Research On Circulation Suppression Method Based On Dynamic Droop Control

When the energy storage system device provides electrical energy to the DC microgrid load,the stability indicators involved are mainly the problems of DC bus voltage stability and power balance distribution.When considering the loss of the entire DC microgrid and the performance of the converter device,circulating current is also an important research object,which is essential to maintain the stable operation of the DC microgrid system.This paper mainly studies the multiple parallel converters in the low-voltage DC microgrid to effectively solve the problem of circulating current while balancing the power distribution.The DC microgrid system uses the traditional fixed coefficient droop control strategy,and there are two problems:(1)The droop control function will be affected by circuit parameters(especially line impedance),and the inconsistent output voltage of the parallel converter port will cause the occurrence of circulating current.(2)Excessive droop coefficient leads to DC microgrid bus voltage deviation.In order to solve the above problems,this paper first proposes a variable coefficient dynamic droop control circulating current suppression method,using the calculated line resistance analog and the selected initial droop coefficient as the reference value to dynamically adjust the droop coefficient,and obtain The droop coefficient is used to eliminate the influence of line resistance on the output current distribution,and to improve the circulating current problem caused by the excessive difference in output current distribution caused by the fixed droop coefficient setting.At the same time,in order to compensate the bus voltage drop caused by the droop control,an average current loop or a voltage adjustment loop is given to increase the bus voltage.The core of the above dynamic droop control method lies in the design of the dynamic droop coefficient adjustment algorithm and bus voltage compensation design.However,because this control method needs to calculate the analog value of the line resistance,the deviation of the collected data and control parameters will affect the output current distribute precision,which leads to insufficient precision of circulation suppression.In order to solve the problem of circulating current suppression accuracy,this paper proposes a dynamic droop control strategy based on discrete consensus algorithm,taking the output voltage deviation of the port of the adjacent converter as the input,iteratively calculating the voltage,and taking the resulting droop coefficient disturbance as the output The quantity feedback is adjusted to the droop controller,according to the real-time dynamic adjustment of each time period,to improve the accuracy of circulating current suppression,and at the same time,to ensure the balanced distribution of power.By constructing a simulation model of the DC microgrid system,the feasibility of circulating current suppression under dynamic droop control and dynamic droop control based on discrete consensus algorithm is verified respectively,and the inverter device with the same or different initial droop coefficient setting value is used for switching The conversion of the operating mode is compared,and the effect of the circulation suppression under different working conditions is compared.Compared with the traditional droop method,the two control methods can effectively control the power balance distribution and solve the problems of circulating current and bus voltage stability.