DFIG Rotor Converter State Feedback for SSCI Oscillation Damping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for mitigating sub-synchronous control interaction (SSCI) in doubly fed induction generators (DFIG) are limited in their ability to efficiently dampen oscillations and require significant changes to the wind turbine power system, making them inefficient and inflexible.
Innovation Solution
A state feedback controller is implemented to control the rotor side converter of a DFIG, utilizing multiple states and feedback structures to make the system passive in a predefined frequency range, thereby damping oscillations without additional controllers or modifying reference values, ensuring robustness across varying grid configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to mitigate sub-synchronous control interaction, then some damping effect is achieved, but the system requires significant changes to the wind turbine power system structure
Solution Approach 1:
The patent implements a feedback mechanism where the converter controller continuously monitors system oscillations and adjusts converter control parameters in real-time to provide damping. The feedback loop detects sub-synchronous oscillations and modifies the converter's impedance characteristics dynamically, eliminating the need for structural changes to the power system while achieving reliable oscillation damping.
Solution Approach 2:
The patent changes the operational parameters of the converter controller, specifically adjusting impedance parameters and control gains based on detected oscillation frequencies. By dynamically modifying these parameters, the system achieves effective damping without requiring physical structural changes to the wind turbine power system architecture.
2Productivity
If series capacitors are added to compensate for line impedance, then line capacity is boosted, but sub-synchronous oscillations are introduced
Solution Approach 1:
The patent converts the harmful sub-synchronous oscillations generated by series capacitor compensation into a controllable phenomenon. By detecting these oscillations and using them as feedback signals, the converter controller adjusts its impedance to provide counteracting damping forces, thereby transforming the harmful oscillatory effect into a basis for active damping control.
Solution Approach 2:
The converter controller acts as an intermediary between the series capacitor compensation system and the DFIG. It mediates the interaction by dynamically adjusting converter parameters to counteract the harmful effects of series capacitor-induced oscillations while preserving the beneficial line capacity enhancement.
3Reliability
If additional controllers or reference value modifications are implemented to damp oscillations, then oscillation damping is achieved, but the control structure becomes more complex
Solution Approach 1:
The patent makes the existing converter controller multi-functional by enabling it to perform both its primary power conversion function and oscillation damping function simultaneously. Through parameter adaptation based on detected oscillations, the single controller handles multiple tasks without requiring additional dedicated damping controllers, thus avoiding control structure complexity.
Solution Approach 2:
The converter controller performs self-adjustment by automatically detecting oscillations and modifying its own control parameters. This self-service capability eliminates the need for external or additional controllers, as the existing controller adapts its behavior to provide damping while maintaining its primary functions.
Data Source
AI summary
A control system for controlling the operation of a doubly fed induction generator of an electrical power system, such as a wind turbine, is provided. A rotor side converter coupled to a rotor of the DFIG is controlled by the control system. The control system includes an outer controller to generate a reference value for a control variable in accordance with which the operation of the DFIG is to be controlled and an inner controller that receives the reference value and provides feedback control of the rotor side converter. The inner controller is a state feedback controller obtains at least one state of the power system or the power grid that is different from the control variable. The control structure of the state feedback controller causes the electrical power system to act as a passive system at least in a predefined frequency range.