Research On Cyber-physical Co-Simulation And Stability Control For Power System With Renewable Energy

With the increase in size of interconnected power systems,the network structure and the operating mode become more and more complex,which inevitability causes stability problems,such as low frequency oscillations(LFO).LFO represent an oscillatory interaction among multi-areas of the network.It has been an important factor of destroying the system stability,reducing the transmission capacity and limiting the interconnected capability of the network.In recent years,cyber-physical simulation technology has been widely applied in the power system analysis,which provides condition for analyzing the interaction between information flow and power flow,and investigating the power system operation and the performance of power applications of control and optimization,under different cyber system status.Besides,with the increasing wind penetration,the Doubly-fed Induction Generators(DFIGs)are one of the common used wind generation types,for their advantages in relatively small size,low power rating of the back-to-back power electronic converters,high energy efficiency and separately controlling the power and the voltage(or reactive power).Moreover,DFIGs have the capacity to damp the inter-area oscillations and to supply critical impacts on interconnected power system damping performance.The performed fundamental research and the related innovative achievement in this thesis are summarized as follows:1.For analyzing the power system operation and the performance of power system applications,a hybrid simulation model is proposed,which is utilized to evaluate the Wide-area damping control(WADC)performance under practical communication system.The hybrid simulation model consists of communication system model,power system model and wide-area control center model.The communication system adopts the practical communication network.Power system modeling and simulating are based on SIMULINK/MATLAB.The control algorithm is designed based on residue methods,and implemented by C++ language.Via the above three models,a closed-loop system of WADC is set up.The case study shows the validation of the hybrid model and investigates the performance of the control method under communication latency.2.In order to investigate the degree to which a cyber-contingency affects power system operations,it is firstly categorized that the potential impacts on the information flow respected by end-to-end information features.Then a simplified co-simulation model is then put forth for analyzing the interdependencies between energy and information flows,and obtaining the quantitative relation between information features and power system operations.As the operational characteristics of a cyber system can be entirely captured by all end-to-end information flows,our developed model is hence termed as the information flow based co-simulation model.The information flow based model features in low complexity and covering potential cyber contingencies.Moreover,the quantitative relation can provide requirements for the planning and operation of cyber systems.The effectiveness and advantages of the proposed model is illustrated by the comparison between the proposed model and commercial software.Furthermore,a wide-area damping control application is taken as an example to demonstrate physical impacts of various cyber-contingencies.3.For adapting the strong nonlinearity,time-varying structure,and complex operating conditions in the interconnected power system with the integration of wind farm,an improved model-free adaptive control(MFAC)is proposed to damp out the interarea oscillation for wind farm.The improved MFAC employs the pseudo-partial derivative(PPD)to linearize the nonlinear power system dynamically,considering WADC requirements and system disturbances.In addition,to compensate for communication delays in a wide-area measurement system(WAMS),an adaptive delay compensator(ADC)is employed to reimbursed both constant and variable delays.Via theoretical analysis and simulation,the damping performance of the proposed controller,under power system uncertainties,disturbances and communication delays,is shown.4.Adopting the MFAC,which is one of the data-driven methods,a novel data-driven model-free adaptive WADC is proposed.The proposed controller consists of control direction correction,PPD updating,and one-step-ahead weighted predictive control,which has advantages in unknown control direction,zero-steady-state controller output,and considered disturbances.Moreover,the stability of the closed-loop system considering disturbances is analyzed.Finally,case studies with various uncertainties,disturbances and communication delay scenarios are set up,and the effectiveness of the proposed control strategy is validated.In the dissertation,the established cyber-physical simulation method provides a way to analyze the interaction mechanism of information flow and power flow,and investigate the power system operation and the performance of power applications,under different cyber system status.Moreover,the WADC for wind farm is designed to enhance the interconnect-ed power system stability,which overcomes the strong nonlinearity,time-varying structure,complex operating conditions,and communication latency in wide-area control of power systems,...