Decoupled Newton Algorithms in the Harmonic Domain for the Harmonic Interaction of Line Commutated Converters With AC Systems

Under certain nonideal conditions, the harmonic interaction of line commutated converters with the ac network must be represented by suitable models with high level of detail. A complex and robust solution of this problem is achieved in previous works by means of an iterative procedure in the harmonic domain, where ac and dc harmonics and switching instants are updated simultaneously. This simultaneous method is a full Newton solution (FNS) and therefore it offers a very good convergence, but the integration of the converter model into the whole iterative process (WIP) is complicated due to the heterogeneous form of the Jacobian matrix. The main object of this paper is to present alternative procedures based on decoupled Newton solutions (DNS), where a sequential method of solving the iterative process is used. It leads to a much more modular approach for performing the WIP, since the integration of the converter in the WIP is significant simplified, even when the converter presents any dc side structure. Several critical cases and experiments have been tested in order to show the performance and the convergence properties of the DNS in comparison with FNS.