Research On Wide - Area Fuzzy Damping Control Of Power System

With the expansion of power system, the interconnected low frequency oscillation between power gird has become an important problem of power system stability. The traditional power system stabilizers which adopt the local variables as the input signals can not solve this problem quite well. Wide-area measurement system can provide wide area feedback signals. These signals can be used in excitation control for enhancing multimachine system damping and restrain inter-area low frequency oscillation. The time delay inevitably exists during the communication of a wide-area signal and will degrade the control effects. Fuzzy control is a kind of nonlinear control and it does not need to set up complicated mathematical model. Also it has good robustness and adaptability. Therebefore, it is of vital significance to apply fuzzy control to wide-area damping control to compensate communication time delay and enhance power system damping which eventually improves power system stability in the wide-area measurement system.Herein, we apply wide-area feedback signals as supplementary stability signals in excitation control, as it generates communication delay compensated by fuzzy control technology. Three kinds of wide-area damping controllers based on fuzzy control technology are designed including Mamdani type, fuzzy adaptive PID control and Takagi-Sugeno model. Fuzzy control rules play a significant role in designing fuzzy logical controllers. The fuzzy rules proposed before are usually determined by experts’experience. The strategy of determining fuzzy rules is introduced in the process of designing Mamdani type fuzzy controllers that exhibits high performance. In fuzzy adaptive PID control based wide-area damping controller, the proportional-integrative-derivative controller compensates the time delay of wide-area signal. Meanwhile, the fuzzy inference system adjusts adaptively the gain of PID controller. In the wide-area damping controller which combines Takagi-Sugeno fuzzy inference system with the cloud model, Takagi-Sugeno fuzzy inference system compensates the time delay of wide-area signal and the cloud model sets the weight value of Takagi-Sugeno inference system, enhancing the robustness of the control system. Digital simulation results show that the designed controllers can compensate communication time delay, enhance the damping of interconnected power system, suppress low frequency oscillation and improve the stability of power system.Applying semi-physical real-time simulation technology in power system can not only simulate actual operating characteristics of the grid, but also solve the problems of environment restriction in real system testing and the trouble of complex modeling, which makes the research achievements approach the practical situation. RT-LAB has great advantages in high-precision real-time simulation of large power grid and can accurately simulate various electromagnetic transient process in power system. Herein, a hardware-in-the-loop simulation progect for wide-area damping controller is presented with RT-LAB real-time simulator. The modeling of a four-machine two-area power system is realized based on RT-LAB real-time simulation software and Takagi-Sugeno and fuzzy adaptive PID control based wide-area damping controllers are implemented with digital signal processor. RT-LAB real-time simulation platform and digital signal processor based wide-area damping controller constitute hardware-in-the-loop simulation system. The experiment results verify the correctness and feasibility of the theory analysis and the effectiveness of the wide-area damping controllers’ application.