Dynamic Average-Value Modeling of Three-Level T-Type Grid-Connected Converter System

Three-level T-type converter (3LT2C) possesses the advantages of simple structure and high efficiency, which makes it appealing especially in low- and medium-voltage applications. Dynamic average-value modeling (AVM) has become an effective methodology for small-signal analysis and large-signal transients of power electronic subsystems in power systems applications. In this paper, a dynamic AVM for the three-phase 3LT2C is presented for the first time. The proposed model is derived using the state-space average approach, where the averaging process is implemented over each pulsewidth modulation switching period. The ac- and dc-side dynamics are represented by a fourth-order time-invariant system. The accuracy of the developed AVM is validated against the detailed switching model, while demonstrating its computational advantages. The new model is also verified using experimental tests on a prototype.