Harmonic Control of Converter via Intermediary Deviation
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Solution Overview
Problem
Conventional harmonic control in vector-controlled drives for permanent magnet synchronous generators, particularly in wind turbines, faces challenges such as high control effort, poor dynamic performance, and instabilities due to the coexistence of fundamental and harmonic current controllers, which results in inadequate control of low harmonic frequencies and increased 2f harmonic levels during fault-tolerant operations.
Innovation Solution
An arrangement and method for determining an operation parameter reference for a generator side converter portion, which includes arithmetic elements to derive harmonic and fundamental current errors, and controllers to determine reference current deviations, allowing for a modified fundamental current error to be used in determining the operation parameter reference, thereby enabling effective control of multiple harmonics and improving system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fundamental current controller and a harmonic current controller are added in parallel to provide final control voltage to converter drive, then harmonic control capability is improved, but control stability deteriorates and dynamics become slow for lower harmonic orders
Solution Approach 1:
The patent introduces an intermediary variable (harmonic current reference deviation) that mediates between the harmonic current controller and the fundamental current controller. This deviation is added to the fundamental current reference before being processed by the fundamental current controller, allowing harmonic control without direct parallel connection that causes instability.
Solution Approach 2:
The patent merges the harmonic control function into the existing fundamental current control structure. Instead of separate parallel controllers, the harmonic current reference deviation is integrated into the fundamental current reference signal, combining both control functions through a unified control path that maintains stability.
2Reliability
If additional harmonic current controllers are added in parallel with fundamental current controller, then harmonic control is enabled, but control effort increases and dynamic performance deteriorates
Solution Approach 1:
The harmonic control is merged into the fundamental control loop by adding the harmonic current reference deviation to the fundamental current reference. This unified approach eliminates the need for separate parallel control paths, reducing overall control complexity and improving dynamic response.
Solution Approach 2:
The patent extracts only the necessary harmonic correction component (harmonic current reference deviation) from a full harmonic control implementation. This selective extraction provides adequate harmonic control without the burden of complete harmonic analysis, improving computational efficiency and dynamic performance.
3Loss of time
If feed-forward path based on machine model is added to improve transient performance, then voltage demand for current reference is determined, but implementation complexity increases due to large number of parameters
Solution Approach 1:
The patent extracts and utilizes only the essential parameter (harmonic current reference deviation) needed for harmonic control, avoiding the need to implement a complete machine model with numerous parameters. This selective approach provides sufficient transient performance improvement without excessive complexity.
Solution Approach 2:
The patent changes the control approach from using multiple machine model parameters to using a single derived parameter (harmonic current reference deviation). This parameter transformation simplifies the feed-forward path while maintaining its effectiveness in improving transient response.
Data Source
AI summary
An arrangement for determining an operation parameter reference for controlling a generator side converter portion coupled to a generator is provided, including: at least one arithmetic element configured to derive at least one harmonic current error by subtracting a generator output current from at least one harmonic current reference; at least one harmonic current controller configured to determine at least one harmonic reference current deviation based on the harmonic current error; another arithmetic element configured to derive a fundamental current error by subtracting the generator output current from a sum of a fundamental current reference and the at least one harmonic current reference; still another arithmetic element configured to determine a modified fundamental current error as a sum of the fundamental current error and the harmonic reference current deviation; a fundamental current controller adapted to determine the operation parameter reference based on the modified fundamental current error.