Probabilistic assessment of Wind Farm Disconnection by Power Grid Failures

Abstract

This paper presents a probabilistic methodology to assess the risk of wind plants tripping due to faults in the transmission network. The proposed approach combines Monte- Carlo simulation with the “zone of vulnerability” concept to calculate the expected number of wind farm disconnections, considering uncertainty in both the composition of load and its representative parameters and the failure rate of transmission lines. Detailed dynamic simulations are conducted to accurately trace voltage excursion at the point of interconnection. The results of these simulations can be used to properly evaluate the possibility of a wind plant being disconnected when a fault in the grid occurs. Loads are represented by a composite load model, which includes induction motors, constant-MVA load, static models with voltagesensitive representation, and other special loads. The parameters of the load model as well as the failure rate of transmission lines are treated as random variables with a normal distribution. Numerical examples on a generic power system model were performed to demonstrate the proposed approach. Each analysis was conducted for different fault ride-through characteristics and wind farm locations. The proposed methodology can be used for different purposes. For example, it could be applied to provide technical justification for the adoption of a particular fault ride-through standard, or it could be applied to evaluate the impact of older wind plants on system reliability to assess the need to retrofit them to comply with more restrictive fault ride-though requirements.