A method and system for controlling an electric machine

Abstract

The application relates to the technical field of motor control, and discloses a motor control method and system, the motor control method comprising the following steps: in the case of detecting the existence of an alternating current zero crossing point, determining the motor's electrical angle increment of the current alternating current zero crossing point relative to the last alternating current zero crossing point; determining the electrical angle of the current alternating current zero crossing point based on the electrical angle of the last alternating current zero crossing point and the electrical angle increment; determining the target phase path that needs to be turned on at present according to the comparison result of the electrical angle of the current alternating current zero crossing point and a plurality of conduction control intervals; and controlling the target phase path to be turned on at the current alternating current zero crossing point. The motor control method can reduce the instantaneous current during motor starting, effectively limit the current impact, reduce the transient stress borne by the channel device, the line and the load body, and realize motor soft starting through accurate electrical angle tracking and zero-crossing-synchronized phase separation conduction control.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and in particular to a motor control method and system. Background Technology

[0002] In industrial power systems, high-power asynchronous motors often employ direct online starting, which involves instantaneously connecting them to the power grid at full voltage via a contactor or solid-state switch. However, direct online starting causes a rapid build-up of current at the moment the three-phase circuit is turned on, resulting in a current waveform that is almost a sudden increase. The load experiences significant electromagnetic and mechanical shocks at the moment of connection, greatly increasing the transient stress on the circuit components, wiring, and the load itself, and significantly reducing system reliability and motor lifespan. Summary of the Invention

[0003] In view of this, embodiments of this application provide a motor control method and system that can effectively improve the problem of large inrush current during motor startup.

[0004] In a first aspect, embodiments of this application provide a motor control method, including: When an AC zero-crossing point is detected in any phase of the motor, the electrical angle increment of the motor relative to the previous AC zero-crossing point is determined based on the three-phase AC frequency of the motor and the operating frequency of the control terminal. The initial electrical angle of the current AC zero-crossing point is obtained by summing the electrical angle increment with the electrical angle of the previous AC zero-crossing point. The initial electrical angle is compensated based on the electrical angle compensation value to obtain the compensated electrical angle. The electrical angle of the current AC zero-crossing point is determined based on the comparison result between the compensated electrical angle and the maximum electrical angle corresponding to the AC cycle. Based on the comparison results of the current AC zero-crossing electrical angle and multiple conduction control intervals, the target phase path that needs to be turned on is determined. The conduction control interval is the advance trigger angle interval relative to the starting boundary of the electrical angle commutation zone within each electrical angle commutation zone. The target phase path is controlled to be turned on when the current AC zero crossing point is reached.

[0005] In a first possible embodiment of the first aspect, determining the electrical angle increment of the motor relative to the previous AC zero-crossing point based on the three-phase AC frequency of the motor and the operating frequency of the control terminal includes: Calculate the ratio of the operating frequency of the control terminal to the frequency of the three-phase AC power to obtain the number of control terminal clock cycles in each AC cycle; The electrical angle increment is obtained by calculating the ratio of the AC cycle to the number of clock cycles in the control terminal.

[0006] In a second possible embodiment of the first aspect, determining the electrical angle of the current AC zero-crossing point based on the comparison result between the compensated electrical angle and the maximum electrical angle corresponding to the AC cycle includes: Under the condition that the compensation electrical angle is greater than or equal to the maximum electrical angle, the difference between the compensation electrical angle and the maximum electrical angle is taken as the electrical angle of the current AC zero-crossing point; When the compensated electrical angle is less than the maximum electrical angle, the compensated electrical angle is taken as the electrical angle of the current AC zero-crossing point.

[0007] In a third possible embodiment of the first aspect, before determining the target phase path to be activated based on the comparison results of the electrical angle of the current AC zero-crossing point and multiple conduction control intervals, the method further includes: The electrical angle of a single AC cycle is divided into multiple electrical angle commutation zones based on a preset interval. The target conduction control quantity is determined based on the number of cycles of the aforementioned AC cycle; Under the condition that the target conduction control amount is less than the preset division interval, the difference between each electrical angle commutation zone and the target conduction control amount is calculated to obtain the minimum value of each conduction control interval; The conduction control interval is obtained by taking the electrical angle commutation region as the maximum value of the corresponding conduction control interval.

[0008] In a fourth possible embodiment of the first aspect, determining the target conduction control quantity based on the number of cycles of the AC cycle includes: Under the condition that the number of cycles is zero, the preset initial conduction control quantity is used as the target conduction control quantity; Under the condition that the number of cycles is greater than zero, the product of the single incremental conduction control quantity and the number of cycles is calculated to obtain the increment of the conduction control quantity; The sum of the increment of the conduction control quantity and the preset initial conduction control quantity is taken as the target conduction control quantity.

[0009] In a fifth possible embodiment of the first aspect, each of the conduction control intervals corresponds to the conduction of a different phase path, and determining the target phase path to be conducted based on the comparison results of the current AC zero-crossing angle and multiple conduction control intervals includes: Under the condition that the electrical angle of the current AC zero-crossing point falls within one of the conduction control intervals, the phase path that is turned on corresponding to the conduction control interval is taken as the target phase path; If the electrical angle of the current AC zero-crossing point does not fall within all of the said conduction control intervals, it is determined that there is no target phase path.

[0010] In a sixth possible embodiment of the first aspect, it further includes: Under the condition that the target conduction control quantity is greater than or equal to the preset division interval, the three-phase path of the motor is controlled to conduct when the current AC zero crossing point is reached; Upon receiving a motor shutdown command, the motor is controlled to stop working, and the target conduction control quantity and the number of AC cycles are initialized to their initial values.

[0011] In a seventh possible embodiment of the first aspect, each phase path of the motor is respectively connected to a thyristor circuit, and controlling the target phase path to conduct at the current AC zero-crossing point includes: A drive signal is sent to the thyristor circuit connected to the target phase path, so that the thyristor circuit turns on the target phase path when it receives the drive signal; Each phase path of the motor is connected to a current sampling circuit and a voltage sampling circuit respectively. Detecting the presence of an AC zero-crossing point in any phase path of the motor includes: The current sampling circuit acquires multiple current sampling values ​​for each phase path, and the voltage sampling circuit acquires multiple voltage differences between the corresponding two connected phase paths. Based on the voltage difference, multiple voltage sample values ​​for each phase path are determined; If the voltage sampling value or the current sampling value of any phase path alternates between positive and negative, the existence of the AC zero-crossing point is determined.

[0012] Secondly, embodiments of this application provide a motor control system, including: a control terminal and a motor; The control terminal is used to execute the above-described motor control method to control the operation of the motor.

[0013] In a first possible embodiment of the second aspect, the motor control system further includes: a plurality of thyristor circuits, a current sampling circuit, and a voltage sampling circuit; Each phase path of the motor is respectively connected to a thyristor circuit and a current sampling circuit, and two phase paths of the motor are respectively connected to a voltage sampling circuit. The thyristor circuit is used to turn on the corresponding connected phase path when a drive signal is received from the control terminal. Each of the current sampling circuits is used to acquire multiple current sampling values ​​of the corresponding connected phase path; Each of the voltage sampling circuits is used to acquire multiple voltage differences between the corresponding connected two-phase paths.

[0014] The embodiments of this application have the following beneficial effects: This embodiment of a motor control method includes: when an AC zero-crossing point is detected in any phase path of the motor, determining the electrical angle increment of the current AC zero-crossing point relative to the previous AC zero-crossing point based on the three-phase AC frequency of the motor and the operating frequency of the control terminal; determining the electrical angle of the current AC zero-crossing point based on the electrical angle of the previous AC zero-crossing point and the electrical angle increment; determining the target phase path to be turned on based on the comparison results of the electrical angle of the current AC zero-crossing point and multiple conduction control intervals, wherein the conduction control interval is the advance trigger angle interval relative to the starting boundary of the electrical angle commutation zone within each electrical angle commutation zone; and controlling the target phase path to be turned on at the current AC zero-crossing point. Based on the above scheme, this motor control method, through precise electrical angle tracking and zero-crossing synchronized phase conduction control, can reduce the instantaneous current during motor startup, effectively limit current surges in the initial stage of load connection, reduce transient stress on channel devices, lines, and the load body, and achieve soft start of the motor. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of a first structure of the motor control system according to an embodiment of this application is shown; Figure 2 A second structural schematic diagram of the motor control system according to an embodiment of this application is shown; Figure 3 A circuit diagram of a thyristor circuit according to an embodiment of this application is shown; Figure 4 A circuit diagram of a current sampling circuit according to an embodiment of this application is shown; Figure 5 A circuit diagram of a voltage sampling circuit according to an embodiment of this application is shown; Figure 6 A schematic flowchart of a first embodiment of the motor control method of this application is shown; Figure 7 A second flowchart of the motor control method according to an embodiment of this application is shown.

[0017] Explanation of key component symbols: 100 - Motor control system; 110 - Control terminal; 120 - Motor; 130 - Thyristor circuit; 140 - Current sampling circuit; 150 - Voltage sampling circuit. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0019] The components of the embodiments of this application described and illustrated in the accompanying drawings can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] In the following text, the terms "comprising," "having," and their cognates, which may be used in various embodiments of this application, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more combinations thereof. Furthermore, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0021] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of this application pertain. Terms (such as those defined in commonly used dictionaries) shall be interpreted as having the same meaning as in their contextual meaning in the relevant technical field and shall not be construed as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of this application.

[0022] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] First, this application provides a motor control system 100. Please refer to... Figure 1 This is a structural block diagram of a motor control system 100 provided in an embodiment of this application. The motor control system 100 may include a control terminal 110 and a motor 120.

[0024] In one embodiment, the control terminal 110 can process information and / or data related to the motor control method to perform one or more functions described in this application. For example, when an AC zero-crossing point is detected in any phase path of the motor 120, the control terminal 110 can determine the electrical angle increment of the motor 120 relative to the previous AC zero-crossing point based on the three-phase AC frequency of the motor 120 and the operating frequency of the control terminal; determine the electrical angle of the current AC zero-crossing point based on the electrical angle and electrical angle increment of the previous AC zero-crossing point; determine the target phase path that needs to be turned on based on the comparison results of the electrical angle of the current AC zero-crossing point and multiple conduction control intervals, wherein the conduction control interval is the advance trigger angle interval relative to the starting boundary of the electrical angle commutation zone within each electrical angle commutation zone; and control the target phase path to be turned on at the current AC zero-crossing point. This enables the motor 120 to achieve a soft start without impact. By accurately tracking the zero-crossing point and dynamically calculating the electrical angle, the corresponding target phase path is triggered within each commutation interval, thereby smoothly establishing the terminal voltage and current, effectively suppressing starting surges, and reducing electromagnetic and mechanical shocks.

[0025] In one embodiment, such as Figure 2 As shown, the motor control system 100 also includes multiple thyristor circuits 130. Exemplarily, each phase path of the motor 120 is connected to a thyristor circuit 130. The thyristor circuit 130 is used to turn on the corresponding connected phase path upon receiving a drive signal sent by the control terminal 110. The phase paths of the motor 120 include three-phase paths: U, V, and W.

[0026] In one implementation, such as Figure 3 As shown, the thyristor circuit 130 includes an anti-parallel thyristor structure, using two thyristors (such as...) Figure 3 As shown, KD1 and KD2 are connected in reverse parallel between the input and output sides of the same phase path, so that they are responsible for the two directions of AC current respectively, realizing bidirectional AC conduction. Figure 3 As shown, the input side is AC line terminal VI, which connects four parallel fuses (such as...). Figure 3 The components F1, F2, F3, and F4 shown serve as overcurrent protection for the main circuit, preventing excessive current from burning out components during short circuits. Output side (e.g., Figure 3 The VO shown is the corresponding phase output port that is sent to the load of motor 120 after being controlled to conduct by the thyristor. Varistors RVA and RVb can be connected to both the output and input sides to absorb surge overvoltage on the input side. The connection node between varistor RVA and RVb is connected to a current-limiting resistor R19 for withstand voltage cutoff.

[0027] The thyristor circuit 130 also includes diodes (such as...) Figure 3As shown in D1 and D2), and multiple current-limiting resistors connected in parallel with diode D1 (such as... Figure 3 R15, R16, R17 (as shown), and multiple current-limiting resistors connected in parallel with diode D2 (such as...) Figure 3 R12, R13, and R14 (shown) are used for reverse voltage clamping to protect the gate from reverse high voltage surges.

[0028] The thyristor circuit 130 also includes an externally configured isolation driver (such as...). Figure 3 The isolation drive optocouplers U1 and U2 shown are used to achieve electrical isolation between the low-voltage side of the control terminal 110 and the high-voltage side of the thyristor, and to drive the gate circuits of the anti-parallel thyristors respectively. Wherein, the low-voltage side: drive signal input terminal (e.g., Figure 3 As shown in Figure O1, a current-limiting resistor R1, a pull-down resistor R2, and a filter capacitor C2 are connected in sequence to ensure a stable drive signal. The isolated drive optocoupler is driven by the drive signal, and after conduction, it triggers the photosensitive thyristor inside the optocoupler. High-voltage side: The output of the isolated drive optocoupler is connected through a resistor network (such as...). Figure 3 The resistors shown are R3, R4, R5, R6, R7, and R8, as well as multiple current-limiting resistors connected in parallel (such as...). Figure 3 R9, R10, and R11 (as shown) drive the gates of thyristors KD1 and KD2.

[0029] The thyristor circuit 130 also includes a snubber protection network: such as Figure 3 Resistors R23 and R24, capacitors C4 and C5, as shown, constitute an RC absorption / buffer network to suppress voltage rise / fall rates and spikes during thyristor turn-off or grid disturbances, preventing false triggering and reducing voltage stress on the device. Specifically, resistor R23 controls current limiting and interference suppression on the input side, while resistor R24 ​​is located in the power loop absorption network to suppress transient overvoltages and the effects of voltage rise / fall rates across the thyristor.

[0030] The thyristor circuit 130 also includes an output current acquisition sub-circuit: the current sampling chip U4 can directly measure the AC circuit current and output an initial current sampling signal. The current sampling chip U4 is powered by power supply VCC, filtered and decoupled by capacitor C2, and the output pin VOUT of the current sampling chip U4 is filtered by resistor R18 and capacitor C3 to output the final current sampling signal (e.g., ...). Figure 3 The lin shown is used by the subsequent control / protection circuit.

[0031] In this embodiment, the drive signal passes through an optocoupler, which then provides a trigger current to the gate of the thyristor through a resistor network, triggering the silicon controlled rectifier (SCR) to conduct. The core characteristics of a thyristor are gate-triggered conduction, latching after conduction, and natural turn-off at zero crossing. In the AC circuit of motor 120, as long as a trigger pulse is given to the gate by the drive signal at the appropriate time, the thyristor will conduct. Even if the drive signal is removed after conduction, it will remain on as long as the main circuit current is greater than the holding current. It will only turn off when the AC current naturally crosses zero. Thus, the characteristics of the thyristor can be used to control the AC current of motor 120.

[0032] In another embodiment, the motor control system 100 further includes a plurality of current sampling circuits 140 and a plurality of voltage sampling circuits 150. Exemplarily, each phase path of the motor 120 is respectively connected to a thyristor circuit 130 and a current sampling circuit 140, and two phase paths of the motor 120 are respectively connected to a voltage sampling circuit 150. Each current sampling circuit 140 is used to acquire multiple current sampling values ​​of the corresponding connected phase path; each voltage sampling circuit 150 is used to acquire multiple voltage differences between the corresponding two connected phase paths.

[0033] In this embodiment, a voltage sampling circuit 150 and a current sampling circuit 140 can be respectively set at the input or output end of each phase path to obtain channel operation information. The control terminal 110 can then determine the AC zero-crossing point of each phase path based on the collected current sampling value and voltage difference.

[0034] In one embodiment, each voltage sampling circuit 150 is used to connect two phase paths and collect the voltage difference between the two phase paths respectively. For example, each voltage sampling circuit 150 collects the voltage difference between UV, VW, and WU, thereby enabling the control terminal 110 to indirectly deduce the voltage of each phase path. The voltage calculation formula for each phase path is:

[0035] In the formula, This indicates the voltage of the U-phase path. This represents the voltage difference between the U-phase path and the V-phase path. This represents the voltage difference between the W-phase path and the U-phase path. This indicates the voltage across phase V. This represents the voltage difference between the V-phase path and the W-phase path. This indicates the voltage of phase W.

[0036] In another embodiment, each voltage sampling circuit 150 has the same circuit structure, which is used to convert the differential AC voltage between two phases into a low-voltage signal that can be collected by the control terminal 110, while realizing overvoltage protection, differential amplification, buffering and filtering, and adapting to the analog-to-digital conversion input of the control terminal 110.

[0037] Taking the voltage sampling circuit 150, which collects the output voltage difference between the U-phase path and the V-phase path, as an example, the voltage sampling circuit 150 first performs a high-impedance voltage divider on the output voltage of the U-phase path and the output voltage of the V-phase path, such as... Figure 4 As shown, the high-voltage divider resistor chain in the U-phase path includes resistors R25, R26, R27, R28, R29, and R30; the high-voltage divider resistor chain in the V-phase path includes resistors R31, R32, R33, R34, R35, and R36. The voltage divider branch in the U-phase path is connected to two anti-parallel Schottky diodes D3, and the voltage divider branch in the V-phase path is connected to two anti-parallel Schottky diodes D4, to prevent overvoltage damage to the op-amp input stage.

[0038] After voltage division, the signal is sent to the two input terminals of operational amplifier U3 to achieve differential input. The non-inverting input terminal of the operational amplifier is connected to the parallel node of resistor R39, resistor R40, and capacitor C10. The inverting input terminal and output terminal of the operational amplifier are both connected to the parallel node of resistor R37, resistor R38, and capacitor C7. The positive power supply terminal of the operational amplifier is grounded through filter capacitor C9, and the negative power supply terminal is grounded through filter capacitor C8. The output signal of the operational amplifier is further divided by the voltage divider network composed of resistors R41 and R42 to a low-voltage signal that can be acquired by control terminal 110 (such as...). Figure 4 As shown in the VREF diagram, the voltage sampling terminal of the control terminal 110 can be connected to the connection node of the voltage divider network and the filter capacitor C11, and the filter capacitor C11 is grounded.

[0039] In another embodiment, the voltage sampling circuit 150 includes a current sensor and a signal processing sub-circuit. The current sensor is used to connect to the input or output terminal of each phase path to collect current signals. The signal processing sub-circuit is used to process the collected current signals to obtain a current analog signal that can be collected by the control terminal 110.

[0040] like Figure 5 As shown, this signal processing sub-circuit processes the current signal (such as...) acquired by the current sensor through voltage divider resistors R43 and R44 and filter capacitor C12. Figure 5The voltage divider and filter (as shown in lin2) are then input to the voltage follower U5. The feedback resistor R45 directly shorts the output and inverting input, creating a unity-gain, non-amplifying / attenuating buffer. Decoupling capacitors C13 and C14 are connected in parallel at the power supply to filter out power supply noise. Resistor R46 and capacitor C15 form a low-pass filter to further filter out high-frequency noise and smooth the signal waveform. The final output current analog signal (such as...) Figure 5 The signal (lin3) shown is fed into the AD (Analog-to-Digital) sampling channel of the control terminal 110. The connection node between the AD sampling channel of the control terminal 110 and capacitor C15 can be connected to two Schottky diodes (such as...) connected in reverse parallel. Figure 5 D5 (shown) is used to prevent abnormal op-amp outputs (such as overshoot or negative voltage) from damaging the input channel of the control terminal 110.

[0041] In this embodiment, the thyristor circuits 130 corresponding to each of the three-phase channels of the motor 120 are all connected to the control terminal 110. The control terminal 110 outputs gate drive signals, which are then isolated and driven to act on the thyristor power devices. The control terminal 110 collects and calculates the three-phase voltage difference and current sampling values ​​to determine the controlled conduction, full conduction, and protection of the three-phase paths.

[0042] For ease of understanding, the following embodiments of this application will be described in terms of... Figure 1 and Figure 2 Taking the motor control system 100 shown as an example, and referring to the accompanying drawings, the motor control method provided in the embodiments of this application will be described.

[0043] Figure 6 A flowchart of a motor control method according to an embodiment of this application is shown. Exemplarily, the motor control method includes the following steps: S210, when an AC zero-crossing point is detected in any phase of the motor 120, the electrical angle increment of the motor 120 relative to the previous AC zero-crossing point is determined based on the three-phase AC frequency of the motor 120 and the operating frequency of the control terminal.

[0044] In one embodiment, the current sampling circuit 140 acquires multiple current sampling values ​​for each phase path, and the voltage sampling circuit 150 acquires multiple voltage differences between corresponding connected two phase paths; based on the voltage differences, multiple voltage sampling values ​​for each phase path are determined. If the voltage or current sampling value of any phase path exhibits alternating positive and negative changes, an AC zero-crossing point is determined to exist.

[0045] In this embodiment, multiple discrete current sampling values ​​of each phase current are independently acquired by the current sampling circuit 140, while the voltage sampling circuit 150 collects the voltage difference between two phase paths, and then calculates the voltage sampling value of each phase. Subsequently, the sign change of the voltage or current sequence of each phase is monitored. Once the adjacent sampling values ​​of a certain phase alternate between positive and negative or negative and positive, it is determined that there is an AC zero-crossing point in that interval, thereby obtaining an AC period reference and realizing high-precision, synchronized multi-phase zero-crossing detection.

[0046] In another embodiment, the ratio of the operating frequency of the control terminal to the frequency of the three-phase AC power is calculated to obtain the number of clock cycles of the control terminal 110 in each AC cycle; the ratio of the AC cycle to the number of clock cycles of the control terminal 110 is calculated to obtain the electrical angle increment.

[0047] For example, the operating frequency of the control terminal refers to the reference clock speed at which the control terminal's master clock or timer samples / interrupts. For instance, if the operating frequency of the control terminal is 6.4 kHz, it means that 6400 sampling, calculation, or control actions are performed per second. The three-phase AC frequency refers to the number of times the three-phase sinusoidal voltage / current waveform completes its periodic alternating change per second. For example, the three-phase AC frequency is calibrated according to 50 Hz.

[0048] In this embodiment, after detecting the zero crossing, the control terminal 110 calculates the electrical angle increment corresponding to each control cycle according to the AC cycle and the number of clock cycles of the control terminal 110, and accumulates and updates the current electrical angle position in each control cycle, which serves as the timing reference for three-phase triggering.

[0049] For example, in one embodiment, a complete AC cycle is considered as 360°. By accurately calculating the ratio of the control terminal's operating frequency (e.g., 6.4 kHz) to the three-phase AC frequency (50 Hz), it is determined that the control terminal 110 can execute 128 control cycles within each AC cycle, i.e., the number of control terminal clock cycles. The 360° electrical angle is then divided into 128 equal parts, resulting in an electrical angle increment of 2.8125°.

[0050] S220, calculate the sum of the electrical angle increment and the electrical angle of the previous AC zero-crossing point to obtain the initial electrical angle of the current AC zero-crossing point.

[0051] In this embodiment, after detecting the AC zero-crossing point of one phase path, the current initial electrical angle position is updated by accumulating this increment at each AC zero-crossing point, thereby achieving continuous and high-resolution electrical angle tracking throughout the entire cycle.

[0052] S230, the initial electrical angle is compensated based on the electrical angle compensation value to obtain the compensated electrical angle, and the electrical angle of the current AC zero crossing point is determined based on the comparison result between the compensated electrical angle and the maximum electrical angle corresponding to the AC cycle.

[0053] In one embodiment, the formula for calculating the compensation electrical angle is:

[0054] This indicates the compensation electric angle at the current AC zero-crossing point. This represents the electrical angle at the zero point of the previous alternating current. This represents the electrical angle compensation value. The electrical angle compensation value is set according to the actual situation and is used to correct the electrical angle deviation caused by inherent system delays and measurement errors, such as ADC sampling delay, digital filter group delay, zero-crossing comparison lag, and hardware signal transmission delay. Indicates the operating frequency of the control terminal. Indicates the frequency of three-phase alternating current. Indicates the communication cycle.

[0055] In another embodiment, when the compensated electrical angle is greater than or equal to the maximum electrical angle corresponding to the AC cycle, the difference between the compensated electrical angle and the maximum electrical angle is taken as the electrical angle of the current AC zero-crossing point. When the compensated electrical angle is less than the maximum electrical angle, the compensated electrical angle is taken as the electrical angle of the current AC zero-crossing point.

[0056] In this embodiment, the electrical angle value is always kept within the electrical angle range of the AC cycle (e.g., 0°~360°). Since the electrical angle continuously increases through the accumulation of compensation values, long-term operation may exceed the electrical angle range of the AC cycle, such as reaching 365° or 722°. Therefore, when the compensated electrical angle is greater than or equal to the maximum electrical angle corresponding to the AC cycle, i.e., greater than or equal to 360°, the maximum electrical angle is subtracted and the angle is rolled back, thus avoiding judgment logic errors caused by angle overflow.

[0057] S240, based on the comparison results of the current AC zero-crossing electrical angle and multiple conduction control intervals, determine the target phase path that needs to be turned on. The conduction control interval is the advance trigger angle interval relative to the starting boundary of the electrical angle commutation zone within each electrical angle commutation zone.

[0058] In one embodiment, the electrical angle commutation zone is an electrical angle reference sector defined based on the motor's 120° back EMF or the grid voltage phase. The electrical angle of a single AC cycle is divided into multiple electrical angle commutation zones based on a preset interval. In this embodiment, the electrical angle of a complete AC cycle is uniformly divided into several discrete electrical angle commutation zones according to a preset interval, and each electrical angle commutation zone constitutes an independent commutation decision unit. For example, if the preset interval is 60°, the corresponding electrical angle commutation zones are 60°, 120°, 180°, 240°, 300°, and 360°.

[0059] Exemplary, the conduction control interval determines how much angle in advance the thyristor is triggered within each electrical angle commutation zone. Each electrical angle commutation zone is equivalent to a natural commutation boundary, and a certain conduction control amount must be applied before the boundary to trigger the thyristor. The larger the conduction control amount, the earlier the thyristor turns on. During the soft start of motor 120, the thyristor is not triggered within the electrical angle commutation zone, but rather triggered by the conduction control amount applied in advance at that point. The larger the conduction control amount, the earlier the thyristor turns on, and the longer the proportion of conduction time within a single cycle, i.e., the equivalent conduction interval. For example, in a 60° electrical angle commutation zone, if triggered 30° in advance, the conduction lasts for approximately 30° of electrical angle; if triggered only 10° in advance, the conduction lasts for only approximately 10°. Since the output voltage waveform of motor 120 is the integral average of the input sinusoidal voltage within the conduction interval, the wider the conduction interval, the higher the average voltage obtained by the load within one cycle, i.e., the equivalent DC voltage or effective value, thus driving a larger current. Therefore, by adjusting the electrical angle commutation zone, the output power can be continuously and steplessly adjusted to achieve 120 soft start of the motor.

[0060] In one embodiment, the target conduction control quantity is determined based on the number of cycles of the AC cycle. When the number of cycles is zero, the preset initial conduction control quantity is used as the target conduction control quantity. When the number of cycles is greater than zero, the product of the single incremental conduction control quantity and the number of cycles is calculated to obtain the incremental value of the conduction control quantity. The sum of the incremental value of the conduction control quantity and the preset initial conduction control quantity is used as the target conduction control quantity.

[0061] In this embodiment, the number of cycles is counted in units of AC cycles. When the number of cycles is zero, such as during the first power-on or restart, a preset small conduction control value, such as 28 degrees, is directly used to ensure a low-impact start-up. When the number of cycles is greater than zero, the number of cycles and the single incremental conduction control value are linearly accumulated. The formula for calculating the target conduction control value is:

[0062] Indicates the first The target conduction control quantity at the next loop iteration. This indicates the preset initial conduction control value. Indicates the number of loops. This indicates the single-increment conduction control amount, which can be set according to the actual situation. For example, the single-increment conduction control amount can be set to 0.2 degrees.

[0063] It is understandable that the target conduction control quantity gradually increases according to the AC cycle from the start of the motor at 120, so that the actual triggering time of the thyristor is gradually moved forward, that is, the conduction time is gradually extended, so that the output voltage / current rises smoothly and without impact from near zero to the rated value, effectively suppressing the starting surge current and mechanical shock.

[0064] In one embodiment, under the condition that the target conduction control amount is less than the preset interval, the difference between each electrical angle commutation zone and the target conduction control amount is calculated to obtain the minimum value of each conduction control interval. The electrical angle commutation zone is taken as the maximum value of the corresponding conduction control interval to obtain the conduction control interval.

[0065] In this embodiment, to avoid overlap or exceeding of the target conduction control value between the electrical angle commutation zone and the target conduction control value, the target conduction control value is offset in the negative direction based on the electrical angle commutation zone, provided that the target conduction control value is less than the preset interval. This results in the minimum value of the conduction control interval, and the maximum value is obtained using the electrical angle commutation zone as the maximum value, thus forming a conduction control interval with a width equal to the target conduction control value. This ensures that only one effective trigger window exists within each commutation zone, and the window position dynamically scales with the target conduction control value. The smaller the target conduction control value, the narrower the window and the later the trigger. As the target conduction control value increases, the window moves in the negative direction and widens, eventually approaching the natural commutation boundary.

[0066] In another embodiment, if the electrical angle of the current AC zero-crossing point falls within one of the conduction control intervals, the phase path corresponding to the conduction control interval is taken as the target phase path; if the electrical angle of the current AC zero-crossing point does not fall within all conduction control intervals, it is determined that there is no target phase path.

[0067] In this embodiment, the control terminal 110 compares the current AC zero-crossing angle with the conduction control interval to determine whether to enter the corresponding trigger window. Each conduction control interval corresponds to the conduction of different phase paths. For example, when the current AC zero-crossing angle falls near [60-duty, 60], drive signals for phases W and U are output; when it falls near [120-duty, 120], drive signals for phases V and W are output; when it falls near [180-duty, 180], drive signals for phases U and V are output; when it falls near [240-duty, 240], drive signals for phases W and U are output; when it falls near [300-duty, 300], drive signals for phases V and W are output; when it falls near [360-duty, 360], drive signals for phases U and V are output. "Duty" represents the target conduction control amount.

[0068] S250 controls the target phase path to conduct when the current AC zero crossing point.

[0069] In one embodiment, a drive signal is sent to the thyristor circuit 130 connected to the target phase path, so that the thyristor circuit 130 turns on the target phase path when it receives the drive signal.

[0070] In this embodiment, when the triggering condition is met, i.e., the electrical angle of the current AC zero-crossing point falls within the corresponding conduction control interval, the control terminal 110 controls and outputs the corresponding drive signal for the two target phase paths, causing the thyristors in the relevant thyristor circuit 130 to be controlled and turned on. When the triggering window condition is not met, the system waits for the next trigger interval. This method conforms to the working characteristics of thyristor trigger-on and zero-crossing turn-off, and can complete the controlled connection of AC load without using mechanical contact hard switching.

[0071] In one embodiment, such as Figure 7 As shown, the motor control method also includes the following steps: S260, under the condition that the target conduction control quantity is greater than or equal to the preset interval, the three-phase path of the control motor 120 is turned on when the current AC zero crossing point is reached.

[0072] In this embodiment, to ensure a smooth transition between soft start and steady-state operation, a stage switching logic is set: when the target conduction control quantity is less than the preset division interval, the soft start mode of selecting two-phase combination conduction by interval is adopted; when the target conduction control quantity increases to the preset division interval, the control terminal 110 switches to three-phase full conduction output.

[0073] S270, upon receiving a command to shut down motor 120, controls motor 120 to stop working and initializes the target conduction control quantity and the number of AC cycles to their initial values.

[0074] In this embodiment, if a motor 120 shutdown command is received, after the motor 120 stops working, the target conduction control quantity is initialized to a preset initial conduction control quantity, and the number of AC cycles is initialized to zero, so as to re-establish the initial conditions for the next start of the motor 120.

[0075] This application also provides a control terminal 110, which, by way of example, includes a processor and a memory, wherein the memory stores a computer program, and the processor executes the computer program to enable the control terminal 110 to perform the above-described motor control method.

[0076] The processor can be an integrated circuit chip with signal processing capabilities. The processor can be a general-purpose processor, including at least one of a Central Processing Unit (CPU), Graphics Processing Unit (GPU), Network Processor (NP), Digital Signal Processor (DSP), Application-Specific Integrated Circuit (ASIC), Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The general-purpose processor can be a microprocessor or any conventional processor, capable of implementing or executing the methods, steps, and logic block diagrams disclosed in the embodiments of this application.

[0077] Memory can be, but is not limited to, Random Access Memory (RAM), Read Only Memory (ROM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (EPROM), and Electrically Erasable Programmable Read-Only Memory (EEPROM). Memory is used to store computer programs, and the processor can execute these programs upon receiving execution instructions.

[0078] This application also provides a computer-readable storage medium for storing the computer program used in the control terminal 110 described above. For example, the computer-readable storage medium may include, but is not limited to, various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0079] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the flowcharts and block diagrams in the accompanying drawings show the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code, which contains one or more executable instructions for implementing a specified logical function. It should also be noted that, as an alternative implementation, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0080] In addition, the functional modules or units in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0081] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a smartphone, personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0082] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A motor control method, characterized in that, include: When an AC zero-crossing point is detected in any phase of the motor, the electrical angle increment of the motor relative to the previous AC zero-crossing point is determined based on the three-phase AC frequency of the motor and the operating frequency of the control terminal, including: Calculate the ratio of the operating frequency of the control terminal to the frequency of the three-phase AC power to obtain the number of control terminal clocks in each AC cycle; calculate the ratio of the AC cycle to the number of control terminal clocks to obtain the electrical angle increment. The initial electrical angle of the current AC zero-crossing point is obtained by summing the electrical angle increment with the electrical angle of the previous AC zero-crossing point. The initial electrical angle is compensated based on the electrical angle compensation value to obtain the compensated electrical angle. The electrical angle of the current AC zero-crossing point is determined based on the comparison result between the compensated electrical angle and the maximum electrical angle corresponding to the AC cycle, including: When the compensation electrical angle is greater than or equal to the maximum electrical angle, the difference between the compensation electrical angle and the maximum electrical angle is taken as the electrical angle of the current AC zero-crossing point; when the compensation electrical angle is less than the maximum electrical angle, the compensation electrical angle is taken as the electrical angle of the current AC zero-crossing point. The electrical angle of a single AC cycle is divided into multiple electrical angle commutation zones based on a preset interval; a target conduction control quantity is determined based on the number of cycles of the AC cycle; under the condition that the target conduction control quantity is less than the preset interval, the difference between each electrical angle commutation zone and the target conduction control quantity is calculated to obtain the minimum value of each conduction control interval; the electrical angle commutation zone is taken as the maximum value of the corresponding conduction control interval to obtain the conduction control interval. Based on the comparison results between the current AC zero-crossing electrical angle and multiple conduction control intervals, the target phase path that needs to be turned on is determined. The conduction control interval is the advance trigger angle interval relative to the starting boundary of the electrical angle commutation zone within each electrical angle commutation zone. The target phase path is controlled to be turned on when the current AC zero crossing point is reached.

2. The motor control method according to claim 1, characterized in that, Determining the target conduction control quantity based on the number of cycles of the AC cycle includes: Under the condition that the number of cycles is zero, the preset initial conduction control quantity is used as the target conduction control quantity; Under the condition that the number of cycles is greater than zero, the product of the single incremental conduction control quantity and the number of cycles is calculated to obtain the increment of the conduction control quantity; The sum of the increment of the conduction control quantity and the preset initial conduction control quantity is taken as the target conduction control quantity.

3. The motor control method according to claim 1, characterized in that, Each of the aforementioned conduction control intervals corresponds to the conduction of different phase paths. The determination of the target phase path to be conducted based on the comparison results between the electrical angle of the current AC zero-crossing point and multiple conduction control intervals includes: Under the condition that the electrical angle of the current AC zero-crossing point falls within one of the conduction control intervals, the phase path that is turned on corresponding to the conduction control interval is taken as the target phase path; If the electrical angle of the current AC zero-crossing point does not fall within all of the said conduction control intervals, it is determined that there is no target phase path.

4. The motor control method according to claim 2, characterized in that, Also includes: Under the condition that the target conduction control quantity is greater than or equal to the preset division interval, the three-phase path of the motor is controlled to conduct when the current AC zero crossing point is reached; Upon receiving a motor shutdown command, the motor is controlled to stop working, and the target conduction control quantity and the number of AC cycles are initialized to their initial values.

5. The motor control method according to claim 1, characterized in that, Each phase path of the motor is connected to a thyristor circuit, and controlling the target phase path to conduct when the current AC zero-crossing point is achieved includes: A drive signal is sent to the thyristor circuit connected to the target phase path, so that the thyristor circuit turns on the target phase path when it receives the drive signal; Each phase path of the motor is connected to a current sampling circuit and a voltage sampling circuit respectively. Detecting the presence of an AC zero-crossing point in any phase path of the motor includes: The current sampling circuit acquires multiple current sampling values ​​for each phase path, and the voltage sampling circuit acquires multiple voltage differences between the corresponding two connected phase paths. Based on the voltage difference, multiple voltage sample values ​​for each phase path are determined; If the voltage sampling value or the current sampling value of any phase path alternates between positive and negative, the existence of the AC zero-crossing point is determined.

6. A motor control system, characterized in that, include: Control terminal and motor; The control terminal is used to execute the motor control method as described in any one of claims 1-5 to control the operation of the motor.

7. The motor control system according to claim 6, characterized in that, Also includes: Multiple thyristor circuits, current sampling circuits, and voltage sampling circuits; Each phase path of the motor is respectively connected to a thyristor circuit and a current sampling circuit, and two phase paths of the motor are respectively connected to a voltage sampling circuit. The thyristor circuit is used to turn on the corresponding connected phase path when a drive signal is received from the control terminal. Each of the current sampling circuits is used to acquire multiple current sampling values ​​of the corresponding connected phase path; Each of the voltage sampling circuits is used to acquire multiple voltage differences between the corresponding connected two-phase paths.

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