A method for improving the harmonic distribution of output current in a segmented drive system

Abstract

A segmented electric drive system includes a DC power bus including DC voltage sources and capacitors connected in parallel, an inverter including a plurality of inverter segments, a motor including a plurality of stator winding segments, each connected to an inverter segment, and a controller. The controller receives a control signal and sends a switching signal to each inverter segment, where the switching signal is based on a discontinuous space vector pulse width modulation (DSVPWM) scheme for the segmented inverter. The DSVPWM scheme includes a set of inverse sawtooth carrier signals at optimal phase shift angles relative to each other.

Description

Background Technology

[0001] This invention relates to a method for operating a segmented electric drive system.

[0002] The goal of an electric vehicle motor drive system is to generate a smooth rotating magnetic field with a specified magnitude and direction (vector) to control the rotation of the wheels. To generate this magnetic field vector ("net vector") in a brushless motor, the drive system needs to add together multiple base vectors generated by the stator coils. Although the stator coils are located in fixed positions around the stator, the drive system can still generate the net vector by changing the magnitude and polarity of the base vectors.

[0003] The drive system can control the amplitude and polarity of the base vector using multiple variable voltage AC signals, but the power supply for the motor drive system is a DC battery with a fixed voltage level. The inverter's role in the motor drive system is to convert the fixed voltage DC power supply into multiple variable AC signals required to control the motor. The inverter cannot directly change the voltage from the fixed voltage DC power supply, but it can simulate the variable voltage AC signals by using "pulse width modulation"—connecting and disconnecting the fixed voltage DC power supply in a specific pattern to simulate the rise and fall of the variable voltage AC signals.

[0004] The controller of the motor drive system is responsible for determining the switching sequence required to generate the desired variable voltage AC signal. First, the controller must determine the amplitude and polarity of each desired basis vector. Then, for each basis vector to be generated, the controller calculates the AC signal required to produce those amplitudes—this calculated signal is called the "reference signal." Once the controller has the reference signal, it compares it to the "carrier signal"—a fundamental high-frequency signal used to create a modulated signal approximating the reference signal by altering one or more characteristics of the carrier signal to match it. In this case, to create the modulated signal (as used here, a signal modulated by pulse width modulation), the controller overlays the reference signal onto the carrier signal. Based on where the reference signal intersects the carrier signal and whether the carrier signal value exceeds the reference signal value at a given time, the controller sets the modulated signal value to digital low or digital high.

[0005] The modulation signal is a signal sent by the controller to the inverter switches to generate a switching cycle—a high digital modulation signal value opens the switch, and a low digital modulation signal value closes the switch (and vice versa). For example, in a three-legged inverter, three sets of switches open and close rapidly, generating three pulse-width modulated signals that serve as the AC signal for the motor. From these AC signals, the stator generates the base vectors needed to create the net vector and directional magnetic field.

[0006] Switching processes generate "upstream" ripple current—even though the DC voltage source is intended to be at a constant voltage, load changes cause ripple current at the source. This ripple current is highly undesirable—it wastes power, heats components, degrades battery performance, and impairs overall performance. Ripple current can be reduced and / or eliminated by adding a capacitor connected in parallel with the DC voltage source, but the inefficiency in inverter systems necessitates increasingly larger capacitors, depending on the severity of the inefficiency.

[0007] To reduce inefficiencies that cause DC bus ripple current, U.S. Patent Application No. 8,373,372 (“Su”) discloses a segmented inverter that primarily uses two inverters whose associated stator coils are connected in parallel. By introducing a phase shift (specifically, a phase shift between carrier signals) between the signals segmented by the two inverters, the segmented drive system disclosed in Su reduces ripple current, thereby reducing the capacitance required to maintain DC bus stability.

[0008] Ripple current is not the only consideration for inverter efficiency. The process of switching the inverter switches on and off introduces power losses, referred to in this context as "switching losses." Inverter switching losses can be reduced by decreasing the amount of switching performed. The most effective way to reduce switching losses is to use a "discontinuous" switching scheme, where only some switch groups are pulse-modulated at any given time. However, this approach leads to a significant increase in ripple current, negating the benefits of the segmented drive system disclosed in Su. Furthermore, discontinuous switching schemes increase total harmonic distortion, which risks compromising the system.

[0009] The goal is to find a method for operating segmented drive systems that reduces switching losses, decreases capacitor ripple current, and improves the total harmonic distribution of the output current. Summary of the Invention

[0010] This invention discloses a segmented electric drive system. In one embodiment, the drive system includes a DC power bus, an inverter connected to the DC power bus, a motor connected to the inverter, and a controller for operating the inverter. In one embodiment, the DC power bus includes a DC voltage source and a capacitor connected in parallel with the DC voltage source. In one embodiment, the inverter includes a plurality of inverter segments, wherein each inverter segment includes a plurality of inverter switch pairs, each inverter switch pair being connected in parallel with the DC power bus. In one embodiment, the motor includes a plurality of stator winding segments. In one embodiment, each of the plurality of stator winding segments is assigned to each inverter segment. In one embodiment, each stator winding segment includes at least one stator winding for each of the plurality of inverter switch pairs of the associated inverter segment. In one embodiment, the controller receives a control signal and sends a switching signal to each inverter segment. In one embodiment, the control signal corresponds to a desired stator magnetic field vector. In one embodiment, the switching signal sent to each inverter segment corresponds to Space Vector Pulse Width Modulation (SVPWM), which is used to generate a desired stator magnetic field vector by combining multiple base vectors generated by multiple stator winding segments. In one embodiment, each base vector is generated by the activity of an inverter switch pair to generate a pulse width modulated signal through at least one of its corresponding stator windings according to the SVPWM operating schedule. In one embodiment, during a given period of the SVPWM operating schedule, at least one stator winding of the multiple stator winding segments is not driven by the activity of any inverter switch pair from its corresponding inverter switch pair. In one embodiment, the switching signal that generates the pulse width modulated signal for each inverter switch pair is determined by comparing a carrier signal with a reference signal, wherein the carrier signal sent to each inverter segment is phase-shifted by a phase shift angle value relative to the carrier signal sent to at least one other inverter segment, wherein the phase shift angle value is an optimal value determined to produce the best results in terms of capacitor ripple current and input ripple current.

[0011] In another disclosed embodiment, the carrier signal associated with each of the plurality of inverter switch pairs is a sawtooth carrier signal. In another disclosed embodiment, the carrier signal associated with each of the plurality of inverter switch pairs is a reverse sawtooth carrier signal.

[0012] In another disclosed embodiment, the carrier signal and reference signal associated with an inverter segment are at an optimal phase shift angle relative to the carrier signal and pulse width modulation signal associated with each of the plurality of inverter segments. In another disclosed embodiment, the optimal phase shift angle is determined using a mathematical model of the inverter. In another disclosed embodiment, the optimal phase shift angle is a fixed value during operation of the drive system. In another disclosed embodiment, achieving the optimal phase shift angle reduces capacitor ripple current.

[0013] The present invention also discloses a vehicle including a segmented electric drive system, the drive system comprising: a DC power bus including a DC voltage source and a capacitor connected in parallel with the DC voltage source; an inverter including a plurality of inverter segments, wherein each inverter segment includes a plurality of inverter switch pairs, and each inverter switch pair is connected in parallel with the DC power bus; An electric motor connected to the inverter, wherein the electric motor includes a plurality of stator winding segments, wherein each of the plurality of stator winding segments is assigned to a respective inverter segment, and wherein each stator winding segment includes at least one stator winding of each of the plurality of inverter switch pairs for the associated inverter segment; and a controller, wherein the controller receives a control signal and sends a switching signal to each inverter segment, wherein the control signal corresponds to a desired stator magnetic field vector, wherein the switching signal sent to each inverter segment corresponds to space vector pulse width modulation (SVPWM), the SVPWM being used to generate the desired stator magnetic field vector by combining a plurality of base vectors generated by the plurality of stator winding segments, wherein each base vector is generated by the activity of the inverter switch pairs generating pulse width modulation signals through their corresponding at least one stator winding according to an SVPWM operating schedule, and wherein during a given period of the SVPWM operating schedule, at least one stator winding of the plurality of stator winding segments is not driven by any inverter switch pair activity from its corresponding inverter switch pair; The switching signal for generating the pulse width modulation signal for each inverter switch pair is determined by comparing the carrier signal with a reference signal, wherein the carrier signal sent to each inverter segment is phase-shifted by a phase shift angle value relative to the carrier signal sent to at least one other inverter segment, wherein the phase shift angle value is an optimal value determined to produce the best results in terms of capacitor ripple current and input ripple current.

[0014] Other aspects, features, and techniques will be apparent to those skilled in the art from the following detailed description of the embodiments. Attached Figure Description

[0015] The features, objects, and advantages of the disclosed embodiments will become more apparent from the following detailed description when considered in conjunction with the accompanying drawings, in which the same reference numerals are consistently used to identify correspondingly, and wherein: Figure 1 It is a perspective view depicting an exemplary embodiment of an electric vehicle in which a segmented drive system may be installed.

[0016] Figure 2 This is a block diagram depicting an exemplary embodiment of a segmented drive system.

[0017] Figure 3 This is a circuit diagram depicting an exemplary embodiment of a segmented drive system.

[0018] Figure 4A This is a side view depicting an exemplary embodiment of an electric motor for an electric vehicle. Figure 4B It is a description used for Figure 3 A side view of an exemplary magnetic field coordinate system for motor A.

[0019] Figure 5 It is a graph depicting an exemplary embodiment of multiple carrier signals and corresponding multiple modulation signals for a segmented drive system.

[0020] Figure 6A It is a graph depicting an exemplary embodiment of a drive system using space vector pulse width modulation. Figure 6B It is a graph depicting an exemplary embodiment of a drive system using discontinuous space vector pulse width modulation.

[0021] Figure 7A This is a graph comparing the capacitor ripple current values ​​between an exemplary embodiment of a drive system using SVPWM and an exemplary embodiment of a drive system using DSVPWM. Figure 7B This is a graph comparing the input ripple current values ​​between an exemplary embodiment of a drive system using SVPWM and an exemplary embodiment of a drive system using DSVPWM.

[0022] Figure 8A This is a graph comparing capacitor ripple current values ​​between exemplary embodiments of segmented drive systems using DSVPWM with different phase shift values. Figure 8B It is a graph depicting a comparison of input ripple current values ​​between exemplary embodiments of a segmented drive system using DSVPWM with different phase shift values.

[0023] Figure 9AIt is a graph depicting a comparison of capacitor ripple current values ​​between an exemplary embodiment of a drive system using standard SVPWM and an exemplary embodiment of a drive system using a specific DSVPWM. Figure 9B It is a graph depicting a comparison of the input ripple current values ​​between an exemplary embodiment of a drive system using standard SVPWM and an exemplary embodiment of a drive system using a specific DSVPWM.

[0024] Figure 10A is a graph showing the total phase current waveform and spectrum of an exemplary prior art embodiment. Figure 10B is a graph showing the amplitude of harmonic frequencies of an exemplary prior art embodiment.

[0025] Figure 11A This is a graph showing the total phase current waveform and spectrum of an exemplary embodiment of a segmented drive system using a specific DSVPWM. Figure 11B This is a graph of the amplitude of the harmonic frequency in an exemplary embodiment of a segmented drive system using a specific DSVPWM. Detailed Implementation

[0026] One aspect of this disclosure relates to a method for operating a segmented motor drive system, wherein the method uses optimal phase shift control with specific discontinuous space vector pulse width modulation (SDSVPWM) to improve the output current harmonic characteristics of the system while maintaining a low DC bus current ripple value.

[0027] Throughout this document, references to "an embodiment," "some embodiments," "embodiment," or similar terms mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment. Therefore, these phrases appearing in different places throughout this specification do not necessarily refer to the same embodiment. Furthermore, particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments without limitation. For example, two or more innovative methods or systems described herein can be combined in a single method or system, but this application is not limited to the specific exemplary combinations of the methods or segmented motor drive systems described herein.

[0028] As used herein, the term “a” or “an” shall mean one or more. The term “multiple” refers to two or more. The term “another” is defined as a second or more. The terms “comprising” and / or “having” are open-ended (e.g., including). As used herein, the term “or” shall be interpreted as inclusive or meaning any one or any combination thereof. Thus, “A, B, or C” means “any one of the following: A; B; C; A and B; A and C; B and C; A, B, and C.” Exceptions to this definition will only occur if the combination of elements, functions, steps, or actions is inherently mutually exclusive in some way.

[0029] The character "N" in this text refers to the last member of the set or the total number of members in the set. The character "X" in this text refers to a variable member of the set. The characters "A", "B", "C", etc., represent specific but undefined members of the set.

[0030] As used herein, the term “input ripple current” refers to the ripple current that can be measured at the voltage source of the DC power bus, while the term “capacitor ripple current” refers to the ripple current that can be measured at the capacitor of the DC power bus.

[0031] Detailed descriptions of various embodiments are provided; however, it should be understood that the disclosed embodiments are merely exemplary and may be implemented in various and alternative forms. The drawings are not necessarily drawn to scale; certain features may be exaggerated or minimized to show detail of particular components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but only as a representative basis for teaching those skilled in the art to employ the disclosed embodiments in various ways.

[0032] Figure 1 This is a perspective view depicting an exemplary embodiment of an electric vehicle 100 in which a segmented drive system 200 may be installed. The electric vehicle 100 depicted herein is exemplary. The segmented drive system 200 can be installed in any vehicle for use with an electric motor drive system.

[0033] Figure 2 This is a block diagram depicting an exemplary embodiment of a segmented drive system 200. In one embodiment, the segmented drive system 200 may include a controller 210, a DC power bus 215, a segmented inverter 220, a motor 230, and a plurality of wheels 240. The operation method may be incorporated as part of the controller 210, which in one embodiment is designed to control the segmented inverter 220 at its commanded values ​​with good dynamic and steady-state response. In one embodiment, the segmented inverter 220 supplies power to the motor 230, and the motor 230 in turn applies torque to the plurality of wheels 240. In one embodiment, the segmented inverter 220 may receive power from the DC power bus 215 and convert the received DC power into at least one AC signal.

[0034] In one embodiment, controller 210 receives a control signal corresponding to a desired stator magnetic field vector. This control signal may include a torque command related to a desired value of the rotational force to be applied to at least one of the plurality of wheels 240. In one embodiment, controller 210 receives data relating to the operating conditions of the segmented drive system 200 and other components of the electric vehicle 100. In one embodiment, controller 210 generates inverter signals to be sent to each inverter segment 225. A space vector pulse width modulation (SVPWM) process can be used to calculate the switching signal to generate the desired stator magnetic field vector by combining multiple base vectors.

[0035] Figure 3 This is a circuit diagram depicting an exemplary embodiment of the segmented drive system 200.

[0036] In one embodiment, the DC power bus 215 may include providing a voltage value. V dc DC voltage source 216 and provides capacitor value C d Capacitor 217. Capacitor 217 can be used to eliminate voltage level irregularities caused by factors such as ripple current, so that the DC power bus 215 provides a stable voltage level to the segmented inverter 220. In one embodiment, the segmented drive system 200 experiencing high ripple current values ​​may need to use a capacitor with a higher capacitance value. C d The use of capacitor 217 increases the cost of the system.

[0037] In one embodiment, the segmented inverter 220 includes a plurality of inverter segments 225. 1-N In one embodiment, each inverter is segmented into 225 sections. X Includes multiple inverter switch pairs 226 UX 226 VX and 226 WX Each inverter switch pair 226 is connected in parallel with the DC power bus 215. Figure 2 The segmented inverter described in the image consists of two inverter segments, 225. 1-2 However, according to the requirements of the segmented drive system 200, the segmented inverter 220 may include three or more inverter segments 225.

[0038] In one embodiment, the motor 230 includes a plurality of stator winding segments 235. X In one embodiment, each inverter is segmented into 225 sections. X It is assigned and segmented with the stator winding 235 X Associated. In one embodiment, each stator winding is segmented 235.X Includes multiple stator windings 232 UX 232 VX and 232 WX In one embodiment, each stator winding is segmented 235. X Including 225 sections for the relevant inverter X Multiple inverter switches for 226 UX 226 VX and 226 WX At least one stator winding 232 of each inverter switch pair 226.

[0039] In one embodiment, the basis vector described in paragraph

[0034] can be segmented 235 by multiple stator windings. 1-N Each base vector is generated by stator winding 232. In one embodiment, each base vector generated by stator winding 232 is generated by the activity of associated inverter switch pair 226 to generate a pulse width modulation signal according to an SVPWM operating schedule. In one embodiment, multiple stator windings are segmented 235 during a given period of the SVPWM operating schedule. 1-N At least one stator winding 232 is not driven by the activity of any inverter switch pair 226 from its corresponding inverter switch pair 226. The SVPWM scheme in which at least one stator winding is not driven by the activity of any inverter switch pair during a given cycle can be described as discontinuous space vector pulse width modulation (DSVPWM).

[0040] Figure 4A This is a side view depicting an exemplary embodiment of an electric motor 230 for an electric vehicle 100. In one embodiment, the electric motor 230 includes a rotor 231 and a stator having a plurality of stator windings 232. In one embodiment, the rotor 231 may include permanent magnets. In one embodiment, the stator windings 232 may receive power from a segmented inverter 220 to generate a magnetic field via space vector pulse width modulation. In one embodiment, the motor drive system 200 rotates the magnetic field of the stator to cause rotation of the rotor 231 and propel the electric vehicle 100. In one embodiment, some stator windings 232 may be juxtaposed with some other stator windings 232, allowing for implementations such as... Figure 2 and Figure 3 The segmented drive system 200 is depicted in the figure.

[0041] Figure 4B It is a description used for Figure 4A A side view of an exemplary magnetic field coordinate system for an electric motor 230. In one embodiment, the electric motor 230 has a rotation angle value Ɵ. The rotation angle Ɵ can represent the advance angle of the motor, where the advance angle is the angle between the stator rotating magnetic field and the rotor rotating magnetic field.

[0042] Figure 5 It describes multiple carrier signals 310 used in the segmented drive system 200. 1-N and the corresponding multiple modulation signals 330 I-N A graph illustrating an exemplary embodiment. In one embodiment, a switching signal for generating a pulse-width modulated signal for each inverter switch pair 226 is determined by comparing a carrier signal 310 with a reference signal 320. The reference signal may be an AC sinusoidal signal for a set of co-located stator windings 332 to generate a base vector. Multiple modulation signals 330 I-N Each modulation signal 330 in the above can be a pulse width modulation signal, which is configured to replicate an analog AC signal using a digital binary signal.

[0043] In one embodiment, multiple modulation signals 330 I-N Each of these corresponds to multiple inverter segments 225 1-N One inverter segment 225 is provided, such that each inverter segment 225 receives a modulation signal 330. In one embodiment, the modulation signal 330 is used to generate the modulation signal 330. 1-N carrier signal 310 1-N They are phase-shifted relative to each other; in one embodiment, the phase shift is a phase shift angle with a value α.

[0044] It should be noted that, although embodiments of the systems disclosed herein use, for example... Figure 5 The reverse sawtooth carrier signal of the carrier signal described in the figure is optimally executed, but a segmented drive system can be implemented using a sawtooth carrier signal or a triangular carrier signal.

[0045] Figure 6A This is a graph depicting an exemplary embodiment of a drive system using SVPWM with multiple modulation signals. In one embodiment, a three-phase motor can use three sets of stator windings and three modulation signals. S a , S b and S c The three basis vectors generated by each modulation signal can be added together to produce the desired stator magnetic field vector.

[0046] Figure 6B This is a graph depicting an exemplary embodiment of multiple modulation signals used in a drive system employing DSVPWM. In one embodiment, the modulation signals can be... Figure 6AThe three basis vectors are reduced to two. In this embodiment, the third basis vector effectively has zero amplitude, and the corresponding stator winding set is not operated with any inverter switching activity. In this case, the stator winding set (here) is used for... S a The modulation signal is kept constant and no switching is required. This can reduce switching losses caused by the segmented inverter 220 by up to 33%, but it also introduces additional undesirable effects into the system, such as increased capacitor ripple current, increased input ripple current, and increased total harmonic distortion.

[0047] Figure 7A This is a graph comparing the capacitor ripple current values ​​between an exemplary embodiment of a drive system using SVPWM and an exemplary embodiment of a drive system using DSVPWM. Figure 7B This is a graph comparing the input ripple current values ​​between an exemplary embodiment of a drive system using SVPWM and an exemplary embodiment of a drive system using DSVPWM. Figure 7A and 7B As shown, compared with the drive system using the SVPWM switching scheme, regardless of the modulation index, the drive system using the DSVPWM switching scheme will produce a higher capacitor ripple current value (about 20% higher) and a significantly higher input ripple current value (more than 100% higher).

[0048] Figure 8A This is a graph comparing capacitor ripple current values ​​between exemplary embodiments of segmented drive systems using DSVPWM with different phase shift values. Figure 8B This is a graph comparing the input ripple current values ​​between exemplary embodiments of a segmented drive system using DSVPWM with different phase shift values. In one embodiment, the increase in capacitor ripple current and the increase in input ripple current can be reduced by introducing a phase shift between the signals of each of the plurality of inverter segments 225. In one embodiment, the phase shift angle value α can be adjusted for optimization. Figure 8A and 8B The effect of an adjusted phase shift angle value α according to one embodiment is described. In one embodiment, even using an improved phase shift angle value results in a measurable reduction in both capacitor ripple current and input ripple current, while using an optimal phase shift angle value α produces the best ripple current result.

[0049] In one embodiment, the optimal value of the phase shift angle is determined using an analog inverter. In one embodiment, a mathematical model of the segmented inverter 220 is used to iterate the value of the phase shift angle α. The segmented drive system 200 can then use the phase shift angle value that produces the best simulation results in terms of capacitor ripple current and input ripple current. In one embodiment, the optimal phase shift angle value may depend on multiple inverter segments 225. 1-N The number of inverter segments 225 in the system.

[0050] Figure 9A It is a graph depicting a comparison of capacitor ripple current values ​​between an exemplary embodiment of a drive system using standard SVPWM and an exemplary embodiment of a drive system using a specific DSVPWM, wherein the specific DSVPWM is a DSVPWM switching scheme implemented on a segmented drive system, wherein there is an optimal phase shift angle value between the carrier signal and the modulation signal in the inverter segment. Figure 9B This is a graph comparing the input ripple current values ​​between an exemplary embodiment of a drive system using standard SVPWM and an exemplary embodiment of a drive system using a specific DSVPWM. Figure 9A and 9B As shown, using the optimal phase shift angle value for a specific DSVPWM results in the capacitor ripple current value and the input ripple current value remaining almost unchanged under all modulation index values, thus allowing the use of discontinuous switching schemes to reduce switching losses without incurring ripple current loss.

[0051] Figure 10A is a graph of the total phase current waveform and spectrum of an exemplary prior art embodiment, such as a drive system using standard SVPWM. Figure 10B is a graph of the amplitude of harmonic frequencies in an exemplary prior art embodiment. As shown in Figures 10A and 10B, the exemplary prior art drive system uses a switching frequency of 7.5 kHz. At this frequency, the exemplary prior art drive system experiences a 7.5 kHz primary harmonic with an amplitude of approximately 1.1% of the fundamental frequency amplitude. In this embodiment, the primary harmonic at 15 kHz is eliminated by phase shift, but some primary harmonics remain at 30 kHz with an amplitude of approximately 0.4% of the fundamental frequency amplitude.

[0052] Figure 11A This is a graph showing the total phase current waveform and spectrum of an exemplary embodiment of a segmented drive system using a specific DSVPWM. Figure 11B This is a graph showing the harmonic frequency amplitude of an exemplary embodiment of a segmented drive system using a specific DSVPWM. (Example:) Figure 11A and 11BAs illustrated, the primary harmonics of the exemplary segmented drive system are pushed down from 7.5 kHz to 15 kHz in the systems of Figures 10A and 10B, and the amplitude is reduced to approximately 0.8% of the fundamental frequency amplitude. This embodiment can also reduce the amplitudes of the primary harmonics at 22.5 kHz, 30 kHz, 37.5 kHz, and 45 kHz to less than 0.2% of the fundamental frequency amplitude. These results can be achieved by using the optimal phase shift angle that leads to harmonic cancellation.

[0053] Although this disclosure references exemplary embodiments, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the claimed embodiments.

Claims

1. A segmented electric drive system, comprising: A DC power supply bus, comprising a DC voltage source and a capacitor connected in parallel with the DC voltage source; An inverter comprising multiple inverter segments, wherein each inverter segment comprises multiple inverter switch pairs, and each inverter switch pair is connected in parallel with the DC power bus. A motor connected to the inverter, wherein the motor includes a plurality of stator winding segments, wherein each of the plurality of stator winding segments is assigned to a respective inverter segment, and wherein each stator winding segment includes at least one stator winding for each of the plurality of inverter switch pairs for the associated inverter segment; and A controller, wherein the controller receives a control signal and sends a switching signal to each inverter segment, wherein the control signal corresponds to a desired stator magnetic field vector, wherein the switching signal sent to each inverter segment corresponds to Space Vector Pulse Width Modulation (SVPWM), the SVPWM being used to generate the desired stator magnetic field vector by combining multiple base vectors generated by the plurality of stator winding segments, wherein each base vector is generated by the activity of an inverter switch pair generating a pulse width modulation signal through at least one of its corresponding stator windings according to an SVPWM operating schedule, and wherein during a given period of the SVPWM operating schedule, at least one stator winding of the plurality of stator winding segments is not driven by any inverter switch pair activity from its corresponding inverter switch pair; The switching signal for generating the pulse width modulation signal for each inverter switch pair is determined by comparing the carrier signal with a reference signal, wherein the carrier signal sent to each inverter segment is phase-shifted by a phase shift angle value relative to the carrier signal sent to at least one other inverter segment, wherein the phase shift angle value is an optimal value determined to produce the best results in terms of capacitor ripple current and input ripple current.

2. The drive system according to claim 1, wherein, The carrier signal associated with each of the plurality of inverter switch pairs is a sawtooth carrier signal.

3. The drive system according to claim 1, wherein, The carrier signal associated with each of the plurality of inverter switch pairs is a reverse sawtooth carrier signal.

4. The drive system according to claim 1, wherein, The optimal value of the phase shift angle is determined by using a mathematical model of the inverter.

5. The drive system according to claim 1, wherein, The optimal value of the phase shift angle is a fixed value during the operation of the drive system.

6. A vehicle including a segmented electric drive system, the drive system comprising: A DC power supply bus, comprising a DC voltage source and a capacitor connected in parallel with the DC voltage source; An inverter comprising multiple inverter segments, wherein each inverter segment comprises multiple inverter switch pairs, and each inverter switch pair is connected in parallel with the DC power bus. A motor connected to the inverter, wherein the motor includes a plurality of stator winding segments, wherein each of the plurality of stator winding segments is assigned to a respective inverter segment, and wherein each stator winding segment includes at least one stator winding for each of the plurality of inverter switch pairs for the associated inverter segment; and A controller, wherein the controller receives a control signal and sends a switching signal to each inverter segment, wherein the control signal corresponds to a desired stator magnetic field vector, wherein the switching signal sent to each inverter segment corresponds to Space Vector Pulse Width Modulation (SVPWM), the SVPWM being used to generate the desired stator magnetic field vector by combining multiple base vectors generated by the plurality of stator winding segments, wherein each base vector is generated by the activity of an inverter switch pair generating a pulse width modulation signal through at least one of its corresponding stator windings according to an SVPWM operating schedule, and wherein during a given period of the SVPWM operating schedule, at least one stator winding of the plurality of stator winding segments is not driven by any inverter switch pair activity from its corresponding inverter switch pair; The switching signal for generating the pulse width modulation signal for each inverter switch pair is determined by comparing the carrier signal with a reference signal, wherein the carrier signal sent to each inverter segment is phase-shifted by a phase shift angle value relative to the carrier signal sent to at least one other inverter segment, wherein the phase shift angle value is an optimal value determined to produce the best results in terms of capacitor ripple current and input ripple current.

7. The vehicle according to claim 6, wherein, The carrier signal associated with each of the plurality of inverter switch pairs is a sawtooth carrier signal.

8. The vehicle according to claim 6, wherein, The carrier signal associated with each of the plurality of inverter switch pairs is a reverse sawtooth carrier signal.

9. The vehicle according to claim 6, wherein, The optimal value of the phase shift angle is determined by using a mathematical model of the inverter.

10. The vehicle according to claim 6, wherein, The optimal value of the phase shift angle is a fixed value during the operation of the drive system.

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