Converter Control for Interharmonic Pendulum Moments
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Solution Overview
Problem
Existing methods for operating converters coupling electrical machines to AC voltage networks face challenges in managing interharmonic pendulum moments, which can lead to critical operating states due to incomplete decoupling between network and machine sides, requiring flexible load handling and precise mechanical property measurements.
Innovation Solution
A method that determines a torque-related machine current component, calculates the actual machine torque, filters the torque difference using a bandpass filter tuned to natural frequencies, and generates a compensation signal to superimpose on control signals, allowing for interharmonic compensation without requiring mechanical data of the electrical machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a converter couples an electrical machine to an AC voltage network, then energy conversion between network and machine is achieved, but interharmonic pendulum moments occur due to incomplete decoupling
Solution Approach 1:
The patent detects interharmonic pendulum moments and generates compensation signals that superimpose on control signals to actively counteract the harmful moments. By converting the harmful oscillations into detectable signals and then into compensating actions, the system transforms the problem into a solvable control task, eliminating the pendulum moments while maintaining energy conversion functionality
Solution Approach 2:
The patent implements a feedback mechanism where pendulum moment detection signals are continuously monitored, processed through bandpass filters tuned to natural frequencies, and used to generate real-time compensation signals. This closed-loop feedback system dynamically adjusts control signals to counteract detected interharmonic oscillations, resolving the contradiction between maintaining power conversion and eliminating harmful pendulum moments
2Measurement precision
If mechanical property measurements are used to compensate for pendulum moments, then compensation precision is improved, but device complexity and measurement requirements increase
Solution Approach 1:
The patent introduces electrical current measurements as an intermediary substitute for direct mechanical property measurements. By measuring electrical quantities (currents) that are easily obtainable and processing them through bandpass filters and compensation algorithms, the system achieves pendulum moment compensation without requiring complex mechanical sensors or direct mechanical data, thus reducing device complexity while maintaining detection accuracy
Solution Approach 2:
The patent replaces mechanical measurement systems with electrical measurement and processing systems. Instead of using mechanical sensors to directly measure pendulum moments or mechanical properties, the system uses electrical current measurements combined with signal processing (bandpass filtering, frequency analysis) to detect and compensate for interharmonic oscillations, substituting a simpler electrical system for a complex mechanical measurement system
Data Source
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AI summary
The invention relates to a method for operating an inverter (10, 48, 50) for coupling an electric machine (12, 46) which is designed for operation on AC voltage, with an AC voltage network (16), comprising the steps: - determining a torque -related machine current component composed of electrical machine currents of the electrical machine (12), - detecting an actual value for a magnetic flux, - determining an actual value of a machine torque of the electric machine (12, 46) by linking the detected magnetic flux to the torque-related machine current component, - determining a torque difference between the actual value of the machine torque and a setpoint value of the machine torque of the electric machine (12, 46), - filtering the torque difference by means of a bandpass filter (28) which is tuned to a machine-side natural frequency, - determining a compensation signal (30) by processing a filter output signal (32) of the bandpass filter (28), and superimposing the compensation signal (30) on the network control signal and/or the machine control signal.