A General-Purpose Multiterminal DC Load-Flow

This paper presents a novel method for solving the load-flow problem of a general multiterminal dc network in an integrated ac-dc system. The method can handle a great variety of converter controls and operating conditions of the dc system. It has also the ability to handle discrete tap-step and tap limits of the converter transformer, to impose overcurrent limit at the terminal and to represent the combined behavior of the converter control and tap changer during steady-state and transient conditions; all within the iterative procedure. This method iterates directly on the dc voltage equations using a digital current reference balancer to update the dc currents. Since the digital current reference balancer has a simple closed form solution, the computation effort per iteration is extremely small. Numerical examples are presented to demonstrate the various features of the method. The convergence characteristic of the method is good. Storage requirement is only a few percent of that required by other techniques which manipulate with the full Jacobian matrix. Test results showed that the method is considerably faster than previous dc load-flow techniques.