Dynamic current limiting control system of rotating motor

Abstract

A control system for generating a modified torque command for a rotating electric machine in a battery electric vehicle (BEV) includes a microprocessor capable of reading executable commands stored in a non-volatile memory, configured to be electrically connected to an inverter, determine a rated maximum current for the rotating electric machine, and generate a modified torque command for the rotating electric machine. A sensor input indicative of or estimating a temperature of at least a portion of the BEV is received, a modified maximum current is output based on the received sensor input, and a torque command is generated to the rotating electrical machine based on the modified maximum current.

Description

Technical Field

[0001] The present invention relates to control systems, and more particularly to motor control systems. Background Art

[0002] Vehicles are increasingly being propelled by at least one rotating electric machine (sometimes also referred to as an electric motor). The use of rotating electric machines involves control systems that regulate the supply of DC voltage from the vehicle battery to the rotating electric machine. As more and more vehicles use rotating electric machines, control systems used with these machines can more efficiently and optimally regulate the supply of AC current to the motor. Summary of the invention

[0003] In one implementation, a control system for generating a modified torque command for a rotating electric machine in a battery electric vehicle (BEV) includes a microprocessor capable of reading executable commands stored in a non-volatile memory, configured to be electrically connected to an inverter, determine a rated maximum current of the rotating electric machine, receive a sensor input indicating a temperature of at least a portion of the BEV or estimating the temperature, output a modified maximum current based on the received sensor input, and generate a torque command for the rotating electric machine based on the modified maximum current.

[0004] In another implementation, a control system for generating a modified torque command for a rotating electric machine in a BEV includes a microprocessor capable of reading executable commands stored in a non-volatile memory, configured to be electrically connected to an inverter, including a power loss building block that determines at least one power loss of the rotating electric machine, a thermal building block that monitors at least one temperature at the BEV, and a maximum phase determination block that determines a rated maximum current of the rotating electric machine and modifies the rated maximum current to generate a modified maximum current for generating a torque command for the rotating electric machine.

[0005] In yet another implementation, a method for generating a modified torque command for a rotating electric machine in a BEV includes the steps of determining a rated maximum current of the rotating electric machine; receiving a sensor input indicating a temperature of at least a portion of the BEV or estimating the temperature; outputting a modified maximum current based on the received sensor input; and generating a torque command for the rotating electric machine based on the modified maximum current. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a block diagram depicting an implementation of a battery electric vehicle with a control system.

[0007] Figure 2 is a diagram depicting the implementation of the current plane used by the control system.

[0008] Figure 3 It is a block diagram that depicts how the control system is implemented.

[0009] Figure 4 It is a graph depicting the maximum available torque of a rotating electrical machine. DETAILED DESCRIPTION

[0010] A control system regulates the supply of electrical power to the electric machines (also called motors) of a battery electric vehicle (BEV). As part of this regulation, the control system is programmed with a number of constraints or limits that prevent the system from overtaxing the electric drive system. That is, the electric drive system may have a rated capacity that the torque commands issued by the control system should not exceed. For example, the rated capacity of the electric motor may be determined by parameters such as maximum torque per ampere (MTPA), maximum torque per volt (MTPV), inverter voltage limit, and maximum current (I s，max ) variables. Based on these variables, the electric drive system can output a limited amount of torque at the output shaft. In some implementations, the rated capacity of the motor can be defined by I s，max and MTPA. s，max Usually reflects the maximum continuous or continuous operating current of the electric drive system. Figure 2 The implementation of this relationship is shown in Figure 2. s，max，1 ) can be determined based on the thermal capabilities of the electric drive system and its cooling system given a particular coolant temperature and flow rate. However, for limited periods of time, the electric drive system can have current levels higher than the rated maximum current, thereby increasing the torque or power of the electric drive system. The control system can monitor various operating variables of the electric motor and / or BEV and determine a modified maximum current (I s，max，2 ) and a duration for operating at the modified maximum current. The control system may generate a torque command for the electric drive system, receive inputs from the motor and the BEV, determine a modified maximum current, and based on the modified maximum current (I s，max，2 ) to generate different torque commands. The control system can also set the duration of generating different torque commands, after which the control system can return to using the rated maximum current (I s，max，1 ).

[0011] Go to Figure 1 , showing an implementation of an electrical system 10. The system 10 includes an electrical grid 12 and a battery electric vehicle (BEV) 14 that can receive power from the electrical grid 12. The electrical grid 12 can include any of a plurality of electrical generators and electrical transmission mechanisms. The generator (not shown) produces AC power, which can then be transmitted to a location remote from the generator for residential and commercial use. The generator can be coupled to the electrical grid 12, which transmits the AC power from the generator to an end user, such as a residence or business.

[0012] The BEV 14 includes one or more rotating electrical machines 16 (also referred to as motors) including a stator having stator windings and a rotor that can be angularly displaced relative to the stator (not shown). In one implementation, the rotating electrical machine 16 (also referred to as motors) is a permanent magnet synchronous electrical machine that includes a rotor having a plurality of angularly spaced permanent magnets. The permanent magnets can be made of any of a variety of different materials, one example of which is a neodymium alloy or other rare earth elements. As described above, the stator windings can receive an electric current, the supply of which can be regulated by a control system 18 that causes the angular displacement of the rotor relative to the stator. The control system 18 can include an array of power control electronics and microprocessors that facilitate the operation of the rotating electrical machine 16. These electronic devices can include an inverter implemented using a plurality of MOSFETs that are turned on and off in the direction of the motor controller according to a choreographed sequence and timing to cause the rotor angular motion. The control system 18 can output a current command that regulates the current supplied to the rotating electrical machine 16. As part of a field-oriented control system, the current command can be divided into orthogonal (I q ) and DC (I d ) current commands. The motor controller may be implemented using one or more microprocessors with input / output and non-volatile memory where data may be stored and accessed. In addition to the inverter, the control system 18 may include a DC-DC converter to regulate the voltage level of the power supplied to the motor 16. The control system 18 may also include one or more thermistors for determining the ambient temperature and the temperature of the rotating motor 16.

[0013] The BEV service device 20 (also referred to as a BEV charging station) can receive AC power from the power grid 12 and provide the power to the BEV 14. The BEV service device 20 may include an input that receives AC power from the power grid 12 and transmits the AC power to an onboard vehicle battery charger included on the BEV 14. The onboard vehicle battery charger 22 may include an AC / DC inverter so that the AC power received from the power grid 12 can be supplied to the vehicle battery 26. The cable 24 can be removably connected to an electrical outlet on the BEV 14 and electrically links the BEV charging station with the BEV 14 so that AC power can be transmitted between the charging station and the BEV 14. The BEV charging station can be classified as a "Level 2" BEV service device that receives 240VAC from the power grid 12 and supplies 240VAC to the BEV 14. In other implementations, the AC power level input to the charging station and / or the AC power level output from the charging station may be different.

[0014] The term "battery electric vehicle" or "BEV" may refer to a vehicle that is propelled in whole or in part by a rotating electric machine. BEV may refer to an electric vehicle, a plug-in electric vehicle, a hybrid electric vehicle, and a battery-powered vehicle. The vehicle battery 26 may supply DC power converted from AC power to the motor 16 that propels the BEV. As described above, the control system 18 may convert DC power into AC power to cause angular motion of the rotor relative to the stator. The vehicle battery 26 is rechargeable and may include lead-acid batteries, nickel-cadmium (NiCd) batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-polymer batteries, among others. Typical BEV battery voltages are 200 to 800 VDC. The term "electric drive system" may include not only electric motors, but also inverters, vehicle batteries, and other electrical components of the BEV.

[0015] Figure 3 , an implementation of the control system 18 is shown in FIG. The control system 18 includes a power loss building block 30, a thermal building block 32, a maximum phase current determination block 34, a torque limit determination block 36, and a dynamic saturation block 38. The power loss building block 30 receives inputs from sensors monitoring the BEV 14 and estimates the losses of thermally critical components. The inputs include phase current, power factor, modulation index, fundamental frequency, and DC link voltage. The control system 18 can use these inputs to determine system losses, such as conduction losses, switching losses, core losses, capacitor and battery equivalent series resistance (ESR) losses, etc. The thermal building block 32 can receive the losses determined from the power loss building block 30 and data indicating the coolant temperature and coolant flow rate of the BEV 14. Based on the input, the thermal building block 32 can generate a temperature value of the BEV 14 during operation. The temperature value can reflect the temperature of the stator of the rotating electric machine 16, the rotor of the rotating electric machine 16, the bulk capacitor, the power semiconductor and / or the bus, etc.

[0016] The hot spot temperature from the thermal building module 32 can be provided to the maximum phase current determination block 34. The maximum phase current determination block 34 can use the temperature to dynamically determine a modified maximum current value that is independent of the continuous rating of the rotary electric machine 16. In one implementation, a lookup table can be stored in a memory at the control system 18, the lookup table including various temperature inputs and corresponding limiting temperature / current combinations associated with these inputs. The modified maximum current value can be provided to the torque limit determination block 36. The torque limit determination block 36 can also receive the values ​​of the fundamental frequency, DC link voltage, and magnet temperature of the rotor to calculate the positive maximum torque limit and the negative maximum torque limit. Then, the positive maximum torque limit and the negative maximum torque limit determined at the torque limit determination block 36 can be supplied to the dynamic saturation block 38 together with the unlimited torque command. The dynamic saturation block 38 can generate different or limited torque commands based on the calculated positive maximum torque limit and negative torque limit. The control system 18 can repeat this process during operation to modify the torque command as conditions change. Figure 4 A graph showing the maximum positive torque limit as a function of the angular velocity of the output shaft of the rotary electric machine 16. A first curve 402 represents the torque limit based on a rated maximum current value and a second curve 404 represents the torque limit based on a modified maximum current value.

[0017] It should be understood that the above is a description of one or more embodiments of the present invention. The present invention is not limited to the specific embodiments disclosed herein, but is limited only by the following claims. In addition, the statements contained in the above description relate to specific embodiments and should not be interpreted as limitations on the scope of the present invention or the definition of the terms used in the claims, unless the terms or phrases are clearly defined above. Various other embodiments and various changes and modifications to the disclosed embodiments will become apparent to those skilled in the art. All such other embodiments, changes and modifications are intended to fall within the scope of the appended claims.

[0018] As used in this specification and claims, the terms "eg," "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a list of one or more components or other items, should each be interpreted as open-ended, meaning that the list is not to be construed as excluding other additional components or items. Other terms should be interpreted using their broadest reasonable meaning unless used in a context that requires a different interpretation.

Claims

1. A control system for generating a modified torque command for a rotating electric machine in a battery electric vehicle (BEV), comprising: A microprocessor capable of reading executable commands stored in a non-volatile memory, configured to be electrically connected to the inverter, determine a rated maximum current of the rotating electric machine, receive a sensor input indicating a temperature of at least a portion of the BEV or estimating the temperature, output a modified maximum current based on the received sensor input, and generate a torque command for the rotating electric machine based on the modified maximum current. 2 . The control system of claim 1 , wherein the microprocessor determines at least one power loss of the BEV.

3. The control system of claim 1, wherein the microprocessor determines a temperature of a stator winding, a temperature of a rotor, a temperature of a bulk capacitor, a temperature of a power semiconductor, or a temperature of a bus bar.

4. The control system of claim 1 wherein the sensor input comprises coolant temperature or coolant flow rate.

5. The control system of claim 1 wherein the microprocessor determines a rated maximum current of the electric drive system.

6. A control system for generating a modified torque command for a rotating electric machine in a battery electric vehicle (BEV), comprising: A microprocessor capable of reading executable commands stored in a non-volatile memory, configured to be electrically connected to an inverter, includes a power loss building block that determines at least one power loss of the rotating electric machine, a thermal building block that monitors at least one temperature at the BEV, and a maximum phase determination block that determines a rated maximum current of the rotating electric machine and modifies the rated maximum current to generate a modified maximum current, for generating a torque command for the rotating electric machine.

7. The control system of claim 6, wherein the microprocessor determines the at least one power loss of the rotating electric machine based on phase current, power factor, modulation index, fundamental frequency, or DC link voltage.

8. The control system of claim 6, wherein the thermal architecture module determines a temperature of a stator winding, a temperature of a rotor, a temperature of a bulk capacitor, a temperature of a power semiconductor, or a temperature of a bus bar.

9. The control system of claim 6, wherein the microprocessor receives sensor inputs including coolant temperature or coolant flow rate.

10. The control system of claim 6, wherein the rated maximum current of the rotary electric machine is stored in a lookup table at the BEV.

11. A method for generating a modified torque command for a rotating electric machine in a battery electric vehicle (BEV), comprising the steps of: (a) determining the rated maximum current of the rotating electrical machine; (b) receiving a sensor input indicative of a temperature of at least a portion of the BEV or estimating the temperature; (c) outputting a modified maximum current based on the received sensor input; as well as (d) generating a torque command for the rotating electric machine based on the modified maximum current.

12. The method of claim 11 further comprising the step of determining at least one power loss of the BEV.

13. The method of claim 11 further comprising the step of determining a temperature of a stator winding, a temperature of a rotor, a temperature of a bulk capacitor, a temperature of a power semiconductor, or a temperature of a busbar.

14. The method of claim 11, wherein the sensor input comprises coolant temperature or coolant flow rate.

15. The control system of claim 11 further comprising the step of determining a rated maximum current of the electric drive system.

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