DFIG Compensator for Sub-Synchronous Oscillation Suppression
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Solution Overview
Problem
Sub-synchronous oscillations in power generation systems, particularly in double-fed induction generators (DFIG), cause instability and damage due to negative damping effects, leading to operational reliability issues and equipment damage.
Innovation Solution
A power generation system incorporating a double-fed induction generator, a power converter, and a controller with a rotor side and grid side converter, where the controller includes a compensator with a specific transfer function to counteract the negative resistance effect and suppress sub-synchronous oscillations, using damping parameters to enhance internal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If series compensation components are added to the transmission line to increase power transfer capability, then the power transfer capability is improved, but sub-synchronous oscillations occur causing system instability
Solution Approach 1:
The patent introduces a compensator as an intermediary device between the DFIG and the series-compensated transmission line. This compensator acts as a mediator that blocks the harmful sub-synchronous oscillations while allowing the series compensation to remain in place for enhancing power transfer capability. The compensator includes control circuits that detect and suppress SSO before it can affect the transmission line stability.
Solution Approach 2:
The patent converts the harmful negative damping effect into a beneficial control action. By detecting the sub-synchronous oscillations and using active power filtering with the compensator, the system transforms the harmful oscillatory energy into controllable electrical signals that can be actively suppressed. The control system uses the oscillation detection to generate counteracting control signals that stabilize the system.
2Productivity
If a double-fed induction generator is used to enable variable speed operation, then the energy capture efficiency is improved, but negative damping effect causes sub-synchronous oscillation instability
Solution Approach 1:
The patent implements dynamic control of the DFIG through the compensator that adjusts control parameters in real-time based on operating conditions. The variable impedance control and active power filtering dynamically adapt to different wind speeds and generator operating points, maintaining stability across the entire operating range while preserving the benefits of variable speed operation for energy capture.
Solution Approach 2:
The patent employs feedback control mechanisms where the compensator continuously monitors the electrical parameters of the DFIG and transmission line, detects sub-synchronous oscillations, and adjusts control signals to suppress the oscillations. The feedback loop includes oscillation detection, analysis, and active compensation that adapts to changing system conditions to maintain stability.
Data Source
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AI summary
The present invention discloses a power generation system 1 including a double-fed induction generator 10, a power converter 20, and a controller 30. The double-fed induction generator 10 includes a rotor 31 and a stator 12 coupled to a grid 50. The power converter 20 includes a rotor side converter 31 coupled to the rotor of the generator, a grid side converter 22 coupled to the grid, and a DC bus coupled between the rotor side converter and the grid side converter. The controller 30 includes a rotor side controller 31 for controlling the rotor side converter and a grid side controller 32 for controlling the grid side converter. The rotor side controller 31 includes a compensator 60 having a transfer function and configured to counter a negative resistance effect of the generator to suppress sub-synchronous oscillations. The present invention further discloses a system for suppressing sub-synchronous oscillations and a method for controlling operation of a power system.