DFIG Converter Series Damping Circuit for Grid Fault Ride-Through
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Solution Overview
Problem
Double fed induction generators (DFIGs) face challenges in withstanding grid faults due to high transient rotor voltages and current peaks, leading to potential loss of control and damage during grid faults, particularly low voltage ride through (LVRT) conditions.
Innovation Solution
The implementation of series-connected damping resistances and bypass switching devices coupled with the DFIG rotor side converter, allowing for reduced current peaks at both the rotor and stator sides, facilitated by a damping controller that adjusts the operating mode based on grid fault occurrences and clearances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If series-connected damping resistances are added to reduce current peaks, then reliability is improved, but device complexity increases
Solution Approach 1:
The damping resistance is pre-connected in series with the rotor winding before fault occurrence. When a grid fault is detected, the bypass switch is activated to short-circuit the damping resistance, allowing it to have been prepared and connected in advance without affecting normal operation. This preliminary connection approach allows the system to quickly respond to faults without adding complex control mechanisms.
Solution Approach 2:
A bypass switch is introduced as an intermediary component between the damping resistance and the rotor winding. This switch acts as a mediator that can selectively connect or disconnect the damping resistance based on grid conditions. During normal operation, the switch bypasses the resistance; during faults, it activates the resistance to limit current peaks, thereby protecting the converter without requiring direct integration of complex protection circuits.
2Object-generated harmful factors
If damping resistance is activated during grid faults, then rotor side current peaks are reduced, but use of energy increases due to power dissipation in the resistance
Solution Approach 1:
The damping resistance is activated only periodically during grid fault conditions rather than continuously. The bypass switch controls the activation timing, enabling the resistance only when voltage sags or current peaks are detected, and deactivating it when normal operation resumes. This periodic activation minimizes energy dissipation while providing protection exactly when needed.
Solution Approach 2:
The damping resistance is used temporarily to rush through the critical fault period by limiting current peaks during the brief fault duration. Once the fault is cleared and normal operation resumes, the bypass switch immediately deactivates the resistance, allowing the system to skip the energy-intensive damping phase and return to efficient normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables continued control of the DFIG converter during grid faults, mitigating damage and improving the system's ability to support the grid by reducing rotor side current spikes and transient voltages, thus enhancing low voltage ride through capabilities.
Implementation Method 1
series-connected damping resistances and bypass switching devices coupled with the DFIG rotor side converter, by which current peaks at both the rotor side and stator side can be advantageously reduced
Data Source
AI summary
A double fed induction generator (DFIG) converter, methods and computer readable mediums are presented in which rotor side current spikes are attenuated by selectively activating at least one series damping circuit to conduct current through a series damping circuit resistance coupled in series between one or more DFIG rotor leads and a grid side converter in response to a grid fault occurrence or a grid fault clearance, and selectively bypassing the series damping circuit resistance after activating the series damping circuit.