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 generally relates to robust control of a permanent magnet assisted synchronous reluctance motor (“PM-SyR”). Various embodiments relate to sensorless robust closed-loop control starting from zero or low speed.

Background Art

[0002] The deployment of sensorless permanent magnet synchronous motor (“PMSM”) systems has begun in specific fan and blower drive applications, such as not only heating, ventilation, and air conditioning (“HVAC”) systems but also various other commercial and industrial motor-driven products. A sensorless PMSM (also referred to as a sensorless PMSM system) is one type of advanced electronically controlled motor (“ECM”) or ECM system. A sensorless PMSM system can generally supply high peak efficiency at rated operating speed and can have a relatively large high-efficiency operating speed range. In addition to this, the variable speed of a sensorless PMSM system enables low-capacity operation during off-peak periods such as at night, which can result in significant energy savings. In addition to this, these electronically controlled PMSM systems can also provide opportunities for artificial intelligence control and remote control through various communication technologies such as cloud communication in order to improve energy savings in operation, accessibility, monitoring, safety, and reliability.

[0003] Recent PMSMs are designed to have magnets embedded inside the rotor structure, which are commonly referred to as interior PMSMs (IPMSMs). Often, IPMSMs use Nd-Fe-B rare earth magnets to provide high performance with certain electromagnetic, mechanical, and economic benefits. Specifically, Nd-Fe-B based IPMSMs can reach a certain power density or torque density rating with a small motor body size under appropriate cooling system design, which can be useful in many applications such as electric vehicles and other applications where a relatively small motor size offers advantages. The known design rules and principles of IPMSMs are widely applied in various applications such as industrial drive devices, electric vehicle motors, and wind turbine generators. These usages have led to an increasing demand for Nd-Fe-B magnets. However, due to the limited supply of rare earth magnets, the price of Nd-Fe-B magnets has continued to rise, thereby increasing the cost of IPMSM systems. For this and other reasons, the development of new types of motors that can supply comparable performance at low cost is desired.

[0004] Recently, due to its performance and low cost, the permanent magnet assisted synchronous reluctance (PM-SyR) motor has been becoming relatively attractive and popular. Generally, a PM-SyR motor is an electric motor that combines the characteristics of both a permanent magnet and a synchronous reluctance motor. It has a stator with winding coils that generate a rotating magnetic field, and a rotor that has salient poles that alternate in a north and south pole pattern as well as permanent magnets. The shape and configuration of the rotor magnetic barrier with permanent magnets generate not only reluctance torque but also PM flux torque so as to contribute to the output torque of the motor. The combination of permanent magnets and the reluctance effect in the rotor results in a motor with high torque density and efficiency. Basically, the PM-SyR motor provides improved performance by inserting magnets into the rotor magnetic barrier, and thus has evolved from a synchronous reluctance motor to improve mainly not only the power factor but also other performance metrics.

[0005] Typically, in design and manufacturing, low-cost ferrite magnets are used in the motor. A synchronous reluctance motor generally has a relatively large saliency coefficient L q / L d (5 - 6) and the reluctance torque dominates the total torque generating ability in addition to the main flux torque generated by the magnets. On the other hand, due to the use of ferrite magnets, the main flux can be very small in comparison with that of Nd-Fe-B rare earth permanent magnet materials.

[0006] Overall, since the PM-SyR motor is basically a special type of IPMSM, generally, control techniques for fan or blower drive applications, such as stable closed-loop startup control and robust control under harsh operating conditions, can also be similarly applied to the PM-SyR motor. Generally, for example, 1) the techniques, methods, and control schemes disclosed in U.S. Patent No. 10,784,805, titled "SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL FROM ZERO OR LOW SPEED," issued to Bojoi et al. on September 22, 2020; 2) U.S. Patent No. 10,819,264, titled "ROBUST STARTING SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," issued to Bojoi et al. on October 27, 2020; and 3) U.S. Patent No. 11,239,772, titled "SYSTEMS AND METHODS FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," issued to Bojoi et al. on February 1, 2022, can be applied to PM-SyR motor control, and all of these patent documents are hereby incorporated by reference in their entirety. The IPMSM control methods may have an application to the PM-SyR motor, but there is room for improvement in the PM-SyR motor control based on its specific characteristics. For example, the present disclosure provides improved motor control for the PM-SyR motor at startup of the motor (i.e., at zero or very low speeds), particularly for the purpose of polarity detection.

[0007] For example, due to its ability to supply relatively high performance with significant cost savings, a relatively large number of commercial and industrial fans and blowers are driven by PM-SyR motor systems, and thus there is a need for new control systems and methods specific to PM-SyR motors. For example, there is a need for a control scheme that can address the inherent problems of PM-SyR motors at startup (e.g., zero or very low speed) in order to provide high-efficiency and stable speed control for commercial and industrial fan and blower drive 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 include motor startup control that uses closed-loop control from a stopped state including a range of zero motor speed or low motor speed. The rotor characteristic detection method, according to one embodiment of the present disclosure, includes a signal injection method that can detect specific rotor characteristics such as rotor position, rotor speed, and rotor magnetic polarity of a motor having rotor magnetic anisotropy or saliency.

[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 magnetic flux path in the rotor barrier bridge.

[0010] The variation in inductance generated by the leakage flux path within the rotor barrier bridge improves the stability and reliability of polarity detection by small current pulses in the polarity detection process. The magnetic flux density within the main flux path and the leakage flux path in motor design affects the underlying characteristics during polarity detection and furthermore is one of the factors contributing to its effectiveness. The effectiveness of polarity detection can be verified at the motor design stage, for example, to ensure proper starting from a stop or low-speed range based on the initial rotor speed / position determined from methods such as high-frequency injection methods.

[0011] Due to low magnetic performance, ferrite-based PM-SyR motors set up a low magnetic flux density within the unsaturated main flux path. Furthermore, the motor barriers generate a large magnetic resistance. Thus, the stator magnetomotive force (「MMF」) generated by the stator winding current cannot saturate the main magnetic path and is only in the leakage flux path within the barrier bridge. It is the saturation of the leakage flux path within this barrier bridge that allows the high-frequency injection method to detect the rotor position based on the prominence setup on the rotor surface structure. Furthermore, the change in the leakage flux path within the barrier bridge affected by the stator current can also be utilized to determine the polarity of the rotor at a stop or low speed.

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

[0013] Before describing embodiments of the present invention in detail, it should be understood that the present invention is not limited to the details of operation or to the details of the construction and arrangement of components set forth in the following description or shown in the drawings. The present invention can be implemented in various other embodiments and can also be practiced and carried out by alternative means not explicitly disclosed herein. It should also 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 their variations should be interpreted as including not only the items listed hereinafter and their equivalents, but also further items and their equivalents. Furthermore, enumerations may be used in the description of various embodiments. Unless explicitly stated otherwise to the contrary, the use of enumerations should not be construed as limiting the present invention to any specific order or number of components. Also, the use of enumerations should not be construed as excluding any further steps or components that can be combined with or within the enumerated steps or components from the scope of the present invention. Any reference to a claim element as "at least one of X, Y, and Z" should be interpreted as including any one of X, Y, or Z individually, any combination of X, Y, and Z, such as X, Y, Z; X, Y; X, Z; Y, Z, etc.

[0014] This patent or patent application file includes 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 United States Patent and Trademark Office upon request and payment of the necessary fee.

Brief Description of the Drawings

[0015]

FIG. 1A-1B

[0016]

FIG. 2

[0017]

FIG. 3A

[0018]

FIG. 3B

[0019]

FIG. 4

[0020]

FIG. 5

[0021]

FIG. 6

[0022]

FIG. 7A-7B

[0023]

FIG. 8

[0024]

FIG. 9A

[0025]

FIG. 9B

[0026]

FIG. 10A-10D

[0027]

FIG. 11A

[0028]

FIG. 11B

[0029]

FIG. 12A

[0030]

FIG. 12B

[0031]

FIG. 13A-13B

[0032]

FIG. 13C

[0033]

FIG. 14

[0034]

FIG. 15A-15C

[0035]

FIG. 16A-16D

[0036]

FIG. 17A-17D

Embodiments for Carrying Out the Invention

[0037] The present disclosure generally relates to control methods used in connection with permanent magnet assisted synchronous reluctance ("PM-SyR") motors. FIGS. 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 commutated 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 in a particular direction, thereby generating an airflow. The fan can generate a defined airflow to meet the airflow requirements, typically based on the configuration and / or programming of motor electronics normally incorporated within the motor.

[0038] Some of the components and control elements suitable for use in embodiments of the present disclosure having a PM-SyR motor are the same or similar components and control elements described in connection with a sensorless interior permanent magnet synchronous motor ("IPMSM") in U.S. Patent No. 10,784,805, titled "SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL FROM ZERO OR LOW SPEED," issued to Bojoi et al. on September 22, 2020; U.S. Patent No. 10,819,264, titled "ROBUST STARTING SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," issued to Bojoi et al. on October 27, 2020; and U.S. Patent No. 11,239,772, titled "SYSTEMS AND METHODS FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," issued to Bojoi et al. on February 1, 2022, and these patent documents are hereby incorporated by reference in their entirety.

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

[0040] Optionally, 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 installed at the upper part of the motor body with respect to the heat - dissipation ribs by using a back - pack configuration and an interface, which will be described in more detail later. The frame 227 is fixed to (or integrated with) the stator or its sub - components, for example, to the heat - dissipation ribs along the outside of the cylindrical stator 223, and provides a mechanical structure for supporting and fixing the motor in a fixed position together with a foot - mounting structure. In alternative embodiments, the PM - SyR motor system can include additional, different, or fewer components configured in similar or different ways to provide a PM - SyR that can be arranged and / or mounted in basically any suitable manner.

[0041] The described motor embodiment has a housing or enclosure 234 that includes a front-end shield 221, a mid-shield 229, and a rear-end shield 230. The three shields can be joined to cooperate in forming the motor enclosure 234 or motor housing. A lubricating or oil sealing body can surround a drive shaft 233 that extends outward from the motor enclosure 234 and seals the front-end shield 221. In an alternative embodiment, the motor enclosure can be formed from additional, fewer, or different, component parts that cooperate to house the motor in basically any suitable manner that enables the motor to convert electrical energy to mechanical energy, for example, to rotate the drive shaft. In this embodiment, the 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 a PM-SyR motor electronic circuit that includes a 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 in order to generate a magnetic field that rotates over time due to the oscillation of the line current. The stator can basically have any suitable winding configuration that defines an appropriate number of stator poles that are complementary to the rotor poles. This embodiment includes a three-phase stator winding configuration having four stator poles. Once in the steady state, the rotor 225 rotates in the step with the stator 223, for example, via permanent magnets embedded within the rotor, and as a result, rotates the drive shaft 233 of the stator. The motor can include a bearing assembly 222 that supports and positions the rotor 225 in order to maintain the air gap between the stator 223 and the rotor 225 in a small and consistent state. The motor control system 226 can include a controller on a printed circuit board physically coupled to the motor controller enclosure 224.

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

[0044] Hereinafter, with reference to FIG. 4, an overview of the motor control system 226 according to the present disclosure will be described. Generally, the motor control system 226 can 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, additional or fewer microcontrollers may be present. The first microcontroller 444 (referred to as MCU-1) is configured by various motor control algorithms and schemes to perform calculations that provide dynamic motor response within a timing range in microseconds. Thus, the MCU-1 microcontroller 444 includes a microcontroller with relatively powerful computing power. The second microcontroller 447 (referred to as MCU-2) is implemented by intelligent detection and monitoring algorithms to perform detection, monitoring, and interface functions. Generally, the computing power of the second microcontroller (MCU-2) 447 may depend on the sophistication of the implemented detection algorithm. Communication including real-time communication between the two microcontrollers 444, 447 can be processed on a controller area network (bus) or other communication path by using the CAN protocol or another suitable protocol. Details regarding the various motor controller software of the present disclosure, including both motor control algorithms and detection algorithms, will be described in more detail later.

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

[0046] Referring to FIG. 4, one embodiment of the motor control system 226 includes, without limitation, a power supply circuit 441 (e.g., an inverter) for converting a three-phase power supply 450 into an appropriate voltage, current, and frequency, a drive circuit 442 for driving the stator windings of the motor based on a drive command, and a detection circuit 442 for detecting one or more motor characteristics used in one or more motor control methods or motor speed estimation methods. An exemplary embodiment of this motor control system 226 is configured by one or more motor control methods (e.g., one or more motor speed estimation methods) configured to provide a drive command to the drive circuit 442 based on the detected motor characteristics, and includes a microcontroller unit 444 and a command input interface 445 for providing 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. Further, the monitoring interface 446 can also transmit the received detection 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 basically any communication protocol such as a wireless communication protocol such as Bluetooth or WiFi.

[0047] Another microcontroller unit 447 can be configured to have not only various detection and monitoring algorithms that can receive output variables from the other microcontroller 444, but also additional sensors 448 such as sensors installed within the motor 234 and / or the motor controller housing 224. For example, the additional detection circuit 448 can include a temperature sensor, a vibration sensor, or basically any other sensor that can provide an appropriate sensor output (e.g., a sensor output that notifies of motor performance, motor efficiency, and / or motor operating state).

[0048] Many motor control algorithms, including embodiments of the PM-SyR motor control algorithm described herein, can probably be best understood by referring to a clearly defined vector reference frame. FIG. 5 defines a vector reference frame 30 for a general radial interior PMSM motor that is adopted. This same adopted vector reference frame can be utilized in relation to a PM-SyR motor, which is a specific type of interior PMSM motor. The stator 36 includes three-phase windings (a-b-c) 35 that each carry three-phase currents (i a , i b , i c ) when powered on, in which case they can be converted to a stationary frame (α-β) 31. The rotor 37 that rotates at the synchronous speed can have a salient structure, and as a result, different permeabilities and inductances are brought about between the pole center line d-axis and the line q-axis that is perpendicular to it, which are together referred to as the synchronous rotor frame (d-q 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 having two poles, and PM-SyR high-frequency injection and polarity detection can be utilized in relation to basically any motor having a magnetic salient structure that includes rotors having other numbers of poles, such as the embodiment of FIG. 2 showing a rotor having four poles.

[0049] Figure 6 shows a cross-section for illustration of a normal 4-pole combination of two types of motors, a synchronous reluctance (SyR) motor (left side) 61 and a PM-SyR motor (right side) 62. Generally, when constructing either of these two motors, there is no significant difference in the stator winding structure 63. The SyR motor is a synchronous motor whose rotor has a plurality of magnetic flux barriers 64. In this drawing, the SyR motor includes three magnetic flux barriers 64 as shown. The generated torque is due to magnetic anisotropy as shown in Figure 6. When the stator generates a stationary magnetic field, the high permeability axis of the rotor will align with the magnetic field so as to minimize the system energy. When the stator magnetic field becomes a rotating magnetic field, the rotor will rotate in the same direction. Even when the SyR motor has small rotor losses and as a result high efficiency in operation, since the stator requires a large amount of reactive current to magnetize the machine, this has a small power factor (0.6 - 0.7).

[0050] The PM-SyR motor is a development of the SyR motor. The PM-SyR motor uses magnets 65 within the magnetic flux barriers 64 to improve the power factor (right side of Figure 6), thereby bringing about an improvement in efficiency in relation to the SyR motor (without the magnets shown in the left half of Figure 6).

[0051] As shown in Figure 6, the definition of the (d,q) rotor frame can be defined by using the following two different conventional methods. · PM notation: The d-axis is defined by the north pole of the magnet as it occurs in the case of surface-mounted PM (SMPM) motors and interior PM (IPM) motors. In the case of this reference frame, the magnetic flux vector of the magnet is aligned with the d-axis. · SyR notation: The d-axis is defined as the direction of maximum permeability. In the case of this reference frame, the magnetic flux vector of the magnet is located on the negative q-axis.

[0052] Any reference frame (or, alternatively, an entirely different reference frame) can be used in the implementation of the PM-SyR motor controller according to the present disclosure. However, in order to maintain compatibility with previous patent applications for interior permanent magnet motors (incorporated by reference above), the adopted reference frame utilized throughout the present disclosure uses the PM notation. Of course, note that any notation (or, alternatively, an entirely different notation) can be adopted. Accordingly, the magnetic model of PM-SyR (where cross-saturation is ignored) and the electromagnetic torque have the same following 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 the PM-SyR motor and the IPM motor is the different relationship between the reluctance torque due to magnetic anisotropy and the permanent magnet torque due to the magnet. In the PM-SyR motor, especially when using ferrite magnets, the reluctance torque may account for the majority of torque generation, or may be dominant in relation to the torque generation produced by the ferrite permanent magnet. Furthermore, the main magnetic flux produced by the ferrite permanent magnet may not be as strong as that produced by other high-performance magnets such as Neodymium-Fe-B magnets, and as a result, a lower saturation state than the stator magnetic flux path is brought about under no-load conditions of the main magnetic field.

[0055] Known interior permanent magnet control techniques can, in theory, be applied to control a PM-SyR motor system over its entire speed range for a given load condition. However, there are certain problems that can arise in the context of PM-SyR motor control that do not exist in other types of interior permanent magnet motors. For example, in the case of a permanent magnet assisted synchronous reluctance motor, often the position dependence of the inductance generated by the magnetic saliency of the rotor is 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 startup. Therefore, an improved motor control method can be provided to improve the performance, reliability, and other metrics of PM-SyR motor control. For example, a method for efficiently and effectively determining the magnetic polarity of rotor magnetic poles whose pole positions are known (e.g., estimated) can significantly improve the motor control method.

[0056] I. Rotor Magnet Polarity Detection for PM-SyR Motors

[0057] Since the torque generation of a PM-SyR motor based on ferrite magnets is dominated by reluctance torque rather than permanent magnet torque, some effective starting methods may not function reliably at starting speeds of zero or very low. The stop position of a PM-SyR motor will not align with the d-axis, but instead will generally align with an intermediate angle between the d-axis and the q-axis, which is the general case. Therefore, IPM starting methods that rely on d-axis or q-axis alignment at zero or low speeds are generally not feasible for PM-SyR motors.

[0058] High-frequency injection ("HFI") is the basis for one form of rotor pole position detection. High-frequency injection generally means injecting a high-frequency current into the stator windings of an AC motor. In response to the high-frequency current being injected into the stator windings, this generates a magnetic field that interacts with the rotor of the motor. By analyzing the rotor's response to the injected current, further control of the motor becomes possible. By injecting a 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 control the speed of the motor relatively accurately. U.S. Patent No. 10,784,805, entitled "SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL FROM ZERO OR LOW SPEED," issued to Bojoi et al. on September 22, 2020, the entire contents of which are incorporated herein by reference, describes a manner in which HFI can be utilized to control the startup of an interior permanent magnet synchronous motor.

[0059] The HFI method with a pulsed carrier generally has an electrical angle uncertainty of 180 degrees when tracking the d-axis of the 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 magnets in relation to the stator, but it cannot determine the magnetic polarity of the permanent magnets. For example, referring to FIGS. 7A-7B, the previous HFI method can determine that the permanent magnets are positioned as shown in FIGS. 7A and 7B, but the method cannot distinguish the polarity of the magnets and, thus, cannot distinguish between two different rotor positions. The reason is that the HFI method depends on the magnetic saliency that is the same along the d-axis regardless of whether the permanent magnet is a north pole magnet or a south pole magnet.

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

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

[0062] To perform the polarity detection, a special voltage waveform can be used as the detection profile. In one embodiment, the waveform includes two voltage pulses of +V pulse and -V pulse whose phases are shifted by 180 electrical degrees, that is, the second voltage pulse waveform is shifted by a time equal to half of its period. FIG. 8 shows two voltage pulses having a specific amplitude V pulse 81 and a time length t pulse 82 on the detected axis and on the negative detected axis, and the distance is the span length 83 of the motor rotor pole.

[0063] Assuming a low speed range (-10 to +10 RPM) or no rotor movement, the equation for the detected d-axis voltage is as follows.

Equation

[0064] By ignoring the voltage drop on the stator resistance, (11) becomes the following equation.

Number

[0065] The d-axis voltage includes two voltage pulses 84 of the same volt-seconds defined as shown in FIG. 8.

Number

[0066] The d-axis current i d as it changes, the d-axis inductance L d The characteristics of the variation can be obtained by processing a magnetic model method that represents the current-versus-flux relationship. These curves are different from those of the IPM motor in the case of the PM-SyR motor, which means that the methods for accurately detecting 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 when it is less than a specific current value, such as within the range of 0 A to about i d <2.5 A, the d-axis magnetic flux linkage λ d increases with a steep slope 91, and as a result, the d-axis inductance L d increases rapidly and non-linearly (there is a direct relationship between the d-axis magnetic flux linkage and the d-axis inductance). In contrast, when the d-axis current is negative, i.e., i d <0, the magnetic behavior of the d-axis magnetic flux linkage λ d and the inductance L d has a high degree of linearity as the d-axis current changes. For efficient and effective PM-SyR polarity detection, the obvious contrast in the response to this positive and negative d-axis current can be utilized. In short, the controller can be configured to apply a positive voltage pulse and a negative voltage pulse to the stator winding configuration. Based on the current response to the positive voltage pulse and the negative voltage pulse, the magnetic polarity of the magnetic pole can be determined based on the relative magnitude of the current response.

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

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

[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 is non-linear and increasing rapidly. Beyond this point, the d-axis inductance L d changes to different variation characteristics. This characteristic is unique to the ferrite PM-SyR motor and can be utilized to make the polarity detection relatively accurate and stable with a relatively small current when the d-axis current is less than this reflection point. As will be described later, the polarity detection method can be adapted to other types and configurations of PM-SyR motors, such as those using other types of magnets or PM-SyR motors having different numbers and configurations of magnetic flux barriers.

[0071] Hereinafter, the exemplary control logic for polarity detection of the ferrite PM-SyR motor will be described in detail. · Current response (I pulse ) to the positive current pulse (+V pulse1) is a negative current pulse (-V pulse ) for the current response (I pulse2 ) is less than, then the PM-SyR high-frequency injection (HFI) appropriately detects the d-axis, and the motor controller utilizes the detected HIF position. · Positive voltage pulse (+V pulse ) for the current response (I pulse1 ) is greater than the current response (I pulse ) for the negative current pulse (-V pulse2 ) for, then the HFI of PM-SyR detects the negative d-axis, and thus the motor controller applies a correction to the detected d-axis HFI position (the amount of correction may depend on the number of magnetic poles, for example, in the case of a 4-pole rotor, an electrical angle 90-degree correction can be utilized).

[0072] In a state where the volt-second value of the injected voltage is the same, the amplitude of the response current pulse will be different as shown in FIG. 10A or FIG. 10B (in this case as well, it is shown by a 2-pole embodiment for ease of explanation). As shown in FIG. 10A, when I pulse1 <I puse2 , then the positive direction of the rotor axis, i.e., the correct magnetic pole polarity 104 in FIG. 10A, is the estimated

Number

[0073] In the first case depicted in relation to FIGS. 10A to 10B, the first current pulse 101 is less than the second one 102, and thus the HFI method provides the correct estimated rotor positions matching the actual rotor positions 103 and 104. That is,

Number

Number

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

[0075] In addition to this, since position and speed can be detected through the HFI process prior to polarity detection, in order to improve the accuracy when the rotor is rotating at a low speed (e.g., about 10 RPM or less), the position / speed information can be used as an input to the polarity detection current pulse integration process in Equation (5). pulse It can be used as an input to the polarity detection current pulse integration process in Equation (5).

[0076] II. Polarity Detection Effectiveness in PM - SyR Motors

[0077] In FIGS. 9A and 9B, the d - axis inductance L dThe characteristics of the increase are shown. These exemplary values can be obtained through the acquisition of magnetic models and empirical tests. The same relationship between the magnetic flux variation and the d-axis current can be obtained by finite element analysis (FEA) of the motor design. FIG. 11A shows the FEA design model of an exemplary ferrite PM-SyR motor. The stator 111 of the motor includes polyphase windings 112 embedded within slot groups (three slot groups A, B, and C in this embodiment). The motor stator 111 of this PM-SyR motor is basically the same as the stator of an induction motor. The rotor 116 is a synchronous reluctance rotor having a plurality of magnetic flux barriers 115, and these magnetic flux barriers 115 can also be referred to as rotor barriers or magnet barriers.

[0078] Also, the rotor 116 can also be referred to as the rotor core. The rotor core can be manufactured from a soft magnetic material such as laminated silicon steel. This can be formed as a disk having a central shaft hole. The rotor core can be divided into several magnetic poles, and these magnetic poles are generated by stamping or punching slots 115 within the core. The slots 115 generate magnetic flux barriers that prevent magnetic flux from flowing in the wrong direction. The rotor core can be mounted on the motor shaft and rotated by the magnetic field generated by exciting a stator winding configuration (e.g., a three-phase stator winding configuration).

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

[0080] The rotor flux barrier 115 can be configured in a specific pattern to control the magnetic flux and to generate torque. One configuration of the flux barrier is the segmented flux barrier rotor, in which case the rotor has alternating magnetic poles and flux barriers. The flux barriers within the segmented rotor can be manufactured from a non-magnetic material and positioned between the magnetic poles to create a path of low magnetic reluctance. This enables a high magnetic flux density to be generated within the magnetic poles, which generates torque as the rotor rotates. The configuration and structure of the flux barrier 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 the flux barrier for a given motor can depend on the specific requirements of the motor, including not only torque and efficiency but also manufacturing and cost constraints.

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

[0082] The rotor core can include a plurality of rotor bridges spanning the flux barriers / slots. Perhaps, as best shown in FIG. 11B, the bridges can include outer or surface bridges such as bridges B1, B2, B3, etc. that go towards the boundary lines of the rotor. Also, as shown in FIG. 11A, the rotor can include inner bridges (e.g., bridge B4 that goes towards the inner layer of the rotor core). A rotor bridge generally means a mechanical component that connects rotor segments into one. A PM-SyR motor generally includes alternately changing flux barriers 115 and rotor segments 120. In order to ensure that the rotor segments 120 stay in a fixed position and maintain proper alignment during motor operation, rotor bridges can be used to connect the rotor segments into one. The rotor bridges can be manufactured from non-magnetic materials and can be arranged towards the ends of the rotor segments, thereby 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 according to specific embodiments of the PM-SyR motor, such as the diameter of the rotor, the number of rotor segments, and the operating conditions. Generally, the bridges are designed to be light enough and strong enough to withstand the centrifugal force generated during motor operation while providing a slight magnetic interference to the magnetic field within the motor. Generally, the size of the bridges is balanced to provide appropriate mechanical strength to the rotor structure while keeping the leakage magnetic flux low. In this regard, it is preferable that the width of the bridges is as small as possible because generally, the larger the bridge, the larger the leakage magnetic flux, but the manufacturing requirements generally require the bridge to be larger than about 1.0 mm in thickness to satisfy the desired mechanical rotor strength.

[0083] The stator lamination refers to a component within an electric motor manufactured from thin sheets of electrical steel. The sheets can be stacked together and then cut and formed into a specific shape to create the stator core. The stator lamination generally bears the responsibility of providing a magnetic field that interacts with the rotor to generate the electromagnetic force that produces the desired rotational torque or mechanical power. The thin sheets of steel (or other materials) used within the stator lamination can be coated with an insulating material to prevent current from flowing between the sheets and generating energy losses in the form of heat. Also, holes can be punched in the sheets to accommodate wires, usually copper windings, that carry current through the stator. The shape and size of the holes, as well as the spacing between the sheets, can be selected based on various factors and can affect the performance of the motor based on various metrics.

[0084] The rotor lamination is similar to the stator lamination. It is also composed of thin sheets of electrical steel that are stacked together and then cut and formed into a specific shape to create the rotor core. The rotor lamination rotates within the magnetic field generated by the stator, thereby generating the desired rotational torque or mechanical power. Similar to the stator lamination, the thin sheets of steel used in the rotor lamination are also coated with an insulating material to prevent energy losses due to eddy currents. The shape and size of the rotor lamination 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 in relation to the stator, there is a main magnetic flux path between the rotor magnetic flux path segment 120 and the stator 111. There is also an air-gap leakage magnetic flux path (e.g., through B1, B2, B3) through a surface bridge having a directionally magnetized magnetic flux density generated by the permanent magnet 117.

[0086] Figure 12A shows a no-load operating state FEA magnetic field distribution map for an exemplary PM-SyR motor. That is, the 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 located at or near magnetic saturation due to the magnetic field of the magnets. The particular rotor barrier design structure and the resulting flux density 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. In Figure 12A, the north and south poles are depicted, but at startup, these polarities are unknown and only the position of the rotor is known. For the illustrated 4-pole rotor, the method of polarity detection can determine whether the d-axis is in the illustrated position heading towards one of the north poles or, alternatively, whether the d-axis is pointed towards one of the south poles. In this 4-pole configuration, there are two north poles and two south poles. For example, in other configurations 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 whether the d-axis is aligned with a south or north pole.

[0087] The behavior of the motor at startup can be affected by the magnetic saturation of the stator and rotor. Saturation of the stator or rotor generally means the point at which the magnetic field cannot increase further (or increases at a relatively small rate) even when the current flowing through the windings increases. The reason is that the magnetic properties of the core material are fully utilized and cannot support further magnetic flux.

[0088] When the stator or rotor is saturated, any increase in the current through the winding only results in an increase in power loss in the form of heat, rather than an increase in magnetic field strength. To avoid saturation, the stator and rotor can be designed to have carefully selected magnetic properties suitable for the application. In addition to this, the shape and size of the lamination can also be selected to ensure that there is no or almost no area where the magnetic flux is concentrated and a magnetic field that can cause local saturation is present, so that the magnetic flux is evenly distributed.

[0089] Since the magnetic field flows through different parts of the stator and winding depending on the range of factors (such as stator excitation and / or permanent magnets), the magnetic flux density at a specific location can be greater than or less than others due to not only the relative positions of the stator and rotor, but also the positions, timings, and / or interactions of different magnetic fields.

[0090] Generally, during startup, the stator lamination is not yet saturated, and the magnetic flux density in the stator is still very small. For example, in one embodiment, the stator tooth 121 has a maximum of about 0.8 Tesla for both the stator tooth 121 and the stator yoke area 122, indicating that the magnetic field of the permanent magnet is small and the main magnetic path is not saturated in the unloaded state.

[0091] During startup, the rotor lamination is also generally not saturated. In addition to this, since the width of the carrier or the height of the ferrite permanent magnet is very large, the rotor reluctance is large, resulting in a small d-axis inductance L d compared to that of an IPM motor with Nd-Fe-B magnets.

[0092] However, the no-load leakage flux density through many of the surface bridges is large and is located at or near magnetic saturation (e.g., above ~1.6 Tesla). For example, high flux density areas may exist within the bridges of each of the flux barriers B1, B2, and B3, such as when measuring above about 1.6 Tesla.

[0093] It is worth noting that magnetic saturation has a directional component with respect to itself, i.e., the surface bridges have a directionally magnetized flux density due to the magnetic field generated by the magnets. This directionally magnetized flux density within the bridge is located within the leakage flux path (in relation to the main flux path). This means that when the main flux path between the rotor segment and the stator flows in the same direction as the leakage flux path, the magnetic field will further magnetize the leakage flux path until saturation (if not already fully saturated), while if it flows in the opposite direction to the leakage flux path, this will demagnetize the leakage flux path. During normal operation, the saturation / desaturation of the bridges has a relatively minor impact on the motor operation (if present). However, during startup, d due to the small d-axis inductance L, these bridge saturation situations located within the leakage path can cause a large change in the d-axis inductance when a positive or negative voltage is applied to the stator windings.

[0094] When a positive d-axis voltage is applied within the winding, the flux density within the main magnetic path increases linearly as the main flux increases, while the leakage flux density within the rotor bridges decreases rapidly because the magnetomotive force (MMF) generated by the stator windings is opposite to the MMF generated by the ferrite permanent magnets, resulting in an increase in the main flux. Considering the unsaturated state 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 the stator are different from those in FIG. 12A, and thus the surface bridge magnetic flux density is different. At the exemplary rotor position depicted in FIG. 12B, the magnetic flux density within the bridge is significantly smaller (e.g., ~1 Tesla). Thus, when selecting the magnitude of the voltage pulse, these are selected such that they are demagnetized to be close to zero, regardless of whether the leakage magnetic flux path of the surface bridge starts in a state where the leakage magnetic flux path is fully saturated or only partially saturated. Further, the selection can be performed such that the leakage magnetic flux is not magnetized in the opposite direction. As a result, in a given motor configuration, there exists a window of potential voltage pulse magnitudes that provides a clear contrast between the positive and negative voltage pulses (e.g., in the resulting inductance and thus in the response current). That is, the magnitude of the voltage pulse can be selected to generate a high inductance over the entire range of starting magnetic 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 specific magnitude can be selected. Exemplary graphs such as FIGS. 13A - 13C can be useful. Referring to FIG. 13A, in response to applying a d-axis current of -8.0 to 8.0 A, a distinct variation in the d-axis inductance L d 131 can be observed. The d-axis inductance L d reaches a peak at approximately 2.5 A, and thereafter, the d-axis inductance L d decreases so as to return to its original value as the positive d-axis current increases beyond 2.5 A.

[0097] FIG. 13B graphs the leakage magnetic flux in three bridges as the d-axis current varies from -8 A to 8 A. As the magnetic flux density in bridge B1 decreases to zero, the d-axis inductance L dhas reached its peak value. The inductance initially increases because the leakage flux path is demagnetized due to the direction of the flux path. However, a further increase beyond 2.5 A results in magnetization of the leakage flux path in the opposite direction, which leads to 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 has a high degree of linearity because the leakage flux path is already saturated.

[0098] Figure 13C graphs the d-axis current versus flux in Wevers. That is, Figure 13 shows the flux curve when the d-axis current is applied over the entire range, indicating that a non-linear flux curve occurs within the limited current range of 1 to 4.0 A of the d-axis current. Outside this d-axis current range (e.g., less than 1.0 A and greater than 4.0 A), the curve has a high degree of linearity due to the non-saturated state.

[0099] As a result, when a d-axis voltage is applied and a response current i d is generated, considering the non-saturation or linear saturation in the main flux path, the d-axis inductance L d that is non-linear and rapidly increases in the positive direction while aligned with the d-axis direction is dominated by the change in leakage flux within the bridge, while on the other hand, there is almost no change in the negative direction. This insight can be utilized to enable the detection of the difference in current amplitude when two voltage pulses of +V pulse and -V pulse are applied.

[0100] One aspect of the present disclosure relates to the selection of the magnitudes of positive and negative voltage pulses for exciting the stator of a sensorless permanent magnet assisted synchronous reluctance motor during startup polarity detection. The method includes determining the characteristics of the 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, Nd-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 demagnetizes the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic desaturation and the other magnetizes the surface bridge magnetic flux density to maintain or achieve leakage flux magnetic saturation. The d-axis current and its reflection can be used to select the magnitudes of the polarity detection positive and negative voltage pulses such that one of the positive and negative voltage pulses generates the d-axis current value and the other generates the identified corresponding d-axis reflected current value. Selecting the appropriate magnitudes of these positive and negative voltage pulses can enable simple and efficient polarity detection of the PM-SyR motor.

[0101] FIG. 14 shows an exemplary FEA verification / result showing two d-axis current responses I pulse 141 and I pulse 142 when two individual voltage pulses +V pulse1 and -V pulse2 are applied. The current response difference is approximately 2.5 A, and I pulse1 is less than I pulse2 , meaning that the d-axis does not require correction. If the current responses are opposite (i.e., if I pulse1 is greater than I pulse2 ), it may be necessary to apply a correction factor to the d-axis current. The amount of correction is 180 electrical degrees.

[0102] There are additional 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 dcan affect the peak value. Such motor characteristics can be utilized to adapt the PM-SyR polarity detection method. That is, in order to provide accurate polarity detection based on various characteristics of the PM-SyR motor, the predicted responses (or the difference in responses) of two currents I pulse1 and I pulse2 can be adjusted.

[0103] III. Example of HFI Polarity Detection Implementation in a PMSyR Motor

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

[0105] The following steps can inform not only the selection of volt-seconds for the positive and negative voltage pulses applied on the axis detected by the controller, but also other parameter selections.

[0106] Selection of Voltage Pulse Length

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

[0108]

Equation

[0109] Here,

[0110] T s is the sampling period,

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

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

[0113] Current I d acquisition and injection flux A(Vs) selection

[0114] The ferrite PM-SyR motor has rotor bridge characteristics that can be utilized for improved polarity detection. The non-linearity resulting from the PM-SyR rotor bridge characteristics produces a reflection point below a specific d-axis current i d less than.

[0115] The peak d-axis current is caused by the non-linearity of the leakage flux path in the bridge, so 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 from the current response to a negative voltage pulse. A large current may not give a relatively large difference in detection. A good option is to select a d-axis current above the current at the reflection point. In the case of the MUT, 2.5 A is selected as the I d reference value. Based on preliminary analysis, the flux is selected as follows.

[0116]

Equation

[0117] Amplitude V of the voltage pulse pulse selection

[0118] The amplitude of the voltage pulse can be selected based on Equation (5). That is, this can be determined by the controller, or it can also be set during the configuration of the motor based on the timing of the voltage pulse and the desired d-axis current. Also, the amplitude of the voltage pulse can, for example, take into account the dead-time phenomenon of the inverter according to the following equation,

[0119]

Number

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

[0121]

Number

[0122] Here, dt_error_vector[] is a vector including the dead time error (pu) in relation to the DC link voltage, and dt_points is the size of this vector.

[0123] In the case of this implementation form specific to the MUT, the magnitude of V pulse is approximately 70 V. The controller can generate or read V pulse and its characteristics during motor initialization or startup.

[0124] Selection of HFI Frequency and Voltage

[0125] Since the generation of cos(ω h t) used for HFI voltage generation needs to be executed in a state synchronized with the sampling frequency, the selected frequency can be a divisor of the sampling frequency. In addition to this, the divisor can be an even number. For example, the selected frequency can be selected as 500 Hz (32 samples for one high-frequency period).

[0126] In an exemplary embodiment, the motor under test (MUT) is a 2.2 kw PM-SyR motor having the following inductances.

[0127]

Number

[0128] When the injection frequency is 500 Hz, the d-axis reactance of HF is as follows.

[0129]

Number

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

[0131] In the case of the MUT, the HFI voltage is selected as 60 V. Therefore, the peak value of the d-axis current is as follows.

[0132]

Number

[0133] Tracking of loop PI controller gain

[0134] Regarding the proportional-integral (PI) of the HFI tracking loop, it is well understood in the art. In the case of the MUT in this example, the same gain is used for a bandwidth of approximately 25 Hz.

[0135]

Number

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

[0137] Figure 15A shows the speed command and the actual speed 151 following the command speed.

[0138] Figure 15B is the waveform 152 of the stator phase currents i a 、i b 、and i c in real time in the starting process. Figure 15C shows the control variable state update. In the case of MUT, I pulse1 <I pulse2 presents the reference and estimated speeds, the motor current, and the different control flags 153, 154, and 155 used for sensorless control. The speed value and the linear observer used for the transition from HFI are set at 350 rpm and 400 rpm, respectively. For more details, refer to U.S. Patent No. 10,819,264, titled "ROBUST STARTING SYSTEM AND METHOD FOR INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTOR CONTROL," issued to Bojoi et al. on October 27, 2020, which is incorporated herein by reference.

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

[0140] Terms indicating directions such as "vertical direction", "horizontal direction", "uppermost part", "lowermost part", "upper part", "lower part", "inside", "inward", "outside", "outward", etc. are used to assist in explaining the present invention based on the orientation of the illustrated embodiment. The use of terms indicating directions should not be construed as limiting the present invention to any one or more specific orientations.

[0141] The above description relates to the present embodiments of the present invention. Various changes and modifications can be made without departing from the spirit of the present invention as defined in the appended claims and relatively broad aspects, and these need to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be construed as an exhaustive description of all embodiments of the present invention or as limiting the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any one or more individual elements of the described invention can be replaced by alternative elements that provide substantially similar functions or otherwise provide adequate operation. This includes, for example, currently known alternative elements such as those that may be known to those skilled in the art at the present time, and alternative elements that may be developed in the future such as those that may be recognized as alternatives by those skilled in the art during development. Furthermore, the disclosed embodiments also include a plurality of features that are described in corresponding states and can cooperate to provide a collection of benefits. The present invention is not limited to embodiments that include all of these features or provide all of the described benefits, except to the extent explicitly described otherwise 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 of 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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