Wind Turbine Grid Frequency Detection Under Voltage Disturbances
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Solution Overview
Problem
Current methods for detecting and regulating power grid frequency in wind turbines face challenges in precision, speed, and adaptability, particularly due to disturbances from filter capacitor switching, sudden power changes, high-voltage ride-through, and low-voltage ride-through, leading to misresponse in inertia and primary frequency regulation.
Innovation Solution
A method and apparatus that convert three-phase voltage into two-phase voltage, decouple and filter positive and negative sequence components to obtain orthogonal voltage components, allowing for precise detection of power grid frequency and its change rate, and use this information to control wind turbine power for effective frequency regulation without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional frequency detection methods are used in wind turbines, then the system structure remains simple, but the detection precision and response speed are insufficient under grid disturbances
Solution Approach 1:
The patent replaces traditional mechanical frequency detection methods with a signal processing-based approach using coordinate transformation (Clark and Park transformations) and phase-locked loop technology. This substitution enables high-precision frequency detection by converting three-phase voltage signals into rotating reference frame components, allowing accurate extraction of frequency information even under distorted grid conditions without requiring additional hardware sensors.
Solution Approach 2:
The patent introduces intermediate signal processing steps including Clark transformation to convert three-phase signals to two-phase stationary coordinates, followed by Park transformation to rotate into synchronous rotating coordinates. These intermediary transformations serve as mathematical mediators that decouple positive and negative sequence components, enabling precise frequency detection while maintaining system simplicity through software-based processing.
2Reliability
If wind turbine participates in frequency regulation, then grid frequency stability improves, but misresponse occurs under voltage disturbances such as filter capacitor switching and ride-through events
Solution Approach 1:
The patent applies preliminary anti-action by introducing a disturbance detection and identification mechanism that anticipates harmful effects before they cause misresponse. The system continuously monitors voltage signals for characteristics of filter capacitor switching, high-voltage ride-through, and low-voltage ride-through events. When disturbances are detected, the control system preemptively adjusts frequency regulation actions to prevent misresponse, ensuring reliable operation under varying grid conditions.
Solution Approach 2:
The patent implements feedback control by continuously comparing detected frequency and voltage conditions against reference values and adjustment thresholds. The phase-locked loop provides real-time feedback on frequency deviations, while the disturbance detection mechanism feeds back information about grid conditions to modulate the frequency regulation response. This closed-loop feedback ensures accurate frequency regulation while avoiding misresponse to transient disturbances.
3Measurement precision
If high-precision frequency detection is implemented, then frequency regulation accuracy improves, but detection speed may be reduced due to complex signal processing
Solution Approach 1:
The patent applies preliminary action by pre-configuring the coordinate transformation matrices and phase-locked loop parameters before actual frequency detection begins. The Clark and Park transformation matrices are pre-calculated based on expected operating conditions, and the phase-locked loop is pre-synchronized to the nominal grid frequency. This preliminary preparation enables the system to rapidly process incoming voltage signals and achieve high-precision frequency detection without computational delays during transient events.
Data Source
AI summary
A Method and an apparatus for detecting a power grid frequency are provided. The method comprises: converting a collected three-phase voltage at a point of common coupling into a two-phase voltage; transforming the two-phase voltage to obtain a voltage positive sequence component to be decoupled and a voltage negative sequence component to be decoupled; decoupling the voltage positive sequence component to be decoupled and the voltage negative sequence component to be decoupled, and filtering a decoupled voltage positive sequence component to obtain a voltage positive sequence fundamental component; performing inverse transformation on the voltage positive sequence fundamental component to obtain a set orthogonal voltage components in a two-phase stationary coordinate system; obtaining a phase angle of a power grip based on the set orthogonal voltage components; and obtaining a power grip frequency. A method and an apparatus for regulating a power grip frequency are further provided.