Research On Fault Tolerant Control For Load Frequency Control System In Power Grid Under Sensor Faults

In recent years,safe and high-quality electric energy supply is one of the important factors that guarantee the rapid development of today’s society.People’s lives and industrial production are inseparable from stable electric energy.However,with the increasing complexity of domestic power grids and the widespread application of new energy technologies,the traditional load frequency control strategy is difficult to guarantee the quality of the power grid frequency.In addition,the probability of occurrence of various faults will inevitably increase.The system uncertainties caused by faults seriously affect the control performance of the system,and bring new challenges to the frequency control of the power grid.Considering that the load frequency control system directly participates in the frequency modulation of the power grid,and maintains the balance between power generation and consumption,it plays an important role in the social development.Therefore,it is necessary to design a reasonable and reliable control strategy to ensure the quality of the power grid frequency.In this paper,combining fault detection,fault estimation,sliding mode control and other related technologies,the fault-tolerant control scheme is studied for the power grid load frequency control system under sensor faults.The main contents of this paper are as follows:1.The structure and working principle of the power grid load frequency control system are studied,and the mathematical model of the multi-area and multi-generation units power grid load frequency control system is established.At the same time,the analysis and modeling of possible sensor fault signals lay the foundation for the following research methods.2.Aiming at the problem of grid load disturbance and system parameter uncertainty,a disturbance reconstruction sliding mode load frequency control strategy based on interval observer is designed.The interval observer is used to observe the state of each control area,and the system model and the observed interval information are combined to realize the online estimation of the system uncertainty.A sliding mode controller based on disturbance reconstruction is designed to ensure the frequency stability of the system under load disturbance and system parameter uncertainty.In addition,because the interval residuals produced by the interval observer and the sensor output are not sensitive to disturbances and system parameters,online detection of sensor faults can be carried out.The effectiveness of the proposed method is verified by theoretical analysis and simulation experiments.3.From the perspective of multi-area interconnected power grids,a distributed sensor fault estimation strategy is designed using the correlation information between different areas.The H_∞performance method is used to suppress the influence of system uncertainties on fault estimation and ensure the reliability of the estimated fault information.The estimated information is used to compensate the sensor measurement online,and an adaptive integral sliding mode fault-tolerant controller is designed.Based on theoretical analysis,it is proved that the designed fault-tolerant controller can ensure the system’s gradual stability under disturbances,parameter uncertainties and sensor faults.The simulation verifies the effectiveness of the method.4.Aiming at the system where hybrid energy storage participates in frequency modulation,this paper establishes a power grid load frequency control system model with hybrid energy storage system,and proposes a load frequency fault-tolerant control strategy based on sliding mode observer.A sliding mode observer is designed for each control area of the power grid.The sensor fault is regarded as an auxiliary state variable of the system for fault reconstruction.The sliding mode discontinuous input is used to ensure the accuracy of the fault reconstruction signal.An integral sliding mode fault-tolerant controller based on observer is designed.Based on theoretical analysis,the system is proved to be stable.The effectiveness and superiority of this method are verified through comparative simulation experiments.