Cascaded H-bridge power supply permanent magnet motor high-frequency injection position-free control method

Abstract

The invention discloses a high-frequency injection position-free control method for a cascaded H-bridge power supply permanent magnet motor, and the method comprises the steps: independently configuring an H-bridge module of each phase of a cascaded H-bridge converter into a square wave output mode, and configuring the remaining H-bridge modules of each phase of the cascaded H-bridge converter into a conventional modulation mode of carrier phase shift; rotation transformation is used for extracting motor rotor position information and position offset information, a moving average filtering algorithm is designed based on the characteristic of high sampling rate of a cascaded H bridge, the influence of harmonic voltage in an injected square wave signal is eliminated, then a phase-locked loop technology is used for obtaining a motor rotor position observation result, and position-free control is achieved. According to the method, the upper limit of the signal injection frequency of the cascaded H-bridge motor system is increased from half of the switching frequency to the switching frequency, a signal separation link involved in the position-free control is facilitated, the disturbance caused by the injected high-frequency signal can be reduced, the observation signal-to-noise ratio and accuracy of the motor rotor position can be improved, and the operation performance of the position-free control is improved.

Description

Technical Field

[0001] The invention relates to a motor system, and in particular discloses a high-frequency injection position-free control method for a cascade H-bridge powered permanent magnet motor, belonging to the field of motors. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in high-power applications such as energy extraction due to their simple structure and high power density. To improve the reliable operation of permanent magnet electric drive systems and reduce costs, position-free control methods are often used to online observe the motor rotor position for vector control, eliminating the need for position sensors. In high-speed regions, the motor's extended back EMF is typically measured online based on the motor model. However, in the low-speed region, due to the extremely low signal-to-noise ratio, high-frequency signal injection is required to observe the motor's position. To facilitate signal separation, the injected signal frequency should be as high as possible. Furthermore, to increase the capacity of single-unit electric drive equipment, the industry is using a cascaded H-bridge topology to power motor systems, increasing the voltage and power levels of the motor system. However, in high-power applications, the switching frequency of the converter's power devices is relatively low due to limited heat sink capacity. The signal injection frequency of existing standard cascaded H-bridge converter-powered PMSM systems with orthogonal square wave injection without position control can only reach half the switching frequency, resulting in a very low final signal injection frequency, limiting the improvement of the motor system's position-free control performance. Summary of the Invention

[0003] Technical problem: The purpose of the present invention is to address the deficiencies of the above-mentioned background technology and provide a high-frequency injection positionless control method for a cascaded H-bridge powered permanent magnet motor, so as to solve the technical problem that the signal injection frequency of the existing high-frequency injection positionless control method can only reach half of the switching frequency, thereby resulting in a decrease in the positionless control performance, and achieve the purpose of the invention to improve the positionless control performance of the cascaded H-bridge powered permanent magnet synchronous motor system.

[0004] Technical solution: A high-frequency injection position-free control method for a cascaded H-bridge powered permanent magnet motor of the present invention comprises the following steps: Step 1: Configure one H-bridge module per phase of the cascaded H-bridge converter to a square wave output mode. The modulation wave signal of this type of H-bridge module does not include a reference voltage signal provided by the motor controller. The frequency of the square wave signal reaches the switching frequency of the power device. The fundamental amplitude of the output square wave signal is adjusted by adjusting the phase shift angle of the square waves of the two bridge arms of the H-bridge module to complete high-frequency signal injection, wherein the high-frequency signal is in square wave form. The number of H-bridge modules per phase of the cascaded H-bridge converter is greater than or equal to 2. The phase shift angle of the square wave signal output by the three-phase cascaded H-bridge converter is set to 240 degrees, that is, the square wave signal output by phase A leads the square wave signal by 2 / 3 of the square wave period of the phase B signal and leads the square wave signal by 4 / 3 of the square wave period of the phase C signal. Step 2: Based on the high-frequency signal injection in step 1, the remaining H-bridge modules in each phase of the cascaded H-bridge converter are configured in a conventional modulation mode with carrier phase shifting, with the reference voltage as the modulated target output voltage. The motor vector control is performed while the high-frequency signal injection is performed in step 1. Step 3: Based on the high-frequency signal injection and motor vector control implemented in steps 1 and 2, a current sensor is used to sample the motor stator phase current, a high-pass filter is used to extract the high-frequency component of the phase current, and a rotational transformation is used to extract the rotor position information superimposed with the high-frequency signal and the rotor position offset information superimposed with the high-frequency signal; Step 4: Use a moving average filtering algorithm to filter out the high-frequency signal contained in the rotor position information superimposed with the high-frequency signal and the rotor position bias information superimposed with the high-frequency signal in step 3, to obtain the rotor position information and the rotor position bias information, wherein the window length of the moving average filtering is set to the ratio of the sampling frequency to the frequency of the injected high-frequency signal; Step 5: Based on the rotor position information and rotor position offset information obtained in step 4, the normalized sine and cosine values ​​of the permanent magnet motor rotor position angle are calculated. The motor rotor position is further calculated using phase-locked loop technology to achieve position-free control.

[0005] in: In step 1, an H-bridge module of each phase of the three-phase output of the cascaded H-bridge converter is separately configured as a square wave output mode, and the output voltage of the bridge arm 1 in the H-bridge module in the square wave output mode is defined as , the output voltage of bridge arm 2 is , then the output voltage of the H-bridge module is , configure bridge arm 1 and bridge arm 2 to output a square wave voltage with a duty cycle of 50%, and adjust the phase shift angle of the two bridge arm square waves The goal of achieving adjustable amplitude of the fundamental wave of the square wave voltage output by the H-bridge module is achieved.

[0006] In step 2, the modulation is configured according to the number of remaining H-bridge modules. Specifically, if carrier phase shift modulation is used, the carrier phase shift angle depends on the number of remaining H-bridge modules in each phase. If carrier stacking modulation is used, the number of stacked carriers also depends on the number of remaining H-bridge modules in each phase, so as to ensure the decoupling operation of the H-bridge module configured in square wave output mode and other H-bridge modules.

[0007] In step 3, the high-pass filter is used to extract the high-frequency component of the phase current. , whose discrete sampling values The expression is , in and are the average inductance and differential inductance of the permanent magnet motor, respectively, and their expressions are ; and They are the motor d-axis and q-axis inductances, It is the phase lag angle caused by the voltage signal digital and modulation delay. is the phase advance angle introduced by the high-pass filter, θ e is the motor rotor position in electrical degrees; A 1 is the high-frequency current amplitude coefficient, and its expression is ,ω h is the angular frequency of the injected signal, V 1 is the amplitude of the injected signal, Indicates that the variable is The sampling results at the moment, T s is the switching period, It is switching cycles, is a positive integer; Using Rotation Transformations Extract the rotor position information superimposed with the high-frequency signal from the high-frequency current response results expression: ; Use rotation transformation Extract rotor position bias information superimposed with high-frequency signals from high-frequency current response results expression: .

[0008] In step 4, a moving average filtering algorithm is used to filter out the high-frequency signals contained in the rotor position information and the rotor position bias information in step 3. and The expression after filtering out high-frequency signals is: , ,in, and They are motor rotor position information and rotor position offset information respectively; is the window length of the moving average filter, which is set to the ratio of the sampling frequency to the frequency of the injected high-frequency signal. Is a positive integer, indicating the The discrete sampling results correspond to time; It is a non-negative integer, representing the sequence number of the data in the moving average filter window.

[0009] In step 5, the normalized sine and cosine values ​​of the permanent magnet motor rotor position angle are obtained, and the expression is: .

[0010] Beneficial effects: The present invention provides a method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor, which has the following advantages: (1) The present invention configures one H-bridge module of each phase of the cascaded H-bridge converter to a square wave signal injection mode, while the other modules are configured to a reference voltage modulation mode, thereby realizing decoupling modulation of the high-frequency injection signal and the reference voltage signal. This increases the frequency of the high-frequency signal injected for observing the rotor position of the motor in the zero-speed zone from half the switching frequency of the power device to the switching frequency, which is beneficial for separating the motor base frequency signal and the high-frequency response signal, and does not affect the modulation performance of the cascaded H-bridge topology, thereby improving the accuracy of rotor position observation.

[0011] (2) The moving average filter algorithm used in the present invention can not only eliminate the influence of high-frequency signals in the process of extracting rotor position information and rotor position bias information, but also eliminate the influence of high-frequency current harmonics caused by voltage harmonic components in the injected high-frequency square wave signal on rotor position observation, thereby improving the signal-to-noise ratio of motor position observation.

[0012] (3) By increasing the injection signal frequency and eliminating the influence of the injection signal harmonic components, the present invention can improve the signal-to-noise ratio of the motor rotor position observation while reducing the high-frequency current disturbance caused by the high-frequency signal injection, so that the cascaded H-bridge powered permanent magnet synchronous motor system can obtain better rotor position observation performance and position-free control performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a flow chart of high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor provided by the present invention.

[0014] Figure 2 This is the implementation principle diagram of high-frequency injection without position control signal injection for existing standard cascade H-bridge powered permanent magnet motors.

[0015] Figure 3 This is a flow chart of high-frequency injection position-free control signal processing for an existing standard cascade H-bridge powered permanent magnet motor.

[0016] Figure 4 This is a schematic diagram of the implementation principle of high-frequency injection without position control signal injection for a cascaded H-bridge powered permanent magnet motor provided by the present invention.

[0017] Figure 5 This is a flow chart of high-frequency injection position-free control signal processing for a cascaded H-bridge powered permanent magnet motor provided by the present invention.

[0018] Figure 6 This is the experimental result of extracting rotor position information by high-frequency injection without position control of the existing standard cascade H-bridge powered permanent magnet motor.

[0019] Figure 7This is the experimental result of extracting rotor position information by high-frequency injection and position-free control of the cascaded H-bridge powered permanent magnet motor provided by the present invention.

[0020] Figure 8 This is the experimental result of the rotor position observation error of the existing standard cascade H-bridge powered permanent magnet motor with high frequency injection and no position control.

[0021] Figure 9 This is the experimental result of the rotor position observation error of the cascaded H-bridge powered permanent magnet motor provided by the present invention with high frequency injection and position-free control. DETAILED DESCRIPTION

[0022] 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 part of the embodiments of the present invention, not all of the 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.

[0023] like Figure 1 The flow chart of high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor provided by the present invention includes the following steps: Step 1: individually configuring one H-bridge module of each phase of the cascaded H-bridge converter to a square wave output mode, wherein the modulation wave signal of such an H-bridge module does not include a reference voltage signal provided by a motor controller, the square wave signal frequency reaches the switching frequency of the power device, and the fundamental amplitude of the output square wave signal is adjusted by adjusting the phase shift angle of the square waves of the two bridge arms of the H-bridge module to complete high-frequency signal injection, wherein the high-frequency signal is in square wave form; the number of H-bridge modules per phase of the cascaded H-bridge converter is greater than or equal to 2; the phase shift angle of the square wave signal output by the three-phase cascaded H-bridge converter is set to 240 degrees, that is, the square wave signal output by phase A leads the square wave signal by 2 / 3 of the square wave period of the B-phase signal and leads the square wave signal by 4 / 3 of the square wave period of the C-phase signal; Step 2: Based on the high-frequency signal injection in step 1, the remaining H-bridge modules in each phase of the cascaded H-bridge converter are configured in a conventional modulation mode with carrier phase shifting, with the reference voltage as the modulated target output voltage. The motor vector control is performed while the high-frequency signal injection is performed in step 1. Step 3: Based on the high-frequency signal injection and motor vector control implemented in steps 1 and 2, a current sensor is used to sample the motor stator phase current, a high-pass filter is used to extract the high-frequency component of the phase current, and a rotational transformation is used to extract the rotor position information superimposed with the high-frequency signal and the rotor position offset information superimposed with the high-frequency signal; Step 4: Use a moving average filtering algorithm to filter out the high-frequency signal contained in the rotor position information superimposed with the high-frequency signal and the rotor position bias information superimposed with the high-frequency signal in step 3, to obtain the rotor position information and the rotor position bias information, wherein the window length of the moving average filtering is set to the ratio of the sampling frequency to the frequency of the injected high-frequency signal; Step 5: Based on the rotor position information and rotor position offset information obtained in step 4, the normalized sine and cosine values ​​of the permanent magnet motor rotor position angle are calculated. The motor rotor position is further calculated using phase-locked loop technology to achieve position-free control.

[0024] like Figure 2 The schematic diagram of the implementation of high-frequency injection without position control signal injection for the existing standard cascade H-bridge powered permanent magnet motor is shown in FIG. is the amplitude of the injected square wave signal, and The injected α Axis and β Shaft high frequency square wave voltage signal, and are the α-axis and β-axis voltage reference values ​​output by the motor controller respectively. V dc is the DC bus voltage of the H-bridge module. T s1 Each H-bridge module in each phase performs reference voltage modulation and high-frequency signal injection simultaneously, so the final voltage modulation signal of each phase is and satisfy , written in complex vector form: .from Figure 2 It can be seen that in the existing standard cascade H-bridge powered permanent magnet synchronous motor high-frequency signal injection position-free control, the modulation of the high-frequency signal and the modulation of the reference voltage are performed simultaneously in the H-bridge module, which results in the injection frequency of the orthogonal square wave signal being limited to half the carrier frequency, restricting the improvement of the permanent magnet motor high-frequency injection position observation performance and position-free control performance.

[0025] like Figure 3 The flowchart of the existing standard cascade H-bridge powered permanent magnet motor high frequency injection position-free control signal processing is shown in FIG. is the motor phase current complex vector in the stationary αβ coordinate system, Represents the high-frequency component of the motor phase current obtained through the high-pass filter, and They are respectively Use rotation transformation separately and The rotor position information and position offset information superimposed with the high-frequency signal are obtained. θe is the rotor position, and are the average inductance and differential inductance of the permanent magnet motor, respectively, and their expressions are . and They are the motor d-axis and q-axis inductances respectively. It is the phase lag angle caused by the voltage signal digital and modulation delay. is the phase advance angle introduced by the high-pass filter, ω h is the angular frequency of the injected signal. is the amplitude coefficient of the current response generated by injecting high-frequency signals using the existing injection method, and its expression is: , express The discrete sampling result at the moment. Figure 2 and Figure 3 The principle of position observation without position control using the existing standard cascade H-bridge high-frequency injection is introduced. The fundamental component of the injected high-frequency square wave voltage signal is expressed as: (1) The current response component caused by this voltage component is: (2) Furthermore, in the existing standard high-frequency injection position-free control, the signal is sampled at the peak and trough positions of the carrier wave, and the sampling period is T s1 ,like Figure 2 On the other hand, the frequency of the injected high-frequency signal is half of the carrier frequency, so From this, the high-frequency current response obtained by discrete sampling and high-pass filtering can be calculated: (3) Furthermore, a rotation transformation is used for the high frequency current response and Available and , are the rotor position information and position offset information superimposed with high-frequency signals. Furthermore, since the phase difference between two adjacent discrete samplings of the high-frequency signal is 180 degrees, the mean of the two adjacent discrete values ​​can be calculated to eliminate the and The high-frequency signal in and , further through complex multiplication and per-unit operation, the sine and cosine complex vectors of the rotor position angle can be obtained . Finally, the phase-locked loop technology is used to obtain the rotor position angle of the motor. Further, the limitations of the existing standard high-frequency injection method are analyzed: since the frequency of the injected square wave voltage signal reaches half of the carrier frequency and needs to be synchronized with the carrier, a high-frequency square wave signal is usually superimposed on the modulation wave of a single H-bridge module. However, this will affect the modulation performance of the cascaded H-bridge converter topology and introduce new current harmonics. For example, the H-bridge module that injects the square wave voltage signal breaks the balance of the carrier phase shift strategy in which the carrier frequency subharmonics of each H-bridge module cancel each other out, and introduces carrier frequency current harmonics, which is twice the carrier angular frequency 2. ω c For example, the corresponding current harmonic expression is: (4) in p and n Represent the positive sequence and negative sequence components respectively. c 2 means the frequency of this variable is twice the carrier frequency. γ is the phase of the corresponding current harmonic. The current harmonic is transformed by rotation and Then becomes: (5) After averaging two adjacent discrete sampling values, we can obtain: (6) It can be seen that the additional harmonics cannot be eliminated by the averaging of adjacent sampling values ​​and will eventually be mixed into the extracted rotor position angle sine and cosine components, resulting in a decrease in the position observation signal-to-noise ratio.

[0026] like Figure 4 The schematic diagram of the implementation of high-frequency injection without position control signal injection of the cascade H-bridge powered permanent magnet motor provided by the present invention is shown, wherein is the output voltage of arm 1 in the H-bridge module in square wave output mode, is the output voltage of bridge arm 2, then Is the output voltage of the H-bridge module in square wave mode. Configure both bridge arm 1 and bridge arm 2 to output a duty cycle of 50% and an amplitude of V dc / 2 square wave voltage, and and There are values ​​between square waves of The phase shift angle is V dc is the DC voltage value of the H-bridge module. It is a three-level signal with a period of square wave signal. Its fundamental amplitude can be changed by modifying the phase shift angle At this time, the frequency of the square wave signal is equal to the switching frequency of the power device, achieving the technical goal of increasing the signal injection frequency to the switching frequency. The fundamental component of the injected high-frequency voltage signal It can be expressed using a complex vector as ,in V 1 is the fundamental amplitude of the injected signal, ω h is the angular frequency of the injected signal. The high-frequency signal injection method of the present invention differs from existing standard high-frequency signal injection methods in that the H-bridge module in square-wave injection mode does not participate in the synthesis of the motor control reference voltage. This decouples the injected signal from the low-frequency control signal by independently configuring the H-bridge in high-frequency square-wave output mode. Using the present method, the upper limit of the square-wave signal injection frequency is increased from half the switching frequency to the switching frequency.

[0027] like Figure 5 The flowchart of the high-frequency injection position-free control signal processing of the cascade H-bridge powered permanent magnet motor provided by the present invention is shown, wherein A 1 is the amplitude coefficient of the current response generated by injecting high-frequency signals, and the expression is , V 1 is the fundamental amplitude of the injected high-frequency square wave voltage signal. is the window length of the moving average filter, which is set to the ratio of the sampling frequency to the frequency of the injected high-frequency signal. Without loss of generality, when the sampling frequency is set to 12kHz and the switching frequency / signal injection frequency is set to 500Hz, = 24. According to Figure 2 and Figure 3 The principle of position observation without position control using high-frequency injection of an existing standard cascade H-bridge is introduced. The expression of the injected high-frequency square wave voltage signal is: (7) Furthermore, the high frequency current response The expression is: (8) Furthermore, the expression of the high-frequency current discrete sampling value after discrete sampling and high-pass filtering is: (9) Furthermore, a rotation transformation is used for the high frequency current response and Available and , which are the rotor position information and position offset information superimposed with high-frequency signals. Further, the moving average filtering algorithm is used to eliminate the high-frequency components in the high-frequency current response signal to obtain and , further through complex multiplication and per-unit operation, the sine and cosine complex vectors of the rotor position angle can be obtained Finally, the phase-locked loop technology is used to obtain the rotor position angle of the motor. Furthermore, the moving average filtering algorithm provided by the present invention can eliminate the influence of harmonic voltage in the injected high-frequency square wave voltage signal. The main harmonic order of the square wave voltage signal is 6 n ±1 time, n is a positive integer, Subvoltage harmonics For example, the expression is: (10) in yes The amplitude of the sub-voltage harmonic. Furthermore, the high-frequency current response caused by the harmonic voltage signal is: (11) This current component passes through the signal Figure 5 Rotation transformation and The expression after the action is: (12) It can be seen that The harmonic voltage signal of the order of the current harmonic is 6. n Second and times, which are all integer multiples of the fundamental period of the injected signal. Using a moving average filtering algorithm with a window length equal to the ratio of the fundamental period to the sampling frequency can eliminate the influence of harmonic voltages in the injected voltage signal, that is, satisfying: (13) Therefore, the high-frequency injection position-free control method provided by the present invention can not only increase the signal injection frequency to facilitate signal separation and extraction of rotor position information, but also better eliminate the influence of harmonic components in the injected voltage signal without affecting the normal modulation performance of the cascaded H-bridge converter, thereby obtaining a higher rotor position information signal-to-noise ratio, and can achieve better motor rotor position observation effect under the premise of lower high-frequency current harmonic disturbance.

[0028] like Figure 6 and Figure 7 The experimental results of high-frequency injection without position control to extract rotor position information of cascaded H-bridge powered permanent magnet motor are shown in the figure. Figure 6 Using the existing standard high frequency injection method, Figure 7The high-frequency injection method provided by the present invention was used. The experiment was completed on a laboratory prototype. The cascaded H-bridge converter contains three cascaded H-bridge modules per phase. The power device uses IGBT. The switching frequency is limited to 500Hz. The motor is a low-power prototype processed in the laboratory. The square wave signal frequency of the existing standard high-frequency injection method is The frequency of the square wave signal in the high-frequency injection method provided by the present invention is increased to 500 Hz. and They are the α-axis and β-axis high-frequency current waveforms extracted by the high-pass filter, θ α and θ β are the normalized cosine and sine values ​​of the rotor position angle, respectively. It can be seen that the rotor position angle sine and cosine values ​​obtained by the existing standard cascade H-bridge powered permanent magnet synchronous motor high-frequency injection position-free control have a large amount of harmonic interference, while the high-frequency injection position-free control provided by the present invention can extract smooth rotor position angle sine and cosine values, significantly improving the signal-to-noise ratio of the rotor position observation. Furthermore, thanks to the higher signal injection frequency, the high-frequency injection position-free control provided by the present invention causes a lower high-frequency current disturbance amplitude than the existing standard high-frequency injection method.

[0029] like Figure 8 and Figure 9 The experimental results of high-frequency injection of position-free rotor position observation error in a cascaded H-bridge powered permanent magnet motor are shown in the figure. Figure 8 Using the existing standard high frequency injection method, Figure 9 The high frequency injection method provided by the present invention is used. The superscript “^” represents the observed variable, and the superscript “~” represents the observation error of the variable. Figure 8 and Figure 9 It can be seen that the maximum observation error of the motor rotor position using the existing standard high-frequency injection method is about 47°, while the maximum observation error of the motor rotor position using the high-frequency injection method provided by the present invention is about 6°. Figures 6 to 9 The experimental results verify that the present invention can improve the signal-to-noise ratio and accuracy of the rotor position observation of the cascaded H-bridge powered permanent magnet synchronous motor while reducing high-frequency current disturbances.

[0030] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor, characterized in that: The method comprises the following steps: Step 1: Configure one H-bridge module per phase of the cascaded H-bridge converter to a square wave output mode. The modulation wave signal of this type of H-bridge module does not include a reference voltage signal provided by the motor controller. The frequency of the square wave signal reaches the switching frequency of the power device. The fundamental amplitude of the output square wave signal is adjusted by adjusting the phase shift angle of the square waves of the two bridge arms of the H-bridge module to complete high-frequency signal injection, wherein the high-frequency signal is in square wave form. The number of H-bridge modules per phase of the cascaded H-bridge converter is greater than or equal to 2. The phase shift angle of the square wave signal output by the three-phase cascaded H-bridge converter is set to 240 degrees, that is, the square wave signal output by phase A leads the square wave signal by 2 / 3 of the square wave period of the phase B signal and leads the square wave signal by 4 / 3 of the square wave period of the phase C signal. Step 2: Based on the high-frequency signal injection in step 1, the remaining H-bridge modules in each phase of the cascaded H-bridge converter are configured in a conventional modulation mode with carrier phase shifting, with the reference voltage as the modulated target output voltage. The motor vector control is performed while the high-frequency signal injection is performed in step 1. Step 3: Based on the high-frequency signal injection and motor vector control implemented in steps 1 and 2, a current sensor is used to sample the motor stator phase current, a high-pass filter is used to extract the high-frequency component of the phase current, and a rotational transformation is used to extract the rotor position information superimposed with the high-frequency signal and the rotor position offset information superimposed with the high-frequency signal; Step 4: Use a moving average filtering algorithm to filter out the high-frequency signal contained in the rotor position information superimposed with the high-frequency signal and the rotor position bias information superimposed with the high-frequency signal in step 3, to obtain the rotor position information and the rotor position bias information, wherein the window length of the moving average filtering is set to the ratio of the sampling frequency to the frequency of the injected high-frequency signal; Step 5: Based on the rotor position information and rotor position offset information obtained in step 4, the normalized sine and cosine values ​​of the permanent magnet motor rotor position angle are calculated. The motor rotor position is further calculated using phase-locked loop technology to achieve position-free control.

2. A method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor according to claim 1, characterized in that: In step 1, an H-bridge module of each phase of the three-phase output of the cascaded H-bridge converter is separately configured as a square wave output mode, and the output voltage of the bridge arm 1 in the H-bridge module in the square wave output mode is defined as , the output voltage of bridge arm 2 is , then the output voltage of the H-bridge module is , configure bridge arm 1 and bridge arm 2 to output a square wave voltage with a duty cycle of 50%, and adjust the phase shift angle of the square waves of the two bridge arms The goal of achieving adjustable amplitude of the fundamental wave of the square wave voltage output by the H-bridge module is achieved.

3. The method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor according to claim 2, characterized in that: In step 2, the modulation is configured according to the number of remaining H-bridge modules. Specifically, if carrier phase shift modulation is used, the carrier phase shift angle depends on the number of remaining H-bridge modules in each phase. If carrier stacking modulation is used, the number of stacked carriers also depends on the number of remaining H-bridge modules in each phase, so as to ensure the decoupling operation of the H-bridge module configured in square wave output mode and other H-bridge modules.

4. A method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor according to claim 3, characterized in that: In step 3, the high-pass filter is used to extract the high-frequency component of the phase current. , whose discrete sampling values The expression is ， in and are the average inductance and differential inductance of the permanent magnet motor, respectively, and their expressions are ; and are the motor d-axis and q-axis inductances, It is the phase lag angle caused by the voltage signal digital and modulation delay. is the phase advance angle introduced by the high-pass filter, θ e is the motor rotor position in electrical degrees; A 1 is the high-frequency current amplitude coefficient, and its expression is , ω h is the angular frequency of the injected signal, V 1 is the amplitude of the injected signal, Indicates that the variable is The sampling results at the moment, T s is the switching period, It is switching cycles, is a positive integer; Using Rotation Transformations Extract the rotor position information superimposed with the high-frequency signal from the high-frequency current response results expression: ; Use rotation transformation Extract rotor position bias information superimposed with high-frequency signals from high-frequency current response results expression: .

5. A method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor according to claim 4, characterized in that: In step 4, a moving average filtering algorithm is used to filter out the high-frequency signals contained in the rotor position information and the rotor position bias information in step 3. and The expression after filtering out high-frequency signals is: , ,in, and They are motor rotor position information and rotor position offset information respectively; is the window length of the moving average filter, which is set to the ratio of the sampling frequency to the frequency of the injected high-frequency signal. Is a positive integer, indicating the The discrete sampling results correspond to time; It is a non-negative integer, representing the sequence number of the data in the moving average filter window.

6. A method for high-frequency injection position-free control of a cascaded H-bridge powered permanent magnet motor according to claim 5, characterized in that: In step 5, the normalized sine and cosine values ​​of the permanent magnet motor rotor position angle are obtained, and the expression is: .

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