Zero current control-based belt speed restarting method of permanent magnet synchronous motor

Abstract

The embodiment of the invention relates to the technical field of permanent magnet synchronous motor control, and particularly provides a permanent magnet synchronous motor belt speed restarting method based on zero current control, a computer readable storage medium and computer equipment. The belt speed restarting method comprises the following steps that the stator current of the permanent magnet synchronous motor is adjusted to zero, and the rotor position and rotating speed information of the permanent magnet synchronous motor are preliminarily estimated; the electromagnetic torque of the permanent magnet synchronous motor is adjusted to zero, and the preliminarily estimated rotor position and rotating speed are accurately estimated; and finishing belt speed restarting of the permanent magnet synchronous motor by adopting a position sensorless control strategy corresponding to the rotating speed according to the accurate estimation result of the rotor position and the rotating speed information. With such a configuration, it is possible to improve the accuracy of position information and effectively suppress current shock during tape speed restart.

Description

Technical Field

[0001] The present invention relates to the technical field of control of permanent magnet synchronous motors, and specifically provides a permanent magnet synchronous motor belt speed re-start method based on zero current control, a computer-readable storage medium, and a computer device. Background Art

[0002] Permanent Magnet Synchronous Motor (PMSM) has been widely used in rail transit, electric vehicles, industrial automation and other fields due to its advantages in high efficiency, high power density and low noise. However, the high-performance control of permanent magnet synchronous motors requires a high degree of reliance on accurate measurement of rotor position and speed. In application scenarios in related fields, under certain specific working conditions, permanent magnet synchronous motors are required to quickly and smoothly resume normal operation after losing power to ensure production continuity and system reliability. Specifically, the process of restarting a permanent magnet synchronous motor after a power outage during operation is called belt speed re-throw.

[0003] In traditional applications, position sensors such as photoelectric encoders or resolvers are usually used to obtain position information for vector control. The use of position sensors not only increases the scale and cost of the system, but also reduces the reliability of the system. Therefore, position sensorless control for permanent magnet synchronous motors has become one of the research hotspots in recent years. In position sensorless control, accurate acquisition of the initial rotor position and speed of the motor is required to achieve smooth and stable belt speed re-throw. However, for position sensorless control systems, the rotor position information of the permanent magnet synchronous motor before restarting is unknown. If the vector control scheme is directly started at this time, problems such as low starting torque, reverse rotation, and overcurrent faults may occur.

[0004] As an improvement, the existing position sensorless control belt speed re-throwing method mainly includes back electromotive force detection method, zero current control method, virtual resistance method and short circuit current method. The back electromotive force detection method requires the addition of an additional voltage sensor or sampling circuit; the zero current control method sets the current command to zero and estimates the initial position and speed of the rotor by outputting the voltage. The advantage of this method is that it can quickly estimate the initial value of the rotor. However, since the estimated value is calculated based on a certain instantaneous voltage command, the estimated result fluctuates greatly; the virtual resistance method can effectively avoid the phenomenon of current shock when the belt speed is re-thrown, but since the resistance value of the virtual resistance will change with the change of the rotor speed, the position estimation accuracy will also be affected by the speed; the short circuit current method determines the initial position information of the motor by analyzing the response of the stator current on the basis of applying a zero voltage vector to the motor for multiple times. Therefore, the convergence speed of the short circuit current method is fast, but the robustness of the parameters is poor and the sampling requirements are high. Summary of the invention

[0005] The present invention aims to solve the above-mentioned technical problems to at least a certain extent and / or solve at least part of the above-mentioned technical problems. The present invention proposes a permanent magnet synchronous motor speed re-throwing method based on zero current control, aiming to ensure that the permanent magnet synchronous motor speed re-throwing process can be quickly completed within the full speed application range.

[0006] In the first aspect, the present invention provides a method for re-investing a permanent magnet synchronous motor with speed based on zero current control, and the control method comprises the following steps: adjusting the stator current of the permanent magnet synchronous motor to zero, and preliminarily estimating the rotor position and speed information of the permanent magnet synchronous motor; adjusting the electromagnetic torque of the permanent magnet synchronous motor to zero, and accurately estimating the preliminarily estimated rotor position and speed; and according to the results of the accurate estimation of the rotor position and speed information, adopting a position sensorless control strategy corresponding to the speed to complete the re-investing of the permanent magnet synchronous motor with speed.

[0007] For the above-mentioned permanent magnet synchronous motor speed re-investment method based on zero current control, in a possible implementation manner, the "adjusting the stator current of the permanent magnet synchronous motor to zero and preliminarily estimating the rotor position and speed information of the permanent magnet synchronous motor" includes: using a proportional resonant (PR) controller to adjust the stator current of the permanent magnet synchronous motor to zero; using a phase locked loop (PLL) detector to extract the rotor position and speed information of the permanent magnet synchronous motor to preliminarily estimate the rotor position and speed information.

[0008] For the above-mentioned permanent magnet synchronous motor speed re-start method based on zero current control, in a possible implementation manner, the “adopting a PR controller to adjust the stator current of the permanent magnet synchronous motor to zero” includes: the voltage equation of the permanent magnet synchronous motor in a stationary coordinate system is:

[0009]

[0010] In the formula, u α and u β are the voltages of the α-axis and β-axis of the stationary coordinate system, i α and i β are the currents of the α-axis and β-axis, θ r Indicates the rotor position, R s L is the stator resistance and inductance related parameters α , L β and L αβ The relationship between the dq-axis equivalent inductance is:

[0011]

[0012] Where, L d Indicates the d-axis equivalent inductance, L q represents the q-axis equivalent inductance;

[0013] Among them, the voltage equation of the permanent magnet synchronous motor in the rotating coordinate system is:

[0014]

[0015] In the formula, u sd and u sq are the d-axis and q-axis voltages, respectively, i sd and i sq are the d-axis and q-axis currents, ω r is the rotor speed, ψ m is the permanent magnet flux, p is the differential operator;

[0016] Among them, the transfer function of the PR controller is:

[0017]

[0018] In the formula, ω c is a non-ideal resonant frequency.

[0019] For the above-mentioned permanent magnet synchronous motor speed re-start method based on zero current control, in a possible implementation manner, the “adjusting the electromagnetic torque of the permanent magnet synchronous motor to zero and accurately estimating the initially estimated rotor position and speed” includes: under the zero current control strategy, the stator current is always equal to zero, at this time, i sd =0,isq =0,i α =0,i β =0, and substituting into the above formula (1) and formula (3), we can get:

[0020]

[0021] The flux linkage and electromagnetic torque can be written as follows in the rotating coordinate system:

[0022]

[0023] When the reference voltage output by the PR controller is and When , based on formula (5), the voltage expression under zero current control can be calculated as:

[0024]

[0025] In the formula, is the α-axis reference voltage, is the β-axis reference voltage, is the preliminary estimate of the rotor phase, This is a preliminary estimate of the rotor speed.

[0026] For the above-mentioned permanent magnet synchronous motor speed re-investment method based on zero current control, in a possible implementation manner, the "adjusting the electromagnetic torque of the permanent magnet synchronous motor to zero and accurately estimating the initially estimated rotor position and speed" includes: the electromagnetic torque equation of the permanent magnet synchronous motor in the rotating coordinate system is:

[0027]

[0028] In the formula, ψ d ,ψ q are the d-axis and q-axis flux, respectively, and p n is the pole pair number, T e is the electromagnetic torque;

[0029] Among them, the electromagnetic torque depends on the stator current and torque angle δ, so the equation of electromagnetic torque can also be written as follows:

[0030]

[0031] In the formula, I s is the effective value of the stator phase current, L is the effective stator lamination length, r is the air gap radius, B m is the fundamental amplitude of permanent magnet flux, N s is the number of turns of the phase coil;

[0032] Given that the electromagnetic torque command value is zero, the torque angle is close to zero, so equation (8) can be written as:

[0033] T e =k Te sinδ≈k Te δ (14)

[0034] In the formula, δ is the torque angle. When the observed rotor speed is greater than the actual speed, δ is greater than 0, otherwise δ is less than 0.

[0035] For the above-mentioned permanent magnet synchronous motor speed re-investment method based on zero current control, in a possible implementation manner, the "according to the results of the accurate estimation of the rotor position and speed information, adopting a position sensorless control strategy corresponding to the speed to complete the speed re-investment of the permanent magnet synchronous motor" includes: when the accurately estimated speed of the permanent magnet synchronous motor is less than or equal to a first preset speed, adopting a first position sensorless control strategy to complete the speed re-investment of the permanent magnet synchronous motor; and / or when the accurately estimated speed of the permanent magnet synchronous motor is greater than a second preset speed, adopting a second position sensorless control strategy to complete the speed re-investment of the permanent magnet synchronous motor; wherein, the second preset speed is greater than or equal to the first preset speed.

[0036] For the above-mentioned permanent magnet synchronous motor speed re-investment method based on zero current control, in a possible implementation manner, the first position sensorless control strategy is a position sensorless control strategy based on pulsating square wave injection; and / or the second position sensorless control strategy is a position sensorless control strategy of a model reference adaptive observer.

[0037] For the above-mentioned method for re-investing the speed of a permanent magnet synchronous motor based on zero current control, in a possible implementation manner, the "according to the result of the accurate estimation of the rotor position and speed information, adopting a position sensorless control strategy corresponding to the speed to complete the speed re-investment of the permanent magnet synchronous motor" includes: when the speed of the permanent magnet synchronous motor is less than or equal to the first preset speed, adopting a position sensorless control strategy based on pulsating square wave injection, the high-frequency pulse voltage signal injected into the estimated rotor reference system is:

[0038]

[0039] The high-frequency induced current caused by the component of the high-frequency pulse voltage signal in the stationary coordinate system can be expressed as:

[0040]

[0041] In the formula, θ ris the rotor position, Δθ is the rotor position estimation error, i αh is the high frequency induced current on the α axis, i βh is the high frequency induced current of β axis;

[0042] When the speed of the permanent magnet synchronous motor is greater than the second preset speed, the speed and position of the rotor in the normal position sensorless control strategy are estimated by starting the model reference adaptive observer:

[0043]

[0044] The speed adaptation mechanism is:

[0045]

[0046] Technical effects:

[0047] It can be seen that the preferred embodiment of the present invention has the following advantages:

[0048] 1. The zero current control method based on the PR regulator can effectively avoid the current shock during the belt speed re-throw process. Specifically, the design of the current regulator is completed in a stationary coordinate system, so the rotor position information is not required. Compared with the PI regulator, it is more suitable for the belt speed re-throw condition of the permanent magnet synchronous motor, such as being able to achieve zero static error tracking of the voltage at a specific frequency, and having better anti-interference ability.

[0049] 2. The position-free speed re-throw of the permanent magnet synchronous motor can be achieved without adding additional hardware, which saves components and reduces costs.

[0050] 3. When the belt speed re-investment method approximately estimates the rotor position information in the first step, it does not need to use parameters such as the rotor position information of the permanent magnet synchronous motor, so it has stronger parameter robustness.

[0051] 4. Compared with the traditional zero current control method, the present invention uses a PLL detector to extract the rotor position and speed information in the output voltage of the PR regulator, which speeds up the convergence of the rotor position and speed information and thus makes the estimation result smoother.

[0052] 5. The rotor position information optimization method based on zero torque control designed by the present invention utilizes the characteristic that the torque angle is proportional to the output torque in the zero torque control mode, so that the rotor position information output by the PR regulator further converges to the actual value, thereby further improving the estimation accuracy of the rotor position information.

[0053] 6. Compared with the short-circuit current method which requires multiple injections (applying a zero voltage vector to the motor), the rotor position detection method of the present invention can maintain high accuracy within the full speed application range of the permanent magnet synchronous motor, and can ensure rapid completion of the speed re-throw process within the full speed application range.

[0054] In summary, in the preferred embodiment of the present invention, the permanent magnet synchronous motor speed re-investment method based on zero current control adopted by the present invention can improve the estimation accuracy and convergence speed of the rotor position information of the permanent magnet synchronous motor, can effectively suppress the current shock during speed re-investment, and has stronger parameter robustness.

[0055] In a second aspect, the present invention provides a computer-readable storage medium, which includes a memory, wherein the memory is suitable for storing multiple program codes, and the program codes are suitable for being loaded and run by a processor to execute any of the aforementioned methods for re-starting a permanent magnet synchronous motor with speed based on zero current control.

[0056] It can be understood that the computer-readable storage medium has all the technical effects of the permanent magnet synchronous motor speed re-investment method based on zero current control as described in any of the above items, which will not be repeated here.

[0057] It is understood by those skilled in the art that the present invention implements all or part of the processes in the method for re-investing the speed of a permanent magnet synchronous motor based on zero current control, which can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned various method embodiments can be implemented. Among them, the computer program includes computer program code, and it can be understood that the program code includes but is not limited to the program code for executing the above-mentioned method for re-investing the speed of a permanent magnet synchronous motor based on zero current control. For the convenience of explanation, only the part related to the present invention is shown. The computer program code can be in the form of source code, object code, executable file or some intermediate form. The computer-readable storage medium may include: any entity or device, medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium that can carry the computer program code. It should be noted that the content contained in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electric carrier signals and telecommunication signals.

[0058] In a third aspect, the present invention provides a computer device comprising a memory and a processor, wherein the memory is suitable for storing a plurality of program codes, and the program codes are suitable for being loaded and run by the processor to execute any of the aforementioned methods for re-starting a permanent magnet synchronous motor with speed based on zero current control.

[0059] It is understandable that the device has all the technical effects of any of the above-mentioned methods for re-starting the speed of a permanent magnet synchronous motor based on zero current control, which will not be described in detail here. The device can be a computer-controlled device formed by various electronic devices.

[0060] The computer device may include a processor, a memory, an input / output interface, a communication interface, a display unit and an input device. The processor, the memory and the input / output interface are connected via a system bus, and the communication interface, the display unit and the input device are connected to the system bus via the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and the external device. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a mobile cellular network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a thermal management control method for a power battery is implemented. The display unit of the computer device is used to form a visually visible picture, which can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the computer device shell, or an external keyboard, touchpad or mouse. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0062] Figure 1 A schematic flow chart showing a method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to an embodiment of the present invention;

[0063] Figure 2 A timeline diagram showing a method for re-projecting with speed according to an embodiment of the present invention;

[0064] Figure 3 The logic block diagram of zero current control based on PR regulator in a stationary coordinate system is shown;

[0065] Figure 4 A block diagram showing low pass filtering and normalization of a voltage signal;

[0066] Figure 5 A logic block diagram showing an initial estimation of rotor position and speed information based on a PLL controller implementation;

[0067] Figure 6 The normalized voltage phasor diagram is shown;

[0068] Figure 7 A block diagram showing an optimization strategy for rotor position and speed based on zero torque control; and

[0069] Figure 8 A block diagram of a belt speed re-throw method based on hybrid position sensorless control is shown. DETAILED DESCRIPTION

[0070] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0071] It should be noted that in the description of the present invention, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0072] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installation", "setting", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal connection of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0073] In addition, in order to better illustrate the present invention, many specific details are given in the following specific embodiments. Those skilled in the art should understand that the present invention can also be implemented without certain specific details. In some examples, the position sensorless control principle well known to those skilled in the art is not described in detail in order to highlight the main purpose of the present invention.

[0074] The method for re-throwing a permanent magnet synchronous motor with speed based on zero current control of the present invention provides a method for re-throwing a permanent magnet synchronous motor with speed without position sensor in the full speed range. The method adopts a zero current control strategy based on a PR regulator, which can effectively suppress the phenomenon of current shock in the permanent magnet synchronous motor during the re-throwing process. Since the method does not need to use the parameters of the permanent magnet synchronous motor (compared with the existing zero current control technology), it has stronger parameter robustness and faster convergence speed. As described below, it can basically restore the free-running IPMSM to a normal state quickly within 350ms.

[0075] Main reference Figure 1 In a possible implementation manner, the belt speed re-throwing method based on zero current control provided by the present invention comprises the following steps:

[0076] S100, using a PR regulator to adjust the current of the stator of the permanent magnet synchronous motor to zero, and using a PLL to extract the rotor position and speed information of the permanent magnet synchronous motor to make a preliminary estimate of the rotor position and speed;

[0077] S200, adjusting the electromagnetic torque of the permanent magnet synchronous motor to zero, and using a zero torque control method to accurately estimate the initially estimated rotor position and speed;

[0078] S300, based on the accurate estimation results of the rotor position and speed, a position sensorless control strategy corresponding to the speed is adopted to complete the belt speed re-investment of the permanent magnet synchronous motor, thereby restoring the free-running permanent magnet synchronous motor to a normal position sensorless control strategy.

[0079] Regarding "using a position sensorless control strategy corresponding to the rotational speed to complete the speed re-investment of the permanent magnet synchronous motor, thereby restoring the free-running permanent magnet synchronous motor to a normal position sensorless control strategy", in a possible implementation, the present invention uses a hybrid position sensorless control scheme to re-invest the permanent magnet synchronous motor at speed. For example, under low-speed conditions, a control strategy based on pulsating square-wave injection (PSWI) can be used. In this way, the high-frequency induced current can be separated from the stator current by utilizing the symmetry of the input signal, and the rotor speed and position can be obtained from the high-frequency induced current by using a signal extraction method. Under medium and high-speed conditions, a model reference adaptive system (MRAS) observer can be used to estimate the speed and position of the rotor for the normal position of sensorless control. The mode selector can switch the position sensorless control strategy according to the accurately estimated rotor speed, and a speed hysteresis loop is set during the switching process to ensure a smooth transition between the two control schemes. For example, when the accurately estimated rotor speed is greater than the upper limit of the hysteresis switching threshold, the position-free control strategy of the MRAS observer can be selected, and when the accurately estimated rotor speed is less than or equal to the lower limit of the hysteresis switching threshold, the position-free control strategy based on pulsating square wave injection can be selected.

[0080] First, define the three-phase coordinate system, stationary coordinate system, and rotating coordinate system of the IPMSM. The three-phase coordinate system of the IPMSM consists of three coordinate axes with a phase difference of 120° (referred to as axis A, axis B, and axis C). Figure 6 The α-axis and β-axis of the stationary coordinate system are perpendicular to each other, where the α-axis of the stationary coordinate system coincides with the A-axis in the three-phase coordinate system. The rotating coordinate system of the IPMSM is a coordinate system that rotates with time, where the d-axis and q-axis of the rotating coordinate system are perpendicular to each other, where the angle between the d-axis of the rotating coordinate system and the A-phase of the three-phase coordinate system is the rotor position angle θ. r .

[0081] Among them, the voltage equation of IPMSM in the stationary coordinate system is:

[0082]

[0083] In the formula, u α and u β are the voltages of the α-axis and β-axis respectively, i α and i β are the currents of the α-axis and β-axis, θ r Indicates the rotor position, R s is the stator resistance, and the inductance related parameters L α , Lβ and L αβ The relationship between the dq-axis equivalent inductance is:

[0084]

[0085] Where, L d Indicates the d-axis equivalent inductance, L q represents the q-axis equivalent inductance.

[0086] Among them, the voltage equation of IPMSM in the rotating coordinate system is:

[0087]

[0088] In the formula, u sd and u sq are the d-axis and q-axis voltages, respectively, i sd and i sq are the d-axis and q-axis currents, ω r is the rotor speed, ψ m is the permanent magnet flux, and p is the differential operator.

[0089] In order to reduce the current impact when the belt speed is re-thrown, in the present invention, a PR controller is used to adjust the stator current to zero. The transfer function of the non-ideal PR controller is:

[0090]

[0091] In the formula, ω c is a non-ideal resonant frequency.

[0092] Under the zero current control strategy, the stator current is always equal to 0. At this time, i sd =0,i sq =0,i α =0,i β =0, and substituting it into formula (1) and formula (3), we can get:

[0093]

[0094]

[0095] The flux linkage and electromagnetic torque can be written as follows in the rotating coordinate system:

[0096]

[0097] When the reference voltage output by the PR controller is and When , based on the above formula (5), the voltage expression under zero current control can be calculated as:

[0098]

[0099] In the formula, is the α-axis reference voltage, is the β-axis reference voltage, is the preliminary estimate of the rotor phase, is the preliminary estimated value of the rotor speed (the superscript “^” of a variable indicates the estimated value of the variable).

[0100] In a possible implementation, in order to obtain a more accurate estimation result of the rotor position, a low-pass filter is used to suppress the high-frequency noise in the output voltage. For example, the transfer function of the low-pass filter is:

[0101]

[0102] In the formula, f L is the cutoff frequency of the low-pass filter.

[0103] In a possible implementation, in order to estimate the rotor position information in the full speed range using the same control parameters, the amplitude of the output voltage signal needs to be normalized as follows:

[0104]

[0105] In the formula, is the filtered α-axis output voltage, is the filtered β-axis output voltage, is the normalized α-axis output voltage, is the normalized β-axis output voltage.

[0106] Theoretically, the rotor position information can be directly estimated using the inverse tangent method according to equation (8) through equation (11):

[0107]

[0108] However, in practical applications, even if the estimation result is filtered, there will still be large fluctuations. In order to obtain a smoother rotor position, the present invention extracts rotor position and speed information based on a circuit of a phase locked loop (PLL) controller.

[0109] It should be noted that the phase-locked loop controller is a feedback control system that uses an external reference signal to control the frequency and phase of the oscillation signal inside the loop, thereby achieving automatic tracking of the output signal frequency to the input signal frequency, and is usually used in closed-loop tracking circuits. The working process of the phase-locked loop controller is: the output signal is fed back to the input end, and after loop adjustment, the output angular frequency is equal to the input, and the phase difference between the input signal and the output signal is constant, thereby achieving phase locking.

[0110] like Figure 5 As shown in the figure, the normalized and filtered voltage signal can be used for preliminary estimation of rotor position and speed information. is the normalized α-axis output voltage, is the normalized β-axis output voltage. After Park transformation, the output is the normalized q-axis and d-axis voltage reference value. and Consider the d-axis voltage reference value is the error signal, After the proportional link k p_pll and integral link k p_pll / s. Among them, k p_pll An important parameter used to adjust the response of the PLL control loop, mainly used to adjust the amplification degree of the error signal to achieve rapid correction of phase or frequency errors. p_pll / sIn the phase-locked loop, the phase or frequency error is integrated to gradually eliminate the steady-state error, so that the error tends to zero when the system reaches stability, thereby maintaining accurate phase lock. The PI regulator adjusts the frequency and phase of its output signal according to the filtered error signal, thereby making the frequency of the output signal consistent with the frequency of the input signal. The voltage vector position θ is determined by integrating the output frequency v , and then the rotor position and speed are extracted from it according to formula (18).

[0111] The electromagnetic torque equation of IPMSM in the rotating coordinate system is:

[0112]

[0113] In the formula, ψ d ,ψ q are the d-axis and q-axis flux, respectively, and p n is the pole pair number, T e is the electromagnetic torque.

[0114] Among them, the electromagnetic torque depends on the stator current and torque angle δ, so the equation of electromagnetic torque can also be written as follows:

[0115]

[0116] In the formula, I s is the effective value of the stator phase current, L is the effective stator lamination length, r is the air gap radius, B m is the fundamental amplitude of permanent magnet flux, N s is the number of turns of the phase coil.

[0117] Given that the electromagnetic torque command value is zero, the torque angle is close to zero, so equation (8) can be written as:

[0118] T e =k Te sinδ≈k Te δ (14)

[0119] In the formula, δ is the torque angle. When the observed rotor speed is greater than the actual speed, δ is greater than 0, otherwise δ is less than 0. Therefore, the estimated rotor speed can be accurately converged to the actual speed based on the observed value of the rotor speed and the torque closed-loop control. And make the estimated position of the rotor converge accurately to the actual position

[0120] For the switch to the normal sensorless control scheme, the mode selector can switch the sensorless control strategy according to the estimated speed of the rotor (accurate estimation result), and set the speed hysteresis loop during the switching process to ensure a smooth transition between the two sensorless control strategies. For example, when the estimated speed of the rotor is less than or equal to the lower limit of the hysteresis loop switching threshold (when the IPMSM is in the low speed range), the PSWI-based sensorless control strategy can be adopted, and when the estimated speed of the rotor is greater than the upper limit of the hysteresis loop switching threshold (when the IPMSM is in the medium and high speed range), the speed and position information of the rotor in the normal sensorless control scheme can be estimated by starting the MRAS observer.

[0121] Main reference Figure 1 and Figure 2 In a specific implementation, the method for re-starting a permanent magnet synchronous motor with speed based on zero current control includes the following three steps:

[0122] S1, using the PR controller to adjust the stator current to zero, and then making a preliminary estimate of the rotor position and speed information based on the PLL controller;

[0123] S2. Adjust the electromagnetic torque to zero and accurately estimate the rotor position and speed based on the torque angle.

[0124] As in this example;

[0125] S3, the mode selector selects the appropriate positionless control algorithm according to the speed of the motor, and restores the free-running motor to the normal positionless sensor control strategy based on the hybrid positionless sensor solution to achieve belt speed re-investment.

[0126] Reference Figure 2 In this example, when the timing is 100s, the current is controlled to zero; when the timing is 250s, it switches to the torque fine-tuning stage to obtain more accurate position information; when the timing is 350ms, it switches to the normal position sensorless control scheme. Therefore, the free-running IPMSM can be quickly restored to a normal state within 350ms.

[0127] The following will specifically explain the above three-step method for realizing the belt speed re-start method of the permanent magnet synchronous motor.

[0128] 1. Realize stator zero current control based on PR controller:

[0129] Among them, the transfer function of the ideal PR controller can be written as:

[0130]

[0131] In the formula, K p and K i The controllers represent the proportional and integral gains of the PR controller, ω n is the ideal resonant frequency.

[0132] It can be seen that since the gain of the PR regulator at the ideal resonant frequency is infinite, the ideal PR regulator can achieve zero-error tracking of the stator current. However, in the case of high gain, the system is more susceptible to noise, which poses a challenge to system stability. In order to solve this problem, a non-ideal PR controller is used in the present invention, and its transfer function is:

[0133]

[0134] In the formula, ω c is a non-ideal resonant frequency.

[0135] like Figure 3 As shown, is the α-axis reference current, is the β-axis reference current, is the α-axis reference voltage, is the β-axis reference voltage, θ V is the output voltage phase. is 0 to ensure that the dynamic stator current is zero and the output voltage phase θ V The reference voltage Calculated according to the following formula:

[0136]

[0137] When the stator current is 0, the output voltage of the inverter is synchronized with the electromotive force of the IPMSM. The stator voltage of the IPMSM is consistent with the reference voltage output by the inverter. Based on the above formula (5), the reference voltage can be calculated respectively. and speed The relationship between:

[0138]

[0139] In the formula, is the preliminary estimate of the rotor phase, This is a preliminary estimate of the rotor speed.

[0140] Among them, the output voltage phase θ V Contains the rotor speed and position information, specifically:

[0141]

[0142] Theoretically, the rotor position can be estimated directly using formulas (17), (19) and (20), but in practical applications, even if the estimation results are filtered, large fluctuations will still occur. In order to obtain a smoother rotor initial position and a more accurate estimation result, the present invention uses a PLL-based rotor position and speed observer. For example, when the stator current is adjusted to zero, the phase-locked loop observer immediately starts to work.

[0143] The phase-locked loop is used to extract the initial speed and position information of the rotor, and the normalized αβ axis output voltage is transformed into a normalized dq axis voltage reference value by Park. Respectively through the proportional gain function k p_pll and integral controller k p_pll / s, the rotor speed is determined by the output signal proportional integral filter, and the voltage vector position θ is obtained by integrating the speed. v , and then use formula (19) to extract the rotor position information. At the same time, by adjusting the input voltage signal, the extraction result can be made smoother.

[0144] In order to obtain the smooth voltage of the phase-locked loop observer, a low-pass filter is used to suppress the high-frequency noise in the output voltage signal, and its transfer function is:

[0145]

[0146] In the formula, f L is the cutoff frequency of the low-pass filter.

[0147] like Figure 4 As shown in the figure, in order to use the same control parameters to estimate the rotor position information in the full speed range, the amplitude of the output voltage signal needs to be normalized:

[0148]

[0149] Based on the PR controller, the stator current is adjusted to zero. At this time, the normalized voltage and The equation in the rotating reference frame can be expressed as:

[0150]

[0151] When the belt speed re-throw method is activated for 50 ms, the initial values ​​of the rotor speed and position are extracted from the output values ​​of the PR-based regulator to speed up the convergence of the observer.

[0152] 2. Estimation of rotor position and speed based on zero torque control optimization

[0153] The torque estimate for the IPMSM is:

[0154]

[0155] In the formula, is the estimated value of electromagnetic torque, is the estimated value of d-axis flux, is the estimated value of q-axis magnetic flux.

[0156] According to formula (7), the magnetic flux is:

[0157]

[0158] like Figure 7 As shown in Figure 1, when the torque is set to 0, the torque angle is also close to 0. According to formula (8), the electromagnetic torque can be described in the dq rotating coordinate system as:

[0159] T e =k Te sinδ≈k Te δ (26)

[0160] in δ is the torque angle. When the observed rotor speed is greater than the actual speed, δ is greater than 0, otherwise δ is less than 0. Therefore, the estimated position can be accurately converged to the actual position based on the observed value of the speed and the torque closed-loop control.

[0161] 3. Switch to normal sensorless control solution

[0162] In the application of rail transit traction system, the speed range of IPMSM is relatively wide, and a single position sensorless control strategy cannot guarantee the stable operation of IPMSM in the entire speed range. In view of this, the present invention adopts a hybrid position sensorless control strategy based on the combination of MRAS observer and pulsating square wave injection for subsequent normal position sensorless operation. It is applicable to the normal position sensorless operation using any other signal injection-based or model-based position sensorless control strategy. Specifically, in the aforementioned example hybrid positionless scheme, a hybrid position sensorless control strategy based on the combination of MRAS observer and pulsating square wave injection can be adopted. However, the positionless control strategy at medium and high speeds can be replaced by any other model-based position sensorless control strategy, and the positionless control strategy at low speed can be replaced by any other signal injection-based control strategy. The mode selector is based on the estimated speed of the rotor. Switch to the position-free control strategy, switch the control scheme such as Figure 8 Specifically, a speed hysteresis loop is set during the switching process to ensure a smooth transition between the two position sensorless control strategies. For example, in this example, when When the position-free control strategy based on MRAS observer is selected, When , the position-free control strategy based on pulsating square wave injection is selected, where ω th_H is the upper limit of the hysteresis switching threshold, is ω th_L The lower limit of the hysteresis switching threshold, the position sensorless control scheme in this example is described in detail below.

[0163] Among them, when the IPMSM is in the low speed range, the position sensorless control strategy based on PSWI is adopted, and the high-frequency pulse voltage signal injected into the estimated rotor reference system is:

[0164]

[0165] When the IPMSM is in the low speed range, the high-frequency induced current caused by the component of the high-frequency pulse voltage signal in the stationary coordinate system can be expressed as:

[0166]

[0167] In the formula, θ r is the rotor position, Δθ is the rotor position estimation error, i αh is the high frequency induced current on the α axis, i βh is the β-axis high-frequency induced current. Using the symmetry of the input signal, the stator current can be decomposed into the high-frequency induced current i αh and i βh , and then further extract the rotor speed and position information.

[0168] When the IPMSM is in the mid-to-high speed range, the mode selector starts the MRAS observer to estimate the speed and position of the rotor in the normal position sensorless control strategy:

[0169]

[0170] As mentioned above, adding a superscript ^ to a parameter indicates an estimated value of that parameter.

[0171]

[0172] Citing Popov's superstability theory, the speed adaptation mechanism is:

[0173]

[0174] It can be seen that in the preferred embodiment of the present invention, compared with the existing belt speed re-throwing method, the estimation of the rotor position has a faster convergence speed and high estimation accuracy. In addition, the zero current control method based on the PR regulator can effectively suppress the current impact during re-throwing, and does not need to use motor parameters in the regulator design process, and has strong parameter robustness. In addition, the present invention can quickly realize the belt speed re-throwing of PMSM in the full speed range.

[0175] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, different steps do not have to be performed in such an order. They can be performed simultaneously or in other orders, and some steps can also be added, replaced or omitted.

[0176] It should be noted that, although the above-mentioned specific method for re-starting the permanent magnet synchronous motor with speed based on zero current control is introduced as an example, those skilled in the art will appreciate that the present invention should not be limited thereto. In fact, the user can flexibly adjust the relevant steps and the parameters in the steps according to the actual application scenarios and other situations.

[0177] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for re-starting a permanent magnet synchronous motor with a speed based on zero current control, characterized in that: The belt speed re-casting method comprises the following steps: The stator current of the permanent magnet synchronous motor is adjusted to zero, and the rotor position and speed information of the permanent magnet synchronous motor are preliminarily estimated; The electromagnetic torque of the permanent magnet synchronous motor is adjusted to zero, and the initially estimated rotor position and speed are accurately estimated; According to the result of accurate estimation of the rotor position and speed information, a position sensorless control strategy corresponding to the speed is adopted to complete the belt speed re-start of the permanent magnet synchronous motor.

2. The method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 1, characterized in that: The "adjusting the stator current of the permanent magnet synchronous motor to zero and preliminarily estimating the rotor position and speed information of the permanent magnet synchronous motor" includes: Using a PR controller to adjust the stator current of the permanent magnet synchronous motor to zero; The rotor position and speed information of the permanent magnet synchronous motor are extracted by using a phase-locked loop detector to preliminarily estimate the rotor position and speed information.

3. The method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 1, characterized in that: The "adopting a PR controller to adjust the stator current of the permanent magnet synchronous motor to zero" include: Among them, the voltage equation of the permanent magnet synchronous motor in the stationary coordinate system is: In the formula, u α and u β are the voltages of the α-axis and β-axis of the stationary coordinate system, i α and i β are the currents of the α-axis and β-axis, θ r Indicates the rotor position, R s L is the stator resistance and inductance related parameters α , L β and L αβ The relationship between the dq-axis equivalent inductance is: Where, L d Indicates the d-axis equivalent inductance, L q represents the q-axis equivalent inductance; Among them, the voltage equation of the permanent magnet synchronous motor in the rotating coordinate system is: In the formula, u sd and u sq are the d-axis and q-axis voltages, respectively, i sd and i sq are the d-axis and q-axis currents, ω r is the rotor speed, ψ m is the permanent magnet flux, p is the differential operator; Among them, the transfer function of the PR controller is: In the formula, ω c is a non-ideal resonant frequency.

4. The method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 3 is characterized in that: The “adjusting the electromagnetic torque of the permanent magnet synchronous motor to zero and accurately estimating the preliminarily estimated rotor position and speed” includes: Under the zero current control strategy, the stator current is always equal to zero. sd =0,i sq =0,i α =0,i β =0, and substituting into the above formula (1) and formula (3), we can get: The flux linkage and electromagnetic torque can be written as follows in the rotating coordinate system: When the reference voltage output by the PR controller is and Based on formula (5), the voltage expression under zero current control can be calculated as: In the formula, is the α-axis reference voltage, is the β-axis reference voltage, is the preliminary estimate of the rotor phase, This is a preliminary estimate of the rotor speed.

5. According to the method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 4, the "adjusting the electromagnetic torque of the permanent magnet synchronous motor to zero and accurately estimating the initially estimated rotor position and speed" comprises: The electromagnetic torque equation of the permanent magnet synchronous motor in the rotating coordinate system is: In the formula, ψ d ,ψ q are the d-axis and q-axis flux, respectively, and p n is the pole pair number, T e is the electromagnetic torque; Among them, the electromagnetic torque depends on the stator current and torque angle δ, so the equation of electromagnetic torque can also be written as follows: In the formula, I s is the effective value of the stator phase current, L is the effective stator lamination length, r is the air gap radius, B m is the fundamental amplitude of permanent magnet flux, N s is the number of turns of the phase coil; Given that the electromagnetic torque command value is zero, the torque angle is close to zero, so equation (8) can be written as: T e =k Te sinδ≈k Te d (14) In the formula, δ is the torque angle. When the observed rotor speed is greater than the actual speed, δ is greater than 0, otherwise δ is less than 0.

6. The method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 1, characterized in that: The "accurate estimation of the rotor position and speed information and using a position sensorless control strategy corresponding to the speed to complete the belt speed re-investment of the permanent magnet synchronous motor" includes: When the accurately estimated speed of the permanent magnet synchronous motor is less than or equal to a first preset speed, a first position sensorless control strategy is used to complete the belt speed re-investment of the permanent magnet synchronous motor; and / or When the accurately estimated rotation speed of the permanent magnet synchronous motor is greater than a second preset rotation speed, a second position sensorless control strategy is used to complete the belt speed re-investment of the permanent magnet synchronous motor; Wherein, the second preset speed is greater than or equal to the first preset speed.

7. The method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 6, characterized in that: The first position sensorless control strategy is a position sensorless control strategy based on pulsating square wave injection; and / or The second position sensorless control strategy is a position sensorless control strategy of a model reference adaptive observer.

8. The method for re-starting a permanent magnet synchronous motor with speed based on zero current control according to claim 7, characterized in that: The "accurate estimation of the rotor position and speed information and using a position sensorless control strategy corresponding to the speed to complete the belt speed re-investment of the permanent magnet synchronous motor" includes: When the speed of the permanent magnet synchronous motor is less than or equal to the first preset speed, a position sensorless control strategy based on pulsating square wave injection is adopted, and the high-frequency pulse voltage signal injected into the estimated rotor reference system is: The high-frequency induced current caused by the component of the high-frequency pulse voltage signal in the stationary coordinate system can be expressed as: In the formula, θ r is the rotor position, Δθ is the rotor position estimation error, i αh is the high frequency induced current on the α axis, i βh is the high frequency induced current of β axis; When the speed of the permanent magnet synchronous motor is greater than the second preset speed, the speed and position of the rotor in the normal position sensorless control strategy are estimated by starting the model reference adaptive observer: i s ′ q =i sq ,i s ′ q =i sq , u s ′ q =u sq . The speed adaptation mechanism is:

9. A computer-readable storage medium, the storage medium comprising a memory, the memory being suitable for storing a plurality of program codes, characterized in that: The program code is suitable for being loaded and run by a processor to execute the permanent magnet synchronous motor belt speed re-start method based on zero current control according to any one of claims 1 to 8.

10. A computer device, comprising a memory and a processor, wherein the memory is suitable for storing a plurality of program codes, wherein: The program code is suitable for being loaded and run by the processor to execute the permanent magnet synchronous motor speed re-start method based on zero current control according to any one of claims 1 to 8.

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