Alternating current motor synchronous modulation method based on phase-locked loop and PWM generator

Abstract

The invention relates to an AC motor synchronous modulation method based on a phase-locked loop and a PWM generator, and belongs to the technical field of motor control, and the method comprises the steps: determining a voltage phase angle outputted by an AC motor based on an output voltage of vector control of the AC motor, and converting the voltage phase angle into a synchronous phase angle of a carrier wave based on a carrier wave ratio; the synchronous phase angle is used for determining a sine input signal of the phase-locked loop; determining a cycle count increment adjustment value of the carrier based on the sinusoidal input signal; and correcting the cycle count increment value of the carrier based on the cycle count increment adjustment value. According to the alternating current motor synchronous modulation method based on the phase-locked loop, the period ratio and the phase relation of the carrier wave and the modulation wave are fixed, so that the harmonic content of the output voltage and the harmonic content of the output current are kept consistent in the synchronous modulation process, extra harmonic voltage and current cannot be generated, and overall harmonic treatment of a system is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to an AC motor synchronous modulation method and a PWM generator based on a phase-locked loop. Background Art

[0002] In AC drive systems, high-power inverters are a crucial component of the entire system. The inverter voltage is high, resulting in significant switching losses and heat generation. To address these issues, the switching frequency is typically limited to a few hundred Hz. This reduced switching frequency leads to more pronounced inverter output distortion, seriously impacting the operational stability of the traction system. This necessitates improvements to the inverter's switching modulation strategy to improve the inverter's output characteristics and enhance the traction system's operational performance.

[0003] Currently, the most commonly used modulation techniques in AC motor inverters are sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM). SPWM is a carrier modulation method that generates control pulses for the inverter's switching devices by comparing the modulating wave with the signal wave. SVPWM, based on volt-second balance, synthesizes a reference voltage vector using two adjacent effective voltage vectors. At high power and low switching frequencies, using traditional SPWM and SVPWM asynchronous modulation strategies to modulate the inverter results in severe inverter output distortion, making it unsuitable for traction system operation.

[0004] When the fundamental frequency is low, the number of pulses within a fundamental cycle is high. Even with asynchronous modulation, the inverter output performance can still meet the traction system's operational requirements. Therefore, simpler asynchronous modulation is used when the fundamental frequency is low. When the fundamental frequency is high, the carrier frequency of conventional asynchronous modulation is relatively low, and the modulation effect of conventional asynchronous modulation strategies no longer meets the system's control performance requirements. In such cases, overmodulation is often used in low-power applications to reduce the inverter system's output harmonics. In traction drives, due to the high power of the inverter, the asymmetry of overmodulation often has a significant impact on the overall system performance. Therefore, in high-power applications, optimized synchronous modulation strategies are generally used to address the problem of inverter system output distortion.

[0005] Regarding synchronous modulation at low switching frequencies, the most common synchronous modulation strategies are as follows: intermediate 60° modulation strategy, Selective Harmonic Elimination-PWM (SHE-PWM) strategy, Current Harmonic Minimum-PWM (CHM-PWM) strategy, and SVPWM synchronous modulation strategy.

[0006] The middle 60° modulation strategy only generates switching pulses within the middle 60° range of the positive and negative half-cycles of each modulation wave, and does not control the inverter within the other modulation wave ranges. Therefore, compared with traditional modulation methods, this modulation method can effectively reduce the switching frequency, and the middle 60° modulation strategy can ensure that the PWM pulses remain symmetrical within the positive and negative half-waves. The middle 60° synchronous modulation strategy is relatively simple to implement, but it also suffers from high output harmonics and large torque ripple. In more precise control applications, it often cannot meet the control requirements of the system. Middle 60° modulation is suitable for applications where harmonic characteristics are not too demanding and the hardware facilities are outdated.

[0007] The SHE-PWM strategy improves inverter output performance by eliminating specific harmonics. A disadvantage of the SHE-PWM method is that it requires solving transcendental equations to calculate the inverter switching angle. This process is complex and often difficult to implement in real time. Currently, offline calculations are commonly used to determine the switching angle.

[0008] The current harmonic minimization PWM modulation strategy uses the total current harmonics as the objective function and solves for a series of switching angles that minimize this objective function. Like SHE-PWM, the optimal solution of the CHM-PWM objective function also requires solving trigonometric transcendental equations, which is more complex to implement.

[0009] The basic concepts behind the PWM modulation strategy for specific harmonic elimination and the current harmonic minimization PWM modulation strategy are similar: both achieve optimal output waveforms through precise control of the switching angle. However, the disadvantage of both approaches is that they require solving trigonometric transcendental equations to determine the optimal switching angle, making implementation more complex.

[0010] The SVPWM synchronous modulation strategy ensures symmetry within the positive and negative half-wave cycles and quarter-cycles of a fundamental wave by setting symmetrical sampling points and switching sequences in the complex plane of the resultant vector, maintaining the symmetry of the PWM pulses across the three-phase PWM pulses. This modulation strategy effectively optimizes the inverter's output characteristics and is an effective solution for addressing output waveform distortion in high-power, low-switching-frequency inverters. The SVPWM synchronous modulation strategy employs a variety of sampling point locations, as well as a wide variety of switching sequences and zero vectors for different sampling points. Therefore, SVPWM synchronous modulation offers greater design flexibility compared to other synchronous modulation schemes. However, research on the SVPWM synchronous modulation strategy has focused on the modulation strategy's characteristics and improvements, with few implementation solutions for its application in closed-loop vector control of three-phase AC motors. When applying the SVPWM synchronous modulation strategy to a vector-based control system for a three-phase AC motor, the resultant vector's rotation period is not fixed and exhibits an angular offset from the d-axis. This creates challenges in the algorithm's compatibility with the rotor's magnetic field orientation process, complicating the SVPWM synchronous modulation strategy's sampling sector division and pulse generation comparison value calculation. Summary of the Invention

[0011] In view of this, it is necessary to provide an AC motor synchronous modulation method and PWM generator based on a phase-locked loop to solve the problems of high output harmonics and complex calculation process of the existing synchronous modulation method.

[0012] In order to solve the above problems, in a first aspect, the present invention provides an AC motor synchronous modulation method based on a phase-locked loop, comprising: Determine the voltage phase angle of the AC motor output based on the output voltage of the AC motor vector control, and convert the voltage phase angle into a synchronous phase angle of the carrier based on the carrier ratio; the synchronous phase angle is used to determine the sinusoidal input signal of the phase-locked loop; Determining a cycle count increment adjustment value of a carrier based on the sinusoidal input signal; Based on the cycle count increment adjustment value, the cycle count increment value of the carrier is corrected.

[0013] In a possible implementation, determining a carrier cycle count increment adjustment value based on the sinusoidal input signal includes: Based on the sinusoidal input signal, a voltage component in a synchronous phase static coordinate system is generated by a generalized second-order integrator; Performing a PARK transformation on the voltage component to obtain a DC component in a synchronous phase rotating coordinate system; PI regulation is performed on the DC component to generate the cycle count increment adjustment value.

[0014] In a possible implementation, the correcting the cycle count increment value of the carrier based on the cycle count increment adjustment value includes: The cycle count increment adjustment value and the cycle count increment base value are superimposed to obtain the cycle count increment value.

[0015] In a possible implementation, the synchronization phase angle is expressed as follows:

[0016] in, represents the synchronization phase angle, represents the voltage phase angle, Indicates the carrier ratio.

[0017] In a possible implementation, the sinusoidal input signal is expressed as follows:

[0018] in, represents a sinusoidal input signal, Indicates the synchronization phase angle.

[0019] In a possible implementation, the expression of the cycle count increment value is as follows:

[0020] in, Indicates the cycle count increment value, Indicates the cycle count increment base value, Indicates the cycle count increment adjustment value.

[0021] In a possible implementation, the carrier ratio is determined based on a ratio between a frequency of the carrier and an electrical frequency of the AC motor.

[0022] In a possible implementation, the angle used for the PARK transformation is determined by a carrier generator according to a current count value and a period value.

[0023] In a second aspect, the present invention further provides a PWM generator, comprising: An angle calculator, configured to determine a voltage phase angle output by the AC motor based on an output voltage of the AC motor's vector control, and convert the voltage phase angle into a synchronous phase angle of the carrier based on a carrier ratio; the synchronous phase angle is used to determine a sinusoidal input signal of a phase-locked loop; a phase-locked loop, configured to determine a cycle count increment adjustment value of a carrier based on the sinusoidal input signal; The carrier generator is configured to correct the cycle count increment value of the carrier based on the cycle count increment adjustment value.

[0024] In a possible implementation, the phase-locked loop includes: SOGI module, PARK module and PI regulator; The SOGI module is configured to generate a voltage component in a synchronous phase static coordinate system based on the sinusoidal input signal; The PARK module is used to perform a PARK transformation on the voltage component to obtain a DC component in a synchronous phase rotating coordinate system; The PI regulator is used to perform PI regulation on the DC component to generate the cycle count increment adjustment value.

[0025] The beneficial effects of the present invention are as follows: the AC motor synchronous modulation method and PWM generator based on the phase-locked loop provided by the present invention obtain the current output voltage phase angle according to the output voltage of the vector control of the AC motor, use the carrier ratio to convert the current output voltage phase angle of the motor into the carrier phase angle that needs to be locked, use the phase-locked loop to lock the carrier phase angle, and the phase-locked loop output is used to adjust the incremental count value of the carrier, thereby adjusting the period of the carrier to maintain a fixed carrier ratio with the frequency of the modulation wave, realizing synchronous modulation, so that the period ratio and phase relationship of the carrier and the modulation wave are fixed, so that the harmonic content of the output voltage and current are consistent during the synchronous modulation process, and no additional harmonic voltage and current are generated, which is beneficial to the overall harmonic control of the system, and the calculation process is relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is a flow chart of an embodiment of a synchronous modulation method for an AC motor based on a phase-locked loop provided by the present invention; Figure 2 The principle diagram of the AC motor vector control with synchronous modulation provided by the present invention; Figure 3 A schematic structural diagram of an embodiment of a PWM generator provided by the present invention; Figure 4 A schematic diagram of the structure of the generalized second-order integrator provided by the present invention; Figure 5 This is a second flow chart of an embodiment of the phase-locked loop-based AC motor synchronous modulation method provided by the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] In the description of the embodiments of the present invention, unless otherwise specified, "plurality" means two or more. "And / or" describes the association relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0030] The terms "first," "second," and so on, used in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, technical features designated as "first" or "second" may explicitly or implicitly include at least one such feature.

[0031] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0032] The present invention provides an AC motor synchronous modulation method and a PWM generator based on a phase-locked loop, which are respectively described below.

[0033] Figure 1 This is a flow chart of an embodiment of the AC motor synchronous modulation method based on a phase-locked loop provided by the present invention, as shown in FIG. Figure 1 As shown, the AC motor synchronous modulation method based on a phase-locked loop includes: S101. Determine the voltage phase angle output by the AC motor based on the output voltage of the AC motor's vector control, and convert the voltage phase angle into a synchronous phase angle of the carrier based on a carrier ratio; the synchronous phase angle is used to determine a sinusoidal input signal of a phase-locked loop.

[0034] S102: Determine a carrier cycle count increment adjustment value based on the sinusoidal input signal.

[0035] S103: Correct the cycle count increment value of the carrier based on the cycle count increment adjustment value. The execution subject of the AC motor synchronous modulation method based on a phase-locked loop provided by the present invention may be a pulse width modulation (PWM) generator.

[0036] In step S101, the vector control of the AC motor is performed by decomposing the stator current vector of the AC motor into a current component that generates a magnetic field and a current component that generates a torque, and controlling each of the components, thereby achieving high-performance speed regulation of the AC motor. For example, Figure 2 As shown, Figure 2 This is a schematic diagram of the AC motor vector control principle with synchronous modulation provided by the present invention.

[0037] Based on the output voltage of the AC motor's vector control, the voltage phase angle of the AC motor output can be determined. Then, based on the carrier ratio, the voltage phase angle is converted into the synchronous phase angle of the carrier. The synchronous phase angle is further converted into a sinusoidal input signal for the phase-locked loop.

[0038] In step S102, a phase-locked loop is used to lock the carrier phase angle, and the output of the phase-locked loop is used to adjust the incremental count value of the carrier, thereby adjusting the period of the carrier to maintain a fixed carrier ratio with the frequency of the modulation wave to achieve synchronous modulation.

[0039] For example, the phase-locked loop can use SOGI to convert the sinusoidal input signal Decomposed into two orthogonal sine waves and , and then perform PARK transformation to convert it into DC component and , then Perform PI regulation, and its output is the cycle count increment adjustment value of the phase-locked loop .

[0040] In step S103, the cycle count increment value of the carrier is corrected based on the cycle count increment adjustment value.

[0041] Increment the cycle count by Output to the carrier generator to correct the cycle count increment value of the triangular carrier , the resulting triangular carrier frequency will have a ratio of N to the frequency of the output voltage, and the phase remains fixed.

[0042] The carrier generator is usually implemented by a counter, and the period count increment value determines the step speed of the counter, thereby determining the frequency of the carrier signal.

[0043] To sum up, the AC motor synchronous modulation method based on the phase-locked loop provided in the embodiment of the present invention obtains the current output voltage phase angle according to the output voltage of the vector control of the AC motor, uses the carrier ratio to convert the current output voltage phase angle of the motor into the carrier phase angle that needs to be locked, and uses a phase-locked loop to lock the carrier phase angle. The phase-locked loop output is used to adjust the incremental count value of the carrier, thereby adjusting the period of the carrier so that it maintains a fixed carrier ratio with the frequency of the modulation wave to achieve synchronous modulation, so that the period ratio and phase relationship of the carrier and the modulation wave are fixed. Therefore, during the synchronous modulation process, the harmonic content of the output voltage and current remain consistent, and no additional harmonic voltage and current are generated, which is beneficial to the overall harmonic control of the system, and the calculation process is relatively simple.

[0044] In some embodiments of the present invention, the carrier ratio is determined based on a ratio between a frequency of the carrier and an electrical frequency of the AC motor.

[0045] The expression of the synchronization phase angle is as follows:

[0046] in, represents the synchronization phase angle, represents the voltage phase angle, Indicates the carrier ratio.

[0047] In some embodiments of the present invention, the sinusoidal input signal is expressed as follows:

[0048] in, represents a sinusoidal input signal, Indicates the synchronization phase angle.

[0049] The carrier ratio of PWM and modulation wave can be determined according to the requirements. , the calculation formula is as follows:

[0050] in, is the frequency of the triangular carrier in the PWM generator, is the electrical frequency of the motor.

[0051] Output voltage according to vector control of AC motor and , calculate the output voltage phase angle of the AC motor , the calculation formula is as follows:

[0052] According to the voltage phase angle Ratio to carrier , calculate the synchronous phase angle of PWM carrier , the calculation formula is as follows;

[0053] Thus, according to the synchronization phase angle , calculate the sinusoidal input signal of the phase-locked loop , the calculation formula is as follows:

[0054] The AC motor synchronous modulation method based on a phase-locked loop provided by the embodiment of the present invention determines the carrier ratio N to be adopted and adjusts the motor control amount according to the motor control amount. and Calculate the voltage phase angle , and then calculate the carrier synchronization phase angle based on the carrier ratio , and calculate the input signal of the phase-locked loop , a phase-locked loop is used to lock the carrier phase angle, and the phase-locked loop output is used to adjust the incremental count value of the carrier, thereby adjusting the carrier period to maintain a fixed carrier ratio with the frequency of the modulating wave, thereby achieving synchronous modulation.

[0055] In some embodiments of the present invention, determining a carrier cycle count increment adjustment value based on the sinusoidal input signal includes: Based on the sinusoidal input signal, a voltage component in a synchronous phase static coordinate system is generated by a generalized second-order integrator; Performing a PARK transformation on the voltage component to obtain a DC component in a synchronous phase rotating coordinate system; PI regulation is performed on the DC component to generate the cycle count increment adjustment value.

[0056] In some embodiments of the present invention, the angle used for the PARK transformation is determined by a carrier generator according to a current count value and a period value.

[0057] The sinusoidal input signal After passing through the second-order generalized integrator (SOGI), the voltage component in the synchronous phase static coordinate system is generated and .

[0058] Using PARK transformation and Converted into synchronous phase rotation coordinate system and The angle used for PARK conversion is the angle calculated by the carrier generator based on the current count value and period value. .

[0059] The PARK transformation calculation formula is as follows:

[0060] The DC component As input, after passing through the PI regulator, the output cycle count increment adjustment value .

[0061] In some embodiments of the present invention, the correcting the cycle count increment value of the carrier based on the cycle count increment adjustment value includes: The cycle count increment adjustment value and the cycle count increment base value are superimposed to obtain the cycle count increment value.

[0062] In some embodiments of the present invention, the expression of the cycle count increment value is as follows:

[0063] in, Indicates the cycle count increment value, Indicates the cycle count increment base value, Indicates the cycle count increment adjustment value.

[0064] The phase-locked loop output Input to the carrier generator as an incremental value superimposed on the carrier cycle count increment base value The carrier generator cycle count increment value The calculation formula is as follows:

[0065] The embodiment of the present invention provides a synchronous modulation method for an AC motor based on a phase-locked loop, which , output to the carrier generator, and use it to correct the period increment value of the triangular carrier The resulting triangular carrier frequency will have a ratio of N to the output voltage frequency, and the phase remains fixed. This keeps the period ratio and phase relationship between the carrier and modulating waves constant. Therefore, during the synchronous modulation process, the harmonic content of the output voltage and current remains consistent, preventing the generation of additional harmonic voltages and currents, which is beneficial to the overall harmonic control of the system.

[0066] In order to better implement the AC motor synchronous modulation method based on the phase-locked loop in the embodiment of the present invention, based on the AC motor synchronous modulation method based on the phase-locked loop, correspondingly, Figure 3 As shown, an embodiment of the present invention further provides a PWM generator, the PWM generator comprising: An angle calculator, configured to determine a voltage phase angle output by the AC motor based on an output voltage of the AC motor's vector control, and convert the voltage phase angle into a synchronous phase angle of the carrier based on a carrier ratio; the synchronous phase angle is used to determine a sinusoidal input signal of a phase-locked loop; a phase-locked loop, configured to determine a cycle count increment adjustment value of a carrier based on the sinusoidal input signal; The carrier generator is configured to correct the cycle count increment value of the carrier based on the cycle count increment adjustment value.

[0067] Optionally, the phase-locked loop includes: SOGI module, PARK module and PI regulator; The SOGI module is configured to generate a voltage component in a synchronous phase static coordinate system based on the sinusoidal input signal; The PARK module is used to perform a PARK transformation on the voltage component to obtain a DC component in a synchronous phase rotating coordinate system; The PI regulator is used to perform PI regulation on the DC component to generate the cycle count increment adjustment value.

[0068] The PWM generator provided in the above embodiment can implement the technical solution described in the above phase-locked loop-based AC motor synchronous modulation method embodiment. The specific implementation principles of the above modules or units can be found in the corresponding contents in the above phase-locked loop-based AC motor synchronous modulation method embodiment, which will not be repeated here.

[0069] Optionally, Figure 4 The schematic diagram of the structure of the generalized second-order integrator provided by the present invention is as follows: Figure 4 As shown, k is the adjustment factor, which is generally 0.707, and ω is the angular velocity of the carrier. Figure 4 Here, 1 / s is the integral operator in control theory, and its function is the same as the integrator in the PI controller.

[0070] Based on the PWM generator provided in the above embodiment, the present invention also provides an AC motor synchronous modulation method based on a phase-locked loop. First, the carrier ratio to be adopted is determined, and the current output voltage phase angle of the motor is converted into the carrier phase angle to be locked according to the carrier ratio. Then, a phase-locked loop is used to lock the carrier phase angle. The output of the phase-locked loop is used to adjust the incremental count value of the carrier, thereby adjusting the period of the carrier so that it maintains a fixed carrier ratio with the frequency of the modulation wave, thereby realizing synchronous modulation.

[0071] AC motor vector control with synchronous modulation Figure 2 As shown, the final output of vector control is the voltage component in the stationary coordinate system and , the PWM generator is based on and Generate PWM output.

[0072] According to the characteristics of AC motor vector control, Figure 5 The second embodiment of the flow chart of the synchronous modulation method of an AC motor based on a phase-locked loop provided by the present invention is as follows: Figure 5 As shown, the invention provides a synchronous modulation method for an AC motor based on a phase-locked loop, comprising: Step S501: First, determine the carrier ratio of PWM to modulation wave according to the requirements. , the calculation formula is as follows: (1) in, is the frequency of the triangular carrier in the PWM generator, is the electrical frequency of the motor; Step S502: Output voltage according to vector control and Calculate the output voltage phase angle , the calculation formula is as follows: (2) Step S503: and Calculate the synchronous phase angle of the PWM carrier , the calculation formula is as follows; (3) Step S504: Calculates the sinusoidal input signal to the phase-locked loop , the calculation formula is as follows: (4) Step S505: After passing through the generalized second-order integrator SOGI module, the synchronous phase static coordinate system is generated. and ; Step S506: Use PARK transformation to convert and Converted into synchronous phase rotation coordinate system and The angle used for PARK conversion is the angle calculated by the carrier generator based on the current count value and period value. ; Step S507: As input, after passing through the PI regulator, the output ; Step S508: Input to the carrier generator as an incremental value superimposed on the carrier cycle count increment base value The carrier generator cycle count increment value The calculation formula is as follows: (5) Repeat steps S501 to S508 during the operation of the inverter.

[0073] The method of the present invention makes the period ratio and phase relationship of the carrier wave and the modulation wave fixed, so that the harmonic content of the output voltage and current remains consistent during the synchronous modulation process, and no additional harmonic voltage and current are generated, which is beneficial to the overall harmonic control of the system.

[0074] The present invention solves the problems of high output harmonics and large torque pulsation of the intermediate 60° modulation strategy, complex SHE-PWM and CHM-PWM algorithms, and large computational complexity, as well as the problem of severe coupling between the SVPWM synchronous modulation strategy algorithm and magnetic field orientation, making actual engineering application difficult.

[0075] Those skilled in the art will appreciate that all or part of the process flow of the above-described method embodiment can be implemented by instructing related hardware (such as a processor, controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0076] The above is a detailed introduction to the synchronous modulation method and PWM generator of the AC motor based on the phase-locked loop provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A synchronous modulation method for an AC motor based on a phase-locked loop, characterized in that: include: Determining a voltage phase angle output by the AC motor based on an output voltage of the vector control of the AC motor, and converting the voltage phase angle into a synchronous phase angle of the carrier based on a carrier ratio; The synchronization phase angle is used to determine the sinusoidal input signal of the phase-locked loop; Determining a cycle count increment adjustment value of a carrier based on the sinusoidal input signal; Based on the cycle count increment adjustment value, the cycle count increment value of the carrier is corrected.

2. The AC motor synchronous modulation method based on a phase-locked loop according to claim 1, characterized in that: The step of determining a carrier cycle count increment adjustment value based on the sinusoidal input signal includes: Based on the sinusoidal input signal, a voltage component in a synchronous phase static coordinate system is generated by a generalized second-order integrator; Performing a PARK transformation on the voltage component to obtain a DC component in a synchronous phase rotating coordinate system; PI regulation is performed on the DC component to generate the cycle count increment adjustment value.

3. The AC motor synchronous modulation method based on a phase-locked loop according to claim 1, characterized in that: The step of correcting the cycle count increment value of the carrier based on the cycle count increment adjustment value includes: The cycle count increment adjustment value and the cycle count increment base value are superimposed to obtain the cycle count increment value.

4. The AC motor synchronous modulation method based on a phase-locked loop according to claim 1, characterized in that: The expression of the synchronization phase angle is as follows: in, represents the synchronization phase angle, represents the voltage phase angle, Indicates the carrier ratio.

5. The AC motor synchronous modulation method based on a phase-locked loop according to claim 1, characterized in that: The expression of the sinusoidal input signal is as follows: in, represents a sinusoidal input signal, Indicates the synchronization phase angle.

6. The AC motor synchronous modulation method based on a phase-locked loop according to claim 1, characterized in that: The expression of the cycle count increment value is as follows: in, Indicates the cycle count increment value, Indicates the cycle count increment base value, Indicates the cycle count increment adjustment value.

7. The AC motor synchronous modulation method based on a phase-locked loop according to claim 1, characterized in that: The carrier ratio is determined based on a ratio between the frequency of the carrier and the electrical frequency of the AC motor.

8. The AC motor synchronous modulation method based on a phase-locked loop according to claim 2, characterized in that: The angle used in the PARK conversion is determined by a carrier generator based on the current count value and the period value.

9. A PWM generator, characterized in that: include: An angle calculator, configured to determine a voltage phase angle output by the AC motor based on an output voltage of the AC motor's vector control, and convert the voltage phase angle into a synchronous phase angle of the carrier based on a carrier ratio; the synchronous phase angle is used to determine a sinusoidal input signal of a phase-locked loop; a phase-locked loop, configured to determine a cycle count increment adjustment value of a carrier based on the sinusoidal input signal; The carrier generator is configured to correct the cycle count increment value of the carrier based on the cycle count increment adjustment value.

10. The PWM generator according to claim 9, characterized in that: The phase-locked loop comprises: SOGI module, PARK module and PI regulator; The SOGI module is configured to generate a voltage component in a synchronous phase static coordinate system based on the sinusoidal input signal; The PARK module is used to perform a PARK transformation on the voltage component to obtain a DC component in a synchronous phase rotating coordinate system; The PI regulator is used to perform PI regulation on the DC component to generate the cycle count increment adjustment value.

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