Newton solution for the steady-state interaction of AC/DC systems

The steady-state interaction of a six-pulse converter with a Thevenin equivalent of the three-phase AC and DC systems is solved. The converter is represented by harmonic phasor mismatch equations, and the interaction between the converter and AC and DC systems is embodied in the solution of harmonic mismatch equations for the converter terminal conditions. Since there are a large number of simultaneous nonlinear equations to be solved, a sparse Newton-type solution is developed that exploits the harmonic three-port nature of the converter, and the relatively weak interaction between switching angles and terminal harmonics. The resulting solution is fast, and closely matches a time domain simulation of the test system.