VDCOL parameters design of multi-infeed HVDC based on a simplified model of DC P-Q coupling recovery

When several high voltage direct current (HVDC) systems simultaneously recover after severe faults, absorbing large amounts of reactive power from the receiving AC systems, presents new challenges for the transient voltage stability of multi-infeed HVDC (MIDC) systems. Actually DC power recovery characteristics could be controllable to some extent by selecting voltage dependant current order limiter (VDCOL) parameters, but the quantitative relationship is complex and not easy to use. This paper, with experiment method based on PSCAD/EMTDC package and the CIGRE HVDC benchmark system, explored the converter bus voltage profile and the relationship of HVDC MW (P)and reactive power (Q) consumed by the converter during and after various faults. Through numerical analysis, the characteristic equation on P-Q has been fit out. With which and VDCOL characteristics, a simplified model of DC P-Q coupling recovery was constructed. Finally, based on the above model, a design method of VDCOL parameters was proposed with an objective function considering minimum sum of reactive power demand peaks of MIDC recovery. Some examples with different rated power combinations of MIDC systems were studied to demonstrate the feasibility of the proposed method.