Discharging method of new energy automobile for bus high voltage

Abstract

The invention discloses a discharging method of a new energy automobile for bus high voltage. The discharging method comprises the following steps that firstly, when a hybrid control unit(HCU) sends out a discharging instruction, a battery management system enables a high-voltage battery and an inverter to be disconnected; secondly, a motor controller controls six power switching devices in the inverter, so that the direct-axis current of a permanent magnet synchronous motor is reduced along with reduction of the bus voltage, the quadrature-axis current is zero all the time, and thus the energy of a bus capacitor is consumed inside the permanent magnet synchronous motor; and thirdly, when the bus voltage value is lowered to be within a safe voltage range within given time, the motor controller enables three phases of the permanent magnet synchronous motor to be initiatively shortly circuited, or the direct-axis current and the quadrature-axis current of the permanent magnet synchronous motor are made to be both zero, and otherwise, the motor controller enables the three phases of the permanent magnet synchronous motor to be initiatively shortly circuited and feeds back a discharging overtime fault to the HCU. By means of the discharging method, the discharging time is short, safety and reliability are achieved, and the bus voltage cannot rise again after discharging is completed.

Description

technical field [0001] The present application relates to a method for safely discharging high voltage of a busbar by a new energy vehicle. Background technique [0002] see figure 1 , The motor drive system of new energy vehicles (electric vehicles, hybrid vehicles, etc.) mainly includes high-voltage batteries, inverters, and permanent magnet synchronous motors. A high-voltage battery refers to a battery pack with an output DC voltage higher than 100V, which is controlled by a battery management system (BMS). The inverter is used to convert the DC output from the high-voltage battery into AC to drive the permanent magnet synchronous motor. The motor controller is used to control the turn-on or turn-off of each power switching device in the inverter, and to control the permanent magnet synchronous motor. Common control strategies of motor controllers for permanent magnet synchronous motors include PWM (pulse width modulation), SPWM (sine wave pulse width modulation), SVPW...

AI Technical Summary

Problems solved by technology

However, if the permanent magnet synchronous motor is pulled up again at high speed (such as being dragged by the engine in a collision condition), the energy of the permanent magnet synchronous motor will be fed back to the bus capacitor, causing the bus voltage to cause high voltage risk again

see image 3 , the existing Freewheel mode is used as a safe mode, and the safe mode is entered after the bus voltage drops below the safe voltage range of 60V. However, the energy of the permanent magnet synchronous motor is fed back to the bus capacitor, causing the bus voltage to rise again, causing high voltage risk

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