Investigation of HVDC inverter with series compensation on analogue simulator

An analogue simulator was used to investigate the performance of the MOV (metal-oxide varistor) and series capacitor arrangements, especially the fault recovery performance of the latter. The SCD (series capacitor device) was found to be a feasible VCD (voltage control device) that considerably improves recovery from faults for weak AC systems by effectively increasing the SCR (short-circuit ratio). MOV+FC (fixed shunt capacitor) application is effective for the control of dynamic overvoltages. However, it does not strengthen the AC system. This results in slower recovery and instability in many situations unless constant current control is used. When the SCD is employed for DC systems feeding into weak AC systems, system recovery is faster with constant power control than with constant current control. Application of the SCD increases the power stability limit. Application of the SCD showed harmonic distortion due to the inrush current of transformers in combination with the SCD. It is therefore recommended that before SCD is chosen for a system, sufficient harmonic studies with a fuller representation of the AC system be performed