To reduce fuel consumption and emissions in plug-in hybrid electric vehicles (PHEVs), it is equally important to select an appropriate drive train topology as it is to develop a suitable power flow control strategy. While there are many control strategies that have been developed and presented, most are expansions of hybrid electric vehicle (HEV) control strategies and do not maximize the true potential the PHEV offers as a result of its ability to operate in electric-only mode over a significant distance. In this paper, state-of-the-art control strategies are reviewed and classified in detail. PHEV controllers mostly operate on either a rule-based or an optimization-based algorithm, each having its own advantages and disadvantages. An overview of the controllers is given, and an analysis on which strategy is more suitable to maximize PHEV performance in different drive cycle conditions is provided. Finally, a new classification for PHEV control strategies based on the operation of the vehicle is presented and verified through simulation results.