A variable speed AC motor drive, fed by a 3-phase AC supply, often consists of a 3-phase bridge diode rectifier, a DC link capacitor and a pulse width modulated inverter. Recently, a new type of capacitor, known as film capacitor or slim capacitor has become popular for use in DC links. This capacitor has a lower value of capacitance and a longer life span than the conventional electrolytic capacitor. However, drives with slim DC link fed by a soft grid exhibits the tendency to oscillate at higher frequencies. This can be attributed to the LC resonance between the grid inductance and the small DC link capacitance which results in a significant unwanted voltage ripples on the DC link. The unwanted harmonics affects the performance of the motor and distorts current drawn from the grid. The objective of this paper is to formulate, model and test a control algorithm to dampen the effects of the LC oscillations. This paper proposes a novel method of compensation that estimates the ideal DC link voltage without unwanted ripple and feed-forwards the estimated DC link voltage to the motor drive algorithm thereby altering the behavior of motor drive to be resistive to the ripple. By doing so the current drawn by the motor from the grid will be less distorted thereby, improving the power factor of the system and ensuring the system adheres to the harmonic standards.
|Title of host publication||2019 IEEE 13th International Conference on Power Electronics and Drive Systems, PEDS 2019|
|Publication status||Published - 9 Jul 2019|