Wind Turbine Sub-Synchronous Oscillation Suppression
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Solution Overview
Problem
Modern wind turbines experience detrimental subsynchronous oscillations due to interactions with the grid, leading to resonance phenomena and torque oscillations that compromise operational safety, and increasing damping in converter controllers results in slower reaction to power changes, adversely affecting operational properties.
Innovation Solution
A second control channel with a field-oriented controller and its own coordinate conversion unit operating at a frequency lower than the mains frequency is introduced, allowing for active counteraction of subsynchronous oscillations without slowing the conventional controller, and this additional controller is designed to work in a separate frequency range to combat subsynchronous interactions effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If greater damping is incorporated into the inverter controller to prevent subsynchronous oscillations, then the threshold frequency for critical subsynchronous oscillations is raised, but the inverter reacts more slowly to changes in power requirements
Solution Approach 1:
The control system is segmented into two independent control channels: a first control channel for power control operating at grid frequency, and a second control channel for subsynchronous oscillation suppression operating at subsynchronous frequency. Each channel has its own coordinate conversion unit with appropriate frequency, allowing independent optimization without mutual interference. This segmentation enables the second channel to provide damping without slowing down the first channel's power response.
2Reliability
If a second control channel with subsynchronous frequency coordinate conversion is added, then subsynchronous oscillation suppression is improved, but the device complexity increases
Solution Approach 1:
The second control channel is integrated into the existing inverter controller hardware, sharing common components such as processors, memory, and output interfaces. The coordinate conversion unit for subsynchronous frequency reuses the same hardware resources as the grid-frequency control, allowing the controller to perform multiple functions (power control and subsynchronous damping) without proportionally increasing hardware complexity.
Data Source
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AI summary
The invention relates to a wind turbine with a wind rotor (1), a generator (2) driven by it with converter (5) for generating electrical power, which is delivered to a grid (9) via a connecting line (3), and a converter control (6) which has a first control channel (7) for controlling the power delivery to the grid (9) and for exciting the generator (2), wherein a second control channel (8) different from the first control channel (7) is provided, which is designed as a field-oriented controller and for this purpose has its own coordinate conversion unit (82) which is provided with a rotating coordinate system (θSS) with a frequency which is smaller in magnitude than the grid frequency (θ).The invention further extends to a corresponding method for operating a wind turbine, characterized by the steps of: compensating for subsynchronous vibrations by means of a second control channel (8) that performs field-oriented control; performing a separate coordinate transformation in the second control channel for the subsynchronous frequency range; outputting the signals by means of a control core; performing a separate coordinate inverse transformation at the output of the control core; and combining these output signals with output signals of the first control channel. The invention provides an improved system and an improved method for avoiding or reducing subsynchronous vibrations.