Study On Feedback Control With Time-delay Of Wide-area Power System Based On Hamilton Theory

Wide-area measurement system provides a good data-exchange platform for monitoring and optimization controlling the entire grid. It is improves the stability of the power system, but it also highlights the delay quality of the power system. In recent years, the stability and control of wide-area power system with time delay to become a research hotspot, and the fruitful results are achieved. The time-delay power system has developed rapidly, particularly, the stability analysis and control of time-delay linear system based on linear control theory has been an unprecedented development. However, the various nonlinear characteristics exist in the field of power engineering technology, and coupled with unavoidable time-delay. Therefore, there is a broader application space for the method of the stability and control design problems of nonlinear time-delay systems, and the method can be applied in the complex power systems with multi-machine.The generalized Hamilton system based on energy approach is a more general class of nonlinear systems, and it has a superiority of a clear structure and meaning in terms of stability of nonlinear systems. So it is applied in many practical control systems, and became one of the important methods of non-linear control problem. The challenges of this method facing in the application, which is the nonlinear system converted to an equivalent system in the form of generalized Hamilton issues, have been studied in depth and better implementation. However, a large time-delay exists in the system will inevitably affect the stability of the power system, and may even lead to system instability. In this paper, taking the time-delay characteristics of the wide-area power system as the core, the stability and wide-area power system control with time-delay have been studied. Hoping the results of this paper will provide some effective ways to the study of time-delay power system. The main contents and conclusions of this paper are summarized as following.The power system has multiple time delays as wide-area measurement information with different transmission distances. The model of power system with multiple time delays is constructed considering two parts of the damping controller signals: The first level of control is derived from local signals without time delays; The second level of control is supplied by a coordinator using global states with different multiple time delays. The delay fractioning based on Lyapunov-Krasovskii approach is used to derive a delay-dependent steady stability criterion, and the criteria of stability are formulated as feasibility problems of linear matrix inequality(LMI). The model is reduced by the model reduction method. The time-delay output feedback control is realized for wide-area power system. And the maximum delay times is calculated. The relationship between the delay fractioning and the parameter of the wide-area controller is discussed, as well as the control effect of the inter-area oscillation. The interaction of the inter-area machines is fully considered by the design method of multiple time-delay controllers. And it is improved the inhibitory effect on inter-area oscillation. The conservative of the system will reduce with the increase of the delay fractioning, as well as increase the effectiveness of the wide-area controller.The Hamilton model of interconnected grid with AVR and PSS devices is constructed based on Hamilton systems theory. Based on the proposed model, the corresponding Lyapunov-Krasovskii functional is given to derive a delay-dependent steady stability criterion in term of matrix inequalities. Time delay margin delay can be calculated which makes closed loop power system is stable. The relationship between the damping performance of WADC and the time delay margin has been investigated. Thus corresponding control parameters of WADC are given. The delay Hamilton system stability is analyzed and coordination controller is designed. The relationship between the parameters of the wide-area controller and the delay margin is analyzed, and the value of the delay margin is calculated. These ideas and methods are promoted to the power system which contained devices, such as SVC, TCSC FACTS. The time-delay Hamilton system model considering wide-area delay signal is built. Then the coordination control problems between the generator excitation and these devices are analyzed. When taking into account the transmission signal delay, the gain of the wide-area controller increase with reduction of the transmission time-delay. Delay margin has important guiding significance for the design parameters of the wide-area controller.According to the characteristics of the power system, the stability and control methods of the time-delay generalized Hamilton system considering the coupling terms is analyzed. The delay part of the feedback control is converted into differential equations through a series of mathematical transformations, and the delay link is implicated in the dynamic differential model of the system. The multi-machine power system considering feedback stagnation and transfer conductance is expressed as a pseudo- generalized dissipative Hamilton system, and the wide-area feedback controller and robust controller are achieve respectively, based on the pseudo-generalized dissipative Hamilton system theorem and controller design method. The simulation results of show that the generator excitation controller considering time-delay can reduce the impact of time-delay on system dynamic performance, and increase the delay margin and the robustness of the system.