Decentralized Parametric Stabilization And Application For Interconnected Systems With Time-Varying Quantization

Abstract:In many practical large-scale nonlinear systems, it is often the case that there exist uncertain parameters and variations of these parameters result in moving or even disappeared equilibrium, which directly leads to the systems unstable. Therefore, the study of nonlinear stability of the system parameters is significant. With the development of the network control technology and the improvement of the performance of the hardware digital devices, the problem of quantization has become a hotspot in the control field now. Time-varying quantizer based on its adjustable parameters, can dynamically adjust the range of values of the quantizer, has been widely applied in the quantitative feedback controller design. This thesis investigates decentralized parametric stabilization for interconnected systems with time-varying quantizer and applies it to the power system. The main contents of this thesis are shown as follows:(1) The analysis of parametric stability and the design of decentralized state feedback controller are studied for interconnected systems with quantization which consist of N subsystems. The output of each controller is quantized by a logarithmic quantizer before it is input to subsystem, and the quantizer parameters would affect stability of the system. Firstly, the decentralized state feedback controller is proposed to make the closed-loop system parametric stability. Then, the time-varying quantizer is used to quantize the control input and the state of each subsystem. And the controllers are designed by adjusting the quantizers’ parameters in a decentralized manner depended on local information to make the interconnected large-scaled systems parametric stability. Finally, an example is proposed to illustrate the effectiveness of the proposed method.(2) The H∞control problem of nonlinear systems is studied for interconnected systems with quantization. Firstly, the decentralized state feedback controller is proposed to make the closed-loop system parametric stability and with the same H∞disturbance attenuation level as on no quantizers circumstance. Then, the time-varying quantizer is used to quantize the control input and the state of each subsystem. Made the closed-loop system parametric stability By updating the quantizers’ parameters decentralized control method, also with H∞disturbance attenuation level. Finally, the simulation results show that by using the designed quantized controllers, the interconnected large-scaled systems are parametric stabilized.(3) The theory of analysis of parametric stability and the method of design of decentralized state feedback controller are applied in the interconnected power systems. In the actual power system, q-axis current is proportional to exciting current in the case of unsaturated flux. The excitation current is seen as the uncertain parameter, and build the power system model. And construct the designed controllers and the quantizers’parameters in a decentralized manner depended on local information, so the closed-loop power system is still parametric stability. Finally, an example is proposed to illustrate the effectiveness of the proposed method. Figures(16), tables (0), references (75).