Method and system for operating a variable voltage controller

Abstract

Systems and methods are described for operating an inverter electrically coupled to a battery and an electric machine that provides propulsion to a vehicle. The systems and methods can selectively adjust a duty cycle of an inverter transistor in response to a battery voltage and a dead time between when a first transistor is deactivated and when a second transistor is activated.

Description

TECHNICAL FIELD

[0001] The present description relates to methods and systems for operating a variable voltage controlled inverter for an electric or hybrid vehicle. The methods and systems can be particularly useful for adjusting a boost voltage or a buck voltage to provide a desired propulsion motor torque or to provide a regenerative capability of the vehicle.

[0002] BACKGROUND AND SUMMARY

[0003] A vehicle can include an electric machine for providing propulsion torque to accelerate the vehicle. The electric machine can also provide braking torque to the vehicle whereby the kinetic energy of the vehicle can be converted to electrical energy and stored for later use. The electric machine can be electrically coupled to a battery or other electrical energy storage device via an inverter. The inverter can convert direct current (DC) from the battery to alternating current (AC) to power the electric machine. Alternatively, the inverter can convert alternating current to direct current to charge the battery. The inverter can include a buck circuit and a boost circuit to increase the battery voltage or decrease the motor voltage. For example, when the inverter is operating in a boost mode, the battery voltage can be increased via storing electrical energy in a magnetic field of an inductor and then discharging the inductor to the motor. The voltage developed across the inductor plus the battery voltage results in an output voltage that is greater than the battery voltage. However, if the voltage output from the battery and inductor is higher or lower than a desired voltage in which the motor is effectively operated, the use of power by the motor can not be as effective as desired.

[0004] The inventors herein have recognized the above problems and have developed a variable voltage controlled inverter operating method that includes receiving data to a controller and switching transistors of the variable voltage controlled inverter via the controller at a duty cycle in response to a desired output voltage of the variable voltage controlled inverter not being less than a battery voltage, the duty cycle being adjusted in response to the battery voltage.

[0005] By switching transistors of the variable voltage controlled inverter at a duty cycle in response to a battery voltage when a desired output voltage of the variable voltage controlled inverter is not less than the battery voltage, it is possible to provide a technical result that improves the efficiency of the electrical system. In particular, the efficiency of the motor can be improved. Moreover, if the inverter is operating in a buck mode, the battery charge efficiency can be improved by precisely controlling the battery charge voltage.

[0006] The present description can provide several advantages. In particular, the scheme can reduce boosting when the battery charge is low. Moreover, the scheme can increase the battery voltage boost capability by allowing the inverter to boost to a higher voltage. Additionally, the scheme can be applied while operating the inverter in a buck or boost mode.

[0007] The above-described advantages and other advantages of the present description and features of the present description will be appreciated from the following detailed description taken in conjunction with the accompanying drawings, which are by way of illustrations, from which:

[0008] It is understood that the foregoing summary of the present description is intended by way of illustration in providing a selection of concepts which are further described with further detail in the DETAILED DESCRIPTION. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined exclusively by the claims following the DETAILED DESCRIPTION. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background or any part of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0009] The advantages described herein will be more fully understood from the following examples, taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a schematic diagram of an inverter.

[0011] Figure 2 is a schematic diagram of a hybrid vehicle system.

[0012] Figure 3 shows an example control block diagram for compensating for inverter buck or boost voltage.

[0013] Figure 4 shows an example dead time between boost transistor deactivation and buck transistor activation.

[0014] Figure 5 shows a flowchart of a method for operating an inverter in a boost mode.

[0015] Figure 6 shows a flowchart of a method for operating an inverter in a buck mode. DETAILED DESCRIPTION

[0016] The present description relates to variable voltage control inverters for operating a vehicle, the vehicle including electric machines for effort to propel the vehicle and effort to decelerate the vehicle. The inverter can be configured as Figure 1 shown. The inverter can be included in a vehicle drivetrain as Figure 2 shown. The inverter can be operated via a controller as Figure 3 shown. The output voltage of the inverter can be adjusted in response to a dead time between boost transistor deactivation and buck transistor activation or a dead time between buck transistor deactivation and boost transistor activation as Figure 4 shown. The inverter can be operated in a boost mode according to the method of Figure 5 and the inverter can be operated in a buck mode according to the method of Figure 6 ​

[0017] Referring to Figure 1 FIG. 1 shows an inverter 100 electrically coupled to an electrical energy storage device 175 (e.g., a battery). In this example, the electrical energy storage device includes a plurality of battery cells connected in series to increase the voltage of the electrical energy storage device 175. Also shown is the inverter 100 electrically coupled to an electric machine 140 (e.g., a three-phase electric machine that can operate as a motor or an alternator). The inverter 100 includes a controller 102 that can communicate with a vehicle system controller 255 shown as being in communication via a controller area network (CAN) 299. The controller 102 is electrically coupled to the bases of transistors 106, 108, and 110-115. The controller 102 can supply control signals to independently activate and deactivate the transistors 106, 108, and 110-115. The controller 102 includes inputs and outputs 2 (e.g., digital inputs, digital outputs, analog inputs, analog outputs), a non-transitory memory 3 (e.g., read-only memory or electrically erasable memory), and a transitory memory 4. The controller 102 can sense the voltage at node 103 and the current flowing through the inductor 104 via a current sensor 199. Figure 2

[0018] The transistors 106, 108, and 110-115 are shown as insulated gate bipolar transistors (IGBTs), but in alternative configurations, they can be metal oxide field effect transistors (MOSFETs), field effect transistors (FETs), or other known types of transistors. The controller 102 can activate an IGBT via supplying a higher potential voltage to the gate of the transistor 106, 108, and 110-115. The controller 102 can deactivate an IGBT via supplying a lower potential voltage to the gate of the transistor 106, 108, and 110-115. The gates of the transistors 106 and 108 are indicated by the letter“G.” The collectors of the transistors 106 and 108 are indicated by the letter“C.” The emitters of the transistors 106 and 108 are indicated by the letter“E.” The transistors 110-115 have similar bases, emitters, and collectors as indicated for the transistors 106 and 108. The transistors 106 and 108 also include diodes 107 and 109 forward biased between the respective emitters and collectors. Current can flow between the collectors and emitters of the transistors 106 and 108 when they are activated. When the transistors 106 and 108 are deactivated, current is prevented from flowing between the collectors and emitters of the transistors 106 and 108. The transistors 110-115 operate similarly. The transistors 110-115 can be selectively activated and deactivated to convert DC to AC.

[0019] ​The inductor 104 is shown directly electrically coupled to the transistors 106 and 108. The inductor 104 is also directly electrically coupled to the capacitor 150, the capacitor 152, and the electrical energy storage device 175. The capacitor 151 is shown electrically coupled to the capacitor 150 and the negative side of the electrical energy storage device 175.

[0020] In the boost mode, the controller 102 can selectively activate the transistor 108, which can be referred to as a boost transistor, to charge the inductor 104 from the charge provided by the positive terminal 133a via the electrical energy storage device 175. The inductor 104 resists current flow as it begins to store electrical energy in a magnetic field. When the boost transistor 108 is closed, the polarity on the left-hand side of the inductor 104 is positive. When the boost transistor 108 is open, the current flow through the inductor 104 decreases and its magnetic field begins to collapse. The polarity of the inductor 104 changes so that the right-hand side of the inductor 104 has a positive polarity because its collapsing magnetic field supports current flow to continue to the load. The voltage of the electrical energy storage device 175 and the voltage developed across the inductor 104 are connected in series, thereby providing the voltage of the electrical energy storage device 175 plus the voltage of the inductor 104 at node 180. The voltage at node 180 minus a small voltage drop across the diode 107 is developed at node 101, which is the output of the variable voltage controlled inverter boost circuit and the input to the transistors 110-115 when the VVC is operating in the boost mode, because the diode 107 is forward biased. Charge can be stored in the capacitor 131 to smooth the output voltage of the boost circuit at node 101. The voltage at node 101 is a DC voltage. The variable voltage controlled inverter boost circuit can include the capacitors 150-152, the inductor 104, the boost transistor 108, the diode 109, the diode 107, the capacitor 131, and the resistor 130. The voltage at node 101 is supplied to the transistors 110-115, which are turned on and off to provide three-phase AC power to the motor 140. Whenever the boost transistor 108 is commanded to be activated, the buck transistor 106 is commanded to be deactivated so as to prevent a short circuit between node 101 and node 181.

[0021] If the motor 140 requires only a small amount of power, then the battery voltage minus a small voltage drop across the inductor 104 and the diode 107 can be supplied at node 101 by deactivating the buck transistor 106 and the boost transistor 108.

[0022] In the step-down mode, the motor 140 supplies charge to the inductor 104. Specifically, the three-phase AC output of the motor is converted to a DC voltage at node 101 via the controller 102 switching transistors 110-115. The inductor 104 charges via activation of the transistor 106, which can be referred to as a step-down transistor. The inductor 104 resists current flow as it begins to store electrical energy in a magnetic field. When the step-up transistor 106 is closed, the polarity on the right-hand side of the inductor 104 is positive. When the step-down transistor 106 is open, the current flow through the inductor 104 decreases and its magnetic field begins to collapse. The polarity of the inductor 104 changes so that the left side of the inductor 104 has a positive polarity because its collapsing magnetic field supports current flow to continue to the load (e.g., the electrical energy storage device 175). The amount of time that the inductor 104 is allowed to charge is controlled so that the voltage developed across the inductor 104 is less than the voltage output via the motor 140. The diode 109 couples the right side of the inductor 104 to node 181, which is coupled to the negative battery terminal 133b. The voltage developed across the inductor 104 is connected to the positive terminal 133a of the electrical energy storage device 175. Charge from the inductor 104 flows to the terminal 133a so that the electrical energy storage device can charge. The voltage at node 103 is controlled via adjusting the amount of time that the step-down transistor 106 is activated (e.g., closed to allow current flow through the transistor). Whenever the step-down transistor 106 is activated, the step-up transistor 108 is deactivated (e.g., open to inhibit current flow through the transistor). Charge can be stored in the capacitors 150-152 to smooth the output voltage of the step-down circuit at node 103. The voltage at node 103 is a DC voltage. The variable voltage controlled inverter step-down circuit can include the capacitors 150-152, the inductor 104, the step-down transistor 106, the diode 109, the capacitor 131, and the resistor 130. The voltage at node 103 is the output voltage of the variable voltage controlled inverter step-down circuit. The controller 102 can monitor the voltages at nodes 103 and 101. Further, the controller 102 can adjust the duty cycle of the signals supplied to the step-up transistor 108 and the step-down transistor 106 in response to the voltages at nodes 103 and 101.

[0023] Figure 2 is a block diagram of a vehicle 225 including a powertrain or driveline 200. Figure 2 The powertrain of includes an engine 202. The powertrain 200 is shown to include a vehicle system controller 255, an engine controller 12, an inverter 100 Figure 1The vehicle system controller 255 can communicate with the engine controller 12, the motor controller 102 included in the inverter 100, the transmission controller 254, and the brake controller 250. The vehicle system controller 255 can provide commands to the engine controller 12, the motor controller 102, the transmission controller 254, and the brake controller 250 to achieve driver input requests and other requests based on vehicle operating conditions. The vehicle system controller 255 can receive information from the engine controller 12, the motor controller 102, the transmission controller 254, and the brake controller 250. The information can include torque output limits for devices or components controlled not to be exceeded, torque input limits for devices or components controlled not to be exceeded, torque outputs of controlled devices, sensor and actuator data, diagnostic information (e.g., information about a deteriorating transmission, information about a deteriorating engine, information about a deteriorating motor, information about a deteriorating brake). The vehicle system controller 255 can provide commands to the engine controller 12, the motor controller 102, the transmission controller 254, and the brake controller 250 to achieve driver input requests and other requests based on vehicle operating conditions.

[0024] For example, in response to a driver releasing an accelerator pedal and a vehicle speed, the vehicle system controller 255 can request a desired wheel torque or wheel power level to provide a desired vehicle deceleration rate. The desired wheel torque can be provided by the vehicle system controller 255 requesting a first braking torque from the motor controller 102 and a second braking torque from the brake controller 250, the first and second torques providing a desired braking torque at the wheels 216.

[0025] In other examples, the division of control of the powertrain devices can be divided in different ways as shown. For example, a single controller can replace the vehicle system controller 255, the engine controller 12, the motor controller 102, the transmission controller 254, and the brake controller 250. Alternatively, the vehicle system controller 255 and the engine controller 12 can be a single unit, while the motor controller 102, the transmission controller 254, and the brake controller 250 are independent controllers. Figure 2

[0026] In this example, the powertrain 200 can be powered by the engine 202 and the motor 140. In other examples, the engine 202 can be omitted. The engine 202 can be started via the motor 140 (e.g., an integrated starter / generator or motor / generator). Further, the torque of the engine 202 can be adjusted via torque actuators 204 such as fuel injectors, throttle, etc.

[0027] The engine output torque can be transmitted through the dual mass flywheel 215 to the input or first side 235 of the powertrain decoupling clutch. The decoupling clutch 236 can be electrically or hydraulically actuated. The downstream or second side 234 of the decoupling clutch 236 is mechanically coupled to the motor input shaft 237. ​

[0028] The motor 140 can be operated to provide torque to the powertrain 200 or to convert the powertrain torque into electrical energy for storage in the electrical energy storage device 175 in a regenerative mode. The motor 140 is in electrical communication with the energy storage device 175. The motor 140 directly drives the powertrain 200 or is directly driven by the powertrain 200. In other examples, the motor 140 can be included in a power-split hybrid vehicle, or the motor 140 can be the sole source of propulsion. There are no belts, gears, or chains coupling the motor 140 to the powertrain 200. Instead, the motor 140 rotates at the same rate as the powertrain 200. The electrical energy storage device 175 (e.g., a high voltage battery or power source) can be a battery, a capacitor, or an inductor. The downstream side of the motor 140 is mechanically coupled to the pump impeller 285 of the torque converter 206 via the shaft 241. The upstream side of the motor 140 is mechanically coupled to the disconnect clutch 236. The motor 140 can be coupled to the powertrain 206 via the shaft 241. Figure 1 Motor controller 102 is shown instructed to operate as a motor or a generator to provide positive or negative torque to powertrain system 200 .

[0029] The torque converter 206 includes a turbine 286 for outputting torque to an input shaft 270. The input shaft 270 mechanically couples the torque converter 206 to the automatic transmission 208. The torque converter 206 also includes a torque converter bypass lockup clutch 212 (TCC). When the TCC is locked, torque is transferred directly from the impeller 285 to the turbine 286. The TCC is electrically operated by the controller 12. Alternatively, the TCC can be hydraulically locked. In one embodiment, the torque converter can be referred to as a component of the transmission.

[0030] When torque converter lockup clutch 212 is fully disengaged, torque converter 206 transmits engine torque to automatic transmission 208 via fluid transfer between torque converter turbine 286 and torque converter pump impeller 285, thereby achieving torque multiplication. Conversely, when torque converter lockup clutch 212 is fully engaged, engine output torque is directly transferred to the input shaft (not shown) of transmission 208 via the torque converter clutch. Alternatively, torque converter lockup clutch 212 can be partially engaged, thereby enabling adjustment of the amount of torque directly transferred to the transmission. Transmission controller 254 can be configured to adjust the amount of torque transmitted by the torque converter by adjusting torque converter lockup clutch 212 in response to various engine operating conditions or based on driver-driven engine operation requests.

[0031] The automatic transmission 208 includes a gear clutch (e.g., gears 1-10) 211 and a forward clutch 210. The automatic transmission 208 is a fixed-ratio transmission. The gear clutch 211 and the forward clutch 210 can be selectively engaged to change the ratio of the actual total revolutions of the input shaft 270 to the actual total revolutions of the wheels 216. The gear clutch 211 can be engaged or disengaged by adjusting the fluid supplied to the clutch via the shift control solenoid 209. Torque output from the automatic transmission 208 can also be transferred to the wheels 216 via the output shaft 260 to propel the vehicle. Specifically, the automatic transmission 208 can divert the input drive torque at the input shaft 270 in response to vehicle travel conditions before transmitting the output drive torque to the wheels 216. The transmission controller 254 selectively activates or engages the TCC 212, the gear clutch 211, and the forward clutch 210. The transmission controller also selectively deactivates or disengages the TCC 212, the gear clutch 211, and the forward clutch 210.

[0032] In addition, a frictional force can be applied to the wheels 216 by engaging the frictional wheel brakes 218. In one example, the frictional wheel brakes 218 can be engaged in response to the driver depressing his foot on the brake pedal (not shown) and / or in response to an instruction within the brake controller 250. In addition, the brake controller 250 can apply the brakes 218 in response to information and / or requests issued by the vehicle system controller 255. In the same manner, the frictional force on the wheels 216 can be reduced by disengaging the wheel brakes 218 in response to the driver releasing his foot from the brake pedal, brake controller instructions, and / or vehicle system controller instructions and / or information. For example, as part of an automated engine stop procedure, the vehicle brakes can apply a frictional force to the wheels 216 via the controller 250.

[0033] In response to a request to accelerate the vehicle 225, the vehicle system controller can obtain a driver demand torque or power request from the accelerator pedal or other device. The vehicle system controller 255 then allocates a fraction of the requested driver demand torque to the engine and the remainder to the electric machine. The vehicle system controller 255 requests engine torque from the engine controller 12 and electric machine torque from the electric machine controller 102. If the electric machine torque plus the engine torque is less than a transmission input torque limit (e.g., a threshold value that is not to be exceeded), the torque is passed to the torque converter 206, which then relays at least a fraction of the requested torque to the transmission input shaft 270. In response to shift schedules and TCC lockup schedules that can be based on input shaft torque and vehicle speed, the transmission controller 254 selectively locks the torque converter clutch 212 and engages the gears via the geared clutch 211. In some cases, when it can be desirable to charge the electric energy storage device 175, a charge torque (e.g., a negative electric machine torque) can be requested while there is a non-zero driver demand torque. The vehicle system controller 255 can request increased engine torque to overcome the charge torque to satisfy the driver demand torque.

[0034] In response to a request to decelerate the vehicle 225 and provide regenerative braking, the vehicle system controller can provide a negative desired wheel torque based on vehicle speed and brake pedal position. The vehicle system controller 255 then allocates a fraction of the negative desired wheel torque to the electric machine 140 (e.g., a desired driveline wheel torque) and the remainder to the friction brake 218 (e.g., a desired friction brake wheel torque). In addition, the vehicle system controller can inform the transmission controller 254 that the vehicle is in regenerative braking mode so that the transmission controller 254 causes the gears 211 to shift based on unique shift schedules to improve regenerative efficiency. The electric machine 140 supplies a negative torque to the transmission input shaft 270, but the negative torque provided by the electric machine 140 can be limited by the transmission controller 254, which outputs a transmission input shaft negative torque limit (e.g., a threshold value that is not to be exceeded). In addition, the negative torque of the electric machine 140 can be limited by the vehicle system controller 255 or the electric machine controller 102 based on operating conditions of the electric energy storage device 175 (e.g., limited to less than a threshold negative threshold torque). Any portion of the desired negative wheel torque that cannot be provided by the electric machine 140 due to transmission or ISG limits can be allocated to the friction brake 218 so that the desired wheel torque is provided by a combination of negative wheel torque from the friction brake 218 and the ISG 240.

[0035] Accordingly, torque control of various powertrain components can be governed by the vehicle system controller 255, with local torque control of the engine 202, transmission 208, electric machine 140, and brakes 218 provided via the engine controller 12, electric machine controller 102, transmission controller 254, and brake controller 250.

[0036] As one example, engine torque output can be controlled by controlling a combination of spark timing, fuel pulse width, fuel pulse timing, and intake air for a spark ignition engine. In the case of a diesel engine, the controller 12 can control engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and intake air. In all cases, engine control can be performed on a cylinder-by-cylinder basis to control engine torque output.

[0037] The electric machine controller 102 can control torque output and electric machine generation from the electric machine 140 by adjusting current flow into and out of the armature winding, as is known in the art.

[0038] The transmission controller 254 receives transmission input shaft position via a position sensor 271. The transmission controller 254 can convert transmission input shaft position to input shaft speed via differentiating the signal from the position sensor 271 or counting a number of known angular distance pulses over a predetermined time interval. The transmission controller 254 can receive transmission output shaft torque from a torque sensor 272. Alternatively, the sensor 272 can be a position sensor or a torque and position sensor. If the sensor 272 is a position sensor, the controller 254 can count shaft position pulses over a predetermined time interval to determine transmission output shaft speed. The transmission controller 254 can also differentiate transmission output shaft speed to determine transmission output shaft acceleration.

[0039] The brake controller 250 receives wheel speed information via wheel speed sensors 221 and receives brake requests from the vehicle system controller 255. The brake controller 250 can also receive brake pedal position information from a brake pedal sensor (not shown) either directly or through the CAN 299. The brake controller 250 can provide braking in response to wheel torque commands from the vehicle system controller 255. The brake controller 250 can also provide anti-lock and vehicle stability braking to improve vehicle braking and stability. As such, the brake controller 250 can provide a wheel torque limit (e.g., a threshold negative wheel torque that is not to be exceeded) to the vehicle system controller 255 so that negative motor torque does not result in exceeding the wheel torque limit. For example, if the controller 250 issues a negative wheel torque limit of 50 N-m, then the motor torque is adjusted to provide less than 50 N-m (e.g., 49 N-m) of negative torque at the wheel, including accounting for transmission gearing.

[0040] Thus, Figure 1 and Figure 2 The system of provides a system comprising an inverter comprising a boost transistor, a buck transistor, and a controller comprising executable instructions stored in a non-transitory memory to adjust, via the controller, a duty cycle applied to the boost transistor or the buck transistor in response to a desired output voltage of the variable voltage controlled inverter not being less than a battery voltage, the duty cycle adjusted in response to the battery voltage. The system further comprises a battery electrically coupled to the inverter and a motor electrically coupled to the inverter. The system further comprises additional instructions to adjust the duty cycle further in response to a dead time between the boost transistor being activated and the buck transistor being deactivated. The system further comprises additional instructions to command the buck transistor to activate and the boost transistor to deactivate at substantially the same time. The system further comprises additional instructions to switch the boost transistor at the duty cycle via the controller in response to the desired output voltage of the variable voltage controlled inverter being less than the battery voltage and the desired output voltage of the variable voltage controlled inverter being greater than the battery voltage minus a threshold voltage. The system comprises where the desired output voltage is a voltage at a collector of the boost transistor.

[0041] Referring now to Figure 3 , a block diagram of a controller that can be incorporated into the method of Figure 5 and Figure 6 Further, Figure 3 The variable voltage controller (VVC) 300 of can be incorporated into the system of Figure 1 and Figure 2 .

[0042] The motor torque request and the current motor speed are input to the variable voltage control boost / buck table 302. When the motor torque request is marked as positive, the variable voltage control boost / buck table 302 can output a target boost voltage (Target_V). The boost voltage is the voltage at node 101. Figure 1 When the motor torque request is marked as negative, the variable voltage control boost / buck table 302 can output a target buck voltage. The buck voltage is the voltage at node 103. Figure 1 The target boost or buck voltage is input to block 304.

[0043] The VVC compensated buck or boost voltage is determined at the block via the following equation:

[0044]

[0045]

[0046] where Max_duty_cycle is the maximum duty cycle of the control signal (e.g., the signal supplied to the base of the transistor) supplied to the buck transistor when the variable voltage controller is operating in the buck mode, Max_duty_cycle is the maximum duty cycle of the control signal supplied to the boost transistor when the VVC is operating in the boost mode, Switch_period is the period of the control signal supplied to the buck transistor when the VVC is operating in the buck mode, Switch_period is the period of the control signal when the VVC is operating in the boost mode, VVC_comp_voltage is the VVC compensated voltage, and Vbatt is the voltage of the battery or the voltage of the electrical energy storage device. When the motor torque request is marked as positive, the VVC can operate in the boost mode. When the motor torque request is marked as negative, the VVC can operate in the buck mode. The VVC compensated buck or boost voltage is input to block 304.

[0047] At block 304, the VVC 300 selects the maximum value from the VVC compensated buck or boost voltage and the target voltage. The operation of block 304 can be expressed via the following equation:

[0048] Vdc_cmd = max(rarget_V, VVC_comp_voltage) Equation (3)

[0049] where Vdc_cmd is the voltage command during the buck mode and during the boost mode Figure 1the command voltage at node 101, max is a function of the larger of argument 1 (Target_V) and argument 2 (VVC_comp_voltage), and Target_V is the target voltage determined at 302. Block 304 outputs the command voltage to the VVC controller at block 308.

[0050] Block 308 can be a proportional / integral / derivative (PID) controller or other known type of controller that receives the command voltage and closed-loop feedback adjusts the duty cycle of the signal supplied to the buck transistor or the boost transistor. In one example, in boost mode, the voltage at node 101 is subtracted from the command voltage Vdc_cmd to provide a voltage error, and the duty cycle of the signal supplied to the boost transistor is adjusted in response to the voltage error. In another example, during buck mode, the voltage at node 101 is controlled via the controller 102 in response to the voltage at node 101 to control the voltage at node 103. Specifically, the voltage at node 101 is related to the voltage at node 103 via the following equation:

[0051] V 103 · I i104 = V 101 · I L

[0052] where V 103 is the voltage at node 103 or the voltage at the battery (which can also be referred to as V batt ), Ii104 is the current flowing through the inductor 104, V 101 is the voltage at node 101 (which can be referred to as V dc_cmd ), and I L is the current of the load (e.g., motor 140). The load current I L is a function of the motor speed and torque determined from the desired vehicle braking torque. The controller 102 then adjusts the switching of the transistor 106 in response to I i104 , V 101 , and I L to provide the desired voltage at node 103 (V 103 ) during buck mode. The VVC controller 308 supplies a duty cycle control signal to the buck transistor 106 or to the boost transistor 108.

[0053] Reference is now made to Figure 4, showing a graph illustrating a dead time between activating the boost transistor and deactivating the buck transistor. As previously described, the boost transistor can be commanded to activate a predetermined amount of time (e.g., a dead time) after the buck transistor is commanded to deactivate, or the buck transistor can be commanded to activate a predetermined amount of time (e.g., a dead time) after the boost transistor is commanded to deactivate, to reduce the likelihood of a short between nodes 101 and 181. The dead time compensates for the additional time it takes for the activated transistor to deactivate compared to the short amount of time it takes to activate the deactivated transistor. As such, to reduce the likelihood of a short between nodes 101 and 181 in Figure 1 Figure 1 , a dead time can be set to reduce the likelihood of a short between boost transistor 108 and buck transistor 106. The dead time allows the current flowing through the deactivated transistor to stop before the current flowing through the activated transistor begins.

[0054] In this example, the dashed line 402 represents the operating state of boost transistor 108, and the solid line 404 represents the operating state of buck transistor 106. When traces 402 and 404 are at a lower level near the horizontal axis, the buck transistor and the boost transistor are deactivated and do not allow current to flow through the transistors. When traces 402 and 404 are at a higher level near the value one positioned along the vertical axis, the buck transistor and the boost transistor are activated and allow current to flow through the transistors.

[0055] At time to, the boost transistor is activated and the buck transistor is deactivated. Between time to and time ti, the boost transistor is commanded to deactivate. After a predetermined dead time has elapsed (at time t2), the buck transistor is commanded to activate to prevent the buck transistor and the boost transistor from being activated at the same time. The boost transistor is actually deactivated at time ti, and a short time later the buck transistor is commanded to activate at time t2. The time between time ti and time t2 is the dead time, and it reduces the likelihood of a short between nodes 101 and 181 in Figure 1

[0056] The buck transistor remains activated and the boost transistor is deactivated until time t3, just before the buck transistor is commanded to deactivate. At time t3, the buck transistor is actually deactivated. At time t4, the boost transistor is commanded to activate. Thus, the deactivated transistor changes state before the other transistor is activated. In this way, it is possible to reduce the likelihood of a short between nodes 101 and 181 in Figure 1

[0057] Referring now to Figure 5 , a method for operating a VVC in a boost mode is shown. Figure 5 The method ofmay be included as stored in​​Figure 1 and Figure 2 In addition, in the physical or real world, Figure 5 and Figure 6 The method can be used with Figure 1 and Figure 2 The system works collaboratively to receive data and adjust actuators to control Figure 1 and Figure 2 system. Figure 5 The method controls the operation of VVC.

[0058] At 502 , method 500 determines Figure 1 The target VVC boost voltage (Target_V) to be present at node 101 of FIG. 1 is determined. In one example, the target voltage is a function of the motor torque request (e.g., 100 Newton-meters) and the motor speed (e.g., 2000 RPM). The target voltage can be empirically determined and stored in a table referenced by the motor torque request and the motor speed. In one example, the values ​​in the table are the boost voltages that provide the highest motor efficiency at the current motor speed and motor torque request. The values ​​can be determined by operating the motor at various input voltages for the current motor speed and motor torque request and determining the motor efficiency at the different boost voltages. Method 500 proceeds to 504.

[0059] At 504, method 500 determines the desired boost voltage for the VVC. In one example, the desired boost voltage is determined by selecting the maximum of two values. These two values ​​are the target voltage (Target_V) determined at 502 and a value equal to the battery voltage divided by the maximum duty cycle of the control signal supplied to the boost transistor (Max_duty_cycle as determined via Equation 1). This operation is performed at Figure 3 The method 500 proceeds to 506 .

[0060] At 506, method 500 judges whether the desired voltage determined at 504 is less than (lower than) the voltage of the battery or electrical energy storage device 175. If so, the answer is yes and method 500 proceeds to 510. Otherwise, the answer is no and method 500 proceeds to 508. If the desired voltage is less than the battery voltage, the battery voltage is boosted via VVC to improve motor efficiency when the motor operates as a motor and propels the vehicle.

[0061] At 508, method 500 enters VVC boost mode and begins switching the boost transistor on and off (e.g., activating and deactivating) to boost the battery voltage. Each time the boost transistor is commanded on or activated, the buck transistor is also commanded off. The boost transistor switches at a predetermined frequency based on the VVC hardware (e.g., the VVC inductor). Method 500 proceeds to 512.

[0062] At 512 , method 500 determines a VVC duty cycle and limits the VVC duty cycle to compensate for and provide dead time between deactivating the boost transistor and activating the buck transistor or between deactivating the buck transistor and activating the boost transistor. In one example, the VVC duty cycle is determined via the following equation:

[0063]

[0064] Where VVC_duty is the VVC duty cycle of the signal supplied to the base of the boost transistor, Vdc_cmd is the desired boost voltage determined at 504, and Vbatt is the voltage of the battery or electrical energy storage device 175. Additionally, the value of VVC_duty may be maintained at a value less than a threshold value MaxVVCDuty. The value of MaxVVCDuty may be a predetermined amount less than the value of Max_duty_cycle. For example, if Max_duty_cycle is 0.9, then MaxVVCDuty may be 0.88. The threshold MaxVVCDuty ensures that the maximum duty cycle of the signal applied to the boost transistor does not exceed Max_duty_cycle. The method 500 applies a signal having a duty cycle equal to the limit value of VVC_duty to the boost transistor to control Figure 1 In addition, the VVC and / or inverter are switched via the switch Figure 1 The transistors 110 to 115 will Figure 1 The boosted voltage at node 101 is converted to AC power and then applied to the motor. The motor propels the vehicle. Method 500 proceeds to exit.

[0065] At 510, method 500 determines whether the target voltage (Target_V) is less than the battery voltage (Vbatt) minus a threshold voltage (e.g., 10 volts). The threshold voltage provides hysteresis between the battery voltage at which the battery voltage is boosted and provided to the motor and the battery voltage at which the battery voltage is not boosted and provided to the motor. If method 500 determines that the target voltage (Target_V) is less than the battery voltage minus the threshold voltage, the answer is yes and method 500 proceeds to 514. Otherwise, the answer is no and method 500 proceeds to 512.

[0066] At 514, the method 500 exits the boost mode and stops sending the switching signal to the boost transistor. However, the battery voltage can continue to be supplied to the motor as long as the sign of the motor torque request is positive. The method 500 proceeds to exit.

[0067] Thus, the method 500 can transition between a boost mode in which the battery voltage is increased via the boost circuit and supplied to the motor and a mode in which the battery voltage is supplied to the motor without boosting. Moreover, when the battery voltage is boosted, the boost can be responsive to the battery voltage.

[0068] Reference is now made to Figure 6 , showing a method for operating a VVC in a buck mode. Figure 6 The method of Figure 1 and Figure 2 The method of Figure 5 and Figure 6 The method of Figure 1 and Figure 2 The method of Figure 1 and Figure 2 The method of Figure 6 The method of

[0069] At 602, the method 600 determines Figure 1 the target VVC voltage (Target_V) that will exist at the node 101 of In one example, the target voltage is a function of the motor torque request (e.g., -100 Newton-meters) and the motor speed (e.g., 2000 RPM). The target voltage can be empirically determined and stored into a table referenced via the motor torque request and the motor speed. In one example, the values in the table are target voltages that provide the highest motor efficiency at the current motor speed and motor torque request. The values can be determined via operating the motor as an alternator at various input power levels for the current motor speed and motor torque request and determining the motor efficiency at different target voltages. The method 600 proceeds to 604.

[0070] At 604, the method 600 determines a desired buck voltage for the VVC. In one example, the desired buck voltage is determined by selecting the maximum of two values. The two values are the target voltage (Target_V) determined at 602 and a value equal to the battery voltage divided by the maximum duty cycle of the control signal supplied to the buck transistor. This operation is described at 304 of Figure 3 The method 600 proceeds to 606.

[0071] At 606, the method 600 determines whether the target voltage determined at 602 is less than (less than) the voltage of the battery or electrical energy storage device 175. If yes, then the answer is yes and the method 600 proceeds to 610. Otherwise, the answer is no and the method 600 proceeds to 608. If the target voltage is less than the battery voltage, then the battery voltage is stepped down or reduced via the VVC to improve battery charging efficiency and motor efficiency when the motor is operated as an alternator and brakes the vehicle.

[0072] At 608, the method 600 enters the VVC step-down mode and begins to turn on and off (e.g., activate and deactivate) the step-down transistors to step down the motor voltage to be near the battery voltage. Each time a step-down transistor is commanded to turn on or activate, the step-up transistor is also commanded to turn off. The step-down transistors switch at a predetermined frequency based on the VVC hardware (e.g., VVC inductor). The method 600 proceeds to 612.

[0073] At 612, the method 600 determines the VVC duty cycle and limits the VVC duty cycle to provide a dead time between deactivating the step-up transistor and activating the step-down transistor or between deactivating the step-down transistor and activating the step-up transistor. In one example, the VVC duty cycle is determined via Equation 4. Further, the value of VVC_duty can be kept to a value less than a threshold MaxVVCDuty. The value of MaxVVCDuty can be a predetermined amount less than the value of Max_duty_cycle. For example, if Max_duty_cycle is 0.9, then MaxVVCDuty can be 0.88. The threshold MaxVVCDuty ensures that the maximum duty cycle of the signal applied to the base of the step-down transistor does not exceed Max_duty_cycle. The method 600 applies a signal to the step-down transistor with a duty cycle equal to the limited value of VVC_duty to control the stepped down voltage at node 103 of Figure 1 Further, the VVC and / or the inverter applies the stepped down voltage at node 103 to the battery. The method 600 proceeds to exit. Figure 1 Further, the VVC and / or the inverter applies the stepped down voltage at node 103 to the battery. The method 600 proceeds to exit.

[0074] At 610, the method 600 determines whether the target voltage (Target_V) is less than the battery voltage (Vbatt) minus a threshold voltage (e.g., 10 volts). The threshold voltage provides a hysteresis between when the motor voltage is stepped down and the battery voltage to which the electrical energy storage device is provided and when the motor voltage is not stepped down and the motor voltage to which the electrical energy storage device is provided. If the method 600 determines that the target voltage (Target_V) is less than the battery voltage minus the threshold voltage, then the answer is yes and the method 600 proceeds to 614. Otherwise, the answer is no and the method 600 proceeds to 612.

[0075] At 614 , method 600 exits buck mode and stops sending switching signals to the buck transistor. However, as long as the sign of the motor torque request is negative, the motor output voltage can continue to be supplied to the electrical energy storage device. Method 600 proceeds to exit.

[0076] Thus, method 600 can transition between a step-down mode in which the motor output voltage is stepped down via a step-down circuit and supplied to an electrical energy storage device, and a mode in which the motor output voltage is supplied to the electrical energy storage device without stepping down the voltage. Furthermore, when the motor voltage is stepped down, it can be stepped down in response to the battery voltage.

[0077] Figure 5 and Figure 6 A method for operating a variable voltage controlled inverter is provided. The method includes: receiving data to a controller; and, in response to a desired output voltage of the variable voltage controlled inverter being not less than a battery voltage, switching a transistor of the variable voltage controlled inverter via the controller at a duty cycle, the duty cycle being adjusted in response to the battery voltage. The method includes: wherein the transistor is a boost transistor, and further includes: adjusting the duty cycle in response to a dead time between the deactivated boost transistor and the activated buck transistor. The method also includes: stopping switching the transistor via the controller in response to the desired output voltage being less than the battery voltage minus a threshold voltage. The method includes: wherein the threshold voltage is a hysteresis voltage that prevents stopping switching of the transistor when the desired output voltage decreases. The method also includes: switching the transistor at a predetermined frequency (e.g., 10 kHz), and wherein the transistor is a boost transistor. The method includes: wherein the desired output voltage is a DC voltage. The method also includes: converting the DC voltage to an AC voltage. The method also includes: supplying the AC voltage to a motor to propel a vehicle.

[0078] Figure 5 and Figure 6A method for operating a variable voltage controlled inverter is also provided. The method includes: receiving data to a controller; and, in response to a desired output voltage of the variable voltage controlled inverter being less than a battery voltage and the desired output voltage being greater than the battery voltage minus a threshold voltage, switching a transistor of the variable voltage controlled inverter via the controller at a duty cycle, the duty cycle being adjusted in response to the battery voltage. The method also includes: applying the output voltage of the variable voltage controlled inverter to a motor. The method also includes: not switching the transistor via the controller in response to the desired output voltage being less than the battery voltage minus the threshold voltage. The method includes wherein the transistor is a boost transistor, and further includes: adjusting the duty cycle in response to a dead time between the deactivated boost transistor and the activated buck transistor. The method includes: commanding the boost transistor to turn on at substantially the same time as the buck transistor is commanded to turn off. The method also includes: ceasing switching the transistor via the controller in response to the desired output voltage being less than the battery voltage minus the threshold voltage.

[0079] It should be noted that the example control and estimation routines included herein can be used with various engine 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 a control system including a controller and various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. Accordingly, the various actions, operations, and / or functions described may be performed in the order described, in parallel, or omitted in some cases. Similarly, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the described actions, operations, and / or functions may be performed repeatedly. Furthermore, at least a portion of the described actions, operations, and / or functions may be embodied as code to be programmed into the non-transitory memory of a computer-readable storage medium in the control system. When the actions are performed by executing instructions in a system including various engine hardware components and one or more controllers, the control actions may also transform the operating states of one or more sensors or actuators in the physical world.

[0080] This description ends here. Those skilled in the art will recognize numerous variations and modifications upon reading this description without departing from the spirit and scope of this description. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations may advantageously utilize this description.

[0081] According to the invention, there is provided a variable voltage controlled inverter operation method, the method having: receiving data to a controller; and switching a transistor of the variable voltage controlled inverter via the controller by a duty cycle in response to a desired output voltage of the variable voltage controlled inverter not being less than a battery voltage, the duty cycle adjusted in response to the battery voltage.

[0082] According to an embodiment, the transistor is a boost transistor, and the method is further characterized by adjusting the duty cycle further in response to a dead time between the boost transistor being deactivated and a buck transistor being activated.

[0083] According to an embodiment, the method is further characterized by stopping switching the transistor via the controller in response to the desired output voltage being less than the battery voltage minus a threshold voltage.

[0084] According to an embodiment, the threshold voltage is a hysteresis voltage that prevents stopping switching the transistor when the desired output voltage is less.

[0085] According to an embodiment, the method is further characterized by switching the transistor at a predetermined frequency, and wherein the transistor is a boost transistor.

[0086] According to an embodiment, the desired output voltage is a DC voltage.

[0087] According to an embodiment, the method is further characterized by converting the DC voltage to an AC voltage.

[0088] According to an embodiment, the method is further characterized by supplying the AC voltage to a motor, thereby propelling a vehicle.

[0089] According to the invention, there is provided a variable voltage controlled inverter operation method, the method having: receiving data to a controller; switching a transistor of the variable voltage controlled inverter via the controller by a duty cycle in response to a desired output voltage of the variable voltage controlled inverter being less than a battery voltage and the desired output voltage of the variable voltage controlled inverter being greater than the battery voltage minus a threshold voltage, the duty cycle adjusted in response to the battery voltage.

[0090] According to an embodiment, the method is further characterized by applying an output voltage of the variable voltage controlled inverter to a motor.

[0091] According to an embodiment, the method is further characterized by not switching the transistor via the controller in response to the desired output voltage being less than the battery voltage minus the threshold voltage.

[0092] According to an embodiment, the transistor is a boost transistor, and the method further comprises adjusting the duty cycle further in response to a dead time between the deactivated boost transistor and an activated buck transistor.

[0093] According to an embodiment, the boost transistor is commanded on at substantially the same time as the buck transistor is commanded off.

[0094] According to an embodiment, the method is further characterized by stopping switching the transistor via the controller in response to the desired output voltage of the variable voltage controlled inverter being less than the battery voltage minus a threshold voltage.

[0095] According to the present invention, a system is provided having an inverter including a boost transistor, a buck transistor, and a controller including executable instructions stored in a non-transitory memory to adjust a duty cycle applied to the boost transistor or the buck transistor via the controller in response to a desired output voltage of the variable voltage controlled inverter not being less than a battery voltage, the duty cycle adjusted in response to the battery voltage.

[0096] According to an embodiment, the system is further characterized by a battery electrically coupled to the inverter and a motor electrically coupled to the inverter.

[0097] According to an embodiment, the system is further characterized by additional instructions to adjust the duty cycle further in response to a dead time between the deactivated boost transistor and an activated buck transistor.

[0098] According to an embodiment, the system is further characterized by additional instructions to command the buck transistor to activate and the boost transistor to deactivate at substantially the same time.

[0099] According to an embodiment, the system is further characterized by additional instructions to switch the boost transistor via the controller at the duty cycle in response to a desired output voltage of the variable voltage controlled inverter being less than a battery voltage and the desired output voltage of the variable voltage controlled inverter being greater than the battery voltage minus a threshold voltage.

[0100] According to an embodiment, the desired output voltage is a voltage at a collector of the boost transistor.

Claims

1. A method for operating a variable voltage controlled inverter, the method comprising: Receive data to the controller; as well as adjusting a desired output voltage of the variable voltage controlled inverter according to a ratio of a battery voltage to a duty cycle, wherein, in response to the ratio of the battery voltage to the duty cycle being greater than a target voltage, adjusting a command voltage of the variable voltage controlled boost circuit according to the ratio of the battery voltage to the duty cycle by a controller; switching transistors of the variable voltage controlled inverter via the controller according to a command voltage of a variable voltage controller boost circuit; In response to a ratio of the battery voltage to the duty cycle being less than a target voltage, the commanded output voltage is adjusted in response to the target voltage, the target voltage being based on a motor torque request and a motor speed, and the transistor is switched at a predetermined frequency, and wherein the transistor is a boost transistor.

2. The method of claim 1 , wherein the transistor is a boost transistor, and further comprising: The duty cycle is further adjusted in response to a dead time between the boost transistor being deactivated and the buck transistor being activated.

3. The method of claim 2, further comprising: Switching the transistor is stopped via the controller in response to the desired output voltage being less than the battery voltage minus a threshold voltage. 4 . The method of claim 3 , wherein the threshold voltage is a hysteresis voltage that prevents stopping switching of the transistor when the desired output voltage decreases. The method of claim 1 , wherein the desired output voltage is a DC voltage.

6. The method of claim 5, further comprising: The DC voltage is converted into an AC voltage.

7. The method of claim 6, further comprising: The AC voltage is supplied to the electric motor, thereby propelling the vehicle.

8. A variable voltage controlled inverter operating system, the system comprising: An inverter comprising a boost transistor, a buck transistor, and a controller, the controller comprising executable instructions stored in a non-transitory memory to adjust a desired output voltage of a variable voltage controlled inverter according to a ratio of a battery voltage to a duty cycle, wherein, in response to a ratio of the battery voltage to the duty cycle being greater than a target voltage, the controller adjusts a command voltage of a variable voltage controlled boost circuit according to the ratio of the battery voltage to the duty cycle; the controller adjusts a duty cycle applied to the boost transistor or the buck transistor according to the command voltage of the variable voltage controller boost circuit; and in response to a ratio of the battery voltage to the duty cycle being less than a target voltage, the command output voltage is adjusted in response to the target voltage, the target voltage being based on a motor torque request and a motor speed, and the transistor is switched at a predetermined frequency, and wherein the transistor is a boost transistor.

9. The system of claim 8, further comprising a battery electrically coupled to the inverter and a motor electrically coupled to the inverter.

10. The system of claim 8, further comprising additional instructions to adjust the duty cycle further in response to a dead time between the boost transistor being deactivated and the buck transistor being activated.

11. The system of claim 8, further comprising additional instructions to command the buck transistor to activate and the boost transistor to deactivate at substantially the same time.

12. The system of claim 8, further comprising additional instructions to switch the boost transistor at the duty cycle via the controller in response to a desired output voltage of the variable voltage controlled inverter being less than a battery voltage and the desired output voltage of the variable voltage controlled inverter being greater than the battery voltage minus a threshold voltage.

13. The system of claim 12, wherein the desired output voltage is a voltage at a collector of the boost transistor.

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