Real-Time Modeling and HIL Simulation of Stacked Low-Inertia Converters with Soft-Switching and Fast Dynamic Control

Abstract

This paper presents the challenges in modeling of low-inertia soft-switching converters, such as soft-switching solid-state transformers (S4T), particularly for implementing fast-dynamic control using hardware-in-the-loop (HIL) tools. The low-inertia design leads to increased control challenges as decoupling between the input and the output is reduced. The control becomes more complex when such low-inertia converters need to be stacked using modular S4T modules (M-S4T) for medium voltage applications. Control of an M-S4T is a multi-objective, multi-degree-of-freedom problem, which requires fast-dynamic control. The non-idealities of the controller, sensors and communication channels etc. should be considered in modelling for HIL simulation to verify such fast-dynamic control algorithm. This paper discusses the challenges and a methodology to model such low inertia converters to perform an HIL real-time (RT) simulation. A quasi-real-time (QRT) HIL model is proposed to simulate this type of converters and controls. Simulation results of the HIL model of an M-S4T under steady state and transient conditions are compared to experimental results, showing that the QRT HIL model can simulate the low inertia physical converter with fast dynamic control accurately.