Research On Parallel Technology Based On The Droop Control Of Three-phase Inverter

The distributed generation is unanimously considered as the main development pattern of theelectric power industry in the21stcentury with the advantages of safety, energy conservation,environmental protection and advanced technology etc. Furthermore, the combination of distributedgeneration and the grid can improve the security and flexibility of the system. With the continuousdevelopment of the distributed generation, higher requirements of capacity, stability and extensibilityof the system are proposed. Parallel inverter technology is an effective measure to achieve theserequirements. In addition, with the promotion of more-electric aircraft&all-electric aircraft and theincreasing of the airborne electronic equipments, the parallel inverter technology also has goodprospects in aviation occasions since it can address the needs of capacity, stability, reliability andextensibility of the airborne electronic equipments. Therefore, there’s important significance toresearch on the parallel inverter technology.First, the existing structure and control methods of parallel inverter system are reviewed in thispaper. In contrast, the droop control method as the research hotspot is widely concerned because ofthe outstanding advantages, such as strong anti-jamming capability, easy maintenance and reliableoperation. However, the stability of the system and the detailed design of system parameters of droopcontrol remain to be further analysis. Therefore, the three phase inverter parallel system based on thedroop control method is chosen to be researched in this paper. The purpose of this paper is to discussthe stability of the parallel system and to optimized design the parameters of the system, thusimproving the performance indicators of the system and providing theoretical guidance for theoptimum design of droop control strategy.Then, the small signal model based on the dynamic vector method of the traditional droopcontrol is carried out in this paper. On this basis, the stability of the active power frequency systemand the reactive power amplitude system are analyzed in depth. Also, the range of the droopcoefficients which maintain the stable operation of the system is deduced. Furthermore, optimumdesign method of the droop coefficients is given, providing the theoretical foundation for engineeringdesign. However, there’re several drawbacks of the traditional droop control, such as poor dynamicperformance and small static error. Thus, an improved droop control method is introduced and smallsignal model of the improved droop system is given. Thereby, the law of the impact of variousparameters on the system performance is found out and the optimum design method of each parameter is given, which provide a theoretical basis for follow-up study.Finally, the MATLAB/Simulink simulation for both traditional method and the improved droopcontrol method are made. Meanwhile, an experimental platform of a three phase inverter parallelsystem based on TMS320F28335is built. And the design method for both hardware and software aregiven. The simulation experimental results verify the correctness of the theoretical analysis andtessibility of the improved droop control method.