Dynamic interactions between HVDC systems connected to AC buses in close proximity

As AC/DC systems become further integrated, multiple-infeed converter (MIC) systems can be expected to become more common. Different categories of MIC systems are defined, and: (1) the impact of the AC system strength; and (2) the coordination of the reactive power demand of the converters on the dynamic performance of such systems are discussed. Analog or physical simulator study results are presented which provide some insight into the dynamic behavior of one category of such systems. In relation to MIC systems which have a common AC bus or are connected to AC buses which are electrically close to each other, the following conclusions can be drawn: (1) careful evaluation of interactions between converters is necessary since even a remote fault affecting one DC system may affect other DC systems within the MIC system; (2) coordination of reactive powers at the common AC bus is necessary to avoid unnecessary mode shifts; and (3) coordination of the operating and control characteristics (i.e. VDCL characteristics) of converters within a MIC system is essential for satisfactory dynamic behavior of the total system