An Examination of an Interaction Model between AC and DC Transmission Lines

In the populated area, parallel running or crossing of AC and DC line may happen. Then there are needs of analyzing the interaction between AC and DC line for the better control and protection. For the demand, the interaction model has to provide capabilities to represent highly accurate DC initialization, dynamics in low frequency as well as higher frequency and excitations at specified frequency including resonance phenomena. This paper concerns the phase domain modeling and presents a modification of frequency characteristics in low frequency band for the accurate DC initialization, newly devised fitting techniques for the modified characteristics which use only real data, and an approximation method which makes the approximation error to be zero at the specific frequency. The examination of the phase domain interaction model constituted by these methods showed the high reliability in DC initialization and dynamic responses. Also the steady state outputs of the model following AC excitation agree well with those of the equivalent pi circuit.