Grid code analysis considering converter-based grid voltage support during faults

Modern power systems are increasingly integrated with power electronic converters, which allow precise control of active and reactive current injections within a certain range of operation. Power converters are usually required to provide grid voltage support service in case of fault. This poses the challenge to determine the current injection from a converter that maintains the grid voltage while not surpassing the converter's current limitation. Conventional grid codes simply set the linear relationship between the voltage droop and the grid-support current, consequently not providing the optimized voltage support. In this paper, the grid voltage support operation of power converters is analysed from an optimization perspective. A formulation for the analysis of faults in a generic system is presented. Numerical cases have been studied with different fault scenarios. The optimized solutions show the traditional grid code can be potentially improved in order to maintain the grid voltage closer to the nominal value during the fault. In this line, two improved adaptations of this grid code have been proposed. These two alternative grid codes have been found to be near-optimal as they just differ slightly from the optimized results despite only injecting reactive power.

Automated summary

Modern power systems with power electronic converters require precise control of current injections. Conventional grid codes fail to provide optimized voltage support during faults. This paper analyzes the grid voltage support operation and proposes improvements to maintain the grid voltage close to the nominal value. Two alternative grid codes are proposed, which inject only reactive power but achieve near-optimal results.