Performance Analysis of Hybrid Cascaded Multilevel Converter for HVDC Transmission

HVDC transmission systems deals with bulk amount of power, therefore protection of these systems is highly important. This paper presents newly introduced voltage source converter with DC fault blocking capability, called hybrid cascaded multilevel converter. This converter has ability to prevent any uncontrolled fault current to flow from AC to DC side during DC faults, without the action of AC circuit breaker. This feature blocks power exchange between AC and DC side and may eliminate need of DC circuit breaker. Converter provides various features of multilevel converter and is able to operate over an extended modulation index range, independent of load power factor. This paper presents DC fault blocking capability of hybrid cascaded multilevel converter. System performance before fault and during fault is examined through extensive MATLAB simulation.