Research On Networked Control For Cyber-Physical Power System

The power system is increasingly interacting deeply with the information system by utilizing communication, computation and control technologies to enhance the reliability, to reduce cost and to provide varieties of real-time services for customers, and is becoming cyber-physical power system (CPPS). Implementation of synchronous phasor measurement techniques and wide-area measument system (WAMS) can gather fine-grained synchronous data of the whole grid, which is the base of networked control for cyber-physical power system and also generates some challenges at the same time. Those challenges include that high-volume data gathered to the control center brings pressure to information systems for sampling, storing and processing, and network-induced time delay, data packet dropout/disordering and network congestion give adverse impacts on the control loop.In this thesis typical characteristics of CPPS are analyzed. On the base of recalling the present research status of CPPS and networked control of CPPS, it is proposed that to study and then to implement the networked control theory suitable for CPPS are effective means to overcome the adversary impact on the stable operation of power system brought by the non-ideal communication. The compendious frame of the whole thesis is as follows.Firstly, the architecture of wide-area monitoring and control system of CPPS is illustrated. Analysis on the functions and working principles of the components is addressed. Investigations on the characteristics of time delay and data packet dropouts due to different transport layer protocols are carried out.Secondly, the small signal model of CPPS is introduced. After the analysis of the structures and working principle of the designed event-triggering wide-area damping control system, the Hm wide-area damping controller (WADC) design problem for inter-area oscillations in CPPS is addressed. The full-state coupled event-triggering condition is used to determine the released instants that the phasor states collected by the phasor data concentrator. Based on the delay-system method of networked control system (NCS) and the Jensen’s inequality, linear matrix inequality (LMI)-based controller design criterion is deduced. The guiding idea for choosing appropriate event-trigger parameter is proposed based on the interrelations analysis among delay margin, dynamic response performance, and disturbance reject index and event-trigger parameter.Thirdly, the general design procedures are summarized to design WADC for CPPS by applying NCS theories when the power system is described by detailed model. Considering time delay and modelling the phenomenon of data packet dropout as equivalent delay and stochastic process having Bernoulli distribution respectively, WADC via dynamci output feedback (DOF) is designed. Moreover, nonlinear time domain simulations verify the effectiveness of the propoed method.Finally, considering the fact that the controller updates at discrete time and the physical process dynamic evolves continuously in load frequency control (LFC), the digital proportional-integral-derivative (PID) design problem is converted into design of static output feedback (SOF) of the augmented system. Digital PID controllers are seperately designed for the traditional LFC and the LFC under deregulated environment. The control gain can be directly obtained by applying LMI-based criteria, and the calculation complexity is less. Moreover, the designed controllers have simple structures, and easy for engineering implementation.