| In today’s world,energy consumption is increasing and environmental problems are becoming more and more prominent.Microgrids with green energy as the carrier have become a hot issue in the world.However,the microgrid is different from the large power grid,and its working status changes from time to time,so higher requirements are put forward for the control of the microgrid.This article starts with the control of the microgrid,and designs different control strategies for the three situations of the grid-connected state,the island state and the transition process between the two.The research content of this article is expanded from the following parts:(1)Aiming at the structure of the optical storage microgrid,this paper establishes a mathematical model for the battery and energy storage converter of the energy storage unit,and designs the parameters of the LC filter device required by the system.According to the characteristics of the photovoltaic cell,the MPPT control based on the conductance increment method is adopted to make the photovoltaic cell always maintain the maximum power output.Use constant voltage control for photovoltaic grid-connected inverters.Using simulation software to build a 45 k W photovoltaic grid-connected power generation system,through the power quality analysis of output power,voltage and current,it is concluded that the designed photovoltaic grid-connected power generation system meets the requirements.(2)Aiming at two working states of microgrid,this paper proposes that the energy storage converter as the main controller adopts a dual-mode control method.When the microgrid is connected to the grid,the fuzzy algorithm is combined with the traditional PQ control,and an adaptive PQ controller based on the fuzzy algorithm is designed.Control the output power of the energy storage unit.When the microgrid is operating in islands,according to the influence of the moment of inertia and the damping coefficient in the virtual synchronization control,an adaptive virtual synchronization controller is designed.Control the voltage and frequency in the islanding state,and ensure the stability of the frequency when the load fluctuates.The optical storage microgrid is established by simulation software,and the control strategy of the dual-mode energy storage converter designed in this paper can be verified by switching on and off the load to ensure the stability of the multi-mode operation of the microgrid.(3)Aiming at the transient process when the microgrid working mode is switched,this paper designs a seamless switching control technology,including islanding detection module and pre-synchronization module.The traditional islanding detection algorithm AFDPF has a greater impact on the power quality of the microgrid.This paper proposes an islanding detection algorithm based on AFD-AFDPF cooperative detection,which can reduce the influence of disturbance current on the power quality of microgrid.Then the seamless switching technology is combined with the control technology of the dual-mode energy storage converter designed in the previous section,the improved control strategy of the energy storage converter in different operation modes of the microgrid.Finally,the simulation analysis is performed on the microgrid without seamless switching technology and the microgrid with seamless switching technology.compare the data in the transient process of state switching.The results prove that the microgrid with seamless switching technology can effectively suppress the impulse voltage and impulse current during the transient process of mode switching. |
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