公开(公告)号：US20170324353A1

公开(公告)日：2017-11-09

申请号：US15586057

申请日：2017-05-03

Applicant: ABB Technology Oy

Inventor： Tero Viitanen ,  Jarno Alahuhtala ,  Mikko Saarinen

IPC: H02M7/5395 ,  H02M1/08 ,  H02M1/084 ,  H02M1/14

CPC classification number: H02M7/5395 ,  G01R31/028 ,  G01R31/42 ,  H02M1/083 ,  H02M1/084 ,  H02M1/14 ,  H02M7/487

Abstract: A method for monitoring a change in a capacitance in an electric system, and an electric system comprising a multilevel inverter and at least two capacitances connected in series between a negative DC pole and a positive DC pole of the inverter, wherein the connection point between the capacitances is connected to one of the at least one middle DC pole of the inverter, and a controller configured to provide by the inverter an AC current component to one of the at least one middle DC pole of the inverter, which AC current component is distributed between the two capacitances connected to the middle DC pole, and monitor resulting AC voltage components in the two capacitances, and determine on the basis of a difference between the monitored AC voltage components a change in at least one of the two capacitances.