Improved efficiency of traction inverters for electric vehicles

Abstract

Vehicle control system comprising a system control unit for determining speed and torque depending on user input and vehicle operating mode, a battery for supplying direct current, an electric motor configured to generate torque at speed depending on an alternating voltage, an inverter for converting the direct current to alternating current using a first transistor and a second transistor, and an inverter control for determining a dead time in response to the torque and speed, removing a first switching control signal from the first transistor, waiting for a duration equal to the dead time, and applying a second switching control signal to the second switching transistor, with the dead time being continuously updated in response to changes in torque and speed.

Description

introduction

[0001] The present description relates generally to electric motors and battery systems and in particular to a method and device for utilizing an adjustable dead time in a traction inverter to minimize line losses and prevent overshoot in the phase legs of the inverter by using power devices with minimal switching times and gate charges to enable shorter dead times.

[0002] Electric motors are used in electric vehicles (EVs) to convert electrical energy from the battery into mechanical energy to drive the wheels. There are generally 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 may have a single motor under the hood or four motors, one for each wheel.

[0003] EV motors are typically powered by three-phase alternating current (AC). Since EV batteries supply direct current (DC), the DC voltage must be converted to three-phase AC. This conversion is performed by an inverter. An inverter acts as a power electronic interface between the battery and the electric motor, converting the DC voltage stored in the battery into an AC voltage suitable for the motor. 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 optimal vehicle performance, efficiency, and responsiveness.

[0004] Inverters typically use switching transistors that are switched on and off at regular intervals to convert the DC voltage into three AC voltages, each supplying a different winding of the AC motor. To prevent short circuits in the inverter when multiple transistors are switched on simultaneously, a deliberate interval is inserted between the switch-off of one transistor and the switch-on of another. This time interval is commonly referred to as dead time. While essential for safety, the dead time can also lead to inefficiencies due to increased conduction losses across the freewheeling diode during this period. It is desirable to optimize the inverter's dead time to minimize energy waste, thus enabling the deployment of systems and procedures for vehicle propulsion and driver assistance systems.Further desirable features and properties of the present disclosure will become apparent from the following detailed description and the attached claims in conjunction with the attached drawings and the preceding technical field and background. Summary

[0005] This paper presents methods and systems for controlling vehicles and associated electrical systems for providing propulsion systems for vehicles, methods for manufacturing and operating such systems, as well as motor vehicles and other equipment such as aircraft, trucks, buses, forklifts, construction vehicles, and other electric vehicles equipped with battery-powered electric motors. As an example, and without limitation, various embodiments of systems for optimizing the efficiency of a traction inverter are presented. These systems implement adaptive dead-time control, minimize line losses, and ensure that no shoot-through events occur. They also employ power devices with fast switching characteristics and low gate charges to enable shorter dead times.

[0006] According to an exemplary embodiment of the present description, an inverter controller for an electric motor comprises a system controller for determining a torque and a system speed for an electric motor, wherein the electric motor generates the torque at the system speed in response to an AC voltage, a battery for supplying a DC voltage, an inverter with a first transistor and a second transistor for converting the DC voltage into the AC voltage, and an inverter controller for determining a dead time in response to the torque and the speed and for removing a first switching control signal from the first transistor, waiting for a duration equal to the dead time, and applying a second switching control signal to the second transistor, wherein the dead time is continuously updated in response to a change in torque and a change in speed.

[0007] According to another exemplary embodiment of the present description, a temperature sensor is further provided for detecting a first temperature of the first transistor and a second temperature of the second transistor, wherein the dead time is determined as a function of the first temperature and the second temperature.

[0008] According to another exemplary embodiment of the present description, wherein the inverter control is configured to adjust the dead time by setting a rise rate of the first switching control signal and the second switching control signal.

[0009] According to another exemplary embodiment of the present description, wherein the rate of increase is increased in response to a decrease in battery voltage.

[0010] According to another exemplary embodiment of the present description, wherein the inverter control is configured to adjust the dead time depending on at least one vehicle speed, one throttle position, one steering angle and one battery voltage.

[0011] According to another exemplary embodiment of the present description, wherein the inverter control is configured to adjust the dead time depending on the magnitude of the inverter output current, the junction temperature and / or the temperature of the power module.

[0012] According to another exemplary embodiment of the present description, wherein the inverter control is configured to adjust the dead time depending on a set of gate driver parameters of the first and / or the second transistor.

[0013] According to another exemplary embodiment of the present description, wherein the inverter control is configured to decrease the dead time in response to a reduced inverter current and / or a reduced bus voltage and to increase the dead time in response to an increase in inverter current and / or an increased bus voltage.

[0014] According to another exemplary embodiment of the present description, wherein the inverter control is configured to adjust the dead time depending on the switching frequency of the electric motor.

[0015] According to another exemplary embodiment of the present description, a method for controlling an inverter for an electric motor for vehicle applications comprises determining a torque and motor speed for an electric motor by a system controller, generating the torque at the motor speed by the electric motor in response to an alternating voltage, supplying a direct voltage by a battery, converting the direct voltage into the alternating voltage by an inverter with a first transistor and a second transistor, determining a dead time by an inverter controller as a function of the torque and speed, removing a first switching control signal from the first transistor, waiting a time equal to the dead time, and applying a second switching control signal to the second transistor.where the dead time is continuously updated depending on changes in torque and rotational speed.

[0016] According to another exemplary embodiment of the present description, wherein the first transistor and the second transistor are wide bandgap semiconductors.

[0017] According to another exemplary embodiment of the present description, wherein the first transistor and the second transistor have a variable gate driver voltage level and wherein the dead time is determined as a function of the variable gate driver voltage level.

[0018] According to another exemplary embodiment of the present description, wherein the inverter control is configured to continuously adjust the dead time in response to a change in torque, rotational speed, vehicle speed, throttle position, brake actuation level, steering angle, temperature of the first transistor, temperature of the second transistor, or a change in battery voltage.

[0019] According to another exemplary embodiment of the present description, wherein the inverter control is further configured to update a dead-time register in a PWM output section of a control hardware prior to issuing a new current command in response to the fact that the new current command exceeds a threshold.

[0020] According to another exemplary embodiment of the present description, wherein the inverter control is further configured to update a dead-time register in a PWM output section of a control hardware prior to issuing a new current command in response to the fact that the new current command is below a threshold.

[0021] According to another exemplary embodiment of the present description, the inverter control is further configured to update the dead time so that it becomes effective after a predetermined number of PWM cycles.

[0022] According to another exemplary embodiment of the present description, wherein the inverter control is communicatively coupled to a lookup table and / or a closed-form equation for the dead time to be varied in order to minimize the inverter line loss, current harmonic, torque harmonic and / or noise, vibration and roughness level.

[0023] According to another exemplary embodiment of the present description, wherein the dead time within a basic cycle of a waveform of the alternating voltage is applied to reduce line loss under a creepage condition with low speed and high torque.

[0024] According to another exemplary embodiment of the present description, a drive system for a vehicle comprises a system controller for receiving user input via a user interface and for determining a speed and motor torque in response to the user input and a vehicle operating mode, a battery for supplying a direct current, a three-phase electric motor configured to generate the motor torque with the speed in response to an alternating voltage, an inverter for converting the direct current into the alternating voltage using a first transistor and a second transistor, and an inverter controller for determining a dead time in response to the torque and speed and for removing a first switching control signal from the first transistor, waiting for a duration equal to the dead time, and applying a second switching control signal to the second transistor.where the dead time is continuously updated in response to a change in torque and a change in rotational speed.

[0025] According to another exemplary embodiment of the present description, wherein the inverter control is configured to continuously adjust the dead time in response to a change in torque, rotational speed, vehicle speed, throttle position, brake actuation level, steering angle, first transistor temperature, second transistor temperature, and a change in the magnitude of a battery voltage. Brief description of the drawings

[0026] The exemplary embodiments are described below in conjunction with the following drawings, where the same numbers denote the same elements: Fig. Figure 1 illustrates a vehicle with one or more electric motors and battery systems in various embodiments; Fig. Figure 2 illustrates an EV drive system in various configurations; Fig. Figure 3 shows a schematic representation of an EV drive system in various embodiments; Fig. Figure 4 shows a block diagram of an EV drive inverter control system in various embodiments; and Fig. Figure 5 shows a flowchart illustrating an exemplary procedure for controlling an EV drive inverter in various embodiments. Detailed description

[0027] The following detailed description is merely exemplary and is not intended to limit applications and uses. Furthermore, there is no intention to be bound by any express or implied theories presented in the preceding technical field, background, summary, or the following detailed description.As used herein, the term “module” refers to any hardware, software, firmware, electronic control component, processing logic and / or processor device, individually or in any combination, including but not limited to: application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), electronic circuit, processor (common, dedicated or group) and memory executing one or more software or firmware programs, combinational logic circuit and / or other suitable components providing the described functionality.

[0028] Embodiments of the present description can be described here in the form of functional and / or logical block components and various processing steps. Such block components can be implemented by any number of hardware, software, and / or firmware components configured to perform the specified functions. For example, in one embodiment of the present description, various integrated circuit components may be used, such as memory elements, digital signal processing elements, logic elements, lookup tables, or the like, which, under the control of one or more microprocessors or other embodiments, can perform a variety of functions.Furthermore, the person skilled in the art will recognize that the embodiments of the present description can be used in conjunction with any number of systems and that the systems described here are merely exemplary embodiments of the present description.

[0029] For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, control, machine learning, image analysis, and other functional aspects of the systems (and the individual components of the systems) are not described in detail here. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and / or physical couplings between the different elements. It should be noted that in an embodiment of the present description, many alternative or additional functional relationships or physical connections may exist.

[0030] In Fig. Figure 1 shows a vehicle 10 with one or more electric motors and battery systems, which in particular uses a dynamically adjustable traction inverter to minimize line losses and prevent overshoot in the phase legs of the inverter by using power devices with minimal switching times and gate charges to enable shorter dead times.

[0031] As in Fig. As shown in Figure 1, the vehicle 10 generally comprises a chassis 12, a body 14, front wheels 16, and rear wheels 18. The body 14 is arranged on the chassis 12 and essentially encloses components of the vehicle 10. The body 14 and the chassis 12 can together form a frame. The wheels 16 and 18 are each rotatably connected to the chassis 12 near a corner of the body 14.

[0032] In the embodiment shown, vehicle 10 is depicted as a passenger car, but it should be noted that any other vehicle, including motorcycles, trucks, sport utility vehicles (SUVs), recreational vehicles (RVs), watercraft, aircraft, etc., can also be used. In various embodiments, vehicle 10 can be an autonomous vehicle that is automatically controlled to transport passengers and / or cargo from one place to another. In one exemplary embodiment, vehicle 10 can have a Level Two or higher automation system. A Level Two automation system means "partial automation." However, in other embodiments, the autonomous vehicle can be a so-called Level Three, Four, or Five automation system. A Level Three automation system means "conditional automation."A Level Four system means "high automation" and refers to the driving mode-dependent execution of all aspects of the dynamic driving task by an automated drive system, even if a human driver does not respond appropriately to a request for intervention. A Level Five system means "full automation" and refers to the complete execution of all aspects of the dynamic driving task by an automated drive system under all road and environmental conditions that can be handled by a human driver.

[0033] It is understood, however, that vehicle 10 can also be a conventional vehicle without autonomous driving functions. Vehicle 10 can implement the functions and procedures for generating a virtual view with harmonized colors as described herein.

[0034] As shown, the vehicle 10 generally comprises a drive system 20, a transmission system 22, a steering system 24, a braking system 26, a sensor system 28, an actuator system 30, at least one data storage device 32, at least one control unit 34, and a communication system 36. The drive system 20 may, in various embodiments, comprise an internal combustion engine, an electric machine such as a traction motor, a fuel cell drive system, and / or a combination thereof. The transmission system 22 is configured to transmit the power of the drive system 20 to the vehicle wheels 16 and 18 according to selectable gear ratios. In various embodiments, the transmission system 22 may be a continuously variable automatic transmission, a continuously variable transmission, a manual transmission, or another suitable transmission.

[0035] The braking system 26 is configured to exert a braking torque on the vehicle wheels 16 and 18. The braking system 26 can, in various embodiments, comprise friction brakes, cable brakes, a regenerative braking system such as an electric motor, and / or other suitable braking systems. The steering system 24 influences the position of the vehicle wheels 16 and 18. In some embodiments considered within the scope of this description, the steering system 24 may not include a steering wheel, although it is shown with one for illustrative purposes.

[0036] The sensor system 28 comprises one or more devices 40a-40n that detect observable conditions in the external and / or internal environment of the vehicle 10. The devices 40a-40n may include, but are not limited to, radars, lidars, global positioning systems (GPS), optical cameras, thermal cameras, ultrasonic sensors, and / or other sensors. The devices 40a-40n are further configured to detect observable conditions of the vehicle 10. The devices 40a-40n may include, but are not limited to, speed sensors, position sensors, inertial sensors, temperature sensors, pressure sensors, etc.

[0037] The actuator system 30 comprises one or more actuator devices 42a-42n that control one or more vehicle features, such as, but not limited to, the drive system 20, the transmission system 22, the steering system 24, and the braking system 26. In various embodiments, the vehicle features may also include interior and / or exterior features of the vehicle, such as doors, a trunk, and cabin features such as air conditioning, music, lighting, etc. (not numbered).

[0038] The communication system 36 is configured to wirelessly transmit information to and from other units 48, such as, but not limited to, other vehicles (“V2V” communication), infrastructure (“V2I” communication), remote systems and / or personal devices (described in more detail in relation to Fig. 2) In an exemplary embodiment, the communication system 36 is a wireless communication system configured to communicate over a wireless local area network (WLAN) using IEEE 802.11 standards or using cellular data communication. However, additional or alternative communication methods, such as a dedicated short-range communication (DSRC) channel, are also considered within the scope of this description. DSRC channels refer to one-way or two-way short- to medium-range wireless communication channels specifically designed for use in motor vehicles, and to a number of protocols and standards.

[0039] The data storage device 32 stores data for use in the automatic control of functions of the vehicle 10. In various embodiments, the data storage device 32 stores defined maps of the drivable environment. The defined maps can contain a variety of data not related to road data, such as altitude, climate, lighting, etc. In various embodiments, the defined maps can be predefined and retrieved from a remote system (as in Fig. 2 (described in more detail). For example, the defined maps can be compiled by the remote system and transmitted to the vehicle 10 (wirelessly and / or via cable) and stored in the data storage device 32. As can be seen, the data storage device 32 can be part of the controller 34, separate from the controller 34, or part of the controller 34 and part of a separate system.

[0040] The controller 34 comprises at least one processor 44 and a computer-readable device or medium 46. The processor 44 can be any custom or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among several processors connected to the controller 34, a semiconductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, any combination thereof, or generally any device for executing instructions. The computer-readable devices or media 46 can comprise volatile and non-volatile memory, such as read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM).KAM is a persistent or non-volatile memory that can be used to store various operating variables while the processor 44 is switched off. The computer-readable memory device or media 46 can be implemented using any number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrical PROMs), EEPROMs (electrically erasable PROMs), flash memory, or other electrical, magnetic, optical, or combined memory devices capable of storing data, some of which represent executable instructions used by the device 34 in controlling and executing functions of the vehicle 10.

[0041] The instructions can comprise one or more separate programs, each containing an ordered list of executable instructions for implementing logical functions. When executed by the processor 44, the instructions receive and process signals from the sensor system 28, perform logic, calculations, procedures, and / or algorithms to automatically control the components of the vehicle 10, and generate control signals for the actuator system 30 to automatically control the components of the vehicle 10 based on the logic, calculations, procedures, and / or algorithms. Although in Fig. Where only one controller 34 is shown, embodiments of the vehicle 10 may have any number of controllers 34 which communicate via any suitable communication medium or combination of communication media and which cooperate to process the sensor signals, perform logic, calculations, procedures and / or algorithms and generate control signals to automatically control features of the vehicle 10.

[0042] In various embodiments, one or more instructions from the controller 34 are included in the surround-view display system 100 and, when executed by the processor 44, process image data from at least one optical camera of the sensor system 28 to extract features from the images in order to determine the ground plane. The instructions executed by the processor 44 use the ground plane to determine information about the camera orientation. The camera orientation information is then used to assemble the image data into an environmental view from a specific perspective. In various embodiments, the sensor devices 40a to 40n include one or more cameras that capture an external environment of the vehicle 10 and generate the image data (e.g., optical cameras configured to capture color images of the environment).The cameras are arranged to each cover a specific field of view of the vehicle's surroundings. The image data from each camera is combined to create a complete view of the environment, based, for example, on the camera's pose and position relative to the vehicle and the ground.

[0043] It becomes clear that control 34 of the in Fig. The embodiments shown in Figure 1 may differ. For example, the control unit 34 may be coupled to or otherwise utilize one or more remote computer systems and / or other control systems, for example, as part of one or more of the aforementioned devices and systems of the vehicle. While this exemplary embodiment is described in connection with a fully functional computer system, the person skilled in the art will recognize that the mechanisms of the present description can be distributed as a program product with one or more types of non-volatile, computer-readable, signal-carrying media used to store the program and its instructions and to carry out its distribution, such as…A non-volatile, computer-readable medium that carries the program and contains computer instructions stored therein to cause a computer processor (such as processor 44) to execute and run the program. Such a program product can take a variety of forms, and the present description applies equally regardless of the specific type of computer-readable signal-carrying medium used to carry out the distribution. Examples of signal-carrying media include writable media such as floppy disks, hard disks, memory cards, and optical media, as well as transmission media such as digital and analog communication links. In certain embodiments, cloud-based storage and / or other techniques may also be used. Similarly, the computer system of controller 34 may also differ in other ways from the one described in [reference to be added]. Fig. 1. The embodiment shown may differ, for example, in that the computer system of the controller 34 may be coupled with one or more remote computer systems and / or other control systems or may otherwise use them.

[0044] Fig. Figure 2 shows a schematic representation of an EV drive system 200. The schematic shows the battery 210, the inverter 220, and the drive motor 230. The battery 210 is configured to supply the inverter circuit 220 with direct current. The inverter 220 is configured to receive the direct current from the battery 210 and convert the direct current into three-phase alternating current, which is required by the electric motor 230 to rotate the multiple wheels 240.

[0045] The energy source for an electric car is the battery 210, a high-performance energy storage system designed to provide a robust power supply to the electric motor 230. Unlike conventional combustion engines, which run on gasoline, EVs rely on these rechargeable batteries 210. Each battery 210 can be configured from numerous lithium-ion cells strategically connected in series and parallel to achieve the desired output voltage and capacity. The battery 210 operates through a precisely defined electrochemical process that takes place between the anode and the cathode. The positive anode, typically made of lithium cobalt oxide (LiCoO2), and the negative graphite cathode are key to generating electricity. During discharge, lithium ions oscillate between the electrodes, flowing from the anode to the cathode.This ion movement is accompanied by a corresponding flow of electrons through an external circuit, which ultimately drives the electric motor 230. To reverse this process and replenish the battery's energy reserves, the vehicle is connected to a charging station. The electrons from the charger flow in the opposite direction, causing the lithium ions to migrate back to the anode. This carefully controlled flow of ions and electrons determines the charge and discharge cycles that the battery 210 undergoes throughout its service life.

[0046] The battery management system (BMS) is responsible for the efficient and safe operation of the 210 battery. This sophisticated computer system regulates factors such as cell voltage, current, and temperature. By monitoring these parameters, the BMS optimizes battery performance, extends its service life, and prioritizes safety. This is achieved by constantly balancing the voltages of the individual cells within the battery, thus preventing overcharging or over-discharging that could lead to damage. Furthermore, the BMS serves as a crucial communication hub, transmitting real-time data on the battery's condition and remaining range to the vehicle's onboard diagnostic system. This information is essential for the driver to make informed decisions regarding charging needs and to optimize their journey.

[0047] Within the EV drive system 200, the DC-AC inverter 220 acts as a critical interface between the high-voltage battery 210 and the electric motor 230. The inverter 220 is configured to efficiently convert the DC output signal of the battery 210 into a precisely controlled, three-phase AC current, which is supplied to the electric motor 230. Using devices such as insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs) in a pulse-width modulation (PWM) scheme, the inverter 220 synthesizes the desired AC waveforms. This three-phase AC output is characterized by three sinusoidal waveforms, each offset by 120 degrees from the others.This strategic manipulation by the inverter 220 is crucial because it generates a rotating magnetic field in the electric motor 230. The configuration of the switching sequence determines the speed and torque of the motor 230 to enable smooth and efficient vehicle operation.

[0048] In some exemplary embodiments, the inverter 220 utilizes high-performance devices (such as IGBTs or MOSFETs) as core components, while gate driver circuits and advanced control algorithms ensure their precise and efficient operation. Sensors can be used to monitor voltage and current changes within the system, providing real-time data to the BMS. This continuous feedback loop enables ongoing adjustments and optimizations, ensuring that the inverter operates at peak efficiency under varying operating conditions. Furthermore, thermal management plays a crucial role in maximizing the inverter's efficiency. Low-resistance materials, high switching speeds, and continuously adjustable dead times can be employed in the design to minimize internal energy losses.During regenerative braking, the inverter 220 can be used to recover kinetic energy from the vehicle's deceleration and convert this energy back into direct current, effectively recharging the battery 210. This regenerative energy conversion increases the vehicle's overall range and illustrates the bidirectional function of the inverter 220 in the EV drive system 200.

[0049] The 230 electric motor utilizes the principles of electromagnetism and can be either an induction motor or a permanent magnet synchronous motor (PMSM) with high efficiency and power density. Unlike internal combustion engines, the PMSM converts the electrical energy stored in the DC battery into mechanical rotation via the 120 inverter to power the vehicle. The 230 electric motor has two main components: the stator and the rotor. The stator is a rigid, cylindrical housing containing strategically placed permanent magnets. Surrounding the stator is the rotor, a rotating shaft made of laminated steel segments. Windings, i.e., coils of precisely wound conductive material, are embedded within these segments.The interaction between the three-phase alternating current supplied by inverter 220 and the permanent magnets in the stator induces a current in the rotor windings. This induced current generates an alternating magnetic field around the rotor. The resulting interaction between these two magnetic fields exerts a torque on the rotor, causing it to rotate continuously in the direction of the rotating magnetic field generated by the stator. By controlling the frequency and voltage of the three alternating current phases supplied by inverter 220, the speed and torque of the electric motor 230 are regulated. This granular control ultimately determines the acceleration and overall power output of the vehicle.

[0050] The rotational force generated by the electric motor 230 is generally directly proportional to the current and the strength of the magnetic field. However, to achieve optimal vehicle performance, this output speed typically needs to be further adjusted by a torque transmission system. In some exemplary embodiments, a reduction gear acts as a crucial intermediate element, functioning as a speed multiplier. This gear converts the motor's high speed and low torque into a lower speed and high torque ideally suited for driving the wheels. This important reduction allows the motor to operate in its most efficient range while providing the substantial torque required to overcome the vehicle's inertia, rotate each of the multitude of wheels 240, and propel the vehicle forward.

[0051] Fig. Figure 3 shows a schematic representation of an EV drive system 300. The schematic shows the battery 210, the inverter 220, and the drive motor 330. The battery 310 is configured to supply direct current to the inverter circuit 320. The inverter 320 is configured to receive the direct current from the battery 310 and convert the direct current into three-phase alternating current, which the electric motor 330 requires. The inverter 320 rapidly switches the plurality of power switching devices 324, such as transistors, in a predetermined sequence, thus generating a pulsating direct current output. In some exemplary embodiments, filters, such as...A decoupling capacitor 322, placed between the power and ground terminals of the inverter 320, is used to filter out noise and maintain a stable supply voltage during switching. Alternatively, one or more load capacitors or inductors may be used to remove unwanted harmonics, resulting in a clean, three-phase AC waveform at the inverter 320. Each phase carries a specific alternating current, carefully tuned to generate a rotating magnetic field in the motor. Each of the windings 332 in the stators of the drive motor 330 is connected to one of these three current phases. As the current flows through the windings 332, it generates a magnetic field. The interaction of the three phase-shifted currents produces a rotating magnetic field.

[0052] The inverter 320 rapidly switches the plurality of power switching devices 324, such as transistors, in a predetermined sequence, generating a pulsating DC output. The inverter controller 340 is configured to generate control signals to switch the plurality of power switching devices 324 in the desired sequence and for the desired duration, including the necessary dead time to prevent possible short circuits. In some exemplary embodiments, filters, such as a decoupling capacitor 322 placed between the power and ground terminals of the inverter 320, are used to filter out noise and maintain a stable supply voltage during switching, or one or more load capacitors or inductors are used to remove unwanted harmonics, resulting in a clean, three-phase AC waveform at the inverter 320.Each phase carries a specific alternating current, carefully tuned to generate a rotating magnetic field in the motor. Each of the windings 332 in the stators of the drive motor 330 is connected to one of these three current phases. As the current flows through the windings 332, it generates a magnetic field. The interaction of the three phase-shifted currents produces a rotating magnetic field.

[0053] In the drive motor 330, the rotating magnetic field of the stators interacts with the windings or magnets in the rotor of the drive motor 330. This interaction induces a current in the rotor windings 332, which in turn generates a force according to Lenz's law. This force causes the rotor to attempt to align itself with the rotating magnetic field, resulting in continuous rotation of the motor shaft. This rotating field is the driving force behind the rotation of the motor shaft and ultimately propels the vehicle forward. The inverter control allows for precise adjustment of the frequency and voltage of the AC output. This finely tuned control enables the system to precisely regulate the motor speed and torque, thus ensuring smooth, efficient, and optimized operation of the electric vehicle.

[0054] Dead time is a critical parameter in switching inverters, referring to a short interval during which both the high-side and low-side power switching devices of the same inverter branch are intentionally switched off. This intentional pause is a safety measure to prevent simultaneous conduction, which can lead to a short circuit and damage the inverter components. If both switches are conducting, they create a direct path between the positive and negative DC supply terminals, resulting in excessive current flow. While the dead time is necessary to prevent short circuits, it also results in a period during which current flows through a freewheeling diode or body diode (3). rdquadrant conduction). During this time, the output voltage of the inverter 320 is either zero or the DC link voltage, depending on the phase current direction. The phase current direction determines whether the high-side or low-side freewheeling diode conducts current. Current conduction through the freewheeling diode generates higher losses than the conduction losses through the channels of the power switching devices 324, which is why the inverter has a lower efficiency during the dead time. The dead-time-related conduction losses can be substantial, especially at higher switching frequencies, as the time the freewheeling diode conducts current increases. Consequently, the total power dissipation within the inverter 320 increases, leading to potential thermal management problems and a further reduction in efficiency.Although WBG devices like lateral GaN HEMTs do not contain an intrinsic body diode, they can still behave like diodes, albeit lossy ones, allowing the device to conduct reverse current even when it is "OFF". Therefore, reducing dead time can also improve the efficiency of GaN-based inverters.

[0055] In some exemplary embodiments, the slew rate can be a function of the dead time. The slew rate is the rate of change of the voltage or current of a signal. Increasing the slew rate can lead to a reduction in the electromagnetic radiation of the inverter 320. However, increasing the slew rate allows for a shorter dead time, which can improve the efficiency of the inverter 320. For example, in inverters for electric vehicle traction, silicon carbide (SiC) can be used, which has a fixed dead time of, say, ~2.5 µs in the gate drivers. This fixed dead time can lead to significant conduction losses during operation in the third quadrant, where the gate-source junction is reverse-biased, resulting in a large voltage drop associated with conduction in the third quadrant. rdThis leads to increased line losses in the quadrants. As the switching frequency increases, the duration of the dead time also increases as a percentage of the switching period of these line losses, further exacerbating the problem. There are two dead time intervals during each switching cycle. It is desirable to use an adjustable dead time in the 320 inverter to minimize line losses while preventing shoot-through in the inverter's phase legs, and to use switching devices with minimal switching times and gate charges to enable shorter dead times.

[0056] Fig. Figure 4 shows a block diagram illustrating the control of an inverter for an EV drive system 400. The inverter control system 400 can include a system controller 410, an inverter controller 420, a gate driver 430, an inverter power stage 440, an electric motor 460, and a temperature sensor 450.

[0057] The system controller 410 in an electric vehicle is responsible for overall vehicle management, while the inverter controller 420 specifically manages the power conversion between direct current from the battery and alternating current for the electric motor 460. In some exemplary embodiments, the system controller 410 can send data to the inverter controller 420 to ensure optimal performance, efficiency, and safety. The data transmitted from the system controller to the inverter controller 420 can include motor speed and torque requirements, vehicle mode, battery state of charge (SOC), battery temperature, vehicle speed, and safety information.

[0058] The 410 control unit can determine the desired motor speed and torque based on driver inputs such as accelerator pedal position and vehicle dynamics. It sends this data to the 420 inverter control unit, which adjusts the inverter's power output accordingly. The 410 control unit can also transmit the current vehicle speed and mode, such as driving, reversing, and regenerative braking, to the 420 inverter control unit, enabling the latter to adapt its operation to the prevailing driving conditions and apply various control strategies, including regenerative braking and traction control. Similarly, the 410 control unit can provide the 420 inverter control unit with the current battery state of charge (SOC) and battery temperature received from the battery management system.Furthermore, the 420 control unit can send safety-relevant information such as error codes or emergency shutdown commands to the 420 inverter control unit. This helps to prevent catastrophic failures and ensure vehicle safety.

[0059] The inverter controller 420 is configured to convert direct current from the battery into three-phase alternating current to power the electric motor 460, depending on the data received from the system controller 410. The inverter controller 420 controls the gate drivers 430, which are used to switch the transistors in the inverter power stage 440. The inverter controller 420 can control the frequency and voltage of the AC output to enable precise control of the motor speed and torque. During regenerative braking, the inverter controller 420 can control the switching of the inverter to convert the vehicle's kinetic energy into electrical energy and store it in the battery 460.The inverter control unit 420 can monitor its own operation and detect errors or abnormal conditions in order to take protective measures to prevent damage to itself or other components of the system.

[0060] To optimize system efficiency, the example Inverter 420 controller is configured with a real-time controllable dead-time setting to determine and adjust the dead time to prevent shoot-through between the upper and lower circuit breakers in each phase section of the EV drive system. At power-up, the dead time can be set to a predefined value to prevent shoot-through. An Inverter 420 controller can establish a standard power-up dead time by evaluating several operating parameters. The Inverter 420 controller can first calculate the worst-case current and voltage scenarios the inverter might encounter, taking into account factors such as the maximum load current and minimum input voltage.Real-time dead time can be applied within a basic sinusoidal current cycle to achieve further loss reduction at low speeds and high torque. The Inverter 420 controller can then consider the temperature range in which the inverter is operated, as elevated temperatures can increase switching losses and reduce device performance. The Inverter 420 controller can then evaluate driver delays and gate drive parameters that affect MOSFET turn-on and turn-off times. Finally, based on device characteristics and operating conditions, the Inverter 420 controller calculates the most unfavorable switching times.By taking these factors into comprehensive consideration, the inverter's 420 control unit can determine a suitable standard dead time, ensuring safe and efficient operation under the most demanding conditions.

[0061] To prevent power surges and ensure safe operation, the 420 inverter controller in EVs can use a predetermined dead time during power-up. This dead time establishes a minimum interval between the switching off of one switch and the switching on of the other, preventing direct connection of the DC supply terminals. To improve efficiency and reduce losses, especially at low speeds and high torques, real-time dead-time modulation can be implemented. By dynamically adjusting the dead time within a fundamental oscillation period of the sinusoidal current, the inverter's switching behavior can be optimized, resulting in lower power losses and improved overall efficiency.

[0062] The inverter controller 420 can use various algorithms to determine the minimum required dead time. These algorithms can consider different operating conditions, including discrete current, voltage, temperature, and gate driver parameters. By analyzing these factors, the controller can accurately calculate the required dead time to prevent shoot-through, where both switches of a half-bridge are turned on simultaneously. To minimize line losses, the inverter controller 340 can then dynamically adjust the dead time at any given operating point. Predefined data can be used to calculate the optimal dead time based on factors such as switching frequency, load current, and temperature received from the temperature sensor 450.By continuously monitoring these parameters, the controller can quickly adjust the dead time to ensure the switches conduct for the minimum required duration while preventing short circuits. This dynamic adjustment not only reduces power loss but also improves the overall efficiency and reliability of the inverter system. Furthermore, wide-bandgap (WBG) switches, such as gallium nitride (GaN) and silicon carbide (SiC), offer significant advantages for inverter design. Their low gate charge enables faster switching times and lower delays, resulting in reduced dead time. This is particularly beneficial in high-frequency applications where minimizing dead time is crucial for improving efficiency and reducing power losses.By incorporating WBG switches, inverters can achieve higher switching frequencies and lower overall system losses. While the presented system uses a temperature sensor (450) as an example to derive the optimal dead time based on factors such as switching frequency, load current, and detected temperature, it is not limited to this specific configuration. The integration of various automotive sensors, including but not limited to current and speed / position sensors, is being considered. Such additional sensor data can provide valuable contextual information that significantly influences the selection of the optimal dead time, thereby improving the adaptability and overall performance of the system.

[0063] In some exemplary embodiments, the inverter controller 420 can determine the amplitude and frequency of the inverter 440's output current based on vehicle conditions and driver input. The inverter controller 420 can adjust the dead time depending on the vehicle's operating conditions, such as vehicle speed, driver pedal position, battery voltage, inverter output current, and the measured or estimated temperature of the junction or power module. The inverter controller 420 can adjust the gate driver parameters, such as the slew rate, depending on the vehicle's operating conditions, driver pedal position, battery voltage, inverter output current, and the measured or estimated temperature of the junction or power module.The Inverter 420 controller can adjust the dead time depending on the gate driver parameters. The switching rate can be increased at lower battery voltages while complying with EMC / EMI regulations. The faster slew rate allows for a reduction in dead time. The Inverter 420 controller can reduce the dead time at lower current commands and / or bus voltages and increase the dead time at higher current commands and / or bus voltages to reduce line losses over the EV driving cycle. In some exemplary embodiments, the dead time can be adjusted depending on the switching frequency and / or the fundamental frequency of the drive motor.

[0064] In some exemplary embodiments, the inverter controller 420 can update a dead-time register in the pulse-width modulated (PWM) output section of the control hardware before issuing a new current command if the new current command exceeds a threshold. The inverter controller 420 can update the dead-time register within the PWM output section of the control hardware after issuing a new current command if the new current command is below a threshold. The inverter controller 420 can allow the new dead time to take effect in the next PWM cycle or after a predetermined number of PWM cycles. The inverter controller 420 can include a lookup table or a closed-form equation for the dead time, which can be varied as a function of several variables to achieve various objectives, such as…minimizing inverter line losses and minimizing current / torque harmonics and noise, harshness and vibration (NHV).

[0065] A gate driver 430 in an electric vehicle inverter system is configured to control the switching of power semiconductor devices such as insulated-layer bipolar transistors (IGBTs) or MOSFETs in the inverter power stage 440. By providing precise high-current and high-speed switching signals in response to control signals received from the inverter controller 420, the gate drivers 430 ensure efficient power conversion and accurate control of the inverter's output voltage and frequency. This, in turn, enables precise control of the electric motor's speed and torque, thus contributing to the overall performance and efficiency of the electric vehicle's drive system.In some exemplary embodiments, the gate driver 430 can provide variable gate driver voltage levels, including negative voltages, variable gate driver current levels, variable gate driver impedance, and dead time selection depending on the defined gate driver voltage level.

[0066] The inverter power stage 440 can be configured for the actual conversion of direct current from the battery 455 into alternating current to drive the electric motor 460. This conversion is achieved through the use of electronic switches, typically power MOSFETs or IGBTs. These switches are arranged in a bridge configuration, which allows the DC voltage to be rapidly switched between positive and negative terminals, thus generating a pulsating DC voltage. This pulsating DC voltage is then filtered to produce the desired AC output. The inverter power stage 440 receives switching voltages from the gate drivers 430, which control the switching of the electronic switches. The inverter power stage 440 can also include passive components such as capacitors and inductors, which filter the output waveform and provide impedance matching.In some exemplary embodiments, the switching devices are WBG semiconductors with low gate charge, which allow for shorter possible dead times.

[0067] Fig. Figure 5 shows a flowchart illustrating an exemplary method 500 for controlling an inverter for driving an electric vehicle according to one embodiment. The method 500 is configured to dynamically adjust an inverter for an EV drive motor to minimize line losses while preventing shoot-through in the inverter's phase legs by using power devices with minimal switching times and gate charges to enable shorter dead times.

[0068] Method 500 is initially configured to define a standard dead time. In some exemplary embodiments, the standard dead time can be defined during system design and stored in memory or a lookup table. To determine the standard dead time, Method 500 can load dead time tables from memory or the like. In some exemplary embodiments, the method can define a standard power-on dead time by comprehensively evaluating various operating parameters. By considering factors such as maximum load current, minimum input voltage, temperature range, driver delays, gate driver parameters, and device characteristics, Method 500 can calculate the worst-case current and voltage scenarios.This analysis enables the determination of a suitable standard dead time, ensuring safe and efficient operation under the most demanding conditions. In some exemplary embodiments, the lookup tables can define torque and speed ranges with predefined dead times. These lookup tables can also include current temperature and gate driver parameters.

[0069] In response to the setting of the default dead time, procedure 500 is next configured to read the current instructions Is* from the Control Panel or similar. If the current instructions Is* are greater than a first threshold (I1) of 540, procedure 500 sets the dead time to a first dead time (td1) of 545. Procedure 500 then determines whether to exit the td-setting algorithm. If the current instructions Is* are less than a first threshold (I1) of 560, the procedure sets the dead time to a second dead time (td2) of 555. Procedure 500 determines whether to exit the td-setting algorithm.

[0070] If the algorithm for setting the dead time is to be terminated (560), the algorithm is terminated (570). If the algorithm for setting the dead time is to be continued, which corresponds to a situation where the dead time is constantly being varied, the procedure for reading the current instruction Is (530) returns.

[0071] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that a large number of variants exist. The exemplary embodiment or embodiments are merely examples and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description is intended to provide the person skilled in the art with a practical guide for implementing the exemplary embodiment or embodiments. It is understood that various modifications to the function and arrangement of the elements can be made without departing from the scope of the disclosure as set out in the appended claims and their statutory equivalents.

Claims

[1] Inverter control for an electric motor, comprising: a control system for determining torque and speed for an electric motor; the electric motor for generating torque at rotational speed depending on an alternating voltage; a battery to supply a direct current voltage; an inverter comprising a first transistor and a second transistor for converting the direct current voltage into alternating current voltage; and an inverter control for determining a dead time depending on the torque and speed and for removing a first switching control signal from the first transistor, waiting for a time period equal to the dead time, and applying a second switching control signal to the second transistor, wherein the dead time is continuously updated depending on a change in torque and a change in speed. [2] Inverter control for the electric motor according to claim 1 further comprises a temperature sensor for detecting a first temperature of the first transistor and a second temperature of the second transistor, wherein the dead time is determined as a function of the first temperature and the second temperature. [3] Inverter control for the electric motor according to claim 1, wherein the inverter control is configured to adjust the dead time by setting a rise rate of the first switching control signal and the second switching control signal. [4] Inverter control for the electric motor according to claim 3, wherein the rate of increase is increased in response to a decrease in battery voltage. [5] Inverter control for the electric motor according to claim 1, wherein the inverter control is configured to adjust the dead time depending on at least one vehicle speed, one throttle position, one steering angle and one battery voltage. [6] Inverter control for the electric motor according to claim 1, wherein the inverter control is configured to adjust the dead time depending on at least one parameter of the inverter output current, a junction temperature and a power module temperature. [7] Inverter control for the electric motor according to claim 1, wherein the inverter control is configured to set the dead time as a function of a set of gate driver parameters of the first and / or the second transistor. [8] Inverter control for the electric motor according to claim 1, wherein the inverter control is configured to decrease the dead time in response to a reduced inverter current and / or a reduced bus voltage and to increase the dead time in response to an increased inverter current and / or an increased bus voltage. [9] Inverter control for the electric motor according to claim 1, wherein the inverter control is configured to adjust the dead time depending on the switching frequency of the inverter or the fundamental frequency of the electric motor. [10] Method for controlling a switching inverter for an electric motor for vehicle applications comprises: Determining the torque and speed of an electric motor using a controller; Generating torque by the electric motor at a given speed depending on an alternating voltage; which supply a DC voltage via a battery; Converting direct current to alternating current using an inverter with a first transistor and a second transistor; and Determining a dead time by an inverter control as a function of the torque and speed, and removing a first switching control signal from the first transistor, waiting a time equal to the dead time, and applying a second switching control signal to the second transistor, whereby the dead time is continuously updated as a function of a change in torque and a change in speed.

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