Fast, accurate and stable simulation of power electronic systems using virtual resistors and capacitors

Simulation of power electronic circuits remains a problem due to the high level of stiffness brought about by the modelling of switches as biresistors i.e. very low turn-on resistance and very high turn-off resistance. The merits and drawbacks of two modelling methods that address this problem are discussed. A modelling solution for ensuring numerically stable, accurate and fast simulation of power electronic systems is proposed. The solution enables easy connectivity between power electronic elements in the simulation model. It involves the modelling of virtual capacitance at switching nodes to soften voltage discontinuity due to the switch current suddenly going to zero. Undesirable ringing effects that may arise due to the interaction between the virtual capacitance and circuit inductance are eliminated by modelling virtual damping resistors in parallel to inductors that are adjacent to switching elements. A midpoint configuration method is also introduced for modelling shunt capacitors. A DC traction system is simulated using this modelling strategy and the results are included. Simulation results obtained using this modelling strategy are validated by comparison with the established mesh analysis technique of modelling. The simulation performance is also compared with the Power System Blockset commercial software