DFIG Wind Turbine Transient Model for Grid Frequency Analysis
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Solution Overview
Problem
The increasing penetration of renewable power generation, particularly from doubly-fed induction generator (DFIG) wind turbines, complicates power system frequency dynamics due to weak inertia characteristics, and existing models fail to effectively analyze the contribution of DFIG wind turbines to frequency stability without frequency-supporting control schemes.
Innovation Solution
A simplified transient model of DFIG wind turbines is developed, incorporating an equivalent circuit model and an equivalent rotor motion model, which includes three state variables to quantify contributions to post-disturbance frequency in both center of inertia and frequency spatial variation frames, allowing for stabilization of power grid frequency through proportional-integral controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detailed model of DFIG wind turbine is used for frequency dynamics analysis, then the accuracy of frequency contribution assessment is improved, but the model complexity and computational burden increase significantly
Solution Approach 1:
The patent extracts only the essential dynamic characteristics of the DFIG wind turbine that are relevant to frequency dynamics analysis. By identifying and retaining only the critical state variables and dynamic behaviors that influence frequency response, the model achieves sufficient accuracy for frequency contribution assessment while eliminating unnecessary complex details that would increase computational burden.
Solution Approach 2:
The patent applies local quality by focusing modeling efforts on specific aspects of the DFIG system that are most important for frequency dynamics. Rather than modeling the entire system with equal detail, the approach concentrates computational resources on the rotor motion, electromagnetic torque, and power output characteristics that directly affect frequency response, while using simplified representations for other components.
2Ease of operation
If the DFIG wind turbine operates in MPPT mode without frequency-supporting control schemes, then the ease of operation is improved, but the frequency stability of the power system deteriorates due to weak inertia characteristics
Solution Approach 1:
The patent implements feedback mechanisms where the simplified transient model continuously monitors the operational state of the DFIG wind turbine and provides information about its frequency contribution. This feedback enables the development of control strategies that can adjust operating parameters to provide frequency support while maintaining MPPT operation, thus resolving the contradiction between operational simplicity and frequency stability.
Solution Approach 2:
The patent utilizes parameter changes by modifying the operating point parameters of the DFIG wind turbine based on system frequency conditions. By dynamically adjusting parameters such as rotor resistance, capacitor reactance, or control loop gains in response to frequency deviations, the system can provide inertia-like support and frequency regulation while operating in MPPT mode, thereby maintaining both ease of operation and frequency stability.
Data Source
AI summary
A method implemented in a power grid including a DFIG wind turbine is provided. The method includes: assuming the DFIG wind turbine to be operated in a MPPT mode; generating a simplified transient model of the DFIG wind turbine, the simplified transient model including an equivalent circuit model, and an equivalent rotor motion model in a nonlinear form; linearizing the equivalent rotor motion model in the nonlinear form to be an equivalent rotor motion model in a linear form with respect to a steady-state operating point of the DFIG wind turbine; and determining a first contribution and a second contribution of the DFIG wind turbines to a post-disturbance frequency of the power grid, in a center of inertia (COI) frequency frame and in a frequency spatial variation frame, respectively, by incorporating the simplified transient model of the DFIG wind turbine into a frequency dynamics analysis.