Multirate analysis method for a power electronic system by multi-domain partitioning

Power electronic system in general is mixed in multi-domains which have their own change rates in variables. Such a system is called multirate and it can be simulated efficiently for the numerical integration process by utilizing the characteristic. Mainly two methods have been proposed for the multirate analysis. One is the circuit partitioning method which divides a system with large energy storage elements into subcircuits which have their own optimum time steps. For example, a system where converters and inverters are connected in cascade with large capacitors, are divided into subcircuits and processed efficiently. The other is the envelope-following (EF) method which computes only selected voltage and current ripples to be able to follow their envelopes efficiently. The skip switch cycles can be adjusted optimally according to the rates of the envelopes. A new multirate method is proposed in this paper and it is an extended combination of the above two methods to have both advantages. First the proposed method is described briefly about the computation flow. Then precise numerical processes, for example, how to select step sizes of the fast ans slow domains and the iteration correction process considering the interactions between the domains, are described. Finally simulation examples of motor drive systems are investigated and validated to show effectiveness of the proposed method.