REVISTA DYNA ENERGÍA

Key words:

Control en cascada, Filtro activo de potencia, Compensación de armónicos de corriente, Controladores PI, Calidad de la energía, Compensación de potencia reactiva, Cascade control, active power filter, current harmonics compensation, PI controllers, energy quality, reactive power compensation

Article type:

ARTICULO DE INVESTIGACION / RESEARCH ARTICLE

Section:

RESEARCH ARTICLES

ABSTRACT:
A common strategy to control a single phase active power filter is that called “cascade control” which is composed by two loops, one internal loop for the output current and one external loop for the dc bus voltage regulation; for each control loop, a PI controller is assigned, which needs to be tuned correctly. The objective of this work is to propose a systematic tuning-methodology that allows to obtain the proportional gain kP and the time constant Ti for PI controllers. PI controllers have been chosen because of their simplicity, easiness to implement and its wide industrial use. Even though the active filter model is non-linear, a way of representing it as a two transfer function connected in cascade was found. From this representation and doing necessary assumptions, the model was simplified, making that those both loops could be tuned separately. Assuming that the control scheme is implemented in a digital device, the sampling frequency fs has been taken as a reference. The PI tuning of the internal loop is carried out making the closed loop transfer function have unit gain with zero phase. This last allows a good reference tracking in the harmonic current frequencies range. Likewise, the PI tuning of the external loop is based on the calculation of the parameters to the step response, in order to regulate the dc bus voltage. To validate the consistency of the methodology, results are presented with different values of sampling frequency and voltage of the electrical grid. Simulation and experimental results are shown.

Keywords: Cascade control, active power filter, current harmonics compensation, PI controllers, energy quality, reactive power compensation.