A　voltage　balancer　remains　a　good　solution　of　power　transfer　for　bipolar　dc　grids,　which,　however,　would　increase　the　costs　due　to　its　requirement　for　additional　hardware　support.　In　this　article,　an　auxiliary　power　transfer　strategy　is　proposed　by　using　the　inactive　motor　drives　affiliated　with　the　bipolar　dc　grid.　During　idle　periods　of　the　motor　drive,　one　inverter　bridge　arm　is　connected　with　the　bipolar　dc　grid　at　their　neutral　points,　allowing　bidirectional　power　transfer　between　the　upper　and　lower　dc-bus　sources.　The　proposed　strategy　share　part　of　the　voltage　balancer＇s　power　transfer　burden　without　requiring　additional　hardware　and　affecting　the　normal　operations　of　the　motor　drive.　In　addition,　its　effectiveness　is　verified　by　experimental　results　on　an　interior　permanent　magnet　synchronous　motor　drive,　showing　that　the　power　flows　among　the　upper　and　lower　dc-bus　power　supplies　are　controlled　effectively.　Also,　the　active　control　of　the　dc-bus　voltages　could　be　achieved　by　modulation　of　the　phase　currents.　©　1982-2012　IEEE.