Flexible HVDC Non-linear Control Strategy Research And Simulation Analysis

Flexible HVDC use full-controlled high-voltage high-power electronic devices, such as GTO, IGBT, etc.. The control method of between VSC-HVDC and ordinary rectifier and inverter are similar, but they are very different in the control objects.So the control strategies and methods are bound to have great specificity. Based on small-signal linear control strategy for power system operation in complex power system environments have significant limitations. This study, based on previous work, focus on the non-linear control strategies of VSC-HVDC control system.First of all, any control system design are inseparable from the mathematical model, the second depart of this dissertation studied the detailed mathematical model of VSC-HVDC system in the symmetry conditions, including the model of three-phase stationary ABC coordinate system and the DQ coordinates system witch suitable for control system design more. The converter station and its control system in the power system connected both up and down level system, for the clarity of structure and tasks of control systems, described the three levels architecture of VSC-HVDC control system.VSC-HVDC control model has a characteristics that is a multi-variable, Non-linear and strong coupling system. The third chapter introduces the feedback linearization decoupling control strategy. Studied the principles of the control strategy and applied it to design controller for VSC-HVDC. Designed a DC voltage-Reactive power controller and Active-Reactive power controller. The simulation model has build based on MATLAB/Simulink simulation environment. Simulation results show that controller designed based on feedback linearization control strategies achieved a linear decoupling control object.Based on another features that is the stable operating point variable, the model can not be accurate, disturbances frequently such as mechanical and electrical parameters of the VSC-HVDC system, the ADRC control theory, in the fourth chapter introduced in. The theory of ADRC Originated from PID control strategies, However, the ADRC controller performance better than the classical PID. Studied the principles of the control strategy and applied it to design controller of VSC-HVDC. Designed a one order inner-current controller. The simulation model has build based on MATLAB/Simulink simulation environment. Simulation results show that controller designed based on ADRC strategies has better anti-disturb ability, fast response and anti-overshoot than PID controller.