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

Journal Article · · IEEE Journal of Emerging and Selected Topics in Power Electronics

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 toward 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 an MV HT prototype are reported for the first time. Comparative simulations are performed on a modified IEEE 34-bus system. 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, 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.

Research Organization:
National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
DOE Contract Number:
AC36-08GO28308
OSTI ID:
1889681
Report Number(s):
NREL/JA-5D00-84104; MainId:84877; UUID:93b341b4-75c3-4910-aafd-ac783d01419a; MainAdminID:67588
Journal Information:
IEEE Journal of Emerging and Selected Topics in Power Electronics, Vol. 10, Issue 4
Country of Publication:
United States
Language:
English

References (61)

Voltage Synthesis Using Dual Virtual Quadrature Sources—A New Concept in AC Power Conversion journal November 2008
Technical and Economic Impact of PV-BESS Charging Station on Transformer Life: A Case Study journal July 2019
Review of grid applications with the Zurich 1MW battery energy storage system journal March 2015
Assessment of overvoltage mitigation techniques in low‐voltage distribution networks with high penetration of photovoltaic microgeneration journal February 2018
Module Power Balance Control and Redundancy Design Analysis of Cascaded PV Solid-State Transformer Under Fault Conditions journal February 2021
Incorporating a Nodal Reactive Power Pricing Scheme Into the DisCo’s Short-Term Operation journal July 2019
Sizing and SOC Management of a Smart-Transformer-Based Energy Storage System journal August 2018
New Modulation and Impact of Transformer Leakage Inductance on Current-Source Solid-State Transformer journal January 2022
Control Strategy for Single-Phase Open-Circuit Operation of a Modular Solid-State Transformer journal September 2019
Neutral Current Optimization Control for Smart Transformer-Fed Distribution System Under Unbalanced Loads journal April 2021
Communication-Independent Power Balance Control for Solid State Transformer Interfaced Multiple Power Conversion Systems journal April 2020
Multilevel Medium-Frequency Link Inverter for Utility Scale Photovoltaic Integration journal July 2015
Control of Three-Phase Solid-State Transformer With Phase-Separated Configuration for Minimized Energy Storage Capacitors journal September 2020
A Rotational Control in Medium-Voltage Modular Solid-State Transformer-Based Converter System journal November 2019
Distributed FACTS—A New Concept for Realizing Grid Power Flow Control journal November 2007
Radial distribution test feeders conference August 2022
Benefits of Distribution-Level Power Electronics for Supporting Distributed Generation Growth journal April 2013
Stacked Low-Inertia Converter or Solid-State Transformer: Modeling and Model Predictive Priority-Shifting Control for Voltage Balance journal August 2021
A Reduced Switch Count Single-Stage Three-Phase Bidirectional Rectifier With High-Frequency Isolation journal November 2018
The economic effect of electricity net-metering with solar PV: Consequences for network cost recovery, cross subsidies and policy objectives journal December 2014
Defining a degradation cost function for optimal control of a battery energy storage system conference June 2013
Robust Predictive Control for Modular Solid-State Transformer With Reduced DC Link and Parameter Mismatch journal December 2021
Convex Optimization book January 2004
Field upgradeable transformer: A fractionally-rated voltage regulator for the distribution system conference September 2016
Power Electronics at the Grid Edge : The key to unlocking value from the smart grid journal December 2014
Solar PV Integration Challenges journal May 2011
7.2 kV Three-Port Single-Phase Single-Stage Modular Soft-Switching Solid-State Transformer with Active Power Decoupling and Reduced DC-Link conference March 2020
99% Efficient 10 kV SiC-Based 7 kV/400 V DC Transformer for Future Data Centers journal June 2019
SiC-Based 5-kV Universal Modular Soft-Switching Solid-State Transformer (M-S4T) for Medium-Voltage DC Microgrids and Distribution Grids journal October 2021
Analytical Expression-Based Modulation for Soft-Switched Matrix-Based Dual-Active-Bridge (S2MB-DAB) Single-Phase AC-DC Converter journal January 2021
A Hybrid Modular DC Solid-State Transformer Combining High Efficiency and Control Flexibility journal April 2020
Design of a Protection Concept for a 100-kVA Hybrid Transformer journal April 2020
Applicability of Solid-State Transformers in Today’s and Future Distribution Grids journal January 2019
Field test results for a 3-phase 12.47 kV 1 MVA power router conference September 2016
An Integrated Controllable Network Transformer—Hybrid Active Filter System journal March 2015
Power flow control in networks using controllable network transformers journal July 2010
Power Router for Meshed Systems Based on a Fractionally Rated Back-to-Back Converter journal October 2014
Hybrid Transformer With Matrix Converter journal June 2016
AC Voltage Sag/Swell Compensator Based on Three-Phase Hybrid Transformer With Buck-Boost Matrix-Reactance Chopper journal August 2014
Evaluation of topologies and optimal design of a hybrid distribution transformer conference September 2015
The Smart Transformer: A solid-state transformer tailored to provide ancillary services to the distribution grid journal June 2017
Current-Source Solid-State DC Transformer Integrating LVDC Microgrid, Energy Storage, and Renewable Energy Into MVDC Grid journal January 2022
Review of Solid-State Transformer Technologies and Their Application in Power Distribution Systems journal September 2013
Smart transformer/large flexible transformer journal December 2020
Soft-Switching Solid-State Transformer With Reduced Conduction Loss journal May 2021
15 kV SiC MOSFET: An Enabling Technology for Medium Voltage Solid State Transformers journal June 2017
Characterization of 3.3-kV Reverse-Blocking SiC Modules for Use in Current-Source Zero-Voltage-Switching Converters journal January 2021
Protection of MV Converters in the Grid: The Case of MV/LV Solid-State Transformers journal March 2017
The Impact of Charging Plug-In Hybrid Electric Vehicles on a Residential Distribution Grid journal February 2010
LV Grid Voltage Regulation Using Transformer Electronic Tap Changing, With PV Inverter Reactive Power Injection journal December 2015
Distributed Power Electronics: An Enabler for the Future Grid journal December 2016
Integration of Electric Vehicles in the Electric Power System journal January 2011
Business Models for Deploying and Operating Energy Storage and Risk Mitigation Aspects journal July 2014
Energy Storage Valuation Under Different Storage Forms and Functions in Transmission and Distribution Applications journal July 2014
Design and Strategy for the Deployment of Energy Storage Systems in a Distribution Feeder With Penetration of Renewable Resources journal July 2015
Smart Transformer-Fed Variable Frequency Distribution Grid journal January 2018
On Integration of Solid-State Transformer With Zonal DC Microgrid journal June 2012
Impedance Modeling and DC Bus Voltage Stability Assessment of a Solid-State-Transformer-Enabled Hybrid AC–DC Grid Considering Bidirectional Power Flow journal August 2020
Auxiliary Power Supply for Medium-/High-Voltage and High-Power Solid-State Transformers journal May 2020
Concurrent Voltage Control and Dispatch of Active Distribution Networks by Means of Smart Transformer and Storage journal August 2018
Power Electronic Traction Transformer—Medium Voltage Prototype journal July 2014