System and method for controlling a traction motor

Abstract

The present invention provides a system (100) and method (200) for controlling a traction motor. The system (100) includes a power source (110), a traction motor (120), and a control unit (140). The control unit is configured to detect a braking operation, determine a state of charge of the power source (110), operate the traction motor (120) to receive torque from wheels (130) of the vehicle and provide electrical energy to the power source (110) when the state of charge of the power source (110) is less than a first predetermined value during the braking operation, and operate the traction motor (120) to receive electrical energy from the power source (110) and provide braking torque to the wheels (130) by generating a counter torque when the state of charge of the power source (110) is equal to or greater than the first predetermined value during the braking operation. Reference: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the control of traction motors, and more particularly to systems and methods for controlling traction motors that provide braking torque to a vehicle. [Background technology]

[0002] As vehicle technology advances, there is an increasing focus on enhancing driver assistance and the overall driving experience. Most current electric or hybrid vehicles are equipped with regenerative braking, where energy is recovered during braking and stored back in the battery. Regenerative braking involves recovering some of the kinetic energy that would normally be converted to heat and converting it into electricity. Several conventional techniques exist for controlling regenerative braking. It is well known that when the regenerative braking contribution is set to a significant value, it results in better fuel economy, better braking control response, and better overall vehicle behavior.

[0003] However, regenerative braking, which charges the battery of an electric or hybrid vehicle, also depends on the battery's SoC (State of Charge). In existing systems, regenerative braking is configured to automatically turn off whenever the SoC reaches a threshold, such as 90% or higher, to maintain better battery life. The problem with this limitation is that this automatic switch-off of regenerative braking can occur suddenly, even during use / driving conditions, any time the SoC crosses the threshold. This abrupt switch-off of regenerative braking leads to a sudden reduction in braking response to any given input to the basic braking system, thereby leading to a sudden loss of vehicle control. This leads to a significant loss of occupant trust in the braking system, thereby creating a major road safety issue. Furthermore, this loss of regenerative braking poses an additional safety risk when the vehicle is climbing a slope.

[0004] Certain existing systems for regenerative braking control address the problem of preventing battery overcharging by turning off regenerative braking through various techniques. Other existing systems focus on the contribution of regenerative braking when the battery's SoC exceeds a threshold by dumping the regenerated kinetic energy with a rheostat, preventing it from contributing any useful work. This also results in additional components and an increase in the vehicle's overall weight. However, none of the prior art addresses the problem of loss of braking response and loss of vehicle control due to switching off regenerative braking when the SoC crosses a certain threshold. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need in the art for a system and method for controlling a traction motor that addresses at least the above-mentioned problems. [Means for solving the problem]

[0006] In one aspect, the present invention relates to a system for controlling a traction motor. The system includes a power source, a traction motor, and a control unit. The control unit is configured to detect a braking operation and determine a state of charge of the power source. The control unit is further configured to operate the traction motor to receive torque from wheels of a vehicle and provide electrical energy to the power source when the state of charge of the power source is less than a first predetermined value during the braking operation. The control unit is further configured to operate the traction motor to receive electrical energy from the power source and provide braking torque to the wheels by generating a counter torque when the state of charge of the power source is equal to or greater than the first predetermined value during the braking operation.

[0007] In one embodiment of the present invention, the control unit has a first phase high-side MOSFET and a first phase low-side MOSFET, a second phase high-side MOSFET and a second phase low-side MOSFET, and a third phase high-side MOSFET and a third phase low-side MOSFET.

[0008] In another embodiment of the present invention, the control unit is configured to sense a speed of the vehicle when the state of charge of the power source is greater than or equal to a first predetermined value, and is further configured to turn on the low-side MOSFET of the first phase, the low-side MOSFET of the second phase, and the low-side MOSFET of the third phase for a predetermined operating angle and turn off the high-side MOSFET of the first phase, the high-side MOSFET of the second phase, and the high-side MOSFET of the third phase for a predetermined time to operate the traction motor to provide a braking torque to the wheels of the vehicle by generating a counter torque when the speed of the vehicle is less than a second predetermined value.

[0009] In another embodiment of the present invention, the control unit is configured to turn on the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET for a predetermined operating angle and turn off the first phase high-side MOSFET, the second phase high-side MOSFET, and the third phase high-side MOSFET for a predetermined time when the vehicle speed is greater than or equal to a second predetermined value. The control unit is also configured to sense temperatures of the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET.

[0010] In another embodiment of the present invention, the control unit is configured to turn on the first phase high-side MOSFET, the second phase high-side MOSFET, and the third phase high-side MOSFET for a predetermined operating angle and turn off the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET for a predetermined time, when the temperatures of the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET are greater than or equal to a third predetermined value, to operate the traction motor to provide braking torque to the wheels of the vehicle by generating a counter torque.

[0011] In another aspect, the present invention provides a method for controlling a traction motor that provides braking torque to a vehicle, the method including the steps of detecting a braking operation of the vehicle, determining a state of charge of a power source of the vehicle, operating the traction motor to receive torque from wheels of the vehicle and provide electrical energy to the power source of the vehicle when the state of charge of the power source is less than a first predetermined value during the braking operation, and operating the traction motor to receive electrical energy from the power source and provide braking torque to wheels of the vehicle by generating a counter torque when the state of charge of the power source is equal to or greater than the first predetermined value during the braking operation.

[0012] In one embodiment of the present invention, the method includes sensing a speed of the vehicle when a state of charge of the power source is greater than or equal to a first predetermined value; and when the speed of the vehicle is less than a second predetermined value, turning on a low-side MOSFET of a first phase, a low-side MOSFET of a second phase, and a low-side MOSFET of a third phase for a predetermined operating angle and turning off a high-side MOSFET of the first phase, a high-side MOSFET of a second phase, and a high-side MOSFET of a third phase for a predetermined time to operate the traction motor to generate a counter torque and thereby provide a braking torque to the wheels of the vehicle.

[0013] In one embodiment of the present invention, the method includes operating a traction motor to provide braking torque to wheels of the vehicle by generating counter torque by turning on a first phase low-side MOSFET, a second phase low-side MOSFET, and a third phase low-side MOSFET for a predetermined operating angle and turning off a first phase high-side MOSFET, a second phase high-side MOSFET, and a third phase high-side MOSFET for a predetermined time when a speed of the vehicle is greater than or equal to a second predetermined value; and sensing temperatures of the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET.

[0014] In a further embodiment of the invention, the method includes turning on the first phase high-side MOSFET, the second phase high-side MOSFET, and the third phase high-side MOSFET for a predetermined operating angle and turning off the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET for a predetermined time when temperatures of the first phase low-side MOSFET, the second phase low-side MOSFET, and the third phase low-side MOSFET are greater than or equal to a third predetermined value to operate the traction motor to provide braking torque to the wheels of the vehicle by generating a counter torque.

[0015] Reference will now be made to embodiments of the present invention, examples of which may be illustrated in the accompanying drawings. These drawings are intended for purposes of illustration and not limitation. While the invention will generally be described in the context of these embodiments, it will be understood that it is not intended to limit the scope of the invention to these particular embodiments. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 illustrates a system for controlling a traction motor that provides braking torque to a vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 illustrates a control unit of a system for controlling a traction motor according to an embodiment of the present invention. [Figure 3] FIG. 1 illustrates a method for controlling a traction motor that provides braking torque to a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to the control of traction motors. More particularly, the present invention relates to systems and methods for controlling traction motors that provide braking torque to a vehicle. The systems and methods of the present invention are typically used in vehicles such as two-wheel electric or hybrid vehicles, three-wheel electric or hybrid vehicles, four-wheel electric or hybrid vehicles, or other multi-wheel electric or hybrid vehicles, as appropriate.

[0018] FIG. 1 illustrates a system 100 for controlling a traction motor 120 that provides braking torque to a vehicle. As illustrated, the system 100 includes a power source 110. In one embodiment, the power source 110 comprises a battery (not shown) or a battery pack (not shown) comprised of multiple batteries. The system 100 further includes a traction motor 120 electrically connected to the power source 110 of a vehicle (not shown). The traction motor 120 is operably connected to at least one wheel 130 of the vehicle. Thus, during a traction operation, the power source 110 provides power to the traction motor 120, which in turn provides traction or torque to the at least one wheel 130 of the vehicle. During a braking operation, the traction motor 120 converts the kinetic energy of the at least one wheel 130 into electrical energy, which is provided to charge the power source 110. In one embodiment, the traction motor 120 may be operably connected to multiple wheels of the vehicle via a driveline (not shown), or the system 100 may have multiple traction motors 120, each connected to a respective wheel (130) of the vehicle.

[0019] As further shown in FIG. 1 , system 100 includes a control unit 140. Control unit 140 is coupled to traction motor 120 and configured to control the operation of traction motor 120. Control unit 140 is configured to detect vehicle braking. In this regard, in one embodiment, control unit 140 is coupled to a brake switch 150 of the vehicle. When a brake pedal or brake lever (not shown) is depressed or activated, brake switch 150 is activated to illuminate the brake lights. Brake switch 150 is in communication with control unit 140, which detects activation of brake switch 150, thereby detecting vehicle braking. Control unit 140 is also configured to determine a state of charge of power source 110. Thus, control unit 140 determines whether the state of charge of power source 110 is less than, equal to, or greater than a first predetermined value.

[0020] Additionally, control unit 140 is configured to operate traction motor 120 to receive torque from vehicle wheels 130 and provide electrical energy to vehicle power source 110 when the state of charge of power source 110 is less than a first predetermined value during a braking operation. Thus, when control unit 140 determines that the state of charge of power source 110 is less than the first predetermined value during a braking operation, control unit 140 operates traction motor 120 to perform regenerative braking by receiving torque from wheels 130 and providing electrical energy to power source 110.

[0021] If, during a braking operation, the control unit 140 determines that the state of charge of the power source 110 is equal to or greater than a first predetermined value, the regenerative braking described above is not performed to prevent the power source 110 from overcharging and to improve the lifespan of the power source 110. However, to prevent a loss of braking response or vehicle control during this condition, when the state of charge of the power source 110 is equal to or greater than the first predetermined value during a braking operation, the control unit 140 is configured to receive electrical energy from the power source 110 and operate the traction motor 120 to provide a braking torque to the vehicle wheels 130 by generating a counter torque. In this manner, the counter torque generated by the traction motor 120 has a similar effect on the braking operation as regenerative braking, thereby ensuring that the braking characteristics or resulting braking response are consistent regardless of the state of charge of the power source 110. This ensures a reliable and consistent braking operation, which leads to a better passenger experience and a safer riding condition. In one embodiment, the first predetermined value for the state of charge of the power source 110 is 90%. Thus, in operation, during a braking maneuver, if the state of charge is less than 90%, control unit 140 performs regenerative braking by operating traction motor 120 to receive torque from wheels 130 and provide electrical energy to power source 110. Conversely, during a braking maneuver, if the state of charge is 90% or greater, control unit 140 operates traction motor 120 to receive electrical energy from power source 110 and generate counter torque such that the resulting braking response and vehicle control remain the same while braking with constant effort.

[0022] In one embodiment, as shown in FIG. 2 , the control unit 140 includes a first-phase high-side metal-oxide-semiconductor field-effect transistor (MOSFET) 140A and a first-phase low-side MOSFET 140A′. The control unit 140 further includes a second-phase high-side MOSFET 140B and a second-phase low-side MOSFET 140B′. The control unit 140 further includes a third-phase high-side MOSFET 140C and a third-phase low-side MOSFET 140C′. In this regard, the high-side MOSFETs 140A, 140B, and 140C are connected to the positive terminal of the power supply 110, and the low-side MOSFETs 140A′, 140B′, and 140C′ are connected to the negative terminal of the power supply 110. Furthermore, the first-phase, second-phase, and third-phase MOSFETs are respectively connected to phase coils of the traction motor 120 to control the traction motor 120 in three phases.

[0023] The counter torque generated by traction motor 120 also depends on the vehicle's speed. To account for this, in one embodiment, control unit 140 is configured to sense the vehicle's speed when the state of charge of power source 110 is greater than or equal to a first predetermined value. If the sensed vehicle speed is less than a second predetermined value, control unit 140 is configured to operate traction motor 120 to provide braking torque to vehicle wheels 130 by turning on first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ for a predetermined operating angle and turning off first phase high-side MOSFET 140A, second phase high-side MOSFET 140B, and third phase high-side MOSFET 140C for a predetermined time to generate a counter torque. In one embodiment, the second predetermined value of vehicle speed is 25 Kmph. At lower vehicle speeds, such as when the speed is below the second predetermined value, less current needs to flow through the MOSFET to generate counter torque, and therefore the MOSFET is not thermally stressed.

[0024] However, the above techniques may lead to an increase in the temperature of the low-side MOSFET, especially when performed at high vehicle speeds, such as speeds equal to or greater than the second predetermined value. Accordingly, when the sensed vehicle speed is equal to or greater than the second predetermined value, control unit 140 is configured to operate traction motor 120 to provide braking torque to vehicle wheels 130 by turning on first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ for a predetermined operating angle and turning off first phase high-side MOSFET 140A, second phase high-side MOSFET 140B, and third phase high-side MOSFET 140C for a predetermined time to generate a counter torque. Furthermore, to address the issue of temperature rise of the low-side MOSFETs, the control unit 140 is also configured to sense the temperatures of the first phase low-side MOSFET 140A′, the second phase low-side MOSFET 140B′, and the third phase low-side MOSFET 140C′ if the sensed rate is greater than or equal to a second predetermined value.

[0025] In one embodiment, if control unit 140 determines that the temperatures of first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ are greater than or equal to a third predetermined value, control unit 140 adjusts accordingly as follows: To provide counter torque under such conditions, control unit 140 is configured to operate traction motor 120 to provide braking torque to vehicle wheels 130 by turning on first phase high-side MOSFET 140A, second phase high-side MOSFET 140B, and third phase high-side MOSFET 140C for a predetermined operating angle and turning off first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ for a predetermined time to generate counter torque. Thus, essentially, when the temperature of the turned-on low-side MOSFETs 140A', 140B', and 140C' crosses the third predetermined value, the counter torque due to operation of traction motor 120 is generated by high-side MOSFETs 140A, 140B, and 140C instead of low-side MOSFETs 140A', 140B', and 140C', thereby reducing thermal stress on low-side MOSFETs 140A', 140B', and 140C' and high-side MOSFETs 140A, 140B, and 140C. Furthermore, by controlling the net circulating power and / or circulating current in high-side MOSFETs 140A, 140B, and 140C and low-side MOSFETs 140A', 140B', and 140C', the amount of counter torque can also be controlled, thereby defining the required braking effect.

[0026] In another aspect, the present invention relates to a method 200 for controlling a traction motor 120 that provides braking torque to a vehicle. Method steps included in a method 200 for controlling a traction motor 120 according to an embodiment of the present invention are illustrated in FIG. 3. As shown, in step 202, a braking operation of the vehicle is detected by the control unit 140. In step 204, the state of charge of the vehicle's power source 110 is detected by the control unit 140. The control unit 140 determines, among other things, whether the state of charge of the power source 110 is less than, equal to, or greater than a first predetermined value. If, in step 204, it is determined that the state of charge of the power source 110 is less than the first predetermined value during a braking operation, the method 200 proceeds to step 222, in which the control unit 140 operates the traction motor 120 to receive torque from the vehicle's wheels 130 and provide electrical energy to the vehicle's power source 110 for regenerative braking. Thereafter, in step 224, the control unit 140 checks again for braking, and if braking is detected, i.e., the brake switch 150 is detected to be on, the method 200 returns to step 222 and continues operation, and if braking is not detected, i.e., the brake switch 150 is detected to be off, the process is stopped in step 226 until a braking operation is detected.

[0027] If, during a braking operation, it is determined in step 204 that the state of charge of power source 110 is greater than or equal to a first predetermined value, then method 200 proceeds to step 206. In step 206, the speed of the vehicle is sensed by control unit 140. In step 206, control unit 140 determines whether the speed of the vehicle is greater than, equal to, or less than a second predetermined value. If, in step 206, it is determined that the speed of the vehicle is less than the second predetermined value, then method 200 proceeds to step 216. In step 216, the first phase low-side MOSFET 140A′, the second phase low-side MOSFET 140B′, and the third phase low-side MOSFET 140C′ are turned on by the control unit 140 for a predetermined operating angle, and the first phase high-side MOSFET 140A, the second phase high-side MOSFET 140B, and the third phase high-side MOSFET 140C are turned off by the control unit 140 for a predetermined time to operate the traction motor 120 to provide braking torque to the vehicle wheels 130 by generating a counter torque. Thereafter, in step 218, the control unit 140 checks again for braking, and if braking is detected, i.e., the brake switch 150 is detected to be on, the method 200 returns to step 206 and continues operation, and if braking is not detected, i.e., the brake switch 150 is detected to be off, the process is stopped in step 220 until braking is detected.

[0028] If, in step 206, it is determined that the vehicle speed is greater than or equal to the second predetermined value, method 200 proceeds to step 208. In step 208, first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ are turned on by control unit 140 for a predetermined operating angle, and first phase high-side MOSFET 140A, second phase high-side MOSFET 140B, and third phase high-side MOSFET 140C are turned off by control unit 140 for a predetermined time to operate traction motor 120 to provide braking torque to vehicle wheels 130 by generating a counter torque. Method 200 then proceeds to step 210.

[0029] In step 210, the temperatures of first-phase low-side MOSFET 140A′, second-phase low-side MOSFET 140B′, and third-phase low-side MOSFET 140C′ are sensed by control unit 140. Accordingly, in step 210, control unit 140 determines whether the temperatures of first-phase low-side MOSFET 140A′, second-phase low-side MOSFET 140B′, and third-phase low-side MOSFET 140C′ are less than, equal to, or greater than a third predetermined value. If, in step 210, it is determined that the temperatures of low-side MOSFETs 140A′, 140B′, and 140C′ are less than the third predetermined value, the method proceeds to step 214. In step 214, first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ are turned on by control unit 140 for a predetermined operating angle, and first phase high-side MOSFET 140A, second phase high-side MOSFET 140B, and third phase high-side MOSFET 140C are turned off by control unit 140 for a predetermined time to operate traction motor 120 to provide braking torque to vehicle wheels 130 by generating counter torque. After step 214, method 200 continues operation by returning to step 206.

[0030] If, in step 210, it is determined that the temperatures of low-side MOSFETs 140A′, 140B′, and 140C′ are greater than or equal to the third predetermined value, method 200 proceeds to step 212. In step 212, first phase high-side MOSFET 140A, second phase high-side MOSFET 140B, and third phase high-side MOSFET 140C are turned on by control unit 140 for a predetermined operating angle, and first phase low-side MOSFET 140A′, second phase low-side MOSFET 140B′, and third phase low-side MOSFET 140C′ are turned off by control unit 140 for a predetermined time to operate traction motor 120 to provide braking torque to vehicle wheels 130 by generating a counter torque. After step 212, method 200 continues operation by returning to step 206.

[0031] Advantageously, the present invention provides a system and method for controlling a traction motor that provides braking torque to a vehicle such that, during a braking operation, a counter torque is generated and regenerative braking is terminated when the state of charge of the power source exceeds a first predetermined value. Because the counter torque affects braking characteristics similar to regenerative braking, there is no loss of braking response and loss of vehicle control due to regenerative braking being switched off when the SoC crosses a certain threshold. Therefore, a passenger does not perceive any difference in braking feel or response when regenerative braking is on or off. This ensures greater passenger trust and confidence in the braking system, ensuring a safer passenger experience.

[0032] Furthermore, the present invention eliminates the need for a rheostat to dump regenerative power, eliminating the need for additional components and reducing complexity and cost. The present invention does not require any additional hardware or external power source assistance to provide counter torque to achieve the same braking effect. The present invention also ensures that there is no loss of braking action or loss of braking characteristics or response, even when the state of charge is high and the vehicle is climbing a grade, thereby enhancing vehicle safety.

[0033] The consistent braking characteristics and braking response regardless of the state of charge of the power source provided by the present invention is expected to result in a consistent level of passenger confidence in the braking system, which translates into an overall better and safer passenger experience.

[0034] Although the present invention has been described with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention as defined in the claims below. [Explanation of symbols]

[0035] 100 Traction motor control system 110 Power supply 120 Traction Motor 130 wheels 140 Control Unit 140A First Phase High-Side MOSFET 140B Second Phase High-Side MOSFET 140C Third Phase High-Side MOSFET 140A' Low-side MOSFET of the first phase 140B' Second Phase Low-Side MOSFET 140C' Third Phase Low-Side MOSFET 150 Brake switch

Claims

1. A system (100) for controlling a traction motor (120) that provides braking torque to a vehicle, comprising: a power source (110); the traction motor (120) electrically connected to the power source (110) of the vehicle, the traction motor (120) operably connected to at least one wheel (130) of the vehicle; A control unit (140) comprising: Detecting a braking operation of the vehicle; determining a state of charge of the power source (110); operating the traction motor (120) to receive torque from the wheels (130) of the vehicle and to provide electrical energy to the power source (110) of the vehicle when a state of charge of the power source (110) is less than a first predetermined value during the braking operation; receiving electrical energy from the power source (110) and operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque when the state of charge of the power source (110) is equal to or greater than the first predetermined value during the braking operation; a control unit (140) configured as follows: A system (100) comprising:

2. The control unit (140) a first phase high-side MOSFET (140A) and a first phase low-side MOSFET (140A'); a second phase high-side MOSFET (140B) and a second phase low-side MOSFET (140B'); a third phase high-side MOSFET (140C) and a third phase low-side MOSFET (140C'); The system (100) of claim 1, comprising:

3. The control unit (140) detecting a speed of the vehicle when the state of charge of the power source (110) is equal to or greater than the first predetermined value; and operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque by turning on the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') for a predetermined operating angle and turning off the first phase high-side MOSFET (140A), the second phase high-side MOSFET (140B), and the third phase high-side MOSFET (140C) for a predetermined time when the speed of the vehicle is less than a second predetermined value. The system (100) of claim 2, configured to:

4. The control unit (140) operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque by turning on the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') for a predetermined operating angle and turning off the first phase high-side MOSFET (140A), the second phase high-side MOSFET (140B), and the third phase high-side MOSFET (140C) for a predetermined time when the speed of the vehicle is equal to or greater than the second predetermined value; sensing temperatures of the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C'); The system (100) of claim 3, configured to:

5. The control unit (140) and operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque by turning on the first phase high-side MOSFET (140A'), the second phase high-side MOSFET (140B'), and the third phase high-side MOSFET (140C') for a predetermined operating angle and turning off the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') for a predetermined time when temperatures of the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') are equal to or greater than a third predetermined value. The system (100) of claim 4, configured to:

6. A method (200) for controlling a traction motor (120) that provides braking torque to a vehicle, comprising: a control unit (140) detecting a braking operation of the vehicle; the control unit (140) determining a state of charge of the vehicle's power source (110); the control unit (140) operating the traction motor (120) to receive torque from wheels (130) of the vehicle and provide electrical energy to the power source (110) of the vehicle when the state of charge of the power source (110) is less than a first predetermined value during the braking operation; the control unit (140) receiving electrical energy from the power source (110) and operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque when the state of charge of the power source (110) is equal to or greater than the first predetermined value during the braking operation; A method (200) comprising:

7. the control unit (140) detecting the speed of the vehicle when the state of charge of the power source (110) is greater than or equal to the first predetermined value; the control unit (140) turning on a first phase low-side MOSFET (140A'), a second phase low-side MOSFET (140B'), and a third phase low-side MOSFET (140C') for a predetermined operating angle and turning off a first phase high-side MOSFET (140A), a second phase high-side MOSFET (140B), and a third phase high-side MOSFET (140C) for a predetermined time when the speed of the vehicle is less than a second predetermined value, thereby operating the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque; The method (200) of claim 6, comprising:

8. the control unit (140) turns on the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') for a predetermined operating angle when the speed of the vehicle is equal to or greater than the second predetermined value; turning off the first phase high-side MOSFET (140A), the second phase high-side MOSFET (140B), and the third phase high-side MOSFET (140C) for a predetermined time to operate the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque; the control unit (140) sensing temperatures of the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C'); 8. The method (200) of claim 7, comprising:

9. the control unit (140) turns on the first phase high-side MOSFET (140A), the second phase high-side MOSFET (140B), and the third phase high-side MOSFET (140C) for a predetermined operating angle when temperatures of the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') are equal to or greater than a third predetermined value; turning off the first phase low-side MOSFET (140A'), the second phase low-side MOSFET (140B'), and the third phase low-side MOSFET (140C') for a predetermined time to operate the traction motor (120) to provide a braking torque to the wheels (130) of the vehicle by generating a counter torque.

9. The method (200) of claim 8, comprising:

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