WO2023236855A1

WO2023236855A1 - Control circuit for realizing power balance of a plurality of synchronous motors and control method therefor

Info

Publication number: WO2023236855A1
Application number: PCT/CN2023/097938
Authority: WO
Inventors: 竺伟; 杜琼; 王永红
Original assignee: 上海能传电气有限公司
Priority date: 2022-06-07
Filing date: 2023-06-02
Publication date: 2023-12-14
Also published as: CN114826027A

Abstract

The present application relates to a control circuit for realizing power balance of a plurality of synchronous motors, and a control method therefor. The control circuit comprises a power frequency synchronous motor, n variable frequency synchronous motors, and n frequency converters, wherein n is a positive integer, and n is greater than or equal to 1. The n frequency converters are connected by means of a communication bus to form a control loop. Current and voltage sampling circuits are provided between the n frequency converters and the corresponding n variable frequency synchronous motors, respectively. The power frequency synchronous motor is provided with a voltage and current sampling loop connected to the frequency converter, and is also connected to a power grid by means of a power frequency switch to form a power frequency driving loop. The power frequency synchronous motor is connected to driving shafts of the n variable frequency synchronous motors by means of a connector to realize power coupling transmission.

Description

Control circuit and control method to achieve power balance of multiple synchronous motors

This application claims priority to the Chinese patent application with application number 202210636118.8, which was submitted to the China Patent Office on June 7, 2022. The entire content of this application is incorporated into this application by reference.

Technical field

The present application relates to an electrical control circuit, such as a control circuit and control method for achieving power balance of multiple synchronous motors, and belongs to the technical field of electrical device control.

Background technique

With the rapid development of industry, industrial control systems have become increasingly mature and mature. Frequency converters have been widely used in various industrial control systems. Especially in production, multi-motor transmission systems and multi-motor transmission systems that are mechanically connected to each other are often encountered. Transmission refers to a production machinery or multiple motors running synchronously in a process section. Their movements have a constraint relationship with each other, are non-independent operations, and are connected to each other through physical connectors, such as a mill system. , coaxial transmission by two electric motors, usually using a transmission method connected together through a gear box, or the two electric motors are driven through the meshing of the gear and the external gear of the mill. In the current production process, two frequency converters are basically used to drive two synchronous motors. Based on the production process requirements, the speed of the motors is basically not adjusted at the actual application site. Two frequency converters are usually used. The main purpose is to realize soft The starter and the two electric motors have balanced power distribution. The solution of using two frequency converters for two motors not only increases the investment cost of the frequency conversion equipment in the early stage, but also increases the maintenance cost in the later period.

Contents of the invention

The purpose of this application is to solve the shortcomings of related technologies and design a control circuit and control method to achieve power balance of multiple synchronous motors. The starting and power balance distribution functions of n+1 synchronous motors can be realized through n frequency converters. , reducing the investment cost and maintenance workload of frequency converter equipment in industrial control systems.

In the first aspect, this application provides a control circuit for achieving power balance of multiple synchronous motors. The control circuit includes: 1 power frequency synchronous motor Ms, n variable frequency synchronous motors and n frequency converters. The n frequency converters are The sequence of the variable frequency synchronous motors is recorded as the first variable frequency synchronous motor M1, the second variable frequency synchronous motor M2... the nth variable frequency synchronous motor Mn, and the sequence of the n frequency converters is recorded as the first frequency converter VFD1, the second frequency converter VFD2... ...The nth frequency converter VFDn, where n is a positive integer, and n is greater than or equal to 1, the n frequency converters each have a frequency converter control system, and the n frequency converters are connected to each other through a communication bus. In the control loop, current and voltage sampling circuits are respectively provided between the n frequency converters and the corresponding n variable frequency synchronous motors to form a sampling loop. The connecting circuits of the bus connecting the n frequency converters and the frequency variable synchronous motors are respectively There is a corresponding frequency converter power supply switch QF. The power frequency synchronous motor Ms is provided with a voltage and current sampling circuit connected to the first frequency converter VFD1 and forming a sampling loop. The power frequency synchronous motor Ms communicates with the power frequency through the power frequency switch QFs. The synchronous motor is connected to the busbar to form a power frequency drive circuit. At the same time, the power frequency synchronous motor Ms and the drive shafts of n variable frequency synchronous motors are connected to each other using connectors to achieve power coupling transmission.

In the second aspect, this application provides a control method for a control circuit to achieve power balance of multiple synchronous motors. The power balance control circuit includes n frequency converter control systems, n is a positive integer, and n is greater than or equal to 1, Data interaction between n frequency converter control systems is carried out through the communication bus. After the power frequency synchronous motor Ms and the variable frequency synchronous motor are started, the first frequency converter VFD1 samples the voltage and current of the power frequency synchronous motor Ms and sends the work frequency to the frequency converter. The sampling results of the voltage and current of the frequency synchronous motor Ms are input to the power frequency synchronous motor observer, so that the real-time power Power_s and real-time torque Torque_s of the power frequency synchronous motor Ms are obtained through the power frequency synchronous motor observer, and the real-time speed Speed_s of the power frequency synchronous motor Ms is obtained through The speed measuring device directly measures or obtains it through the industrial frequency synchronous motor observer. The real-time torque Torque_s of the industrial frequency synchronous motor and the reference torque given by n variable frequency synchronous motors are calculated by the average value calculator to obtain the system average torque T_Average. Each unit The difference between the reference torque given by the variable frequency synchronous motor and the system average torque T_Average is multiplied by the torque difference adjustment proportion coefficient Ks to obtain the torque difference compensation value of each variable frequency synchronous motor. Similarly, the torque difference compensation value of the variable frequency synchronous motor is The real-time speed is directly measured by a speed measuring device or the frequency converter samples the voltage and current of the variable frequency synchronous motor, and then the voltage of the variable frequency synchronous motor is and current sampling results are input to the frequency conversion synchronous motor observer, so that the real-time speed Speed_s of the power frequency synchronous motor Ms is obtained through the frequency conversion synchronous motor observer as the speed given signal of the frequency converter, which is synchronized with the real-time speed of the frequency conversion synchronous motor and the frequency conversion After subtracting the motor torque difference compensation value, the corresponding speed difference signal is obtained. The obtained speed difference signal is input to the speed regulator, and the updated reference torque given of the variable frequency synchronous motor is obtained through the speed regulator. After the update The reference torque is given by the torque current regulator to adjust the output, and then drives the corresponding variable frequency synchronous motor through the respective frequency converter execution unit. Finally, it is controlled by the n frequency converter control system to realize the synchronization of n+1 units through the n frequency converters. The power balance of the electric motor works.

Description of the drawings

Figure 1 is a schematic diagram of the equipment connection used in this application to start a power frequency excitation synchronous motor using mechanical interlocking rotation.

Figure 2 is a schematic diagram of the equipment connection in this application where the frequency converter is used to first drive the industrial frequency synchronous motor and then switch to the industrial frequency.

Figure 3 is a schematic diagram of the equipment connection used in this application to start the power frequency synchronous motor and achieve phase synchronization with the power grid using mechanical interlocking rotation.

Figure 4 is a schematic block diagram of the work flow of the power balance control method of this application.

Figure 5 is a flow chart of power balance control in this application.

In the picture:

1. Power frequency synchronous motor voltage sampling circuit;

2. Power frequency synchronous motor current sampling circuit;

3. Voltage sampling circuit of variable frequency synchronous motor;

4. Current sampling circuit of variable frequency synchronous motor;

9. Communication bus;

10. The power frequency synchronous motor is connected to the busbar;

11. Frequency conversion synchronous motor connection bus;

12. Load;

13. Connectors;

14. Excitation device;

15. Synchronous switching of reactors;

16. Grid voltage sampling circuit;

50. The first frequency converter VFD1 control system; 60. The second frequency converter VFD2 control system; 70. The nth frequency converter VFDn control system.

Detailed ways

The present application will be described below in conjunction with the accompanying drawings and specific embodiments.

According to the accompanying drawings 1 to 3, this application is a control circuit and a control method for achieving power balance of multiple synchronous motors. The control circuit for achieving power balance of multiple synchronous motors described in this application includes one power frequency synchronous motor. Ms, n frequency conversion synchronous motors (M1...Mn) and n frequency converters (VFD1...VFDn) (n is a positive integer, and n≥1), the n frequency converters are connected through the communication bus 9 to form a control Loop, the n frequency converters and the corresponding n frequency converters are respectively provided with current and voltage sampling circuits to form a sampling loop, that is, the voltage sampling circuit 3 of the variable frequency synchronous motor and the current sampling circuit 4 of the variable frequency synchronous motor, The connection circuits between the n frequency converters and the variable frequency synchronous motor connecting bus 11 are respectively provided with corresponding frequency converter power supply switches QF, and the power frequency synchronous motor Ms is connected to the first frequency converter VFD1 and forms a sampling loop. The voltage and current sampling circuit is a power frequency synchronous motor voltage sampling circuit 1 and a power frequency synchronous motor current sampling circuit 2. The power frequency synchronous motor Ms is connected to the power frequency synchronous motor connecting bus 10 through the power frequency switch QFs to form a power frequency drive circuit. At the same time, the power frequency synchronous motor Ms and the drive shafts of n variable frequency synchronous motors are connected to each other using conventional physical connectors 13 and connection methods such as transmission shafts, gearboxes, and belts to achieve power coupling transmission. The load 12 is driven by the power frequency synchronous motor Ms It works with the transmission shaft of n frequency conversion synchronous motors.

According to Figure 1, the equipment used to start a power frequency excitation synchronous motor using mechanical interlocking rotation includes 1 power frequency synchronous motor Ms, n frequency conversion synchronous motors (M1...Mn) and n frequency converters. (VFD1...VFDn) (n is a positive integer, and n≥1), the power frequency synchronous motor uses an excitation synchronous motor, and the variable frequency synchronous motor uses an excitation synchronous motor or a permanent magnet synchronous motor. The n frequency converters are connected through the communication bus 9 to form a control loop. The n frequency converters are respectively connected to the circuits of the corresponding n frequency conversion synchronous motors, and are respectively provided with corresponding n frequency conversion synchronous motors to form a sampling circuit. The circuit includes the voltage sampling circuit 3 of the variable frequency synchronous motor and the current sampling circuit 4 of the variable frequency synchronous motor. The connection circuits between the n frequency converters and the variable frequency synchronous motor connecting bus 11 are respectively provided with corresponding frequency converter power supply switches QF. The power frequency synchronous motor Ms is provided with a power frequency synchronous motor voltage sampling circuit 1 and a power frequency synchronous motor current sampling circuit 2 that are connected to the first frequency converter VFD1 and form a sampling circuit. The power frequency synchronous motor Ms passes through the power frequency switch QFs It is connected with the power frequency synchronous motor connecting bus 10 to form a power frequency drive circuit. At the same time, the power frequency synchronous motor Ms and the drive shafts of n variable frequency synchronous motors use conventional physical connectors 13 and connection methods such as transmission shafts, gearboxes, and belts to communicate with each other. Connect to realize power coupling transmission.

When starting, the power frequency switch QFs is in the off state, the excitation current is not input, and the frequency converter power supply switches QF respectively provided on the connecting circuit of the n frequency converters and the variable frequency synchronous motor connecting bus 11 are closed, and the frequency converter drives the variable frequency synchronous The motor runs until the power frequency speed. Since the power frequency synchronous motor Ms adopts mechanical connection and is driven by the power transmitted through the coupling, the power frequency synchronous motor Ms runs to the power frequency speed. At this time, the power frequency switch QFs is closed, and the power frequency synchronous motor Ms gradually passes through the power frequency synchronous motor Ms. The provided excitation device 14 inputs excitation current, and the power frequency synchronous motor Ms completes the power frequency driving operation.

According to Figure 2, a control circuit is adopted that first drives the industrial frequency synchronous motor with a frequency converter and then switches to industrial frequency operation. A first switch KM1 is provided between the first frequency converter VFD1 and the first variable frequency synchronous motor M1. The connection circuit between the output line of the frequency converter VFD1 and the first switch KM1 is sequentially provided with a synchronous switching reactor 15 and a second switch KMs, and the second switch KMs is connected to the industrial frequency synchronous motor Ms. The connection relationship of other equipment is consistent with the above-mentioned equipment connection relationship when starting the power frequency excitation synchronous motor using mechanical interlocking rotation. The power frequency synchronous motor described in this circuit uses an excitation synchronous motor or a permanent magnet synchronous motor.

When starting, the power frequency switch QFs is in the disconnected state, and the voltage sampling circuit 1 is connected above the switch QFs. And connect to the first frequency converter VFD1, collect the frequency, amplitude and phase of the three-phase voltage of the power frequency synchronous motor connected to the bus 10 in real time, close the corresponding frequency converter power supply switch (QF1...QFn) of each frequency converter, and close the second switch Switch KMs, turn off the first switch KM1, the circuit of the first frequency converter VFD1 driving the power frequency synchronous motor Ms is connected, and the first frequency converter VFD 1 drives the power frequency synchronous motor Ms to the power frequency speed, if the power frequency synchronous motor Ms As an excitation synchronous motor, the excitation output is first controlled by the first frequency converter. Each variable frequency synchronous motor (M1...Mn) is constrained by the mechanical connector and rotates synchronously with the power frequency synchronous motor Ms. When the first frequency converter VFD1 drives the power After the frequency synchronous motor Ms reaches the rated speed, the first frequency converter VFD1 adjusts the output voltage so that the output voltage of the first frequency converter VFD1 is consistent with the frequency and frequency of the three-phase voltage of the power frequency synchronous motor connecting bus 10 to which the power frequency synchronous motor Ms will be connected. The amplitude and phase are consistent, then close the power frequency switch QFs, open the second switch KMs, and the power frequency drive circuit is connected. If the power frequency synchronous motor Ms is an excitation synchronous motor, the excitation device switches to power frequency automatic control and power frequency synchronization. The electric motor Ms performs power frequency drive operation. Then the first switch KM1 is closed, and the circuit in which the first frequency converter VFD1 drives the variable frequency synchronous motor M1 is connected. Each frequency converter (VFD1...VFDn) drives the corresponding variable frequency synchronous motor (M1...Mn) to run by synchronously tracking the rotation speed.

According to Figure 3, a circuit that uses mechanical interlocking rotation to start the power frequency synchronous motor and realize phase synchronization with the power grid (i.e., the power frequency synchronous motor connecting bus 10) is connected between the power frequency switch QFs and the power frequency synchronous motor connecting bus 10. The connection circuit is also provided with a voltage sampling circuit connected to the first frequency converter VFD1, and forms a grid voltage sampling circuit 16. The connection relationship of other equipment is the same as that mentioned above when starting the power frequency excitation synchronous motor using mechanical interlocking rotation. consistent. The power frequency synchronous motor described in this circuit uses an excitation synchronous motor or a permanent magnet synchronous motor.

When starting, the power frequency switch QFs is in the open state, and the frequency converter power supply switches QF respectively provided on the connecting circuits of the n frequency converters and the variable frequency synchronous motors connecting bus 11 are closed, and the frequency converters drive the variable frequency synchronous motors to run until the power frequency Speed, if the power frequency synchronous motor Ms uses an excitation synchronous motor, the excitation cabinet outputs no-load excitation current. Since the power frequency synchronous motor Ms is mechanically connected and driven by the power transmitted through the coupling, the power frequency synchronous motor Ms runs to the power frequency speed, then the first frequency conversion The device VFD1 gradually adjusts the power frequency synchronous motor Ms speed by comparing the power grid voltage sampling and the power frequency synchronous motor voltage sampling results, so that the power generation voltage of the power frequency synchronous motor is consistent with the frequency and phase of the power grid voltage where the power frequency synchronous motor is located. At this time Close the power frequency switch QFs, gradually input the excitation current through the excitation device set by the power frequency synchronous motor Ms, and the power frequency synchronous motor Ms completes the power frequency drive operation.

The above control circuit in this application implements a control method for power balance of multiple synchronous motors, specifically as follows:

According to Figures 4 and 5, the control method for achieving power balance of multiple synchronous motors described in this application includes a control system (sequence) of n frequency converters (VFD1...VFDn) (n is a positive integer, and n≥1) Denoted as: the first frequency converter VFD1 control system 50, the second frequency converter VFD2 control system 60,... the nth frequency converter VFDn control system 70), and the frequency converter control systems perform data interaction through the communication bus. The first frequency converter VFD1 control system 50 includes an average value calculator, a power frequency synchronous motor observer, a first variable frequency synchronous motor observer, a first speed regulator, a first torque current regulator and a first frequency converter execution unit. The second frequency converter VFD2 control system 60 includes a second variable frequency synchronous motor observer, a second speed regulator, a second torque current regulator and a second frequency converter execution unit. The nth frequency converter VFDn control system 70 includes an nth variable frequency synchronous motor observer, an nth speed regulator, an nth torque current regulator and an nth frequency converter execution unit.

When the power frequency synchronous motor Ms and the variable frequency synchronous motor (M1...Mn) complete starting, the first frequency converter VFD1 samples the voltage and current of the power frequency synchronous motor Ms and inputs the sampling result of the voltage and current of the power frequency synchronous motor Ms into Power frequency synchronous motor observer, so that the real-time power Power_s and real-time torque Torque_s of the power frequency synchronous motor Ms can be obtained through the power frequency synchronous motor observer. The real-time speed Speed_s can be measured directly using the speed measuring device s, or through the power frequency synchronous motor The observer obtains, the real-time torque Torque_s of the power frequency synchronous motor and the reference torque given (T ₁ *...T _n *) of n variable frequency synchronous motors are calculated by the average value calculator to obtain the system average torque T_Average, each variable frequency synchronous motor The difference between the reference torque given by the motor (T ₁ *...T _n *) and the system average torque T_Average is multiplied by the torque difference adjustment proportion coefficient Ks to obtain the torque difference compensation value (Terrork_1... .Terrork_n).

Similarly, the real-time speed (Speed_1...Speed_n) of the variable frequency synchronous motor can be calculated using the corresponding It can be directly measured by the speed measuring device, or the frequency converter (VFD1...VFDn) can sample the voltage and current of the variable frequency synchronous motor (M1...Mn), and input the voltage and current sampling results of the variable frequency synchronous motor to the variable frequency synchronous motor observer, respectively. Obtained through variable frequency synchronous motor observer.

The real-time speed Speed_s of the power frequency synchronous motor Ms is used as the speed given signal of the frequency converter, and the speed is obtained by subtracting it from the real-time speed (Speed_1...Speed_n) of the variable frequency synchronous motor and the torque difference compensation value (Terrork_1...Terrork_n) of the variable frequency synchronous motor. Difference signal (Speeddiff_1...Speeddiff_n), input the obtained speed difference signal (Speeddiff_1...Speeddiff_n) to the speed regulator (1...n), and obtain the frequency of the variable frequency synchronous motor through the speed regulator (1...n) The updated reference torque given (T ₁ *...T _n *), the updated reference torque given (T ₁ *...T _n *) is adjusted by the torque current regulator (1...n) and then passed The frequency converter execution unit (1...n) drives the corresponding variable frequency synchronous motor (M1...Mn) to achieve the power balance of n+1 synchronous motors.

The average calculator uses the following formula to calculate the system average torque T_Average:

If the power of n variable-frequency synchronous motors is not the same, the reference torque reference (T ₁ *...T _n *) of the variable-frequency synchronous motor and the real-time torque Torque_s of the industrial frequency synchronous motor can be proportionally distributed according to their respective rated powers. That is, the torque is calibrated in percentage according to the rated torque.

In the synchronous motor observer, the three-phase current sampling signal Current of the synchronous motor is represented by I _a , I _b and I _c respectively, and the three-phase voltage sampling signal Voltage is represented by U _a , U _b and U _c respectively, and is calculated using the following formula Real-time power Power, real-time torque Torque and real-time speed Speed:

Torque＝K _m ×I _d formula (5)

Among them, K _m is a fixed proportional constant, determined by the parameters of the synchronous motor.
Power=Torque×Speed Formula (6)

The power frequency synchronous motor Ms voltage sampling signal Ms_Voltage and current sampling signal Ms_Current can be calculated through the power frequency synchronous motor observer to obtain real-time power Power_s, real-time torque Torque_s and real-time speed Speed_s.

Similarly, the voltage sampling signal (M1_Voltage...Mn_Voltage) and current sampling signal (M1_Current...Mn_Current) of each variable frequency synchronous motor (M1...Mn) can be calculated through the corresponding variable frequency synchronous motor observer to obtain the real-time power (Power_1. ..Power_n), real-time torque (Torque_1...Torque_n) and real-time speed (Speed_1...Speed_n).

The speed regulator uses the speed difference Speeddiff as an input signal and calculates the updated reference torque given value T* according to the following formula:
T ^* ＝K _P ×Speeddiff+K _i ∫Speeddiff dt Formula (7)

In formula (7), t is the integration time, Kp and Ki are the proportional coefficient and the integral coefficient respectively, and the values of Kp and Ki are determined by the parameters of the synchronous motor.

The frequency converter takes the speed difference (Speeddiff_1...Speeddiff_n) as the input signal, and calculates the updated reference torque given (T ₁ *...T) of the corresponding variable frequency synchronous motor through the corresponding speed regulator (1...n) _n *).

The torque current regulator is based on the updated reference torque reference T* and real-time torque Torque of the synchronous motor, and calculates the reference torque voltage V* according to the following formula:
V ^* ＝K _P (T ^* -Torque)+K _i ∫ (T ^* -Torque)dt Formula (8)

In formula (8), t is the integration time, Kp and Ki are the proportional coefficient and the integral coefficient respectively, Kp The values of and Ki are determined by the synchronous motor parameters.

The values of Kp and Ki in the formula (7) and formula (8) are calculated as follows:

Among them: L _σ is the leakage inductance of the motor, I _rated is the rated current of the motor, U _rated is the rated voltage of the motor, T _Currentloop is the regulator execution cycle, and R _s is the motor stator resistance.

The frequency converter takes the updated reference torque reference (T ₁ *...T _n *) and real-time torque (Torque_1...Torque_n) of the variable frequency synchronous motor as input signals, and calculates them through the torque current regulator (1...n) Obtain the corresponding reference torque voltage (V ₁ *...V _n *) of the variable frequency synchronous motor.

The inverter execution unit generates three SPWM (Sinusoidal Pulse Width Modulation, sinusoidal pulse width modulation) waves based on the reference torque voltage (V ₁ *...V _n *). The inverter execution unit is a three-phase inverter composed of power switching tubes. device. Power switch tubes all use MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, metal-oxide semiconductor field-effect transistor) and IGBT (Insulated Gate Bipolar Transistor, insulated gate bipolar transistor), IGCT (Intergrated Gate Commutated Thyristors, integrated gate commutated thyristor) and other switching devices.

In this application, by setting up a voltage and current sampling circuit and a power frequency drive circuit, the frequency converter obtains the voltage and current sampling signals of the power frequency synchronous motor, and then controls the output power of the corresponding variable frequency synchronous motor to be consistent with the power frequency synchronous motor, realizing n units Compared with related technologies, the frequency converter controls the starting and power balance of n+1 synchronous motors, reducing the cost investment and maintenance workload of the frequency converter equipment. Taking the mill transmission system as an example, the price of frequency converter equipment is calculated as 300 yuan per kilowatt. A mill system with a power of 10MW can save 1.5 million yuan in investment in frequency converter equipment.

Example 1:

Referring to Figure 1, Figure 4 and Figure 5 in this embodiment, in this embodiment, the power frequency synchronous motor adopts an excitation synchronous motor, and the variable frequency synchronous motor adopts an excitation synchronous motor or a permanent magnet synchronous motor.

The working process and control principle of power balance control in this application are as follows:

Stage 1: Turn off the power frequency switch QFs, the Ms excitation current of the power frequency synchronous motor is not input, close the inverter power supply switch (QF1...QFn), connect the inverter drive circuit, start the corresponding drive of each inverter (VFD1...VFDn) The variable frequency synchronous motor (M1..Mn) operates. Since it is mechanically connected to the power frequency synchronous motor Ms, the power frequency synchronous motor Ms rotates synchronously with other variable frequency synchronous motors.

Stage 2: When the power frequency synchronous motor Ms reaches the rated speed, the power frequency switch QFs is closed, the power frequency drive circuit is connected, the excitation current is gradually input, and the power frequency synchronous motor Ms realizes power frequency drive operation.

Stage 3: The first frequency converter VFD1 acquires the voltage and current sampling signals of the industrial frequency synchronous motor Ms, and controls the corresponding variable frequency synchronous motor (M1...Mn) through the frequency converter (VFD1...VFDn) control system through the power balance control method of this application. The output power is consistent with the power frequency synchronous motor Ms.

Example 2:

This embodiment refers to Figure 2, Figure 4 and Figure 5.

Stage 1: Open the power frequency switch QFs, close the frequency converter power supply switch (QF1...QFn), close the second switch KMs, open the first switch KM1, and the first frequency converter VFD1 drives the power frequency synchronous motor Ms circuit to connect, The first frequency converter VFD 1 drives the power frequency synchronous motor Ms to the power frequency speed. The variable frequency synchronous motor (M1...Mn) is constrained by the mechanical connector and rotates synchronously with the power frequency synchronous motor Ms.

Stage 2: When the first frequency converter VFD1 drives the power frequency synchronous motor Ms to reach the rated speed, the first frequency converter VFD1 adjusts the output voltage so that the output voltage of the first frequency converter VFD1 is consistent with the frequency of the grid voltage where the power frequency synchronous motor Ms is located. , the amplitude and phase are consistent, then close the power frequency switch QFs, open the second switch KMs, the power frequency drive circuit is connected, and the power frequency synchronous motor Ms runs with power frequency drive.

Stage 3: Close the first switch KM1, the first frequency converter VFD1 drives the first variable frequency synchronous motor M1 and the circuit is connected. Each frequency converter (VFD1...VFDn) drives the corresponding variable frequency synchronous motor (M1...Mn) by synchronously tracking the speed. run.

Stage 4: The first frequency converter VFD1 obtains the voltage and current sampling signals of the industrial frequency synchronous motor Ms, and controls the corresponding variable frequency synchronous motor (M1...Mn) through the frequency converter (VFD1...VFDn) control system through the power balance control method of this application. ) output power is consistent with the power frequency synchronous motor Ms.

Example 3:

This embodiment refers to Figure 3, Figure 4 and Figure 5.

Stage 1: Open the power frequency switch QFs, close the inverter power supply switch (QF1...QFn), connect the inverter drive circuit, start each inverter (VFD1...VFDn) to drive the corresponding variable frequency synchronous motor (M1...Mn) to run, Since the power frequency synchronous motor Ms is mechanically connected and rotates synchronously with other variable frequency synchronous motors, when the power frequency synchronous motor Ms reaches the rated speed, if the power frequency synchronous motor is an excitation synchronous motor, the first frequency converter VFD1 controls the power frequency synchronization The excitation device of the motor outputs no-load excitation current.

Stage 2: The first frequency converter VFD1 adjusts the speed of the driven variable frequency synchronous motor by comparing the grid voltage sampling and the power frequency synchronous motor voltage sampling, so that the power generation voltage of the power frequency synchronous motor is equal to the frequency sum of the power grid voltage where the power frequency synchronous motor is located. The phases are consistent. If the power frequency synchronous motor is an excitation synchronous motor, the first frequency converter VFD1 can control the excitation current output by the excitation device of the power frequency synchronous motor so that the generated voltage amplitude of the excitation synchronous motor is consistent with the grid voltage amplitude, and then When the power frequency switch QFs is closed, the power frequency drive circuit is connected, and the power frequency synchronous motor Ms realizes power frequency drive operation.

Stage 3: The first frequency converter VFD1 obtains the voltage and current sampling signals of the industrial frequency synchronous motor Ms, and controls the corresponding variable frequency synchronous motor (M1...Mn) through the frequency converter (VFD1...VFDn) control system through the power balance control method of this application. ) output power is consistent with the power frequency synchronous motor Ms.

The control circuit and control method provided by this application to achieve power balance of multiple synchronous motors are suitable for transmission systems of multiple synchronous motors with mechanical connections, such as grinding mill applications, where n + 1 synchronous motors are realized through n frequency converters. Soft start and balanced power distribution reduce the cost of the inverter equipment. cost and maintenance workload.

Claims

A control circuit to achieve power balance of multiple synchronous motors, including 1 industrial frequency synchronous motor Ms, n variable frequency synchronous motors and n frequency converters. The n frequency variable synchronous motors are sequentially recorded as the first variable frequency synchronous motor M1 , the second frequency converter synchronous motor M2...the nth frequency converter synchronous motor Mn, the order of the n frequency converters is recorded as the first frequency converter VFD1, the second frequency converter VFD2...the nth frequency converter VFDn, where n is a positive integer , and n is greater than or equal to 1, the n frequency converters each have a frequency converter control system, and the n frequency converters are connected to each other through a communication bus to form a control loop, and the n frequency converters are connected to the corresponding There are current and voltage sampling circuits between the n variable frequency synchronous motors to form a sampling loop. The connection circuits between the n frequency converters and the variable frequency synchronous motors are respectively provided with corresponding frequency converter power supply switches QF. The power frequency synchronous motor Ms is equipped with a voltage and current sampling circuit connected to the first frequency converter VFD1 and forming a sampling loop. The power frequency synchronous motor Ms is connected to the power frequency synchronous motor connecting bus through the power frequency switch QFs to form a power frequency drive loop. The frequency synchronous motor Ms and the drive shafts of the n variable frequency synchronous motors are connected to each other using connectors to achieve power coupling transmission.
The control circuit for achieving power balance of multiple synchronous motors according to claim 1, wherein the connector includes a transmission shaft, a gearbox and a belt.
The control circuit for achieving power balance of multiple synchronous motors according to claim 1, wherein: when the power balance control circuit uses mechanical interlocking rotation to start the power frequency excitation synchronous motor, the power frequency synchronous motor adopts It is an excitation synchronous motor, and the variable frequency synchronous motor adopts an excitation synchronous motor or a permanent magnet synchronous motor.
The control circuit for achieving power balance of multiple synchronous motors according to claim 1, wherein: the power balance control circuit adopts a frequency converter to first drive the power frequency synchronous motor and then switch to power frequency operation, and the power frequency synchronization The motor adopts an excitation synchronous motor or a permanent magnet synchronous motor, and a first switch KM1 is provided between the first frequency converter VFD1 and the first variable frequency synchronous motor M1. The output line of the first frequency converter VFD1 goes to the first switch The connection circuit between KM1 is provided with a synchronous switching reactor and a second switching switch KMs in sequence, and the second switching switch KMs is connected to the power frequency synchronous motor Ms.
The control circuit for achieving power balance of multiple synchronous motors according to claim 1, wherein: the power balance control circuit uses a mechanical interlocking rotation method to start the power frequency synchronous motor and achieve phase synchronization with the busbar connected to the power frequency synchronous motor. When the power frequency synchronous motor is used, it is an excitation synchronous motor or a permanent magnet synchronous motor. The connection circuit between the power frequency switch QFs and the power frequency synchronous motor connecting bus is also provided with a voltage sampling device connected to the first frequency converter VFD1 circuit, and form a bus voltage sampling loop for connecting the power frequency synchronous motor.
The control circuit for realizing power balance of multiple synchronous motors according to claim 1, wherein: the power frequency switch QFs is in the off state when starting, and the frequency converter drives the variable frequency synchronous motor to run until the power frequency speed. Since the power frequency synchronous motor Ms is mechanically connected and driven by the power transmitted through the coupling. The power frequency synchronous motor Ms runs to the power frequency speed. At this time, the power frequency switch QFs is closed, and the power frequency synchronous motor Ms completes the power frequency driving operation.
The control circuit for realizing power balance of multiple synchronous motors according to claim 1, wherein: the first frequency converter VFD1 obtains the voltage and current sampling signals of the industrial frequency synchronous motor Ms, and passes the frequency converter provided by each frequency converter respectively. The control system controls the output power of the corresponding variable frequency synchronous motor to be consistent with the power frequency synchronous motor Ms.
A control method for a control circuit that realizes power balance of multiple synchronous motors according to any one of claims 1 to 7, the power balance control circuit includes n frequency converter control systems, n is a positive integer, and n is greater than or Equal to 1, n frequency converter control systems perform data exchange through the communication bus. After the power frequency synchronous motor Ms and the variable frequency synchronous motor complete starting, the first frequency converter VFD1 samples the voltage and current of the power frequency synchronous motor Ms, The sampling results of the voltage and current of the power frequency synchronous motor Ms are input to the power frequency synchronous motor observer, so that the real-time power Power_s and real-time torque Torque_s of the power frequency synchronous motor Ms are obtained through the power frequency synchronous motor observer. The real-time power frequency synchronous motor Ms The speed Speed_s is directly measured by a speed measuring device or obtained through a power frequency synchronous motor observer. The real-time torque Torque_s of the power frequency synchronous motor and the reference torque given by n variable frequency synchronous motors are calculated by the average calculator to obtain the system average torque T_Average. , the difference between the reference torque reference of each variable frequency synchronous motor and the system average torque T_Average is multiplied by the torque difference adjustment proportion coefficient Ks to obtain each variable frequency synchronous motor. Frequency synchronous motor torque difference compensation value. Similarly, the real-time speed of the variable frequency synchronous motor is directly measured by a speed measuring device or the frequency converter samples the voltage and current of the variable frequency synchronous motor, and the sampling results of the voltage and current of the variable frequency synchronous motor are input to Frequency conversion synchronous motor observer, thus obtaining through the frequency conversion synchronous motor observer, the real-time speed Speed_s of the power frequency synchronous motor Ms is used as the speed given signal of the frequency converter, and is compared with the real-time speed of the frequency conversion synchronous motor and the torque difference compensation value of the frequency conversion synchronous motor After subtraction, the corresponding speed difference signal is obtained. The obtained speed difference signal is input to the speed regulator, and the updated reference torque given of the variable frequency synchronous motor is obtained through the speed regulator. The updated reference torque given The output is adjusted by the torque current regulator, and then the corresponding variable frequency synchronous motor is driven by the respective frequency converter execution unit. Finally, the power balance of the n + 1 synchronous motors through the n frequency converters is realized through the control of the n frequency converter control system.
The control method of a control circuit for achieving power balance of multiple synchronous motors according to claim 8, wherein the sequence of the n frequency converter control systems is recorded as: the first frequency converter VFD1 control system, the second frequency converter VFD2 control system System...nth frequency converter VFDn control system, the first frequency converter VFD1 control system includes an average value calculator, a power frequency synchronous motor observer, a first variable frequency synchronous motor observer, a first speed regulator, a first Torque current regulator and first frequency converter execution unit, the second frequency converter VFD2 control system includes a second variable frequency synchronous motor observer, a second speed regulator, a second torque current regulator and a second frequency converter Execution unit, the nth frequency converter VFDn control system includes the nth variable frequency synchronous motor observer, the nth speed regulator, the nth torque current regulator and the nth frequency converter execution unit;

The formula used by the average value calculator to calculate the system average torque T_Average is:

At the same time, when the power of n variable-frequency synchronous motors is different, the reference torque reference of the variable-frequency synchronous motor and the real-time torque Torque_s of the industrial frequency synchronous motor are proportionally distributed according to their respective rated powers, and the torque is proportional to the rated torque. Perform percentage calibration, and the reference rotation of n frequency conversion synchronous motors is The given order of moments is recorded as T 1 *...T n *;

In the synchronous motor observer, the three-phase current sampling signal Current of the synchronous motor is represented by I a , I b and I c respectively, the three-phase voltage sampling signal Voltage is represented by U a , U b and U c respectively, the real-time power Power, real-time power Torque Torque and real-time speed Speed are calculated using the following formula:

Torque=K m ×I d formula (5),

where K m is a fixed proportional constant, determined by the parameters of the synchronous motor,
Power=Torque×Speed formula (6),

The power frequency synchronous motor Ms voltage sampling signal Ms_Voltage and current sampling signal Ms_Current are calculated by the power frequency synchronous motor observer to obtain real-time power Power_s, real-time torque Torque_s and real-time speed Speed_s. Similarly, the voltage sampling signal and current sampling signal of each variable frequency synchronous motor are The signal is calculated by the corresponding frequency conversion synchronous motor observer to obtain real-time power, real-time torque and real-time speed. The voltage sampling signal sequence is recorded as: M1_Voltage...Mn_Voltage, and the current sampling signal sequence is recorded as: M1_Current.. .Mn_Current, the real-time power sequence is recorded as: Power_1...Power_n, the real-time torque sequence is recorded as: Torque_1...Torque_n, and the real-time speed sequence is recorded as: Speed_1...Speed_n;

The speed regulator uses the speed difference signal Speeddiff as an input signal and calculates the reference torque given value T* according to the following formula:
T * ＝K P ×Speeddiff+K i ∫Speeddiff dt Formula (7),

Among them, t is the integration time, Kp and Ki are the proportional coefficient and the integral coefficient respectively. The values of Kp and Ki are determined by the parameters of the synchronous motor.

The frequency converter uses the speed difference signal as an input signal, and calculates the updated reference torque given by the corresponding variable frequency synchronous motor through the corresponding speed regulator. The sequence is recorded as: T1*...Tn*, the corresponding speed of n frequency converters. The sequence of difference signals is recorded as: Speeddiff_1...Speeddiff_n;

The torque current regulator is based on the updated reference torque reference T* and real-time torque Torque of the synchronous motor, and calculates the reference torque voltage V* according to the following formula:
V * ＝K P (T * -Torque)+K i ∫ (T * -Torque)dt Formula (8)

Among them, t is the integration time, Kp and Ki are the proportional coefficient and the integral coefficient respectively. The values of Kp and Ki are determined by the parameters of the synchronous motor.

The frequency converter uses the updated reference torque reference and real-time torque of the variable frequency synchronous motor as input signals, and calculates the corresponding reference torque voltage of the variable frequency synchronous motor through the corresponding torque current regulator. The frequency variable synchronous motor updates The subsequent reference torque given sequence is recorded as: T1*...Tn*, the real-time torque sequence is recorded as: Torque_1...Torque_n, and the reference torque voltage sequence of the variable frequency synchronous motor is recorded as: V1*...Vn*.