混合通信攻击下基于VSG的孤岛微电网分布式动态事件触发二次调频策略OA

Distributed secondary frequency regulation in virtual synchronous generator(VSG)-based islanded microgrids usually relies on consensus algorithms to achieve frequency restoration and active-power allocation.However,such methods strongly depend on communication links among distributed generation(DG)converters.Denial-of-service(DoS)attacks can block information transmission,while deception attacks can tamper with communication data.The combined action of these two types of attacks may cause more severe damage to microgrids.Existing studies on microgrid secondary control under hybrid attacks mainly focus on direct-current microgrids or droop-controlled alternating-current microgrids,and are difficult to directly apply to VSG-based alternating-current islanded microgrids.Conventional periodic communication mechanisms impose high communication bandwidth overhead and computational burden,while static event-triggered mechanisms may still be frequently triggered by small errors during the steady-state stage.Although dynamic event-triggered mechanisms have been introduced in existing studies,they are all established under the premise of reliable communication links.Under an event-triggered communication mechanism,the attack occurrence interval cannot be directly regarded as the actual affected interval of the microgrid,making the coordinated design of the converter secondary frequency regulation controller and the triggering mechanism more complex.To address these problems,this paper develops a distributed dynamic event-triggered secondary frequency regulation strategy for VSG-based islanded microgrids under hybrid communication attacks. First,a distributed sequential hybrid attack model is established by considering the relationship between attack intervals and event-triggered instants.Effective attack intervals and actual affected intervals are defined according to the triggering instants of each DG converter.A binary attack indication variable is introduced to describe whether each DG is attacked at a triggering instant,and a scaling factor is adopted to uniformly describe DoS attacks and multiplicative deception attacks.In this way,the model can uniformly characterize distributed attack scenarios in which different communication links are subjected to different attack strategies,as well as global attack scenarios.On this basis,a distributed consensus-based secondary frequency regulation controller against hybrid attacks is designed by incorporating the VSG primary frequency regulation dynamics and active-power coordination requirements.The frequency reference and active-power reference are regulated through local information exchange.A dynamic event-triggered mechanism is further introduced,in which the triggering threshold is adjusted online according to the local consensus error and measurement error,thereby reducing unnecessary communication updates during the steady-state stage.Finally,the effects of hybrid attack constraints and the maximum triggering interval are simultaneously considered in the Lyapunov analysis.Sufficient conditions for the asymptotic convergence of the system are derived,and the tuning principles of triggering parameters for practical applications are investigated. A case study is built in Matlab/Simulink for an islanded microgrid system containing six VSG converters operating in parallel.In the communication topology,only DG2 and DG6 can directly obtain the virtual leader frequency information,while the remaining DGs complete distributed secondary frequency regulation through a sparse communication network.Under load disturbances,the system exhibits steady-state frequency deviations when only VSG primary frequency regulation is used.After the secondary frequency regulation controller is activated,the frequencies of all DGs recover to values close to the rated value,and the active-power outputs of DG1～DG6 satisfy the preset active-power allocation relationship.In the distributed hybrid attack scenario,the maximum DoS attack duty cycle on the communication links reaches 53.73%,and the maximum deception attack duty cycle reaches 45.28%,representing a relatively severe attack scenario within the theoretical stability boundary.Without the attack mitigation strategy,the frequency regulation performance of the system deteriorates significantly.After the designed attack mitigation strategy is introduced,periodic triggering,static event triggering,and dynamic event triggering can all achieve frequency restoration and active-power coordination.Compared with periodic communication,the dynamic event-triggered mechanism slightly increases the transient adjustment time but significantly reduces the communication burden.When the periodic communication interval is 0.1 ms,the average number of communication triggering events for each converter within 8 s is approximately 67.3×103 under DoS attacks.After the dynamic event-triggered mechanism is adopted,DG5 has the largest average number of triggering events,with only 529 events,reducing the number of communication triggering events by approximately 99%.Compared with the static event-triggered mechanism,the dynamic event-triggered mechanism further reduces the average number of triggering events by 49.61%while maintaining similar frequency regulation performance. The proposed strategy is further verified under global hybrid attacks,communication delays,parameter variations,and complex communication conditions.In the global hybrid attack scenario,the DoS attack and deception attack duty cycles are set to 21.62%and 14.55%,respectively,and four operating conditions are verified:pure DoS attack,amplification attack,attenuation attack,and scaling hybrid attack.All four types of attacks increase the average frequency deviation of the system and prolong the recovery process.Nevertheless,the proposed strategy can still restore the system frequency to the rated value,and it shows better control performance under the global amplification attack.Under 10～100 ms constant communication delays and time-varying communication delays,the system frequency can still be restored to the rated value.The extended case with eight DGs and the backup communication link reconfiguration case show that when the communication topology remains connected and at least one converter can obtain the leader frequency information,the designed strategy can still achieve frequency restoration and active-power allocation.When the attack intensity exceeds the theoretical tolerance range,the attacked link needs to be isolated and the connected topology should be reconstructed through a backup communication link to restore accurate active-power allocation.