Discrete-State Event-Driven Numerical Prototyping of Megawatt Solid-State Transformers and AC/DC Hybrid Microgrids

Abstract

Solid-state transformers (SSTs) enable electric energy distribution with higher flexibility, sustainability and efficiency, and the AC/DC hybrid microgrid (MG) is one of the representative applications. However, the design and analysis of SSTs and MGs were limited by lack of fast simulation tools that can accurately and efficiently handle systems with massive number of switching devices. This article demonstrates how the discrete-state event-driven (DSED) approach allows an accurate and faster simulation of the SSTs and MGs than the state of the art and benefit the practical design. The numerical prototyping of a hybrid MG composed of a megawatt SST together with multiple converters (e.g. PVs, EVs and batteries) is presented in this article. The performance is compared with existing simulation approaches. Various scenarios are investigated, including the grid-connected mode, the islanded mode, and the mode transition considering the communication delay. A time cost of several hours is decreased to tens of seconds with same accuracy using DSED, enabling faster simulations for complicated tasks. It is discussed how the speed and accuracy benefit the practical SST and MG design.

Keywords

• Communication delays
• grid-connected
• hybrid microgrid
• islanded mode
• simulation
• solid-state transformer