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Cooperative Control For Microgrids Based On Consensus Algorithm Of Multi-Agent Systems

Posted on:2022-08-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:M X ShiFull Text:PDF
GTID:1482306572976169Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
With the large-scale grid connection of distributed renewable energy such as photovoltaic and wind power,microgrid,as an effective way to integrate various distributed generators(DG),has attracted widespread attention.Realizing the safe and stable operation of microgrid by coordinating distributed power supply is of great significance to promote the development and utilization of renewable energy.Consensus algorithm of multi-agent systems(MAS),which makes the state of agents consistent by the communication between agents,provides a feasible method to coordinate the DGs in microgrids.Traditional distributed control mainly considers ideal communication network and the DGs are deemed multi-agents with the same dynamic characteristics.Nevertheless,the difference of power characteristics between DGs,the delays and bandwidth limitation of communication network,and cyber security issues all bring serious challenges to the application of consensus algorithms in microgrids.Therefore,it is necessary to carry out further research on the application of multi-agent consensus algorithm in microgrids.In this paper,the microgrid cooperative control based on consensus algorithm of MAS are investigated from the aspects of system modeling,control scheme,theoretical analysis and simulation verification in both DC microgrids and AC microgrids.Besides,complex operating conditions such as different power characteristics,non-ideal communication and cyber-attacks are considered.The specific research contents are as follows.(1)A distributed control method for ESs based on one-order consensus algorithm is proposed in Photovoltaics-Energy storages(PV-ES)DC microgrids.With the information exchange among neighbored ESs,the average bus voltage is restored to the rated value and the output power of ESs is allocated proportionally according to the State of Charge(So C).The proposed control is suitable for ESs with different rated power.The output power of ESs can be bounded automatically when it approaches to the limitation.Besides,a cooperation control method among PVs,ESs and controllable loads are designed by considering the So C limit of ESs.The effectiveness of the proposed method is verified by simulations.(2)The communication delays will lead to steady state errors of the conventional observer-based average voltage control,or even cause instability.To overcome this problem,a consensus optimal control based on proportional-integral(PI)consensus algorithm is proposed.The average voltage restoration and proportional power sharing of ESs are transformed into an optimization problem.Through the steady-state analysis,it is proved that the steady-state operating point of the proposed control strategy is not affected by the time delay.On this basis,a scattered transformation is applied to the exchanging variables,which further improves the system stability under delays.Simulations are conducted to verify the effectiveness of the PI-consensus optimal control and scattering transformation.(3)Based on the PI consensus optimal control,this paper proposes a sampled-data-based(SDB)event-triggered control for DC microgrids.The communication is triggered and controller is updated only when the predefined event-triggered conditions(ETCs)are met,which significantly saves the resources of communication and computer.It can realized average voltage control and proportional power sharing with limited communication bandwidth.Besides,each distributed generator(DG)only has one ETC,which simplifies the control structure.Lyapunov-Krasovskii functional method are applied to achieve the sufficient conditions for the asymptotic stability of the proposed event-triggered control.The effectiveness of the proposed event-triggered control are verified by simulations.(4)The traditional distributed control for AC microgrid suffers from steady state errors caused by initial values or time times.To address this issue,this paper proposes PI consensus-based distributed voltage control and frequency control,to realize the voltage/frequency restoration and reactive/active power sharing.Steady state analysis demonstrate the high accuracy of the proposed control under none-zero initial values and time delays.Detailed small-signal model of the AC microgrid is established to analysis the effects of the controller parameters on the system stability.Simulation results verify the effectiveness of the proposed control and the accuracy of the theoretical analysis.(5)To solve the problem of cyber-attacks in AC microgrids,an integrated distributed control structure is built,which can restore the system frequency and voltage to the rated value,and realize proportional distribution of active and reactive power with the least information exchange.Based on the integrated control structure,distributed resilient frequency control and resilient voltage control are proposed for the potential sensor and actuator attacks.Small-signal stability analysis and H?output feedback control are applied to guarantee the system stability and L2 gain performance.The effectiveness of the proposed control strategy is verified by simulation comparison...
Keywords/Search Tags:DC microgrid, AC microgrid, multi-agent consensus algorithm, distributed control, delays, event-triggered mechanism, cyber-attack
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