Open winding permanent magnet synchronous motor current measurement bias error correction method

Abstract

The invention relates to a current measurement bias error correction method, in particular to a current measurement bias error correction method for an open-winding permanent magnet synchronous motor. The problem that an existing current measurement bias error correction strategy only aims at a permanent magnet synchronous motor, and a correction strategy aiming at an open-winding permanent magnet synchronous motor does not exist is solved. The method comprises the following steps: constructing an open winding permanent magnet synchronous motor control system containing a three-phase current measurement bias error; constructing a voltage model transfer function of a dq0 axis; according to a given voltage model of the dq0 axis of the motor and the output voltage of the dq0 axis, a predicted current of the dq0 axis is obtained; converting the dq0-axis predicted current into an alpha beta 0-axis predicted current, comparing the alpha beta 0-axis predicted current with an actually measured alpha beta 0-axis current, and obtaining a current measurement bias error of the alpha beta 0-axis through a low-pass filter; and the current measurement bias error of the rotation alpha beta 0 axis is converted into the bias error of the three-phase current through an equation obtained through Clark conversion. The invention belongs to the technical field of motor control.

Description

Technical Field

[0001] This invention relates to a method for correcting bias error in current measurement, belonging to the field of motor control technology. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) possess advantages such as high power density, large torque-to-inertia ratio, and high efficiency, leading to their widespread application in industries such as robotics, electric vehicles, and aerospace. Recently, a novel topology called the open-winding PMSM has been extensively studied, in which the neutral point of the PMSM is opened and powered by dual inverters. The open-winding PMSM inherits the advantages of traditional PMSMs, exhibiting higher DC voltage utilization, multi-level modulation performance, redundant switching combinations, and better fault tolerance, making it more suitable for high-power applications such as electric vehicles and marine propulsion.

[0003] Typically, three current sensors are used in open-winding permanent magnet synchronous motors to measure phase current. The output of the current sensors is usually a voltage signal, which is converted to a suitable range through matching and noise filtering circuits, allowing it to be processed by an analog-to-digital converter. Various factors in the current sensors and related circuits, such as resistance, operational amplifiers, aging, component tolerances, nonlinearity, and thermal drift, all affect the current measurement. Current measurement errors can produce periodic torque ripples at the same or twice the frequency of the stator fundamental current. Furthermore, current measurement bias errors degrade the performance of dead-zone compensators in voltage source inverters, as most dead-zone compensation schemes rely on the direction of the phase current, and current measurement bias errors provide incorrect information to the dead-zone compensator, thus severely impacting the operational performance of the open-winding permanent magnet synchronous motor control system.

[0004] Currently, existing current measurement bias error correction strategies only apply to permanent magnet synchronous motors (PMSMs), and there are no correction strategies for open-winding PMSMs. Therefore, there is an urgent need in this field for a method to correct current measurement bias errors in open-winding PMSMs. Summary of the Invention

[0005] To address the problem that existing current measurement bias error correction strategies only apply to permanent magnet synchronous motors and lack a correction strategy for open-winding permanent magnet synchronous motors, this invention proposes a current measurement bias error correction method for open-winding permanent magnet synchronous motors.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: The steps of the present invention include:

[0007] Step 1: Construct a control system for an open-winding permanent magnet synchronous motor that includes three-phase current measurement bias error;

[0008] Step 2: Based on the voltage equation of the dq0 axis, construct the voltage model transfer function of the dq0 axis;

[0009] Step 3: Based on the given voltage model of the motor dq0 axis and the output voltage of the dq0 axis, obtain the predicted current of the dq0 axis;

[0010] Step 4: Transform the predicted current of the dq0 axis into the predicted current of the αβ0 axis through the inverse Park transform. Compare the predicted current of the αβ0 axis with the actual measured current of the αβ0 axis, and obtain the current measurement bias error of the αβ0 axis through a low-pass filter.

[0011] Step 5: Using the equation obtained through Clark transformation, the current measurement bias error of the αβ0 axis is converted into the bias error of the three-phase current, and then the three-phase current of the system is corrected.

[0012] Furthermore, the voltage equation for the dq0 axis of the open-winding permanent magnet synchronous motor in step 2 is as follows:

[0013]

[0014] In formula (1), u n i represents the voltage of the dq0 axis winding. n L represents the current in the dq0 axis winding. n Let n represent the inductance of the dq0 axis winding, where n = d, q, 0, R represents the resistance of the motor, and ω represents the resistance of the motor. e θ represents the electric angular velocity of the motor rotor. e Indicates the position of the motor rotor, Ψ f1 Ψ represents the flux linkage of the permanent magnet in the motor rotor. f3 This indicates the third flux linkage of the permanent magnet in the motor rotor;

[0015] The voltage model transfer function for the dq0 axis is as follows:

[0016]

[0017] in:

[0018]

[0019] In formulas (2), (3) and (4), s represents the Laplace operator, and G n (s) represents the voltage model along the dq0 axis, e n Let n represent the back electromotive force along the dq0 axis, where n = d, q, 0.

[0020] Furthermore, the predicted current along the dq0 axis in step 3 is:

[0021]

[0022] In formula (5), This represents the predicted current along the dq0 axis. Represent the given voltage equation, Let n represent the given back electromotive force, where n = d, q, 0.

[0023] Furthermore, in step 4, the predicted current along the dq axis is transformed into the αβ axis using an inverse Park transformation as follows:

[0024]

[0025] In formula (6), Represents the predicted current along the αβ axis;

[0026] The predicted current of the αβ0 axis is subtracted from the actual measured current of the αβ0 axis, and the current measurement bias error of the αβ0 axis is obtained by passing it through a low-pass filter.

[0027] Furthermore, in step 5, the relationship between the αβ0 axis and the three phases abc obtained according to the Clark transformation is as follows:

[0028]

[0029] In formula (7), Δi n (n = a, b, c, α, β, 0) represents the bias error;

[0030] By obtaining accurate three-phase current measurement bias error, the open-winding permanent magnet synchronous motor system can be corrected, thereby improving the system's operating performance.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention can obtain accurate three-phase current bias error, and then correct the open-winding permanent magnet synchronous motor system, thereby improving the system's operating performance;

[0033] 2. After using this invention, the current waveform, electromagnetic torque, and speed waveform are corrected to normal waveforms in a short time;

[0034] 3. This invention can effectively correct bias errors, and the current waveform, electromagnetic torque and speed waveform have virtually no fluctuations. Attached Figure Description

[0035] Figure 1 This is a control block diagram of the method of the present invention;

[0036] Figure 2 This is a structural diagram of the current measurement bias error calculation module of the method of the present invention;

[0037] Figure 3 It shows the waveforms of the three-phase currents before and after introducing the current measurement bias error;

[0038] Figure 4 It shows the waveforms of electromagnetic torque and speed before and after introducing current measurement bias error;

[0039] Figure 5 The waveforms of the three-phase currents before and after introducing the method of this invention are shown in the case of current measurement bias error.

[0040] Figure 6 The waveforms of electromagnetic torque and rotational speed before and after introducing the method of this invention are shown in the case of current measurement bias error.

[0041] Figure 7 The waveform diagram of the three-phase current when the motor speed changes is shown in the present invention under the condition of current measurement bias error.

[0042] Figure 8 The present invention provides waveforms of electromagnetic torque and speed when the motor speed changes, provided that there is a current measurement bias error.

[0043] Figure 9 The present invention provides a waveform diagram of the three-phase current when the current measurement bias error changes, under the condition that current measurement bias error exists.

[0044] Figure 10 The waveforms of electromagnetic torque and rotational speed in the present invention are shown when the current measurement bias error changes, under the condition that current measurement bias error exists. Example

[0045] Example 1

[0046] A method for correcting bias error in current measurement of an open-winding permanent magnet synchronous motor, comprising the following steps:

[0047] Step 1: Construct a control system for an open-winding permanent magnet synchronous motor that includes three-phase current measurement bias error;

[0048] Step 2: Construct the voltage model transfer function for the dq0 axis based on the voltage equation of the dq0 axis;

[0049] Step 3: Based on the given voltage model of the motor dq0 axis and the output voltage of the dq0 axis, obtain the predicted current of the dq0 axis;

[0050] Step 4: Transform the predicted current of the dq0 axis into the predicted current of the αβ0 axis through the inverse Park transform. Compare the predicted current of the αβ0 axis with the actual measured current of the αβ0 axis, and obtain the current measurement bias error of the αβ0 axis through a low-pass filter.

[0051] Step 5: Using the equation obtained through Clark transformation, the current measurement bias error of the αβ0 axis is converted into the bias error of the three-phase current, and then the three-phase current of the system is corrected.

[0052] Among them, the open-winding permanent magnet synchronous motor system in step one, such as Figure 1 As shown, the dq-axis reference current i d * and i q *Subtract feedback current i d and i q Obtain the error current Δi d and Δi q The reference voltage u is obtained through PI regulation. d * and u q *. u d *、u q The * and zero-sequence reference voltage u0* undergo an inverse Park transformation, converting from the synchronous rotating coordinate system dq0 axis to the stationary coordinate system αβ0 axis. Using an SVPWM modulation strategy, the current passes through the open-winding permanent magnet synchronous motor system, and then the three-phase measured current i is detected by a current sensor. nm (n = a, b, c), at this point, all three-phase currents carry measurement bias errors. Given a zero-sequence reference current i0* = 0, the result of subtracting the zero-sequence current i0 from i0* and the zero-sequence current angular frequency ω... e Both are used as inputs to the quasi-proportional resonant controller, which eliminates the main third harmonic in the zero-sequence current and outputs the zero-sequence reference voltage u0*.

[0053] In step two, the voltage equation for the dq0 axis of the open-winding permanent magnet synchronous motor is:

[0054]

[0055] In formula (8), u n i n L n (n = d, q, 0) represent the voltage, current, and self-inductance of the dq0 axis winding, respectively; R is the resistance of the motor; ω e Let θ be the electric angular velocity of the motor rotor. e ψ represents the position of the motor rotor. f1 For the permanent magnet flux linkage of the motor rotor, ψ f3 The permanent magnet of the motor rotor has a third magnetic flux linkage.

[0056] Transform equation (8) into the complex frequency domain:

[0057]

[0058] Simplifying equation (9), we obtain the voltage model transfer function for the dq0 axis as follows:

[0059]

[0060] in:

[0061]

[0062] s is the Laplace operator, G n (s), e n (n = d, q, 0) represent the voltage model and back electromotive force along the dq0 axis, respectively.

[0063] In step three, the predicted current along the dq0 axis is as follows:

[0064]

[0065] in

[0066]

[0067] and (n = d, q, 0) represent the predicted current along the dq0 axis, the given voltage equation, the given back electromotive force, and the given inductance, respectively. Given the motor resistance.

[0068] In step four, the basic idea behind estimating the current measurement bias error is that the frequency of the current measurement bias error differs from other machine variables, thus it can be extracted using a frequency method. Then, the error current is obtained by subtracting the predicted result from the measured current to eliminate the measurement error. A simple method is to low-pass filter the error current to obtain a constant current measurement bias error.

[0069] The three-phase current equations considering bias error are as follows:

[0070] i nm =i n +Δi n (16),

[0071] In formula (16), i nm i n and Δi n (n = a, b, c) represent the three-phase measured current, the three-phase actual current, and the three-phase current measurement bias error, respectively.

[0072] The bias error of formula (16) converted to the dq0 axis is:

[0073]

[0074] In formula (17), Δi n (n = d, q, 0) represents the current measurement bias error along the dq0 axis.

[0075] As can be seen from equation (17), since the bias error is reflected in the dq axis current as a first harmonic, if a low-pass filter is used to filter the dq axis directly, there will be a large error. Therefore, a low-pass filter cannot be used to filter it directly.

[0076] The bias error of equation (16) converted to the αβ0 axis is:

[0077]

[0078] In formula (18), Δi n (n = α, β, 0) represents the current measurement bias error along the αβ0 axis.

[0079] As can be seen from equation (18), the bias error is reflected in the αβ axis current as a DC component, which can be directly filtered by a low-pass filter to obtain the bias component.

[0080] The predicted current along the dq axis is transformed into the αβ axis using the inverse Park transform as follows:

[0081]

[0082] In formula (19), The predicted current is for the αβ axis.

[0083] The error between the measured current and the predicted current contains information about the current measurement bias error, which can be obtained by filtering the error. The current measurement bias error of the αβ0 axis is obtained by subtracting the predicted current of the αβ0 axis from the actual measured current and passing the result through a low-pass filter.

[0084]

[0085] in

[0086]

[0087] In formulas (20) and (21), Q n (n = α, β, 0) is a low-pass filter along the αβ0 axis, i nm (n = α, β, 0) represents the measured current along the αβ0 axis.

[0088] In step five, the relationship between the αβ0 axis and the three phases abc is derived from the Clark transformation of equation (18) as follows:

[0089]

[0090] With accurate three-phase current bias error obtained, the open-winding permanent magnet synchronous motor system can be corrected, thereby improving the system's operating performance. The overall bias error calculation module is as follows: Figure 2As shown.

[0091] Verifying the effectiveness of the present invention

[0092] Build the corresponding system simulation model in the Matlab / Simulink environment.

[0093] During simulation, the motor's given speed was 1000 rpm, and the load torque was 6 N·m. The three-phase current waveform, electromagnetic torque, and speed waveforms are as follows: Figure 3 and Figure 4 As shown, bias currents of 2A, 3A, and -2A are introduced into the three phases, respectively. As can be seen from the figure, after introducing the bias error, the current waveform exhibits significant fluctuations, and the electromagnetic torque and speed waveforms also show large pulsations. After introducing the correction method of this invention, as... Figure 5 and Figure 6 As shown, the current waveform, electromagnetic torque, and speed waveform were corrected to normal waveforms in a short time.

[0094] When the motor speed changes, the three-phase current waveform, electromagnetic torque, and speed waveform are as follows: Figure 7 and Figure 8 As shown. By Figure 7 As can be seen, when the motor speed changes from 1000 r / min to 1500 r / min, the method of this invention can also effectively correct the bias error, and the current waveform, electromagnetic torque and speed waveform remain basically unchanged.

[0095] When the three-phase current bias error is changed from 2A, 3A, and -2A to 3A, -2A, and 3A respectively, the three-phase current waveform, electromagnetic torque, and speed waveform are as follows: Figure 9 and Figure 10 As shown in the figure, although the three-phase current waveform was disturbed after the bias error was changed, the method of the present invention corrected the current waveform, electromagnetic torque and speed waveform to normal waveforms over time.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for correcting bias error in current measurement of an open-winding permanent magnet synchronous motor, characterized in that, The specific steps include: Step 1: Construct a control system for an open-winding permanent magnet synchronous motor that includes three-phase current measurement bias error; Step 2: Based on the voltage equation of the dq0 axis, construct the voltage model transfer function of the dq0 axis; Step 3: Based on the given voltage model of the motor dq0 axis and the output voltage of the dq0 axis, obtain the predicted current of the dq0 axis; Step 4: Transform the predicted current of the dq0 axis into the predicted current of the αβ0 axis through the inverse Park transform. Compare the predicted current of the αβ0 axis with the actual measured current of the αβ0 axis, and obtain the current measurement bias error of the αβ0 axis through a low-pass filter. Step 5: Using the equation obtained through Clark transformation, the current measurement bias error of the αβ0 axis is converted into the bias error of the three-phase current, and then the three-phase current of the system is corrected.

2. The method for correcting bias error in current measurement of an open-winding permanent magnet synchronous motor according to claim 1, characterized in that, The voltage equation for the dq0 axis of the open-winding permanent magnet synchronous motor in step 2 is: In formula (1), u n i represents the voltage of the dq0 axis winding. n L represents the current in the dq0 axis winding. n Let n represent the inductance of the dq0 axis winding, where n = d, q, 0, R represents the resistance of the motor, and ω represents the resistance of the motor. e θ represents the electric angular velocity of the motor rotor. e Indicates the position of the motor rotor, Ψ f1 Ψ represents the flux linkage of the permanent magnet in the motor rotor. f3 This indicates the third flux linkage of the permanent magnet in the motor rotor; The voltage model transfer function for the dq0 axis is as follows: in: In formulas (2), (3) and (4), s represents the Laplace operator, and G n (s) represents the voltage model along the dq0 axis, e n Let n represent the back electromotive force along the dq0 axis, where n = d, q, 0.

3. The method for correcting bias error in current measurement of an open-winding permanent magnet synchronous motor according to claim 1, characterized in that, The predicted current along the dq0 axis in step 3 is: In formula (5), This represents the predicted current along the dq0 axis. Represent the given voltage equation, Let n represent the given back electromotive force, where n = d, q, 0.

4. The method for correcting bias error in current measurement of an open-winding permanent magnet synchronous motor according to claim 1, characterized in that, In step 4, the predicted current along the dq axis is transformed into the αβ axis using an inverse Park transformation as follows: In formula (6), Represents the predicted current along the αβ axis; The predicted current of the αβ0 axis is subtracted from the actual measured current of the αβ0 axis, and the current measurement bias error of the αβ0 axis is obtained by passing it through a low-pass filter.

5. The method for correcting bias error in current measurement of an open-winding permanent magnet synchronous motor according to claim 1, characterized in that, In step 5, the relationship between the αβ0 axis and the three phases abc obtained according to the Clark transformation is as follows: In formula (7), Δi n (n = a, b, c, α, β, 0) represents the bias error; By obtaining accurate three-phase current measurement bias error, the open-winding permanent magnet synchronous motor system can be corrected, thereby improving the system's operating performance.

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