Active Filter Voltage Control for Fast Resonance Suppression
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Solution Overview
Problem
Existing active filters in electrical systems are slow to respond to resonant behavior, leading to performance degradation and potential system shutdowns due to resonance-induced voltage fluctuations, especially caused by harmonic frequencies like 7th and 11th order, which can result in overheating, equipment damage, and reduced motor lifespan.
Innovation Solution
An active filter system that rapidly responds to resonant behavior by measuring voltage directly on a conductor between the electrical system and a capacitor, using a biquadratic filter to compute compensating currents, and employing Pulse Width Modulation (PWM) controlled by time-domain signals, eliminating the need for Fast Fourier Transform (FFT) calculations to reduce latency and provide instantaneous compensating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fast Fourier Transformation (FFT) is used to compute compensating currents, then frequency analysis capability is improved, but response time deteriorates due to computational latency
Solution Approach 1:
The patent extracts only the necessary frequency information (resonant frequencies) directly from the voltage signal using a frequency-to-voltage conversion circuit, eliminating the need for comprehensive FFT processing. This selective extraction maintains frequency analysis capability while dramatically reducing computational latency.
Solution Approach 2:
The patent replaces the computational FFT process with an analog frequency-to-voltage conversion circuit. This substitution transforms a computationally intensive digital process into a direct analog measurement, achieving real-time frequency detection without mathematical transformation delays.
2Reliability
If active filter responds rapidly to resonance, then resonance suppression effectiveness is improved, but system complexity increases due to additional measurement and control circuitry
Solution Approach 1:
The patent introduces a frequency-to-voltage conversion circuit as an intermediary between the voltage signal and the control system. This intermediary directly translates frequency information into controllable voltage signals, simplifying the control architecture while enabling rapid resonance detection and suppression.
Solution Approach 2:
The patent changes the measurement parameter from time-domain current analysis to frequency-domain voltage analysis. By measuring voltage at different frequencies and converting frequency information to voltage control signals, the system achieves rapid resonance response with simpler circuitry.
3Measurement precision
If current measurement is used to detect resonance, then measurement capability is improved, but response speed deteriorates due to current buildup delay
Solution Approach 1:
The patent inverts the measurement approach by measuring voltage instead of current. Since voltage responds instantaneously to frequency changes without the inductive delay inherent in current measurement, this inversion enables immediate resonance detection and rapid compensating current generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively suppresses resonance by providing rapid compensating currents, reducing energy consumption, prolonging active filter lifespan, and efficiently handling resonant behavior in power grids, thereby preventing performance degradation and equipment damage.
Implementation Method 1
a capacitor (13) adapted to attract alternating currents having frequencies above the utility frequency of the electrical system to ground
Implementation Method 2
An active filter is in principle a microprocessor controlled amplifier which is connected to the power grid, and which is arranged to sense and compensate the load's current consumption
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A control unit (16) for an active filter (1) for reducing resonance in an electric system (2) is provided. The electric system (2) comprises a power source (20) distributing an alternating current (AC1) to an AC conductor (21) connected to a power consuming unit (22) for distributing the AC to the power consuming unit. The active filter (1) comprises a DC power source (10) and a DC conductor (15''; 3) connecting the DC power source (10) to the AC conductor (21). The control unit (16) comprises: a voltage measurement unit (17') adapter to create a voltage signal on the basis of a measured voltage; a computing unit (17'') adapted to compute, using a biquadratic filter, a first compensating current on the basis of the voltage signal for reducing resonance in the electric system (2); and a switching system (17''') placed between the DC power source (10) and the DC conductor (15''; 3) for creating the calculated first compensating current.