Current reconstruction method for permanent magnet motor driving system

Abstract

The invention provides a current reconstruction method for a permanent magnet motor driving system, which is used for solving the problem of fault-tolerant operation when a current sensor breaks down due to strong electromagnetic interference on a permanent magnet motor for a multi-rotor unmanned aerial vehicle. According to the method, a first-order sliding-mode observer is designed for observing current, and on the premise that estimated current and actual current are assumed to have the same phase, a current reconstruction algorithm is designed by using an error between a measured value and an observed value of alpha-phase current on a static coordinate system, and # xa7b5 orthogonal to the alpha-phase current is obtained; the error between the measured value and the observed value of the phase current is further substituted into the designed first-order sliding mode observer to realize current observation, so that the target of reconstructing the B-phase current and the C-phase current by using the sampled A-phase current is achieved; therefore, an accurate current feedback signal is provided for current fault-tolerant control of the permanent magnet motor when the current sensor fails under strong electromagnetic interference.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a current reconstruction method for a permanent magnet motor drive system. Background Art

[0002] In recent years, with the rapid development of technologies such as multi-rotor drones and new energy vehicles, permanent magnet motors have been widely used due to their high efficiency and high reliability. Under complex operating conditions such as strong electromagnetic interference, the current sampling signal of the permanent magnet motor drive system is prone to current signal loss, current sensor failure and other faults, affecting the operating reliability of the permanent magnet motor. For this reason, the current reconstruction technology of permanent magnet motors has received extensive attention and research.

[0003] Reference [Tian Lisi, Zong Nailong, Liu Liwei, et al. Research on hybrid pulse width modulation technology of permanent magnet synchronous motor based on single current sensor [J / OL]. Transactions of China Electrotechnical Society, 1-12] proposed a method for reconstructing three-phase AC current using a single DC current sensor. However, such methods often require the design of special pulse width modulation technology to overcome the influence of factors such as dead zone, and require the design of compensation algorithms to solve problems such as errors caused by time-sharing. Reference [Fang Yuchao, Wang Bo, Wang Yuankui, et al. Research on position sensorless fault-tolerant control algorithm of embedded permanent magnet synchronous motor under current sensor fault state [J]. Journal of Electric Machines and Control, 2024, 28(08): 1-9.] proposed a position sensorless control method for embedded permanent magnet synchronous motor based on phase current reconstruction, and designed a current state observer to realize current reconstruction; but this method is sensitive to changes in motor parameters. Reference [Chen Yuexuan, Ge Xinglai, Zuo Yun, et al. A Current Sensor Fault-Tolerant Control Strategy for Speed-Sensorless Induction Motor Drives Based on the SEPLL Current Reconstruction Scheme," in IEEE Transactions on Industry Applications, vol. 59, no. 1, pp. 845-856, Jan.-Feb. 2023, doi: 10.1109 / TIA.2022.3204733.] proposed a phase current reconstruction method based on an improved second-order generalized integrator and a frequency-locked loop. However, the dynamic characteristics of the reconstructed current by this method are poor. Reference [Y. Zuo et al.,"Current Sensor Fault-Tolerant Control for Speed-Sensorless Induction Motor Drives Based on the SEPLL Current Reconstruction Scheme," in IEEE Transactions on Industry Applications, vol. 59, no. 1, pp. 845-856, Jan.-Feb. 2023, doi: 10.1109 / TIA.2022.3204733.] proposed a phase current reconstruction method based on an improved single-phase phase-locked loop. However, the dynamic characteristics of the reconstructed current by this method are also poor. Summary of the invention

[0004] In view of the technical problem that traditional permanent magnet motor drive systems are prone to current sensor failure and other faults under strong electromagnetic interference, the present invention proposes a current reconstruction method for a permanent magnet motor drive system, which uses the sampled A-phase current to achieve rapid reconstruction of the B-phase and C-phase currents.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A current reconstruction method for a permanent magnet motor drive system, the steps of which are as follows:

[0007] Step S1: Use a voltage sensor to collect the stator A phase voltage u of the permanent magnet motor A and B phase voltage u B , and the voltage u A 、u B Transformed to the two-phase stationary αβ coordinate system, the stator voltage u is obtained α 、u β ;

[0008] Step S2: Use a current sensor to collect the A-phase current i of the permanent magnet motor. A , and the current i A Transformed to the two-phase stationary αβ coordinate system, the current i is obtained α , satisfying: i α =i A ; where i α is the α-axis component of the stator current of the permanent magnet motor in the stationary αβ coordinate system;

[0009] Step S3: According to the stator voltage u α 、u β and current i α , construct the following sliding mode observer, satisfying:

[0010]

[0011] in, represents the α-axis component of the estimated current, represents the β-axis component of the estimated current, k represents the sliding mode gain, sgn() is the sign function, L s Represents the stator inductance of the permanent magnet motor, R s represents the stator resistance of the permanent magnet motor, represents the α-axis current observation error, △i β represents the β-axis current observation error;

[0012] Step S4: According to the A phase current i A and current estimation Get the reconstructed b-phase current and the reconstructed c-phase current satisfy:

[0013]

[0014] Preferably, the voltage u A 、u B Transformed to the two-phase stationary αβ coordinate system, the stator voltage u is obtained α 、u β The method is:

[0015]

[0016] Among them, u α is the α-axis component of the stator phase voltage of the permanent magnet motor in the stationary αβ coordinate system, u β It is the β-axis component of the stator phase voltage of the permanent magnet motor in the stationary αβ coordinate system.

[0017] Preferably, the β-axis current observation error Δi β The expression is:

[0018] △i β =△Isinθ i ;

[0019] Where △I represents the current error amplitude, θ i is the angle of the current vector.

[0020] Preferably, the angle θ of the current vector i The expression is:

[0021]

[0022] Among them, θ r represents the rotor position angle of the permanent magnet motor, i dref represents the d-axis current reference value of the permanent magnet motor drive system, i qref It represents the q-axis current reference value of the permanent magnet motor drive system.

[0023] Preferably, the reconstruction method of the current error amplitude ΔI is:

[0024] Step 3.1: Observe the error △i based on the α-axis current α , β-axis current observation error △i β The angle θ between the current vector i Construct the first current error variable ε1 to satisfy:

[0025] ε1=△i α sinθ i -△i β cosθi ;

[0026] Step 3.2: According to the angle θ of the current vector i And the first current error variable ε1, construct the second current error variable ε2, satisfying:

[0027] ε2=2ε1cos(2θ i )sin(4θ i );

[0028] Step 3.3: After the second current error variable ε2 passes through a low-pass filter, a third current error variable ε3 is obtained, which satisfies:

[0029]

[0030] Among them, s represents the Laplace operator, ω c Represents the cutoff frequency of the low-pass filter;

[0031] Step 3.4: The third current error variable ε3 is passed through a proportional-integral controller to obtain a current error amplitude △I, which satisfies:

[0032]

[0033] Among them, k p represents the proportional gain of the proportional-integral controller, k i Represents the integral gain of the proportional-integral controller.

[0034] Beneficial effects of the present invention: The present invention designs a method for reconstructing the β-axis current error based on the α-axis current error, and designs a current sliding mode observer to realize the observation of the α-axis and β-axis currents, thereby realizing the reconstruction of the B-phase and C-phase currents. This method is not only not affected by parameters such as inductance, but also can obtain faster dynamic current reconstruction performance by adjusting the proportional integral controller, providing a guarantee for realizing fault-tolerant control of a permanent magnet motor drive system based on a single-phase current sensor under current sensor failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is a control block diagram of the B-phase current and C-phase current reconstruction method based on the sliding mode observer of the present invention.

[0037] Figure 2 is the β-axis current observation error △i of the present invention β Reconstruction method and control block diagram of the reconstruction method of the current error amplitude △I.

[0038] Figure 3 This is the B-phase current reconstruction result obtained by using the method of the present invention.

[0039] Figure 4 This is the C-phase current reconstruction result obtained by using the method of the present invention. DETAILED DESCRIPTION

[0040] 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.

[0041] like Figure 1 As shown, an embodiment of the present invention provides a current reconstruction method for a permanent magnet motor drive system, and the specific steps are as follows:

[0042] Step S1: Use a voltage sensor to collect the stator A phase voltage u of the permanent magnet motor A and B phase voltage u B , and the voltage u A 、u B Transformed to the two-phase stationary αβ coordinate system, the stator voltage u is obtained α 、u β ,satisfy:

[0043]

[0044] Among them, u α is the α-axis component of the stator phase voltage of the permanent magnet motor in the stationary αβ coordinate system, u β It is the β-axis component of the stator phase voltage of the permanent magnet motor in the stationary αβ coordinate system.

[0045] Step S2: Use a current sensor to collect the A-phase current i of the permanent magnet motor. A , and the current i A Transformed to the two-phase stationary αβ coordinate system, the current i is obtained α , satisfying: i α =i A ; where i α is the α-axis component of the stator current of the permanent magnet motor in the stationary αβ coordinate system.

[0046] Step S3: According to the stator voltage u α 、uβ and current i α , construct the following sliding mode observer, satisfying:

[0047]

[0048] in, represents the α-axis component of the estimated current, represents the β-axis component of the estimated current, k represents the sliding mode gain, sgn() is the sign function, L s Represents the stator inductance of the permanent magnet motor, R s Represents the stator resistance of the permanent magnet motor, △i α represents the α-axis current observation error, which satisfies: △i β Represents the β-axis current observation error, represented by △i α and current reconstruction algorithm to obtain;

[0049] like Figure 2 As shown, the β-axis current observation error △i β The reconstruction method satisfies:

[0050] △i β =△Isinθ i ;

[0051] Where △I represents the current error amplitude, θ i is the angle of the current vector.

[0052] The angle of the current vector θ i satisfy:

[0053]

[0054] Among them, θ r Represents the rotor position angle of the permanent magnet motor, which can be measured using an encoder. dref represents the d-axis current reference value of the permanent magnet motor drive system, i qref It represents the q-axis current reference value of the permanent magnet motor drive system.

[0055] The reconstruction method of the current error amplitude △I is:

[0056] Step 3.1: Observe the error △i based on the α-axis current α , β-axis current observation error △i β The angle θ between the current vector i Construct the first current error variable ε1 to satisfy:

[0057] ε1=△i α sinθ i -△i β cosθ i ;

[0058] Step 3.2: According to the angle θ of the current vector i And the first current error variable ε1, construct the second current error variable ε2, satisfying:

[0059] ε2=2ε1cos(2θ i )sin(4θ i );

[0060] Step 3.3: After the second current error variable ε2 passes through a low-pass filter, a third current error variable ε3 is obtained, which satisfies:

[0061]

[0062] Among them, s represents the Laplace operator, ω c Represents the cutoff frequency of the low-pass filter;

[0063] Step 3.4: The third current error variable ε3 is passed through a proportional-integral controller to obtain a current error amplitude △I, which satisfies:

[0064]

[0065] Among them, k p represents the proportional gain of the proportional-integral controller, k i Represents the integral gain of the proportional-integral controller.

[0066] Step S4: According to the A phase current i A and current estimation Get the reconstructed b-phase current and the reconstructed c-phase current satisfy:

[0067]

[0068] In order to verify the effectiveness of the present invention, a simulation verification is carried out. The motor parameters used in the experiment are shown in Table 1.

[0069] Table 1 Permanent magnet motor parameters

[0070]

[0071] During simulation, the permanent magnet motor adopts a dual-loop control strategy of speed outer loop and current inner loop, wherein the current inner loop adopts model predictive control technology and the speed outer loop adopts proportional integral control technology. A 、Stator A phase voltage u A and B phase voltage u B , to achieve reconstruction of phase B current and phase C current.

[0072] During the simulation, starting from 0s, the motor runs at a speed of 750r / min and a load of 10Nm. At 0.3s, the load suddenly increases to 30Nm, and at 0.5s, the motor speed drops from 750r / min to 150r / min. Figure 3 The reconstruction result of the B phase current obtained by the method of the present invention is given. Figure 4 The C-phase current reconstruction result obtained by the method of the present invention is given.

[0073] Depend on Figure 3 It can be seen that when the load suddenly increases at 0.3s, the current reconstruction accuracy of phase B of the method proposed in the present invention is very high, and the current reconstruction error is When the speed suddenly changes at 0.5s, the reconstructed current returns to stability after a transient process. The current reconstruction error after steady state is about 0.14A, accounting for about 1.22% of the actual current, indicating that the reconstruction accuracy of phase B current reaches 98.78%.

[0074] Depend on Figure 4 It can be seen that when the load suddenly increases at 0.3s, the current reconstruction accuracy of phase C of the method proposed in the present invention is also very high, and the current reconstruction error is When the speed suddenly changes at 0.5s, the reconstructed current returns to stability after a transient process. The current reconstruction error after steady state is about 0.17A, accounting for about 1.48% of the actual current, indicating that the reconstruction accuracy of phase C current reaches 98.52%.

[0075] The above simulation examples illustrate that the method proposed in the present invention can quickly realize the reconstruction of the B-phase current and the C-phase current based on the A-phase current sensor, and the current reconstruction accuracy in the steady state is higher than 90%, which verifies the effectiveness of the solution of the present invention.

[0076] The above description is only a preferred 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 principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A current reconstruction method for a permanent magnet motor drive system, characterized in that: The steps are as follows: Step S1: Use a voltage sensor to collect the stator A phase voltage u of the permanent magnet motor A and B phase voltage u B , and the voltage u A 、u B Transformed to the two-phase stationary αβ coordinate system, the stator voltage u is obtained α 、u β ; Step S2: Use a current sensor to collect the A-phase current i of the permanent magnet motor. A , and the current i A Transformed to the two-phase stationary αβ coordinate system, the current i is obtained α , satisfying: i α =i A ; where i α is the α-axis component of the stator current of the permanent magnet motor in the stationary αβ coordinate system; Step S3: According to the stator voltage u α 、u β and current i α , construct the following sliding mode observer, satisfying: in, represents the α-axis component of the estimated current, represents the β-axis component of the estimated current, k represents the sliding mode gain, sgn() is the sign function, L s Represents the stator inductance of the permanent magnet motor, R s represents the stator resistance of the permanent magnet motor, represents the α-axis current observation error, △i β represents the β-axis current observation error; Step S4: According to the A phase current i A and current estimation Get the reconstructed b-phase current and the reconstructed c-phase current satisfy:

2. The current reconstruction method of a permanent magnet motor drive system according to claim 1, characterized in that: The voltage u A 、u B Transformed to the two-phase stationary αβ coordinate system, the stator voltage u is obtained α 、u β The method is: Among them, u α is the α-axis component of the stator phase voltage of the permanent magnet motor in the stationary αβ coordinate system, u β It is the β-axis component of the stator phase voltage of the permanent magnet motor in the stationary αβ coordinate system.

3. The current reconstruction method of a permanent magnet motor drive system according to claim 1, characterized in that: The β-axis current observation error △i β The expression is: △i β =△Isinθ i ; Where △I represents the current error amplitude, θ i is the angle of the current vector.

4. The current reconstruction method of a permanent magnet motor drive system according to claim 3, characterized in that: The angle θ of the current vector i The expression is: Among them, θ r represents the rotor position angle of the permanent magnet motor, i dref represents the d-axis current reference value of the permanent magnet motor drive system, i qref It represents the q-axis current reference value of the permanent magnet motor drive system.

5. The current reconstruction method of a permanent magnet motor drive system according to claim 3 or 4, characterized in that: The reconstruction method of the current error amplitude △I is: Step 3.1: Observe the error △i based on the α-axis current α , β-axis current observation error △i β The angle θ between the current vector i Construct the first current error variable ε1 to satisfy: ε1=△i α sinθ i -△i β cosθ i ; Step 3.2: According to the angle θ of the current vector i And the first current error variable ε1, construct the second current error variable ε2, satisfying: ε2=2ε1cos(2θ i )sin(4θ i ); Step 3.3: After the second current error variable ε2 passes through a low-pass filter, a third current error variable ε3 is obtained, which satisfies: Where s represents the Laplace operator, ω c Represents the cutoff frequency of the low-pass filter; Step 3.4: The third current error variable ε3 is passed through a proportional-integral controller to obtain a current error amplitude △I, which satisfies: Among them, k p represents the proportional gain of the proportional-integral controller, k i Represents the integral gain of the proportional-integral controller.

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