System and method for permanent magnet assisted synchronous reluctance motor control from zero or low speed

Abstract

To provide a system and method for robust sensorless control of a permanent magnet assisted synchronous reluctance (PM-SyR) motor.SOLUTION: A system and method includes startup control of a motor with known rotor position / speed, but unknown rotor magnetic polarity of a motor exhibiting rotor magnetic anisotropy or saliency. The system and method includes a rotor characteristic detection method for a PM-SyR motor that detects rotor magnetic polarity based on the variation of the inductance that is caused by leakage flux paths in rotor barrier bridges and utilizes the detected rotor magnetic polarity for improved motor startup.SELECTED DRAWING: Figure 1A-1B

Description

[Technical field]

[0001] The present invention relates generally to robust control of permanent magnet assisted synchronous reluctance motors ("PM-SyR"). Various embodiments relate to sensorless robust closed loop control starting from zero or low speed. [Background technology]

[0002] Sensorless permanent magnet synchronous motor ("PMSM") systems are beginning to be deployed in certain fan and blower driven applications, such as heating, ventilation, and cooling ("HVAC") systems, as well as various other commercial and industrial motor driven products. Sensorless PMSMs (also referred to as sensorless PMSM systems) are a type of advanced electronically controlled motor ("ECM") or ECM system. Sensorless PMSM systems can generally provide high peak efficiency at rated operating speeds as well as have a relatively large high efficiency operating speed range. In addition, the variable speed of sensorless PMSM systems also allows for low capacity operation during off-peak periods, such as at night, which can result in significant energy savings. In addition, these electronically controlled PMSM systems can also provide opportunities for artificial intelligence control and remote control through various communication technologies, such as cloud communication, to improve operating energy savings, accessibility, monitoring, safety, and reliability.

[0003] Modern PMSMs are designed with magnets embedded inside the rotor structure, which is usually referred to as an internal PMSM ("IPMSM"). Often, IPMSMs use Ned-Fe-B rare earth magnets to provide high performance with certain electromagnetic, mechanical, and economic benefits. In particular, Ned-Fe-B based IPMSMs can reach certain power density or torque density rates with small motor body sizes under proper cooling system design, which can be useful in many applications such as electric vehicles and other applications where relatively small motor sizes provide advantages. Known IPMSM design rules and principles are widely applied in various applications such as industrial drives, electric vehicle motors, and wind turbine generators. These uses have led to an increasing demand for Ned-Fe-B magnets. However, due to limited supply of rare earth magnets, the price of Ned-Fe-B magnets continues to rise, thereby increasing the cost of IPMSM systems. For this and other reasons, it is desirable to develop new types of motors that can provide comparable performance at a lower cost.

[0004] Recently, due to its performance and low cost, permanent magnet assisted synchronous reluctance (PM-SyR) motors are becoming relatively attractive and popular. In general, PM-SyR motors are electric motors that combine features of both permanent magnet and synchronous reluctance motors. It has a stator with wound coils that generate a rotating magnetic field, and a rotor with permanent magnets as well as salient poles that alternate in a north and south magnetic pole pattern. The shape and configuration of the rotor magnetic barrier with the permanent magnets creates PM flux torque as well as reluctance torque to contribute to the motor's output torque. The combination of the permanent magnets in the rotor and the reluctance effect creates a motor with high torque density and efficiency. Basically, PM-SyR motors are evolved from synchronous reluctance motors to provide improved performance by inserting magnets into the rotor magnetic barrier, thereby primarily improving power factor as well as other performance metrics.

[0005] Typically, low-cost ferrite magnets are used in the motor in design and manufacture. Synchronous reluctance motors generally have a relatively large saliency factor L q / L d (5-6), and the reluctance torque dominates the total torque generating capability in addition to the main flux torque generated by the magnets. Meanwhile, due to the use of ferrite magnets, the main flux can be very small in comparison with that of Ned-Fe-B rare earth permanent magnet materials.

[0006] Overall, because PM-SyR motors are essentially a specialized type of IPMSM, control techniques for fan or blower drive applications in general, such as stable closed-loop start-up control and robust control under harsh operating conditions, are equally applicable to PM-SyR motors. Generally, for example, U.S. Pat. No. 10,784,805, issued on September 22, 2020 to Bojoi et al. and entitled "SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL FROM ZERO OR LOW SPEED," U.S. Pat. No. 10,819,264, issued on October 27, 2020 to Bojoi et al. and entitled "ROBUST STARTING SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," and U.S. Pat. No. 10,819,264, issued on February 1, 2022 to Bojoi et al. and entitled "SYSTEMS AND METHODS FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL." No. 11,239,772, entitled "IPMSM CONTROL," may be applied to PM-SyR motor control, all of which are incorporated herein by reference in their entirety. While IPMSM control methods may have application to PM-SyR motors, there is room for improvement to PM-SyR motor control based on its particular characteristics. For example, the present disclosure provides improved motor control for PM-SyR motors during motor start-up (i.e., at zero or very low speeds), particularly for polarity detection.

[0007] For example, because a relatively large number of commercial and industrial fans and blowers are driven by PM-SyR motor systems due to their ability to deliver relatively high performance with significant cost savings, there is a need for new control systems and methods specific to PM-SyR motors. For example, there is a need for control schemes that can handle the inherent problems of PM-SyR motors at start-up (e.g., zero or very low speeds) to provide efficient and stable speed control of commercial and industrial fan and blower driven applications. Summary of the Invention

[0008] The present invention provides a system and method for stable sensorless control of a permanent magnet assisted synchronous reluctance (PM-SyR) motor. The system and method includes start-up control of the motor using closed loop control from a stopped condition including zero motor speed or low motor speed range. The rotor characteristic detection method includes a signal injection method that can detect certain rotor characteristics such as rotor position, rotor speed, and rotor magnetic polarity of a motor having rotor magnetic anisotropy or saliency, according to one embodiment of the present disclosure.

[0009] Due to the inherent characteristics of PM-SyR motors, especially ferrite PM-SyR motors, conventional IPMSM rotor characteristic detection methods are not accurate. The present disclosure provides an improved rotor characteristic detection method for PM-SyR motors that can detect rotor position, rotor speed, and rotor magnetic polarity based on the variation of inductance generated by the leakage flux path in the rotor barrier bridge.

[0010] The inductance variation created by the leakage flux path in the rotor barrier bridge improves the stability and reliability of polarity detection due to the small current pulses in the polarity detection process. The flux density in the main flux path and the leakage flux path in the motor design influences the underlying characteristics during polarity detection and also factors into its effectiveness. The effectiveness of polarity detection can be verified during the motor design stage to ensure proper starting from a stop or low speed range based on the initial rotor speed / position determined from, for example, high frequency injection methods.

[0011] Due to the poor magnetic performance, ferrite-based PM-SyR motors set up a low magnetic flux density in the main magnetic flux path that is not saturated. Furthermore, the motor barriers generate a large reluctance. Therefore, the stator magnetomotive force ("MMF") generated by the stator winding current cannot saturate the main magnetic path, but only the leakage flux path in the barrier bridge. It is this saturation of the leakage flux path in the barrier bridge that allows the high frequency injection method to detect the rotor position based on the saliency setup on the rotor surface structure. Furthermore, the change of the leakage flux path in the barrier bridge influenced by the stator current can also be exploited to determine the rotor polarity at standstill or low speed.

[0012] These and other objects, advantages, and features of the present invention may be more fully understood and appreciated with reference to the following detailed description of the present embodiments and drawings.

[0013] Before describing the embodiments of the invention in detail, it is to be understood that the invention is not limited to the details of operation or to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention can be implemented in various other embodiments and can be practiced and carried out in alternative ways not expressly disclosed herein. It is also to be understood that the phrases and terms used in the specification are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof should be construed to encompass not only the items listed thereafter and their equivalents, but also additional items and their equivalents. Furthermore, enumerations may be used in the description of various embodiments. Unless expressly stated to the contrary, the use of enumerations should not be construed as limiting the invention to any particular order or number of components. Nor should the use of enumerations be construed as excluding from the scope of the invention any additional steps or components that may be combined with or within the recited steps or components. Any reference to a claim element as "at least one of X, Y, and Z" should be construed to include any of X, Y, or Z individually, and any combination of X, Y, and Z, such as X, Y, Z, X, Y, X, Z, and Y, Z.

[0014] The patent or patent application file contains at least one drawing executed in color. Copies of this patent or patent application with one or more color drawings will be provided by the U.S. Patent and Trademark Office upon request and payment of the necessary fee. [Brief description of the drawings]

[0015] [Figure 1A-1B] 1A and 1B show front and side views of a commercial centrifugal fan or blower diagram, thereby showing the rotating fan wings and airflow direction prior to motor start-up.

[0016] [Diagram 2] FIG. 2 illustrates an exploded view of a ferrite PM-SyR motor according to one embodiment of the present disclosure.

[0017] [Figure 3A] FIG. 3A shows an assembled front perspective view of the PM-SyR of FIG.

[0018] [Figure 3B] FIG. 3B shows an assembled rear perspective view of the PM-SyR of FIG.

[0019] [Figure 4] FIG. 4 illustrates a block diagram of a control system according to one embodiment of the present disclosure.

[0020] [Diagram 5] FIG. 5 shows the reference axes for a PMSM.

[0021] [Figure 6] FIG. 6 shows the SyR motor frame reference notation as well as the PM motor frame reference notation.

[0022] [Figure 7A-7B] 7A and 7B show the detection of magnet polarity by the peak value of the current pulse, where the signal injection method detects the magnet polarity in the d-axis.

[0023] [Figure 8] FIG. 8 shows an example voltage pulse for the magnetic polarity detection method, illustrating the pulse amplitude, width, and position.

[0024] [Figure 9A] FIG. 9A shows the direct magnetic model, which shows the d-axis magnetic flux increasing rapidly with increasing current.

[0025] [Figure 9B] FIG. 9B shows the inverse magnetic model, which shows increased inductance and reduced current compared to the negative one.

[0026] [Figure 10A-10D] Figures 10A and 10B show magnet polarity detection by peak value of current pulse, where the polarity detection method detects magnet polarity on the d-axis. Figures 10C and 10D show magnet polarity detection by peak value of current pulse, where the polarity detection method detects magnet polarity on the negative d-axis.

[0027] [Figure 11A] 11A-11B show one embodiment of a ferrite PM-SyR motor, with FIG. 11A showing a partial view of the motor structure and the rotor with a magnetic carrier inserted with magnets.

[0028] [Figure 11B] 11A-11B show one embodiment of a ferrite PM-SyR motor, with FIG. 11B showing leakage flux paths in the rotor lamination barrier bridge.

[0029] [Figure 12A] FIG. 12A shows the no-load FEA results, which show the magnetic flux density distribution and leakage flux density in the bridge.

[0030] [Figure 12B] FIG. 12B shows partial no-load FEA results, illustrating the magnetic flux density distribution and leakage magnetic flux density in the bridge where the rotor was positioned differently relative to the stator than in FIG. 12A.

[0031] [Figure 13A-13B] Figure 13A shows the change in d-axis inductance to reach a peak versus d-axis current, and Figure 13B shows the change in magnetic flux density in the bridge with d-axis current.

[0032] [Figure 13C] FIG. 13C shows the magnetic flux variation when the d-axis current is changed.

[0033] [Figure 14] FIG. 14 shows the FEA simulation results, which show the current pulses for polarity detection.

[0034] [Figures 15A-15C] 15A-15C show test results of the entire start-up process from zero speed to target speed, where FIG. 15A shows the speed command and actual speed follow-up, FIG. 15B shows the actual phase currents during the start-up process, and FIG. 15C shows the control variable state updates.

[0035] [Figures 16A-16D] 16A-16D show zoomed-in output in the start-up process, where FIG. 16A shows velocity, FIG. 16B shows position angle determination in the polarity detection process, FIG. 16C shows current pulses during polarity detection with alignment to the d-axis, and FIG. 16D is the control variable update.

[0036] [Figures 17A-17D] 17A-17D show the rotor polarity detection process with reverse alignment to the d-axis, FIG. 17B shows position angle compensation of 180 electrical degrees, and FIG. 17C shows the current pulse waveform for a negative polarity detection result. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The present disclosure is generally directed to control methods used in conjunction with permanent magnet assisted synchronous reluctance ("PM-SyR") motors. Figures 1A and 1B show front and side schematic views, respectively, of an exemplary commercial or industrial centrifugal fan 10 utilizing such a motor. The figures show exemplary components including fan blades 11, an electronically controlled motor ("ECM") 12 (specifically, a PM-SyR motor), and an assembly structure 13. As the fan blades 11 are driven by the ECM 12, they rotate at a particular speed and direction of rotation, thereby generating airflow. The fan can generate a prescribed airflow to meet airflow requirements based on the configuration and / or programming of the motor electronics, which are typically contained within the motor.

[0038] Some of the components and control elements suitable for use in embodiments of the present disclosure having PM-SyR motors are described in 1) U.S. Pat. No. 10,784,805, issued on September 22, 2020 to Bojoi et al. and entitled "SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL FROM ZERO OR LOW SPEED," 2) U.S. Pat. No. 10,819,264, issued on October 27, 2020 to Bojoi et al. and entitled "ROBUST STARTING SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," and 3) U.S. Pat. No. 10,819,264, issued on February 1, 2022 to Bojoi et al. and entitled "SYSTEMS AND METHODS FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL." The same or similar components and control elements are described in connection with a sensorless interior permanent magnet synchronous motor ("IPMSM") in U.S. Pat. No. 11,239,772 entitled "Sensorless Interior Permanent Magnet Synchronous Motor ("IPMSM") Control Circuit, which are incorporated herein by reference in their entireties.

[0039] 2 and 3A-3B show exploded front and rear perspective views, respectively, of an exemplary embodiment of a PM-SyR motor 300 in accordance with an embodiment of the present disclosure. The motor depicted is a PM-SyR motor system 300 that uses low-cost ferrite magnet material.

[0040] Briefly, the exemplary PM-SyR motor system 300 includes a motor control system 224, a stator 223, and a rotor 225. This embodiment of the stator 223 is surrounded by heat dissipation ribs 240. The motor control system 224 is mounted on top of the motor body to the heat dissipation ribs using a backpack configuration and interfaces, which are described in more detail below. A frame 227 is secured to (or integral with) the stator or subcomponents thereof, such as the heat dissipation ribs along the exterior of the cylindrical stator 223, and together with the foot mounting structure provides a mechanical structure to support and secure the motor in place. In alternative embodiments, the PM-SyR motor system can include additional, different, or fewer components, which can be configured in similar or different ways to provide a PM-SyR that can be arranged and / or mounted in essentially any suitable manner.

[0041] The depicted embodiment of the motor has a housing or enclosure 234 including a front end shield 221, a mid shield 229, and a rear end shield 230. The three shields can be coupled to cooperatively form a motor enclosure 234 or motor housing. A lubricant or oil seal can surround a drive shaft 233 that extends out of the motor enclosure 234 and seals the front end shield 221. In alternative embodiments, the motor enclosure can be formed from additional, fewer, or different components that cooperate to house the motor in essentially any suitable manner that enables the motor to convert electrical energy to mechanical energy, for example, to rotate the drive shaft. In this embodiment, a motor controller housing 224 is attached at the top of the motor stator 223. The motor controller housing 224 can include a base housing 250 and a cover 252 that cooperate to provide a sealed motor controller enclosure for the PM-SyR motor electronics, including the PM-SyR motor controller 226.

[0042] The motor control system 226 has the ability to drive the multi-phase AC electromagnetic system of the stator 223 to generate a magnetic field that rotates in time with the oscillation of the line current. The stator can have essentially any suitable winding configuration that defines a suitable number of stator poles that are complementary to the rotor poles. This embodiment includes a three-phase stator winding configuration with four stator poles. Once in a steady state, the rotor 225 rotates in steps with the stator 223, for example, via permanent magnets embedded in the rotor, thereby rotating the stator drive shaft 233. The motor can include a bearing assembly 222 having one or more bearings that support and position the rotor 225 to maintain a small and consistent air gap between the stator 223 and the rotor 225. The motor control system 226 can include a controller on a printed circuit board that is physically coupled to the motor controller enclosure 224.

[0043] The motor controller enclosure can provide an airflow passage for dissipation of heat generated by the electronic components. Between the mid shield 229 and the rear end shield 230 can be included a rotating fan 229 that drives airflow through the base housing 250 of the motor controller system 224, over the PCB of the motor controller 226, and through ventilation holes in the cover 252 of the motor controller housing. The rear end cover 230 has ventilation holes that allow airflow through for cooling purposes.

[0044] A general description of the motor control system 226 according to the present disclosure will now be given with reference to FIG. 4. In general, the motor control system 226 may include one or more microcontrollers, microprocessors, and / or other programmable electronic circuits programmed to perform the functions described herein. In this embodiment, there are two microcontrollers or microprocessors, but in alternative embodiments, there may be more or fewer microcontrollers. The first microcontroller 444 (referred to as MCU-1) is configured with various motor control algorithms and methods to perform calculations that provide dynamic motor response with timing ranges in microseconds. Thus, the MCU-1 microcontroller 444 includes a microcontroller with relatively strong computing power. The second microcontroller 447 (referred to as MCU-2) is implemented with intelligent sensing and monitoring algorithms to perform sensing, monitoring, and interface functions. In general, the computing power of the second microcontroller (MCU-2) 447 may depend on the sophistication of the sensing algorithms implemented. Communications, including real-time communications between the two microcontrollers 444, 447, may be handled over a controller area network (bus) or other communications path using the CAN protocol or another suitable protocol. Details regarding the various motor controller software of the present disclosure, including both motor control and sensing algorithms, are described in further detail below.

[0045] The hardware architecture of the two microcontrollers provides flexibility for both the motor control and the system control interfaces to extend their functionality separately without impact on each other. Other electronic components may include, without limitation, one or more field programmable gate arrays, systems on chips, volatile or non-volatile memory, discrete circuits, integrated circuits, application specific integrated circuits (ASICs), and / or other hardware, software, or firmware. Such components, whether combined as a single unit or distributed across multiple units, may be physically configured in any suitable manner, such as by mounting them on one or more circuit boards or otherwise configuring them. Such components may be physically distributed at different locations within the motor 300, or they may reside in a common location on top of the motor assembly, such as, for example, in the motor controller housing 224. When physically distributed, the components may communicate using any suitable serial or parallel communications protocol, such as, without limitation, SCI, WiFi, Bluetooth, FireWire, I2C, CAN, RS-232, RS-485, and Universal Serial Bus (USB).

[0046] 4, one embodiment of the motor control system 226 includes a combination of various different electronic components including, without limitation, a power circuit 441 (e.g., an inverter) for converting a three-phase power source 450 to an appropriate voltage, current, and frequency, a drive circuit 442 for driving the stator windings of the motor based on drive commands, and a sensing circuit 442 for sensing one or more motor characteristics used in one or more motor control methods or motor speed estimation methods. This exemplary embodiment of the motor control system 226 includes a microcontroller unit 444 configured with one or more motor control methods (e.g., one or more motor speed estimation methods) configured to provide drive commands to the drive circuit 442 based on the sensed motor characteristics, and a command input interface 445 that provides various command inputs to the controller 444. The command input interface 445 can be configured to receive commands from an external device, such as a product system controller or another higher level control board. The motor control system can include a monitoring interface 446 for monitoring motor operation including one or more motor control methods. The monitoring interface 446 can also communicate the received sensing and monitoring information to an external device, such as a higher level control board. For example, the command input interface 445 and the monitoring interface 446 can communicate with an external device via a transceiver or other communication device by utilizing essentially any communication protocol, such as a wireless communication protocol, such as Bluetooth or WiFi.

[0047] The further microcontroller unit 447 can be configured with further sensors 448, such as sensors located within the motor 234 and / or motor controller housing 224, as well as various sensing and monitoring algorithms that can receive output variables from the other microcontroller 444. For example, the further sensing circuitry 448 can include temperature sensors, vibration sensors, or essentially any other sensor that can provide an appropriate sensor output (e.g., a sensor output indicative of motor performance, motor efficiency, and / or motor operating conditions).

[0048] Many motor control algorithms, including the embodiments of the PM-SyR motor control algorithms described herein, are perhaps best understood with reference to a clearly defined vector reference frame. In FIG. 5, a vector reference frame 30 is defined for a generic radial interior PMSM motor employed. This same vector reference frame may be utilized in relation to a PM-SyR motor, which is a specific type of interior PMSM motor. The stator 36 is configured such that when powered on, each of the three phase currents (i a , i b , i c ) which can be transformed to a stationary frame (α-β) 31. The rotor 37, rotating at synchronous speed, can have a salience structure resulting in different permeabilities and inductances between the pole center line d-axis and the perpendicular line q-axis, together referred to as the synchronous rotor frame (dq-axis) 33. For example, the rotor structure of the rotor 37 is a two-pole rotor design for ease of explanation. However, various embodiments are not limited to rotors with two poles, and PM-SyR high frequency injection and polarity detection can be utilized in connection with essentially any motor having a magnetic salience structure including rotors with other numbers of poles, such as the embodiment of FIG. 2 showing a rotor with four magnetic poles.

[0049] FIG. 6 shows an example cross section of a typical 4-pole combination of two types of motors: a Synchronous Reluctance (SyR) motor (left) 61 and a PM-SyR motor (right) 62. In general, there is no significant difference in the stator winding structure 63 when building either of these two motors. A SyR motor is a synchronous motor whose rotor has multiple flux barriers 64. In this drawing, the SyR motor includes three flux barriers 64 as shown. The torque generated is due to magnetic anisotropy, as shown in FIG. 6. When the stator generates a stationary magnetic field, the high permeability axis of the rotor will align with the magnetic field to minimize system energy. When the stator magnetic field becomes a rotating field, the rotor will rotate in the same direction. Even though the SyR motor has small rotor losses and thus high efficiency in operation, it has a small power factor (0.6 to 0.7) because the stator requires a large reactive current to magnetize the machine.

[0050] The PM-SyR motor is an evolution of the SyR motor, which uses magnets 65 in the flux barrier 64 to improve the power factor (right side of FIG. 6) and thus improve efficiency relative to the SyR motor (without the magnets shown in the left half of FIG. 6).

[0051] As shown in FIG. 6, the definition of the (d,q) rotor frame can be defined by using two different conventional approaches: PM notation: The d-axis is defined by the north pole of the magnet, as occurs in the case of Surface Mounted PM (SMPM) and Internal PM (IPM) motors. In this reference frame, the flux vector of the magnet is aligned with the d-axis. SyR notation: The d-axis is defined as the direction of maximum magnetic permeability. In this reference frame, the magnet's flux vector lies on the negative q-axis.

[0052] Any reference frame (or entirely another reference frame) may be used in the implementation of a PM-SyR motor controller according to the present disclosure. However, to maintain compatibility with previous patent applications for interior permanent magnet motors (previously incorporated by reference), the adopted reference frame utilized throughout this disclosure uses PM notation. Of course, it should be noted that any notation (or entirely another notation) may be adopted. Thus, the magnetic model (where cross saturation is neglected) and electromagnetic torque for PM-SyR has the same mathematical form as in an IPM device:

number

[0053] Where: T m is the electromagnetic torque of the motor, T rel is the reluctance torque due to magnetic anisotropy, T PM is the PM torque due to the magnet.

[0054] One difference between PM-SyR and IPM motors is the different relationship between the reluctance torque due to magnetic anisotropy and the permanent magnet torque due to the magnets. In PM-SyR motors, especially when using ferrite magnets, the reluctance torque may be the majority of the torque generation or may be dominant in relation to the torque generation generated by the ferrite permanent magnets. Furthermore, the main magnetic flux generated by ferrite permanent magnets may not be as strong as that generated by other high performance magnets such as Ned-Fe-B magnets, resulting in a lower saturation state than the stator flux path under main field, no load conditions.

[0055] Known interior permanent magnet control techniques can theoretically be applied to control a PM-SyR motor system over its entire speed range with certain load conditions. However, there are certain problems that can arise in the context of PM-SyR motor control that are not present in other types of interior permanent magnet motors. For example, in the case of permanent magnet assisted synchronous reluctance motors, the position dependency of inductance generated by the rotor magnetic salience is often used to estimate the pole position in the low or zero speed range. However, in these situations, the polarity of the rotor magnetic poles is unknown, which can create problems during start-up. Therefore, improved motor control methods can be provided to improve the performance, reliability, and other metrics of PM-SyR motor control. For example, a method to efficiently and effectively determine the magnetic polarity of rotor magnetic poles whose pole positions are known (e.g., estimated) can significantly improve motor control methods.

[0056] I. Rotor magnet polarity detection for PM-SyR motors

[0057] Because torque generation in ferrite magnet based PM-SyR motors is dominated by reluctance torque, not permanent magnet torque, some effective starting methods may not work reliably at zero or very low starting speeds. This is typically the case because the stopping position of a PM-SyR motor will not be aligned with the d-axis, but instead will typically be aligned with an intermediate angle between the d-axis and q-axis. Thus, IPM starting methods that rely on d-axis or q-axis alignment at zero or low speeds are generally not viable for PM-SyR motors.

[0058] High frequency injection ("HFI") is the basis of one form of rotor pole position detection. High frequency injection generally refers to injecting high frequency current into the stator winding of an AC motor. In response to the high frequency current being injected into the stator winding, it generates a magnetic field that interacts with the rotor of the motor. By analyzing the rotor's response to the injected current, further control over the motor is possible. By injecting high frequency current into the stator, a rotating magnetic field can be generated that is out of phase with the normal operation of the motor. This can be used to reduce the starting current of the motor or to more accurately control the speed of the motor. U.S. Pat. No. 10,784,805, issued Sep. 22, 2020 to Bojoi et al. and entitled "SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL FROM ZERO OR LOW SPEED," previously incorporated by reference in its entirety, describes a manner in which HFI can be utilized to control the start-up of an interior permanent magnet synchronous motor.

[0059] HFI methods with pulsed carriers generally have an uncertainty of 180 electrical degrees in tracking the d-axis of a motor because it goes to zero twice in one electrical cycle. That is, the HFI method can determine the rotor position in terms of the position of the magnet relative to the stator, but cannot determine the magnetic polarity of the permanent magnet. For example, referring to Figures 7A-7B, previous HFI methods can determine that the permanent magnet is positioned as shown in Figures 7A and 7B, but the method cannot distinguish the polarity of the magnet and therefore cannot distinguish between two different rotor positions. This is because the HFI method relies on magnetic salience being the same along the d-axis regardless of which permanent magnet is a north pole magnet and which is a south pole magnet.

[0060] As shown in Figures 7A-7B, two possible situations can occur. In the first case, the HFI position detection method detects the motor's d-axis (positive). In this situation, the rotor's actual main flux axis 71, the rotor's estimated main flux axis 72, and the rotor magnets' flux linkage vector position 73 are all aligned together in Figure 7A. In the second case, the HFI method detects the negative d-axis. Referring to Figure 7B, the rotor's actual main flux axis 74 and the rotor magnets' flux linkage vector position 76 are aligned, but the rotor's estimated main flux axis 75 differs from the actual main flux axis 74 by 180°.

[0061] Therefore, after the execution of the HFI method, further testing is required to identify whether the detected axis is the positive d-axis (FIG. 7A) or the negative d-axis (FIG. 7B), i.e., to detect the magnet polarity.

[0062] To perform polarity detection, a special voltage waveform can be used as the detection profile. In one embodiment, the waveform is +V pulse and -V pulse 8 shows a waveform of a particular amplitude V on the sensed axis and on the negative sensed axis. pulse 81 and time length t pulse 8 shows two voltage pulses having a distance 82 that is the span length 83 of the motor rotor pole.

[0063] By assuming low speed range (-10 to +10 RPM) or no rotor motion, the equation for the detected d-axis voltage is:

number

[0064] By neglecting the voltage drop across the stator resistance, (11) becomes:

number

[0065] The d-axis voltage includes two voltage pulses 84 of identical volt-seconds defined as shown in FIG.

number

[0066] d-axis current i d The d-axis inductance L changes as d The characteristics of the variations can be obtained by processing magnetic model methods that express the relationship between current and magnetic flux. These curves are different in the case of PM-SyR motors than in IPM motors, which means that the methods to accurately detect the polarity are different.

[0067] As shown in FIG. 9A, in the case of the PM-SyR motor, the d-axis current i d is positive, but from 0A to about i d Below a certain current value, such as within the range of <2.5A, the d-axis flux linkage λ d increases with a steep slope 91, resulting in a d-axis inductance L d increases rapidly and nonlinearly (there is a direct relationship between the d-axis flux linkage and the d-axis inductance). In contrast, when the d-axis current is negative, i.e., i d <0, when the d-axis flux linkage λ d and inductance L d The magnetic behavior of the PM-SyR is highly linear with changes in d-axis current. This pronounced contrast in response to positive and negative d-axis currents can be exploited for efficient and effective PM-SyR polarity detection. If necessary, the controller can be configured to apply positive and negative voltage pulses to the stator winding configuration. Depending on the current response to the positive and negative voltage pulses, the magnetic polarity of the poles can be determined based on the relative magnitude of the current response.

[0068] The pulse magnitudes can be selected such that one of the positive and negative voltage pulses demagnetizes the directionally magnetized flux density in one or more of the rotor surface bridges and the other further magnetizes the flux density in at least one of the surface bridges. When the flux density in one or more of the rotor surface bridges is demagnetized, the inductance increases, resulting in a lower relative response current than when the flux density in the rotor surface bridges is further magnetized.

[0069] The magnetic model can be further processed in MATLAB® or another analysis tool to obtain an inverse magnetic model of the relationship between the magnetic flux fluctuation and the current. Figure 9B shows such a characteristic curve for an example PM-SyR motor. A magnetic flux fluctuation of 0.2Vs applied in both the positive and negative directions results in a very large d-axis current difference (2.2A).

[0070] There is a reflection point "A" on the magnetic model curve 92. In the range from 0 to this point, the d-axis inductance L d increases nonlinearly and rapidly. Above this point, the d-axis inductance L d changes to different variation characteristics. This characteristic, along with the relatively small current when the d-axis current is below this reflection point, is unique to ferrite PM-SyR motors and can be exploited to make polarity detection relatively accurate and stable. As described below, the polarity detection method can be adapted to accommodate other types and configurations of PM-SyR motors, for example, PM-SyR motors that utilize other types of magnets or have different numbers and configurations of flux barriers.

[0071] Exemplary control logic for polarity detection in a ferrite PM-SyR motor is described in detail below. Positive current pulse (+V pulse ) vs. current response (I pulse1) is a negative current pulse (-V pulse ) vs. current response (I pulse2 ), then the PM-SyR radio frequency injection (HFI) properly detects the d-axis and the motor controller utilizes the detected HIF position. Positive voltage pulse (+V pulse ) vs. current response (I pulse1 ) is a negative current pulse (-V pulse ) vs. current response (I pulse2 ), the PM-SyR HFI detects a negative d-axis and, therefore, the motor controller applies a correction to the detected d-axis HFI position (the amount of correction may depend on the number of poles, but for a 4-pole rotor, for example, a 90 electrical degree correction may be utilized).

[0072] With the same volt-second value of the injected voltage, the amplitude of the response current pulse will be different, as shown in FIG. 10A or FIG. 10B (again, shown with a bipolar embodiment for ease of illustration). As shown in FIG. 10A, I pulse1 puse2 If so, then the positive direction of the rotor shaft, i.e., the correct magnet polarity 104 in FIG. 10A, is estimated.

number

[0073] In the first case depicted in connection with Figures 10A-10B, the first current pulse 101 is less than the second one 102, and therefore the HFI method provides a correct estimated rotor position that matches the actual rotor positions 103 and 104.

number

number

[0074] In comparison to known HFI methods (such as those described in U.S. Patent No. 10,784,805, previously incorporated by reference in its entirety), the logic for detecting the correct polarity for ferrite PM-SyR motors is unexpectedly generally reversed from that for IPM motors. The two types of motors have different structures and characteristics that cause this, as will be described below.

[0075] In addition, since the position and speed can be detected through the HFI process before polarity detection, the position / speed information can be stored in the t pulse It can be used as the input to the polarity-detecting current pulse integration process in equation (5).

[0076] II. Polarity detection effectiveness in PM-SyR motors

[0077] In FIG. 9A and FIG. 9B, the d-axis inductance L dThe characteristics of the increase in flux variation and d-axis current are shown. These example values ​​can be obtained through magnetic modeling and empirical testing. The same relationship between flux variation and d-axis current can be obtained by finite element analysis (FEA) of the motor design. FIG. 11A shows an example ferrite PM-SyR motor FEA design model. The motor stator 111 includes multi-phase windings 112 embedded within slot groups (three slot groups A, B, C in this embodiment). The motor stator 111 of the PM-SyR motor is essentially the same as the stator of an induction motor. The rotor 116 is a synchronous reluctance rotor with a number of flux barriers 115, which may also be referred to as rotor barriers or magnet barriers.

[0078] The rotor 116 may also be referred to as a rotor core. The rotor core may be made of a soft magnetic material, such as laminated silicon steel. It may be shaped as a disk with a central shaft hole. The rotor core may be divided into several poles, which are created by stamping or punching slots 115 in the core. The slots 115 create a flux barrier that prevents magnetic flux from flowing in the wrong direction. The rotor core may be mounted on a motor shaft and rotated by a magnetic field created by exciting a stator winding arrangement (e.g., a three-phase stator winding arrangement).

[0079] A permanent magnet assisted synchronous motor has permanent magnets 117 in slots 115 in a rotor 116. The permanent magnets provide a small amount of torque that aids in starting the motor and improves the power factor and efficiency of the motor.

[0080] The rotor flux barriers 115 can be configured in a particular pattern to control the magnetic flux and generate torque. One configuration of flux barriers is a segmented flux barrier rotor, where the rotor has alternating poles and flux barriers. The flux barriers in a segmented rotor can be made from non-magnetic materials and positioned between the poles to create paths of low magnetic reluctance. This can create high flux density in the poles, which creates torque as the rotor rotates. The configuration and structure of the flux barriers can vary, for example, concentrated flux barriers, semi-distributed flux barriers, and distributed flux barriers are some of the different possible configurations. The selection of flux barriers for a given motor can depend on the specific requirements of the motor, including torque and efficiency, as well as manufacturing and cost constraints.

[0081] Ferrite permanent magnets (or other types of permanent magnets) can be placed in some or all of the slots / flux barriers for power factor improvement. In the depicted embodiment, the rotor 116 includes three layers of flux barriers in a reluctance motor design, where each barrier includes multiple magnets 117. For ease of illustration, FIG. 11A depicts only one-quarter of a four-pole motor, thereby highlighting the relationship between the stator 111 and rotor 116.

[0082] The rotor core may include multiple rotor bridges that span the flux barriers / slots. Perhaps as best shown in FIG. 11B, the bridges may include outer or surface bridges, such as bridges B1, B2, B3 toward the rotor perimeter. The rotor may also include inner bridges (e.g., bridge B4 toward the inner layer of the rotor core), as shown in FIG. 11A. Rotor bridges generally refer to mechanical components that connect the rotor segments together. PM-SyR motors generally include alternating flux barriers 115 and rotor segments 120. To ensure that the rotor segments 120 stay in place and maintain proper alignment during motor operation, rotor bridges may be used to connect the rotor segments together. The rotor bridges may be made of non-magnetic material and may be located toward the ends of the rotor segments, connecting them to form the rotor assembly 116. The bridges can provide mechanical stability to the rotor and can prevent axial movement or any deformation between the rotor segments. The characteristics and number of rotor bridges can vary depending on the specific embodiment of the PM-SyR motor, such as the rotor diameter, the number of rotor segments, and the operating conditions. In general, the bridges are designed to be light and strong enough to withstand the centrifugal forces generated during motor operation while providing little magnetic interference to the magnetic field within the motor. In general, the size of the bridges is balanced to provide adequate mechanical strength of the rotor structure while keeping the leakage flux low. In this respect, it is preferable that the width of the bridges is as small as possible, since the larger the bridge, the greater the leakage flux, although manufacturing requirements generally require the bridges to be greater than about 1.0 mm thick to meet the desired mechanical rotor strength.

[0083] Stator laminations refer to components in electric motors that are manufactured from thin sheets of electrical steel. The sheets can be laminated together and then cut and formed into specific shapes to produce the stator core. Stator laminations are generally responsible for providing the magnetic field that interacts with the rotor to generate electromagnetic forces that generate the desired rotational torque or mechanical power. The thin sheets of steel (or other materials) used in the stator laminations can be coated with an insulating material to prevent current from flowing between the sheets and generating energy loss in the form of heat. The sheets can also be punched with holes to accommodate wires, usually copper windings, that carry the current through the stator. The shape and size of the holes as well as the spacing of the sheets can be selected based on various factors and can affect the performance of the motor based on various metrics.

[0084] Rotor laminations are similar to stator laminations. They are also composed of thin sheets of electrical steel that are laminated together and then cut and formed into a specific shape to create the rotor core. The rotor laminations rotate within the magnetic field generated by the stator, thereby generating the desired rotational torque or mechanical power. Like stator laminations, the thin sheets of steel used in rotor laminations are also coated with insulating materials to prevent energy loss due to eddy currents. The shape and size of the rotor laminations can be designed to optimize the performance of the motor by considering factors such as torque, speed, and power factor.

[0085] At any given rotor position relative to the stator, there is a main flux path between rotor flux path segment 120 and the stator 111. There is also a no-load leakage flux path through the surface bridges (e.g., through B1, B2, B3) with the directionally magnetized flux density produced by the permanent magnets 117.

[0086] FIG. 12A shows a no-load operating condition FEA magnetic field distribution map for an example PM-SyR motor. That is, the magnetic flux density distribution throughout the stator and rotor due to the magnetic field generated by the permanent magnets is depicted. As depicted, many of the no-load leakage flux paths through the bridges (e.g., B1, B2, B3) are at or near magnetic saturation due to the magnetic fields of the magnets. The particular rotor barrier design and resulting magnetic flux densities allow for a stable starting motor control algorithm with accurate polarity detection. The rotor magnetic polarities for this rotor position are shown at 125 and 126. Although north and south poles are depicted in FIG. 12A, at start-up, these polarities are unknown and only the rotor position is known. In the case of the four-pole rotor shown, the method of polarity detection can determine whether the d-axis is in the depicted position toward one of the north poles or, alternatively, whether the d-axis is pointed toward one of the south poles. In this 4 pole configuration, there are two north poles and two south poles. In other configurations, for example having 6, 8, 10 or even more poles, there may be 3, 4, or 5 north poles and 3, 4, or 5 south poles. In these situations, the polarity detection method can determine if the d-axis is aligned with the south or north pole.

[0087] Motor behavior at start-up can be affected by stator and rotor magnetic saturation, which generally refers to the point at which the magnetic field cannot increase further (or increases at a relatively slow rate) when the current flowing through the windings is increased, because the magnetic properties of the core material become fully utilized and cannot support any more magnetic flux.

[0088] When the stator or rotor saturates, any increase in current through the windings only results in increased power loss in the form of heat, not increased magnetic field strength. To avoid saturation, the stator and rotor can be designed with carefully selected magnetic properties suited to the application. In addition, the shape and size of the laminations can be selected to ensure that the magnetic flux is evenly distributed and that there are no or few areas of magnetic field concentration that can lead to local saturation.

[0089] Because the magnetic fields flow through different portions of the stator and windings depending on a range of factors (e.g., stator excitation and / or permanent magnets), the magnetic flux density at certain locations may be greater or less than others due to the relative positions of the stator and rotor as well as the location, timing, and / or interaction of the different magnetic fields.

[0090] Typically, during start-up, the stator laminations are not yet saturated and the magnetic flux density in the stator is still very small. For example, in one embodiment, the stator teeth 121 have a maximum of about 0.8 Tesla for both the stator teeth 121 as well as the stator yoke area 122, indicating that the permanent magnet field is small and the main magnetic path is not saturated at no load.

[0091] At start-up, the rotor laminations are also generally not saturated. In addition, the rotor reluctance is large because the width of the carrier or the height of the ferrite permanent magnet is very large, which results in a small d-axis inductance L compared to that of an IPM motor with Ned-Fe-B magnets. d This has resulted in...

[0092] However, the no-load leakage flux density through many of the surface bridges is large, which is at or near magnetic saturation (e.g., .about.1.6 Tesla or greater). There may be high flux density areas within the bridges at the top of each flux barrier, e.g., measuring greater than about 1.6 Tesla.

[0093] It is worth noting that magnetic saturation has a directional component to it, i.e. the surface bridge has a directional magnetized flux density due to the magnetic field generated by the magnets. This directional magnetized flux density in the bridge is located in the leakage flux path (relative to the main flux path). This means that if the main flux path between the rotor segments and the stator flows in the same direction as the leakage flux path, the magnetic field will further magnetize the leakage flux path up to the point where it saturates (if it is not already fully saturated), but if it flows in the opposite direction to the leakage flux path, this will demagnetize the leakage flux path. During normal operation, saturation / desaturation of the bridge (if it exists at all) has a relatively small effect on motor operation. However, during start-up, the d-axis inductance L d Since is small, these bridge saturation situations located in the leakage path can result in large changes in d-axis inductance when positive or negative voltages are applied to the stator windings.

[0094] When a positive d-axis voltage is applied in the winding, the flux density in the main magnetic path increases linearly with the increase in the main flux, while the leakage flux density in the rotor bridge decreases rapidly because the magnetomotive force (MMF) generated by the stator winding opposes the MMF generated by the ferrite permanent magnets, resulting in an increase in the main flux. By considering the non-saturation condition in the stator, the increase in the main flux and the decrease in the leakage flux drive the d-axis inductance to a relatively large value.

[0095] Referring to FIG. 12B, the relative positions of the rotor and stator are different from FIG. 12A, and therefore the surface bridge flux density is different. In the example rotor position depicted in FIG. 12B, the flux density in the bridge is much smaller (e.g., .about.1 Tesla). Thus, when the voltage pulse magnitudes are selected, they should be selected such that the leakage flux paths of the surface bridge are demagnetized close to zero, regardless of whether the leakage flux paths start in a fully saturated or only partially saturated state. Furthermore, the selection can be made such that the leakage flux is not magnetized in the opposite direction. As a result, for a given motor configuration, there is a window of potential voltage pulse magnitudes that provide a clear contrast between positive and negative voltage pulses (e.g., in the resulting inductance and therefore in the response current). That is, the voltage pulse magnitudes can be selected to generate a high inductance over the entire range of starting flux density saturation for one of the negative / positive voltage pulses and a relatively low inductance for the other voltage pulse.

[0096] By determining the characteristics of a given PM-SyR motor, a voltage pulse of a particular magnitude can be selected. Example graphs such as FIGS. 13A-13C may be useful. With reference to FIG. 13A, the d-axis inductance L changes in response to an applied d-axis current of -8.0 to 8.0 A. d 131. The obvious fluctuation of the d-axis inductance L d reaches a peak at about 2.5 A, and then the d-axis inductance L d decreases back to its original value as the positive d-axis current increases above 2.5 A.

[0097] FIG. 13B graphs the leakage flux in the three bridges as the d-axis current varies from −8 A to 8 A. As the flux density in bridge B1 decreases to zero, the d-axis inductance L dreaches its peak value. The inductance initially increases because the leakage flux paths are demagnetized due to the direction of the flux paths. However, a further increase beyond 2.5 A results in magnetization of the leakage flux paths in the opposite direction, thereby resulting in a reduction in the d-axis inductance. Furthermore, when a negative d-axis current (e.g., 0 to -8) is applied, the d-axis inductance L d is highly linear because the leakage flux paths are already saturated.

[0098] Figure 13C plots d-axis current versus magnetic flux in a Wevers: Figure 13 shows the magnetic flux curves when the full range of d-axis current is applied, thereby showing that a nonlinear magnetic flux curve occurs within a limited current range of d-axis currents from 1 to 4.0 A. Outside this d-axis current range (e.g., below 1.0 A and above 4.0 A), the curve is highly linear due to non-saturation.

[0099] As a result, the d-axis voltage is applied and the response current i d By considering non-saturation or linear saturation in the main flux path when generating d It is the change in leakage flux in the bridge that dominates, while the change in the negative direction is almost nonexistent. This insight is pulse and -V pulse This can be exploited to enable detection of the difference in current amplitude when two voltage pulses are applied.

[0100] One aspect of the disclosure relates to selecting positive and negative voltage pulse magnitudes for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection. The method includes determining a characteristic of surface bridge magnetic flux density over a range of positive and negative d-axis current values ​​for a sensorless permanent magnet assisted synchronous reluctance motor having a particular configuration (e.g., ferrite, Ned-Fe-B, or rare earth permanent magnet configuration). The method includes identifying a d-axis current value and a corresponding d-axis reflected current value, where one is demagnetizing the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic desaturation and the other is magnetizing the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic saturation. The d-axis current and its reflection can be utilized to select voltage pulse magnitudes of the polarity detection positive and negative voltage pulses such that one of the positive and negative voltage pulses produces a d-axis current value and the other produces the identified corresponding d-axis reflected current value. This method of selecting appropriate magnitudes of positive and negative voltage pulses can enable simple and efficient polarity detection of PM-SyR motors.

[0101] Figure 14 shows two individual voltage pulses, +V pulse and -V pulse Two d-axis current responses I pulse1 141 and I pulse2 142. The current response difference is about 2.5A, and I pulse1 I pulse2 This means that the d-axis does not require correction. pulse1 I pulse2 If the d-axis current is greater than 180 electrical degrees, a correction factor will need to be applied to the d-axis current. The amount of correction is 180 electrical degrees.

[0102] There are further factors that can affect the polarity detection result. For example, the width of the bridge affects the amount of leakage flux and the d-axis inductance L dSuch motor characteristics can be exploited to adapt the PM-SyR polarity detection method. That is, two current responses I are used to provide accurate polarity detection based on the various characteristics of the PM-SyR motor. pulse1 and I pulse2 The expected response (or difference in response) of the two can be adjusted.

[0103] III. Example of HFI polarity detection implementation in PMSyR motor

[0104] In this exemplary embodiment, the motor under test (MUT) is a 2.2 kW ferrite-based PM-SyR motor driven by direct flux control ("DFC") with high frequency injection ("HFI") control method. The digital controller uses a sampling frequency of 16 kHz. The supply inverter is fed from a single phase rectifier at 220Vac, so the DC link voltage is 310Vdc.

[0105] The following steps may inform the selection of volt-seconds for the positive and negative voltage pulses applied on the axis detected by the controller, as well as other parameter selections.

[0106] Voltage Pulse Length Selection

[0107] The length of the voltage pulse can be selected as:

[0108]

number

[0109] Where:

[0110] T s is the sampling period,

[0111] f s is the sampling frequency which was 16kHz.

[0112] In one embodiment, N pulses = 30, which results in a time length of the voltage pulse equal to 1.9 ms.

[0113] current I d and selection of injected magnetic flux A(Vs)

[0114] Ferrite PM-SyR motors have rotor bridge characteristics that can be exploited for improved polarity detection. The nonlinearity due to the PM-SyR rotor bridge characteristics is a function of the specific d-axis current i d Generates less than 100 reflection points.

[0115] Since the peak d-axis current is caused by the nonlinearity of the leakage flux path in the bridge, the difference value is limited by the ability of the leakage flux to vary; that is, the d-axis current response to a positive voltage pulse is significantly different than the current response to a negative voltage pulse. Large currents may not give a significant difference in detection. A good choice is to choose a d-axis current greater than the current at the reflection point. In the case of the MUT, 2.5A is I d As a reference value, the magnetic flux is selected as follows based on a preliminary analysis:

[0116]

number

[0117] Voltage pulse amplitude V pulse Selection

[0118] The amplitude of the voltage pulses can be selected based on equation (5), i.e., it can be determined by the controller or can be set during motor configuration based on the timing of the voltage pulses and the desired d-axis current. The amplitude of the voltage pulses can also take into account the dead-time phenomenon of the inverter, for example, by the following equation:

[0119]

number

[0120] Here, A = 0.2 (Vs) and N pulse = 30, and f s = 16 kHz, while the maximum inverter dead time can be calculated from a look-up table (LUT) that maps the dead time phenomenon.

[0121]

number

[0122] where dt_error_vector[] is a vector containing the dead-time error (pu) relative to the DC link voltage, and dt_points is the size of this vector.

[0123] In the case of this specific implementation of the MUT, V pulse The magnitude of is approximately 70V. The controller automatically detects the V pulse and its characteristics can be generated or read.

[0124] HFI Frequency and Voltage Selection

[0125] cos(ω) used for HFI voltage generation h Since the generation of t) needs to be performed in synchronism with the sampling frequency, the selected frequency may be a submultiple of the sampling frequency. In addition, the submultiple may be an even number. For example, the selected frequency may be selected as 500 Hz (32 samples per high frequency period).

[0126] In one exemplary embodiment, the motor under test (MUT) is a 2.2 kW PM-SyR motor with the following inductance:

[0127]

number

[0128] For an injection frequency of 500 Hz, the HF d-axis reactance is:

[0129]

number

[0130] The MUT stator resistance is 3.2Ω at ambient 25° C., therefore the stator resistance is much smaller than the d-axis HF reactance.

[0131] For the MUT, the HFI voltage is selected as 60V, so the peak value of the d-axis current is:

[0132]

number

[0133] Tracking Loop PI Controller Gains

[0134] Proportional integral ("PI") HFI tracking loops are well understood in the art. For the MUT in this example, the same gain is used for a bandwidth of about 25 Hz.

[0135]

number

[0136] The MUT, a 2.2 kW PM-SyR motor, can be tested on the test rig. Since the focus is on polarity detection, the MUT can be tested under no load conditions, from standstill to starting up to 1000 RPM. The results are presented in Figures 15-17.

[0137] FIG. 15A shows the velocity command and the actual velocity 151 which follows the commanded velocity.

[0138] FIG. 15B shows the stator phase current i in real time during the starting process. a , i b , and i c FIG. 15C shows the control variable state update. In the case of the MUT, I pulse1 pulse2 presents the reference and estimated speeds, motor currents, and different control flags 153, 154, and 155 used by the sensorless control. The speed values ​​used for the transition from HFI and the linear observer are set at 350 rpm and 400 rpm, respectively. For further details, see U.S. Pat. No. 10,819,264, issued Oct. 27, 2020 to Bojoi et al. and entitled “ROBUST STARTING SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL,” previously incorporated by reference.

[0139] 16A-16D show an example start-up period of a motor utilizing the PM-SyR start-up control according to the present disclosure. Referring to FIG. 16C, during magnetic polarity detection 162, the positive current pulse has a peak value of 1.65A and the negative current pulse has a peak value of -3.81A. As a result, the PM-SyR HFI polarity detection method properly detects the d-axis of the MUT. In FIG. 16B, the position signal curve is flat (because no change was required due to the PM-SyR HFI polarity detection method). Conversely, FIG. 17 shows a start-up case where the positive current pulse has a larger peak value than the negative current pulse. As a result, the estimated angle is corrected by 180 electrical degrees, as shown in FIG. 17B.

[0140] ​Directional terms such as "vertical", "horizontal", "top", "bottom", "upper", "lower", "inner", "inward", "outer", "outward" and the like are used to aid in describing the invention based on the orientation of the illustrated embodiments. The use of directional terms should not be construed as limiting the invention to any particular orientation or orientations.

[0141] The above description relates to the current embodiment of the invention. Various modifications and changes may be made without departing from the spirit and relatively broad aspects of the invention as defined in the appended claims, which must be interpreted in accordance with the principles of patent law, including the doctrine of equivalents. The present disclosure has been presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the invention or as limiting the scope of the claims to the specific elements shown or described in connection with these embodiments. For example, and without limitation, any one or more individual elements of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide sufficient operation. This includes, for example, currently known alternative elements, such as those that may be currently known to those of skill in the art, and alternative elements that may be developed in the future, such as those that may be recognized as alternatives upon development by those of skill in the art. Furthermore, the disclosed embodiments also include multiple features that are described in a corresponding state and that may cooperate to provide a collection of benefits. The invention is not limited solely to embodiments that include all of these features or provide all of the described benefits, except to the extent that they are otherwise expressly recited in the issued claims. For example, any reference to a claim element in the singular using the articles "a," "an," "the," or "said" should not be construed as limiting the element to the singular.

Claims

1. 1. A sensorless permanent magnet assisted synchronous reluctance motor, comprising: an attached stator having a three-phase stator winding configuration; a rotor including a magnetically permeable core having a plurality of flux barriers dividing the core into a plurality of main rotor flux path segments for controlling flow of magnetic flux within the rotor, the plurality of flux barriers carrying a plurality of permanent magnets, the magnetically permeable core including a plurality of surface bridges coupling the plurality of rotor flux path segments together, the rotor rotatable relative to the stator via excitation of the three-phase stator winding arrangement of the stator, the plurality of permanent magnets generating a plurality of rotor poles having magnetic polarities; a main flux path between at least one of the plurality of rotor flux path segments and the stator; a no-load leakage flux path through at least one of the plurality of surface bridges having a directionally magnetized flux density generated by at least one of the plurality of permanent magnets; and 1. A motor control system comprising: power supply, a sensing circuit configured to sense one or more electrical properties of the stator; and a controller, The controller: applying positive and negative voltage pulses to the three-phase stator winding configuration, the magnitudes of the positive and negative voltages being: one of the positive voltage pulse and the negative voltage pulse demagnetizes the directionally magnetized magnetic flux density within the at least one of the plurality of surface bridges; and the other of the positive voltage pulse and the negative voltage pulse further magnetizes the magnetic flux density within the at least one of the plurality of surface bridges. It is selected as detecting a current response to the positive voltage pulse and a current response to the negative voltage pulse; determining the magnetic polarity of the plurality of magnetic poles based on a relative magnitude of the current response to the positive voltage pulse and the current response to the negative voltage pulse; generating a drive command during start-up of the motor based on the determined magnetic polarity of the plurality of magnetic poles; a motor control system configured to a drive circuit for generating excitation signals for the three-phase stator winding arrangement of the stator in accordance with the drive commands upon start-up of the motor; A motor having

2. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the current response to one of the positive voltage pulse and the negative voltage pulse is a current response in a d-axis direction, and the current response to the other of the positive voltage pulse and the negative voltage pulse is a current response in a negative d-axis direction.

3. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the magnetically permeable core includes a plurality of inner bridges coupling the plurality of rotor flux path segments together to increase mechanical integrity of the rotor.

4. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the plurality of permanent magnets comprises at least one of a plurality of ferrite magnets, a plurality of neodymium magnets, and a plurality of rare earth magnets.

5. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the plurality of flux barriers are configured with slots for the magnets to position the magnets within the barriers.

6. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the negative voltage pulse and the positive voltage pulse have the same magnitude such that one of the positive voltage pulse and the negative voltage pulse desaturates the directionally magnetized magnetic flux density in the at least one of the plurality of surface bridges and the other of the positive voltage pulse and the negative voltage pulse saturates the directionally magnetized magnetic flux density in the at least one of the plurality of surface bridges.

7. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the magnitudes of the positive and negative voltage pulses are selected such that one of the positive and negative voltage pulses desaturates the directionally magnetized flux density in the at least one of the plurality of surface bridges without substantially directionally saturating the leakage flux path through the at least one of the plurality of surface bridges in an opposite direction of the directionally magnetized flux density in the no-load leakage flux path.

8. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the magnitudes of the positive and negative voltage pulses are selected such that one of the positive and negative voltage pulses desaturates the directionally magnetized flux density in the at least one of the plurality of surface bridges to about zero Tesla.

9. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the magnitudes of the positive and negative voltage pulses are selected based on characteristics of the sensorless permanent magnet assisted synchronous reluctance motor such that one of the positive and negative voltage pulses desaturates the directionally magnetized flux density in the at least one of the plurality of surface bridges, resulting in a d-axis inductance increasing above a predetermined threshold, and the other of the positive and negative voltage pulses further magnetizes the flux density in the at least one of the plurality of surface bridges, resulting in a d-axis inductance remaining below the predetermined threshold.

10. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the magnitudes of the positive and negative voltage pulses are selected based on characteristics of the sensorless permanent magnet assisted synchronous reluctance motor and such that a threshold difference in d-axis inductance is produced in response to the positive and negative voltage pulses.

11. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the motor control system detects a rotor position at a starting moment to obtain a rotor position at a starting moment and positions of the rotor poles having unknown magnetic polarity.

12. 2. The sensorless permanent magnet assisted synchronous reluctance motor of claim 1, wherein the motor control system detects low speed rotor motion during starting and detects positions of the rotor poles having unknown magnetic polarity by taking the low speed rotor motion into account.

13. 1. A method for determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor, the sensorless permanent magnet assisted synchronous reluctance motor including a stator having a three-phase stator winding configuration and a rotor including a magnetically permeable core having a plurality of flux barriers carrying a plurality of permanent magnets and a plurality of surface bridges, the plurality of permanent magnets generating a plurality of rotor poles having magnetic polarity, the method comprising: one of a positive voltage pulse and a negative voltage pulse demagnetizing a directionally magnetized magnetic flux density within at least one of the plurality of surface bridges; and the other of the positive voltage pulse and the negative voltage pulse further magnetizes the magnetic flux density within the at least one of the plurality of surface bridges. selecting the magnitudes of the positive voltage and negative voltage pulses; applying the positive and negative voltage pulses to the three-phase stator winding arrangement of the rotor; detecting a current response to the positive voltage pulse; detecting a current response to the negative voltage pulse; determining the magnetic polarity of the plurality of magnetic poles based on the current response to the positive voltage pulse and the current response to the negative voltage pulse; A method for determining magnetic polarity having

14. 14. The method for determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor as recited in claim 13, wherein the current response to one of the positive voltage pulse and the negative voltage pulse is a current response in a d-axis direction, and the current response to the other of the positive voltage pulse and the negative voltage pulse is a current response in a negative d-axis direction.

15. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor of claim 13, wherein determining the magnetic polarity of the plurality of magnetic poles comprises determining the magnetic polarity of the plurality of magnetic poles based on known positions of the plurality of rotor magnetic poles and relative magnitudes of the current response to the positive voltage pulse and the current response to the negative voltage pulse.

16. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor as claimed in claim 13, wherein the plurality of permanent magnets comprises at least one of a plurality of ferrite magnets, a plurality of neodymium magnets, and a plurality of rare earth magnets.

17. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor of claim 13, wherein the negative voltage pulse and the positive voltage pulse have the same magnitude such that one of the positive voltage pulse and the negative voltage pulse desaturates the directionally magnetized magnetic flux density in the at least one of the plurality of surface bridges and the other of the positive voltage pulse and the negative voltage pulse saturates the directionally magnetized magnetic flux density in the at least one of the plurality of surface bridges.

18. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor of claim 13, wherein selecting the magnitudes of the positive and negative voltage pulses includes selecting the magnitudes such that one of the positive and negative voltage pulses desaturates the directionally magnetized flux density in the at least one of the plurality of surface bridges without substantially saturating the leakage flux path through the at least one of the plurality of surface bridges in an opposite direction of the directionally magnetized flux density in a no-load leakage flux path.

19. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor of claim 13, wherein selecting the magnitudes of the positive and negative voltage pulses includes selecting the magnitudes of the positive and negative voltage pulses such that one of the positive and negative voltage pulses desaturates the directionally magnetized magnetic flux density in the at least one of the plurality of surface bridges to about zero Tesla.

20. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor of claim 13, wherein selecting the magnitudes of the positive and negative voltage pulses includes selecting the magnitudes of the positive and negative voltage pulses based on characteristics of a sensorless permanent magnet assisted synchronous reluctance motor such that one of the positive and negative voltage pulses desaturates the directionally magnetized magnetic flux density in the at least one of the plurality of surface bridges, resulting in a d-axis inductance increasing above a predetermined threshold, and the other of the positive and negative voltage pulses further magnetizes the magnetic flux density in the at least one of the plurality of surface bridges, resulting in a d-axis inductance remaining below the predetermined threshold.

21. 14. The method of determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor of claim 13, wherein selecting the magnitudes of the positive and negative voltage pulses includes selecting the magnitudes of the positive and negative voltage pulses based on a characteristic of the sensorless permanent magnet assisted synchronous reluctance motor such that a threshold difference in d-axis inductance is produced in response to the positive and negative voltage pulses.

22. 14. The method for determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor as claimed in claim 13, comprising detecting rotor position at a starting moment to obtain a motor position at a starting moment and positions of the rotor poles having unknown magnetic polarity.

23. 14. The method for determining magnetic polarity of a sensorless permanent magnet assisted synchronous reluctance motor as recited in claim 13, comprising detecting a low speed rotor motion during a starting moment, and detecting positions of the plurality of rotor poles having unknown magnetic polarity by considering a low speed rotor motion with the detected low speed rotor motion.

24. 1. A method for selecting magnitudes of positive and negative voltage pulses for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection, the sensorless permanent magnet assisted synchronous reluctance motor including a stator having a three-phase stator winding configuration and a rotor including a magnetically permeable core having a plurality of flux barriers carrying a plurality of permanent magnets and a plurality of surface bridges, the plurality of permanent magnets generating a plurality of rotor poles having magnetic polarities, the method comprising: determining a characteristic of surface bridge magnetic flux density over a range of positive and negative d-axis current values ​​for a sensorless permanent magnet assisted synchronous reluctance motor having a particular configuration; identifying a d-axis current value and a corresponding d-axis reflected current value, the d-axis current value demagnetizing the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic desaturation, and the corresponding d-axis reflected current value magnetizing the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic saturation; one of the positive voltage pulse and the negative voltage pulse produces the identified d-axis current value that demagnetizes the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic desaturation; and so that the other of the positive voltage pulse and the negative voltage pulse generates the identified corresponding d-axis reflected current value that magnetizes the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic saturation. selecting a voltage pulse magnitude for the polarity detection positive and negative voltage pulses; A method for determining magnetic polarity having

25. identifying a range of d-axis current values ​​and corresponding d-axis reflected current values, the d-axis current values ​​demagnetizing the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic desaturation, and the corresponding d-axis reflected current values ​​magnetizing the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic saturation; one of the positive voltage pulse and the negative voltage pulse produces a d-axis current value within the range of d-axis current values ​​that demagnetizes the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic desaturation; and so that the other of the positive voltage pulse and the negative voltage pulse produces a corresponding d-axis reflected current value that magnetizes the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic saturation. selecting a voltage pulse magnitude for the polarity detection positive and negative voltage pulses; 25. The method for selecting magnitudes of positive and negative voltage pulses for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection as claimed in claim 24, comprising:

26. determining a characteristic of the surface bridge flux density includes determining a characteristic of the surface bridge flux density over a range of positive and negative d-axis current values ​​for a sensorless permanent magnet assisted synchronous reluctance motor for a plurality of different rotor positions; 25. The method for selecting magnitudes of positive and negative voltage pulses for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection as recited in claim 24, wherein identifying the range of d-axis current values ​​and corresponding d-axis reflected current values ​​includes identifying d-axis current values ​​and corresponding d-axis reflected current values ​​at a plurality of different rotor positions.

27. 25. The method for selecting magnitudes of positive and negative voltage pulses for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection as recited in claim 24, wherein the particular motor configuration includes a four-pole permanent ferrite magnet synchronous reluctance motor configuration.

28. 25. The method for selecting magnitudes of positive and negative voltage pulses for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection as recited in claim 24, wherein the particular motor configuration includes a four-pole permanent rare earth magnet synchronous reluctance motor configuration.

29. The method for selecting magnitudes of positive and negative voltage pulses for exciting a stator of a sensorless permanent magnet assisted synchronous reluctance motor during start-up polarity detection as recited in claim 24, wherein the specific motor configuration includes a four-pitch permanent Ned-Fe-B magnet synchronous reluctance motor configuration.

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