Permanent magnet synchronous motor starting control method, permanent magnet synchronous motor system and storage medium

Abstract

The application provides a starting control method of a permanent magnet synchronous motor, a permanent magnet synchronous motor system and a storage medium, and the method comprises the following steps: turning off all upper bridge arm power switch tubes of a three-phase inverter; selecting the maximum value in three-phase current effective values as a maximum current effective value; obtaining a current error by subtracting a preset phase current limit value from the maximum current effective value, and outputting a current compensation value after PI adjustment of the current error according to the current error; obtaining a voltage error by subtracting a preset bus voltage limit value from a bus voltage instantaneous value and then superimposing the current compensation value, and outputting a conduction duty cycle of lower bridge arm power switch tubes of the three-phase inverter after PI adjustment of the voltage error according to the voltage error; and when the motor speed is confirmed to have been reduced to a safe range according to the conduction duty cycle and the maximum current effective value, performing a zero vector braking operation. The application can quickly brake the motor, and meanwhile, short-circuit current impact during zero vector braking is avoided.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet synchronous motor technology, specifically to a starting control method for a permanent magnet synchronous motor, a permanent magnet synchronous motor system using the starting control method, and a computer-readable storage medium using the starting control method. Background Technology

[0002] With increasingly stringent energy conservation and environmental protection requirements, high-efficiency and energy-saving permanent magnet synchronous motors (PMSMs) are gradually replacing traditional brushed DC motors and asynchronous motors, becoming the mainstream choice for wind turbine drive systems. When using sensorless vector control (FOC), the starting performance of a PMSM is extremely sensitive to the initial rotor position and speed. When the wind turbine is in standby or power-off state, external natural wind or internal system airflow will cause the fan blades to rotate freely, creating a tailwind (same direction as the target direction) or headwind (opposite direction to the target direction) state. If the traditional three-stage starting process (positioning, open-loop, closed-loop) is followed at this time, serious problems such as starting failure, overcurrent protection failure, loss of synchronization, and even damage to the motor and controller are highly likely to occur.

[0003] To overcome these shortcomings, existing motor starting solutions require the motor to be positioned using zero-vector braking control before starting. However, zero-vector braking dissipates rotational mechanical energy by directly short-circuiting the lower arm of the three-phase inverter, utilizing the motor's internal resistance. This generates a large current at the moment of short-circuiting, impacting the power module and motor and easily damaging components.

[0004] Therefore, a more optimized motor starting control method needs to be considered. Summary of the Invention

[0005] The first objective of this invention is to provide a starting control method for a permanent magnet synchronous motor that can brake the motor quickly while avoiding short-circuit current impact during zero-vector braking.

[0006] The second objective of this invention is to provide a permanent magnet synchronous motor system that can brake the motor quickly while avoiding short-circuit current impact during zero-vector braking.

[0007] A third objective of this invention is to provide a computer-readable storage medium that can rapidly brake a motor while avoiding short-circuit current surges during zero-vector braking.

[0008] To achieve the aforementioned first objective, the starting control method for a permanent magnet synchronous motor provided by the present invention includes: when the permanent magnet synchronous motor receives a starting command, turning off all upper bridge arm power switches of the three-phase inverter to put the motor windings in a freewheeling state; sampling in real time to obtain the instantaneous values ​​of the three-phase phase currents and the bus voltage, and calculating the effective values ​​of the three-phase phase currents based on the instantaneous values ​​of the three-phase phase currents, selecting the maximum value among the effective values ​​of the three-phase phase currents as the maximum effective value of the current; subtracting the preset phase current limit value from the maximum effective value of the current to obtain the current error, and outputting the current compensation value after adjusting the current limit PI based on the current error; subtracting the preset bus voltage limit value from the instantaneous value of the bus voltage and then superimposing the current compensation value to obtain the voltage error, and outputting the duty cycle of the lower bridge arm power switches of the three-phase inverter after adjusting the voltage limit PI based on the voltage error; and performing zero-vector braking operation when it is confirmed that the motor speed has dropped to a safe range based on the duty cycle and the maximum effective value of the current.

[0009] As can be seen from the above scheme, in the starting control method of the permanent magnet synchronous motor of the present invention, after the motor receives the starting command, the upper bridge arm is completely shut off first, and the winding forms a freewheeling circuit. The complete driving voltage is not applied instantaneously, which avoids the instantaneous large inrush current caused by directly outputting the driving vector when the rotor position is unknown and the back EMF is extremely low in the initial stage of starting. Simultaneously, a dual closed-loop PI control is implemented using a phase current limiting loop and a bus voltage limiting loop. The voltage loop limits the bus voltage, and the current loop feedback limits the short-circuit current, enabling rapid braking. Zero-vector braking is only performed when the motor speed is reduced to a safe range, preventing the generation of large currents and avoiding the impact of short-circuit current.

[0010] In a further proposed solution, the current compensation value is obtained using the following formula: ;in, For the current period Current error under, This is the current compensation value. This is the phase current limit value. This is the effective value of the maximum current. This is the proportionality coefficient of the current loop. The integral coefficient of the current loop is... This represents the instantaneous value of the bus voltage.

[0011] Therefore, by using a discrete-periodic proportional-integral (PI) algorithm to solve for the current compensation value in real time, and using the difference between the effective value of the maximum phase current and the preset phase current limit value as the current error input to the PI regulator, the current of the motor's three-phase windings can be continuously constrained within a safe threshold. Simultaneously, setting an upper limit constraint on the bus voltage amplitude for the current compensation value avoids current loop integral saturation and prevents duty cycle and current oscillations caused by voltage limit PI regulator input overflow.

[0012] In a further scheme, the duty cycle is obtained by the following formula: ;in, For the current period Voltage error under, This is the bus voltage limit value. This is the instantaneous value of the bus voltage. This is the current compensation value. To enable the duty cycle, This is the proportional gain of the voltage loop. This represents the coefficient of the voltage loop integral element.

[0013] Therefore, directly superimposing the current compensation value output from the current loop onto the bus voltage deviation to construct the voltage error can quickly correct the voltage regulation reference during current overload, prioritizing the reduction of the lower bridge arm's duty cycle to suppress inrush current. Furthermore, the voltage loop uses a discrete periodic proportional-integral algorithm to solve for the lower bridge arm's duty cycle, ensuring that the bus voltage and winding current remain stably near preset safety limits during steady-state motor operation. Simultaneously, setting a maximum value limit constraint on the output duty cycle avoids integral saturation of the voltage loop, preventing continuous overcurrent in the windings caused by exceeding the duty cycle limit.

[0014] In a further scheme, the step of confirming that the motor speed has dropped to a safe range based on the duty cycle and the effective value of the maximum current includes: when the duty cycle is greater than the preset duty cycle and the effective value of the maximum current is less than the preset current value, it is determined that the motor speed has dropped to a safe range.

[0015] Therefore, by using the duty cycle and the effective value of the maximum current to jointly determine the motor speed, the motor speed is confirmed to have dropped to a safe range only when both conditions are met: the duty cycle is greater than the preset duty cycle and the effective value of the maximum current is less than the preset current value. This can avoid false braking caused by a slight increase in the duty cycle under high-speed conditions, and avoid braking delay caused by continuous overcurrent under heavy load and low speed, thus improving the accuracy of speed determination.

[0016] In a further proposed scheme, the preset duty cycle ranges from 0.85 to 0.98; the preset current value is less than 1.5 times the rated current of the motor.

[0017] Therefore, limiting the preset duty cycle to the range of 0.85 to 0.98 ensures that the lower bridge arm of the voltage loop can only enter the high duty cycle range when the motor speed drops significantly and the back electromotive force decays sufficiently, thus distinguishing between medium- and high-speed operating conditions and low-speed operating conditions. Simultaneously, limiting the preset current value to less than 1.5 times the motor's rated current, this threshold matches the short-term safe current carrying capacity of the windings and power switches, effectively shielding heavy-load, high-current, low-speed operating conditions from braking trigger conditions.

[0018] In a further proposed solution, when performing zero-vector braking, the following steps are also included: continuously monitoring the phase current of the motor, and exiting zero-vector braking when the phase current is detected to be stable and less than the hardware protection threshold.

[0019] Therefore, it can be seen that during the execution of zero-vector braking, the motor phase current is continuously collected in real time, and the zero-vector braking mode is exited only when the phase current tends to stabilize and the phase current amplitude is less than the hardware protection threshold. This can ensure that the motor decelerates sufficiently and avoid the heat loss of the windings and power switching tubes caused by long-term ineffective braking.

[0020] In a further scheme, after performing the zero-vector braking operation, the method further includes: applying a fixed d-axis current of a preset amplitude to the motor winding to generate a positioning torque that forcibly pulls the motor rotor to a preset zero electrical angle position, and using the zero electrical angle position as the initial reference position for subsequent startup; after positioning is completed, executing IF open-loop control to accelerate the motor rotor from rest to a preset speed; when the motor speed reaches a preset closed-loop cut-in speed threshold, switching the control strategy from IF open-loop control to field-oriented closed-loop control.

[0021] Therefore, after zero-vector braking is completed, a fixed d-axis current of a preset amplitude is applied to the motor windings. A constant positioning torque is used to force the rotor to a uniform zero electrical angle, providing a precise initial reference position for subsequent motor startup. After the rotor is positioned at zero degrees, open-loop IF control is used to gradually accelerate the rotor from rest to the preset speed. IF open-loop control does not rely on weak low-speed back EMF for angle observation, adapting to the zero-speed to low-to-medium speed acceleration range and reducing the inrush current during low-speed acceleration. When the motor speed reaches the closed-loop cutoff speed threshold, the IF open-loop control switches to field-oriented closed-loop control. At this point, the back EMF amplitude of the motor is sufficient, and the rotor angle observation accuracy meets the requirements of closed-loop control.

[0022] In a further proposed solution, the effective value of the maximum current is obtained by the following formula: ;in, This is the effective value of the phase current of phase A. This represents the instantaneous value of the phase current in phase A. This is the effective value of the phase current in phase B. This represents the instantaneous value of the phase current in phase B. This is the effective value of the C-phase current. This represents the instantaneous value of the C-phase current. This is the effective value of the maximum current.

[0023] Therefore, by using the N-point sliding window root mean square formula to independently calculate the effective values ​​of the phase currents of phases A, B, and C, and selecting the maximum effective value among the three phase currents as the maximum effective value of the current loop feedback, the high-frequency current ripple caused by the PWM switch can be effectively filtered out, and the instantaneous current spike can be avoided from interfering with the regulation loop.

[0024] To achieve the second objective of the present invention, the present invention provides a permanent magnet synchronous motor system including a processor and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, it implements the steps of the above-described starting control method for the permanent magnet synchronous motor.

[0025] To achieve the third objective of the present invention, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a controller, implements the steps of the above-described starting control method for a permanent magnet synchronous motor. Attached Figure Description

[0026] Figure 1 This is a flowchart of an embodiment of the starting control method for the permanent magnet synchronous motor of the present invention.

[0027] Figure 2 This is a schematic diagram of an embodiment of the starting control method for a permanent magnet synchronous motor according to the present invention.

[0028] Figure 3 This is a flowchart of the zero-vector braking operation performed in an embodiment of the starting control method for a permanent magnet synchronous motor of the present invention.

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0030] Example of a starting control method for a permanent magnet synchronous motor: The starting control method for the permanent magnet synchronous motor of the present invention is an application program used in a permanent magnet synchronous motor system to control the starting of the permanent magnet synchronous motor. In this embodiment, the permanent magnet synchronous motor system adopts a permanent magnet synchronous motor driven by a three-phase inverter.

[0031] like Figure 1 and Figure 2As shown, in this embodiment, the starting control method for the permanent magnet synchronous motor first executes step S1. When the permanent magnet synchronous motor receives the starting command, it turns off all the upper bridge arm power switches of the three-phase inverter, putting the motor windings in a freewheeling state. During the initial starting stage, the rotor position is unknown, and the back electromotive force is extremely low. If the upper and lower bridge arms are simultaneously turned on to output drive vectors, the bus voltage will be directly applied to the winding inductance, generating a large surge current that can easily cause overcurrent damage to the power transistors. Therefore, when the permanent magnet synchronous motor receives the starting command, the controller outputs a blocking signal to turn off all the upper bridge arm power switches of the A, B, and C phases of the three-phase inverter, disconnecting the power supply path from the positive DC bus to the motor windings. Since the three-phase motor windings are inductive components, the inductance stores magnetic field energy, preventing the phase current from disappearing instantaneously. After turning off all the upper bridge arms, the windings can form a closed freewheeling circuit through the lower bridge arm power switches of each phase or their reverse-parallel freewheeling diodes, ensuring the windings are always in a continuous freewheeling state. In this state, the controller can constrain the magnitude of the winding freewheeling current simply by adjusting the duty cycle of the lower bridge arm power transistor, thereby avoiding the generation of a huge inrush current by directly applying the bus voltage when the rotor position is unknown and the back EMF is weak in the early stage of startup.

[0032] After turning off all the upper arm power switches of the three-phase inverter, step S2 is executed to obtain the instantaneous values ​​of the three-phase current and the bus voltage of the motor in real time. The effective values ​​of the three-phase current are calculated based on these instantaneous values, and the maximum value among them is selected as the maximum effective current value. The motor system controller samples the instantaneous values ​​of the three-phase current (A, B, and C) and the DC bus voltage in real time during each control cycle and performs analog-to-digital conversion. In this embodiment, an N-point sliding window root mean square operation is used to calculate the effective value of each phase current. High-frequency current ripple generated by the PWM switch is filtered out by averaging across multiple sampling points, eliminating instantaneous current spike interference, and outputting the equivalent effective current value of the output winding and power switch thermal load. After obtaining the effective values ​​of the three phase currents, the maximum value among them is selected as the maximum effective current value.

[0033] Specifically, the effective value of the maximum current is obtained by the following formula: ; in, This is the effective value of the phase current of phase A. This represents the instantaneous value of the phase current in phase A. This is the effective value of the phase current in phase B. This represents the instantaneous value of the phase current in phase B. This is the effective value of the C-phase current. This represents the instantaneous value of the C-phase current. This is the effective value of the maximum current.

[0034] By using the N-point sliding window root mean square formula, the effective values ​​of the phase currents of phases A, B, and C are calculated independently, and the maximum value among the three effective values ​​of the phase currents is selected as the maximum effective value of the current loop feedback. This can effectively filter out the high-frequency current ripple caused by the PWM switch and avoid instantaneous current spikes interfering with the regulation loop.

[0035] After obtaining the maximum effective current value, step S3 is executed. The current error is obtained by subtracting the preset phase current limit value from the maximum effective current value. Based on the current error, the current limit PI regulator is adjusted, and the current compensation value is output. The current error is obtained by calculating the difference between the preset phase current limit value and the real-time obtained maximum effective current value. This current error can intuitively reflect the degree to which the maximum equivalent current of the three-phase winding deviates from the safe current limiting threshold. The current error is input into the current limit PI regulator for proportional-integral calculation. The proportional component quickly outputs a dynamic correction amount based on the current error of the current cycle to suppress sudden inrush overcurrent.

[0036] In this embodiment, the current compensation value is obtained by the following formula: ; in, For the current period Current error under, This is the current compensation value. This is the phase current limit value. This is the effective value of the maximum current. This is the proportionality coefficient of the current loop. The integral coefficient of the current loop is... This represents the instantaneous value of the bus voltage.

[0037] The current compensation value is solved in real time using a discrete periodic proportional-integral algorithm. The difference between the effective value of the maximum phase current in the three phases and the preset phase current limit value is used as the current error input to the PI regulator, which can continuously constrain the current of the motor's three-phase windings within a safe threshold. At the same time, an upper limit constraint on the bus voltage amplitude is set on the current compensation value to avoid current loop integral saturation and prevent duty cycle and current oscillations caused by voltage limit PI regulator input overflow.

[0038] After obtaining the current compensation value, step S4 is executed. The preset bus voltage limit value is subtracted from the instantaneous bus voltage value, and then the current compensation value is added to obtain the voltage error. Based on the voltage error, the voltage limit PI regulation is performed, and the duty cycle of the lower arm power switch of the three-phase inverter is output. In order to drive the lower arm power switch to achieve braking deceleration, the corresponding duty cycle needs to be obtained. During this stage, all upper arm power switches of the three-phase inverter are kept off throughout, and the conduction time of the three-phase lower arm power switches is controlled solely by the output duty cycle. The larger the duty cycle, the longer the conduction time of the lower arm power switch, the higher the conduction degree of the winding freewheeling circuit, and the faster the inertial mechanical energy of the motor is consumed. The smaller the duty cycle, the higher the equivalent impedance of the freewheeling circuit, and the winding freewheeling current is forcibly suppressed. Finally, the single output duty cycle uniformly controls the three-phase lower arm to achieve dual closed-loop constraints of current and bus voltage during braking deceleration.

[0039] In this embodiment, the duty cycle is obtained by the following formula: ; in, For the current period Voltage error under, This is the bus voltage limit value. This is the instantaneous value of the bus voltage. This is the current compensation value. To enable the duty cycle, This is the proportional gain of the voltage loop. This represents the coefficient of the voltage loop integral element.

[0040] By directly superimposing the current compensation value output from the current loop onto the bus voltage deviation to construct the voltage error, the voltage regulation reference can be quickly corrected during current overload, prioritizing the reduction of the lower bridge arm's conduction duty cycle to suppress inrush current. Furthermore, the voltage loop employs a discrete-period proportional-integral algorithm to calculate the lower bridge arm's conduction duty cycle, ensuring that the bus voltage and winding current remain stably maintained near preset safety limits during steady-state motor operation. Simultaneously, setting a maximum value limit constraint on the output duty cycle prevents integral saturation of the voltage loop, thus preventing continuous overcurrent in the windings caused by exceeding duty cycle limits.

[0041] After obtaining the duty cycle, step S5 is executed. Once the motor speed has been confirmed to have dropped to a safe range based on the duty cycle and the effective value of the maximum current, zero-vector braking is performed. If zero-vector braking is directly applied while the motor is operating at high speed, the large kinetic energy of the rotor will be converted into feedback current, causing a surge in bus voltage and potentially damaging power devices due to overvoltage and overcurrent. Therefore, zero-vector braking should only be performed after the motor speed has been reduced to a safe range.

[0042] In this embodiment, the step of confirming that the motor speed has dropped to a safe range based on the duty cycle and the effective value of the maximum current includes: determining that the motor speed has dropped to a safe range when both the duty cycle and the effective value of the maximum current are greater than a preset duty cycle and less than a preset current value. The preset duty cycle and preset current value can be preset based on experimental data. For example, the preset duty cycle ranges from 0.85 to 0.98, preferably 0.95; the preset current value is less than 1.5 times the rated current of the motor. Limiting the preset duty cycle to the range of 0.85 to 0.98 ensures that the lower bridge arm of the voltage loop output can only enter this high duty cycle range when the motor speed drops significantly and the back electromotive force is sufficiently decayed, thus distinguishing between medium- and high-speed operating conditions and low-speed operating conditions. Simultaneously limiting the preset current value to less than 1.5 times the rated current of the motor matches the short-term safe current carrying limit of the winding and power switch, shielding heavy-load, high-current, low-speed operating conditions from braking triggering conditions.

[0043] Because the back electromotive force (EMF) of the motor is high at high speeds, the duty cycle of the voltage loop output is low. As the speed gradually decreases, the back EMF decays, and the duty cycle continuously increases. When the duty cycle exceeds the preset duty cycle threshold, it indicates that the speed has dropped significantly. Simultaneously, the motor feedback current decreases with the speed reduction. When the effective value of the maximum current falls below the preset current value, it indicates that the motor is currently in a light-load safe operating condition. Only when both conditions are met simultaneously is the motor speed determined to have dropped to a safe range, and then zero-vector braking is performed. This avoids false braking caused by a slight increase in the duty cycle at high speeds, and also avoids braking delay caused by continuously exceeding the current limit at low speeds under heavy loads, thus improving the accuracy of speed judgment.

[0044] During zero-vector braking, all upper bridge arms are kept continuously off, while the power switches of the three lower bridge arms (A, B, and C) are kept continuously on. At this time, the three-phase windings form a low-impedance closed freewheeling circuit through the fully on lower bridge arms. The induced current generated by the motor's inertia driving the rotor to rotate circulates within the windings and the lower bridge tube circuit, relying on the windings to consume the remaining mechanical energy, thus achieving energy-saving braking.

[0045] In this embodiment, the zero-vector braking operation further includes: continuously monitoring the phase current of the motor; and exiting zero-vector braking when the phase current stabilizes and is less than the hardware protection threshold. The hardware protection threshold can be preset based on experimental data. To avoid directly exiting zero-vector braking when current fluctuations are large and high in amplitude, which could lead to voltage spikes caused by sudden changes in the winding inductive current and hardware overcurrent / overvoltage faults, adaptive braking exit is required through real-time monitoring of the phase current state. This ensures that the motor fully consumes its inertial kinetic energy while avoiding electrical shocks during switching.

[0046] The controller continuously collects instantaneous current values ​​across multiple phases. Stability is assessed by comparing the current difference and fluctuation amplitude between adjacent sampling periods. If the current fluctuation is less than a preset fluctuation threshold for M consecutive periods, the current is considered stable, indicating that most of the motor's inertial kinetic energy has been consumed. Furthermore, the hardware protection threshold is the critical value for overcurrent protection activation of the power transistors, windings, and other hardware. Even if the current is stable, if the amplitude is higher than this threshold, zero-vector braking continues, further consuming residual energy. Only when both conditions are met—current stability and amplitude below the hardware protection threshold—is the zero-vector braking operation terminated.

[0047] See Figure 3 After performing zero-vector braking, step S6 is executed, applying a fixed d-axis current of a preset amplitude to the motor windings to generate a positioning torque that forcibly pulls the motor rotor to a preset zero electrical angle position, which is then used as the initial reference position for subsequent starting. After zero-vector braking, the rotor's stationary angle is random, and the back electromotive force is weak in the low-speed range, making it difficult to accurately identify the rotor position without sensor control. In this situation, direct starting can easily lead to problems such as reverse rotation, jitter, and stalling. Therefore, by applying a fixed d-axis current of a preset amplitude to the motor windings, the rotor is forced to return to the preset zero electrical angle position, eliminating the initial magnetic pole angle during starting and reducing the acceleration inrush current.

[0048] After forcibly pulling the motor rotor to the preset zero electrical angle position, step S7 is executed. After positioning is completed, IF (current-frequency) open-loop control is performed to accelerate the motor rotor from rest to the preset speed. After the rotor is positioned at zero degrees, IF open-loop acceleration is used to ensure the reliability of zero-speed start-up. Pre-positioning the rotor's initial electrical angle using the d-axis current can significantly reduce the instantaneous inrush current during IF open-loop start-up. IF open-loop control is a well-known technique to those skilled in the art and will not be described in detail here.

[0049] After the motor rotor accelerates from a standstill to a preset speed, step S8 is executed to determine if the motor speed has reached a preset closed-loop cut-in speed threshold. This closed-loop cut-in speed threshold can be preset based on experimental data. To improve motor control accuracy, the transition from open-loop start-up to closed-loop operation needs to be completed when the motor speed reaches the closed-loop cut-in speed threshold. Therefore, during the IF open-loop acceleration process, the controller calculates the real-time motor speed based on the current output given electrical frequency and continuously compares the real-time speed with the preset closed-loop cut-in speed threshold.

[0050] If the motor speed does not reach the preset closed-loop entry speed threshold, the IF open-loop boost and frequency increase acceleration will continue. If the motor speed reaches the preset closed-loop entry speed threshold, step S9 will be executed, switching the control strategy from IF open-loop control to field-oriented closed-loop control. When the real-time speed is greater than or equal to the preset closed-loop entry speed threshold, the motor speed is considered to have met the conditions for closed-loop control. The controller will then terminate the IF open-loop control and switch to field-oriented closed-loop control to improve control accuracy.

[0051] As described above, in the starting control method of the permanent magnet synchronous motor of the present invention, after the motor receives the starting command, the upper bridge arm is completely shut off first, and the winding forms a freewheeling circuit. The complete drive voltage is not applied instantaneously, which avoids the instantaneous large inrush current caused by directly outputting the drive vector when the rotor position is unknown and the back EMF is extremely low during the initial stage of starting. Simultaneously, a dual closed-loop PI control is implemented using a phase current limiting loop and a bus voltage limiting loop. The voltage loop limits the bus voltage, and a current loop feedback is introduced to limit the short-circuit current, enabling rapid braking. Zero-vector braking is only performed when the motor speed is reduced to a safe range, preventing the generation of large currents and avoiding the impact of short-circuit current.

[0052] Example of a permanent magnet synchronous motor system: The permanent magnet synchronous motor system in this embodiment includes a controller, which executes a computer program to implement the steps in the above-described permanent magnet synchronous motor start-up control method embodiment.

[0053] For example, a computer program can be divided into one or more modules, one or more of which are stored in memory and executed by a controller to perform the present invention. One or more modules can be a series of computer program instruction segments capable of performing specific functions, which describe the execution process of the computer program in a permanent magnet synchronous motor system.

[0054] A permanent magnet synchronous motor system may include, but is not limited to, a controller and a memory. Those skilled in the art will understand that a permanent magnet synchronous motor system may include more or fewer components, or a combination of certain components, or different components; for example, a permanent magnet synchronous motor system may also include input / output devices, network access devices, buses, etc.

[0055] For example, the controller can be a Central Processing Unit (CPU), or other general-purpose controllers, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose controller can be a microcontroller or any conventional controller. The controller is the control center of the permanent magnet synchronous motor system, connecting all parts of the system through various interfaces and lines.

[0056] The memory can be used to store computer programs and / or modules. The controller implements various functions of the permanent magnet synchronous motor system by running or executing the computer programs and / or modules stored in the memory, and by calling the data stored in the memory. For example, the memory may mainly include a program storage area and a data storage area, wherein the program storage area may store the operating system, application programs required for at least one function, etc. In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital card (SD), flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0057] Examples of computer-readable storage media: If the modules integrated in the permanent magnet synchronous motor system of the above embodiments are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the permanent magnet synchronous motor start-up control method can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by the controller, it can implement the steps of the above embodiments of the permanent magnet synchronous motor start-up control method. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The storage medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content contained in computer-readable media may be appropriately added to or subtracted from the requirements of legislation and patent practice in a jurisdiction. For example, in some jurisdictions, computer-readable media may not include electrical carrier signals and telecommunication signals, in accordance with legislation and patent practice.

[0058] It should be noted that the above are only preferred embodiments of the present invention, but the design concept of the invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept also fall within the protection scope of the present invention.

Claims

1. A starting control method for a permanent magnet synchronous motor, applied to a permanent magnet synchronous motor system driven by a three-phase inverter, characterized in that: include: When the permanent magnet synchronous motor receives the start command, it turns off all the upper bridge arm power switches of the three-phase inverter, so that the motor windings are in a freewheeling state. The instantaneous values ​​of the three-phase current and the bus voltage of the motor are obtained by real-time sampling, and the effective values ​​of the three-phase current are calculated based on the instantaneous values ​​of the three-phase current. The maximum value among the effective values ​​of the three-phase current is selected as the maximum effective value of the current. The current error is obtained by subtracting the preset phase current limit value from the maximum effective current value. The current compensation value is then output after the current limit is adjusted by PI based on the current error. The voltage error is obtained by subtracting the preset bus voltage limit value from the instantaneous bus voltage value and then adding the current compensation value. The voltage error is then used to perform voltage limit PI regulation and output the duty cycle of the lower bridge arm power switch of the three-phase inverter. When the motor speed has been confirmed to have dropped to a safe range based on the duty cycle and the effective value of the maximum current, a zero-vector braking operation is performed.

2. The starting control method for a permanent magnet synchronous motor according to claim 1, characterized in that: The current compensation value is obtained by the following formula: ； in, For the current period The current error mentioned below, This is the phase current limit value. The maximum effective value of the current. This is the current compensation value. This is the proportionality coefficient of the current loop. The integral coefficient of the current loop is... The instantaneous value of the bus voltage.

3. The starting control method for a permanent magnet synchronous motor according to claim 1, characterized in that: The duty cycle is obtained by the following formula: ； in, For the current period Voltage error under, This is the bus voltage limit value. The instantaneous value of the bus voltage. This is the current compensation value. The duty cycle is the on-state. This is the proportional gain of the voltage loop. This represents the coefficient of the voltage loop integral element.

4. The starting control method for a permanent magnet synchronous motor according to any one of claims 1 to 3, characterized in that: The steps for confirming that the motor speed has dropped to a safe range based on the duty cycle and the effective value of the maximum current include: When the conduction duty cycle is greater than the preset duty cycle and the effective value of the maximum current is less than the preset current value, it is determined that the motor speed has dropped to a safe range.

5. The starting control method for a permanent magnet synchronous motor according to claim 4, characterized in that: The preset duty cycle ranges from 0.85 to 0.98; The preset current value is less than 1.5 times the rated current of the motor.

6. The starting control method for a permanent magnet synchronous motor according to any one of claims 1 to 3, characterized in that: When performing zero-vector braking, it also includes: The phase current of the motor is continuously monitored. When the phase current is found to be stable and less than the hardware protection threshold, the zero-vector braking is discontinued.

7. The starting control method for a permanent magnet synchronous motor according to claim 6, characterized in that: After performing the zero-vector braking operation, the following steps are also included: A fixed d-axis current of a preset amplitude is applied to the motor winding to generate a positioning torque that forcibly pulls the motor rotor to a preset zero electrical angle position, and the zero electrical angle position is used as the initial reference position for subsequent startup. After positioning is completed, IF open-loop control is executed to accelerate the motor rotor from a standstill to a preset speed; When the motor speed reaches the preset closed-loop cut-in speed threshold, the control strategy is switched from the IF open-loop control to the field-oriented closed-loop control.

8. The starting control method for a permanent magnet synchronous motor according to any one of claims 1 to 3, characterized in that: The effective value of the maximum current is obtained by the following formula: ； in, This is the effective value of the phase current of phase A. This represents the instantaneous value of the phase current in phase A. This is the effective value of the phase current in phase B. This represents the instantaneous value of the phase current in phase B. This is the effective value of the C-phase current. This represents the instantaneous value of the C-phase current. This refers to the effective value of the maximum current.

9. A permanent magnet synchronous motor system, comprising a processor and a memory, characterized in that: The memory stores a computer program, which, when executed by the processor, implements the steps of the starting control method for a permanent magnet synchronous motor as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by the controller, it implements the steps of the starting control method for a permanent magnet synchronous motor as described in any one of claims 1 to 8.

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