Sampled current compensation method based on extended state observer

Abstract

The sampling current compensation method based on the extended state observer solves the problem that the current sampling compensation method based on the current loop has a small application range and is limited by the number and position of current sensors, and belongs to the field of motor driving.The application comprises the following steps: obtaining sampling current i dm 、 qm 、 z1m 、 z2m , sampling voltage u d 、 u q 、 u z1 、 u z2 , u d 、 u q 、 u z1 、 u z2 、 i dm 、 i qm 、 i z1m 、 i z2m , and error current i de 、 i qe , obtained by current observation are input into an extended state observer to obtain an estimated value, the extended state observer comprises a d-q plane extended state observer and a z1-z2 plane extended state observer; error current i de 、 i qe 、 i z1e 、 i z2e , is obtained according to the estimated value; and the error current obtained is subtracted from the sampling current in the rotating coordinate system to realize error compensation of the sampling current.The compensation method of the application is independent of the number and position of current sensors and has a wide application range.

Description

Technical Field

[0001] This invention relates to a sampling current compensation method based on an extended state observer, belonging to the field of motor drive. Background Technology

[0002] Dual three-phase permanent magnet synchronous motor drive control systems offer advantages such as low voltage, high power, and low torque ripple, leading to their widespread application in new energy vehicles, ships, and aerospace. To suppress zero-sequence current, the two windings of a dual three-phase motor typically employ a neutral-point isolated operating mode. In this mode, the dual three-phase drive system can utilize six-phase current sensors or two groups of four sensors to reduce costs. Two groups of current sensors correspond to two windings, with two current sensors placed on any two phases of one winding. Current sampling involves processes such as current sensor processing, computational circuitry, and AD conversion. Errors in the sensors, operational amplifier zero-drift, AD conversion errors, and calibration all contribute to measurement errors. These errors typically manifest as gain and bias errors, causing first- and second-order torque ripples, respectively. The winding configuration of a dual three-phase motor theoretically suppresses the prominent sixth-order torque ripple problem found in three-phase motors, making the low-frequency torque ripple caused by sampling current errors even more significant. Therefore, appropriate compensation methods are needed to compensate for the current sampling.

[0003] Traditional current sampling compensation methods treat current sampling as interference in the forward path of the speed loop for suppression and compensation. This type of method is simple in principle and robust, starting with the idea of ​​torque ripple suppression, and targeting the i-axis related to torque ripple. q Compensation was performed, which effectively suppressed torque ripple caused by current sampling. However, the above method did not eliminate the phase current bias and asymmetry caused by current sampling. The phase current still contained abundant harmonics. The stator resistance and leakage inductance corresponding to the resistance and inductance in the z1-z2 plane of the dual three-phase motor were relatively small, resulting in large harmonic currents, increased winding heating, and reduced efficiency of the electric drive control system. Another method is based on the current loop, which subtracts the estimated compensation current from the feedback current or corrects the gain and bias of the current sampling online. The core of this method is to extract the relevant current ripples and estimate the compensation current, which can effectively improve the phase current waveform, suppress torque ripples, and accelerate the compensation response speed. However, under low-speed conditions, the frequencies of the 1st and 2nd currents are very close, the cascaded resonators or notch filters have many setting parameters, and the extraction effect of the ripple current is poor. The estimation of the compensation current is related to the motor model, the number and location of the current sensors, and the applicability of the algorithm is small. Summary of the Invention

[0004] To address the limitations of existing current sampling compensation methods based on current loops, which have a limited scope of application and are restricted by the number and location of current sensors, this invention provides a sampling current compensation method based on an extended state observer.

[0005] The application provides a sampling current compensation method based on an extended state observer, comprising:

[0006] S1, collecting current and voltage signals of a motor to obtain current i dm , i qm , i z1m , i z2m and voltage u d , u q , u z1 , u z 2;

[0007] i dm , i qm are d-axis current and q-axis current of the sampling current in a rotating coordinate system, respectively, z1m , i z2m are z1-axis current and z2-axis current of the sampling current in the rotating coordinate system, respectively, d and u q are d-axis voltage and q-axis voltage of the sampling voltage in the rotating coordinate, respectively, z1 , u z2 are z1-axis voltage and z2-axis voltage of the sampling voltage in the z1-z2 plane, respectively;

[0008] S2, inputting u d , u q , u z1 , u z2 , i dm , i qm , i z1m , i z2m and the current observed error current i de , i qe to an extended state observer to obtain an estimated value i de , i qe are d-axis error current and q-axis error current of the sampling current in the rotating coordinate system, respectively;

[0009] The extended state observer is a four-dimensional current loop extended state observer, comprising a d-q plane extended state observer and a z1-z2 plane extended state observer, and the d-q plane extended state observer is:

[0010]

[0011] wherein e d , e q are estimation errors of i dm , i qm , respectively, are i dm , iqm ω e is the electrical angular velocity, β1=2ω eso , ω eso is the bandwidth of the extended state observer, ψ f is the permanent magnet flux linkage amplitude, L d , L q are the d-axis inductance and q-axis inductance of the motor respectively;

[0012] The z1-z2 plane extended state observer is:

[0013]

[0014] wherein e z1 , e z2 are the estimation errors of i z1m , i z2m respectively; is the estimation value of i z1m , i z2m , R s is the stator resistance of the motor, L l is the leakage inductance of the motor, are the estimation values of error voltages generated by the d-axis error current and the q-axis error current respectively, are the estimation values of error voltages generated by the z1-axis error current and the z2-axis error current respectively;

[0015] S3, according to the obtained estimation value obtain error currents i de , i qe , i z1e , i z2e ; i z1e , i z2e are the z1-axis error current and the z2-axis error current of the sampling current in the rotating coordinate system respectively;

[0016] S4, subtract the obtained error currents from the sampling current in the rotating coordinate system to realize error compensation of the sampling current.

[0017] As a preferred, in S3, the compensation currents i de , i qe , i z1e , i z2e are:

[0018]

[0019] s represents a pull-type transformation expression.

[0020] As preferred, the motor is a double three-phase permanent magnet synchronous motor, four-phase current sensors are used, which are respectively placed in the A phase, B phase, X phase and Y phase of the motor to collect current, the double three-phase permanent magnet synchronous motor mathematical model in the rotating coordinate system is obtained by using Clarke-Park transformation according to the vector space decoupling method, and the voltage u d 、u q 、u z1 、u z2 .

[0021] As preferred, the double three-phase permanent magnet synchronous motor mathematical model is:

[0022]

[0023] The beneficial effects of the present application, the designed expansion state observer can observe multiple harmonics, the observation ability is only related to ω eso , and the setting is simple; the compensation method of the present application is independent of the number and position of the current sensor, and has wide application range. For the double three-phase permanent magnet synchronous motor drive control system, the present application realizes current sampling compensation based on the current loop, suppresses torque ripple, improves current waveform, and improves the problem of efficiency reduction caused by high harmonic content of phase current. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the main power topology diagram of the double three-phase permanent magnet synchronous motor drive control system with 30° phase angle;

[0025] Figure 2 is the sampling current error compensation method and control block diagram of the double three-phase permanent magnet synchronous motor;

[0026] Figure 3 is the control block diagram of the four-dimensional current loop of decoupling control;

[0027] Figure 4 is the control block diagram of the speed loop;

[0028] Figure 5 is the control block diagram of the q-axis sampling current compensation method;

[0029] Figure 6 is the comparison waveform diagram of six-phase current before and after the compensation method is added;

[0030] Figure 7 is the comparison waveform diagram of speed before and after the compensation method is added;

[0031] Figure 8 is the comparison waveform diagram of electromagnetic torque before and after the compensation method is added. DETAILED DESCRIPTION

[0032] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0033] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0034] The present application will be further described below in combination with the accompanying drawings and specific embodiments, but not as a limitation of the present application.

[0035] The sampling current compensation method based on the extended state observer in the embodiment is applied to the control of the dual three-phase permanent magnet synchronous motor, and the control principle of the dual three-phase permanent magnet synchronous motor is as shown in Figure 2 , including a speed loop, a current loop and a compensation method; the specific control process includes:

[0036] A four-phase current sensor is used, which is placed in the A phase, the B phase, the X phase and the Y phase. According to the vector space decoupling method, the Clarke-Park transformation is used to obtain the mathematical model of the dual three-phase permanent magnet synchronous motor in the rotating coordinate system, and the sampling current and the sampling voltage are obtained.

[0037] The control strategy is a maximum torque current ratio vector control method, and for the surface-mounted motor, i d =0 control; the sampling current error compensation scheme is based on the current loop, the voltage equation considering the sampling current error is derived, the extended state observer is used to observe the sampling error voltage in the d-q, z1-z2 plane based on the sampling current and the sampling voltage, the error current is obtained according to the mathematical relationship between the error voltage and the error current, and the error current is subtracted from the sampling current for compensation.

[0038] After the sampling current compensation, the control method based on the speed loop and the current loop double closed loop is used to drive and control the dual three-phase permanent magnet synchronous motor.

[0039] Specifically, the embodiment is designed based on the vector control method of the current loop and the speed loop double closed loop. The three-phase winding of the 14kW dual three-phase permanent magnet synchronous motor is independently star-connected with a phase shift angle of 30°. The main circuit is a voltage source type six-phase inverter circuit, and the bus voltage is 650V, as shown in Figure 1 . The control strategy is the vector control strategy of i d =0, the control system adopts the control method of the current loop and the speed loop double closed loop, and the torque current i qref is output by the speed loop as the input given of the q-axis current loop, and the excitation current i dGiven as 0, the z1-z2 plane current i of the dual three-phase motor z1 , z2 Given as 0 to suppress harmonic current.

[0040] The Clarke transformation matrix based on the space vector decoupling method is

[0041]

[0042] In this embodiment, only the αβ plane is rotated and transformed, and the corresponding Park transformation matrix is

[0043]

[0044] In the formula, θ = ω e t, ω e is the electrical angular velocity, 0 is the zero matrix, and I is the 4-order unit matrix. Neglecting the zero sequence current plane, the voltage equation of the dual three-phase permanent magnet synchronous motor in the rotating coordinate system can be obtained as

[0045]

[0046] In the formula, L d = L q = 3L m + L l , and the electromagnetic torque expression in the rotating coordinate system is represented as

[0047] T e = 3p n [(L d -L q )i d i q +i q ψ f ] (4)

[0048] Setting the current loop and the speed loop: the current loop of this embodiment is a PI controller. According to the control requirements, it is set to

[0049]

[0050] In the formula, k p_d , k i_d are the d-axis proportional and integral gains of the PI controller, k p_q , k i_q are the q-axis proportional and integral gains of the PI controller, k p_z1 , k i_z1 are the z1-axis proportional and integral gains of the PI controller, k p_z2 , k i_z2 are the z2-axis proportional and integral gains of the PI controller, and ω cThe bandwidth of current loop. Ignoring the delay and nonlinear factors of inverter output, the open-loop transfer function of current loop is set as a first-order system, and the control block diagram of four-dimensional current loop is shown in Fig. Figure 3 ix (s) is the mathematical expression of current loop controller, and x is d, q, z1, z2.

[0051] The speed loop is set as a second-order system. Ignoring the influence of damping coefficient, the current loop is regarded as a well-set first-order system, and the speed loop PI controller is set as

[0052]

[0053] In the formula, k p_s , k i_s are the proportional and integral gains of PI controller, ω s is the bandwidth of speed loop, K T represents the torque coefficient, and J represents the moment of inertia. The control parameters of speed loop PI controller are obtained by substituting the speed loop bandwidth and the parameters of dual three-phase motor into formula (6), and the control block diagram of speed loop is shown in Fig. Figure 4

[0054] The motor model considering current measurement error is derived. The measurement error current can be summarized as bias error current and gain error current, and the A-phase current is taken as the reference current

[0055] i a = I cos (ωt + φ) (7)

[0056] The other five-phase currents have similar forms, in which I is the phase current amplitude, φ is the current phase angle, and

[0057]

[0058] The sampling current error can be expressed as

[0059]

[0060] In the formula, i ae , i be , i ce , i xe , i ye , i ze are the sampling current errors of each phase, ΔI a , ΔI b , ΔI x , ΔI y are the sampling bias currents of each phase, i a , i b , i x , i y are the actual currents of the measured phase, and k​​a , k b , k x , k y is the measured gain. The sampling current error includes two parts, bias error current and gain error current, which are analyzed separately below. Based on the vector space method, the Clarke-Park transformation is performed on the sampling current, and the current error expression in the d-q, z1-z2 plane can be obtained

[0061]

[0062] Substituting the bias error current into the above equation, we have

[0063]

[0064] where I off and can be expressed as

[0065]

[0066] Substituting the gain error current into equation (9), we have

[0067]

[0068] where I scale1 , I scale2 and can be expressed as

[0069]

[0070] From equation (4), since the surface-mounted permanent magnet synchronous motor has L d = L q , the electromagnetic torque output is determined by i q , and the current bias error and gain error will generate q-axis currents at the fundamental frequency and 2 times the frequency, forming torque pulsations at the fundamental frequency and 2 times the frequency. Only compensating the q-axis current can suppress the torque pulsations, but the error currents of the d-axis, z1-axis and z2-axis currents are not compensated, especially the stator resistance and leakage inductance corresponding to the impedance in the z1-z2 plane are small, and the thermal effect of the harmonic current is more significant. Therefore, an appropriate compensation method is needed to suppress the harmonic current.

[0071] Step one, sample the motor rotor position to get the current motor electrical angle θ, and take the derivative of θ to get the current motor electrical angular velocity ω e , and according to the number of motor pole pairs, the current motor mechanical angular velocity ω m can be obtained;

[0072] The four-phase current sensor containing bias error and gain error is placed in phase A, phase B, phase X and phase Y to collect phase current, six-phase sampling current is obtained according to Kirchhoff's current law, and four-dimensional current in d-q, z1-z2 plane is converted from six-phase current in natural coordinate system according to vector space decoupling method and Clarke-Park transformation: i dm qm z1m z2m ; i dm ; i qm are d-axis current and q-axis current of sampling current in rotating coordinate system, i z1m z2m are z1-axis current and z2-axis current of sampling current in rotating coordinate system.

[0073] The u ab bc ca xy yz zx line voltage sampled from inverter output is calculated according to Kirchhoff's voltage law to obtain six-phase phase voltage, and four-dimensional voltage in d-q, z1-z2 plane is converted from six-phase voltage in natural coordinate system according to vector space decoupling method and Clarke-Park transformation: u d q z1 z2 ; u d and u q are d-axis voltage and q-axis voltage of sampling voltage in rotating coordinate, u z1 z2 are z1-axis voltage and z2-axis voltage of sampling voltage in z1-z2 plane.

[0074] The bus voltage sampled is taken as PWM wave generation reference bus voltage.

[0075] Step two, establish extended state observer, the extended state observer of the embodiment is four-dimensional current loop extended state observer, including d-q plane extended state observer and z1-z2 plane extended state observer:

[0076] The sampling current in d-q plane and z1-z2 plane is re-expressed as

[0077]

[0078] In the formula, i dm qm z1m z2m ​​​​​​​​​​​​​​​​is the sampled current after Clarke-Park transformation, i d q z1 z2 is the actual current after Clarke-Park transformation, i de qe z1e z2e is the sampled current error after Clarke-Park transformation, substituting equation (14) into equation (3) can obtain the voltage equation of current sampling error:

[0079]

[0080] The bias current is estimated by the linear extended state observer, and the above equation is rewritten as

[0081]

[0082] The d-q plane extended state observer is constructed:

[0083]

[0084] The z1-z2 plane extended state observer is constructed:

[0085]

[0086] Substitute u d q z1 z2 dm qm z1m z2m and the error current i de qe observed at present into the d-q plane extended state observer and the z1-z2 plane extended state observer, and the estimated value

[0087] Step three, according to the estimated value obtained, the error current is obtained. The disturbance observed by the d-q plane and z1-z2 plane extended state observer is

[0088]

[0089] The compensation current i de qe z1e z2e is:

[0090] ​​​​​​​​​​​​​​​​​

[0091] s represents a pull-type transformation expression.

[0092] In formula (17), u d,q Obtained by coordinate transformation of the sampled line voltage, i dm,qm Obtained by coordinate transformation of the sampled four-phase current, ω e Obtained by sampling of the motor position sensor, i de,qe Obtained from the output of the compensation method, the motor parameters are known, and an extended state observer in the d-q plane can be constructed; formula (18) has no current coupling term in the d-q plane, and the required system state parameters are similar to formula (16).

[0093] Step four,

[0094] Subtract the estimated current error from the sampled current in the rotating coordinate system to achieve the sampling current error compensation. The compensated current suppresses the current ripple in the d-q plane and the z1-z2 plane, and is used as the feedback current of the current loop to control the motor current. The output of the current loop is given voltage, which is subjected to inverse Clarke-Park transformation based on vector space decoupling to obtain six-phase given phase voltage u abc , u xyz , u abc , u xyz After SPWM modulation, the drive signal is sent to control the power module of the six-phase inverter to generate waves, and the inverter outputs six-phase voltage to realize the driving of the dual three-phase motor. The block diagram of the sampling current error compensation method of the q-axis extended state observer is shown in Figure 5 . The comparison waveforms of the six-phase current before and after the compensation method are shown in Figure 6 , the comparison waveforms of the speed before and after the compensation method are shown in Figure 7 , and the comparison waveforms of the electromagnetic torque before and after the compensation method are shown in Figure 8 .

[0095] Although the present application is described herein with reference to particular embodiments, it is to be understood that these examples are merely illustrative of principles and applications of the present application. It should therefore be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present application as defined by the appended claims. It should be understood that the features described in connection with one embodiment can be used in conjunction with other embodiments described herein. It should be understood that the features described in connection with one embodiment can be used in conjunction with other embodiments described herein.

Claims

1. A sampling current compensation method based on an extended state observer, characterized in that, include: S1. Acquire the current and voltage signals of the motor to obtain the current i. dm i qm i z1m i z2m and voltage u d u q u z1 u z2 ; i dm i qm These represent the d-axis current and q-axis current of the sampled current in the rotating coordinate system, i z1m i z2m These represent the z1-axis current and z2-axis current of the sampled current in the rotating coordinate system, respectively. d and u q These represent the d-axis voltage and q-axis voltage of the sampled voltage in a rotating coordinate system, respectively. z1 u z2 These are the z1-axis voltage and z2-axis voltage of the sampled voltage in the z1-z2 plane, respectively; S2, u d u q u z1 u z2 i dm i qm i z1m i z2m And the error current i obtained from the current observation de i qe The input is fed into the extended state observer to obtain the estimated value. i de i qe These are the d-axis error current and q-axis error current of the sampled current in the rotating coordinate system, respectively. The extended state observer is a four-dimensional current loop extended state observer, including a dq-plane extended state observer and a z1-z2-plane extended state observer. The dq-plane extended state observer is as follows: Where e d e q For i respectively dm i qm The estimation error, i dm i qm The estimated value, ω e Let β1 be the electric angular velocity, and β1 = 2ω. eso ω eso To extend the bandwidth of the state observer, ψ f L is the amplitude of the permanent magnet flux linkage. d L q These are the d-axis inductance and q-axis inductance of the motor, respectively. The z1-z2 plane expansion state observer is: Among them, e z1 e z2 For i respectively z1m i z2m The estimation error; For i z1m i z2m The estimated value, R s L is the stator resistance of the motor. l For the leakage inductance of the motor, These are the estimated values ​​of the error voltages generated by the d-axis error current and the q-axis error current, respectively. These are the estimated values ​​of the error voltages generated by the error currents of the z1 and z2 axes, respectively. S3. Based on the obtained estimated values Obtain the error current i de i qe i z1e i z2e i z1e i z2e These are the z1-axis error current and z2-axis error current of the sampled current in the rotating coordinate system, respectively. S4. Subtract the obtained error current from the sampled current in the rotating coordinate system to achieve error compensation of the sampled current.

2. The sampling current compensation method based on an extended state observer according to claim 1, characterized in that, In S3, the compensation current i de i qe i z1e i z2e for: s represents the Laplace transform expression.

3. The sampling current compensation method based on an extended state observer according to claim 1, characterized in that, The motor is a dual three-phase permanent magnet synchronous motor. Four-phase current sensors are used, placed on phases A, B, X, and Y of the motor to collect current data. A Clarke-Park transformation is applied using the vector space decoupling method to obtain a mathematical model of the dual three-phase permanent magnet synchronous motor in a rotating coordinate system, and the voltage u is determined. d u q u z1 u z2 .

4. The sampling current compensation method based on an extended state observer according to claim 3, characterized in that, The mathematical model of a dual three-phase permanent magnet synchronous motor is as follows:

5. A computer-readable storage device storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the sampling current compensation method based on the extended state observer as described in any one of claims 1 to 4.

6. A sampling current compensation device based on an extended state observer, comprising a storage device, a processor, and a computer program stored in the storage device and executable on the processor, characterized in that, The processor executes the computer program to implement the steps of the sampling current compensation method based on the extended state observer as described in any one of claims 1 to 4.

7. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the sampling current compensation method based on the extended state observer as described in any one of claims 1 to 4.

8. A control method based on the sampling current compensation method based on the extended state observer as described in claim 1, characterized in that, Torque current i is obtained using the speed loop qref As the input given to the q-axis current in the current loop, the sampling current compensation method based on the extended state observer as described in claim 1 is used to obtain the error-compensated sampling current, which serves as the sampling current of the current loop. The output given voltage of the current loop is used to obtain the three-phase voltage u of the two windings based on the inverse Clarke-Park transform of vector space decoupling. abc u xyz u abc u xyz After SPWM modulation, a drive signal is sent to control the power module of the six-phase inverter to generate waves. The six-phase inverter outputs six-phase voltage to realize the drive of the dual three-phase permanent magnet synchronous motor.

9. The control method according to claim 8, characterized in that, The PI controller for the current loop is: In the formula, k p_d k i_d These represent the d-axis proportional and integral gains of the PI controller, respectively, and k p_q k i_q These are the q-axis proportional and integral gains of the PI controller, respectively, k p_z1 k i_z1 These are the z1-axis proportional and k values ​​of the PI controller, respectively. p_z2 k i_z2 These are the z2-axis proportional and integral gains of the PI controller, respectively, ω c This represents the bandwidth of the current loop.

10. The control method according to claim 8, wherein the PI controller for the speed loop is: In the formula, k p_s k i_s These are the proportional and integral gains of the PI controller, ω. s ω is the bandwidth of the speed loop. c K is the bandwidth of the current loop. T J represents the torque coefficient and J represents the moment of inertia.

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