Research On Partial Power Converter Communication And Energy Management

A DC micro-grid is a controllable system in which distributed energy source(DES)is connected to the same DC bus and provides energy to the load and local.As an important means of power transmission in the smart grid in the future,DC micro-grid can integrate various renewable energy sources,energy storage devices and traditional AC power grids locally.In recent years,with the development of DC renewable power,energy storage and power load,DC micro-grid systems have received more and more attention.The DC micro-grid is a system that relies on power electronics technology to operate.Therefore,improving the transmission efficiency of power electronic equipment in the micro-grid can improve the transmission efficiency of the entire micro-grid system.At the same time,the communication between the DES in the micro-network is very important.By realizing the information exchange between the DES,the energy can be efficiently distributed among the power source,the power equipment and the energy storage device.Thereby improving the controllability and economy of the micro-grid operation.Aiming at the problem of power transmission efficiency of micro-grid,a scheme of controlling the power flow between distributed energy sources by partial power converter(PPC)is proposed.The PPC topology is constructed by cascading dual active bridge(DAB)and four quadrant DC-DC converters.The comparison analysis and mathematical model of PPC and traditional full power converter are completed.Also the simulation analysis in the SIMULINK environment is completed,and the voltage and current control of the PPC is realized.Finally,the experimental prototype is designed,and the feasibility of the circuit topology in power flow control is verified by experiments.Aiming at the shortcomings of communication of power electronic equipment and the limited number of micro-network DES,a method of coordinating distributed energy operation by means of distributed management is proposed by using DC bus as communication medium and pulse voltage as communication method.When the system is running,the bus voltage is controlled by the main module and the slave module is controlled to coordinate the insufficient and excessive energy on the DC bus.The system controls the slave module transmit power to the DC bus,when the energy on the DC bus is insufficient.And it controls the slave module to draw from the DC bus when the energy on the DC bus is too much so that the bus voltage remains constant.The communication between the master module and the different slave modules is realized by pulsed voltages of different pulse widths,and combined with the droop control method for multi-module power distribution.Through the setting of the communication protocol of the master and the slave module in the micro-grid,the energy management of the system during the island operation is realized.The PPC prototype can achieve a transmission efficiency of 96.8%when power transmission is performed in the functional experiments.Experiments have been carried out to verify the mutual transmission of energy between different levels of voltage.Under the condition of changing the bus load,the master module controls the slave modules and realizes the energy management in the micro-grid.