Inverter Current Sampling Timing for Accurate Phase Detection
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Solution Overview
Problem
In existing inverter devices, the accuracy of phase current values acquired by the controller is compromised due to varying timing of switching elements on the low electric potential side, and the current acquisition timing is not specifically addressed, leading to potential inaccuracies in current detection.
Innovation Solution
A power conversion device with an inverter and a current detector that acquires phase current detection values at specific timings, allowing the controller to compare phase voltage commands with carrier wave signals to control switching elements, thereby calculating accurate phase current values by accounting for offset currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the switching element on the low electric potential side is controlled to switch on and off based on carrier waveform comparison, then the inverter can efficiently convert DC voltage to AC voltages, but the current acquisition timing changes accordingly, leading to deterioration of phase current detection accuracy
Solution Approach 1:
The patent applies preliminary action by determining the current acquisition timing in advance based on the selected carrier waveform (first or second). The controller is configured to acquire current detection values at predetermined timings that correspond to specific switching states, ensuring accurate current detection regardless of which carrier waveform is used for PWM control. This pre-planned timing strategy eliminates the accuracy deterioration that would otherwise result from dynamic timing changes.
2Stability of the object's composition
If different carrier wave signals are used for different phases to control switching elements, then the inverter can achieve better voltage balance and reduce ripple, but the current acquisition timing becomes complex and varies across phases
Solution Approach 1:
The patent applies segmentation by dividing the three phases into two groups: phases using the first carrier wave signal and phases using the second carrier wave signal. For each group, specific current acquisition timings are predetermined. This segmented approach allows the system to maintain voltage balance stability through different carrier waves while managing timing complexity through systematic classification of acquisition moments for each phase group.
3Adaptability or versatility
If the current acquisition timing is not specifically determined, then the control system remains flexible, but the accuracy of phase current values deteriorates
Solution Approach 1:
The patent applies dynamics by making the current acquisition timing adaptive to the selected carrier waveform while remaining predetermined. The controller dynamically selects acquisition timings based on whether the first or second carrier waveform is used, but these timings are established in advance rather than calculated in real-time. This dynamic yet predetermined approach maintains control flexibility while ensuring detection accuracy.
Data Source
AI summary
A power conversion device is configured to acquire, from a current detector at a timing A, a first phase current detection value in a first phase being a phase corresponding to a phase voltage command to be compared to a first carrier wave signal, calculate a first phase current calculation value corresponding to the first phase based on an acquisition result, acquire, from the current detector at a timing B, a second phase current detection value in a second phase being a phase corresponding to a phase voltage command to be compared to a second carrier wave signal, and to calculate a second phase current calculation value corresponding to the second phase based on an acquisition result.