Power factor optimal control method based on vector control of large-inertia asynchronous motor

Abstract

The application belongs to the technical field of asynchronous motor variable frequency speed regulation, and particularly relates to a power factor optimal control method based on vector control of a large-inertia asynchronous motor, which comprises the following steps: step one, calculating a rotor flux given initial value Flux0; step two, determining a slip angular velocity w corresponding to optimal power factor operation sy ; step three, reading a real-time speed difference e value; step four, motor overspeed determination; step five, when the motor overspeed value -e in step four reaches a set value A, reading a real-time torque current Is q , and performing step six; when the motor overspeed value -e in step four does not reach the set value A, directly performing step seven with the rotor flux given value Flux set = Flux0; step six, calculating a rotor flux given value given value Flux set ; step seven, calculating and outputting an excitation current constant value given value Isd set .

Description

Technical Field

[0001] This invention belongs to the field of variable frequency speed control technology for asynchronous motors, specifically relating to a power factor optimal control method based on vector control of a large inertia asynchronous motor. Background Technology

[0002] In short-term, high-power applications (such as fusion research and electromagnetic catapults), a mature and reliable power supply solution typically utilizes high-power pulse generator sets to provide electricity to power-consuming equipment, in order to reduce the impact on the power grid during the investment in power transformation and distribution facilities and the power consumption process. A pulse generator set consists of a drive motor, flywheel, and synchronous generator coaxially connected, using mechanical energy storage and pulse discharge to achieve the conversion and transfer of electrical energy. A key characteristic of this solution is that the energy accumulation (acceleration period) and storage (waiting for discharge period) time (T1) are much longer than the discharge time (T2). High-power pulse generator sets either have extremely large shaft rotational inertia or extremely high speeds, both of which place high demands on the unit's speed regulation performance. During T1, a large amount of electrical energy is consumed to accelerate and stabilize the unit. Therefore, how to efficiently utilize electrical energy and reduce energy loss during the energy conversion process is crucial to the energy-saving effect of this power supply system.

[0003] Energy consumption mainly includes mechanical losses and electrical losses. The former is primarily related to the hardware construction process and inherent mechanical properties of the equipment, while the latter is mainly related to the control algorithm during speed regulation and the electrical properties of some hardware devices. This invention mainly focuses on optimizing the speed control algorithm of high-power pulse generator sets to improve the operating power factor of the drive motor, thereby reducing unnecessary energy consumption caused by excessive reactive power transmission. This achieves the goals of improving the capacity utilization of speed regulation equipment, reducing power loss, and increasing the service life of the equipment (frequency converter, drive motor).

[0004] Current mainstream high-power variable frequency speed control mainly includes VVVF control, vector control, and direct torque control. VVVF control is simple to implement but has relatively poor control performance, mainly suitable for applications with low speed control requirements. Direct torque control has superior speed control performance, but its low-speed performance is not yet mature and needs further improvement. Vector control has excellent speed control performance; although its implementation depends on motor parameters, with the mature application of dynamic parameter identification and various compensation methods, its speed control performance can currently meet the needs of most high-performance speed control applications (including pulse generator speed control). However, in traditional vector control, the inverter's output power factor is greatly affected by the motor load. A relatively high operating power factor for a certain speed range is usually achieved by selecting a suitable excitation current setpoint. For high-power speed control systems with variable loads and variable operating speeds, it is difficult to achieve high power factor operation throughout the entire range. Summary of the Invention

[0005] This invention proposes a power factor optimal control method based on vector control of a large inertia asynchronous motor, which solves the technical problem in the prior art that it is impossible to dynamically track the real-time output electromagnetic torque of the asynchronous motor and calculate the optimal real-time setpoint of the excitation current.

[0006] The technical solution of this invention:

[0007] The power factor optimal control method based on vector control of large inertia asynchronous motors includes the following steps:

[0008] Step 1: Before implementing the power factor optimal control algorithm based on vector control of a large inertia asynchronous motor, the initial rotor flux given value Flux0 is calculated by comprehensively considering the unit's starting torque, stator voltage, stator current, power factor, and on-site commissioning experience.

[0009] Step 2: Determine the slip angular velocity w corresponding to the optimal power factor during operation. sy When the target slip angular velocity value w is obtained during operation with the optimal power factor input, sy And input the initial value Flux0 of the rotor flux calculated in step one;

[0010] Step 3: Read the real-time speed difference e value;

[0011] Step 4: Motor overspeed determination: When the real-time speed difference e read in Step 3 is the motor overspeed value -e, determine whether the motor overspeed value -e reaches the set value A of the power factor optimal control method algorithm for the activation speed condition.

[0012] Step 5: When the motor overspeed value -e from Step 4 reaches the set value A, read the real-time torque current Is. q Proceed to step six; when the motor overspeed value -e in step four does not reach the set value A, the rotor flux setpoint Flux set =Flux0 proceeds directly to step seven;

[0013] Step Six: Calculate the rotor flux setpoint. set ;

[0014] Step 7: Calculate and output the excitation current setpoint Isd set .

[0015] Step two includes: the operating slip angular velocity w when different motors are running. s It has a unique operating power factor And power factor With the operating slip angular velocity w s The increase in shows a trend of first increasing and then decreasing;

[0016] Therefore, through the optimal power factor and determining the slip angular velocity ω corresponding to the optimal power factor operation by restricting the magnitudes of the stator voltage and current of the motor during the speed regulation process sy .

[0017] The third step includes: the real-time speed difference e = F set - F run ;

[0018] When the motor speed has not reached the set speed stage, the value of e is greater than zero;

[0019] When the motor speed exceeds the set speed stage, the value of e is less than zero, which is the motor overspeed value -e;

[0020] where F run is the real-time speed and position feedback value of the motor obtained by the DSP main control board through the optical encoder; Fs et is the target speed given value in the vector control speed loop.

[0021] In the fourth step, the input speed condition for whether the motor overspeed value -e reaches the input speed condition setting value A of the power factor optimal control method algorithm includes: 0 <= A < e0, and the stator has the debugging effect of current stability and smooth transition; e0 is the speed overshoot.

[0022] The real-time torque current Is q value in the fifth step is obtained by calculating the three-phase stator current collected by the current sensor in the vector control main program through 3s / 2r. The real-time torque current Is q indirectly reflects the magnitude of the real-time output electromagnetic torque of the asynchronous motor.

[0023] The sixth step of calculating the rotor flux reference value Flux set includes:

[0024] Through the following formula (1):

[0025] Flux set = Lm * Is q / (Tr * Wsy)………………………(1)

[0026] Calculate the rotor flux reference value Flux set , where Lm is the mutual inductance of the motor, Tr is the rotor time constant of the asynchronous motor, and Isq is the torque current.

[0027] The seventh step includes: passing the calculated rotor flux reference value Flux set

[0028] Through the following formula (2):

[0029] Isd set=Flux set / Lm……………………(2)

[0030] The real-time setpoint of the excitation current is calculated and output to the vector control main program, which executes the dual closed-loop vector control algorithm for current and speed. (Isd) set The excitation current is a real-time setpoint value, and it is only activated after the speed reaches the set value; Isd set0 This is the initial setpoint for the excitation current, which is a constant value until the speed reaches the setpoint.

[0031] Step two also includes:

[0032] w smin <=w sy <=w smax ; in,

[0033] To determine the minimum and maximum values ​​of the ideal operating power factor of the parametric asynchronous motor, w smin w smax To determine the minimum and maximum values ​​of the ideal slip angular velocity of the asynchronous motor.

[0034] Step five also includes: the adjustment of the power factor optimal control method needs to be based on the real-time output torque of the motor to calculate the excitation current setpoint, ensuring that the motor slip angular velocity is maintained at the ideal slip angular velocity ω. sy Nearby; since there is no torque parameter in the vector control process, the stator current torque component is used for conversion.

[0035] The beneficial effects of this invention are:

[0036] This invention adds a flux linkage regulator algorithm to rotor field-oriented vector control, which can dynamically track the real-time output electromagnetic torque of the asynchronous motor, calculate the optimal real-time setpoint of the excitation current, and achieve optimal power factor control. This algorithm effectively inherits the speed regulation performance advantages of vector control in the field of high-power asynchronous motor speed regulation; it enables the asynchronous motor to operate at the optimal power factor under different speeds and loads; and it satisfies the requirements for rapid and smooth adjustment of the excitation current.

[0037] Furthermore, by loading the waveform after applying the flux linkage adjustment algorithm described in this invention, the slip angular velocity was maintained near the optimal value during the acceleration and steady-speed phases, and the power factor was also maintained at a high level. Through simulation analysis, it was verified that after adding the flux linkage regulator algorithm described in this invention to the vector control algorithm, the speed regulation performance of the asynchronous motor was not reduced, and the motor was able to operate with a high power factor under different loads and different speed ranges. Attached Figure Description

[0038] Figure 1 This is a flowchart of the power factor optimal control method based on vector control of a large inertia asynchronous motor as described in this invention.

[0039] Figure 2 This is a schematic diagram of the vector control principle upon which the present invention is based.

[0040] Figure 3 The vector control speed response curve is applicable to the present invention;

[0041] Figure 4 This is a graph showing the power factor, slip, and angular velocity relationship of a typical wound-rotor asynchronous motor.

[0042] Figure 5 This is a graph showing the trend of torque and speed over time.

[0043] Figure 6 The curves show the changes in power factor and slip angular velocity over time. Detailed Implementation

[0044] The following describes in detail, with reference to the accompanying drawings and embodiments, a power factor optimal control method based on vector control of a large inertia asynchronous motor according to the present invention.

[0045] like Figure 2 As shown, this invention is based on traditional current and speed dual closed-loop rotor field-oriented vector control. The working principle of the entire control system is as follows:

[0046] The DSP main control board acquires the real-time motor speed and position feedback value Frun through an optical encoder, compares it with the speed setpoint Fset, and the deviation result e is adjusted by the speed regulator ASR to obtain the stator current torque component Isq in the two-phase rotating coordinate system of vector control. set The stator phase currents Isa, Isb, and Isc detected by the Hall sensors are transformed into Isd and Isq values ​​in a two-phase rotating coordinate system through a 3s / 2r transformation (Clarke transformation + Park transformation). The reference signal Isd is used. set Isq set The voltage reference components Vsd and Vsq are obtained by comparing the difference with Isd and Isq respectively, and adjusting the current (ACR1, ACR2) and converting them. Then, Vsd and Vsq are transformed by 2r / 3s (Park inverse transform and Clarke inverse transform) to obtain the voltage reference signals Vsa, Vsb and Vsc in the three-phase stationary coordinate system. These signals are then sent to the FPGA board for PWM trigger pulse distribution to drive the inverter to generate the corresponding voltage to supply the motor.

[0047] In traditional vector control, Isd set It is a fixed value, which needs to be selected with reference to the motor hardware parameters and engineering debugging results. The focus of this invention is Isd.se The dynamic adjustment algorithm for t, such as Figure 1 The specific implementation process is as follows:

[0048] Step 1: Before implementing the power factor optimal control algorithm based on vector control of a large inertia asynchronous motor, the initial rotor flux given value Flux0 is calculated by comprehensively considering the unit's starting torque, stator voltage, stator current, power factor, and on-site commissioning experience.

[0049] Step 2: Determine the slip angular velocity w corresponding to the optimal power factor during operation. sy When the target slip angular velocity value w is obtained during operation with the optimal power factor input, sy Input the initial value Flux0 of the rotor flux obtained in step one;

[0050] Step two includes: the operating slip angular velocity w when different motors are running. s It has a unique operating power factor And power factor With the operating slip angular velocity w s The increase in shows a trend of first increasing and then decreasing;

[0051] Therefore, through the optimal power factor And during speed regulation, the magnitude of the motor stator voltage and current is limited to determine the slip angular velocity w corresponding to the optimal power factor during operation. sy .

[0052] In addition, w smin <=w sy <=w smax ;

[0053] in, To determine the minimum and maximum values ​​of the ideal operating power factor of the parametric asynchronous motor, w smin w smax To determine the minimum and maximum values ​​of the ideal slip angular velocity of the asynchronous motor.

[0054] Step 3: Read the real-time speed difference e value, including: real-time speed difference e = F set -F run ;

[0055] When the motor speed has not reached the set speed stage, the value of e is greater than zero;

[0056] When the motor speed exceeds the set speed range, the value of e is less than zero, which is the motor overspeed value -e;

[0057] Among them, F run The DSP main control board obtains real-time motor speed and position feedback values ​​via an optical encoder; Fset is the target speed given value in the vector control speed loop.

[0058] Step Four: Motor overspeed determination: When the real-time speed difference e value read in Step Three is the motor overspeed value -e, and it is judged whether the motor overspeed value -e reaches the input speed condition setting value A of the power factor optimal control method algorithm;

[0059] In the said Step Four, whether the motor overspeed value -e reaches the input speed condition setting value A of the power factor optimal control method algorithm includes: 0 <= A < e0, and the stator has the debugging effect of current stability and smooth transition; e0 is the speed overshoot.

[0060] Step Five: When the motor overspeed value -e in Step Four reaches the set value A, read the real-time torque current Is q , and proceed to Step Six; the real-time torque current Is in the said Step Five q value is obtained from the three-phase stator current collected and calculated by the current sensor in the vector control main program through 3s / 2r, and the real-time torque current Is q indirectly reflects the magnitude of the real-time output electromagnetic torque of the asynchronous motor.

[0061] The said Step Five also includes: The adjustment of the power factor optimal control method needs to calculate the excitation current given value at this time according to the real-time output torque of the motor to ensure that the motor slip angular velocity is maintained near the ideal slip angular velocity ω sy ; Since there is no torque parameter in the vector control process quantity, the stator current torque component is used for conversion.

[0062] When the motor overspeed value -e in Step Four does not reach the set value A, the rotor flux given value Flux set = Flux0 and directly proceed to Step Seven;

[0063] Step Six: Calculate the rotor flux given value Flux set , including: Through the following formula (1):

[0064] Flux set = Lm * Is q / (Tr * Wsy) ………………………(1)

[0065] Calculate the rotor flux given value Flux set , where Lm is the mutual inductance of the motor, Tr is the rotor time constant of the asynchronous motor, and Isq is the torque current.

[0066] The magnetizing current given value and the rotor flux are two corresponding control quantities, and are directly converted through the formula.

[0067] Step Seven: Calculate and output the excitation current fixed value given value Isdset This includes: calculating the rotor flux setpoint Flux set The following formula (2) is used:

[0068] Isd set =Flux set / Lm……………………(2)

[0069] The real-time setpoint of the excitation current is calculated and output to the vector control main program, which executes the dual closed-loop vector control algorithm for current and speed. (Isd) set The excitation current is a real-time setpoint value, and it is only activated after the speed reaches the set value; Isd set0 This is the initial setpoint for the excitation current, which is a constant value until the speed reaches the setpoint.

[0070] also, Figure 4 middle, The power factor of an asynchronous motor during operation, w s This refers to the slip angular velocity (the difference between the flux linkage angular velocity and the mechanical angular velocity) during motor operation. To determine the minimum and maximum values ​​of the ideal operating power factor of the parametric asynchronous motor, w sy This refers to the slip angular velocity of an asynchronous motor when it operates at its optimal power factor.

[0071] Figure 3 In the middle, F set is the target speed setpoint in the vector control speed loop, Frunz is the actual speed stability value, and e0 is the speed overshoot.

[0072] Figure 2 In the middle, F set Frun is the target speed setpoint in the vector control speed loop, Frun is the real-time speed and position feedback value of the motor obtained by the DSP main control board through the photoelectric encoder, Isa, Isb, and Isc are the three-phase stator currents of the asynchronous motor, and Isd and Isq are the excitation current and torque current after the three-phase stator currents are vector-directed according to the rotor flux linkage. set Isq set Here, is the given value of excitation current and torque current, e is the difference between the given speed and the actual speed, Flux0 is the initial value of rotor flux, θ is the rotor flux position angle, ASR is the speed regulator, and ACR1 and ACR2 are current regulators.

[0073] In an example, to verify the effectiveness of the present invention, simulation analysis was performed using the Simulink platform. This simulation used a 300MVA pulse generator set to drive the motor parameters and simulated some of its operating conditions.

[0074] Figure 5To enhance the speed and torque response waveforms after adding the excitation regulator, the motor accelerates from zero speed with constant torque, reaching the target speed of 300 r / min in approximately 11 seconds. After maintaining a steady speed for 13 seconds, it begins constant torque acceleration towards the new target speed of 500 r / min, reaching 500 r / min in 23 seconds and maintaining a steady speed. Even with the addition of the flux regulator, the speed control system maintains excellent speed regulation performance, exhibiting good dynamic tracking of speed and torque.

[0075] Figure 6 In the diagram, the same parameter has two waveforms: the upper waveform represents the effect before adding the flux linkage regulator, and the lower waveform represents the effect after adding the flux linkage regulation algorithm. Before optimization, the power factor decreases during the steady-state phase, and the power factor decreases as the steady-state speed decreases; the slip angular velocity also changes with the same trend. After flux linkage optimization control, the slip angular velocity remains near its optimal value during acceleration and steady-state phases, thus maintaining a high power factor.

[0076] Simulation results show that, after adding the power factor optimal control method based on vector control of a large inertia asynchronous motor described in this invention to the vector control algorithm, the speed regulation performance of the asynchronous motor is not reduced, and the motor can operate with a high power factor under different loads and speed ranges.

[0077] The embodiments of the present invention have been described in detail above. The present invention is not limited to the above examples. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A power factor optimal control method based on vector control of a large inertia asynchronous motor, characterized in that... It includes the following steps: Step 1: Before inputting the power factor optimal control method algorithm based on the vector control of large inertia asynchronous motor, comprehensively consider the starting torque, stator voltage, stator current, power factor of the unit and on-site commissioning experience to calculate the initial value of the rotor flux given, Flux0 Step 2: Determine the slip angular velocity corresponding to the optimal power factor during operation. When the target slip angular velocity value is obtained by inputting the optimal power factor, the target slip angular velocity value is obtained. And input the initial value Flux0 of the rotor flux calculated in step one; Step 3: Read the real-time speed difference e value; Step 4: Motor overspeed determination: When the real-time speed difference e value read in Step 3 is the motor overspeed value -e, and judge whether the motor overspeed value -e reaches the input speed condition setting value A of the power factor optimal control method algorithm; Step 5: When the motor overspeed value -e from Step 4 reaches the set value A, read the real-time torque current. Is q Proceed to step six; When the motor overspeed value -e in step four does not reach the set value A, the rotor flux setpoint Flux set = Directly proceed to Step 7 with Flux0; Step Six: Calculate the rotor flux setpoint. set ; Step 7: Calculate and output the excitation current setpoint. Isd set； Step two includes: operating slip angular velocity when different motors are running. It has a unique operating power factor And power factor With the operating slip angular velocity The increase in shows a trend of first increasing and then decreasing; Therefore, through the optimal power factor And the slip angular velocity corresponding to the optimal power factor operation during speed regulation is determined by the magnitude limits of the motor stator voltage and current. ; Step six calculates the rotor flux setpoint Flux. set include: Through the following formula (1): Flux set =Lm*Is q / (Tr*Wsy)………………………(1) Calculate the rotor flux setpoint Flux set Where Lm is the mutual inductance of the motor, and Tr is the rotor time constant of the asynchronous motor. Is q For torque current; Step seven includes: calculating the rotor flux setpoint Flux set Through the following formula (2): Isd set =Flux set / Lm…………………………(2) The real-time setpoint of the excitation current is calculated and output to the vector control main program, which then executes the dual closed-loop vector control algorithm for current and speed. Isd set The excitation current is given in real time and is only activated after the speed reaches the set value. Isd set0 This is the initial setpoint for the excitation current, which is a constant value until the speed reaches the setpoint.

2. The power factor optimal control method based on vector control of a large inertia asynchronous motor according to claim 1, characterized in that: Step three includes: real-time speed difference e = F set -F run ; When the motor speed does not reach the set speed stage, the e value is greater than zero; When the motor speed exceeds the set speed stage, the e value is less than zero, which is the motor overspeed value -e; in, F run The DSP main control board obtains the real-time speed and position feedback values ​​of the motor through an optical encoder. F set This is the target velocity setpoint in the vector control velocity loop.

3. The power factor optimal control method based on vector control of a large inertia asynchronous motor according to claim 2, characterized in that: In the said Step 4, whether the motor overspeed value -e reaches the input speed condition setting value A of the power factor optimal control method algorithm includes: 0 <= A < e0, and the stator has the commissioning effect of current stability and smooth transition; e0 is the speed overshoot.

4. The power factor optimal control method based on vector control of a large inertia asynchronous motor according to claim 3, characterized in that: Real-time torque current in step five Is q The value is obtained by calculating the three-phase stator current from the current sensor in the vector control main program, and then passing it through 3s / 2r; it is the real-time torque current. Is q It indirectly reflects the magnitude of the real-time output electromagnetic torque of the asynchronous motor.

5. The power factor optimal control method based on vector control of a large inertia asynchronous motor according to claim 1, characterized in that: Step two also includes: <= <= ; ,in, , To determine the minimum and maximum values ​​of the ideal operating power factor for a parametric asynchronous motor, , To determine the minimum and maximum values ​​of the ideal slip angular velocity of the asynchronous motor.

6. The power factor optimal control method based on vector control of a large inertia asynchronous motor according to claim 1, characterized in that: Step five also includes: adjusting the power factor optimal control method requires calculating the excitation current setpoint based on the real-time output torque of the motor to ensure that the motor slip angular velocity is maintained at the ideal slip angular velocity. Nearby; since there is no torque parameter in the vector control process, the stator current torque component is used for conversion.

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