Dynamic Event-triggered Based Distributed Controland Stability Analysis For Dc Microgrids

With an ever-increasing demand for integrating renewable energy sources into smart grids,,such as wind turbines,photovoltaic panels,and fuel cells,a microgrid has been regarded as a promising solution and gained great popularity all around the world.A microgrid is a small-scale power system consisting of generators,renewable energy resources,energy storage systems,and loads.According to the types of coupling bus,there are AC microgrid,DC microgrid and hybrid AC-DC microgrid.Recently,DC microgrids have been gaining increasing attention due to its high efficiency,reliability,and scalability.In the DC microgrids,the main control objective is to achieve both accurate voltage restoration and precise current sharing.Distributed hierarchical control is widely used to achieve the control goal,which includes primary control and secondary control.The primary control adopts droop control.Due to the deviation of DC bus voltage,the secondary control is used to improve it.The dissertation takes the islanded DC microgrid as the research object and designs distributed secondary controls to achieve the control goal.Most of the distributed secondary controls of DC microgrids are based on consensus algorithm,so the distributed consensus control is researched and analyzed.The primary control adopts droop control to realize power sharing among distributed generators in a decentralized manner.However,due to different load distribution,the DC bus voltage may deviate from its nominal value.In order to perform voltage compensation,the secondary control adopts a dynamic consensus algorithm for the communication strategy,and iteratively converges the voltage and current to the average value in order to achieve the control goal.In order to improve communication efficiency based on the achievement of the control goal,the distributed secondary control for DC microgrid is further researched by improving the control strategy.First,a distributed secondary control based on pinning control is used to selectively apply DC bus voltage feedback to a distributed generator to realize voltage compensation.On this basis,a static event-triggered control is adopted,in which static triggered condition is set.And it only relies on limited non-periodic communication,which greatly reduces the communication cost for the system.Then through the introduction of auxiliary dynamic variables to achieve a dynamic event-triggered control,the triggered mechanism is dynamically adjusted,and it significantly reduces the communication burden of the system.Through the stability analysis of the proposed distributed control methods by the method based on Lyapunov function,the control parameters satisfy stability sufficient conditions.It also proves that Zeno behavior can be excluded under proper event-triggered conditions in the two event-triggered controls.Finally,the selection criteria of control parameters of the design system is analyed in this dissertation.An island DC microgrid test system was built under the MATLAB/Simulink environment,then the effectiveness of several control methods was verified,and the control characteristics were simulated and analyzed.Finally,through the comparison of simulation results,it is verified that the proposed distributed control based on dynamic triggered has significant advantages in communication efficiency.