Method for suppressing current measurement error of ship permanent magnet propulsion motor

Abstract

The invention provides a method for suppressing a current measurement error of a ship permanent magnet propulsion motor, and belongs to the technical field of motor drive control systems. The method comprises the following steps: establishing a ship permanent magnet propulsion motor vector control system model containing a current measurement error; constructing a target resonator with d-axis and q-axis current measurement error phase compensation based on the model; the target resonator is connected to a PI controller of a rotating speed ring in parallel, and the output of the target resonator serves as compensation of d-axis current and q-axis current disturbance of the ship permanent magnet propulsion motor. According to the method, the problem that only q-axis current harmonic can be compensated in the prior art is solved, meanwhile, a controller or a sensor does not need to be added, system redundancy is avoided, and accuracy and calculation efficiency are both achieved.

Description

Technical Field

[0001] This invention relates to the field of motor drive control system technology, and in particular to a method for suppressing current measurement errors in ship permanent magnet propulsion motors. Background Technology

[0002] With increasing demands for energy efficiency and environmental protection in the global shipping industry, permanent magnet synchronous motors (PMSMs) have become a core power solution for ship electric propulsion systems due to their high power density and low loss characteristics. In the vector control of ship permanent magnet propulsion motors, the accuracy of current measurement directly affects the control precision of the motor drive control system. In actual motor control systems, current measurement offset errors are typically caused by factors such as residual current in the current sensor, thermal drift in the conditioning circuit, and operational amplifier deviations; current measurement gain errors are usually caused by the nonlinearity of the current sensor and analog-to-digital converter during current sampling, as well as the quantization error between them.

[0003] In the vector control system of marine propulsion motor, the current measurement error is transformed into the synchronous rotating coordinate system, which causes the q-axis current to have a speed-related pulsation component. This further leads to the presence of primary and secondary pulsation components in the steady-state speed. Traditional resonant controllers with phase compensation can suppress speed pulsation by extracting speed pulsation to compensate for the q-axis current, but the d-axis current measurement error still exists, making it impossible to effectively improve the current quality.

[0004] Therefore, a method is needed to simultaneously improve the d-axis current and q-axis current to suppress the measurement error of the ship's permanent magnet propulsion motor current. Summary of the Invention

[0005] In view of this, the present invention provides a method for suppressing the measurement error of the current of a ship's permanent magnet propulsion motor. Therefore, the present invention provides the following technical solution: A method for suppressing current measurement errors in ship permanent magnet propulsion motors includes: Establish a vector control system model for a ship's permanent magnet propulsion motor that includes current measurement errors; Based on the model, a target resonator with phase compensation for d-axis and q-axis current measurement errors is constructed. The target resonator is connected in parallel to the PI controller of the speed loop, and the output of the target resonator is used as compensation for disturbances in the d-axis current and q-axis current of the ship's permanent magnet propulsion motor.

[0006] Furthermore, the construction of the ship permanent magnet propulsion motor vector control system model, which includes current measurement errors, includes: Construct a mathematical model of a ship's permanent magnet propulsion motor that includes current measurement errors; Based on the mathematical model, the current form is determined by considering both gain error and offset error.

[0007] Furthermore, the mathematical model of the ship's permanent magnet propulsion motor, which includes current measurement errors, is as follows:

[0008] In the formula, This refers to the current offset error in phase A. This refers to the current offset error in phase B. For the A-phase current gain error, For the B-phase current gain error, , and These are the measured values ​​of phase A, B, and C currents. , and These are the actual values ​​of the currents in phases A, B, and C. For electrical angle, It is the phase current amplitude;

[0009] In the formula, The target measured value for the d-axis current. The target measured value for the q-axis current. This is the actual measured value of the d-axis current. This is the actual measured value of the q-axis current. For d-axis current error, This represents the q-axis current error.

[0010] Furthermore, the current forms considering gain error and offset error respectively include: when The system only has gain error:

[0011]

[0012] when The system only has offset error:

[0013] According to the current formulas for gain error and offset error, when there is a current measurement error, the relationship between the harmonics of the d-axis current and the q-axis current is as follows: the amplitudes are equal, and in terms of phase, the q-axis current harmonic leads the d-axis current harmonic by 90°. When adopted In vector control, the electromagnetic torque is expressed as:

[0014] In the formula, For electromagnetic torque, For extreme logarithms, It is a permanent magnet flux linkage.

[0015] The equation of motion for the motor, neglecting the coefficient of friction, is:

[0016] In the formula, For load torque, For rotational inertia, This represents the motor speed.

[0017] Furthermore, the transfer function of the target resonator is:

[0018]

[0019] in For harmonic orders, when only the first-order pulsation is considered, i.e. , The time-domain expression is , The time-domain expression is , and Equal amplitude, phase Advanced 90°, which is the same as the harmonic relationship between the d-axis current and the q-axis current; Output and Compensate for the first harmonic disturbance in the q-axis and d-axis currents respectively. Output and The second harmonic disturbances in the q-axis and d-axis currents are compensated respectively.

[0020] Furthermore, it also includes: The target parameters are selected using the vector margin index, and the stability of the system is verified based on the target parameters.

[0021] Furthermore, the selection of target parameters using the vector margin index includes: Use the bandwidth method to determine the proportional-integral parameters of the control system; Based on the Bode plot and vector margin, the resonant gain and compensation angle are determined to balance compensation performance and stability.

[0022] Furthermore, the determination of the proportional-integral parameters of the control system using the bandwidth method includes: The current loop PI parameters are:

[0023]

[0024] In the formula, and These are the proportional and integral parameters for the d-axis and q-axis currents. For dq axis inductance, For the current loop bandwidth, Stator resistance; The PI parameters of the speed loop are:

[0025]

[0026] In the formula, and For the proportional and integral parameters of the speed loop, This represents the bandwidth of the speed loop.

[0027] Furthermore, the resonant gain and compensation angle include: The first-order resonant gain is equal to the second-order resonant gain.

[0028] The first-order compensation angle is half the second-order compensation angle.

[0029] Advantages and positive effects of the present invention: This method utilizes a target resonant controller with phase compensation to simultaneously compensate for d-axis and q-axis current harmonics caused by current measurement errors, thereby suppressing current measurement errors in ship permanent magnet propulsion motors and avoiding the limitations of single compensation. This method solves the problem of existing technologies only being able to compensate for q-axis current harmonics. Furthermore, this method eliminates the need for additional controllers or sensors, avoiding system redundancy, and combines accuracy with computational efficiency. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a vector control system for a ship's permanent magnet propulsion motor that includes current measurement errors, as described in the embodiment. Figure 2 This is a structural diagram of the target resonant controller with phase compensation in the embodiment; Figure 3 This example illustrates a vector control system for a ship's permanent magnet propulsion motor that uses a target resonant controller to suppress current measurement errors. Figure 4 The example shows an FFT analysis of the rotational speed at 300 rpm.

[0032] Figure 5 The Bode plots for different resonant gains at 300 rpm are shown in the example.

[0033] Figure 6 The vector margin with or without phase compensation at 300 rpm is shown in the example.

[0034] Figure 7 The waveform of steady-state speed at 300 rpm is shown in the example.

[0035] Figure 8 The d-axis and q-axis current waveforms of the target resonant controller are shown in the example.

[0036] Figure 9 This example demonstrates the analysis of d-axis and q-axis current harmonic amplitudes using different control methods. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] This invention provides a method for suppressing the measurement error of the current of a ship's permanent magnet propulsion motor. By constructing a target resonant controller with phase compensation, the error of the ship's permanent magnet propulsion motor current on the d-axis and q-axis is compensated simultaneously, thereby improving the accuracy of the measurement of the ship's permanent magnet propulsion motor current without increasing the control loop and hardware.

[0040] Example 1 Step 1: Establish a vector control system model for a ship's permanent magnet propulsion motor that includes current measurement errors.

[0041] The current measurement errors of marine permanent magnet propulsion motors include: gain error and offset error; offset error is usually caused by factors such as residual current of the current sensor, thermal drift of the conditioning circuit and deviation of the operational amplifier; gain error is usually caused by the nonlinearity of the current sensor and analog-to-digital converter during the current sampling process, as well as the quantization error between the two.

[0042] In this embodiment, a vector control system model for a ship's permanent magnet propulsion motor, incorporating current measurement errors, is constructed as follows: Figure 1 As shown. In a marine propulsion motor drive system employing two current sensors, the phase current is expressed as follows when current measurement errors exist: (1); In the formula, This refers to the current offset error in phase A. For the B-phase current offset error, For the current gain error of phase A, For the B-phase current gain error, , and These are the measured values ​​of phase A, B, and C currents. , and These are the actual values ​​of the currents in phases A, B, and C. For electrical angle, It is the amplitude of the phase current.

[0043] After coordinate transformation from a three-phase rotating coordinate system to a two-phase stationary coordinate system, the current along the d-axis and q-axis is expressed as: (2); In the formula, The target measured value for the d-axis current. The target measured value for the q-axis current. This is the actual measured value of the d-axis current. This is the actual measured value of the q-axis current. For d-axis current error, This represents the q-axis current error.

[0044] when The system only has gain error: (3); (4); when The system only has offset error: (5); When adopted In vector control, the electromagnetic torque is expressed as: (6); In the formula, For electromagnetic torque, For extreme logarithms, It is a permanent magnet flux linkage.

[0045] The equation of motion for the motor, neglecting the coefficient of friction, is: (7); In the formula, For load torque, For rotational inertia, This represents the motor speed.

[0046] According to equations (1) to (7), when there is a current measurement error in the ship propulsion motor, the d-axis current and q-axis current, speed and torque will produce primary and secondary pulsations. Step 2: Analyze the principle of a traditional resonant controller with phase compensation.

[0047] Considering the disturbances and velocity fluctuations in the d-axis and q-axis currents caused by current measurement errors, trigonometric functions are used for modeling.

[0048] Based on the internal model principle, a series of resonant terms are added to design a periodic harmonic compensation scheme to suppress q-axis current measurement errors.

[0049] The basic transfer function of a traditional resonant controller with phase compensation is expressed as follows: (8); In the formula, Indicates the resonant gain. Indicates the angle of compensation; Indicates the harmonic order.

[0050] Based on the equivalent transformation, the q-axis current measurement error is considered as interference in the forward path of the velocity loop. Based on this viewpoint, a resonant controller with phase compensation is designed in the velocity loop to eliminate the influence of the q-axis current measurement error.

[0051] The resonant controller with phase compensation compensates for the q-axis current measurement error by extracting the primary and secondary pulsations in the rotational speed.

[0052] Step 3: Target resonant controller that simultaneously compensates for measurement errors of d-axis current and q-axis current.

[0053] According to equations (2), (3), (4), and (5), the magnitudes of the harmonics of the d-axis current and the q-axis current are equal, and the phase of the q-axis current harmonics leads the d-axis current harmonics by 90°.

[0054] According to the equation of motion, if there is a current measurement error in the system, it will cause primary and secondary pulsations in the rotational speed. Therefore, according to the internal model principle, a resonant controller can be connected in parallel with the PI controller in the speed loop to suppress the primary and secondary pulsations.

[0055] when , The molecules become ,when The molecule does not contain an imaginary part. Construct a lag behind A 90° path compensates for d-axis current measurement errors.

[0056] The transfer function for constructing a target resonator with phase compensation for d-axis and q-axis current measurement errors is:

[0057]

[0058] in For harmonic orders, when only first-order pulsations are considered ( ), The time-domain expression is , The time-domain expression is , and Equal amplitude, phase Advanced 90°, which is the same as the harmonic relationship between the d-axis current and the q-axis current.

[0059] In summary, this method requires only two resonant controllers to simultaneously suppress the first and second harmonics in the d-axis and q-axis currents. Output and Compensate for the first harmonic disturbance in the q-axis and d-axis currents respectively. Output and The second harmonic disturbances in the q-axis and d-axis currents are compensated separately. The target resonant controller structure is as follows: Figure 2 As shown.

[0060] in and First-order ripple compensation for q-axis and d-axis currents. and This is for second-order ripple compensation of the q-axis and d-axis currents. This is for first-order total disturbance compensation. This is for second-order total disturbance compensation.

[0061] Step 4: Connect the target resonant controller in parallel with the PI controller of the speed loop, such as... Figure 3 As shown, the control output is used to compensate for disturbances in the d-axis and q-axis currents of the ship's permanent magnet propulsion motor.

[0062] Step 5: Use the vector margin index to select appropriate parameters and verify the stability of the system.

[0063] Vector margin is defined as the minimum distance between the Nyquist trajectory corresponding to the open-loop transfer function and the critical point (-1, j0). Preferably, a reasonable value for the vector margin is between 0.5 and 0.8.

[0064] The specific steps are as follows: 1) Use the bandwidth method to determine the proportional-integral (PI) parameters of the control system; The current loop PI parameters are designed as follows: (10); (11); In the formula, and These are the proportional and integral parameters for the d-axis and q-axis currents. For dq axis inductance, For the current loop bandwidth, This is the stator resistance.

[0065] The PI parameters of the speed loop are: (12); (13); In the formula, and For the proportional and integral parameters of the speed loop, This represents the bandwidth of the speed loop.

[0066] 2) Based on the Bode plot and vector margin, and weighing compensation performance against stability, select the target resonant gain. The first-order resonant gain is expressed as... The second-order resonant gain is expressed as .

[0067] like Figure 4 The figure shows an FFT analysis at 300 rpm. The first-order and second-order ripple contents are almost the same, therefore the relationship between the first-order and second-order resonant gains is set as follows: = .

[0068] like Figure 5The diagram shows open-loop Bode plots for different resonant gains. A higher resonant gain results in more significant harmonic suppression. However, it also reduces the system's amplitude-frequency response in the low-frequency range, affecting its resistance to low-frequency interference. The selection of the resonant gain requires a trade-off between suppression effectiveness and stability. 3) Determine the compensation angle (first-order compensation angle) for different speed ranges based on the vector margin. and second-order compensation angle ).

[0069] Adding a compensation angle can reduce the impact of phase lag on system stability. Phase lag mainly comes from sampling delay, PWM inverter delay and signal processing delay. These delays are frequency-related phase lags in the frequency domain, and their magnitude increases proportionally with frequency. (14); In the formula For the phase delay of the system, It is the equivalent total delay time; According to equation (14), the phase lag of the second harmonic is twice that of the first harmonic. Therefore, the relationship of the compensation angle is set as follows: =2 ; To avoid selecting the compensation angle in real time, segmented selection is performed using vector margin. and ; like Figure 6 As shown in the figure, the vector margin with and without phase compensation at different resonant gains at 300 rpm was plotted based on the Nyquist plot. It can be found that adding a certain amount of phase compensation helps to improve the vector margin of the system, thereby improving the stability of the system. The vector margin values ​​of the control system at different speeds, different compensation angles, and different resonant gains are shown in Table 1.

[0070] Table 1

[0071] As shown in Table 1, the vector margin of the system decreases with increasing resonant gain. When the resonant gain is (2,2), the vector margin of the system is consistently between 0.5 and 0.8. Therefore, ( and Set it to (2,2); Based on Table 1, the optimal compensation angles for different speed ranges are summarized in Table 2: Table 2

[0072] Example 3 The implementation case utilizes a model-based design platform to download the code to the motor drive board. The effectiveness of the algorithm is verified based on feedback signals from the host computer. The motor parameters are: rated power of the permanent magnet synchronous motor. W, rated torque magnetic field polar number stator resistance Ω, inductance mH, rotor flux Wb, given a rotational speed of 300 rpm, with current offset errors of 0.1A and -0.15A for phases A and B respectively, and gain error set to... =1.05A, =0.95A. After the motor enters steady state, the sampled d-axis current and q-axis current signals are analyzed.

[0073] Current measurement error always exists. When a control method is applied at time 1 second, the steady-state speed waveform of the motor is as follows: Figure 7 As shown, the fluctuation in steady-state speed decreased from approximately ±45 rpm to approximately ±5 rpm. The steady-state d-axis and q-axis current waveforms of the motor are as follows: Figure 8 As shown, to highlight the effectiveness of this method, as Figure 9 The Fourier analyses of the d-axis and q-axis currents after the target resonator using a PI controller, a traditional controller with phase compensation, and the method described in this paper are shown. The results indicate that: PI controllers cannot suppress periodic primary and secondary pulsations caused by current measurement errors; traditional resonant controllers with phase compensation can only suppress pulsations in the q-axis current; the target resonant controller can simultaneously improve both the d-axis and q-axis currents, reducing the amplitudes of primary and secondary pulsations in the d-axis to 0.005 and 0.002, respectively, and reducing the amplitudes of primary and secondary pulsations in the q-axis to 0.03 and 0.03, respectively. Therefore, the target resonant controller in this method effectively suppresses d-axis current, q-axis current, and speed pulsations.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for suppressing current measurement errors in ship permanent magnet propulsion motors, characterized in that, include: Establish a vector control system model for a ship's permanent magnet propulsion motor that includes current measurement errors; Based on the model, a target resonator with phase compensation for d-axis and q-axis current measurement errors is constructed. The target resonator is connected in parallel to the PI controller of the speed loop, and the output of the target resonator is used as compensation for disturbances in the d-axis current and q-axis current of the ship's permanent magnet propulsion motor.

2. The method according to claim 1, characterized in that, The construction of the vector control system model for a ship's permanent magnet propulsion motor, which includes current measurement errors, includes: Construct a mathematical model of a ship's permanent magnet propulsion motor that includes current measurement errors; Based on the mathematical model, the current form is determined by considering both gain error and offset error.

3. The method according to claim 2, characterized in that, The mathematical model of the ship's permanent magnet propulsion motor, which includes current measurement errors: In the formula, This refers to the current offset error in phase A. This refers to the current offset error in phase B. For the A-phase current gain error, For the B-phase current gain error, , and These are the measured values ​​of phases A, B, and C. , and These are the actual values ​​of the currents in phases A, B, and C. For electrical angle, It is the amplitude of the phase current; In the formula, The target measured value for the d-axis current. The target measured value for the q-axis current. This is the actual measured value of the d-axis current. This is the actual measured value of the q-axis current. For d-axis current error, This represents the q-axis current error.

4. The method according to claim 2, characterized in that, The current forms considering gain error and offset error respectively include: when The system only has gain error: when The system only has offset error: According to the current formulas for gain error and offset error, when there is a current measurement error, the relationship between the harmonics of the d-axis current and the q-axis current is as follows: the amplitudes are equal, and in terms of phase, the q-axis current harmonic leads the d-axis current harmonic by 90°. When adopted In vector control, the electromagnetic torque is expressed as: In the formula, For electromagnetic torque, For extreme logarithms, It is a permanent magnet flux linkage. The equation of motion for the motor, neglecting the coefficient of friction, is: In the formula, For load torque, For rotational inertia, This represents the motor speed.

5. The method according to claim 1, characterized in that, The transfer function of the target resonator is: in For harmonic orders, when only the first-order pulsation is considered, i.e. , The time-domain expression is , The time-domain expression is , and Equal amplitude, in phase Advanced 90°, which is the same as the harmonic relationship between the d-axis current and the q-axis current; Output and Compensate for the first harmonic disturbance in the q-axis and d-axis currents respectively. Output and The second harmonic disturbances in the q-axis and d-axis currents are compensated respectively.

6. The method according to claim 1, characterized in that, Also includes: The target parameters are selected using the vector margin index, and the stability of the system is verified based on the target parameters.

7. The method according to claim 6, characterized in that, The selection of target parameters using the vector margin index includes: Use the bandwidth method to determine the proportional-integral parameters of the control system; Based on the Bode plot and vector margin, the resonant gain and compensation angle are determined to balance compensation performance and stability.

8. The method according to claim 7, characterized in that, The method of determining the proportional-integral parameters of the control system using the bandwidth method includes: The current loop PI parameters are: In the formula, and These are the proportional and integral parameters for the d-axis and q-axis currents. For dq axis inductance, For the current loop bandwidth, Stator resistance; The PI parameters of the speed loop are: In the formula, and For the proportional and integral parameters of the speed loop, This represents the bandwidth of the speed loop.

9. The method according to claim 7, characterized in that, The resonant gain and compensation angle include: The first-order resonant gain is equal to the second-order resonant gain. The first-order compensation angle is half the second-order compensation angle.

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