DC Bus Discharge Control Using Stator Coordinate Transformation
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Solution Overview
Problem
In electric vehicles with permanent magnet synchronous motors, a failed rotor position sensor prevents rapid discharge of the DC bus, posing safety risks due to residual high voltage on the DC bus.
Innovation Solution
A DC bus discharge control method that converts motor current signals into a stator coordinate system, outputs a voltage control signal based on a high-frequency alternating current reference, and controls a switching device using Pulse Width Modulation (PWM) to manage the discharge, independent of rotor rotation angle information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotor position sensor is used to control DC bus discharge, then discharge control can be achieved under normal conditions, but discharge fails when rotor position sensor fails
Solution Approach 1:
The patent extracts the discharge control function from the rotor position sensor dependency. By using stator coordinate system and Clarke transformation, the control system no longer needs rotor position information, effectively removing the single point of failure (rotor position sensor) while maintaining discharge control capability.
Solution Approach 2:
The control system is designed to perform both normal motor control and DC bus discharge functions using the same stator coordinate system framework. The switching device and control algorithm serve multiple purposes: motor operation during normal conditions and active discharge when needed, eliminating the need for separate discharge control hardware.
2Productivity
If high-frequency alternating current is used for discharge, then discharge speed increases, but control complexity increases
Solution Approach 1:
The patent changes the current waveform parameters by using high-frequency alternating current instead of direct current for discharge. This parameter change significantly increases the discharge speed by utilizing the skin effect and proximity effect to increase effective resistance, while the control complexity is managed through the unified stator coordinate system approach.
Solution Approach 2:
The control system implements feedback control by continuously monitoring the DC bus voltage and adjusting the switching device control signals accordingly. The feedback mechanism ensures that the high-frequency alternating current discharge process remains stable and可控, preventing excessive complexity while achieving rapid discharge.
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
Ensures safe and rapid discharge of the DC bus even when the rotor position sensor fails, reducing safety hazards for passengers and maintenance personnel by converting motor current signals into a stator coordinate system and using high-frequency alternating currents to accelerate discharge.
Implementation Method 1
A control signal for controlling the switching device is generated by performing Pulse Width Modulation (PWM) on the three-phase voltage control signal
Implementation Method 2
the motor current signal is converted into the current signal in the stator coordinate system by Clarke transformation
Implementation Method 3
The operation that the voltage control signal in the stator coordinate system is converted into the three-phase voltage control signal may include that: the voltage control signal in the stator coordinate system is converted into the three-phase voltage control signal by Clarke transformation
Implementation Method 4
a voltage control signal in the stator coordinate system is output based on the current signal in the stator coordinate system and a current reference instruction of a preset stator coordinate system, the current reference instruction of the preset stator coordinate system being a high-frequency alternating current
Implementation Method 5
using high-frequency alternating currents to accelerate discharge
Data Source
AI summary
Provided is a Direct Circuit (DC) bus discharge control method, including that: an active discharge instruction is received; a motor current signal is acquired according to the active discharge instruction; the motor current signal is converted into a current signal in a stator coordinate system; a voltage control signal in the stator coordinate system is output based on the current signal in the stator coordinate system and a current reference instruction of a preset stator coordinate system, the current reference instruction of the preset stator coordinate system being a high-frequency alternating current; and the voltage control signal in the stator coordinate system is converted into a three-phase voltage control signal, and a working state of a switching device is controlled according to the three-phase voltage control signal.