A robust digital decoupling control method for high-speed permanent magnet synchronous motor under low carrier frequency ratio

Abstract

The application discloses a kind of low load frequency ratio under high-speed permanent magnet synchronous motor robust digital decoupling control method, belongs to high-speed motor cross-axis current decoupling control field;First, according to the complex coefficient model of surface-mounted permanent magnet synchronous motor (SPMSM) in frequency domain, reconstruct high-speed motor model in discrete domain;By analyzing the oscillation mechanism caused by current decoupling under high base frequency, design system impedance gain modulation loop to suppress high-frequency disturbance;By introducing the internal model control theory, applying the reconstructed discrete domain motor model, adding impedance gain modulation loop, build a digital current controller with enhanced decoupling capability;The application solves the problem of poor decoupling effect of traditional controller when high-speed motor operates under low load frequency ratio condition, expands the speed domain of high-speed motor, and improves the control response characteristics under low load frequency ratio.

Description

Technical Field

[0001] This invention relates to a robust digital decoupling control method for a high-speed permanent magnet synchronous motor with a low carrier frequency ratio, belonging to the field of AC and DC axis current decoupling control for high-speed motors. Background Technology

[0002] High-speed permanent magnet synchronous motors (PMSMs) are characterized by high power density, high speed, and low moment of inertia, resulting in faster response and higher control precision. They are widely used in industrial control, medical devices, and home appliances. However, unlike ordinary motors, high-speed motors amplify control problems that are negligible in ordinary motors, primarily current coupling and control delay. The degree of current coupling is directly proportional to the speed. At high fundamental frequencies, current coupling leads to a deterioration in the dynamic response of the current loop and a reduction in system stability margin. In control delay, phase angle delay introduces an additional coupling term that further crosses the dq-axis currents. The impact of this additional coupling term on the system increases with the fundamental frequency, further deteriorating the dynamic response of the current loop and reducing the system stability margin. In severe cases, this can lead to system instability. Considering chip computing power, switching losses, and cost control, the inverter's control switching frequency is not too high, typically within tens of kHz. When the motor operates at a high fundamental frequency, the carrier frequency ratio (the ratio of the inverter switching frequency to the fundamental frequency) may be less than 10. At low carrier frequency ratios, the current coupling problem of high-speed permanent magnet synchronous motors poses a significant challenge to current controllers.

[0003] PMSM vector control achieves static decoupling of the dq-axis currents in the dq coordinate system, but cannot eliminate the dynamic coupling effect between the dq-axis currents. Based on a PI controller, introducing diagonal decoupling control can achieve dynamic decoupling between the dq-axis currents. Decoupling methods include feedforward decoupling, feedback decoupling, bias decoupling, and internal model decoupling. Feedforward and feedback decoupling methods are susceptible to parameter mismatch, resulting in insufficient dynamic decoupling. The bias decoupling method is relatively complex to implement. The internal model decoupling method has strong parameter robustness and is easy to adjust, but its integral term can cause pre-steady-state oscillations. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a robust digital decoupling control method for high-speed permanent magnet synchronous motors with low carrier frequency ratios. It involves reconstructing an accurate motor model in the discrete domain, designing an impedance gain modulation loop, and introducing an internal model control principle to establish a high-performance current controller with enhanced current decoupling capabilities. This optimizes the steady-state pre-oscillation problem caused by traditional internal model controllers and enhances the parameter robustness of the current controller.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio includes the following steps:

[0007] Step S1: Sample the input voltage, output current, speed and rotor position angle of the three-phase winding of the high-speed motor. The output current is transformed to obtain the current value in the synchronous rotating coordinate system, i.e., the dq coordinate system.

[0008] Step S2: Based on the SPMSM stator voltage equation in the dq coordinate system, establish the complex coefficient model of SPMSM in the frequency domain;

[0009] Step S3: Using the complex coefficient model obtained in Step S2, and considering the zero-order hold-up effect of the inverter, establish the discrete domain SPMSM model G in the dq coordinate system. M (z);

[0010] Step S4: Use the discrete domain SPMSM model G obtained in step S3 M (z) Considering the effect of control delay, which better reflects the actual operating conditions of motor systems, we obtain the discrete-domain SPMSM model G considering the effect of delay. P (z);

[0011] Step S5: To suppress the steady-state pre-oscillation phenomenon caused by internal mode decoupling at high fundamental frequencies, design the system impedance gain modulation loop G. a (z);

[0012] Step S6: To implement the system impedance-gain modulation loop G designed in step S5 a In the differentiating element (z), a first-order low-pass filter with parameter τ is connected in series with the inductor term to obtain the system impedance-gain modulation loop G. b (z);

[0013] Step S7: Add the impedance-gain modulation stage obtained in step S6 to determine the discrete-domain SPMSM transfer function G. Pa (z) enables accurate reconstruction of the high-speed motor model;

[0014] Step S8: Based on the exact reconstruction model of the discrete domain SPMSM obtained in step S7, design a current controller G with enhanced current decoupling capability. c (z).

[0015] A further improvement to the technical solution of the present invention is that: the specific operation of step S1 is as follows: sampling the current output of the three-phase winding of SPMSM, and naming them i respectively. a i b and i c By performing Clark and Park coordinate transformations on the output current of the three-phase windings, the d-axis and q-axis currents i in the synchronous rotating coordinate system, i.e., the dq coordinate system, are obtained. d iq .

[0016] A further improvement to the technical solution of this invention lies in the following: the SPMSM stator voltage equation in the dq coordinate system in step S2 is:

[0017]

[0018] Where u d u q For the d-axis and q-axis voltage components, i d i q Let L be the d-axis and q-axis current components. s R is the equivalent inductance of the winding. s ψ is the equivalent resistance of the winding. f For permanent magnet flux linkage, ω e The rotor's electric angular velocity;

[0019] The specific operation of step S2 is as follows: Based on the stator voltage equation of SPMSM in the time domain, perform Laplace transform to establish the complex coefficient model G of SPMSM in the frequency domain. M (s), the back electromotive force ω e ψ f The term is considered a disturbance, and the input voltage u dq (s) to output current i dq The transfer function of (s) is:

[0020]

[0021] Among them, L s R is the equivalent inductance of the winding. s ω is the equivalent resistance of the winding. e ω is the rotor's electric angular velocity.

[0022] A further improvement to the technical solution of this invention lies in the following: the specific operation of step S3 is as follows: based on the complex coefficient model of SPMSM in the frequency domain, the high-speed motor model is reconstructed in the discrete domain, and the inverter is equivalent to an ideal zero-order hold ZOH:

[0023]

[0024] By combining the frequency domain SPMSM complex coefficient model with z-transform, the discrete domain model G of SPMSM in the dq coordinate system is obtained. M (z), where T s The inverter switching cycle;

[0025]

[0026] A further improvement to the technical solution of this invention lies in the following: Step S4 specifically involves: controlling the delay to be connected in series in the forward path of the current loop, causing a phase angle delay between the command voltage and the actual output voltage, with a delay angle θ. d =ω e T d The control delay in the dq coordinate system is divided into time delay terms. Phase delay term Delay time T d ;

[0027] The expression for the time delay term in the discrete domain:

[0028]

[0029] The expression for phase delay in the discrete domain:

[0030]

[0031] SPMSM discrete-domain model considering control delay:

[0032]

[0033] in

[0034] A further improvement to the technical solution of the present invention is that the specific operation of step S5 is as follows:

[0035] The transfer function in the s-domain is:

[0036] G a (s)=sL a +R a ;

[0037] Among them, L a For the impedance-gain modulation loop inductance term; R a This is the impedance gain modulation loop resistance term;

[0038] The expression for the impedance-gain modulation element in the discrete domain:

[0039]

[0040] A further improvement to the technical solution of this invention lies in: connecting a first-order low-pass filter with parameter τ in series with the inductor term to obtain a new impedance-gain modulation loop G. b (z):

[0041]

[0042] A further improvement to the technical solution of this invention lies in that: the discrete-domain SPMSM transfer function in step S7 is:

[0043]

[0044] A further improvement to the technical solution of the present invention lies in: the current controller G in step S8 that enhances the current decoupling capability. c (z):

[0045]

[0046] In the formula, α is the internal model controller parameter; H = H3(R s +jω e L s (H1+jH2); H1=1-h0cosθ d ;

[0047]

[0048] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows:

[0049] This invention provides an accurate reconstruction model of the discrete domain of a surface-mounted permanent magnet synchronous motor, which is closer to the actual operating motor and reduces the error between the motor model and the real motor.

[0050] This invention designs a current controller with enhanced current decoupling capability, achieving dynamic and static decoupling and delay compensation of the stator current. An impedance-gain modulation loop is designed to enhance the anti-disturbance capability of the high-speed motor under high fundamental frequency conditions, solving the steady-state pre-oscillation problem caused by internal mode decoupling, and improving the tracking performance and parameter robustness of the control system. Attached Figure Description

[0051] Figure 1 This is a vector system block diagram of a robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio based on the present invention.

[0052] Figure 2 This is a structural diagram of the discrete-domain SPMSM mathematical model in this invention;

[0053] Figure 3 This is a structural diagram of the discrete-domain current controller in this invention. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to embodiments:

[0055] A robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio includes the following steps:

[0056] Step S1: Sample the input voltage, output current, speed, and rotor position angle of the three-phase winding of the high-speed motor. The input voltage and output current are transformed to obtain the current value in the synchronous rotating coordinate system (dq coordinate system).

[0057] The coordinate transformation of the sampled current is specifically as follows: sample the current output from the three-phase windings of the SPMSM, and name them i... a i b and i c By performing Clark and Park coordinate transformations on the output current of the three-phase windings, the d-axis and q-axis currents i in the synchronous rotating coordinate system (dq coordinate system) are obtained. d i q .

[0058] Step S2: Based on the SPMSM stator voltage equation in the dq coordinate system, establish the complex coefficient model of SPMSM in the frequency domain.

[0059] The specific steps of the complex coefficient model are as follows: First, the SPMSM stator voltage equation in the dq coordinate system is:

[0060]

[0061] Where u d u q For the d-axis and q-axis voltage components, i d i q Let L be the d-axis and q-axis current components. s R is the equivalent inductance of the winding. s ψ is the equivalent resistance of the winding. f For permanent magnet flux linkage, ω e ω is the rotor's electric angular velocity.

[0062] Based on the stator voltage equation of the SPMSM in the time domain, a Laplace transform is performed to establish the complex coefficient model of the SPMSM in the frequency domain: the back electromotive force (ω) is... e ψ f If the term is considered a disturbance, then the input voltage u dq (s) to output current i dq The transfer function G of (s) M (s) is:

[0063]

[0064] Step S3: Using the complex coefficient model obtained in Step S2, and considering the zero-order hold-up effect of the inverter, establish the discrete domain SPMSM model G in the dq coordinate system. M (z);

[0065] The specific steps for establishing a discrete-domain SPMSM model are as follows: Based on the complex coefficient model of SPMSM in the frequency domain, the high-speed motor model is reconstructed in the discrete domain. The inverter is equivalent to an ideal zero-order hold (ZOH).

[0066]

[0067] By combining the frequency domain SPMSM complex coefficient model with z-transform, the discrete domain model G of SPMSM in the dq coordinate system is obtained. M (z), where T s This refers to the inverter switching cycle.

[0068]

[0069] Step S4: Use the discrete domain SPMSM model G obtained in step S3 M (z) Considering the effect of control delay, which better reflects the actual operating conditions of motor systems, we obtain the discrete-domain SPMSM model G considering the effect of delay. P (z);

[0070] Considering the impact of control delay, a motor model that better reflects the actual operation of a motor system is established: the control delay is connected in series in the forward path of the current loop, causing a phase angle delay between the command voltage and the actual output voltage, with a delay angle θ. d =ω e T d The control delay in the dq coordinate system is divided into time delay terms. Phase delay term Delay time T d .

[0071] The expression for the time delay term in the discrete domain:

[0072]

[0073] The expression for phase delay in the discrete domain:

[0074]

[0075] SPMSM discrete-domain model considering control delay:

[0076]

[0077] in

[0078] Step S5: To suppress the steady-state pre-oscillation phenomenon caused by internal mode decoupling at high fundamental frequencies, design the system impedance gain modulation loop G. a (z);

[0079] Design the system impedance-gain modulation loop G a (z) Specific steps: The transfer function in the s-domain is:

[0080] G a (s)=sL a +R a ;

[0081] Where L a For the impedance-gain modulation loop inductance term; R a This is the impedance gain modulation loop resistance term.

[0082] The expression for the impedance-gain modulation element in the discrete domain:

[0083]

[0084] Step S6: To implement the system impedance-gain modulation loop G designed in step S5 a In the differentiating element (z), a first-order low-pass filter with parameter τ is connected in series with the inductor term to obtain the system impedance-gain modulation loop G. b (z);

[0085] G a (z) The steps for connecting a low-pass filter in series with the inductance term of the differentiating element are as follows: To realize the differentiating element in the impedance-gain modulation element, a first-order low-pass filter with parameter τ is connected in series with the inductance term to obtain a new impedance-gain modulation element:

[0086]

[0087] Set τ to a very small value, so that G b (z) is closer to G a (z) aims to fully utilize the differential element in the impedance gain modulation stage, and here τ = 10μs is taken.

[0088] Step S7: Add the impedance-gain modulation stage obtained in step S6 to determine the discrete-domain SPMSM transfer function G. Pa (z) enables accurate reconstruction of the high-speed motor model;

[0089] The specific process of accurate reconstruction of the high-speed motor model: Considering the control delay and the zero-order hold effect of the inverter, the discrete-domain SPMSM transfer function with the addition of impedance gain modulation is as follows:

[0090]

[0091] Step S8: Based on the exact reconstruction model of the discrete domain SPMSM obtained in step S7, design a current controller G with enhanced current decoupling capability. c (z).

[0092] Design a current controller G c (z) Specific process: Based on the exact reconstruction model of discrete domain SPMSM, a current controller G with enhanced current decoupling capability is designed. c (z) achieves delay compensation. The controller contains a first-order low-pass filter, so G cIn (z), the inductance term of the impedance gain modulation stage does not need to be connected in series with other low-pass filters.

[0093]

[0094] In the formula, α is the internal model controller parameter; H = H3(R s +jω e L s (H1+jH2); H1=1-h0cosθ d ;

[0095]

[0096] Example

[0097] Figure 1 This is a vector system block diagram of a robust digital decoupling control method for high-speed permanent magnet synchronous motors with low carrier frequency ratio based on the present invention. The orange background represents the detected electrical parameters and rotor position signals used in the present invention. The blue background represents the current controller proposed in this invention to enhance the decoupling effect.

[0098] Figure 1 The orange background area represents the electrical parameters and rotor position signals used to detect the three-phase winding input voltage, output current, and speed of the high-speed motor. The sampled three-phase winding currents are named i... a i b and i c By performing Clark and Park coordinate transformations on the output current of the three-phase windings, the d-axis and q-axis currents i in the synchronous rotating coordinate system (dq coordinate system) are obtained. d i q .

[0099] The input voltage, output current, speed, and rotor position angle of the three-phase winding of the high-speed motor are sampled. The input voltage and output current are transformed to obtain the current value in the synchronous rotating coordinate system (dq coordinate system).

[0100] The coordinate transformation of the sampled current is specifically as follows: The current output from the three-phase windings of the SPMSM is sampled and named i... a i b and i c By performing Clark and Park coordinate transformations on the output current of the three-phase windings, the d-axis and q-axis currents i in the synchronous rotating coordinate system (dq coordinate system) are obtained. d i q .

[0101] Based on the SPMSM stator voltage equation in the dq coordinate system, a complex coefficient model of the SPMSM in the frequency domain is established. Input voltage u dq (s) to output current idq The transfer function G of (s) M (s) is:

[0102]

[0103] Where L s R is the equivalent inductance of the winding. s ω is the equivalent resistance of the winding. e ω is the rotor's electric angular velocity.

[0104] Figure 2 This invention is based on the discrete-domain SPMSM mathematical model structure diagram. According to the complex coefficient model of SPMSM in the frequency domain, the high-speed motor model is reconstructed in the discrete domain. The inverter is equivalent to an ideal zero-order hold, and the frequency-domain SPMSM complex coefficient model is subjected to a z-transform to obtain the discrete-domain SPMSM model G in the dq coordinate system. M (z), where T s This refers to the inverter switching cycle.

[0105]

[0106] Considering the impact of control delay, the time delay term and phase delay term are discretized. The expression for the time delay term in the discrete domain is as follows:

[0107]

[0108] The expression for phase delay in the discrete domain:

[0109]

[0110] Multiply by the discrete domain motor model G M (z) yields the accurate SPMSM discrete-domain model considering the effects of control delay:

[0111]

[0112] in

[0113] To suppress the steady-state pre-oscillation phenomenon caused by the integral term in the internal mode decoupling at high fundamental frequencies, an impedance-gain modulation loop is designed for the system, with the s-domain transfer function as follows:

[0114] G a (s)=sL a +R a

[0115] Among them, L a For the impedance-gain modulation loop inductance term; R a This is the impedance gain modulation loop resistance term.

[0116] The expression for the impedance-gain modulation element in the discrete domain:

[0117]

[0118] To realize the differentiating element in the impedance-gain modulation stage, a first-order low-pass filter with parameter τ is connected in series with the inductor term, resulting in a new impedance-gain modulation stage:

[0119]

[0120] Set τ to a very small value, so that G b (z) is closer to G a (z) aims to fully utilize the differential element in the impedance gain modulation stage, and here τ = 10μs is taken.

[0121] Considering control delay and inverter zero-order hold effect, the discrete-domain SPMSM transfer function G with impedance gain modulation stage is... Pa (z) is:

[0122]

[0123] Figure 3 Based on the discrete-domain current controller structure diagram in this invention, and according to the precise reconstruction model of the discrete-domain SPMSM, a current controller G with enhanced current decoupling capability is designed. c (z) achieves delay compensation. The controller contains a first-order low-pass filter, so G c In (z), the inductance term of the impedance gain modulation stage does not need to be connected in series with other low-pass filters.

[0124]

[0125] In the formula, α is the internal model controller parameter; H = H3(R s +jω e L s (H1+jH2); H1=1-h0cosθ d ;

[0126]

[0127] This invention addresses the problem that current coupling and control delay in permanent magnet synchronous motors (PMSMs) operating at high speeds and low carrier frequency ratios can severely impact control stability and dynamic response, potentially leading to system instability. Building upon traditional current decoupling methods, this invention proposes a robust digital decoupling control method for high-speed PMSMs operating at low carrier frequency ratios. By reconstructing an accurate high-speed motor model in the discrete domain, introducing internal model control theory, designing a system impedance-gain modulation loop, and constructing a digital current controller with enhanced decoupling capabilities, this method improves system stability and control response characteristics at low carrier frequency ratios, resolves the steady-state pre-oscillation problem caused by internal model decoupling, and enhances the tracking performance and parameter robustness of the control system.

[0128] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio, characterized in that... Includes the following steps: Step S1: Sample the input voltage, output current, speed and rotor position angle of the three-phase winding of the high-speed motor. The output current is transformed to obtain the current value in the synchronous rotating coordinate system, i.e., the dq coordinate system. Step S2: Based on the SPMSM stator voltage equation in the dq coordinate system, establish the complex coefficient model of SPMSM in the frequency domain; Step S3: Using the complex coefficient model obtained in Step S2, and considering the zero-order hold-up effect of the inverter, establish a discrete-domain SPMSM model in the dq coordinate system. ; Step S4: Utilize the discrete domain SPMSM model obtained in step S3 By considering the impact of control delay, a more realistic operating condition of motor systems is obtained, resulting in a discrete-domain SPMSM model that considers the impact of delay. ; Step S5: To suppress the steady-state pre-oscillation phenomenon caused by internal mode decoupling at high fundamental frequencies, design the system impedance gain modulation loop. ; The specific operation of step S5 is as follows: The transfer function in the s-domain is: ； in, This is the impedance gain modulation loop inductance term; This is the impedance gain modulation loop resistance term; The expression for the impedance-gain modulation element in the discrete domain: Ts is the inverter switching cycle; Step S6: Implement the system impedance-gain modulation loop designed in step S5. In the intermediate differential stage, a parameter with a value of is connected in series in the inductance term. A first-order low-pass filter is used to obtain the system impedance-gain modulation loop. ; Step S7: Add the impedance-gain modulation stage obtained in step S6 to determine the discrete-domain SPMSM transfer function. This enables accurate reconstruction of high-speed motor models; Step S8: Based on the exact reconstruction model of the discrete domain SPMSM obtained in step S7, a current controller with enhanced current decoupling capability is designed by introducing the internal model control principle. .

2. The robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio according to claim 1, characterized in that: The specific operation of step S1 is as follows: sample the current output by the three-phase winding of SPMSM, and name them respectively. , and By performing Clark and Park coordinate transformations on the output current of the three-phase windings, the d-axis and q-axis currents in the synchronous rotating coordinate system, i.e., the dq coordinate system, are obtained. , .

3. The robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio according to claim 1, characterized in that: The SPMSM stator voltage equation in the dq coordinate system in step S2 is as follows: in , For the d-axis and q-axis voltage components, , These are the d-axis and q-axis current components. The equivalent inductance of the winding is... This is the equivalent resistance of the winding. It is a permanent magnet flux linkage. The rotor's electric angular velocity; The specific operation of step S2 is as follows: Based on the stator voltage equation of SPMSM in the time domain, perform Laplace transform to establish the complex coefficient mathematical model of SPMSM in the frequency domain. , will back electromotive force The term is considered a disturbance, and the input voltage is... To output current The transfer function is: in, The equivalent inductance of the winding is... This is the equivalent resistance of the winding. ω is the rotor's electric angular velocity.

4. The robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio according to claim 3, characterized in that: The specific operation of step S3 is as follows: Based on the complex coefficient model of SPMSM in the frequency domain, the high-speed motor model is reconstructed in the discrete domain, and the inverter is equivalent to an ideal zero-order hold ZOH: Combined with frequency domain SPMSM complex coefficient model Transformation yields the SPMSM discrete domain model in the dq coordinate system. ,in The inverter switching cycle; 。 5. A robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio as described in claim 4, characterized in that: The specific operation of step S4 is as follows: a control delay is connected in series in the forward path of the current loop, causing a phase angle delay between the command voltage and the actual output voltage, the delay angle being... The control delay in the dq coordinate system is divided into time delay terms. Phase delay term Delay time ; The expression for the time delay term in the discrete domain: ； The expression for phase delay in the discrete domain: ； SPMSM discrete-domain model considering control delay: ； in ; .

6. The robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio according to claim 1, characterized in that: The specific operation of step S6 is as follows: a first-order low-pass filter with parameter τ is connected in series with the inductor term to obtain a new impedance-gain modulation loop. : 。 7. A robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio as described in claim 5, characterized in that: The discrete-domain SPMSM transfer function in step S7 is: 。 8. A robust digital decoupling control method for a high-speed permanent magnet synchronous motor with low carrier frequency ratio as described in claim 5, characterized in that: The current controller in step S8 that enhances current decoupling capability : In the formula, α is the parameter of the internal model controller; ; ; ; .

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