Modelling and Simulation of Low-Voltage Fault Behavior in Hybrid Multiterminal LCC-VSC HVDC System Integrated with Renewable Energy Sources

Some previous studies argue that under the conditions of a double line to ground fault at the point of common coupling at the inverter end, the AC grid voltage of phases A and B will decrease along with the same level while the phase C will maintain at a stable steady state and this will lead to an excess increase in the voltage level of the high voltage direct current (HVDC) link. Presented in this paper is a model that comprises the hybrid multiterminal line commutated converters and the voltage source converter HVDC system. This model was mathematically modelled and implemented on Matlab/Simulink software in order to investigate the fault behavior, with a particular emphasis on double line to ground fault at different fault resistances. The system under study consists of a fault switch timer, photovoltaic solar array, wind energy conversion system, inverter control for the voltage source converter, Inductor–capacitor–inductor (LCL) filter and PI section line. The findings of this study indicated that during the double line to ground fault at varying fault resistances, the AC grid voltage in phase A will experience a more pronounced decrease compared to phase B. In contrast, phase C will exhibit only a slight reduction in voltage at the inverter end. Similarly, at the inverter end of the hybrid system, it was observed that the AC grid currents for the affected phases, specifically phases A and B, will experience an increase. It is further discovered that phase C will maintain relatively stable condition without increasing or decreasing during a double line to ground fault event. In addition, it is noted that the HVDC link voltage will decrease while the HVDC link current will increase depending on any fault resistance values. Thus, the inferences as a result of this study are presented in this paper.