Improved high-frequency pulsating voltage injection permanent magnet synchronous motor rotor position estimation method

Abstract

The invention relates to an improved high-frequency pulsating voltage injection permanent magnet synchronous motor rotor position estimation method, and belongs to the technical field of permanent magnet synchronous motor control. The method comprises the following steps: injecting a high-frequency voltage signal into a direct axis of an estimated rotating coordinate system # imgabs0 #, and extracting a high-frequency current signal generated under the excitation of the high-frequency voltage signal from a quadrature axis of a # imgabs1 # coordinate system; multiplying the high-frequency current signal by a modulation signal, and obtaining a signal containing rotor position information through a low-pass filter; the rotor position and the rotating speed of the permanent magnet synchronous motor are estimated through a phase-locked loop according to a current signal including rotor position information, and meanwhile, errors generated by stator resistance and a cross coupling term are compensated in the phase-locked loop, so that the rotor position estimation precision is improved. The method helps to improve the rotor position estimation precision of the permanent magnet synchronous motor at a low speed, and is suitable for an actual permanent magnet synchronous motor low-speed position sensorless control system.

Description

Technical Field

[0001] The invention belongs to the technical field of permanent magnet synchronous motor control, and relates to an improved method for estimating the rotor position of a permanent magnet synchronous motor by injecting high-frequency pulse voltage. Background Art

[0002] Permanent magnet synchronous motors have the characteristics of high power density, small size, excellent dynamic performance and strong robustness. They are widely used in new energy vehicles, CNC machine tools, drones, household appliances and other fields. Real-time and accurate acquisition of the motor rotor position is crucial to the realization of permanent magnet synchronous motor vector control. Traditional vector control systems often obtain motor rotor position information by adding mechanical position sensors, but the installation of mechanical position sensors will increase costs, increase motor size, sensors are susceptible to environmental interference, and maintenance is difficult. The introduction of permanent magnet synchronous motor position sensorless control technology has solved the above problems well.

[0003] When the permanent magnet synchronous motor runs at low speed, the high-frequency pulse voltage injection method is often used. The high-frequency pulse voltage injection method injects a high-frequency voltage signal into the direct axis of the rotating reference coordinate system, and obtains the motor rotor position by detecting the high-frequency information in the response signal.

[0004] In the high-frequency pulse voltage injection method, the response current extraction process requires bandpass filters, low-pass filters, etc. for signal separation, but the extensive use of filters will cause system signal delays and attenuation, thereby affecting the dynamic performance of the system. In addition, when estimating the rotor position, the high-frequency pulse voltage injection method ignores the influence of stator resistance and cross-coupling terms, which is prone to estimated position errors, thereby reducing the accuracy of motor rotor position estimation. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an improved method for estimating the rotor position of a permanent magnet synchronous motor using high-frequency pulse voltage injection. Aiming at the existing high-frequency pulse voltage injection method, the use of bandpass filters in the signal extraction process is reduced, the errors caused by stator resistance and cross-coupling terms are compensated in the phase-locked loop, and the dynamic performance of the system and the accuracy of rotor position observation are improved.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] An improved method for estimating the rotor position of a permanent magnet synchronous motor using high-frequency pulse voltage injection comprises the following steps:

[0008] S1, permanent magnet synchronous motor based on d axis current is 0 (i d = 0), to estimate the rotating coordinate system A high frequency voltage signal is injected into the direct axis of The cross axis of the coordinate system extracts the high-frequency current signal generated by the excitation of the high-frequency voltage signal;

[0009] S2, multiplying the high-frequency current signal by a modulation signal, and then passing it through a low-pass filter to obtain a signal containing rotor position information;

[0010] S3. The current signal including the rotor position information is used through a phase-locked loop to estimate the rotor position and speed of the permanent magnet synchronous motor. At the same time, the error caused by the stator resistance and the cross-coupling term is compensated in the phase-locked loop to improve the accuracy of the rotor position estimation.

[0011] Furthermore, in step S1, when estimating the rotation coordinate system Under high frequency excitation, the current expression of permanent magnet synchronous motor is:

[0012]

[0013] In the formula, Respectively Shaft current, Respectively axis, Shaft voltage, represents the average inductance, Represents the semi-differential inductance, L d , L q Respectively represent the d-axis and q-axis inductance, represents the estimated rotor error angle, θ e represents the actual rotor position angle, represents the estimated rotor position angle;

[0014] Estimated Rotation Coordinate System Direct axis injection of high frequency voltage signal where u h Represents the voltage amplitude, ω h Represents the voltage frequency, and the high-frequency voltage signal excitation The high-frequency current signal generated by the coordinate system is:

[0015]

[0016] Then we get The high-frequency current signal generated by the coordinate system quadrature axis under the excitation of the high-frequency voltage signal for

[0017] Furthermore, step S2 is specifically to convert the high frequency current signal With the modulation signal sin(ω h t) and we get:

[0018]

[0019] Because ω h ,ω h1 Both are much higher than the motor rotation angular frequency ω r Therefore, after the signal shown in the above formula passes through the low-pass filter, the rotor position information is obtained. The signal:

[0020]

[0021] Where LPF[·] represents a low-pass filter.

[0022] Further, step S3 specifically includes: transmitting the signal containing the rotor position information The input is a phase-locked loop composed of a PI regulator, which is adjusted by the PI regulator. is 0, making the rotor estimated error angle Keep it at 0, so that the estimated rotor position angle approaches the actual rotor position angle.

[0023] The rotor position estimation error caused by the stator resistance and the cross-coupling term is compensated in the phase-locked loop, including:

[0024] Considering the influence of the stator resistance and cross-coupling term of the permanent magnet synchronous motor, the permanent magnet synchronous motor is estimated in the rotating coordinate system The current expression is:

[0025]

[0026] Z d =R s +jω h L d , Z q =R s +jω h L q

[0027] In the formula, R s is the stator resistance, ω e represents the electrical angular velocity;

[0028] exist Axis injection of high frequency voltage signal from Extraction of high frequency current signal from shaft

[0029]

[0030] With the modulation signal sinω h The signal multiplied by t and input into the phase-locked loop through the low-pass filter is:

[0031]

[0032] when and , a position estimation error occurs at this time, so let have:

[0033]

[0034] It can be seen from the above formula that as the speed and stator resistance increase, the position estimation error will also increase.

[0035] So if in the error function By performing error compensation before adjustment, the error in the rotor position estimation can be reduced. The error compensation to the phase-locked loop is:

[0036] The beneficial effects of the present invention are as follows: compared with the existing high-frequency pulse voltage injection method, the present invention reduces the use of bandpass filters in the signal extraction process, and compensates for the errors caused by the stator resistance and cross-coupling terms in the phase-locked loop, thereby improving the observation accuracy of the permanent magnet synchronous motor rotor position and the system dynamic performance.

[0037] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0039] Figure 1 A system block diagram of the method of the present invention;

[0040] Figure 2 It is the relationship diagram of various coordinate systems of permanent magnet synchronous motor;

[0041] Figure 3 This is the optimized permanent magnet synchronous motor rotor position estimation structure diagram. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0043] See also Figure 1 to Figure 3 , is a permanent magnet synchronous motor rotor position estimation method using an improved high frequency pulse voltage injection method proposed in this embodiment. Figure 1 As shown, this method is based on i d = 0 vector control method, forming a dual closed-loop control of the speed loop and the current loop. In the current loop, the collected three-phase current value is used to obtain the current of the synchronous rotating coordinate system dq through Clarke transformation and Park transformation; then compared with the reference current input in the dq coordinate system, the current error value is obtained through the inner loop current PI controller to obtain the voltage under the synchronous rotating coordinate system dq; finally, after Park inverse transformation, it is used as the input value of space vector pulse width modulation (SVPWM). In the speed loop, the rotating coordinate system is estimated from The high-frequency current signal is generated by the high-frequency voltage signal under the excitation of the quadrature axis Combine it with the modulation signal sin(ω h t), and then pass through a low-pass filter (LPF) and a phase-locked loop (PLL) to obtain the rotor position and speed information of the permanent magnet synchronous motor, and compensate for the errors caused by the stator resistance and cross-coupling terms in the phase-locked loop; compare the actual motor speed with the reference speed, and adjust the speed error value to 0 through the outer loop speed PI controller to achieve speed control.

[0044] The method proposed in this embodiment is specifically described as follows:

[0045] 1. Based on the estimated rotation coordinate system Current model of permanent magnet synchronous motor.

[0046] like Figure 2 The figure shows the relationship between the coordinate systems of the permanent magnet synchronous motor, where α-β is the two-phase stationary coordinate system, dq is the actual rotating coordinate system, To estimate the rotation coordinate system.

[0047] The mathematical model of the permanent magnet synchronous motor in the actual rotating coordinate system dq is:

[0048]

[0049] Among them, u d 、u q are d-axis and q-axis voltages respectively; R s is the stator resistance; i d 、i q are d-axis and q-axis currents respectively; L d , L q are the d-axis and q-axis inductances respectively; ω e is the electrical angular velocity; ψ f is the permanent magnet flux.

[0050] Because the frequency of the high-frequency voltage injection signal is much greater than the rotor rotation frequency, the high-frequency current derivative value is much larger than other items, and the high-frequency inductive reactance is much larger than the stator resistance, so the stator resistance can be ignored. Therefore, to simplify the analysis, the rotor rotation frequency term and stator resistance are ignored. At this time, the mathematical model of the permanent magnet synchronous motor under high-frequency excitation is:

[0051]

[0052] Among them, u dh 、u qh are the d-axis and q-axis voltages under high-frequency excitation, i dh 、i qh They are d-axis and q-axis currents under high-frequency excitation respectively.

[0053] Transform the above equation into a current expression and write it as:

[0054]

[0055] According to the actual rotation coordinate system dq and the estimated rotation coordinate system The relationship between the estimated rotation coordinate system and the actual rotation coordinate system is defined as:

[0056]

[0057] in is the estimated rotor error angle, θ e is the actual rotor position angle, Estimate the position angle for the rotor.

[0058] According to the actual rotation coordinate system dq and the estimated rotation coordinate system The transformation relationship between the permanent magnet synchronous motor and the estimated rotating coordinate system The current expression in is:

[0059]

[0060] Where: They are axis, Shaft voltage; They are axis, Shaft current.

[0061] According to the above formula, we can simplify it:

[0062]

[0063] In the formula, is the average inductance; is a semi-differential inductor.

[0064] 2. Estimated Rotation Coordinate System The high-frequency voltage signal is injected into the direct axis of The cross axis of the coordinate system extracts the high-frequency current signal generated by the excitation of the high-frequency voltage signal.

[0065] Estimated Rotation Coordinate System The direct axis injects the following high-frequency voltage signal:

[0066]

[0067] In the formula, u h is the voltage amplitude; ω h is the voltage frequency.

[0068] Substituting equation (7) into equation (6), the high-frequency response current expression is simplified to:

[0069]

[0070] In fact, from the estimated rotation coordinate system The current signal extracted from the quadrature axis It includes the high-frequency current signal generated by the high-frequency voltage signal excitation The motor's fundamental frequency current i q , high-frequency harmonic current components generated by PWM switching i q , The expression is:

[0071]

[0072] Where I qh ,I q ,I qh1 is the current amplitude, ω h1 is the high-frequency harmonic current frequency generated by the PWM switch. According to formula (8), we can get: In this embodiment, only the high-frequency current signal is taken It can be seen from formula (8) that when When the rotor estimation error angle tends to 0, at which point the estimated rotor position tends to the actual rotor position, thereby achieving the estimation of the rotor position. After processing, the actual rotor position can be obtained.

[0073] 3. High-frequency current signal Multiplied by the modulated signal, the signal containing the rotor position information is obtained through a low-pass filter.

[0074] In the traditional high-frequency pulse voltage injection method, a bandpass filter is used to select the current according to the different current frequencies. However, the use of bandpass filters will cause system signal delay, attenuation and other phenomena, thus affecting the dynamic performance of the system. Therefore, the improved high-frequency pulse voltage injection method proposed in the present invention omits the bandpass filter gating. Instead, directly With the modulation signal sin(ω h t), and then after passing through a low-pass filter (LPF), a current signal containing rotor position information can also be obtained. The details are as follows:

[0075] Directly combine equation (9) with the modulation signal sin(ω h t), we can get the following expression:

[0076]

[0077] Formula (10) can filter out the high-frequency signal by low-pass filter processing. h ,ω h1 Both are much higher than the motor rotation angular frequency ω r ,therefore The first half of the expression, i q expression, After passing through the low-pass filter, the expressions are all 0, leaving a signal containing the rotor position information.

[0078] By adjusting the current signal Mid rotor estimation error angle tends to 0, at which point the estimated rotor position tends to the actual rotor position, thereby achieving the estimation of the rotor position. Specifically, After being modulated by the signal sin(ω h t) and pass through a low-pass filter (LPF), we can get The signal is:

[0079]

[0080] When the rotor position estimation error When it is small enough and gradually approaches 0, the error signal can be linearized. At this time:

[0081]

[0082] It can be seen from formula (12) that if the adjustment but At this time, the estimated rotor position approaches the actual rotor position, thereby realizing the estimation of the rotor position.

[0083] After the above processing, The shaft current component contains the rotor position information of the motor, but the bandpass filter gating is omitted in the signal processing process. By reducing the use of bandpass filters, the delay and attenuation of system signals can be reduced, thereby improving the dynamic performance of system operation.

[0084] 4. The rotor position and speed of the permanent magnet synchronous motor are estimated through a phase-locked loop, and the errors caused by the stator resistance and the cross-coupling term are compensated in the phase-locked loop to improve the accuracy of the rotor position estimation.

[0085] The PI regulator is used to form a phase-locked loop system. The PI controller adjusts is 0, making the rotor position error Keep it at 0, that is, at this time the estimated rotor position angle approaches the actual rotor position angle, so the rotor position can be tracked. The obtained tracking value can be used to realize low-speed position sensorless control of the permanent magnet synchronous motor.

[0086] The traditional high-frequency pulse voltage injection method usually ignores the stator resistance and cross-coupling terms in the voltage equation at low speeds. However, as the speed increases, these two terms will cause rotor position estimation errors and cannot be simply ignored. The improved high-frequency pulse voltage injection method proposed in the present invention takes into account the errors caused by the stator resistance and cross-coupling terms and compensates for them in the phase-locked loop. Figure 3 The figure shows the optimized permanent magnet synchronous motor rotor position estimation system structure. The input of the system is The shaft current component is the output of the estimated motor rotor position and speed information; E c Compensate for rotor position estimation error.

[0087] Among them, considering the influence of stator resistance and cross-coupling terms, combining equations (1), (5) and (8), the current expression of the permanent magnet synchronous motor can be obtained as follows:

[0088]

[0089] Where Z d =R s +jωh L d , Z q =R s +jω h L q .

[0090] exist Axis injection of high frequency voltage signal from The shaft extracts high-frequency current signals Through After processing, the actual rotor position can be obtained. The high frequency response current obtained by the axis is:

[0091]

[0092] Signal and modulation signal sinω h After multiplying by t and passing through the low-pass filter, the error function input to the phase-locked loop is:

[0093]

[0094] But when the above error function hour, This results in a position estimation error. Let’s assume have:

[0095]

[0096] It can be seen from formula (16) that as the speed and stator resistance increase, the position estimation error will also increase.

[0097] So if in the error function By performing error compensation before adjustment, the error in rotor position estimation can be reduced. The relationship between error compensation is:

[0098]

[0099] When estimating the rotor position, the influence of stator resistance and cross-coupling terms are taken into account, and the errors caused by stator resistance and cross-coupling terms are compensated in the phase-locked loop, thereby improving the rotor position observation accuracy.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. An improved method for estimating the rotor position of a permanent magnet synchronous motor using high-frequency pulse voltage injection, wherein the permanent magnet synchronous motor is controlled based on vector control with a d-axis current of zero, characterized in that: The method includes: Estimated Rotation Coordinate System A high frequency voltage signal is injected into the direct axis of The cross axis of the coordinate system extracts the high-frequency current signal generated by the excitation of the high-frequency voltage signal; The high frequency current signal is multiplied by a modulation signal and then passed through a low pass filter to obtain a signal containing rotor position information; The current signal including the rotor position information is passed through a phase-locked loop to estimate the rotor position and speed of the permanent magnet synchronous motor. At the same time, the errors caused by the stator resistance and the cross-coupling term are compensated in the phase-locked loop to improve the accuracy of the rotor position estimation.

2. The method according to claim 1, characterized in that In the estimated rotation coordinate system Under high frequency excitation, the current expression of permanent magnet synchronous motor is: In the formula, Respectively Shaft current, Respectively axis, Shaft voltage, represents the average inductance, Represents the semi-differential inductance, L d , L q Respectively represent the d-axis and q-axis inductance, represents the estimated rotor error angle, θ e represents the actual rotor position angle, represents the estimated rotor position angle; Estimated Rotation Coordinate System Direct axis injection of high frequency voltage signal where u h Represents the voltage amplitude, ω h Represents the voltage frequency, and the high-frequency voltage signal excitation The high-frequency current signal generated by the coordinate system is: Then we get The high-frequency current signal generated by the coordinate system quadrature axis under the excitation of the high-frequency voltage signal for 3. The method according to claim 2, characterized in that The high frequency current signal With the modulation signal sin(ω h t) and we get: Because ω h ,ω h1 Both are much higher than the motor rotation angular frequency ω r Therefore, after the signal shown in the above formula passes through the low-pass filter, the rotor position information is obtained. The signal: Where LPF[·] represents a low-pass filter.

4. The method according to claim 3, characterized in that The signal containing the rotor position information The input is a phase-locked loop composed of a PI regulator, which is adjusted by the PI regulator. is 0, making the rotor estimated error angle Keep it at 0, so that the estimated rotor position angle approaches the actual rotor position angle; The rotor position estimation error caused by the stator resistance and the cross-coupling term is compensated in the phase-locked loop, including: Considering the influence of the stator resistance and cross-coupling term of the permanent magnet synchronous motor, the permanent magnet synchronous motor is estimated in the rotating coordinate system The current expression is: FROM d =R s +jω h L d ,FROM q =R s +jω h L q In the formula, R s is the stator resistance, ω e represents the electrical angular velocity; exist Axis injection of high frequency voltage signal from Extraction of high frequency current signal from shaft With the modulation signal sinω h The signal multiplied by t and input into the phase-locked loop through the low-pass filter is: when and When , a position estimation error occurs. have: The error compensation to the phase-locked loop is:

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