Sub-cycle average models with integrated diodes for real-time simulation of power converters

Real-time simulators for electrical circuits typically employ a fixed time-step solver, where the computation time determines the simulation step size. If forced-commutated power converters are simulated and the controlling PWM signals are sampled once per simulation step the simulation may become inaccurate as the pulses do not naturally coincide with the simulation steps. To improve the accuracy of the simulation results the PWM signal can be averaged over one simulation step and fed into an average model of the converter. In this paper, high-fidelity converter models are presented that can be controlled with instantaneous and averaged signals. The models are based on the time-average method using variable transformers. To obtain general applicability for real-time and offline simulations the average models have been extended with diodes to operate accurately under various conditions, such as continuous/discontinuous conduction mode, commutation blanking-time and rectifier operation of half-bridges.