METHODOLOGIES FOR ANALYSIS OF MULTITERMINAL HVDC SYSTEMS.

摘要

Numerical methods suitable for the study of the steady state (load-flow) and transient stability problem for multiterminal HVDC power systems are presented.;The load flow problem for a multiterminal HVDC power system is stated and solved. The method of solution allows arbitrary configuration of the dc network and series and shunt converters. The dc load flow algorithm developed is suitable for use with arbitrary ac load flow programs with minimum modifications to existing software. Examples include the solution of two multiterminal systems. The algorithm converges in a small number of iterations for different initial data, and is insensitive to starting conditions.;For transient stability analysis, the power system is divided into components: ac network, dc network, dc converters and dc controllers. The simulation of the dc controllers requires considerable flexibility. A method for representing and simulating the dc controllers which does not require the explicit description of the configuration of the controllers in the main computer code, but allows the controller to be described by a user, is described.;Gear's second order method and the trapezoidal rule of integration with an added damping term are proposed and tested as viable alternatives to the ordinary trapezoidal rule of integration for power system simulation. The performance of these methods is shown to be better than the trapezoidal rule implemented with large time steps. The performance of the trapezoidal rule with and without damping is tested in the simulation of a transmission line with a current controller. The trapezoidal rule with damping allows the use of a larger time step in the simulation than the trapezoidal rule without damping.;A dual-step trapezoidal integration method is introduced for the study of systems described by easily separable slow and fast variables. The slow varying variables are integrated with different time steps. The numerical solution of a second order linear equation with a time-varying coefficient is carried out. The results obtained with the dual-step method are compared with those from the trapezoidal rule. The proposed method yields comparable results while requiring fewer computations for the slow varying variable.