Components of HVDC Transmission Systems Components of HVDC Transmission Systems 1. 2. 3. 4. 5. 6. 7. Converters Smoothing reactors Harmonic filters Reactive power supplies Electrodes DC lines AC circuit breakers Iqbalilah Components of HVDC Transmission Systems Converters They perform AC/DC and DC/AC conversion They consist of valve bridges and transformers Valve bridge consists of high voltage valves connected in a 6-pulse or 12-pulse arrangement The transformers are ungrounded such that the DC system will be able to establish its own reference to ground Smoothing reactors They are high reactors with inductance as high as 1 H in series with each pole They serve the following: They decrease harmonics in voltages and currents in DC lines They prevent commutation failures in inverters Prevent current from being discontinuous for light loads Harmonic filters Converters generate harmonics in voltages and currents. These harmonics may cause overheating of capacitors and nearby generators and interference with telecommunication systems Harmonic filters are used to mitigate these harmonics Iqbalilah Component of HVDC Transmission Network Component of HVDC Transmission Network The main components of the HVDC system are mentioned below: 1.Converting Station, 2.Converting Units, 3.Converting Valves, 4.Converting T/Fs, 5.Filters, 6.High-Frequency Filters, 7.Power Source (Reactive), 8.Levelling Reactor, 9.Poles Iqbalilah Component of HVDC Transmission Network 1 Converting Station: At the substation, Rectifier terminal converts an AC to DC whereas Inverter substation converts DC to AC. Every terminal is designed in such a way that they work in both mode (Rectifier and Inverter), so then each terminal is known as converter terminal. A two-terminal HVDC transmission system is having two terminal and one HVDC line. The following Fig. (1) is showing A Typical HVDC Converter Station: Iqbalilah Component of HVDC Transmission Network 2 Converting Unit: As we discuss, converter unit converts AC to DC, and its vice-versa is used at three-phase bridge converters. This circuit is also known as Graetz Circuit. There is 12-pulse bridge converter is used in HVDC transmission, and that converter obtains by connecting two or 6-pulse bridge converter as shown in figure[2]. Iqbalilah Component of HVDC Transmission Network 3 Converting Valves: However new HVDC converter uses 12-pulse converter units and the total number of valves in each group shown in figure 3. Thyristor based modules are used to make series connection valves. The amount of thyristor valve depends upon the required voltage across the valve. Iqbalilah Component of HVDC Transmission Network 4. Converting T/Fs : The converter transformer changes over the AC to DC systems or the other way around. They have two arrangements of three stage windings, First is AC side winding and second is Valve sidewinding. The converter can work with 12 heartbeats for each cycle in the AC supply utilising Star-Delta and Wye-Delta Connection of T/F, which wipes out various consonant current. Anyway here whirlpool current misfortunes are increments because of the music current. The magnetisation in the centre of the converter transformer is a result of the accompanying reasons As we probably are aware, the converter transformer used to change over AC to DC and furthermore DC to AC. They have three stage winding, one is called an AC winding, and the other is Valve sidewinding. The converter worked with 12-heartbeat in every cycle in AC supply utilising star-delta and deltastar association of T/F, which expels various symphonious current, anyway here whirlpool current misfortunes are expanding because of sounds current. The charge in converter T/F centre is a result of the following reasons:-:-[17] a) The AC arrange containing sounds. b) The coordinate voltage from the valve side terminal additionally has a few musics
