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The Manitoba Hydro major transmission system features a topology consisting of very high HVdc penetration level, tightly coupled rectifiers as well as tightly coupled inverters. The tight coupling at the rectifiers or the sending end results in multi-egress system characteristics, where as the tight coupling at the inverters or the receiving end results in its multi-infeed characteristics. This paper...
The paper highlights the main drivers for the Western Link HVDC project from the Transmission Owners' point of view, the main project milestones, the challenges as well as the proposed technical solution. On the technical side the focus is on the key operating and design parameters of the HVDC system. The HVDC converters will apply classic line commutated converter technology requiring harmonic filtering...
The South West scheme is an important part of the development of the Swedish national grid and is a key facility to enable the production of renewable energy, in accordance with Swedish and EU energy policy. It will reinforce the AC network, increase operational reliability, and deal with transmission limitations in southern Sweden and between Sweden and Norway. The paper describes the first phase...
The earlier developed control method using a piecewise linear droop curve, with different droop values for the different segments, has now been optimised for dynamic performance. Non-linearities at the junctions of two linear droop sections have been adressed. Also non-linearity of power based DC voltage control has been adressed. Dynamic instability due to high control gains has been treated and...
The turbo-generator units in the vicinity of HVDC transmission system are vulnerable to Sub-Synchronous Torsional Interactions (SSTI). Based on the AC-DC system decoupling transfer function structure of Generator rotation rate to the electric torque, a novel phase correction method of HVDC supplementary subsynchronous multiple models damping controller is proposed, and a SSDC software for adjusting...
There has been much discussion over how HVDC grids incorporating many converters should be controlled and several methodologies have been proposed. An underlying principle of a proposed method, Voltage Droop control, was the minimisation of the inter-dependency of the control of the individual converters, inferring little, or no, reliance on a communication system. Since then further work has shown...
The growing demand on non-fossil fuel energy has escalated the desire for mega-scale renewable energy power generation. This demand can no longer be satisfied by solely relying on onshore renewable energy power plants (i.e. onshore wind farms, PV farms, etc.). Outcomes from a recent project funded by the Sixth European Union Framework Programme (FP6), “Project Upwind” concluded that larger offshore...
In future HVDC grids, or ‘Supergrids’, high voltage DC circuit breakers will almost certainly be used in order to remove a faulted element of the HVDC Grid whilst allowing power flow to continue on the remaining grid. However, associated with these HVDC circuit breakers will be the need for a means of fast fault detection, location and isolation. This paper presents a none-conventional approach to...
The use of Voltage Source Converter (VSC) based HVDC transmission has been strongly suggested for the interconnection of various power networks. However, VSCs susceptibility to DC faults, particularly the potential damage caused to the converter IGBTs due to overcurrent, is an issue that must be addressed. This paper analyses the behaviour of a VSC-based HVDC system under varying DC fault conditions...
A Modular Multi-level Converter (MMC) is an attractive topology for HVDC Transmission applications due to its modular structure. Since MMCs are essentially Voltage Sourced Converters, their performance under ac side faults is of particular interest. The possible unbalanced over-currents and capacitor voltage fluctuations are of particular concern as they may cause the converter to trip. In this paper,...
This paper proposes a recovery strategy for wind energy-fed voltage source converter high voltage DC transmission systems, capable of maintaining power balance between the AC and DC sides during different AC faults. This prevents the DC link voltage rise as a result of trapped energy. This reduces the voltage and current stresses on the switching devices. Also, the strategy ensures the converters...
DC power flow can be controlled though N-1 different DC lines/cables in a DC grid having N individual AC/DC converters. A large meshed DC grid can have more DC lines, and since we can not control power in all lines/cables, an overload may result. In this paper, two methods are proposed for DC power flow control through DC lines/cables. The first method involves using extra resistors embedded in series...
Manitoba Hydro is currently making plans for the development of Bipole III (BPIII), a 2300MW, +/-500kV HVdc Bipole that will run from Northern Manitoba to the Load centre in the south over a length of approximately 1300km. Both LCC and VSC options are considered for the new BPIII HVdc scheme [1]-[2]. One of the features being investigated is the option to parallel the new Bipole III converters with...
This paper presents the detailed system design of Shanghai Nanhui project — the first VSC-HVDC demonstration project in China. Two 18MW VSC converters based on Modular Multi-level topology are connected to transfer the energy generated by 11 wind turbines into Nanhui AC network. It has been verified that an improvement on voltage quality and fault ride through performance of Nanhui windfarm have been...
In this paper, we present further applications of the timedomain simulation based frequency scanning technique which has been proposed in the earlier literature. The behavior of the complete HVDC system is modelled as the closed loop action of two independent systems (AC system and DC system). The separately obtained frequency scan results of these independent systems are used to get the frequency...
With increasing offshore wind generation, there is a strong argument for implementing a multi-terminal DC grid offshore by the interconnection of individual HVDC links. The point of intersection of three or more lines can be used to interconnect projects with different voltage levels and to control power distribution. It is being proposed that these points, or nodes, be implemented using DC devices...
The Authors have applied their combined experience of more than 50 years involvement in subsea cable projects, to present key issues and areas where effort must be applied to minimise the risk over the project life cycle. Pre-sanction engineering, manufacturing, installation and failure during operation are discussed. Specific issues are mentioned that have resulted in delay, cost escalation, reliability...
This paper considers two reactive power compensation devices for HVDC converter stations, the synchronous condenser (SC) and the Static Synchronous Compensator (STATCOM). The contribution of these devices to the networks inertia is very different. The paper discusses the impact of this inertia on frequency stability in the ac network. The impact is analyzed using analytical studies as well as numerical...
Fault Current Limiters (FCL) limit fault current levels to a more manageable level, this way it becomes possible to increase the transmission ratings of an electrical system, without changing the equipment. Thus, the existing equipment is able to handle the new currents and protect properly the system. In the paper, different types of FCLs are deeply identified, covering their characteristics, advantages...
Offshore wind power is attracting increasing levels of research and investment. The use of HVDC transmission and development of DC grids are topics with similar levels of interest that go hand in hand with the development of large scale, far from shore wind farms. In this paper, technical challenges resulting from the interaction between power electronic DC-DC converters and the cables in a DC transmission...
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