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 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 Modelling and Current-Mode Control of a Modular Multilevel DC-DC Converter

2021 ◽  
Author(s):  
Sandeep Kaler
Keyword(s):  
Mathematical Model ◽  
Urban Areas ◽  
Power Flow ◽  
Distribution Systems ◽  
Control Method ◽  
Fault Tolerant ◽  
Current Mode ◽  
Current Control ◽  
Energy Storage Devices ◽  
State Equations

The visions of multi-terminal direct-current (MTDC) grids, DC distribution systems for densely populated urban areas, and DC microgrids for more straightforward integration of distributed energy resources (including renewable energies, electric vehicles, and energy storage devices) have sparked a great deal of research and development in the recent past. An enabling technology towards the fulfilment of these visions is efficient, highly-controllable, and fault-tolerant AC-DC and DC-DC electronic power converters capable of interfacing networks that operate at different voltage levels. This thesis thus presents the results of an in-depth investigation into the operation and control of a particular class of DC-DC converters. The DC-DC converter studied in this thesis is based upon the so-called modular multi-level converter (MMC) configuration, employing halfbridge submodules and with no galvanic isolation. The thesis first presents the governing dynamic and steady-state equations for the converter. Then, based on the developed mathematical model, it identifies suitable variables, strategies, and feedback loops for the regulation of the submodule DC voltages as well as converter power throughput. In particular, two current-control loops are proposed that, in coordination with one another, not only enable the control of the power flow within the converter, but also promise protection against overloads and terminal shorts. The validity of the mathematical model and effectiveness of the proposed control are verified through off-line simulation of a detailed circuit model as well as experiments conducted on a 1-kW experimental setup. The results of this exercise motivate the extension of the proposed control method to more compact designs with galvanic isolation and enhanced power handing capabilities.

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 Modelling and Current-Mode Control of a Modular Multilevel DC-DC Converter

2021 ◽  
Author(s):  
Sandeep Kaler
Keyword(s):  
Mathematical Model ◽  
Urban Areas ◽  
Power Flow ◽  
Distribution Systems ◽  
Control Method ◽  
Fault Tolerant ◽  
Current Mode ◽  
Current Control ◽  
Energy Storage Devices ◽  
State Equations

The visions of multi-terminal direct-current (MTDC) grids, DC distribution systems for densely populated urban areas, and DC microgrids for more straightforward integration of distributed energy resources (including renewable energies, electric vehicles, and energy storage devices) have sparked a great deal of research and development in the recent past. An enabling technology towards the fulfilment of these visions is efficient, highly-controllable, and fault-tolerant AC-DC and DC-DC electronic power converters capable of interfacing networks that operate at different voltage levels. This thesis thus presents the results of an in-depth investigation into the operation and control of a particular class of DC-DC converters. The DC-DC converter studied in this thesis is based upon the so-called modular multi-level converter (MMC) configuration, employing halfbridge submodules and with no galvanic isolation. The thesis first presents the governing dynamic and steady-state equations for the converter. Then, based on the developed mathematical model, it identifies suitable variables, strategies, and feedback loops for the regulation of the submodule DC voltages as well as converter power throughput. In particular, two current-control loops are proposed that, in coordination with one another, not only enable the control of the power flow within the converter, but also promise protection against overloads and terminal shorts. The validity of the mathematical model and effectiveness of the proposed control are verified through off-line simulation of a detailed circuit model as well as experiments conducted on a 1-kW experimental setup. The results of this exercise motivate the extension of the proposed control method to more compact designs with galvanic isolation and enhanced power handing capabilities.

Protection Scheme for DC Microgrid Distribution System

2012 ◽  
Vol 614-615 ◽  
pp. 1661-1665
Author(s):  
Ling Hui Deng ◽  
Zhi Xin Wang ◽  
Jian Min Duan
Keyword(s):  
Distribution System ◽  
Cost Efficiency ◽  
Power Flow ◽  
Low Voltage ◽  
Dc Microgrid ◽  
Protection Scheme ◽  
High Level ◽  
Bidirectional Power Flow ◽  
Efficiency And Reliability ◽  
Laboratory Prototype

The low voltage DC (LVDC) distribution system is a new concept and a promising technology to be used in the future smart distribution system having high level cost-efficiency and reliability. In this paper, a low-voltage (LV) DC microgrid protection system design is proposed. Usually, an LVDC microgrid must be connected to an ac grid through converters with bidirectional power flow and, therefore, a different protection scheme is needed. This paper describes practical protection solutions for the LVDC network and an LVDC system laboratory prototype is being experimentally tested by MATLAB/SIMULINK. The results show that it is possible to use available devices to protect such a system. But other problems may arise which needs further study.

Analysis of Three Port Full Bridge and Half Bridge DC-DC Converter Interfacing Renewable Energy System

2013 ◽  
Vol 768 ◽  
pp. 3-8 ◽  
Author(s):  
M. Venmathi ◽  
R. Ramaprabha
Keyword(s):  
Renewable Energy ◽  
Power Flow ◽  
Pulse Width Modulation ◽  
Renewable Energy Sources ◽  
Energy System ◽  
Energy Sources ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Conversion Stage ◽  
Bidirectional Power Flow

This paper presents the comparative dynamic analysis of full bridge and half bridge three port dc-dc converter topology interfacing the renewable energy sources along with the energy storage devices. The three port converter comprises the active bridge circuit and the three winding transformer. It uses single power conversion stage with high frequency link to control power flow between the batteries, load and the renewable energy sources. The power flow between the ports is controlled by phase shifting the square wave outputs of the active bridges in combination with pulse width modulation (PWM) technique. The analysis reveals that the battery discharges when the source is not sufficient to supply the load and it was charged when the source alone is capable of supplying the load. Hence there is a bidirectional power flow in the storage port when there is a transition in the source.

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.

A New Interleaved Bidirectional Zero Voltage Switching DC/DC Converter with High Conversion Ratio

2017 ◽  
Vol 26 (06) ◽  
pp. 1750105 ◽  
Author(s):  
Ebrahim Babaei ◽  
Zahra Saadatizadeh ◽  
Behnam Mohammadi Ivatloo
Keyword(s):  
Power Flow ◽  
Low Voltage ◽  
Zero Voltage Switching ◽  
Bidirectional Converters ◽  
Comprehensive Comparison ◽  
Step Down ◽  
High Conversion Ratio ◽  
Bidirectional Power Flow ◽  
Zero Voltage ◽  
Voltage Switching

In this paper, a new interleaved nonisolated bidirectional zero voltage switching (ZVS) dc–dc converter by using one three-windings coupled inductor is proposed. The proposed topology can provide high step-up and high step-down conversion ratios for boost and buck operations, respectively. Moreover, because of interleaving, the proposed converter has low input current ripple at low voltage side in both buck and boost operations. The proposed converter uses lower number of switches to have bidirectional power flow in comparison with other interleaved bidirectional converters. All used switches in the proposed converter are turned on under ZVS. The advantages of the proposed converter in comparison with the conventional interleaved converters are included in the capability of bidirectional power flow, ZVS operation for all switches and high step-up and high step-down voltage gain for boost and buck operations. In this paper, the proposed converter is analyzed completely and all equations of components are extracted as well as the ZVS conditions of all switches. Moreover, a comprehensive comparison between the proposed converter and conventional topologies is presented. To verify the accuracy performance of the proposed converter, the experimental results are given.

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