What is commutation failure?

Commutation failure (CF) is an adverse and frequent dynamic event in high-voltage direct current (HVDC) systems based on line-commutated converter technology. It is most often caused by AC system faults in the receiving-end grid [1].

What are the factors responsible for commutation failure?

Decrease of voltage and voltage distortion is the main reason causing commutation failure. At present, the study on commutation failure is mostly based on the change of fundamental voltage, while the voltage distortion is neglected.

How can we prevent commutation failure?

To avoid commutation failure. circuit turn-off time must be greater than the thyristor turn-off time. circuit turn-off time must be lesser than the thyristor turn-off time.

In which condition commutation failure happens in the rectifier of HVDC system?

System faults on the AC networks connected to a line-commutated HVDC system with thyristor based technology result in voltage disturbances in the form of voltage magnitude reduction and/or phase shift. If the disturbance is severe enough, the power transmission is interrupted by a so called commutation failure.

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 voltage of valves?

Commutation process explained. When just valves 1 and 2 are conducting, the DC voltage is formed from two of the three phase voltages. During the overlap period the DC voltage is formed from all three phase voltages.

Which MTDC system is more reliable?

There is no power interruption in mesh type MTDC system. Therefore, parallel-connected mesh type MTDC system is more reliable than a parallel-connected radial type MTDC system.

What is inverter commutation?

rectifier and inverter circuits must be commutated or. turned off during operation. Commutation is basically the. act of stopping or diverting current flow from a conducting. path in such a circuit.

What is commutation process in SCR?

The turn OFF process of an SCR is called Commutation. Commutation means transfer of current from one circuit to another. A sufficient reverse voltage must be applied across the SCR to regain its forward blocking state.

What is meant by commutation of SCR and list its types?

The turn OFF process of an SCR is called Commutation. The anode or forward current of SCR must be reduced to zero or below the level of holding current and then, A sufficient reverse voltage must be applied across the SCR to regain its forward blocking state.

What does commutation of pension mean?

Commutation is defined as giving up part or all of the pension payable from retirement in exchange for an immediate lump sum. Commutation factors (usually calculated by the Scheme Actuary) are used to determine the amount of pension which needs to be given up in order to provide the lump sum.