A synchronous control method between multiple high-voltage inverters

Abstract

The present invention discloses a method for synchronous control between multiple high-voltage frequency converters. Each power unit collects the A, B, and C three-phase bus voltage values ​​of each high-voltage frequency converter in real time and uploads the collected bus voltage values ​​to a control board connected to the power unit. The control board estimates the actual voltage of the motor connected to each high-voltage frequency converter. Based on the estimated motor voltage and the collected motor current, the control board calculates the motor's active current. Based on the detected active current, the control board calculates the appropriate dynamic rate of change of speed to control the frequency converter to output the appropriate frequency value. Compared with the existing technology, the present invention completely does not rely on speed sensors. Each high-voltage frequency converter is independently controlled based on its own detected motor voltage and motor current signals, meeting the requirements of controlling multiple motors on a belt.

Description

Technical Field

[0001] The present invention relates to the field of high-voltage frequency converter driven motor control, and in particular to a synchronous control method between multiple high-voltage frequency converters. Background Art

[0002] In belt conveyor applications, multiple motors often drive the same belt. When using multiple high-voltage inverters to drive the motors, coordinated control between the inverters is required to maintain a consistent linear speed for the entire belt to operate properly. If the rotation of multiple motors cannot maintain a consistent linear speed, the belt will slip and, in severe cases, tear or break, causing damage to the equipment.

[0003] Currently, the coordinated control of multiple high-voltage inverters on a belt often requires sharing data between multiple inverters through a communication bus. At the same time, it relies on the speed encoder installed on the motor shaft to achieve consistent torque between multiple motors and consistent speed along the entire belt line, thereby meeting normal industrial control needs.

[0004] Existing high-voltage inverters rely heavily on signals from external speed sensors and the inverter's internal high-speed communication bus for synchronous control of multiple units. Loss of on-site speed sensor signals or interference with communication data can lead to failure of synchronous control between multiple inverters, causing the entire belt to shut down.

[0005] In addition, in some special working conditions, due to the installation environment, the distance between the high-voltage inverter and the motor is too long, resulting in the speed sensor signal being particularly susceptible to being affected when the speed sensor is installed, greatly reducing the reliability of the equipment operation. Summary of the Invention

[0006] The purpose of the present invention is to solve the deficiencies in the prior art and to provide a method for synchronous control between multiple high-voltage inverters.

[0007] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0008] A synchronous control method between multiple high-voltage inverters is used to control multiple high-voltage inverters to drive multiple motors, where each high-voltage inverter is connected to one motor, comprising the following steps:

[0009] S1. Connect several power units to the A, B, and C three-phase buses of each high-voltage inverter respectively, collect the A, B, and C three-phase bus voltage values ​​of each high-voltage inverter in real time through each power unit, and upload the collected bus voltage values ​​to the control board connected to the power unit;

[0010] S2. The control board calculates the actual voltage of the motor connected to each high-voltage inverter based on the collected A, B, and C three-phase bus voltage values ​​of each high-voltage inverter;

[0011] S3, the control board calculates the active current of the motor based on the calculated motor voltage and the collected motor current;

[0012] S4. Calculate the actual output frequency of the high-voltage inverter based on the detected active current, and then control the high-voltage inverter to output an appropriate frequency value.

[0013] Furthermore, the step S2 specifically includes:

[0014] S21. Assuming that n power units are connected to the A, B, and C three-phase buses of each high-voltage inverter, the bus voltages collected by the power units on the A-phase bus are Adc1, Adc2, ..., Adcn; the bus voltages collected by the power units on the B-phase bus are Bdc1, Bdc2, ..., Bdcn; and the bus voltages collected by the power units on the C-phase bus are Cdc1, Cdc2, ..., Cdcn.

[0015] S22. Calculate the three-phase DC voltage of each high-voltage inverter A, B, and C respectively:

[0016] Adc=Adc1+Adc2+...+Adcn;

[0017] Bdc=Bdc1+Bdc2+...+Bdcn;

[0018] Cdc=Cdc1+Cdc2+...+Cdcn;

[0019] Where: Adc is the phase-to-phase DC voltage of phase A, Bdc is the phase-to-phase DC voltage of phase B, and Cdc is the phase-to-phase DC voltage of phase C;

[0020] S23. Calculate the bus voltage of each high-voltage inverter separately:

[0021] Udc=(Adc+Bdc+Cdc) / sqrt(3);

[0022] Where: Udc represents the bus voltage of the high-voltage inverter, sqrt(3) represents the square root of 3;

[0023] S24. Assume that the modulation indexes of the three phases A, B, and C of the high voltage inverter are Da, Db, and Dc; calculate the output phase voltages of the three phases A, B, and C of the high voltage inverter, i.e., the three phase voltages of the motor, based on the bus voltage of the high voltage inverter:

[0024] Ua=Udc×((2 / 3)×Da-(1 / 3)×Db-(1 / 3)×Dc);

[0025] Ub=Udc×((2 / 3)×Db-(1 / 3)×Da-(1 / 3)×Dc);

[0026] Uc=Udc×((2 / 3)×Dc-(1 / 3)×Da-(1 / 3)×Db);

[0027] Among them: Ua represents the phase voltage of motor A, Ub represents the phase voltage of motor B, and Uc represents the phase voltage of motor C;

[0028] S25. Assuming that the voltage vector rotation angle of the high-voltage inverter is Dtheta, the actual motor voltage vector angle is Utheta, the actual voltage components Ualpha and Ubeta in the two-phase stationary coordinate system, and the actual voltage components Ud and Uq in the two-phase rotating coordinate system, perform Clakre and Park transformations on the three-phase phase voltages of the motor to obtain:

[0029] Ualpha=Ua;

[0030] Ubeta=(2×Ub+Ua) / sqrt(3);

[0031] Ud=Ualpha×cos(Dtheta)+Ubeta×sin(Dtheta);

[0032] Uq=-Ualpha×sin(Dtheta)+Ubeta×cos(Dtheta);

[0033] Utheta=atan(Uq,Ud).

[0034] Furthermore, the step S3 specifically includes:

[0035] S31. The control board collects the stator currents Ia and Ib of the motor phases A and B, and then performs Clarke transformation to obtain the currents Ialpha and Ibeta in the stator coordinate system:

[0036] Ialpha=Ia;

[0037] Ibeta=(2×Ib+Ia) / sqrt(3);

[0038] S32. Calculate the motor active current Id:

[0039] Id=Ialpha×cos(Utheta)+Ibeta×sin(Utheta).

[0040] Furthermore, the step S4 specifically includes:

[0041] The control board collects the output synchronous frequency of the high-voltage inverter and calculates the actual output frequency of the high-voltage inverter based on the motor active current:

[0042] f = fs - fs × Id × fd;

[0043] Where: f represents the actual output frequency of the high-voltage inverter, fs represents the output synchronous frequency of the high-voltage inverter, and fd represents the adjustable frequency range, which is a value between 0.0 and 0.1.

[0044] Compared with the existing technology, the present invention is completely independent of speed sensors. Each high-voltage inverter is independently controlled through the motor voltage and motor current signals detected by itself, which meets the control requirements of multiple motors on the belt and reduces cost investment. Especially in the control conditions of more than three motors, if one of the inverters fails and automatically exits the system, the entire belt can also be used at a reduced rating to ensure that the belt can run uninterruptedly, greatly improving the reliability of the belt system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Flowchart of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] This embodiment takes the application of belt conveyors as an example. Since belt conveyors often have multiple motors driving the same belt, when multiple high-voltage inverters are used to drive the motors, it is necessary for the inverters to be able to coordinate and control each other to keep the linear speed of the belt consistent so that the entire belt can operate normally. To achieve the above purpose, Figure 1 As shown, this embodiment provides a method for synchronous control between multiple high-voltage inverters, including the following steps:

[0048] 1) Connect several power units to the A, B, and C three-phase buses of each high-voltage inverter, and use each power unit to collect the A, B, and C three-phase bus voltage values ​​of each high-voltage inverter in real time. Assuming that n power units are connected to the A, B, and C three-phase buses of each high-voltage inverter, the bus voltages collected by the power unit on the A-phase bus are Adc1, Adc2...Adcn; the bus voltages collected by the power unit on the B-phase bus are Bdc1, Bdc2...Bdcn; and the bus voltages collected by the power unit on the C-phase bus are Cdc1, Cdc2...Cdcn. The collected bus voltage values ​​are uploaded to the control board connected to the power unit.

[0049] 2) The control board calculates the actual voltage of the motor connected to each high-voltage inverter based on the collected A, B, and C three-phase bus voltage values ​​of each high-voltage inverter;

[0050] (1) Calculate the three-phase DC voltage of each high-voltage inverter A, B, and C separately:

[0051] Adc=Adc1+Adc2+...+Adcn;

[0052] Bdc=Bdc1+Bdc2+...+Bdcn;

[0053] Cdc=Cdc1+Cdc2+...+Cdcn;

[0054] Where: Adc is the phase-to-phase DC voltage of phase A, Bdc is the phase-to-phase DC voltage of phase B, and Cdc is the phase-to-phase DC voltage of phase C;

[0055] (2) Calculate the bus voltage of each high-voltage inverter separately:

[0056] Udc=(Adc+Bdc+Cdc) / sqrt(3);

[0057] Where: Udc represents the bus voltage of the high-voltage inverter, sqrt(3) represents the square root of 3;

[0058] (3) Assuming that the modulation index of the three phases A, B, and C of the high voltage inverter is Da, Db, and Dc; the output phase voltage of the three phases A, B, and C of the high voltage inverter is calculated based on the bus voltage of the high voltage inverter, that is, the three phase voltage of the motor:

[0059] Ua=Udc×((2 / 3)×Da-(1 / 3)×Db-(1 / 3)×Dc);

[0060] Ub=Udc×((2 / 3)×Db-(1 / 3)×Da-(1 / 3)×Dc);

[0061] Uc=Udc×((2 / 3)×Dc-(1 / 3)×Da-(1 / 3)×Db);

[0062] Among them: Ua represents the phase voltage of motor A, Ub represents the phase voltage of motor B, and Uc represents the phase voltage of motor C;

[0063] (4) Assuming that the voltage vector rotation angle of the high-voltage inverter is Dtheta, the actual motor voltage vector angle is Utheta, the actual voltage components Ualpha and Ubeta in the two-phase stationary coordinate system, and the actual voltage components Ud and Uq in the two-phase rotating coordinate system, the Clakre and Park transformations of the three-phase phase voltages of the motor are obtained:

[0064] Ualpha=Ua;

[0065] Ubeta=(2×Ub+Ua) / sqrt(3);

[0066] Ud=Ualpha×cos(Dtheta)+Ubeta×sin(Dtheta);

[0067] Uq=-Ualpha×sin(Dtheta)+Ubeta×cos(Dtheta);

[0068] Utheta=atan(Uq,Ud).

[0069] 3) The control board calculates the active current of the motor based on the calculated motor voltage and the collected motor current;

[0070] (1) The control board collects the stator currents Ia and Ib of the motor phases A and B, and then performs Clarke transformation to obtain the currents Ialpha and Ibeta in the stator coordinate system:

[0071] Ialpha=Ia;

[0072] Ibeta=(2×Ib+Ia) / sqrt(3);

[0073] (2) Calculate the motor active current Id:

[0074] Id=Ialpha×cos(Utheta)+Ibeta×sin(Utheta).

[0075] 4) The control board collects the output synchronous frequency of the high-voltage inverter and calculates the actual output frequency of the high-voltage inverter based on the motor active current:

[0076] f = fs - fs × Id × fd;

[0077] Among them: f represents the actual output frequency of the high-voltage inverter, fs represents the output synchronization frequency of the high-voltage inverter, and fd represents the adjustable frequency range, which is a parameter adjusted by the user on site and is adjusted according to the working conditions. The range is between 0.0-0.1.

[0078] According to the calculated actual output frequency of the high-voltage inverter, it is sent to the high-voltage inverter, which can control the high-voltage inverter to output a suitable frequency value, thereby controlling the connected motor to rotate according to the frequency output by the high-voltage inverter.

[0079] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A synchronous control method between multiple high-voltage frequency converters, used to control multiple high-voltage frequency converters to drive multiple motors, each high-voltage frequency converter is connected to a motor, characterized in that: The following steps are involved: S1. Connect several power units to the A, B, and C three-phase buses of each high-voltage inverter respectively, collect the A, B, and C three-phase bus voltage values ​​of each high-voltage inverter in real time through each power unit, and upload the collected bus voltage values ​​to the control board connected to the power unit; S2. The control board calculates the actual voltage of the motor connected to each high-voltage inverter based on the collected A, B, and C three-phase bus voltage values ​​of each high-voltage inverter; S21. Assuming that n power units are connected to the A, B, and C three-phase buses of each high-voltage inverter, the bus voltages collected by the power units on the A-phase bus are Adc1, Adc2, ..., Adcn; the bus voltages collected by the power units on the B-phase bus are Bdc1, Bdc2, ..., Bdcn; and the bus voltages collected by the power units on the C-phase bus are Cdc1, Cdc2, ..., Cdcn. S22. Calculate the three-phase DC voltage of each high-voltage inverter A, B, and C respectively: Adc=Adc1+Adc2+...+Adcn; Bdc=Bdc1+Bdc2+...+Bdcn; Cdc=Cdc1+Cdc2+...+Cdcn; Where: Adc is the phase-to-phase DC voltage of phase A, Bdc is the phase-to-phase DC voltage of phase B, and Cdc is the phase-to-phase DC voltage of phase C; S23. Calculate the bus voltage of each high-voltage inverter separately: Udc=(Adc+Bdc+Cdc) / sqrt(3); Where: Udc represents the bus voltage of the high-voltage inverter, sqrt(3) represents the square root of 3; S24. Assume that the modulation indexes of the three phases A, B, and C of the high voltage inverter are Da, Db, and Dc; calculate the output phase voltages of the three phases A, B, and C of the high voltage inverter, i.e., the three phase voltages of the motor, based on the bus voltage of the high voltage inverter: Ua=Udc×((2 / 3)×Da-(1 / 3)×Db-(1 / 3)×Dc); Ub=Udc×((2 / 3)×Db-(1 / 3)×Da-(1 / 3)×Dc); Uc=Udc×((2 / 3)×Dc-(1 / 3)×Da-(1 / 3)×Db); Among them: Ua represents the phase voltage of motor A, Ub represents the phase voltage of motor B, and Uc represents the phase voltage of motor C; S25. Assuming that the voltage vector rotation angle of the high-voltage inverter is Dtheta, the actual motor voltage vector angle is Utheta, the actual voltage components Ualpha and Ubeta in the two-phase stationary coordinate system, and the actual voltage components Ud and Uq in the two-phase rotating coordinate system, perform Clakre and Park transformations on the three-phase phase voltages of the motor to obtain: Ualpha=Ua; Ubeta=(2×Ub+Ua) / sqrt(3); Ud=Ualpha×cos(Dtheta)+Ubeta×sin(Dtheta); Uq=-Ualpha×sin(Dtheta)+Ubeta×cos(Dtheta); Utheta=atan(Uq,Ud); S3, the control board calculates the active current of the motor based on the calculated motor voltage and the collected motor current; S31. The control board collects the stator currents Ia and Ib of the motor phases A and B, and then performs Clarke transformation to obtain the currents Ialpha and Ibeta in the stator coordinate system: Ialpha=Ia; Ibeta=(2×Ib+Ia) / sqrt(3); S32. Calculate the motor active current Id: Id=Ialpha×cos(Utheta)+Ibeta×sin(Utheta); S4. Calculate the actual output frequency of the high-voltage inverter based on the detected active current, and then control the high-voltage inverter to output the appropriate frequency value: The control board collects the high-voltage inverter output synchronous frequency and calculates the actual output frequency of the high-voltage inverter based on the motor active current: f = fs - fs × Id × fd; Where: f represents the actual output frequency of the high-voltage inverter, fs represents the output synchronous frequency of the high-voltage inverter, and fd represents the adjustable frequency range, which is a value between 0.0 and 0.1.

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