Three-Phase Inverter Current Sensing With Single-Shunt Correction
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Solution Overview
Problem
Current 3-phase inverter systems using a single current sensor face challenges in accurately measuring currents across all phases due to limitations in maintaining switching states, leading to areas where current measurement is not possible, and fail to detect overcurrents effectively, which can damage controllers and wiring within vehicles.
Innovation Solution
A device and method utilizing a current detection element, such as a shunt resistor, connected to one lower switch of a 3-phase inverter, along with a current measurement unit measuring currents across the other two switches, and a current correction unit to adjust and correct measured values, and an overcurrent detection circuit that monitors DC link, control unit, and motor driving unit currents to block overcurrents by reducing motor or control unit outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current sensor is installed in the DC link to measure 3-phase current, then the system size and cost are reduced, but the current measurement precision deteriorates due to inability to maintain predetermined switching states
Solution Approach 1:
The patent divides the current measurement function into multiple segments: one current sensor measures the DC link current, while three switches are used to sequentially connect different phase windings to measure individual phase currents. This segmentation allows the system to achieve complete 3-phase current measurement capability without requiring three separate current sensors, thus reducing device complexity while maintaining measurement precision through coordinated operation of the segmented components.
2Device complexity
If a single current sensor is used to measure all three phases, then the system is simplified, but the measurement coverage deteriorates due to areas where current measurement becomes impossible
Solution Approach 1:
The patent makes the single current sensor universal by enabling it to measure all three phase currents through the intermediary of three switches. The switches act as multi-functional elements that can connect the current sensor to any of the three phase windings as needed. This allows one sensor to perform the function of three sensors, achieving complete measurement coverage while simplifying the overall system structure.
3Device complexity
If the current detection circuit only measures motor current, then the circuit is simplified, but the overcurrent detection capability deteriorates as it cannot detect abnormalities inside the controller
Solution Approach 1:
The patent introduces the three switches as intermediary elements between the single current sensor and the multiple measurement targets (DC link current and three phase currents). These switches act as mediators that enable the current sensor to access different measurement points sequentially. This intermediary mechanism allows the simplified detection circuit to gain comprehensive overcurrent detection capability by routing measurements through the switching network.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise current detection and overcurrent blocking, reducing material costs, simplifying circuit implementation, and enhancing noise resistance and torque ripple characteristics, thereby preventing failures in vehicle wiring and electronic devices.
Implementation Method 1
a current measurement unit for measuring a current by using the current detection element and the other two of the lower switches
Data Source
AI summary
A device for measuring a current of a three-phase inverter according to an embodiment of the present invention comprises: a current detection element connected to the lower end of one of three lower switches comprising an inverter; a current measurement unit for measuring a current by using the current detection element and the other two lower switches, to which the current detection element is not connected; and a current correction unit for correcting a second current value and a third current value measured using the two lower switches, on the basis of the relationship between a first current value measured using the current detection element and the second and third current values.