Synchronous Motor Current Limiting Without a DC Sensor
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Solution Overview
Problem
Existing synchronous motor driving systems require additional configurations like sensors to accurately estimate and limit direct current, leading to increased cost and potential estimation errors due to neglecting inverter efficiency, which can result in direct current exceeding limits.
Innovation Solution
A synchronous motor driving device that calculates direct current using first and second current values, considers inverter efficiency through a model error extraction unit, and corrects current commands to accurately limit direct current without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensor or hardware filter is added to detect and limit direct current, then direct current estimation accuracy is improved, but device cost and size increase
Solution Approach 1:
The patent replaces physical sensors and hardware filters with a software-based calculation system. The direct current estimation is achieved through computational methods using existing electrical parameters (voltage, current, frequency) rather than additional physical detection devices. This substitution eliminates the need for extra sensors while maintaining estimation accuracy.
Solution Approach 2:
The system uses its own existing measurement capabilities (voltage and current measurements already performed for motor control) to estimate direct current consumption. By leveraging data already collected for other control purposes, the system avoids the need for dedicated measurement sensors, making the existing infrastructure serve multiple functions.
2Device complexity
If active power is calculated from inverter output voltage and current to estimate direct current, then device complexity is reduced, but direct current estimation accuracy deteriorates due to ignoring inverter efficiency
Solution Approach 1:
The patent incorporates inverter efficiency as a correction factor in the direct current estimation calculation. By accounting for the efficiency characteristics of the inverter, the system compensates for power losses and achieves more accurate direct current estimation without adding physical sensors. The efficiency parameter acts as a feedback element that refines the estimation accuracy.
Solution Approach 2:
The system transitions from a simple active power division calculation to a refined calculation that includes inverter efficiency as an additional parameter. This parameter change transforms the estimation formula from P/V to (P/V)/efficiency, significantly improving accuracy while maintaining the software-based approach without additional hardware.
3Reliability
If multiple three-phase windings and multiple inverters are provided for redundancy, then system reliability is improved, but direct current consumption increases
Solution Approach 1:
The patent implements dynamic direct current limitation that adapts to the operational state of the motor and inverter. Rather than static current limits, the system dynamically adjusts current commands based on real-time efficiency calculations and operational conditions. This dynamic approach allows optimal current utilization while maintaining reliability requirements.
Solution Approach 2:
The system changes operational parameters (current commands, voltage levels, frequency) based on calculated direct current consumption and efficiency data. By dynamically adjusting these parameters, the system optimizes energy consumption while ensuring reliability through coordinated control of multiple windings and inverters, preventing excessive direct current draw.
Data Source
AI summary
A synchronous motor driving device which accurately estimates and limits direct current (DC), without a dedicated current detection sensor. The device includes a first DC calculation unit that calculates a first DC based on a first voltage command value, a current value of a winding of a synchronous motor, and a battery voltage; a second DC calculation unit that calculates a second DC based on a current value of the winding of the synchronous motor, a rotation speed of the synchronous motor, and a predetermined motor characteristic; a model error extraction unit calculating inverter efficiency based on the first and second DC; a DC correction unit that calculates an estimated DC on the basis of the first and second DC, and the inverter efficiency; and a DC limiting unit that corrects a current command value of the winding based on the estimated DC and a predetermined DC limit value.