A motor drive method and system for suppressing current ripple

Abstract

The present application relates to the technical field of motor control, and particularly relates to a motor driving method and system for suppressing current fluctuation, which comprises the following steps: receiving a frequency instruction, and generating a forced rotation angle and an instruction input voltage corresponding to the frequency instruction according to a preset V / f relationship; collecting two-phase stator phase currents on the output side of an inverter driving system, and performing synchronous rotation coordinate transformation on the two-phase stator phase currents with the forced rotation angle as a transformation angle to obtain a d-axis feedback current; comparing the d-axis feedback current with a preset d-axis current reference value to obtain a current deviation, and inputting the current deviation into a proportional integral regulator to output a d-axis voltage instruction; determining a q-axis voltage instruction according to the instruction input voltage and the d-axis voltage instruction, so that the amplitude of a voltage vector obtained by combining the d-axis voltage instruction and the q-axis voltage instruction is equal to the amplitude of the instruction input voltage; performing synchronous rotation coordinate inverse transformation on the d-axis voltage instruction and the q-axis voltage instruction with the forced rotation angle as a transformation angle to obtain a three-phase voltage instruction; generating a switching driving signal of the inverter driving system according to the three-phase voltage instruction, and using the switching driving signal to control the inverter driving system to output a three-phase driving voltage to an induction motor. The present application aims to solve the problems that the existing open-loop V / f control of the induction motor is prone to current fluctuation, torque pulsation and decline in running stability, and the existing suppression scheme is greatly dependent on motor parameters, has a complex algorithm and a high implementation cost.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a motor drive method and system for suppressing current fluctuations. Background Technology

[0002] Induction motors are widely used in industrial drives due to their simple structure, low cost, and wide applicability. To balance energy efficiency with system cost, open-loop V / f (voltage-frequency proportional) control is commonly used in variable frequency drive (VFD) applications. This control method is simple to implement and has relatively low requirements for sensor and controller performance, making it suitable for cost-sensitive applications such as pumps and fans. However, under light load, low speed, and variable speed operation, traditional open-loop V / f control is prone to current fluctuations, increased vibration, and decreased operational stability. In severe cases, it can even lead to motor overcurrent heating and power device damage. Existing solutions to address these issues typically rely on motor parameter-based compensation control or the introduction of signal processing techniques such as bandpass and high-pass filters. While these methods can improve low-frequency stability to some extent, they generally suffer from high dependence on the accuracy of motor parameters, complex control algorithms, large computational loads, and high implementation costs, hindering widespread application on resource-constrained, low-cost control platforms. Summary of the Invention

[0003] In view of the above technical problems, the present invention provides a motor drive method and system for suppressing current fluctuations, aiming to solve the problems that existing open-loop V / f control of induction motors is prone to current fluctuations, torque pulsation and decreased operating stability during low-frequency variable speed operation, and that existing suppression schemes are highly dependent on motor parameters, have complex algorithms and high implementation costs.

[0004] Other features and advantages of the invention will become apparent from the following detailed description, or may be learned in part by practice of the invention.

[0005] According to one aspect of the present invention, a motor drive method for suppressing current fluctuations is proposed, the method comprising: Receive frequency commands and generate a forced rotation angle and command input voltage corresponding to the frequency commands based on a preset V / f relationship; The two-phase stator phase currents on the output side of the inverter drive system are collected, and the forced rotation angle is used as the transformation angle to perform synchronous rotation coordinate transformation on the two-phase stator phase currents to obtain the d-axis feedback current. The d-axis feedback current is compared with a preset d-axis current reference value to obtain the current deviation, and the current deviation is input into the proportional-integral regulator to output the d-axis voltage command. The q-axis voltage command is determined based on the command input voltage and the d-axis voltage command, such that the magnitude of the voltage vector synthesized by the d-axis voltage command and the q-axis voltage command is equal to the magnitude of the command input voltage; Using the forced rotation angle as the transformation angle, the d-axis voltage command and the q-axis voltage command are subjected to synchronous rotation coordinate inverse transformation to obtain the three-phase voltage command; The inverter drive system generates a switching drive signal based on the three-phase voltage command, and uses the switching drive signal to control the inverter drive system to output a three-phase drive voltage to the induction motor.

[0006] Furthermore, the forced rotation angle is generated by accumulating the angles from the output frequency formed by the frequency command, and serves as a unified angle parameter for the synchronous rotation coordinate transformation and the synchronous rotation coordinate inverse transformation, so that the current feedback acquisition process and the voltage command inverse transformation process maintain the same rotation reference.

[0007] Furthermore, the frequency command is subjected to ramping processing before being input into the preset V / f relationship to form a continuously varying output frequency; the preset V / f relationship outputs the command input voltage according to the output frequency, and maintains the proportional relationship between the stator voltage and the stator frequency, so as to reduce the impact of command mutations on the operational stability of the induction motor.

[0008] Furthermore, the two-phase stator phase current is the two-phase stator current sampling signal on the output side of the inverter drive system, and the synchronous rotating coordinate transformation is performed on the two-phase stator current sampling signal using the forced rotation angle as the angle parameter to obtain the d-axis feedback current.

[0009] Furthermore, the proportional-integral regulator performs proportional and integral regulation on the current deviation. The proportional regulation is used to quickly correct the instantaneous current deviation, and the integral regulation is used to eliminate steady-state deviation. The result of the proportional regulation and the result of the integral regulation together form the d-axis voltage command so that the d-axis feedback current tracking maintains a constant preset d-axis current reference value.

[0010] Furthermore, the preset d-axis current reference value is set to zero, so that the induction motor operates with a zero d-axis current target in the synchronous rotation coordinate system established by the forced rotation angle, thereby suppressing current fluctuations.

[0011] Furthermore, obtaining the q-axis voltage command specifically includes: The command input voltage is squared to obtain the total voltage square value; The d-axis voltage command is squared to obtain the squared value of the d-axis voltage; The remaining voltage square value is obtained by subtracting the d-axis voltage square value from the total voltage square value. The square root of the squared value of the remaining voltage is used to obtain the q-axis voltage command.

[0012] Furthermore, the d-axis voltage command and the q-axis voltage command are transformed into phase voltage commands through the synchronous rotating coordinate inverse transformation corresponding to the forced rotation angle, and the phase voltage commands are input into the space vector pulse width modulation unit. The space vector pulse width modulation unit generates drive pulses for each power switching device of the three-phase bridge inverter in the inverter drive system according to the phase voltage commands. During the generation of the d-axis voltage command and the q-axis voltage command, the synchronous rotation coordinate transformation, the proportional-integral adjustment, and the space vector pulse width modulation unit are executed synchronously within a unified control cycle.

[0013] According to another aspect of the present invention, a motor drive system for suppressing current fluctuations is provided, comprising: A frequency voltage generation module is used to receive frequency commands and generate a forced rotation angle and command input voltage corresponding to the frequency commands based on a preset V / f relationship. The current sampling and coordinate transformation module is used to collect the two-phase stator phase current on the output side of the inverter drive system, and to perform synchronous rotation coordinate transformation on the two-phase stator phase current using the forced rotation angle as the transformation angle to obtain the d-axis feedback current. The current closed-loop regulation module is used to compare the d-axis feedback current with the preset d-axis current reference value, obtain the current deviation, and input the current deviation into the proportional-integral regulator to output the d-axis voltage command. The q-axis voltage determination module is used to determine the q-axis voltage command based on the command input voltage and the d-axis voltage command, such that the magnitude of the voltage vector synthesized by the d-axis voltage command and the q-axis voltage command is equal to the magnitude of the command input voltage; The coordinate inverse transformation module is used to perform synchronous rotational coordinate inverse transformation on the d-axis voltage command and the q-axis voltage command using the forced rotation angle as the transformation angle, so as to obtain the three-phase voltage command. The drive control module is used to generate a switching drive signal for the inverter drive system according to the three-phase voltage command, and to use the switching drive signal to control the inverter drive system to output a three-phase drive voltage to the induction motor.

[0014] The technical solution of the present invention has the following beneficial effects: This technology can effectively suppress current fluctuations without relying on complex slip tracking, precise motor parameters, or additional digital filtering design, thereby improving motor operation stability and reducing the impact of speed fluctuations, torque pulsation, vibration, and noise caused by current fluctuations. At the same time, because this technical solution adopts a relatively simplified control relationship and low algorithm complexity, it can effectively shorten the controller's operation time and reduce the requirements for microcontroller computing resources, making it more suitable for implementation in low-cost control platforms and possessing good engineering application value. Attached Figure Description

[0015] Figure 1 This is a flowchart of a motor drive method for suppressing current fluctuations, as described in the embodiments of this specification. Figure 2 This is a structural block diagram of a motor drive system for suppressing current fluctuations, as described in an embodiment of this specification. Detailed Implementation

[0016] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of the invention. However, those skilled in the art will recognize that the technical solutions of the invention may be practiced with one or more of these specific details omitted, or other methods, components, systems, steps, etc., may be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of the invention.

[0017] Furthermore, the accompanying drawings are merely illustrative of the invention. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor systems and / or microcontroller systems.

[0018] This invention provides a motor drive method for suppressing current fluctuations. (Refer to...) Figure 1 The diagram shown is a flowchart illustrating a motor drive method for suppressing current fluctuations according to an embodiment of the present invention. Specifically, the method may include the following steps S101-S106: In step S101, a frequency command is received, and a forced rotation angle and command input voltage corresponding to the frequency command are generated according to a preset V / f relationship.

[0019] The forced rotation angle is generated by accumulating the angles from the output frequency formed by the frequency command, and serves as a unified angle parameter for the synchronous rotation coordinate transformation and the inverse synchronous rotation coordinate transformation, so that the current feedback acquisition process and the voltage command inverse transformation process maintain the same rotation reference.

[0020] The frequency command is ramped before being input into the preset V / f relationship to form a continuously varying output frequency. The preset V / f relationship outputs the command input voltage according to the output frequency and maintains the proportional relationship between the stator voltage and the stator frequency to reduce the impact of command mutations on the operational stability of the induction motor.

[0021] In this step, the frequency command is input to the V / f curve module as the frequency setpoint during variable speed operation. After processing by the frequency ramp element, a continuously changing output frequency is formed. The V / f curve module then outputs the command input voltage according to a preset voltage-frequency correspondence, and simultaneously outputs the forced rotation angle corresponding to this output frequency. The basic characteristic of open-loop V / f control is that the stator input voltage changes proportionally to the operating frequency. Therefore, in implementation, a traditional V / f curve can be used to generate the voltage and frequency setpoints, enabling the induction motor to maintain a relatively stable magnetic flux level during variable speed operation and reducing current distortion and operational instability caused by sudden frequency changes. For general V / f control, under steady-state conditions, its stator voltage relationship can be expressed as: ; ; Accordingly, the command value in conventional V / f control can be expressed as: ; ; in, This indicates the stator frequency command value. Indicates the fundamental frequency. This represents the maximum q-axis voltage value under the corresponding fundamental frequency condition. Based on the above relationship, after receiving the frequency command, the V / f curve module can output the input voltage command corresponding to that frequency, providing the amplitude basis for subsequent voltage distribution and pulse width modulation.

[0022] The forced rotation angle is used to establish a synchronous rotation reference base. Its generation is based on the output frequency. In engineering implementation, the electrical angle is obtained by continuously accumulating the output frequency angles. This electrical angle is then used as a shared angle parameter for both synchronous rotation coordinate transformation and inverse synchronous rotation coordinate transformation. This process ensures that the current feedback acquisition process and the voltage command inverse transformation process use the same rotation reference base, guaranteeing consistent reference directions before and after coordinate transformation and avoiding additional errors introduced due to inconsistent angle references. In the corresponding control structure, the command frequency is input to the frequency ramp module, which outputs a reference frequency with a preset slope. This reference frequency then enters the V / f generation module to generate the output phase voltage and output frequency. The output phase voltage and output frequency are then input to the forced rotation angle generation module to form the forced electrical angle. This forced electrical angle is further used as the angle input for the abc-dq transformation and the dq-abc transformation. This processing method does not rely on slip tracking and does not require precise estimation of the rotor angular position, thus simplifying the control process, reducing parameter dependence, and facilitating implementation on low-cost controllers.

[0023] The function of the frequency ramp is to smoothly transition the frequency command, ensuring that the output frequency changes continuously according to a preset rate of change, rather than abruptly. This ensures the continuity of the frequency entering the V / f curve module, thereby enabling the command input voltage and forced rotation angle to change synchronously and continuously. This helps suppress phase current fluctuations, torque pulsations, and speed fluctuations caused by sudden changes in excitation in the low-frequency speed range.

[0024] From a control mechanism perspective, the forced rotation angle and command input voltage generated in this step provide a unified rotational reference for subsequent d-axis feedback current extraction, and also provide a basis for total voltage amplitude constraints for subsequent q-axis voltage determination. Since this control method is based on simplified equations, does not introduce complex filtering designs, and does not require constructing slip compensation formulas based on induction motor parameters, it can provide stable front-end conditions for suppressing low-frequency current fluctuations while maintaining the cost advantage of V / f control.

[0025] In step S102, the two-phase stator phase currents on the output side of the inverter drive system are collected, and the two-phase stator phase currents are synchronously rotated and transformed using the forced rotation angle as the transformation angle to obtain the d-axis feedback current.

[0026] Specifically, the two-phase stator phase current is the two-phase stator current sampling signal on the output side of the inverter drive system, and the synchronous rotation coordinate transformation is performed on the two-phase stator current sampling signal using the forced rotation angle as the angle parameter to obtain the d-axis feedback current.

[0027] In this step, the two-phase stator current sampling signals from the output side of the inverter drive system are used as current feedback information input to the synchronous rotating coordinate transformation stage. These two-phase stator current sampling signals can be obtained by the inverter drive system through real-time detection of the stator-side phase currents, characterizing the actual current state of the induction motor within the current control cycle. In the control structure, the forced rotation angle is directly used as the angle parameter for the abc-to-dq transformation. This angle parameter is used to transform the two-phase stator current sampling signals to the synchronous rotating coordinate system, thereby obtaining the d-axis feedback current. The corresponding control link for this processing method is as follows: the two-phase current measurement results enter the abc-to-dq transformation module, and after calculation in conjunction with the forced rotation angle, the d-axis feedback current is output for subsequent closed-loop regulation. The paper explicitly describes this process, namely, calculating the d-axis current by measuring the two-phase stator phase currents of the inverter and performing a dq transformation based on the forced rotation angle.

[0028] The purpose of synchronous rotating coordinate transformation is to convert the time-varying stator phase current into easily adjustable direct-axis and quadrature-axis components in a rotating reference frame. This step focuses on extracting the direct-axis component, i.e., the d-axis feedback current. Since this angle parameter is not obtained from slip estimation or rotor position tracking, but directly provided by the forced rotation angle generated in the previous stage, the current feedback extraction process and the subsequent voltage inverse transformation process can share the same rotating reference, thus simplifying the control structure. Using this method, a complex slip tracking process is not required in this step, nor is an additional observation loop around the rotor angular position needed, making it more suitable for implementation in control platforms with limited computational resources.

[0029] The d-axis feedback current is a critical feedback variable in this control scheme. This is because the control objective is to maintain the d-axis current constant, and in practice, to make it approach zero, thereby keeping the air gap flux at a stable level and suppressing current fluctuations during transient processes. Based on this control concept, this step not only completes the coordinate mapping of the current measurement but also provides a unique and direct feedback input for subsequent proportional-integral (PI) regulation. In other words, the d-axis feedback current output in this step is not only used for state monitoring but also directly serves as a feedback variable in closed-loop control; its extraction accuracy and update synchronization directly affect the quality of subsequent d-axis voltage command generation.

[0030] In terms of implementation, the two-phase stator current sampling signals can be updated within each control interruption cycle and synchronously entered into the coordinate transformation module along with the forced rotation angle updated within the same cycle. This ensures that the current feedback quantity and the current voltage reference are at the same discrete moment. Each functional module in the control structure operates synchronously with the interruption cycle. The d-axis feedback current obtained after the two-phase current undergoes an abc-to-dq transformation is configured as a constant-value control object, thereby ensuring that the entire current feedback acquisition process and the subsequent adjustment process remain consistent in time. This configuration avoids the accumulation of feedback errors caused by asynchronous sampling and transformation, which is beneficial for improving the stability of control in the low-frequency speed range.

[0031] In step S103, the d-axis feedback current is compared with a preset d-axis current reference value to obtain the current deviation, and the current deviation is input to the proportional-integral regulator to output the d-axis voltage command.

[0032] The proportional-integral regulator performs proportional and integral regulation on the current deviation. The proportional regulation is used to quickly correct the instantaneous current deviation, and the integral regulation is used to eliminate steady-state deviation. The result of the proportional regulation and the result of the integral regulation together form the d-axis voltage command so that the d-axis feedback current tracking maintains a constant preset d-axis current reference value.

[0033] The preset d-axis current reference value is set to zero, so that the induction motor operates with a zero d-axis current target in the synchronous rotation coordinate system established by the forced rotation angle, thereby suppressing current fluctuations.

[0034] In this step, the d-axis feedback current is compared with a preset d-axis current reference value as a closed-loop control quantity. The difference between the two constitutes the current deviation, which is adjusted by the proportional-integral controller to generate the d-axis voltage command. The corresponding control relationship can be expressed as: ; in, This is a d-axis voltage command. and These are the proportional gain and integral gain for the d-axis current, respectively. The difference between the d-axis current reference value and the d-axis feedback current is denoted by s, where s is the Laplace operator. Therefore, the output of the proportional-integral (PI) controller is directly used as the d-axis voltage command for subsequent voltage distribution and inverter output control.

[0035] The proportional control section is used to quickly respond to current deviations occurring within the current control cycle, enabling the d-axis feedback current to approach the reference target in a timely manner. The integral control section is used to cumulatively correct persistent deviations, thereby reducing steady-state error. Together, they improve the adjustment speed while maintaining steady-state control accuracy, keeping the d-axis feedback current constant throughout continuous control. The control objective is set to maintain a constant d-axis current because when the d-axis current is constant, the air gap flux remains at a stable level, which helps suppress current fluctuations during transient processes.

[0036] In the actual implementation, the d-axis current reference value is preset to zero, that is: ; With this setup, the proportional-integral controller operates around the zero d-axis current target, enabling the induction motor to maintain a zero d-axis current control state within the synchronous rotating coordinate system established by the forced rotation angle. The significance of this control approach is that it no longer relies on precise tracking of slip and rotor angular position, but simplifies the control process by maintaining the d-axis current at zero, reducing computational complexity and improving control robustness.

[0037] This step can be implemented within the same control cycle as the current sampling and coordinate transformation stages, ensuring that the calculation of current deviation is synchronized with the update of the proportional-integral controller. After adjustment using this step, the operational stability in the low-frequency range is significantly improved.

[0038] In step S104, a q-axis voltage command is determined based on the command input voltage and the d-axis voltage command, such that the magnitude of the voltage vector synthesized from the d-axis voltage command and the q-axis voltage command is equal to the magnitude of the command input voltage.

[0039] Specifically, obtaining the q-axis voltage command includes: squaring the command input voltage to obtain a total voltage square value; squaring the d-axis voltage command to obtain a d-axis voltage square value; subtracting the d-axis voltage square value from the total voltage square value to obtain a remaining voltage square value; and taking the square root of the remaining voltage square value to obtain the q-axis voltage command.

[0040] In this step, the q-axis voltage command is determined jointly by the command input voltage and the d-axis voltage command. The purpose is to further allocate the corresponding q-axis voltage component, given that the d-axis voltage command has already been generated by the current closed-loop regulation, so that the magnitude of the voltage vector synthesized from the d-axis and q-axis voltage commands is consistent with the magnitude of the command input voltage. This processing method uses a relatively simplified voltage constraint relationship to complete the dq-axis voltage allocation while maintaining a constant total voltage magnitude. The corresponding control relationship can be expressed as: ; in, The command value represents the stator input voltage. This indicates the d-axis voltage command. This indicates the q-axis voltage command. This relationship shows that the q-axis voltage command is not given independently, but is calculated in real time based on the current output result of the d-axis voltage command under the constraint of the total voltage amplitude.

[0041] In terms of the specific implementation process, the acquisition of the q-axis voltage command can be understood as a step-by-step calculation process of the voltage vector components. First, the command input voltage is squared to obtain the total squared voltage value; then, the d-axis voltage command is squared to obtain the d-axis voltage squared value; the total squared voltage value is subtracted from the d-axis voltage squared value to obtain the remaining voltage squared value; finally, the square root operation is performed on the remaining voltage squared value to obtain the q-axis voltage command. After this processing, the d-axis and q-axis voltage components satisfy the voltage vector composition relationship, ensuring that the amplitude of the total voltage command is not destroyed and that the d-axis closed-loop regulation result is naturally mapped to the dq-axis voltage commands required for subsequent inverter control.

[0042] This step is directly connected to the previous step. The d-axis voltage command is output by the proportional-integral controller around the control target of the d-axis feedback current. Since the total voltage amplitude is already determined by the V / f relationship, the q-axis voltage command is obtained through the square root relationship of the aforementioned difference of squares. In this way, the control process does not need to introduce complex induction motor slip tracking formulas, nor does it need to establish additional dynamic compensation models around the motor parameters to complete the construction of the dq-axis voltage commands. Compared to the method of using motor parameters, dynamic compensators, and filters to jointly correct voltage components, this step uses a more direct voltage calculation relationship and has a lower computational load.

[0043] From a control mechanism perspective, the d-axis voltage command primarily serves to maintain the stability of the d-axis current, while the q-axis voltage command, under the constraint of the total voltage amplitude, together with the d-axis voltage command, forms a complete voltage vector. Since the control objective is to keep the d-axis current constant and approach zero, when the d-axis voltage command is updated by closed-loop regulation, the q-axis voltage command is subsequently determined based on the remaining voltage space. This dq-axis voltage allocation result provides a complete input for subsequent synchronous rotating coordinate inverse transformation and space vector pulse width modulation without changing the total amplitude of the command input voltage.

[0044] In step S105, the forced rotation angle is used as the transformation angle to perform synchronous rotation coordinate inverse transformation on the d-axis voltage command and the q-axis voltage command to obtain the three-phase voltage command.

[0045] Specifically, the d-axis voltage command and the q-axis voltage command are transformed into phase voltage commands through the synchronous rotating coordinate inverse transformation corresponding to the forced rotation angle, and the phase voltage commands are input to the space vector pulse width modulation unit. The space vector pulse width modulation unit generates drive pulses for each power switching device of the three-phase bridge inverter in the inverter drive system according to the phase voltage commands. During the generation of the d-axis voltage command and the q-axis voltage command, the synchronous rotating coordinate transformation, the proportional-integral regulation, and the space vector pulse width modulation unit are executed synchronously within a unified control cycle.

[0046] In this step, the d-axis voltage command and the q-axis voltage command enter the synchronous rotating coordinate inverse transformation stage using a forced rotation angle as a unified angle parameter. After the inverse transformation, the voltage components in the rotating coordinate system are restored to the phase voltage commands in the three-phase stationary coordinate system, namely the phase voltage commands va, vb, and vc. The forced rotation angle continues to be used as the angle input for the dq-to-abc transformation here, ensuring that the output reference reference of the voltage command is consistent with the rotating reference reference used in the previous stage current sampling and synchronous rotating coordinate transformation. This guarantees that the entire link from feedback current extraction to voltage reconstruction operates within the same angular framework.

[0047] The role of synchronous rotating coordinate inverse transformation in this step is to convert the two-axis voltage components, already allocated in the dq coordinate system, into three-phase voltage commands that can be directly used for inverter modulation. Since the d-axis voltage command is responsible for stabilizing the d-axis feedback current, and the q-axis voltage command is responsible for supplementing the total voltage vector, the two, after inverse transformation, form a complete set of three-phase voltage commands. These phase voltage commands are then used as inputs for space vector pulse width modulation. After this processing, the dq-axis voltage results obtained from the preceding control stage can be smoothly mapped to the actual three-phase switching control process of the inverter, constituting a transition link from control quantity to execution quantity.

[0048] After receiving the phase voltage command, the space vector pulse width modulation (SVPWM) unit generates the modulation signal for the three-phase bridge inverter based on the phase voltage command. In the specific implementation, the three outputs of the SVPWM module are processed by a comparator and converted into six PWM waveforms, which are then sent to the gate input terminals of the six IGBTs in the inverter drive system to control the on and off of each power switching device in the three-phase bridge inverter. Thus, the inverter drive system outputs the corresponding three-phase drive voltage to the induction motor according to the three-phase voltage command generated in the previous stage, realizing the implementation of the voltage command to the actual motor terminal voltage.

[0049] In step S106, a switching drive signal for the inverter drive system is generated according to the three-phase voltage command, and the switching drive signal is used to control the inverter drive system to output a three-phase drive voltage to the induction motor.

[0050] In this step, the three-phase voltage command is further converted into a switching drive signal executable by the inverter drive system. The inverter drive system then outputs the three-phase drive voltage to the induction motor based on this switching drive signal, thereby implementing the voltage control result obtained from the preceding control stage into the power conversion stage. In the control structure, the d-axis voltage command and q-axis voltage command undergo a synchronous rotating coordinate inverse transformation involving a forced rotation angle to form the phase voltage command. , and The signal is then input to the space vector pulse width modulation (SPWM) stage. The SPWM stage outputs three modulation signals, which are processed by a comparator and converted into six PWM waveforms. These waveforms are then fed into the gate inputs of the six power switching devices inside the inverter, thereby controlling the on / off states of the three-phase bridge inverter and thus generating the corresponding three-phase drive voltages on the output side of the inverter drive system. This execution chain is fully described, i.e., the output... and The phase voltage is obtained after transformation. , and Then, the three outputs of the SVPWM module are converted into six PWM waveforms by a comparator and fed into the gate input terminals of the six IGBTs in the inverter.

[0051] This step corresponds to the interface execution process between the control algorithm and the power circuit. If only the voltage calculation in the dq coordinate system is completed without converting the three-phase voltage command into a specific switching drive signal, the inverter drive system cannot apply the corresponding three-phase drive voltage to the induction motor according to the control target, and the entire current fluctuation suppression process cannot be closed. By sending the three-phase voltage command into the space vector pulse width modulation stage, a pulse control sequence suitable for the three-phase inverter output can be formed under the DC bus voltage condition, enabling the inverter to operate according to the predetermined voltage command and ensuring that the induction motor receives the voltage excitation corresponding to the control target.

[0052] In discrete control implementation, this step runs continuously within a unified control cycle, along with the preceding frequency setting, current sampling, synchronous rotating coordinate transformation, proportional-integral regulation, and q-axis voltage calculation processes. With this setup, the updated d-axis feedback current and voltage commands, as well as the three-phase voltage commands obtained within the current control cycle, can be promptly converted into switching drive signals and applied to the inverter drive system within the same cycle, reducing phase errors and output fluctuations caused by asynchronous updates in various functional components.

[0053] In this embodiment, to continuously suppress current fluctuations during the variable-speed operation of the induction motor, the control process is not executed once, but repeatedly within each control cycle. That is, after completing frequency command processing, stator current sampling, d-axis feedback current acquisition, d-axis voltage command generation, q-axis voltage command determination, three-phase voltage command generation, and switch drive signal output, the two-phase stator current on the output side of the inverter drive system is sampled again in the next control cycle. Based on the updated forced rotation angle, the same control process is repeated, ensuring that the d-axis feedback current continuously tracks the zero-current target and that the inverter drive system continuously outputs a three-phase drive voltage to the induction motor that matches the current control state. Since all modules operate synchronously in a loop according to the interrupt cycle, current feedback, voltage distribution, inverter drive, and motor output constitute a continuous closed-loop update process, thereby continuously suppressing phase current fluctuations in the low-frequency variable-speed range and improving the stability of electromagnetic torque and speed.

[0054] Based on the same line of thought, such as Figure 2 As shown, a motor drive system for suppressing current fluctuations is provided, comprising: The frequency voltage generation module 201 is used to receive frequency commands and generate a forced rotation angle and command input voltage corresponding to the frequency commands according to a preset V / f relationship. The current sampling and coordinate transformation module 202 is used to collect the two-phase stator phase current on the output side of the inverter drive system, and to perform synchronous rotation coordinate transformation on the two-phase stator phase current using the forced rotation angle as the transformation angle to obtain the d-axis feedback current. The current closed-loop regulation module 203 is used to compare the d-axis feedback current with the preset d-axis current reference value, obtain the current deviation, and input the current deviation into the proportional-integral regulator to output the d-axis voltage command. The q-axis voltage determination module 204 is used to determine the q-axis voltage command based on the command input voltage and the d-axis voltage command, such that the magnitude of the voltage vector synthesized by the d-axis voltage command and the q-axis voltage command is equal to the magnitude of the command input voltage; The coordinate inverse transformation module 205 is used to perform synchronous rotation coordinate inverse transformation on the d-axis voltage command and the q-axis voltage command using the forced rotation angle as the transformation angle to obtain the three-phase voltage command. The drive control module 206 is used to generate a switching drive signal for the inverter drive system according to the three-phase voltage command, and use the switching drive signal to control the inverter drive system to output a three-phase drive voltage to the induction motor.

[0055] This system can effectively suppress current fluctuations without relying on complex slip tracking, precise motor parameters, or additional digital filtering design, thereby improving motor operation stability and reducing the impact of speed fluctuations, torque pulsation, vibration, and noise caused by current fluctuations. At the same time, because this system adopts a relatively simplified control relationship and low algorithm complexity, it can effectively shorten the controller's operation time and reduce the requirements for microcontroller computing resources, making it more suitable for implementation in low-cost control platforms and possessing good engineering application value.

[0056] It should be noted that although several modules or units of the device for performing actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to exemplary embodiments of the present invention, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0057] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0058] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A motor drive method for suppressing current fluctuations, characterized in that, The method includes: Receive frequency commands and generate a forced rotation angle and command input voltage corresponding to the frequency commands based on a preset V / f relationship; The two-phase stator phase currents on the output side of the inverter drive system are collected, and the forced rotation angle is used as the transformation angle to perform synchronous rotation coordinate transformation on the two-phase stator phase currents to obtain the d-axis feedback current. The d-axis feedback current is compared with a preset d-axis current reference value to obtain the current deviation, and the current deviation is input into the proportional-integral regulator to output the d-axis voltage command. The q-axis voltage command is determined based on the command input voltage and the d-axis voltage command, such that the magnitude of the voltage vector synthesized by the d-axis voltage command and the q-axis voltage command is equal to the magnitude of the command input voltage; Using the forced rotation angle as the transformation angle, the d-axis voltage command and the q-axis voltage command are subjected to synchronous rotation coordinate inverse transformation to obtain the three-phase voltage command; The inverter drive system generates a switching drive signal based on the three-phase voltage command, and uses the switching drive signal to control the inverter drive system to output a three-phase drive voltage to the induction motor.

2. The motor drive method for suppressing current fluctuations according to claim 1, characterized in that, The forced rotation angle is generated by accumulating the angles from the output frequency formed by the frequency command, and serves as a unified angle parameter for the synchronous rotation coordinate transformation and the inverse synchronous rotation coordinate transformation, so that the current feedback acquisition process and the voltage command inverse transformation process maintain the same rotation reference.

3. The motor drive method for suppressing current fluctuations according to claim 1, characterized in that, The frequency command is ramped before being input into the preset V / f relationship to form a continuously varying output frequency. The preset V / f relationship outputs the command input voltage according to the output frequency and maintains the proportional relationship between the stator voltage and the stator frequency to reduce the impact of command mutations on the operational stability of the induction motor.

4. The motor drive method for suppressing current fluctuations according to claim 1, characterized in that, The two-phase stator phase current is the two-phase stator current sampling signal on the output side of the inverter drive system. The synchronous rotation coordinate transformation is performed on the two-phase stator current sampling signal using the forced rotation angle as the angle parameter to obtain the d-axis feedback current.

5. The motor drive method for suppressing current fluctuations according to claim 1, characterized in that, The proportional-integral regulator performs proportional and integral regulation on the current deviation. The proportional regulation is used to quickly correct the instantaneous current deviation, and the integral regulation is used to eliminate steady-state deviation. The result of the proportional regulation and the result of the integral regulation together form the d-axis voltage command so that the d-axis feedback current tracking maintains a constant preset d-axis current reference value.

6. The motor drive method for suppressing current fluctuations according to claim 5, characterized in that, The preset d-axis current reference value is set to zero, so that the induction motor operates with a zero d-axis current target in the synchronous rotation coordinate system established by the forced rotation angle, thereby suppressing current fluctuations.

7. The motor drive method for suppressing current fluctuations according to claim 1, characterized in that, Obtaining the q-axis voltage command specifically includes: The command input voltage is squared to obtain the total voltage square value; The d-axis voltage command is squared to obtain the squared value of the d-axis voltage; The remaining voltage square value is obtained by subtracting the d-axis voltage square value from the total voltage square value. The square root of the squared value of the remaining voltage is used to obtain the q-axis voltage command.

8. The motor drive method for suppressing current fluctuations according to claim 1, characterized in that, The d-axis voltage command and the q-axis voltage command are inversely transformed by the synchronous rotating coordinates corresponding to the forced rotation angle to generate a phase voltage command, and the phase voltage command is input into the space vector pulse width modulation unit. The space vector pulse width modulation unit generates drive pulses for each power switching device of the three-phase bridge inverter in the inverter drive system according to the phase voltage command. During the generation of the d-axis voltage command and the q-axis voltage command, the synchronous rotation coordinate transformation, the proportional-integral adjustment, and the space vector pulse width modulation unit are executed synchronously within a unified control cycle.

9. A motor drive system for suppressing current fluctuations, characterized in that, include: A frequency voltage generation module is used to receive frequency commands and generate a forced rotation angle and command input voltage corresponding to the frequency commands based on a preset V / f relationship. The current sampling and coordinate transformation module is used to collect the two-phase stator phase current on the output side of the inverter drive system, and to perform synchronous rotation coordinate transformation on the two-phase stator phase current using the forced rotation angle as the transformation angle to obtain the d-axis feedback current. The current closed-loop regulation module is used to compare the d-axis feedback current with the preset d-axis current reference value, obtain the current deviation, and input the current deviation into the proportional-integral regulator to output the d-axis voltage command. The q-axis voltage determination module is used to determine the q-axis voltage command based on the command input voltage and the d-axis voltage command, such that the magnitude of the voltage vector synthesized by the d-axis voltage command and the q-axis voltage command is equal to the magnitude of the command input voltage; The coordinate inverse transformation module is used to perform synchronous rotational coordinate inverse transformation on the d-axis voltage command and the q-axis voltage command using the forced rotation angle as the transformation angle, so as to obtain the three-phase voltage command. The drive control module is used to generate a switching drive signal for the inverter drive system according to the three-phase voltage command, and to use the switching drive signal to control the inverter drive system to output a three-phase drive voltage to the induction motor.

Images