The use of voltage feedback in HVDC converter control

The use of combined voltage and current feedback for converter control was investigated. A simplified linear model for a monopolar dc link was developed for analysis of large and small disturbances. Using parameters from the proposed EPRI - Consolidated Edison 100 MW dc link, an eigenvalue analysis was performed, in which a compensated current feedback control was compared with the system using voltage feedback. Results of the linearized analysis showed that the use of voltage feedback appears to offer greater damping of system oscillations and considerably faster large-signal response than the use of a conventional current regulator. A detailed hybrid computer simulation of the 100 MW dc link was also used in the investigation. The ac system, individual converter valves, converter controls, and the dc line are fully represented in the simulation. Computer studies were made for various operations and disturbances, in which the current control was compared with the system using voltage feedback. Generally the results of the simulation agree with the basic conclusions reached from the linear analysis, however, the use of the simplified linear model for selecting optimum control parameters was in several cases shown to be somewhat inaccurate.