Electric motor control method, apparatus and device, and computer-readable storage medium

Abstract

An electric motor control method, apparatus and device, and a computer-readable storage medium, which belong to the field of electric motor control. Adjusting a firing moment of a thyristor can change a voltage integral value of a specified phase, thereby adjusting a current effective value of the specified phase. Therefore, in the present invention, when voltages of three phases are unbalanced, the phase having the smallest current effective value is used as a reference phase, a firing moment adjustment value is determined for the next thyristor to be fired of each non-reference phase, the firing moment adjustment value is then superimposed on an original firing moment of the corresponding thyristor to be fired, so as to obtain a target firing moment, and finally, the thyristor to be fired is fired at the target firing moment, such that a voltage integral value of the non-reference phase within the next half current cycle is consistent with a voltage integral value of the reference phase, thereby achieving the balance between current effective values of the three phases, suppressing fluctuations in an electric motor torque, prolonging the service life of an electric motor, and improving the user experience.

Description

Motor control method, device, equipment and computer-readable storage medium

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on December 20, 2023, with application number 202311763370.6 and invention name “A motor control method, device, apparatus and computer-readable storage medium”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present invention relates to the field of motor control, and in particular to a motor control method. The present invention also relates to a motor control device, equipment, and computer-readable storage medium. Background Art

[0003] Under ideal conditions, the three-phase voltage of the three-phase asynchronous motor is balanced (symmetrical), so that the effective values ​​of the three-phase current of the three-phase asynchronous motor are equal, and the torque of the three-phase asynchronous motor is relatively stable; however, the three-phase voltage of the three-phase asynchronous motor is unbalanced. Once the three-phase voltage is unbalanced, it will cause an imbalance between the effective values ​​of the three-phase current of the three-phase asynchronous motor, thereby causing fluctuations in the motor torque, reducing the motor service life and affecting the user experience.

[0004] Therefore, how to provide a solution to the above technical problems is a problem that those skilled in the art need to solve at present.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide a motor control method, device, equipment and computer-readable storage medium, which achieves the balance of the three-phase current effective values ​​by taking the phase with the smallest current effective value as the reference phase and controlling the voltage integral value of the non-reference phase during the current continuous period to be equal to the reference phase, thereby reducing torque fluctuations and improving the motor service life and user experience.

[0007] To solve the above technical problems, the present invention provides a motor control method applied to a controller of a three-phase asynchronous motor, comprising:

[0008] When the three-phase voltage of the three-phase asynchronous motor is unbalanced, the phase with the smallest effective current value is used as the reference phase;

[0009] Taking the target integral value equal to the reference phase as the target, determining the trigger moment adjustment value corresponding to each non-reference phase respectively; wherein the target integral value is: the voltage integral value within the current continuous period of the current half cycle;

[0010] For each non-reference phase, superimposing the triggering time adjustment value corresponding to the non-reference phase on the original triggering time of the next thyristor to be triggered to obtain a target triggering time;

[0011] At the target triggering time of the thyristor to be triggered, the thyristor to be triggered in the non-reference phase is triggered.

[0012] On the other hand, for each non-reference phase, superimposing the trigger time adjustment value corresponding to the non-reference phase on the original trigger time of the next thyristor to be triggered to obtain the target trigger time includes:

[0013] For each non-reference phase, the sum of the original turn-off angle of the next thyristor to be triggered and the triggering time adjustment value corresponding to the non-reference is used as the target turn-off angle of the thyristor to be triggered;

[0014] Triggering the to-be-triggered thyristor of the non-reference phase at the target triggering moment of the to-be-triggered thyristor includes:

[0015] At the target turn-off angle after a rising edge of a tube voltage drop of the to-be-triggered thyristor appears, the to-be-triggered thyristor of the non-reference phase is triggered.

[0016] On the other hand, the step of setting the target integral value equal to the target integral value of the reference phase as a target and determining the trigger moment adjustment value corresponding to each non-reference phase includes:

[0017] Taking the front-end integral value of the target integral value of the reference phase as equal as the target, respectively determining the front-end adjustment value corresponding to each non-reference phase;

[0018] Taking the latter-segment integral value of the target integral value of the reference phase as equal as the target, respectively determining the latter-segment adjustment value corresponding to each non-reference phase;

[0019] The sum of the front-end adjustment value and the rear-end adjustment value of a single non-reference phase is used as the triggering time adjustment value corresponding to the non-reference phase;

[0020] The target integral value is: the voltage integral value in the current continuous period of the current half cycle, and the target integral value is divided into the front-end integral value and the back-end integral value by the voltage zero-crossing point.

[0021] On the other hand, after determining the front-end adjustment value corresponding to each non-reference phase by setting the front-end integral value equal to the target integral value of the reference phase as the target, the motor control method further includes:

[0022] In the first half current cycle of determining the three-phase voltage imbalance, using the previous adjustment value of a single non-reference phase as the initial adjustment value at the triggering moment of the corresponding non-reference phase;

[0023] For each non-reference phase, the sum of the original triggering time of the initial thyristor to be triggered in the first half current cycle of the three-phase voltage imbalance and the initial adjustment value of the triggering time corresponding to the non-reference phase is determined as the target triggering time of the initial thyristor;

[0024] At the target triggering time of the initial thyristor, the initial thyristor of the non-reference phase is triggered.

[0025] On the other hand, when the three-phase voltages of the three-phase asynchronous motor are unbalanced, using the phase with the smallest effective current value as the reference phase includes:

[0026] When the multiple voltage imbalance of the three-phase asynchronous motor is greater than a preset threshold, a phase with the smallest effective current value is used as a reference phase.

[0027] On the other hand, the motor control method further includes:

[0028] When the current multiple voltage imbalance is greater than the preset threshold, if there is a non-reference phase whose trigger moment adjustment value is zero, the alarm is controlled to sound an alarm.

[0029] On the other hand, when the three-phase voltages of the three-phase asynchronous motor are unbalanced, using the phase with the smallest effective current value as the reference phase includes:

[0030] When the three-phase voltage of the three-phase asynchronous motor is unbalanced during the soft starting process, the phase with the smallest effective voltage value or the phase with the smallest effective current value is used as the reference phase;

[0031] When the three-phase voltages of the three-phase asynchronous motor are unbalanced after starting, the phase with the smallest effective current value is used as the reference phase.

[0032] To solve the above technical problems, the present invention further provides a motor control device, which is applied to a controller of a three-phase asynchronous motor, comprising:

[0033] A first determining module is configured to use a phase with the smallest effective current value as a reference phase when the three-phase voltage of the three-phase asynchronous motor is unbalanced;

[0034] A second determination module is configured to determine a trigger moment adjustment value corresponding to each non-reference phase, taking a target integral value equal to the target integral value of the reference phase as a target; wherein the target integral value is: a voltage integral value within a continuous current period of a current half cycle;

[0035] a calculation module configured to, for each of the non-reference phases, superimpose the triggering time adjustment value corresponding to the non-reference phase on the original triggering time of the next thyristor to be triggered to obtain a target triggering time;

[0036] An action module is configured to trigger the to-be-triggered thyristor of the non-reference phase at the target triggering moment of the to-be-triggered thyristor.

[0037] To solve the above technical problems, the present invention further provides a motor control device, comprising:

[0038] memory for storing computer programs;

[0039] The processor is configured to implement the steps of the motor control method described above when executing the computer program.

[0040] To solve the above technical problems, the present invention further 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 motor control method described above are implemented.

[0041] The present invention provides a motor control method. Considering that the voltage integral value of a specified phase can be changed by adjusting the triggering moment of a thyristor, thereby adjusting the effective current value of the specified phase, the present invention uses the phase with the smallest effective current value as the reference phase when the three-phase voltage is unbalanced, determines a triggering moment adjustment value for the next thyristor to be triggered in each non-reference phase, and then superimposes the triggering moment adjustment value on the original triggering moment of the corresponding thyristor to be triggered to obtain a target triggering moment. Finally, the thyristor to be triggered is triggered at the target triggering moment, so that the voltage integral value of the non-reference phase in the next half current cycle is consistent with the reference phase, thereby achieving a balance of the effective values ​​of the three-phase current, suppressing the fluctuation of the motor torque, and improving the motor service life and user experience.

[0042] The present invention also provides a motor control device, equipment and computer-readable storage medium, which have the same beneficial effects as the above motor control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the relevant technologies and the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] FIG1 is a schematic flow chart of a motor control method provided by the present invention;

[0045] Figure 2 is a schematic diagram of the structure of the soft start main circuit;

[0046] FIG3 is a schematic diagram of the electric energy angle relationship of a three-phase asynchronous motor;

[0047] FIG4 is a logic diagram of a motor control method provided by the present invention;

[0048] FIG5 is a waveform diagram of a three-phase current root mean square value provided by the present invention;

[0049] FIG6 is a schematic diagram of the effect of a motor control provided by the present invention;

[0050] FIG7 is a schematic structural diagram of a motor control device provided by the present invention;

[0051] FIG8 is a schematic structural diagram of a motor control device provided by the present invention. DETAILED DESCRIPTION

[0052] The core of the present invention is to provide a motor control method, device, equipment and computer-readable storage medium. By taking the phase with the smallest current effective value as the reference phase and controlling the voltage integral value of the non-reference phase during the current continuous period to be equal to the reference phase, the three-phase current effective value is balanced, thereby reducing torque fluctuations, improving the motor service life and user experience.

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0054] Please refer to FIG1 , which is a flow chart of a motor control method provided by the present invention. The motor control method is applied to a controller of a three-phase asynchronous motor, including:

[0055] S101: When the three-phase voltage of the three-phase asynchronous motor is unbalanced, the phase with the smallest effective current value is used as the reference phase;

[0056] Specifically, considering the technical problems in the above background technology, and considering that the voltage integral value of the specified phase can be changed by adjusting the triggering moment of the thyristor, thereby adjusting the effective current value of the specified phase, it is theoretically possible to adjust the effective current value of the three phases to a balanced state by adjusting the triggering moment of the thyristor. At the same time, considering that the turn-off angle is zero after the motor is started, it is impossible to increase the voltage integral value of the corresponding phase by advancing the triggering moment of the thyristor. However, whether during the motor starting process or after the start-up is completed, the voltage integral value of the corresponding phase can be reduced by delaying the triggering moment of the thyristor. Therefore, in an embodiment of the present invention, when the three-phase voltage of the three-phase asynchronous motor is unbalanced, the phase with the smallest effective current value is used as the reference phase, and the thyristor triggering moment of the non-reference phase (the other two phases) is delayed, so that the effective current values ​​of the three phases are equal. Therefore, in this step, when the three-phase voltage of the three-phase asynchronous motor is unbalanced, the phase with the smallest effective current value can be used as the reference phase so that it can be used as the data basis for subsequent steps.

[0057] S102: Taking the target integral value equal to the reference phase as the target, determine the trigger time adjustment value corresponding to each non-reference phase; wherein the target integral value is: the voltage integral value within the current continuous period of the current half cycle;

[0058] Specifically, in order to better illustrate the embodiments of the present invention, please refer to Figures 2 to 4. Figure 2 is a structural diagram of the soft start main circuit, Figure 3 is a schematic diagram of the electric energy angle relationship of the three-phase asynchronous motor, and Figure 4 is a logical diagram of a motor control method provided by the present invention. In the soft start main circuit of Figure 2, U A 、U B , and U C The voltages of the three phases ABC are respectively provided to the motor through the on-off control of the two thyristors on each phase. The 3M in Figure 2 can refer to a three-phase asynchronous motor. In Figure 3, α is the triggering thyristor angle delayed after the voltage zero crossing moment. is the freewheeling angle, also known as the power angle, γ is the zero current time interval, also known as the turn-off angle, and θ is the current time interval, also known as the conduction angle. In Figure 4, u a -u c They are the voltage waveforms of the three phases ABC, i a -i c They are the current waveforms of the three phases ABC respectively. Multiple lowercase letters t with different subscripts represent different moments, and each different subscript S represents a different voltage integral. Under ideal conditions, the effective voltage values ​​of the three phases ABC with a phase difference of 120 degrees in the current continuous period within half a current cycle should be balanced (i.e., equal), so that the voltage integral values ​​of the three phases ABC with a phase difference of 120 degrees in the current continuous period within half a current cycle are equal, which is (S) in Figure 4.A +S A- )=(S B +S B- )=(S C +S C- ), but due to the imbalance of the three-phase grid voltage, the effective values ​​of the three-phase voltages may be different, which leads to the difference in the voltage integral values ​​of the three phases ABC with a phase difference of 120 degrees in the current continuous period within half a current cycle when the shutdown angle is adjusted according to the normal control method, which is (S A +S A- )、(S B +S B- ) and (S C +S C- ) are not equal, so the embodiment of the present invention can find the reference phase, and then set the target integral value equal to the reference phase as the target, and determine the trigger time adjustment value corresponding to each non-reference phase respectively, with the purpose of making the adjusted target integral value of the non-reference phase equal to the target integral value of the reference phase, achieving the balance of the three-phase voltage integral value so as to balance the three-phase current effective value. The target integral value here refers to the voltage integral value in the current continuous period of the current half cycle, such as (S A +S A- )、(S B +S B- ) and (S C +S C- ) is the voltage integral value of the three-phase current continuous period in the current half cycle.

[0059] The triggering moment referred to in the embodiment of the present invention refers to the moment when each thyristor is triggered to conduct, that is, the moment when the current in FIG4 occurs, for example, t a1 With t a4 wait.

[0060] S103: For each non-reference phase, superimpose the triggering time adjustment value corresponding to the non-reference phase on the original triggering time of the next thyristor to be triggered to obtain the target triggering time;

[0061] Specifically, when the three-phase voltage is symmetrical, the turn-off angle γ will decrease to zero at a certain rate, and the current will eventually become continuous, and the soft start process will end. However, when the three-phase voltage is asymmetrical (i.e., unbalanced) (C vuf(Complex Voltage Unbalance Factor, complex voltage imbalance is not 0). If you want to make the effective values ​​of the three-phase currents equal, you need to superimpose the trigger moment adjustment value Δγ on the original shutdown angle γ of the non-reference phase. The shutdown angle is γ+Δγ, where γ decreases with time and Δγ changes with the change of the three-phase imbalance. Δγ is the trigger moment adjustment value in the embodiment of the present invention. If the soft start is completed and the three-phase voltage is still unbalanced, Δγ cannot be equal to zero, that is, at the moment of steady-state operation, the thyristor still has a certain shutdown angle, which ensures that the "energy" input to the three-phase winding end of the motor is equal as much as possible. As for the size of Δγ, it depends on the three-phase imbalance. If the three-phase voltage becomes symmetrical at a certain moment, Δγ will immediately be zero.

[0062] Specifically, based on the above principle, in this step, for each non-reference phase, the sum of the original triggering time of the next thyristor to be triggered and the triggering time adjustment value corresponding to the non-reference phase can be used as the target triggering time of the thyristor to be triggered. For example, in FIG4 , in (S A1 +S A1- )、(S B1 +S B1- ) and (S C1 +S C1- ) half current cycle, the triggering time adjustment value of the non-reference phase can be calculated, and then the triggering time adjustment value is superimposed on the triggering time of the thyristor in the next half current cycle. For example, for phase C, the triggering time adjustment value can be calculated in (S A1 +S A1- )、(S B1 +S B1- ) and (S C1 +S C1- ) The trigger time adjustment value obtained in this half current cycle is superimposed on S C2- The original triggering time of this thyristor is t c11 , t after adding the trigger time adjustment value c11 Become t c12 , so that in the next half current cycle, the target integral values ​​of the three phases are equal and the effective current values ​​are also equal. Therefore, in this step, for each non-reference phase, the triggering time adjustment value corresponding to the non-reference phase is superimposed on the original triggering time of the next thyristor to be triggered to obtain the target triggering time, which is used as the data basis for subsequent steps.

[0063] S104: triggering the thyristor to be triggered in the non-reference phase at the target triggering time of the thyristor to be triggered.

[0064] Specifically, after obtaining the target triggering time of the next thyristor to be triggered of each non-reference phase, the thyristor to be triggered of the non-reference phase can be triggered at the target triggering time of the thyristor to be triggered, so that the target integral values ​​of the three phases are equal and the effective current values ​​are also equal.

[0065] The present invention provides a motor control method. Considering that the voltage integral value of a specified phase can be changed by adjusting the triggering moment of a thyristor, thereby adjusting the effective current value of the specified phase, the present invention uses the phase with the smallest effective current value as the reference phase when the three-phase voltage is unbalanced, determines a triggering moment adjustment value for the next thyristor to be triggered in each non-reference phase, and then superimposes the triggering moment adjustment value on the original triggering moment of the corresponding thyristor to be triggered to obtain a target triggering moment. Finally, the thyristor to be triggered is triggered at the target triggering moment, so that the voltage integral value of the non-reference phase in the next half current cycle is consistent with the reference phase, thereby achieving a balance of the effective values ​​of the three-phase current, suppressing the fluctuation of the motor torque, and improving the motor service life and user experience.

[0066] Based on the above embodiment:

[0067] As an optional embodiment, for each non-reference phase, the triggering time adjustment value corresponding to the non-reference phase is added to the original triggering time of the next thyristor to be triggered to obtain the target triggering time, which includes:

[0068] For each non-reference phase, the sum of the original turn-off angle of the next thyristor to be triggered and the triggering time adjustment value corresponding to the non-reference is used as the target turn-off angle of the thyristor to be triggered;

[0069] At the target triggering time of the thyristor to be triggered, the thyristor to be triggered of the non-reference phase includes:

[0070] At the target turn-off angle after the rising edge of the tube voltage drop of the to-be-triggered thyristor appears, the to-be-triggered thyristor of the non-reference phase is triggered.

[0071] Specifically, based on the principles introduced above, in an embodiment of the present invention, for each non-reference phase, the sum of the original turn-off angle of the next thyristor to be triggered and the trigger moment adjustment value corresponding to the non-reference can be used as the target turn-off angle of the thyristor to be triggered (that is, the trigger moment adjustment value).

[0072] Specifically, referring to FIG3 , the motor control method in the embodiment of the present invention uses the current zero-crossing point as the reference point, i.e., time t2. With t2 as the timing starting point, the thyristor is triggered by delaying the thyristor by an angle γ. Since the motor is an inductive load, the current has "inertia" and the current will cross the zero axis back and forth near the end of the motor's freewheeling. It will be inaccurate to judge the end of the freewheeling by the current value. Therefore, the leading edge (rising edge) of the thyristor's tube voltage drop is selected as the current zero-crossing point, and the thyristor is triggered by delaying a certain time (γ+Δγ) after this point as the reference point. This directly controls the turn-off time of the thyristor. This triggering method is called turn-off angle control.

[0073] As an optional embodiment, taking the target integral value equal to the reference phase as the target, determining the trigger moment adjustment value corresponding to each non-reference phase includes:

[0074] Taking the front-end integral value in the target integral value of the reference phase as equal as the target, respectively determining the front-end adjustment value corresponding to each non-reference phase;

[0075] Taking the latter integral value of the target integral value of the reference phase as equal as the target integral value, respectively determining the latter adjustment value corresponding to each non-reference phase;

[0076] The sum of the front-end adjustment value and the rear-end adjustment value of a single non-reference phase is used as the triggering moment adjustment value of the non-reference phase;

[0077] The target integral value is: the voltage integral value in the current continuous period of the current half cycle, and the target integral value is divided into a front-end integral value and a rear-end integral value by the voltage zero-crossing point.

[0078] Specifically, in Figure 4, when the three-phase voltage is unbalanced, the three-phase unbalanced voltage is integrated within the current continuous period (conduction angle) of half a current cycle. The integral here is represented by "area." Using the "area" of the phase with the smallest voltage amplitude as a reference, the "areas" of the two phases with larger voltage amplitudes are adjusted. Using the "area equality" principle, the thyristor turn-off angle adjustment Δγ of the non-reference phase is calculated. This ensures that the energy received by the three-phase windings is approximately equal, indirectly improving the torque and speed of the motor. Assume that the voltage amplitude of phase A is the smallest and the three-phase voltage frequency is the same. The following uses phase A as a reference and adjusts phase C as an example to illustrate the adjustment process. The adjustment process for phase B is the same as that for phase C.

[0079] Among them, when the voltage is balanced, the corresponding three-phase voltage integral value S x , (x=A,B,C,A-,B-,C-) should be approximately equal. For AC phase, S x for:

[0080] When the power supply voltage is balanced, SA ≈S C ,S A- ≈S C- , that is, S A +S A- ≈S C +S C- ,Furthermore, the effective values ​​of the two-phase AC currents are equal.

[0081] Specifically, when the power supply voltage is unbalanced (the amplitude voltage of phase A is the smallest), that is, |u C |>|u A If the ramp trigger signals of the six thyristors (normally the turn-off angle will continue to decrease and linearly decrease to zero in a ramp shape) decrease at the same rate, there will always be S in the entire startup process, regardless of whether the current is continuous or not. C >S A ,S C- >S A- Because the motor is a symmetrical load, when the motor terminal voltage is not equal, the winding current is naturally not equal, and the main rotating magnetic field is not circular, which causes the torque to fluctuate.

[0082] At the moment when voltage imbalance is detected (at (S A +S A- )、(S B +S B- ) and (S C +S C- ) in the next cycle, the positive and negative "areas" of phase A voltage are used as reference (S A1 ,S A1- is a known value), adjust the C-related broken angle ramp trigger signal (the oblique dotted line in Figure 4 is the starting point for adjusting the C-phase trigger signal).

[0083] Adjusting the signal is a three-step process:

[0084] (1) Step 1: Let S C1 =S A1 (in Calculate the positive "area" corresponding to the cut-off angle adjustment Δt1 = tc7 - tc6, that is, "taking the front-end integral value in the target integral value of the reference phase as the target, and determining the front-end adjustment value corresponding to each non-reference phase respectively."

[0085] (2) Step 2: Let S C1- =S A1- (in Calculate the negative "area" corresponding to the cut-off angle adjustment Δt2 = tc10 -tc9, that is, "taking the latter-stage integral value equal to the target integral value of the reference phase as the target, and determining the latter-stage adjustment value corresponding to each non-reference phase respectively."

[0086] (3) The third step: Let Δt = Δt1 + Δt2. For the thyristor VT2 in the negative half cycle of phase C (i.e. the next thyristor to be triggered), the original triggering is t 11 Time is postponed to t 12 The delay time is Δt, which is the same as the previous "taking the sum of the front adjustment value and the rear adjustment value of a single non-reference phase as the trigger moment adjustment value corresponding to the non-reference phase".

[0087] A similar method is used to adjust thyristor VT5 during the positive half-cycle of phase C. The original triggering is delayed from t13 to t14, and this method is repeated for each subsequent cycle. Since the phase C voltage amplitude is larger, delaying the thyristor triggering ensures consistent RMS values ​​for the AC phase currents, reducing torque ripple.

[0088] Calculation method of Δt1 and Δt2:

[0089] Calculation of Δt1. In actual engineering applications, the feasibility of the algorithm is also taken into consideration. Here is the calculation method of Δt1. Because phase A is ahead of phase C, before the thyristor trigger signal of phase C arrives, the "area" S A1 can be calculated in advance. The lower limit of the integral is unknown, u C (t) is unknown, and Δt1 must be calculated in advance of tc6. It is unrealistic to calculate the adjustment value of the "future" moment with unknown quantities. Here, although the three-phase voltage amplitudes are different, the voltage waveform within half a cycle is still symmetrical. The "right side area" S of the half cycle can be C1 pass (k is an odd number) axisymmetric to the "area on the left", that is, the tc4~tc5 interval of phase C.

[0090] Let S C1 =S A1 , calculate tc5-tc4, then tc5-tc4=tc8-tc7, then Δt1=0.5Ts-tc6-(tc5-t4), T s is the voltage cycle.

[0091] Calculation of Δt2: The value of Δt2 is used at time t11, let S C1- =S A1- , calculate tc9 (integral upper limit), the unadjusted freewheeling angle tc10 of the C-phase thyristor can be directly read, and Δt2=tc10 can be directly calculated -tc9.

[0092] Specifically, the method for adjusting the turn-off angle of the thyristor of phase C is given above with phase A as a reference. The adjustment method of phase B is the same as that of phase C.

[0093] As an optional embodiment, after determining the front-end adjustment value corresponding to each non-reference phase respectively by setting the front-end integral value equal to the target integral value of the reference phase as the target, the motor control method further includes:

[0094] In the first half current cycle for determining three-phase voltage unbalance, the preceding adjustment value of a single non-reference phase is used as the initial adjustment value at the triggering moment of the corresponding non-reference phase;

[0095] For each non-reference phase, the sum of the original triggering time of the initial thyristor to be triggered in the first half current cycle of the three-phase voltage unbalance is determined, and the initial adjustment value of the triggering time corresponding to the non-reference phase is used as the target triggering time of the initial thyristor;

[0096] At the target triggering time of the initial thyristor, the initial thyristor of the non-reference phase is triggered.

[0097] Specifically, referring to FIG4 , it can be seen that, assuming that the three-phase voltage imbalance is determined within the voltage cycle on the left side of the dotted line at the starting point of the slope trigger signal correction, then the right side of the dotted line is the first cycle to be adjusted. Since the motor control method in the foregoing article uses the trigger moment adjustment value calculated in the first half current cycle to adjust the trigger moment of the thyristor to be triggered in the next half current cycle, the first cycle to be adjusted on the right side of the dotted line cannot fully obtain the trigger moment adjustment value (that is, the sum of the front adjustment value and the rear adjustment value) based on the voltage integral data of the previous half current cycle, but the front-end adjustment value can be calculated based on the data of the first half current cycle. Therefore, in order to adjust the trigger moment of the thyristor to be triggered in the first half current cycle of the non-reference phase, the trigger moment adjustment value of the thyristor to be triggered in the first half current cycle is not obtained. The thyristor is regulated and controlled. In an embodiment of the present invention, within the first half current cycle for determining three-phase voltage imbalance, the front-end adjustment value of a single non-reference phase can be used as the initial adjustment value of the triggering moment corresponding to the non-reference phase. Then, for each non-reference phase, the sum of the original triggering moment of the initial thyristor to be triggered within the first half current cycle for determining three-phase voltage imbalance and the initial adjustment value of the triggering moment corresponding to the non-reference phase is used as the target triggering moment of the initial thyristor. At the target triggering moment of the initial thyristor, the initial thyristor of the non-reference phase is triggered. This can achieve regulation of the first thyristor to be triggered after determining three-phase voltage imbalance, thereby better achieving the balance of the effective value of the three-phase current and suppressing torque fluctuation.

[0098] As an optional embodiment, when the three-phase voltage of the three-phase asynchronous motor is unbalanced, using the phase with the smallest effective current value as the reference phase includes:

[0099] When the complex voltage imbalance of the three-phase asynchronous motor is greater than a preset threshold, the phase with the smallest effective current value is used as the reference phase.

[0100] Specifically, considering that the complex voltage imbalance can be used to quickly and accurately determine whether the three-phase voltage is balanced, in an embodiment of the present invention, when the complex voltage imbalance of the three-phase asynchronous motor is greater than a preset threshold, the phase with the smallest current effective value can be used as the reference phase.

[0101] The preset threshold value can be set independently, and is not limited in the embodiment of the present invention.

[0102] As an optional embodiment, the motor control method further includes:

[0103] When the current complex voltage imbalance is greater than a preset threshold, if there is a non-reference phase whose adjustment value is zero at the triggering moment, the alarm is controlled to sound an alarm.

[0104] Specifically, considering that in the case of three-phase voltage imbalance, the trigger moment adjustment value of the non-reference phase should theoretically be greater than zero, therefore, in an embodiment of the present invention, when the current multiple voltage imbalance is greater than a preset threshold, if there is a non-reference phase with a trigger moment adjustment value of zero, the control alarm can be sounded so that the staff can detect the abnormal situation in time and make adjustments to improve the reliability of the control.

[0105] The alarm may be of various types, such as a buzzer, etc., which is not limited in the embodiment of the present invention.

[0106] As an optional embodiment, when the three-phase voltage of the three-phase asynchronous motor is unbalanced, using the phase with the smallest effective current value as the reference phase includes:

[0107] When the three-phase voltage of the three-phase asynchronous motor is unbalanced during the soft start process, the phase with the smallest effective voltage value or the phase with the smallest effective current value is used as the reference phase;

[0108] When the three-phase voltage of the three-phase asynchronous motor is unbalanced after starting, the phase with the smallest effective current value is used as the reference phase.

[0109] Specifically, considering that during the soft start process, the magnitude relationship between the three-phase voltage effective values ​​is consistent with the magnitude relationship between the three-phase current effective values, and after starting, if the voltage imbalance still exists, the magnitude relationship between the three-phase voltage effective values ​​and the magnitude relationship between the three-phase current effective values ​​may be different, so after starting, the phase with the smallest current effective value can be used as the reference phase, and during the starting process, the phase with the smallest voltage effective value or the phase with the smallest current effective value can be used as the reference phase, which further improves the reliability of motor control.

[0110] Specifically, the control effect of the motor control method is also verified in the embodiment of the present invention. Please refer to FIG5 , which is a waveform diagram of a three-phase current root mean square value provided by the present invention. x_rms (x=A, B, C) is the waveform of the RMS value of the single-phase current. The above-mentioned adjustment scheme is implemented at 1.5s. Before 1.5s, the difference in the RMS values ​​of the three-phase currents is more obvious, and the RMS values ​​of the three-phase currents are ranked as follows: B>C>A. In the period from 1.5s to 3.5s, the RMS values ​​of the three-phase currents can be made almost equal through the above-mentioned control scheme. However, there is still an imbalance in the three-phase voltage after starting, that is, in the period after 3.5s in Figure 5, when the above-mentioned control scheme is not adopted, the RMS values ​​of the three-phase currents show obvious differences, and the RMS values ​​of the three-phase currents are ranked as follows: B>A>C. At this time, the phase with the smallest RMS voltage value may still be phase A, but the phase with the smallest RMS current value is phase C. Therefore, in the embodiment of the present invention, the phase with the smallest RMS current value can be used as the reference phase after starting.

[0111] Specifically, to better verify the control effect of the motor control method, please refer to Figure 6, which is a schematic diagram of the effect of a motor control method provided by the present invention. The upper half of Figure 6 is a waveform diagram of the rotor speed of a three-phase asynchronous motor, and the lower half is a waveform diagram of the electromagnetic torque. With respect to the rotor speed, the normal speed waveform is the rotor speed waveform when the three-phase voltage is balanced, and the speed waveform is relatively smooth. However, when the three-phase voltage is unbalanced, the rotor speed waveform is in the form of "unadjusted speed" and the speed waveform has large jitter. After the control process described above in the embodiment of the present invention, an adjusted speed waveform is obtained, which is very consistent with the normal speed waveform. With respect to the electromagnetic torque, the normal torque waveform is the electromagnetic torque waveform when the three-phase voltage is balanced, and the electromagnetic torque fluctuation is small. However, when the three-phase voltage is unbalanced, the electromagnetic torque waveform is in the form of "unadjusted torque" and the steady-state fluctuation can reach 3800Nm, which is large. After the control process described above in the embodiment of the present invention, an adjusted torque waveform is obtained, which is very consistent with the normal torque waveform, and the steady-state fluctuation is as low as 2560Nm.

[0112] Please refer to FIG7 , which is a schematic diagram of the structure of a motor control device provided by the present invention. The motor control device is applied to a controller of a three-phase asynchronous motor, including:

[0113] A first determining module 71 is configured to use a phase with the smallest effective current value as a reference phase when the three-phase voltage of the three-phase asynchronous motor is unbalanced;

[0114] The second determination module 72 is configured to determine the trigger timing adjustment value corresponding to each non-reference phase, with the target integral value being equal to the target integral value of the reference phase as the target; wherein the target integral value is the voltage integral value within the current continuous period of the current half cycle;

[0115] A calculation module 73 is configured to add a triggering time adjustment value corresponding to the non-reference phase to the original triggering time of the next thyristor to be triggered for each non-reference phase to obtain a target triggering time;

[0116] The action module 74 is configured to trigger the to-be-triggered thyristor in the non-reference phase at a target triggering moment of the to-be-triggered thyristor.

[0117] For an introduction to the motor control device provided by an embodiment of the present invention, please refer to the aforementioned embodiment of the motor control method, and the embodiment of the present invention will not be described in detail here.

[0118] Please refer to FIG8 , which is a schematic diagram of the structure of a motor control device provided by the present invention. The motor control device includes:

[0119] Memory 81, for storing computer programs;

[0120] The processor 82 is configured to implement the steps of the motor control method in the aforementioned embodiment when executing the computer program.

[0121] For an introduction to the motor control device provided by the embodiment of the present invention, please refer to the aforementioned embodiment of the motor control method, and the embodiment of the present invention will not be described in detail here.

[0122] The present invention further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the motor control method in the aforementioned embodiment are implemented.

[0123] For an introduction to the computer-readable storage medium provided in an embodiment of the present invention, please refer to the aforementioned embodiment of the motor control method, and the embodiment of the present invention will not be described in detail here.

[0124] In this specification, the various embodiments are described in a progressive manner, with each embodiment focusing on the differences from the other embodiments. Similar or identical parts between the various embodiments may be referred to in conjunction with each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and for relevant parts, reference may be made to the method description. It should also be noted that, in this specification, relational terms such as first and second, etc., are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the process, method, article, or device comprising that element.

[0125] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A motor control method, characterized in that, A controller applied to a three-phase asynchronous motor, comprising: When the three-phase voltages of the three-phase asynchronous motor are unbalanced, taking the phase with the minimum effective current value as the reference phase; Taking the equality with the target integral value of the reference phase as the target, and respectively determining the trigger time adjustment values corresponding to each non-reference phase; wherein, the target integral value is: the voltage integral value within the current continuous time period of the current half cycle; For each of the non-reference phases, adding the trigger time adjustment value corresponding to the non-reference phase to the original trigger time of the next thyristor to be triggered to obtain the target trigger time; At the target trigger time of the thyristor to be triggered, triggering the thyristor to be triggered of the non-reference phase.

2. The motor control method according to claim 1, wherein The step of, for each of the non-reference phases, adding the trigger time adjustment value corresponding to the non-reference phase to the original trigger time of the next thyristor to be triggered to obtain the target trigger time includes: For each of the non-reference phases, taking the sum of the original turn-off angle of the next thyristor to be triggered and the trigger time adjustment value corresponding to the non-reference phase as the target turn-off angle of the thyristor to be triggered; The step of, at the target trigger time of the thyristor to be triggered, triggering the thyristor to be triggered of the non-reference phase includes: At the target turn-off angle after the rising edge of the tube voltage drop of the thyristor to be triggered, triggering the thyristor to be triggered of the non-reference phase.

3. The motor control method according to claim 2, wherein The step of taking the equality with the target integral value of the reference phase as the target and respectively determining the trigger time adjustment values corresponding to each non-reference phase includes: Taking the equality with the front-segment integral value in the target integral value of the reference phase as the target, and respectively determining the front-segment adjustment values corresponding to each non-reference phase; Taking the equality with the rear-segment integral value in the target integral value of the reference phase as the target, and respectively determining the rear-segment adjustment values corresponding to each non-reference phase; Taking the sum of the front-segment adjustment value and the rear-segment adjustment value of a single non-reference phase as the trigger time adjustment value corresponding to the non-reference phase; Wherein, the target integral value is: the voltage integral value within the current continuous time period of the current half cycle, and the target integral value is divided by the voltage zero crossing into the front-segment integral value and the rear-segment integral value.

4. The motor control method according to claim 3, characterized in that After the step of taking the equality with the front-segment integral value in the target integral value of the reference phase as the target and respectively determining the front-segment adjustment values corresponding to each non-reference phase, the motor control method further includes: Within the first half cycle of the current when it is determined that the three-phase voltages are unbalanced, taking the front-segment adjustment value of a single non-reference phase as the initial trigger time adjustment value corresponding to the non-reference phase; For each of the non-reference phases, taking the sum of the original trigger time of the initial thyristor to be triggered within the first half cycle of the current when it is determined that the three-phase voltages are unbalanced and the initial trigger time adjustment value corresponding to the non-reference phase as the target trigger time of the initial thyristor; At the target trigger time of the initial thyristor, triggering the initial thyristor of the non-reference phase.

5. The motor control method according to claim 1, characterized in that The step of, when the three-phase voltages of the three-phase asynchronous motor are unbalanced, taking the phase with the minimum effective current value as the reference phase includes: When the complex voltage unbalance degree of the three-phase asynchronous motor is greater than a preset threshold, the phase with the minimum effective current value is taken as the reference phase.

6. The motor control method according to claim 5, characterized in that, The motor control method further includes: When the current complex voltage unbalance degree is greater than the preset threshold, if there is a non-reference phase with a trigger time adjustment value of zero, the alarm is controlled to give an alarm.

7. The motor control method according to any one of claims 1 to 6, characterized in that The step of taking the phase with the minimum effective current value as the reference phase when the three-phase voltages of the three-phase asynchronous motor are unbalanced includes: When the three-phase voltages of the three-phase asynchronous motor are unbalanced during the soft start process, the phase with the minimum effective voltage value or the phase with the minimum effective current value is taken as the reference phase; When the three-phase voltages of the three-phase asynchronous motor are unbalanced after starting, the phase with the minimum effective current value is taken as the reference phase.

8. A motor control device, characterized in that, A controller applied to a three-phase asynchronous motor includes: A first determination module, configured to take the phase with the minimum effective current value as the reference phase when the three-phase voltages of the three-phase asynchronous motor are unbalanced; A second determination module, configured to take the target integral value equal to that of the reference phase as the target, and respectively determine the trigger time adjustment value corresponding to each non-reference phase; wherein the target integral value is: the voltage integral value within the current continuous current period of half a current cycle; A calculation module, configured to, for each non-reference phase, superimpose the trigger time adjustment value corresponding to the non-reference phase on the original trigger time of the next thyristor to be triggered to obtain the target trigger time; An action module, configured to trigger the thyristor to be triggered of the non-reference phase at the target trigger time of the thyristor to be triggered.

9. A motor control device, characterized in that, including: A memory, configured to store a computer program; A processor, configured to implement the steps of the motor control method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the motor control method according to any one of claims 1 to 7 are implemented.

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