Diode rectifiers-synchronous machine system has a wide range of applications in isolated power system,whose low frequency oscillation emerges under certain parameters.Considerable error is produced when the state space averaging model is used to analyze its small signal stability.Therefore,this paper has presented a periodic orbit model of diode rectifiers-synchronous machine system to solve these problems.Using trapezoidal integration method,it is possible to derive equation of periodic orbit and its Poincaré mapping.Jacobian matrix of the Poincaré mapping of periodic orbit can be calculated by chain derivative method.Besides,stability margin index and linearized Poincaré mapping model have also been proposed.Thus small signal stability of diode rectifiers-synchronous machine system can be assessed through orbitally asymptotical stability of its periodic orbit so as to lay a foundation for isolated power system analysis and its control design.Simulation test demonstrates that the proposed model and algorithm are effective and practicable.
