The minimisation of disturbances on the electricity supply network when controlling industrial, resistive loads

Unacceptable disturbances can arise on the electricity supply network, in certain situations, when either burst firing or phase angle, thyristor load control is used. In order to combat situations where the disturbances created by either of these control methods exceed the recommended limits an investigation has been conducted into an operating mode which involves both phase angle and burst firing control. This mode is called soft-start, soft-finish, burst firing and incorporates a phase angle component on the leading and trailing edge of each burst fire. Consequently, this operational mode is modelled for the control of industrial, resistive loads. To construct this model several series of experimental data were required to supplement the derived algorithms. The model, which computes the voltage and current harmonics and voltage fluctuation disturbances, is then incorporated in a computer program. This program compares the disturbances with the acceptable limits and postulates the optimal ramp length for operation such that the disturbances on the electricity supply network will be minimised. The computer program also permits closer examination of the disturbances, should a reduction in a particular order of harmonic be desirable