Power Converter Switching Control for LC Resonance Distortion
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Solution Overview
Problem
Existing power conversion devices suffer from distortion of input current due to resonance phenomena in LC resonant circuits, which are not adequately addressed by proportional control, leading to insufficient reduction of waveform disturbances.
Innovation Solution
A power conversion device that includes a controller to monitor and compensate the switching operation of a power conversion unit based on the frequency component closest to the resonant frequency of the DC unit, using integral control and Fourier transform to reduce the frequency component causing distortion in the input current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If proportional control is used to compensate the manipulated variable based on the voltage across the reactor, then the control operation is simple, but the offset in proportional control causes insufficient reduction of input current distortion
Solution Approach 1:
The patent introduces feedback control by monitoring the voltage across the reactor and using it to compensate the manipulated variable. The controller continuously adjusts the switching operation based on the detected reactor voltage, creating a closed-loop system that eliminates the offset problem of proportional control and reduces input current distortion effectively
Solution Approach 2:
The patent changes the control parameter from simple proportional adjustment to compensated manipulation variable adjustment based on reactor voltage. By dynamically adjusting the manipulated variable according to the detected reactor voltage, the system achieves better control precision and reduces waveform distortion while maintaining operational simplicity
2Quantity of substance
If the capacitance of the capacitor in the LC filter is reduced to 1/100 or less of the conventional one to eliminate electrolytic capacitors, then the device size and cost are reduced, but resonance phenomena occur causing distortion of input current
Solution Approach 1:
The patent converts the harmful resonance phenomenon into a beneficial control target. By detecting the reactor voltage which reflects the resonance state, the system uses this information to compensate the manipulated variable, thereby eliminating the harmful distortion effects while maintaining the low-capacitance design benefits
Solution Approach 2:
The patent uses the reactor voltage as an intermediary parameter to bridge the capacitor and the control system. The reactor voltage serves as a mediator that provides information about the resonance state, enabling the controller to adjust the switching operation and eliminate distortion without requiring large capacitor values
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 solution effectively reduces the frequency component causing distortion in the input current, stabilizes the compensation operation, and prevents excessive influence on the switching operation, thereby minimizing input current distortion.
Implementation Method 1
a DC unit (12) that includes a capacitor (12a) and a reactor (12b), the capacitor (12a) smoothing a ripple caused by the switching operation in the power conversion unit (13)
Implementation Method 2
compensates a manipulated variable of control of the switching operation in the power conversion unit (13) in accordance with at least a frequency component closest to a resonant frequency (fLC) of the DC unit (12)
Data Source
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AI summary
A controller (50) controls a switching operation in a power conversion unit (13). The controller (50) monitors an indicator value correlated with a disturbance that distorts an input current (idc) supplied to the power conversion unit (13), and compensates a manipulated variable of control of the switching operation in the power conversion unit (13) in accordance with at least a frequency component closest to a resonant frequency (fLC) of a DC unit (12) among a plurality of frequency components that are included in variations in the indicator value and that correspond to integral multiples of a power source frequency (fp) of an AC power source (20).