Current Reference Generation Based on Next-Generation Grid Code Requirements of Grid-Tied Converters During Asymmetrical Faults

Increased penetration of converter-based power generation has enforced system operators to require ancillary services from distributed generation in order to support the grid and improve the power system stability and reliability. Recent and next-generation grid codes require asymmetrical current provision during unbalanced faults for optimal voltage support. To address this, based on the highly used flexible positive- and negative-sequence control method for current reference generation, this paper presents a general current reference strategy for asymmetrical fault control, where a direct and explicit method is proposed to calculate power references and controller gains while simultaneously complying with converter current limitation and fulfilling the next-generation grid code requirements. The proposed method is tested for three distinct asymmetrical grid faults considering the requirements for dynamic voltage support of the recently revised German grid code as well as the next-generation grid codes. It is shown that the proposed method can improve the fault ride-through performance during asymmetrical faults compared with conventional solutions and comply with modern grid code requirements in a general and flexible manner.