| Abstract |
Two control algorithms are proposed for controlling a PWM step-up rectifier that is connected to an
asymmetrical grid: a feedforward and a feedback controller. Both methods are compared to a standard
symmetrical control method. The control objective is to maintain a constant output power, regardless
of the asymmetry in the grid. The quality of the input currents has to be optimised, which means an
optimised power factor. The theoretical basis for a controller with such characteristics is the
instantaneous power theory. Simulations show that the proposed asymmetrical feedforward control
reduces the ripple on the output power considerably, however, the output voltage gets an offset value
due to a time delay and discrete time effects caused by the data processing, respectively, the digital
controller. The simulation results for the feedback controller are promising: a large asymmetry up to
25% in the power supply can be handled by the feedback controller and yields an output power
variation of about 4%, depending on the capacitor size. |
