Full-Bridge Power Converter Control for Zero-Crossing Alignment
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Solution Overview
Problem
In power conversion apparatuses with full-bridge circuits, phase shifts between detected and actual voltages can lead to overcurrents due to misalignment in switching timing, which existing peak-current-mode control methods fail to adequately address.
Innovation Solution
A control apparatus that determines zero-up-crossing and zero-down-crossing timings based on specific determination values relative to the detected voltage, ensuring accurate polarity determination and synchronized switching of switches to prevent overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If peak-current-mode control is used to control reactor current to a current command value, then the output current distortion is reduced, but overcurrents occur due to phase shift between detected voltage and actual voltage causing misalignment in switching timing
Solution Approach 1:
The control apparatus determines the polarity of the actual voltage in advance by comparing the detected voltage with predetermined first and second determination values before executing switching operations. This preliminary polarity determination ensures that switching timing is correctly aligned with the actual voltage polarity, preventing overcurrents while maintaining accurate current control.
Solution Approach 2:
The patent introduces first and second determination values as intermediary reference levels for comparing the detected voltage. These determination values act as mediators to accurately infer the actual voltage polarity despite phase shifts or offsets in the detected voltage signal, enabling reliable switching timing without directly measuring the actual voltage.
2Device complexity
If the detected voltage is used directly for switching timing without polarity determination, then the control is simple, but phase shifts cause misalignment in switching timing leading to overcurrents
Solution Approach 1:
The control apparatus performs preliminary polarity determination by comparing the detected voltage with first and second determination values before executing switching operations. This preliminary action ensures correct switching timing alignment with the actual voltage polarity while maintaining relatively simple control logic.
Solution Approach 2:
The patent changes the parameter comparison threshold by using two different determination values (first and second) instead of a single zero-crossing threshold. This parameter change enables accurate polarity determination even when the detected voltage has phase shifts or offsets, improving switching timing alignment without significantly increasing complexity.
Data Source
AI summary
A control apparatus for a power conversion apparatus acquires a detected voltage of an alternating-current power supply. The control apparatus determines a period from when the detected voltage exceeds a first determination value for determining a zero-up-crossing timing of an actual voltage of the alternating-current power supply until the detected voltage falls below a second determination value for determining a zero-down-crossing timing of the actual voltage to be a period during which the actual voltage has a positive polarity, and determines a period from when the detected voltage falls below the second determination value until the detected voltage exceeds the first determination value to be a period during which the actual voltage has a negative polarity. The first determination value is less than the detected voltage when the actual voltage is zero, and the second determination value is greater than the detected voltage when the actual voltage is zero.