Inverter Control Device Alternating DC Current Detection
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Solution Overview
Problem
Conventional inverter control devices face efficiency challenges in converting direct current (DC) to three-phase alternating current (AC) voltage, leading to reduced combined efficiency of the inverter main circuit and motor supplied with AC voltage.
Innovation Solution
An inverter control device that alternately uses DC current values detected during monotonically increasing and decreasing unit periods of a triangular wave carrier signal for voltage command computation, allowing for flexible voltage command change periods that are multiples of the unit period, thereby improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the voltage command change period is set to include three or more and an odd number of unit periods as in conventional techniques, then the control structure is simplified, but the combined total efficiency of the inverter main circuit and motor is reduced
Solution Approach 1:
The voltage command change period is segmented into an even number of unit periods (two or more), allowing alternating detection timing between monotonically increasing and decreasing carrier signal periods. This segmentation enables efficient DC current value selection that improves combined total efficiency while maintaining manageable control complexity through structured periodic operation.
2Device complexity
If DC current values are detected at fixed timing in conventional techniques, then the detection process is simplified, but errors in DC current detection increase
Solution Approach 1:
The detection timing of DC current values is dynamically adjusted to alternate between monotonically increasing and decreasing periods of the triangular wave carrier signal. This dynamic timing selection optimizes measurement conditions for each detection cycle, reducing detection errors while maintaining a relatively simple detection process structure.
Solution Approach 2:
The DC current value detection is performed periodically with alternating timing relative to the triangular wave carrier signal phases. By systematically switching detection timing between increasing and decreasing carrier periods, the method achieves improved measurement precision through periodic optimization of detection conditions.
3Device complexity
If the voltage command value computation uses DC current values from single detection timing, then the computation process is simplified, but the control adaptability is reduced
Solution Approach 1:
DC current values are detected in advance at optimized timing points during both monotonically increasing and decreasing carrier signal periods. This preliminary detection at multiple optimized timing points provides the computation process with high-quality input data, improving control adaptability while keeping the computation process itself relatively simple.
Data Source
AI summary
It provides an inverter main circuit converting a DC-voltage into three-phase AC-voltages, a DC-current detection unit detecting the DC-current value of a DC-current flowing in the main circuit, and an inverter control unit generating a drive signal for controlling operation of the main circuit using a voltage command value corresponding to each phase of the three-phase AC-voltages and a triangular-wave carrier. Using a time period during which the triangular-wave carrier monotonically increases or decreases as a unit period, the control unit provides control to alternately use, as the DC-current value for use in computation of the voltage command value, the DC-current value detected in the unit period in which the triangular-wave carrier monotonically increases and the DC-current value detected in the unit period in which the triangular-wave carrier monotonically decreases, for every voltage command value control period set to three times or more and an integer multiple of the unit period.