A microcontroller‐based soft‐starter for residential air‐conditioners: harmonic analysis

Abstract

Purpose

The purpose of this paper is to reduce the inrush current and dip in voltage for energy‐ saving purposes in relation to residential air‐conditioning systems.

Design/methodology/approach

The paper focuses on the experimental harmonic investigation of a window‐type residential AC unit line current under time‐based soft‐starting control strategy. The control strategy assumes that only source voltage and current measurements are available. The soft‐starter is based on power electronic devices controlled through a firing signal generated by a programmed microcontroller during the first 500 ms.

Findings

The harmonic content shows the effect of the soft‐starter in exciting high‐frequency components of the line current. Harmonics investigations show that the high frequencies – even or odd multiples – of the fundamental line frequency are all excited by the soft‐starter approach. Some of these frequencies may harm the life cycle of the air‐conditioner.

Research limitations/implications

The real data harmonic analysis shows that the adopted approach excites the entire frequency spectrum of the signal. A better monitoring of the harmonics is required. A closed loop adaptive soft‐starting control may perform much better than a time‐based soft‐starting strategy.

Originality/value

The paper assesses the power quality related to time‐based soft‐starting strategy of a residential air‐conditioning system to reduce the inrush current and the dip in voltage, both with a serious effect on energy savings, especially when the AC load is around 65 per cent of the total power demand load.

Citation

El Ferik, S., Ahmed, C.B., Ben Amor, L. and Hussain, S.A. (2008), "A microcontroller‐based soft‐starter for residential air‐conditioners: harmonic analysis", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 27 No. 5, pp. 1081-1097. https://doi.org/10.1108/03321640810890780