Answer: HVDC lines do not require any reactive power compensation because of following reason
1. There is no charging current in HVDC line.
2. HVDC lines operates on unity power factor.
Yes .At terminal ends HVDC transmission requires reactive power compensation.
By HVDC transmission we cannot transmit reactive power.
And at terminal ends there are converters( Rectifier and Inverter). For this converter reactive power is needed. Specifically at the load end, there should be reactive power compensation for load requirements.