Control method and device of inverter

Abstract

The application discloses a control method and device of an inverter, wherein a direct current end of the inverter is connected with a direct current power supply, and an alternating current end of the inverter is connected with a motor; the control method comprises the following steps: controlling whether the inverter emits a wave according to a relationship between a wave blocking signal, a torque current setting value of the motor and a current threshold value, and a relationship between a rotating speed measurement value of the motor and a rotating speed threshold value. In a no-load or light-load working condition of the motor, the application can intermittently block the PWM signal output by the inverter, so that the current of the inverter and the motor is zero during the wave blocking period; after waiting for a period of time, the inverter emits a wave again to make the motor output power so that the motor reaches a preset rotating speed or a preset torque, the loss of the inverter and the motor is reduced, the inverter and the motor generate less heat, and the system efficiency is improved.

Description

Technical Field

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

[0002] In some applications, such as power tools, electric vehicles, home appliances, and robots, motors can operate under no-load or light-load conditions for extended periods. For permanent magnet synchronous motors, brushless DC motors, and electrically excited synchronous motors, the motor current can be close to zero and the motor speed can be maintained constant under no-load, non-field weakening conditions. However, because the inverter output is a high-frequency PWM signal, it cannot perfectly follow the motor's back EMF. Even under no-load conditions, these motors inevitably exhibit harmonic currents, leading to increased losses in both the motor and inverter, reduced system efficiency, and increased heat generation in both the inverter and motor.

[0003] Generally, increasing the switching frequency of the PWM signal can be considered to reduce motor losses. As the switching frequency increases, the ripple current will decrease, and the copper losses in the motor will also decrease. However, increasing the switching frequency will increase the inverter's switching losses, and the motor's iron losses may also increase with the switching frequency. Therefore, increasing the switching frequency of the inverter's output PWM wave has a limited effect on reducing motor losses. Summary of the Invention

[0004] This application aims to provide a control method and device for an inverter to solve the problems that when the motor is running under no-load or light-load conditions, the PWM signal output by the inverter causes increased losses in the motor and inverter, reduced system efficiency, and excessive heat generation in the motor and inverter.

[0005] This application provides a control method for an inverter, wherein the DC terminal of the inverter is connected to a DC power supply, and the AC terminal of the inverter is connected to a motor; the control method includes:

[0006] The inverter is controlled to generate a waveform based on the relationship between the blocking signal, the motor torque current setpoint and the current threshold, and the relationship between the motor speed measurement value and the speed threshold.

[0007] In another aspect, this application provides a control device for an inverter, wherein the DC terminal of the inverter is connected to a DC power supply, and the AC terminal of the inverter is connected to a motor; the control device includes:

[0008] The drive module is configured to output a drive signal to control the inverter to generate waves when enabled, and not to output a drive signal when disabled.

[0009] The blocking module is used to control whether the drive module is enabled based on the blocking signal, the relationship between the motor's torque current setpoint and current threshold, and the relationship between the motor's speed measurement value and speed threshold.

[0010] The inverter control method and apparatus provided in this application embodiment can intermittently block the PWM signal output by the inverter when the motor is under no-load or light-load conditions, so that the current of the inverter and the motor are zero during the blocking period. After waiting for a period of time, the signal is re-embedded to enable the motor to output power and reach the preset speed or preset torque, thereby reducing the losses of the inverter and the motor, reducing the heat generation of the inverter and the motor, and improving the system efficiency. Attached Figure Description

[0011] Figure 1 This is a control block diagram of an inverter provided in an embodiment of this application;

[0012] Figure 2 The sealing signal S provided in the embodiments of this application gEN A schematic diagram of the implementation process;

[0013] Figure 3 The sealing signal S provided in the embodiments of this application gEN A waveform diagram;

[0014] Figure 4 The sealing signal S provided in the embodiments of this application gEN1 A schematic diagram of the implementation process;

[0015] Figure 5 The sealing signal S provided in the embodiments of this application gEN1 A schematic diagram illustrating the implementation process.

[0016] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0017] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0018] In the description of this application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] The variables and their definitions involved in the embodiments of this application are as follows:

[0020] i a i b i c Current of motor stator phases A, B, and C

[0021] cmp a ,cmp b ,cmp c PWM output of inverter phases A, B, and C

[0022] ω r Speed ​​measurement value

[0023] θ r : Angular position signal

[0024] Speed ​​setting value

[0025] Torque current setpoint

[0026] i sq Torque current feedback value

[0027] Excitation current set value

[0028] i sd Excitation current feedback value

[0029] u sd Excitation shaft (d-axis) voltage

[0030] u sq Torque axis (q-axis) voltage

[0031] S gEN1 The sealing signal generated according to the sealing period

[0032] S gEN2 : The blocking signal generated based on the torque current setpoint

[0033] S gEN3 : Sealing signal generated based on speed measurement value

[0034] S gEN Final blocking signal

[0035] Figure 1 This is a control block diagram of an inverter provided in an embodiment of this application.

[0036] like Figure 1 As shown, the DC terminal of the inverter is connected to a DC power supply V. dc The AC terminal of the inverter is connected to the motor M.

[0037] The inverter's control unit includes an abc / dq module, a speed control module, a current control module, a waveform generation algorithm processing module, a drive module, and a waveform blocking module.

[0038] The motor speed measurement value ω obtained by the speed measurement module r and angular position signal θ r , the angle position signal θ r The data is fed into the abc / dq module and analyzed based on the stator A, B, and C phase currents i of the motor. a i b i c Converted into torque current feedback value i sq and excitation current feedback value i sd .

[0039] The speed control module is based on the set speed value. and rotational speed measurement value ω r The difference is used for control to obtain the torque current setpoint.

[0040] The current control module will feed back the torque current value i sq and excitation current feedback value i sd Control to and set value and Consistent, generating excitation shaft (d-axis) voltage u sd and torque axis (q-axis) voltage u sq .

[0041] The excitation shaft (d-axis) voltage u sd Torque axis (q-axis) voltage u sq Angular position signal θ r After processing by the PWM generation algorithm, the PWM generation quantities (cmp) of phases A, B, and C of the inverter are obtained. a ,cmp b ,cmp c .

[0042] The drive module is configured to output drive signals to control the inverter's PWM output when enabled, i.e., based on the PWM output values ​​(cmp) of phases A, B, and C of the inverter. a ,cmp b ,cmp c The inverter is controlled to generate a waveform; when disabled, it cannot output a drive signal, meaning the inverter stops generating a waveform or is in a waveform blocking period. When the inverter stops generating a waveform or is in a waveform blocking period, the abc\dq module, speed control module, current control module, and waveform generation algorithm processing module do not operate.

[0043] The blocking module is used to control whether the drive module is enabled based on the blocking signal, the relationship between the motor's torque current setpoint and current threshold, and the relationship between the motor's speed measurement value and speed threshold.

[0044] exist Figure 1 In the example, the S output of the sealing module gEN The signal, if low, enables the driver module; if high, it disables the driver module. Conversely, it's easy to see that the opposite is also true.

[0045] S gEN Signal Implementation Reference Figures 2-3 Explanation:

[0046] like Figure 3 As shown, the sealing signal S gEN1 The period is T, and the high level time is T. on The low level lasts for TT. on ;

[0047] When torque current setting value Below the current threshold i sqon Sealing signal S gEN2 A low level indicates a low level; otherwise, a high level indicates a high level.

[0048] When the speed measurement value ω r Above the speed threshold ω roff Sealing signal S gEN3 A low level indicates a low level; otherwise, a high level indicates a high level.

[0049] If the wave signal S gEN1 S gEN2 S gEN3 All are low level, the S output of the blocking module gEN The signal is low level if it is low level otherwise.

[0050] It should be noted that the terms "higher than" and "lower than" may or may not include cases where "equal to" is used.

[0051] Current threshold i sqon Speed ​​threshold ω roff Adjust the current threshold i according to actual application requirements. sqon The larger the value, the wider the torque range of the motor it can adapt to, but the greater the torque fluctuation within the effective torque range; speed threshold ω roff The lower the value, the wider the effective rotational speed range. In a preferred embodiment, the current threshold i can be... sqon Set the speed threshold ω to 10% of the motor's rated current. roff Set to 50% of the motor's rated speed.

[0052] In addition, the equation of motion of the motor is T e T is the electromagnetic torque of the motor. L Let J be the load torque of the motor, J be the moment of inertia of the motor, and ω be the moment of inertia of the motor. m Let t be the mechanical speed of the motor, and t be the time.

[0053] The inverter does not generate a waveform, and the current in both the inverter and the motor is zero (ignoring the field weakening condition). The motor outputs no torque, Te = 0. For the motor, even under no-load conditions, the load torque TL will still have a value due to frictional losses. From the motor's equation of motion, we know that when S... gEN1 When the signal is low, the motor speed will decrease due to the load torque TL. To minimize the decrease in motor speed, S... gEN1 The low-level signal duration should not be too long, the sealing period T should not be too long, and the high-level duration T within the sealing period should be... on It is necessary to ensure that the motor speed is sufficient to recover to the set speed.

[0054] In this example, the sealing signal S generated during the sealing period gEN1 The generated flowchart is as follows Figures 4-5 As shown.

[0055] like Figures 4-5 As shown, the sealing period T is obtained using the motor's angular position signal. The motor's angular position alternates between 0 and 360°. The motor's angular position signal is divided into N equal parts (N can be either an integer or a fraction) to obtain the sealing period T. Then, based on the duty cycle within the sealing period, the high-level time T is obtained. on If the timing t within the current wave blocking cycle is less than T on At that time, the blocking signal S gEN1 If it is high, otherwise the blocking signal S gEN1 This is a low level. In this example, N is set to 4, and the transmission duty cycle is set to 30%.

[0056] Another embodiment of this application provides a control method for an inverter, the method comprising:

[0057] The inverter is controlled to generate a waveform based on the relationship between the blocking signal, the motor torque current setpoint and the current threshold, and the relationship between the motor speed measurement value and the speed threshold.

[0058] In one example, the blocking signal includes a first-level signal and a second-level signal;

[0059] When the blocking signal is a first level signal, the torque current setting value is lower than the current threshold, and the speed measurement value is higher than the speed threshold, the inverter is controlled not to generate a wave; otherwise, the inverter is controlled to generate a wave.

[0060] In one example, the sealing signal is determined in the following way:

[0061] First, the sealing period of the sealing signal is obtained based on the angular position signal of the motor. Then, the time corresponding to the second level signal of the sealing signal is obtained based on the duty cycle of the sealing signal. The sealing signal includes a first level signal and a second level signal.

[0062] In one example, the angular position signal is divided into N equal parts to obtain the sealing period of the sealing signal.

[0063] In one example, the duty cycle of the blocking signal is between 20% and 40%.

[0064] In one example, before the step of basing the data on the relationship between the blocking signal, the motor torque current setpoint and the current threshold, and the relationship between the motor speed measurement and the speed threshold, the method further includes:

[0065] The torque current setting value is obtained based on the measured speed value and the speed setting value.

[0066] In one example, before the step of basing the data on the relationship between the blocking signal, the motor torque current setpoint and the current threshold, and the relationship between the motor speed measurement and the speed threshold, the method further includes:

[0067] Acquire the motor's angular position signal and speed measurement value.

[0068] The above method is applicable not only to encoder-based vector control applications with motor position measurement devices, but also to encoderless vector control applications without motor position measurement devices; it is applicable not only to applications involving motor speed control and position control, but also to applications involving motor torque control; and it is applicable not only to applications employing vector control strategies, but also to applications employing control strategies such as the six-step method.

[0069] For encoderless applications, the motor's speed and position signals are no longer obtained by the speed measurement module, but are calculated by the observer. During the period when the blocking command is in effect, the back EMF voltage of the motor can be sampled and the motor's speed and position signals are obtained through the observer; during the period when the blocking logic is invalid and the blocking command is in effect, the inverter's output voltage and current are still used to obtain the speed and position signals through the observer.

[0070] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. A control method for an inverter, wherein the DC terminal of the inverter is connected to a DC power supply, and the AC terminal of the inverter is connected to a motor; characterized in that, The control method includes: Based on the relationship between the blocking signal, the motor torque current setpoint and the current threshold, and the relationship between the motor speed measurement value and the speed threshold, the inverter is controlled to generate a wave. The blocking signal includes a first-level signal and a second-level signal; When the blocking signal is a first level signal, the torque current setting value is lower than the current threshold, and the speed measurement value is higher than the speed threshold, the inverter is controlled not to generate a wave; otherwise, the inverter is controlled to generate a wave.

2. The control method according to claim 1, characterized in that, The sealing signal is determined in the following manner: First, the sealing period of the sealing signal is obtained based on the angular position signal of the motor. Then, the time corresponding to the second level signal of the sealing signal is obtained based on the duty cycle of the sealing signal. The sealing signal includes a first level signal and a second level signal.

3. The control method according to claim 2, characterized in that, The angular position signal is divided into N equal parts to obtain the sealing period of the sealing signal.

4. The control method according to claim 2, characterized in that, The duty cycle of the blocking signal is between 20% and 40%.

5. The control method according to claim 1, characterized in that, Before the step of basing the equation on the relationship between the sealed signal, the motor's torque current setpoint and the current threshold, and the relationship between the motor's speed measurement and the speed threshold, the method further includes: The torque current setting value is obtained based on the measured speed value and the speed setting value.

6. The control method according to claim 1, characterized in that, Before the step of basing the equation on the relationship between the sealed signal, the motor's torque current setpoint and the current threshold, and the relationship between the motor's speed measurement and the speed threshold, the method further includes: Acquire the motor's angular position signal and speed measurement value.

7. A control device for an inverter, wherein the DC terminal of the inverter is connected to a DC power supply, and the AC terminal of the inverter is connected to a motor; characterized in that, The control device includes: The drive module is configured to output a drive signal to control the inverter to generate waves when enabled, and not to output a drive signal when disabled. The blocking module is used to control whether the drive module is enabled based on the blocking signal, the relationship between the motor's torque current setpoint and the current threshold, and the relationship between the motor's speed measurement value and the speed threshold. The blocking signal includes a first-level signal and a second-level signal; The blocking module is further configured to control the drive module to be disabled when the blocking signal is a first level signal, the torque current setting value is lower than the current threshold, and the speed measurement value is higher than the speed threshold; otherwise, control the drive module to be enabled.

8. The control device according to claim 7, characterized in that, The sealing module is further configured to first obtain the sealing period of the sealing signal based on the angular position signal of the motor, and then obtain the time corresponding to the second level signal of the sealing signal based on the duty cycle of the sealing signal; wherein the sealing signal includes a first level signal and a second level signal.

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