ドメイン分割連成方式によるパワーエレクトロニクスシステムのマルチレート解析法

Abstract

A power electronic system generally has multiple domains, and the rate of change of variables varies across the domains. Such systems are called multirate systems and they can be efficiently simulated by adopting numerical integration process according to the multirate characteristic. Two methods for performing the multirate analysis have been proposed. The first method is the circuit partitioning method in which a system is divided with large energy-storage elements into subcircuits which have their own optimum time step sizes for numerical integration. For example, a system in which converters and inverters are connected in cascade with large capacitors is divided into subcircuits and analyzed efficiently. The other method is the envelope-following (EF) method; in this method only selected voltage and current ripples are computed so that the envelopes corresponding to these ripples can be accurately determined. The number of skipped switch cycles can be adjusted optimally according to the variation rates of the envelopes. A new multirate method is proposed in this study. It is a combination of the two abovementioned methods, and therefore, it has the advantages of both the methods. First, the computational flow of the proposed method is described briefly. Then, precise numerical processes, for example, the selection of the step sizes of the fast and slow domains and the iteration correction taking into consideration the interactions between the domains, are described. Finally, a simulated motor drive system is investigated to verify the effectiveness of the proposed method.