An adaptive time step control algorithm for nonlinear time domain envelope transient

In this paper we propose a new adaptive time step control algorithm for the slow time dimension of time domain envelope transient (TD-ENV) simulation. The algorithm uses two models: the first is the set of differential-algebraic equations that represent the circuit. The second is a ´coarse´ model that is cheap to evaluate. The optimum time step is estimated from an error term obtained from the coarse model. The accurate model is then solved using the near optimum time step. The acceptable error for the time step estimation is adapted according to the dynamics of the system. We describe the time step control algorithm and present a case study of the transient analysis of a rectifier circuit powered by a high-frequency pulse train with a slowly varying pulse duty cycle. The simulations show that few time steps are rejected compared with a traditional time step control algorithm.