Title: Solid-State Transformer and Hybrid Transformer With Integrated Energy Storage in Active Distribution Grids: Technical and Economic Comparison, Dispatch, and Control

Abstract

Solid-state transformer (SST) and hybrid transformer (HT) are promising alternatives to the line-frequency transformer (LFT) in smart grids. The SST features medium-frequency isolation, full controllability for voltage regulation, reactive power compensation, and the capability of battery energy storage system (BESS) integration with multiport configuration. The HT has a partially-rated converter for fractional controllability and can integrate a small BESS. Fast grid-edge voltage fluctuations from increased solar photovoltaic (PV) and electric vehicle (EV) penetration are difficult to manage for mechanical load tap changers. Hence, along with the trend towards more BESS in the grid, the controllability and the storage integration capability of the SST and HT are of strong interest. However, a review of literature shows existing SST and HT research is mostly at converter level, while system-level assessments are scarce. Assessing technical and economic impacts is critical to understanding the benefits and role of the SST and HT to guide future research, which is presented for the first time in this article. Experimental results from medium-voltage (MV) SST and MV HT prototypes are shown to confirm equipment-level feasibility, where the voltage controllability waveforms of a MV HT prototype are reported for the first time. Comparative simulations are performed on amore » modified IEEE 34-bus system. Here, a grid-model-less decentralized grid-edge voltage control method and a day-ahead BESS dispatch method are proposed for the SST and HT. The simulations show that the SST and HT with integrated storage can host more PV, achieve peak shaving, mitigate voltage fluctuation and reverse power flow, and support energy arbitrage for operational cost reduction, as compared to the LFT. Moreover, comprehensive analyses of net present value (NPV) and internal rate of return (IRR) are performed under different installed PV capacities, HT’s partial converter ratings, and BESS capacities. Sensitivities to future cost reductions of the PV and BESS are studied. Although the NPV and IRR are currently negative, 60% capital cost reduction or 150% revenue increase will make the SST and HT economically viable in the use case studied.« less

Authors:

Zheng, Liran  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-8764-2377"

Marellapudi, Aniruddh ^[1]; Chowdhury, Vikram Roy ^[2]; Bilakanti, Nishant ^[3]; Kandula, Rajendra Prasad ^[4]; Saeedifard, Maryam  ^[1];

• Search DOE PAGES for author "Saeedifard, Maryam"
• Search DOE PAGES for ORCID "0000-0001-8859-7339"

Grijalva, Santiago ^[1]; Divan, Deepak  ^[1]

• Search DOE PAGES for author "Divan, Deepak"
• Search DOE PAGES for ORCID "0000-0001-8697-8891"

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+ Show Author Affiliations

1. Georgia Inst. of Technology, Atlanta, GA (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
3. Electric Power Research Inst., Knoxville, TN (United States)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Tue Jan 18 00:00:00 EST 2022

Research Org.:

Georgia Institute of Technology, Atlanta, GA (United States)

Sponsoring Org.:

USDOE Advanced Research Projects Agency - Energy (ARPA-E)

OSTI Identifier:

1892475

Grant/Contract Number:  

AR0000899

Resource Type:

Accepted Manuscript

Journal Name:

IEEE Journal of Emerging and Selected Topics in Power Electronics

Additional Journal Information:

Journal Volume: 10; Journal Issue: 4; Journal ID: ISSN 2168-6777

Publisher:

IEEE

Country of Publication:

United States

Language:

English

Subject:

25 ENERGY STORAGE; 14 SOLAR ENERGY; 17 WIND ENERGY; 24 POWER TRANSMISSION AND DISTRIBUTION; 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 42 ENGINEERING; distributed renewable energy resource (DER); solid-state transformer (SST); hybrid transformer (HT); power electronic transformer (PET); medium-frequency transformer (MFT); active distribution network (ADN); load tap changer (LTC); electric vehicle (EV).