Vehicle Driving Device Harmonic Reduction via Dual-Phase Current Calculation
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Solution Overview
Problem
Conventional field-oriented control (FOC) methods for motor control in hybrid electric vehicles face challenges in accurately measuring feedback signals, leading to increased harmonics and decreased motor efficiency, especially when output power is high.
Innovation Solution
A vehicle driving device and method that utilizes two synchronized three-phase stator windings with current sensors and power modules to measure and control phase currents, reducing harmonics and improving efficiency by calculating and compensating the third-phase current based on first- and second-phase currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional FOC theory is used to control motor output power, then the motor can operate in driving and power generating modes, but harmonics increase and feedback current measurement stability deteriorates when output power is too large
Solution Approach 1:
The patent divides the three-phase current measurement into two independent measurement channels. Each channel measures one phase current using a current sensor, and the third phase current is calculated through coordinate transformation. This segmentation reduces the impact of harmonics on any single measurement channel, improving measurement stability at high power levels.
Solution Approach 2:
The patent introduces an intermediary calculation process using coordinate transformation (Clark and Park transformations) to derive the third phase current from the two measured phase currents. This intermediary approach filters out harmonic disturbances that would otherwise directly affect all three phase measurements, enhancing feedback reliability.
2Ease of manufacture
If conventional FOC theory with two current sensors is used, then cost is reduced compared to three sensors, but measurement accuracy and feedback signal precision deteriorate due to harmonic effects
Solution Approach 1:
The patent implements a feedback mechanism where the calculated third phase current is used alongside the two measured phase currents to control the inverter's duty cycle. This feedback loop continuously adjusts the motor operation based on accurate current information, maintaining measurement precision while using only two current sensors.
Solution Approach 2:
The patent replaces the mechanical approach of using three physical current sensors with a hybrid system that combines two physical sensors with computational methods (coordinate transformation and calculation). This substitution maintains measurement accuracy while reducing hardware costs.
3Ease of operation
If FOC theory is applied, then motor control is achieved, but device complexity increases due to assumptions and feedback signal accuracy requirements
Solution Approach 1:
The patent makes the control system universal by using the same coordinate transformation and calculation methodology for both driving mode and power generating mode operations. This multi-functional approach simplifies the control logic despite the complexity of FOC theory, as the same computational framework handles different operating conditions.
Data Source
AI summary
A vehicle driving device is driven by a power unit. A three-phase motor includes a first stator winding and a second stator winding. The first stator winding is connected in parallel to the second stator winding, and the first stator winding and the second stator winding are synchronized with each other. A first current sensor is coupled to the first stator winding for measuring a first-phase current. A second current sensor is coupled to the first stator winding for measuring a second-phase current. A third-phase current of the first stator winding is generated according to a calculating procedure of the first-phase current and the second-phase current. A duty cycle between a first power module and a second power module is controlled according to a feedback compensation of the first-phase current, the second-phase current and the third-phase current.