Dual three-phase permanent magnet motor current control method and system under high speed and low carrier wave ratio

Abstract

The invention discloses a dual three-phase permanent magnet motor current control method and system under high speed and low carrier wave ratio, and belongs to the technical field of permanent magnet motor control. The method mainly comprises the following steps: reconstructing a motor mathematical model by adopting VSD conversion and Park conversion; designing a linear expansion state observer; a reference value of an output voltage vector is obtained in combination with deadbeat predictive current control; and performing time delay compensation and angle delay compensation on the output voltage vector to obtain a reference value of a final output voltage vector, sending the reference value to an SVPWM module for modulation, and outputting a PWM pulse signal for driving a motor. No motor parameter is used in the current loop design process, system errors caused by mismatching of the motor parameters can be avoided, and the system robustness is improved; meanwhile, only one control parameter needs to be determined, the parameter setting difficulty is greatly reduced, and stable operation of the high-speed permanent magnet motor under the low carrier wave ratio is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-performance permanent magnet synchronous motor control, and in particular relates to a current control method and system for a dual three-phase permanent magnet motor under high speed and low carrier ratio. Background Art

[0002] High-speed multi-phase permanent magnet synchronous motors are widely used in electric vehicles, aerospace, and electric ship propulsion due to their high power density, high efficiency, high overload capacity, high power factor, wide speed range, and high redundant degrees of freedom.

[0003] For these high-speed motors, the speed can exceed 10,000 RPM and the fundamental frequency can reach 1 kHz, while the switching frequency of the IGBT is generally less than 10 kHz, resulting in the system's carrier ratio (i.e., the ratio of the carrier frequency to the fundamental frequency) being less than 10. Therefore, operation at a low carrier ratio is a typical operating condition for high-speed permanent magnet motor drive systems. However, low carrier ratio operation will increase the modulation and control delay of the motor drive system, which inevitably poses a threat to the stability of the control loop. The current loop has the highest response speed requirements in the motor drive system, and its performance is particularly sensitive to the control delay and is most significantly affected.

[0004] In actual operation, factors such as changes in motor parameters, nonlinearity of the inverter, and fluctuations in back-EMF will introduce disturbances into the control system, thereby causing steady-state fluctuations in the controller and resulting in a decrease in dynamic performance.

[0005] When multi-phase permanent magnet synchronous motors operate under high-speed and low-carrier ratio conditions, reasonably compensating for delays, enhancing anti-interference capabilities, and improving system stability are issues that need to be addressed urgently. Summary of the invention

[0006] In order to solve the above problems in the prior art, the present invention provides a current control method and system for a dual three-phase permanent magnet motor under high speed and low carrier ratio.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention first provides a current control method for a dual three-phase permanent magnet motor under high speed and low carrier ratio, which specifically comprises the following steps:

[0009] 1) Detect the stator current i of the dual three-phase permanent magnet motor a 、i b 、i c 、i u 、i v 、i w , mapped to the dqxy subspace through VSD transformation and Park transformation, and the current components of the d-axis, q-axis, x-axis and y-axis in the dqxy subspace are obtained;

[0010] 2) The current reference value of the q axis is obtained by the PI regulator, and the current reference values ​​of the d axis, the x axis and the y axis are all set to 0; according to the current reference value and the actual current value of the x axis and the y axis, the voltage reference values ​​of the x axis and the y axis are obtained by the PI regulator;

[0011] 3) Design a linear extended state observer, estimate the disturbance of the dual three-phase permanent magnet motor through the linear extended state observer, and obtain the disturbance estimation values ​​of the d-axis and q-axis;

[0012] 4) according to the current reference values ​​of the d-axis and the q-axis and the disturbance estimation value, the voltage reference values ​​of the d-axis and the q-axis of the motor are obtained by a deadbeat predictive current control method;

[0013] 5) Performing time delay compensation and angle delay compensation on the voltage reference values ​​of the d-axis and the q-axis to obtain the final voltage reference values ​​of the d-axis and the q-axis; performing angle delay compensation on the voltage reference values ​​of the x-axis and the y-axis to obtain the final voltage reference values ​​of the x-axis and the y-axis;

[0014] 6) The final voltage reference values ​​of the d-axis, q-axis, x-axis and y-axis are synthesized through SVPWM modulation to obtain a switch control signal, and the switch control signal is used for driving control of the motor.

[0015] Secondly, the present invention also provides a dual three-phase permanent magnet motor current control system under high speed and low carrier ratio, which is used to implement the above method.

[0016] The beneficial effects of the present invention are:

[0017] The present invention discloses a current control method and system for dual three-phase permanent magnet motors under high speed and low carrier ratio. By designing an extended state observer to estimate the disturbance of the system, it is used in a deadbeat predictive current control system, avoiding the use of motor parameters, getting rid of the dependence on the motor model, and improving the anti-disturbance and robustness of the system. At the same time, the entire control system only needs to design one control parameter without complex parameter setting. The delay compensation link is introduced in the current regulator to ensure the operating stability of the high-speed multi-phase permanent magnet synchronous motor under low carrier ratio conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a block diagram of the dual three-phase permanent magnet synchronous motor control system of the present invention;

[0019] Figure 2 It is the driving circuit topology diagram of dual three-phase permanent magnet synchronous motor;

[0020] Figure 3 The dqxy axis current diagram of the traditional deadbeat predictive current control when all motor parameters are matched;

[0021] Figure 4 The dqxy axis current diagram of the method of the present invention when all motor parameters are matched;

[0022] Figure 5 The motor parameters do not match (0.1R, 2ψ f ,1.2L s ) in the case of conventional deadbeat predictive current control, dqxy axis current diagram;

[0023] Figure 6 The motor parameters do not match (0.1R, 2ψ f ,1.2L s ) case, the dqxy axis current diagram of the method of the present invention. DETAILED DESCRIPTION

[0024] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0025] The present invention aims to solve the problem of mismatch between controller parameters and actual motor parameters through an extended state observer, improve the robustness of the system, solve the large delay problem of the system under low carrier ratio conditions through delay compensation, and enhance the stability of the system. To achieve the above purpose, the design ideas are described below from three aspects: the mathematical model of dual three-phase permanent magnet motor, the linear extended state observer, and the deadbeat predictive current control.

[0026] (I) Mathematical model of dual three-phase permanent magnet motor

[0027] The present invention uses space vector decoupling matrix and Park transformation to reconstruct the motor mathematical model as follows:

[0028] Vector space decomposition (VSD) transformation has been widely used in multi-phase motor drive systems due to its excellent decoupling performance. By using the VSD transformation matrix, the motor variables i of the dual three-phase permanent magnet synchronous motor are a 、i b 、i c 、i u 、i v 、i w It is mapped to three orthogonal subspaces, namely the fundamental αβ subspace, the harmonic xy subspace and the zero-sequence o1o2 subspace. The expression of the VSD transformation matrix is:

[0029]

[0030] Since the two neutral points of the dual three-phase permanent magnet synchronous motor are isolated, there is no zero-sequence current component in the zero-sequence o1o2 subspace. The current component of the fundamental αβ subspace is mapped to the dq synchronous rotating reference system in the dqxy subspace through Park transformation. The Park transformation from the αβ stationary reference system of the fundamental αβ subspace to the dq synchronous rotating reference system is expressed as:

[0031]

[0032] where θ e is the rotor electrical angle position. The voltage equation of the dual three-phase permanent magnet synchronous motor in the dqxy subspace is:

[0033]

[0034] Among them, R s is the stator resistance, ψ f is the permanent magnet flux, ω e is the electrical angular velocity, u, i and L represent the stator voltage, stator current and stator inductance respectively. The subscripts d / q and x / y represent the components in the dq and xy subspaces respectively. x and e y It includes the high-order harmonic back-electromotive force components in the xy subspace and the harmonic interference voltage components caused by the nonlinearity of the inverter.

[0035] (II) Linear Extended State Observer

[0036] Extended State Observer (ESO) is a control algorithm for state estimation of dynamic systems. The goal of ESO is to estimate all state variables of the system, including disturbances or unknown inputs in the controlled system.

[0037] The steps of designing a linear extended state observer in the present invention are as follows:

[0038] The first-order super-local model of the dq axis of the surface-mounted dual three-phase permanent magnet synchronous motor is expressed by a complex vector as follows:

[0039]

[0040] Among them, f dq =(-R s i dq -jω e L s i dq -jω e ψ f ) / L s is the dq axis disturbance, Ls is the d-axis inductance or the q-axis inductance. Since the present embodiment adopts a surface-mounted permanent magnet synchronous motor, its d-axis inductance and q-axis inductance are the same. dq and the disturbance term f dq Considered as the state variable of the system, combined with the current estimation error, a linear extended state observer (ESO) is designed for estimation:

[0041]

[0042] Among them, e rr is the observer error, for i dq 、f dq The estimated value of dq and f dq are the dq axis current and disturbance, β1 and β2 are the error feedback gains of ESO.

[0043] Disturbance actual value f dq To the disturbance estimate The s-domain transfer function is:

[0044]

[0045] Where s is the Laplace operator. In order for the system to remain stable, the roots of the characteristic equation should all have negative real parts, so that both roots of the characteristic equation fall on -w b Department:

[0046] s 2 -β1s-β2=(s+w b ) 2

[0047] Therefore, combining the above two equations, we can get β1 and β2 as follows:

[0048] β1=-2w b

[0049] β2=-w b 2

[0050] Among them, w b The bandwidth of the ESO to be designed determines the stability and dynamic performance of the ESO. In order to respond quickly, the bandwidth of the ESO should be increased while ensuring the stability of the system. The values ​​of β1 and β2 affect the distribution of the closed-loop poles of the system, thereby affecting the stability of the ESO. Therefore, it is necessary to select reasonable β1 and β2 to ensure the stability of the system and the controller to achieve better control performance.

[0051] In order to design w in z domain b, the current estimate and disturbance estimate are discretized as:

[0052]

[0053] in, i dq (k)=[i d (k)i q (k)] T ,u dq (k)=[u d (k)u q (k)] T , T sa is the sampling period, and k is the sampling time.

[0054] According to the discretized expressions of the current estimate and the disturbance estimate, the actual current value i dq To current estimate The z-domain transfer function is:

[0055]

[0056] Its characteristic equation is:

[0057] z 2 -(T sa β1+2)z+1+T sa β1-T sa 2 β2=0

[0058] The pole expressions obtained by solving the above characteristic equation are as follows:

[0059] z 1,2 =1-w b T sa

[0060] According to the extreme expression transformation, we can get w b The expression is as follows:

[0061]

[0062] According to w b The expression of b So that the pole z 1,2 is within the unit circle in the z plane. If w b Too small (z 1,2 If w is close to 1), the dynamic response speed of the system will slow down, the transition process of the system (such as rise time, peak time, and stabilization time) will be longer, and the dynamic performance of the system will deteriorate. b Too large (z 1,2If the input signal is close to 0, the system will be more sensitive to high-frequency noise, the robustness of the system will be affected, and the system will react too violently to changes in the input signal, which may cause unnecessary vibration or disturbance. 1,2 =0.5, which has a better dynamic response while maintaining system stability.

[0063] (III) Deadbeat Predictive Current Control

[0064] Deadbeat Predictive Current Control (DPCC) is an advanced strategy that achieves high-precision and fast-response current control by predicting future current trajectories. The deadbeat predictive current control method uses model prediction technology to obtain the reference value of the output voltage vector to achieve current control.

[0065] In the present invention, a deadbeat predictive current control method is used to obtain a reference value of the output voltage vector, which is as follows:

[0066] The first-order super-local complex vector model of the dq axis of the surface-mounted dual three-phase permanent magnet synchronous motor is discretized by first-order forward difference as follows:

[0067]

[0068] Among them, due to f dq (k) cannot be obtained directly, so f is used dq Estimated value of (k) Assume that the current i of the system at time k+1 is dq (k+1) reaches the current reference value Then the reference value of the output voltage vector is expressed as:

[0069]

[0070] in, is the output of the speed loop, indicating the current reference value that needs to be tracked at the next moment. and Represents the d-axis component and q-axis component of the current reference value at time k+1.

[0071] Since digital control systems currently operate at low carrier ratios, certain modulation and control delays will occur, which poses a threat to the stability of the control loop. In order to solve this problem, the present invention needs to compensate for the generated delays accordingly. The steps of calculating the delay in the control system of the present invention and compensating for the angle delay are as follows:

[0072] The control system of the present invention has a control delay of about one cycle and a modulation delay of half a cycle in the αβ sub-plane. Therefore, the delay link F in the dq sub-planedelay (s) includes two parts: time delay and angle delay. The delay link of the digital control system in the dq sub-plane can be approximately expressed by the first-order Taylor formula:

[0073]

[0074] Among them, τ d For delay, f sa is the sampling frequency, is the voltage reference vector.

[0075] Due to the delay link F delay There is a fixed angle delay in (s), which reduces the phase margin of the system, so angle delay compensation is required. Angle delay compensation link F pc (s) is expressed as:

[0076]

[0077] Among them, j is an imaginary number, ω e is the actual electrical angular velocity.

[0078] The delay link in the dq sub-plane can be discretized as:

[0079]

[0080] Accordingly, the angle delay compensation link can be discretized as:

[0081]

[0082] The output voltage vector is subjected to time delay compensation and angle delay compensation, and the reference value of the final output voltage vector is obtained as follows:

[0083] Considering the one-shot time delay of the digital control system, the angle delay compensation link F is adopted pc (z) Compensating for the angle delay in the control system, the reference value of the final output voltage vector can be rewritten as:

[0084]

[0085] Among them, θ d =ω e τ d =1.5ω e T sa , It is the reference value of the current loop output voltage vector.

[0086] Figure 1This is a block diagram of the control system proposed in the present invention. Based on the above design ideas, the present invention proposes a current control method for a dual three-phase permanent magnet motor under high speed and low carrier ratio, and the implementation process of the method is as follows:

[0087] 1) Detect the stator current i of the dual three-phase permanent magnet motor a 、i b 、i c 、i u 、i v 、i w , mapped to the dqxy subspace through VSD transformation and Park transformation, and the current components of the d-axis, q-axis, x-axis and y-axis in the dqxy subspace are obtained;

[0088] 2) The current reference value of the q axis is obtained by the PI regulator of the speed outer loop, and the current reference values ​​of the d axis, x axis and y axis are all set to 0, and the x axis and y axis currents are controlled by the PI regulator. However, this is only for the purpose of implementing the present invention, and is not limited to this method;

[0089] Specifically, given the reference electrical angular velocity And obtain the actual electrical angular velocity ω of the motor variable through the feedback loop e , Figure 1 In the figure, * represents the superscript ref; the reference electrical angular velocity is subtracted from the actual electrical angular velocity and then input into the PI regulator, and the q-axis current reference value is obtained through adjustment by the PI regulator.

[0090] Through another PI regulator, the voltage reference values ​​of the x-axis and y-axis are obtained according to the current reference values ​​of the x-axis and y-axis and the actual stator current; the process of obtaining the voltage reference value from the current reference value and the actual stator current through the PI regulator is a common use of the PI regulator in the field, and this embodiment does not explain this process in detail.

[0091] 3) Design a linear extended state observer, estimate the disturbance of the dual three-phase permanent magnet motor through the linear extended state observer, and obtain the disturbance estimation values ​​of the d-axis and q-axis;

[0092] Specifically, the error feedback gain of the linear extended state observer of this embodiment is designed according to the design ideas described above; the disturbance of the dual three-phase permanent magnet motor is estimated by using the designed linear extended state observer, and the obtained disturbance estimation value is as follows:

[0093]

[0094] 4) According to the current reference value and disturbance estimation value of the d-axis and q-axis, the voltage reference value of the d-axis and q-axis of the motor is obtained by the zero-beat predictive current control method. Due to the delay in the control system, the voltage reference value also needs to be compensated and adjusted.

[0095] 5) Perform angle delay compensation on the voltage reference values ​​of the x-axis and y-axis to obtain the final voltage reference values ​​of the x-axis and y-axis. The expressions are as follows:

[0096]

[0097] in is the current reference value of the x-axis and y-axis, K p and K i are the parameters of the PI regulator.

[0098] The voltage reference values ​​of the d-axis and q-axis obtained by the deadbeat predictive current control method are compensated for time delay and angle delay to obtain the final voltage reference values ​​of the d-axis and q-axis. The expressions are as follows:

[0099]

[0100] The angular delay compensation for the x-axis and y-axis voltage reference values ​​is consistent with the angular delay compensation for the d-axis and q-axis voltage reference values.

[0101] 6) The final voltage reference values ​​of the d-axis and q-axis, and the voltage reference values ​​of the x-axis and y-axis are synthesized through the SVPWM modulation strategy to generate a final PWM pulse signal, which is used for the drive control of the motor.

[0102] Figure 2 The topology diagram of the drive circuit of a dual three-phase permanent magnet synchronous motor. The motor adopts a dual Y structure, and the phase difference between the two three-phase windings is 30°. Based on the dual three-phase configuration of the motor, the inverter consists of two parallel three-phase bridges, and each three-phase bridge adopts a two-level topology. The inverter has a total of six phases, and each phase bridge arm is composed of two IGBT or MOSFET switching devices.

[0103] The motor used in this embodiment is a surface-mounted dual three-phase permanent magnet synchronous motor. The parameters of the dual three-phase permanent magnet synchronous motor and the controller parameters are shown in Table 1.

[0104] Table 1

[0105] parameter Numeric Rated voltage U 360V Rated speed n 18000rpm <![CDATA[Rated torque T e > 331N·m Rated power P 612kW Phase current effective value I 298A <![CDATA[DC voltage U dc > 1000V Pole pair number p 3 pairs Stator resistance R 7.7mΩ <![CDATA[dq-axis inductance L s > 116.4851uH <![CDATA[xy-axis inductance L z > 60.0549uH <![CDATA[Permanent magnet flux linkage ψ f > 0.0894Wb Moment of inertia J <![CDATA[0.15kg·m 2 ]]> <![CDATA[Switching frequency f s > 12.5kHz <![CDATA[Sampling and control frequency f sa > 12.5kHz <![CDATA[Control period T sa > 0.08ms

[0106] Specifically, at t=10s, a load of 162N·m is suddenly added, and at t=14s, the added load of 162N·m is suddenly unloaded. The expected speed is 18000rpm, the base frequency is 900Hz, the switching frequency is 12.5kHz, and the carrier ratio is close to 14, which belongs to the low carrier ratio working condition. Figure 3 and Figure 4 As shown, Figure 3 The dqxy axis current diagram of the traditional deadbeat predictive current control when all motor parameters are matched; Figure 4The dqxy axis current diagram of the method of the present invention is shown in the case where the motor parameters are matched. By comparison, it is found that when the controller parameters and the motor parameters are matched, the current ripple of the traditional zero-beat predictive current control method is large and the current tracking effect is good. The current tracking performance and current ripple performance of the method proposed in the present invention are better than those of the traditional zero-beat predictive current control method. Based on the above working conditions, the controller parameters are adjusted to be mismatched with the motor parameters (0.1R, 2ψ f ,1.2L s ),like Figure 5 and Figure 6 As shown, Figure 5 The dqxy axis current diagram of the traditional deadbeat predictive current control when the motor parameters do not match; Figure 6 The dqxy axis current diagram of the method of the present invention is shown in the case where the motor parameters do not match. By comparison, it is found that when the controller parameters do not match the motor parameters (0.1R, 2ψ f ,1.2L s ), the current ripple of the traditional deadbeat predictive current control method is further increased, the current waveform is bad, and the q-axis current cannot track the given value. The current tracking performance and current ripple performance of the method proposed in the present invention are similar to those before, and the current tracking effect and current ripple performance are good. It can be seen that the method proposed in the present invention enhances the anti-disturbance ability of the system by adding an observer, avoiding the steady-state error and even instability caused by parameter mismatch.

[0107] In summary, the method proposed in the present invention can avoid the use of motor parameters by designing an extended state observer, thereby improving the robustness and anti-interference of the system; by compensating for the inherent large delay in the digital control system, the stable and efficient operation of the high-speed permanent magnet synchronous motor under low carrier ratio is ensured; the algorithm parameter setting of the current controller is simple and effective. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

[0108] This embodiment also proposes a dual three-phase permanent magnet motor current control system under high speed and low carrier ratio, which is used to implement the above method. The terms "module", "unit", etc. used below can implement a combination of software and / or hardware of predetermined functions. Although the system described in the following embodiments is preferably implemented in software, it is also possible to implement hardware, or a combination of software and hardware. The system includes:

[0109] A mapping transformation module is used to detect the stator current of the dual three-phase permanent magnet motor and map it to the dqxy subspace;

[0110] A current reference module, used to obtain a current reference value in the dqxy subspace, and also used to obtain a voltage reference value of the x-axis and the y-axis according to the current reference values ​​of the x-axis and the y-axis;

[0111] A disturbance estimation module, used for estimating the disturbance of the dual three-phase permanent magnet motor;

[0112] A deadbeat prediction module, used for obtaining voltage reference values ​​of the d-axis and the q-axis according to current reference values ​​of the d-axis and the q-axis;

[0113] A delay compensation module is used to perform delay compensation on the voltage reference values ​​of the d-axis and the q-axis to obtain the final voltage reference values ​​of the d-axis and the q-axis;

[0114] The signal control module is used to output a switch control signal using the final voltage reference values ​​of the d-axis and the q-axis and the voltage reference values ​​of the x-axis and the y-axis.

[0115] For the system embodiment, since it basically corresponds to the method embodiment, the relevant parts can refer to the partial description of the method embodiment, and the implementation methods of the remaining modules will not be repeated here. The system embodiment described above is only schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of the present invention. Ordinary technicians in this field can understand and implement it without paying creative work.

[0116] The embodiments of the system of the present invention can be applied to any device with data processing capabilities, and the device with data processing capabilities can be a device or apparatus such as a computer. The system embodiments can be implemented by software, or by hardware or a combination of software and hardware. Taking software implementation as an example, as a device in a logical sense, the corresponding computer program instructions in the non-volatile memory are read into the memory by the processor of any device with data processing capabilities and run.

Claims

1. A method for controlling current of a dual three-phase permanent magnet motor at high speed and low carrier ratio, characterized in that: include: 1) Detect the stator current i of the dual three-phase permanent magnet motor a 、i b 、i c 、i u 、i v 、i w , mapped to the dqxy subspace through VSD transformation and Park transformation, and the current components of the d-axis, q-axis, x-axis and y-axis in the dqxy subspace are obtained; 2) The current reference value of the q axis is obtained through the PI regulator, and the current reference values ​​of the d axis, the x axis and the y axis are all set to 0; according to the current reference value and the actual current value of the x axis and the y axis, the voltage reference values ​​of the x axis and the y axis are obtained through the PI regulator; 3) Design a linear extended state observer, estimate the disturbance of the dual three-phase permanent magnet motor through the linear extended state observer, and obtain the disturbance estimation values ​​of the d-axis and q-axis; 4) according to the current reference values ​​of the d-axis and the q-axis and the disturbance estimation value, the voltage reference values ​​of the d-axis and the q-axis of the motor are obtained by a deadbeat predictive current control method; 5) Performing time delay compensation and angle delay compensation on the voltage reference values ​​of the d-axis and the q-axis to obtain the final voltage reference values ​​of the d-axis and the q-axis; performing angle delay compensation on the voltage reference values ​​of the x-axis and the y-axis to obtain the final voltage reference values ​​of the x-axis and the y-axis; 6) The final voltage reference values ​​of the d-axis, q-axis, x-axis and y-axis are synthesized through SVPWM modulation to obtain a switch control signal, and the switch control signal is used for driving control of the motor.

2. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 1 is characterized in that: Step 1) is as follows: first, the stator current i of the dual three-phase permanent magnet motor is converted into a 、i b 、i c 、i u 、i v 、i w It is mapped to the fundamental αβ subspace, the harmonic xy subspace and the zero-sequence o1o2 subspace, where there is no current component in the zero-sequence o1o2 subspace; the current component in the fundamental αβ subspace is mapped to the dq synchronous rotating reference system in the dqxy subspace through Park transformation to obtain the current components of the d-axis and q-axis; the current component in the harmonic xy subspace is the current component of the x-axis and y-axis.

3. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 1 is characterized in that: In step 3), the design of the linear extended state observer specifically includes: The dq axis of the dual three-phase permanent magnet motor is expressed by a complex vector first-order hyperlocal model as follows: Among them, f dq =(-R s i dq -jω e L s i dq -jω e ψ f ) / L s is the dq axis disturbance, R s is the dq axis resistance, i dq is the stator current of d-axis and q-axis, u dq is the stator voltage of the d-axis and q-axis, ψ f is the permanent magnet flux of the motor, j is an imaginary unit, ω e is the electrical angular velocity, L s is the d-axis inductance or the q-axis inductance; For the dual three-phase permanent magnet motor that can be represented by the above model, the expression of the linear extended state observer is as follows: Among them, e rr is the observer error, and for i dq and f dq The estimated value of dq and f dq is the dq axis current and disturbance, L s is the d-axis inductance or q-axis inductance, β1 and β2 are the error feedback gains of the ESO; Discretize the expression of the linear extended state observer and obtain the actual current value i according to the discretized expression. dq To current estimate The z-domain transfer function is obtained, and the characteristic equation of the z-domain transfer function is obtained; based on the characteristic equation, the values ​​of the error feedback gains β1 and β2 of the ESO are designed as: β1＝-2w b β2＝-w b 2 where w b is the bandwidth of ESO, z 1,2 are the poles of the characteristic equation of the z-domain transfer function.

4. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 3 is characterized in that: The poles of the characteristic equation are set to z 1,2 =0.

5.

5. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 3 is characterized in that: The discretized expression of the linear extended state observer is: Among them, T sa is the sampling period, k represents the sampling time; The z-domain transfer function is: The characteristic equation of the z-domain transfer function is: z 2 -(T sa β1+2)z+1+T sa β1-T sa 2 β2=0 where z is the z-domain variable.

6. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 1 is characterized in that: Step 4) is specifically as follows: Calculate the voltage reference values ​​of the d-axis and q-axis according to the current reference values ​​of the d-axis and q-axis and the disturbance estimation value The calculation expression is: where u dq (k) is the motor voltage of the d-axis and q-axis at the current moment, is the current reference value at the next moment, i dq (k) is the motor current of the d-axis and q-axis at the current moment, T sa is the sampling period, k represents the sampling time, is the disturbance estimate of the d-axis and q-axis at the current moment, L s is the d-axis inductance or the q-axis inductance.

7. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 1 is characterized in that: In step 5), the voltage reference values ​​of the d-axis and the q-axis are subjected to time delay compensation and angle delay compensation to obtain the final voltage reference values ​​of the d-axis and the q-axis, and the expressions are as follows: in, is the final voltage reference value of the d-axis and q-axis at time k+1, L s is the d-axis inductance or the q-axis inductance, is the current reference value of the d-axis and q-axis at time k+2, i dq (k+1) is the current component of the d-axis and q-axis at time k+1, T sa is the sampling period, k represents the sampling time, θ d =1.5ω e T sa is the angular delay, f sa is the sampling frequency.

8. The current control method of dual three-phase permanent magnet motor under high speed and low carrier ratio according to claim 1 is characterized in that: The carrier ratio of the dual three-phase permanent magnet motor is lower than 15.

9. A high-speed and low-carrier ratio dual three-phase permanent magnet motor current control system, used to implement the method described in claim 1, characterized in that: The system comprises: A mapping transformation module is used to detect the stator current of the dual three-phase permanent magnet motor and map it to the dqxy subspace; A current reference module, used to obtain a current reference value in the dqxy subspace, and also used to obtain a voltage reference value of the x-axis and the y-axis according to the current reference values ​​of the x-axis and the y-axis; A disturbance estimation module, used for estimating the disturbance of the dual three-phase permanent magnet motor; A deadbeat prediction module, used for obtaining voltage reference values ​​of the d-axis and the q-axis according to current reference values ​​of the d-axis and the q-axis; A delay compensation module is used to perform delay compensation on the voltage reference values ​​of the d-axis and the q-axis to obtain the final voltage reference values ​​of the d-axis and the q-axis; The signal control module is used to output a switch control signal using the final voltage reference values ​​of the d-axis and the q-axis and the voltage reference values ​​of the x-axis and the y-axis.

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