A grid side converter current controller for accurate current injection under normal and fault ride through operation

Modern grid codes for interconnection of distributed energy resources have become more restrictive due to the massive integration of renewable energy sources. The interconnected renewable energy sources must operate accurately under normal and abnormal grid conditions in order to meet the grid requirements. In addition, the renewable energy systems require fault ride through capability in order to support the power grid under balanced or unbalanced low voltage grid faults. Therefore, the development of advanced current controller techniques is essential for the grid side power electronic converters in order to increase the renewable energy systems penetration and satisfy the grid codes. This paper proposes a current controller technique, which enables the appropriate operation of the grid side converter under unbalanced grid faults and harmonic distorted grid conditions. The proposed current controller is designed using multiple synchronous reference frames and can inject full positive or full negative sequence balanced sinusoidal currents under abnormal grid conditions. The accurate performance with robustness against unbalanced and harmonic distorted grid voltage indicates that the proposed current controller can be a useful tool in the fault ride through control of renewable energy systems.