孤岛微网并联逆变器环流抑制与母线电压控制

Circulating current restraining and bus voltage control of parallel inverters in islanding micro-grid

针对孤岛微网中采用传统下垂控制的并联微源逆变器之间存在较大环流及母线电压和频率偏移问题,文中从环流的一般性定义出发,分析了环流与负荷功率分配之间的定量关系,在此基础上将环流抑制问题转化为功率精确分配问题,并提出了一种母线电压和频率自恢复的改进鲁棒下垂控制方法。将PI控制器引入无功电压控制环中,实现无功功率的精确分配并加快其动态分配过程,进而抑制稳态环流,改善动态均流效果;通过对母线电压和频率进行闭环控制来实现其自动恢复,提高母线电压质量;针对逆变器并机后出现的新的功率分配不均衡的问题,提出了对应的解决方法。通过PSCAD/EMTDC仿真算例验证了所提方法的正确性和有效性。

Aiming at the problem of large circulating current and bus voltage and frequency deviation in islanding microgrid parallel micro-source inverters system with traditional droop control,the quantitative relation between circulating current and load power sharing was analyzed according to the general definition of circulating current,on this basis,the problem of circulating current restraining was transformed into the problem of accurate power sharing,and an improved robust droop control method with bus voltage and frequency self-recovery function was proposed.The PI controller was introduced into the reactive power-voltage control loop to realize the accurate reactive power sharing and accelerate its dynamic sharing process,which can restrain the steady-state circulating current and improve the dynamic current sharing performance.The bus voltage and frequency closed-loop control were adopted to track its rated value and enhance bus voltage quality.In view of the new problem of power sharing disproportion after other inverters paralleling,the corresponding solution was proposed.The PSCAD/EMTDC cases simulation results show the correctness and validity of the proposed scheme.