Overvoltage ride-through requirements in the Finnish converter dominated power system

Additional reactive current injection is often required in the grid codes from converter-connected power plants to mitigate overvoltages and to increase residual voltages during faults. This paper studies the effect of additional inductive current injection on overvoltages using electromagnetic transient (EMT) simulations with manufacturer-specific wind power plant (WPP) models. The objective of the study is to propose additional inductive current injection and overvoltage ride-through (OVRT) requirements for the next Finnish grid code revision and to study whether additional capacitive current injection requirement can cause overvoltages after fault clearing. The study is conducted by using two grid models: 1) a simple model consisting of few WPP models and a meshed network and 2) a large-scale model representing the western part of the Finnish transmission system. The study revealed that fault ride-through (FRT) mode of the WPPs contributes to overvoltages after fault clearing, due to the pre-disturbance reactive power produced by the wind turbines following voltage recovery. Utilizing additional inductive current injection significantly reduced the overvoltages. Furthermore, additional capacitive current injection magnitude had an insignificant effect on the overvoltage occurring after fault clearing. Based on the results, additional inductive current injection and OVRT requirements were proposed for the Finnish grid code revision.