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.

scholarly journals AC Microgrids Protection: A Digital Coordinated Adaptive Scheme

2021 ◽  
Vol 11 (15) ◽  
pp. 7066
Author(s):  
Noor Hussain ◽  
Yousef Khayat ◽  
Saeed Golestan ◽  
Mashood Nasir ◽  
Juan C. Vasquez ◽  
...  
Keyword(s):  
Power Flow ◽  
Low Voltage ◽  
Short Circuit ◽  
Operation Mode ◽  
Modes Of Operation ◽  
Protection Scheme ◽  
Adaptive Protection ◽  
System States ◽  
Reliable Solution ◽  
Bidirectional Power Flow

A significant challenge for designing a coordinated and effective protection architecture of a microgrid (MG) is the aim of an efficient, reliable, and fast protection scheme for both the grid-connected and islanded modes of operation. To this end, bidirectional power flow, varying short-circuit power, low voltage ride-through (LVRT) capability, and the plug-and-play characteristics of distributed generation units (DGUs), which are key issues in a MG system must be considered; otherwise, a mal-operation of protection devices (PDs) may occur. In this sense, a conventional protection system with a single threshold/setting may not be able to fully protect an MG system. To tackle this challenge, this work presents a comprehensive coordinated adaptive protection scheme for AC MGs that can tune their protection setting according to the system states and the operation mode, and is able to switch the PDs’ setting. In the first step of the proposed adaptive algorithm, an offline setting will be adopted for selective and sensitive fault detection, isolation, and coordination among proposed protective modules. As any change in the system is detected by the proposed algorithm in the online step, a new set of setting for proposed modules will be performed to adapt the settings accordingly. In this way, a new set of settings are adapted to maintain a fast and reliable operation, which covers selective, sensitive, and adaptive requirements. The pickup current (Ip) and time multiple settings (TMS) of directional over-current relays (DOCR), as well as coordinated time delays for the proposed protection scheme for both of the grid-connected and islanded modes of operation, are calculated offline. Then, an online adaptive protection scheme is proposed to detect different fault types in different locations. The simulation results show that the proposed method provides a coordinated reliable solution, which can detect and isolate fault conditions in a fast, selective and coordinated adaptive pattern.

scholarly journals New Protection Scheme in Loop Distribution System with Distributed Generation

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5897 ◽  
Author(s):  
Hun-Chul Seo
Keyword(s):  
Distributed Generation ◽  
Distribution System ◽  
Power Flow ◽  
Distribution Systems ◽  
Fault Location ◽  
Electromagnetic Transients ◽  
Radial Distribution System ◽  
Protection Scheme ◽  
Protection Method ◽  
Bidirectional Power Flow

Loop distribution systems are increasingly used for reasons such as increased distributed generation (DG) and increased demand for a reliable and high-quality power supply. Because the loop distribution system involves bidirectional power flow, the method for protection of the radial distribution system cannot be applied. Therefore, a protection method is proposed herein for loop distribution systems. In this study, the existence of DG is also considered. According to the proposed method, the fault point is estimated on the basis of the equivalent circuit of the distribution system. Then, the fault section is determined and separated from the distribution system. The separation of DG is determined depending on whether the frequency and voltage are maintained within the steady state ranges. The proposed method is modelled and verified using the Electromagnetic Transients Program. Simulations according to the fault location are performed and analyzed. The results show that the method accurately determines the fault section so that normal power can be supplied to the healthy sections in the distribution system.

scholarly journals Smart charging for electric vehicles to minimise charging cost

2017 ◽  
Vol 231 (6) ◽  
pp. 526-534 ◽  
Author(s):  
Yue Wang ◽  
David Infield ◽  
Simon Gill
Keyword(s):  
Electric Vehicle ◽  
Electric Vehicles ◽  
Distribution System ◽  
Power Flow ◽  
Optimal Power Flow ◽  
Low Voltage ◽  
Wholesale Price ◽  
Heuristic Method ◽  
Domain Model ◽  
Smart Charging

This paper assumes a smart grid framework where the driving patterns for electric vehicles are known, time variations in electricity prices are communicated to householders, and data on voltage variation throughout the distribution system are available. Based on this information, an aggregator with access to this data can be employed to minimise electric vehicles charging costs to the owner whilst maintaining acceptable distribution system voltages. In this study, electric vehicle charging is assumed to take place only in the home. A single-phase Low Voltage (LV) distribution network is investigated where the local electric vehicles penetration level is assumed to be 100%. Electric vehicle use patterns have been extracted from the UK Time of Use Survey data with a 10-min resolution and the domestic base load is generated from an existing public domain model. Apart from the so-called real time price signal, which is derived from the electricity system wholesale price, the cost of battery degradation is also considered in the optimal scheduling of electric vehicles charging. A simple and effective heuristic method is proposed to minimise the electric vehicles’ charging cost whilst satisfying the requirement of state of charge for the electric vehicles’ battery. A simulation in OpenDSS over a period of 24 h has been implemented, taking care of the network constraints for voltage level at the customer connection points. The optimisation results are compared with those obtained using dynamic optimal power flow.

scholarly journals A Bidirectional Double Uneven Power Converter Based DC–DC Converter for Solid-State Transformers

Electronics ◽  
2018 ◽  
Vol 7 (11) ◽  
pp. 334 ◽  
Author(s):  
Kiwoo Park ◽  
Kyo-Beum Lee
Keyword(s):  
Solid State ◽  
Distribution System ◽  
Power Flow ◽  
Power Converter ◽  
Small Scale ◽  
Power Semiconductor ◽  
Switching Losses ◽  
Zero Current Switching ◽  
Zero Current ◽  
Bidirectional Power Flow

This paper presents a novel bidirectional double uneven power (BiDUP) based dc-dc converter and its design and control methods. The proposed converter utilizes two dual active bridge (DAB) converters with different power ratings in a special way to realize zero current switching (ZCS), where both turn-on and turn-off switchings occur under the zero-current condition. A design example of the proposed BiDUP converter is presented for medium voltage (MV) and high-power solid-state transformer (SST) systems where both voltage transformation and bidirectional power flow are required. The main features of the proposed converter are to reduce both the switching losses in power semiconductor devices and the filter inductance requirement simultaneously. To verify the feasibility of the proposed converter, a simulation study on the BiDUP converter based SST in a distribution system is presented. Furthermore, to validate the operational principle of the proposed converter, an experimental study using a small-scale prototype is also presented.

scholarly journals Bidirectional Power Flow Control in AC/DC Hybrid System under AC and DC Fault Conditions

2019 ◽  
Vol 3 (2) ◽  
Author(s):  
Wai Wai Hnin
Keyword(s):  
Power Flow ◽  
Storage System ◽  
Control Technique ◽  
Diesel Generator ◽  
Dc Microgrid ◽  
Photovoltaic Array ◽  
Hybrid Microgrid ◽  
Dc Bus ◽  
Bidirectional Power Flow ◽  
Ac Microgrid

This paper presents a hybrid AC-DC microgrid to reduce the process of multiple conversions in an individual AC microgrid or DC microgrid. The proposed hybrid microgrid compose of both AC microgrid and DC microgrid connected together by bidirectional interlink converter (BIC). Utility grid, 150kVA diesel generator (DG) and 100kW AC load are connected in AC microgrid. DC microgrid is composed of 100 kW photovoltaic array (PV), 20kW battery energy storage system (BESS) and 20kW DC load. The droop control technique is applied to control the system for power sharing within the sources in AC/DC hybrid microgrid in proportion to the power rating. When the faults occur at AC bus, protection signal applied to breaker for isolating the healthy and faults system. DC faults occur at DC bus, DC breaker isolate the AC and DC bus. The system performance for power flow sharing on hybrid AC-DC microgrid is demonstrated by using MATLAB/SIMULINK.

scholarly journals Analysis and Design of Coupled Inductor for Interleaved Buck-Type Voltage Balancer in Bipolar DC Microgrid

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2775
Author(s):  
Jung-min Park ◽  
Hyung-jun Byun ◽  
Bum-jun Kim ◽  
Sung-hun Kim ◽  
Chung-yuen Won
Keyword(s):  
Dynamic Response ◽  
Coupling Coefficient ◽  
Distribution System ◽  
Low Voltage ◽  
Magnetic Coupling ◽  
Two Stage ◽  
Dc Microgrid ◽  
Analysis And Design ◽  
Load Variation ◽  
Key Factor

A voltage balancer (VB) can be used to balance voltages under load unbalance in either a bipolar DC microgrid or LVDC (Low voltage DC) distribution system. An interleaved buck-type VB has advantages over other voltage balance topologies for reduction in output current ripple by an aspect of configuration of a physically symmetrical structure. Similarly, magnetic coupling such as winding two or more magnetic components into a single magnetic component can be selected to enhance the power density and dynamic response. In order to achieve these advantages in a VB, this paper proposes a VB with a coupled inductor (CI) as a substitute for inductors in a two-stage interleaved buck-type VB circuit. Based on patterns of switch poles under load variation, the variation in inductor currents under four switching patterns is induced. The proposed CI is derived from self-inductance based on the configuration structure that has a two-stage interleaved buck type and mathematical design results based on the coupling coefficient, where the coupling coefficient is a key factor in the determination of the dynamic response of the proposed VB in load variation. According to the results, a prototype scale is implemented to confirm the feasibility and effectiveness of the proposed VB.

scholarly journals Economic Load Dispatch of a Grid-Tied DC Microgrid Using the Interior Search Algorithm

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 634 ◽  
Author(s):  
Kamil Khan ◽  
Ahmad Kamal ◽  
Abdul Basit ◽  
Tanvir Ahmad ◽  
Haider Ali ◽  
...  
Keyword(s):  
Energy Storage ◽  
Power Flow ◽  
Search Algorithm ◽  
Operating Cost ◽  
Daily Cost ◽  
Dc Microgrid ◽  
Battery Energy Storage ◽  
Power Scheduling ◽  
Battery Energy ◽  
Bidirectional Power Flow

This paper presents the effectiveness of the interior search algorithm in economic power scheduling of a grid-tied DC microgrid with renewable generation (wind and photovoltaic) and battery energy storage. The study presents the modelling and simulation of various DC/DC converters for tracking maximum power from wind and photovoltaic sources and the bidirectional power flow of battery energy storage. The DC microgrid and its controllers were modelled and simulated in MATLAB/Simulink. The generating units were dispatched economically using the interior search algorithm with the objective to minimize the operating cost of the microgrid. The simulated results verify the effectiveness of the interior search algorithm as the daily cost of microgrid operation was reduced by 11.25%.

scholarly journals Integrating Photovoltaic Systems in Power System: Power Quality Impacts and Optimal Planning Challenges

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Aida Fazliana Abdul Kadir ◽  
Tamer Khatib ◽  
Wilfried Elmenreich
Keyword(s):  
Power Systems ◽  
Power System ◽  
Power Quality ◽  
Distribution System ◽  
Power Flow ◽  
Harmonic Distortion ◽  
Integrated System ◽  
Optimal Planning ◽  
High Penetration ◽  
Bidirectional Power Flow

This paper is an overview of some of the main issues in photovoltaic based distributed generation (PVDG). A discussion of the harmonic distortion produced by PVDG units is presented. The maximum permissible penetration level of PVDG in distribution system is also considered. The general procedures of optimal planning for PVDG placement and sizing are also explained in this paper. The result of this review shows that there are different challenges for integrating PVDG in the power systems. One of these challenges is integrated system reliability whereas the amount of power produced by renewable energy source is consistent. Thus, the high penetration of PVDG into grid can decrease the reliability of the power system network. On the other hand, power quality is considered one of the challenges of PVDG whereas the high penetration of PVDGs can lead to more harmonic propagation into the power system network. In addition to that, voltage fluctuation of the integrated PVDG and reverse power flow are two important challenges to this technology. Finally, protection of power system with integrated PVDG is one of the most critical challenges to this technology as the current protection schemes are designed for unidirectional not bidirectional power flow pattern.

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