Motor Neutral Point Charging Torque Suppression
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Solution Overview
Problem
Conventional charging systems for electric vehicles require heavy and expensive step-up converters to boost charging voltage from 400V to 800V, and they can generate torque in the motor during charging, posing safety risks if the vehicle moves during charging.
Innovation Solution
An apparatus that controls the charging system using a motor-driving system, which includes a voltage controller and a current command generator to suppress torque by setting specific phase currents to zero based on the rotor angle, ensuring that the motor neutral point voltage follows a voltage command and the torque of the motor is maintained at zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a step-up converter is used to boost charging voltage from 400V to 800V, then the charging voltage requirement is met, but the system becomes heavy, bulky, and expensive
Solution Approach 1:
The motor neutral point, originally designed for motor operation, is made to serve dual purposes: motor driving and voltage boosting for battery charging. By utilizing the motor coils and inverter switching elements for both functions, the system eliminates the need for a separate step-up converter, reducing weight and cost while meeting the 800V charging requirement
Solution Approach 2:
The motor-neutral-point charging system uses the motor's own coils and the inverter's switching elements to perform the voltage boosting function. The motor components serve themselves by converting the 400V charging input to 800V output through controlled switching, eliminating the need for external boosting equipment
2Device complexity
If the motor-neutral-point charging method is used to avoid additional devices, then cost and weight are reduced, but torque may occur in the motor causing safety risks
Solution Approach 1:
The control apparatus continuously monitors the motor neutral point voltage and compares it with the voltage command. Based on this feedback, the voltage controller adjusts the neutral point current command to maintain the voltage relationship, while the current command generator ensures torque remains zero by coordinating phase currents with the rotor angle
Solution Approach 2:
The system dynamically changes current parameters based on rotor angle positions. By setting one of the three-phase currents to zero and adjusting the remaining two phases according to the rotor angle, the system maintains zero torque while enabling voltage boosting. The voltage controller and current command generator coordinate to adjust current magnitudes and phases to satisfy both voltage command and zero-torque requirements
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 solution effectively prevents the motor from generating torque during charging, thereby preventing accidental movement of the vehicle and ensuring safety by stabilizing the neutral point voltage and managing the current flow efficiently without additional devices or costs.
Implementation Method 1
an inverter for receiving DC power stored in the battery at a time of driving of the motor to convert the received DC power into three-phase AC power
Implementation Method 2
the motor configured for generating torque using the three-phase AC power output by the inverter
Data Source
AI summary
An apparatus for controlling a charging system using a motor-driving system is configured to suppress the occurrence of torque in a motor when a battery is charged by receiving the supply of external charging current to a neutral point of the motor.