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Due to the expected proliferation of HVDC systems up to and beyond 2020 into the Great British transmission network, it is anticipated that in some locations two or more HVDC converter stations will be installed with only a short electrical distance between them and will form a multi-infeed (MI)-HVDC system. This is a particular concern in the North of Scotland. This paper investigates the impact...
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Tapping energy from a HVDC transmission line to serve small remote communities has been considered by researchers and HVDC manufacturers since the 1960s. Many HVDC taps proposed consider the performance of diodes, Thyristors and GTOs and the utilization of bulky and expensive high voltage transformers. This paper proposes a novel HVDC tap topology, the n-phase multi-modular series tap (MMST), which...
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In this paper, a Sequential Approach is described to design the supplementary damping controller of a Thyristor-Controlled Series Compensator (TCSC) and a Static Synchronous Compensator (STATCOM) with a multi-model system to enhance power system small-signal stability under different operating conditions and with respect to various disturbance scenarios. Control objectives including regional pole...
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In this paper, a new control strategy for Thyristor Controlled Series Compensator (TCSC) to mitigate Sub-Synchronous Resonance (SSR) problems is introduced. Different from conventional sub-synchronous damping controller, this scheme involves using only local measurements which can be effectively obtained at the TCSC side. The structure of the control strategy enables selection of multiple torsional...
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One of the greatest challenges faced by Zhoushan Project is that AC-isolated island can easily be formed due to the weakness of the AC grid connected to the VSC system and vulnerability to typhoon attack. A strategy based on frequency variation is introduced, which does not rely on breakers' status of AC grid. As a multi-terminal project, the AC-DC topology is complex, which brings new challenge to...
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In order to reliably and safely operate future multi-terminal HVDC grids, different protection strategies are currently being developed and presented in the literature. Especially for large DC grids, it is important to investigate how the choice of the protection strategy influences AC system stability during DC fault clearance and system restoration. This paper contributes to the understanding of...
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The parallel routing of high voltage AC and DC systems on the same transmission tower is one new option for a timely integration of HVDC technology into existing AC power grids, enhancing the latter's flexibility. However, the rare event of an intersystem fault is a new fault type which might occur in these configurations. Previous studies indicate that existing protection concepts are necessary but...
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Reliable and cost effective power transmission from North of Scotland offshore wind farms towards Scotland, England and Norway using a 7-terminal MMC DC grid is studied. The proposed DC grid employs a 5-port inductor-capacitor-inductor (LCL) fault tolerant MMC DC hub which interconnects several HVDC cables. The hub achieves power flow control between different terminals, DC voltage stepping using...
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The traditional Electromagnetic Transients Program (EMTP) is very slow for the lager-scale power systems simulation due to the small time step. To accelerate the EMTP simulations speed, a novel multi-rate method is proposed. This method is based on the rotating transformation of single phase coordinate and frequency reducing. The part of power electronic devices is simulated with a small time step,...
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The inductor-capacltor-lnductor (LCL) fault tolerant DC/DC converters have shown promising properties in DC voltage stepping using no internal AC transformer. This paper details design and modelling a 5kW, 250V/400V LCL IGBT based DC transformer. The design is to be prototyped at CITCEA-UPC in Barcelona and put into a five terminal mock up DC grid located at Electrical Engineering and Power Electronics...
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Ferroresonance is phenomena, which emerged in case of different circumstances like; short circuit, breaker phase failure. In addition, line and plant outage is another cause of ferroresonance. This study investigates occurrence of ferroresonance in case of line and plant outage in Manitoba Hydro 230 kV electrical network and enhance flexible mitigation of ferroresonance. The network is simulated In...
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Security of supply is a critical design consideration of STATCOM and HVDC schemes. A crucial piece of technology to achieve this is the cooling system. If this system is not designed with high reliability in mind, failures and unscheduled outages could occur, causing degradation in the all-important high availability expected from the scheme and ultimately loss in revenue for a Transmission System...
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Reliable cable systems are essential for offshore wind operation. Industry trends have led to a large number of offshore cable connections being installed recently, with 11027 MW of offshore wind connected at the end of 2015 compared to just 2955 MW in 2010 [1]. Despite the increase in connections, the publically available reliability data in this area is almost non-existent. With several connections...
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In high voltage direct current (HVDC) transmission systems, based on voltage source converters (VSC) with overhead line (OHL) segments, DC line faults have a strong impact on the converter's power electronic devices. Fault tolerant multilevel converters are able to limit and control these fault currents after their detection. Especially for low impedance and AC/DC intersystem faults the detection...
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To ensure a reliable fault clearing, a backup protection scheme is required for selective HVDC grid protection. One way to achieve this is to use both voltage and current measurements to distinguish uncleared faults from cleared ones during the fault clearing process of the primary protection. This paper studies the applicability of such a backup protection algorithm in meshed bipolar HVDC grids and...
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In the future, the established point-to-point HVDC transmission will be expanded to multi-terminal HVDC grids due to the increasing amount of regenerative energy generation. This change will lead to new challenges and requirements for grid-system operators and vendors e.g. in terms of transmission strategy, project planning, control strategies and multi-vendor intercompatibility. Within this paper,...
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High Voltage Direct Current (HVDC) cables are traditionally very expensive and typically comprise up to 70% [1,2] of a transmission project's total capital cost depending on the system voltage, the cable installation route and the overall distance. HVDC cables fall into three insulation types: mass-impregnated (MI), self-contained fluid-filled (SCFF) and cross-linked polyethylene (XLPE). General Electric...
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Up to now, the maximum rated current and power of existing HVDC transmission projects are up to 5000A and 8000MW respectively. The Shanghaimiao-Shandong ±800kV HVDC project which is currently under construction will have a higher transmission capacity with a rated current of up to 6250A. The converter valve for Shanghaimiao-Shandong HVDC project is one of the key equipment which needs significant...
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Due to recent political developments in Germany new High Voltage Direct Current (HVDC) transmission right-of-ways will have to be realised preferably as cable systems, especially near densely populated areas. Hence, overhead line (OHL) systems in combination with underground cable sections near urban areas — so-called partial underground cabling systems — become a viable option. This however leads...
