US-20260124931-A1 - IMPROVED ELECTRIC VEHICLE TRACTION INVERTER EFFICIENCY

US20260124931A1US 20260124931 A1US20260124931 A1US 20260124931A1US-20260124931-A1

Abstract

A vehicle propulsion system including a system controller for determining a rotational speed and a rotational torque in response to a user input and a vehicle operating mode, a battery for supplying a DC current, an electric motor configured to generate the rotational torque at the rotational speed in response to an AC voltage, an inverter for transforming the DC current into the AC current using a first transistor and a second transistor, and an inverter controller for determining a dead time in response to the rotational torque and the rotational speed and for removing a first switching control signal from the first transistor, waiting a time duration equal to the dead time, and applying a second switching control signal to the second switching transistor and wherein the dead time is continuously updated in response to a change in the torque and a change in the rotational speed.

Inventors

Renato Amorim Torres
Chandra S. Namuduri
Yilun Luo

Assignees

GM Global Technology Operations LLC

Dates

Publication Date: 20260507
Application Date: 20241101

Claims (20)

1 . An inverter controller for an electric motor comprising: a system controller for determining a rotational torque and a rotational speed for an electric motor; the electric motor for generating the rotational torque at the rotational speed in response to an AC voltage; a battery for supplying a DC voltage; an inverter including a first transistor and a second transistor for transforming the DC voltage into the AC voltage; and an inverter controller for determining a dead time in response to the rotational torque and the rotational speed and for removing a first switching control signal from the first transistor, waiting a time duration equal to the dead time, and applying a second switching control signal to the second transistor and wherein the dead time is continuously updated in response to a change in the rotational torque and a change in the rotational speed.
2 . The inverter controller for the electric motor of claim 1 , further including a temperature sensor for detecting a first temperature of the first transistor and a second temperature of the second transistor and wherein the dead time is determined in response to the first temperature and the second temperature.
3 . The inverter controller for the electric motor of claim 1 , wherein the inverter controller is configured to adjust the dead time by adjusting a slew rate of the first switching control signal and the second switching control signal.
4 . The inverter controller for the electric motor of claim 3 , wherein slew rate is increased in response to a decrease in a battery voltage.
5 . The inverter controller for the electric motor of claim 1 , wherein the inverter controller is configured to adjust the dead time in response to at least one of a vehicle speed, a throttle position, a steering angle, and a battery voltage.
6 . The inverter controller for the electric motor of claim 1 , wherein the inverter controller is configured to adjust the dead time in response to at least one of an inverter output current magnitude, a junction temperature and a power module temperature.
7 . The inverter controller for the electric motor of claim 1 , wherein the inverter controller is configured to adjust the dead time as a function of a set of gate driver parameters of at least one of the first transistor and the second transistor.
8 . The inverter controller for the electric motor of claim 1 , wherein the inverter controller is configured to reduce the dead time in response to at least one of a reduced inverter current and a reduced bus voltage and to increase the dead time in response to at least one of an increase in an inverter current and an increased bus voltage.
9 . The inverter controller for the electric motor of claim 1 , wherein the inverter controller is configured to adjust the dead time in response to a switching frequency of inverter or the a fundamental frequency of the electric motor.
10 . A method of controlling a switching inverter for an electric motor for vehicular applications comprising: determining, by a system controller, for a rotational torque and a rotational speed for an electric motor; generating, by the electric motor, the rotational torque at the rotational speed in response to an AC voltage; supplying, by a battery, a DC voltage; transforming the DC voltage into the AC voltage by an inverter including a first transistor and a second transistor; and determining, by an inverter controller, a dead time in response to the rotational torque and the rotational speed and for removing a first switching control signal from the first transistor, waiting a time duration equal to the dead time, and applying a second switching control signal to the second transistor and wherein the dead time is continuously updated in response to a change in the rotational torque and a change in the rotational speed.
11 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the first transistor and the second transistor are wide bandgap semiconductors.
12 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the first transistor and the second transistor have a variable gate driver voltage level and wherein the dead time is determined in response to the variable gate driver voltage level.
13 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the inverter controller is configured to continuously adjust the dead time in response to a change in at least one of the rotational torque, the rotational speed, a vehicle speed, a throttle position, a braking application level, a steering angle, a temperature of the first transistor, a temperature of the second transistor, a change in a magnitude of a battery voltage, and a change in a magnitude of a phase current.
14 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the inverter controller is further configured to update a dead time register within a PWM output section of a controller hardware prior to issuing a new current command in response to the new current command is higher than a threshold.
15 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the inverter controller is further configured to update a dead time register within a PWM output section of a controller hardware prior to issuing a new current command in response to the new current command is lower than a threshold.
16 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , where the inverter controller is further configured to update the dead time to be effective after a predetermined number of PWM cycles.
17 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the inverter controller is communicatively coupled to at least one of a look-up table and a closed form equation for the dead time to be varied to minimize at least one of an inverter conduction loss, a current harmonic, a torque harmonic and a noise, vibration and harshness level.
18 . The method of controlling the switching inverter for the electric motor for vehicular applications of claim 10 , wherein the dead time is applied within a fundamental cycle of a waveform of the AC voltage in order reduce a conduction loss.
19 . A vehicle propulsion system comprising: a system controller for receiving a user input via a user interface and for determining a rotational speed and a rotational torque in response to the user input and a vehicle operating mode; a battery for supplying a DC current; a three phase electric motor configured to generate the rotational torque at the rotational speed in response to an AC voltage; an inverter for transforming the DC current into the AC voltage using a first transistor and a second transistor; and an inverter controller for determining a dead time in response to the rotational torque and the rotational speed and for removing a first switching control signal from the first transistor, waiting a time duration equal to the dead time, and applying a second switching control signal to the second transistor and wherein the dead time is continuously updated in response to a change in the rotational torque and a change in the rotational speed.
20 . The vehicle propulsion system of claim 19 , wherein the inverter controller is configured to continuously adjust the dead time in response to a change in at least one of the rotational torque, the rotational speed, a vehicle speed, a throttle position, a braking application level, a steering angle, a temperature of the first transistor, a temperature of the second transistor, a change in a magnitude of a battery voltage.

Description

INTRODUCTION The present disclosure generally relates to electric vehicle motors and battery systems, and more particularly relates to a method and apparatus to utilize adjustable dead time in a traction inverter to minimize the conduction losses while simultaneously preventing any shoot-through in the inverter phase legs by utilizing power devices with minimum switching times and gate charges to enable shorter dead times. Electric motors are used in electric vehicles (EV) to convert electrical energy from the battery into mechanical energy to turn the wheels. Typically, there are two main types of electric motors used in EVs: induction motors and permanent magnet synchronous motors (PMSMs). Modern EVs typically have two electric motors, one for each axle, but some EVs can have a single motor located under the hood or four motors, one for each wheel. EV motors are typically driven by three phase alternating current (AC) currents. As EV batteries supply direct current (DC) voltage, the DC voltage has to be converted to three phase AC. This conversion is performed by an inverter. An inverter serves as a power electronic interface between the battery and the electric motor to convert the DC power stored in the battery into AC power that is compatible with the motor's requirements. By precisely regulating the voltage and frequency of the AC output, the inverter enables precise control of the motor's speed and torque. This control is essential for achieving optimal vehicle performance, efficiency, and responsiveness. Inverters typically employ switching transistors which are switched on and off at regular intervals to go convert the DC voltage into three AC voltages, with each of the AC voltages supplied to a different winding of the AC motor. To prevent shorts circuits from occurring in the inverter when multiple transistors are simultaneously turned on, a deliberate interval is introduced between switching off one transistor before turning on another. This time interval is typically referred to as dead time. While it is essential for safety, dead time can also introduce inefficiencies due to increased conduction losses across the freewheeling diode during this period. It is desirable to efficiently provide employ inverter deadtimes as efficiently as possible to reduce any energy waste in order to provide systems and methods for vehicle propulsion and driver assistance systems. Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. SUMMARY Disclosed herein are vehicle control methods and systems and related electrical systems for provisioning vehicle propulsion systems, methods for making and methods for operating such systems, and motor vehicles and other equipment such as aircraft, trucks, buses, forklifts, construction vehicles and other electric vehicles equipped with battery powered electric motors. By way of example, and not limitation, there are presented various embodiments of systems to optimize a traction inverter's efficiency by implementing adaptive dead time control, to minimize conduction losses while ensuring zero shoot-through events, and to employ power devices with rapid switching characteristics and low gate charges to enable shorter dead times. In accordance with an exemplary embodiment of the present disclosure, an inverter controller for an electric motor including a system controller for determining a rotational torque and a rotational speed for an electric motor, the electric motor for generating the rotational torque at the rotational speed in response to an AC voltage, a battery for supplying a DC voltage, an inverter including a first transistor and a second transistor for transforming the DC voltage into the AC voltage, and an inverter controller for determining a dead time in response to the rotational torque and the rotational speed and for removing a first switching control signal from the first transistor, waiting a time duration equal to the dead time, and applying a second switching control signal to the second transistor and wherein the dead time is continuously updated in response to a change in the rotational torque and a change in the rotational speed. In accordance with another exemplary embodiment of the present disclosure further including a temperature sensor for detecting a first temperature of the first transistor and a second temperature of the second transistor and wherein the dead time is determined in response to the first temperature and the second temperature. In accordance with another exemplary embodiment of the present disclosure wherein the inverter controller is configured to adjust the dead time by adjusting a slew rate of the first switching control signal and the second switching control signal. In accordance with another exemplary embodime