The Research On The Improved Droop Control Strategy Of DC Microgrid Converter

As a power grid structure which can make effective use of distributed power generation energy,DC microgrid has the advantages of simple structure,high energy utilization efficiency and easy control,and has gradually become a hot research topic.The coordinated control of DC microgrid is the key to the safe and stable operation of DC microgrid.In this paper,the operation,control and coordination of the isolated DC microgrid,which includes energy storage unit,distributed power generation unit and load unit,are studied.In this paper,the isolated DC microgrid and its contained components are analyzed and modeled mathematically,for the main component of the control system——DC converter main circuit and control circuit are designed,the Boost converter circuit is selected for the photovoltaic unit,the two-way DC-DC converter is selected for the battery unit,and the simulation model is established.Then the traditional control method of DC microgrid is analyzed,and some shortcomings of traditional droop control are pointed out:voltage-free adjustment can not be achieved,and the exit line impedance will cause uneven distribution of the power of the converter.In view of voltage regulation,it is proposed that the secondary regulation of droop control and the three adjustments of droop control are proposed to make up for the deficiency of the traditional droop control in voltage control.In view of the difference of power distribution of converter caused by line impedance difference,a power adaptive distribution control strategy based on virtual impedance is proposed.By introducing the impedance information obtained by active identification into the droop control,the precise distribution of load power is realized,thus improving the energy efficiency.Then according to the different power balance situation,the DC microgrid operating state is divided into four categories,the operation state analysis is carried out,and then the different control methods proposed in this paper are applied to the four types of operating state,and different control coordination strategies are designed.Finally,the simulation verification is carried out on the Matlab/Simulink simulation platform,and the results show that the control strategy can be accurately distributed under all operating conditions,while the bus voltage can always be maintained at a high voltage level,which proves the validity and practicability of the proposed method.And the proposed control strategy has no communication network requirements,economically reliable and has plug-and-play function.