Wind Turbine Converter Mode Switching for Grid Resonance Control
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Solution Overview
Problem
Large-scale wind turbine generator systems face resonance issues with the power grid due to unadjusted converter impedance characteristics, particularly when series compensation capacitors are operational or removed, leading to unstable operation.
Innovation Solution
A method and apparatus for controlling wind turbine converters to switch between voltage-source and current-source operation modes based on super-synchronous oscillation components and phase angles of grid-side voltage and current, reducing resonance by adjusting operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the converter operates in grid-following mode with capacitive output impedance, then active-power controlling is achieved by injecting active current in phase with grid voltage, but the converter is prone to resonate with inductive transmission line causing unstable operation
Solution Approach 1:
The patent implements dynamic switching between grid-following and grid-forming modes based on detected grid conditions. The converter dynamically adjusts its output impedance characteristics by changing operation modes, transforming from fixed capacitive impedance to variable impedance that can be inductive or capacitive depending on grid state, thereby avoiding resonance and ensuring stable operation
Solution Approach 2:
The patent changes the operational parameters of the converter by switching between two distinct operation modes. In grid-following mode, the converter operates with capacitive output impedance for standard power control. When resonance risk is detected, it switches to grid-forming mode with inductive output impedance, fundamentally changing the impedance parameter to eliminate resonance with the transmission line
2Power
If series compensation capacitor is put into use making transmission line capacitive, then power transmission capability is improved, but the converter may resonate with capacitive line causing unstable operation
Solution Approach 1:
The patent uses feedback control to detect changes in transmission line impedance characteristics caused by series compensation capacitor engagement. When the line becomes capacitive, the system receives feedback about this condition and automatically switches the converter from grid-forming mode to grid-following mode, preventing resonance while allowing the series compensation to maintain improved power transmission capability
Data Source
AI summary
A wind turbine generator set, and a control method and apparatus for a wind power converter are provided. The control method includes extracting a super-synchronous oscillation component of a grid-side voltage of a wind power converter and a super-synchronous oscillation component of a grid-side current of the wind power converter. The control method also includes determining a phase angle of equivalent impedance of the wind power converter based on the super-synchronous oscillation component of the grid-side voltage and the super-synchronous oscillation component of the grid-side current. The control method further includes setting an operation mode of the wind power converter based on the super-synchronous oscillation component of the grid-side voltage and/or the super-synchronous oscillation component of the grid-side current, and the phase angle.