Adjusting converter controls for paralleled DC converters using a digital transient simulation program

A description is given of how accurate system modeling of a DC system with an electromagnetic transient simulation program can be used to study and correct interbipole oscillations between converters connected into a parallel multiterminal system. The authors show how too decide on the details of the modeling that is required and demonstrate that it is often not enough to use prepackaged, generic HVDC control models supplied with these programs. The details of control models that are used in electromagnetic simulation programs are shown to have a significant impact, in some cases, on the simulation results. In particular, a case of 6 Hz oscillations, in the DC current of two converters of the Nelson River System, is accurately simulated, and it is shown that control modifications suggested by the simulation actually do eliminate the interbipole oscillations