Nonlinear HVDC link model reduction in multi AC-HVDC power system state estimation

Attempting to reduce the order of the HVDC link subspace in a multi AC-HVDC state estimator from 11 states to 4 increases the complexity and nonlinearity of the HVDC link measurement equations, decreases the HVDC link estimate accuracy, and increases the density of nonzero HVDC link Jacobian partial derivative terms.