What do you mean by line-commutated converter?
Line-commutated converters (LCCs) are the conventional, mature and well-established technology used to convert electric power from AC to DC or vice versa.
What causes commutation?
Excessive sparking burns the brushes and commutator surface. If the brushes are shifted too far in the proper direction as if the commutating field is too strong, an excessive voltage is introduced in the coil undergoing commutation, causing the current to reverse prematurely, and over-commutation results.
What is commutation in HVdc?
Commutation failure can be defined as an adverse dynamic event that occurs when a converter valve that is supposed to turn off, continues to conduct without trans- ferring its current to the next valve in the firing sequence.
What happens during commutation?
The commutation failure is characterized in that: the angle γ is smaller than the minimum value at which the converter valve restores its blocking capability; the DC voltage of the six-pulse inverter drops to zero within a certain period; the DC current is increased instantly; the current on the AC side of the valve is …
What is commutation technique?
The process used for turning off a thyristor is called commutation. By the commutation process, the thyristor operating mode is changed from forward conducting mode to forward blocking mode. So, the thyristor commutation methods or thyristor commutation techniques are used to turn off.
What methods are used to reduce commutation?
There are three methods of improving commutation: Resistance Commutation. EMF commutation. Compensating winding.
Which kind of commutation method is used HVDC system?
Most of the HVDC systems in operation today are based on line-commutated converters (LCC). The term line-commutated indicates that the conversion process relies on the line voltage of the AC system to which the converter is connected in order to effect the commutation from one switching device to its neighbour.
What is MTDC system?
A multiterminal DC (MTDC) system has more than two converter stations, some of them operating as rectifiers and others as inverters. The simplest way of building a MTDC system from an existing two terminal system is to introduce tappings.