Showing papers by "Juan Manuel Campos Carrasco published in 2004"

Modeling of a three level converter used in a synchronous rectifier application

Abstract: In this paper it is presented a modeling process of a five-level neutral point clamped converter used in a synchronous rectifier application and the resulting model that describes the dynamics for such converter. The highly nonlinear model, originally in abc-coordinates, is also expressed in its alphabetagamma-coordinates. Special attention is given to the gamma-component of the control input, which represents a degree of freedom that can be used for the balancing of the capacitors voltages. It is shown that the sum of capacitors voltages is a natural state of the system since it is necessary to control the total voltage on the DC side and, indeed, it reduce considerably the model expression which describes the dynamics of that voltage. It is also shown that the controller gamma-component has a minimum influence on the sum of the capacitors voltages, but it has a strong influence on the difference, hence its importance in the capacitors voltages balance. Simulations are presented to validate the proposed model. This new modeling approach and resulting model it is expected to stimulate new control proposals in the future

Control of a three level converter used as a synchronous rectifier

Abstract: We present an adaptive controller for a three level synchronous rectifier. The controller guarantees regulation and balance of the output capacitors voltages, as well as a close to unity power factor, simultaneously. The design is based on a model in /spl alpha//spl beta//spl gamma/-coordinates of the three level converter. Special attention is given to the /spl gamma/-component of the control input, since it has direct influence in the balancing of the capacitors voltages, represented here as the arithmetic difference of voltages. Moreover, it is shown that this difference is polluted by a periodic disturbance, which is also compensated by the proposed controller by adding an adaptive term to the control law. After some transformations, this adaptive term is finally reduced to a bank of resonant filters. Simulations results are presented to asses the performance of the proposed controller.

DSP-based doubly fed induction generator test bench using a back-to-back PWM converter

Abstract: Present paper describes the design of a doubly fed induction generator (DFIG) test bench with active crowbar, using PWM voltage-fed inverters connected between the grid and the rotor. A vector-control scheme is proposed in order to control the power-side and the rotor-side of the converter. A control board, based on a digital signal processor (DSP) and a FPGA, has been developed to manage the overall equipment. Real-time system supervision is implemented by a monitor program.

Simple and advanced three dimensional space vector modulation algorithm for four-leg multilevel converters topology

Abstract: In this paper, a novel three-dimensional space vector algorithm for four-legs multilevel converters is presented. It can be applied to active power filters or neutral current compensator applications for compensating harmonics and zero sequence using natural coordinates. This technique greatly simplifies the selection of the 3-D space where a given voltage vector is supposed to be found. The algorithm drastically reduces the algorithm complexity and the calculations of the active vectors with the corresponding switching time which generate the reference voltage vector. In addition, the low computational cost of the proposed algorithm is always the same and it is independent of the number of levels of the converter.

Generalized analytical approach of the calculation of the harmonic effects of single phase multilevel PWM inverters

Abstract: This paper introduces a generalized analytical approach for calculating the total harmonic distortion THD and its weighted value WTHD for multilevel PWM inverters. The calculation considers one single phase and it can apply to any number of levels of the inverter in general. Although the analysis is based on the assumption of a high number of pulses, the developed equations can also be applied for lower frequency ratios fs/f1. The analytical formulas require the characteristic parameters of the PWM only, which are the modulation factor m, the switching frequency fs, the fundamental frequency f1, the effective inductance L and the DC link voltage inverters with a number of levels N are considered. It must be noticed that some differences appear between the case of N odd and N even. Several parametric curves arc calculated to define the specifications of an inverter with N levels in order to fulfill the harmonic voltage recommendations trying to reduce the output signal filtering.