Researches on modularized average model for three-phase VSIs

To remedy defects possessed by existing average models of three-phase voltage source inverters (VSIs), a general-formed model was proposed and derived that is suitable to implement modular simulations. During deriving the switching model, the inverter is divided into several units and the units are interfaced only by independent inductor currents and independent capacitor voltages. No extra constraints are applied except Kirchhoff's Current Law (KCL) and Kirchhoff's Voltage Law (KVL); during establishing the equivalent circuit for the average model, redundant variables and redundant equations are properly introduced, which makes the obtained model include all non-switching components within the original real circuit and that each phase can be calculated separately. Compared with existing models, the proposed model removes the requirements to properties of three-phase ac waveforms. Moreover, due to that the units are functionally isolated with each other, the model can be applied in situations where the load is non-linear or have harmonic current sources, if only being locally modified according to the real circuit. Further discussions and simulation examples are provided to verify the models' validity.