The Stability Analysis of a Multi-Port Single-Phase Solid-State Transformer in the Electromagnetic Timescale

Abstract

This paper proposes an overall practical stability assessment for a multi-port single-phase solid-state transformer (MS3T) in the electromagnetic timescale. When multiple stable subsystems are combined into one MS3T, the newly formed MS3T has a certain possibility to be unstable. Thus, this paper discusses the stability assessment of the MS3T in detail. First and foremost, the structure of the MS3T and its three stage control strategies are proposed. Furthermore, the stability analysis of each of the MS3T’s subsystems is achieved through the closed loop transfer function of each subsystem, respectively, including an AC-DC front-end side converter, dual active bridge (DAB) with a high-frequency (HF) or medium-frequency (MF) transformer, and back-end side incorporating DC-AC and dc-dc converters. Furthermore, the practical impedance stability criterion in the electromagnetic timescale, which only requires two current sensors and one external high-bandwidth small-signal sinusoidal perturbation current source, is proposed by the Gershgorin theorem and Kirchhoff laws. Finally, the overall stability assessment, based on a modified impedance criterion for the MS3T is investigated. The overall practical stability assessment of the MS3T can be validated through extensive simulation and hardware results.

Adaptive integral sliding mode controller for solid state transformer based on generalized averaged model andT‐Sfuzzy method

“…where the notation d ¼ ϕ=π represents the phase-shift ratio between the primary and secondary bridges of DAB, d 2 and T 2 are the duty ratio and the cycle time of s 4 τ ð Þ. Similarity, applying Equations ( 3) and ( 5) to (7) to Equation ( 14), the following equations can be got:…”

“…There are many topologies of SST presented in References 5–7, mainly includes: single‐phase SST, three‐phase SST, cascade‐based SST and modular‐based SST. But the most basic and widely evaluated one is the three stages single‐phase one as shown in Figure 1 7 . And the structure of it will be described in the next section.…”

A Hierarchical Coordinative Control Strategy for Solid State Transformer Based DC Microgrids

“…Compared with the traditional transformer, the multi-stage SST provides a direct interface to the DC microgrid, and the energy density can be improved through a high frequency transformer (HFT). The SST is expected as a crucial equipment for utilization of distributed generations (DGs) [4] and construction of the Energy Internet [5,6].…”

Stabilisation and transient performance improvement of DC MGs with CPLs: non‐linear reset control approach

“…Nowadays, the applications of MGs have been commonly studied in a large number of research papers. However, due to the conventional power grid system, which usually depends on alternating current (AC) systems, the research on MGs is mostly addressed for the AC structures [1–3]. On the other hand, emerging and advances of different sustainable power sources with direct current (DC) couplings, the arrangement of DC MGs has turned a promising and interesting topic.…”