CN110768267B - Factory power control system and control method thereof - Google Patents

Abstract

Provided are a plant power control system and a control method thereof, which improve the power factor of the whole power system of a plant. The plant power control system is provided with: a power inverter (5) located between the power system (1) and each motor (10); a reactive power load device (3) connected to the power system; a control device (4) for instructing reactive power supplied from each power converter to the power system; and a reactive power detection device (2) for detecting reactive power, wherein the control device calculates a reactive power demand for canceling the reactive power detected by the reactive power detection device from the reactive power supplied from each power converter to the power system, and calculates a command value for allocating the reactive power demand to each power converter for each power converter from the residual power of each power converter based on the reactive power demand and predetermined information related to each motor.

Description

Factory power control system and control method thereof

Technical Field

The invention relates to a plant (plant) power control system and a control method thereof.

Background

Patent document 1 is known as a system for improving the power factor of a plant power supply. Patent document 1 discloses the following technique: provided is a factory power factor control method of a factory power control system which optimally controls the power factor of the whole factory by utilizing the surplus of the current capacity (current capacity) of an inverter drive (inverter drive) having a large power ratio in the factory to the maximum extent. That is, in patent document 1, reactive power is supplied from the control system to the plant in a direction to reduce reactive power received from the system by the plant.

Prior art literature

Patent document 1: japanese patent No. 3682544

Disclosure of Invention

Problems to be solved by the invention

Patent document 1 describes improvement of the power factor of a plant power supply, but does not describe the value of reactive power to be distributed to a plurality of inverter drives and the output timing thereof, and there is room for improvement.

For example, in a factory such as steel rolling, at the moment when a rolling motor engages a steel sheet, torque increases suddenly and the rotational speed decreases, so that the power converter increases a torque current command to maintain the rotational speed. Since the torque current increases, the residual current of the current capacity of the power converter decreases, and thus, sufficient reactive power cannot be supplied from the power converter, and there is a possibility that the power factor of the entire plant power supply decreases.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a plant power control system and a control method thereof, which can effectively improve the power factor of the whole plant.

Means for solving the problems

In order to solve the above problems, a plant power control system according to an aspect of the present invention includes: a power inverter provided for each of the motors between a power system of a factory and each of the motors; reactive power load equipment connected to the power system; a control device that generates a predetermined instruction that instructs reactive power supplied from each power converter to the power system; and a reactive power detection device for detecting reactive power at a power receiving point of the reactive power load device and the power system, wherein the control device calculates a reactive power demand for canceling the reactive power detected by the reactive power detection device based on reactive power supplied from each power converter to the power system, and the control device calculates a command value for assigning the calculated reactive power demand to each power converter for each power converter based on the reactive power demand and predetermined information related to each motor, based on the residual power of each power converter.

Effects of the invention

According to the present invention, the command value for assigning the reactive power demand to each power converter can be calculated from the residual power of each power converter, and the power factor of the entire plant can be effectively improved.

Drawings

Fig. 1 is an overall configuration diagram of a plant power control system according to embodiment 1.

Fig. 2 is a structural diagram of the power control apparatus.

Fig. 3 is an explanatory diagram showing a positional relationship between the motor group and the steel plate.

Fig. 4 is a graph showing changes in torque and speed of the motor.

Fig. 5 is a flowchart showing a process of predicting a time when a steel sheet reaches a motor (corresponding power inverter).

Fig. 6 is a flowchart of a process of determining a reactive power command.

Fig. 7 is a flowchart showing another process of determining a reactive power command.

Fig. 8 is an explanatory diagram showing a reactive power distribution state in the related art to be compared with the present embodiment.

Fig. 9 is an explanatory diagram showing a reactive power distribution state in the present embodiment.

Fig. 10 is an explanatory diagram showing another positional relationship between the power converter group and the steel sheet.

Fig. 11 is an overall configuration diagram of a plant power control system according to embodiment 2.

Fig. 12 is a structural diagram of the power control apparatus.

Fig. 13 is a flowchart of the arrival time prediction process.

Fig. 14 is a flowchart of another arrival time prediction process.

Fig. 15 is an explanatory diagram showing a positional relationship between the motor group and the steel plate.

Fig. 16 is a flowchart of a process of determining a reactive power command.

Fig. 17 is a configuration diagram of a power control device according to embodiment 3.

Fig. 18 is a functional configuration diagram for estimating the steel plate speed from the sensor signal.

Fig. 19 is a graph showing changes in torque and speed of the motor.

Fig. 20 is a structural diagram of a power control device according to embodiment 4.

Fig. 21 is an overall configuration diagram of a plant power control system according to embodiment 5.

Fig. 22 is a structural diagram of the power factor adjustment device.

Fig. 23 is a structural diagram of the power control apparatus.

Fig. 24 is a graph showing a distribution state of reactive power.

Fig. 25 is an overall configuration diagram of a plant power control system according to embodiment 6.

Fig. 26 is a structural diagram of the power control apparatus.

Fig. 27 is a flowchart of a process of determining a reactive power command.

Fig. 28 is a structural diagram of a power control device according to embodiment 7.

Fig. 29 is a flowchart of a process of determining a reactive power command.

Fig. 30 is a structural diagram of a power control device according to embodiment 8.

Fig. 31 is a flowchart of a process of comparing reactive power.

Fig. 32 is a configuration diagram of a power control device according to embodiment 9.

Fig. 33 is a functional configuration diagram for predicting active power.

Fig. 34 is an explanatory diagram showing a positional relationship between the motor group and the steel plate.

Fig. 35 is a flowchart of a process of predicting an insufficient amount of reactive power.

Description of the reference numerals

1: power supply, 2: reactive power detection device, 3: hysteretic power factor load device, 4: control device, 5: power converter, 6: transformer for power converter, 7: transformer for hysteretic power factor load device, 8: current detector, 9: supply voltage detector, 10: motor, 11: calender roll upper portion, 12: calender roll lower part, 13: steel sheet, 15: transmission unit, 16: reactive power instruction determining unit, 17: arrival time prediction unit, 18: motor arrangement storage unit, 19: rated apparent power store, 20: receiving section, 21: sensor, 23: steel plate speed estimating unit, 24: actual speed calculation unit, 25: speed correction coefficient learning unit, 26: speed correction coefficient storage unit, 27: steel plate speed estimated value calculation unit, 29: sensor detection value storage means, 30: speed information storage device, 31: torque information storage device, 32: stored data changing unit, 33: external interface, 34: transformer for power factor adjustment device, 35: power factor adjustment device, 36: switch, 37: capacitor, 38: reactive power distribution calculation unit, 39: alarm display unit, 40: reactive power comparison section, 41: log data storage unit, 42: active power prediction unit, 43: reactive power shortage prediction unit, 44: reactive power predictions.

Detailed Description

The present embodiment will be described with reference to the drawings. The embodiments to be described below do not limit the invention according to the claims, and all of the elements and combinations thereof described in the embodiments are not necessarily essential to the solution of the invention.

In the present embodiment, the steel plant in which the steel sheet is rolled is described as an example, but the present invention is applicable to plants other than the steel plant. For example, the present embodiment can be applied to a factory having a plurality of motors driven in cooperation.

In the present embodiment, as will be described below, the power factor of the entire plant power supply is improved by predicting the torque current of each power converter included in the plant power control system so that reactive power is preferentially supplied from the power converter having a large residual current of the current capacity.

The plant power control system according to the present embodiment includes: the power supply system includes motors 10A to 10C that receive electric energy to rotate, power converters 5A to 5C disposed between the motors 10A to 10C and the power system 1, a reactive power load device 3 connected to the power system 1, a control device 4 that generates a reactive power command or a reactive current command to be supplied from the plurality of power converters 5A to 5C to the power system 1, a communication network CN1 that connects the power converters 5A to 5C to the control device 4, and a reactive power detection device 2 that measures or estimates reactive power of a power receiving point RP at which the power system 1 and the reactive power load device 3 are connected.

The control device 4 calculates a total reactive power output target value or reactive current output target value in each of the power converters 5A to 5C from the reactive power estimated value detected by the reactive power detection device 2. The control device 4 determines a reactive power command or a reactive current command to be instructed to each of the power converters 5A to 5C by using at least one of the reactive power output target value or the reactive current output target value, the arrangement information of each of the motors 10A to 10C, the active power detection value, the active current command value, the active current detection value, the torque command value, and the torque detection value, the command value or the detection value of the angular velocity of each of the motors 10A to 10C, and the rated apparent power of each of the power converters 5A to 5C.

The control device 4 may further include an arrival time prediction unit 17, and the arrival time prediction unit 17 predicts the arrival time at which the steel sheet 13, which is the object of processing in the factory, arrives at the motors 10A to 10C using the arrangement information of the motors 10A to 10C, at least one of the active power detection value, the active current command value, the active current detection value, the torque command value, and the torque detection value of the power converters 5A to 5C, and the command value or the detection value of the angular velocity of the motors 10A to 10C. The control device 4 may further include a reactive power command determining unit 16, and the reactive power command determining unit 16 may calculate the reactive power command or the reactive current command instructed to each of the power converters 5A to 5C using the rated apparent power, the total reactive power output target value or the reactive current output target value of the power converters 5A to 5C, and the arrival time of the steel sheet 13 predicted by the arrival time predicting unit 17.

The control device 4 includes a receiving unit 20C that receives the outputs of the sensors 21A to 21C, and the arrival time predicting unit 17 can predict the arrival time of the steel sheet 13 using the arrangement information of the motors 10A to 10C, at least one of the active power detection values, the active current command values, the active current detection values, the torque command values, and the torque detection values of the power converters 5A to 5C, the command values or the detection values of the angular velocities of the motors 5A to 5C, and the outputs of the sensors 21A to 21C.

[ example 1 ]

First, a plant power control system according to embodiment 1 will be described with reference to fig. 1 to 10.

Fig. 1 shows the overall configuration of the plant power control system according to the present embodiment. The plant power control system includes, for example, a power supply 1, a plurality of power converters 5A to 5C, a control device 4, a power supply voltage detector 9, a current detector 8, a reactive power detector 2, a hysteresis power factor load device 3 connected via a hysteresis power factor load device transformer 7, power converter transformers 6A to 6C, motors 10A to 10C, upper rolls 11A to 11C, and lower rolls 12A to 12C, and one or more steel sheets 13 pass between the rolls 11A to 11C and the rolls 12A to 12C.

The power supply 1 of the factory corresponds to a "power system". The hysteretic power factor load device 3 corresponds to a "reactive power load device". The control device 4 is a Controller (CTL) that controls the power converters 5A to 5C, and can also be referred to as a power control device. The steel plate 13 is an object to be subjected to the processing by the motors 10A to 10C.

The reactive power detection device 2 detects or estimates the reactive power (reactive power detection value Q) received by the hysteretic power factor load device 3 from the system based on the detection value of the current detector 8 and the detection value of the power supply voltage detector 9 _M ). Reactive power detection value Q _M It can be estimated from at least any two of active power, apparent power, and power factor. Reactive power detection value Q _M The estimation may be performed based on the difference between the reactive power of the power supply 1 and the reactive powers of the power converters 5A to 5C. The control device 4 is based on the reactive power detection value Q _M And signals (speed information, torque information, active power information) obtained from the power converters 5A to 5C, calculate reactive power commands, and assign the calculated reactive power commands to the power converters 5A to 5C and instruct them at predetermined timings.

The power converters 5A to 5C control the rotational speeds of the corresponding motors 10A to 10C, respectively. That is, power inverter 5A controls motor 10A, power inverter 5B controls motor 10B, and power inverter 5C controls motor 10C.

The motors 10A to 10C are mechanically connected to the calender roll upper portions 11A to 11C and the calender roll lower portions 12A to 12C. The rolling roller upper portions 11A to 11C and the rolling roller lower portions 12A to 12C roll the steel sheet 13.

The details of the control device 4 will be described with reference to fig. 2. In the figure, for example, the term "receiving portion" is denoted by "receiving" and "portion" is abbreviated.

The control device 4 includes, for example, hardware such as a processor, a memory, a storage device, an input/output interface, and a communication interface, an operating system, and software such as a predetermined computer program (all not shown). The control device 4 may be configured as a computer, a programmable controller, or a control panel. The processor as the arithmetic device reads a predetermined computer program into the memory and executes the program, thereby realizing the function as the control device 4. Further, a function that can be realized as a computer program may be installed as a hardware circuit.

The control device 4 includes a reactive power command determining unit 16, an arrival time predicting unit 17, a motor arrangement storing unit 18, a rated apparent power storing unit 19, a transmitting unit 15, and receiving units 20A and 20B. When the reception unit 20A and the reception unit 20B are not particularly distinguished, they are sometimes referred to as a reception unit 20. In the same manner as in other configurations, letters are attached to the reference numerals, and description of the letters may be omitted.

The receiving unit 20A receives the reactive power detection value output from the reactive power detection device 2. The receiving unit 20B receives torque information (torque command or torque feedback or active current command or active current detection value), speed information (speed command or speed feedback), and active power information (active power command or active power detection value) output from each power inverter 5A, 5B, 5C to the corresponding motor 6A, 6B, 6C. The torque information may be an active power command or an active power detection value.

The arrival time predicting unit 17 calculates an arrival time prediction value at which the steel sheet 13 arrives at the upper portion 11 or the lower portion 12 of the reduction roll based on the torque information and the speed information received by the receiving unit 20B and the motor arrangement read out from the motor arrangement storing unit 18, and outputs the arrival time prediction value to the reactive power command determining unit 16.

The reactive power command determining unit 16 calculates a reactive power command based on the arrival time prediction value read from the arrival time predicting unit 17, the rated apparent power read from the rated apparent power storing unit 19, the reactive power detection value received by the receiving unit 20A, and the active power detection value of each power converter received by the receiving unit 20B, and outputs the reactive power command to the transmitting unit 15.

The transmitting unit 15 outputs the reactive power command for each power converter read from the reactive power command determining unit 16 to the power converters 5A, 5B, and 5C. The reactive power command determining unit 16 may determine the reactive current command instead of the reactive power command value.

The reactive power command determination unit 16 and the arrival time prediction unit 17 will be described with reference to fig. 3. Fig. 3 shows a change in the positional relationship between the motor groups 10A to 10C and the steel plate 13. In fig. 3, 3 sets of calender rolls are shown. The 1 st rolling rolls 11A, 12A are brought into contact with the steel sheet 13 at the earliest and rolled. The 2 nd rolling rolls 11B, 12B further roll the steel sheet 13 rolled by the 1 st rolling rolls 11A, 12A. The 3 rd rolling rolls 11C, 12C finally roll the steel sheet 13. In the figure, 3 sets of calender rolls are shown for convenience of explanation, but the present invention is not limited to this, and a plurality of sets of calender rolls may be present.

In FIG. 3, the calender rolls 11A, 12A are arranged at a position X _A The calender rolls 11B, 12B are arranged at the position X _B The calender rolls 11C, 12C are arranged at the position X _C . The left side in fig. 3 is set as upstream, the right side is set as downstream, and the steel plate 13 moves from upstream to downstream.

Time t ₁₁ The rolling of the steel sheet 13 is started from the upstream side of the casting rolls 11A and 12A. Time t ₁₂ The steel sheet 13 is rolled by the rolling rolls 11A and 12A. Time t ₁₃ The steel sheet 13 is completely rolled by the rolling rolls 11A and 12A, and is positioned downstream of the rolling rolls 11A and 12A. Time t ₁₄ The state in which the steel sheet 13 starts to be rolled by the rolling rolls 11B, 12B is shown. Time t ₁₅ Indicating that the steel sheet 13 is beginning to be rolledThe rolls 11C and 12C are rolled. In fig. 3, the steel sheet 13 is not simultaneously rolled by the plurality of rolling rolls 11 and 12. In the following, the calender roll may be abbreviated as a roll.

Fig. 4 shows a time change between the torque of the motor 10A and the speed of the motor 10A (angular velocity. Hereinafter, the same). In fig. 4, at time t ₁₁ The steel sheet 13 reaches the motor 10A, and the speed of the motor 10A is reduced due to the torque generated for rolling the steel sheet 13. In a speed controller (not shown) that controls the power inverter 5A of the motor 10A, an acceleration torque for following the speed command value is generated. At time t ₁₂ Since the rolling process is performed on the steel sheet 13, a torque is generated for rolling the steel sheet 13. At time t ₁₃ The rolling is ended, and therefore, the torque of the motor 10A becomes small.

The process of the arrival time prediction unit 17 will be described with reference to fig. 5. In fig. 5, a time t at which the calculated steel plate 13 reaches the rollers 11B and 12B corresponding to the power converter 5B is set to _B Examples of (a) are described. Hereinafter, the steel sheet 13 reaching the rollers 11, 12 may be abbreviated as the steel sheet 13 reaching the power converter 5. To be precise, when the steel sheet 13 contacts the rolling rolls 11 and 12, the torque and speed of the motor 10 connected to the rolls 11 and 12 are changed, and the output of the power inverter 5 of the motor 10 is controlled to be changed.

In fig. 5, the time t is reached _B The time when the steel sheet 13 reaches the rolling rolls 11B and 12B.

The control device 4 reads the motor arrangement and the torque τ of the power inverter 5A _A (t) speed command V _A (t) Motor configuration X of Power inverter 5B _B Torque τ _B (t)(S101)。

The control device 4 controls the torque tau _A (t) and a predetermined threshold TH ₁ By comparison, it is determined whether or not the steel sheet 13 is being rolled by the rolling rolls 11A, 12A (S102). The control device 4 is at torque τ _A (t) ratio threshold TH ₁ If it is large (yes in S102), it is determined that the steel sheet 13 is being rolled by the rolling rolls 11A and 12A, and the flow proceeds to step S103. On the other hand, the control device 4 is operating at a torque τ _A (t) ratio threshold TH ₁ If it is small (no in S102), it is determined that the steel sheet 13 is not being rolled by the rolling rolls 11A and 12A, and the process proceeds to step S107.

In step S103, the control device 4 detects the timing at which the steel sheet 13 reaches the reduction rolls 11A and 12A. The control device 4 calculates a time t-t before 1 cycle of the flowchart operation from the time t _CAL Torque τ of _A (t-t _CAL ) Threshold value TH ₁ If it is large (S103: yes), it is determined that it is at time t-t _CAL The steel sheet 13 is rolled by the rolling rolls 11A and 12A, and the process advances to step S105.

On the other hand, the control device 4 is operating at a torque τ _A (t-t _CAL ) Threshold value TH ₁ If it is small (no in S103), it is determined that the rolling of the steel sheet 13 by the rolling rolls 11A and 12A is started at time t, and the flow proceeds to step S104.

The control device 4 rolls the steel sheet 13 passing through the rolls 11A and 12A from the rolls 11A and 12A _{STA_EST} Reset to 0 (S104).

The control device 4 updates the distance of the steel sheet 13 passing through the rolling rolls 11A, 12A (S105). The distance of the steel sheet 13 passing through the rolling rolls 11A, 12A can be calculated by equation 1.

[ 1 ]

L _{STA_EST} (t)＝L _{STA_EST} (t-t _CAL )+V _A (t)×t _CAL

Wherein V is _A (t) is the moving speed of the steel sheet 13 during the rolling by the rolls 11A, 12A. Speed V of movement of steel sheet 13 during rolling by rolls 11A, 12A _A (t) can be calculated by equation 2.

[ 2 ]

V _A (t)＝r _A ×ω _A (t)

Wherein r is _A Is the radius (m) of the roller 11A. Omega _A And (t) is the angular velocity (rad/sec) of the roller 11A.

Next, the control device 4 updates the time when the steel sheet 13 reaches the rolling rolls 11B, 12B (S106). The time tB at which the steel sheet 13 reaches the reduction rolls 11B, 12B can be calculated by equation 3.

[ 3 ] of the following

t _{B_EST} (t)＝t+(X _B -X _A -L _{STA_EST} (t))/V _A (t)

The control device 4 compares the torque τ of the power converter 5B _B (t) and a predetermined threshold TH _1B It is determined whether or not the steel sheet 13 is being rolled by the rolling rolls 11B, 12B (S107). At torque τ _B (t) ratio threshold TH _1B If it is large (yes in S107), the control device 4 determines that the steel sheet 13 is being rolled by the rolling rolls 11B and 12B, and proceeds to step S108.

On the other hand, at torque τ _B (t) ratio threshold TH _1B If it is small (no in S107), the control device 4 determines that the steel sheet 13 is not being rolled by the rolling rolls 11B and 12B, and proceeds to step S109.

In step S108, the control device 4 updates the time when the steel sheet 13 reaches the reduction rolls 11B, 12B. At time t, the steel plate 13 is in the process of arriving, and the arrival time prediction value t is updated by equation 4 _{B_EST} 。

[ 4 ] of the following

t _{B_EST} (t)＝t

In step S109, the control device 4 detects the timing at which the rolling of the steel sheet 13 by the rolling rolls 11B, 12B is completed. The control device 4 is at a time t-t before 1 cycle from the time t _CAL Torque τ of _B (t-t _CAL ) Threshold value TH _1B If it is large (S109: yes), it is determined that it is at time t-t _CAL The rolling of the steel sheet 13 by the rolling rolls 11B, 12B is completed, and the process advances to step S110.

On the other hand, the control device 4 is operating at a torque τ _B (t-t _CAL ) Threshold value TH _1B If it is small (S109: NO), it is determined that the steel sheet 13 is being rolled by the rolling rolls 11A, 12A at time t, and the present process is ended.

In step S110, the control device 4 updates the time when the steel sheet 13 reaches the reduction rolls 11B and 12B. Since the arrival of the steel plate 13 is completed at time t, the arrival time prediction value is reset to a large value by equation 5.

[ 5 ]

t _{B_EST} (t)＝t+t _SETB

For example, time t _SETB A value sufficiently larger than the maximum value of the time taken for the steel sheet 13 to reach the roller 12B from the roller 12A at the time of operation.

The process of fig. 5 described above shows an example in which the arrival times of the calender rolls 11B, 12B are predicted, and the arrival times of the calender rolls 11C, 12C can be calculated from the same process as that of fig. 5. Therefore, the explanation of the method for predicting the time when the steel sheet 13 reaches the rolls 11C and 12C is omitted.

An example of the processing of the reactive power command determination unit 16 will be described with reference to fig. 6. The control device 4 reads in the reactive power detection value Q _M Arrival time prediction value t calculated by arrival time prediction unit 17 at which steel sheet 13 arrives at each inverter 5A to 5C _B 、t _C Rated apparent power S _A 、S _B 、S _C Active power P _A 、P _B 、P _C And proceeds to step S202.

The control device 4 calculates reactive power Q for calculating the distribution of the power converters 5A to 5C to the power system 1 in the plant in step S202 _REFA 、Q _REFB 、Q _REFC Reactive power demand Q for use in internal operations _TMP And proceeds to step S203.

In order to make the power factor of the plant receiving power from the system 1", the reactive power demand needs to be calculated to cancel the reactive power detection value. Then, the control device 4 calculates the reactive power demand Q according to the reference 6 _TMP 。

[ 6 ]

Q _TMP ＝-Q _M

In step S203, the control device 4 predicts the arrival time t at which the load (steel plate 13) arrives at the power converters 5B and 5C _B 、t _C A comparison is made. The control device 4 at t _B >t _C If so (yes in S203), the process proceeds to step S204. On the other hand, the control device 4 at t _B >t _C If not (no in S203), the process proceeds to step S210.

In step S204, controlReactive power command Q of device 4 to power converter 5B _REFB And performing operation. The reactive power command can be calculated using equation 7.

[ 7 ]

Q _REFB ＝SIGN(Q _TMP )×MIN(ABS(Q _TMP ),SQRT(S _B ² -P _B ² ))

Where SIGN is a function of positive output 1, 0 when the input in brackets is positive, and negative output-1. MIN is a function of the smallest value in the inputs within the output bracket. ABS is a function of the absolute value of the input in the output bracket.

Predicted value t at steel plate arrival time _B Unlike the present time t (in the case where the rolls 11B, 12B are not in the rolling process), it can be assumed that the active power in the rolls 11B, 12B is sufficiently small. Thus, the active power P can be set in equation 7 _B Fixed to 0, without P _B Is a detection value of (a).

When the reactive current command is given instead of the reactive power command, the reactive current output command may be calculated by using the rated apparent current instead of the rated apparent power and using the active current instead of the active power in equation 7.

In step S205, the control device 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power demand Q by means of 8 _TMP So that the reactive power demand amount corresponding to the reactive power command calculated by equation 7 is changed.

[ 8 ] of the following

Q _TMP ＝Q _TMP -Q _REFB

In step S206, the reactive power demand Q is determined _TMP Whether it becomes 0. In the reactive power requirement Q _TMP When =0 is satisfied (yes in S206), control device 4 determines that the necessary reactive power is supplied by power converter 5B, and the flow of actions proceeds to step S209.

On the other hand, in the reactive power demand Q _TMP When =0 is not satisfied (S206: no), the control device 4 determines that the necessary reactive power cannot be supplied by the power converter 5BStep S207 is entered.

In step S207, the control device 4 calculates a reactive power command Q of the power converter 5C _REFC . The reactive power command can be calculated using equation 9.

[ 9 ] of the invention

Q _REFc ＝SIGN(Q _TMP )×MIN(ABS(Q _TMP ),SQRT(S _c ² -P _c ² ))

Predicted value t at steel plate arrival time _C In the case where the current time t is different from the present time t (in the case where the roll 11C is not in the rolling process), since it can be assumed that the active power in the roll 11C is sufficiently small, the active power P can be also calculated in the expression 9 _C Fixed to 0, without P _C Is a detection value of (a).

In step S208, the control device 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power demand Q by means of 10 _TMP So that the reactive power demand amount corresponding to the reactive power command calculated by equation 9 is changed.

[ 10 ] of the following

Q _TMP ＝Q _TMP -Q _REFC

In step S209, the control device 4 causes the reactive power command Q of the power converter 5C to be set _REFC Zero.

In step S210, the control device 4 instructs the reactive power Q of the power converter 5C _REFC And performing operation. The reactive power command can be calculated using equation 9.

In step S211, the control device 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power demand Q by means of 10 _TMP So that the reactive power demand amount corresponding to the reactive power command calculated by equation 9 is changed.

In step S212, the control device 4 determines the reactive power demand Q _TMP Whether it becomes 0. The control device 4 requests the reactive power Q _TMP When =0 is satisfied (yes in S212), it is determined that the necessary reactive power is supplied by the power converter 5C, and the flow advances to step S215. On the other hand, the control device 4 is configured to Reactive power requirement Q _TMP If=0 is not satisfied (S212: no), it is determined that the necessary reactive power cannot be supplied by the power converter 5C, and the flow advances to step S213.

In step S213, the control device 4 calculates a reactive power command Q of the power converter 5B _REFB . The reactive power command can be calculated using equation 7.

In step S214, the control device 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power demand Q by means of 8 _TMP So that the reactive power demand amount corresponding to the reactive power command calculated according to equation 7 in step S213 is changed.

In step S215, the control device 4 causes the reactive power command Q of the power converter 5B to be set _REFB Zero.

In step S216, the control device 4 determines the reactive power demand Q _TMP Whether it becomes 0. The control device 4 requests the reactive power Q _TMP When =0 is satisfied (yes in S216), it is determined that the necessary reactive power is supplied through the power converters 5B and 5C, and the flow advances to step S218.

On the other hand, the control device 4 requests the reactive power Q _TMP When the value of =0 is not satisfied (S216: no), it is determined that the necessary reactive power cannot be supplied by the power converters 5B and 5C, and the flow advances to step S217.

In step S217, the control device 4 instructs the reactive power Q of the power converter 5A _REFA And performing operation. The reactive power command can be calculated using equation 11.

[ 11 ]

Q _REFA ＝SIGN(Q _TMP )×MIN(ABS(Q _TMP ),SQRT(S _A ² -P _A ² ))

In step S218, the control device 4 causes the reactive power command Q of the power converter 5A to be set _REFA Zero.

The process of the reactive power command determining unit 16 in the case where the number of converters 5 is 4 or more will be described with reference to the flowchart of fig. 7.

The control device 4 reads in the reactive power detection value Q _M The arrival time prediction value t at which the steel sheet 13 calculated by the arrival time prediction unit 17 arrives at each of the power converters 5A, 5B _B 、t _C 、...、t _N Rated apparent power S _A 、S _B 、S _C 、...、S _N Active power P _A 、P _B 、P _C 、...、P _N (S301), and then proceeds to step S302.

The control device 4 calculates the reactive power demand Q _TMP (S302), the process advances to step S303. In order to make the power factor "1", the reactive power demand needs to be calculated to cancel the reactive power detection value, and therefore, the control device 4 can calculate the reactive power demand with the equation 12.

[ 12 ]

Q _TMP ＝-Q _M

In step S303, the control device 4 sets an initial value. As an initial value, k=1, n=number of converters is set.

In step S304, the control device 4 compares the arrival time prediction values of the load arriving at the respective converters 5B to 5N, and instructs the reactive power of the power converter 5K at the kth time of the arrival time prediction value to be Q _REFK And performing operation. Since the arrival time of the steel plate 13 at the power inverter 5A with which the steel plate 13 first contacts cannot be estimated, the power inverter 5A is not included in the derivation of the power inverter 5K with the K-th late arrival time prediction value. The converter reactive power command can be calculated using equation 13.

[ 13 ] the process comprises

Q _REFK ＝SIGN(Q _TMP )×MIN(ABS(Q _TMP )，SQRT(S _K ² -P _K ² ))

In step S305, the control device 4 updates the reactive power demand Q _TMP . The control device 4 calculates by equation 14 such that the reactive power demand amount corresponding to the reactive power command calculated by equation 13 is changed.

[ 14 ]

Q _TMP ＝Q _TMP -Q _REFK

In step S306, the control device 4 determines the reactive power demand Q _TMP Whether it becomes 0. The control device 4 requests the reactive power Q _TMP When the value of =0 is satisfied (yes in S306), it is determined that the necessary reactive power is supplied to the inverter at the kth time of arrival time prediction value, and the present process is terminated.

On the other hand, the control device 4 requests the reactive power Q _TMP When the value of =0 does not hold (S306: no), it is determined that the inverter at the kth late stage of the arrival time prediction value cannot supply the necessary reactive power, and the flow advances to step S307.

In step S307, the control device 4 compares K with N-1. If K < N-1 is satisfied (yes in S307), the control device 4 proceeds to step S308. On the other hand, if K < N-1 is not satisfied (S307: no), the control device 4 proceeds to step S309.

In step S308, the control device 4 increases the value of K by 1 to update the value, and the flow advances to step S304. The control device 4 can specify the inverter at the time of arrival prediction value k+1st in step S304 by updating K to k+1.

In step S309, the control device 4 calculates a reactive power command Q of the power converter 5A _REFA The present process is ended. Reactive power command Q of power converter 5A _REFA Can be calculated by equation 11.

Fig. 8 is a schematic diagram of the reactive power compensation over time in the related art prepared for comparison with the present embodiment. Fig. 9 is a schematic diagram of the reactive power compensation of the present embodiment over time. The relation between the actual active power, reactive power, and apparent power is represented by vector sum, but is not illustrated, and is therefore schematically represented by one dimension in fig. 8 and 9. Time t in FIG. 8 _d The response time from the power converter 5 to the reactive power command until the power converter 5 can supply reactive power. The horizontal axis of fig. 8 and 9 is a time axis, and the vertical axis represents power.

In fig. 8, at time t ₁₁ 、t ₁₄ 、t ₁₅ When the steel plate 13 reaches the power converters 5A, 5B, 5C and the load increases suddenly, the total of the active power and the reactive power command in the power converters 5A to 5C is higher than the rated apparent power (hereinafter, also referred to as rated power).

In general, the power converter 5 has a function (limiter) of suppressing a current command so as not to exceed a rated power for the purpose of protecting equipment. Therefore, if the load increases suddenly, the limiter operates, and the power converter 5 becomes unable to supply reactive power as instructed by the reactive power command.

Furthermore, a response time t is required from the power converter 5 being indicated to be able to supply the desired reactive power _d . Thus, as shown in FIG. 8, a response time t is generated _d A corresponding amount of time period during which reactive power commanded by reactive power cannot be supplied.

In the present embodiment shown in fig. 9, the inverter having a late arrival time prediction value of the steel plate 13 is given priority to the reactive power command. Therefore, even when the load increases suddenly, the power converter 5 can supply reactive power as instructed by the reactive power command.

For example, at time t ₁₁ And time t ₁₄ Between them, the arrival time prediction value of the steel sheet 13 satisfies t _{B_EST} <t _{C_EST} Therefore, the reactive power command is preferentially distributed to the power converter 5C than to the power converter 5B.

At the time when the steel sheet 13 completes passing between the rollers 11B, 12B corresponding to the motor 10B and at the time t when the steel sheet 13 reaches the following rollers 11C, 12C ₁₅ Between them, the arrival time prediction value of the steel sheet 13 satisfies t _{B_EST} >t _{C_EST} Is a relationship of (3). Therefore, the control device 4 preferentially distributes the reactive power command to the power converter 5B over the power converter 5C.

According to the present embodiment configured as described above, by preferentially supplying reactive power from the power converter 5 having a large residual current capacity, it is possible to reduce the distribution of reactive power to the motor having an early arrival time of the steel sheet 13, which is a cause of an increase in load. Therefore, according to the present embodiment, the required reactive power amount can be efficiently and stably supplied from the power converter 5, and the power factor of the plant power system 1 can be improved.

In the present embodiment, since it is estimated that the steel sheet 13 reaches the rollers 11 and 12 based on the output state of the power converter 5 and the output of reactive power is distributed, a sensor for detecting the presence of the steel sheet 13 is not required. Therefore, the power control system of the plant can be improved simply at a relatively low cost. However, in the present embodiment, the output of reactive power cannot be distributed largely to the power converters 5A corresponding to the rollers 11, 12 that are in contact with the steel sheet 13 at the earliest. This is because the moment at which the steel sheet 13 contacts the rolls 11, 12 is unknown. The structure capable of detecting the arrival of the steel sheet 13 more accurately will be described later.

In the foregoing description, it is assumed that the length of one steel sheet is shorter than the distance between any of the plurality of rolling rolls, but as shown in fig. 10, even when the length of one steel sheet is longer than the distance between any of the plurality of rolling rolls, the reactive power can be outputted from the power converter 5 at an appropriate timing by the same principle as in fig. 2, 5 and 7, and the power factor of the entire plant can be improved.

[ example 2 ]

Embodiment 2 will be described with reference to fig. 11 to 16. The following examples including the present example correspond to the modification of embodiment 1, and therefore, description will be given centering on differences from embodiment 1. In the plant power control system of the present embodiment, sensors 21A to 21C that detect the steel plate 13 are used.

Fig. 11 is a block diagram of a plant power control system according to the present embodiment. The overall structure shown in fig. 11 differs from the overall structure of embodiment 1 described in fig. 1 in the point where the sensors 21A, 21B, 21C are added. Without particular distinction, it is sometimes referred to as a sensor 21.

The sensor 21 may be capable of detecting at least the presence of the steel plate 13. The sensor 21 can also be referred to as, for example, a steel plate detector. The sensor 21 of the present embodiment is configured as a sensor that detects the thickness dimension of the steel plate 13. Each sensor 21 is located upstream of the corresponding roller 11, 12 and is disposed in the vicinity of the upper roller 11. That is, the 1 st sensor 21A is disposed in the vicinity of the upstream side of the roller 11A, the 2 nd sensor 21B is disposed in the vicinity of the upstream side of the roller 11B, and the 3 rd sensor 21C is disposed in the vicinity of the upstream side of the roller 11C. The signals detected by the sensors 21 are input to the control device 4 via the communication network CN 2.

Fig. 12 shows the structure of the control device 4B. The configuration shown in fig. 12 differs from the configuration of embodiment 1 described in fig. 2 in that a receiving unit 20C for receiving a signal from a sensor 21 is added.

In the control device 4B of the present embodiment, the signal of the sensor 21 disposed in the vicinity of the upstream side of each of the rolls 11 and 12 can be used, and therefore, the approach of the steel sheet 13 to the first rolling rolls 11A and 12A can be detected. Further, the accuracy of prediction of the time when the steel sheet 13 reaches the following calender rolls 11B, 11C, 11N and calender rolls 12B, 12C, 12N can be improved.

The process of the arrival time prediction unit 17 will be described with reference to fig. 13 and 14. The flowchart of fig. 13 shows the processing for the power converter 5A. The flowchart of fig. 14 shows a process flow for the power converter 5B.

Fig. 15 shows an example for explaining the positional relationship between the steel plate 13 and the rollers 11, 12 and the sensor 21 in fig. 13 and 14.

In fig. 15, the calender rolls 11A and 12A are arranged at the position X _A The calender rolls 11B, 12B are arranged at the position X _B The calender rolls 11C, 12C are arranged at the position X _C . The sensor 21A is arranged at the position X _AS The sensor 21B is disposed at the position X _BS The sensor 21C is disposed at the position X _CS . The left side of fig. 15 is upstream and the right side is downstream. It is assumed that the steel plate 13 moves downstream from upstream.

Time t ₃₁ The steel plate 13 is shown in a state of reaching the sensor 21A. Time t ₃₂ The rolling rolls 11A and 12A are shown in a state where rolling of the steel sheet 13 is started. Time t ₃₃ The rolling of the rolling rolls 11A, 12A for the steel sheet 13 is completed and is positioned downstream of the rolling rolls 11A, 12A. Time t ₃₄ Showing the steel plate 13 reaching the sensor21B. Time t ₃₅ The rolling rolls 11B and 12B are shown in a state where rolling of the steel sheet 13 is started.

Returning to fig. 13. In fig. 13, the control device 4B reads the motor arrangement XA and the torque τ of the power inverter 5A at time t _A (t) speed command V _A (t), and the detection value D of the sensor 21A _STA (t)(S401)。

The control device 4B controls the torque τ _A (t) and threshold TH _1A A comparison is made (S402). At torque τ _A (t) is greater than a predetermined threshold TH _1A If it is large (yes in S402), the control device 4B determines that the steel sheet 13 is being rolled, and proceeds to step S403. On the other hand, if the control device 4B determines that the torque τ is the torque τ _A (t) not more than threshold TH _1A Large (S402: no), the flow advances to step S404.

In step S403, the control device 4B updates the arrival time prediction value of the steel sheet 13. At time t, since the steel sheet 13 is in the process of reaching the rolling rolls 11A, 12A, the control device 4B updates the predicted arrival time value t of the steel sheet 13 by the following equation 15 _A _ _EST (t)。

[ 15 ] of the following

t _{A_EST} (t)＝t

Where t is the current time.

In step S404, the control device 4B detects the detection value D of the sensor 21 _STA (t) and threshold TH _2A A comparison is made. At D _STA >TH _2A If so (yes in S404), the sensor 21 recognizes the presence of the steel plate 13 at time t, and the process proceeds to step S405. On the other hand, in D _STA >TH _2A If not (S404: NO), this means that the sensor 21A does not recognize the presence of the steel sheet 13 at time t, and the present process ends.

In step S405, the control device 4B controls the time (t-t _CAL ) Detection value D of the sensor of (2) _STA (t-t _CAL ) And a predetermined threshold value TH _2A A comparison is made. At D _STA (t-t _CAL )>TH _2A If so (yes in S405), the control device 4B ends the present process. On the other hand, control ofDevice 4B at D _STA (t-t _CAL )>TH _2A If not (no in S405), it is determined that the steel sheet 13 has reached the sensor 21B at time t, and the process proceeds to step S406.

In step S406, the control device 4B updates the time when the steel sheet 13 reaches the reduction rolls 11A, 12A by the following equation 16.

[ 16 ] the process comprises

t _{A_EST} (t)＝t+t _SETAS

Wherein t is _SETAS The time from the start of the sensor 21A to the arrival of the steel sheet 13 at the rolling rolls 11A and 12A is recognized. Time t _SETAS The distance (X) between the sensor 21A and the calender rolls 11A, 12A can be used _A -X _AS ) And the speeds V of the calender rolls 11A, 12A _A (t) is estimated by the following equation 17.

[ 17 ] of the following

t _SETAS (t)＝(X _A -X _AS )/V _A (t)

Wherein t is _SETAS May be set to a predetermined value.

In fig. 14, the control device 4B reads the motor arrangement and the torque τ of the power inverter 5A _A (t) speed command V _A (t) detection value D of sensor 21B _STB (t), and motor configuration X of power converter 5B _B Torque τ _B (t)(S501)。

Steps S502 to S506 are similar to steps S202 to S206 in fig. 6, and therefore, the description thereof is omitted.

In step S507, the control device 4B controls the time (t-t _CAL ) Torque τ of _A (t-t _CAL ) And a threshold value TH _1A A comparison is made. Control device 4B at τ _A (t-t _CAL )>TH _1A If so (yes in S507), it is determined that the rolling by the rolls 11A and 12A is completed at the time t, and the flow advances to step S508. On the other hand, the control device 4B at τ _A (t-t _CAL )>TH _1A If not (S507: no), the flow proceeds to step S509.

In step S508, the control device 4B saves the time t at which the rolling of the steel sheet 13 by the rolls 11A, 12A is completed _ENDA Motor speed V _A (t _ENDA ). And proceeds to step S509.

In step S509, the control device 4B detects the detection value D of the sensor 21 _STB (t) and a predetermined threshold TH _2B A comparison is made. At D _STB >TH _2B If so (yes in S509), the sensor 21B recognizes the presence of the steel sheet 13 at time t, and the process advances to step S510. On the other hand, in D _STB >TH _2B If not (S509: NO), it means that the sensor 21B does not recognize the presence of the steel sheet 13 at time t, and the process proceeds to step S512.

In step S510, the control device 4B sets the time (t-t _CAL ) Detection value D of sensor 21B of (2) _STB (t-t _CAL ) And a predetermined threshold value TH _2B A comparison is made. At D _STB (t-t _CAL )>TH _2B If so (yes in S510), the control device 4B proceeds to step S512. On the other hand, in D _STB (t-t _CAL )>TH _2B If not (S510: no), the control device 4B determines that the steel sheet 13 has reached the sensor 21B at time t, and proceeds to step S511.

In step S511, the control device 4B calculates the time when the steel sheet 13 reaches the rolling rolls 11B and 12B according to the following equation 18, and updates the time.

[ 18 ]

t _{A_EST} (t)＝t+t _SETBS

Wherein t is _SETBS The time from the start of the sensor 21B to the arrival of the steel sheet 13 at the rolling rolls 11B and 12B is recognized. Time t _SETBS The distance (X) between the sensor 21B and the calender rolls 11B, 12B can be used _B -X _BS ) And the speed V at the end of the rolling rolls 11A, 12A _A (t _ENDA ) The estimation is performed by equation 19.

[ 19 ] the process comprises

t _SETBS (t)＝(X _B -X _BS )/V _A (t _ENDA )

Wherein t is _SETBS May be set to a predetermined value.

Steps S512 to S515 are similar to steps S207 to S210 in fig. 6, and therefore, the description thereof is omitted.

Fig. 14 shows the arrival time prediction value t of the predicted rolling rolls 11B, 12B _B The arrival time prediction unit 17 related to the calender rolls 11C, 12C can also be realized by performing an operation according to the same flowchart as fig. 14.

The process of the reactive power command determination unit 16 will be described with reference to fig. 16. Steps S601 to S603 are similar to steps S301 to S303 described in fig. 7, and therefore, the description thereof is omitted.

In step S604, the control device 4B compares the arrival time prediction values of the load arriving at each of the converters 5, and calculates the reactive power command Q of the power converter 5K having the K-th delay of the arrival time prediction values _REFK . The reactive power command can be calculated using equation 13.

Steps S605 to S606 are similar to steps S305 to S306 described in fig. 7, and therefore, the description thereof is omitted.

In step S606, the control device 4B determines the reactive power demand Q _TMP Whether it becomes 0. In the reactive power requirement Q _TMP When =0 is satisfied (yes in S606), the control device 4B determines that the necessary reactive power is supplied to the inverter 5K at the kth time of arrival prediction value, and ends the present process.

On the other hand, in the reactive power demand Q _TMP When =0 does not hold (S606: no), the control device 4B determines that the inverter 5K having the K-th late arrival time prediction value cannot supply the necessary reactive power, and proceeds to step S607.

In step S607, the control device 4B compares "K" and "N". If K < N is satisfied (yes in S607), the process advances to step S608. If K < N is not satisfied (S607: no), the present process ends.

The sensor 21 does not have to be a detector for detecting the thickness of the steel sheet, and may be capable of detecting at least the presence or absence of the steel sheet. In the case of detecting the presence or absence of a steel sheet by "1 (with steel sheet)" or "0 (without steel sheet)", the threshold value TH _2A 、TH _2B 、...、TH _2N The value may be set to a value larger than 0 and smaller than 1.

The present embodiment thus constructed also has the same operational effects as those of embodiment 1. In addition, in the present embodiment, since the signal of the sensor 21 for detecting the steel plate 13 can be used, the change in the state of the power converter 5 can be predicted more accurately than in embodiment 1, and the output of the reactive power can be distributed at an appropriate timing effectively.

[ example 3 ]

Embodiment 3 will be described with reference to fig. 17 to 19. Fig. 17 shows a control device 4C of the plant power control system according to the present embodiment. The configuration shown in fig. 17 differs from the configuration of embodiment 2 described in fig. 12 in that a steel plate speed estimating unit 23 is added. Hereinafter, the steel plate speed estimating unit 23 may be abbreviated as the speed estimating unit 23.

The steel plate speed estimating unit 23 is provided for reducing a difference between an actual value (actual value) and a predicted value (estimated value) of the speed at which the steel plate 13 moves. This is because the actual value and the estimated value of the speed of the steel sheet 13 may be different from each other due to occurrence of slip or the like between the steel sheet 13 and the rollers 11 and 12. The speed estimating unit 23 calculates an estimated value of the speed based on the angular speed information from the power converter 5 and the signal from the sensor 21.

Fig. 18 shows the structure of the speed estimating unit 23. The speed estimating unit 23 includes, for example, a sensor detection value storage device 29, an actual speed calculating unit 24, a speed correction coefficient learning unit 25, a speed correction coefficient storage unit 26, a steel plate speed estimation value calculating unit 27, a speed information storage device 30, and a torque information storage device 31. The names of the above structures are omitted appropriately in fig. 18.

The sensor detection value storage device 29 stores the detection value of the sensor 21 and outputs the detection value to the actual speed calculation unit 24. The speed information storage device 30 stores the speed information and outputs the speed information to the speed correction coefficient learning unit 25. The torque information storage device 31 stores torque information and outputs the torque information to the speed correction coefficient learning unit 25. The speed correction coefficient storage unit 26 stores the speed correction coefficient input from the speed correction coefficient learning unit 25 and outputs the speed correction coefficient to the response speed estimating unit.

Description of the inventionThe actual speed calculation unit 24. On the other hand, the actual steel plate speed between the rolls 11A and 11B is the time t at which the start detection sensor 21B is used ₃₄ And time t at which rolling of the steel sheet by the roller 11B is started ₃₅ The operation is performed based on equation 20.

[ 20 ]

V _{ACT_AB} ＝(X _B -X _BS )/(t ₃₅ -t ₃₄ )

The processing of the speed correction coefficient calculation unit 25 will be described. Estimated value V of steel plate speed before correction _{EST_AB0} T=t of fig. 15 considered as the foregoing ₃₃ (t=t of the flowchart of fig. 14) _ENDA ) The speed of the roller 11A can be calculated by equation 21.

[ 21 ] of the formula

V _{EST_ABO} ＝V _A (t _ENDA )

When the ratio of the estimated value of the steel sheet speed to the actual steel sheet speed is set as the correction coefficient α, the correction coefficient α is expressed by the formula 22.

[ 22 ]

α＝V _{ACT_AB} /V _{EST_ABO}

For example, the correction coefficient α is learned from each of the torque information stored in the torque information storage device 31 and the speed information stored in the speed information storage device 31. In this case, the correction coefficient α is given by a two-dimensional table of torque and speed.

The information for learning the correction coefficient α is not limited to the torque and the speed, and for example, at least one of the torque, the speed, the thickness of the steel sheet, the temperature of the steel sheet, the component ratio of the steel sheet, and the like may be obtained from the outside, and the correction coefficient α may be learned for at least one of these.

For example, in the case where the correction coefficient α is learned by torque, speed, and thickness of the steel sheet, the correction coefficient α may be set as a three-dimensional table so that the thickness of the steel sheet 13 can be input to the speed correction coefficient learning unit 25 in fig. 18.

The processing of the steel plate speed estimated value calculation unit 27 will be described. When the correction coefficient α is used, the estimated value of the corrected steel plate speed can be calculated by equation 23.

[ 23 ]

V _{EST_AB} ＝α×V _{EST_ABO}

An example of the speed command correction based on equations 20 to 23 will be described with reference to fig. 19. Let t ₃₄ And t ₃₅ Average velocity V of steel sheet between _{ACT_AB} As the actual steel plate speed, the steel plate speed V before correction obtained from the speed of the roller 11A is corrected _{EST_AB0} Can estimate the actual steel plate speed.

The present embodiment thus constructed also has the same operational effects as those of embodiment 2. In addition, in the present embodiment, since the difference between the actual moving speed and the estimated speed of the steel plate 13 can be corrected, the change in the state of the power converters 5 can be predicted more accurately than in embodiment 2, and the reactive power can be outputted from each power converter 5 at an appropriate timing.

[ example 4 ]

Embodiment 4 will be described with reference to fig. 20. Fig. 20 shows a configuration of a control device 4D used in the plant power control system of the present embodiment. The control device 4D according to the present embodiment differs from the control device 4C described in fig. 17 in that a point of adding the stored data changing unit 32 and the external interface 33A for changing the data of the stored data changing unit 32 from the outside is added to fig. 20. In fig. 20, the motor arrangement storage unit 18 is abbreviated as "M", and the rated apparent power storage unit 19 is abbreviated as "S".

The stored data changing unit 32 has a function of changing the motor arrangement stored in the motor arrangement storage unit 18, the rated apparent power stored in the rated apparent power storage unit 19, and the stored data including the speed command value, the torque command value, the rolling time, and the speed correction coefficient stored in the steel sheet speed estimating unit 32, respectively.

The present embodiment thus constructed can also provide the same operational effects as those of embodiment 3. In the present embodiment, the user such as the system manager can correct all or part of the parameters that are the basis for calculating the value and timing of the reactive power output from each power converter 5. Therefore, according to the present embodiment, for example, when the arrangement of the motor 10 is changed by a plant equipment update or the like, the user can change the information of the motor arrangement and the rated apparent power by the stored data changing unit 32. Thus, even after the plant equipment is updated, the reactive power command determining unit 16 can compensate for the necessary reactive power.

[ example 5 ]

Embodiment 5 will be described with reference to fig. 21 to 24. Fig. 21 is an overall configuration diagram of the plant power control system according to the present embodiment. The difference between this embodiment and embodiment 1 is that the transformer 34 and the power factor adjustment device 35 are added to this embodiment.

The power factor adjustment device 35 is connected to the plant power supply 1 via a transformer 34. The power factor adjustment device 35 is connected to the control device 4E via a communication path CN 3.

Fig. 22 is a structural diagram of the power factor adjustment device 35. The power factor adjustment device 35 includes, for example, a plurality of capacitors 37A, 37B, and 37C, and switches 36A, 36B, and 36C connected in series with the capacitors 37A, 37B, and 37C. The power factor adjustment device 35 can either connect or disconnect the capacitor 37A, 37B, 37C to or from the system by turning on or off the switch 36A, 36B, 36C. The structure of the power factor adjusting device 35 is not limited to the example shown in fig. 22. For example, a reactive power compensation device (Static Var Compensator) or the like may be used as the power factor adjustment device.

Fig. 23 shows the structure of the control device 4E according to the present embodiment. The control device 4E of the present embodiment differs from the control device 4 described in embodiment 1 in that the control device 4E of the present embodiment is added with a receiving unit 20D that receives the reactive power supply schedule from the power factor adjustment device 35 and a function 38 that calculates the distribution of reactive power.

The control device 4E receives the reactive power supply schedule implemented by the power factor adjustment device 35 from the power factor adjustment device 35 via the receiving unit 20D. The control device 4E distributes the required amount of reactive power to the power factor adjustment device 35 and each power converter 5.

The reactive power distribution calculation unit 38 calculates the reactive power to be compensated by the reactive power command determination unit 16 of the control device 4E by obtaining the difference between the reactive power detection value of the reactive power detection device 2 received by the reception unit 20A and the reactive power supply plan of the power factor adjustment device 35 received by the reception unit 20D.

Fig. 24 shows an example of a case where the power factor adjustment device 35 and the power converter are combined to compensate for reactive power. The upper stage of fig. 24 shows the time-dependent change of the reactive power detected by the reactive power detection device 2. In the middle section of fig. 24, a situation is shown in which the power factor adjustment device 35 compensates for reactive power. The lower stage of fig. 24 shows the output state of the reactive power output from each power converter 5.

As shown in fig. 24, the reactive power is controlled by the power factor adjusting device 35 by turning on and off the capacitor 37, and therefore, the reactive power cannot be completely compensated by the capacitor 37 of the power factor adjusting device 35 alone.

In the present embodiment, the compensation of the reactive power by the power factor adjustment device 35 and the power factor compensation function by each power converter 5 are combined to compensate the power factor of the entire plant power control system. In addition, in the present embodiment, since the power factor compensation function of the power converter 5 is used, the capacity of the capacitor necessary for the power factor adjustment device 35 can be reduced, and the cost of the power factor adjustment device 35 can be reduced.

[ example 6 ]

Embodiment 6 will be described with reference to fig. 25 to 27. Fig. 25 is an overall configuration diagram of the plant power control system according to the present embodiment. The difference between the structure of the present embodiment shown in fig. 25 and the structure of embodiment 5 described in fig. 21 is the point at which a signal flows from the control device 4F to the power factor adjustment device 35 in the present embodiment.

Fig. 26 shows the structure of the control device 4F according to the present embodiment. The difference between the control device 4F shown in fig. 26 and the control device 4 described in fig. 2 is that the control device 4F of the present embodiment includes a point of the transmitting unit 15A.

The processing of the reactive power command determining unit 16 included in the control device 4F of the present embodiment will be described with reference to fig. 27.

Steps S701 to S706 are similar to steps S601 to S606 described in fig. 16, and therefore, the description thereof is omitted.

In step S707, the control apparatus 4F compares "K" and "N". When K < N is satisfied (yes in S707), the control device 4F determines that the inverter 5 having the time of arrival prediction value k+1st is present, and proceeds to step S708.

On the other hand, if K < N is not satisfied (S707: no), since the inverter at the time of arrival prediction value k+1st is not present, the control device 4F determines that reactive power compensation by the power factor adjustment device 35 is necessary, and the flow of actions proceeds to step S709.

In step S708, the control device 4F updates the value of K, and returns to step S704. By increasing the value of the variable K by 1, the inverter at the time of arrival prediction value k+1st late can be specified in step S704.

In step S709, the control device 4F transmits the reactive power output command Q to the power factor adjustment device 35 _TMAPREF 。

The present embodiment thus constructed also has the same operational effects as those of embodiment 5. In the present embodiment, in the case where reactive power cannot be compensated only by the power converter 5, reactive power is compensated in cooperation with the power factor adjustment device 35. This can improve the power factor of the entire plant.

[ example 7 ]

Embodiment 7 will be described with reference to fig. 28 and 29. Fig. 28 is a block diagram of a control device 4G included in the plant power control system according to the present embodiment. The control device 4G according to the present embodiment is different from the control device 4 of embodiment 1 described in fig. 2 in the point of having the alarm display unit 39. The alarm display unit 39 is connected to the reactive power command determination unit 16, and outputs an alarm in response to a command from the reactive power command determination unit 16.

Fig. 29 is a flowchart showing the processing of the reactive power command determination unit 16 provided in the control device 4G. Steps S801 to S808 are similar to steps S701 to S708 described in fig. 27, and therefore, the description thereof is omitted.

In step S809, the control device 4G causes the alarm display unit 39 to display a predetermined warning. As a predetermined warning, for example, a message such as "N converters cannot compensate according to reactive power demand" is displayed on the display. Instead of or in addition to the display, a warning may be provided by voice. The predetermined warning need not be a text message, and may be, for example, a warning to the user by turning on a display lamp.

The predetermined alert may also contain a proposal from the plant power control system. The proposal includes at least any one of a short-term proposal and a long-term proposal. Short-term proposals refer to what can be implemented relatively early to compensate for reactive power. Short-term proposals are for example the correction of reactive power supply plans by the power factor adjustment device 35. That is, the control device 4G calculates whether or not the reactive power can be compensated by changing at least one of the number of capacitors 37 to be turned on/off and the timing of turning on/off the capacitors 37, and if it is determined that the reactive power can be compensated, proposes to the user a correction of the reactive power supply schedule of the power factor adjustment device 35. A long-term proposal refers to a proposal that is implemented for a longer time than a short-term proposal. The long-term proposals include, for example, proposals for replacement or addition of the power converter 5, replacement or addition of the power factor adjustment device 35, and the like, which are updated in relation to the power equipment of the plant.

The present embodiment thus constructed also has the same operational effects as those of embodiment 1. In addition, in the present embodiment, since the warning is output when the reactive power cannot be compensated, the user can confirm the warning and take countermeasures, and the convenience of use for the user is improved.

[ example 8 ]

Embodiment 8 will be described with reference to fig. 30 and 31. Fig. 30 is a block diagram of a control device 4H included in the plant power control system according to the present embodiment. The control device 4H of the present embodiment is different from the control device 4 of embodiment 1 in that a reactive power comparing unit 40, a log data storing unit 41, and an external interface 33B for inputting and outputting data of the log data storing unit 41 to the outside are added.

The reactive power comparing unit 40 receives the reactive power detected by the reactive power detecting device 2 via the receiving unit 20A, and receives the information of the reactive power output from each power converter 5 via the receiving unit 20B. The reactive power comparing unit 40 compares the reactive power received from the receiving unit 20A with the reactive power received from the receiving unit 20B, and if it is determined that the reactive power cannot be compensated, stores predetermined log data in the log data storage unit 41.

The process of the reactive power comparing unit 40 provided in the control device 4H will be described with reference to the flowchart of fig. 31.

The control device 4H reads the reactive power detection value Q from the receiving unit 20A _M Reactive power Q is read from receiving unit 20B _A 、Q _B 、Q _C 、...、Q _N (S901)。

The control device 4H calculates the total reactive power requirement Q _REF0 (S902). Total reactive power requirement Q _REF0 The calculation can be performed by the following equation 24.

[ 24 ] of the following

Q _REFO ＝-Q _M

The control device 4H calculates the reactive power Q _A 、Q _B 、Q _C 、...、Q _N Sum Q of _TOTAL (S903)。Q _TOTAL Represented by the following formula 25. Q is the same as above _N N is the number of power converters.

[ 25 ] of the following

Control device 4 pair Q _TOTAL And Q _REF0 A comparison is made (S904). At Q _TOTAL <Q _REF0 If so (yes in S904), the control device 4H proceeds to step S905. On the other hand, at Q _TOTAL <Q _REF0 If not (S904: NO), the control device 4H ends the present routineAnd (5) processing.

The control device 4H stores predetermined log data in the log data storage unit 41 (S905). The predetermined log data is, for example, a reactive power detection value received by the receiving unit 20A, at least one of the active power, reactive power, torque, and speed of each power converter 5 received by the receiving unit 20B, and a time stamp at the time of storing the log data. Instead, any data at a plurality of time points may be stored in the log data storage unit 41.

The user can take out and use the log data stored in the log data storage unit 41 via the external interface 33B. These log data can contribute to, for example, improvement of reactive power distribution methods due to change of a threshold value or the like, determination of rated apparent capacity of the power converter 5 at the time of future equipment update, and the like.

The present embodiment thus constructed also has the same operational effects as those of embodiment 1. In addition, in the present embodiment, when the reactive power cannot be compensated, since predetermined log data is stored, the user can make the log data contribute to cause analysis, future equipment update, and the like, and the convenience of use for the user is improved.

[ example 9 ]

Embodiment 9 will be described with reference to fig. 32 to 35. Fig. 32 is a block diagram of a control device 4J included in the plant power control system according to the present embodiment. The control device 4J of the present embodiment is different from the control device 4 of embodiment 1 in the following points: an active power predicting unit 42, a reactive power shortage predicting unit 43, a receiving unit 20E, and a transmitting unit 15A are added, the power factor adjusting device 35 is connected to the transmitting unit 15A, and the reactive power predicting value 44 is connected to the receiving unit 20E.

Fig. 33 is a block diagram of the active power prediction unit 42. Fig. 34 shows an example of the positional relationship among the steel sheet 13, the rollers 11, 12, and the sensor 21.

In fig. 34, the calender rolls 11A, 12A are arranged at a position X _A The calender rolls 11B, 12B are arranged at the position X _B The calender rolls 11C, 12C are arranged at the position X _C . The sensor 21A is arranged at the position X _AS Sensor 21B is arranged at the position X _BS The sensor 21C is disposed at the position X _CS . The explanation will be given with the left side of fig. 34 being the upstream side, the right side being the downstream side, and the steel sheet 13 moving from the upstream side to the downstream side.

Time t ₄₁ A state in which the rolling of the steel sheet 13 by the rolling rolls 11A, 12A is started is shown. Time t ₄₂ The rolling of the steel sheet 13 by the rolling rolls 11A and 12A is completed, and the steel sheet 13 is positioned downstream of the rolling rolls 11A and 12A. Time t ₄₃ A state in which the rolling of the steel sheet 13 by the rolling rolls 11B, 12B is started is shown. Time t ₄₄ The rolling of the steel sheet 13 by the rolling rolls 11B and 12B is completed, and the steel sheet 13 is positioned downstream of the rolling rolls 11B and 12B.

Returning to fig. 33. The active power prediction unit 42 includes, for example, an arrival time storage device 44, an active power storage device 45, a speed information storage device 30, a torque information storage device 31, an active power learning unit 46, and an active power prediction value calculation unit 47. In the drawings, names of the respective structures are appropriately abbreviated.

The active power learning unit 46 has a function of learning the active power of each power converter 5 at a future point in time. For example, in fig. 34, when a certain steel plate 13 is passed through the power converter 5A (from time t ₄₁ By time t ₄₂ ) The active power of the power converter 5A of (1) is P _{A_DB} When the same steel plate 13 passes through the power converter 5B (from time t ₄₃ By time t ₄₄ ) The active power of the power converter 5B of (1) is P _{B_DB} . If the active power P of the power converter 5A is to be used _{A_DB} Active power P with power converter 5B _{B_DB} If the ratio of (2) is set to the correction coefficient β, the correction coefficient β is expressed by the following equation 26.

[ 26 ]

β＝P _{B_DB} /P _{A_DB}

By learning the correction coefficient β shown in equation 26 in association with the speed information, the torque information, and the like, it is possible to base on the active power information P during rolling of the steel sheet 13 at the power converter 5A _A The same steel is predicted from equation 27, speed information, torque information, and correction coefficient βPlate 13 presses delayed active power P at power converter 5B _{B_PRED} 。

[ 27 ] of the following formula

P _{B_PRED} ＝β×P _A

The active power prediction value calculation unit 47 has a function of predicting active power at an arbitrary point in time in the future. Future arbitrary time point t+t _ARB Predicted value P of active power of (2) _PRED Can be calculated by the following equation 28. Wherein t is _ARB Is an arbitrary time.

[ 28 ]

P in formula 28 _{i_PRED} (t+t _ARB ) Determined as follows. That is, for any time t+t _ARB And the arrival time prediction value (t _{A_EST} 、t _{B_EST} 、...、t _{N_EST} ) Comparing, at the time t+t predicted to be at an arbitrary time _ARB When the steel sheet 13 arrives, the predicted value of the active power learned by the active power learning unit 46 is set to P _{i_PRED} (t+t _ARB ). When it is predicted that the steel sheet 13 does not arrive, the active power at the time of no load is set to the active power predicted value P _{i_PRED} (t+t _ARB )。

The process performed by the reactive power shortage prediction unit 43 will be described with reference to the flowchart of fig. 35.

The control device 4J reads the predicted value P of the active power from the active power prediction unit 42 _A (t+t _ARB )、P _B (t+t _ARB )、...、P _N (t+t _ARB ) The predicted value Q of the total reactive power demand is read from the receiving unit 20D _REF0 (t+t _ARB ) The rated apparent power S is read from the rated apparent power storage unit 19 _A 、S _B 、...、S _N (S1001)。

The control device 4J calculates a predicted value of reactive power that can be supplied at an arbitrary time point in the future (S1002). Arbitrary in the futureTime point t+t _ARB Predictive value Q of reactive power that can be supplied _PRED (t+t _ARB ) Can be calculated by the following equation 29.

[ 29 ]

The control device 4J predicts the value Q of the reactive power that can be supplied at any future time point _PRED (t+t _ARB ) And a predicted value Q of the total reactive power demand _REF0 (t+t _ARB ) The comparison is performed (S1003). At Q _PRED (t+t _ARB )>Q _REF0 (t+t _ARB ) If this is true (S1003: yes), the control device 4J advances to step S1004. On the other hand, if the control device 4J determines that Q _PRED (t+t _ARB )>Q _REF0 (t+t _ARB ) Not true (S1003: no), the present process is ended.

In step S1004, the control device 4J transmits the reactive power output command Q to the power factor adjustment device 35 _TMAPREF 。

The present embodiment thus constructed also has the same operational effects as those of embodiment 1. In the present embodiment, the instruction can be given to the power factor adjustment device 35 before the remaining reactive power of each power converter 5 is insufficient with respect to the total reactive power demand. Thus, in the present embodiment, the power factor adjustment device 35 can be operated quickly, and a decrease in the power factor due to the response delay time of the power factor adjustment device 35 can be suppressed.

Claims (14)

1. A plant power control system is provided with:

a power inverter provided for each of the motors between a power system of a factory and each of the motors;

reactive power load equipment connected to the power system;

a control device that generates a predetermined instruction indicating reactive power supplied from each of the power converters to the power system; and

Reactive power detection means for detecting reactive power at a power receiving point of the reactive power load device and the power system,

the control device calculates a reactive power demand for canceling the reactive power detected by the reactive power detection device based on the reactive power supplied from each of the power converters to the power system,

the control device calculates, for each of the power converters, a command value for distributing the calculated reactive power demand to each of the power converters, based on an arrival time prediction value calculated based on the motor arrangement information and predicting that an object arrives at each of the power converters, using the reactive power demand and motor arrangement information indicating a positional relationship of each of the motors as predetermined information on each of the motors.

2. The plant power control system of claim 1,

the control device further uses, as the predetermined information, either torque information or active power information output from each of the power converters, angular velocity information of each of the motors output from each of the power converters, and rated apparent power of the power converters.

3. The plant power control system of claim 2,

the control device uses any one of the motor arrangement information, the torque information, or the active power information, each of the angular velocity information, and load increase timing information indicating a timing at which a load of each of the power converters increases, as predetermined information.

4. The plant power control system of claim 3,

the control device calculates the load increase timing based on either the active power information or the torque information and the angular velocity information, and determines a predetermined timing based on the calculated load increase timing.

5. The plant power control system of claim 4,

each motor applies a predetermined process to the object,

the plant power control system further includes an object detector that detects a position of the object,

the control device calculates the load increase timing based on either the active power information or the torque information, each of the angular velocity information, and the output of the object detector.

6. The plant power control system of claim 5,

the control device further comprises an angular velocity information storage unit for storing each piece of angular velocity information in association with time information,

The control device corrects each of the angular velocity information based on the angular velocity information stored in the angular velocity information storage unit.

7. The plant power control system of claim 4,

the control device rewrites all or a part of the calculated parameters for at least any one of the reactive power demand, the command value, the load increase timing, and the predetermined timing from the outside.

8. The plant power control system of claim 7,

the control device may be configured to rewrite all or a part of at least one of the motor arrangement information, the rated apparent power, and the angular velocity information from outside.

9. The plant power control system according to any one of claim 2 to 8,

the control device calculates the command value for each of the power converters based on any one of a reactive power supply plan of a reactive power compensation device connected to the power system, the motor arrangement information, the torque information, or the active power information, each of the angular velocity information, the rated apparent power, and the reactive power demand.

10. The plant power control system according to any one of claim 1 to 8,

the control device indicates, to a reactive power compensation device connected to the power system, an output of an insufficient amount of reactive power supplied from each of the power converters to the power system.

11. The plant power control system according to any one of claim 1 to 8,

the control device outputs an alarm when it is determined that the reactive power supplied from each of the power converters to the power system and the reactive power detected by the reactive power detection device are unbalanced.

12. The plant power control system according to any one of claim 1 to 8,

the control device stores predetermined log data when it is determined that the reactive power supplied from each of the power converters to the power system and the reactive power detected by the reactive power detection device are unbalanced.

13. The plant power control system according to any one of claim 2 to 8,

the control device further comprises:

an active power prediction unit configured to predict an active power of each of the power converters; and

and a reactive power shortage prediction unit that predicts a shortage of reactive power by using the predicted value of reactive power at the power receiving point, the rated apparent power, and the active power predicted by the active power prediction unit.

14. A control method of a power control system of a factory,

the plant power control system includes: a power inverter provided for each of the motors between a power system of a factory and each of the motors; reactive power load equipment connected to the power system; a control device that generates a predetermined instruction indicating reactive power supplied from each of the power converters to the power system; and reactive power detection means for detecting reactive power at the power receiving points of the reactive power load device and the power system,

the control device calculates a reactive power demand for canceling the reactive power detected by the reactive power detection device based on the reactive power supplied from each of the power converters to the power system,

the control device calculates, for each of the power converters, a command value for distributing the calculated reactive power demand to each of the power converters, based on an arrival time prediction value calculated based on motor configuration information indicating a positional relationship of each of the motors, the arrival time prediction value being calculated based on the motor configuration information, using the reactive power demand and motor configuration information indicating a positional relationship of each of the motors,

And transmitting each calculated command value to each corresponding power converter.

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