Developments in phase-variable modelling for thyristor-controlled reactive-power compensators

Of the different control objectives of reactive-power compensators based on thyristor-controlled reactors, the advances in modelling methods and computer simulation of the paper relate specifically to the mode of voltage-magnitude control in which each phase is controlled individually. For this control objective, a comprehensive analysis formulation is developed in phase-variable notation in a form which can directly be incorporated into Newton-Raphson network analysis in which each phase retains its separate identity. The main context of the development is that of the supply from transmission networks of loads of substantial imbalance between the separate phases. The analysis and evaluation facilities to which the developments of the paper can lead, provide means by which the response of compensators with individual phase-voltage-magnitude control functions can be investigated for the conditions of pronounced imbalance in steady-state primary system operation. Following the analysis derivations and the developments in phase-variable modelling for thyristor-controlled compensators, a representative design investigation is given in the paper in which phase-to-phase loads are supplied from a section of a 220 kV network. In this particular application, the effectiveness of individual phase-voltage-magnitude control in lowering operating imbalance is quantified.