A harmonic domain model for the interaction of the HVdc convertor with ac and dc systems.
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
This thesis describes a new steady state analysis of the HVdc convert.or. Previous work is reviewed, and problems ,vith accurate modelling of the convertor, and poor solution methods are discussed. A set of equations are derived that fully model the convertor in the steady state. The analysis of the convertor employs positive frequency harmonic phasor equations, and harmonic sampling using the discrete convolution. The equations so obtained are differentiable when decomposed to real and imaginary parts.
A fast and robust sparse Newton solution of the convertor equations is developed. Solutions a.re then obtained for a variety of unba.lanced and resonant test systems, which are validated against time domain simulations. Since the ac/dc system and switching instant interactions are unified in a single unified solution, rapid convergence is obtained in all cases. Several other implementations of the Newton solution are investigated, and a sequence components solution is found to offer greater sparsity.
The Jacobian matrix of the Newton solution is used to derive linearised relation ships between convertor variables. Of particular interest is the direct cakulation of the convert.or impedance, at an operating point, including the effect of control, commutation, and unbalance. Since the convert.or impedance can be phase dependent, a new tensor representation of impedance is proposed, interpreted, and utilised in a tensor nodal analysis.