Boost converter for pulsed electromechanical control

Abstract

To operate electric machines such as motors and generators at higher levels of efficiency.SOLUTION: A boost circuit is arranged to reduce rise and fall times of pulsed power used for pulsed control operation of electric machines. Magnetic energy present in the electric machine at the end of a pulse is extracted by the boost circuit to reduce the pulse fall time. The energy is stored by the boost circuit and then applied at the beginning of a subsequent pulse to reduce the rise time. By reducing rise and fall times compared to a case of not using such a boost circuit, machine efficiency is improved.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to U.S. Provisional Patent Application No. 62 / 819,097, filed on 15 March 2019, which is incorporated herein by reference in its entirety.

[0002] This application relates, in general, to electromechanical pulsing control for selectively delivering a desired output in a more energy-efficient manner, and more specifically to a boost converter circuit with improved rise and fall times for pulsing an electromechanical device. [Background technology]

[0003] The term “machine” as used herein is intended to be interpreted broadly to mean both electric motors and generators. Electric motors and generators are very similar in structure. Both include a stator with multiple poles and a rotor. When a machine is operating as a motor, it converts electrical energy into mechanical energy. When operating as a generator, it converts mechanical energy into electrical energy.

[0004] Electrical machinery can operate using either direct current (DC) or alternating current (AC).

[0005] Typical DC machines include brushless, electrically excited, permanent magnet, series wound, shunt wound, brushed, compound wound, and others.

[0006] In the case of AC machinery, there are generally two types: asynchronous and synchronous. An example of an asynchronous electric machine is a three-phase induction motor.

[0007] Modern electric machines have relatively high energy conversion efficiency. However, the energy conversion efficiency of most electric machines can vary significantly based on their operating loads. In many applications, machines are required to operate under a wide variety of different operating load conditions. As a result, machines typically operate at the highest level of efficiency, or close to the highest level, at certain times, while operating at a lower level of efficiency at other times.

[0008] Battery-powered electric vehicles provide a good example of electric machines that operate at a wide range of efficiency levels. During a typical driving cycle, an electric vehicle accelerates, travels at a constant speed, decelerates, brakes, turns corners, etc. Within a certain rotor speed and / or torque range, the electric machine operates at its most efficient operating point, i.e., at or near its "sweet spot". Outside of these ranges, the operation of the electric machine becomes less efficient. As the operating conditions change, along with the rotor speed and / or torque changes, the machine transitions between high and low levels of operating efficiency. If the electric machine could be made to operate in a greater proportion of the driving cycle in the efficient operating region, the range of the vehicle for a given battery charge level would be increased. Since the limited range of battery-powered electric vehicles is a major commercial impediment to their use, extending the operating range of the vehicle would be highly advantageous.

[0009] Therefore, there is a need to operate electric machines, such as motors and generators, at a higher level of efficiency. SUMMARY OF THE INVENTION

[0010] This application relates to pulsed control for improving the operating efficiency of electromechanical devices such as motors and generators. In one non-exclusive embodiment, such a pulsed-controlled machine includes a power supply, a stator having windings, a rotor whose design is determined by the motor topology, a machine controller configured to selectively operate the machine in pulsed mode, and a power converter coupled between the power supply and the electromechanical device. The power converter is arranged to supply pulsed input power to the windings of the machine's stator in response to the machine controller. In addition, the power converter may include a boost circuit. The boost circuit is arranged to shorten the rise and fall times of the pulsed power compared to the rise and fall times of the pulsed power without the boost circuit. At the end of a pulse, the boost circuit extracts at least a portion of the magnetic energy present in the electromechanical device to shorten the fall time of the pulse, stores at least a portion of the energy, and at the start of a subsequent pulse, applies at least a portion of the energy to shorten the rise time. By shortening the rise and fall times of pulsed power, the efficiency of the electrical machinery and the entire electrical system is improved.

[0011] The present invention and its advantages can be best understood by referring to the following description in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a typical torque / speed / efficiency graph illustrating the energy conversion efficiency of a representative electric motor under different operating conditions. [Figure 2] Figure 2 is a graph illustrating the pulsed current signal applied to an electric motor. [Figure 3A] Figure 3A is a torque-to-efficiency map of a motor operating at a fixed speed while transitioning from zero to peak efficiency torque. [Figure 3B]Figure 3B shows the torque versus the work lost for an exemplary motor operating at a fixed speed while transitioning from zero to peak efficiency torque. [Figure 4] Figure 4 illustrates a pulse-controlled electromachine according to a non-exclusive embodiment of the present invention. [Figure 5A] Figure 5A schematically represents a continuous three-phase AC waveform with a peak value of 50 amperes. [Figure 5B] Figure 5B shows a pulsed waveform with a 50% duty cycle that provides the same power output as the continuous waveform in Figure 5A. [Figure 5C] Figure 5C shows a pulsed waveform with a 50% duty cycle that provides the same power output as the continuous waveform in Figure 5A. [Figure 6A] Figure 6A is a typical circuit that models the current flow through the three phases A, B, and C of an exemplary motor. [Figure 6B] Figure 6B is a typical circuit that models the current flow through the three phases A, B, and C of an exemplary motor. [Figure 7A] Figure 7A is a circuit diagram illustrating a prior art power converter. [Figure 7B] Figure 7B is an exemplary prior art timing diagram showing the switching state and voltage of the power converter shown in Figure 5A. [Figure 7C] Figure 7C is an exemplary prior art timing diagram showing the switching state and voltage of the power converter shown in Figure 5A. [Figure 7D] Figure 7D is an exemplary prior art timing diagram showing the switching state and voltage of the power converter shown in Figure 5A. [Figure 7E] Figure 7E is an exemplary prior art timing diagram showing the switching state and voltage of the power converter shown in Figure 5A. [Figure 7F] Figure 7F is an exemplary prior art timing diagram showing the switching state and voltage of the power converter shown in Figure 5A. [Figure 8]Figure 8 shows a power converter including a boost circuit according to one non-exclusive embodiment of the present invention. [Figure 9A] Figure 9A is a signal diagram illustrating how a boost circuit according to one non-exclusive embodiment of the present invention improves rise and fall times during pulsed controlled operation of a power converter. [Figure 9B] Figure 9B is a signal diagram illustrating how a boost circuit according to one non-exclusive embodiment of the present invention improves rise and fall times during pulsed controlled operation of a power converter. [Figure 9C] Figure 9C is a signal diagram illustrating how a boost circuit according to one non-exclusive embodiment of the present invention improves rise and fall times during pulsed controlled operation of a power converter. [Figure 10] Figure 10 illustrates, as a function of time, an exemplary voltage available for driving an electromachine according to one non-exclusive embodiment of the present invention. [Figure 11] Figure 11 illustrates, as a function of time, exemplary voltages available for driving an electromachine according to one non-exclusive embodiment of the present invention. [Figure 12] Figure 12 shows another power converter including a boost circuit according to another non-exclusive embodiment of the present invention. [Figure 13] Figure 13 is a flowchart illustrating the steps for pulsed control operation of an electromechanical device in a vehicle according to the present invention. [Figure 14] Figure 14 illustrates the modulation of energy supplied to a motor according to another embodiment of the present invention.

[0013] In drawings, similar reference numerals may be used to specify similar structural elements. It should also be noted that depictions in drawings are illustrative and not necessarily to scale. [Modes for carrying out the invention]

[0014] This application relates, in general, to pulsed control of a wide variety of electromechanical devices (e.g., electric motors and generators) that would otherwise operate continuously. Pulsed control intelligently and intermittently pulses the machine on and off, not only (1) meeting operational requirements but also (2) improving overall efficiency. More specifically, under selected operating conditions, the electromechanical device is intermittently pulsed at a more efficient energy conversion operation level to deliver the desired average output more efficiently than would be achieved by conventional continuous mechanical operation. Pulsed operation causes the electromechanical torque to be intentionally modulated, however, the modulation is controlled so as not to generate noise or vibration unacceptable for the intended application.

[0015] For the sake of brevity, the various types of pulsed control of electromechanical devices provided herein are described in the context of three-phase induction electric motors in vehicles. However, this description should not be construed as limiting in any respect. Rather, the pulsed control described herein can be used with many types of electromechanical devices, namely electric motors and generators. For example, the pulsed control of machines described herein may be used with any type of machine, whether AC (e.g., induction motors, synchronous motors, any number of poles, etc.) or DC (e.g., brushless, electrically excited, permanent magnet, series wound, shunt wound, brushed, compound wound, etc.). In addition, such pulsed control of electromechanical devices is not limited to electric vehicles but may be used in any application. In particular, pulsed control may be used in systems where the acceleration and deceleration rates need to be lower than in vehicle applications, such as electric motors for heating systems, cooling systems, and ventilation systems.

[0016] Pulsed engine control is described in U.S. Patent Application Publication No. 16 / 353,159, filed March 14, 2019, as well as in U.S. Provisional Patent Application No. 62 / 644,912, filed March 19, 2018, U.S. Provisional Patent Application No. 62 / 658,739, filed April 17, 2018, and U.S. Provisional Patent Application No. 62 / 810,861, filed February 26, 2019. Each of the aforementioned applications is incorporated herein by reference in its entirety.

[0017] three phase induction machine An induction machine includes two main components: a stationary stator and a rotating rotor. In a three-phase machine, the stator may include a three-coil winding section excited by a three-phase AC input. When the three-phase AC input passes through the three-phase winding section, a rotating magnetic field (RMF) is generated. The rotational speed of the RMF is the synchronous speed (N) of the electromachine. s This is known as an induction motor. The rotor is typically a "squirrel cage" or "wound" rotor, both of which have multiple conductive elements electrically short-circuited at their ends. According to Faraday's law, the RMF induces an electric current in the conductive elements of the rotor. The induced current establishes an induced magnetic field, which interacts with the magnetic field generated in the stator coil. The interaction of the rotor magnetic field and the stator magnetic field generates an electromagnetic force (EMF) that causes the rotor to rotate. This type of motor is called an induction motor because the current is induced on the conductive elements of the rotor by electromagnetic induction, and therefore it is opposed to a direct conductive path.

[0018] Three-phase induction motors offer many advantages. Firstly, they are inherently self-starting. Secondly, the rotor rotation speed is easy to control. Rotor rotation speed (N r ) is always the synchronous speed (N s It is slightly slower than ). This difference is known as slip and can be expressed as a percentage. Slip %=(N s -N r ) / N s Formula (1)

[0019] The frequency of the three-phase AC power supplied to the stator winding controls the RMF rotational speed and, therefore, the synchronous frequency. The rotor rotational speed can then be controlled based on equation (1) defined above.

[0020] The frequency supplied to the three-phase winding section is the synchronous speed (N s The amplitude of the applied AC controls the output torque of the electromachine. When the amplitude increases or decreases, the output of the machine increases or decreases, respectively.

[0021] Vehicle motor efficiency map Referring to Figure 1, exemplary vehicle motor efficiency maps 10 under different load and speed conditions are illustrated. Map 10 plots torque (N*m) along the vertical axis as a function of motor speed (RPM) along the horizontal axis. The maximum steady-state output power is shown by curve 12.

[0022] The area below the peak torque / speed curve 12 is mapped to multiple regions, each labeled with a percentage of operating efficiency. For the specific motor shown, the following characteristics are evident: ●The most efficient operating range, or "sweet spot," is the operating range denoted by 14, which generally corresponds to the range of 4,500 to 6,000 RPM when the torque output is in the range of approximately 40 to 70 N*m. In range 14, the energy conversion efficiency is on the order of 96%, and this range is the "sweet spot" where the motor operates in its most efficient operating range. ●When the motor speed increases and exceeds approximately 6,000+ RPM, efficiency tends to decrease regardless of output torque. ●When the output torque exceeds 70 N*m or falls below 40 N*m, the efficiency percentage tends to decrease from its peak, and in some cases, it decreases quite significantly. For example, when the motor is operating at approximately 2,000 RPM and output torque of 100 N*m, the efficiency is approximately 86%. When the torque output drops below approximately 30 N*m, the efficiency decreases regardless of motor speed and approaches zero under no load. ●At any given motor speed, there is a correspondingly most efficient output torque, which is graphically represented by the maximum efficiency curve 16.

[0023] Map 10, as illustrated, was obtained from an electric motor used in a 2010 Toyota Prius. Map 10 is for an internal permanent magnet synchronous motor. It should be understood that Map 10 is illustrative and should not be construed as limiting in any way. Similar maps can be generated for almost any electric motor, such as a three-phase induction motor, whether used in a vehicle or for any other application.

[0024] As can be seen from Map 10, the motor is generally most efficient when operating within the speed and torque range of the sweet spot 14. If the operating conditions can be controlled so that the motor spends a larger proportion of time operating within or near the sweet spot 14, the overall energy conversion efficiency of the motor can be significantly improved.

[0025] However, from a practical standpoint, many driving situations require the motor to operate outside the sweet spot speed and torque range. In electric vehicles, because there is no transmission, the ratio of the electric motor's rotational speed to the wheel's rotational speed is generally fixed. In this case, the motor speed may vary between zero when the vehicle is stationary and relatively high RPMs when traveling at highway speeds. Torque requirements can also vary significantly depending on factors such as whether the vehicle is accelerating or decelerating, traveling uphill or downhill, moving on a horizontal plane, braking, etc.

[0026] As shown in Figure 1, at any given motor speed, there exists a corresponding most efficient output torque, graphically represented by the maximum efficiency curve 16. Conceptually, if the desired motor torque is below the most efficient output torque at the current motor speed, the overall efficiency of the motor can be improved by pulsing the motor, thereby allowing the motor to operate at or near the sweet spot for some time and at a low or zero torque output level for the rest of the time. The average torque thus generated is controlled by controlling the duty cycle of the sweet spot operation.

[0027] Referring to Figure 2, a graph 20 is shown plotting the total current applied to an electric motor on the vertical axis versus time on the horizontal axis. The applied current can be the sum of all the currents of the three phases of a three-phase motor. For illustrative purposes, we assume that each applied current of amperes produces an output torque of 1 N*m. In this particular example, the desired motor output torque is 10 N*m, which requires a current of 10 amperes, as shown by the dashed line 22. In this example, the most efficient torque output of the motor is 50 N*m, corresponding to an applied current of 50 amperes.

[0028] In conventional operation, the motor continuously generates the desired torque of 10 N*m, as long as this value remains constant. Using pulsed control, the motor is pulsed to deliver a torque of 50 N*m during 20% ​​of the time, as represented by pulse 24. For the remaining 80% of the time, the motor is off. Therefore, the motor's net output meets the operational requirement of 10 N*m. Since the motor operates more efficiently delivering 50 N*m than delivering 10 N*m, pulsing the motor using a 20% duty cycle improves the motor's overall efficiency while continuing to meet the average torque requirement.

[0029] In the example above, the duty cycle is not necessarily limited to 20%. As long as the desired motor output does not exceed 50 N*m, the desired motor output can be met by changing the duty cycle. For example, if the desired motor output changes to 20 N*m, the duty cycle of a motor operating at 50 N*m can be increased to 40%, if the desired motor output changes to 40 N*m, the duty cycle can be increased to 80%, if the desired motor output changes to 5 N*m, the duty cycle can be reduced to 10%, and so on. In general, pulsed motor control can be advantageously used whenever the desired motor torque falls below the maximum efficiency curve 16 in Figure 1.

[0030] On the other hand, when the desired motor torque is greater than or equal to the maximum efficiency curve 16, the motor may be operated in a conventional (continuous or non-pulsed) manner to deliver the desired torque. Pulsed operation offers an opportunity for efficiency improvement only when the motor needs to deliver an average torque below the average torque corresponding to the point of maximum operating efficiency.

[0031] It should be noted that the current and torque values, as well as the time scale, provided in Figure 2 are illustrative and not intended to limit the possibilities in any way. In actual motor pulsing embodiments, the pulse duration used may vary significantly based on the design needs of any particular system. However, generally, the period scale of each on / off cycle is expected to be on the order of 10 microseconds to 0.10 seconds (i.e., pulsing at frequencies in the range of 10 to 100,000 Hz), for example, 0.2 to 20 milliseconds (50 to 5000 Hz), as will be discussed in more detail below. Furthermore, there are a wide variety of different motors, each with its own unique efficiency characteristics. Moreover, at different motor speeds, a given motor will have different efficiency curves. The nature of the curve may vary depending on the specific motor. It should also be recognized that the current pulse does not necessarily have to be a horizontal peak as depicted in Figure 2. Similarly, the current does not need to reach zero during the off period and may be any value other than zero. An important characteristic of the current waveform is that for a certain proportion of time, the motor operates in or near the most efficient range of the current motor speed.

[0032] Improved efficiency due to increased torque growth rate The vast majority of current motor converters are typically designed for continuous, non-pulsed operation. Such motors generally transition relatively rarely from a de-energized state to an energized state. Consequently, little design effort is made to manage such transitions. When design efforts are made to manage transitions, they are usually aimed at achieving a smooth transition rather than a rapid one. Therefore, the transition from energized to energized state is often speed-limited (i.e., not relatively rapid) for most motors.

[0033] The applicant has found that in motor systems that periodically transition from an unenergized motor state to a peak efficiency state, such as when using pulsed operation, further efficiency improvements can even be achieved if the transition occurs as quickly as possible. For example, a rapid transition from zero torque to peak efficiency torque reduces the time the motor spends transitioning, which is the time the efficiency is below peak, thus improving the overall average motor efficiency. This relationship is illustrated in Figures 3A and 3B.

[0034] Referring to Figure 3A, a torque-to-efficiency map is illustrated for an exemplary motor operating at a fixed speed (e.g., 6000 rpm). In this exemplary map, the range of torque output from 0.0 Nm to 250 Nm is plotted along the horizontal axis, while the motor efficiency from 0.0 percent to 100 percent is plotted along the vertical axis. Curve 26 illustrates the motor's transition from zero to peak efficiency torque. During this transition, as depicted by the shaded region 27, the efficiency is significantly lower at peak efficiency torque 28.

[0035] Referring to Figure 3B, a map is presented illustrating the torque versus the work lost for an exemplary motor operating at a fixed speed during the transition from zero to peak efficiency torque. In this map, work loss (W) is plotted along the vertical axis, while the motor's torque output is plotted along the horizontal axis. As shown by curve 29, the motor's work loss increases as the torque output increases during the transition from zero to peak efficiency torque. Therefore, the faster the transition time from zero to peak efficiency torque, the less work is done and the less energy is consumed by the motor.

[0036] By substituting time for torque along the horizontal axis and then integrating the region below curve 29, the energy consumed by the motor over a given transition time can be calculated. For example, the applicant found that for an exemplary motor, 7234.5 joules of energy were used over a transition time of 0.5 seconds, while only 723.4 joules were used over a transition time of 0.05 seconds. This comparison demonstrates that the faster the transition time from zero to peak efficiency torque, the less energy is consumed by losses. Note that in this example, it is assumed that no acceleration of the load occurs, and therefore no energy is added to the inertia of the load.

[0037] Different motors will exhibit different transitions from zero to peak efficiency torque, peak efficiency torque, peak efficiency torque, and work losses. Therefore, the maps in Figures 3A and 3B should be viewed as illustrative only and should not be interpreted as limiting in any way.

[0038] Power converter A power inventor is a known device used with an electric motor to convert a DC power supply, such as power generated by a battery or capacitor, into three-phase AC input power applied to the motor stator windings. In response, the stator windings generate the RMF described above.

[0039] Referring to Figure 4, a diagram of a power controller 30 for pulsed operation of an electromachine is shown. The power controller 30 includes a power converter 32, a DC power supply 34, an electromachine 36, and a pulse controller 38. The power converter 32 may operate as a power inverter or a power rectifier depending on the direction of energy flow through the system. When the electromachine operates as a motor, the power converter 32 is responsible for generating three-phase AC power from the DC power supply 34 to drive the induction motor 36. The three-phase input power, shown as phases A37a, B37b, and C37c, is applied to the windings of the stator of the electromachine 36 to generate RMF as described above. The lines depicting the various phases 37a, 37b, and 37c are drawn with arrows, and the ends of the arrows indicate that when the machine is used as a motor, current can flow from the power converter 32 to the electromachine 36, and when the machine is used as a generator, current can flow from the electromachine 36 to the power converter 32. When the electrical machine operates as a generator, the power converter 32 operates as a power rectifier, and the AC power coming from the electrical machine 36 is converted into DC power to be stored in the DC power supply.

[0040] The pulse controller 38 is responsible for selectively pulsing the three-phase input power. During conventional (i.e., continuous) operation, the three-phase input power is continuous, i.e., not pulsed. In contrast, during pulsed operation, the three-phase input power is pulsed. In non-exclusive embodiments, the pulsed operation may be implemented using any of the approaches described herein, such as the approaches described with respect to Figures 5B, 5C, and Figures 8 to 14.

[0041] Referring to Figures 5A to 5C, plots are shown illustrating the difference between the continuous three-phase input power supplied to the induction motor 36 and the pulsed three-phase input power. In each plot, current is plotted on the vertical axis and time is plotted along the horizontal axis.

[0042] Figure 5A illustrates the conventional sinusoidal three-phase input currents 42a, 42b, and 42c delivered to the induction machine 36. Phase B, represented by curve 42b, lags phase A, represented by 42a, by 120 degrees. Phase C, represented by curve 42c, lags phase B by 120 degrees. The sinusoidal period is τ. The three-phase input powers 42a, 42b, and 42c are continuous (not pulsed) and have a specified maximum amplitude of approximately 50 amperes. It should be noted that 50 amperes is merely a representative maximum current, and the maximum current may have any value.

[0043] Figures 5B and 5C illustrate two examples of different pulsed three-phase current waveforms, 44a, 44b, and 44c, and 46a, 46b, and 46c, each having a 50% duty cycle and a peak amplitude of approximately 100 amperes. As in Figure 5A, the period of the underlying sine wave is τ, but here the sine wave is modulated into on and off states. The delivered currents in Figures 5B and 5C deliver the same average torque as the continuously applied three-phase input current in Figure 5A (assuming that torque is proportional to current, which is a common occurrence). The difference between the pulsed currents 44a-c and 46a-c lies in the duration of each current pulse and the alternating "off" periods. In Figure 5B, the current pulses 44a-c have alternating "off" periods of equal length. The length of each on and off period is 2τ. In Figure 5C, the current pulses 46a-c and the alternately spaced "off" periods also have equal durations. In this case, the duration is τ / 2. In both examples, the duty cycle is 50%. However, the durations of the "on" and "off" periods are different, meaning the pulse modulation frequencies are different. The pulse modulation frequency can vary based on the type of electromechanism used, noise and vibration considerations, the current operating rotor speed, and other factors.

[0044] Figures 5B and 5C illustrate an application where "on" motor drive pulses are spaced evenly while the motor is operating at a desired steady-state output level. While this approach works well in many situations, it is not a requirement. The duty cycle does not have to be 50% and can be adjusted to match the desired average output torque. In Figures 5B and 5C, the phases of the on / off pulses are synchronized with the applied AC power. However, in some embodiments, the phases of the on / off pulses do not have to be synchronized with the phases of the applied AC power. Thus, the relative size and / or timing of the motor drive pulses can be varied, as long as they are averaged to deliver the desired average torque.

[0045] Physical properties and limitations of motors In any motor, the speed at which it transitions from zero to peak efficiency torque is ultimately limited by its physical properties. Generally, the transition speed is based on the physical properties of how quickly an electric field is constructed in the motor, which is in turn limited by the applied voltage, the back electromotive force (BEMF) of the electric motor, and the inductance of the motor windings.

[0046] Assuming that the setpoint of the power converter 32 is incremented at time zero and that there is no feedback, control to the output stage of each phase will saturate. As a result, either the low-power or high-power device of each motor phase will be hard-on. This makes six combinations possible, including the following: 1. Phases A and B are positive, and phase C is negative. 2. Phase A is positive, and phases B and C are negative. 3. Phases B and C are positive, and phase A is negative. 4. Phase B is positive, and phases A and C are negative. 5. Phases C and A are positive, and phase B is negative. 6. Phase C is positive, and phases A and B are negative.

[0047] In each of these six possible combinations, the current flow within the motor 36 at time zero is such that (a) one phase is the total current, and (b) the other two phases divide the current. The ratio of these currents is determined by the rotor position at time zero, as will be further explained below.

[0048] Referring to Figure 6A, a typical circuit is shown that models the current flowing through the three phases A, B, and C.

[0049] Each phase A, B, and C is represented by its self-inductance ("LS"), its mutual inductance ("LM"), its resistance ("R"), and its BEMF.

[0050] In the given case, Ic = Ia + Ib. Since the sum of the currents flowing through the mutual inductances is zero, the mutual inductances do not affect the current flow. As a result, assuming that the motor's BEMF is zero, the equivalent circuit is reduced as shown in Figure 6B. This circuit takes time to build up the current to a given value. TIFF0007866278000001.tif15161

[0051] If BEMF is not zero, the applied voltage to each phase will be different. Since the phase impedance and phase current are balanced, the neutral point of the winding in this case is Vbus * 2 / 3. If winding B is connected to the negative rail, the neutral point voltage is Vbus / 3. This is because the currents Ia, Ib, and Ic of phases A, B, and C are defined as follows. TIFF0007866278000002.tif36161

[0052] Since all the above values ​​are instantaneous, the values ​​at time zero are determined by the instantaneous BEMF values ​​of each phase, which in turn are determined by the rotor position within one electrical cycle or pole-pair pitch. It should also be noted that as time progresses, the instantaneous BEMF voltage per phase, the voltage applied to the motor inductance, and the rate of increase of the motor phase current also progress.

[0053] The intention is for the current to reach its desired value, so that the phase can supply the required torque. Since the current is usually controlled using field-oriented control (FOC), the phase current is replaced by the rotational coordinate values ​​"iq" (quadrature current) and "id" (DC current). The vector sum of id and iq is equal to the peak value of the phase current, and ArcTan id / iq is the angle. The cosine of the angle is the power factor. Therefore, deriving the values ​​of id and iq using the Direct Quadrature Zero transform yields the following equation. TIFF0007866278000003.tif38161

[0054] A closer examination of the above equation reveals that the BEMF waveform Vpk affects only iq (orthogonal current), both of which are influenced by the bus voltage Vbus and the rotor angular position θ. Since neither the angle nor the motor BEMF can be changed without changing the motor, the only parameter that can be controlled to affect the rate of increase of the phase current and therefore the motor torque is the applied bus voltage Vbus. One aspect of the present invention therefore proposes shortening this transition time by temporarily increasing or "boosting" the bus voltage to a value higher than the normal operating bus voltage during the transition time from zero to peak efficiency torque during pulsation.

[0055] Note that when the converter is turned off, the energy stored in the electric motor winding is returned to the bus voltage supply. If the supply cannot absorb this energy, the bus capacitance absorbs it, causing the bus voltage to rise. Due to the amount of capacitance across the bus supply, in this normal process, the bus voltage usually rises only a very small percentage and generally is not sufficient to be considered boosting the bus voltage. However, if this energy is taken in independently, for example, taken in and stored in a storage device such as a capacitor or battery, it would be possible to return the energy to the motor in the form of a boosted voltage and reuse it.

[0056] Alternatively, during the "off" period, it would be possible to use a charge pump or a separate voltage source to increase the bus voltage by a separate boost voltage source. This boost supply is designed not to charge the main bus capacitance but to charge a separate capacitance capable of discharging to the motor over the on-transition time from zero to the required torque.

[0057] Conventional power converter circuit In this way, the motor's inherent inductance can temporarily delay / slow down the voltage / power steps between the on and off motor states. During continuous (non-pulsed) operation, these temporary effects tend to have a relatively minimal impact on the overall motor operation. However, when using rapid pulsing as contemplated herein, the net effect of the temporary effects can be significant, providing an incentive to shorten the pulse transition times at the rising and falling edges.

[0058] Referring to FIG. 7A, a circuit diagram of a representative prior art power converter 32 is shown. The power converter circuit 32 includes three pairs of switches labeled S1 through S6. Each pair of switches S1 - S2, S3 - S4, and S5 - S6 is connected between two voltage buses (+V BUS ) and (-V BUSIt is connected in series with two voltage buses (+V BUS ) and (-V BUS The potential between the switch and the switch is the potential available to operate the electromachine 36. Each switch, S1 to S6, may have bypass diodes (D1 to D6) electrically connected in parallel with the switch. These diodes help prevent voltage spikes that could be generated during switch operation and damage the switch.

[0059] The diode also provides a path for reusing current that the switch might interrupt. This is especially important when the electromachine 36 is used as a generator. Switches S1 to S6 can each be a MOSFET (metal-oxide-semiconductor field-effect transistor) switch with a diode incorporated. Alternatively, other types of transistors, such as insulated-gate bipolar transistors (IGBTs), may be used, though not limited to them.

[0060] The connection to the stator coil winding section of the electrical machine 36 is made between each pair of switches. For phase A, the connection is between switch pair S1 and S2, and is designated as 37a. For phase B, the connection is between switch pair S3 and S4, and is designated as 37b. For phase C, the connection is between switch pair S5 and S6, and is designated as 37c.

[0061] Within the electrical machine 36, the phase stator windings may be modeled as an inductor 31, a resistor 33, and a mutual inductance 35, respectively. In Figure 7A, these elements are only given reference numerals for phase C, but similar elements also exist in the windings of phases A and B.

[0062] Switches S1 to S6 can be collectively referred to as a switching network that controls the power flowing through the electrical machine 36.

[0063] When the electric machine 36 is operated as a motor, switches S1 to S6 operate in a conventional manner, applying current to each of the stator windings. For example, the switches may be operated as a 6-step inverter that supplies AC power to the electric machine 36.

[0064] Figure 7B shows the switching sequence for obtaining six steps of output from the power converter 32. Each switch is opened with a time delay for half a cycle period. For each winding, current can flow to one switch in the top row and one or two switches in the bottom row. The switch pairs S1-S2, S3-S4, and S5-S6 are never turned on simultaneously, which short-circuits the DC power supply 34.

[0065] Figure 7C shows the voltage between point A and point B as voltage V. ab This is shown as follows.

[0066] Similarly, Figures 7D and 7E show the voltages between point B and point C, and between point C and point A, respectively. By summing these voltages, it is possible to determine the voltage between each phase and the neutral point.

[0067] Figure 7F shows the resulting phase voltage of phase A. The resulting 6-step waveform approximates a sine wave with frequency ω and is generally called a modulated signal. The phase voltages of phases B and C are shifted by 120° and 240°, respectively, relative to the voltage of phase A.

[0068] It should be noted that the electrical machine 36 can operate not only as a motor but also as a generator. When operating as a generator, energy flows from the electrical machine 36 to the DC power supply 34. The power converter 32 acts as a three-phase rectifier, not an inverter.

[0069] In typical prior art systems, a switching network is used to control the power flowing to an electric motor by pulse-width modulation (PWM) control. PWM control reduces the amount of time that the switching network is in an active configuration of switches S1-S6, allowing power to flow to the electric motor. That is, the proportion of time that switches S1-S6 are in an inactive configuration, i.e., the proportion of time when S1, S3, and S5, or S2, S4, and S6 are all off, increases as the desired electric motor torque output decreases.

[0070] Power converter with boost circuit Figure 8 shows a power converter circuit 132 including a boost circuit according to one non-exclusive embodiment of the present invention. Compared to the prior art power converter circuit 32 shown in Figure 7A, the power converter circuit 132 also includes additional switches SA and SB, which are controlled by a pulse controller 38, respectively. They may be controlled by a common signal line 41 (as shown in Figure 8) or they may have independent control lines (not shown in Figure 8). When switch SA is turned on, a positive supply voltage (+V DC ) but, (+V BUS It is coupled to the negative power supply voltage (-V). When switch SB is turned on, it is coupled to the negative power supply voltage (-V). DC ) but (-V BUS It is joined to ().

[0071] During operation, the pulse controller 38 operates to selectively turn switch SA or switch SB on and off by applying a pulse waveform to signal line 41, thereby electrically connecting the pulse controller 38 to switches SA and SB. When switches SA and SB are on, current can be delivered to the electromachine 36. Conversely, when SA and / or SB are off, no current is delivered to the electromachine 36, or only transient current is delivered.

[0072] The power converter circuit 132 also includes a capacitor C1, which has one conductive plate (+VBUS ) is coupled, and the other conductive plate is (-V BUS ) are coupled to the switches SA and SB, as well as capacitor C1, which are sometimes collectively called a boost circuit, because their purpose is to provide +V at the start of the "on" pulse, as described below. BUS Bus and -V BUS This is because it increases the initial voltage on the bus. In various embodiments, the boost circuit may be integrated into the switching network or may consist of an element separate from the switching network.

[0073] As mentioned above, the objective of pulsed motor control is to operate the electromachine 36 at substantially the most efficient level of the current machine speed during the "on" period and to cut off the power (supply zero or negligible power) during the "off" period. For example, the power supplied during the off period can be less than 10%, 5%, 1%, 0.5%, or 0.1% of the power supplied during the "on" period. The operating point during operation in the "on" period may be within 5%, 2%, or 1% of the maximum operating efficiency point of the motor at the current motor speed. The transition through the low-efficiency operating region between the "off" and "on" periods should be as fast as possible to maximize efficiency. Therefore, the power transition between the "on" and "off" states of the machine power ideally has a leading edge that transitions vertically straight up and a trailing edge that transitions vertically straight down. Such a "perfect" pulse 60 is schematically shown in Figure 9A, which illustrates an ideal motor drive current-to-time ratio for pulsed control with a 50% duty cycle. In this figure, the current pulse represents the sum of the currents of all phases. The current pulse is shown as a horizontal peak, but this is not necessarily the case.

[0074] In real-world situations, generating such perfect pulses is difficult due to numerous practical limitations. For example, the inductive aspects of both the electromachine 36 and the power converter 32 circuits slow down the rise and fall times of the current. The actual response of a particular machine will vary depending on the electrical characteristics of the electromachine 36, the rotational speed of the electromachine, and the available bus voltage. Generally, the actual rise and fall of a pulse occur more gradually; that is, the transition occurs over time. The nature of rise and fall in real-world situations is schematically illustrated in Figure 9B. As can be seen in the figure, there is a ramp-up period (rise time) 62 required for the current to actually rise from zero to the desired "on" power level, and a ramp-down period (fall time) 64 required for the current to actually fall from the "on" power level to zero.

[0075] During the ramp-up and ramp-down periods of the power, the electrical machine 36 continues to consume or generate power. However, the operating efficiency of the machine decreases during these transition periods. Generally, machine efficiency decreases as the operating current decreases from its maximum efficiency condition (curve 16 in Figure 1) towards zero, and the energy conversion efficiency deteriorates significantly as the current level approaches zero. Therefore, pulse distortion, represented by the ramp-up and ramp-down periods of the current, impairs the efficiency improvement obtained as a result of pulsed operation. Generally, the smaller the rise time / fall time ratio to pulse length, the smaller the impact of transient switching effects on the energy conversion efficiency of the machine during pulsed operation.

[0076] It should be noted that the transient effects shown in Figure 9B are illustrative in nature and do not necessarily reflect the actual rise / fall times associated with the operation of any particular electromachine. The relative scale of the rise time ratio to pulse length can vary widely based on the characteristics of the machine used (which primarily determines the rise and fall times), the pulsation frequency (which is primarily determined by the control scheme used), and the pulse width (which is determined by the control scheme and the machine load). The voltage available to power the electromachine and the machine's rotational speed also affect the pulse rise and fall times. If the pulsation is slow compared to the machine response, the rise / fall time may be only a small fraction of the pulse width, and the impact of transient switching effects on machine performance may be minimal. Conversely, if the pulsation is very rapid and / or the machine response is slow, the rise / fall time may be a significant fraction of the pulse width, and in some situations may even exceed the pulse width. If not carefully managed, transient efficiency losses associated with switching can significantly reduce, or even eliminate, the theoretical improvements achievable through pulsed operation. Therefore, when determining the appropriate pulsed frequency and control scheme for any particular application, it is crucial to consider the transient switching effects associated with pulsed operation.

[0077] The capacitor C1 included in the power converter circuit 132 in Figure 8 is provided to improve the rise and fall times of the current. Capacitor C1 may store energy from the electromechanism 36 during the ramp-down period and supply energy to the electromechanism 36 during the ramp-up period. As a result, the turn-on and turn-off transitions are faster than when they occur without capacitor C1.

[0078] To better understand the operation of the power converter 132, we assume that the power converter 132 is initially in the "on" state and the electromachine 36 is operating as a motor. This suggests that switches SA and SB are turned on, which allows current to flow from the positive terminal of the DC power supply 34 through the power converter 132 to the electromachine 36 and back to the negative terminal of the DC power supply 34. Switches S1 through S6 oscillate in the configuration shown in Figure 7B to apply AC power to the electromachine 36.

[0079] To stop the motor operation, turn off switches SA and SB, and turn on +V BUS Bus and -V BUS The bus may be made to have a different potential from each terminal of the DC power supply 34. Since the circuit is open at this time, current should have stopped flowing through the circuit. However, there may be considerable energy associated with the magnetic field generated by the current in the electromachine 36. At least some of this energy may be extracted from the electromachine 36 and taken up and stored in the capacitor C1. This increases the potential difference between the positive voltage bus and the negative voltage bus. For example, line +V BUS The potential above corresponds to the positive terminal +V of the DC power supply. DC The potential may increase beyond that of line-V BUS The potential above corresponds to the negative terminal -V of the DC power supply. DC The potential may decrease to below +V. Since switches S1 to S6 all have bypass diodes, the unidirectional current from the electromechanism 36 is +V regardless of the switch position. BUS Also, -V BUS Note that it is possible for current to flow from the line to the electrical machine 36. When switches SA and SB are turned off, or at the same time, one of switches S1 to S6, which may have been on when switches SA and SB were opened, turns off, +V BUS Line and -V BUS No current flows through any of these switches between the line and the electrical machine 36.

[0080] If motor operation is desired again, switches S1 to S6 may be turned on in one of the patterns shown in Figure 7B. The switching pattern must correspond to the rotor rotation angle so that the phase of the applied current matches the correct phase and power is supplied to the electromachine 36 again. Switches SA and SB are +V BUS The voltage is +V DC It drops down to -V BUS ga -V DC It closes when it rises to a certain level. This circuit configuration and control method is designed so that the initial voltage applied to the electromechanism 36 at the start of the "on" phase is high, thereby advantageously shortening the pulse rise time.

[0081] Figure 10 is an example of the circuit shown in Figure 8 +V BUS Waveform and -V BUS The waveform versus time is illustrated. The pulse generator 38 generates a digital waveform 43 consisting of a string of digital "0"s and "1"s. A 1 may correspond to an electromachine 36 that is "on," and a 0 may correspond to an electromachine that is "off." In Figure 10, the electromachine 36 is pulsed with a 40% duty cycle. However, this is merely an example, and any duty cycle may be used. +V BUS The rail voltage is 45V during the ramp-down period. BOOST It rose to -V BUS The rail voltage is 47V during the ramp-down period. BOOST Descend to +V BUS Bus and -V BUS The magnitude of the bus voltage change may be equal or different. +V BUS Voltages of 45 and -V BUSThe voltage 47 remains relatively constant during the motor's off time because energy from the motor's ramp-down is stored in capacitor C1. When the pulse generator waveform 43 returns to digital "1", the energy stored in capacitor C1 is supplied to the electromechanism 36 through switch array S1~S6. This dissipates the charge in capacitor C1, and the energy stored in capacitor C1 is used to drive the motor, resulting in a voltage of +V BUS The voltage of the rail is 45V (+V). DC It is returned to -V BUS The voltage of the rail is 47V DC The motor operation during the "on" period is maintained by turning on switches SA and SB, allowing the motor to be driven using energy from the DC power supply 34. In effect, the boost circuit increases the available potential between the positive and negative voltage buses to drive the electromechanism at the start of at least one pulse in a series of pulses. It should be noted that the positive and negative voltage buses are relative terms, and the respective potentials of these buses relative to ground potential can be either positive or negative. The boost circuit may be used to increase the available potential for driving the electromechanism for all pulses in a series of pulses.

[0082] An exemplary power converter with a boost circuit is shown in Figure 8 as having switches adjacent to both the positive and negative terminals of the DC power supply, but this is not a requirement. In some embodiments, only a single switch may be required.

[0083] Switches SA and SB, used in conjunction with capacitor C1, can reduce power rise and fall times by half, one-fifth, one-tenth, or even less, depending on the circumstances. The voltage across capacitor C1 can be higher than the power supply voltage by storing energy recovered from the motor during ramp-down. The magnitude of the voltage increases with the amount of magnetic energy that can be extracted and taken up. This can significantly reduce transient switching effects associated with pulsed operation, which can sometimes be detrimental.

[0084] Examples of improved rise and fall times are schematically shown in Figure 9C. As is clear from the figure, the ramp-up rise time 66 at the rising edge of the pulse is faster / shorter compared to the corresponding ramp-up time 62 shown in Figure 9B. Similarly, the ramp-down time 68 at the falling edge of the pulse is faster / shorter compared to the corresponding ramp-down time 64 shown in Figure 9B. Therefore, it should be recognized that electromachines designed with pulsed control in mind, or electromachines modified to improve the transient response of the machine to power pulses, may benefit even more from pulsed operation than existing machines.

[0085] It should be recognized that the appropriate pulsing frequency for various machines implemented by the pulse controller 38 can vary considerably based on the machine's structure, operating environment, and operating range. Some electromachines may be suitable with switching frequencies on the order of 10–50 kHz, while others may be better suited to much lower frequencies, such as 10–500 Hz. The optimal pulsing frequency for any given machine will depend on a wide range of factors, including the machine's type, load, and / or application.

[0086] It should be noted that the details of the boost circuit used to reduce the rise and fall times of power to or from an electromachine may vary depending on the type of electromachine and its operating regime. For example, in some cases, one of switch SA or switch SB may be removed from the power converter circuit 132. Other types of power converter circuits and control strategies may be used. For example, in some situations, a Z-source inverter may be used, in which a diode, two inductors, and two capacitors are located between the power supply and the switching network.

[0087] The voltage boost level and size of capacitor C1 can be appropriately selected to match the electromechanism and its inductive and resistive characteristics, thereby reducing the transient rise / fall times associated with the on / off pulsing of the machine. Preferably, the respective capacitances and boost voltage levels are also selected to maximize the overall mechanical efficiency during pulsing, including inefficiencies associated with the transient phenomenon itself and any overshoot effects that may occur due to the use of capacitor C1. Since capacitor C1 is used to improve the transient response, it may be opportunistically recharged during periods when the motor is not powered, for example, during the off period of the electromechanism. This mode of operation is described in more detail in the following description relating to Figure 11.

[0088] Depending on the motor speed and load, the rise and fall times may be steep. BUS Voltage and -V BUS In some cases, the energy stored in the motor's magnetic field may be insufficient to adequately boost the voltage. In such cases, it may be desirable to boost the potential difference across the electromachine during the off-period between pulses. Exemplary voltage waveforms illustrating two boost cycles 73a and 73b are shown in Figure 11. It should be noted that, depending on the operating conditions of the electromachine, more or fewer boost cycles may be used. An appropriate switching network and control strategy are necessary to implement this type of control.

[0089] Referring to Figure 12, another power converter 200 is illustrated, which includes a boost circuit 202 according to another embodiment of the present invention. The power converter 200 includes switches S1 and S2 for phase A, switches S3 and S4 for phase B, and switches S5 and S6 for phase C. Each pair of switches S1-S2, S3-S4, and S5-S6 are connected to two voltage buses (+V BUS ) and (-V BUS It is connected in series with two voltage buses (+V BUS ) and (-V BUS The potential between the switches S1 and S6 is the potential available to operate the electromachine 36. The switches S1 to S6 are collectively called the switching network that controls the power flowing through the machine 36. When operating as a motor, power from the DC power supply is supplied via the switching network of switches S1 to S6. The switching network then supplies phase energy to the three phases of the stator windings of the machine 36 as described above. Similarly, when operating as a generator, the energy flow is from the machine 36 to a storage device such as a battery.

[0090] The boost circuit 202 includes a boost power supply 204, a switch 206, a capacitor C1, a battery, and a control signal 208 generated by the pulse controller 38. Since the pulse controller 38 has been described previously, a detailed description will not be repeated in this specification for brevity.

[0091] In various embodiments, the boost power supply 204 may be a dedicated circuit (e.g., a charge pump or a separate voltage source) and / or a storage device such as another capacitor and / or battery, capable of generating a boost voltage. In embodiments described later, at least a portion of the energy stored by the storage device may be drawn from the motor 38 itself. For example, when machine 36 is operating as a generator, or when machine 36 is operating as a motor and transitions from an on state to an off state, such as during pulsation, the generated energy can be converted into certain components and stored in the boost circuit 202, for example, in a capacitor C1 and / or battery. The stored energy can then be used to generate a positive rail (+V) during a positive transition as described below. BUS It can "boost" ).

[0092] Switch 206 can be any type of switch capable of switching between the positive (+) and negative (-) electrodes of the boost power supply 204. This switch is expected to be constructed using semiconductor devices. In one specific, but non-exclusive, embodiment, switch 206 is a single-pull double-throw switch.

[0093] As is well known in the art, during continuous motor operation, phase power is supplied to the stator windings of machine 36 via switches S1 and S2 for phase A, switches S3 and S4 for phase B, and switches S5 and S6 for phase C. Ultimately, this results in a continuous output of motor torque, as described above.

[0094] During pulsed operation, the pulse controller 38 controls the switch 206 via the control signal 208 to control the boost circuit 202. In a positive pulse transition, the switch 206 is activated to the positive rail (+V). BUSConnect the ) to the positive (+) terminal of the boost power supply 204. As a result, the boost power supply 204, which works in conjunction with capacitor C1 and the battery, will have a positive rail (+V BUS It acts to boost the voltage of the positive rail (+V). By increasing or boosting the voltage of the positive rail, the transition time is shortened. When the energy stored in the boost circuit decreases or the peak torque level is achieved, the control signal 208 acts to boost the voltage of the positive rail (+V). BUS The switch is instructed to connect ) to the negative (-) terminal of the boost power supply 204. As a result, the boost voltage is on the positive rail (+V). BUS ) will be effectively removed.

[0095] The effect of the boost circuit 202 is also illustrated in Figures 9A and 9C. In particular, Figure 9A shows an ideal pulse with no transition time, and Figure 9B shows a pulse in the “actual situation” where the transition time is indicated by reference numeral 62. As previously mentioned, the inductive aspects of both the electromechanism 36 and the circuits of the power converter 200 slow down the rise and fall times of the current. Figure 9C shows the transition assisted by the boost circuit 202. As can be easily understood by comparison, the “boosted” transition time 66 shown in Figure 9C is significantly shorter (i.e., faster) than the transition time 62 shown in Figure 9B.

[0096] In the embodiment shown in Figure 12, capacitor C1 is connected to the positive rail (+V BUS ) and negative rail (-V BUS ) are arranged in parallel with the respective pairs of switches S1-S2, S3-S4, and S5-S6. In one non-exclusive embodiment, the size of C1 is derived from the ripple current of the power converter 200 when it is acting as an inverter. This arrangement improves the boost circuit 202's ability to reduce the rise and fall times of pulses.

[0097] Operation flow diagram Figure 13 is a flowchart 70 illustrating the steps for pulsed control operation of an electric motor having the characteristics shown in Figure 1.

[0098] In the first step, step 72, the current motor output and current motor speed are checked.

[0099] In decision step 74, a decision is made, based on the current motor output and current motor speed, whether the motor should be operated in continuous mode or pulsed mode. In other words, a decision is made as to whether the desired motor torque is above or below the most efficient output torque for the current motor speed (i.e., the maximum efficiency curve 16 of the motor map shown in Figure 1). If it is above, the motor is operated in continuous mode. If it is below, it may be advantageous to operate the motor in pulsed mode.

[0100] In step 76, if the current motor torque exceeds the output torque that is most efficient for the current motor speed, the motor is operated in continuous mode 76.

[0101] In step 78, determine the power output or magnitude of the "on" pulse that provides substantially maximum efficiency operation at the current motor speed.

[0102] In step 80, a desired pulse duty cycle is determined for operation in pulsed mode so that the average output power or torque matches the desired output.

[0103] In step 82, the motor is operated in pulsed mode using the determined pulse duty cycle and pulsed power output. By using a boost power converter circuit 132, or a power controller 30 having some other power converter circuit capable of storing and releasing magnetic energy from an electromechanical device, the rise and fall times of the pulses can often be significantly reduced, further improving motor efficiency.

[0104] Steps 72-82 above are performed continuously while the motor is operating. At any given motor speed, there is a corresponding most efficient output torque, which is graphically shown in Figure 1 by the maximum efficiency curve 16. Since the instantaneous motor output requirement and / or current motor speed changes, a decision is made to operate the motor in either continuous mode or pulsed mode as needed. From a conceptual standpoint, if the desired motor torque is below the most efficient output torque for the current motor speed, the overall efficiency of the motor can be improved by pulsed operation. As a result, in the case of electric motor-powered vehicles, the overall efficiency of the vehicle is improved. In other words, the range the vehicle can travel between battery recharges is increased.

[0105] Figure 14 shows a system 300 for modulating the energy supplied to a machine 36, according to another non-exclusive embodiment of the present invention. The system 300 includes a machine 36, a power converter 32, a torque control determination module 302, a feedback sensor 304 for generating a feedback signal 306 representing the angular position of the rotor of the machine 36, and a torque and speed estimation unit 308.

[0106] During the operation of system 300, the torque modulation determination module 302 receives a torque request. In response, the torque modulation determination module 302 determines whether the requested torque is less than the peak efficiency torque of machine 36 when it is operating as a motor.

[0107] Otherwise, that is, if the torque requirement is greater than the peak efficiency torque, the machine 36 is operated as a motor in continuous mode. In that case, the torque requirement waveform 310 supplied to the power converter 32 represents the continuous operation of the machine 36 operating as a motor.

[0108] On the other hand, if the torque requirement is less than the peak efficiency torque of machine 36, machine 36 is operated as a motor in pulsed mode. In this case, the torque modulation determination module 302 generates a modulated waveform 310 for the power converter 32, causing machine 36, operating as a motor, to switch between or pulse between the motor's peak efficiency torque and a low torque, the average value of which is substantially equal to the required torque. In various embodiments, the low torque can be zero, but is not necessarily zero. Assuming that the average of the low torque and the peak efficiency torque is substantially equal to the required torque, the low torque can be any other torque value greater than zero.

[0109] The power converter 32 includes a switching network comprising pairs of switches S1-S2 for phase A, pairs of switches S3-S4 for phase B, and pairs of switches S5-S6 for phase C, all of which are not shown in the diagram for clarity. As previously mentioned, switches S1-S6 are controlled by the power converter 32 to operate the machine 36 either (1) continuously as a motor producing a continuous torque output when the torque requirement is greater than the peak efficiency torque, or (2) in pulse mode when the torque requirement is less than the peak efficiency torque. The power converter 32 can control the energy supplied to the machine 36 using one of a number of different protocols, such as pulse width modulation (PWM), direct torque control (DTC), hysteresis, or "dead beat" control, which is a form of current modulation.

[0110] In alternative embodiments, a boost power converter such as 132 in Figure 8 or 200 in Figure 12 may be used. The boost version of power converter 32 improves the efficiency and performance of the motor operation of machine 36 by increasing the rise and / or fall times of pulses during pulsed operation.

[0111] The feedback sensor 304 generates a feedback signal 306 representing the angular position of the rotor of the machine 36. The feedback signal is supplied to the power converter 32 and the torque and speed estimation unit 308, respectively. At known rotor angular positions, the torque and speed estimation unit 308 can provide the torque modulation determination module 302 with accurate estimates of the motor's torque and speed. In response, the waveform 310 can be adjusted, if necessary, to precisely control the timing of the switching network in the power converter 32 (i.e., the timing of turning switches S1-S6 on / off) so that the timing of phases A, B, and C of the energy is matched to the current position of the rotor. As a result, the operation of the machine 36 as a motor is smooth and efficient. It should be noted that the use of the feedback sensor 304 is not mandatory, and other techniques can be used to measure or estimate the angular position of the rotor of the machine 36. For example, one of several sensorless approaches may be used.

[0112] Other types of motors and generators There are a wide variety of electric motors and generators, including both DC and AC motors / generators, and these are known and commercially available. While the structure, control, and energy conversion efficiency vary considerably depending on the type of electric motor and generator, most electric motors and generators are designed to operate within a certain range of operating conditions, and their energy conversion efficiency often varies significantly within that range. Generally, the control principles described herein can be applied to any type of machine to improve efficiency, assuming that the operating range includes a region below the maximum efficiency curve 16 shown in Figure 1.

[0113] Currently, some motors in the prior art operate using pulse-width modulation (PWM) control. However, such motors are driven without considering what the most efficient energy conversion level is. Therefore, it is also possible to improve the energy conversion efficiency of such motors using the approach described above.

[0114] Many types of motors, including brushless DC motors, induction motors, synchronous AC motors, switched reluctance motors, etc., are conventionally driven by a continuous, and sometimes variable, drive current to deliver the desired torque output. The drive current is often controlled by controlling the output voltage of an inverter and / or converter (which acts as the voltage input to the motor). Generally, by changing the relative phase between the rotor and stator magnetic fields, a motor can be operated as a generator. Therefore, the circuits and control methods described for motors are equally applicable when using electromechanical devices as generators. The pulsed control described is particularly useful when operating such motors and generators in regions below their respective points of maximum energy conversion efficiency.

[0115] Accordingly, the embodiments described herein should be considered illustrative rather than restrictive, and the invention may be modified within the scope of the appended claims and equivalents, rather than being limited to the details given herein.

Claims

1. In electrical machinery, stator and, Rotor and, The winding section and, Storage devices and A controller configured to operate the aforementioned electromachine in pulse mode, During the pulse, the electromechanical unit is in the ON state and generates an operational output. Between pulses, the electromechanical unit is in the off state and does not generate an output, and the controller... A power converter coupled between a power source and the electromachine, wherein, in response to the controller, when operating in pulse mode, When the aforementioned electrical machine operates as a motor, pulsed power is delivered to the winding portion of the electrical machine, or The system includes a power converter configured to receive pulsed power from the winding portion of the electrical machine when the electrical machine is operating as a generator, When the controller operates the electromechanism in pulse mode, the winding section and the storage device cooperate, During the first transition at the end of the pulse from the ON state to the OFF state, energy is collected and stored in the storage device. An electromachine characterized in that, during a second transition at the start of the next pulse from the off state to the on state, the energy collected and stored in the storage device is applied to the electromachine, thereby shortening the transition time in the second transition compared to the case where the stored energy is not applied.

2. An electrical machine according to claim 1, characterized in that the energy collected from the winding portion is magnetic energy from the winding portion.

3. In the electrical machine according to claim 1, The storage device for storing the collected energy is connected between the first power rail and the second power rail. An electromachine characterized in that the collected and stored energy is applied by the storage device such that the potential difference between the first power rail and the second power rail increases in the second transition.

4. The electrical machine according to claim 3, wherein the storage device is a capacitor, and the capacitor has a first plate connected to the first power rail and a second plate connected to the second power rail.

5. In the electrical machine according to claim 4, An electromachine characterized in that the capacitor is configured to (a) store the energy collected during the first transition, and (b) in each of the second transitions, apply the stored energy such that the potential difference between the first power rail and the second power rail increases.

6. An electric machine according to claim 1, characterized in that the controller is further configured to control the operation of the electric machine in either a continuous mode or a pulse mode.

7. In the electrical machine according to claim 6, the controller further comprises: (a) Check whether the requested output of the electrical machine is greater than or less than the threshold of the electrical machine. (b) If the requested output is greater than the threshold, the electromachine is operated in the continuous mode, (c) An electromachine configured to operate in pulse mode when the requested output is smaller than the threshold.

8. In the electric machine according to claim 1, the controller further operates the electric machine in the pulse mode, (d) Define the amplitude for one or more pulses, and if the defined amplitude is greater than or equal to the threshold, (e) Define a duty cycle for the one or more pulses, (f) The system is configured to define the frequency of the one or more pulses, The amplitude, duty cycle, and frequency are defined such that the working output of the electromachine during one or more pulses matches the requested output of the electromachine.

9. An electric machine according to claim 1, characterized in that the first transition occurs at the falling edge of each pulse and the second transition occurs at the rising edge of each pulse.

10. The electromachine according to claim 1 further comprises a boost circuit, An electromachine characterized in that the boost circuit includes the storage device and one or more switches connected between the power supply and the switch network, the switch network controlling power to and / or from the electromachine.

11. An electric machine according to claim 10, wherein the boost circuit further includes a boost power supply, and the boost power supply is selectively connected to one or both of the first power rail and the second power rail by one or more switches.

12. The electric machine according to claim 11, characterized in that the boost circuit effectively increases the potential between the first power rail and the second power rail at the rising edge of each of the second transitions.

13. An electric machine according to claim 1, further comprising a switch network including a set of switches connected between a first power rail and a second power rail in each phase of the electric machine, wherein the collected energy is continuously applied to each phase of the switch network when the electric machine is operating in pulse mode.

14. In the electrical machine described in claim 1, the electrical machine is DC motor or DC generator, AC motor or AC generator, inductor, Pulse width controlled electromechanical device, An electrical machine characterized by being one of the following: a synchronous AC machine.

15. In the apparatus, A power converter connected between a power source and an electrical machine, (a) an on-pulse period during which the electromachine operates above a predetermined efficiency threshold and generates a working output by transmitting or receiving pulsed power, (b) A power converter configured to operate the electric machine in pulse mode by alternating between a second period during the on-pulse period, in which the electric machine does not generate much work output, and a second period during which the electric machine does not generate much work output. The apparatus is characterized by comprising a boost circuit connected to the power converter, wherein the boost circuit includes a capacitor and one or more switches connected between a power supply and a switch network, and the switch network controls the power to and / or from the electromachine, thereby shortening the rise time of pulsed power compared to when the boost circuit is not present.

16. The apparatus described in claim 15 is further, The apparatus comprises a decision module configured to receive a request signal and to make a decision to operate the electromachine in continuous mode or pulse mode in response to the reception of the request signal, wherein in pulse mode, the electromachine transitions between (a) the on-pulse period and (b) a second period between the on-pulse periods.

17. In the apparatus according to claim 16, the decision module is If the request signal is greater than the predetermined efficiency threshold, the electromachine is operated in the continuous mode. The apparatus is characterized in that, when the request signal is smaller than the predetermined efficiency threshold, the electromachine is operated in the pulse mode.

18. The apparatus according to claim 15 further comprises a decision module configured to receive a request signal, The decision module, upon receiving the request signal, If the received request signal is smaller than the predetermined efficiency threshold, a decision is made to operate the electromachine in the pulse mode. The power converter is configured to generate a modulated waveform for operating in the pulse mode, causing the electromachine to transition between (a) the on-pulse period and (b) the second period between the on-pulse periods. The apparatus is characterized in that the average output of the electromechanism during the on-pulse period and the second period matches the requested signal.

19. The apparatus according to claim 18 further comprises a feedback sensor for generating a feedback signal indicating the angular position of the rotor of the electromachine, The apparatus is characterized in that the decision module is further configured to adjust the modulated waveform using the feedback signal.

20. The apparatus according to claim 19 further comprises a torque and speed estimator, the estimator providing the decision module with estimated values ​​of the torque and speed of the electromachine in response to the feedback signal.

21. In the apparatus according to claim 15 The power converter includes a switch network, The device is characterized in that the switch network has a set of switches connected between a first power rail and a second power rail in each phase of the electrical machine.

22. The apparatus according to claim 15, wherein the boost circuit is further configured to collect and store energy from the winding portion of the electromechanism during the falling time of the pulsed power, and to apply the collected and stored energy to the power rail during the rising time of the pulsed power.

23. In the apparatus according to claim 15, the power converter further comprises (a) Pulse width modulation (PWM), (b) Direct Torque Control (DTC), (c) Hysteresis, and (d) Current modulation, the apparatus is configured to control the flow of energy to or from the electromachine using one of these protocols.

24. In the apparatus according to claim 15, the electrical machine is DC motor or DC generator, AC motor or AC generator, inductor, Pulse width controlled electromechanical device, A device characterized by being one of the following: a synchronous AC machine.

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