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Types of HVDC converters- Electromechanical and Line-commutated converters

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HVDC converters can take numerous special forms. Early HVDC structures, constructed till the Nineteen Thirties, had been efficiently rotary converters and used electromechanical conversion with motor-generator units related in the collection at the DC facet and in parallel at the AC facet. However, all HVDC structures were constructed for the reason that Forties used digital (static) converters. Electronic converters for HVDC are divided into the foremost categories. Line-commutated converters (HVDC classic) are made with digital switches that may simplest be become on. Voltage-sourced converters are made with Frontier Utilities switching gadgets that may become on and off.

Line-commutated converters (LCC) used mercury-arc valves till the Nineteen Seventies or thyristors from the Nineteen Seventies to the prevailing day. Voltage-supply converters (VSC), which were first regarded in HVDC in 1997, use transistors, normally the Insulated-gate bipolar transistor (IGBT). As of 2012, each the road-commutated and voltage-supply technology are important, with line-commutated converters used especially wherein very excessive potential and performance are needed, and voltage-supply converters used especially for interconnecting vulnerable AC structures, for connecting massive-scale wind electricity to the grid or for HVDC interconnections which might be probable to be elevated to come to be Multi-terminal HVDC structures in future. The marketplace for voltage-supply converter HVDC is developing fast, pushed partially via way of means of the surge in funding for offshore wind electricity, with one unique kind of converter, the Modular Multi-Level Converter (MMC) rising as a front-runner.

Electromechanical converters

As early because the 1880s, the blessings of DC long-distance transmission had been beginning to come to be obvious and numerous business electricity transmission structures had been positioned into operation.

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The maximum success of those who used the gadget invented via way of means of René Thury had been primarily based totally on the precept of connecting numerous motor-generator units in the collection at the DC facet. The best-recognized instance became the 2 hundred km, Lyon–Moutiers DC transmission scheme in France, which operated commercially from 1906 to 1936 transmitting electricity from the Moutiers hydroelectric plant to the town of Lyon. Kimbark reviews that this gadget operated pretty reliably; however, the overall stop-to-stop performance became negative via way of means of contemporary standards. From the Nineteen Thirties onwards, considerable studies commenced taking region into static options the usage of gas-crammed tubes – mainly mercury-arc valves but additionally thyratrons – which held the promise of drastically better performance. Very small mechanical rotary converters remained in use for the area of interest packages in unfavorable environments, which include planes and vehicles, as an electricity conversion approach from batteries to the excessive voltages required for radio and RADAR, till the Sixties and the transistor era.

Line-commutated converters

Most of the HVDC structures in operation these days are primarily based totally on line-commutated converters (LCC). The period line-commutated suggests that the conversion technique is predicated on the road voltage of the AC gadget to which the converter is hooked up to impact the commutation from one switching tool to its neighbor. Line-commutated converters use switching gadgets that might be both uncontrolled (which include diodes) or that may simplest become on (now no longer off) via way of means of managing action, which include thyristors. Although HVDC converters can, in precept, be made from diodes, such converters can simplest be utilized in rectification mode and the shortage of controllability of the DC voltage is a severe disadvantage. Consequently, in practice, all LCC HVDC structures use both grid-managed mercury-arc valves (till the Nineteen Seventies) or thyristors (to the prevailing day). In a line-commutated converter, the DC cutting-edge does now no longer alternate route; it flows thru a massive inductance and may be taken into consideration nearly constant.