Research On Power Decoupling Droop Control Strategy In Micro-grid

Micro-grid is an important branch of smart grid,which can realize "plug and play" to ensure good power quality while reducing the impact on large power grids.There are many types of inverter control strategies in micro-grid systems.In order to reduce construction costs,weaken or eliminate the mutual interference of different control loops,droop control strategies that do not require tie lines for signal transmission are favored.Combined with the actual low-voltage micro-grid system,the resistance-to-inductance ratio(R/X)of the line parameters is relatively high,which does not meet the line resistance characteristics of traditional centralized power generation systems.Directly using of traditional droop control strategies may cause problems such as power quality degradation and output power coupling.In order to realize the reasonable application of droop control in low-voltage micro-grid,the improvement measures of droop control strategy are emerging in an endless stream at this stage.Common improved droop control measures generally include virtual impedance-based improved droop control strategy,adaptive improved droop control strategy,etc.,which are usually introduced The virtual impedance may cause the voltage amplitude to drop;the improved droop control strategy based on self-adaptation is to increase the tie line between different DGs based on the traditional droop control strategy,so that the advantages of the traditional droop control strategy are reduced.From the perspective of the output power of the traditional droop control strategy,this paper introduces a conversion matrix,derives an improved droop control expression considering the line inductance and resistance parameters at the same time,and then designs an improved droop control strategy based on power decoupling.The impedance parameter of the line needs to be used in the controller design of the improved droop control strategy based on power decoupling.Based on this,this paper introduces the synchronous phasor measurement technology(Phasor measurement unit for synchronous measurement,PMU).This technology can perform online real-time monitoring of line parameters,and provides reliable parameter support for the design of the droop controller.In order to verify the effectiveness of the proposed improved droop control strategy based on power decoupling in the system with high line resistance-to-inductance ratio,this paper uses MATLAB/Simulink simulation software to build a system model for simulation.Set different operating states to perform system operation simulation analysis,and compare the simulation results in each case with the simulation results of the improved droop control strategy based on virtual impedance.The comparison summarizes the improved droop control strategy based on power decoupling.While ensuring the good power quality of the system,it can also solve the coupling problem of output active power and reactive power,and overcoming the problem of unreasonable distribution of output power.