A Discharge Method for Electric Vehicle Bus Capacitor Based on Maximum Copper Loss of Motor Winding

Abstract

The invention discloses a method for discharging a busbar capacitor of an electric vehicle based on the maximum copper consumption of a motor winding, and belongs to the technical field of busbar capacitor discharging methods. Aiming at the requirement that the bus voltage of the vehicle needs to drop to a safe voltage within 3s in an emergency, the present invention proposes a discharge method using the permanent magnet synchronous motor winding as a discharge resistor, according to the current limit circle and voltage limit during the discharge process of the bus capacitor The relationship between the ellipse and the power limit circle, by taking the maximum copper loss of the winding as a constraint to select the current trajectory, it is determined that the current trajectory during the discharge process moves along the current limit circle first, and then approaches along the tangent of the power limit circle when the speed is lower than the turning speed At the origin, the bus capacitance is quickly discharged through the track with the largest copper consumption. The invention realizes the rapid discharge of the bus capacitance in the emergency situation of the electric vehicle, and also has the advantages of low cost and high safety.

Description

technical field [0001] The invention relates to a method for discharging a bus capacitor, in particular to a method for discharging a bus capacitor of an electric vehicle based on the maximum copper consumption of a motor winding. Background technique [0002] Electric vehicles have the advantages of economy, environmental protection and high efficiency, and gradually become the mainstream of future transportation. The permanent magnet synchronous motor has the characteristics of high power density and good dynamic performance, so it is widely used as the main drive motor of electric vehicles. The electric vehicle drive system mainly includes a circuit breaker, a bleeder circuit, a thin-film bus capacitor, a three-phase inverter, a permanent magnet synchronous motor, and a motor controller. Since the current electric vehicle drive system voltage is relatively high, which far exceeds the safe voltage of the human body, GB / T 18384.3 needs to have an active discharge function ...

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Problems solved by technology

However, the traditional method based on bleeder resistors is not only bulky and heavy, which severely limits the power density of the electric vehicle drive system, so it is of great value to study the method based on permanent magnet synchronous motor windings

[0003] In order to improve the power density of the drive system and reduce the cost, there are currently two commonly used discharge methods. One is to short-circuit the upper and lower bridge arms of a certain phase of the three-phase inverter, and consume energy in the form of heat on the power switch tube of the motor. However, the large current generated by this discharge method will cause damage to the inverter; the second method is to use the permanent magnet synchronous motor winding as a discharge device to consume energy on the winding

In the prior art, the method of using ESO to stabilize the bus voltage at a safe voltage has been proposed, but this method may not be able to reduce the bus voltage to a safe voltage when the moment of inertia is large, and because only constant voltage is considered, the winding has not been realized. The maximum copper consumption power discharge, which leads to the fact that the method may not be able to meet the discharge time required by the national standard, so the present invention proposes a method for electric vehicle bus capacitor discharge based on the maximum copper consumption of the motor winding, which has the advantages of simple calculation, high reliability and discharge Advantages of speed

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