Multi-terminal DC Distribution Research Articles

A Novel Solid-State Circuit Breaker With Self-Adapt Fault Current Limiting Capability for LVDC Distribution Network

DC fault current limitation is important for the low-voltage dc distribution network, because the existing dc selective protection cannot act fast enough. However, the typical dc fault current limiting method—installing dc reactors directly in the dc system—will lead to negative influence on the system normal operation and dc circuit breaker (DCCB) fast isolation. This paper proposed a novel solid-state circuit breaker (SSCB) with self-adapt fault current limiting capability, namely, no negative influence on the dc distribution network normal operation, swift fault current limiting response to the dc fault, and efficient cooperation between the fault current limitation and isolation. The hybrid configuration strategy of the proposed SSCB and mechanical DCCB for multiterminal dc distribution network is proposed to reduce the conducting power loss and investment from the scale of the whole system. Finally, the experiment tests and simulation cases are carried out to verify the working principle and superiorities of the proposed SSCB.

Study on DC Breaker Fault Current and Its Limiting Method of Multiterminal Flexible DC Distribution System

The multiterminal flexible DC (MTDC) distribution system has become a hot research topic for its advantages such as new energy load accessibility and high reliability of power supply. However, the fault current during short-circuit faults will be more complicated and serious because of the multiple operating modes and specific converter structure in MTDC distribution system. The high fault current will affect the safety of equipment and system operation. As a result, it is necessary to study the fault current generation mechanism and current limiting method of the DC distribution system. In this paper, the generation mechanism, transient characteristics, and the influencing factors of the fault current in the DC breaker during the short-circuit faults are analyzed by theoretical analysis and simulations separately based on a ±10 kV three-terminal flexible DC distribution system. The current limiting devices are analyzed, and its configuration position and parameter calculation method are proposed. On this basis, the parameters of the current limiting reactor and its effects on each position are analyzed by electromagnetic transient simulations. The current limiting scheme is proposed and its reliability is verified. The study results can provide some reference for overcurrent analysis and current limiting measures of the multiterminal DC distribution system.

Rapid modelling for flexible DC distribution network considering droop control

With the growth of DC electricity load, the difficulty to improve the power quality, and the increasing penetration of renewable power, flexible DC distribution network, which contains complex renewable energy generation equipment and a large number of power electronic converters, become an important research direction. The modelling of the DC distribution network is an essential step for the research on the coordination control. However, the traditional modelling will be a burden for simulation software. This article models all electrical devices as equivalent power sources based on the proportional–integral control and the power–voltage curve, ignoring the complex internal control processes. Based on the simplified models of power, load, DC/DC converters, and AC/DC converters considering droop control, a simplified model of a multi-terminal flexible DC distribution network is derived. Taking the impact of droop control into account, the simulation of DC distribution power flow under the different distribution of generation and load is done. Results show that the simplified model of DC distribution network with droop control can accurately and rapidly simulate the transient process and steady states of the testing network.

Fault Detection and Location of Photovoltaic Based DC Microgrid Using Differential Protection Strategy

A new differential current-based fast fault detection and location scheme for multiple Photovoltaic-based dc microgrid is proposed in this paper. A multiterminal dc (MTDC) distribution network is an effective solution for present grid scenario, where local distribution is incorporated primarily by power electronics based dc loads. PV systems with auxiliary power sources and local loads are used for MTDC connection, especially when ac utility grid is integrated with it by voltage source converters. Pole to pole and pole to ground faults are basically considered as dc distribution network hazards. As PV is connected through dc cable, high resistive dc arc fault is also studied in present literature. The proposed PV system is considered with arc-fault circuit interrupters as backup protection and is used to detect arcing series fault. Fast acting dc switching is considered for proposed differential current-based unit protection. A discrete frame differential current solution is considered to classify the fault type by modified cumulative sum average approach. By calculating unknown dc cable resistance accurately by non-iterative Moore-Penrose pseudo inverse technique, the fault distance is calculated. TMS320C6713 DSP based test-bench is used for verification of the scheme.

Coordinated Voltage Control Scheme for Multi-Terminal Low-Voltage DC Distribution System

Coordinated Voltage Control Scheme for Multi-Terminal Low-Voltage DC Distribution System

Modeling of Electric Components in Multi-terminal DC Distribution Network

As the existing AC power system is faced with development bottleneck such as the integration of renewable energy sources, high power quality and so on, the introduction of multi-terminal DC distribution network in the future smart grids is of significant importance. This paper presents a novel modeling method of electric components from the view of control instead of the detailed modeling of each IGBT-based converter. Three models are put forward to imitate the electrical characteristics of load-converter module, source-converter module and DC transformer. The proposed three models can cover all electric components in the DC distribution network, which lays the foundation for the further research on the DC distribution network. A six-terminal DC distribution network is constructed in Mat lab/Simulink based on the three proposed models, which verifies the correctness of the proposed modeling method.

Multi‐terminal medium voltage DC grids fault location and isolation

Voltage source converters (VSCs) are highly vulnerable to DC fault current; thus, protection is one of the most important concerns associated with the implementation of multi-terminal VSC-based DC networks. This study proposes a protection strategy for medium voltage DC distribution systems. The strategy consists of a communication-assisted fault location method and a fault isolation scheme that provides an economic, fast and selective protection by means of using the minimum number of DC circuit breakers. This study also introduces a backup protection which is activated if communication network fails. The effectiveness of the proposed protection strategy is analysed through real-time simulation studies by use of the hardware-in-the-loop approach. Furthermore, the effects of fault isolation process on the connected loads are also investigated. The results show that the proposed strategy can effectively protect multi-terminal DC distribution networks and VSC stations against different types of faults.

Call for Papers: HVDC Transmission and Large Scale Energy Storage

European Transactions on Electrical Power will publish a Special Issue entitled ‘HVDC Transmission and Large Scale Energy Storage’. The Guest Editor for this issue will be Prof. Brian K. Johnson of the University of Idaho. Voltage source converter HVDC technologies and applications UHVDC (+/−800 kV) transmission technologies and applications Multiterminal HVDC systems DC transmission and distribution in urban power systems AC to DC line conversion Developments in power converter technologies for HVDC and energy storage Integrated storage and renewable generation in regional bulk power systems Applications of energy storage to improve AC/DC transmission system performance Use of HVDC systems and energy storage as shock absorbers to limit the propagation of major power grid disturbances The papers should be in English and of a maximum of 25 pages, including references and illustrations. All submitted papers will be reviewed by at least three reviewers and selected based on their originality, significance, relevance, and clarity of presentation. Completed papers should conform to the journal's style and according to the instructions for authors which can be found on the journal's homepage, under “For Authors”. http://www.interscience.wiley.com/journal/etep/home/forauthors.html. Papers have to be submitted online via the journal's homepage at the URL above, under “Online Submission”. Authors must initially select Prof. Deqiang Gan as the Submitting Editor. Each submission must be clearly identified as a submission for this special issue and the special issue code, HVDC, must be entered in the Special Issue Title field, when requested. Submissions due: 31 August 2008