scholarly journals Current Control Strategies for a Star Connected Cascaded H-Bridge Converter Operating as MV-AC to MV-DC Stage of a Solid State Transformer

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4607
Author(s):  
Sebastian Stynski ◽  
Marta Grzegorczyk ◽  
Cezary Sobol ◽  
Radek Kot
Keyword(s):  
Solid State ◽  
Control Algorithm ◽  
Power Flow ◽  
Low Voltage ◽  
Control Strategies ◽  
Current Control ◽  
Renewable Energy Resources ◽  
Solid State Transformer ◽  
Voltage Transformer ◽  
Current Harmonics

Nowadays, the increasing number of nonlinear loads and renewable energy resources pose new challenges for the standard electrical grid. Conventional solutions cannot handle most of them. The weakest component in the whole system is a conventional distribution (converting medium to low AC voltage) transformer. It should not operate with unbalanced, heavily distorted voltage and cannot control power flow or compensate current harmonics. One of the promising solutions to replace the conventional transformer and thus minimize power flow and grid distortions is a power electronics device called a solid state transformer (SST). Depending on the SST topology, it can have different functionalities, and, with the proper control algorithm, it is able to compensate any power imbalances in both low voltage (LV) and medium voltage (MV) grid sides. In the case of a three energy conversion stage SST, the LV and the MV stages can be treated separately. This paper focuses on the MV-AC to the MV-DC stage only based on a star-connected cascaded H-bridge converter. In this paper, a simple control solution for such a converter enabling different current control strategies to distribute power among the phases in an MV grid in the case of voltage imbalances is proposed. Simulation and experimental results proved good performance and verified the validity of the proposed control algorithm.

scholarly journals Design of Three Phase Solid State Transformer Deployed within Multi-Stage Power Switching Converters

2019 ◽  
Vol 9 (17) ◽  
pp. 3545 ◽  
Author(s):  
Umair Tahir ◽  
Ghulam Abbas ◽  
Dan Glavan ◽  
Valentina Balas ◽  
Umar Farooq ◽  
...  
Keyword(s):  
Solid State ◽  
Power Flow ◽  
Harmonic Distortion ◽  
Iron Core ◽  
Switching Frequency ◽  
Switching Converters ◽  
Renewable Energy Resources ◽  
Solid State Transformer ◽  
Power Switching ◽  
Bidirectional Power Flow

This paper presents a symmetrical topology for the design of solid-state transformer; made up of power switching converters; to replace conventional bulky transformers. The proposed circuitry not only reduces the overall size but also provides power flow control with the ability to be interfaced with renewable energy resources (RESs) to fulfill the future grid requirements at consumer end. The proposed solid-state transformer provides bidirectional power flow with variable voltage and frequency operation and has the ability to maintain unity power factor; and total harmonic distortion (THD) of current for any type of load within defined limits of Institute of Electrical and Electronics Engineers (IEEE) standard. Solid state transformer offers much smaller size compared to the conventional iron core transformer. MATLAB/Simulink platform is adopted to test the validity of the proposed circuit for different scenarios by providing the simulation results evaluated at 25 kHz switching frequency.

scholarly journals An Isolated Soft-Switched DC-DC Converter For Interconnection Of Medium- And Low-Voltage DC Grids

2021 ◽  
Author(s):  
Hossein Saeedifard
Keyword(s):  
Mathematical Model ◽  
Power Flow ◽  
Low Voltage ◽  
Control Strategies ◽  
Soft Switching ◽  
Potential Candidate ◽  
Renewable Energy Resources ◽  
Energy Storage Devices ◽  
State Equations ◽  
Bidirectional Power Flow

As the electric power grid increasingly hosts energy storage devices, renewable energy resources, plug-in hybrid and electric vehicles, and data centers, it is expected to benefit in the future from a multi-layer DC structure meshed within its legacy AC architecture. As such a multi-layer grid structure evolves, interconnection of DC grids with different voltage levels will become necessary. For such interconnections and for power-flow control, efficient isolated DC-DC converters are a key enabling technology. This thesis thus presents the results of an in-depth investigation into the operation, modulation, control, and performance assessment of a particular DC-DC converter configuration. The proposed DC-DC converter, which is based upon a hybrid combination of the conventional dual-active-bridge topology and the modular multi-level converter (MMC) configuration, is a potential candidate topology for interconnection of medium- and low-voltage DC grids. The thesis first introduces the circuit topology and presents the basics of operation and governing steady-state equations for the converter. Then, based on the developed mathematical model, it identifies a suitable modulation strategy for the converter bridges and submodules, as well as strategies for the regulation of the MMC submodule capacitor voltages and soft switching of the constituent semiconductor devices. The proposed converter topology offers significant benefits including galvanic isolation, utilization of the transformer’s leakage inductance, soft switching for high-frequency operation, and bidirectional power flow capability. The validity of the mathematical model, effectiveness of the proposed modulation and control strategies, and the realization of soft switching are verified through off-line simulation of a detailed circuit model as well as experiments conducted on a 1-kW experimental setup.

scholarly journals Active Hybrid Solid State Transformer Based on Multi-Level Converter Using SiC MOSFET

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 66 ◽  
Author(s):  
Chun-gi Yun ◽  
Younghoon Cho
Keyword(s):  
Solid State ◽  
Power Flow ◽  
Voltage Drop ◽  
Renewable Energy Sources ◽  
Current Control ◽  
Oxide Semiconductor ◽  
Prototype System ◽  
Solid State Transformer ◽  
Multi Level ◽  
Level Converter

As the types of loads have been diversified and demand has increased, conventional distribution transformers are difficult to maintain the constant voltage against voltage drop along with distance, grid voltage swell/sag, and various loads. Also, it is hard to control the power flow when connecting renewable energy sources. Active hybrid solid state transformer (AHSST) is application to keep the voltage and power quality. AHSST is a system that combines conventional distribution transformer and converter. Accordingly, it can be applied directly to distribution infrastructure and it has both the advantages of solid state transformer (SST) and conventional transformer. AHSST is capable of active voltage and current control and power factor control. It has a simpler structure than SST and it can perform the same performance with the lower rating converter. This paper presents two stage AHSST system based on multi-level converter. The converter is composed of the back-to-back converter using silicon carbide (SiC) metal-oxide semiconductor field effect transistor (MOSFET). Proposed system has a wider voltage and power flow control range, lower filter size, and simpler control sequence than existing AHSST systems. The performance of the proposed system was verified by prototype system experiments.

scholarly journals Design of Three Phase Solid State Transformer Deployed within Multi-Stage Power Switching Converters

2019 ◽  
Author(s):  
Umair Tahir ◽  
Ghulam Abbas ◽  
Dan Ovidiu Glavan ◽  
Valentina E. Balas ◽  
Umar Farooq ◽  
...  
Keyword(s):  
Solid State ◽  
Power Flow ◽  
Harmonic Distortion ◽  
Iron Core ◽  
Switching Frequency ◽  
Switching Converters ◽  
Renewable Energy Resources ◽  
Solid State Transformer ◽  
Power Switching ◽  
Bidirectional Power Flow

This paper presents a symmetrical topology for the design of solid-state transformer, made up of power switching converters, to replace conventional bulky transformers. The proposed circuitry not only reduces the overall size but also provides power flow control with the ability to be interfaced with renewable energy resources (RESs) to fulfill the future grid requirements at consumer end. Solid state transformer provides bidirectional power flow with variable voltage and frequency operation and has the ability to maintain unity power factor, and current total harmonic distortion (THD) for any type of load within defined limits of IEEE standard. Solid State Transformer offers much smaller size as compared to that of the conventional iron core transformer. MATLAB/Simulink platform is adopted to test the validity of the proposed circuit for different scenarios by providing the simulation results evaluated at 25 kHz switching frequency.

scholarly journals An Isolated Soft-Switched DC-DC Converter For Interconnection Of Medium- And Low-Voltage DC Grids

2021 ◽  
Author(s):  
Hossein Saeedifard
Keyword(s):  
Mathematical Model ◽  
Power Flow ◽  
Low Voltage ◽  
Control Strategies ◽  
Soft Switching ◽  
Potential Candidate ◽  
Renewable Energy Resources ◽  
Energy Storage Devices ◽  
State Equations ◽  
Bidirectional Power Flow

As the electric power grid increasingly hosts energy storage devices, renewable energy resources, plug-in hybrid and electric vehicles, and data centers, it is expected to benefit in the future from a multi-layer DC structure meshed within its legacy AC architecture. As such a multi-layer grid structure evolves, interconnection of DC grids with different voltage levels will become necessary. For such interconnections and for power-flow control, efficient isolated DC-DC converters are a key enabling technology. This thesis thus presents the results of an in-depth investigation into the operation, modulation, control, and performance assessment of a particular DC-DC converter configuration. The proposed DC-DC converter, which is based upon a hybrid combination of the conventional dual-active-bridge topology and the modular multi-level converter (MMC) configuration, is a potential candidate topology for interconnection of medium- and low-voltage DC grids. The thesis first introduces the circuit topology and presents the basics of operation and governing steady-state equations for the converter. Then, based on the developed mathematical model, it identifies a suitable modulation strategy for the converter bridges and submodules, as well as strategies for the regulation of the MMC submodule capacitor voltages and soft switching of the constituent semiconductor devices. The proposed converter topology offers significant benefits including galvanic isolation, utilization of the transformer’s leakage inductance, soft switching for high-frequency operation, and bidirectional power flow capability. The validity of the mathematical model, effectiveness of the proposed modulation and control strategies, and the realization of soft switching are verified through off-line simulation of a detailed circuit model as well as experiments conducted on a 1-kW experimental setup.

scholarly journals Synchronized Control of Voltage and Current Harmonics in Distributed Generation System using Fuzzy Controller

2019 ◽  
Vol 8 (12) ◽  
pp. 1179-1182
Keyword(s):  
Distributed Generation ◽  
Energy Demand ◽  
Power Flow ◽  
Fuzzy Controller ◽  
Low Voltage ◽  
Load Condition ◽  
Control Technique ◽  
Current Harmonics ◽  
Simultaneous Control ◽  
Unbalanced Load

The worldwide energy demand is increasing due to increase in population and economic growth. The grid is gradually replaced by Distributed generation systems (DGs). Recently low voltage DG interfacing converter on the non linear load compensation is performed by unified power flow converter. The proposed control technique is analyzed for Simultaneous control of voltage and power under unbalanced load condition using MATLAB/SIMULINK software

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

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2250 ◽  
Author(s):  
Rui Wang ◽  
Qiuye Sun ◽  
Qifu Cheng ◽  
Dazhong Ma
Keyword(s):  
Stability Analysis ◽  
Solid State ◽  
Single Phase ◽  
Control Strategies ◽  
Current Source ◽  
Practical Stability ◽  
Stability Assessment ◽  
Solid State Transformer ◽  
The Stability ◽  
Signal Sinusoïdal

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.

Review on the Development of Solid State Transformer

2021 ◽  
pp. 119-126
Author(s):  
Bharat Bhushan Khare ◽  
Rajeev Shankar Pathak ◽  
Sanjeev Sharma ◽  
Vinod Kumar Singh
Keyword(s):  
Solid State ◽  
Smart Grid ◽  
Energy Distribution ◽  
Power Flow ◽  
Electric Energy ◽  
Global Market ◽  
Transformer Oil ◽  
Solid State Transformer ◽  
Solid State Transformers ◽  
Compact Size

According to future renewable electric energy distribution and management (FREEDM) system, solid state transformers play an important role in smart grid technologies. They have several advantages over conventional transformers such as bi-directional power flow, light in weight, compact size, etc. They also compensate the environmental issues which are created due to transformer oil. Because of various advantages over traditional transformer, SST is preferred widely at the present time. So in this chapter, the various architectures, needs, and applications of solid state transformers are discussed. The global market of SST has continuously improved because it has several applications and benefits.

Surveying Solid-State Transformer Structures and Controls: Providing Highly Efficient and Controllable Power Flow in Distribution Grids

2020 ◽  
Vol 14 (1) ◽  
pp. 56-70 ◽  
Author(s):  
Felipe Ruiz ◽  
Marcelo A. Perez ◽  
Jose R. Espinosa ◽  
Tomasz Gajowik ◽  
Sebastian Stynski ◽  
...  
Keyword(s):  
Solid State ◽  
Power Flow ◽  
Solid State Transformer ◽  
Highly Efficient ◽  
Distribution Grids
Sign in / Sign up

Export Citation Format

Share Document