A method for calibrating initial position of a resolver based on high-frequency voltage injection

Abstract

The present application relates to a kind of based on high-frequency voltage injection's resolver initial position calibration method, belong to permanent magnet synchronous motor control field technical field, solve the problem of the existing resolver initial position calibration mode cumbersome, error is larger.Based on high-frequency voltage injection's resolver initial position calibration method, comprising: to permanent magnet synchronous motor inject high-frequency voltage signal, and real-time acquisition permanent magnet synchronous motor three-phase winding in high-frequency current signal;Based on the high-frequency current signal of each sampling time, obtain the resolver initial position compensation of corresponding sampling time;To the resolver initial position compensation of continuous multiple sampling time, carry out stability analysis, and the resolver initial position compensation after stabilization is used as resolver initial position calibration quantity.This method can effectively solve the problem of the existing resolver initial position calibration mode cumbersome, error is larger, effectively improve calibration speed and calibration accuracy.

Description

Technical Field

[0001] This invention relates to the technical field of permanent magnet synchronous motor control, and in particular to a method for calibrating the initial position of a rotary transformer based on high-frequency voltage injection. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) possess advantages such as high torque-to-inertia ratio, high power density, fast dynamic response, strong overload capacity, and a wide constant power range, leading to their widespread application in aerospace, electric vehicles, industrial control, and power generation in recent years. The excellent characteristics of PMSMs are based on superior control algorithms, typically direct torque control (DTC) and vector control, both of which require precise rotor position and speed information. Currently, there are two methods for determining the rotor position information of PMSMs: 1) obtaining rotor position and speed information through sensors; 2) estimating rotor position and speed information using sensorless technology. Method 1 typically uses sensors such as photoelectric encoders and resolvers. Compared to photoelectric encoders, resolvers have stronger tolerance to harsh environments and higher reliability, making them a preferred choice.

[0003] A resolver is a sensor that precisely measures the angular position and velocity of a rotating component through the magnetic coupling of its primary winding and two secondary windings. Typically, its primary winding and two orthogonal secondary windings are mounted on the motor rotor and stator, respectively. The excitation signal applied to the primary winding couples into sine and cosine output signals in the two secondary windings. Demodulation and conversion of these output signals yield the angular position and speed information of the motor rotor. Due to factors such as installation position deviations, the rotor position calculated by the resolver usually deviates from the actual rotor position of the permanent magnet synchronous motor (PMSM), affecting the performance of the PMSM control system. To identify and eliminate this error, a common practice is to simultaneously observe the back EMF of the PMSM and the zero-crossing signal of the resolver position signal using an oscilloscope, measure the error using the oscilloscope, and finally compensate for the error in the control algorithm. However, this process introduces errors from human observation, making it difficult to achieve the required product consistency, and the debugging process is cumbersome, impacting debugging efficiency. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a method for calibrating the initial position of a rotary transformer based on high-frequency voltage injection, in order to solve the problems of cumbersome and large error in existing rotary transformer initial position calibration methods.

[0005] This invention discloses a method for calibrating the initial position of a rotary transformer based on high-frequency voltage injection, comprising:

[0006] Inject a high-frequency voltage signal into the permanent magnet synchronous motor and collect the high-frequency current signal in the three-phase winding of the permanent magnet synchronous motor in real time;

[0007] Based on the high-frequency current signal at each sampling time, the initial position compensation amount of the rotary transformer at the corresponding sampling time is obtained.

[0008] Stability analysis was performed on the initial position compensation of the rotary transformer at multiple consecutive sampling times, and the stable initial position compensation of the rotary transformer was used as the initial position calibration value of the rotary transformer.

[0009] Based on the above solution, the present invention also makes the following improvements:

[0010] Furthermore, the method also includes:

[0011] Before injecting a high-frequency voltage signal into the permanent magnet synchronous motor, the permanent magnet synchronous motor under test is driven by a prime mover to rotate at a fixed angular speed.

[0012] Furthermore, a high-frequency voltage signal is injected into the permanent magnet synchronous motor, including:

[0013] A high-frequency voltage signal is injected onto the d-axis of the two-phase rotating coordinate system, as shown in formula (1).

[0014] (1)

[0015] in, This represents the high-frequency voltage signal injected along the d-axis of a two-phase rotating coordinate system. , These represent the amplitude and frequency of the high-frequency voltage signal, respectively. Indicates time.

[0016] Furthermore, the step of injecting a high-frequency voltage signal on the d-axis of the two-phase rotating coordinate system and acquiring the high-frequency current signal in the three-phase windings of the permanent magnet synchronous motor in real time includes:

[0017] A high-frequency voltage signal is injected into the d-axis of the two-phase rotating coordinate system. At the same time, the high-frequency current signal is transformed into the two-phase rotating coordinate system. The d-axis and q-axis components of the high-frequency current signal are integrated and then input into the two-phase rotating coordinate system. The rotor prediction position is also input into the two-phase rotating coordinate system. Then, the transformation from the two-phase rotating coordinate system to the two-phase stationary coordinate system is performed to obtain the voltage signal in the two-phase stationary coordinate system.

[0018] The voltage signal in the two-phase stationary coordinate system is programmed to form the PWM control signal of the three-phase full-bridge circuit of the permanent magnet synchronous motor;

[0019] Based on the PWM control signal, high-frequency voltage injection is achieved into the permanent magnet synchronous motor.

[0020] Furthermore, at each sampling moment, the acquired high-frequency current signal is subjected to the following closed-loop control to obtain the initial position compensation amount of the rotary transformer at the corresponding sampling moment:

[0021] Based on the rotor's predicted position, the acquired high-frequency current signal is transformed to obtain the q-axis high-frequency current signal;

[0022] Bandpass filtering is applied to the q-axis high-frequency current signal;

[0023] Multiply the bandpass filtered signal by Then, PI control and integral calculation are performed to obtain the initial position compensation amount of the rotary transformer.

[0024] The sum of the initial position compensation of the rotary transformer and the actual rotor position output by the rotary transformer is used as the updated rotor prediction position for coordinate transformation at the next sampling time.

[0025] Furthermore, the initial position compensation amount of the rotary transformer at the corresponding sampling time is obtained according to the following formula. :

[0026] (2);

[0027] in, This represents the signal after bandpass filtering of the q-axis high-frequency current signal.

[0028] , , , These represent the direct-axis inductance and quadrature-axis inductance of the motor, respectively.

[0029] Furthermore, the initial rotor predicted position is set to 0, or to the actual rotor position output by the resolver at the first sampling time.

[0030] Furthermore, the acquired high-frequency current signal is transformed from a three-phase stationary coordinate system to a two-phase rotating coordinate system to obtain the q-axis high-frequency current signal.

[0031] Furthermore, before performing coordinate transformation on the acquired high-frequency current signal, signal conditioning and AD conversion are performed on each phase current signal in the high-frequency current signal.

[0032] Furthermore, each phase current signal corresponds to a signal conditioning circuit, which is used to condition the current signal of that phase.

[0033] The signal conditioning circuit includes: operational amplifier U1, resistors R1-R3, diodes D1 and D2, and capacitor C1; wherein...

[0034] The non-inverting input terminal of operational amplifier U1 is used as the current signal input terminal, and a resistor R1 is connected between the non-inverting input terminal of operational amplifier U1 and ground; the inverting input terminal of operational amplifier U1 is connected to the output terminal of operational amplifier U1.

[0035] The output terminal of operational amplifier U1 is connected to one end of resistor R2, and the other end of resistor R2 is connected to one end of resistor R3, one end of capacitor C1, the anode of diode D1, and the cathode of diode D2.

[0036] The other end of resistor R3 and the cathode of diode D1 are both connected to power supply VCC;

[0037] The other end of capacitor C1 and the anode of diode D2 are both grounded;

[0038] The other end of the resistor R2 serves as the signal output terminal, used to output the signal conditioning result of the phase current signal.

[0039] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0040] The initial position calibration method for a rotary transformer based on high-frequency voltage injection provided in this embodiment obtains the d-axis and q-axis components of the current by injecting a high-frequency voltage signal, acquiring the corresponding signal, and performing coordinate system transformation. The q-axis current component contains both low-frequency and high-frequency components. This is achieved through software programming. Figure 3 The bandpass filter shown extracts the high-frequency current component from the q-axis current component. The high-frequency q-axis current component is multiplied by a factor determined through software programming. This allows for the extraction of components containing the rotor position signal. The software algorithm uses the position signal output from the resolver as a reference. Figure 3 The feedforward of the phase-locked loop shown is stabilized by adjusting the parameters of the PI controller. After stabilization, the output of the PI controller is the initial position error of the rotary transformer to be compensated, thus achieving the compensation of the initial position error of the rotary transformer.

[0041] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0042] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0043] Figure 1A flowchart of an initial position calibration method for a rotary transformer based on high-frequency voltage injection is provided for an embodiment of the present invention;

[0044] Figure 2 This is a hardware block diagram of a permanent magnet synchronous motor.

[0045] Figure 3 A block diagram of the software implementation of the initial position calibration method for a rotary transformer based on high-frequency voltage injection;

[0046] Figure 4 This is a schematic diagram of a signal conditioning circuit. Detailed Implementation

[0047] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0048] A specific embodiment of the present invention discloses a method for calibrating the initial position of a rotary transformer based on high-frequency voltage injection, the flowchart of which is shown below. Figure 1 As shown, it includes the following steps:

[0049] Step S1: Inject a high-frequency voltage signal into the permanent magnet synchronous motor and collect the high-frequency current signal in the three-phase winding of the permanent magnet synchronous motor in real time;

[0050] Step S2: Based on the high-frequency current signal at each sampling time, obtain the initial position compensation amount of the rotary transformer at the corresponding sampling time;

[0051] Step S3: Perform stability analysis on the initial position compensation amount of the rotary transformer at multiple consecutive sampling times, and use the stabilized initial position compensation amount of the rotary transformer as the initial position calibration amount of the rotary transformer.

[0052] Compared with the prior art, this embodiment injects a high-frequency voltage signal into the permanent magnet synchronous motor and collects and processes the high-frequency current signal in the three-phase winding of the permanent magnet synchronous motor in real time to obtain the corresponding initial position compensation amount of the rotary transformer. The stabilized initial position compensation amount of the rotary transformer is then converted into the initial position calibration amount of the rotary transformer. This process is relatively simple and fast, and can quickly determine the accurate initial position calibration amount of the rotary transformer in a short time.

[0053] like Figure 2 As shown (where the solid line portion is directly related to the content of this invention), this invention consists of 6 IGBT devices VT 1~6 and 6 anti-parallel diodes VD 1~6The actuator is composed of VT1, VT4, VD1, and VD4 forming phase A, VT2, VT5, VD2, and VD5 forming phase B, and VT3, VT6, VD3, and VD6 forming phase C. The midpoints of the phase A, B, and C bridge arms are connected to the winding ends of the permanent magnet synchronous motor. The control chip outputs PWM through a corresponding control algorithm. 1~6 Control signal, controls VT 1~6 The control chip samples the current in the three-phase windings of the motor (i.e., the current sensor and conditioning circuit) for switching on and off. i a , i b and i c The control chip acquires the rotor position signal output from the resolver. PWM is implemented through programming. 1~6 The output of the control signal. Three-phase full-bridge (consisting of 6 IGBT devices VT) 1~6 and 6 anti-parallel diodes VD 1~6 (Construction) Received PWM 1~6 The control signal enables high-frequency voltage injection into the permanent magnet synchronous motor (PMSM). The controller samples the current in the PMSM windings and calculates the rotor position signal using a decoding algorithm. By comparing the calculated rotor position signal with the rotor position signal output from the resolver, the controller calibrates the initial position of the resolver. The specific method is described below:

[0054] Before performing step S1, the method also includes:

[0055] Before injecting a high-frequency voltage signal into the permanent magnet synchronous motor, the permanent magnet synchronous motor under test is driven by a prime mover to rotate at a fixed angular speed, thereby driving the permanent magnet synchronous motor to rotate and thus obtaining the actual position of the rotor output by the rotary transformer.

[0056] Here, the fixed angular speed is typically set below the rated speed. At this point, the electrical frequency of the permanent magnet synchronous motor... As shown in equation (1).

[0057] (1)

[0058] in, This represents the number of pole pairs in a permanent magnet synchronous motor. This indicates the rotational speed at a fixed angle.

[0059] In step S1, a high-frequency voltage signal is injected into the permanent magnet synchronous motor. Specifically, a high-frequency voltage signal can be injected into the d-axis of a two-phase rotating coordinate system, as shown in formula (2).

[0060] (2)

[0061] in, This represents the high-frequency voltage signal injected along the d-axis of a two-phase rotating coordinate system. The high-frequency voltage signal injected into the q-axis of the two-phase rotating coordinate system is 0; , These represent the amplitude and frequency of the high-frequency voltage signal, respectively. Indicates time. For example, 10% of the rated voltage can be used. Desirable This ensures that low-frequency vector control and high-frequency signal extraction and processing do not interfere with each other.

[0062] The method of injecting a high-frequency voltage signal onto the d-axis of a two-phase rotating coordinate system and acquiring the high-frequency current signal in the three-phase windings of a permanent magnet synchronous motor in real time is as follows: Figure 3 As shown, it can be expressed as:

[0063] Step S11: Inject a high-frequency voltage signal onto the d-axis of the two-phase rotating coordinate system. Simultaneously, transform the acquired high-frequency current signal to the two-phase rotating coordinate system. Integrate the d-axis and q-axis components of the high-frequency current signal and input them into the two-phase rotating coordinate system. Also input the predicted rotor position into the two-phase rotating coordinate system. Then, perform a transformation from the two-phase rotating coordinate system to the two-phase stationary coordinate system to obtain the voltage signal in the two-phase stationary coordinate system. The voltage signal in the two-phase stationary coordinate system can be expressed as: and .

[0064] Step S12: Program the voltage signal in the two-phase stationary coordinate system to form the PWM control signal of the three-phase full-bridge circuit of the permanent magnet synchronous motor;

[0065] It should be noted that the two-phase rotating coordinate system uses existing methods to process the above signals and the rotor predicted position, thereby obtaining the signal after processing by the two-phase rotating coordinate system.

[0066] Step S13: Based on the PWM control signal, high-frequency voltage injection is performed on the permanent magnet synchronous motor.

[0067] After injecting a high-frequency voltage signal on the d-axis of the two-phase rotating coordinate system, the inductance of the permanent magnet synchronous motor changes with the rotor position. By selecting the above high-frequency voltage signal, a current signal that changes with the inductance can be excited, and then the rotor position signal can be calculated. The high-frequency voltage signal and the excited current signal satisfy formula (3):

[0068] (3)

[0069] Substituting equation (2) into equation (3), the high-frequency current components of the d-axis and q-axis can be calculated, as shown in equation (4):

[0070] (4)

[0071] in, This represents the signal after bandpass filtering of the q-axis high-frequency current signal. This represents the signal after bandpass filtering of the d-axis high-frequency current signal. , , , These represent the direct-axis inductance and quadrature-axis inductance of the motor, respectively. This indicates the actual position of the rotor. Since the direction of the q-axis is consistent with the direction of the rotor's N pole, the subsequent analysis process is based on the q-axis component. The q-axis high-frequency current component is obtained from equation (4) as shown in equation (5):

[0072] (5)

[0073] Multiply both sides of the equation We can obtain:

[0074] (6)

[0075] From formula (6), we can obtain that multiplying both sides of the equation by... Then, the signal It is divided into two parts: high-frequency components and low-frequency components, with the low-frequency components containing rotor position information. .

[0076] like Figure 3 As shown, the transfer function of the phase-locked loop can be assumed to be... Then (6) is equivalent to (7):

[0077] (7)

[0078] Since the proportional-integral circuit has low-pass characteristics, the high-frequency components in (7) are approximately equal to 0, as shown in (8).

[0079] (8)

[0080] Then (7) can be simplified as shown in (9).

[0081] (9)

[0082] The purpose of this embodiment is to compensate for the initial inherent positional error that exists during the installation of the rotary transformer. Let's assume that this inherent positional error is... The position signal output by the rotary transformer is Then the actual position of the rotor can be represented by (10).

[0083] (10)

[0084] like Figure 3 As shown, the position signal output by the rotary transformer Since it has been fed forward into the phase-locked loop, equation (9) can be transformed into equation (11).

[0085] (11)

[0086] As shown in (11), when Figure 3 After the phase-locked loop shown stabilizes, that is... When it is very small, (11) can be expressed by (12).

[0087] (12)

[0088] like Figure 3 As shown, at each sampling moment, the acquired high-frequency current signal is subjected to the following closed-loop control (i.e., the function of a "phase-locked loop") to obtain the initial position compensation amount of the rotary transformer at the corresponding sampling moment:

[0089] Step S21: Based on the rotor's predicted position, perform coordinate transformation on the acquired high-frequency current signal to obtain the q-axis high-frequency current signal;

[0090] For example, the initial rotor predicted position is set to 0, or to the actual rotor position output by the rotary transformer at the first sampling time. In step S21, the acquired high-frequency current signal is transformed from a three-phase stationary coordinate system to a two-phase rotating coordinate system to obtain the q-axis high-frequency current signal.

[0091] Step S22: Perform bandpass filtering on the q-axis high-frequency current signal;

[0092] Step S23: Multiply the bandpass filtered signal by Then, PI control and integral calculation are performed to obtain the initial position compensation amount of the rotary transformer.

[0093] By reversing equation (11), the initial position compensation amount of the rotary transformer can be obtained. The calculation method is shown in formula (12):

[0094] (12).

[0095] Step S24: The sum of the initial position compensation of the rotary transformer and the actual rotor position output by the rotary transformer is used as the updated rotor prediction position for coordinate transformation at the next sampling time.

[0096] Furthermore, before performing coordinate transformation on the acquired high-frequency current signal, signal conditioning and AD conversion can be performed on each phase current signal separately. Specifically, each phase current signal corresponds to a signal conditioning circuit, which is used to condition the signal of that phase current signal.

[0097] The signal conditioning circuit is as follows Figure 4 As shown, the system includes: operational amplifier U1, resistors R1-R3, diodes D1 and D2, and capacitor C1. The non-inverting input of operational amplifier U1 serves as the current signal input, and resistor R1 is connected between the non-inverting input and ground. The inverting input of operational amplifier U1 is connected to its output. The output of operational amplifier U1 is connected to one end of resistor R2, and the other end of resistor R2 is connected to one end of resistor R3, one end of capacitor C1, the anode of diode D1, and the cathode of diode D2. The other end of resistor R3 and the cathode of diode D1 are both connected to the power supply VCC. The other end of capacitor C1 and the anode of diode D2 are both grounded.

[0098] The other end of the resistor R2 serves as the signal output terminal, used to output the signal conditioning result of the phase current signal.

[0099] When the power supply VCC is 3V, if the voltage at the signal output terminal is higher than 3V or lower than 0V, in order to protect the downstream DSP control chip, the voltage at the signal output terminal is limited to 3V or 0V, which serves as hardware limiting. Here, R2 = R3. The current signal acquired in step S2... , and The signals are input to their respective conditioning circuits, which process them to control the voltage at the output terminal between 0 and 3V, facilitating subsequent digital processing. After an analog-to-digital (A / D) conversion, the signal conditioning and A / D conversion results for the current moment can be obtained.

[0100] In step S3, when the initial position compensation of the rotary transformer at multiple consecutive sampling times tends to stabilize, the stabilized initial position compensation of the rotary transformer can be used as the initial position calibration value of the rotary transformer.

[0101] In practice, the criteria for judging stability are not uniform. Stability margins or other stability evaluation criteria can be set in advance to make stability judgments.

[0102] In summary, in this embodiment, by injecting a high-frequency voltage signal, acquiring the corresponding signal, and performing coordinate system transformation, the d-axis and q-axis components of the current are obtained. The q-axis current component contains both low-frequency and high-frequency components. This is achieved through software programming. Figure 3The bandpass filter shown extracts the high-frequency current component from the q-axis current component. The high-frequency q-axis current component is multiplied by a factor determined through software programming. This allows for the extraction of components containing the rotor position signal. The software algorithm uses the position signal output from the resolver as a reference. Figure 3 The feedforward of the phase-locked loop shown is stabilized by adjusting the parameters of the PI controller. After stabilization, the output of the PI controller is the initial position error of the rotary transformer to be compensated, thus achieving the compensation of the initial position error of the rotary transformer.

[0103] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0104] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calibrating the initial position of a rotary transformer based on high-frequency voltage injection, characterized in that, include: Inject a high-frequency voltage signal into the permanent magnet synchronous motor and collect the high-frequency current signal in the three-phase winding of the permanent magnet synchronous motor in real time; Based on the high-frequency current signal at each sampling time, the initial position compensation amount of the rotary transformer at the corresponding sampling time is obtained. Stability analysis was performed on the initial position compensation of the rotary transformer at multiple consecutive sampling times, and the stable initial position compensation of the rotary transformer was used as the initial position calibration value of the rotary transformer. Injecting high-frequency voltage signals into a permanent magnet synchronous motor includes: A high-frequency voltage signal is injected onto the d-axis of the two-phase rotating coordinate system, as shown in formula (1). （1） in, This represents the high-frequency voltage signal injected along the d-axis of a two-phase rotating coordinate system. , These represent the amplitude and frequency of the high-frequency voltage signal, respectively. Indicates time; At each sampling moment, the acquired high-frequency current signal is subjected to the following closed-loop control to obtain the initial position compensation amount of the rotary transformer at the corresponding sampling moment: Based on the rotor's predicted position, the acquired high-frequency current signal is transformed to obtain the q-axis high-frequency current signal; Bandpass filtering is applied to the q-axis high-frequency current signal; Multiply the bandpass filtered signal by Then, PI control and integral calculation are performed to obtain the initial position compensation amount of the rotary transformer. The sum of the initial position compensation of the rotary transformer and the actual rotor position output by the rotary transformer is used as the updated rotor prediction position for coordinate transformation at the next sampling time.

2. The method for initial position calibration of a rotary transformer based on high-frequency voltage injection according to claim 1, characterized in that, The method further includes: Before injecting a high-frequency voltage signal into the permanent magnet synchronous motor, the permanent magnet synchronous motor under test is driven by a prime mover to rotate at a fixed angular speed.

3. The method for initial position calibration of a rotary transformer based on high-frequency voltage injection according to claim 2, characterized in that, The process of injecting a high-frequency voltage signal onto the d-axis of a two-phase rotating coordinate system and acquiring high-frequency current signals from the three-phase windings of the permanent magnet synchronous motor in real time includes: A high-frequency voltage signal is injected into the d-axis of the two-phase rotating coordinate system. At the same time, the high-frequency current signal is transformed into the two-phase rotating coordinate system. The d-axis and q-axis components of the high-frequency current signal are integrated and then input into the two-phase rotating coordinate system. The rotor prediction position is also input into the two-phase rotating coordinate system. Then, the transformation from the two-phase rotating coordinate system to the two-phase stationary coordinate system is performed to obtain the voltage signal in the two-phase stationary coordinate system. The voltage signal in the two-phase stationary coordinate system is programmed to form the PWM control signal of the three-phase full-bridge circuit of the permanent magnet synchronous motor; Based on the PWM control signal, high-frequency voltage injection is achieved into the permanent magnet synchronous motor.

4. The method for initial position calibration of a rotary transformer based on high-frequency voltage injection according to claim 3, characterized in that, The initial rotor predicted position is set to 0, or to the actual rotor position output by the resolver at the first sampling time.

5. The method for initial position calibration of a rotary transformer based on high-frequency voltage injection according to claim 4, characterized in that, The high-frequency current signal is transformed from a three-phase stationary coordinate system to a two-phase rotating coordinate system by a coordinate transformation to obtain the q-axis high-frequency current signal.

6. The method for initial position calibration of a rotary transformer based on high-frequency voltage injection according to claim 5, characterized in that, Before performing coordinate transformation on the acquired high-frequency current signal, signal conditioning and AD conversion are performed on each phase current signal in the high-frequency current signal.

7. The method for initial position calibration of a rotary transformer based on high-frequency voltage injection according to claim 6, characterized in that, Each phase current signal corresponds to a signal conditioning circuit, which is used to condition the current signal of that phase. The signal conditioning circuit includes: operational amplifier U1, resistors R1-R3, diodes D1 and D2, and capacitor C1; wherein... The non-inverting input terminal of operational amplifier U1 is used as the current signal input terminal, and a resistor R1 is connected between the non-inverting input terminal of operational amplifier U1 and ground; the inverting input terminal of operational amplifier U1 is connected to the output terminal of operational amplifier U1. The output terminal of operational amplifier U1 is connected to one end of resistor R2, and the other end of resistor R2 is connected to one end of resistor R3, one end of capacitor C1, the anode of diode D1, and the cathode of diode D2. The other end of resistor R3 and the cathode of diode D1 are both connected to power supply VCC; The other end of capacitor C1 and the anode of diode D2 are both grounded; The other end of the resistor R2 serves as the signal output terminal, used to output the signal conditioning result of the phase current signal.

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