Abstract: In the energy strategies of hybrid electric vehicles，traditional equivalent consumption minimization strategy (ECMS)，which has a feedback circuit on the basis of the battery state of charge (SOC)，may lead to an
increase in fuel consumption because the inappropriate value of punishment function causes excessive-punishment．In order to solve this problem，a method on the basis of variable reference of SOC is proposed． In this method，with the pre-knowledge on the driving cycle，the cycle is divided into several kinematics fragments． In arbitrary fragment，the value of braking recovery energy in this fragment is subtracted from the initial residual capacity value of battery，and the difference value is taken as the new SOC-reference of punishment function when the ECMS tends to discharge largely． On this basis，an equivalent factor is established． Finally，a simulation model with ECMS framework is run under the NEDC cycle． Simulation results show that，in comparison with the traditional ECMS on the basis of the fixed SOC-reference，the proposed method helps improve fuel economy and maintain power balance．

Key words: hybrid electric vehicle, regenerative braking, equivalent fuel consumption minimization strategy, state of charge, penalty function