Wind Turbine Power Conversion Virtual Impedance Control
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Solution Overview
Problem
Wind turbines face mechanical stress and electrical torque oscillations during grid faults or wind gusts, and impedance mismatches in power conversion systems can cause undesired harmonic distortions in the grid, leading to potential damage and increased costs.
Innovation Solution
A power conversion system with a source side converter, line side converter, DC link, and a controller that generates switching signals based on current or torque and a virtual impedance signal for system damping or reactive power compensation when abnormal conditions are detected, using sensors to monitor signals and adjust converter operations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a DFIG with power electronics converter is used to convert mechanical power to electrical energy, then efficient power conversion is achieved, but impedance mismatch causes sub-sync oscillations and low frequency oscillations in the grid voltage and current
Solution Approach 1:
The patent introduces a virtual impedance controller as an intermediary component between the power electronics converter and the grid. This virtual impedance acts as a mediator that decouples the converter from direct grid interactions, eliminating impedance mismatch issues while maintaining efficient power conversion. The virtual impedance controller processes current references and generates switching signals without direct grid impedance coupling.
Solution Approach 2:
The patent dynamically adjusts the virtual impedance parameters (resistive and inductive components) based on operating conditions. By changing these parameters adaptively, the system maintains optimal power conversion efficiency while compensating for varying grid conditions and preventing oscillations across different operational states.
2Productivity
If the wind turbine operates during grid fault or wind gust conditions, then power generation continues, but mismatch of electrical torque and mechanical torque causes huge mechanical stress on the tower and gearbox
Solution Approach 1:
The virtual impedance controller implements preliminary anti-action by preemptively adjusting the electrical torque through current reference modulation before mechanical torque mismatches can develop. During grid faults or wind gusts, the controller anticipates torque imbalances and compensates by adjusting the electrical torque output, preventing huge mechanical stress on the tower and gearbox while maintaining power generation continuity.
3Productivity
If electrical torque oscillations occur, then power conversion continues, but the mechanical system's lifetime is influenced and costs increase
Solution Approach 1:
The patent implements a feedback mechanism where the virtual impedance controller continuously monitors the actual current and compares it with the reference current. This feedback loop detects torque oscillations and automatically adjusts the switching signals to eliminate oscillations, protecting the mechanical system from fatigue damage while maintaining continuous power conversion operation.
Data Source
AI summary
A system includes a source side converter for being electrically coupled to a generator of a power source, a line side converter for being electrically coupled to a power network, a DC link coupled between the source side converter and the line side converter, and a controller for generating source side switching signals based on a current or torque of the generator and a virtual impedance signal for system damping or reactive power compensation when at least one detected signal of the system is not normal. A method for controlling the system is also included.