Research On Coordinated Control And Strategy Of Source, Load And Storage Without Communication In Microgrid

At present,optimal centralized control which is based on state information collection and communication is widely used in micro-grid.However,the realization of full communication coverage in microgrid will greatly increase the construction cost.At the same time,the high-speed real-time transmission of great amount of data also requires high-level performance of the communication system.Besides,the failure of communication system could put the microgrid at great security risks.Therefore,it is of great significance to study the coordinated control of micro-grid without communication.Firstly,based on the simulation of photovoltaic cells,the influence factors of its output characteristics are analyzed,as well as the classical battery management strategy,so as to select the appropriate control strategy in the non-communication coordinated control.The conductance increment method in MPPT control is optimized by the variable step size to realize the fast and efficient tracking of maximum photovoltaic power.In view of the failure of fully absorption of energy at the maximum PV power,which is due to the limited regulation capacity of the micro-grid,reduction power control is introduced to improve the PV system,so as to adjust the PV output power according to the frequency fluctuation,so that PV could participate in regulating frequency control.The PQ control strategy of grid-connected control is studied,and the effectiveness of the design is verified by model simulation.Secondly,the traditional droop control strategy is improved by being introduced virtual power related to SOC into the power reference value to realize the adaptive power regulation of energy storage and achieve the same drop speed of SOC.In order to improve the power supply quality,PI control is introduced in the droop control loop to compensate the voltage drop caused by Q-U droop control.For power overshoot and the following power oscillation problem caused by multiple energy storages' simultaneous response to load fluctuation,the working condition of other energy storage units in the system can be deduced by analyzing the difference between the expected frequency regulation and the actual frequency variation.So as to set a reasonable reference amount of power to reduce the power grid frequency fluctuation,and the validity of the system is verified by model simulation.Finally,the frame of non-communication coordination control is studied.The operating state of the microgrid is divided into several regions according to the bus voltage and frequency.Combined with PV in frequency control and the optimization strategy of droop control,both the active and reactive power balance of each interval was analyzed.The control strategy and the control combination of each unit were optimized,and the logical switching was reasonably coordinated and optimized.By introducing the operation holding regions,the frequent switching of partition boundary control is minimized.The simulation model is built to verify the feasibility and effectiveness of non-communication coordination control.