A Low-Voltage Ride-Through Method With Transformer Flux Compensation Capability of Renewable Power Grid-Side Converters

With the growing penetration of renewable energy resources, the grid operators place higher emphasis on their grid integration requirements. The low-voltage ride-through (LVRT) capability is one of the most important issues for maintaining the grid stability. This paper proposes a LVRT technique for effective utilization of the ampere capacity of the grid-connected converter to meet the LVRT requirement, and to reduce the potential post-sag inrush current of the transformer within the grid-connected converter system. This technique precisely manages the peak value of converter´s phase current while performing the transformer flux compensation and the current injection for full utilization of the ampere capacity without the risk of triggering the overcurrent protection. The operation principles of the proposed method is explained, and laboratory test results are presented for validation.