Compact Fluorescent Lamps phase dependency modelling and harmonic assessment of their widespread use in distribution systems
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
This thesis presents the research on CFL's phase dependency modelling to prvodie an improved harmonic assessment of their widespread use in distribution system. Conventionally, CFL is modelled as fixed harmonic current source, which ignores the harmonic interaction with the ac electrical network. However, with different magnitude and phase angle of the applied voltage, CFL's harmonic current injection will be varied. This leads to the methodology of using a Norton equivalent circuit to model CFL's harmonic behaviour.
In a small voltage distortion range, such as 5% VTHD, the CFL admittance is phase dependent with the phase angle of the applied voltage. This dependency character is described by tensors, which are widely used in physics to represent the invariant relationship between vectors under rotation of coordinate axes. Two methods are purposed to find the optimal value of the linearized admittance tensors on a perturbation level of 3.26% of VTHD. The first method is to average the tensor results from the original admittance plots based on select points. In the second method, the admittances are rearranged into one double traced circle, and then find the linearized admittance tensor. Both methods show strong agreement and good validity. This also provides an opportunity to analyze the harmonic behaviour of small rating nonlinear electronic devices from a new prospective.
This proposed CFL model is applied to a typical New Zealand distribution network with comparison of using conventional fixed harmonic current source approach. The VTHD caused by large quantity of CFLs is given a more realistic "worst case" scenario. The harmonic interference with ripple control system is also discussed.