Composite resonance; a circuit approach to the waveform distortion dynamics of an HVdc converter

A frequency domain analysis is applied to a controlled HVDC power converter interconnecting AC and DC power networks. The converter is considered as a three-port network, and described using transfer functions. Using AC and DC power system frequency dependent impedances, an equivalent electrical circuit is constructed. The concept of composite resonance is introduced to emphasise the interaction between the AC and DC systems, and a simplified damping factor derived to predict the dynamics of waveform distortion during transient recovery. The frequency domain analysis is verified by dynamic simulation