Power transfer of electric motor with segmented windings

Abstract

Some embodiments disclosed herein relate to power transfer in an electric motor having segmented windings. In some embodiments, the control system may determine a d-axis command voltage for a secondary winding and a q-axis command voltage for the secondary winding of the electric motor based on a primary winding voltage, a primary winding current, a secondary winding current, and a rotor electrical position. The control system may generate a gate control signal based on the determined d-axis command voltage and q-axis command voltage of the secondary winding and transmit the gate control signal to an inverter coupled to the secondary winding to control power transfer between the primary winding and the secondary winding. Other embodiments may be disclosed or claimed.

Description

Technical Field

[0001] The present disclosure relates to electric motors. In particular, embodiments of the present disclosure relate to power transmission of electric motors having segmented windings. Background Art

[0002] An electric motor can generally be described as having a stator and a rotor. The stator is fixed in place, and the rotor operates relative to the stator. In an electric motor, the stator is generally the current-carrying component of the electric motor that produces a magnetic field that interacts with the rotor. The rotor of an electric motor includes a magnetic rotor, and the magnetic field produced by the stator is controlled to cause the rotor to rotate.

[0003] The stator of an electric motor typically consists of a series of steel laminations that are stacked together and contain slots to hold copper wire windings. These windings are used to create a magnetic field that interacts with the magnetic field of the rotor to produce torque. The windings in the stator can be arranged in different ways depending on the specific type of motor. The most common arrangement is a three-phase winding, which consists of three sets of windings spaced 120 degrees apart around the stator. Each set of windings is connected to a different phase of the power supply, which creates a rotating magnetic field when the motor is powered. In a three-phase motor, the windings are typically made up of coils of insulated copper wire. The number of turns in each coil, as well as the thickness of the wire, will depend on the specific motor design and the desired operating characteristics.

[0004] The windings in the stator are responsible for creating the magnetic field that interacts with the rotor to produce torque. When power is applied to the motor, the magnetic field in the stator begins to rotate, which also causes the rotor to turn. The speed of the electric motor is determined by the frequency of the power supply and the number of poles in the stator windings.

[0005] Electric motors in propulsion mode typically use closed loop current control to regulate torque and speed. The windings are powered by a controllable energy / source, such as by using a battery and a voltage source inverter (VSI) with pulse width modulation (PWM) control.

[0006] Electric motors, particularly in vehicles, can be used in direct grid-tied alternating current (AC) power transfer applications, such as where a vehicle's power source (e.g., a battery) is charged from the grid or the power source is used to power systems external to the vehicle. Such applications may be referred to as grid-to-vehicle (G2V), vehicle-to-grid (V2G), vehicle-to-load (V2L), or vehicle-to-house (V2H) charging. Such direct grid-tied applications typically utilize segmented winding motors, where a primary winding (winding 1) is coupled to an external energy / power source, and a secondary winding (winding 2) is coupled to an on-board controllable energy / power source. In addition, embodiments of the present invention help provide control over the magnitude and direction of power flow between the primary winding and the secondary winding. Summary of the invention

[0007] In one exemplary embodiment, a control system for an electric motor is provided. The control system includes a processor and the processor coupled to a memory. The memory stores instructions that, when executed by the processor, cause the control system to: receive voltage and current from a primary winding of the electric motor; receive current from a secondary winding of the electric motor; receive a rotor electrical position from a rotor of the electric motor; determine a d-axis command voltage of the secondary winding and a q-axis command voltage of the secondary winding based on the primary winding voltage, the primary winding current, the secondary winding current, and the rotor electrical position; generate a gate control signal based on the determined d-axis command voltage and q-axis command voltage of the secondary winding; and transmit the gate control signal to an inverter coupled to the secondary winding to control electric power transmission between the primary winding and the secondary winding.

[0008] In addition to one or more features described herein, the voltage from the primary winding is a three-phase voltage, the current from the primary winding is a three-phase current, and the current from the secondary winding is a three-phase current.

[0009] In addition to one or more features described herein, the electric motor includes a segmented winding electric machine.

[0010] In addition to one or more features described herein, the segmented winding electric machine is a permanent magnet synchronous machine, a synchronous reluctance machine, or a wound field synchronous machine.

[0011] In addition to one or more features described herein, a segmented winding electric machine includes a secondary winding coupled to a rechargeable energy storage system and a primary winding coupled to an external power source.

[0012] In addition to one or more features described herein, the d-axis command voltage is associated with the d-axis along the direction of the north pole of the magnet or the north pole of the magnetic field generated by the rotor field winding.

[0013] In addition to one or more features described herein, the d-axis command voltage is associated with reactive power transfer of the electric motor.

[0014] In addition to one or more features described herein, the q-axis command voltage is associated with a q-axis that is perpendicular to the d-axis, wherein the q-axis is 90 degrees ahead of the north pole associated with the d-axis.

[0015] In addition to one or more features described herein, the q-axis command voltage is associated with real power transfer in the electric motor.

[0016] In addition to one or more features described herein, determining the d-axis command voltage of the secondary winding and the q-axis command voltage of the secondary winding is further based on a d-axis leakage inductance and a q-axis leakage inductance measured from the electric motor.

[0017] In addition to one or more features described herein, the gate control signal rotates the electric motor at a speed synchronized with a grid voltage associated with the electric motor.

[0018] In addition to one or more features described herein, the speed of synchronization with the grid voltage is based on the grid frequency and the number of magnetic poles associated with the electric motor.

[0019] In addition to one or more features described herein, the speed synchronized with the grid voltage is based on the determined amount of torque.

[0020] In addition to one or more features described herein, the electric motor has a reluctance torque, and a d-axis command voltage is determined based on a d-axis current associated with the determined amount of torque.

[0021] In addition to one or more features described herein, the electric motor has no reluctance torque, and the q-axis command voltage is determined based on the q-axis current associated with the determined amount of torque.

[0022] In addition to one or more features described herein, a d-axis command voltage of the secondary winding and a q-axis command voltage of the secondary winding are determined based on a desired torque to achieve a speed synchronized with a grid voltage associated with the electric motor.

[0023] In addition to one or more features described herein, a gate control signal is generated by applying a pulse width modulation (PWM) process to the determined d-axis command voltage and q-axis command voltage of the secondary winding.

[0024] In addition to one or more features described herein, the PWM process is a space vector pulse width modulation (SVPWM) process.

[0025] In one exemplary embodiment, an electric motor is provided. The electric motor includes a rotor, a stator, a primary winding coupled to the stator, a secondary winding coupled to the stator, an inverter coupled to the primary winding, and a control system coupled to the rotor, the primary winding, the secondary winding, and the inverter. The control system includes a processor; and a memory connected to the processor and storing instructions, which, when executed by the processor, cause the control system to: receive voltage and current from the primary winding of the electric motor; receive current from the secondary winding of the electric motor; receive rotor electrical position from a rotor of the electric motor; determine a d-axis command voltage of the secondary winding and a q-axis command voltage of the secondary winding based on the primary winding voltage, the primary winding current, the secondary winding current and the rotor electrical position; generate a gate control signal based on the determined d-axis command voltage and q-axis command voltage of the secondary winding; and transmit the gate control signal to an inverter connected to the secondary winding to control electric power transmission between the primary winding and the secondary winding.

[0026] In one exemplary embodiment, a vehicle is provided. The vehicle includes an electric motor, the electric motor including: a rotor; a stator; a primary winding, the primary winding coupled to the stator; a secondary winding, the secondary winding coupled to the stator; an inverter, the inverter coupled to the secondary winding; and a control system coupled to the electric motor. The control system includes a processor; and a memory coupled to the processor and storing instructions, the instructions, when executed by the processor, cause the control system to: receive voltage and current from the primary winding of the electric motor; receive current from the secondary winding of the electric motor; receive rotor electrical position from the rotor of the electric motor; determine a d-axis command voltage of the secondary winding and a q-axis command voltage of the secondary winding based on the primary winding voltage, the primary winding current, the secondary winding current, and the rotor electrical position; generate a gate control signal based on the determined d-axis command voltage and q-axis command voltage of the secondary winding; and transmit the gate control signal to an inverter coupled to the secondary winding to control electric power transmission between the primary winding and the secondary winding.

[0027] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, advantages and details appear, by way of example only, from the following detailed description, which refers to the accompanying drawings, in which:

[0029] Figure 1is a schematic diagram of a vehicle for use in conjunction with one or more embodiments of the present disclosure;

[0030] Figure 2A is a schematic diagram showing two charging scenarios of an electric vehicle according to an embodiment of the present disclosure;

[0031] Figure 2B is a schematic diagram illustrating various direct grid connections to an electric vehicle according to an embodiment of the present disclosure;

[0032] Figure 3A is a schematic diagram showing power flow between windings of an electric motor according to an embodiment of the present disclosure;

[0033] Figure 3B is a schematic diagram of a transformer and associated voltage waveforms according to an embodiment of the present disclosure;

[0034] Figure 4 is a schematic diagram of a control system coupled to an electric motor according to various embodiments.

[0035] Figure 5A , Figure 5B and Figure 5C Including showing the embodiment according to the present disclosure Figure 4 A diagram depicting the logic executed by the control system;

[0036] Fig. 6A An example of a diagram showing dq axis vectors for a G2V application according to one or more embodiments of the present disclosure is shown;

[0037] Figure 6B An example of a graph showing dq axial quantities for a V2G application according to one or more embodiments of the present disclosure is shown;

[0038] Figures 7A-7H including graphs illustrating aspects of G2V and V2G scenarios according to various aspects of the present invention; and

[0039] Figure 8 is a flow chart illustrating a process according to various aspects of the invention. DETAILED DESCRIPTION

[0040] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0041] According to an exemplary embodiment, a control system for an electric motor is provided. The control system can determine a d-axis command voltage and a q-axis command voltage based on measured characteristics of the electric motor. The control system can use the d-axis and q-axis command voltages to generate gate control signals to control the transfer of electric power between the primary winding and the secondary winding of the electric motor. In this way, embodiments of the present invention can help control the electric motor during bidirectional direct grid-connected power transfer applications such as V2G, G2V, V2H, V2L, and vehicle-to-vehicle (V2V) power transfer.

[0042] Reference now Figure 1 , a schematic diagram of a vehicle 100 used in conjunction with one or more embodiments of the present disclosure is shown. The vehicle 100 includes a charging port 102, a battery 104, and an electric motor 106. In one embodiment, the vehicle 100 is a hybrid vehicle utilizing both an internal combustion engine and an electric motor. In another embodiment, the vehicle 100 is an electric vehicle utilizing only an electric motor. In an exemplary embodiment, the vehicle 100 is configured to be connected to a high voltage power source (i.e., a voltage source of at least 200 volts (V)) for charging the battery 104 via the charging port 102. The electric motor 106 is configured to receive power from the battery 104 to provide propulsion for the vehicle 100. In an exemplary embodiment, the battery 104 is configured to supply direct current (DC) power to an inverter (not shown), which converts the DC power into three-phase alternating current (AC) power. The three-phase AC power is supplied to the electric motor 106 to propel the vehicle 100.

[0043] Reference now Figure 2A , a schematic diagram illustrating two charging scenarios for an electric vehicle is shown. In this example, in a first scenario, the vehicle can be charged via an AC direct grid connection from an outlet 201 connected to an onboard charging system 202. The onboard charging system is connected to a battery management system (BMS) 204, which manages the charging of the vehicle battery (a lithium-ion battery in this example) 206. In a second scenario, a DC fast charging system 208 can charge the battery 206 via the BMS 204.

[0044] Reference now Figure 2B, a schematic diagram showing various direct grid connections to an electric vehicle is shown. In this example, the vehicle's electric motor can be coupled to a direct grid connection, such as a V2L connection 210, a V2H connection 212, or a V2G connection 214, through an integrated inverter system 240. The vehicle's electric motor also includes a segmented winding motor 230, which includes windings A1, A2, B1, B2, C1, and C2. The segmented winding motor 230 is coupled to a battery 220 via a second integrated inverter system 250, and to a first integrated inverter system 240. In this example, DC power transmission is indicated by a shaded arrow 260, while AC power transmission is indicated by a shaded arrow 265.

[0045] Reference now Figure 3A , a schematic diagram showing the power flow between the windings of an electric motor is shown. In this example, an electric motor 300 includes a stator 301 and a rotor 302. In this example, the stator 301 includes a first (primary) set of windings 310 and a second (secondary) set of windings 320, which together constitute a three-phase (3-ph) set of windings. The winding sets 310, 320 are configured to generate an electromagnetic field, and the rotor 302 includes one or more magnets 303, which are configured to interact with the electromagnetic field generated by the winding sets 310, 320. In some embodiments, the rotor can have magnets or rotor windings. When the rotor windings are excited by current, the rotor becomes an electromagnet.

[0046] exist Figure 3A In the example depicted in FIG, bidirectional power flow between primary winding 310 and secondary winding 320 is shown by arrow 305. Typically, electric motors in propulsion mode use closed loop current control to regulate torque and speed. The windings are powered by a controllable energy / power source, such as a battery and a voltage source inverter (VSI) with PWM control.

[0047] For direct grid-connected AC power transmission, such as G2V, V2G, etc., segmented winding electric motors (such as Figure 3A As shown in Figure 3A As shown, the secondary 3-ph winding set 320 is fed by a controllable energy / power source (i.e., battery 220). The primary 3-ph winding set 310 is directly fed by the power system (i.e., 230 volt (rms) 3-ph AC grid 330). In conventional systems, the voltage and current in the primary grid-side winding 310 cannot be directly controlled. As described in more detail below, embodiments of the present disclosure enhance existing power control methods to achieve simple and robust power transfer control.

[0048] Reference now Figure 3B, shows a schematic diagram of a transformer and associated voltage waveforms. In this example, point markers 350 indicate the phase of voltages Vp and Vs, which are in phase in this example. Transformer waveform diagram 360 graphically shows that Vp and Vs are in phase with each other and therefore have a zero degree phase shift.

[0049] exist Figure 3B In the transformer depicted in Figure 1, the primary (left) winding is associated with Vp, and the secondary (right) winding is associated with Vs. The voltage relationship between the two windings is determined by the turns ratio and the load characteristics. The load characteristics refer to the active power P, reactive power Q, and power factor transferred through the two windings. Once the transformer is designed, the turns ratio is known.

[0050] Will Figure 3B The relationship between the primary and secondary windings in the Figure 3A The primary winding 310 and the secondary winding 320 in the embodiment of the present invention are connected to the AC grid 330, so the primary winding voltage (grid voltage) is known by measurement. The voltage of the secondary winding 320 connected to the rechargeable energy storage system (battery 220) is controllable. Embodiments of the present invention can be used to manipulate load characteristics (P, Q and More specifically, the system may control the voltage amplitude and phase angle of the secondary winding 320 relative to the primary winding 310 grid voltage in order to control power flow.

[0051] In some embodiments, a dq axis reference frame can be used to control the electric motor 300. In particular, the voltage / current vectors are projected onto the d-axis and the q-axis, where the d-axis is the axis along the direction of the north pole of the magnet (or the north pole of the magnetic field generated by the rotor field windings), and the q-axis is the axis perpendicular to the d-axis. The q-axis is 90 degrees in front of the north pole of the magnetic field. The components (voltage / current) along the d-axis are generally related to establishing the magnetic field and reactive power (e.g., power not related to torque production) in the electric motor. The components along the q-axis are generally related to torque production that contributes to active power transfer.

[0052] The magnitude of the voltage / vector is calculated as The phase angle of the voltage vector can be expressed as θ = atan (v d / v q It can be seen that when the system controls the amplitude and phase angle of the grid voltage in the secondary winding 320 relative to the primary winding 310, the system is controlling the d-axis voltage (v d ) and q-axis voltage (v q ).

[0053] According to the dual three-phase winding motor (for example, Figure 3AThe dq axis voltage expression of the segmented winding motor depicted in FIG. 3 can be derived to obtain the secondary winding 320 (in Figure 3A In the example, the dq axis voltage is fed by the inverter system 307 and the primary winding 310 (in Figure 3A In the example, the primary winding 310 is connected to the power system 330) and the relationship between the dq axis voltages is as follows.

[0054] For example, v q1 and v q2 The difference between them is ω re L ld (i d1 -i d2 ). This difference is the electrical speed of the rotor ω re Electrical speed, d-axis leakage inductance L ld and the d-axis current difference between the two windings (i d1 -i d2 ) function.

[0055] Similarly, v d1 and v d2 The difference between them is -ω re L lq (i q1 -i q2 ) is. This difference is the rotor electrical speed ω re Electrical speed, q-axis leakage inductance L lq and the q-axis current difference between the two windings (i q1 -i q2 ) function.

[0056] Therefore, the dq axis voltage on the grid side can be expressed as:

[0057] v d1 =-ω re L lq (i q1 -i q2 )+v d2

[0058] v q1 =ω re L ld (i d1 -i d2 )+v q2

[0059] In the previous equation, v d1 and v q1 They are the d-axis voltage and q-axis voltage on the grid side. They are uncontrollable but measurable. The system can measure the rotor electrical speed ω re And the leakage inductance L ld and L lqThe current in both windings 310, 320 is also available. d1 -i d2 ) and (i q1 -i q2 ) is also known. The system can use this information to calculate the voltage of the secondary winding 320 as v d2 and v q2 They also reflect the output voltage from the inverter system 307 .

[0060] As mentioned before, the d-axis component is related to reactive power, and the q-axis component is related to active power. To control the power flow (i.e., active power and reactive power), the system can, given the measured primary winding voltage v d1 and v q1 Under the condition of controlling the secondary winding voltage 320 v d2 and v q2 , so that the d-axis component (i d1 -i d2 ) can be controlled to vary reactive power flow, and (i q1 -i q2 ) can be controlled to vary the active power flow.

[0061] Reference now Figure 4 , shows a schematic diagram of a control system coupled to an electric motor according to various embodiments. In this example, a control system 400 is coupled to an electric motor 300 to control the operation of the electric motor 300 via gate control signals provided to an inverter system 307 using measurements received from components of the electric motor 300.

[0062] In some exemplary embodiments, control system 400 includes at least one processor, such as a general purpose processor, a central processing unit, an application specific integrated circuit (ASIC), a digital signal processor, a field programmable gate array (FPGA), a digital circuit, an analog circuit, or a combination thereof. In some embodiments, control system 400 includes a processor in communication with a memory to store data and instructions executable by the processor to retrieve measurements from electric motor 300 and control the electric motor (e.g., via gate control signals sent to inverter system 307).

[0063] The control system 400 can measure the three-phase voltage v of the primary winding 310 1abc , and the three-phase current i of both the primary winding 310 and the secondary winding 320 1abc and i 2abc The control system 400 can also measure the rotor electrical position θ re To calculate the rotor electrical speed ω re , and is used for Park transformation (i.e., converting three-phase components into dq-axis components).

[0064] Reference now Figure 5A , Figure 5B and Figure 5C , a diagram illustrating the logic executed by the control system 400 is shown. Figure 5A , the current difference between the primary winding 310 and the secondary winding 320 is calculated. In this example, 1800 rpm is the 60 Hz synchronous speed of the 4-pole motor, which rotates at a speed synchronized with the grid voltage. Embodiments of the present invention may operate with any other suitable electric motor configuration. For example, for a 6-pole motor, the 60 Hz synchronous speed is 1200 rpm; and for an 8-pole motor, the 60 Hz synchronous speed is 900 rpm. Embodiments of the present invention may also operate in conjunction with different synchronous speeds (e.g., 50 Hz), in which case the synchronous speed is changed accordingly. Figure 5A In the example shown, the difference between the commanded 1800-rpm speed and the measured motor speed rpm is the speed difference Δrpm.

[0065] exist Figure 5B In this example, the control system 400 determines the d-axis command voltage V2d-cmd. d1 , rotor electrical speed, leakage inductance and q-axis current difference to determine the desired v d2 In addition, the control system 400 can add an additional voltage control target to control reactive power. This target will be Figure 5B The output of the Proportional Integral (PI) Controller block shown in Figure 1.

[0066] In some embodiments, the control system can measure the difference between the commanded d-axis current and the feedback d-axis current and then send the difference through a PI controller to obtain a commanded or, for example, reference d-axis voltage. The control system 400 can determine the commanded d-axis current Δidcmd2, which is the output of the PI controller, where the input of the PI controller is the reactive power difference Q cmd -Q fdbk As can be seen, reactive power is directly related to the d-axis current. The control system 400 uses the measured dq-axis voltage and current to determine the feedback reactive power Q based on the reactive power equation of the electric motor. fdbk .

[0067] like Figure 5C As shown, the control system 400 uses all q-axis components to determine v 2qcmd In this example, the difference P between the commanded active power and the fed-back active power is cmd –P fdbk The PI controller is used to generate the q-axis current command. The feedback active power P is determined based on the dc current and dc voltage. fdbkIn an exemplary embodiment, it is necessary to control the electric motor speed to synchronize the electric motor with the grid frequency. The electric motor speed is a result of the torque, and the torque is generated based on the current. Therefore, the control system can send the speed difference Δrpm through the PI controller to generate an appropriate current command.

[0068] In some embodiments, the control system 400 may not necessarily use the d-axis vector to determine the speed controller, depending on the type of electric motor. For example, an electric motor with reluctance torque is associated with the d-axis current, so the speed controller can be placed on the d-axis to generate Δi dcmd However, if the electric motor does not have reluctance torque, the control system can use the q-axis vector to determine the speed controller.

[0069] Return to reference Figure 4 , the control system 400 can be used in Figure 5A , Figure 5B and Figure 5C The resulting dq axis voltage command value (v 2dcmd and v 2qcmd ) to determine the gate signal for controlling the inverter system 307. Figure 4 As shown, the dq axis voltage commands are sent to a PWM generation process. In this example, the PWM generation process is a space vector pulse width modulation (SVPWM) process, but other PWM processes may be used in alternative embodiments.

[0070] In the PWM process, the dq axis voltage is first converted to a three-phase abc reference voltage using an inverse partial transformation. The three-phase reference voltage is then compared with a carrier waveform (eg, a triangle or sawtooth carrier, etc.) to generate the on and off gate signals for the inverter system 307.

[0071] Reference now Fig. 6A and Figure 6B , shows an example of a diagram of dq axis vectors for G2V applications and V2G applications with d axis current 605 and q axis current 610, respectively. Fig. 6A In the example of the G2V application graph 600 shown, the primary winding 310 current i w1 The secondary winding 320 has a positive iq and consumes power from the grid 330. The secondary winding 320 has a negative iq and delivers power to the battery 220.

[0072] exist Figure 6B In the example of the V2G application curve graph 650 shown, the primary winding 310 current i w1 has a negative iq and delivers power to the grid 330. The secondary winding 320 has a positive iq and consumes power from the battery 220. Fig. 6A and Figure 6BIf it is an electrically excited synchronous machine, a field winding may be required. field The size of the field can vary depending on machine design and power requirements.

[0073] As previously described, embodiments of the present invention provide direct voltage control for direct grid-tied power transfer using segmented winding electric motors. In particular, control system 400 directly generates a command voltage v d2 and v q2 , without specifying how large the d-axis and q-axis currents are needed. This is a significant enhancement over current control methods that specify and control the magnitude of the d-axis and q-axis currents.

[0074] Although the control system 400 does not specify the d-axis and q-axis currents in the control signal, the resulting current vector can be reflected in Fig. 6A and Figure 6B The vector relationship shown.

[0075] For example, in Fig. 6A In the G2V scenario shown, the primary winding 310 current vector i w1 is automatically placed on the q-axis current by direct voltage control. As mentioned above, the q-axis component is related to the active power and in this example i w1 Entirely on the positive q-axis. Therefore, the secondary winding 320 consumes active power from the external grid to function like a motor.

[0076] In some embodiments, a unity power factor is desired in the primary winding 310 to help the user avoid the adverse consequences associated with a low power factor. Thus, in some embodiments, the primary winding current i w1 It should preferably have only a q-axis component and no d-axis component. Alternatively, if the control system 400 controls the electric motor 300 to consume reactive power from the grid or deliver reactive power to the grid, the primary winding 310 may have a positive or negative d-axis component (note that the d-axis current component is related to reactive power).

[0077] Similarly, in Fig. 6A In the case of the secondary winding current i w2 lies on the negative q axis, and it has negative i q Current. The negative q-axis current causes the secondary winding 320 to act as a generator to deliver power to the battery 220. The secondary winding 320 current does not necessarily have only the q-axis current. Instead, the secondary winding 320 current may have a positive or negative d-axis component. The control system 400 may control the secondary winding d-axis current to manipulate the magnetic field within the electric motor 300 so that the primary winding 310 current is always placed on the q-axis current, thereby ensuring a unity power factor on the grid side.

[0078] exist Fig. 6A and6B In the example, the field winding current i field Is a current vector that only exists in wound-field synchronous motors. In some embodiments, the field winding is wound on the rotor to form an electromagnetic field. Changing its current will change the size of the rotor magnetic field. If it is a motor, this rotor magnetic field is needed to produce torque, or in some embodiments, this rotor magnetic field is needed to establish a field for power transfer. In contrast, in a permanent magnet synchronous motor, magnets are mounted on the rotor to establish the magnetic field. Therefore, permanent magnet motors do not have a field winding current vector.

[0079] In some embodiments, the magnitude of the field winding current can be tuned for direct grid-tied power transfer. Stronger field winding current allows stronger fields, greater magnetic flux, higher back EMF in the windings, and therefore more power to be transferred.

[0080] The field winding current also has the same function as the d-axis current in both windings. Increasing the field winding current will build more reactive power in the motor and allow for lower d-axis currents in both windings. For example, if the primary winding 310 has a positive d-axis current resulting in a low power factor, the system can increase the secondary winding 320 d-axis current or increase the field winding current to build more field / reactive power in the motor in order to reduce the d-axis primary winding current.

[0081] For the vehicle-to-grid scenario, the control system 400 can reverse the current vectors of the primary winding 310 and the secondary winding 320 in terms of their q-axis components. Thus, the primary winding 310 acts as a generator that delivers power to the grid 330. The secondary winding 320 acts as a motor that consumes power from the battery 220. Thus, power is delivered from the onboard battery pack to an external source or load. The vehicle-to-load scenario has the same current vector relationship.

[0082] Reference now Figures 7A-7H , graphs illustrating aspects of G2V and V2G scenarios according to aspects of the present invention are shown. Each graph is depicted with reference to three operational phases of the control system 400, namely speed ramp up 702, voltage synchronization 704, and power transfer 706.

[0083] During the speed ramp 702, the secondary winding 320 is disconnected from the grid 330. The primary winding 310 current is controlled by the inverter to produce torque, such as Fig. 7A , which illustrates the change in torque 710 over time 712 . Figure 7B The change in speed 716 over time 718 is shown.

[0084] Figure 7CActive power 722 is shown over time 724. In this example, the power of winding 1 is shown via graph line type 732, and the power of winding 2 is shown via graph line type 734. At 736 in the graph, the active power is 15 kW (e.g., G2V scenario), while at 738, the active power is 5 kW (e.g., V2G scenario).

[0085] Fig.7D The current (Phase A) 728 is shown as a function of time 730. In this example, the current of winding 1 is shown via graph line type 772 and the current of winding 2 is shown via graph line type 774.

[0086] Fig. 7E The current (q-axis current) 742 is shown as a function of time 744. The q-axis current of winding 1 is shown via graph line type 776, and the q-axis current of winding 2 is shown via graph line type 778. As shown in the graph, the primary winding 310 has a positive q-axis current, as shown by the curve of graph line type 778. Fig. 7E As a result, the motor speed increases until it reaches 1800 rpm (i.e., Figure 7B 60Hz synchronous speed for a 4-pole motor as shown).

[0087] During the voltage synchronization phase 704 and the power transfer phase 706, the torque is generally around 0 Nm because a relatively small positive torque is required to maintain the 1800 rpm synchronous speed. During the voltage synchronization phase 704, the electric motor 300 is mechanically decoupled from the shaft, otherwise the vehicle would move.

[0088] During the voltage synchronization phase 704, the primary winding 310 is still disconnected from the grid 330. The secondary winding 320 has negative active power (mainly copper losses, i.e., P=i 2 r), such as Figure 7C The winding 2 curve in FIG. 734 is shown. The current in the primary winding 310 is zero because the primary winding 310 is open circuit.

[0089] Figure 7F d-axis current 748 is shown as a function of time 750. The d-axis current of winding 1 is shown via graph line type 780, and the d-axis current of winding 2 is shown via graph line type 782. The current of primary winding 310 is calculated using Figure 7F The high d-axis current shown in the curve line 782 in the graph is used to increase the flux of the motor so that the back EMF of the secondary winding 320 can be maintained at a level as high as the grid voltage. In some embodiments, during the voltage synchronization stage 704, the back EMF of the secondary winding 320 has the same voltage amplitude, frequency and phase angle as the grid voltage.

[0090] In the power transfer phase 706, Figures 7A-7H A G2V scenario (between the 2nd and 3rd seconds on each graph) and a V2G scenario (between the 3rd and 4th seconds on each graph) are shown. During the G2V scenario, the primary winding 310 has positive active power that consumes grid power. The secondary winding 320 has negative active power that delivers grid power to the battery 220. During V2G, the polarity of the active power is swapped. Power flows from the battery 220 to the grid 330.

[0091] During G2V, the primary winding 310 has a positive iq and the secondary winding 320 has a negative iq, as shown in FIG. Fig. 7E As shown, they are symmetrical about the x-axis. In addition, the secondary winding 320 has a positive id to strengthen the magnetic field inside the motor and provide reactive power. Therefore, the d-axis current of winding 1 is maintained at 0A, as shown in FIG. Figure 7F shown.

[0092] Therefore, during G2V, due to Figure 7F The d-axis current of the primary winding 310 is 0A, and the reactive power of the primary winding 310 is Figure 7G is zero, and the primary winding 310 power factor is Figure 7H The power factor is maintained at 1 (integral power factor 764).

[0093] Figure 7G The reactive power 754 is shown over time 756. The reactive power of winding 1 is shown by graph line type 784 and the reactive power of winding 2 is shown by graph line type 786. Figure 7H The power factor 760 is shown as a function of time 762. The power factor of winding 1 is shown by graph line type 788 and the power factor of winding 2 is shown by graph line type 790.

[0094] The d-axis current of the secondary winding 320 is not 0 A during the power transmission phase 706, such as Figure 7F As shown. The reactive power of the secondary winding 320 is Figure 7G As a result, the power factor of the secondary winding 320 is only about -0.5. Figure 7H During V2G, the primary winding 310 can still maintain its power factor at -1, as shown by the curve 790 in FIG. Figure 7H The curve graph is shown as line type 788.

[0095] Reference now Figure 8 , showing examples of processes that may be performed according to various embodiments. Figure 8 Process 800 in may be performed by any suitable device or combination of means, such as by a processor of control system 400 executing computer-readable instructions stored in a memory of control system 400 .

[0096] In this example, process 800 includes receiving a voltage and a current from a primary winding of an electric motor at 805. The process also includes receiving a current from a secondary winding of the electric motor at 810. In some embodiments, the electric motor includes a segmented winding motor. The segmented winding motor can be a permanent magnet synchronous motor, a synchronous reluctance motor, or a wound field synchronous motor. In some embodiments, the segmented winding motor includes a secondary winding (e.g., winding 320) coupled to a rechargeable energy storage system (e.g., battery 220 via inverter system 307) and a primary winding (e.g., winding 310) coupled to an external power source (e.g., power source 330).

[0097] Process 800 also includes receiving a rotor electrical position from a rotor of the electric motor at 815 and determining a secondary winding d-axis command voltage and a secondary winding q-axis command voltage based on the primary winding voltage, the primary winding current, the secondary winding current, and the rotor electrical position at 820 .

[0098] Process 800 also includes generating a gate control signal based on the determined d-axis command voltage and q-axis command voltage of the secondary winding at 825. The process also includes transmitting the gate control signal to an inverter coupled to the secondary winding to control power transfer between the primary winding and the secondary winding at 830.

[0099] In some embodiments, the voltage from the primary winding is a three-phase voltage, the current from the primary winding is a three-phase current, and the current from the secondary winding is a three-phase current.

[0100] In some embodiments, the d-axis command voltage is associated with a d-axis along the direction of the north pole of the magnet or the north pole of the magnetic field generated by the rotor field winding.The d-axis command voltage may be associated with reactive power transfer of the electric motor.

[0101] In some embodiments, the q-axis command voltage is associated with a q-axis that is perpendicular to the d-axis, wherein the q-axis is 90 degrees ahead of a north pole associated with the d-axis. Controlling the q-axis command voltage may be associated with active power transfer in the electric motor.

[0102] In some embodiments, determining the d-axis command voltage of the secondary winding and the q-axis command voltage of the secondary winding is further based on the d-axis leakage inductance and the q-axis leakage inductance measured from the electric motor.

[0103] In some embodiments, the gate control signal is used to rotate the electric motor at a speed synchronized with a grid voltage associated with the electric motor. In some cases, the speed synchronized with the grid voltage is also based on the grid frequency and the number of magnetic poles associated with the electric motor. In other cases, the speed synchronized with the grid voltage is based on the determined torque amount. In some embodiments, the electric motor has a reluctance torque, and the d-axis command voltage is determined based on the d-axis current associated with the determined torque amount. In other embodiments, the electric motor does not have a reluctance torque, and the q-axis command voltage is determined based on the q-axis current associated with the determined torque amount.

[0104] In some embodiments, a d-axis command voltage for the secondary winding and a q-axis command voltage for the secondary winding are determined based on a desired torque to achieve a speed that is synchronized with a grid voltage associated with the electric motor.

[0105] In some embodiments, the gate control signal is generated by applying a pulse width modulation (PWM) process to the determined d-axis command voltage and q-axis command voltage of the secondary winding. For example, in some embodiments, the PWM process is a space vector pulse width modulation (SVPWM) process.

[0106] The terms "one" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced item. Unless the context clearly indicates otherwise, the term "or" means "and / or". References to "aspects" throughout the specification mean that a particular element (e.g., a feature, structure, step, or characteristic) described in conjunction with that aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it should be understood that the described elements may be combined in any suitable manner in the various aspects.

[0107] When an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

[0108] Unless otherwise indicated herein, all test standards are the most current standards in effect as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0109] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0110] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A control system coupled to an electric motor, the control system comprising: processor; as well as a memory coupled to the processor and storing instructions that, when executed by the processor, cause the control system to: receiving a voltage and a current from a primary winding of the electric motor; receiving current from a secondary winding of the electric motor; receiving a rotor electrical position from a rotor of the electric motor; determining a d-axis command voltage of the secondary winding and a q-axis command voltage of the secondary winding based on the primary winding voltage, the primary winding current, the secondary winding current, and the rotor electrical position; generating a gate control signal based on the determined d-axis command voltage and q-axis command voltage of the secondary winding; as well as The gate control signal is transmitted to an inverter coupled to the secondary winding to control electric power transmission between the primary winding and the secondary winding. 2 . The control system of claim 1 , wherein the voltage from the primary winding is a three-phase voltage, the current from the primary winding is a three-phase current, and the current from the secondary winding is a three-phase current.

3. The control system according to claim 1, wherein: The electric motor comprises a segmented winding electric machine.

4. The control system according to claim 3, wherein: The segmented winding motor is a permanent magnet synchronous motor, a synchronous reluctance motor or a wound field synchronous motor.

5. The control system of claim 3, wherein the segmented winding motor includes the secondary winding coupled to a rechargeable energy storage system and the primary winding coupled to an external power source.

6. The control system according to claim 1, wherein: The d-axis command voltage is associated with the d-axis in the direction of the north pole of the magnet or the north pole of the magnetic field generated by the rotor field winding.

7. The control system according to claim 6, wherein: The d-axis command voltage is associated with reactive power delivery of the electric motor.

8. The control system of claim 1, wherein the q-axis command voltage is associated with a q-axis that is perpendicular to the d-axis, wherein the q-axis is 90 degrees ahead of a north pole associated with the d-axis.

9. The control system according to claim 8, wherein: The q-axis command voltage is associated with real power transfer in the electric motor.

10. The control system according to claim 1, wherein: Determining the d-axis command voltage of the secondary winding and the q-axis command voltage of the secondary winding is also based on d-axis leakage inductance and q-axis leakage inductance measured from the electric motor.

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