The paper analysis theSbattery pack technology,Scompares the differences of battery pack modes,Sdetermines the series parallel connection for batterySpack with medium voltage.For the battery mode after comparingSdesign of the main circuitStopology structure,Sadopts a neutral point clamped three-level singleSlevelSStopology storageSconverter.SThen theSthree-levelconverterSis analyzed,uses the LCLresonancesuppression technology,StakesStheScontrolstrategySofSdouble loopSproportional integral. FinallySa15kWSstorage converterSprototype is developedSto verifySthe superiority and the feasibility of the scheme.