Transient process of power systems is increasingly dependent on and challenged by renewable generation(RG). From its multiscale normal/switch elements

RG forms an internal voltage to network as system source and determines the system transient. Due to multiscale feature

these normal/switch elements are activated sequentially after a fault

causing the RG's internal voltage to exhibit complex multiscale dynamics

which in turn makes the system transient behavior distinct from that of traditional systems. The multiscale formation of RG's internal voltage is thus essential for transient and needs to be studied. Existing models of RG are mostly established with original connection of normal/switch elements

but not in multiscale view. Therefore

taking inertia-controlled type-4 wind turbine(WT) as an example

this paper thus proposes a cascaded multiscale modeling method for system transient mechanism analysis. First

multiscale sequential activation of normal/switch controls is shown. It is illustrated that multiscale feature is essential for internal voltage formation. Second

the cascaded multiscale model of inertia-controlled type-4 WT is proposed and the internal voltage formation in multiscale view is revealed

which is formed from parallel feedbacks and serial responses. Finally

based on the proposed model

it is explained the interaction process between WTs to influence energy accumulations of their multiscale physical elements. Simulations for model validation are also included.