Power flow modeling of hybrid AC/DC systems

This chapter discusses the power flow of a combined AC/DC system. In its most simple form, the converters can be modeled as power injections to the AC system with coupled active power injections and independent reactive power setpoints. The detailed models described in the chapter include the converter losses and limits and allow for various representations of converters, either including transformers and/or filters. The power flow equations for the DC grid were derived for various converter control representations, including constant active power, voltage droop, and constant DC voltage. The advantage of using a sequential approach is that the models can relatively easy be combined with existing AC power flow software. The chapter shows the program flow structure of MatACDC, as an example. The power flow algorithm sequentially solves the AC and DC system power flow, thereby respectively keeping all converter powers and voltages constant.