Unified Controller for Wind Turbine Grid Stability
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Solution Overview
Problem
Wind turbine generators face control instability due to weak and resonant grid connections, which can lead to sub-synchronous resonance modes and interaction with power electronic converter controllers, causing instability in both variable frequency operation and super synchronous frequencies.
Innovation Solution
A unified controller system that dynamically parses and directs torque and DC link voltage control signals between generator side and grid side converters using multivariable control strategies, such as frequency and amplitude parsing, to stabilize the system and mitigate the effects of weak or resonant grid conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If series compensation is used to compensate for weak grid connection, then transmission capability is increased, but sub-synchronous resonance modes are excited causing control instability
Solution Approach 1:
The patent introduces an intermediary control mechanism that mediates between the series compensation system and the power electronic converter controllers. The controller monitors grid conditions and dynamically adjusts control parameters to prevent resonant mode coupling, acting as a buffer that allows series compensation to enhance transmission capability while blocking the propagation of harmful resonance effects to the converters.
Solution Approach 2:
The patent dynamically changes control parameters based on grid conditions. The controller detects weak or resonant grid conditions and adjusts converter control parameters in real-time to avoid exciting sub-synchronous resonance modes. This parameter adaptation allows the system to maintain stable operation while utilizing series compensation for improved transmission capability.
2Productivity
If variable frequency operation is used in wind turbine generators, then efficiency is improved, but control complexity increases due to resonance risks
Solution Approach 1:
The patent employs dynamic control strategies that adapt to variable frequency operation. The controller dynamically adjusts control parameters based on operating conditions, allowing the wind turbine generator to operate efficiently at variable frequencies while automatically preventing excitation of resonant modes. This dynamic adaptation manages control complexity by using condition-based parameter adjustment rather than fixed complex control structures.
Data Source
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AI summary
A power generating system (60) includes an energy source (12) coupled to a DC link (28) through a first power converter (14) and a second power converter (16) to couple the DC link to a power grid (22). A first controller (82) in the power generating system regulates voltage on the DC link and a second controller (80) regulates a parameter of the energy source. A dynamic parsing controller (81) coupled to the first power converter and the second power converter selectively parses the output signals of the first and second controllers and generates operating commands for the first and second power converters based at least in part on the parsed output signals.