HVDC meshed multi-terminal networks for offshore wind farms: Dynamic model, load flow and equilibrium

Abstract

This paper presents sufficient conditions for the existence of an equilibrium point of multi-terminal HVDC (MT-HVDC) network for offshore applications. Newton's method is used both as a computational tool and as the basis for proving the existence and uniqueness of the equilibrium. A simple but generalized dynamic model of the MT-HVDC grid for offshore wind farm applications is presented which is non-linear due to the constant power loads with droop regulation. The classic Kantorovitch theorem is used to define the requirements for the existence of the equilibrium and the super-convergence of Newton's method starting from voltages close to 1pu. Finding this equilibrium is equivalent to the power flow in power systems applications. Computational results corroborate the requirements for equilibrium as well as the convergence of the algorithm in a realistic MT-HVDC grid.