Multiple level APF based on cascaded H-bridge is presently one of the best solutions for suppressing harmonics and compensating reactive current in the medium voltage field. And the issue on how to protect voltage balance of the DC side is a difficult point in the application of medium voltage place. Therefore

in this paper

the mathematical model of medium voltage cascaded APF is set up

its fluctuation process is deducted in detail and a new method on layer control voltage balance is proposed. The upper voltage stabilizing adjusts real time active current command by way of improved ip-iqalgorithm and self-adaptive PI parameters so to output stably the balance of total voltage of each phase. The lower grading control is to compensate variables of modulation wave based on one nominal current on the basis of main modulation wave so to achieve the voltage balance of each unit of each phase. The device improves not only detection accuracy and response speed of harmonic current

but also achieves the purpose of the current tracking and reactive power compensation of APF. Finally

it is shown by the simulation and experimental result that the method can be used effectively in the field of medium voltage APF.