Capacitor Discharge Control via Stationary Axis Voltage Inversion
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Solution Overview
Problem
Existing discharge control devices for capacitors in motor vehicles face difficulties in discharging capacitors when an abnormality occurs in the sensor that detects the rotational position of the motor rotor, leading to potential motor rotation during discharge.
Innovation Solution
A discharge control device that generates command values for voltages applied to the α and β axes in an αβ stationary coordinate system, inverting the voltage phase in a predefined period to consume capacitor charges without rotating the motor, using a voltage phase table and ensuring the sum of currents in these axes is zero during a cycle, and repeating this process until the capacitor voltage reaches a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the q-axis current value is set to zero based on rotor rotational position detected by a sensor to discharge the capacitor without rotating the motor, then the motor does not rotate during discharge, but when the sensor malfunctions, the discharge cannot be performed reliably
Solution Approach 1:
The invention extracts the discharge control from dependency on rotor position detection by using a stationary coordinate system (αβ坐标系) instead of the rotating dq coordinate system. The control device generates voltage commands directly in the stationary coordinate system without requiring transformation based on rotor angle, thereby removing the sensor dependency while maintaining effective discharge control.
Solution Approach 2:
Instead of controlling the motor in the rotating dq coordinate system that requires rotor position information, the invention inverts the approach by using the stationary αβ coordinate system where voltage commands are generated independently of rotor position. This inversion eliminates the need for sensor feedback while achieving the same discharge objective.
2Productivity
If the voltage phase is inverted in a predefined period to discharge the capacitor, then the capacitor is discharged efficiently without motor rotation, but the control system becomes more complex
Solution Approach 1:
The invention implements periodic inversion of the voltage phase applied to the motor windings. By alternating the voltage phase between positive and negative directions at predetermined intervals, the control device efficiently dissipates capacitor energy through the motor windings while preventing sustained motor rotation. This periodic action achieves rapid discharge while maintaining manageable control logic.
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 method reliably discharges the capacitor without rotating the motor, even when the rotational position sensor is abnormal, by controlling the voltage phases in the αβ coordinate system to prevent motor rotation and efficiently manage capacitor discharge.
Implementation Method 1
performs discharging of a capacitor (15) by causing electric charges accumulated in the capacitor (15) to be consumed by windings of a motor (18)
Data Source
AI summary
A discharge control device performs discharging of a capacitor, in a state in which a battery is not connected to an inverter that drives a motor, by causing electric charges accumulated in the capacitor connected to the inverter to be consumed by windings of the motor. The discharge control device performs the discharging of the capacitor by sequentially generating command values for voltages applied to a α axis and a β axis while causing a voltage phase in an αβ stationary coordinate system having a rotation axis of a rotor of the motor as an origin and defined by the α axis and the β axis orthogonal to each other to be inverted in a predefined period.