Analysis of the Implication of Current Limits in Grid Forming Wind Farm

TL;DR

This paper investigates the modeling accuracy and stability challenges of grid forming control in wind farms, especially during current limiting events and grid phase jumps, to improve system stability in weak grid conditions.

Contribution

It evaluates the adequacy of aggregated GFC-WF modeling and analyzes synchronization stability issues during current limiting in wind turbines.

Findings

Aggregated GFC-WF modeling can capture key dynamics.

Current limiting can cause loss of synchronization stability.

Grid phase jumps challenge GFC stability during operation.

Abstract

There is an ongoing trend of reduction in short circuit power at the grid connection point due to decommissioning of synchronous generation plants causing system strength issues in wind power plants. Whereas wind power plant rating and export cable length are increasing, further weakening the system strength and accompanied by stability challenges. Under such a scenario, a grid forming control demonstrated to operate in a weaker system has value creation potential for application in wind turbine generators. In addition, the grid forming control can also enable a wind power plant to operate in islanded mode, provide inertially and phase jump active power support. However, the application of grid forming control has challenges because grid forming control applied to a power converter (GFC) has a voltage source behavior and does not stiffly control the grid side active power and thus requires a separate current limiting mechanism. However, there could be potential challenges in maintaining the synchronism of GFC when the current limit is triggered, particularly during the grid voltage phase jump event. Modeling and capturing such a phenomenon is a challenge in a wind farm with many wind turbines. To that end, this paper investigates the modeling adequacy of the aggregated GFC-WF to a single GF-WTG of total WF rating in capturing GFC-WF dynamics. The challenges related to loss of synchronization stability when one or more wind turbine generators enter current limited operation during a grid phase jump events are also evaluated in this paper.