Inverter Voltage Command Modification for Current Detection

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Solution Overview

Problem

Conventional 3-phase inverter current detection methods using shunt resistors require complex calculations and lengthy processing times, especially when determining injection voltages and adjusting voltage commands, which can be burdensome for systems with slow CPU speeds and increase computation time.

Innovation Solution

A 3-phase inverter controller with a voltage command modification unit that determines injection and compensation voltages within measurable areas, minimizing calculations by using a sector-based approach and eliminating division calculations, thereby reducing computation time and enabling efficient current detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional current detection methods using shunt resistors are employed, then current detection capability is achieved, but calculation complexity and processing time increase significantly

Engineering Contradiction:

Improvecurrent detection accuracyVSAvoidcalculation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the complex calculation components (division operations and intricate injection voltage determination) from the current detection process. By removing these computationally intensive elements while retaining the essential current detection functionality through simplified voltage command modification, the system achieves accurate current detection with reduced calculation complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of calculating injection voltages to force current detection in disabled areas, the patent inverts the approach by modifying voltage commands to keep operations within measurable areas where current detection is naturally enabled. This reversal eliminates the need for complex injection voltage calculations while maintaining detection accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If complex injection voltage determination is performed, then current detection coverage is expanded, but processing time increases

Engineering Contradiction:

Improvecurrent detection coverageVSAvoidprocessing time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent segments the voltage hexagon into measurable and unmeasurable areas, and further divides measurable areas into sectors. By determining sector information and using pre-calculated sector-specific parameters, the system achieves comprehensive current detection coverage across all measurable areas without performing complex real-time calculations, thus reducing processing time while maintaining adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary determination of sector information and prepares sector-specific parameters in advance. This pre-processing approach allows the main control loop to execute simple lookups and basic calculations rather than complex real-time computations, significantly reducing processing time while maintaining expanded current detection coverage.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If division calculations are included in voltage command modification, then calculation precision is maintained, but computation time increases

Engineering Contradiction:

Improvevoltage command precisionVSAvoidcomputation speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces expensive division calculations with cheaper arithmetic operations (addition, subtraction, multiplication) that can be executed rapidly. By using alternative mathematical approaches that achieve the same precision goals through computationally efficient operations, the system maintains voltage command precision while dramatically improving computation speed for real-time control applications.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Speed

If CPU speed is increased to handle complex calculations, then processing speed improves, but system cost increases

Engineering Contradiction:

Improveprocessing speedVSAvoidsystem cost

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent changes the computational parameters from complex division-based calculations to simpler arithmetic operations. By reformulating the voltage command modification algorithm to use addition, subtraction, and multiplication instead of division, the system achieves the same processing speed and accuracy using lower-performance, lower-cost microcontrollers, thereby reducing overall system cost while maintaining real-time processing capability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP2822171B1Apparatus for modifying voltage command for detecting output current in inverter

Publication Date: 2023.05.17 LSIS CO LTD

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Figure 2(a)~2(d)
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AI summary

An apparatus for modifying voltage command for detecting output current in inverter is disclosed to modify a PWM voltage command by determining a sector in a voltage hexagon, the sector having a PWM voltage command therein, by comparing the PWM voltage command, determining an area, the area having the PWM voltage command, within a current detection disabled area by converting a minimum sampling time to a minimum sampling PWM and using the converted minimum sampling PWM, and determining an adjusting voltage and a restoring voltage using a minimum injection voltage based on the determined area.