floating capacitor converters. In the proposed scheme, the voltage balancing across the floating capacitors is achieved... more

This paper proposes a multilevel power conversion concept based on the combination of neutral-point-clamped (NPC) and floating capacitor converters. In the proposed scheme, the voltage balancing across the floating capacitors is achieved by using a proper selection of redundant switching states, and the neutral-point voltage is controlled by the classical dc offset injection. Experimental results are illustrated in the paper to demonstrate the system operation

The aim of this paper is to propose a current control of VSCs connected to the grid through an LCL-filter. The proposed algorithm controls the grid current using only two sensors. Other variables are obtained with a state estimator, and... more

The aim of this paper is to propose a current control of VSCs connected to the grid through an LCL-filter. The proposed algorithm controls the grid current using only two sensors. Other variables are obtained with a state estimator, and the possible disturbances of the system are attenuated with active damping. The control algorithm has been proved for different disturbances, such as temporal variations in the components of the model and perturbations in the grid, and also with the linear and nonlinear models.

The output voltage of PWM power inverters shows harmonic distortion due to several causes; the main ones are the modulation algorithm, nonlinearities due to the output filter, dead times, voltage drops across the switches and modulation... more

The output voltage of PWM power inverters shows harmonic distortion due to several causes; the main ones are the modulation algorithm, nonlinearities due to the output filter, dead times, voltage drops across the switches and modulation of the dc bus voltage. The distortion is more evident when using low dc bus voltages. As a result, motors driven by these inverters have important torque pulsations. This work proposes to reduce the distortion produced by dead times and voltage drops across the switches, using a simple algorithm that recalculates the width of each PWM pulse, preserving the ideal area. The algorithm takes advantage of the fact that the dead times are not always necessary, but only when the load current changes its sign. By simulation, the THD was reduced from 18% to 0.29% in a single-phase inverter. The proposed algorithm only needs products and sums, so it is suitable for being implemented on a DSP with low processing load. Experimental results were obtained from a non-optimized laboratory prototype, showing a reduction of the THD from 17.9% to 0.59%.

A circuit model simulating the electrical characteristics of a fluorescent lamp operating at high frequency is proposed. The model is based on exponential approximation that represents the lamp equivalent resistance variation as a... more

A circuit model simulating the electrical characteristics of a fluorescent lamp operating at high frequency is proposed. The model is based on exponential approximation that represents the lamp equivalent resistance variation as a function of power, constructed by experimental results for several power levels. Simulation results and experimental data are presented to verify the feasibility of the model and, moreover, an electronic ballast example using the proposed model is presented to further demonstrate its applications.

This paper deals with a flexible production system modeled by re-entrant C; a system decomposed into two fundamental multi-productive stations and three classes, a part follows the route fixed by the system, where each one is processed... more

This paper deals with a flexible production system modeled by re-entrant C; a system decomposed into two fundamental multi-productive stations and three classes, a part follows the route fixed by the system, where each one is processed first by station 1 for the first step, then by station 2 for the second step, and again by the first station for third and last step before leaving the system. We assume that there is an infinite supply of work available, so that there are always parts ready for processing step 1, and that the first station gives preemptive priority to buffer 3. Several performance measures have been used to evaluate the system performances considering two scenarios; high priority with service conservation and high priority with loss of parts. So, performances due to varying its parameters are investigated through expanded Monte Carlo simulations.

In this paper a single-switch power supply based on the shunt class E amplifier is presented. A simple and easy method to analyze the complete system is proposed and one way to provide compensation to parameter's variation of the ozone... more

In this paper a single-switch power supply based on the shunt class E amplifier is presented. A simple and easy method to analyze the complete system is proposed and one way to provide compensation to parameter's variation of the ozone generator and to reduce the size of the resonant inductor is proposed and studied too. The selected topology offers a low-cost and high-power density source that efficiently supplied the system. Experimental results are congruent with the specifications and a high ozone concentration is obtained.

This paper presents an embedded frequency response analyzer (EFRA) for fuel cells (FC) based on a low-cost digital signal processor (DSP). Frequency response analysis technique provides valuable information of different electrochemical... more

This paper presents an embedded frequency response analyzer (EFRA) for fuel cells (FC) based on a low-cost digital signal processor (DSP). Frequency response analysis technique provides valuable information of different electrochemical processes that occur inside the FC. The small size and low power consumption allows this special device to be embedded into the FC controller or the power conditioning stage. The system is capable of measuring automatically the frequency response of the FC at different operating points, even when the FC is operating with load. These measurements can be used to characterize the FC at design stage and to perform on-line monitoring of the FC state during continuous operation. The proposed instrument uses the lock-in amplification technique, which allows very accurate and precise measurements even in the presence of high noise levels. The proposed hardware and signal processing technique are described in this paper including experimental result of a 1.2 kW proton exchange membrane fuel cell (PEMFC) system

Fulfilling the new grid codes constitutes one of the main challenges for the wind power industry, that is specially concerned about the new fault-ride-through requirements. Enhancing the operation of wind-turbines in front of grid faults... more

Fulfilling the new grid codes constitutes one of the main challenges for the wind power industry, that is specially concerned about the new fault-ride-through requirements. Enhancing the operation of wind-turbines in front of grid faults is not only an important issue for new wind farms, but also for the existing ones, as, at the present time, the classical squirrel cage