To implement the objective of smart grids，it is essential to introduce the state-of-the-art computing，communication and sensing technologies.Traditionally，the theoretical foundation and methodologies of power systems and information systems are independent.Thus，the existing power system analysis and control methods cannot adequately take into account the impacts of the information system.The cyber physical system（CPS）represents a new research area with a focus on integrating physical and information systems so as to build a new and powerful industrial system.Based on CPS and the characteristics of power systems，the concept of a cyber physical power system（CPPS）framework is presented.Several mathematical tools including the differential and algebraic equation set，finite automation，stochastic process and queueing theory are introduced to formulate the steady-state and dynamic models of CPPS.The steady-state and dynamic analysis of information systems is then introduced，and on this basis，the research direction for reliability and security of CPPS is developed.The networked control of CPPS is finally discussed，and new methods based on the delay and data loss compensation are proposed.