A high-speed permanent magnet synchronous motor position identification method

Abstract

The application discloses a high-speed permanent magnet synchronous motor position identification method, samples motor a, b, c three-phase currents, carries out Clarke transformation on the obtained currents to obtain the currents of alpha axis and beta axis on a two-phase static coordinate system, estimates the output voltage of alpha axis and beta axis according to the SVPWM conduction time calculated in the last control period, obtains a position estimation reference quantity by directly processing the current voltage, and uses a phase-locked loop to calculate the angle and speed of the position estimation reference quantity and thereby calculates motor position information, the application uses the output characteristics of a voltage source inverter to obtain a calculation formula not influenced by discretization errors, and improves the position identification precision under a low load frequency ratio.

Description

Technical Field

[0001] This invention belongs to the field of motor control technology, specifically relating to a method for position identification of a high-speed permanent magnet synchronous motor. Background Technology

[0002] High-speed motors offer advantages such as high power density and high reliability when driving high-speed loads, and are mainly used in flywheel energy storage, aerospace, and electric vehicles. Among them, high-speed permanent magnet synchronous motors (PMSMs) have the highest power density due to their use of permanent magnet excitation, and are widely used in the aforementioned fields. Because the response speed and reliability of rotor position sensors are difficult to guarantee at high speeds, high-speed PMSMs often employ sensorless control methods. Currently, commonly used position identification methods based on sliding diaphragm observers have low computational complexity and good stability at high speeds, but the observed signal suffers from chattering. Introducing filters can suppress chattering, but when the motor operates at ultra-high speeds or low carrier frequency ratios (the ratio of control frequency to motor fundamental frequency), the chattering frequency of the signal approaches the motor's fundamental frequency, making effective filtering difficult. Furthermore, the introduction of filters can introduce phase lag in position identification.

[0003] To address the error problem in position identification of high-speed permanent magnet synchronous motors, existing solutions mainly focus on two aspects: compensating for errors in the sliding diaphragm observer algorithm and using algorithms without a sliding diaphragm observer. Patent CN114826042B proposes injecting high-frequency disturbances into the rotor position estimation signal based on the sliding diaphragm observer method and extracting the response of the disturbance signal from the q-axis current signal for position signal compensation. This method eliminates the need for motor parameters and can compensate for rotor signal errors caused by various factors in one go. However, this method requires injecting a high-frequency position signal, which may fail to meet position compensation requirements and could interfere with normal motor operation when the motor's fundamental frequency is high or the carrier frequency is low. Patent CN116488514B utilizes a reduced-order Kalman filter to obtain motor position and angle estimates, reducing the computational burden of the Kalman filter. However, it still requires real-time calculation of a third-order Kalman filter algorithm, which is computationally complex and difficult to tune. Patent CN113078851B improves the flux linkage observer of the current model method by using a flux linkage calculation method based on the current model, which has a higher anti-interference capability. However, this method uses the estimated position of the previous cycle when calculating the rotor position in the current cycle, which still results in a phase lag problem in the estimation results at low carrier frequency ratios. Summary of the Invention

[0004] The purpose of this invention is to provide a position identification method for a high-speed permanent magnet synchronous motor, in order to solve the identification error problem of existing position identification methods when operating at low carrier frequency ratios.

[0005] The technical solution to achieve the purpose of this invention is as follows:

[0006] A method for position identification of a high-speed permanent magnet synchronous motor, which obtains the rotor position of the motor through the following formula. and rotational speed :

[0007] ;

[0008] ;

[0009] in and These are the position estimation reference values ​​for discretized permanent magnet synchronous motors. The angle and rotational speed are calculated using a phase-locked loop. The inductance is in a two-phase stationary coordinate system. This is the resistance of the stator winding.

[0010] The significant advantages of this invention compared to existing technologies are:

[0011] This invention presents a position identification method for high-speed permanent magnet synchronous motors. By directly processing the current and voltage, a position estimation reference value is obtained, avoiding the chattering problem associated with using a sliding diaphragm observer. Furthermore, the method utilizes the output characteristics of a voltage source inverter in the reference value calculation to obtain a calculation formula unaffected by discretization errors, thus improving position identification accuracy at low carrier frequency ratios. The position identification accuracy of this method remains unaffected by changes in winding resistance caused by motor temperature or skin effect. Attached Figure Description

[0012] Figure 1 This is an overall flowchart of the method of the present invention.

[0013] Figure 2 The diagram shows the motor control block diagram (within the dashed box) for applying the method of this invention. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015] Combination Figure 1 , Figure 2 , Figure 1 This is an overall flowchart of the method of the present invention. Figure 2 The diagram shows the motor control block diagram (within the dashed box) for applying the method of this invention. All variables marked in the diagram are sampled values. This embodiment of a position identification method for a high-speed permanent magnet synchronous motor includes the following steps:

[0016] Step 1: Acquisition and Conversion of Current and Voltage

[0017] Sample the three-phase currents of motor a, b, and c , , The obtained currents are then subjected to Clarke transformation to obtain the currents along the α and β axes in the two-phase stationary coordinate system. , The output voltages of the α-axis and β-axis are estimated based on the SVPWM conduction time calculated from the previous control cycle. , .

[0018] Step 2: Calculate the location estimation reference value

[0019] Based on the relationship between current, voltage, and back EMF of a salient-pole permanent magnet synchronous motor

[0020]

[0021] achievable

[0022]

[0023] in, The stator voltage is located in a two-phase stationary coordinate system. The stator current is in a two-phase stationary coordinate system. The back potential in the two-phase stationary coordinate system ( , (These represent the back electromotive forces along the α-axis and β-axis of the two-phase stationary coordinate system, respectively). The inductance is in a two-phase stationary coordinate system. The resistance of the stator winding, is the differential factor.

[0024] From the above equation, we can see that the voltage is passed through a low-pass filter. Subtracting the current, we can obtain the value of the back EMF after filtering by the same filter. Select Reference value for position estimation of permanent magnet synchronous motor ,have

[0025]

[0026] Under SVPWM control using a voltage source inverter, the inverter outputs several voltage vectors to synthesize a specific output voltage in each control cycle. Since the control system only cares about the parameter values ​​at the beginning of the control cycle, the output voltage can be approximated as constant in each control cycle. This can be obtained by solving the differential equation. The discretization calculation formula is as follows

[0027]

[0028] in, The sampling period is For intermediate variables (initialized to 0), add a variable name after the variable name. This represents the value of the variable at the k-th sampling time.

[0029] Step 3: Phase-Locked Loop Calculation The angle and speed are used to calculate the motor position information.

[0030] The calculation can be performed using a phase-locked loop. Angle and rotational speed (Angular velocity) Since the rate of change of the motor's electrical parameters is much greater than the rate of change of the motor's speed, it can be assumed that the motor's speed remains essentially constant during the time required for the phase-locked loop to converge. (From step two) Definition achievable With permanent magnet flux of motor The relationship is

[0031]

[0032] in, Permanent magnet flux linkage in a two-phase stationary coordinate system ( , (These represent the permanent magnet flux linkages on the α-axis and β-axis of the two-phase stationary coordinate system, respectively). It is the imaginary unit.

[0033] Therefore, the position of the motor rotor and rotational speed It can be obtained from the following formula

[0034]

[0035]

[0036] The following will explain the use of d-axis command current in permanent magnet motors. In vector control, the position identification accuracy of this method is not affected by the error of the winding resistance R.

[0037] Let the measured winding resistance be... ( ),at this time The definition has been changed to (back potential) Through the filter (Reference value for estimated location)

[0038]

[0039] Due to calculation Sometimes it is also used ,Depend on Calculated This is the actual value.

[0040] In fact, the position estimation reference value calculated at this time (equivalent to) Through the filter The obtained position estimate reference value is

[0041]

[0042] Based on the relationship between the two-phase synchronous coordinate system and the two-phase stationary coordinate system, we can obtain

[0043]

[0044] in , , These are the d-axis current, q-axis current, and q-axis back EMF in the two-phase synchronous coordinate system, respectively. Since the d-axis of the two-phase synchronous coordinate system is located along the direction of the magnetic flux linkage, the d-axis back EMF in the two-phase synchronous coordinate system is 0.

[0045] Let the rotor angle identified at this time be... ,

[0046]

[0047] Let intermediate quantity The above formula can be transformed into

[0048]

[0049] There is an angle error When using The vector control will identify the measured current on the d-axis. Controlling it to 0 will reduce the actual d-axis current. Adjust to ,at this time ,thereby This indicates that even if there is an error in the winding resistance, the position identification angle will still converge to the true value when the system is stable.

Claims

1. A method for position identification of a high-speed permanent magnet synchronous motor, characterized in that, The motor rotor position is obtained using the following formula. and rotational speed : ； ； in and These are the position estimation reference values ​​for discretized permanent magnet synchronous motors. The angle and rotational speed are calculated using a phase-locked loop. The inductance is in a two-phase stationary coordinate system. The resistance of the stator winding; Discretized permanent magnet synchronous motor position estimation reference for: ； in, The sampling period is As an intermediate variable, Let be the stator current in the two-phase stationary coordinate system at the k-th sampling time. Let be the stator voltage in the two-phase stationary coordinate system at the (k-1)th sampling time.

2. The high-speed permanent magnet synchronous motor position identification method according to claim 1, characterized in that, The stator voltage in the two-phase stationary coordinate system is obtained by the following formula: ； in The back electromotive force in the two-phase stationary coordinate system. , These represent the back electromotive forces on the α-axis and β-axis of the two-phase stationary coordinate system, respectively.

3. The high-speed permanent magnet synchronous motor position identification method according to claim 1, characterized in that, The stator current in the two-phase stationary coordinate system is obtained by sampling the three-phase current of the motor and performing Clarke transformation.

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