Active Filter Control for Wind Converter Oscillation Damping
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Solution Overview
Problem
Existing converter systems in wind turbines generate low-frequency harmonic voltage sources that cause oscillations and resonances, leading to grid code compliance issues and potential disconnection from the utility grid, with existing solutions either requiring additional hardware or complicating the main control loop.
Innovation Solution
Implement an active filter system in software or hardware that works independently of the main converter controller, using existing voltage and current measurements to dampen low-frequency harmonic oscillations and shape converter impedance at specific frequencies, without requiring bandpass filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active filter system is implemented to dampen low-frequency harmonic oscillations, then oscillation damping performance is improved, but device complexity increases
Solution Approach 1:
The control system is segmented into two independent parts: the main converter controller and the active filter system. The active filter system is further divided into multiple active filter portions, each targeting specific frequency ranges. This segmentation allows the active filter to be designed and tuned independently for optimal oscillation damping without redesigning the entire control system.
Solution Approach 2:
The active filter system acts as an intermediary between the converter and the grid. It processes the measurement values of current and voltage, generates appropriate control signals, and injects compensating currents to dampen oscillations. This intermediary function isolates the main converter controller from the complex oscillation damping tasks.
2Reliability
If the active filter system is integrated into the main converter controller, then control coordination is improved, but device complexity increases
Solution Approach 1:
The control architecture is segmented into independent modules: the main converter controller handles primary conversion functions, while the active filter system handles oscillation damping. These segmented modules communicate through standardized interfaces using measurement values and control signals, achieving coordination without integration.
Solution Approach 2:
The active filter system is designed to be self-sufficient, using its own set of measurement values from the existing measurement system to generate control signals. It independently processes these measurements, applies the active filter control algorithm, and produces control signals without requiring intervention or redesign of the main converter controller.
3Measurement precision
If bandpass filters are used in the active filter system, then frequency selectivity is improved, but device complexity increases
Solution Approach 1:
Physical bandpass filters are replaced with a digital signal processing approach. The active filter portions use control algorithms that process measurement values in the frequency domain, achieving frequency selectivity through computational methods rather than physical filtering components. This substitution eliminates the need for additional passive filter hardware.
Solution Approach 2:
The system achieves frequency selectivity by changing the parameters of the active filter portions, specifically their center frequencies and bandwidths. Each active filter portion is configured with specific parameters to target particular oscillation frequencies, allowing flexible frequency selection without physical filter components.
4Reliability
If multiple active filter portions are used for different frequencies, then oscillation damping coverage is improved, but device complexity increases
Solution Approach 1:
Multiple active filter portions are designed with a universal structure and control algorithm. Each portion handles a specific frequency range but uses the same fundamental approach: receiving measurement values, processing them through the active filter control algorithm, and generating control signals. This universality allows scaling to multiple frequencies without proportionally increasing overall system complexity.
Data Source
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Figure 3~4
AI summary
Damping oscillations using active filters It is described an arrangement (50) for controlling a converter (9, 15) of a power generation system, in particular a wind turbine (1), the converter being connected to a connection point (21) to a utility grid (23), the arrangement comprising: a measurement section (31) adapted to provide measurement values indicative of values of current (33) and volt- age (35) at the connection point (21); a main converter controller (27) adapted to receive the measurement values (33, 35) and to generate a main converter control signal (37) based on the measurement values; an active filter system (29) adapted to receive the measurement values (33, 35) and to generate an active filter control signal (39) based on the measurement values; an addition element (30) adapted to add the main converter control signal (37) and the active filter control signal (39) and to supply the sum signal (41) as a control signal to the converter (9, 15).