AC motor non-cascade control method, device and system

Abstract

The invention discloses a non-cascade control method, device and system for an alternating current motor. Firstly, in order to solve the problem of non-matching disturbance suppression, a nonlinear disturbance observer is designed to achieve estimation and compensation of matching disturbance and non-matching disturbance in a system, a corrected time-varying sliding mode surface is provided, and the sliding mode surface can reduce the influence of disturbance estimation errors to a certain extent. In addition, a current constraint problem under non-cascade control is considered, and a nonlinear damping item is introduced to realize dynamic constraint of the current. Compared with a traditional non-cascade control method, the method provided by the invention has stronger anti-interference capability, and can ensure that the current of the motor runs within a safe range.

Description

Technical Field

[0001] The invention relates to a non-cascade control method for an AC motor with the capability of modifying a sliding mode surface and current constraint, and belongs to the field of AC motor control. Background Art

[0002] AC motors have the advantages of high efficiency, high power density, high torque-to-inertia ratio, low noise and easy maintenance. They are widely used in robotics, automobiles, machine tools, aerospace and other fields.

[0003] In AC motor drive systems, traditional vector control typically uses a cascaded control structure, with the inner loop being the current loop and the outer loop being the speed loop. The speed loop's control period is typically 5 to 10 times that of the current loop. In contrast, non-cascaded control offers the advantages of a simpler structure and direct control of the q-axis voltage at a given speed. This eliminates the need for controlling the q-axis voltage via the current loop output, reducing latency.

[0004] However, the non-cascade control structure of AC motors also presents some unresolved issues. The equivalent mathematical model of the speed loop under non-cascade control is a second-order system. In addition to being affected by matching disturbances, the system is also affected by non-matching disturbances that act on different channels from the control input. These non-matching disturbances, mainly arising from factors such as external load torque, unmodeled dynamics, and parameter uncertainty, can have a significant negative impact on system performance and stability. Because non-matching disturbances act on the same channel as the current, they can cause the current to exceed the safe operating range, and their impact on the output current is difficult to eliminate. Therefore, suppressing non-matching disturbances is of great significance for improving system performance.

[0005] Furthermore, in non-cascade control mode, current is no longer limited by an external reference value but is directly controlled as an internal system state variable. This characteristic makes overcurrent protection particularly important. The controller must constrain the current amplitude in real time to prevent it from exceeding a safe range. Excessive current can not only degrade system dynamic performance (such as causing oscillation or response delays) but can also cause component overheating or even permanent damage.

[0006] To address the problem of mismatched disturbance suppression in the non-cascade control framework of AC motors, a fuzzy sliding mode speed controller based on a load torque observer can achieve robust speed control under changes in motor parameters and load torque, and to a certain extent, reduce the chattering in the sliding mode control. To improve the dynamic response speed of the system, a terminal sliding mode surface can be used to design the sliding mode controller, and a nonlinear disturbance observer can be combined to compensate for system disturbances. However, the stability of the controller cannot be guaranteed when the load torque changes. To enhance the system's mismatched disturbance suppression capability, a single-loop control strategy based on a mixed reaching law sliding mode control and a time-varying nonlinear disturbance observer is proposed. The proposed control strategy ensures that the system exhibits strong robustness under parameter changes and load disturbances. To simplify controller design and system stability analysis, a new sliding mode control method has been proposed for second-order nonlinear systems with mismatched disturbances. It designs a sliding mode surface using mismatched disturbance estimates, achieving effective suppression of mismatched disturbances.

[0007] The above methods primarily focus on controller design for non-cascaded anti-interference control of AC motors and do not consider system overcurrent protection. In practical engineering applications, conservative controller parameter settings are often chosen to ensure the current remains within a safe operating range, but this approach can restrict the system's dynamic performance to a certain extent. To address the current safety constraints of AC motors in automobiles, model predictive control schemes can achieve fast, real-time current constraints. However, this approach suffers from high computational complexity and insufficient anti-interference capabilities. To reduce computational complexity, a penalty term for the q-axis current can be introduced into the controller. This nonlinear function of the q-axis current is used to automatically adjust the control gain to achieve the current constraint. However, this method does not fully consider disturbance factors in the control design phase. Disturbances in the system are simply offset by the controller's integral action, which can compromise the system's robustness in the presence of complex external disturbances.

[0008] In general, there are relatively few studies on the problem of balancing anti-interference and overcurrent protection under non-cascade control of AC motors. Therefore, in the field of non-cascade control of AC motors, it is still of great significance to carry out research on disturbance suppression and current constraint control strategies. Summary of the Invention

[0009] The technical problem to be solved by the present invention is: in order to effectively enhance the anti-interference ability of the system, on the basis of the existing method, the mismatched disturbance is estimated by a disturbance observer, and a new current constraint controller is designed based on the estimation results. The controller has strong anti-interference ability while ensuring current constraint.

[0010] The present invention adopts the following technical solutions to solve the above technical problems:

[0011] The present invention first proposes a non-cascade control method for an AC motor, comprising the steps of:

[0012] S1. For the second-order dynamic model of AC motor, two nonlinear disturbance observers are designed to estimate the matching disturbance and non-matching disturbance in the system. The second-order nonlinear disturbance observer estimates the non-matching disturbance and its derivative, and the first-order nonlinear disturbance observer estimates the matching disturbance.

[0013] S2. Design a controller using the modified sliding surface; for the modified sliding surface, design correction variables using estimated values ​​of non-matching disturbance derivatives, and design a system controller using the modified sliding surface.

[0014] S3. Use q-axis current to design dynamic constraint items. For dynamic constraint items, design the relationship between virtual resistance and current to achieve dynamic adjustment of constraint items with current size.

[0015] S4. Design a system controller based on the disturbance estimation value, the corrected sliding surface, and the q-axis current-related dynamic constraint terms. Specifically, when the system is disturbed by a sudden load, the correction coefficient can correct the sliding surface, reducing the impact of the disturbance estimation error and improving the system's ability to suppress mismatched disturbances. When the system current is large, the q-axis current-related constraint terms can achieve dynamic current constraints.

[0016] As a preferred solution of the method of the present invention, the system controller is designed as follows:

[0017]

[0018] Among them, u q (t) is the controller output signal, s(t) is the sliding mode variable, x1(t) = ω * (t)-ω(t),ω * (t) is the speed reference value, ω(t) is the motor mechanical speed, The magnitude of the motor's q-axis current, and is the non-matching disturbance and its derivative estimate, is the matching disturbance estimate, η(t) is the sliding surface correction coefficient, R v (t) is the size of the virtual resistor, c, k1 and k2 are adjustable coefficients, a and b are system parameters, and f(t) is the system modelable dynamic term.

[0019] As a preferred solution of the method of the present invention, the state equation of the AC motor can be expressed as:

[0020]

[0021] Among them, u d (t),u q(t), i d (t) and i q (t) is the d-axis and q-axis components of the stator voltage and current, n p is the number of motor pole pairs, L d and L q is the d-axis and q-axis inductance, B is the friction coefficient, J is the moment of inertia, ψ f is the flux linkage size, R is the stator phase resistance, T L (t) is the load torque. Considering the uncertainty of motor parameters, the above formula can be rewritten as:

[0022]

[0023] Among them, the expressions of d1(t), d2(t) and f(t) are:

[0024]

[0025] Among them, ΔR, ΔL d , ΔL q and Δψ f Represent the difference between the actual value and the nominal value of the motor parameter. Select the system state variable x1(t)=ω * (t)-ω(t), x2(t)=i q (t), the speed error equation and voltage equation of the AC motor can be expressed as:

[0026]

[0027] Among them, d1(t) is the non-matching disturbance and d2(t) is the matching disturbance.

[0028] The second-order nonlinear disturbance observer that estimates the mismatched disturbance and its derivative is expressed as:

[0029]

[0030] Among them, z 11 (t) and z 12 (t) is the intermediate variable of the second-order nonlinear disturbance observer, l 11 and l 12 is the gain coefficient of the second-order nonlinear disturbance observer.

[0031] The first-order nonlinear disturbance observer expression for estimating the matching disturbance is:

[0032]

[0033] Among them, z 21 (t) is the intermediate variable of the first-order nonlinear disturbance observer, l21 is the gain coefficient of the first-order nonlinear disturbance observer.

[0034] As a preferred solution of the method of the present invention, the sliding surface after correction of the correction variables is designed as follows:

[0035]

[0036] Among them, η(t) is the correction variable, and its expression is:

[0037]

[0038] in, is the mismatched disturbance estimation error, m>0, n>0, and Δ is a small positive constant.

[0039] As a preferred solution of the method of the present invention, the size of η(t) is related to the mismatching disturbance estimation error. After the mismatching disturbance estimation value converges, the correction coefficient has no effect.

[0040] As a preferred solution of the method of the present invention, the expression for designing the virtual resistance is:

[0041]

[0042] Among them, R v (t) is the virtual resistance, ε1>0, ε2>0, ρ>0. ρ is related to the constraint range of the desired q-axis current, i.e. q (t)∈[-ρ,ρ].

[0043] On the other hand, the present invention provides a non-cascade control device for an AC motor, comprising:

[0044] A second-order nonlinear disturbance observer is used to obtain estimates of the mismatched disturbance and its derivatives;

[0045] A first-order nonlinear disturbance observer is used to obtain matching disturbance estimates;

[0046] The correction variable module is used to correct the disturbance term in the sliding surface by designing correction variables according to the disturbance change after the system is subjected to the non-matching load disturbance;

[0047] The virtual resistance module is used to solve the current over-limit problem of non-cascade control of AC motors and designs dynamic constraints that change with the q-axis current.

[0048] The system controller directly feeds forward the estimated matching disturbance to compensate for it. When the system is subject to load disturbances, the correction variable is used to modify the sliding surface, reducing the impact of disturbance estimation errors and improving the load disturbance suppression capability. A virtual resistor is used to dynamically limit the q-axis current.

[0049] The controller output signal is used as the q-axis voltage and combined with the d-axis PI current controller to realize the speed control of the AC motor.

[0050] The present invention also proposes an electronic system, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method steps of the present invention.

[0051] Finally, the present invention also provides a computer-readable storage medium storing computer instructions, wherein the computer instructions are used to enable the computer to execute the steps of the method of the present invention.

[0052] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0053] First, the control method provided by the present invention designs two nonlinear disturbance observers to estimate the matching disturbance and non-matching disturbance in the system, which can better suppress the non-matching disturbance.

[0054] At the same time, the present invention takes into account the changing characteristics of the instantaneous disturbance estimation value of the disturbance action, proposes a correction coefficient to correct the sliding surface function, and designs the system controller through the corrected sliding surface function. The sliding surface can reduce the impact of the disturbance estimation error on the system to a certain extent, and improve the AC motor drive system's ability to suppress load disturbances.

[0055] In addition, the present invention considers the current constraint problem under non-cascade control, adopts the active damping approach to design a virtual resistor that changes dynamically with the motor's q-axis current, and adds this dynamic constraint term to the controller to achieve dynamic constraint of the q-axis current.

[0056] In summary, compared with the traditional cascade control method, the present invention has stronger anti-interference ability, realizes the effective suppression of mismatch disturbance, and can constrain the q-axis current at the startup time to ensure that the motor current operates within a safe range. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a structural block diagram of the control method proposed in the present invention.

[0058] Figure 2 These are the speed simulation curves of different control methods.

[0059] Figure 3 is the modified variable η(t) curve.

[0060] Figure 4 It is the simulation curve of q-axis current of different control methods. DETAILED DESCRIPTION

[0061] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be interpreted as limiting the present invention.

[0062] This paper proposes a non-cascaded control method for AC motors with a modified sliding surface and current constraint capabilities. Based on the AC motor's second-order dynamic model, two nonlinear disturbance observers are designed to estimate the matching and mismatching disturbances present in the system. The second-order nonlinear disturbance observer estimates the mismatching disturbance and its derivative, while the first-order nonlinear disturbance observer estimates the matching disturbance.

[0063] Aiming at the modified sliding surface, the estimated value of the non-matching disturbance derivative is used to design the correction variable, and the system controller is designed based on the modified sliding surface.

[0064] For dynamic constraints, the relationship between virtual resistance and current is designed to achieve dynamic adjustment of constraints with current size.

[0065] The system controller is designed based on the disturbance estimation value, the corrected sliding surface, and the q-axis current-related dynamic constraint terms. When the system is subjected to sudden load disturbances, the correction coefficient can modify the sliding surface, reducing the impact of the disturbance estimation error and improving the system's mismatched disturbance suppression capability. When the system current is large, the q-axis current-related constraint terms can achieve dynamic current constraints.

[0066] The following is a specific embodiment of the present invention, and specific embodiment 1 is as follows:

[0067] First, a second-order nonlinear disturbance observer is designed to estimate the non-matching disturbance and its derivative, and a first-order nonlinear disturbance observer is designed to estimate the matching disturbance. Then, a correction coefficient related to the non-matching disturbance is designed to correct the sliding surface. By correcting the sliding surface, the system controller is designed to reduce the impact of the disturbance estimation error and improve the system's ability to suppress load disturbances. Finally, a virtual resistor that changes dynamically with the q-axis current is designed, and a damping term is introduced in the controller to achieve dynamic constraints on the q-axis current. The control block diagram of the system is shown in the figure below. Figure 1 As shown. The second-order dynamic model of the AC motor is:

[0068]

[0069] Among them, u d (t),u q (t), i d (t) and i q (t) is the d-axis and q-axis components of the stator voltage and current, n p is the number of motor pole pairs, L d and L qis the d-axis and q-axis inductance, B is the friction coefficient, J is the moment of inertia, ψ f is the flux linkage size, R is the stator phase resistance, T L (t) is the load torque. Considering the uncertainty of motor parameters, the above formula can be rewritten as:

[0070]

[0071] Among them, the expressions of d1(t), d2(t) and f(t) are:

[0072]

[0073] Among them, ΔR, ΔL d , ΔL q and Δψ f Represents the difference between the actual value and the nominal value of the motor parameter. Select the system state variable x1(t)=ω * (t)-ω(t), x2(t)=i q (t), combined with formula (2), the speed error equation and voltage equation of the AC motor can be expressed as:

[0074]

[0075] Among them, d1(t) is the non-matching disturbance and d2(t) is the matching disturbance.

[0076] According to equation (4), a second-order nonlinear disturbance observer is designed to estimate d1(t) and The expression of the observer is:

[0077]

[0078] Among them, z 11 (t) and z 12 (t) is the intermediate variable of the second-order nonlinear disturbance observer, l 11 and l 12 is the gain coefficient of the second-order nonlinear disturbance observer.

[0079] Similarly, a first-order nonlinear disturbance observer can be designed to estimate the matching disturbance d2(t). The observer expression is:

[0080]

[0081] Among them, z 21 (t) is the intermediate variable of the first-order nonlinear disturbance observer, l 21 is the gain coefficient of the first-order nonlinear disturbance observer.

[0082] The sliding surface function after correction by the correction variable can be expressed as:

[0083]

[0084] Among them, η(t) is the correction variable, and its expression is:

[0085]

[0086] in, is the mismatched disturbance estimation error, where m>0, n>0, and Δ is a small positive constant. The correction variable is related to the mismatched disturbance derivative estimate. When the system is subjected to a sudden load increase, the disturbance derivative estimate is initially large, and the correction variable is large. When the system is subjected to a sudden load decrease, the disturbance derivative estimate is initially small, and the correction variable is small. To prevent overcompensation, after the disturbance estimate converges to the actual value, the disturbance estimation error is considered small, and the correction variable η(t) = 1.

[0087] According to the variation law of the correction variable η(t) described in formula (8), it is necessary to determine the estimated value of the non-matching disturbance When it converges to the actual value. According to the second-order nonlinear disturbance observer (5), we can get:

[0088]

[0089] According to formula (9), when the system is subjected to sudden disturbance, the estimated value of the non-matching disturbance is When it converges to the actual value, reaches its maximum value, so the problem of judging when the perturbation estimate converges to the actual value is transformed into When does it reach its maximum value? At the initial moment when the system is subjected to a sudden disturbance, the disturbance derivative is large, and the estimated value of the disturbance derivative estimated in the disturbance observer is At the initial moment of sudden disturbance, it converges from zero to a larger value. According to formula (9), we can know that the disturbance estimate After convergence, Converges to zero, perturbed derivative estimate It has a large rate of change near the extreme value, so it can be based on To judge Whether it reaches the extreme value, where T s To control the period, Ω is a small real number greater than zero.

[0090] To achieve current constraint, a damping term that changes dynamically with the q-axis current is introduced into the controller. The equivalent virtual resistance of this damping term is designed as:

[0091]

[0092] Among them, Rv (t) is the virtual resistance, ρ>0, ε1>0, ε2>0, ρ is related to the constraint range of the desired q-axis current, i.e. q (t)∈[-ρ,ρ].

[0093] The modified sliding surface (7) is used to design the system controller, and the current constraint term is designed according to the virtual resistance expressed by formula (10). The system controller expression is:

[0094]

[0095] Therefore, the design steps of the non-cascade control method for AC motor proposed by the present invention are as follows:

[0096] Step 1: Select the nonlinear disturbance observer gain l 11 , l 12 , l 21 Increasing the observer gain is beneficial to improving the estimation speed of disturbances. Due to the limitation of the control system bandwidth, an excessively large observer gain will cause the system to oscillate and amplify the noise signal. Therefore, there is an upper limit to the selection of the observer gain.

[0097] Step 2: Select the sliding surface correction variable η(t). The correction variable correlation coefficients m and n determine the degree of correction of the disturbance estimate. The larger the m and n, the greater the correction amplitude. However, excessive correction amplitude may lead to overcompensation. Therefore, there is an upper limit for the selection of m and n.

[0098] Step 3: Select the virtual resistor R v (t), the virtual resistance is determined by ρ, ε1, ε2 and the motor q-axis current, ρ is related to the expected current constraint range, satisfying i q (t)∈[-ρ,ρ], ε1 and ε2 determine the degree of constraint of the virtual resistance. Smaller ε1 and ε2 cannot produce sufficient constraints, while larger ε1 and ε2 will limit the dynamic performance of the system. Therefore, the selection of ε1 and ε2 needs to balance the constraint ability and the dynamic response speed of the system.

[0099] Step 4: Design the system controller based on the estimated correlated disturbance, the selected modified sliding surface and the designed virtual resistor.

[0100] Step 5: The digital signal processor collects the three-phase current signal through the analog-to-digital converter and the motor rotor position and speed signal through the encoder, and outputs the control quantity u according to the sliding mode controller expression q (t).

[0101] Step 6: Based on the obtained speed and current single-loop controller output u q (t) is given as the q-axis voltage, and the d-axis current loop adopts The PI control method outputs the d-axis voltage given by u d (t), the speed control of the AC motor is achieved through SVPWM modulation.

[0102] To further illustrate the effectiveness of the proposed control strategy, simulation analysis is carried out in Matlab / Simulink, and the AC motor parameter settings are shown in Table 1. The proposed RNCSMC-CC method is compared with SMCADRC and NCSMC.

[0103] The parameters of the three controllers are shown in Table 2, k ip1 、k ii1 are the proportional coefficient and integral coefficient of the d-axis current loop of SMCADRC, NCSMC and the proposed RNCSMC method, k ip2 、k ii2 The proportional and integral coefficients of the q-axis current loop in the SMCADRC method are used, and ω0 is the velocity loop observer parameter in the SMCADRC method. The bus voltage is set to 200 V, and the reference speed of the AC motor is set to 2000 rpm. The simulation conditions are that the AC motor starts at no load, and the rated load torque is applied at 6 seconds and removed at 12 seconds. Figure 2 、 Figure 3 、 Figure 4 Table 3 shows the simulation test results.

[0104] Table 1 AC motor parameters

[0105] parameter Numerical parameter Numerical Rated voltage (V) 200 Permanent magnet flux (Wb) 0.12025 Rated current (A) 5.3 <![CDATA[Moment of inertia (kg.m 2 )]]> 0.0132 Rated power (kW) 1 Friction coefficient (Nms / rad) 0.005 Rated torque (Nm) 4.78 d-axis inductance (mH) 2.95 Pole pairs 5 q-axis inductance (mH) 2.95

[0106] Table 2 Simulation control parameters of different control methods

[0107]

[0108] Table 3 Performance indicators of loading simulation test with different methods

[0109]

[0110] like Figure 2 As shown in Figure 2, all three control methods can achieve speed control without overshoot, and the non-cascade control method NCSMC has a relatively fast starting speed. In the simulation, the different load characteristics of the actual loading and unloading processes are taken into account, so the speed change Δn and recovery time t of each method are calculated. r There are certain differences in the loading and unloading processes. By comparing Table 3, we can see that the invented RNCSMC-CC has stronger anti-interference ability and faster recovery time. Figure 3 The simulation results show that when the system is subjected to sudden load disturbance, the system will correct the sliding surface to reduce the impact of disturbance estimation error. Figure 4The simulation results show that the proposed non-cascade control method RNCSMC-CC can realize the dynamic constraint of the q-axis current and ensure that the motor operates within a safe range.

[0111] Embodiment 2: This embodiment proposes a non-cascade control device for an AC motor, comprising:

[0112] A second-order nonlinear disturbance observer is used to obtain estimates of the mismatched disturbance and its derivatives;

[0113] A first-order nonlinear disturbance observer is used to obtain matching disturbance estimates;

[0114] The correction variable module is used to correct the disturbance term in the sliding surface by designing correction variables according to the disturbance change after the system is subjected to the non-matching load disturbance;

[0115] The virtual resistance module is used to solve the current over-limit problem of non-cascade control of AC motors and designs dynamic constraint items that change dynamically with the q-axis current.

[0116] The system controller directly feeds forward the estimated matching disturbance to compensate. When the system is subjected to load disturbance, the correction variable is used to modify the sliding surface, reducing the impact of the disturbance estimation error and improving the load disturbance suppression capability. The damping term in the system controller is used to dynamically limit the q-axis current.

[0117] The specific implementation content of each of the above units corresponds one-to-one to the steps of the method proposed in Example 1 of the present invention, and will not be repeated here.

[0118] Example 3: This example provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method of the present invention are implemented, which will not be repeated here.

[0119] Embodiment 4: This embodiment further proposes an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor.

[0120] It should be noted that the processing flow of Examples 2 to 4 corresponds to the specific steps of the method provided in the embodiment of the present invention, and has the functional modules and beneficial effects corresponding to the execution method. For technical details not fully described in this embodiment, please refer to the method provided in the embodiment of the present invention.

[0121] The program code for implementing the methods of the present application can be written in any combination of one or more programming languages. Such program code can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the program code is executed by the processor or controller, the functions / operations specified in the flow charts and / or block diagrams are implemented. The program code can be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0122] In the context of the present application, a machine-readable medium can be a tangible medium that can contain or store a program for use by an instruction execution system, device or equipment or used in combination with an instruction execution system, device or equipment. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, device or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium can include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0123] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0124] The above is only a preferred embodiment of the present invention. 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. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0125] 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. Such changes and modifications are intended to fall within the scope of the invention as claimed.

Claims

1. A non-cascade control method for an AC motor, characterized in that: Including steps: S1. For the second-order dynamic model of AC motor, two nonlinear disturbance observers are designed to estimate the disturbances in the system. The second-order nonlinear disturbance observer estimates the non-matching disturbance and its derivative, and the first-order nonlinear disturbance observer estimates the matching disturbance. S2, using the estimated value of the non-matching disturbance derivative to design the correction variable, and using the correction coefficient to correct the sliding surface function; S3. For the dynamic constraint items related to the q-axis current, a virtual resistor that changes dynamically with the motor's q-axis current is designed to achieve dynamic adjustment of the constraint items with the current size. S4. Designing a system controller based on the disturbance estimate, the modified sliding surface function, and the q-axis current-related dynamic constraints; S5, collect three-phase current signals and motor rotor position and speed signals, and output the control quantity u according to the sliding mode controller expression q (t); S6, u q (t) is given as the q-axis voltage, and the d-axis current loop adopts The PI control method outputs the d-axis voltage given by u d (t), the speed control of the AC motor is achieved through SVPWM modulation.

2. The method according to claim 1, characterized in that The system controller expression in S4 is: Among them, u q (t) is the controller output signal, which is the given voltage of the q axis, s(t) is the sliding mode variable, x1(t) = ω * (t)-ω(t),ω * (t) is the speed reference value, ω(t) is the motor mechanical speed, is the motor q-axis current, and is the non-matching disturbance and its derivative estimate, is the matching disturbance estimate, η(t) is the sliding surface correction variable, R v (t) is the size of the designed virtual resistor, c, k1 and k2 are adjustable coefficients, a and b are system parameters, and f(t) is the system modelable dynamic term.

3. The method according to claim 2, characterized in that The state equation of the AC motor is expressed as: Among them, u d (t),u q (t), i d (t) and i q (t) are the d-axis and q-axis components of the stator voltage and current, respectively, n p is the number of motor pole pairs, L d and L q are the d-axis and q-axis inductances, B is the friction coefficient, J is the moment of inertia, ψ f is the permanent magnet flux, R is the stator phase resistance, T L (t) is the load torque, and the above formula can be rewritten as: Among them, the expressions of d1(t), d2(t) and f(t) are: Among them, ΔR, ΔL d , ΔL q and Δψ f Represent the difference between the actual value and the nominal value of the motor parameter, let Select the system state variable x1(t)=ω * (t)-ω(t), x2(t)=i q (t), the speed error equation and voltage equation of the AC motor are expressed as: Among them, d1(t) is the non-matching disturbance, and d2(t) is the matching disturbance; The second-order nonlinear disturbance observer that estimates the mismatched disturbance and its derivative is expressed as: Among them, z 11 (t) and z 12 (t) is the intermediate variable of the second-order nonlinear disturbance observer, l 11 and l 12 is the gain coefficient of the second-order nonlinear disturbance observer; The first-order nonlinear disturbance observer expression for estimating the matching disturbance is: Among them, z 21 (t) is the intermediate variable of the first-order nonlinear disturbance observer, l 21 is the gain coefficient of the first-order nonlinear disturbance observer.

4. The method according to claim 1, wherein In step S2, the sliding surface function after the correction variable is modified is designed as: Where a is the system parameter, c is the adjustable coefficient, and η(t) is the correction variable. The expression is: in, is the mismatched disturbance estimation error, m>0, n>0, and Δ is a small positive constant.

5. The method according to claim 4, characterized in that The size of η(t) is related to the mismatched disturbance estimation error. After the mismatched disturbance estimation value converges, the correction coefficient has no effect.

6. The method according to claim 1, characterized in that The expression of virtual resistance in the current dynamic constraint term is: Among them, R v (t) is the virtual resistance, ε1>0, ε2>0, ρ>0, ρ is related to the constraint range of the desired q-axis current, i q (t) is the q-axis component of the stator current, satisfying i q (t)∈[-ρ,ρ].

7. A non-cascade control device for an AC motor, characterized in that: include: A second-order nonlinear disturbance observer is used to obtain estimates of the mismatched disturbance and its derivatives; A first-order nonlinear disturbance observer is used to obtain matching disturbance estimates; The correction variable module designs correction variables to correct the disturbance terms in the sliding surface according to the disturbance change law after the system is disturbed by the mismatched load; The virtual resistance module is used to solve the current over-limit problem of non-cascade control of AC motors and designs dynamic constraints that change with the q-axis current. The system controller directly feeds forward the estimated matching disturbance to compensate. When the system is subjected to load disturbance, the correction variable is used to modify the sliding surface, reducing the impact of the disturbance estimation error and improving the load disturbance suppression capability. A virtual resistor is used to dynamically limit the q-axis current.

8. The non-cascade control device for an AC motor according to claim 7, characterized in that: The expression of the system controller is: Among them, u q (t) is the controller output signal, s(t) is the sliding mode variable, x1(t) = ω * (t)-ω(t),ω * (t) is the speed reference value, ω(t) is the motor mechanical speed, is the motor q-axis current, and is the non-matching disturbance and its derivative estimate, is the matching disturbance estimate, η(t) is the sliding surface correction variable, R v (t) is the size of the designed virtual resistor, c, k1 and k2 are adjustable coefficients, a and b are system parameters, and f(t) is the system modelable dynamic term; The controller output signal is used as the q-axis voltage and combined with the d-axis PI current controller to realize the speed control of the AC motor.

9. An electronic system comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, characterized in that the instructions are executed by the at least one processor so that the at least one processor can execute the method described in any one of claims 1-6.

10. A computer-readable storage medium storing computer instructions, characterized in that: The computer instructions are used to enable the computer to execute the method according to any one of claims 1 to 6.

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