The Analysis Of The Influence For Voltage Stability In Power System With HVDC

Safety and quality of power supply is the foundation of the national economy, The economic environment puts forward higher requirements to the development of power system,the interconnecting of the power system is the objective requirement for the rational use of the resources to support the economic development, HVDC can satisfy the requirement of the interconnection for the system with long-distance and large-capacity.The voltage stability of the power system will be affected with HVDC joining in the system,in this paper,the auther use the theory of bifurcation and continuous flow algorithm by M file programming in MATLAB to research on the dynamic voltage stability in the ac/dc system of modified 3 machines and 9 nodes with differential algebraic model,especially for the further research of the bifurcation points closely related to the dynamic voltage instability, The main research content is as follows:1) To research on the flow calculation in ac/dc system with HVDC joining in power system, based on the method of unified iterative for equations in ac/dc system,get the solution through the newton-raphson method considering the main control approach in inverters.2) Get the equilibrium solution curve namely QU curve of ac/dc system with continuous flow algorithm based on local parameterized,in the process of solving, judging the change of characteristic root in characteristic matrix at each equilibrium solution to get the HP bifurcation,the SIB bifurcation and the SNB bifurcation of the system with continuation method,by tracking the locus of characteristic roots in the system to illustrate the characteristics of the HP bifurcation and SNB bifurcation. Programmed to realize time domain simulation under small disturbance.3) Discuss the voltage stability level in power system with the way of ac and dc transmission,and the effect on voltage stability margin with different control methods in inverter and the magnification of proportional and integral in the controller.As there are more parameters and variables in ac/dc system,this paper study the influence of several typical dc control parameters on voltage stability margin by using bifurcation theory,using the method of calculating double parameters bifurcation boundary to research voltage stability margin.4) Through the bifurcation theory and the method of modal to choose the optimal installation location of SVC in ac/dc system, and analyze the effect on the voltage stability margin of the parameters in SVC.5) By introducing a kind of SVC based on high-pass filtering control, research the the choosing method in two-dimensional of controller parameters to achieve the purpose of eliminating HP bifurcation in the ac/dc system with two kinds of operation modes, Through the method of characteristic root and time domain simulation to instruct to its correctness.