DFIG Wind Turbine Frequency Modeling for Grid Inertia Support
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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 and spatial variation in modern power systems.
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 adjustments through PI controllers to stabilize grid frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If renewable power generation penetration is increased, then power system transformation and modernization are advanced, but frequency dynamics stability deteriorates due to weak inertia characteristics
Solution Approach 1:
The patent introduces virtual inertia control as an intermediary mechanism between renewable power generation and the power grid. The virtual inertia controller simulates the inertia effect of traditional synchronous generators by adjusting the active power output of DFIG wind turbines in response to frequency changes, thereby maintaining frequency dynamics stability while accommodating high renewable penetration.
Solution Approach 2:
The patent changes the operational parameters of DFIG wind turbines by implementing virtual inertia control that dynamically adjusts active power output based on frequency deviation. The control scheme modifies the power-angle relationship and inertia characteristics of the wind turbine, transforming it from a passive load-following device to an active frequency-supporting resource.
2Measurement precision
If simplified transient model of DFIG wind turbine is developed, then frequency dynamics analysis capability is improved, but model complexity is reduced
Solution Approach 1:
The patent extracts the essential frequency dynamics characteristics of DFIG wind turbines by developing a simplified transient model that focuses only on the critical elements affecting frequency response. The model extracts the virtual inertia effect and power-frequency relationship while omitting detailed control loop dynamics and electrical transients, achieving accurate frequency dynamics analysis with reduced complexity.
Solution Approach 2:
The patent segments the DFIG wind turbine system into distinct functional components for modeling: mechanical subsystem, electrical subsystem, and virtual inertia control subsystem. This segmentation allows the complex system to be analyzed through modular simplified models, where each segment can be independently characterized and then integrated for overall frequency dynamics analysis.
3Reliability
If virtual inertia control scheme is implemented, then frequency support capability is improved, but control system complexity increases
Solution Approach 1:
The patent implements a universal virtual inertia control scheme that can be applied to DFIG wind turbines operating under different conditions (MPPT mode, constant power mode, etc.). The control architecture uses a standardized frequency-feedback mechanism that works across various operational scenarios, providing consistent frequency support capability without requiring separate control strategies for each operating mode.
Solution Approach 2:
The patent employs feedback control where the virtual inertia controller continuously monitors frequency deviation and adjusts active power output accordingly. The feedback mechanism uses frequency deviation as the control input and active power adjustment as the control output, creating a closed-loop system that automatically maintains frequency stability without requiring complex predictive algorithms or multiple control layers.
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.