Power Converter Controller Harmonic Compensation
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Solution Overview
Problem
In closed loop control systems, particularly in power converters, a finite phase delay is introduced due to the time lag between sampling feedback signals and updating the switching pattern, which affects control loop stability and introduces harmonic currents, especially in applications like wind turbines and network-connected PWM bridges.
Innovation Solution
A controller that includes a harmonic compensation signal in the control signal to reduce higher harmonics originating from the time delay, allowing for updated switching patterns without prolonging the delay artificially, and using a modulation signal generator and compensation generator to create a summing signal that compensates for these harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the switching pattern is updated frequently to reduce phase delay, then control loop stability is improved, but higher harmonics are introduced in the output power
Solution Approach 1:
The patent identifies that updating the switching pattern at non-zero vector midpoints introduces higher harmonics, but this same approach reduces phase delay. The invention converts this harmful effect by introducing a harmonic compensation signal that actively counteracts the introduced harmonics, thereby allowing the beneficial reduced phase delay to be realized without the harmful harmonic distortion
Solution Approach 2:
The controller proactively applies a harmonic compensation signal before the harmonic distortion can significantly degrade performance. By calculating and applying the compensation signal based on predicted harmonic content from non-standard switching updates, the system prevents rather than merely reacts to harmonic problems
2Object-generated harmful factors
If multiple current samples are taken during a PWM period to achieve good attenuation of harmonic currents, then harmonic attenuation is improved, but a finite phase delay is introduced in the control loop
Solution Approach 1:
The system performs preliminary harmonic compensation by calculating the expected harmonic content from multiple samples and applying a compensation signal in advance. This allows the use of multiple samples for accurate harmonic attenuation while the pre-calculated compensation signal counteracts the phase delay effects before they manifest in the output
Data Source
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AI summary
There is provided a controller (116) for a converter (102) and a respective method of operating such a controller (116). The converter (102) receives an input power and provides an output power by a switching operation wherein in an embodiment the output power has at least two phases. In accordance with embodiments, the controller (116) comprises an input (118) for receiving a feedback signal (114) depending on the output power of the converter (102); and an output for providing a control signal (122) to the converter (102) to thereby control the switching operation of the converter (102), the control signal (122) corresponding to a switching pattern that is updated in response to the feedback signal (114); the control signal (122) including an harmonic compensation signal (123) which reduces higher harmonics in the output power, the higher harmonics originating from a time delay between taking the feedback signal (114) and the updating of the switching pattern.