Direct digital closed-loop control of h.v. d.c. convertors

As an alternative to present analogue-based control schemes, the basic design characteristics and dynamic performance of a newly proposed direct digital control are described. Tests are carried out in a specially designed scaled-down model provided with the necessary monitoring facilities for direct digital control. Special emphasis is given to the performance of relatively weak a.c. systems, and therefore the model includes suitable representation of the system parameters and of the filters normally used. It is shown that the implementation of equidistant-firing control by means of digital feedback loops provides fast recoveries from convertor and line disturbances.