Refined microcomputer control for HVdc converters

The control techniques of an existing microcomputer converter controller [1] are refined and presented in this paper. The control design has been tested extensively with detailed computer simulation of both 2-terminal and multi-terminal dc transmission systems [2]. Due to its ac voltage-states tracking capability, improved current regulator performance and an adjustable low-voltage-dependent current order limit (LVDCOL), it has been able to provide rapid recovery even in the most severe case involving a solid 3-phase fault at an inverter bus connected to weak ac systems.