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.
Highlights
With the high expansion of distributed renewable energy utilization, the Energy Internet (EI), the future renewable electric energy delivery and management (FREEDM) system, and microgrids have been widely researched [1,2,3,4]
The impedance-based approach was first proposed by Middlebrook [19,20,21,22,23,24]
To verify the effectiveness of the proposed overall practical stability assessment for the MS3T in the electromagnetic timescale, simulations in MATLAB/Simulink were conducted for a 10 kW/50 the electromagnetic timescale, simulations in MATLAB/Simulink were conducted for a 10kW / 50Hz
Summary
With the high expansion of distributed renewable energy utilization, the Energy Internet (EI), the future renewable electric energy delivery and management (FREEDM) system, and microgrids have been widely researched [1,2,3,4]. To the literature, small-signal stability the small-signal stability assessment pays According more attention toexisting the steady state, which is studied in the assessment in the electromagnetic timescale alwaysliterature, adopts asmall-signal linearized method around a steady electromagnetic timescale. Compared with traditional power systems, theoperating small-signal electromagnetic adopts a linearized method around a steady pointstability [11,12,13]. Compared with stability assessment of the MS3T systems dominated by power electric [14]. Nature this paper focusesdominated on the small-signal critical issue due to the low-inertia andconverters negative-impedance of systems by power stability assessment, which adopts a linearized around a steady operating point, which for theadopts. This paper focusesmethod on the small-signal stability assessment, in the electromagnetic timescale. A linearized method around a steady operating point, for the MS3T in the electromagnetic timescale
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