A vector control method for permanent magnet synchronous motor

Abstract

The application provides a permanent magnet synchronous motor vector control method, and relates to the field of permanent magnet synchronous motor control. The permanent magnet synchronous motor vector control method carries out vector control calculation to obtain an output voltage; the vector control output voltage is synthesized into a voltage vector; the modulation degree and modulation interval of the voltage vector according to the current RS-SHEPWM modulation model output voltage are calculated; the modulation model output voltage vector is tracked through a voltage vector tracking controller; a first-order low-pass filter is used to track the amplitude M of the voltage vector; a phase-locked loop is used to track the phase θ of the voltage vector; and finally, the combination of vector control and synchronous RS-SHEPWM modulation is realized. The application improves the pulse width modulation part of the traditional vector control algorithm, realizes the combination of vector control and synchronous RS-SHEPWM modulation through the proposed voltage vector tracking controller, realizes the suppression effect of low-order harmonics, maintains the stability of the controller, and the controller structure is simple and the calculation burden is small.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor control technology, specifically a vector control method for permanent magnet synchronous motors. Background Technology

[0002] In applications such as rail transit traction systems and ship propulsion systems, permanent magnet synchronous motors (PMSMs) are gradually replacing asynchronous motors due to their advantages of light weight, small size, high efficiency, high torque density, and wide operating speed range. However, for such megawatt-level high-power systems, the controller switching frequency is generally limited to below 1kHz to protect the lifespan of semiconductor power devices. Lowering the switching frequency increases current harmonics, causing motor overheating and affecting the insulation life of the motor windings. Therefore, research on control algorithms for high-power PMSMs operating under low carrier ratio conditions has significant application value.

[0003] Current research both domestically and internationally primarily focuses on synchronous optimized pulse width modulation (PWM) techniques, which can directly and effectively reduce current harmonics and improve controller stability. The most common strategies include selective harmonic elimination PWM (SHE-PWM) and current harmonic minimum PWM (CHM-PWM). Both strategies require solving complex transcendental equations, typically employing offline calculations and online lookup table solutions, resulting in poor dynamic performance. However, Regular-Sampled Selective Harmonic Elimination PWM (RS-SHEPWM) transforms the lookup table into an approximate algebraic equation calculation, enabling online calculation of switching angles and improving the dynamic response speed of the control algorithm. However, because the input parameters of this modulation method are related to voltage amplitude and frequency, it is typically only applied to V / F controlled inverters, lacking a method for combining it with vector control of permanent magnet synchronous motors. Therefore, in the control scenarios of high-power permanent magnet synchronous motors, an online calculation algorithm that simultaneously achieves low-order harmonic elimination and high dynamic response speed is desired. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a vector control method for permanent magnet synchronous motors. While maintaining the original control hardware, it improves the suppression effect of low-order harmonics and retains the high dynamic response speed characteristics of vector control. The controller has a simple and stable structure, low computational burden, and is easy to promote and use.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] Firstly, a vector control method for a permanent magnet synchronous motor is provided, including:

[0009] The three-phase current, bus voltage, rotor position, and rotor speed of the motor are sampled; the sampled three-phase current and rotor position are subjected to Clarke transform and Park transform to obtain the two-phase synchronous rotating coordinate current; the average current of the motor is calculated by combining the two-phase synchronous rotating coordinate current and passing it through a low-pass filter.

[0010] The calculated average motor current and the given current command are used to perform current closed-loop vector control and current decoupling calculation to obtain the decoupled control voltage.

[0011] The decoupled control voltages are synthesized into a voltage vector, and the voltage vector is expressed in modulus-angle form.

[0012] The voltage vector is tracked by both magnitude and angle. The compensation modulation is obtained by tracking the magnitude, and the compensation angular velocity is obtained by tracking the angle.

[0013] Based on the system's setting of the power device switching frequency limit, the number of switching angles in a quarter-cycle of the low-order harmonic elimination modulation algorithm and its corresponding modulation frequency are calculated under the current compensation angular velocity. The switching angles of the rule sampling low-order harmonic elimination modulation algorithm are calculated, and the switching angles are converted into the comparison values ​​of the counting period and level switching set by the PWM modulation module to adjust the motor excitation and torque.

[0014] Preferably, the formula for calculating the two-phase synchronous rotating coordinate current is:

[0015]

[0016]

[0017] Among them, i a i b i c i represents the sampled three-phase current of the motor. d i q Represents the two-phase synchronous rotating coordinate current, i α i β This represents the stationary coordinate current of two phases.

[0018] Preferably, the step of combining the two-phase synchronous rotating coordinate currents and passing them through a low-pass filter to calculate the average motor current specifically includes:

[0019] The structure of the low-pass filter is as follows:

[0020]

[0021] Where Y(z) is the filter output value, which is the average motor current i dave i qave X(z) is the filter input value, which is the two-phase synchronous rotating coordinate current i. d i q The filter parameters are b0 = 1, b1 = -1.8089, b2 = 1, a0 = 1, a1 = -1.9370, and a2 = 0.9389.

[0022] Preferably, the step of performing current closed-loop vector control and current decoupling calculations using the calculated average motor current and the given current command to obtain the decoupled control voltage specifically includes:

[0023]

[0024] The decoupled control voltage is u. dref u qref R s L is the stator resistance. d L q These are the d-q axis inductances, ψ f For permanent magnet flux linkage; take controller parameter K. dp =2πf BW L d K di =2πf BW R s K qp =2πf BW L q K qi =2πf BW R s f BW This refers to the bandwidth of the vector controller.

[0025] Preferably, the step of synthesizing the decoupled control voltages into a voltage vector and expressing the voltage vector in modulus form specifically includes:

[0026] For a two-level inverter, the voltage vector magnitude is equivalent to the modulation index, and the calculation formula is as follows:

[0027]

[0028]

[0029] Among them, M uref Indicates the adjustment system, |U ref | is the reference voltage amplitude, U DC This refers to the bus voltage.

[0030] The angle of the voltage vector relative to the d-axis is calculated as follows:

[0031]

[0032] Where, θ uref The angle is relative to the d-axis.

[0033] Preferably, the step of tracking the magnitude and angle of the voltage vector, obtaining the compensation modulation through magnitude tracking, and obtaining the compensation angular velocity through angle tracking, specifically includes:

[0034] To track the magnitude of the voltage vector, a first-order low-pass filter is used.

[0035]

[0036] Where, k M This represents the bandwidth of the low-pass filter.

[0037] The phase-locked loop controller G tracks the angle of the voltage vector. C for:

[0038]

[0039] Where, ω n Let ζ be the natural frequency and ζ be the controller damping ratio.

[0040] Modulation angle θ u and compensating angular velocity ω comp Existence Relationship The transfer function for tracking the angle of the voltage vector is:

[0041]

[0042] When the damping ratio ζ = 1, the system is in a critically damped state, and the controller bandwidth is ω. n ;

[0043] Based on the RS-SHEPWM modulation characteristics, the modulation wave period with N quarter-cycle switching angles is divided into T... num = 3(N+1) modulation intervals. The angle of the voltage vector output by the modulation is determined by the modulation algorithm interval. Let the modulation interval output by the current modulation algorithm be T. k :

[0044]

[0045] Where, θ e Rotor position;

[0046] Calculate the compensated angular velocity ω comp :

[0047]

[0048] Preferably, the step of calculating the number of switching angles in a quarter-cycle of the low-harmonic cancellation modulation algorithm and its corresponding modulation frequency under the current compensated angular velocity, based on the system setting power device switching frequency limit, calculating the switching angles of the rule sampling low-harmonic cancellation modulation algorithm, and converting the switching angles into the comparison value of the counting period and level switching set by the PWM modulation module, and adjusting the motor excitation and torque, specifically includes:

[0049] Based on the RS-SHEPWM modulation characteristics, the equivalent carrier ratio for the number of quarter-cycle switching angles N is 2N+1; the switching frequency limit of the system power devices is set to f. swmax When N is n, take the largest positive integer that satisfies the inequality:

[0050] (2N+1)ω u <2πf swmax

[0051] Current modulation algorithm fundamental frequency ω u And the actual modulation frequency f corresponding to the number of quarter-cycle switching angles N u for:

[0052]

[0053] Because RS-SHEPWM switching angles have the characteristics of quarter-cycle symmetry, half-wave symmetry, and three-phase symmetry, the full-cycle switching angle can be calculated by using the formula to calculate the quarter-cycle switching angle. The switching angle calculation is as follows:

[0054] Rising edge switching angle:

[0055]

[0056] Falling edge switching angle:

[0057]

[0058] in,

[0059] In a second aspect, a computer-readable storage medium is provided for storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform any of the methods described.

[0060] Thirdly, a computing device is provided, comprising:

[0061] One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described.

[0062] (III) Beneficial Effects

[0063] This invention discloses a vector control method for permanent magnet synchronous motors, which combines vector control with a low-harmonic cancellation modulation algorithm. It can also be applied to the combination of vector control with other synchronization optimization algorithms. Furthermore, the controller structure is simple and computationally inexpensive. In addition, the use of a rule-based sampling low-harmonic cancellation modulation algorithm capable of real-time online calculation gives this control method both the advantages of low-harmonic cancellation and high dynamic response speed. Attached Figure Description

[0064] Figure 1 This is a flowchart of the method of the present invention;

[0065] Figure 2 This is a schematic diagram of the control structure combining synchronous RS-SHEPWM modulation and vector control in an embodiment of the present invention;

[0066] Figure 3 This is a schematic diagram illustrating the relationship between two voltage vectors in the voltage vector tracking controller of this invention.

[0067] Figure 4 This is a schematic diagram showing the relationship between the angle calculated by RS-SHEPWM modulation and three-phase PWM in an embodiment of the present invention. Detailed Implementation

[0068] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0069] Example

[0070] like Figure 1 As shown, an embodiment of the present invention provides a vector control method for a permanent magnet synchronous motor, comprising:

[0071] The three-phase current, bus voltage, rotor position, and rotor speed of the motor are sampled; the sampled three-phase current and rotor position are subjected to Clarke transform and Park transform to obtain the two-phase synchronous rotating coordinate current; the average current of the motor is calculated by combining the two-phase synchronous rotating coordinate current and passing it through a low-pass filter.

[0072] The calculated average motor current and the given current command are used to perform current closed-loop vector control and current decoupling calculation to obtain the decoupled control voltage.

[0073] The decoupled control voltages are synthesized into a voltage vector, and the voltage vector is expressed in modulus-angle form.

[0074] The voltage vector is tracked by both magnitude and angle. The compensation modulation is obtained by tracking the magnitude, and the compensation angular velocity is obtained by tracking the angle.

[0075] Based on the system's setting of the power device switching frequency limit, the number of switching angles in a quarter-cycle of the low-order harmonic elimination modulation algorithm and its corresponding modulation frequency are calculated under the current compensation angular velocity. The switching angles of the rule sampling low-order harmonic elimination modulation algorithm are calculated, and the switching angles are converted into the comparison values ​​of the counting period and level switching set by the PWM modulation module to adjust the motor excitation and torque.

[0076] Step 1: Sampling and Calculation of Current, Voltage, and Rotor Position

[0077] Please see Figure 2 Specifically, the sampling of the three-phase current is denoted as i. a i b i c Sampling bus voltage U DC Sampling rotor position θ e and rotor speed ω e The three-phase current i a i b i c and rotor position θ e After Clarke and Park transformations, the two-phase synchronous rotating coordinate current i is obtained. d i q The calculation formula is as follows:

[0078]

[0079]

[0080] A second-order, one-section low-pass Chebyshev Type II filter is used, with input i d i q The average current i is calculated dave i qave The filter structure is as follows:

[0081]

[0082] Where Y(z) is the filter output value (i.e., i ... dave i qave X(z) is the filter input value (i.e., i).d i q The filter parameters are b0 = 1, b1 = -1.8089, b2 = 1, a0 = 1, a1 = -1.9370, and a2 = 0.9389.

[0083] The subsequent steps two through five all use the modulation algorithm frequency f. u Calculations are performed to determine the control method based on the variable switching frequency.

[0084] Step 2: Calculation of the permanent magnet synchronous motor vector controller

[0085] Take the current i calculated in step one dave i qave , with a given current command i dref i qref and feedback current i dave i qave The difference is calculated, input to the proportional-integral controller (PI controller), then a current decoupling term is added, and finally the control voltage u is obtained. dref u qref :

[0086]

[0087] Among them, R s L is the stator resistance. d L q These are the d-q axis inductances, ψ f It is a permanent magnet flux linkage. The controller parameter K is taken. dp =2πf BW L d K di =2πf BW R s K qp =2πf BW L q K qi =2πf BW R s f BW This refers to the bandwidth of the vector controller.

[0088] Step 3: Voltage Vector Mode-Angle Conversion

[0089] For a two-level inverter, the voltage vector magnitude is equivalent to the modulation index, and the calculation formula is as follows:

[0090]

[0091]

[0092] Among them, |U ref | represents the reference voltage amplitude.

[0093] The angle of the voltage vector relative to the d-axis is calculated as follows:

[0094]

[0095] Step 4: Voltage Vector Tracking Controller Calculation

[0096] Please see Figure 3 The modulation algorithm outputs a voltage vector. and reference voltage vector The relationship between the magnitude and angle is established. This step enables the tracking of the two voltage vectors.

[0097] A first-order low-pass filter is used for magnitude tracking of the voltage vector, and the controller bandwidth is set to k. M :

[0098]

[0099] The angle tracking of the voltage vector is achieved using controller G. C , with modulation angle θ u and reference voltage angle θ uref The difference is used as negative feedback to adjust the compensation angular velocity ω. comp First, the modulation angle θ u The calculation is as follows:

[0100]

[0101] Among them, T k This represents the modulation range output by the current modulation algorithm. Based on the characteristics of RS-SHEPWM modulation, such as... Figure 4 As shown, one modulation wave period is divided into T num = 3(N+1) modulation intervals.

[0102] Then, calculate the compensated angular velocity ω. comp :

[0103] ω comp =G C (θ uref -θ u )

[0104] When controller G C Designed for At that time, the transfer function of the angle tracking controller is expressed as:

[0105]

[0106] Where, ω n Let ω be the natural frequency and ζ be the controller damping ratio. When the damping ratio ζ = 1, the system is in a critically damped state, and the controller bandwidth is ω. nTo synchronize the adjustment rates of the modulus and angle, the bandwidth k of both is... M and ω n Set them to be equal.

[0107] Step 5: Regular sampling low-order harmonic cancellation modulation calculation

[0108] Current compensated angular velocity ω comp Increase rotor rotation speed ω e Obtain the fundamental frequency ω of the modulation algorithm u :

[0109] ω u =ω comp +ω e

[0110] Please see Figure 4 The RS-SHEPWM modulation characteristic means that the carrier ratio is equivalent to 2N+1 for the number of quarter-cycle switching angles N. Therefore, the switching frequency of the system power devices is limited to f. swmax When N is n, N takes the largest positive integer that satisfies the inequality.

[0111] (2N+1)ω u <2πf swmax

[0112] Simultaneously, calculate the fundamental frequency ω of the current modulation algorithm. u And the actual modulation frequency corresponding to the number of quarter-cycle switching angles N is:

[0113]

[0114] Please see Figure 4 Taking N=3 as an example, it shows how the switching angle calculated by the formula can be applied to three-phase PWM output through quarter-cycle symmetry, half-wave symmetry and three-phase symmetry.

[0115] Rising edge switching angle:

[0116]

[0117] Falling edge switching angle:

[0118]

[0119] in,

[0120] Based on the modulation interval T output by the current modulation algorithm k Based on the location, apply the corresponding switching angle and output a PWM signal to the inverter.

[0121] Embodiments of this application may be provided as methods or computer program products. Therefore, this application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application may be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0122] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0123] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0124] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0125] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A vector control method for a permanent magnet synchronous motor, characterized in that, include: The three-phase current, bus voltage, rotor position, and rotor speed of the motor are sampled. The sampled three-phase currents and rotor position are subjected to Clarke and Park transformations to obtain two-phase synchronous rotating coordinate currents; the average motor current is calculated by combining the two-phase synchronous rotating coordinate currents and passing them through a low-pass filter. The calculated average motor current and the given current command are used to perform current closed-loop vector control and current decoupling calculation to obtain the decoupled control voltage. The decoupled control voltages are synthesized into a voltage vector, and the voltage vector is expressed in modulus-angle form. The voltage vector is tracked by both magnitude and angle. The compensation modulation is obtained by tracking the magnitude, and the compensation angular velocity is obtained by tracking the angle. Based on the system-set power device switching frequency limit, calculate the number of switching angles in a quarter cycle of the low-order harmonic elimination modulation algorithm and its corresponding modulation frequency under the current compensation angular velocity, calculate the switching angles of the rule sampling low-order harmonic elimination modulation algorithm, and convert the switching angles into the comparison value of the counting period and level switching set by the PWM modulation module to adjust the motor excitation and torque; The process of tracking the magnitude and angle of the voltage vector, obtaining the compensation modulation through magnitude tracking, and obtaining the compensation angular velocity through angle tracking, specifically includes: To track the magnitude of the voltage vector, a first-order low-pass filter is used. in, Indicates adjustment system, This indicates a compensation adjustment system. This represents the bandwidth of the low-pass filter. Phase-locked loop controller performs angle tracking of voltage vector. for: in, For natural frequency, The controller damping ratio; Modulation angle and compensated angular velocity Existence Relationship , The fundamental frequency of the modulation algorithm. The rotor rotation speed; The transfer function for tracking the angle of the voltage vector is: in, For relative Angle of the axis; damping ratio At this time, the system is in a critically damped state, and the controller bandwidth is the natural frequency. ; Based on the RS-SHEPWM modulation characteristics, the number of switching angles in a quarter-cycle is: The modulation wave period is divided into There are several modulation intervals, and the angle of the voltage vector output is determined by the modulation algorithm interval. Let the current modulation algorithm output modulation interval be... : in, Rotor position; Calculate the compensated angular velocity : 。 2. The vector control method for a permanent magnet synchronous motor according to claim 1, characterized in that: The formula for calculating the current in the two-phase synchronous rotating coordinate system is as follows: in, , , This represents the sampled three-phase current of the motor. , This represents the current in a two-phase synchronous rotating coordinate system. , This represents the stationary coordinate current of two phases.

3. The vector control method for a permanent magnet synchronous motor according to claim 1, characterized in that: The process of combining the two-phase synchronous rotating coordinate currents and passing them through a low-pass filter to calculate the average motor current specifically includes: The structure of the low-pass filter is as follows: in, The filter output value is the average motor current. , ; The input value for the filter is the two-phase synchronous rotating coordinate current. , The filter parameters are taken as follows: , , , , , .

4. The vector control method for a permanent magnet synchronous motor according to claim 3, characterized in that: The process of using the calculated average motor current and the given current command to perform current closed-loop vector control and current decoupling calculations to obtain the decoupled control voltage specifically includes: in, , Given a current command, the decoupled control voltage is: , , For stator resistance, , They are respectively Shaft inductor, For permanent magnet flux linkage; obtain controller parameters , , , , This refers to the bandwidth of the vector controller.

5. The vector control method for a permanent magnet synchronous motor according to claim 4, characterized in that: The process of synthesizing the decoupled control voltages into a voltage vector and expressing the voltage vector in modulus-angle form specifically includes: For a two-level inverter, the voltage vector magnitude is equivalent to the modulation index, and the calculation formula is as follows: in, For reference voltage amplitude, This refers to the bus voltage. Voltage vector relative The angle of the axis is calculated as follows: 。 6. The vector control method for a permanent magnet synchronous motor according to claim 5, characterized in that: The process involves setting a switching frequency limit for the power devices based on the system settings, calculating the number of switching angles in a quarter-cycle of the low-harmonic elimination modulation algorithm at the current compensated angular velocity and their corresponding modulation frequencies, calculating the switching angles of the rule-based sampling low-harmonic elimination modulation algorithm, and converting the switching angles into a comparison value between the counting period and level switching set by the PWM modulation module. This process then adjusts the motor excitation and torque, specifically including: Based on the RS-SHEPWM modulation characteristics, the number of switching angles in a quarter cycle The equivalent carrier ratio is Set the system power device switching frequency limit to hour, Take the largest positive integer that satisfies the inequality: Current modulation algorithm base frequency and the number of switching angles in a quarter cycle The corresponding actual modulation frequency for: Because RS-SHEPWM switching angles have the characteristics of quarter-cycle symmetry, half-wave symmetry, and three-phase symmetry, the full-cycle switching angle can be calculated by using the formula to calculate the quarter-cycle switching angle. The switching angle calculation is as follows: Rising edge switching angle: Falling edge switching angle: in, , , , , .

7. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods according to claims 1-6.

8. A computing device, characterized in that, include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods according to claims 1-6.

Images