Power Conversion Module Frequency Control for THD Reduction
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Solution Overview
Problem
Power conversion devices with multiple modules in parallel face increased Total Harmonic Distortion (THD), leading to larger, heavier, and more costly harmonic reduction devices due to waveform distortions from individual modules.
Innovation Solution
A frequency controller regulates the operating frequencies of power conversion modules to establish specific relationships, such as differences being multiples of the output AC power frequency, to minimize THD by adjusting each module's frequency within a range that optimizes the output AC power quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple power conversion modules operate in parallel with identical frequencies, then the system achieves high efficiency and easy expandability, but the Total Harmonic Distortion (THD) increases due to waveform distortion combining
Solution Approach 1:
The patent changes the frequency parameter of power conversion modules from identical to offset frequencies. Specifically, it sets the frequency of the second module to be offset from the first module by a specific amount (e.g., 50Hz for 60Hz systems), which fundamentally alters the harmonic interaction and reduces THD while maintaining system efficiency and scalability
2Object-generated harmful factors
If multiple power conversion modules operate with offset frequencies to decrease THD, then harmonic distortion is reduced, but the device complexity increases due to frequency control requirements
Solution Approach 1:
The patent simplifies the control complexity by establishing a fixed, predetermined frequency offset relationship between modules. Rather than requiring complex adaptive control, the system uses a simple parameter setting where the second module's frequency is consistently offset from the first by a specific value, making the control system manageable while effective
3Object-generated harmful factors
If THD is reduced through frequency control, then the size and cost of harmonic reduction devices can be minimized, but the manufacturing precision requirements increase for frequency regulation
Solution Approach 1:
The patent reduces manufacturing precision requirements by using a relatively large frequency offset (e.g., 50Hz for 60Hz systems). This substantial offset creates a clear separation between harmonic components, making the system less sensitive to small frequency variations and easing the precision requirements for frequency regulation hardware and software
Data Source
AI summary
The present disclosure relates to frequency control of power conversion modules for decreasing THD (Total Harmonic Distortion) in a power conversion device in which a plurality of power conversion modules operate in parallel. In one aspect of the present disclosure, an embodiment provides a power conversion device comprising a plurality of power conversion modules being connected in parallel to receive input power and provide output AC power, and a frequency controller controlling each operating frequency of the plurality of power conversion modules, wherein, the frequency controller may include a function as a first frequency regulating step for regulating each operating frequency of the plurality of power conversion modules, so that the operating frequencies of the plurality of power conversion modules have a specific relationship with each other.