Research On Stability Control Of Angle And DoS Attack Frequency For Power CPS

To provide efficient,convenient,and flexible power transmission and distribution capabilities,power generation,transmission,distribution,and power supply have become more and more complex and modern communication networks and control technologies have also intergrated into power system,leading to power cyber physical system（Power CPS）.If there is short of damping,it will generate low-frequency oscillations.If the demand from industrial production change sharply,it also leads to sharply load changes.These issue will further affect the stability of angle and frequency of power system,causing bus voltage fluctuations and even regional blackouts.With the rapid development of the synchrophasor measurement technology and wide area measurement system applications,PMU can collect the global information of power grid in real time,and the dispatch control center can achieve monitoring and control of the power system.Therefore,the hierarchical structure of networked control is designed for the local control and the global cooperative control of the power system,which can improve the stability and control performance of the power system.Currently,the communication networks such as Ethernet.wireless communication,and GPS satellite communication are employed,however the limited bandwidth leads to problems such as network-induced delay,packet losses and misordering,and there exist even multi-source interferences,leading to non-negligible impact on the angle stability of the power system.Moreover,malicious network attacks such as DoS attacks will cause the failure of communication networks and information systems,which further make it impossible for the dispatch control center to monitor and control,increasing multi-point failure range of power system.To improve the stability and control performance of angle and frequency of the power CPS networked system,this paper focuses on the stability control of angle and DoS attack frequency for power CPS.The research contributions mainly include the following aspects:（1）The disturbances and noise will reduce the accuracy of angle stability of the single generator in networked automatic voltage control system for power CPS.To solve the problem,the ZOH and LZOH sorting strategies are firstly designed to solve the data packet misordering.Then,H₂/H_∞ filter approach is proposed to decline the noise interference,and the average exponential stability of the error system is theoretically analyzed.Finally,simulation results confirm that the proposed filter approach can make the angle and electrical angular velocity deviation of the generator tend to stability under network-induced delay and noise environment.（2）The interarea low-frequency oscillations reduce angle stability of multi-generator for multi-area networked damping control system of power CPS.To overcome the problem,considering the network-induced delay and the limited bandwidth constraint,an improved event triggering mechanism is firstly designed,and the system model including event trigger parameters and network-induced delays is established.Then,the asymptotically stablility is proved,and the stability criteria is given.Furthermore,to obtain the time-delay stability range and reduce the system conservation,a co-design method is proposed by considering the time-delay boundary range,event trigger mechanism parameters and H_∞ performance index.Finally,under networked system environment with external disturbances,simulation results confirm that the designed robust H_∞ controller can achieve the stability of multi-area generators.（3）The intermittent DoS attacks will block sampled data traffic in single-area networked load frequency control system for power CPS.For the problem,the closed loop model of networked load frequency control system is firstly established by considering DoS attack characteristics,and the exponential stability of system is proved and the exponential stability condition is given.Then,the quantitative relationship between DoS attack strength（i.e.,Proportion of time intervals between DoS attacks and no DoS attacks）and the frequency stability is provided.Finally,the frequency stability of one-area networked load frequency control system for power CPS is compared on the different DoS attack strength in simulation experiments,which confirm the feasibility and effectiveness of the proposed method.（4）The intermittent DoS attacks will break global sampled data traffic in multi-area networked load frequency control system for power CPS.To solve the problem,the interconnection structure of multi-area networked load frequency control system is firstly analyzed.Then,a quadratic event trigger is designed to improve communication efficiency,and the impact of intermittent DoS attacks for event trigger mechanism is also analyzed.Furthermore,a closed loop switch control system model is established,and the exponential stability of system is theoretically analyzed and the quantitative relationship between DoS attack strength and the multi-area frequency stability is provided.Finally,the changes of global data traffic are analyzed and the impact on frequency stability are compared on different DoS attack strength in simulation,which confirm the guiding role of the frequency stability determination index.