Development of a simulation model in low-voltage network for power harmonics study to achieve energy efficiency

Abstract

Greenhouse gases emissions have caused severe climate change problems worldwide. The reduction of the greenhouse gases emissions has become a global concern. To this, many counteracting measures have been proposed. The improvement of the energy efficiency of electrical network in buildings is one of the promising measures. On the other hand, the proliferation of power electronic devices has caused severe power harmonic problems in the LV electrical power distribution system. Excessive current harmonics in the LV electrical network will result in extra energy wastage and will deteriorate the circuit power factor. The interactions between current harmonics and the cable impedance of the LV electrical network would cause extra circuit copper loss and voltage distortions. A distorted voltage supply would influence the operation of power electronic devices and would cause even more current harmonics injection. This situation will be even worse in Hong Kong where most buildings are accommodating multiple tenants, with large amount of harmonic-generating loads extensively installed all over the LV electrical network. To achieve energy efficiency of building LV electrical network, it is important to study the impact of voltage distortion and harmonic current generation by distributed nonlinear loads on network copper loss. This thesis reports on the development of a measurement based simulation model for power harmonics study to achieve energy efficiency of building LV electrical network. A practical LV electrical network supplying distributed loads is simulated to study the relationship between voltage harmonics distortion and the network copper loss. Measurements have been conducted on selected nonlinear loads under wide range of voltage distortions to analyze the impact of supply voltage distortion on current harmonics generation. The attenuation/amplification effects on current harmonics are also studied. The effect of voltage distortions, the skin and proximity effects of circuit conductors at harmonic frequencies and the harmonic attenuation/amplification effect of current harmonics are considered in the simulation studies. Measurement data of fan coil units, desktop computers and T5 fluorescent luminaries are used to obtain the electrical load models. The accuracy of the models is verified by experiment tests. It is found that the background voltage harmonic distortion can significantly affect the total network copper loss in LV electrical network. Moreover, with an appropriate circuit arrangement, the total network copper loss caused by current harmonics of distributed nonlinear loads would be reduced. Based on the findings of this study, the building LV electrical network can be designed and managed in a more energy efficient manner.

Date of Award	15 Feb 2013
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Chung Fai Norman TSE (Supervisor) & Wing Hong Ricky LAU (Co-supervisor)