variable voltage controller

Abstract

A variable voltage controller is disclosed. A vehicle includes an inverter connected to an energy storage device having a variable output voltage and including a first pair of battery partitions. The vehicle includes a controller configured to operate a first set of switches to arrange electrical connections between the first pair of battery partitions such that the variable output voltage is higher than the battery voltage of one of the battery partitions. Operation of the switches is responsive to a parameter indicating a rotational speed of a motor electrically connected to the inverter exceeding a first predetermined threshold.

Description

Technical Field

[0001] The present disclosure relates to a variable voltage controller. Background Art

[0002] The motor and associated inverter draw power from the bus. A variable voltage controller (VVC) regulates the bus voltage to meet the varying voltage demands of the motor and inverter. A VVC typically has a boost converter structure that includes two high-speed switches (e.g., IGBTs) configured to selectively conduct current from an inductor. High-speed switching results in significant switching losses, and the inductor may require additional cooling or add unnecessary bulk to the inverter system. Summary of the Invention

[0003] A vehicle includes an inverter connected to an energy storage device, the energy storage device having a variable output voltage and including a first pair of battery sections. The vehicle includes a controller configured to operate a first set of switches to arrange electrical connections between the first pair of battery sections such that the variable output voltage is greater than a battery voltage of one of the first pair of battery sections. Operation of the switches is responsive to a parameter indicative of a rotational speed of an electric motor electrically connected to the inverter exceeding a first predetermined threshold.

[0004] A vehicle includes an inverter connected to an energy storage device, the energy storage device having a variable output voltage and including a first pair of battery partitions. The vehicle includes a controller configured to operate a first set of switches to arrange electrical connections between the first pair of battery partitions such that the variable output voltage is equal to the battery voltage of one of the battery partitions. Operation of the switches is responsive to a parameter indicative of a rotational speed of an electric motor electrically connected to the inverter falling below a second predetermined threshold.

[0005] According to one embodiment of the present invention, the first predetermined threshold is lower than a voltage requirement associated with the rotational speed of the motor.

[0006] A vehicle includes an inverter connected to an energy storage device, the energy storage device having a variable output voltage and including modular battery cell groups. The vehicle includes a controller configured to: operate to organize the modular battery cell groups into switch groups arranged in series and in parallel so that the variable output voltage is consistent with a voltage requirement of the inverter based on a predetermined range. The operation is responsive to a rotational speed of a motor, electrically connected to the inverter, falling within one of a plurality of predetermined ranges.

[0007] According to an embodiment of the present invention, the arrangement defines that each battery partition is connected in series with each other.

[0008] According to an embodiment of the present invention, the arrangement defines that each battery partition is connected in parallel with each other.

[0009] According to one embodiment of the present invention, the first predetermined range is lower than a voltage requirement associated with a rotational speed of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of a VVC supplying power to a bus bar, which supplies power to an inverter connected to a vehicle's motor and generator;

[0011] Figure 2 is a schematic diagram of a VVC supplying power to a bus bar that supplies power to a motor and a generator of a vehicle, the vehicle including a first battery partition pair and a second battery partition pair;

[0012] Figure 3A is a schematic diagram of a VVC supplying power to a bus that supplies power to a motor and a generator of a vehicle, the vehicle including a first battery partition pair and a second battery partition pair organized in parallel, each battery partition pair having parallel battery partitions;

[0013] Figure 3B yes Figure 3A Schematic representation of VVC in;

[0014] Figure 4A is a schematic diagram of a VVC supplying power to a bus bar that supplies power to a motor and a generator of a vehicle, the vehicle including a first battery partition pair and a second battery partition pair organized in series, each battery partition pair having battery partitions connected in series;

[0015] Figure 4B yes Figure 4A Schematic representation of VVC in;

[0016] Figure 5A is a schematic diagram of a VVC supplying power to a bus that supplies power to a motor and a generator of a vehicle, the vehicle including a first battery partition pair and a second battery partition pair organized in parallel, each battery partition pair having battery partitions connected in series;

[0017] Figure 5B yes Figure 5A Schematic representation of VVC in;

[0018] Figure 6 It is an algorithm for controlling the switching of VVC;

[0019] Figure 7 is a graph depicting the first threshold, the second threshold, the dead band, and the switching transient. DETAILED DESCRIPTION

[0020] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various alternative forms. The figures are not necessarily drawn to scale; some features may be exaggerated or reduced to show details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to utilize the present invention in various ways. It will be understood by those of ordinary skill in the art that the various features shown and described with reference to any one of the figures may be combined with features shown in one or more other figures to produce embodiments that are not explicitly shown or described. The combinations of features shown provide representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be expected for specific applications or implementations.

[0021] Depending on the speed and torque requirements of the attached motor, the inverter may have varying voltage requirements. For example, a higher motor speed requirement may require a higher inverter bus voltage. This means that the inverter bus voltage must be variable to provide a wide range of usable motor speeds without losses. The bus voltage can be adjusted by organizing switches and battery partitions. Switches organize the connections between battery partitions, arranging them in parallel or series. This organization changes the voltage output of the entire energy storage device.

[0022] The switch can be any type of connection and disconnection mechanism. Typically, IGBTs are used in similar VVC applications; however, such high-frequency switching is not essential. Low-frequency switches (e.g., solenoids, relays) can be used to organize battery zones and pairs of zones. Other types of switches or connection mechanisms (e.g., MOSFETs, BJTs) can also be used.

[0023] Reference Figure 1 , an electric drive system 100 is shown. The electric drive system 100 includes an energy storage device 102. The energy storage device 102 may include multiple energy sources. For example, capacitors, chemical batteries, rectifiers, commutators, photovoltaic cells, fuel cells, etc. The energy storage device may include a pair of battery partitions 104, 106. The battery partitions 104, 106 may be any energy source listed above or not listed. For example, the battery partitions 104, 106 may be battery modules of a battery assembly. The battery assembly typically includes dozens or hundreds of individual battery modules. The battery modules 104, 106 may include lithium-ion, nickel-cadmium, or other battery chemistries.

[0024] The controller 101 may be configured to operate the switch group 108 to arrange the electrical connection between the first battery partition 104 and the second battery partition 106. As described above, the switches may be of any type. The switch group 108 includes a first switch S1 110, a second switch S2 114, and a third switch S3 112. When S1 110 and S2 114 are closed and S3 112 is open, the battery partitions 104, 106 and the busbar V dc When S1 110 and S2 114 are open and S3 112 is closed, a parallel circuit is formed between the battery partitions 104, 106 and the busbar V dc 122 form a series circuit. The DC link capacitor 120 can be used to stabilize V dc The bus voltage is 122 V dc 122 supplies power to at least one inverter 124, 126 connected to the same or different motors 128, 130. The inverters 124, 126 may include switches independent of the switch bank 108. The inverters 124, 126 use pulse width modulation (PWM) to generate sinusoidal signals for the motors 128, 130. The motors can operate in either a drive mode or a generator mode.

[0025] The switch group 108 may be configured to organize the battery partitions 104, 106 in response to the rotational speed of the motor 128 exceeding a predetermined threshold. For example, a motor 128 having a rotational speed exceeding 1000 rpm may require a higher bus voltage (V dc 122) to achieve or maintain such a rotational speed. The energy storage device 102 can be organized so that the battery modules 104, 106 are connected in series to increase the output voltage of the energy storage device 102. In a similar manner, the switch group 108 can be configured to organize the battery partitions 104, 106 in response to the rotational speed of the motor 128 being less than a predetermined threshold. For example, a motor 128 having a rotational speed less than 1000 rpm may require a lower bus voltage (V dc 122). The energy storage device 102 can be organized so that the battery modules 104, 106 are connected in parallel to reduce the output voltage of the energy storage device 102. The controller 101 can be configured to program the switch positions according to the speed of the motors 128, 130.

[0026] The controller 101 can be configured to predict threshold transitions to ensure that sufficient voltage is available to the inverter. For example, during acceleration or deceleration events, the motor may have a rate of change. The controller can be configured to preemptively increase the output voltage of the energy storage device 102 by organizing or arranging switches when the motor speed is expected to exceed a threshold. The preemptive change can be based on the switching time of the switches. For example, a relay may require 15 ms to stabilize after actuation. Therefore, the controller 101 can be configured to arrange the switch group 108 at least 15 ms before the threshold is exceeded, based on the instantaneous rate of change or the historical rate of change of the motor.

[0027] Multiple inverters 124 and 126 and motors 128 and 130 can draw power from the same voltage bus 122. The controller 101 can select one of the motors 128 and 130 as the basis for the voltage requirement. For example, the controller 101 can use the motors 128 and 130 in motor mode. The controller 101 can use the speed of the drive motor 128 as the basis for the voltage requirement. The controller 101 can use a combination of the motor speed and the generator speed as the basis for the voltage requirement. The controller 101 can use the highest voltage requirement from one of the drive motors 128.

[0028] Reference Figures 2 to 5B , shows an electric drive system 200. The electric drive system 200 includes an energy storage device 232. As described above, the energy storage device 232 may include multiple energy sources. The energy storage device 232 may include a first battery partition pair 202 (204 and 206). The first battery partition pair 202 (204 and 206) may be any energy source listed above or not listed. As described above, the first pair of battery partition pairs 202 (204 and 206) may be battery modules of a battery assembly. The energy storage device 232 may include a second battery partition pair 242 (244 and 246). The second battery partition pair 242 (244 and 246) may be any energy source listed above or not listed. The second battery partition pair 242 (244 and 246) may be a battery module of a battery assembly or a separate battery assembly as described above. The first battery partition pair 202 and the second battery partition pair 242 include a first switch group 208 and a second switch group 248, respectively. The third switch group 260 may be configured to arrange electrical connections between the first battery partition pair 202 and the second battery partition pair 242 .

[0029] The controller 201 can be configured to operate the switch groups 208 and 248 to arrange the electrical connection between the first battery partition pair 202 (204 and 206) and the electrical connection between the second battery partition pair 242 (244 and 246). Each of the switch groups 208, 248, and 260 includes a first switch (S1 210, S4 250, S7 262), a second switch (S2 214, S5 254, S8 266), and a third switch (S3 212, S6 252, S9 264).

[0030] When S1 210 and S2 214 are closed and S3 212 is open, a parallel circuit is formed between battery partitions 204 and 206. When S1 210 and S2 214 are open and S3 212 is closed, a series circuit is formed between battery partitions 204 and 206. When S4 250 and S5 254 are closed and S6 252 is open, a parallel circuit is formed between battery partitions 244 and 246. When S4 250 and S5 254 are open and S6 252 is closed, a series circuit is formed between battery partitions 244 and 246.

[0031] The first battery partition pair 202 and the second battery partition pair 242 of the energy storage device 232 can be arranged through the third switch group 260. When S7 262 and S8 266 are closed and S9 264 is open, the first battery partition pair 202 and the second battery partition pair 242 are connected to the bus V dc When S7 262 and S8 266 are disconnected and S9 264 is closed, the first battery partition pair 202 and the second battery partition pair 242 are connected to the busbar V dc 222 form a series circuit.

[0032] The DC link capacitor 220 can be used to stabilize V dc 222 bus voltage. V dc 222 supplies power to at least one inverter 224, 226 connected to the same or different motors 228, 230. The inverters 224, 226 may include switches independent of the switch groups 208, 248, 260. The inverters 224, 226 use pulse width modulation (PWM) to generate sinusoidal signals for the motors 228, 230. The motors can operate in either a drive mode or a generator mode.

[0033] Energy storage device 232 can be configured to provide any number of voltage values ​​to inverter 224. For example, energy storage device 232 may have four battery modules, each with a 100-volt output. In a parallel configuration, energy storage device 232 has a voltage output of 100 volts. In a hybrid configuration, energy storage device 232 has a voltage output of 200 volts. In a series configuration, energy storage device 232 has a voltage output of 400 volts.

[0034] like Figure 3A and Figure 3B As shown, the battery modules 204, 206, 244, 246 can be arranged in parallel in each battery partition pair 202, 242, and the first battery partition pair 202 and the second battery partition pair 242 can be arranged in parallel, schematically forming a fully parallel electric drive system 300. The parallel electric drive system 300 has an energy storage device 380, which has a plurality of busbars V dc 322 and the DC link capacitor 320 are connected in parallel to the battery modules 304, 306, 344, 346. The voltage on the bus V dc 322 supplies power to a pair of inverters 324, 326 connected to motors 328, 330. dc 322 is equal to the voltage of one of the battery modules 304, 306, 344, 346. Any number of inverters or motors can be used. Multiple inverters can power a single motor, and vice versa.

[0035] like Figure 4A and Figure 4B As shown, the battery modules 204, 206, 244, 246 can be arranged in series in each battery partition pair 202, 242, and the first battery partition pair 202 and the second battery partition pair 242 can be arranged in series, schematically forming a fully series electric drive system 300. The series electric drive system 300 has an energy storage device 380, and the energy storage device 380 has a plurality of busbars V dc 322 and the DC link capacitor 320 are connected in series with the battery modules 302, 304, 342, 344. The voltage on the bus V dc 322 supplies power to a pair of inverters 324, 326 connected to motors 328, 330. dc 322 is equal to the sum of the voltages of the battery modules 302, 304, 342, and 344. Any number of inverters or motors can be used. Multiple inverters can power a single motor, and vice versa.

[0036] like Figure 5A and Figure 5BAs shown, the battery modules 204, 206, 244, 246 and the first battery partition pair 202 and the second battery partition pair 242 can be arranged in a mixed combination of parallel circuits and series circuits to form a desired output voltage. For example, the first battery partition pair 202 and the second battery partition pair 242 can be arranged in parallel, and the battery module 204 and the battery module 206 can be arranged in series, and the battery module 244 and the battery module 246 can be arranged in series, schematically forming an electric drive system 300 with a variable voltage. The electric drive system 300 has an energy storage device 380, and the energy storage device 380 has a plurality of parallel busbars V dc 322 and the DC link capacitor 320 are connected in series with the battery modules 304 and 306, both connected to the bus V dc 322 and the DC link capacitor 320 in series with the battery modules 344 and 346 and the bus V dc 322 and the first battery partition pair 202 and the second battery partition pair 242 connected in parallel with the DC link capacitor 320. The voltage V on the bus dc 322 supplies power to a pair of inverters 324, 326 connected to motors 328, 330. dc 322 is equal to the sum of the voltages of battery modules 304 and 306 or the sum of the voltages of battery modules 344 and 346. Any number of inverters or motors can be used. Multiple inverters can power a single motor, and vice versa.

[0037] Reference Figure 6 , a flowchart 400 is shown. Flowchart 400 can be embedded in a controller as an algorithm for implementing the teachings of the present disclosure. The controller can be any combination of a processor, memory, and other hardware for controlling machinery, receiving user input, and coordinating vehicle functions. The controller can be a separate and distinct device or a single entity. At step 402, processing begins. At step 404, the motor acceleration is monitored. The motor acceleration provides information for predictive analysis. At step 406, the maximum time for switch transitions is determined or retrieved. The maximum time for switch transitions can be based on the number of switches that need to be transitioned, the average time required for the switches that need to be actuated to close, the maximum time required for one of the switches that need to be actuated to close, or other methods. At step 408, the sign of the acceleration is determined.

[0038] Crossing a predetermined threshold with positive acceleration may require active switching to ensure that there is sufficient voltage available to the inverter for the motor speed. For example, the inverter may require a voltage greater than 300 volts to provide a drive signal to a motor with a speed greater than a predetermined threshold (e.g., 1000 RPM). To ensure proper torque delivery, the controller may arrange the switches to provide sufficient voltage before the voltage is needed. If the motor is accelerating (as determined in step 408), the controller may anticipate crossing the threshold based on the magnitude of the acceleration or other factors (e.g., driving history, environment) in step 414. In step 416, the controller operates the switches to arrange the electrical connections between the battery modules and between the battery module pairs to meet the inverter voltage requirements so that the conversion is performed before crossing the required threshold. For example, if the average switch closure time is 15 ms and the inverter and motor are expected to require a higher voltage within 30 ms based on the acceleration of the motor, the controller may close the switches within 10 ms to ensure that the voltage requirement is met before the higher voltage is needed.

[0039] If the motor is decelerating, the controller may be configured with a deadband to ensure that sufficient voltage is available in case the speed or torque command fluctuates. At step 408, after determining the sign of the acceleration, the controller may determine at step 410 whether the motor has crossed the threshold plus the deadband. The controller may be configured to operate the switches to arrange the electrical connections to meet the voltage requirements of the inverter so that the transition is performed after crossing the threshold and the deadband. The controller may wait for a period of time after crossing a predetermined threshold before actuating the switches to reduce the voltage of the energy storage device. The controller may wait for a period of time before reducing the voltage, or establish a deadband that is a specific proportion (e.g., 10%) of the predetermined threshold. At step 418, the algorithm is repeated.

[0040] Reference Figure 7, a graph 500 is shown. Graph 500 includes a motor speed curve 502. The motor speed curve 502 may be related to the voltage required by the inverter to achieve that speed. A first threshold 504 is shown. To ensure that the inverter has a usable voltage before the first threshold, the controller may be configured to initiate switching at a switch configuration threshold 506. The motor speed curve 502 may have a slope that indicates motor acceleration. The slope of the speed curve 502 may be used to predict when the motor will cross the first threshold 504. A second threshold 508 is shown. To ensure that the inverter has a usable voltage before the second threshold, the controller may be configured to initiate switching at a switch configuration threshold 510. The motor speed curve 502 may have a slope that indicates motor acceleration. The slope of the speed curve 502 may be used to predict when the motor will cross the second threshold 508. Thresholds 504 and 508 may also form a range that defines a desired voltage associated with the motor speed. For example, a range may be formed between zero motor speed and the first threshold 504. Another range is formed between the first threshold 504 and the second threshold 508 .

[0041] A deadband 512 can be used to prevent unnecessary switching during acceleration. A deadband 512 is associated with each of the first threshold 504 and the second threshold 508. Each deadband 512 can be different. The deadband can be determined based on the number of switches that need to be changed or other factors.

[0042] The words used in the specification are descriptive words rather than restrictive words, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of the various embodiments can be combined to form further embodiments of the present invention that may not be clearly described or shown. Although various embodiments have been described as providing advantages or being better than other embodiments or the implementation of the prior art for one or more desired characteristics, it will be appreciated by those skilled in the art that one or more features or characteristics can be compromised to achieve desired overall system properties according to specific applications and implementations. These properties may include but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Thus, embodiments described as not meeting expectations as well as other embodiments or the implementation of the prior art in one or more characteristics are not outside the scope of the present disclosure and can be expected to be used for specific applications.

Claims

1. A vehicle comprising: an inverter connected to an energy storage device having a variable output voltage and including a first pair of battery partitions; The controller is configured to: in response to an expected rotation speed of the motor exceeding a first predetermined threshold based on a magnitude of acceleration of the motor electrically connected to the inverter, operate the first group of switches based on switching times of the first group of switches to arrange electrical connections between the first pair of battery partitions before the rotation speed of the motor exceeds the first predetermined threshold, so that the variable output voltage is higher than the battery voltage of one battery partition in the first pair of battery partitions.

2. The vehicle according to claim 1, wherein: In response to the speed of the motor exceeding a first predetermined threshold, the first set of switches is operated such that the first pair of battery sections are arranged in series.

3. The vehicle according to claim 1, wherein: The energy storage device includes a second pair of battery partitions, and the controller is further configured to: in response to the speed of the motor exceeding a first predetermined threshold, operate a second set of switches associated with the second pair of battery partitions so that the variable output voltage is higher than the battery voltage of one battery partition in the second pair of battery partitions.

4. The vehicle according to claim 3, wherein: In response to the speed of the motor exceeding a first predetermined threshold, the second set of switches is operated such that a second pair of battery sections are arranged in series.

5. The vehicle according to claim 3, wherein: The controller is further configured to, in response to the rotational speed of the motor exceeding a second predetermined threshold, operate the third set of switches to arrange the electrical connections between the first pair of battery partitions and the second pair of battery partitions so that the variable output voltage is higher than the sum of the battery voltages of one battery partition in the first pair of battery partitions and the battery voltages of one battery partition in the second pair of battery partitions.

6. The vehicle according to claim 1, wherein: At least one of the switches is a solenoid relay.

7. The vehicle of claim 1, wherein: At least one of the first pair of battery partitions and the second pair of battery partitions includes a bus link capacitor.

8. The vehicle of claim 1, wherein: The first predetermined threshold is lower than a voltage requirement associated with the rotational speed of the electric machine.

9. A vehicle comprising: an inverter connected to an energy storage device having a variable output voltage and including a first pair of battery partitions; a controller configured to, in response to an expected rotational speed of the motor exceeding a first predetermined threshold based on a magnitude of acceleration of the motor electrically connected to the inverter, operate the first set of switches based on switching times of the first set of switches to arrange electrical connections between the first pair of battery partitions such that the variable output voltage is higher than a battery voltage of one of the first pair of battery partitions before the rotational speed of the motor exceeds the first predetermined threshold, In response to the motor speed dropping below a second predetermined threshold, the first set of switches is operated to arrange electrical connections between the first pair of battery partitions so that the variable output voltage is equal to the battery voltage of one of the first pair of battery partitions.

10. The vehicle of claim 9, wherein: In response to the rotational speed of the motor dropping below a second predetermined threshold, the first set of switches is operated to connect the first pair of battery sections in parallel.

11. The vehicle of claim 9, wherein: The energy storage device includes a second pair of battery partitions, and the controller is further configured to: in response to the speed of the motor dropping below a third predetermined threshold, operate the second set of switches to arrange the electrical connections between the second pair of battery partitions so that the variable output voltage is equal to the battery voltage of one of the second pair of battery partitions.

12. The vehicle of claim 11, wherein: In response to the speed of the motor dropping below a third predetermined threshold, the second set of switches is operated to connect the second pair of battery partitions in parallel.

13. The vehicle of claim 11, wherein: The controller is further configured to, in response to the rotational speed of the motor dropping below a third predetermined threshold, operate a third set of switches associated with the first pair of battery partitions and the second pair of battery partitions so that the variable output voltage is equal to the battery voltage of the one battery partition in the first pair of battery partitions and the battery voltage of the one battery partition in the second pair of battery partitions.

14. The vehicle of claim 9, wherein: The switch is a solenoid relay.

15. The vehicle of claim 9, wherein: At least one of the first pair of battery partitions and the second pair of battery partitions includes a bus link capacitor.

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