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This paper describes the study of a topology of modular multilevel converters for integrating battery energy storage into a medium (13.8 kV) distribution system. The main benefit of this topology is to remove the need for a bulk 60 Hz transformer that is normally used to step up the output of a voltage source inverter to the medium voltage level. A SiC-based power electronics interface presented in this paper provides an efficient solution without the large and costly transformer. Using medium voltage SiC devices (≥ 10 kV SiC MOSFETs), with their high breakdown voltage, enables the system to meet and withstand medium voltage application, using a minimized number of cascaded modules. This SiC-based power electronics interface significantly reduces the complexity usually faced when Si devices are used directly in medium voltage applications. The voltage and state of charge balancing control for battery modules is also simplified and performs well. The simulation and experimental results, performed on a low-voltage prototype, verify the proposed topology that is presented in this paper.
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Insights on Blackstart Provisioning Using a Synchronous Generator and Grid-Forming Inverter Using EMT Simulations
Grid-forming inverters (GFMIs) have been identified as critical assets in ensuring modern power system reliability. Their ability to synthesize an internal voltage reference while emulating synthetic inertia has sparked extensive research. These characteristics have recently piqued interest in their capacity to provide blackstart ancillary services. The blackstart of a bulk power system poses significant challenges, namely the large transients from the energization of unloaded transformers, rotational motor loads, and long transmission cables, which have been effectively studied using conventional synchronous generators (SGs). The concept of an inverter-based resource (IBR)-based blackstart continues to be an open research area necessitating further investigations due to the known limitations of IBRs such as low short-circuit current capabilities. This paper presents a blackstart case study of a bulk power system investigating the performances of a conventional SG to a GFMI when utilizing hard switching methods. The paper qualitatively investigates the transient inrush currents from the transformer and rotational load energization sequences. Additional examinations into the significance of the GFMI’s current-limiting schemes and voltage control loop compensator gains are presented. Furthermore, the harmonic distortions from the transformer energization sequence are also evaluated. Finally, a full network energization case is presented to demonstrate how both sources can provide blackstart provisioning services. The models are developed in EMTDC/PSCAD using real-world transmission planning data.
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- Award ID(s):
- 1914635
- PAR ID:
- 10633061
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Energies
- Volume:
- 17
- Issue:
- 16
- ISSN:
- 1996-1073
- Page Range / eLocation ID:
- 4067
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/en17164067
