Traction to auxiliary power transfer in modular ev drivetrain

Abstract

A method for controlling a modular multilevel converter (MMC) is provided. The method includes: commanding a plurality of full-bridge submodules to each selectively conduct a current from a respective battery and to apply a torque-producing alternating current (AC) voltage to an electric motor to cause the electric motor to produce a torque; determining a carrier phase angle based on an auxiliary current command; commanding, based on the carrier phase angle, the plurality of full-bridge submodules to apply a zero-sequence AC voltage to the electric motor, thereby inducing a zero-sequence AC current in the electric motor, wherein the zero-sequence AC current causes the electric motor to produce zero net torque; and rectifying an AC current from the electric motor having the zero-sequence AC voltage, thereby supplying a direct current (DC) auxiliary current to an auxiliary load and in accordance with the auxiliary current command.

Description

TRACTION TO AUXILIARY POWER TRANSFER IN MODULAR EV DRIVETRAINCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This PCT International Patent Application claims the benefit of U.S. Provisional Patent Application No. 63 / 666,267 filed July 1, 2024 the contents of which is incorporated herein by reference in its entirety.FIELD

[0001] The present disclosure relates generally to a modular multilevel power converter system, such as a system for powering electric vehicles (EVs), such as passenger cars and trucks. More specifically, the present disclosure relates to a multilevel power converter system configured to transfer power to an auxiliary DC load.BACKGROUND

[0002] Multilevel Converters (MCs) have emerged as alternative topology to conventional two level inverters used in electric vehicles (EVs). MCs show superior performance in medium to high voltage level applications with improved waveform quality and low stress on switching components. Research indicates that Modular Multilevel converters (MMCs) can enhance EV driving range by 10-15%, prolong battery life, and halve charging times, offering substantial benefits in terms of cost and performance. MMCs directly integrate battery modules into the powertrain, effectively managing functions typically handled by a Battery Management System (BMS).

[0003] However, integrating batteries within MMC systems introduces challenges, notably the absence of a direct mechanism to recharge an auxiliary battery (e.g. a 12V or 48V battery), which powers various EV subsystems such as headlights, onboard computing, air conditioning and so on. Traditional EV powertrains employ an Auxiliary Power Module (APM) to charge the auxiliary battery from the high-voltage traction battery by utilizing the DC link.The unique architecture of MMC systems, lacking a direct DC link, complicates the inclusion of an APM, posing a barrier to commercial viability due to compromised auxiliary load functionality.

[0004] Recent research has focused on minimizing APM size and weight while maintaining cost-efficiency. Strategies include higher switching frequencies using Gallium nitride (GaN) switches to reduce passive component size or sharing components between the onboard charger (OBC) and the APM, also known as converter integration. Despite these innovations, integrating the APM with the OBC is not feasible for MMC-based EVs, necessitating an alternative approach.SUMMARY

[0005] The present disclosure provides a method for controlling a modular multilevel converter (MMC) is provided. The method includes: commanding a plurality of full-bridge submodules to each selectively conduct a current from a respective battery and to apply a torque-producing alternating current (AC) voltage to an electric motor to cause the electric motor to produce a torque; determining a carrier phase angle based on an auxiliary current command; commanding, based on the carrier phase angle, the plurality of full-bridge submodules to apply a zero-sequence AC voltage to the electric motor, thereby inducing a zerosequence AC current in the electric motor, wherein the zero-sequence AC current causes the electric motor to produce zero net torque; and rectifying an AC current from the electric motor having the zero-sequence AC voltage, thereby supplying a direct current (DC) auxiliary current to an auxiliary load and in accordance with the auxiliary current command.

[0006] The present disclosure also provides an electrified vehicle (EV). The EV includes: a traction motor configured to propel the EV; a multilevel converter for generating alternating current (AC) power; a controller; and a rectifier. The multilevel converter includes a plurality of full-bridge submodules each including: a respective battery and a power converterhaving a plurality of switching transistors. The rectifier is configured to rectify an AC current from the electric motor and to supply a direct current (DC) auxiliary current to an auxiliary load and in accordance with an auxiliary current command. The controller is configured to: command the plurality of full-bridge submodules to each selectively conduct a current from a respective battery and to apply a torque-producing alternating current (AC) voltage to the electric motor to cause the electric motor to produce a torque; determine a carrier phase angle based on the auxiliary current command; and command, based on the carrier phase angle, the plurality of full-bridge submodules to apply a zero-sequence AC voltage to the electric motor, thereby inducing a zero-sequence AC current in the electric motor, wherein the zero-sequence AC current causes the electric motor to produce zero net torque.

[0007] These and other aspects of the present disclosure are disclosed in the following detailed description of the embodiments, the appended claims, and the accompanying figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Further details, features and advantages of designs of the invention result from the following description of embodiment examples in reference to the associated drawings.

[0009] FIG. 1 shows a schematic block diagram of a system for operating a traction motor in an electrified vehicle (EV);

[0010] FIG. 2 shows a schematic diagram showing a traction-to-auxiliary (T2A) power converter including a modular multilevel converter (MMC), in an aspect of the present disclosure;

[0011] FIG. 3 shows a schematic diagram of a full bridge submodule within the MMC, and with a graphic illustration of switching signals for operation thereof ;

[0012] FIG. 4 shows a schematic diagram of a Thevenin equivalent circuit seen by a load in the T2A power converter;

[0013] FIG. 5 shows a schematic block diagram illustrating a control system for operating the MMC in the T2A power converter and to regulate power transfer to an auxiliary load, and in accordance with and aspect of the present disclosure;

[0014] FIGS. 6A-6B show graphs illustrating electromagnetic torque (in Nm) and Speed (in RPM), respectively, as a function of time and over a common time scale; and

[0015] FIGS. 7A-7B show graphs illustrating current in an auxiliary load and modulation index, respectively, as a function of time and over a common time scale;

[0016] FIG. 8 shows a flow chart listing steps in a method for controlling traction-to- auxiliary (T2A) power converter, in accordance with the present disclosure.DETAILED DESCRIPTION

[0017] Referring to the drawings, the present invention will be described in detail in view of following embodiments.

[0018] To overcome the technical limitations of the existing approaches, the present disclosure provides a novel Traction to Auxiliary (T2A) power transfer topology for MMC- based electric vehicle (EV) drivetrains. Utilizing phase shifted synchronized pulse-width modulation (SPWM) techniques, the proposed system integrates auxiliary power functionality directly into the MMC leveraging zero sequence subcircuit of the drivetrain. It eliminates the dedicated hardware and associated switching losses. Key components added in the proposed topology are a resonant capacitor 134, which may also be called a compensation capacitor, having capacitance Cr, a diode bridge rectifier 136 and a filter capacitor 138 having capacitance Cf.

[0019] The present disclosure provides a novel, fully integrated Traction to Auxiliary (T2A) power transfer topology utilizing the zero-sequence current in MMCs drivetrains for EVs. The zero sequence, often an underutilized degree of freedom, can be used to transfer power to auxiliary battery while dq axis operation of the motor is undisturbed. Specifically, thephase shifted SPWM technique in Cascaded H bridge topology is described. Some of the several advantages of this system includes no additional active switches required, no extra switching action required during driving, seamless operation of traction to auxiliary power transfer leaving driving subsystem undisturbed and utilization of high switching harmonic to control the output current.

[0020] The present disclosure introduces a flexible and efficient solution to integrate T2A functionality in MMCs. It not only enables MMC drivetrains to power the auxiliary battery, but do so at a substantially reduced cost, as it requires no additional active switches.

[0021] FIG. 1 shows a block diagram of system 10 for operating a traction motor in an electrified vehicle (EV). The system 10 is provided in a vehicle 12 having four wheels 14. The system 10 includes a DC power supply 16 and an inverter 20. The DC power supply 16 provides DC power to the inverter 20 via a DC bus 18. The system 10 may represent a conventional design. In some cases, auxiliary loads, such as low voltage (LV) battery charging may be powered using one or more DC-DC converters that draw DC power from the DC bus 18.

[0022] The inverter 20 has at least three pairs of solid-state switches 22, such as field effect transistors (FETs) configured to switch current from a DC power supply 23 and to generate an AC power upon a set of motor leads 24. The motor leads 24 transmit electrical power between the inverter 20 and an electric motor 26. The electric motor 26 may be a permanent magnet synchronous motor (PMSM). The electric motor 26 may be used as a motor, a generator, or as a motor / generator that functions as both a motor and a generator. The electric motor 26 may be configured as a traction motor that is coupled to one or more of the wheels 14 of the vehicle 12 for driving the vehicle 12. Alternatively, the electric motor 26 may be used for one or more ancillary functions in the vehicle 12, such as for operating an actuator, a fan, a pump, etc. In some embodiments, the system 10 of the present disclosure may have a non- vehicular application, such as for motor control in industrial or manufacturing applications.

[0023] A first current sensor 28a is arranged to measure current in one of the motor leads 24, and a second current sensor 28b is arranged to measure current in another one of the motor leads 24. In some embodiments, and as shown on FIG. 1, the current sensors 28a, 28b measure A-phase current ia, and B-phase current ib on corresponding ones of the motor leads 24. However, the system 10 may measure current on any two or three of the motor leads 24. The system 10 may include other sensors, such as voltage sensors configured to measure voltages upon or between the motor leads 24. If voltage sensors are available, they can be used as inputs for the provided approach.

[0024] The system 10 of FIG. 1 also includes an electronic control unit (ECU) 30, which may also be called a governing controller, in communication with the current sensor 28 to measure the currents in the motor leads 24. The ECU 30 may also be in functional communication with the inverter 20 to control operation of the inverter 20 and / or to monitor parameters measured by sensors associated with the inverter 20. The ECU 30 includes a processor 32 coupled to a storage memory 34. The storage memory 34 stores instructions, such as program code for execution by the processor 32, in an instruction storage 36. The storage memory 34 also includes data storage 38 for holding data to be used by the processor 32. The data storage 38 may record, for example, values of the parameters measured by the current sensor 28 and / or the outcome of functions calculated by the processor 32.

[0025] A speed / position sensor 42 may measure a rotational position 6 of the electric motor 26 that corresponds to an electrical rotational position Qe. Alternatively or additionally, the speed / position sensor 42 may measure a rotational speed co of the electric motor 26 that corresponds to an electrical rotational speed a>eof the electric motor 26. In some embodiments, the speed / position sensor 42 may include an encoder or a resolver connected to a shaft 40 of the electric motor 26. The speed / position sensor 42 may communicate the rotational position 6 and / or the rotational speed co of the electric motor 26 to the ECU 30.

[0026] FIG. 2 shows a schematic diagram showing a traction-to-auxiliary (T2A) power converter 110 including a modular multilevel converter (MMC) 120 configured to provide AC power to an electric motor 26. As shown, the electric motor 26 is a three-phase device having three phase windings with a wye configuration defining an A-phase terminal 24a, a B-phase terminal 24B, a C-phase terminal 24D, and a center tap 24o. However, the electric motor 26 may have a different number of phases and / or a different number of windings.

[0027] The MMC includes a first plurality of A-phase submodules 122a of the fullbridge submodules 122a, 122b, 122c in a series configuration to provide AC power to the A- phase terminal 24a of the electric motor 26. The MMC also includes a second plurality of B- phase submodules 122a of the full-bridge submodules 122a, 122b, 122c in a series configuration to provide AC power to the B-phase terminal 24b of the electric motor 26. The MMC also includes a third plurality of C-phase submodules 122a of the full-bridge submodules 122a, 122b, 122c in a series configuration to provide AC power to the C-phase terminal 24c of the electric motor 26.

[0028] The T2A power converter 110 defines a first output terminal 112o that is connected to the center tap 24o of the electric motor 26. The T2A power converter defines a second output terminal 112n that is connected to a common node n, such as a ground node. Each of the series combinations of the full-bridge submodules 122a, 122b, 122c are connected between the same common node n and a respective one of the phase terminals 24a, 24b, 24c of the electric motor 26.

[0029] As described in the present disclosure, the MMC 120 is configured to supply AC power to operate the electric motor 26, which may be a traction motor for propelling a vehicle. The MMC 120 is independently operable to generate a zero sequence voltage between the first output terminal 112o and the second output terminal 112n and which does not cause the electric motor 26 to produce a torque.

[0030] A controller 30, which may be similar or identical to the controller 30 shown on FIG. 1, controls and coordinates operation of the of the full-bridge submodules 122a, 122b, 122c for both causing the electric motor 26 to produce torque and also to generate the zero sequence voltage for the traction-to-auxiliary function.

[0031] A rectifier 130 is connected across the first output terminal 112o and the second output terminal 112n and is configured to rectify the zero sequence voltage and to supply a low-voltage output current ILV to an auxiliary load 140. The auxiliary load 140 may include, for example, a low-voltage auxiliary battery, such as a 12-volt battery or a 48-volt battery. Additionally or alternatively, the auxiliary load 140 may include one or more inverters each configured to supply AC power to one or more second electric motors. Such second electric motors may be used as additional traction motors to propel the vehicle and / or for other functions, such as a window actuator, a closure actuator, a seat positioning actuator, a power steering actuator, a brake booster actuator, etc..

[0032] The rectifier 130 includes a resonant capacitor 134 connected across the first output terminal 112o and the second output terminal 112n and defining a resonance capacitance Cr. The rectifier 130 also includes a diode bridge 136 having a full-bridge configuration and configured to rectify AC power from the output terminals 112o, 112n and to supply a DC power to the load 140 connected across a DC bus 132h, 1321. The diode bridge 136 supplies the low- voltage output current ILV to the load 140 via the DC bus 132h, 1321. A filter capacitor 138 having a capacitance is connected across the DC bus 132h, 1321 for smoothing the DC output voltage. Other types of rectifiers, such as an active synchronous rectifier, may be used in place of the diode bridge 136.

[0033] The proposed traction-to-auxiliary (T2A) power converter 110 includes connecting the low voltage auxiliary battery across the full bridge rectifier with capacitive filter Cf. This rectifier load is connected across neutral points of the inverter and traction motor(800V e-Drive). A resonating capacitor Cris also connected in parallel to the load. The DC link at the output may be used for any DC load. The applicable loads may include a low-voltage auxiliary battery, such as a 12V or 48V battery and / or an additional e-Drive, facilitating a multimotor architecture.Operating Principle

[0034] Within a cascaded H-bridge multilevel converter, a plurality of full-bridge submodules 122a, 122b, 122c are connected in series in each phase. Within each submodule 122a, 122b, 122c, the output voltage of single leg is sinusoidally pulse width modulated wave. The harmonic content can be found using double Fourier series analysis. Typically, the two legs of full bridge have in phase carrier signals and 180° out of phase modulating signals, producing appropriate SPWM signal to turn on / off the switches. However, carrier signals can be shifted without affecting the fundamental modulating component.

[0035] FIG. 3 shows a schematic diagram of a full bridge submodule 122a, 122b, 122c within the MMC 120, and with a graphic illustration of switching signals for operation thereof.

[0036] As shown, each of the full bridge submodule 122a, 122b, 122c defines two output nodes A, B. Each of the full bridge submodules 122a, 122b, 122c includes a respective battery having a battery voltage VDC, and a set of four switching transistors in an H-bridge configuration to selectively conduct current from the respective battery and to generate AC power on the two output nodes A, B. As also shown, the carrier phase angle 5 corresponds to a time difference between operating corresponding ones of the switching transistors in a conductive mode to conduct current between the battery and a respective one of the two output nodes A, B.

[0037] A submodule output voltage vAZ(t) generated by a given one of the submodules 122a, 122b, 122c, can be represented by equation (1):VdcVdc (1) vAz(t = — + —Mcos a)0t + 0O)where Vdc is a DC submodule battery voltage, M is a modulation index, to0is a modulating frequency, cocis the carrier frequency or switching frequency, 0Ois an initial sequence angle, m corresponds to index of the switching harmonic band, n corresponds to harmonic index within the mthswitching band, and Jnis a Bessel function of order n.

[0038] As evident from equation (1), the output voltage waveform has switching harmonics and sidebands besides the low frequency fundamental component. The voltage output of the submodule 122a, 122b, 122c is given by equation (2):where vAB(t) represents a voltage between output nodes Arepresents a voltage between output node A and a reference (zero) node, and vBZ(t) represents a voltage between output node B and the reference (zero) node.

[0039] Phase shift between the carrier waves within each full bridge submodule 122a, 122b, 122c is defined as intra-phase shift angle (5). Changing 8 varies the switching harmonics without affecting the fundamental modulating component as seen from equation (1). Consequently, phase shift factoris introduced in Fourier series because of the carrier phase shift. Since the T2A power transfer may use only the first switching harmonic, the magnitude of first switching harmonic for the first harmonic and magnitude is found to be:

[0040] It can be shown that zero-sequence voltage vOn(t) has fundamental switching frequency component Fowhich takes the same form as equation (3), except VDCis replacedwith N * VDCwhere N is number of modules per phase. Using phase shift factor Ks, the zerosequence voltage and hence the current supplied to the load can be controlled.

[0041] FIG. 4 shows a schematic diagram of a Thevenin equivalent circuit 150 seen by a load in the T2A power converter. The resonance capacitance Crvalue of the resonant capacitor 134 is chosen to cause resonance at the switching frequency. As such, higher order switching harmonics are suppressed.

[0042] The minimum and maximum zero sequence voltage produced by the MMC 120 corresponds to intra-phase shift angle = 0° , and 8 = 180°, respectively. Thereby, a simple proportional-integral (PI) feedback control can be implemented whereby the controller 30 varies the phase shift angle to produce the desired voltage to track the reference current. The dq axis operation is independent of the operation of zero sequence by the virtue of flux cancellation in stator windings due to zero sequence currents. Zero sequence, however, has dependency on the modulation index M, as evident from equation (3). The modulation index M increases with speed and approaches a value of 1.0 as the electric motor 26 enters a flux weakening region.

[0043] FIG. 5 shows a schematic block diagram illustrating a control system 200 for operating the MMC 120 in the T2A power converter 110 and to regulate power transfer to an auxiliary load 140, and in accordance with and aspect of the present disclosure. The control system 200 may be implemented in hardware and / or software, such as a software program executed by the controller 30.

[0044] The control system 200 takes, as an input, an auxiliary current command Iiy, representing a current demand by the auxiliary load 140 on the DC bus 132h, 1321. The control system 200 includes a subtractor 202 configured to generate a difference signal 203 as a difference between the auxiliary current commandand a DC auxiliary current ILV. The DC auxiliary current ILV may include, for example, a measured value and / or an estimated value ofthe DC current supplied to the auxiliary load 140. The control system 200 also includes a PI control loop 204 that takes the difference signal 203 from the subtractor 202 and generates a control output signal 205. The control output signal 205 may represent a first harmonic magnitude |VQ1')|.

[0045] The control system 200 also includes a first computation block 206 configured to calculate a first intermediate signal 207 based on the control output signal 205 and based on a modulation index M. The first computation block 206 may calculate the first intermediate1 signal 207 by multiplying the control output signal 205 by — — In other words, the firstcomputation block 206 implements one term of equation (3).

[0046] The control system 200 also includes a second computation block 208 configured to calculate a second intermediate signal 209 based on the first intermediate signal207. The second intermediate signal 209 may represent S The second computationblock 208 may calculate the second intermediate signal 209 by multiplying the first1 intermediate signal 207 by - . In other words, the second computation block 208N* Vjyc implements another term of equation (3), but with the additional term N, which represents a number of the full-bridge submodules 122a, 122b, 122c in each series combination.

[0047] The control system 200 also includes an arcsine calculator 210 that computes an inverse sine (sin1) of the second intermediate signal 209 to generate a third intermediate8 signal 211 that represents — The control system 200 also includes a multiplier 212 thatmultiplies the third intermediate signal 211 by a constant value of 2.0 to generate an output signal 213 representing the carrier phase angle 5. The output signal 5 is supplied to a drivetrain214, such as a motion controller that is configured to control operation of the MMC 120 to cause the electric motor 26 to generate torque.

[0048] FIGS. 6A-6B show graphs illustrating electromagnetic torque (in Nm) and Speed (in RPM), respectively, as a function of time and over a common time scale. FIGS. 6A- 6B illustrate operating the T2A power converter 110 using the controller 200 to implement a constant current / Torque control of an internal permanent magnet synchronous motor (IPMSM). With constant torque of 200 N / m, the speed increases linearly unless it saturates to 5000 rpm in 0.7 sec when maximum phase voltage is achieved i.e. M=l. This illustrates a worst-case scenario, where M increases rapidly.

[0049] FIGS. 7A-7B show graphs illustrating current in an auxiliary load and modulation index, respectively, respectively, as a function of time and over a common time scale. Multi-step reference command is given for output current in auxiliary battery. It is observed that charging control system tracks the reference command sufficiently well with rise time in order of milliseconds even in the presence of rapidly changing modulation index M.

[0050] All the full-bridge submodules 122a, 122b, 122c in each phase may not supply equal power, since a switching voltage harmonic of the full-bridge submodules 122a, 122b, 122c is phase shifted by some angle. As such, the voltage harmonic which aligns or makes the least angle with current phasor supplies the maximum active power and least reactive power. The full-bridge submodules 122a, 122b, 122c can be selectively controlled to transfer maximum power at a given instant. A control algorithm can implemented which selects particular ones of the full-bridge submodules 122a, 122b, 122c with maximum power transfer to maintain state of charge (SOC) balance.

[0051] In summary, the present disclosure provides a control system and method for MMC to provide T2A functionality, as required for commercialization. It provides T2A functionality while eliminating dedicated hardware and switching cost. The operating principleis to control and harnesses switching harmonics produced by driving operation to feed the auxiliary battery. The operating principle and control strategies are validated, where the proposed solution tracks reference auxiliary battery current without interfering with the driving operation happening simultaneously.

[0052] FIG. 8 shows a flow chart listing steps in a method 400 for controlling a modular multilevel converter (MMC) and to provide traction-to-auxiliary (T2A) functionality, in accordance with the present disclosure. At least some steps of the method 400 can be performed by the controller 30, in accordance with some embodiments of the present disclosure. As can be appreciated in light of the disclosure, the order of operation within the method is not limited to the sequential execution as illustrated in FIG. 8, but may be performed in one or more varying orders as applicable and in accordance with the present disclosure.

[0053] The method 400 includes commanding, at step 402, a plurality of full-bridge submodules to each selectively conduct a current from a respective battery and to apply a torque-producing alternating current (AC) voltage to an electric motor to cause the electric motor to produce a torque. For example, the controller 30 may command a set of four switching transistors in an H-bridge configuration within each of the full-bridge submodules 122a, 122b, 122c to generate respective AC voltages for application to the phase terminals 24a, 24b, 24c of the electric motor 26 and to cause the electric motor 26 to produce a torque.

[0054] The method 400 also includes determining, at step 404, a carrier phase angle based on an auxiliary current command. For example, the controller 30 may implement the control system 200 in order to generate the output signal 213 representing the carrier phase angle 5.

[0055] The method 400 also includes commanding, at step 406, based on the carrier phase angle, the plurality of full-bridge submodules to apply a zero-sequence AC voltage to the electric motor, thereby inducing a zero-sequence AC current in the electric motor, whereinthe zero-sequence AC current causes the electric motor to produce zero net torque. For example, the controller 30 may command a set of four switching transistors in an H-bridge configuration within each of the full-bridge submodules 122a, 122b, 122c to generate a respective component of the zero-sequence AC voltage, whereby the components of the zerosequence AC voltage, together, cause the electric motor 26 to produce zero net torque while simultaneously transferring power to the auxiliary load 140 via the rectifier 130.

[0056] The method 400 also includes rectifying, at 408, an AC current from the electric motor having the zero-sequence AC voltage, thereby supplying a direct current (DC) auxiliary current to an auxiliary load and in accordance with the auxiliary current command. For example, the rectifier 130 may rectify a zero sequence AC current based on the zero sequence voltage and to supply a low-voltage output current ILV to an auxiliary load 140.

[0057] In some embodiments, the plurality of full-bridge submodules include two or more full-bridge submodules connected in series and connected to a corresponding phase winding of the electric motor.

[0058] In some embodiments, the electric motor includes three phase windings with a wye configuration defining an A-phase terminal, a B-phase terminal, a C-phase terminal, and a center tap; applying each of the torque-producing AC voltage and the zero-sequence AC voltage to the electric motor includes applying a phase voltage between a common node and each of the A-phase terminal, the B-phase terminal, and the C-phase terminal, respectively, and rectifying the AC current from the electric motor further includes conducting the AC current from between the center tap and the common node.

[0059] In some embodiments, the electric motor is a traction motor configured to propel a vehicle.

[0060] In some embodiments, the auxiliary load includes a battery.

[0061] In some embodiments, the auxiliary load includes an inverter configured to supply an auxiliary AC power to a second electric motor.

[0062] In some embodiments, no active switches are disposed in a current path between the plurality of full-bridge submodules and the auxiliary load.

[0063] In some embodiments, the torque-producing alternating current and the DC auxiliary current are independently controlled.

[0064] In some embodiments, commanding the plurality of full-bridge submodules to apply the zero-sequence AC voltage to the electric motor further includes controlling a first switching harmonic of the torque-producing AC voltage.

[0065] In some embodiments, determining the carrier phase angle based on the auxiliary current command further includes using a proportional-integral controller to determine the carrier phase angle.

[0066] The system, methods and / or processes described above, and steps thereof, may be realized in hardware, software or any combination of hardware and software suitable for a particular application. The hardware may include a general purpose computer and / or dedicated computing device or specific computing device or particular aspect or component of a specific computing device. The processes may be realized in one or more microprocessors, microcontrollers, embedded microcontrollers, programmable digital signal processors or other programmable device, along with internal and / or external memory. The processes may also, or alternatively, be embodied in an application specific integrated circuit, a programmable gate array, programmable array logic, or any other device or combination of devices that may be configured to process electronic signals. It will further be appreciated that one or more of the processes may be realized as a computer executable code capable of being executed on a machine readable medium.

[0067] The computer executable code may be created using a structured programming language such as C, an object oriented programming language such as C++, or any other high- level or low-level programming language (including assembly languages, hardware description languages, and database programming languages and technologies) that may be stored, compiled or interpreted to run on one of the above devices as well as heterogeneous combinations of processors processor architectures, or combinations of different hardware and software, or any other machine capable of executing program instructions.

[0068] Thus, in one aspect, each method described above and combinations thereof may be embodied in computer executable code that, when executing on one or more computing devices performs the steps thereof. In another aspect, the methods may be embodied in systems that perform the steps thereof, and may be distributed across devices in a number of ways, or all of the functionality may be integrated into a dedicated, standalone device or other hardware. In another aspect, the means for performing the steps associated with the processes described above may include any of the hardware and / or software described above. All such permutations and combinations are intended to fall within the scope of the present disclosure.

[0069] The foregoing description is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. CLAIMSWhat is claimed is:

1. A method for controlling a modular multilevel converter (MMC), comprising: commanding a plurality of full-bridge submodules to each selectively conduct a current from a respective battery and to apply a torque-producing alternating current (AC) voltage to an electric motor to cause the electric motor to produce a torque; determining a carrier phase angle based on an auxiliary current command; commanding, based on the carrier phase angle, the plurality of full-bridge submodules to apply a zero-sequence AC voltage to the electric motor, thereby inducing a zero-sequence AC current in the electric motor, wherein the zero-sequence AC current causes the electric motor to produce zero net torque; and rectifying an AC current from the electric motor having the zero-sequence AC voltage, thereby supplying a direct current (DC) auxiliary current to an auxiliary load and in accordance with the auxiliary current command.

2. The method of Claim 1, wherein the plurality of full-bridge submodules include two or more full-bridge submodules connected in series and connected to a corresponding phase winding of the electric motor.

3. The method of Claim 1, wherein the electric motor includes three phase windings with a wye configuration defining an A-phase terminal, a B-phase terminal, a C- phase terminal, and a center tap, wherein applying each of the torque-producing AC voltage and the zero-sequence AC voltage to the electric motor includes applying a phase voltage between a common node and each of the A-phase terminal, the B-phase terminal, and the C-phase terminal, respectively, andwherein rectifying the AC current from the electric motor further includes conducting the AC current from between the center tap and the common node.

4. The method of Claim 1, wherein the electric motor is a traction motor configured to propel a vehicle.

5. The method of Claim 1, wherein the auxiliary load includes a battery.

6. The method of Claim 1, wherein the auxiliary load includes an inverter configured to supply an auxiliary AC power to a second electric motor.

7. The method of Claim 1, wherein no active switches are disposed in a current path between the plurality of full-bridge submodules and the auxiliary load.

8. The method of Claim 1, wherein the torque-producing alternating current and the DC auxiliary current are independently controlled.

9. The method of Claim 1, wherein commanding the plurality of full-bridge submodules to apply the zero-sequence AC voltage to the electric motor further includes controlling a first switching harmonic of the torque-producing AC voltage.

10. The method of Claim 1, wherein determining the carrier phase angle based on the auxiliary current command further includes using a proportional-integral controller to determine the carrier phase angle.

11. An electrified vehicle (EV) comprising:an electric motor configured to propel the EV; a multilevel converter for generating alternating current (AC) power, the multilevel converter including a plurality of full-bridge submodules each including: a respective battery and a power converter having a plurality of switching transistors; a rectifier configured to rectify an AC current from the electric motor and to supply a direct current (DC) auxiliary current to an auxiliary load and in accordance with an auxiliary current command; and a controller configured to: command the plurality of full-bridge submodules to each selectively conduct a current from a respective battery and to apply a torque-producing alternating current (AC) voltage to the electric motor to cause the electric motor to produce a torque; determine a carrier phase angle based on the auxiliary current command; and command, based on the carrier phase angle, the plurality of full-bridge submodules to apply a zero-sequence AC voltage to the electric motor, thereby inducing a zero-sequence AC current in the electric motor, wherein the zero-sequence AC current causes the electric motor to produce zero net torque.

12. The electrified vehicle of Claim 11, wherein the plurality of full-bridge submodules include two or more full-bridge submodules connected in series and connected to a corresponding phase winding of the electric motor.

13. The electrified vehicle of Claim 11, wherein the electric motor includes three phase windings with a wye configuration defining an A-phase terminal, a B-phase terminal, a C-phase terminal, and a center tap,wherein applying each of the torque-producing AC voltage and the zero-sequence AC voltage to the electric motor includes applying a phase voltage between a common node and each of the A-phase terminal, the B-phase terminal, and the C-phase terminal, respectively, and wherein rectifying the AC current from the electric motor further includes conducting the AC current from between the center tap and the common node.

14. The electrified vehicle of Claim 11, wherein the auxiliary load includes a battery.

15. The electrified vehicle of Claim 11, wherein the auxiliary load includes an inverter configured to supply an auxiliary AC power to a second electric motor.

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