Vehicle Inverter Control for Rapid Discharge and Torque Suppression
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Solution Overview
Problem
In vehicles equipped with permanent magnet synchronous motors, existing methods struggle to quickly discharge storage units during collisions while minimizing unintentional torque generation, especially when the motor continues to rotate due to counter-electromotive voltage.
Innovation Solution
A control apparatus and method that includes a switching control unit, current setting unit, and collision detection unit to manage the electric connection between the power supply and inverter, setting appropriate exciting and torque current command values to quickly discharge the storage unit while suppressing torque generation, even when the motor is rotating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay is opened to disconnect the inverter or motor from the power supply during maintenance or inspection, then safety is improved, but the charge cannot be discharged quickly when the motor rotation speed is high
Solution Approach 1:
The control unit initiates charge discharge operation immediately after detecting vehicle collision, before the motor rotation speed naturally decreases. This preliminary action ensures that the storage unit charge is discharged quickly even when the motor is still rotating at high speed, resolving the contradiction between safety (relay opened) and discharge time (motor still rotating).
Solution Approach 2:
The control unit changes the operating parameters by setting the exciting current command value to a non-zero value (specifically -50A to -200A) while the motor is rotating, enabling charge discharge at high rotation speeds. This parameter change allows the system to discharge charge quickly without waiting for the motor to slow down naturally.
2Productivity
If current is supplied to the motor to discharge the storage unit charge, then discharge speed is improved, but unintentional torque generation occurs in the permanent magnet synchronous motor
Solution Approach 1:
The control unit applies current only to the d-axis (exciting current component) while keeping the q-axis current (torque current component) at zero. This local quality approach allows charge discharge through the d-axis current while suppressing torque generation by eliminating the q-axis current component, thus resolving the contradiction between discharge speed and unintentional torque generation.
Solution Approach 2:
The control unit changes the current control parameters by setting the exciting current command value (Id*) to a non-zero value and the torque current command value (Iq*) to zero. This parameter configuration enables the motor to function as a load for discharging the storage unit while preventing torque generation, achieving both fast discharge and torque suppression.
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
Enables rapid discharge of the storage unit and prevents unintentional torque generation in the motor during collisions, ensuring safe and efficient operation by adjusting current command values based on rotation speed and terminal voltage.
Implementation Method 1
an inverter that converts the direct current supplied from the power supply to an input stage of the inverter into an alternating current and supplies the alternating current to the alternating current motor
Implementation Method 2
an alternating current motor constituted by a permanent magnet synchronous motor
Implementation Method 3
the torque current component is a current component of the alternating current, supplied from the inverter to the alternating current motor, that is used to apply torque to the alternating current motor
Implementation Method 4
a storage unit provided at the input stage of the inverter
Data Source
AI summary
When a vehicle collision is detected, a electric connection between a power supply and an input stage of an inverter is switched to the disconnected condition. Then, when a rotation speed of an alternating current motor is higher than an allowable rotation speed or a terminal voltage of a storage unit provided at the input stage is higher than an allowable terminal voltage, an exciting current command value is set at a value other than zero and a torque current command value is set at zero, and when the rotation speed is equal to or lower than the allowable rotation speed and the terminal voltage is equal to or lower than the allowable terminal voltage, both command values are set at zero. An exciting current component and a torque current component of an alternating current supplied from the inverter to the motor are controlled according to the set command values.