Power Converter Current Detection Timing Correction
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Solution Overview
Problem
Conventional power converting apparatuses face errors in calculating three-phase currents due to differences in detection timings when using a single current sensor, leading to distorted load currents.
Innovation Solution
A power converting apparatus with a timing signal generator and phase determination signal generator corrects detected current values to represent values at a common reference timing, reducing errors caused by timing differences in current detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one current sensor is provided in the DC bus line to reduce cost and volume, then the number of sensors is reduced, but current detection accuracy deteriorates due to timing differences in detecting currents of different phases
Solution Approach 1:
The patent applies preliminary action by generating timing signals in advance that specify when to detect currents during different switching patterns. The control unit pre-determines the detection timing for each phase current based on the switching states, ensuring that even though detection occurs at different times, the timing is optimized to minimize errors. This allows accurate current reconstruction from a single DC bus sensor without requiring simultaneous detection of all phases.
Solution Approach 2:
The patent changes the timing parameter of current detection dynamically based on switching patterns. Instead of detecting all currents at a fixed time point, the system adjusts detection timing according to which phases are currently conducting current. The control unit selects appropriate detection moments within each PWM cycle based on switching states, transforming the static detection approach into a dynamic one that adapts to real-time operating conditions.
2Measurement precision
If voltage commands are made larger to ensure sufficient detection duration, then current detection becomes reliable, but the original voltage command accuracy is compromised
Solution Approach 1:
The patent introduces an intermediary calculation process that bridges the gap between detected DC bus currents and actual phase currents. The control unit uses switching state information as an intermediary to reconstruct individual phase currents from the composite DC bus current measurements. By combining timing-synchronized detection with switching-pattern-based reconstruction, the system achieves accurate current information without needing to amplify voltage commands.
3Measurement precision
If two current sensors are provided in two phases to detect all three-phase currents, then current detection completeness is improved, but cost and device volume increase
Solution Approach 1:
The patent extracts the current detection function from the individual phase level and relocates it to the DC bus level. Instead of placing sensors in each phase where current information is directly accessible, the system extracts current information from the aggregate DC bus current by detecting at specific timing moments and using switching state information to reconstruct individual phase currents. This extraction approach reduces sensor count while maintaining detection capability.
Solution Approach 2:
The single DC bus current sensor performs multiple functions: it detects currents for all three phases sequentially by measuring at different timing points within PWM cycles. The sensor serves as a universal detection device that, combined with switching state information, can reconstruct any phase current. This multi-functionality replaces what would traditionally require multiple dedicated sensors.
Data Source
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AI summary
A power converting apparatus includes a timing signal generator and a phase determination signal generator provided in an ON/OFF signal generating unit (8) as well as a detected current correction unit (9). On the basis of timing signals (ts1,...) and phase determination signals (ph1,...), the power converting apparatus determines detected current values and phases of the detected current values fed from a DC bus current sensor (3) at timings set in accordance with the timing signals and corrects the detected current values (idc1,...) for the individual phases obtained at the individual timings during PWM cycles to represent values which would be obtained at a reference timing (t0) to thereby reduce errors caused by differences in the current detecting timings for the individual phases.