Sensorless detection method for rotor position

Abstract

The invention provides a control strategy for a rotor-free position sensor LCI driven electro-magnetic synchronous motor based on a sliding-mode observer, and the strategy comprises the steps: introducing an exciting current, rewriting a motor matrix, and replacing a conventional sign function with a Sigmoid function with a boundary layer for the buffeting problem generated by a conventional sliding-mode observer; a sliding mode self-adaptive gain related to the rotating speed of the motor is introduced to reduce the influence of the rotating speed change of the motor on the estimation precision of the rotor position, and an improved normalized phase-locked loop is utilized to extract the rotor position information. According to the invention, aiming at the problems of the traditional sliding mode observer, the improvement of increasing the sliding mode adaptive gain and replacing the boundary layer function is made, and the accuracy of the position detection of the motor rotor without the position sensor is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of speed control of electrically excited synchronous motors, and relates to a sensorless detection method for rotor position, and specifically to a sensorless detection method for rotor position of an LCI driven electrically excited synchronous motor in a high-speed state based on an improved sliding mode observer. Background Art

[0002] With the vigorous development of modern industrial technology, high-power motors have gradually become an important source of power in contemporary society and are widely used in occasions such as pumped storage power stations, large gas turbines, fans, compressors, etc. Load commutated inverters (LCI) drive electrically excited synchronous motors and use thyristors as switching devices. They have simple speed regulation structures, large system capacity, and high economic benefits. Therefore, they are widely used in the field of high-power speed regulation transmission. Thyristors are also semi-controlled devices. In order to more accurately control the start and stop of the motor, it is necessary to obtain the rotor position information and speed information of the motor to control the shutdown of the thyristor. The traditional method is to use position sensors such as Hall sensors or encoders to obtain the required information, but the introduction of sensors will increase the size and design cost of the motor to a certain extent. At the same time, the sensors are also easily affected by conditions such as temperature and humidity, which reduces the measurement accuracy. This is not conducive to the high precision required for motor control, so the development of sensorless control technology is crucial.

[0003] According to the speed range of synchronous motors, the motor position sensorless control technology is generally divided into two categories: in the field of zero speed or low speed, the signal injection method is generally adopted, including the rotation signal injection method, the pulsating signal injection method, etc., but generally speaking, these methods will generate high-frequency noise interference and cause additional losses. Therefore, people have proposed methods such as zero voltage vector injection method and zero-sequence current derivative measurement method to reduce noise interference; in the field of medium speed or high speed, the control methods based on back electromotive force mainly include extended Kalman filter method, Lumberg observer method and sliding mode control method. Among them, the sliding mode control method is widely used in motor control because of its strong robustness and simple algorithm. However, the traditional sliding mode observer uses a sign function as a switching function, which has discontinuity at the zero point, which will bring certain jitter to the system. Therefore, it is of great significance to study a sliding mode observer that can ensure a higher approach speed while weakening the system jitter. Summary of the invention

[0004] The object of the present invention is to provide a sensorless detection method for rotor position to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A sensorless detection method for rotor position, in particular a sensorless detection method for rotor position of an LCI driven electrically excited synchronous motor at high speed state based on an improved sliding mode observer, is implemented by the following steps:

[0007] Step 1: Collect the voltage and current of the electrically excited synchronous motor, perform dq transformation on the acquired current and voltage information, and obtain the system voltage matrix and flux matrix;

[0008] Because the influence of the damping winding is relatively small when the motor is running at high speed, so proceed to step 2:

[0009] Step 2: Simplify the impedance matrix;

[0010] Step 3: Convert the voltage matrix of the simplified impedance matrix to the αβ0 coordinate system to form the transformed voltage matrix and obtain u α and u β The equation of the back electromotive force E is defined as α and E β ;

[0011] Step 4: Take the stator current equation i α and i β Based on this, the sliding mode observer equation is established. and

[0012] Step 5: Subtract the sliding mode observer equation from the stator current equation to obtain the observed current error equation

[0013] Step 6: Propose a Sigmoid function g(n) with a boundary layer;

[0014] Step 7: Design a sliding mode adaptive law q;

[0015] Step 8: Select the sliding surface s(x) on the trajectory of the stator current, and use a positive definite Lyapunov function to analyze the stability of the sliding mode observer equation;

[0016] Step 9: When the current reaches the sliding surface, the back electromotive force is obtained;

[0017] Step 10: Use the improved normalized phase-locked loop to extract the speed information ω r and rotor angle information γ.

[0018] Furthermore, the voltage matrix is:

[0019]

[0020] Where R s is the stator resistance, Rf is the field winding resistance, R Dd and R Dq is the damping winding resistance, p is the differential operator, ω r is the electrical angular velocity; sd and sq is the stator flux, Ψ f is the field winding flux, Ψ Dd and Dq is the damping winding flux.

[0021] Furthermore, the flux matrix is:

[0022]

[0023] Where L d is the direct-axis synchronous inductance, L q is the quadrature-axis synchronous inductance, L f is the field winding inductance, L Dd is the direct-axis damping winding inductance, L Dq is the quadrature-axis damping winding inductance, L ad is the direct-axis armature reaction inductance, L aq is the quadrature-axis armature reaction inductance.

[0024] Furthermore, the simplified impedance matrix is:

[0025]

[0026] Furthermore, the transformed voltage matrix is:

[0027]

[0028] Where γ is the electrical angle of the rotor position.

[0029] Furthermore, E α and E β Defined as the extended back electromotive force, the expression is as follows:

[0030]

[0031] Furthermore, the stator current equation and the sliding mode observer equation are respectively:

[0032]

[0033] in and is the observed value of the stator current α and β components, ν α and ν β is the control input of the sliding mode observer.

[0034] Furthermore, the observed current error equation is simplified to:

[0035]

[0036] The error equations for current and speed are defined as:

[0037] The control input of the sliding mode observer is defined as follows:

[0038]

[0039] Furthermore, in order to reduce the problem of excessive jitter in the observed back EMF due to the discontinuity of the function, the expression of the function is:

[0040]

[0041] Where: x is the error in current.

[0042] Furthermore, the sliding mode adaptive law q is:

[0043]

[0044] in is the observed angular velocity, ω0 is the rated angular velocity, k s is the adaptive law gain, and c is a constant to prevent the initial gain from being zero.

[0045] Furthermore, the sliding surface s(x) is:

[0046]

[0047] Furthermore, q α ,q β The judgment formula is:

[0048]

[0049] Furthermore, the final value range of q is q>max{|q α |,|q β |}, when this condition is met, the sliding mode observer converges.

[0050] Furthermore, the back electromotive force expression is:

[0051] Another object of the present invention is to accurately determine the rotor position in the high-speed state through the above method, and to realize the application of the sensorless detection method of the rotor position in the high-speed state rotor position detection and judgment of the LCI driven electrically excited synchronous motor.

[0052] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0053] 1. The invented high-speed rotor position detection method increases the number of items in matrix analysis and improves the accuracy of rotor position detection results by introducing excitation current;

[0054] 2. The invented high-speed rotor position detection method adopts adaptive gain, and the sliding mode gain can change according to the change of motor speed, ensuring that the system has a large sliding surface speed while reducing the sliding surface chattering;

[0055] 3. The invented high-speed rotor position detection method adopts a Sigmoid function with a boundary layer, which reduces the back-electromotive force jitter generated by the traditional sign function near the zero point and increases the reliability of the rotor position detection result;

[0056] 4. The invented high-speed rotor position detection method adopts an improved normalized phase-locked loop, which improves the zero-crossing problem of the traditional inverse tangent function when extracting the angle to a certain extent, and further improves the reliability of the rotor position observer. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0058] Figure 1 The block diagram of the improved normalized phase-locked loop is shown in FIG.

[0059] Figure 2 This is a block diagram of the high-speed rotor position detection method for an LCI-driven electrically excited synchronous motor based on an improved sliding mode observer;

[0060] Figure 3 To improve the sliding mode observer to estimate the rotor position and the actual rotor position waveform;

[0061] Figure 4 Improved the waveform of the sliding mode observer rotor position and the actual rotor position at 600 to 750 rpm;

[0062] Figure 5 Improved sliding mode observer rotor position estimation error waveform;

[0063] Figure 6 Estimated speed and actual speed comparison waveform;

[0064] Figure 7Comparison between the rotor position of the traditional sliding mode observer and the rotor position of the improved sliding mode observer and the actual rotor position;

[0065] Figure 8 Comparison of rotor position error between traditional sliding mode observer and improved sliding mode observer. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] Example 1

[0068] In order to reduce the influence of the speed in the process of estimating the rotor position and improve the rate at which the system approaches the sliding surface, this embodiment proposes a sliding mode adaptive gain method related to the motor speed, that is, a LCI driven synchronous motor rotor position observation method based on an improved sliding mode observer. Compared with the traditional sliding mode observer, its sliding mode gain is adaptively improved, which effectively improves the rate at which the system approaches the sliding surface. At the same time, in view of the excessive jitter of the observed back electromotive force caused by the discontinuity of the traditional sign function near the zero point, a Sigmoid function with a boundary layer is proposed to replace the sign function. By detecting the terminal voltage and terminal current of the motor, a 3 / 2 transformation is performed on them, and they are input into the improved sliding mode observer together with the excitation current to observe the required back electromotive force. Finally, the speed and rotor position information can be estimated through the PLL, so that the motor rotor position can be judged without relying on the sensor, which significantly improves the reliability of the operation of the LCI driven electric excitation synchronous motor.

[0069] A sensorless detection method for rotor position of the present embodiment, in particular, a sensorless detection method for rotor position of an LCI driven electrically excited synchronous motor at high speed state based on an improved sliding mode observer, is implemented by the following steps:

[0070] Step 1: Collect the voltage and current of the electrically excited synchronous motor, perform dq transformation on the acquired current and voltage information, and obtain the system voltage matrix and flux matrix:

[0071] The voltage matrix is:

[0072]

[0073] Where R s is the stator resistance, R f is the field winding resistance, R Dd and RDq is the damping winding resistance, p is the differential operator, ω r is the electrical angular velocity; sd and sq is the stator flux, Ψ f is the field winding flux, Ψ Dd and Dq is the damping winding flux.

[0074] Furthermore, the flux matrix is:

[0075]

[0076] Where L d is the direct-axis synchronous inductance, L q is the quadrature-axis synchronous inductance, L f is the field winding inductance, L Dd is the direct-axis damping winding inductance, L Dq is the quadrature-axis damping winding inductance, L ad is the direct-axis armature reaction inductance, L aq is the quadrature-axis armature reaction inductance;

[0077] Because the influence of the damping winding is relatively small when the motor runs at high speed, we carry out step 2: simplify the impedance matrix to:

[0078]

[0079] Step 3: Convert the voltage matrix of the simplified impedance matrix to the αβ0 coordinate system to form the transformed voltage matrix and obtain u α and u β The equation of the back electromotive force E is defined as α and E β :The transformed voltage matrix is:

[0080]

[0081] Where γ is the electrical angle of the rotor position.

[0082] E α and E β Defined as the extended back electromotive force, the expression is as follows:

[0083]

[0084] Step 4: Take the stator current equation i α and i β Based on this, the sliding mode observer equation is established. and The stator current equation and sliding mode observer equation are:

[0085]

[0086] in and is the observed value of the stator current α and β components, v α and v β is the control input of the sliding mode observer;

[0087] Step 5: Subtract the sliding mode observer equation from the stator current equation to obtain the observed current error equation

[0088] Furthermore, the observed current error equation is simplified to:

[0089]

[0090] The error equations for current and speed are defined as:

[0091] The control input of the sliding mode observer is defined as follows:

[0092]

[0093] Step 6: Propose a Sigmoid function g(n) with a boundary layer;

[0094] To reduce the problem of excessive observed back-EMF jitter caused by function discontinuity, the function expression is:

[0095]

[0096] Where: x is the error in current.

[0097] Step 7: Design a sliding mode adaptive law q as:

[0098]

[0099] in is the observed angular velocity, ω0 is the rated angular velocity, k s is the adaptive law gain, c is a constant to prevent the initial gain from being 0;

[0100] Step 8: Select the sliding surface s(x) on the trajectory of the stator current, and use a positive definite Lyapunov function to analyze the stability of the sliding mode observer equation;

[0101] The sliding surface s(x) is:

[0102]

[0103] The obtained q α ,q β The judgment formula is:

[0104]

[0105] The final value range of q is q>max{|q α |,|q β |}, when this condition is met, the sliding mode observer converges;

[0106] Step 9: When the current reaches the sliding surface, the back electromotive force is obtained. The back electromotive force expression is:

[0107] Step 10: Use Figure 1 Improved normalized phase-locked loop to extract speed information ω r and rotor angle information γ.

[0108] As can be seen from the figure: Figure 1 It is an improved normalized phase-locked loop structure. Figure 2 This is the overall simulation block diagram of the system. The simulation motor parameters are rated speed of 1500r / min, pole pair number of 2 pairs, motor resistance of 1.62Ω, and simulation time of 5s. Figure 3 Improve the waveform of the sliding mode observer to estimate the rotor position and the actual rotor position of the motor during the 0-1500r / min period. Figure 4 The waveforms of the rotor position estimated by the improved sliding mode observer and the actual rotor position when the motor is running at 600-750r / min. It can be seen from the figure that the two graphs are almost the same, reflecting that the improved sliding mode observer can track the actual rotor position well.

[0109] Figure 5 It is the improved sliding mode observer rotor position estimation error waveform. The locally enlarged waveform in the figure is the rotor position error of the motor during 600-750r / min. The error is between ±2°, which meets the design requirements. Figure 6 The waveforms of the observed speed and the actual speed of the motor. The local enlarged part in the figure is a comparison of the two waveforms during the period of 600-750r / min. The estimated speed can track the actual speed well, verifying the reliability and accuracy of the proposed improved sliding mode observer.

[0110] Figure 7 It is the comparison between the rotor position of the traditional sliding mode observer and the rotor position of the improved sliding mode observer and the actual rotor position. Figure 8 This is a comparison of the rotor position error between the traditional sliding mode observer and the improved sliding mode observer. Figure 7 and Figure 8It can be found from the comparison that compared with the traditional sliding mode observer, the improved sliding mode observer proposed in the present invention has higher rotor position observation accuracy, and reduces the error by about 1% when the motor runs at high speed, which is in line with the expected effect.

[0111] So far, the embodiments of the present invention have been described in detail with reference to the drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail.

[0112] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sensorless detection method for rotor position, characterized in that: A method for detecting the rotor position of an LCI-driven electrically excited synchronous motor at high speed comprises the following steps: Step 1: Collect the voltage and current of the electrically excited synchronous motor, perform dq transformation on the acquired current and voltage information, and obtain the system voltage matrix and flux matrix; Step 2: Simplify the impedance matrix; Step 3: Convert the voltage matrix of the simplified impedance matrix to the αβ0 coordinate system to form the transformed voltage matrix and obtain u α and u β The equation of the back electromotive force E is defined as α and E β ; Step 4: Take the stator current equation i α and i β Based on this, the sliding mode observer equation is established. and Step 5: Subtract the sliding mode observer equation from the stator current equation to obtain the observed current error equation Step 6: Propose a Sigmoid function g(n) with a boundary layer; Step 7: Design a sliding mode adaptive law q; Step 8: Select the sliding surface s(x) on the trajectory of the stator current, and use a positive definite Lyapunov function to analyze the stability of the sliding mode observer equation; Step 9: When the current reaches the sliding surface, the back electromotive force is obtained; Step 10: Use the improved normalized phase-locked loop to extract the speed information ω r and rotor angle information γ.

2. A sensorless detection method for rotor position according to claim 1, characterized in that: The voltage matrix in step 1 is: Where R s is the stator resistance, R f is the field winding resistance, R Dd and R Dq is the damping winding resistance, p is the differential operator, ω r is the electrical angular velocity; sd and sq is the stator flux, Ψ f is the field winding flux, Ψ Dd and Dq is the damping winding flux; The magnetic flux matrix is: Where L d is the direct-axis synchronous inductance, L q is the quadrature-axis synchronous inductance, L f is the field winding inductance, L Dd is the direct-axis damping winding inductance, L Dq is the quadrature-axis damping winding inductance, L ad is the direct-axis armature reaction inductance, L aq is the quadrature-axis armature reaction inductance.

3. A sensorless detection method for rotor position according to claim 1, characterized in that: The simplified impedance matrix described in step 2 is:

4. A sensorless detection method for rotor position according to claim 1, characterized in that: The voltage matrix after transformation in step 3 is: Where γ is the electrical angle of the rotor position; E α and E β Defined as the extended back electromotive force, the expression is as follows:

5. The sensorless detection method of rotor position according to claim 1, characterized in that: The stator current equation and sliding mode observer equation in step 4 are: in and is the observed value of the stator current α and β components, ν α and ν β is the control input of the sliding mode observer.

6. A sensorless detection method for rotor position according to claim 1, characterized in that: The observed current error equation in step 5 is simplified to: The error equations for current and speed are defined as: The control input of the sliding mode observer is defined as follows:

7. A sensorless detection method for rotor position according to claim 1, characterized in that: The function g(n) in step 6 is: Where: x is the error in current.

8. The sensorless detection method of rotor position according to claim 1, characterized in that: The sliding mode adaptation rate q in step seven is: in is the observed angular velocity, ω0 is the rated angular velocity, k s is the adaptive law gain, and c is a constant to prevent the initial gain from being zero.

9. The sensorless detection method of rotor position according to claim 1, characterized in that: The stability expression sliding surface s(x) of the sliding mode observer equation in step 8 is: The obtained q α ,q β The judgment formula is: The final value range of q is q>max{|q α |,|q β |}, when this condition is met, the sliding mode observer converges.

10. Application of the sensorless rotor position detection method according to claim 1 in high-speed rotor position detection and judgment of an LCI-driven electrically excited synchronous motor.

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