Research On The Control Design For Hvdc Based On Multi-Index Nonlinear Control Method

Due to the stability and other aspects limits, traditional AC transmission technology seems powerless while facing today’s long distance and large scale transmission. The development and application of the DC transmission technology provide an effective means to solve such problems:conveying the large capacity power over a long distance, the interconnection of the large area power grids and the interconnection of the asynchronous grids which have frequency difference. With a reasonable control to the DC system, the DC transmission technology can also provide an emergency power to support at AC system fault, improve the AC system’s transient stability. So, the high voltage direct current (HVDC) technology obtains a rapid development and application.Control system is the core to the HVDC technology, the safety and stability of the whole system depends on the performance of the controller. This paper will adopt the Multi-index nonlinear control (MINC) method to design the HVDC controller to obtain good dynamic and static adjustment performances.In chapter3, based on the mathematical model of voltage source inverter type high-voltage direct current transmission (VSC-HVDC) under the dpO axis, then, combined with the rectifier and the system of the synchronous generator excitation control system, a six-order nonlinear model of the converter is established. The coordinated controller is designed from the idea of MINC method and the simulation results validate that the model is correct and the controller is efficient.In the fourth chapter, the additional controller of the DC transmission system is designed. Combined with the generator excitation, the coordinated control model is established. Then this paper designed a Multi-index coordinated controller. The simulation results show that the DC additional controller can improve the transient stability of the system and has excellent control quality.Based on the research of the fourth chapter, the motion characteristic of the steam turbine is considered in this chapter. The multi-index comprehensive controller is designed after adding a new control value:the turbo generator steam value control, and completing the nonlinear model of HVDC and generator. The simulation results show that not only the controller can be balanced in both the dynamic and the static performances of the system well, but also have a strong robustness.