System for peak power management of electrical machines

Abstract

Electric drive system that includes: an electric machine; an inverter that is electrically coupled to the electric machine; and one or more controllers containing executable commands that cause the one or more controllers to generate a state machine configured to control a maximum output power of the electric drive system, wherein the state machine is in exactly one of a plurality of states at any given time, and wherein the plurality of states includes at least one state that allows the output power of the electric drive system to exceed a rated output power of at least one component of the electric drive system, and at least one state that allows the output power of at least one component of the electric drive system to be limited to less than the rated output power of the at least one component.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Application No. 63 / 595,995, entitled "SYSTEM AND METHOD FOR ELECTRIC MACHINE PEAK POWER MANAGEMENT," filed on November 3, 2023. The entire contents of the above-referenced application are hereby incorporated by reference for all purposes. TECHNICAL FIELD

[0002] The present disclosure relates to managing the peak output power of an electric drive system. The electric drive system may be part of an electric vehicle or a hybrid vehicle. BACKGROUND AND SUMMARY

[0003] Electrically powered vehicles can operate continuously at and below their rated operating conditions. Rated continuous operation can depend on various operating conditions, including, but not limited to, load (e.g., the load requested by the driver), component temperatures, and cooling system capacity. Operating components of an electric drive system (e.g., inverter, cables, electric machine, etc.) above their rated operating conditions can degrade the electric drive system. However, an electric drive system can also operate for a period of time above its steady-state operating conditions without system degradation. The period of time can depend on the drive system's operating conditions and the electric drive system's specifications.It may be desirable to operate the electric drive system above its rated operating conditions for a shorter period than the specified time to improve vehicle drivability and performance. For example, it may be desirable to operate the electric drive system above its rated continuous operation during gear shifting or when overtaking another vehicle. Individual components of a drive system may incorporate hardware or software monitors to maintain the electric drive system's operating limits, but programming an electric drive system can be complex and difficult to understand when a large number of inputs and conditions must be considered. In addition, updating and diagnosing an electric drive system, which may include many inputs and conditional instructions, can be difficult and time-consuming.

[0004] The inventors have recognized the above-mentioned problems and developed an electric drive system comprising: an electric machine; an inverter electrically coupled to the electric machine;and one or more controllers containing executable instructions that cause the controller to generate a state machine configured to control the maximum output power of the electric drive system, wherein the state machine is in exactly one of a plurality of states at a time, and wherein the plurality of states include at least one state that allows the output power of the electric drive system to exceed a rated continuous output power of at least one component of the electric drive system and at least one state that allows the output power of at least one component of the electric drive system to be limited to less than the rated continuous output power of the at least one component.;

[0005] By controlling the maximum output power of an electric drive system via a state machine, a power control system can be created that is relatively easy to scale and revise for system upgrades. Furthermore, the state machine can make it easier to understand and diagnose the operation of the power control system while the electric drive system is in use.

[0006] The present description can offer several advantages. In particular, the approach can simplify the development of power control for electric drive systems. Furthermore, this approach enables system diagnostics, making it easier for a technician to assess system operation. Furthermore, the state machine allows for the addition of additional states without significant effort.

[0007] It should be understood that the above summary is intended to introduce, in simplified form, a selection of concepts that are further explained in the detailed description. It is not intended to identify essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address the disadvantages noted above or elsewhere in this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an illustration of an exemplary vehicle including an electric vehicle propulsion system. Fig. 2A-2C show an example configuration of an electric vehicle. Fig. Figure 3 shows an example of a state machine for controlling the maximum output power of an electric drive system. Fig. 4 shows an example of a vehicle operating sequence according to the state machine of Fig. 3 and the systems from Fig. 1-2C. DETAILED DESCRIPTION

[0008] A method and system for controlling the maximum or peak output power of an electric drive system for a vehicle are described. The electric drive system may be integrated into an electric vehicle or a hybrid vehicle. In one example, the electric drive system is integrated into a vehicle as shown in Fig. 1 shown. Fig. 2A-2C show an exemplary powertrain for a vehicle with an electric drive system. A state machine for controlling the maximum output power for an electric drive system is shown in Fig. 3. An example of a sequence for controlling the maximum output power for an electric drive system according to the state machine of Fig. 3 is in Fig. 4 shown.

[0009] Fig. 1 illustrates an example of a vehicle propulsion system 199 for the vehicle 10. In Fig. 1, the mechanical connections between the various components are shown as solid lines, while the electrical connections between various components are shown as dashed lines. The front end of the vehicle is designated 110 and the rear end of the vehicle is designated 111. The vehicle 10 travels in the forward direction when the front end 110 of the vehicle leads the movement of the vehicle 10. The vehicle 10 travels in the reverse direction when the rear end 111 of the vehicle leads the movement of the vehicle 10. In this example, the vehicle 10 is a rear-wheel drive vehicle, but in other examples, the vehicle 10 may be a four-wheel drive or front-wheel drive vehicle.

[0010] The vehicle propulsion system 199 includes a power source 105 (e.g., an electric machine such as a motor), but in other examples, two or more power sources may be provided. In one example, the power source 105 may be a synchronous or induction electric machine operating as a motor or generator. In other examples, the power source 105 may be a direct current (DC) machine. The vehicle propulsion system 199 also includes a transmission 135. The power source 105 is connected to the transmission 135, and the transmission 135 transfers power from its rotor 105a to the transmission 135. The transmission 135 may be mechanically connected to differential gears 106. The differential gears 106 may be coupled to two axleshafts, including a first or right axleshaft 190a and a second or left axleshaft 190b. The vehicle 10 also includes front wheels 102 and rear wheels 103.

[0011] The transmission 135 may be referred to as a step-up transmission and may be configured as shown in the Fig. 2A-2C, or alternatively with a different configuration. The transmission 135 may include one or more clutch actuators (not shown) to shift one or more clutches. The transmission 135 may include a first speed sensor 119 for sensing a speed of the power source 105 and a second speed sensor 185 for sensing a speed of a transmission output shaft. The inverter 115 is electrically coupled to the power source 105 to convert direct current to alternating current (AC) and vice versa. The powertrain controller 116 is electrically coupled to sensors 117 and actuators of the vehicle propulsion system 199. The sensors 117 may include, but are not limited to, inverter switch temperature sensors, electrical machine winding temperature sensors, bus bar temperature sensors, etc.

[0012] The transmission 135 can transmit or receive mechanical power to or from the differential gears 106. The differential gears 106 can transmit or receive mechanical power to or from the rear wheels 103 via the right axle shaft 190a and the left axle shaft 190b. The power source 105 can consume alternating current (AC) power provided via the electrical inverter 115. Alternatively, the power source 105 can supply AC power to the electrical inverter 115. The inverter 115 can be powered by high-voltage direct current (DC) power from the battery 160 (e.g., a traction battery, which may also be referred to as an electrical energy storage device or battery pack). The electrical inverter 115 can convert the DC power from the battery 160 to AC power for the power source 105. Alternatively, the electrical inverter 115 can also be powered by AC power from the power source 105.The electrical inverter 115 can convert the alternating current from the power source 105 into direct current to store it in the battery 160.

[0013] The power source 105 can transmit mechanical power to or receive mechanical power from the transmission 135. For example, the transmission 135 can be a multi-gear set capable of shifting between gears upon command from the powertrain controller 116. The powertrain controller 116 includes a processor 116a and a memory 116b. The memory 116b (e.g., storage media) can include read-only memory, random access memory, and diagnostic memory. The memory can be programmed with computer-readable data representing instructions executable by a processor to perform the methods and control techniques described herein, as well as other variations that are expected but not explicitly listed. For example, the control techniques, methods, and the like described herein can be stored as instructions in non-volatile memory.

[0014] Battery 160 may periodically receive electrical energy from a power source, such as a stationary power grid 5, that is external to the vehicle (e.g., not part of the vehicle). As a non-limiting example, vehicle propulsion system 199 may be configured as a plug-in electric vehicle (EV), where electrical energy may be supplied to battery 160 via stationary power grid 5 and charging station 12. Electrical charge may be supplied to battery 160 via outlet 100.

[0015] The battery 160 may include a BMS controller 139 (e.g., a battery management system controller) and a power distribution box 162. The BMS controller 139 may handle charge balancing between the energy storage elements (e.g., the battery cells) and communication with other vehicle controllers (e.g., the vehicle control unit 152). The BMS controller 139 includes a core processor 139a and memory 139b (e.g., random access memory, read-only memory, and diagnostic memory).

[0016] The vehicle 10 may include a vehicle control unit (VCU) 152 that may communicate with the electric inverter 115, the powertrain controller 116, the friction or wheel brake controller 170, the global positioning system (GPS) 188, the BMS controller 139, and the instrument panel 186 and the components therein via the controller area network (CAN) 120. The VCU 152 includes the memory 114, which may include read-only memory (ROM or non-volatile memory) and random access memory (RAM). The VCU also includes a digital processor or central processing unit (CPU) 153 and inputs and outputs (I / O) 118 (e.g., digital inputs including counters, timers, and discrete inputs, digital outputs, analog inputs, and analog outputs). The VCU can receive signals from the sensors 154 and output control signals to the actuators 156.Sensors 154 may include, but are not limited to, lateral accelerometers, longitudinal accelerometers, yaw rate sensors, inclinometers, temperature sensors, battery voltage and current sensors, and other sensors described herein. Additionally, sensors 154 may include a steering angle sensor 197, a driver demand pedal position sensor 141, vehicle ranging sensors, including RADAR (Radio Detection and Ranging), LIDAR (Light Detection and Ranging), SONAR (Sound Navigation and Ranging), and a brake pedal position sensor 151. Actuators include, but are not limited to, inverters, transmission controllers, displays, human-machine interfaces, friction braking systems, and the battery controller described herein.

[0017] The driver demand pedal position sensor 141 is connected to the driver demand pedal 140 to determine a degree of actuation of the driver demand pedal 140 by the human 142. The brake pedal position sensor 151 is connected to the brake pedal 150 to determine the degree of actuation of the brake pedal 150 by the human 142. The steering angle sensor 197 is configured to determine the steering angle depending on the position of the steering wheel 198.

[0018] The vehicle propulsion system 199 is illustrated with a global positioning system 188 that receives time and position data from one or more GPS satellites 189. The global positioning system may also include geographic maps in ROM to determine the position of the vehicle 10 and the characteristics of the roads on which the vehicle 10 may travel.

[0019] The vehicle propulsion system 199 may also include an instrument panel 186 with which the driver of the vehicle can interact. The instrument panel 186 may include a display system 187 configured to display information to the vehicle operator. The display system 187 may include, as a non-limiting example, a touchscreen or a human machine interface (HMI) that allows the vehicle operator to display graphical information and input commands. In some examples, the display system 187 may be wirelessly connected to the internet (not shown) via a VCU 152. Thus, in some examples, the vehicle operator may communicate with a website or a software application (app) as well as the VCU 152 via the display system 187.

[0020] The instrument panel 186 may also include an operator interface 182 through which the vehicle operator can adjust the operating state of the vehicle. In particular, the operator interface 182 may be configured to enable and / or disable operation of the vehicle powertrain (e.g., the power source 105) based on input from a vehicle operator. Furthermore, a vehicle operator may request an axle mode (e.g., park, reverse, neutral, drive) via the operator interface. Various examples of the operator interface 182 may include interfaces that utilize physical devices, such as a key that can be inserted into the operator interface 182 to activate the vehicle propulsion system 199, including the power source 105, and turn on the vehicle 10.The device can be removed to deactivate the transmission 135 and the power source 105 and to turn off the vehicle 10. The power source 105 can be activated by supplying electrical power to the power source 105 and / or the electrical inverter 115. The power source 105 can be deactivated by ceasing the supply of electrical power to the power source 105 and / or the inverter 115. In other examples, additionally or optionally, a start / stop button manually pressed by the vehicle operator can be used to start or deactivate the power source 105 and to turn the vehicle on or off. In other examples, a remotely controlled electrified axle or electric machine can be initiated by a remote computing device (not shown), e.g.,a mobile phone or smartphone-based system in which a user's mobile phone sends data to a server, and the server communicates with the vehicle control unit 152 to activate the inverter 115 and the power source 105. The spatial orientation of the vehicle 10 is indicated by the axes 175.

[0021] The vehicle 10 is also shown with a wheel or friction brake controller 170. The friction brake controller 170 can selectively apply and release the friction brakes (e.g., 172a and 172b) by flowing hydraulic fluid to the friction brakes. The friction brakes can be applied and released to prevent friction brake lockup on the front wheels 102 and the rear wheels 103. The wheel position or speed sensors 161 can provide wheel speed data to the friction brake controller 170. The vehicle propulsion system 199 can transfer torque to the rear wheels 103 to propel the vehicle 10.

[0022] A human or autonomous driver may request driver-demanded wheel torque or, alternatively, driver-demanded wheel power by applying the driver demand pedal 140 or by communicating a request for driver-demanded wheel torque / power to the vehicle control unit 152. The vehicle control unit 152 may then request torque or power from the power source 105 via instructions to the powertrain controller 116. The powertrain controller 116 may instruct the electric inverter 115 to deliver the driver-demanded wheel torque / power via the electrified powertrain 190 and the power source 105. The electric inverter 115 may convert the direct current from the battery 160 to alternating current and deliver the alternating current to the power source 105. The power source 105 rotates and transmits torque / power to the transmission 135.The transmission 135 can transmit the torque from the power source 105 to the differential gears 106, and the differential gears 106 transmit the torque from the power source 105 to the rear wheels 103 via the axle shafts 190a and 190b.

[0023] When the driver request pedal is fully released, the vehicle control unit 152 may request a small amount of negative or regenerative braking power to gradually decelerate the vehicle 10 if a speed of the vehicle 10 is greater than a threshold speed. The requested regenerative braking power may depend on the driver request pedal position, the battery state of charge (SOC), the vehicle speed, and other conditions. When the driver request pedal 140 is fully released and the vehicle speed is below a threshold, the vehicle control unit 152 may request a small amount of positive torque / power (e.g., drive torque) from the power source 105, which may be referred to as creep torque or creep power.The creep torque or creep power may enable the vehicle 10 to remain stationary when the vehicle 10 is on a slight incline.

[0024] The human or autonomous driver may also request negative or regenerative driver-demand braking torque, or alternatively, driver-demand braking power, by applying the brake pedal 150 or by communicating a request for driver-demand braking power to the vehicle control unit 152. The vehicle control unit 152 may request, via instructions to the powertrain controller 116, that a first portion of the driver-requested braking power be generated via the power source 105. In addition, the vehicle control unit 152 may request that a portion of the driver-requested braking power be provided via the friction brakes 172 by instructing the friction brake controller 170 to provide a second portion of the driver-requested braking power.

[0025] After the vehicle control unit 152 determines the requested braking power, the vehicle control unit 152 may instruct the powertrain controller 116 to deliver the portion of the driver-requested braking power allocated to the power source 105. The power source 105 may convert the vehicle's kinetic energy into alternating current.

[0026] The powertrain controller 116 includes predefined transmission shift schedules that allow the gears of the fixed-ratio transmission 135 to be selectively engaged and disengaged. The shift schedules stored in the powertrain controller 116 can select shift points or events depending on the driver's requested wheel torque and vehicle speed.

[0027] To now Fig. 2A, FIG. shows a first example of a vehicle propulsion system 199. The vehicle 10 may be, for example, a passenger car, a commercial vehicle, or an off-highway vehicle such as a wheel loader, an excavator, a dump truck, a material handling vehicle, a tractor, a harvester, a mining vehicle, or the like. An off-highway vehicle is a vehicle that cannot travel on highways and other roads due to its size, weight, and / or top speed. The vehicle propulsion system 199 includes a power source 105 and a transmission 135. In the illustrated example, the power source 105 is coupled to an inverter 115 via an electrical connection 209 (e.g., multi-phase wires, bus bars, combinations thereof, and the like). Thus, in the illustrated example, the power source 105 is an alternating current (AC) motor.This means that the traction motor may be a multi-phase (e.g., three or more phases) AC motor. In a specific application, the drive source may be a three-phase AC motor. However, in alternative examples, a DC drive source may also be used in the vehicle propulsion system 199.

[0028] The inverter 115 may be electrically connected to the battery 160. Thus, during driving mode and during regeneration mode, when the power source 105 is operated as a motor, electrical energy may flow between the inverter 115 and the battery 160.

[0029] The vehicle propulsion system 199 may further include one or more drive axle assemblies 212 mechanically coupled to one or more output interfaces 214 that may be included in the transmission 135. The drive axle assembly may, in one example, be a rear drive axle assembly. The drive axle assembly may include differentials, axle shafts (e.g., half shafts) coupled to the associated differential, drive wheels coupled to the axle shafts, etc. The drive wheels may be mounted on wheel hubs and contact a driving surface during vehicle operation.

[0030] The power source 105 may include components such as a rotor and a stator that interact electromagnetically during operation to generate motive power. In another example, the motor may be a motor generator configured to generate electrical energy during regeneration operation.

[0031] The transmission 135 may include an input shaft 213 that is mechanically (e.g., directly mechanically) coupled to a rotor shaft in the power source 105. Splined shafts, bolts and flanges, combinations thereof, and / or the like may be used to establish the mechanical connection between the rotor shaft and the input shaft 213. The inputs and outputs of the transmission 135 generally refer to the power flow that occurs when the vehicle is operating in a drive mode in which mechanical power is transferred from the traction motor to the drive wheels to propel the vehicle in a desired direction (e.g., forward or reverse). However, it should be understood that during regeneration operation, the mechanical power flow is in the reverse direction (e.g., from the drive wheels to the traction motor).

[0032] In the example shown, a gear 218 is rigidly coupled to the input shaft 213. The rigid coupling of the components allows both components to rotate. Furthermore, as shown, the gear 218 meshes with a gear 220 on a shaft 222 (e.g., intermediate shaft). The gear 220 is rigidly coupled to the shaft 222. However, in other examples, other gear arrangements and / or other mechanical connections may be established between the input shaft and the intermediate shaft.

[0033] In the illustrated embodiment, the transmission 135 also includes an output shaft 224. A first friction clutch 228 may be mounted on the shaft 222. A second friction clutch 226 may be mounted on the output shaft 224. The second friction clutch 226 may be connected to a second operating gear ratio formed between a gear 230 and a gear 232. The gear 232 may be freely mounted on the shaft 224 via a bearing 233. When the second friction clutch 226 is disengaged, the gear 232 and the output shaft 224 may rotate independently of each other. Likewise, the second friction clutch 228 may be connected to a first operating gear ratio formed between a gear 234 and a gear 236. The second operating gear ratio may be greater than the first operating gear ratio.For example, the first operating gear ratio can be used when starting the vehicle and during lower-speed maneuvers. Conversely, the second operating gear ratio can be used during higher-speed maneuvers. However, in other examples, the first operating gear ratio can be higher than the second operating gear ratio.

[0034] The first friction clutch 228 may include an inner plate carrier 238 (e.g., a hub) fixedly coupled to the shaft 222 and an outer plate carrier 240 (e.g., a drum) fixedly connected to the gear 234. The plate carriers may each include sets of plates 241 configured to frictionally engage and disengage during engagement and disengagement of the clutch. That is, the plates (e.g., friction and spacer discs) may be nested to enable selective torque transmission. For example, the plates may be splined to the carriers. However, other mounting techniques for the plates and carriers are also contemplated. The gear 234 may be freely mounted on the shaft 222. For example, a bearing 242 may be used to mount the gear 234 to the shaft 222. The bearings described here can be outer rings, inner rings and rolling elements (e.g.Balls, cylindrical rollers, tapered cylinders, and the like). Freewheeling assembly refers to the attachment of a gear to a shaft so that the gear and shaft can rotate independently of each other. Gear 234 meshes with a gear 236, which, in the example shown, is rigidly coupled to output shaft 224.

[0035] The second friction clutch 226 may include an outer plate carrier 244 fixedly coupled to the gear 232, an inner plate carrier 246 fixedly coupled to the output shaft 224, and plates 248 in both carriers. Thus, the second friction clutch 226 may have a similar structure to the first friction clutch 228.

[0036] The friction clutches 226, 228 may be wet friction clutches to lower the temperature of the clutches during shifting and thus reduce the risk of overheating of the clutches. Therefore, in such an example, the friction clutches 226, 228 may receive lubricant (e.g., natural and / or synthetic oil) from a lubrication system 250. The lubrication system 250 may include a sump for the lubricant, a pump, lines, passages, valves, and the like that direct the lubricant to the clutches and other components requiring lubrication, such as bearings, gears, and the like. Furthermore, in one example, the lubrication system 250 may be equipped with hydraulic actuation circuits that allow the friction clutches to be hydraulically actuated. The friction clutches may, for example, include hydraulically actuated pistons that are in fluid communication with the actuation circuit.However, in other examples, the hydraulic actuation circuits may be formed in a separate system separate from the lubrication system, or the friction clutches may be actuated electromechanically and / or pneumatically.

[0037] The friction clutches 226, 228 are arranged on different shafts in the transmission, allowing the transmission to achieve better space utilization and load distribution. However, in other examples, the clutches may also be arranged coaxially on the same shaft.

[0038] The output interfaces 214 (e.g., keyways, flanges, yokes, etc.) can be used to attach the output shaft 224 to downstream components. This means, as indicated by arrows 252, a mechanical connection can be established between the output interfaces and the drive axle assemblies 212. Shafts, joints, gears, chains, combinations thereof, and the like can be used to establish the mechanical connection between the output interfaces and the drive axle assemblies.

[0039] It is understood that the transmission 135 may include additional shafts, gears, and / or clutches, which may also be arranged differently in other examples. For example, the transmission 135 may include a second intermediate shaft with another clutch attached thereto and / or an additional shaft that functions as an output shaft. For example, the transmission 135 may have three or more gears in other examples. However, increasing the number of available gears in the transmission increases the size and complexity of the transmission. Therefore, the transmission may in particular be a two-speed transmission to reduce the size and complexity of the transmission and reduce the risk of component wear. The use of a two-speed transmission may be particularly suitable for a traction motor because the motor has a wider power band than, for example, internal combustion engines.

[0040] The storage medium may be programmed with computer-readable data representing instructions executable by a processor to perform the methods and control techniques described herein, as well as other variations that are expected but not explicitly listed. Thus, the control techniques, methods, and the like described herein may be stored as instructions in non-volatile memory.

[0041] For reference, an axis system is Fig. 2A, as well as in Fig. 2B and Fig. 2C. In one example, the z-axis may be a vertical axis (e.g., parallel to a gravitational axis), the x-axis may be a lateral axis (e.g., a horizontal axis), and / or the y-axis may be a longitudinal axis. However, in other examples, the axes may have other orientations.

[0042] The power source 105 may be configured to rotate the rotor shaft in opposite directions corresponding to forward and reverse travel. Therefore, in one example, the transmission 135 may be configured to operate with an equal number of forward and reverse gears. However, in alternative examples, the transmission may also have an asymmetric number of forward and reverse gears.

[0043] Fig. 2B and Fig. 2C show the mechanical power paths 270 and 280 that occur in the transmission 135 of the vehicle drive system 199 in the first operating gear and the second operating gear, respectively. Fig. 2B and 2C, the inverter 115 transfers electrical energy to the drive source 105, and the drive source generates mechanical power and feeds it to the transmission 135. However, as previously mentioned, the inverter 115 may be omitted from the drivetrain in other embodiments.

[0044] In the two mechanical power paths 270 and 280, the power flows from the drive source 105 to the input shaft 213, from the input shaft to the gear 218, from the gear 218 to the gear 220, and from the gear 220 to the shaft 222.

[0045] In performance path 270 from Fig. 2B, the power is then transmitted from shaft 222 through first friction clutch 228 to gear 234, from gear 234 to gear 236, from gear 236 to output shaft 224, and from output shaft 224 to drive axle assemblies 212.

[0046] In contrast, the power in power path 280 is Fig. 2C via the first friction clutch 228 and then from the shaft 222 to the gear 230, from the gear 230 to the gear 232, from the gear 232 via the second friction clutch 226 to the output shaft 224 and from the output shaft 224 to the drive axle assemblies 212.

[0047] The system from Fig. 1-2C provides an electric drive system comprising: an electric machine; an inverter electrically coupled to the electric machine; and one or more controllers containing executable instructions that cause the controller to generate a state machine configured to control the maximum output power of the electric drive system, wherein the state machine is in exactly one of a plurality of states of the state machine at a time, and wherein the plurality of states includes at least one state that allows the output power of the electric drive system to exceed a rated output power of at least one component of the electric drive system and at least one state that allowsthat the output power of at least one component of the electric drive system is limited to less than the rated power of the at least one component. In a first example, the electric drive system includes that the transitions between the plurality of states depend on the operating states of the electric drive system. In a second example, which may include the first example, the electric drive system includes that the operating states of the electric drive system include a first threshold temperature. In a third example, which may include both the first and second examples, the electric drive system includes that the operating states of the electric drive system include a second threshold temperature. In a fourth example, which may include one or more of the first to third examples, the electric drive system includes,that the operating states of the electric drive system include boost states. In a fifth example, which may include one or more of the first or fourth examples, the electric drive system includes the plurality of states including a minimum power state. In a sixth example, which may include one or more of the first to fifth examples, the electric drive system includes the plurality of states including an underload state of the inverter. In a seventh example, which may include one or more of the first to sixth examples, the electric drive system includes the plurality of states including two types of power boost states.

[0048] In Fig. Figure 3 is a graphical representation of an exemplary state machine 300 for managing the maximum or peak output power of an electric vehicle propulsion system. The state machine 300 is a representation of a mathematical model that may be implemented via executable control instructions stored in non-volatile memory, values ​​of variables stored in volatile memory, and operating states of devices and / or actuators. The state machine 300 may receive inputs indicative of the operating states of the vehicle (e.g., electric machine winding temperature, inverter switch temperature, bus bar temperature, vehicle position, positions of other vehicles around the vehicle, vehicle speed, driver demand, ambient temperature, vehicle route data, transmission gear engaged, etc.).The state machine 300 can be viewed as a method for controlling the maximum output torque or maximum output power of the vehicle propulsion system.

[0049] In this example, state machine 300 includes five states 302, 308, 314, 318, and 330, but in other examples, additional or fewer states may be provided. State machine 300 operates such that it can occupy exactly one state at a given time. Entry actions (e.g., changing an operating state of an actuator, changing a value of a variable stored in memory, reading a value of a variable stored in memory, determining an operating state of an actuator, etc.) may be performed by state machine 300 upon transition into and before entering a state. Exit actions (e.g., changing an operating state of an actuator, changing a value of a variable stored in memory, reading a value of a variable stored in memory, determining an operating state of an actuator, etc.)) may be performed by state machine 300 upon transitioning from or exiting a state. State machine 300 may transition from one state (e.g., nominal power state 302) to a second state (e.g., Type 1 power enhancement state) via a transition (e.g., transition 332). State machine 300 also includes a state group 340, which in this example is comprised of three states (e.g., 302, 308, and 330), but in other examples, a state group may include additional or fewer groups. State group 340 indicates that a state entering the state group may enter any state within the group.The state group 340 provides a way to minimize the actual total number of transition lines from one state to other states while still indicating that one state can be entered or exited from any state within the state group.

[0050] The state machine 300 may cooperate with other control routines to control the maximum or peak output of the vehicle propulsion system 199. For example, another control routine may determine a driver-requested torque or power from the vehicle propulsion system 199. The driver-requested torque or power may be a function of the driver-requested pedal position and the vehicle speed. The driver-requested torque or power may be supplied to the state machine 300, and the state machine 300 may output the final driver-requested torque or power of the vehicle propulsion system, which may be a constrained version of the driver-requested torque or power determined from the driver-requested pedal position and the vehicle speed.For example, if the driver-requested torque is 350 Newton meters according to the driver-requested pedal position and vehicle speed, the state machine 300 may command the vehicle propulsion system to provide a torque of 340 Newton meters or another constrained value based on the vehicle's operating conditions when the state machine 300 constrains the vehicle propulsion system 199. Alternatively, the state machine 300 may output a driver-requested torque or power value that must not be exceeded for each state of the state machine 300, and the driver-requested torque or power value that must not be exceeded for each state may be different for each state.Another control routine external to the state machine 300 may receive the driver requested torque or driver requested power not to be exceeded value from the state machine 300, and the external control routine may adjust the driver requested torque or driver requested power such that the final driver requested torque or driver requested power of the vehicle propulsion system is equal to or less than the driver requested torque or driver requested power not to be exceeded value.For example, if the driver requested torque is set to 350 Newton meters based on pedal position and vehicle speed, and the final driver requested torque of the vehicle propulsion system is not to exceed 330 Newton meters, the vehicle propulsion system may be commanded to provide a torque of 330 Newton meters by a control routine that receives the driver requested final torque of the vehicle propulsion system that is not to be exceeded.

[0051] In one example, rated power state 302 is a state where the driver-requested torque or power must be less than a first threshold driver-requested torque or power. The first threshold driver-requested torque or power may be based on a maximum torque or power that can be delivered by the vehicle propulsion system continuously (e.g., for longer than a threshold period of time, e.g., 10 minutes) without causing the vehicle propulsion system components to exceed their respective threshold temperatures and / or degrade to a lower power level.State machine 300 ensures that the commanded torque or power and / or the output torque or power of the vehicle propulsion system is less than or equal to the first driver-requested torque or power threshold when state machine 300 is in the nominal power state. The commanded torque or power or the output torque or power of the vehicle propulsion system may be limited by limiting the current supplied to the power source 105 and / or the inverter 115.The commanded torque or power of the vehicle propulsion system, or alternatively, the output torque or power, may be limited to be less than or equal to the first threshold by increasing or decreasing the commanded torque or power of the vehicle propulsion system, or alternatively, the output torque or power, when transitioning from another state to the rated power state 302.

[0052] The vehicle propulsion system may operate within the minimum power state 308 by limiting the driver-requested torque or power to less than a second threshold of driver-requested torque or power, where the second threshold is less than the first threshold. The second threshold of driver-requested torque or power may be based on a driver-requested torque or power that can be delivered by the vehicle propulsion system when the vehicle propulsion system generates less than a threshold amount of heat for a prescribed period of time (e.g., 5 minutes).The state machine 300 ensures that the commanded torque or power and / or the output torque or power of the vehicle propulsion system is less than or equal to the second driver-requested torque or power threshold when the state machine 300 is in the minimum power state 308. The commanded torque or power of the vehicle propulsion system, or alternatively, the output torque or power, may be constrained to be less than or equal to the first threshold by decreasing the commanded torque or power of the vehicle propulsion system when transitioning from another state to the minimum power state 308.

[0053] The vehicle propulsion system may operate within the Type 1 power enhancement state 330 by limiting the driver-requested torque or power to less than a third threshold driver-requested torque or power value, where the third threshold is greater than the first threshold. The third threshold driver-requested torque or power value may be based on a maximum torque or power that can be delivered by the vehicle propulsion system for more than a first threshold time period but less than continuously (e.g., for more than 1 minute but less than 10 minutes). The third threshold driver-requested torque or power value is greater than the first threshold driver-requested torque or power value.The state machine 300 limits the commanded torque or power and / or the output torque or power of the vehicle propulsion system to less than or equal to the third driver requested torque or power threshold when the state machine 300 is in the Type 1 power enhancement state 330. The commanded torque or power of the vehicle propulsion system or the output torque or power may be limited to be less than or equal to the third threshold by increasing or decreasing the commanded torque or power of the vehicle propulsion system when transitioning from another state to the Type 1 power enhancement state 330.

[0054] The vehicle propulsion system may operate within the Type 2 power boost state 318 by limiting the driver-requested torque or power to less than a fourth threshold driver-requested torque or power, where the fourth threshold is greater than the third threshold. The fourth threshold driver-requested torque or power may be based on a maximum torque or power that can be delivered by the vehicle propulsion system for more than a second threshold time period but less than a third threshold time period (e.g., greater than 3 seconds but less than 2 minutes). The fourth threshold driver-requested torque or power is greater than the third threshold driver-requested torque or power.The state machine 300 limits the commanded torque or power and / or the output torque or power of the vehicle propulsion system to less than or equal to the fourth driver requested torque or power threshold when the state machine 300 is in the Type 2 power boost state 318.

[0055] In this example, the final state that state machine 300 may assume is the underload state of inverter 314. In one example, the underload state of inverter 314 is a state in which the output current of inverter 115 may be limited to less than or equal to a first threshold current. The first threshold electrical current may be based on the specifications of the devices in the inverter and other operating conditions of the vehicle. State machine 300 may limit the inverter's current output by adjusting the on and / or off times of the inverter switches that generate AC power from DC power. The commanded current of the electric machine may be limited by limiting an amount of current commanded by the inverter.The electrical current controlled by the inverter may be limited to be less than or equal to the first electrical current threshold by decreasing the maximum inverter current threshold when transitioning from another state to the underload state of the inverter 314.

[0056] To determine the conditions for transitioning between the different states, the vehicle operating states may be monitored during selected conditions. In particular, during vehicle calibration, it may be determined that a power boost may be desired for selected vehicle states. Furthermore, it may be determined that the selected vehicle operating states can be determined from the values ​​of variables. Therefore, the values ​​of the variables may be used to control the transition into and out of power boost types 1 and 2, as well as into other states. During vehicle calibration, it may, for example, be determined that a power boost type 1 or a power boost type 2 is desired when the vehicle is overtaking a second vehicle, when the vehicle is starting off (e.g.when the vehicle increases speed from a standstill), when shifting the transmission, when the vehicle speed increases, when the vehicle travels in an unintended direction, within a particular speed range or window, when the road grade exceeds a threshold, and during other vehicle operating conditions. The outputs of the various vehicle sensors may serve as the basis for determining whether or not the vehicle operating conditions indicate a request or desire to exit a first particular state and enter a second particular state. The transitions between the various states of the state machine 300 may also include a preemptive power reduction of at least a portion of the vehicle propulsion system 199 depending on one or more temperatures within the vehicle propulsion system 199.

[0057] The transitions between the various states may occur as described herein, but it should be understood that the transitions between the various states are not limited by the description provided herein. A transition from the nominal power state 302 to the minimum power state 308 may follow arrow 304 when the temperature of the vehicle propulsion system 199 is equal to or greater than a first threshold temperature. By transitioning from the nominal power state 302 to the minimum power state 308, the vehicle propulsion system 199 may be preemptively cooled in case the vehicle propulsion system 199 returns to the nominal power state 302 and then enters the Type 1 power boost state 330 or the Type 2 power boost state 318, so that the thermal margin for operation of the vehicle propulsion system 199 in the Type 1 power boost state 330 or the Type 2 power boost state 318 may be maintained.Measures to transition from the nominal power state 302 to the minimum power state 308 may include gradually reducing the driver-requested torque or power by gradually limiting the driver-requested torque or power to a value below a threshold, or alternatively, by gradually lowering the driver-requested torque or power to a not-to-be-exceeded value. The driver-requested torque or power, or alternatively, the commanded driver-requested torque or power, may be limited to a fixed value or a value that changes depending on the vehicle's operating conditions.The state machine 300 may transition from the minimum power state 308 to the nominal power state 302, as indicated by arrow 306, in response to the temperature of the vehicle propulsion system 199 being below the first threshold temperature.

[0058] State machine 300 may exit nominal power state 302 and enter the Type 1 power boost state, as indicated by arrow 332, when the conditions for entering the Type 1 power boost state are met. Conditions may include, but are not limited to, the vehicle performing a gear shift, the vehicle overtaking a second vehicle, the vehicle moving in an unintended direction (e.g., a vehicle rolling backward after stopping on an incline while the vehicle's transmission is in Drive mode), the vehicle traveling on a road with a gradient greater than a threshold, and the vehicle speed increasing. The Type 1 power boost state may have a lower priority than the Type 2 power boost state.The Type 1 power boost state 330 may be invoked from the rated power state 302 when the Type 1 power boost state 330 is desired but less urgent than the Type 2 power boost state 318. The state machine 300 may enter the rated power state 302 from the Type 1 power boost state 330, as indicated by arrow 334, if at least one condition for the Type 1 power boost state 330 is not met. Actions to transition from the rated power state 302 to the Type 1 power boost state 330 may include gradually increasing the driver requested torque or power by limiting the driver requested torque or power, respectively.the requested power is gradually reduced by increasing the threshold value, or alternatively, by gradually decreasing a not-to-be-exceeded value for the driver-requested torque or power. The state machine 300 may transition from the Type 1 power enhancement state 330 to the minimum power state 308, as indicated by arrow 336, in response to a temperature of the vehicle propulsion system 199 being equal to or greater than a first threshold temperature. By transitioning from the Type 1 power enhancement state 330 to the minimum power state 308, the vehicle propulsion system 199 may be preemptively cooled when the vehicle propulsion system 199 enters the Type 2 power enhancement state 318, thus maintaining thermal margin for continued operation in the Type 2 power enhancement state 318.In the Type 1 power enhancement state 330, the vehicle propulsion system 199 may produce higher torque and power than in the nominal power state 302.

[0059] The state machine 300 may transition from the nominal power state 302, the minimum power state 308, or the Type 1 power enhancement state 330 to the Type 2 power enhancement state 318, as indicated by arrow 320, under particularly urgent conditions, such as overtaking another vehicle or merging onto a busy road. The state machine 300 may exit the Type 2 power enhancement state 318 and enter the nominal power state 302, the minimum power state 308, or the Type 1 power enhancement state 330 from the Type 2 power enhancement state 318, as indicated by arrow 322, if at least one condition for the Type 2 power enhancement state 330 is not met.Further, the state machine 300 may exit the Type 2 power boost state 318 and enter the inverter underload state 312, as indicated by arrow 316, when a temperature of the vehicle propulsion system 199 exceeds a second threshold temperature, where the second threshold temperature is greater than the first threshold temperature. Actions to transition from the nominal power state 302, the Type 1 power boost state 330, or the minimum power state 308 to the Type 2 power boost state 318 may include gradually increasing the driver-requested torque or power limit by gradually reducing the driver-requested torque or power limit by increasing the threshold value, or alternatively, gradually decreasing the driver-requested torque or power limit to a not-to-be-exceeded value.In the Type 2 power enhancement state 318, the vehicle propulsion system 199 may produce higher torque and power than in the Type 1 power enhancement state 330.

[0060] Further, the state machine 300 may enter the inverter underload state 314 from the Type 2 minimum power state 308 or the Type 2 power enhancement state 318, as indicated by arrow 316 and arrow 310, when a temperature of the vehicle propulsion system 199 exceeds a second threshold temperature, where the second threshold temperature is greater than the first threshold temperature. The state machine 300 may exit the inverter underload state 314, as indicated by arrow 312, in response to the temperature of the vehicle propulsion system 199 being below the second threshold temperature. The actions for entering the inverter underload state 314 from the Type 2 minimum power state 308 or the Type 2 power enhancement state 318 may include gradually decreasing the maximum inverter output current.

[0061] State machine 300 thus enables the vehicle propulsion system to transition between multiple states to control the management of the maximum or peak output power of an electric propulsion system. The state machine states may include two power-enhancing states, where the torque or power output of the electric propulsion system may exceed the rated power of the electric propulsion system, and two power-decreasing states to reduce the risk of degradation of the electric propulsion system.

[0062] The state machine 300 provides a method of operating a vehicle, comprising moving between states of a state machine to control a maximum output power of the electric drive system, the state machine including a plurality of states and allowing the state machine to enter exactly one state of the state machine and the electric drive system into exactly one state at a time. In a first example, the method further comprises adjusting one or more control parameters to transition from a first of the plurality of states to a second of the plurality of states. In a second example, which may include the first example, the method further comprises receiving inputs and moving between the states in response to the inputs.In a third example, which may include one or both of the first and second examples, the method includes where the states include a group of states, and where each state within the group of states can be entered from a state outside the group of states according to the operating conditions of the vehicle. In a fourth example, which may include one or more of the first to third examples, the method includes where the states include a minimum power state and an underload state of the inverter. In a fifth example, which may include one or more of the first to fourth examples, the method includes where the states also include two types of power boost states.In a sixth example, which may include one or more of the first to fifth examples, the method includes wherein the maximum output power may be increased to be greater than a nominal output power when the state machine is in one of the two types of power increase states.

[0063] State machine 300 also provides a method of operating a vehicle, comprising limiting a driver-requested torque or power for a vehicle propulsion system in response to movement between states of a state machine to control a maximum torque or power output of the electric propulsion system, wherein the state machine includes a plurality of states and allows entry into only one state of the state machine and one state of the electric propulsion system at a time, and wherein limiting the driver-requested torque or power includes setting a maximum commanded driver-requested torque or power. In a first example, the method includes the plurality of states including a Type 1 power boost state and a Type 2 power boost state.In a second example, which may include the first example, the method includes limiting the driver requested torque according to a first temperature threshold when the state machine is in the Type 1 power boost state, and limiting the driver requested torque according to a second temperature threshold when the state machine is in the Type 2 power boost state. In a third example, which may include one or both of the first and second examples, the method includes the Type 2 power boost state enabling a greater maximum torque or maximum power output of the electric drive system than the Type 1 power boost state.In a fourth example, which may include one or more of the first through third examples, the method includes where the Type 2 performance enhancement condition and the Type 1 performance enhancement condition are based on vehicle operating conditions that indicate the urgency to move the vehicle.

[0064] A sequence for controlling the maximum output power according to the system of Fig. 1-2C and the state machine Fig. 3 is in Fig. 4. The sequence from Fig. 4 can be accessed via the system Fig. 1-2C in cooperation with a process that is generated by the state machine from Fig. 3. The curves from Fig. 4 are timed to match, and the vertical lines represent interesting points in the sequence.

[0065] The first curve from above in Fig. Figure 4 is a graph depicting driver demand torque versus time. The vertical axis represents driver demand torque, and driver demand torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Curve 402 represents driver demand torque.

[0066] The second curve from the top in Fig. Figure 4 is a graph of driver-requested torque (e.g., the torque the electric drive system is expected to produce) versus time. The vertical axis represents the commanded driver-requested torque, and the commanded driver-requested torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Curve 404 represents the commanded driver-requested torque.

[0067] The third curve from the top in Fig. Figure 4 is a graph showing the power management state of the electric drive system as a function of time. The vertical axis represents the power management state of the electric drive system, and the numbers listed along the vertical axis are the state identification numbers used to identify the states that are Fig. 3. The horizontal axis represents time, and time increases from the left side of the curve to the right side of the curve. Curve 406 represents the currently enabled power management state.

[0068] The fourth curve from the top in Fig. Figure 4 is a graph of boost conditions (e.g., conditions in which the electric drive system's output power may exceed the electric drive system's maximum output power at rated operating conditions) versus time. The vertical axis represents the boost conditions, and the boost conditions are indicated along the vertical axis. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Curve 408 represents the currently enabled power management state.

[0069] The fifth curve from the top in Fig.4 is a graph of the temperature of the vehicle drive system (e.g., the temperature of the winding of an electric machine, the temperature of the inverter switch, the temperature of the inverter bus bar, etc.) versus time. The vertical axis represents the temperature of the vehicle drive system, and the temperature of the vehicle drive system increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Curve 410 represents the temperature of the vehicle drive system. The dashed horizontal line 450 represents a first threshold temperature, and the dashed horizontal line 452 represents a second threshold temperature.

[0070] At time t0, the driver-requested torque and the commanded driver-requested torque are equal. The power management state is in the rated power state. The boost state is none, and the vehicle propulsion system temperature is below the first and second threshold temperatures.

[0071] At time t1, the driver-requested torque and the commanded driver-requested torque are reduced to zero. The remaining operating conditions remain essentially unchanged.

[0072] At time t2, the driver-requested torque and the commanded driver-requested torque are increased to launch the vehicle from a standstill. The power management state transitions from rated power to the Type 1 power boost state, allowing vehicle launch to be assisted. The boost state indicates launch, and the vehicle's propulsion system temperature begins to rise. Between time t2 and time t3, the vehicle shifts once, and the propulsion system temperature continues to rise.

[0073] At time t3, the temperature of the vehicle's propulsion system exceeds the first threshold. As a result, the power management system switches to the minimum power state, and the commanded driver demand decreases, even though the requested driver demand remains essentially unchanged. This can cause the temperature of the vehicle's propulsion system to cool. The boost state remains during launch. The requested driver demand and the commanded driver demand are reduced at time t4.

[0074] At time t5, the temperature of the vehicle's propulsion system is reduced below the first threshold temperature 450. Consequently, the power management state is changed from minimum power to rated power. The driver-requested and commanded driver-requested torque are zero, and the boost state is none.

[0075] At time t6, the requested driver demand and the commanded driver demand are increased by the vehicle's human driver (not shown). The boost state changes to overtaking, and the power management state changes to power boost type 2. The temperature of the vehicle's propulsion system begins to rise.

[0076] At time t7, the temperature of the vehicle's propulsion system exceeds the second threshold temperature, so the power management state changes to the inverter underload state to cool the inverter. The driver-requested torque remains unchanged, and the commanded driver-requested torque is reduced. The boost state remains overtaking.

[0077] At time t8, the driver-requested torque and the commanded driver-requested torque are reduced. The boost state switches to none, and the power management state changes to the minimum power state because the vehicle propulsion system temperature has dropped below the second threshold temperature.

[0078] At time t9, the temperature of the vehicle's propulsion system drops below the first threshold temperature, so the power management state transitions to the rated power state. The driver-requested torque and the commanded driver-requested torque become equal shortly after time t9. The boost state remains non-boost.

[0079] It should be noted that the example control and estimation routines contained herein can be used with various powertrain and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and executed by the control system, including the controller, in combination with the various sensors, actuators, and other transmission and / or vehicle hardware. Furthermore, portions of the methods can be physical actions performed in the real world to change the state of a device. Thus, the described actions, operations, and / or functions can graphically represent code programmed into the non-transitory memory of the computer-readable storage medium in the vehicle and / or transmission control system.The specific routines described herein may represent one or more arbitrary processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Thus, the various actions, operations, and / or functions illustrated may be performed in the order presented, in parallel, or in some cases, without them. Accordingly, the order of processing is not required to achieve the features and advantages of the examples described herein, but is provided for convenience of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the strategy used. One or more of the method steps described herein may also be omitted if desired.

[0080] Although various embodiments have been described above, they are to be considered as examples and not as limitations. Those skilled in the art will appreciate that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are, therefore, to be considered in all respects as illustrative and not restrictive. Thus, the configurations and routines disclosed herein are exemplary in nature, and the specific examples are not to be considered as limiting, as numerous variations are possible. The technology described above may be used, for example, in electric and hybrid vehicles with induction and synchronous machines.The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions and / or properties disclosed herein.

[0081] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims are to be construed as including one or more such elements, without requiring or excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope than the original claims, are also to be considered included within the subject matter of the present disclosure. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 595,995

[0001]

Claims

[1] Electric drive system comprising: an electrical machine; an inverter electrically coupled to the electric machine; and one or more controllers containing executable instructions that cause the one or more controllers to generate a state machine configured to control a maximum output power of the electric drive system, wherein the state machine is in exactly one of a plurality of states at a time, and wherein the plurality of states includes at least one state that allows the output power of the electric drive system to exceed a rated output power of at least one component of the electric drive system and at least one state that allows the output power of at least one component of the electric drive system to be limited to less than the rated output power of the at least one component. [2] The electric drive system of claim 1, wherein the transitions between the plurality of states depend on operating states of the electric drive system. [3] The electric drive system of claim 2, wherein the operating conditions of the electric drive system include a first threshold temperature. [4] The electric drive system of claim 3, wherein the operating conditions of the electric drive system include a second threshold temperature. [5] Electric drive system according to claim 4, wherein the operating states of the electric drive system include boost states. [6] An electric drive system according to any preceding claim, wherein the plurality of states includes a minimum power state. [7] An electric drive system according to any preceding claim, wherein the plurality of conditions includes an underload condition of the inverter. [8] The electric drive system of claim 7, wherein the plurality of states includes two types of power enhancement states.

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