阅读说明：本技术 高转子磁极开关磁阻电动机的制造敏感控制 (Manufacturing sensitive control of high rotor pole switched reluctance motors ) 是由 M·克里希纳穆尔蒂 T·克利里 T·克内德尔 于 2018-03-31 设计创作，主要内容包括：一种用于利用开关磁阻电机(SRM)控制系统控制SRM的方法。该方法允许在宽范围的速度和载荷上进行自适应脉冲定位。利用初始化机制为SRM提供初始转子位置。在电流波形的初始电流上升阶段期间的相电流波形上定义钉扎点。当电流波形达到钉扎点时,确定电流上升的斜率。然后该斜率被馈送到SRM控制系统的换相模块。来自计算的电感或电流斜率的误差信号被用作到SRM控制系统中的控制回路的输入。时间确定模块确定最佳时间信号以发射下一脉冲。最佳时间信号被馈送到SRM,以用于将多个SRM开关转至接通和关断状态。(A method for controlling a Switched Reluctance Machine (SRM) with an SRM control system. The method allows adaptive pulse positioning over a wide range of speeds and loads. An initialization mechanism is utilized to provide an initial rotor position for the SRM. A pinning point is defined on the phase current waveform during an initial current rise phase of the current waveform. When the current waveform reaches the pinning point, the slope of the current rise is determined. This slope is then fed to the commutation module of the SRM control system. An error signal from the calculated inductance or current slope is used as an input to a control loop in the SRM control system. The time determination module determines an optimal time signal to transmit the next pulse. An optimal time signal is fed to the SRM for turning the plurality of SRM switches on and off.)

1. A method for controlling a switched reluctance machine, SRM, comprising the steps of:

a) providing an SRM control system having a commutation module;

b) providing an initial rotor position for the SRM using an initialization mechanism;

c) defining a pinning point on a phase current waveform during an initial current rise phase of the current waveform;

d) determining a slope of the current rise when the current waveform reaches the pinning point, the slope being fed to the commutation module;

e) calculating an error signal and providing the error signal as an input to a control loop in the SRM control system; and

f) determining an optimal time to transmit a next pulse;

wherein the SRM control system enables adaptive pulse positioning over a wide range of speeds and loads.

2. The method of claim 1, wherein the defined pinning points are static with respect to a base inductance value of the SRM.

3. The method of claim 1, wherein the pinned position is defined at a point on the initial current rise corresponding to a magnitude between 50% and 100% of a steady state current.

4. The method of claim 1, wherein the SRM control system is designed to utilize a basic inductance to calculate the error signal according to a desired inductance value.

5. The method of claim 1, wherein the SRM control system is designed to utilize the measured current rise over a fixed period of time to calculate the error signal from a desired current rise.

6. A method for controlling a switched reluctance machine, SRM, comprising the steps of:

a) providing an SRM control system having a commutation module;

b) providing an initial rotor position for the SRM using an initialization mechanism;

c) defining a pinning point on a phase current waveform during an initial current rise phase of the current waveform, the pinning point being static with respect to a base inductance value of the SRM;

d) determining a slope of the current rise when the current waveform reaches the pinning point, the slope being fed to the commutation module;

e) providing a frequency input signal to the commutation module to obtain a digital estimate for shaft speed;

f) calculating a present speed using the slope of the current rise and the frequency input signal;

g) generating a command current by a regulator unit using a reference speed and the current speed;

h) comparing the command current to a measured current through an internal current loop in the SRM control system; and

i) generating a Pulse Width Modulation (PWM) signal to create a plurality of commutation angles for turning a plurality of switches of the SRM to an on state and an off state;

wherein the SRM control system enables adaptive pulse positioning over a wide range of speeds and loads.

7. The method of claim 6, wherein the pinned position is defined at a point on the initial current rise corresponding to a magnitude between 50% and 100% of steady state current.

8. The method of claim 6, wherein the regulator unit is a proportional-integral unit.

9. An SRM control system for controlling a Switched Reluctance Motor (SRM), comprising:

an initialization module to provide an initial rotor position for the SRM using an initialization mechanism;

a point defining module to define a pinning point on a phase current waveform during an initial current rise phase of the current waveform;

a slope determination module to determine a slope of the current rise when the current waveform reaches the pinning point;

a commutation module to receive a frequency input signal and the slope of the rise in current from the slope determination module;

an error calculation module to calculate an error signal that is fed to a control loop in the SRM control system; and

a time determination module to determine an optimal time to transmit a next pulse;

wherein the SRM control system enables adaptive pulse positioning over a wide range of speeds and loads.

10. The SRM control system of claim 9, wherein the defined pinning points are static with respect to a base inductance value of the SRM.

11. The SRM control system of claim 9, wherein said pinned position is defined at a point on said initial current rise corresponding to a magnitude between 50% and 100% of steady state current.

12. The SRM control system of claim 9, designed to utilize the basic inductance to calculate the error signal according to a desired inductance value.

13. The SRM control system of claim 9, designed to utilize the measured current rise over a fixed period of time to calculate the error signal from a desired current rise.

14. The SRM control system of claim 9, wherein the optimal time determined from the time determination module is utilized to turn the plurality of switches of the SRM to an on state and an off state.

Technical Field

The present disclosure relates generally to methods for controlling Switched Reluctance Motors (SRMs), and more particularly, to methods and systems for controlling SRMs to enable adaptive pulse positioning over a wide range of speeds and loads.

Background

Switched Reluctance Machines (SRMs) are a class of simple motors that operate by reluctance torque. The SRM includes salient rotor and stator poles. Concentrated windings are present on the stator, but no windings or permanent magnets are present on the rotor. These features enable the SRM to achieve very high speeds relative to conventional non-SRM motors. Since there are no windings in the rotor, power is only transferred to the windings in the stator, not the rotor, and due to this simple mechanical structure, the SRM provides lower maintenance costs relative to conventional motors. When current is passed through the stator windings, torque is generated by the tendency of the rotor poles to align with the energized stator poles. Continuous torque can be generated by synchronizing the excitation of each phase with the rotor position. Accurate rotor position information is critical to controlling the torque of the motor.

Several techniques for position estimation using active or passive phase inductances have been proposed. In most approaches, a controlled signal is utilized and can be applied to the phase windings to estimate the inductance and thus determine the rotor position without the use of a position encoder. Some other methods describe automatic calibration of the motor. One such method describes a sensorless rotor position measurement system having a digital processor that receives signals from current and flux sensors of current and flux associated with phase windings of the motor. The current and flux measurements can be made at predicted reference rotor positions. Only one sample of current and flux is taken per energizing cycle. This method is based on a position estimation method, which cannot provide absolute rotor position information.

Another method describes a circuit for controlling a switched reluctance motor by indirect sensing of rotor position within the switched reluctance motor. The method measures the time for the current to rise between two predetermined levels. The measured current rise time may be compared to an expected current rise time to determine whether the conduction interval in the motor phase is in phase with the position of the rotor or lags or leads the position of the rotor. However, this method uses a complex algorithm to calculate the current rise time.

Another method for controlling a switched reluctance motor includes a switched reluctance motor having: a sensor that generates and transmits a sensor signal indicative of an operating characteristic, a controller operatively coupled to the switched reluctance motor and the sensor, and a method performed by the controller. Here, sensorless control of the SRM is achieved by injecting voltage pulses in the phases and measuring the resulting current. However, this method injects additional voltage pulses for controlling the switched reluctance motor.

There is therefore a need for a method for controlling a switched reluctance motor to achieve adaptive pulse positioning. Such a method will reduce manufacturing defects and aging effects in the motor. Furthermore, such a method would adjust the control parameters for each individual motor, rather than for motors manufactured in bulk. Furthermore, such a method will provide accurate rotor position information. Such a method would utilize a simple algorithm to calculate the current rise time. Furthermore, such an approach would not inject additional voltage pulses for controlling the switched reluctance motor. These and other objects are achieved by the present embodiment.

Disclosure of Invention

To minimize the limitations found in the prior art, and to minimize other limitations that will become apparent upon reading the present specification, a preferred embodiment of the present invention provides a Switched Reluctance Motor (SRM) control system that controls an SRM and enables adaptive pulse positioning over a wide range of speeds and loads. The SRM control system includes an initialization module to provide an initial rotor position for the SRM using an initialization mechanism. A point definition module in the SRM control system defines a pinning point on the phase current waveform during an initial current rise phase of the current waveform. The defined pinning points are static with respect to the base inductance value of the SRM.

Preferably, there are two options to determine a new pinning point in order to handle changes in operating conditions and load torque distribution. The first option depends on knowledge of the inductance value of the current that is used for the new operating conditions or that can be calculated. And a second option is to only require the slope of the current profile (desired current rise) over a fixed period based on this inductance if a simplification in the control method allows. When the waveform reaches the pinned current level, the slope of the current (rise) is measured.

A slope determination module in the SRM control system determines a slope of a rise in current when the current waveform reaches a pinning point. The commutation module in the system is designed to receive the frequency input signal and the slope of the rise of the current from the slope determination module. The SRM control system also includes an error calculation module to calculate an error signal. The SRM control system is designed to use the basic inductance or measured current rise to calculate an error signal. In one configuration, the slope 42 of the current rise is utilized to calculate the base inductance that is used to calculate the error signal from the desired inductance. In another configuration, the SRM control system is designed to utilize the current rise measured over a fixed period of time to calculate an error signal from the expected current rise. An error signal from the calculated inductance or current slope is used as an input to a control loop in the SRM control system. The time determination module determines an optimal time to transmit the next pulse.

The preferred method describes the overall control architecture of the SRM control system. According to this control architecture, a reference speed or torque is provided as an input to the system. When the current waveform reaches the pinning point and is fed to the commutation module, the slope of the current rise is calculated. The slope of the current rise is used to calculate the base inductance value. The frequency input signal is provided to another input of the commutation module, which gives a digital estimate of the shaft speed. Input signal using current rise slope and frequencyThe current speed is calculated. The error generator between the reference speed and the current speed is processed by a regulator unit generating a command current. The regulator unit may be a Proportional Integral (PI) regulator. The command current is compared to the measured current by an internal current loop in the SRM control system. Thereafter, a Pulse Width Modulation (PWM) signal is generated to create a plurality of commutation angles for utilizing the time signal T_on、T_offThe plurality of switches of the SRM are turned on and off.

The preferred embodiments include methods for controlling an SRM using an SRM control system. The method begins by providing an SRM control system. Next, an initial rotor position is provided to the SRM using an initialization mechanism. Then, a pinning point is defined on the phase current waveform during an initial current rise phase of the current waveform. Thereafter, when the current waveform reaches the pinning point, the slope of the current rise is determined. The slope is then fed to the commutation module. Thereafter, an error signal from the calculated inductance or current slope is used as an input to a control loop in the SRM control system. Finally, the time determination module determines the optimal time signal to transmit the next pulse. The optimum time signal is fed to the SRM for turning the plurality of SRM switches on and off.

The best efficiency and maximum load capacity of the SRM is obtained when the pinning point of the current waveform is near the top of the initial rise of the current waveform and the pinned point on the inductance profile is near the beginning of the inductance rise for that phase of the motor.

It is a first object of the present invention to provide an SRM control system that enables accurate pulse positioning in a sensorless environment.

It is a second object of the present invention to provide an SRM control system for controlling an SRM such that manufacturing defects and aging effects are reduced in an electric machine.

It is a third object of the present invention to provide an SRM control system that is adaptable to adjust control parameters for each individual motor, rather than for a whole batch of manufactured motors.

It is an additional object of the present invention to provide an SRM control system that utilizes a simple algorithm for calculating the current rise time.

It is yet an additional object of the present invention to provide a SRM control system for controlling a switched reluctance motor without injecting additional voltage pulses.

These and other advantages and features of the invention are described in detail to enable those skilled in the art to understand the invention.

Drawings

Elements in the figures are not necessarily drawn to improve understanding and enhance clarity of various elements and embodiments of the invention. Furthermore, elements that are known and well-known to those of skill in the art are not depicted in order to provide a clear view of the various embodiments of the present invention. Accordingly, the drawings are summarized in form for clarity and conciseness.

FIG. 1 illustrates a block diagram of a Switched Reluctance Motor (SRM) control system in accordance with a preferred embodiment of the present invention;

FIG. 2 illustrates a graphical representation showing the change in inductance profile with respect to the change in electrical angle in accordance with a preferred embodiment of the present invention;

FIG. 3 illustrates the overall control architecture of an SRM control system having speed and current loops in accordance with a preferred embodiment of the present invention;

FIG. 4 illustrates a flow chart of a method for controlling an SRM with an SRM control system in accordance with a preferred embodiment of the present invention;

FIG. 5 illustrates an asymmetric bridge configuration for controlling phase currents of an SRM in accordance with a preferred embodiment of the present invention; and

fig. 6 illustrates pinning points at current waveforms of a three-phase SRM in accordance with a preferred embodiment of the present invention.

Detailed Description

In the following discussion of the various embodiments and applications of the present invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention.

Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not solve any of the problems discussed above, or may only solve one of the problems discussed above. Furthermore, one or more of the problems discussed above may not be fully solved by any of the features described below.

As used herein, the singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. As used herein, "and" may be used interchangeably with "or" unless explicitly stated otherwise. As used herein, the term 'about' means ± 5% of the parameter. All embodiments of any aspect of the invention may be used in combination, unless the context clearly dictates otherwise.

Throughout the specification and claims, the words 'comprise', 'comprising', and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense unless the context clearly requires otherwise; in other words, in the sense of "including but not limited to". The use of singular or plural referents also includes plural and singular referents, respectively. Moreover, when used in this application, the words "herein," "wherein," "however," "above," "below," and the like are to be construed in a generic sense as referring to the entire application, rather than to any specific part of the application.

The description of the embodiments of the present disclosure is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. While specific embodiments of, and examples for, the disclosure are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the disclosure, as those skilled in the relevant art will recognize.

Fig. 1 illustrates a block diagram of a Switched Reluctance Motor (SRM) control system 10 for controlling an SRM 26. The SRM control system 10 enables adaptive pulse positioning over a wide range of speeds and loads. The SRM control system 10 includes an initialization module 12 to provide an initial rotor position to the SRM 26 using an initialization mechanism. In a preferred embodiment, the initialization mechanism is adapted to implement several ways such as hard alignment or any other mathematical way. A point definition module 14 in the SRM control system 10 defines a pinning point on the phase current waveform during an initial current rise phase of the current waveform. The defined pinning points are static relative to the base inductance value of the SRM 26 as a function of the desired operating point. The PI controller for the speed loop controls the amount of time from x (the pinning point) to the turn on of the next phase. If the demand for speed changes, the demand for current also changes. This means that the slope is different and needs to be changed at the pinning point. Between 50% and 100% of the steady state current of the initial current rise, particularly when operating conditions (load torque) change abruptly, a pinning point is defined at a particular selected current magnitude. This also helps to improve accuracy when we enter monopulse mode, and the current waveform begins to level off as it approaches the alignment position. The goal is to have the pinning point sufficiently below or sufficiently far from the bent current distribution.

Preferably, there are two options to determine a new pinning point in order to handle changes in operating conditions and load torque distribution. The first option depends on knowledge of the inductance value of the current that is used for the new operating conditions or that can be calculated. And a second option is to only require the slope of the current profile (desired current rise) over a fixed period based on this inductance if a simplification in the control method allows.

When the current waveform reaches the pinning point, the slope determination module 16 determines a slope 42 of the current rise (see FIG. 3). When the waveform reaches the current level of the needle stick, the slope (rise) of the current is measured. As shown in the graphical representation in fig. 2, if we change the current value, the inductance distribution changes accordingly. This means that the angle corresponding to the position of the needle stick must be changed until the same slope as in the previous case is reached.

Commutation module 18 is designed to receive a slope 42 of the rise in current from slope determination module 16. The SRM control system 10 also includes an error calculation module 20 to calculate an error signalNumber (n). The SRM control system 10 is designed to utilize the basic inductance or measured current rise to calculate an error signal. In one configuration, the slope 42 of the current rise is utilized to calculate the base inductance for calculating the error signal from the desired inductance. In another configuration, the SRM control system 10 is designed to utilize the current rise measured over a fixed period of time to calculate an error signal from the desired current rise. An error signal from the calculated inductance or current slope is used as an input to a control loop 22 in the SRM control system 10. Finally, the time determination module 24 determines the optimal time T_on、T_off40 (see fig. 3) to transmit the next pulse. Optimum time T_on、T_off40 turn the various switches of the SRM 26 on and off. In one configuration of the preferred embodiment, the position is determined to transmit the next pulse.

Fig. 3 shows the overall control architecture of the SRM control system 10 with speed and current loops. Here, a reference Speed (Ref Speed)32 or torque is provided as an input to the system 10. Preferably, the proposed method for controlling the SRM 26 utilizes current feedback. When the current waveform reaches the pinning point and is fed to commutation module 18, the slope 42 of the current rise is calculated. The slope 42 of the current rise is used to calculate the base inductance value. Frequency input signal T_p44 is another input provided to commutation module 18, giving a numerical estimate of shaft speed. Using the slope 42 of the current rise and the frequency input signal T_p44 to calculate the current speed 36. An error generator between the reference speed 32 and the current speed 36 generates a command current (I) by generating a command current_ced)34, and the regulator unit 30. The regulator unit 30 may be a Proportional Integral (PI) regulator. Comparing the command current 34 with the measured current (I) through an internal current loop in the SRM control system 10_phase)38 to generate a Pulse Width Modulated (PWM) signal. PWM signal using time signal T_on、T_off40 create a plurality of commutation angles for turning the plurality of switches of the SRM 26 to on and off states.

Fig. 4 shows a flow chart of a method of controlling the SRM 26 using the SRM control system 10. As shown in block 50, an SRM control system having a commutation module is provided. Next, as shown in block 52, an initial rotor position is provided to the SRM using an initialization mechanism. Then, as indicated in block 54, a pinning point is defined on the phase current waveform during the initial current rise phase of the current waveform. Thereafter, when the current waveform reaches the pinning point as shown in block 56, the slope of the current rise is determined. The slope is then fed to the commutation module. Thereafter, as shown in block 58, an error signal from the calculated inductance or current slope is used as an input to a control loop in the SRM control system. Finally, as indicated at block 60, the time determination module determines the optimal time signal to transmit the next pulse. The optimum time signal is fed to the SRM for turning the plurality of SRM switches on and off.

Fig. 5 illustrates an asymmetric bridging configuration commonly used to control SRMs 26. This configuration allows each phase to be connected between two switches T1, T2, allowing independent control and ensuring that the inverters do not have a shoot-through fault. The on and off signals 40 in fig. 3 are used to control the switches T1 and T2.

Fig. 6 shows three current waveforms for a three-phase motor. In this example, "x" is the pinning point of the current waveform in phase A of the motor. Here, the pinning point is approximately 80% of the steady state current for the operating condition. The best efficiency and maximum load capacity of the SRM is obtained when the pinning point of the current waveform is near the top of the initial rise of the current waveform and the pinned point on the inductance profile is near the beginning of the inductance rise for that phase of the motor.

In the present embodiment, feedback from one commutation pulse is used for the positioning of the next pulse. Alternatively, feedback from the pulse may be used to adjust the position of the next pulse in the same phase, the position reached by the next particular stator-rotor pole combination, or any position in between.

The benefit of using each pulse to modify only pulses of the same phase is that it allows the phases to be adjusted independently due to the non-uniformity of inductance across each phase; however, the position feedback is slowed down by a multiple of the number of phases in the motor. This can be overcome by using the error of the current pulse to input both control loops. In between the two control loops, one control loop adjusts the current phase and the other adjusts all phases to allow both small adjustments between phases while still achieving fast feedback to the main control method.

Modifying only the same stator-rotor pole combination with each pulse has the benefit that it allows for adjustment of non-uniform pole position, air gap and inductance; however, the position feedback is multiplied by the number of phases being slowed down times the number of rotor poles. A method similar to the previous method can be used to introduce additional degrees of freedom while still maintaining fast feedback.

In the current embodiment, an event-based control loop is utilized. Any form of control loop that operates based on the error between the desired inductance (or desired current rise) and the measured inductance (or measured current rise) suffices for the purposes of the preferred embodiments.

In the current embodiment, the current is pinned on the initial rising edge of the pulse; however, any point along an arbitrary waveform may be used as a pinning point.

In the present embodiment, the current rise is used at a specific point on the current rise; however, at the desired waveform position, the phase may be turned off or relaxed (freecoiled), and the current droop/decay at that point may be used in the same manner to control the position.

In the present embodiment, the output of the control loop is the desired time between pulses, and when the time from the last pulse is reached, the next pulse is transmitted. The output of the control loop may also be tuned to be at a desired position on a software encoder that is continuously updated based on the velocity estimate. This method introduces additional error because the software encoder is prone to drift due to errors in the speed measurement, but this method will achieve the same effect. Similarly, a hardware encoder may be used, and this method may position the pulses relative to the hardware encoder.

The method may be further extended to allow the desired inductance (or desired current rise) to be adjusted based on speed, load, or desired optimization. These adjustments may be applied according to a look-up table based on the current operating point, or may be calculated in real time based on an adjustment formula.

The foregoing description of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto and the equivalents of those claims.