Fast Periodic Solution for Twelve-Pulse Converter

Using step-by-step numerical integration, the steady-state solutions of HVDC converter problems are obtained by integrating until all the transients have been damped out. In general, these solutions are expensive to obtain. In this paper the HVDC converter is treated as a piecewise linear configuration. A method is developed which exploits linear network theory, as well as the transposed periodicity in T/6 and three-phase symmetry properties of the converter network. The method, when applied to a 12-pulse converter with eleventh, thirteenth harmonic and HP filters converges toward the steady-state solution within five iterations. The method is intended to be a working tool in the computer-aided-design of HVDC systems. Most planning, developmental, and research work in HVDC continues to rely on analog simulators. The digital computer programs which have been written for HVDC studies are still expensive to use. In part this is because the programs are written to cover all conceivable situations. But quite often the power and generality of these programs are wasted, for example, when one requires repeated runs of the steady-state solution. One sees the need of dedicated programs for each level of HVDC design: in load flow, steady-state, transient, and fault analyses. This paper reports on the continuing research on steady-state HVDC solutions begun in [1]. The objective is to demonstrate that it is possible to extend the same principles to the 12-pulse converter shown in Fig. 1.