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This paper compares how a dc fault affects a multi-terminal dc (MTdc) network depending on the HVDC transmission system topology. To this end, a six-step methodology is proposed for the selection of the necessary dc fault protection measures. The network consists of four voltage-source converters converters radially connected. The converters natural fault response to a dc fault for the different topologies...
This paper presents an average-value model of a line commutated converter-based HVDC system using dynamic phasors. The model represents the low-frequency dynamics of the converter and its ac and dc systems, and has lower computational requirements than a conventional electromagnetic transient (EMT) switching model. The developed dynamic-phasor model is verified against an EMT model of the CIGRE HVDC...
This paper presents a new method based on piecewise analytical formulas to evaluate the valve losses of the modular multilevel converter based high-voltage direct current (MMC-HVDC) transmission systems. According to the generating mechanism, the total valve losses of the MMC are divided into three parts: conduction losses, essential switching losses, and additional switching losses. Due to the large...
A Modular Multilevel Converter (MMC) control system based on converter energy storage is proposed in this paper for two different control modes: active power and dc voltage. The proposed control system decouples the sub-module (SM) capacitor voltages from the dc bus voltage. One of the practical applications is the management of active redundant SMs. A practical HVDC system with 401-level MMCs including...
Different HVDC grid types and the respective protection options are discussed. An earthed bi-pole HVDC grid was modeled in PSCAD, and using simulation results, the necessity of di/dt limiting inductors to contain the rise of fault currents within the capacity of current hybrid DC breakers is demonstrated. The impact of different inductor sizes on current rise was studied. A fault detection and localization...
There is significant interest in building HVDC transmission to carry out transnational power exchange and deliver cheaper electricity from renewable energy sources which are located far from the load centers. This paper presents a market based approach to solve a long-term TEP for meshed VSC-HVDC grids that connect regional markets. This is in general a nonlinear, non-convex large-scale optimization...
A method for solving the optimal power flow (OPF) problem including HVDC connected offshore wind farms is presented in this paper. Different factors have been considered in the proposed method namely, voltage source converter (VSC-HVDC) and line-commutated converter high-voltage DC (LCC-HVDC) link constraints, doubly fed induction generators' (DFIGs) capability curve as well as the uncertainties of...
Based on the inherent characteristic of the carrier-based pulse-width modulation converters, the response of the first carrier frequency harmonic (FCFH) current in the voltage source converter (VSC)-based high-voltage direct current (HVDC) transmission system is analysed under different fault conditions in this paper. A new protection scheme for the VSC-based HVDC transmission systems is proposed...
A nonlinear averaged model of MMCs is proposed that considers the SM capacitor insertion dynamics and takes into account the current control loops that follow widely used vector control approach. A stability analysis framework is presented by exploiting the linear time-periodic (LTP) nature of this system. The averaged model, developed in MATLAB/Simulink, is benchmarked against a detailed model in...
Line-Commutated Converter (LCC) based HVDC lines are widely used to transmit electric power and interconnect asynchronous AC systems. Due to the characteristic of LCC-based HVDC, large amount of reactive power consumed by HVDC potentially deteriorates system voltage stability. Reactive power control is crucial to alleviate adverse impacts of HVDC reactive power consumption from AC network and secure...
This paper presents an approach to fault location in HVDC transmission lines. A superimposed signal calculated from voltages and currents sampled in the same terminal is processed by a morphological filter in order to highlight the wavefronts and allow the fault location. The morphological filter was adopted due to its simplicity and low computational cost. A suitable combination of superimposed signal,...
Currently, the standards used to calculate the short circuit (SC) current ignore the contribution of DC systems to the SC current when short-circuit faults occur in an AC systems. With the rapid development of High Voltage Direct Current systems (HVDC), it has become important to determine whether the contribution of the HVDC system can be ignored when calculating the SC current. This study investigates...
This paper demonstrates the effectiveness of post-fault corrective control action through the planned Western HVDC link in the Great Britain (GB) transmission network. It is shown that both transient as well as oscillatory stability problems could be tackled using such a corrective control strategy which allows higher pre-fault loading of the AC network without compromising security. The corrective...
Increasing uncertainties in power system operation require novel approaches for utilizing operational flexibility to enable a both secure and efficient power supply. This paper presents a real-time coordination approach for adaptive redispatch of generation and load in case of overloads in the electrical transmission network. For this, a previously developed multi-agent system for coordinating power...
Offshore wind farms (WFs) connected to the grid via voltage-source converter based high voltage DC (VSC-HVDC) do not inherently participate in the primary frequency control of the main grid. This paper discusses possible approaches for participation of the offshore WF in the frequency control focusing on the primary frequency response during an overfrequency event caused by a sudden change in the...
The overall system behavior of a three-terminal DC grid with symmetric monopole configuration is the focus of this paper. The modeling of the DC grid test system which includes converter stations, hybrid DC breakers, cables, etc. is carried out in real-time digital simulator (RTDS) platform. For control and protection, ABB's MACH system is used. Some important system aspects of DC grid, e.g. AC fault-ride-through,...
The traveling wave protection performance of traditional DC transmission line can be influenced by fault conditions, so this paper proposes a traveling wave based directional pilot protection method. Analysis shows, for an internal DC line fault, that the forward traveling wave is less than the backward traveling wave at two ends of the proposed line within a short time of post-fault; but in the case...
Using the characteristic difference of transient energy, a transient energy based directional unit protection is proposed. Assuming the positive direction of current is from DC busbar to DC line, for an internal line fault, the detected transient energies on both ends of the line are all negative, which denote the positive direction fault. When an external fault occurs, the transient energy on one...
Direct current transmission based on Voltage Source Converters (VSC-HVDC) has a number of advantages compared with traditional HVDC systems. However, VSC-HVDC systems are subjected to high short circuit currents due to faults in the DC line, which may contribute negatively to the dissemination and advances of this technology. In this context, this paper analyzes the impact of superconducting fault...
The VSC based HVDC link between France and Spain (INELFE project: France-Spain ELectrical INterconnection) will be the most powerful HVDC-VSC link by 2015. This 2000 MW interconnection is composed of 2 independent VSC type links. For system studies and maintenance purposes, replicas of the control systems are acquired by the French (RTE) and the Spanish (REE) Transmission System Operators. This paper...
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