Research On Distributed Finite-time Secondary Control Strategy For Microgrid Under Disturbance

The control system of microgrid is particularly critical because it loses the support of large power grid during the operation of microgrid in island mode.In order to ensure the stable operation of isolated island microgrid,hierarchical control strategy is generally adopted to maintain the stability of voltage and frequency and rational power distribution in microgrid.In the case of a specific sensitive load in the microgrid,the load must be maintained at the rated frequency and voltage,so the system needs to converge within a limited time.In addition,the microgrid is susceptible to the interference of uncertain factors during operation,which may come from internal faults of power devices,changes in system load,etc.,or even network attacks on distributed communication networks.Therefore,in order to solve the above problems,this paper combines the multi-agent theory and the idea of sliding mode control,proposes an improved finite time quadratic control strategy and a disturbance rejection control strategy based on sliding mode control,and realizes the frequency and voltage recovery and the reasonable distribution of active power of the microgrid in a finite time under the condition of unknown disturbance.The main research contents of this paper are as follows:1.The development status of microgrid and the research status of distributed secondary control of microgrid are summarized,and the multi-agent theory,hierarchical control theory of microgrid and sliding mode control are emphatically analyzed.Through simulation experiments,the superiority of finite time consistency over conventional consistency is analyzed.At the same time,a sliding mode controller based on multi-agent is designed,and the effectiveness of the proposed sliding mode control strategy to deal with interference is verified by simulation,which provides theoretical support for the follow-up research of this paper.2.The control objective of secondary control of microgrid in hierarchical control is theoretically deduced,and a traditional finite time distributed secondary control strategy is introduced.Considering the requirement of convergence speed for microgrid system under certain conditions,an improved finite time distributed quadratic control strategy is proposed by introducing linear terms.Compared with the traditional finite time distributed quadratic control strategy,this strategy further speeds up the convergence of the system on the premise of realizing the stability recovery within a finite time.3.In view of the unknown disturbance existing in the actual operating environment of microgrid,considering the simple structure of sliding mode control and its strong robustness to uncertain interference,a distributed finite time secondary control strategy of microgrid based on sliding mode control is proposed in Chapter 3.Firstly,to solve the problem that the reaching speed of the power reaching law is too small when it is far away from the sliding mode plane in the traditional sliding mode control,a double power reaching law is adopted,which has faster reaching speed and better motion quality.Secondly,a distributed finite time secondary controller based on sliding mode control is designed using the double power reaching law.In the face of unknown interference,the controller can effectively eliminate the influence of interference on the microgrid system,and achieve the secondary control goal of the microgrid in a finite time.