Direct Current (DC) Link

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15.07.11 The division head of the researches in the sphere of the superconductivity Victor Sytnikov (R&D Center for power engineering) made the appearance to the FGS UES management personnel
The second appearance under the formed plan of the monthly statements of the “R&D Center for power engineering” leading researches was held for the management personnel of the “FGS UES” JSC.

12.07.11 The representatives of “R&D Center for power engineering” JSC took part in the innovative projects expertise under the forum “Seliger-2011”
From July 6 till July 7, 2011 the specialists of “R&D Center for power engineering” took part in the R&D innovative projects expertise from the youth innovative center “System-Sarov” in the line of “energy efficiency and power saving” under the National youth forum “Seliger-2011”

04.07.11 Siemens LLC and “R&D Center for power engineering” signed the cooperation agreement
The opening ceremony of the plant “Siemens HV devices” LLC (Voronezh) was held the 1 June 2011.

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DIRECT CURRENT (DC) LINK

DC Link is a converter substation designed to convert alternating current into direct and subsequently convert direct current into alternating current of the initial or other frequency.

RDCPE offers design services for DC links for power grids of varying voltage in Russia and CIS states.

One of the outstanding examples of the company’s work in this area is the DC link at Mogocha substation rated at 220 kV, a part of Siberian Energy Systems.

The DC link at Mogocha differs from many well-known conventional examples (such as the ones in Russia-Finland) utilizing thyristor converters due to the use of voltage converters (STATCOM) with powerful transistor valves, which allows for transmission of active power in both directions through a single converter, as well as regulation of reactive power without additional sources of reactive power.

In addition, DC links are able to address a number of significant challenges for today’s energy systems:

connections of two power grids with identical nominal frequencies but different non-fixed phase shifts;
linkages between power grids with varying frequencies and phases;
increased transmission capacity of grid elements with “weak” connections;
normalization of grid operations in case of accidents and restoration of power supply after failure remediation.

Background

Electrical current converters may be designed with conventional DC links (thyristor based), STATCOM based links or asynchronized machines-based links (see Fig. 11 – 12).

Current converter devices:

№	Name	Description	Application	Maker
1.	Conventional thyristor DC link	DC link utilizing a rectifier and an inverter; uses a single operation thyristor. Requires a source of reactive power of 50 to 100% of the link’s installed capacity.	Used for a non-synchronized connection. Not effective in grid networks with lack of reactive capacity. Cannot operate autonomously.	Russia and abroad
2.	STATCOM-based DC link	DC link utilizing two STATCOMS unified by a common continuous current link and interposed in a series of grid lines connecting two electric systems. Provides a wide range of regulation of active and reactive power.	Widely used for non-synchronized connections of any energy systems, including weak intersystem connections. Allows autonomous operation. Used in all grids.	Widely used abroad, design phase underway in Russia
3.	Frequency converter machine	Two asynchronized units with rigidly bound shafts operating, generally speaking, with different frequencies of the electric energy system. Represents an electromechanic equivalent of two-STATCOM DC link. Has a high overload tolerance. Two parts of the system have no electric link.	Used similarly to the example above. Particularly effective for powering the loads sensitive to voltage dips and subscribers with impulse loads.	Not manufactured currently.