Balancing Reactive Current in DFIG Wind Turbine Stator and Inverter
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Solution Overview
Problem
During abnormal power grid events, doubly-fed induction generators (DFIGs) in wind turbine generators face excessive reactive current delivery through the stator, leading to overheating and reduced lifespan, as the majority of reactive current is handled by the stator, which is not efficiently managed by existing technologies.
Innovation Solution
A method and system for balancing reactive current between the stator and grid-side inverter of a DFIG wind turbine generator, controlling the reactive grid-side inverter current based on the overload current capability of the grid breaker to prevent stator overheating, allowing the grid-side inverter to exceed its rated current capacity during abnormal events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the majority of reactive current is delivered via the stator during abnormal power grid events, then the required amount of reactive current can be delivered to the power grid, but the stator heats to undesired temperatures with the risk of shortening the DFIG lifetime
Solution Approach 1:
The patent divides the reactive current delivery function into two separate paths: one through the stator and another through the grid-side inverter. This segmentation allows the reactive current burden to be shared between these two components, preventing excessive current concentration in the stator that would cause overheating, while still achieving the total required reactive current delivery to the power grid during abnormal events
Solution Approach 2:
The grid-side inverter serves as an intermediary component that handles a portion of the reactive current delivery. By introducing this intermediary path, the system reduces the direct reactive current burden on the stator, thereby lowering stator temperature and protecting the DFIG from thermal damage while maintaining grid support capability
Data Source
AI summary
Aspects of the present invention relate to a method for controlling an amount of reactive current provided from a wind turbine generator to a power grid during an abnormal power grid event, said wind turbine generator comprising a doubly-fed induction generator having a rotor and a stator, and a power converter coupling the rotor to the power grid, the power converter comprising a grid-side inverter, wherein the method comprises the step of balancing the reactive current provided to the power grid between a reactive stator current and a reactive grid-side inverter current, wherein the reactive grid-side inverter current is controlled in accordance with a reactive current capacity of a grid breaker receiving the reactive current provided by the grid-side inverter. Aspects of the present invention also relate to a wind turbine generator being capable of performing the method.