Boost rotor supply circuit and method for improving efficiency of pulsed electric machines - Patents.com

Abstract

A boost circuit and method are disclosed for providing a boosted voltage to the rotor of an electric machine. As the electric machine is pulsed on, the boosted voltage helps the rotor quickly overcome the starting inductance, rapidly turning the rotor on. This results in a significantly faster transition time when the electric machine transitions from an off state to an on state at the beginning of the pulse. Reducing the transition time significantly improves the overall efficiency of the electric machine.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 399,983, filed August 22, 2022, which is incorporated herein by reference for all purposes.

[0002] This application relates generally to pulsing control of an electric machine in which the electric machine is selectively controlled to operate between an off state and an on state during a pulse, and more particularly to a boost circuit and method for supplying a boost voltage to a rotor of the electric machine as the electric machine is pulsed on, where the boost voltage helps the rotor quickly overcome its starting inductance, rapidly turning the rotor on and resulting in a significantly faster transition time when the electric machine transitions from an off state to an on state at the beginning of the pulse. [Background technology]

[0003] Most electric machines typically include a stator with multiple poles and a rotor, and operate as either a generator or a motor. When operating as a motor, electrical energy is converted into mechanical energy. When operating as a generator, mechanical energy is converted into electrical energy. Therefore, the terms "electric machine" or "machine" as used herein are intended to be broadly interpreted to refer to both electric motors and generators.

[0004] Electric machines have relatively high energy conversion efficiencies when operating at or near their optimum operating load. However, when operating below the optimum operating load, the energy conversion efficiency can be significantly lower. In many applications, electric machines must operate below the optimum operating load, thereby reducing the overall efficiency of the machine and wasting the energy required to operate the electric machine.

[0005] Pulse control of electric machines is a known approach to improving the efficiency of electric machines. Under selected operating conditions, the electric machine transitions intermittently from an off-state to an on-state during pulses. By operating the electric machine at a high efficiency level to produce power only during the on-pulses, the overall efficiency of the machine is improved while still producing the required power, compared to conventional continuous operation at less than the machine's optimum operating load. Summary of the Invention

[0006] The problem with pulsed control is that it takes a relatively large amount of energy and time to transition an electric machine from an off state to an on state with each pulse.

[0007] Therefore, a need exists to quickly and efficiently transition electric machines from an off state to an on state with each pulse, thereby allowing such electric machines to operate at even higher efficiency levels.

[0008] This application relates to a boost circuit and method for supplying a boosted voltage to the rotor of an electric machine, where the boosted voltage helps the rotor quickly overcome its starting inductance as the electric machine is pulsed on, rapidly turning the rotor on, resulting in a significantly faster transition time each time the electric machine transitions from an off state to an on state at the beginning of a pulse. [Brief explanation of the drawings]

[0009] The invention and its advantages are best understood by referring to the following description taken in conjunction with the accompanying drawings.

[0010] [Figure 1] FIG. 1 is a graph illustrating the pulsing operation of a motor in accordance with a non-limiting embodiment of the present invention.

[0011] [Figure 2] FIG. 2 is a functional block diagram illustrating the architecture of a motor controller in accordance with a non-limiting embodiment of the present invention.

[0012] [Figure 3] FIG. 3 is an operational flow diagram illustrating steps implemented by a motor controller in accordance with a non-limiting embodiment of the present invention.

[0013] [Figure 4A] FIG. 4A is a torque versus efficiency map of a motor operating at a fixed speed during the transition from zero to peak efficiency torque.

[0014] [Figure 4B] FIG. 4B is torque versus lost work for an exemplary motor operating at a fixed speed during the transition from zero to peak efficiency torque.

[0015] [Figure 5A] FIG. 5A is an exemplary boost circuit for boosting a power supply voltage applied to a rotor of an electric machine in accordance with a non-limiting embodiment of the present invention.

[0016] [Figure 5B] FIG. 5B is an exemplary voltage rectifier used by a voltage boost circuit according to a non-limiting embodiment of the present invention.

[0017] [Figure 6] FIG. 6 is a flow diagram illustrating a procedure for boosting the supply voltage applied to the rotor of an electric machine during pulsed operation in accordance with a non-limiting embodiment of the present invention.

[0018] In the drawings, like reference numerals may be used to designate like structural elements, and it should be understood that the depictions in the figures are schematic and not to scale. DETAILED DESCRIPTION OF THE INVENTION

[0019] Electric motors and generators are used in a wide variety of applications and under a wide variety of operating conditions. In general, many modern electric machines have relatively high energy conversion efficiencies. However, the energy conversion efficiency of most electric machines varies significantly with operating load. In general, electric machines have high efficiency when operating at or near their peak operating load. However, when operating at lower loads, efficiency tends to be significantly lower.

[0020] This application relates generally to pulsed control of electric machines (e.g., electric motors and generators) to improve energy conversion efficiency when operating conditions permit. More specifically, under lower load operating conditions, the electric machine is pulsed, transitioning intermittently between off and on states during pulses. By controlling the magnitude, duty cycle, and frequency of the pulses, the electric machine can be controlled to operate exclusively at its higher efficiency level compared to traditional continuous motor control, thereby providing a desired average torque output in a more energy-efficient manner than previously possible.

[0021] Applicant has filed and been granted several U.S. patents covering pulsed motor control of electric machines, including U.S. Patent 10,742,155 (TULA P200B), U.S. Patent 11,228,272 (TULA P200C), and U.S. Patent 10,944,352 (TULA P201), each of which is incorporated herein by reference for all purposes.

[0022] Pulsed Machine Control Referring to Figure 1, a graph 10 illustrating the basic operation of pulsed machine control is shown. In this example, several assumptions are made: The electric machine operates as an electric motor. As plotted on the vertical axis, the motor's maximum torque output is 50 Nm. The motor's peak efficiency range is approximately 95% of its peak power output, or a torque output of approximately 47.5 Nm. In this example, the motor is being called upon to produce an output torque of 10 Nm, which is well below its peak efficiency range.

[0023] In conventional operation, the motor runs continuously to produce the required torque output of 10 Nm, which is represented in Figure 1 by dashed line 12. The drawback of running continuously at a torque output of 10 is that the motor operates well below its peak efficiency range (e.g., above 47.5 Nm in this example).

[0024] In pulsed operation, the motor is pulsed on and off. Between on-pulses, the motor is in an off state and produces little or no torque output. During the on-pulses, the motor: (1) It is in the on state and is operating at or near peak efficiency (i.e., 50). (2) The average torque output of the motor over time while it is intermittently pulsing between off and on states is sufficient to meet the perceived torque demand.

[0025] In this example, the on-pulse frequency occurs once every five time units, as plotted on the horizontal axis. As a result, the motor is pulsed on twenty percent (20%) of the time, as represented by pulse 14. By operating the motor at its peak power (e.g., 50) every five time units (i.e., 20 percent of the time), the requested 10 Nm of torque is produced over time. However, because the motor is only operating at or near peak efficiency during the pulses, the overall operating efficiency of the motor is significantly improved over traditional continuous operation.

[0026] Three-phase winding field synchronous machine In a three-phase wound field synchronous machine, the stator may include a three-coil winding that is excited by a three-phase AC input and a field winding on the rotor that is powered by a DC input. When the three-phase AC input is passed through the three-phase armature windings, a rotating magnetic field (RMF) is generated. The rotational speed of the RMF is equal to the synchronous speed (N s The interaction between the field winding magnetic field and the armature winding magnetic field generates an electromagnetic force (EMF), which causes the rotor to rotate.

[0027] Power Converter 2, a diagram of a power controller 20 for pulsed operation of an electric machine is shown. Power controller 20 includes a power converter 22, a DC power source 24, and an electric machine 26. In this non-limiting embodiment, power converter 22 also includes a pulse controller 28.

[0028] The power converter 22 can be operated as a power inverter or a power rectifier depending on the direction of energy flow in the system.

[0029] When operating the electric machine 26 as a motor, the power converter 22 serves to generate three-phase AC power from the DC power source 24 to drive the electric machine 26. The three-phase input power, designated as phases A, B, and C, is applied to the stator windings of the electric machine 26 to generate RMF as described above.

[0030] During motor operation, pulse controller 28 is responsible for selectively pulsing the three phases of input power supplied to electric machine 26. In conventional (i.e., continuous) operation, the three phases A, B, and C of the input power are continuous (i.e., not pulsed). During pulsed operation, the three phases A, B, and C are selectively pulsed.

[0031] When the electric machine is operating as a generator, the power converter 22 operates as a power rectifier, and the AC power coming from the electric machine 26 is converted to DC power and stored in the DC power source 24 .

[0032] The lines representing phases A, B, and C have arrows at both ends to indicate that current can flow from the power converter 32 to the electric machine 36 when the machine is being used as a motor, and in the opposite direction when the machine is being used as a generator.

[0033] Pulsed Motor Control Referring to FIG. 3, a flow diagram 30 is shown illustrating the steps implemented by pulse controller 28 to provide pulsed controlled operation of electric machine 26 while operating as an electric motor.

[0034] The first step 32 is to determine the current motor power and current motor speed.

[0035] At decision step 34, a decision is made whether to operate the motor in continuous or pulsed mode based on the current motor power output and the current motor speed, in other words, whether the desired motor torque is above or below the most efficient output torque range for the current motor speed (e.g., 47.5 Nm in the example of FIG. 1).

[0036] In step 36, if the current motor torque demand exceeds the most efficient output torque for the current motor speed, the motor is operated in continuous mode.

[0037] In an alternative step 38, if the current motor torque demand is below the most efficient output torque for the current motor speed, the motor is operated in a pulsed mode.

[0038] In step 40, the desired pulse magnitude, duty cycle and frequency for operation in pulsed mode are determined so that the average output power or torque over time matches the desired torque output.

[0039] In step 42, the motor is operated in a pulsed mode using the determined pulse magnitude, duty cycle and frequency of the pulses.

[0040] Steps 32-42 above are performed continuously during motor operation. At any motor speed, there is a corresponding most efficient output torque at which the motor operates at or near maximum efficiency. As instantaneous motor output demand and / or current motor speed change, a decision is made to operate the motor in either continuous or pulsed mode, as appropriate.

[0041] From a conceptual standpoint, the more often the required motor torque is below the most efficient output torque for the current motor speed, the more the overall efficiency of the motor can be improved by pulsing the motor.

[0042] Pulse Rise Time Modern power converters are typically designed for continuous operation, rather than pulsed operation. Such power converters typically transition from a de-energized state to a powered state relatively infrequently. As a result, to date, little design effort has been devoted to managing the transition time for the machine to go from off to pulsed on. When such effort is made, the emphasis is typically on achieving a smooth transition, as opposed to a fast transition. Thus, in most electric machines, the transition from a de-energized (off) state to a powered (pulsed on) state is relatively slow.

[0043] Applicants have discovered that for electromechanical systems that frequently transition from a non-powered state to a peak efficiency state, such as in pulsed operation, further efficiency gains can be realized if the transition occurs as quickly as possible. For example, a fast transition from zero torque to peak efficiency torque improves overall average efficiency because the motor spends less time in a transition below peak efficiency. This relationship is illustrated in Figures 4A and 4B.

[0044] Referring to FIG. 4A, a torque versus efficiency map of an exemplary electric machine operating as a motor at a fixed speed (e.g., 6000 rpm) is shown. In the exemplary map, the range of torque output from 0.0 Nm to 250 Nm is plotted along the horizontal axis, and the motor's efficiency from 0.0 percent to 100 percent is plotted along the vertical axis. Curve 46 shows the motor's transition from zero to peak efficiency torque. During this transition, as depicted by the shaded region 48, the motor operates at a much lower efficiency before reaching or near the motor's peak efficiency, as indicated by reference numeral 50.

[0045] Referring to Figure 4B, a map illustrating torque versus work loss for an exemplary motor operating at a fixed speed during a transition from zero to peak efficiency torque is provided. In this map, work loss (W) is plotted along the vertical axis, and torque output of the motor is plotted along the horizontal axis. As shown by curve 52, the work loss of the motor increases as torque output increases during the transition from zero to peak efficiency torque. Thus, the faster the transition time from zero to peak efficiency torque, the less work is performed and the less energy is consumed by the electric motor.

[0046] By substituting time for torque on the horizontal axis and integrating the area under curve 52, we can calculate the energy consumed by an electric motor for a given transition time. For example, for the exemplary motor, a 0.5-second transition time dissipates 7234.5 joules of energy, while a 0.05-second transition time dissipates only 723.4 joules. This comparison shows that the faster the transition time from zero to peak efficiency torque, the less energy is consumed in losses. Note that this example assumes no load inertia acceleration occurs, so no energy is added to the load. Just as faster rise times increase efficiency, faster pulse fall times can also increase efficiency.

[0047] For different motors, the motor's zero to peak efficiency torque transition, peak efficiency torque, and work loss will all be different. Therefore, the maps of Figures 4A and 4B should be considered merely illustrative and should not be construed as limiting in any way.

[0048] Boosting the rotor power supply voltage Applicant has discovered that by applying a boosted voltage to the rotor at the beginning of each pulse, the electric machine can be significantly reduced in transition time from an OFF state to an ON state when pulsed. The application of the boosted voltage reduces the inherent turn-on time, determined by the rotor's inductance and resistance, allowing the rotor windings to be rapidly energized to the target operating current and develop the desired rotor flux sooner than would be possible without the boosted rotor voltage. By significantly reducing the OFF state to ON state transition time for each pulse, the overall efficiency of the pulsed electric machine can be significantly improved.

[0049] As described in more detail below, the boost voltage applied to the rotor can be generated or otherwise provided in any of several different manners.

[0050] In one embodiment, an external power source, such as a battery or other power source, may be used to provide the boosted voltage, or the boosted voltage may be generated internally within the electric machine.

[0051] 5A, an exemplary electric machine 80 is shown that includes a boost circuit 82. In the following description, the electric machine 80 is operated as a motor. However, as noted above, the electric machine 80 can also be operated as a generator.

[0052] In this embodiment, many of the existing electrical components of the electric machine 80, along with some additional components, are used to generate and store the boosted voltage. As will be described in more detail below, a storage device, such as a capacitor, is charged during the off-state between pulses. The charge in the storage device is then used to "boost" the supply voltage applied to the rotor as the electric machine begins to transition to its on-state with the next on-pulse. This results in a faster turn-on of the rotor, significantly reducing the transition time of the electric machine from its off-state to its on-state compared to a situation without the boosted voltage. Because this embodiment largely uses existing elements of the electric machine 80 to generate the boosted voltage, the benefit of faster transition times is achieved for almost "free" with little overhead from additional circuitry or components.

[0053] The electric machine 80 includes the power converter 22, the pulse controller 28, a stator 82 having three windings labeled A, B, and C, a rotor 84, and a DC power source 85 (e.g., a battery) connected to a first power rail 86 and a second power rail 88.

[0054] Power converter 22 includes three transistor-diode pairs, labeled Q1-Q2, Q3-Q4, and Q5-Q6, which generate three-phase AC power from DC power source 85 to three windings A, B, and C of stator 82, respectively, as is well known in the art.

[0055] As previously mentioned, pulse controller 28 determines whether machine 80 should operate in continuous or pulsed mode. In the latter case, pulse controller 28 determines the pulse magnitude, duty cycle, and frequency depending on factors such as the current speed of the electric machine and / or the instantaneous demand on the electric machine. In response, pulse controller 28 controls power converter 22 to selectively energize windings A, B, and C of stator 82 as needed to achieve the desired pulse magnitude, duty cycle, and frequency. Between pulses, windings A, B, and C are de-energized, and electric machine 80 is in an off-state. In continuous mode, pulse controller 28 directs power converter 22 to continuously energize windings A, B, and C of stator 82.

[0056] Boost circuit 82 includes a rectifier 87, a power storage device such as capacitor C1, and a controller 90 connected between a power rail 86 and another power rail 92. A unidirectional current device such as diode D1 is also connected between rails 86 and 92. In this configuration, diode D1 allows current to flow from power rail 86 to rail 92, but not in the reverse direction.

[0057] During pulsed mode operation of electric machine 80, pulse controller 28 and controller 90 cooperate to (1) recharge capacitor C1 to a target boost voltage when electric machine 80 is in the off state between on-pulses, and (2) provide the boost voltage from capacitor C1 to rotor 84 in addition to the voltage from DC power supply 85 at the beginning of the transition to the next on-pulse. The additional boost voltage at the beginning of the pulse causes rotor 84 to energize more rapidly and turn on faster than would be possible without the boost voltage applied as described above.

[0058] As the rotor is rapidly energized, the charge on capacitor C1 is depleted. Once rotor 84 is fully energized, it is powered solely by DC power supply 85 for the remainder of the on-pulse. With this configuration, the boost voltage is applied only when it is most needed: at the beginning of each pulse, during the transition from the off state to the on state.

[0059] Capacitor C1 is recharged in the off state between on-pulses by pulse controller 28 directing power converter 22 to energize at least one of windings A, B, and / or C of stator 82 for a short period of time after the electric machine transitions from the on state to the off state at the end of each pulse. Typically, the windings are simply de-energized during this transition. However, by energizing at least one of windings A, B, and / or C across the transition and switching any of the inactive phases to the negative bus voltage on power rail 88, an AC voltage is induced in rotor 84 as the rotor moves through the magnetic flux generated by the stator, or as the phases are pulsed. In response, rectifier 87 converts the AC voltage to a DC voltage, which is stored on the storage plates of capacitor C1. When the charge on capacitor C1 reaches the target boost voltage, controller 90 directs power converter 22, via pulse controller 28, to de-energize one or more of stator windings A, B, and / or C. In this manner, controller 90 acts as a voltage clamp that limits the voltage stored on capacitor C1 once the target boost voltage storage is achieved, so that the desired boost voltage is (1) sampled and stored on capacitor C1 and (2) available to rotor 84 at the beginning of the next pulse transition to the on state.

[0060] In various embodiments, the excitation of one or more windings A, B and / or C of stator 82 after the pulse ends can vary widely.

[0061] In one non-limiting embodiment, the excitation is an inverse sinusoidal three-phase voltage waveform that is opposite to that used to drive electric machine 80 during a given on-pulse. For example, if rotor 84 is rotating clockwise at 4000 RPM during a given on-pulse, it will continue to rotate at this speed and direction immediately after the given on-pulse ends. If the stator is intentionally excited with a reverse-rotating (counterclockwise) 4000 RPM magnetic field after the given on-pulse ends, the net effect will be that rotor 84 will effectively be rotating at 8000 RPM, which means there will be more pole-crossings and a higher frequency for the resulting AC voltage induced in rotor 84. In response, the AC voltage is rectified by rectifier 87, and the resulting DC voltage is stored in capacitor C1.

[0062] In yet another embodiment, one (or more) of windings A, B, and C can be statically energized while rotor 84 rotates, causing rotor 84 to generate an AC voltage coinciding with each pole crossing.

[0063] In yet another embodiment, windings A, B, and C may be energized with three-phase AC power, but at a lower frequency or speed relative to the rotation of rotor 84. As a result, the rotor generates AC voltages corresponding to each pole crossing.

[0064] It should be noted that this specification does not exhaustively list all possible embodiments for energizing one or more of windings A, B, and C. Therefore, the embodiments mentioned herein should not be construed as limiting in any way. On the contrary, any embodiment that energizes at least one (or more) of the windings may be used, provided that in such an embodiment, at least one (or all) de-energized phases are selectively switched to the negative bus voltage on power rail 88.

[0065] The above process of charging capacitor C1 to the target boost voltage takes a relatively short time, typically 2-3 milliseconds, until capacitor C1 is charged to the target boost level. Thereafter, for the remainder of the time electric machine 80 is off, one or more of the stator windings are de-energized until the start of the next pulse.

[0066] In various embodiments, the magnitude of the boosted voltage picked up and stored in capacitor C1 can vary widely. Regardless of the magnitude, the boosted voltage helps shorten the turn-on time of rotor 84. For example, if 400 volts is provided by DC power source 85 and an additional 400 volts is picked up and stored in capacitor C1 while electric machine 80 is in the off state between pulses, then a total of 800 volts will be available at the start of the next on-pulse.

[0067] When the next pulse begins, the DC voltage on rail 86 and the boosted voltage on capacitor C1 are connected on rail 92 and supplied to rotor 84 via rectifier 87. Using the voltage values ​​provided in the non-limiting example above, rotor 84 is supplied with 800 volts instead of just 400 volts. The additional 400 volts of voltage quickly energize the windings of rotor 84, generating the desired rotor flux much faster than if only the 400 volts from power supply 85 were used. As a result, the boosted voltage is available just when more voltage is needed to speed up turn-on of rotor 84.

[0068] As the rotor windings are energized during the starting process, the boosted voltage on capacitor C1 is depleted. Then, once steady-state operation is achieved for the remainder of the on-pulse, the DC voltage provided by power supply 85 is used to drive rotor 84. With this configuration, the boosted voltage is applied to the rotor only when it is most needed, and for a very short period of time. As a result, rotor starting time is significantly reduced (e.g., typically 2-3 milliseconds) compared to the maximum 10-100 milliseconds required for a comparable, but non-boosted, electric machine.

[0069] Note that the turn-on inductance of a given electric machine is typically much higher than that of the stator due to the greater number of windings in the rotor compared to the stator. Therefore, the boost voltage is most effectively applied to the rotor rather than the stator. However, the boost voltage can be applied to the stator as well.

[0070] H-bridge rectifier It is common for many electric machines to utilize a transistor-diode H-bridge to assist in demagnetizing and reducing the generation of back electromotive force (EMF) in rotor 84. As described below, applicant has discovered that, in addition to reducing back EMF, such an H-bridge can also be used (1) as a rectifier to convert the AC voltage generated by rotor 84 to a DC voltage for charging storage capacitor C1, and (2) to provide a circuit path to supply a boost and supply voltage to rotor 84 when energized (e.g., during an on-pulse or continuous operation).

[0071] Referring to FIG. 5B, an H-bridge rectifier 94 is shown. The H-bridge rectifier 94 includes a first transistor-diode pair Q7-Q8 and a second transistor-diode pair Q9-Q10. The remaining elements, i.e., rotor 84, DC power supply 85, first and second power rails 86, 88, diode D1, storage capacitor C1, controller 90, and rail 92, operate as described above. Also, for clarity, the remaining components described above with respect to FIG. 5A (e.g., power converter 22, pulse controller 28, and stator 82) are not shown.

[0072] Immediately after the pulse, H-bridge rectifier 94 converts the AC voltage generated by rotor 84 to a DC voltage. If the AC voltage is positive, the diodes associated with transistors Q7 and Q10 are turned on, and the diodes associated with transistors Q8 and Q9 are turned off. If the AC voltage is negative, the diodes associated with transistors Q8 and Q9 are turned on, and the diodes associated with transistors Q7 and Q10 are turned off. The resulting DC voltage is stored on capacitor C1 via power rail 92. Once capacitor C1 reaches the target boost voltage, the charging process is stopped as described above. This charging process ideally occurs within 3 to 5 milliseconds after the end of the on-pulse, after which the rotor drive circuitry is disabled.

[0073] Alternatively, an H-bridge rectifier 94 is also used to provide boost and supply voltage to rotor 84 at the start of each pulse. This voltage on power rail 92 is supplied to rotor 84 by activating transistor-diode pairs Q7, Q10 or Q9, Q8. The target boost voltage stored by capacitor C1 is preferably selected so that (1) it provides enough current so that the rotor's current demands are met in the shortest possible time during nominal operation, and (2) the boost voltage on C1 is fully depleted during nominal steady-state operation of rotor 84, meaning that rotor 84 is energized solely by rail 86, diode D1, power rail 92, and power supply 84 via H-bridge rectifier 94. During normal operation (e.g., during continuous operation or when the rotor is fully energized during a pulse), rotor 84 current is controlled by pulse-width modulation (PWM) drive of H-bridge IGBTs Q8 and Q10, as is known in the art.

[0074] Note that during AC to DC rectification, rotor 84 is effectively demagnetized by H-bridge rectifier 94, reducing or eliminating back EMF.

[0075] The boost circuits described herein have a wide range of applications, including, but not limited to, electric vehicles (EVs), variable-speed, variable-load industrial motor applications, or other applications where pulsed-controlled operation can be used to achieve high efficiency in electric machines. For example, in EVs, as a general rule, the faster the transition time for an electric motor to transition from an off-state to an on-state at the beginning of each pulse, the more efficiently it will operate. With this in mind, components such as capacitor C1 and diode D1, which act as body diodes or full-wave rectifiers for the rotor H-bridge during the off-period, the boost voltage monitoring circuit, and the excitation of phases A, B, and / or C of stator 82, are selected or otherwise defined to achieve an on-pulse transition time of ideally at least 100 ms, and preferably 10 ms or less. To achieve these objectives, capacitor C1 can be sized from 40 uF or less to 100 uF or more, and the boost voltage stored therein can range from the bus voltage to any voltage not exceeding the safe operating voltage of the H-bridge components' operating limits with sufficient safety margin. It should be understood that the values ​​described herein are merely exemplary and should not be construed as limiting in any way. Rather, the size of capacitor C1 and the boost voltage stored therein may vary widely depending on any given application or situation.

[0076] Pulse Control Operation Referring to FIG. 6, a flow diagram 60 illustrating steps for boosting the supply voltage applied to rotor 84 of electric machine 80 is shown.

[0077] At decision step 62, the pulse controller determines whether the current on pulse has ended.

[0078] When the current pulse has ended, in step 64, the pulse controller 28 transitions the electric machine 80 to an OFF state while instructing the power controller 22 to energize one or more of the windings of the stator 82 using any of the embodiments described above or other embodiments not listed herein.

[0079] In step 66, rotor 84 generates an AC voltage in response to energizing one or more windings of stator 82.

[0080] In step 68, rectifier 87 or H-bridge rectifier 94 rectifies the AC voltage to a DC voltage.

[0081] In step 70, a DC voltage is used to charge the storage capacitor C1.

[0082] At decision step 72, it is determined whether the capacitor has reached the target boost voltage. If not, steps 66 through 70 are repeated to continue charging. Typically, recharging to the target boost voltage occurs quickly, on the order of 2-3 milliseconds.

[0083] In step 74, once the target boost voltage is reached, the stator windings of stator 82 are de-energized. Stator 82 then rests for the remainder of the off state until the start of the next on-pulse.

[0084] In step 76, the pulse controller 28 determines when the electric machine should transition on for the next pulse.

[0085] In step 78, the sum of the boost voltage and the voltage from power supply 85 is applied to the rotor, causing it to rapidly turn on. As the boost voltage disappears, the windings of rotor 84 become fully energized, so that only the voltage from power supply 85 is applied to rotor 84 for the remainder of the on-pulse.

[0086] Steps 62-78 are preferably repeated continuously. In this manner, storage capacitor C1 is continually recharged to the target boost voltage immediately after the end of each pulse, so that the boost voltage is available to supply to the rotor at the beginning of the next on-pulse. As a result, the transition time between the off and on states during each on-pulse is significantly reduced, improving the overall operating efficiency of the electric machine.

[0087] Applicants have discovered that the use of boosted voltages as described herein reduces the transition time from the off state to the on state to approximately 2-3 milliseconds, a significant improvement over non-boosted electric machines, resulting in improved overall efficiency of such electric machines.

[0088] It should be noted that other transition times, longer or shorter, may be achievable using boosting as described herein, and the 2-3 millisecond turn-on times referenced herein are merely exemplary and should not be construed as limiting the scope of the invention in any way.

[0089] Generator operation While the above description has primarily described operation of electric machines as motors, this should not be construed as limiting in any way. Rather, boost voltage to the rotor windings as described herein can also be used during operation of such electric machines in pulsed controlled operation as generators.

[0090] Types of Electrical Machines As is apparent from the foregoing discussion, the described boost pulsed machine control can be utilized in a wide variety of different applications to improve the energy conversion efficiency of a wide variety of different types of electric motors and generators. This includes both AC and DC motor / generators. Some representative electric machines that may benefit from the described mechanical pulsing boost embodiments are both AC asynchronous and synchronous electric machines, including: induction machines (IM), switched reluctance machines (SRM), synchronous reluctance machines (SynRM), permanent magnet synchronous reluctance machines (PMaSynRM), hybrid PMaSynRM, externally excited AC synchronous machines (SyncAC), permanent magnet synchronous machines (PMSM), eddy current machines, AC linear machines, AC and DC mechanically commutated machines, axial flux motors, etc. Representative DC electric machines include brushless, electrically excited, permanent magnet, series wound, shunt, brushed, compound, etc.

[0091] Electrical Machinery and Vehicles Electric vehicles are now commonplace and growing in popularity, with predictions that they will surpass or completely replace traditional internal combustion engine vehicles within the next 10 to 20 years.

[0092] An electric vehicle is equipped with one or more onboard machines. When driving the vehicle, the machine acts as a motor, generating torque that propels the vehicle. In an electric vehicle, the electric machine(s) are used alone to generate the required torque. The torque may be positive to propel the vehicle or negative to convert the vehicle's kinetic energy into stored electrical energy. In a hybrid vehicle, the onboard electric machine is used alone or in conjunction with the internal combustion engine to propel the vehicle. In regenerative braking, the machine is typically used to convert mechanical energy into electrical energy that is stored in a storage device such as a battery or capacitor. The stored energy can be used when the electric machine operates as a motor or to power other electrical devices in the vehicle, such as the air conditioner, heater, defroster, various lighting systems, and entertainment systems.

[0093] Pulsing on-board electric machines in vehicles with boosted voltages as described herein promises significant efficiency benefits that can extend the vehicle's range before needing to charge the battery or refuel, as in hybrid vehicles.

[0094] Further embodiments Motors used in heating, ventilation, and air conditioning (HVAC) applications are another good example of an application that can benefit from pulsing control. Several factors contribute to pulsed motor control being suitable for HVAC applications. These include: (a) the motors used in HVAC applications today are dominated by induction motors that do not contain permanent magnets; (b) a high percentage of motors used in HVAC applications (especially those containing variable-speed HVAC capacitors and / or air handlers) spend a significant amount of time operating below their high-efficiency region; and (c) the inertia of the fan or pump typically dominates the inertia of the motor, which tends to further mitigate potential NVH-related effects associated with pulsing.

[0095] Although only a few embodiments of the present invention have been described in detail, it should be understood that the present invention may be embodied in many other forms without departing from the spirit or scope of the present invention. The variously described pulse controllers and other control elements may be implemented, grouped, and configured in a wide variety of different architectures in different embodiments. For example, in some embodiments, the pulse controller may be incorporated into a motor controller or inverter controller, or may be provided as a separate component. Similarly, in a generator, the pulse controller may be incorporated into a generator controller or rectifier controller, and in a combined motor / generator, the pulse controller may be incorporated into a combined motor / generator controller or combined inverter / rectifier controller. In some embodiments, the described control functions may be implemented algorithmically in software or firmware running on a processor. The processor may take any suitable form, including, for example, a general-purpose processor, a microprocessor, a DSP, or the like.

[0096] In general, schemes for pulsed motor control can be implemented digitally, algorithmically, with analog components, or using a hybrid approach. The pulse generator and / or motor controller can be implemented as code running on a processor, programmable logic such as an FPGA (field programmable gate array), circuitry such as an ASIC (application specific integrated circuit), a digital signal processor (DSP), analog components, or other suitable hardware. In certain aspects, the described control schemes can be incorporated into object code running on a digital signal processor (DSP) incorporated into the inverter controller (and / or the rectifier controller in the context of a generator and / or combined inverter / rectifier controller).

[0097] Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims

1. 1. An electric machine comprising: a stator; A rotor, a power converter configured to energize one or more windings of the stator; and a pulse controller configured to control the power converter to selectively energize the one or more windings of the stator, thereby pulsing the electric machine between an off state and an on state; a boost circuit configured to store a boosted voltage in a power storage device when the electric machine is in an off state between on-pulses, and to supply the boosted voltage stored in the power storage device to the rotor while the electric machine transitions from an off state to an on state; Equipped with the boosted voltage causes the rotor to turn on faster, thereby reducing a transition time of the electric machine during a transition from the off state to the on state compared to when the boosted voltage is not supplied to the rotor during the transition. Electrical machinery.

2. The electric machine of claim 1 , wherein the rotor is further configured to generate an AC voltage following a transition of the electric machine from the on state to the off state.

3. The electric machine of claim 2 , further comprising a rectifier configured to rectify the AC voltage generated by the rotor and store a DC voltage in the power storage device of the voltage boost circuit.

4. The electric machine of claim 3 , wherein the rectifier is an H-bridge rectifier including four transistor-diode pairs arranged in an H-bridge configuration.

5. The electric machine of claim 1 , wherein the power storage device of the boost circuit is a capacitor.

6. 6. The electric machine of claim 1, wherein the boost circuit further comprises a controller configured to clamp the storage of the boosted voltage in the power storage device when the power storage device achieves a target boosted voltage to prevent the boosted voltage from exceeding the target boosted voltage.

7. 7. The electric machine of claim 1, wherein the boost circuit further comprises a controller configured to direct the power converter to energize the one or more windings of the stator following an on-pulse for a time sufficient to charge the energy storage device to a target boost voltage.

8. One or more of the windings of the stator are charged until the power storage device is charged to the target boost voltage. (a) using an inverse polyphase sinusoidal voltage waveform that is the opposite of that used to drive the electric machine during a given on-pulse; (b) a static method, or (c) A method of applying current at a frequency or speed different from the rotation of the rotor. The power supply is energized by one of the following methods:

8. An electric machine according to claim 7.

9. The boost circuit comprises: generating an AC voltage in the rotor between the on-pulses by directing the power converter to energize the one or more windings of the stator when the electric machine is in the off-state; When the storage device is charged to a target boost voltage, the rotor stops generating the AC voltage by instructing the power converter to stop energizing the one or more windings of the stator until the electric machine begins a transition to a next on-pulse. a controller configured to: An electric machine according to any one of claims 1 to 8.

10. 10. The electric machine of claim 1, wherein the stator, the rotor, and the power converter are electrically connected between a first power rail and a second power rail, and a power supply voltage is provided to the first power rail by a DC power supply.

11. the stator has three windings, and the power converter supplying three-phase power to the three windings of the stator during the on-pulse when the electric machine is in the on-state; selectively powering one or more of the windings of the rotor between the on-pulses when the electric machine is in the off-state; An electric machine according to any one of claims 1 to 10.

12. The electric machine of claim 1 , wherein the boost circuit includes a rectifier connected between the rotor and the power storage device.

13. 14. An electric machine according to any preceding claim, wherein the boost circuit comprises a controller configured to control recharging of the storage device in the off-state between the on-pulses of the electric machine and to stop recharging of the storage device when a target boost voltage is reached.

14. 15. The electric machine of claim 1, wherein the boost circuit maintains the boosted voltage stored in the power storage device electrically isolated from a power rail that provides a supply voltage to the power inverter.

15. 16. An electric machine as claimed in any preceding claim, wherein the boosted voltage applied to the rotor while the electric machine transitions from the off state to the on state helps to overcome turn-on inductance of the rotor so that the rotor can turn on faster than if the boosted voltage were not applied to the rotor.

16. 1. A method for controlling pulsed operation of an electric machine, comprising: applying a first voltage to a rotor of the electric machine when pulsing on the electric machine to transition the electric machine from an off state to an on state; applying an additional boost voltage to the rotor of the electric machine to pulse-on the electric machine when transitioning the electric machine from the off state to the on state; Including, the additional boost voltage helps overcome the turn-on inductance of the rotor, allowing the rotor to turn on faster than if the boost voltage were not applied to the rotor; method.

17. inducing the rotor to generate an AC voltage between on-pulses of the electric machine in the off-state; rectifying the AC voltage to a DC voltage; When the electric machine is in the off-state, the DC voltage is stored in the storage device between the on-pulses. The boosted voltage is generated by the DC voltage stored in the power storage device is used as the boost voltage when the electric machine transitions from the off state to the on state; 17. The method of claim 16.

18. 20. The method of claim 17, further comprising: ceasing to charge the power storage device with DC voltage when the power storage device reaches a target boost voltage.

19. 20. The method of claim 18, wherein the cessation of the charging of the DC voltage to the power storage device due to the power storage device reaching the target boost voltage occurs in 3 milliseconds or less.

20. (a) energizing at least one winding of a stator when the electric machine is in the off state between on-pulses; (b) generating an AC voltage in the rotor in response to energizing the at least one winding of the stator when the electric machine is in the off state between on-pulses; (c) rectifying the AC voltage to a DC voltage; (d) storing the DC voltage in a power storage device, the DC voltage of the power storage device being used as the boost voltage applied to the rotor when transitioning the electric machine from the off state to the on state when pulsing on the electric machine; 20. The method of any of claims 16 to 19, further comprising:

21. 21. The method of claim 20, further comprising terminating (a) through (d) when the power storage device is charged to a target boosted voltage.

22. energizing at least one winding of a stator when the electric machine is in the off state between on-pulses; (a) energizing the electric machine with an inverse sinusoidal voltage waveform that is the opposite of that used to drive the electric machine during a given on-pulse; (b) statically energizing; or (c) energizing the rotor at a frequency or speed different from the rotation of the rotor; 21. The method of claim 20, comprising one of:

23. 23. The method of any of claims 16 to 22, wherein turning on the rotor with the boosted voltage occurs in 3 milliseconds or less.

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