Power Converter Control Unit for LC Filter Oscillation Suppression
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Solution Overview
Problem
Electric power conversion devices in electric vehicles face malfunctions or shutdowns due to transient oscillations in the LC filter circuit caused by sudden changes in DC power supply voltages, leading to overvoltages across capacitors.
Innovation Solution
An electric power conversion device with a control unit that includes a delay unit with a time constant generation unit, which produces a first control signal by delaying the capacitor voltage and adjusts the conduction ratio to suppress oscillations, ensuring stable operation even with changes in DC power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an LC filter circuit is installed to damp harmonic currents, then harmonic current damping is improved, but electric oscillation and transient voltage oscillation occur causing malfunctions
Solution Approach 1:
The control unit continuously monitors the capacitor voltage in the LC filter circuit and dynamically adjusts the output of the power conversion circuit based on the detected voltage level. This feedback mechanism detects the transient oscillation and automatically counteracts it by modifying the power conversion output, thereby suppressing the electric oscillation and preventing overvoltage without compromising the harmonic damping function of the LC filter.
2Adaptability or versatility
If the voltage of the DC power supply changes suddenly, then power supply adaptability is improved, but transient oscillation and overvoltage occur causing device stoppage
Solution Approach 1:
The control unit is configured to detect changes in capacitor voltage and proactively adjust the power conversion circuit output before the transient oscillation can cause overvoltage or device stoppage. By taking preliminary corrective action upon detecting voltage changes, the system maintains continuous operation and prevents the harmful effects of transient oscillations while adapting to varying DC power supply voltages.
Data Source
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AI summary
Problem to be solved: To provide an electric power conversion device that normally operates, even when the voltage of a DC power supply or the like changes, by suppressing electric oscillations in an LC filter circuit so as to suppress transient oscillations in the voltage of the capacitor. Solution: An electric power conversion device includes a power conversion circuit for receiving electric power from an overhead wire through an LC filter circuit composed of a reactor and a capacitor and converting the electric power to output and a control unit for controlling the power conversion circuit, wherein the control unit is provided with a delay unit for delaying the voltage across the capacitor so as to produce a first control signal, produces a second output voltage instruction from the first control signal and a first output voltage instruction specifying the magnitude of the output voltage of the converted power, and controls the power conversion circuit based on the second output voltage instruction.