Development of Reference Current Calculation Scheme for Grid-Side Converter during Unbalanced Faults

The share of renewable energy is increasing day by day. The European Union set its target to double the share of solar and wind power by 2025 and to triple it by 2030. The renewable energy sources are mostly connected to the grid with converters. Due to the large penetration of the converters, the grid operators demand a specific negative sequence current injection from the converters for the safe and reliable operation. The grid codes define the response of the grid connected converters in case of a fault. The conventional control scheme of the converter is unable to operate properly in unbalanced situations. This paper presents a new control scheme for generating the reference converter's current consisting of positive and negative sequences while ensuring the safety of the converter. It is capable of injecting the negative sequence current to fulfil the recent grid codes, in addition, it complies with the converter's current limitation. The conventional and proposed methods are compared for different types of unbalanced faults. The results demonstrate the capability of the proposed scheme to fulfil the recent grid code requirements while ensuring the safe operation of the converter.