Modelling of large nonlinear loads and thyristor controlled shunt compensators

The experimental modelling of large nonlinear loads (such as arc furnaces), their supply systems and reactive shunt compensation is described. The laboratory model can be programmed to draw a load current which is a scaled copy of a system load or any other waveform that may be required. The modelling of the compensator is based on a thyristor controlled shunt reactor (TCR), using a fast, but very simple, integral of voltage controlling algorithm. The ability of the equipment to model a 56 MVA electric arc furnace is described and it is shown that to model such a load mathematically, a degree of randomness has to be introduced into the synthesised current waveform