Corrección de factor de potencia basada en la estimación digital de la corriente de líneaaplicación en el convertidor Boost en modo de conducción continua

  1. López Martín, Víctor Manuel
Supervised by:
  1. Francisco Javier Azcondo Sánchez Director

Defence university: Universidad de Cantabria

Fecha de defensa: 29 November 2013

Committee:
  1. Paolo Mattavelli Chair
  2. Alberto Pigazo López Secretary
  3. Javier Sebastián Zúñiga Committee member

Type: Thesis

Teseo: 353697 DIALNET lock_openUCrea editor

Abstract

Continuous conduction mode (CCM) power factor correction (PFC) without input current measurement is a step forward with respect to previously proposed PFC digital controllers. Inductor volt-second (vsL) measurement in each switching period enables the digital estimation of the input current, used in the inner current loop. However, an accurate compensation of the small inaccuracies in the measured vsL is required in the estimation, to match the actual current. Otherwise, these errors are accumulated every switching period over the half-line cycle, leading to an appreciable current distortion. A vsL estimation method is proposed in this thesis, measuring the input (vg) and the output voltage (vo). Discontinuous measuring the drain-to-source MOSFET voltage, vds. Parasitic elements also cause a small difference between the estimated voltage across the inductor, based on input and output voltage measurements, and the actual one, which must be taken into account to estimate the current in the proposed sensorless PFC digital controller. This thesis analyzes deeply the current estimation inaccuracies caused by errors in the ON-time estimation, voltage measurements, and the parasitic elements. A new digital feedback control with high resolution is also proposed to cancel the difference between DCM operation time of the real input current TgDCM, and the estimated DCM time TrebDCM. Therefore, the current estimation is calibrated using digital signals during in DCM. A fast feedforward coarse time error compensation is carried out with the measured delay of the drive signal, and then a fine compensation is achieved with the feedback loop that matches the estimated and DCM times. With this contribution, an universal controller is proposed. The digital controller can be used in universal applications due to the ability of the DCM time feedback loop to autotune based on the operation conditions (power level, input voltage, output voltage...), which improves the operation range in comparison with previous solutions. Furthermore, an additional improvement is presented in this controller which the current demanded by the Sensorless PFC rectifier is pure sinusoidal despite the non-sinusoidal input voltage of the grid. This contribution is really interesting in applications where the harmonic limits are stricter (like in aircraft systems) and must be fulfilled independently on the voltage waveshape. This modification is totally done into the digital controller without any need of extra analogs components. Experimental results are shown for a 1 kWboost PFC converter over a wide power and voltage range. The digital controller is implemented in a field programmable gate array (FPGA) with a very simple analog circuitry to adapt the signals needed by the controller. The behaviour of the controller, applied in lighting systems, is also shown.