Wind Turbine Reactive Power Control for Weak-Grid Voltage Stability
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Solution Overview
Problem
Conventional voltage control methods in renewable energy power plants, especially in weak grid environments, face challenges such as destabilization due to slow reaction times and coarse sampling rates, leading to voltage oscillations and non-compliance with grid regulations.
Innovation Solution
A method and system for fast voltage control that involves receiving a reactive power set point, determining terminal voltage deviations, generating a reactive power correction value based on high-frequency deviations, and adjusting the set point to control wind turbine generators or other renewable energy devices, using faster sampling rates to mitigate voltage instability and prevent oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a centralized control scheme is used to control voltage at the point of connection, then voltage control capability is improved, but sampling rate is too low to respond to fast changes in weak grids
Solution Approach 1:
The patent divides voltage control into two segments: centralized control for low-frequency voltage deviations and decentralized local control for high-frequency deviations. Each segment operates at its optimal sampling rate, with the local controller handling fast transients and the centralized controller managing steady-state voltage regulation.
Solution Approach 2:
The patent introduces an intermediary mechanism where the local controller acts as a bridge between the centralized controller and the power network. The local controller receives reactive power setpoints from the centralized controller and supplements them with fast corrective actions based on local voltage measurements, effectively mediating between slow centralized decisions and fast grid dynamics.
2Reliability
If individual units maintain local voltages in a decentralized control strategy, then local voltage stability is improved, but hunting between units occurs and sensitivity to tap changer movement increases
Solution Approach 1:
The patent segments the control function by frequency: the decentralized local controller handles high-frequency voltage deviations while the centralized controller manages low-frequency regulation. This segmentation prevents hunting between units by assigning each unit only local fast-response functionality, while overall system stability is maintained through centralized coordination.
Solution Approach 2:
The patent applies local quality by enabling each individual unit to have its own local voltage control capability for fast response to local disturbances, while the centralized controller provides coordinated overall management. This creates a hierarchical structure where local and global control qualities coexist without conflict.
3Reliability
If centralized control is used, then voltage control at point of connection is improved, but ability to counteract high-frequency oscillations is limited due to coarse sampling resolution
Solution Approach 1:
The patent segments voltage control by frequency spectrum: the centralized controller with coarse sampling handles low-frequency voltage regulation, while the local controller with fine sampling resolution handles high-frequency oscillations and fast transients. This segmentation allows each controller to operate at its optimal resolution.
Solution Approach 2:
The patent adds a temporal dimension to the control architecture by operating controllers at different sampling rates. The local controller samples voltage at high frequency to detect and counteract fast oscillations, while the centralized controller samples at lower frequency for steady-state regulation, creating a multi-rate control system.
Data Source
AI summary
Aspects of the present invention relate to a method of voltage control for at least one wind turbine generator configured to absorb and supply reactive power on demand, the method comprises: receiving a dispatch signal from a power plant controller indicating a reactive power set point; determining a terminal voltage level of the at least one wind turbine generator; generating a reactive power correction value based on a deviation of the terminal voltage level from a voltage set point; adjusting the reactive power set point by the reactive power correction value; and controlling the at least one wind turbine generator according to the adjusted reactive power set point.