Accurate second-order interpolation for power electronic circuit simulation

This paper presents a second-order accurate method for circuit simulation with idealized power electronic switches. The method combines the integration method TR-BDF2 with an improved quadratic interpolation technique for the localization of switch events. Next to preserving second-order accuracy after interpolation, the technique also preserves the capability to damp fast transients caused by small on-resistances and large off-resistances. Conventional interpolation techniques for integration methods do not have this damping property. This results in a loss of accuracy if a switch event occurs shortly after a transition to discontinuous conduction mode. Consequently, the step size required to achieve the desired level of accuracy is sometimes smaller than expected. With the improved interpolation technique, the second-order accuracy associated with TR-BDF2 is not affected at switch events. Numerical experiments confirm the improved accuracy of the proposed method. The method is compared with the simulation tools PSIM and PSCAD, and with the conventional interpolation polynomial of TR-BDF2 as used in Simulink.