Research On Droop Control Strategy Of Island Microgrid

Microgrid power generation system can not only provide us with clean, economical and reliable energy, but also can alleviate the shortage of traditional energy problems. As an important operation mode of microgrid, islanded microgrid has strong compatibility and environmental suitability, which can be used in various landforms and environments. It plays a positive role in reducing pollution emission,decreasing electricity generating and using costs in remote areas and improving electricity quality.As an important control method for islanded microgrid,droop control is widely used because it has the advantages of not relying on the communication system and"plug-and-play" architecture.However, in the droop controlled islanded microgrid, the actual line impedance is mostly resistance-inductance characteristics, which will cause the power coupling problem of the islanded microgrid. Line impedance and load fluctuation can also cause voltage and frequency drop, and so on, so it is difficult to achieve steady control performance. In this paper, the power decoupling, frequency mutation and voltage recovery are studied under the droop control islanded microgrid.(1) Several control methods for microgrid were briefly analyzed. The limitations of traditional methods were analyzed after comparatively analyzing islanded operational advantages of the droop control. Based on the analysis of the theory of droop control,Matlab / Simulink simulation model of droop control was design.(2) Aiming at the power coupling of droop control caused by the line impedance of islanded microgrid,the virtual impedance link was introduced on the basis of the traditional droop control method. The value boundary condition of virtual impedance was concluded by calculation and analysis to realize the decoupling control of the output power of the micro power in droop control.(3) A voltage feedback control method is proposed for the voltage drop caused by active load and virtual impedance in the droop control of islanded microgrid. When the system voltage falls, the feedback link can return to the rated value and maintain stability without using the communication module to quickly adjust the voltage.(4) A dynamic inertial control method was proposed for the frequency mutation caused by reactive load fluctuation. According to different load capacity and dynamic adjustment inertia coefficient,the simulation of the inertial characteristics of the synchronous generator can effectively restrain the system frequency mutation, give the low frequency load shedding or give the protection device sufficient response time to maintain the frequency stability.