Three-stage synchronous motor based on third-order phase-locked loop and its zero-low speed rotor position simplified demodulation method

Abstract

The application discloses a three-stage synchronous motor based on a third-order phase-locked loop and a simplified demodulation method of a rotor position at zero and low speed, and single-phase AC excitation is applied to a main excitation machine of the three-stage synchronous motor to make dq-axis voltage with position error information generated on a stator side of a main generator; a process processing signal with a low-frequency position error signal is constructed through band-pass filtering and product operation; a middle signal is obtained by adopting a wave trap to suppress a second harmonic component of the process processing signal; the middle signal is input into a third-order phase-locked loop to calculate an estimated position of a rotor, sector correction is carried out according to a stator current sign, an initial position angle is obtained, and high-precision rotor position estimation under a zero and low speed working condition of the three-stage synchronous motor is realized. In the demodulation process of the application, the harmonic analysis frequency is clear, the structure of the wave trap cascaded with the third-order phase-locked loop is adopted, low-frequency position error signals and high-frequency harmonics are effectively isolated, and the rotor position estimation precision in the acceleration process of the motor is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a three-stage synchronous motor based on a third-order phase-locked loop and a simplified demodulation method for zero-low-speed rotor position. Background Technology

[0002] With the rapid development of multi-electric aircraft and electric propulsion technology, integrated starting / generating systems have become an important development direction for aviation power systems. Three-stage synchronous motors, due to their advantages of dual-mode operation (starting and generating), high power density, and high reliability, have been widely used in aviation power systems. During the starting control phase, accurate rotor position information is a crucial prerequisite for reliable starting.

[0003] Traditional systems typically rely on mechanical position sensors such as photoelectric encoders and rotary transformers to obtain rotor position information. However, in aerospace applications, mechanical sensors not only increase system size, weight, and assembly complexity, but are also susceptible to performance degradation or even failure due to high-temperature and high-vibration environments, thus reducing the overall reliability of the system. Therefore, sensorless control technology has become a key research focus in the field of aerospace motor control.

[0004] For position estimation of three-stage synchronous motors under zero-speed and low-speed conditions, most studies rely on high-frequency signal injection methods. However, injecting an additional high-frequency signal introduces significant torque ripple. Based on the inherent structural characteristics of three-stage synchronous motors, when a single-phase AC excitation current is injected into the main exciter, even-order harmonics are naturally generated in the main generator excitation winding through a rotating rectifier. This can be considered an indirect high-frequency signal that does not require additional injection. This not only avoids the torque ripple problem caused by additional high-frequency signal injection but also allows for direct extraction of the response voltage on the stator side for position demodulation, offering significant advantages in engineering applications.

[0005] However, existing position demodulation methods based on indirect harmonic injection still have significant shortcomings. Traditional methods typically rely on multi-stage filtering links consisting of bandpass and lowpass filters to separate and extract position-related signals. Moreover, the inherent phase delay of the filters introduces additional errors during demodulation, requiring extra compensation and making the overall process cumbersome. Furthermore, such methods are usually combined with second-order PI phase-locked loops for position estimation, but the application of PI phase-locked loops introduces steady-state error during acceleration, failing to guarantee high-precision position tracking during dynamic processes, thus limiting their application in engineering.

[0006] Therefore, how to simplify the filtering and demodulation structure and improve the position tracking accuracy in the low-speed stage while maintaining the estimation accuracy is an important research topic. Summary of the Invention

[0007] Purpose of the invention: This invention provides a three-stage synchronous motor based on a third-order phase-locked loop and a simplified demodulation method for the zero-low-speed rotor position. This method not only effectively isolates the low-frequency position error signal from the high-frequency harmonics, but also significantly improves the rotor position estimation accuracy during the motor acceleration process.

[0008] Technical solution: The present invention provides a simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop, comprising the following steps:

[0009] A single-phase AC excitation is applied to the main exciter of the three-stage synchronous motor, causing the stator side of the main generator to generate a dq-axis voltage containing position error information;

[0010] A process processing signal containing low-frequency position error signals is constructed by bandpass filtering and product operations;

[0011] The intermediate signal is obtained by using a notch filter to suppress the second harmonic component of the signal during the processing.

[0012] The intermediate signal is input into a third-order phase-locked loop to calculate the estimated rotor position, and then sector correction is performed based on the stator current sign to obtain the initial position angle, thus realizing high-precision rotor position estimation under zero-low speed conditions of a three-stage synchronous motor.

[0013] Furthermore, the three-stage synchronous motor includes: an auxiliary exciter, a main exciter, a rotating rectifier, and a main generator; the auxiliary exciter, main exciter, rotating rectifier, and main generator are connected coaxially in sequence, with the shaft being the motor's rotating shaft.

[0014] Furthermore, a dq-axis voltage containing position error information is generated on the stator side of the main generator. The expression for the dq-axis response voltage is:

[0015]

[0016] in The single-phase excitation frequency of the main exciter. , These are the DC components along the d and q axes, respectively. , These represent the amplitudes of the 2n (n=1,2,3…)th harmonics along the d and q axes, respectively. For the corresponding phase, The position error angle is the difference between the actual position and the estimated position.

[0017] Furthermore, the second harmonic component is extracted from the d-axis or q-axis response voltage signal through bandpass filtering, and this component is directly multiplied by the voltage of the other axis to construct the process processing signal. This converts the high-frequency position error signal into a signal containing a low-frequency observable component. The resulting process processing signal is expressed as follows:

[0018]

[0019] , It consists of the amplitude and phase of the 2k (k=1,2,3…) harmonics, which are obtained by recombination of various harmonics. The even harmonic term of the fundamental frequency is the signal processed by the process, which consists of the second harmonic component, the DC component, and the high-frequency even harmonic component.

[0020] Furthermore, to filter out the second harmonic components with significant amplitudes and frequencies closest to the phase-locked loop bandwidth, the process signal is processed... or A notch filter NF with a center frequency of the second harmonic frequency is applied;

[0021] The transfer function of the notch filter is:

[0022]

[0023] in The center frequency is given, and k is the damping coefficient. Used to filter out second harmonic components, and k=1 is set to keep the DC gain at 1.

[0024] Furthermore, after notch filtering, an intermediate signal is obtained, which consists of a low-frequency component containing position error information and high-frequency even-order harmonics of order 2k (k=2,3,4…). This effectively isolates the low-frequency position error signal from the high-frequency harmonics. The expression is:

[0025] .

[0026] Furthermore, the intermediate signal is input into a third-order phase-locked loop for calculation. The loop filtering structure composed of proportional-integral-double integral elements inside the phase-locked loop effectively suppresses the remaining high-frequency even harmonics and achieves steady-state tracking with zero steady-state error for the low-frequency position signal. Theoretically, the steady-state estimation error of the acceleration signal by the third-order phase-locked loop is zero, thus it has higher position estimation accuracy.

[0027] The effective input component of the phase-locked loop is a low-frequency position signal, and its expression is:

[0028]

[0029] exist When converged to zero, the estimated position angle of the phase-locked loop output may correspond to , , or Therefore, the initial position needs to be corrected; this is achieved by detecting the stator current of the main generator. and The sector number N of the rotor is uniquely determined based on its symbol combination, and the initial position angle output by the third-order phase-locked loop is set according to:

[0030]

[0031] A mapping correction is performed to ensure that the corrected initial position falls within the angle range consistent with the current sector, thereby obtaining the correct rotor initial position angle. .

[0032] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention is based on the dq axis response voltage for demodulation, which avoids the additional error introduced by the filter phase shift and does not require additional error compensation; (2) The present invention adopts a combination of a single bandpass filter and product operation, which makes the filtering and demodulation process simpler and reduces the system complexity; (3) In the demodulation process of the present invention, the harmonic analysis frequency is clear, and the structure of notch filter cascaded third-order phase-locked loop is adopted, which not only realizes the effective isolation of low-frequency position error signal and high-frequency harmonics, but also significantly improves the rotor position estimation accuracy in the motor acceleration process. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the three-stage synchronous motor structure of the present invention.

[0034] Figure 2 This is a block diagram of the sensorless starting control of the three-stage synchronous motor of the present invention.

[0035] Figure 3 This is a graph showing the FFT analysis results of uqh·ud during motor operation according to the present invention.

[0036] Figure 4 The figure shows the simulation results of motor speed, estimated position, actual position and position angle error when the rotor initial position angle is in different sectors during the sensorless start-up process of the three-stage synchronous motor of the present invention. Detailed Implementation

[0037] like Figure 1 As shown, a three-stage synchronous motor based on a third-order phase-locked loop includes four parts: an auxiliary exciter, a main exciter, a rotating rectifier, and a main generator. During the motor's startup process, the auxiliary exciter does not participate in operation, and the system has a two-stage structure at this time.

[0038] The principle block diagram of the three-stage synchronous motor positionless starting control method of the present invention is as follows: Figure 2 As shown, the main exciter uses single-phase AC excitation, and the main generator uses... The field-oriented control uses constant torque to start the motor, and the Park transform uses the estimated position angle to achieve closed-loop control.

[0039] The main exciter of the three-stage synchronous motor is powered by a single-phase AC power supply. The dq-axis response voltage is extracted from the stator side of the main generator. The even-order harmonics carry rotor position error information and can be used as the basic signal source for subsequent position demodulation. The expression for the dq-axis response voltage is:

[0040]

[0041] in The single-phase excitation frequency of the main exciter. , These are the DC components along the d and q axes, respectively. , These represent the amplitudes of the 2n (n=1,2,3…)th harmonics along the d and q axes, respectively. For the corresponding phase, The position error angle is the difference between the actual position and the estimated position.

[0042] Subsequently, the second harmonic component is extracted from the d-axis or q-axis response voltage signal using bandpass filtering, and this component is directly multiplied by the voltage of the other axis to construct the process processing signal. This operation converts the high-frequency position error signal into a signal containing a low-frequency observable component. The resulting process processing signal can be expressed as:

[0043]

[0044] , It consists of the amplitude and phase of the 2k (k=1,2,3…) harmonics, which are obtained by recombination of various harmonics. This refers to the even harmonic term of the fundamental frequency. The signal processed consists of the second harmonic component, the DC component, and the high-frequency even harmonic component, such as... Figure 3 As shown.

[0045] To filter out the second harmonic component with significant amplitude and frequency closest to the phase-locked loop bandwidth, the process signal is processed. or A notch filter (NF) with a center frequency of the second harmonic frequency is applied.

[0046] The transfer function of the notch filter is:

[0047]

[0048] in Here, k is the center frequency, and k is the damping coefficient. (Setting...) Used to filter out second harmonic components, and k=1 is set to keep the DC gain at 1.

[0049] After notch filtering, an intermediate signal is obtained, which consists of a low-frequency component containing position error information and high-frequency even-order harmonics of order 2k (k=2,3,4…). This effectively isolates the low-frequency position error signal from the high-frequency harmonics. The expression is:

[0050]

[0051] The intermediate signal is input into a third-order phase-locked loop (PLL) for calculation. The loop filter structure, consisting of proportional-integral-double integrator elements, effectively suppresses the remaining high-frequency even harmonics and achieves steady-state, zero-steady-state-error tracking of the low-frequency position signal. Compared to a traditional second-order PI PLL, the third-order PLL theoretically has zero steady-state estimation error for the acceleration signal, thus offering higher position estimation accuracy.

[0052] The effective input component of the phase-locked loop is a low-frequency position signal, and its expression is:

[0053]

[0054] exist When converged to zero, the estimated position angle of the phase-locked loop output may correspond to , , or Therefore, initial position correction is necessary. This is achieved by detecting the stator current of the main generator. and The sector number N of the rotor can be uniquely determined based on its symbol combination, and the initial position angle output by the third-order phase-locked loop is determined according to:

[0055]

[0056] A mapping correction is performed to ensure that the corrected initial position falls within the angle range consistent with the current sector, thereby obtaining the correct rotor initial position angle. .

[0057] To verify this method, a model was built for simulation verification. The simulation conditions were as follows: the main exciter excitation frequency was 100Hz, the motor accelerated from a standstill, initial position estimation began at 0.4s, initial position correction was performed at 1s, startup occurred at 1.5s, and the speed reached 145rpm at 3.5s. The simulation results are as follows. Figure 4As shown, during the speed increase process, the position error tends to stabilize after dynamic adjustment, and the steady-state error pulsation is always less than 0.001 rad. The position estimation accuracy is high, which can realize the positionless start of the three-stage synchronous motor, indicating that this invention is feasible.

Claims

1. A simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop, characterized in that, Includes the following steps: A single-phase AC excitation is applied to the main exciter of the three-stage synchronous motor, causing the stator side of the main generator to generate a dq-axis voltage containing position error information; A process processing signal containing low-frequency position error signals is constructed by bandpass filtering and product operations; The intermediate signal is obtained by using a notch filter to suppress the second harmonic component of the signal during the processing. The intermediate signal is input into a third-order phase-locked loop to calculate the estimated rotor position, and then sector correction is performed based on the stator current sign to obtain the initial position angle, thus realizing high-precision rotor position estimation under zero-low speed conditions of a three-stage synchronous motor.

2. The simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop as described in claim 1, characterized in that, A three-stage synchronous motor includes: an auxiliary exciter, a main exciter, a rotating rectifier, and a main generator; the auxiliary exciter, main exciter, rotating rectifier, and main generator are connected coaxially in sequence, with the shaft being the motor's rotating shaft.

3. The simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop as described in claim 1, characterized in that, The main generator stator side generates a dq-axis voltage containing position error information. The expression for the dq-axis response voltage is: in The single-phase excitation frequency of the main exciter. , These are the DC components along the d and q axes, respectively. , These represent the amplitudes of the 2nth harmonics along the d and q axes, respectively, where n = 1, 2, 3… For the corresponding phase, The position error angle is the difference between the actual position and the estimated position.

4. The simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop as described in claim 1, characterized in that, The second harmonic component is extracted from the d-axis or q-axis response voltage signal by bandpass filtering, and this component is directly multiplied by the voltage of the other axis to construct the process processing signal. This converts the high-frequency position error signal into a signal containing a low-frequency observable component. The resulting process processing signal is expressed as follows: , It is the amplitude and phase of the 2kth harmonic obtained by recombination of various harmonics, k=1,2,3…, forming a series of harmonics. The even harmonic term of the fundamental frequency is the signal processed by the process, which consists of the second harmonic component, the DC component, and the high-frequency even harmonic component.

5. The simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop as described in claim 1, characterized in that, To filter out the second harmonic component with significant amplitude and frequency closest to the phase-locked loop bandwidth, the process signal is processed. or A notch filter NF with a center frequency of the second harmonic frequency is applied; The transfer function of the notch filter is: in The center frequency is given, and k is the damping coefficient. Used to filter out second harmonic components, and k=1 is set to keep the DC gain at 1.

6. The simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop as described in claim 1, characterized in that, After notch filtering, an intermediate signal is obtained, which consists of a low-frequency component containing position error information and high-frequency even-order harmonics of order 2k, where k=2,3,4…. This effectively isolates the low-frequency position error signal from the high-frequency harmonics. The expression is: 。 7. The simplified demodulation method for zero-low-speed rotor position of a three-stage synchronous motor based on a third-order phase-locked loop as described in claim 1, characterized in that, The intermediate signal is input into a third-order phase-locked loop for calculation. The loop filtering structure consisting of proportional-integral-double integral elements inside the phase-locked loop effectively suppresses the remaining high-frequency even harmonics and achieves steady-state tracking of the low-frequency position signal without steady-state error. Theoretically, the steady-state estimation error of the acceleration signal by the third-order phase-locked loop is zero, thus it has higher position estimation accuracy. The effective input component of the phase-locked loop is a low-frequency position signal, and its expression is: exist When converged to zero, the estimated position angle of the phase-locked loop output may correspond to , , or Therefore, the initial position needs to be corrected; this is achieved by detecting the stator current of the main generator. and The sector number N of the rotor is uniquely determined based on its symbol combination, and the initial position angle output by the third-order phase-locked loop is set according to: A mapping correction is performed to ensure that the corrected initial position falls within the angle range consistent with the current sector, thereby obtaining the correct rotor initial position angle. .

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