JP7125875B2 - Plant power control system and its control method - Google Patents

Description

The present invention relates to a plant power control system and its control method.

Patent document 1 is known as a system for improving the power factor of a plant power supply. Patent Document 1 describes plant power factor control by a plant power control system that optimally controls the power factor of the entire plant by making the most of the surplus power of the current capacity of the inverter drive, which has a large power ratio in the plant. Techniques are disclosed for providing a scheme. That is, in Patent Literature 1, reactive power is supplied from the control system to the plant in a direction to reduce the reactive power received by the plant from the grid.

Patent No. 3682544

Although Patent Document 1 describes improving the power factor of the plant power supply, it does not describe the value of reactive power to be allocated to a plurality of inverter drives and the output timing thereof, leaving room for improvement.

For example, in a plant such as a steel mill, the moment the rolling motor bites the steel sheet, the torque increases rapidly and the rotation speed drops, so the power converter increases the torque current command to maintain the rotation speed. As the torque current rises, the surplus power of the current capacity of the power converter decreases, so there is a risk that the power converter will not be able to supply sufficient reactive power and the power factor of the entire plant power supply will drop.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a plant power control system and a control method thereof that can efficiently improve the power factor of the entire plant.

In order to solve the above problems, a plant power control system according to one aspect of the present invention includes a power converter provided for each electric motor and positioned between the electric power system of the plant and each electric motor, and a power converter connected to the electric power system. a reactive power load facility, a control device that generates a predetermined command to instruct the reactive power to be supplied from each power converter to the power system, and a reactive power at a power receiving point of the reactive power load facility and the power system. a reactive power detection device, the control device calculates a required amount of reactive power for canceling the reactive power detected by the reactive power detection device with the reactive power supplied from each power converter to the power system, and calculates the reactive power A command value for distributing the calculated reactive power demand amount to each power converter is calculated for each power converter according to the surplus capacity of each power converter based on the requested amount and predetermined information about each electric motor. do.

According to the present invention, a command value for distributing the required amount of reactive power to each power converter can be calculated according to the surplus capacity of each power converter, thereby efficiently improving the power factor of the entire plant. be able to.

1 is an overall configuration diagram of a plant power control system according to a first embodiment; FIG. 1 is a configuration diagram of a power control device; FIG. It is explanatory drawing which shows the positional relationship of an electric motor group and a steel plate. Fig. 4 is a graph showing changes in motor torque and speed; 4 is a flow chart showing a process of predicting a time when a steel plate reaches an electric motor (corresponding power converter); 4 is a flowchart of processing for determining a reactive power command; 9 is a flow chart showing another process for determining a reactive power command; FIG. 10 is an explanatory diagram showing a distribution state of reactive power in a related technique prepared for comparison with the present embodiment; FIG. 3 is an explanatory diagram showing distribution of reactive power in the embodiment; FIG. 10 is an explanatory diagram showing another positional relationship between the power converter group and the steel plate; FIG. 11 is an overall configuration diagram of a plant power control system according to a second embodiment; 1 is a configuration diagram of a power control device; FIG. It is a flow chart of arrival time prediction processing. 10 is a flowchart of another arrival time prediction process; It is explanatory drawing which shows the positional relationship of an electric motor group and a steel plate. 4 is a flowchart of processing for determining a reactive power command; FIG. 11 is a configuration diagram of a power control device according to a third embodiment; FIG. 4 is a configuration diagram of a function for estimating a steel plate speed from a sensor signal; Fig. 4 is a graph showing changes in motor torque and speed; FIG. 11 is a configuration diagram of a power control device according to a fourth embodiment; FIG. 11 is an overall configuration diagram of a plant power control system according to a fifth embodiment; 1 is a configuration diagram of a power factor adjustment device; FIG. 1 is a configuration diagram of a power control device; FIG. It is a graph which shows the distribution condition of reactive power. FIG. 11 is an overall configuration diagram of a plant power control system according to a sixth embodiment; 1 is a configuration diagram of a power control device; FIG. 4 is a flowchart of processing for determining a reactive power command; FIG. 11 is a configuration diagram of a power control device according to a seventh embodiment; 4 is a flowchart of processing for determining a reactive power command; FIG. 11 is a configuration diagram of a power control device according to an eighth embodiment; 4 is a flowchart of processing for comparing reactive powers; FIG. 21 is a configuration diagram of a power control device according to a ninth embodiment; FIG. 4 is a configuration diagram of a function for estimating active power; It is explanatory drawing which shows the positional relationship of an electric motor group and a steel plate. 4 is a flowchart of processing for predicting a shortage of reactive power.

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

In this embodiment, a steel plant that rolls steel sheets will be described as an example, but the present invention can also be applied to plants other than steel plants. For example, this embodiment can be applied to a plant provided with a plurality of electric motors that are driven in cooperation with each other.

In this embodiment, as will be described later, each torque current is predicted for each power converter included in the plant power control system, and reactive power is preferentially supplied from the power converter with a large surplus current capacity. This improves the power factor of the entire plant power supply.

The plant power control system according to the present embodiment includes electric motors 10A to 10C that rotate by receiving electrical energy, power converters 5A to 5C that are arranged between the electric motors 10A to 10C and the power system 1, and the power system 1 Reactive power load equipment 3 connected to, a control device 4 for generating a reactive power command or a reactive current command supplied to the power system 1 from a plurality of power converters 5A to 5C, power converters 5A to 5C and a control device 4, and a reactive power detection device 2 for measuring or estimating the reactive power at the power receiving point RP where the power system 1 and the reactive power load facility 3 are connected.

The control device 4 calculates the 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 . Then, the control device 4 provides the reactive power output target value or the reactive current output target value, the arrangement information of each electric motor 10A to 10C, the active power detection value of each power converter 5A to 5C, the active current command value, the effective Using at least one of a current detection value, a torque command value, and a torque detection value, a command value or detection value of the angular velocity of each electric motor 10A to 10C, and the rated apparent power of each power converter 5A to 5C determines the reactive power command or reactive current command to be commanded to each of the power converters 5A to 5C.

Further, the control device 4 controls at least one of the arrangement information of the electric motors 10A to 10C, the active power detection value, the active current command value, the active current detection, the torque command value, and the torque detection value of each of the power converters 5A to 5C. and an arrival time prediction unit 17 that predicts the arrival time at which the steel plate 13, which is an object to be processed in the plant, reaches the electric motors 10A to 10C using the command value or the detected value of the angular velocity of each electric motor 10A to 10C. be prepared. Furthermore, the control device 4 uses the rated apparent power, the total reactive power output target value or reactive current output target value of the power converters 5A to 5C, and the arrival time of the steel plate 13 predicted by the arrival time prediction unit 17. and a reactive power command determining unit 16 for calculating a reactive power command or a reactive current command to be commanded to each of the power converters 5A to 5C.

The control device 4 includes a receiving unit 20C that receives the outputs of the sensors 21A to 21C. Using at least one of a current command value, an effective current detection value, a torque command value, and a torque detection value, a command value or a detection value of the angular velocity of each electric motor 5A to 5C, and an output of each sensor 21A to 21C, The arrival time of the steel plate 13 can also be predicted.

First, the plant power control system according to the first embodiment will be explained using FIGS. 1 to 10. FIG.

FIG. 1 shows the overall configuration of a plant power control system according to this embodiment. The plant power control system includes, for example, a power supply 1, a plurality of power converters 5A to 5C, a controller 4, a power supply voltage detector 9, a current detector 8, a reactive power detector 2, and a lagging power factor. A lagging power factor load facility 3 connected via a load facility transformer 7, power converter transformers 6A to 6C, electric motors 10A to 10C, rolling roller upper parts 11A to 11C, and rolling roller lower parts 12A. 12C, and one or more steel plates 13 pass between the rolling rollers 11A-11C and the rolling rollers 12A-12C.

The power source 1 of the plant corresponds to the "power system". The lagging power factor load equipment 3 corresponds to "reactive power load equipment". The control device 4 is a controller (CTL) that controls the power converters 5A to 5C, and can also be called a power control device. A steel plate 13 is an object to be processed by each electric motor 10A-10C.

The reactive power detection device 2 detects or detects reactive power (reactive power detection value Q _M ) received from the grid by the lagging power factor load equipment 3 from the detection value of the current detector 8 and the detection value of the power supply voltage detector 9. presume. The reactive power detection value _QM may be estimated from at least any two of active power, apparent power, and power factor. Reactive power detection value _QM may be estimated from the difference between the reactive power of power supply 1 and the reactive power of power converters 5A-5C. The control device 4 calculates a reactive power command based on the reactive power detection value _QM and signals (speed information, torque information, active power information) obtained from the power converters 5A to 5C, and the calculated reactive power A command is distributed to each power converter 5A to 5C and commanded at a predetermined timing.

The power converters 5A-5C respectively control the rotation speeds of the corresponding electric motors 10A-10C. That is, power converter 5A controls motor 10A, power converter 5B controls motor 10B, and power converter 5C controls motor 10C.

Electric motors 10A-10C are mechanically connected to upper rolling rollers 11A-11C and lower rolling rollers 12A-12C. The upper rolling rollers 11A-11C and the lower rolling rollers 12A-12C roll the steel plate 13. As shown in FIG.

Details of the control device 4 will be described with reference to FIG. In the drawings, the word "part" is abbreviated, for example, "receiving part" is indicated as "receiving".

The control device 4 includes, for example, hardware such as a processor, memory, storage, input/output interface, and communication interface, and software such as an operating system and predetermined computer programs (all not shown). The control device 4 can be configured as a computer, or can be configured as a programmable controller or a control panel. The functions of the control device 4 are realized by a processor, which is an arithmetic device, reading a predetermined computer program into a memory and executing it. Note that functions that can be implemented as a computer program may be implemented as a hardware circuit.

The control device 4 includes a reactive power command determination unit 16, an arrival time prediction unit 17, a motor arrangement storage unit 18, a rated apparent power storage unit 19, a transmission unit 15, and reception units 20A and 20B. The receiving section 20A and the receiving section 20B are sometimes called the receiving section 20 when not distinguished from each other. Similarly, other configurations may be described by omitting alphabets for configurations with alphabets attached to reference numerals.

20 A of receiving parts receive the reactive power detection value which the reactive power detection apparatus 2 outputs. The receiving unit 20B outputs torque information (torque command or torque feedback or active current command or active current detection value) and speed It receives information (speed command or speed feedback) and active power information (active power command or active power sensed value). The torque information may be an active power command or an active power detection value.

Based on the torque information and speed information received by the receiving unit 20B and the electric motor arrangement read from the electric motor arrangement storage unit 18, the arrival time prediction unit 17 determines when the steel plate 13 reaches the rolling roller upper part 11 or the rolling roller lower part 12. A time prediction value is calculated, and the arrival time prediction value is output to the reactive power command determination unit 16 .

The reactive power command determination unit 16 determines the arrival time prediction value read from the arrival time prediction unit 17, the rated apparent power read from the rated apparent power storage unit 19, the reactive power detection value received by the reception unit 20A, and the reception unit 20B. A reactive power command is calculated based on the detected active power value of each power converter, and the reactive power command is output to the transmission 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, 5C. The reactive power command determination unit 16 may determine a reactive current command instead of the reactive power command value.

The reactive power command determining unit 16 and the arrival time predicting unit 17 will be described with reference to FIG. FIG. 3 shows changes in the positional relationship between the motor groups 10A to 10C and the steel plate 13. FIG. In FIG. 3, three sets of rolling rollers are shown. The first rolling rollers 11A and 12A initially contact and roll the steel plate 13 . The second rolling rollers 11B, 12B further roll the steel plate 13 rolled by the first rolling rollers 11A, 12A. The third rolling rollers 11C and 12C finally roll the steel plate 13 . In the drawing, three sets of rolling rollers are shown for convenience of explanation, but the present invention is not limited to this, as long as there are a plurality of sets of rolling rollers.

In FIG. 3, rolling rollers 11A and _12A are placed at position XA, rolling rollers 11B and _12B are placed at position XB, and rolling rollers _11C and 12C are placed at position XC. It is assumed that the left side of FIG. 3 is upstream and the right side is downstream, and the steel plate 13 moves from upstream to downstream.

Time t11 indicates a state in which rolling of the steel plate 13 is started from the upstream side of the rolling rollers _11A and 12A. Time t12 indicates a state in which the steel plate ₁₃ is being rolled by the rolling rollers 11A and 12A. Time t13 indicates a state in which the steel plate ₁₃ has completed rolling by the rolling rollers 11A and 12A and is positioned downstream of the rolling rollers 11A and 12A. Time t14 indicates a state in which rolling of the steel plate ₁₃ is started by the rolling rollers 11B and 12B. Time _t15 indicates a state in which rolling of the steel plate 13 is started by the rolling rollers 11C and 12C. In FIG. 3, the steel plate 13 is described as not being rolled by the plurality of rolling rollers 11 and 12 at the same time. Moreover, below, a rolling roller may be abbreviated as a roller.

FIG. 4 shows changes over time in the torque of the electric motor 10A and the speed (angular velocity; the same shall apply hereinafter) of the electric motor 10A. In FIG. 4, at time t11, the steel plate ₁₃ reaches the electric motor 10A, and the torque generated by the rolling of the steel plate 13 reduces the speed of the electric motor 10A. A speed controller (not shown) of the electric power converter 5A that controls the electric motor 10A generates acceleration torque for following the speed command value. At time t12, since the steel plate ₁₃ is being rolled, torque is generated for the rolling of the steel plate 13 . _At time t13, rolling is finished, so the torque of the electric motor 10A is reduced.

The processing of the arrival time prediction unit 17 will be described with reference to FIG. FIG. 5 illustrates an example of calculating the time tB at which the steel plate 13 reaches the rollers _11B and 12B corresponding to the power converter 5B. Below, reaching the rollers 11 and 12 by the steel plate 13 may be abbreviated as reaching the power converter 5 . More precisely, when the steel plate 13 contacts the rolling rollers 11 and 12, the torque and speed of the electric motor 10 connected to the rollers 11 and 12 change, and the output of the power converter 5 controlling the electric motor 10 changes. .

In FIG. 5, the arrival time tB is the time when the steel plate 13 reaches the rolling rollers _11B and 12B.

The control device 4 reads the motor arrangement, torque τ _A (t), and speed command V _A (t) of the power converter 5A, and the motor arrangement X _B and torque τ _B (t) of the power converter 5B (S101). .

The controller 4 determines whether the steel sheet 13 is being rolled by the rolling rollers 11A and 12A by comparing the torque τ _A (t) with a predetermined threshold TH ₁ (S102). If the torque τ _A (t) is greater than the threshold TH ₁ (S102: Yes), the control device 4 determines that the steel plate 13 is being rolled by the rolling rollers 11A and 12A, and proceeds to step S103. On the other hand, when the torque τ _A (t) is smaller than the threshold TH ₁ (S102: No), the control device 4 determines that the steel plate 13 is not being rolled by the rolling rollers 11A and 12A, and proceeds to step S107.

In step S103, the control device 4 detects the timing when the steel plate 13 reaches the rolling rollers 11A and 12A. If the torque τ _A ( _{tt CAL} ) at time t−t _CAL one cycle before time t in the flowchart calculation is greater than threshold TH ₁ (S103: Yes), control device 4 controls time t−t Also in _CAL , it is determined that the steel sheet 13 is being rolled by the rolling rollers 11A and 12A, and the process proceeds to step S105.

On the other hand, when the torque τ _A ( _{tt CAL} ) is smaller than the threshold TH ₁ (S103: No), the control device 4 determines that the rolling of the steel plate 13 by the rolling rollers 11A and 12A has started at time t, The process proceeds to step S104.

The controller 4 resets the distance L _{STA_EST} of the steel sheet 13 that has passed the rolling rollers 11A and 12A after the rolling by the rolling rollers 11A and 12A is started to 0 (S104).

The control device 4 updates the distance of the steel sheet 13 that has passed the rolling rollers 11A and 12A (S105). The distance of the steel plate 13 that has passed through the rolling rollers 11A and 12A can be calculated using Equation (1).

ただし、Ｖ_Ａ（ｔ）は、ローラ１１Ａ，１２Ａにより圧延中の鋼板１３の移動速度である。ローラ１１Ａ，１２Ａにより圧延中の鋼板１３の移動速度Ｖ_Ａ（ｔ）は数２で計算できる。

However, V _A (t) is the moving speed of the steel plate 13 being rolled by the rollers 11A and 12A. The moving speed V _A (t) of the steel plate 13 being rolled by the rollers 11A and 12A can be calculated by Equation (2).

ただし、ｒ_Ａは、ローラ１１Ａの半径（m）である。ω_Ａ（ｔ）は、ローラ１１Ａの角速度(rad/sec)である。

However, _rA is the radius (m) of the roller 11A. ω _A (t) is the angular velocity (rad/sec) of the roller 11A.

Next, the control device 4 updates the time when the steel plate 13 reaches the rolling rollers 11B and 12B (S106). The time tB at which the steel plate 13 reaches the rolling rollers 11B and _12B can be calculated by equation (3).

制御装置４は、電力変換器５Ｂのトルクτ_Ｂ（ｔ）と所定の閾値ＴＨ_１Ｂとを比較することにより、鋼板１３が圧延ローラ１１Ｂ，１２Ｂにより圧延中であるかを判定する（Ｓ１０７）。トルクτ_Ｂ（ｔ）が閾値ＴＨ_１Ｂよりも大きい場合（Ｓ１０７：Ｙｅｓ）、制御装置４は、鋼板１３が圧延ローラ１１Ｂ，１２Ｂにより圧延中であると判定し、ステップＳ１０８へ進む。

The control device 4 determines whether the steel sheet 13 is being rolled by the rolling rollers 11B and 12B by comparing the torque τ _B (t) of the power converter 5B with a predetermined threshold TH _1B (S107). If the torque τ _B (t) is greater than the threshold TH _1B (S107: Yes), the control device 4 determines that the steel sheet 13 is being rolled by the rolling rollers 11B and 12B, and proceeds to step S108.

On the other hand, when the torque τ _B (t) is smaller than the threshold TH _1B (S107: No), the control device 4 determines that the steel plate 13 is not being rolled by the rolling rollers 11B and 12B, and proceeds to step S109.

In step S108, the control device 4 updates the time when the steel plate 13 reaches the rolling rollers 11B and 12B. Since the steel plate 13 is arriving at the time t, the arrival time predicted value _{tB_EST} is updated by Equation (4).

ステップＳ１０９において、制御装置４は、圧延ローラ１１Ｂ，１２Ｂによる鋼板１３の圧延が終了したタイミングを検出する。制御装置４は、時刻ｔより１サイクル前の時刻ｔ－ｔ_ＣＡＬにおけるトルクτ_Ｂ（ｔ－ｔ_ＣＡＬ）が閾値ＴＨ_１Ｂよりも大きい場合（Ｓ１０９：Ｙｅｓ）、時刻ｔ－ｔ_ＣＡＬにおいて圧延ローラ１１Ｂ，１２Ｂによる鋼板１３の圧延が完了したと判定し、ステップＳ１１０へ進む。

In step S109, the control device 4 detects the timing when the rolling of the steel plate 13 by the rolling rollers 11B and 12B is finished. When the torque τ _B ( _{tt CAL} ) at the time t−t _CAL one cycle before the time t is greater than the threshold TH _1B (S109: Yes), the control device 4 controls the rolling roller 11B at the time t−t _CAL . , 12B have completed the rolling of the steel plate 13, and the process proceeds to step S110.

On the other hand, when the torque τ _B ( _{tt CAL} ) is smaller than the threshold TH _1B (S109: No), the control device 4 determines that the steel plate 13 is being rolled by the rolling rollers 11A and 12A at time t, End this process.

In step S110, the control device 4 updates the time when the steel plate 13 reaches the rolling rollers 11B and 12B. Since the steel plate 13 has completed reaching at time t, the predicted arrival time value is reset to a large value according to Equation (5).

例えば、時刻ｔ_ＳＥＴＢは、操業時の鋼板１３がローラ１２Ａからローラ１２Ｂへ到達するのにかかる時間の最大値と比べて十分大きな値とする。

For example, the time t _SETB is set to a sufficiently large value compared to the maximum time required for the steel plate 13 to reach from the roller 12A to the roller 12B during operation.

The processing of FIG. 5 described above shows an example of estimating the arrival times of the rolling rollers 11B and 12B, but the arrival times of the rolling rollers 11C and 12C can also be calculated from the same processing as in FIG. Therefore, the description of the prediction method of the time when the steel plate 13 reaches the rollers 11C and 12C is omitted.

An example of processing of the reactive power command determining unit 16 will be described with reference to FIG. The controller 4 controls the reactive power detection value Q _M , the arrival time prediction values t _B and t _C of the steel plate 13 to each of the converters 5A to 5C calculated by the arrival time prediction unit 17, and the rated apparent powers S _A and S _B , S _C and active powers P _A , P _B , P _C are read, and the process proceeds to step S202.

In step _{S202 ,} the control device 4 _sets the reactive power demand Q Calculate _TMP and proceed to step S203.

In order to set the power factor of the power received by the plant from grid 1 to "1", it is necessary to calculate the reactive power demand so as to cancel out the reactive power detection value. Therefore, the controller 4 calculates the required reactive power Q _TMP from Equation (6).

ステップＳ２０３では、制御装置４は、電力変換器５Ｂと電力変換器５Ｃへの負荷（鋼板１３）の到達時刻予測値ｔ_Ｂ，ｔ_Ｃを比較する。制御装置４は、ｔ_Ｂ＞ｔ_Ｃが成立する場合（Ｓ２０３：Ｙｅｓ）、ステップＳ２０４へ進む。一方、制御装置４は、ｔ_Ｂ＞ｔ_Ｃが成立しない場合（Ｓ２０３：Ｎｏ）、ステップＳ２１０へ進む。

In step S203, control device 4 compares predicted arrival time values tB and tC of the load (steel plate 13) to power converter _5B and power converter _5C . When _tB > _tC is established (S203: Yes), the controller 4 proceeds to step S204. On the other hand, when _tB > _tC is not established (S203: No), the control device 4 proceeds to step S210.

At step S204, the controller 4 calculates a reactive power command Q _REFB for the power converter 5B. Reactive power command can be calculated by Equation 7.

ただし、ＳＩＧＮは、括弧内の入力が正のときは１を、０の時は０を、負のときは－１を出力する関数である。ＭＩＮは、括弧内の入力のうち最も小さい値を出力する関数である。ＡＢＳは、括弧内の入力の絶対値を出力する関数である。

However, SIGN is a function that outputs 1 when the input in parentheses is positive, 0 when it is 0, and -1 when it is negative. MIN is a function that outputs the smallest value among the inputs in parentheses. ABS is a function that outputs the absolute value of the input in brackets.

If the steel plate arrival time predicted value tB is different from the current time t (when the rollers _11B and 12B are not rolling), it can be assumed that the active power in the rollers 11B and 12B is sufficiently small. Therefore, it is possible to fix the active power _PB to 0 in Expression 7 and not use the detected value of _PB .

If a reactive current command is given instead of the reactive power command, the reactive current output command may be calculated using the rated apparent current instead of the rated apparent power and the active current instead of the active power in Expression 7.

In step S205, the controller 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power request amount Q _TMP according to Equation 8 so as to change the reactive power request amount by the reactive power command calculated in Equation 7.

ステップＳ２０６では、無効電力要求量Ｑ_ＴＭＰが０になったかを判定する。無効電力要求量Ｑ_ＴＭＰ＝０が成立する場合（Ｓ２０６：Ｙｅｓ）、制御装置４は、電力変換器５Ｂにより必要な無効電力を供給できたと判断し、ステップＳ２０９へ進む。

In step S206, it is determined whether or not the required reactive power amount Q _TMP has become zero. If the required reactive power amount Q _TMP =0 is satisfied (S206: Yes), the control device 4 determines that the required reactive power has been supplied by the power converter 5B, and proceeds to step S209.

On the other hand, if the required reactive power amount Q _TMP =0 is not satisfied (S206: No), the control device 4 determines that the required reactive power cannot be supplied by the power converter 5B, and proceeds to step S207.

In step S207, control device 4 calculates reactive power command Q _REFC of power converter 5C. Reactive power command can be calculated by Equation 9.

鋼板到達時刻予測値ｔ_Ｃと現在時刻ｔとが異なる場合（ローラ１１Ｃが圧延中でない場合）、ローラ１１Ｃにおける有効電力は十分に小さいと仮定できるため、数９において有効電力Ｐ_Ｃを０に固定し、Ｐ_Ｃの検出値を用いなくてもよい。

If the steel plate arrival time predicted value t _C is different from the current time t (when the roller 11C is not rolling), it can be assumed that the active power at the roller 11C is sufficiently small, so the active power P _C is fixed to 0 in Equation 9. However, the _detected value of PC may not be used.

In step S208, the controller 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power request amount Q _TMP according to Equation 10 so as to change the reactive power request amount by the reactive power command calculated in Equation 9.

ステップＳ２０９では、制御装置４は、電力変換器５Ｃの無効電力指令Ｑ_ＲＥＦＣをゼロにする。

At step S209, the controller 4 sets the reactive power command Q _REFC of the power converter 5C to zero.

In step S210, control device 4 calculates reactive power command Q _REFC of power converter 5C. Reactive power command can be calculated by Equation 9.

In step S211, the controller 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power request amount Q _TMP according to Equation 10 so as to change the reactive power request amount by the reactive power command calculated in Equation 9.

In step S212, the controller 4 determines whether the reactive power demand Q _TMP has become zero. When the required reactive power amount Q _TMP =0 is satisfied (S212: Yes), the control device 4 determines that the required reactive power has been supplied by the power converter 5C, and proceeds to step S215. On the other hand, when the required reactive power amount Q _TMP =0 is not satisfied (S212: No), the control device 4 determines that the required reactive power cannot be supplied by the power converter 5C, and proceeds to step S213.

At step S213, the controller 4 calculates a reactive power command Q _REFB for the power converter 5B. Reactive power command can be calculated by Equation 7.

In step S214, the controller 4 updates the reactive power demand Q _TMP . The control device 4 updates the reactive power request amount Q _TMP according to Equation 8 so as to change the reactive power request amount by the amount of the reactive power command calculated from Equation 7 in step S213.

At step S215, the controller 4 sets the reactive power command Q _REFB of the power converter 5B to zero.

In step S216, the controller 4 determines whether the reactive power demand Q _TMP has become zero. When the required reactive power amount Q _TMP =0 is established (S216: Yes), the control device 4 determines that the required reactive power has been supplied by the power converters 5B and 5C, and proceeds to step S218.

On the other hand, when the reactive power request amount Q _TMP =0 is not established (S216: No), the control device 4 determines that the required reactive power cannot be supplied by the power converters 5B and 5C, and step Proceed to S217.

In step S217, control device 4 calculates reactive power command Q _REFA for power converter 5A. Reactive power command can be calculated by Equation 11.

ステップＳ２１８では、制御装置４は、電力変換器５Ａの無効電力指令Ｑ_ＲＥＦＡをゼロにする。

At step S218, the controller 4 sets the reactive power command Q _REFA of the power converter 5A to zero.

The processing of the reactive power command determination unit 16 when there are four or more converters 5 will be described with reference to the flowchart of FIG.

, _5N (N is the number of converters; the same shall apply hereinafter) to each of the power converters 5A, 5B, . . . Arrival time prediction values _tB , _tC , ..., _tN , rated apparent powers _SA , _SB , _SC , ..., _SN , and active powers _PA , _PB , _PC , ... ·, _PN are read (S301), and then the process proceeds to step S302.

The controller 4 calculates the required reactive power Q _TMP (S302), and proceeds to step S303. In order to set the power factor to "1", it is necessary to calculate the reactive power demand so as to cancel out the reactive power detection value.

ステップＳ３０３では、制御装置４は、初期値を設定する。初期値として、Ｋ＝１、Ｎ＝変換器数を設定する。

In step S303, the control device 4 sets initial values. As initial values, set K=1 and N=the number of converters.

In step S304, the control device 4 compares the predicted arrival time values of the loads to the converters 5B to 5N, and calculates the reactive power command Q _REFK for the power converter 5K with the K-th latest predicted arrival time value. Since the arrival time of steel plate 13 at power converter 5A with which steel plate 13 contacts first cannot be estimated, power converter 5A is not included in the derivation of power converter 5K having the K-th latest predicted arrival time value. The converter reactive power command can be calculated by Equation 13.

ステップＳ３０５では、制御装置４は、無効電力要求量Ｑ_ＴＭＰを更新する。制御装置４は、数１３で計算された無効電力指令分だけ無効電力要求量を変更するように、数１４で計算する。

In step S305, the controller 4 updates the reactive power demand Q _TMP . The controller 4 calculates with Equation 14 so as to change the reactive power request amount by the amount of the reactive power command calculated with Equation 13.

ステップＳ３０６では、制御装置４は、無効電力要求量Ｑ_ＴＭＰが０になったかを判定する。制御装置４は、無効電力要求量Ｑ_ＴＭＰ＝０が成立する場合（Ｓ３０６：Ｙｅｓ）、Ｋ番目に到達時刻予測値が遅い変換器により必要な無効電力を供給できたと判断し、本処理を終了する。

In step S306, the controller 4 determines whether the reactive power demand Q _TMP has become zero. If the required reactive power amount Q _TMP =0 is established (S306: Yes), the control device 4 determines that the required reactive power has been supplied by the converter with the K-th late arrival time prediction value, and terminates this process. do.

On the other hand, when the required reactive power amount Q _TMP =0 is not established (S306: No), the control device 4 determines that the required reactive power cannot be supplied by the converter with the K-th late arrival time prediction value, The process proceeds to step S307.

In step S307, the controller 4 compares K and N-1. If K<N−1 is established (S307: Yes), the controller 4 proceeds to step S308. On the other hand, if K<N−1 does not hold (S307: No), the controller 4 proceeds to step S309.

In step S308, the controller 4 updates the value of K by incrementing it by one, and proceeds to step S304. By updating K to K+1, the controller 4 can specify the converter with the K+1th latest arrival time prediction value in step S304.

In step S309, control device 4 calculates reactive power command Q _REFA for power converter 5A, and ends this process. Reactive power command Q _REFA of power converter 5A can be calculated by Equation (11).

FIG. 8 is a schematic diagram of time change of reactive power compensation in the related art prepared for comparison with the present embodiment. FIG. 9 is a schematic diagram of time change of reactive power compensation according to the present embodiment. Note that the relationship between the actual active power, reactive power, and apparent power is represented by a vector sum, but since it is difficult to illustrate, it is schematically represented in one dimension in FIGS. Time _td in FIG. 8 is the response time from when the reactive power command is given to the power converter 5 until the power converter 5 can supply reactive power. The horizontal axis in FIGS. 8 and 9 is the time axis, and the vertical axis indicates power.

In FIG. 8, at times t ₁₁ , t ₁₄ , and t ₁₅ , when steel plate 13 reaches power converters 5A, 5B, and 5C and the load increases sharply, power converters 5A to 5C have active power and reactive power command exceeds the rated apparent power (hereinafter also referred to as the rated power).

Here, in general, the power converter 5 has a function (limiter) for suppressing the current command so that the rated power is not exceeded in order to protect the equipment. Therefore, when the load suddenly increases, the limiter is activated, and the power converter 5 cannot supply reactive power as instructed by the reactive power command.

Furthermore, it takes a response time _td from when the power converter 5 is instructed until it can supply the desired reactive power. Therefore, as shown in FIG. 8, there occurs a time period during which reactive power cannot be supplied according to the reactive power command for the response time _td .

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

For example, between time t11 and time _{t14, the predicted arrival time value of steel plate 13 satisfies the relationship tB_EST < tC_EST , so power} converter 5C is preferentially disabled over power converter 5B. Power commands are distributed.

Between the time when the steel plate 13 completes passing between the rollers 11B and 12B corresponding to the electric motor 10B and the time _{t15 when the steel plate 13 reaches the next rollers 11C and 12C, the estimated arrival time of the steel plate 13 is t B_EST >} t satisfies the relationship of _{C_EST} . Therefore, control device 4 preferentially distributes the reactive power command to power converter 5B over power converter 5C.

According to the present embodiment configured in this way, reactive power is preferentially supplied from the power converter 5 having a large surplus current capacity, so that the steel plate 13 causing an increase in load reaches the motor with an early arrival time. can reduce the reactive power distribution of Therefore, according to this embodiment, the required amount of reactive power 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 this embodiment, based on the output state of the power converter 5, it is estimated that the steel plate 13 has arrived at the rollers 11 and 12, and the output of reactive power is allocated. No need. Therefore, it is possible to improve the power control system of the plant relatively inexpensively and easily. However, in this embodiment, a large reactive power output cannot be allocated to the power converter 5A corresponding to the rollers 11 and 12 that come into contact with the steel plate 13 first. This is because the time at which the steel plate 13 contacts the rollers 11 and 12 is unknown. A configuration for more accurately detecting the arrival of the steel plate 13 will be described later.

In the description so far, it is assumed that the length of one steel plate is shorter than the distance between any of the plurality of rolling rollers, but as shown in FIG. Even when the distance between any of the rolling rollers is longer than the distance, the reactive power can be output from the power converter 5 at an appropriate timing based on the same principle as in FIGS. It can improve the overall power factor.

A second embodiment will be described with reference to FIGS. 11 to 16. FIG. Each of the following embodiments, including the present embodiment, corresponds to a modification of the first embodiment, so the differences from the first embodiment will be mainly described. In the plant power control system of this embodiment, sensors 21A to 21C that detect the steel plate 13 are used.

FIG. 11 is a configuration diagram of a plant power control system according to this embodiment. The overall configuration shown in FIG. 11 differs from the overall configuration of the first embodiment described in FIG. 1 in that sensors 21A, 21B, and 21C are added. When there is no particular distinction, it may be called the sensor 21 .

The sensor 21 should be able to detect at least the presence of the steel plate 13 . The sensor 21 can also be called a steel plate detector, for example. The sensor 21 of this 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 rollers 11 and 12 and is arranged near the upper roller 11 . That is, the first sensor 21A is provided near the upstream side of the roller 11A, the second sensor 21B is provided near the upstream side of the roller 11B, and the third sensor 21C is provided near the upstream side of the roller 11C. A signal detected by each sensor 21 is input to the control device 4 via the communication network CN2.

FIG. 12 shows the configuration of the control device 4B. The configuration shown in FIG. 12 differs from the configuration of the first embodiment described in FIG. 2 in that a receiving section 20C for receiving signals from the sensor 21 is added.

In the control device 4B of this embodiment, the signal from the sensor 21 arranged in the vicinity of the upstream side of each roller 11, 12 can be used, so that the steel plate 13 is approaching the first rolling rollers 11A, 12A. can be detected. Further, it is possible to improve the prediction accuracy of the time when the steel plate 13 reaches the next rolling rollers 11B, 11C, .

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

FIG. 15 shows an example of the positional relationship between the steel plate 13, the rollers 11 and 12, and the sensor 21 for explaining FIGS. 13 and 14. FIG.

In FIG. 15, it is assumed that rolling rollers 11A and _12A are arranged at position XA, rolling rollers 11B and _12B are arranged at position XB, and rolling rollers _11C and 12C are arranged at position XC. Assume that sensor 21A is placed at position _XAS , sensor 21B is placed at position _XBS , and sensor 21C is placed at position _XCS . The left side of FIG. 15 is upstream, and the right side is downstream. It is assumed that the steel plate 13 moves from upstream to downstream.

Time t31 indicates the state in which the steel plate ₁₃ reaches the sensor 21A. Time _t32 indicates a state in which rolling of the steel plate 13 by the rolling rollers 11A and 12A has started. Time _t33 indicates a state in which the rolling of the steel plate 13 by the rolling rollers 11A and 12A is completed and the rolling rollers 11A and 12A are positioned downstream. Time _t34 indicates the state in which the steel plate 13 reaches the sensor 21B. Time _t35 indicates a state in which rolling of the steel plate 13 by the rolling rollers 11B and 12B has started.

Return to FIG. In FIG. 13, control device 4B reads electric motor arrangement X _A of power converter 5A at time t, torque τ _A (t), speed command V _A (t), and detection value D _STA (t) of sensor 21A. (S401).

The controller 4B compares the torque τ _A (t) with the threshold TH _1A (S402). If the torque τ _A (t) is greater than the predetermined threshold TH _1A (S402: Yes), the control device 4B determines that the steel plate 13 is being rolled, and proceeds to step S403. On the other hand, when the control device 4B determines that the torque τ _A (t) is not larger than the threshold TH _1A (S402: No), the process proceeds to step S404.

In step S<b>403 , the control device 4</b>B updates the predicted arrival time value of the steel plate 13 . At time t, the steel plate 13 is reaching the rolling rollers 11A and 12A, so the control device 4B updates the arrival time predicted value t _{A_EST} (t) of the steel plate 13 by Equation 15 below.

ただし、ｔは現在の時刻である。

However, t is the current time.

In step S404, the control device 4B compares the detection value D _STA (t) of the sensor 21 with the threshold TH _2A . If D _STA >TH _2A is satisfied (S404: Yes), it means that the sensor 21 recognizes the presence of the steel plate 13 at time t, so the process proceeds to step S405. On the other hand, if D _STA >TH _2A does not hold (S404: No), this means that the sensor 21A does not recognize the presence of the steel plate 13 at time t, and this process is terminated.

In step S405, the controller 4B compares the detected value D _STA ( _{tt CAL} ) of the sensor at the time ( _{tt CAL} ) with a predetermined threshold TH _2A . If D _STA ( _{tt CAL} )>TH _2A is established (S405: Yes), the control device 4B terminates this process. On the other hand, if D _STA ( _{tt CAL} )>TH _2A does not hold (S405: No), the control device 4B determines that the steel plate 13 has reached the sensor 21B at time t, and proceeds to step S406.

In step S406, the control device 4B updates the time when the steel sheet 13 reaches the rolling rollers 11A and 12A according to Equation 16 below.

ただし、ｔ_{ＳＥＴＡＳ}は、センサ２１Ａが鋼板１３の認識を開始してから圧延ローラ１１Ａ，１２Ａに鋼板１３が到達するまでの時間である。時刻ｔ_{ＳＥＴＡＳ}は、センサ２１Ａと圧延ローラ１１Ａ，１２Ａとの距離（Ｘ_Ａ－Ｘ_ＡＳ）と、圧延ローラ１１Ａ，１２Ａの速度Ｖ_Ａ（ｔ）とを用いて、下記数１７により推定できる。

However, t _SETAS is the time from when the sensor 21A starts recognizing the steel plate 13 to when the steel plate 13 reaches the rolling rollers 11A and 12A. The time t _SETAS can be estimated by Equation 17 below using the distance (X _A −X _AS ) between the sensor 21A and the rolling rollers 11A and 12A and the velocity V _A (t) of the rolling rollers 11A and 12A.

なお、ｔ_{ＳＥＴＡＳ}は、あらかじめ定めた値にしてもよい。

Note that t _SETAS may be a predetermined value.

In FIG. 14, the control device 4B controls the motor arrangement of the power converter 5A, the torque τ _A (t), the speed command V _A (t), the detection value D _STB (t) of the sensor 21B, and the power converter 5B. The motor arrangement X _B and torque τ _B (t) are read (S501).

Steps S502 to S506 are the same as steps S202 to S206 in FIG. 6, so description thereof will be omitted.

In step S507, the controller 4B compares the torque τ _A ( _{tt CAL} ) at the time ( _{tt CAL} ) with the threshold TH _1A . If τ _A ( _{tt CAL} )>TH _1A is established (S507: Yes), the controller 4B determines that the rolling by the rollers 11A and 12A is completed at time t, and proceeds to step S508. On the other hand, if τ _A ( _{tt CAL} )>TH _1A does not hold (S507: No), the controller 4B proceeds to step S509.

In step S508, the control device 4B saves the time t _ENDA at which the rolling of the steel plate 13 by the rollers 11A and 12A is completed and the motor speed V _A (t _ENDA ). Then, the process proceeds to step S509.

In step S509, the control device 4B compares the detection value D _STB (t) of the sensor 21 with a predetermined threshold TH _2B . If D _STB >TH _2B is satisfied (S509: Yes), it means that the sensor 21B recognizes the presence of the steel plate 13 at time t, so the process proceeds to step S510. On the other hand, if D _STB >TH _2B does not hold (S509: No), it means that the sensor 21B does not recognize the presence of the steel plate 13 at time t, so the process proceeds to step S512.

In step S510, the controller 4B compares the detected value D _STB (tt _CAL ) of the sensor 21B at the time ( _{tt CAL} ) with a predetermined threshold TH _2B . If D _STB ( _{tt CAL} )>TH _2B is established (S510: Yes), the control device 4B proceeds to step S512. On the other hand, if D _STB ( _{tt CAL} )>TH _2B does not hold (S510: No), the control device 4B determines that the steel plate 13 has reached the sensor 21B at time t, and proceeds to step S511.

In step S511, the control device 4B calculates and updates the time at which the steel sheet 13 reaches the rolling rollers 11B and 12B from Equation 18 below.

ただし、ｔ_{ＳＥＴＢＳ}は、センサ２１Ｂが鋼板を認識開始してから圧延ローラ１１Ｂ，１２Ｂに鋼板１３が到達するまでの時間である。時間ｔ_{ＳＥＴＢＳ}は、センサ２１Ｂと圧延ローラ１１Ｂ，１２Ｂとの距離（Ｘ_Ｂ－Ｘ_ＢＳ）と、圧延ローラ１１Ａ，１２Ａによる圧延終了時の速度Ｖ_Ａ（ｔ_ＥＮＤＡ）を用いて、数１９により推定できる。

However, t _SETBS is the time from when the sensor 21B starts recognizing the steel sheet to when the steel sheet 13 reaches the rolling rollers 11B and 12B. The time t _SETBS is estimated by Equation 19 using the distance (X _B −X _BS ) between the sensor 21B and the rolling rollers 11B and 12B and the speed V _A (t _ENDA ) at the end of rolling by the rolling rollers 11A and 12A. can.

なお、ｔ_{ＳＥＴＢＳ}は、あらかじめ定めた値にしてもよい。

Note that t _SETBS may be set to a predetermined value.

Steps S512 to S515 are the same as steps S207 to S210 in FIG. 6, so description thereof will be omitted.

FIG. 14 shows an example of predicting the arrival time prediction value tB of the rolling rollers _11B and 12B, but the arrival time prediction unit 17 for the rolling rollers 11C and 12C also performs calculations according to the same flowchart as in FIG. It can be realized by

Processing of the reactive power command determination unit 16 will be described with reference to FIG. 16 . Steps S601 to S603 are the same as steps S301 to S303 described with reference to FIG. 7, so description thereof will be omitted.

In step S604, the control device 4B compares the predicted arrival time values of the load to each converter 5, and calculates the reactive power command Q _REFK of the power converter 5K with the K-th latest predicted arrival time value. Reactive power command can be calculated by Equation 13.

Steps S605 and S606 are the same as steps S305 and S306 described with reference to FIG. 7, so description thereof will be omitted.

In step S606, the control device 4B determines whether the reactive power request amount Q _TMP has become zero. When the reactive power request amount Q _TMP =0 is established (S606: Yes), the control device 4B determines that the necessary reactive power has been supplied by the converter 5K having the K-th latest arrival time prediction value, and this process is performed. exit.

On the other hand, if the required reactive power amount Q _TMP =0 is not established (S606: No), the control device 4B determines that the required reactive power cannot be supplied by the converter 5K having the K-th late arrival time prediction value. and proceeds to step S607.

In step S607, the control device 4B compares "K" and "N". If K<N is established (S607: Yes), the process proceeds to step S608. If K<N is not established (S607: No), this process is terminated.

Note that the sensor 21 does not necessarily have to be a detector that detects the thickness of the steel plate, and may at least detect the presence or absence of the steel plate. When the presence or absence of a steel plate is detected as “1 (with steel plate)” or “0 (without steel plate)”, the thresholds _{TH 2A} , TH _2B , . It should be set to a small value.

The present embodiment configured in this way also has the same effect as the first embodiment. Furthermore, in this embodiment, the signal of the sensor 21 that detects the steel plate 13 can be used, so that the change in the state of the power converter 5 can be predicted more accurately than in the first embodiment, and the Reactive power output can be distributed with appropriate timing.

A third embodiment will be described with reference to FIGS. 17 to 19. FIG. FIG. 17 shows a control device 4C of the plant power control system according to this embodiment. The configuration shown in FIG. 17 differs from the configuration of the second embodiment described with reference to FIG. 12 in that a steel plate speed estimator 23 is added. The steel plate speed estimator 23 may be abbreviated as the speed estimator 23 hereinafter.

The steel plate speed estimator 23 is a function provided to reduce the difference between the actual value (actual value) and the predicted value (estimated value) of the moving speed of the steel plate 13 . This is because a slip or the like occurs between the steel plate 13 and the rollers 11 and 12, so that the actual value and the estimated value of the speed of the steel plate 13 may differ. Speed estimator 23 calculates an estimated value of speed based on the angular velocity information from power converter 5 and the signal from sensor 21 .

FIG. 18 shows the configuration of the speed estimator 23. As shown in FIG. The speed estimation unit 23 includes, for example, a sensor detection value storage device 29, an actual speed calculation unit 24, a speed correction coefficient learning unit 25, a speed correction coefficient storage unit 26, a steel plate speed estimation value calculation unit 27, and speed information. A storage device 30 and a torque information storage device 31 are provided. The names of the above configurations are appropriately omitted in FIG.

The sensor detection value storage device 29 stores the sensor 21 detection value and outputs it to the actual speed calculation unit 24 . Speed information storage device 30 stores speed information and outputs it to speed correction coefficient learning unit 25 . Torque information storage device 31 stores torque information and outputs it to 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 it to the response speed estimation unit.

The processing of the actual speed calculator 24 will be described. On the other hand, the actual steel plate speed between the rollers 11A and 11B is calculated based on Equation 20 using the time _t34 when the detection of the sensor 21B started and the time _t35 when the rolling of the steel plate by the roller 11B started.

速度補正係数演算部２５の処理を説明する。補正前の鋼板速度の推定値Ｖ_{ＥＳＴ＿ＡＢ０}は、前述の図１５のｔ＝ｔ_３３（図１４のフローチャートのｔ＝ｔ_ＥＮＤＡ）におけるローラ１１Ａの速度とみなし、数２１により演算できる。

The processing of the speed correction coefficient calculator 25 will be described. The pre-correction estimated value V _{EST_AB0} of the steel plate speed can be regarded as the speed of the roller 11A _at t=t ₃₃ in FIG.

鋼板速度の推定値と実際の鋼板速度の比率を補正係数αとすると、補正係数αは数２２で表される。

Assuming that the ratio between the estimated steel plate speed and the actual steel plate speed is a correction coefficient α, the correction coefficient α is expressed by Equation (22).

例えば、トルク情報記憶装置３１に記憶されているトルク情報と、速度情報記憶装置３１に記憶されている速度情報との各々に応じて、補正係数αを学習させる。この場合、補正係数αは、トルクと速度との２次元のテーブルで与えられる。

For example, the correction coefficient α is learned according to 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 used for learning the correction coefficient α need not be limited to torque and speed. For example, at least one of torque, speed, steel plate thickness, steel plate temperature, steel , and the correction coefficient α may be learned for at least one of them.

For example, when the correction coefficient α is learned from the torque, speed, and thickness of the steel plate, a configuration is added so that the thickness of the steel plate 13 can be input to the speed correction coefficient learning unit 25 in FIG. It should be a table.

The processing of the steel plate speed estimated value calculation unit 27 will be described. Using the correction coefficient α, the estimated value of the steel plate speed after correction can be calculated by Equation (23).

図１９を用いて、数２０から数２３による速度指令補正の一例を説明する。ｔ_３４とｔ_３５の間における鋼板の平均速度Ｖ_{ＡＣＴ＿ＡＢ}を実際の鋼板速度とみなし、ローラ１１Ａの速度から求めた補正前の鋼板速度Ｖ_{ＥＳＴ＿ＡＢ０}との比率を補正することで、実際の鋼板速度を推定できる。

このように構成される本実施例も第２実施例と同様の作用効果を奏する。さらに、本実施例では、鋼板１３の実際の移動速度と推定速度との差異を補正できるため、第２実施例よりも正確に電力変換器５の状態の変化を予測することができ、適切なタイミングで各電力変換器５から無効電力を出力させることができる。

An example of speed command correction based on Equations 20 to 23 will be described with reference to FIG. _Considering the average steel plate speed V _{ACT_AB} between _t34 and t35 as the actual steel plate speed, and correcting the ratio of the steel plate speed V _{EST_AB0} before correction obtained from the speed of the roller 11A, the actual steel plate speed is can be estimated.

This embodiment configured in this way also has the same effect as the second embodiment. Furthermore, in this embodiment, the difference between the actual moving speed of the steel plate 13 and the estimated speed can be corrected, so that the change in the state of the power converter 5 can be predicted more accurately than in the second embodiment. Reactive power can be output from each power converter 5 with timing.

A fourth embodiment will be described with reference to FIG. FIG. 20 shows the configuration of a control device 4D used in the plant power control system of this embodiment. The difference between the control device 4D according to this embodiment and the control device 4C described with reference to FIG. 17 is that in FIG. is added. In FIG. 20, the electric motor arrangement storage unit 18 is abbreviated as "M", and the rated apparent power storage unit 19 is abbreviated as "S".

The stored data change unit 32 changes 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 speed command value stored in the steel plate speed estimation unit 32. , torque command value, rolling time, and speed correction coefficient.

The present embodiment configured in this way also has the same effect as the third embodiment. Furthermore, in this embodiment, a user such as a system administrator can modify all or part of the parameters that are the basis for calculating the value and timing of the reactive power to be output from each power converter 5 . Therefore, according to this embodiment, for example, when the arrangement of the electric motors 10 is changed due to equipment update of the plant, etc., the user can change the information on the electric motor arrangement and the rated apparent power using the stored data change unit 32. can be done. As a result, the required reactive power can be compensated by the reactive power command determination unit 16 even after the plant equipment is updated.

A fifth embodiment will be described with reference to FIGS. 21 to 24. FIG. FIG. 21 is an overall configuration diagram of a plant power control system according to this embodiment. The difference between this embodiment and the first embodiment is that a transformer 34 and a power factor adjuster 35 are added in this embodiment.

A power factor adjuster 35 is connected to the plant power supply 1 via a transformer 34 . Also, the power factor adjustment device 35 is connected to the control device 4E via the communication path CN3.

FIG. 22 is a configuration diagram of the power factor adjustment device 35. As shown in FIG. The power factor adjuster 35 includes, for example, a plurality of capacitors 37A, 37B, 37C and switches 36A, 36B, 36C connected in series with each capacitor 37A, 37B, 37C. The power factor adjustment device 35 can connect or disconnect the capacitors 37A, 37B, 37C to or from the system by turning on or off the switches 36A, 36B, 36C. The configuration of the power factor adjustment device 35 is not limited to the example shown in FIG. For example, a static var compensator or the like may be used as the power factor adjustment device.

FIG. 23 shows the configuration of a control device 4E according to this embodiment. The difference between the control device 4E of the present embodiment and the control device 4 described in the first embodiment is that the control device 4E of the present embodiment includes a receiving unit 20D that receives the reactive power supply plan from the power factor adjustment device 35, Another difference is that a function 38 for computing the allocation of reactive power is added.

The controller 4E receives the reactive power supply plan executed by the power factor adjuster 35 from the power factor adjuster 35 via the receiver 20D. Then, the control device 4E distributes the required amount of reactive power to the power factor adjustment device 35 and each power converter 5 .

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

FIG. 24 shows an example in which the power factor adjustment device 35 and a power converter group are combined to compensate for reactive power. The upper part of FIG. 24 shows changes over time in reactive power detected by the reactive power detection device 2 . The middle part of FIG. 24 shows how the power factor adjuster 35 compensates for reactive power. The lower part of FIG. 24 shows the output state of reactive power from each power converter 5 .

As shown in FIG. 24, the power factor adjuster 35 controls the reactive power by turning on and off the capacitor 37, so the reactive power cannot be completely compensated for by the capacitor 37 of the power factor adjuster 35 alone.

Therefore, in this embodiment, the power factor of the entire plant power control system is compensated by combining the reactive power compensation by the power factor adjustment device 35 and the power factor compensation function by each power converter 5 . Furthermore, in this embodiment, since the power factor compensation function of the power converter 5 is used, the capacity of the capacitor required by the power factor adjustment device 35 can be reduced, and the cost of the power factor adjustment device 35 can be reduced.

A sixth embodiment will be described with reference to FIGS. 25 to 27. FIG. FIG. 25 is an overall configuration diagram of the plant power control system according to this embodiment. The difference between the configuration of this embodiment shown in FIG. 25 and the configuration of the fifth embodiment described with reference to FIG.

FIG. 26 shows the configuration of a control device 4F according to this embodiment. The difference between the control device 4F shown in FIG. 26 and the control device 4 described with reference to FIG. 2 is that the control device 4F of this embodiment includes a transmitter 15A.

Processing of the reactive power command determination unit 16 of the control device 4F of the present embodiment will be described with reference to FIG.

Steps S701 to S706 are the same as steps S601 to S606 described with reference to FIG. 16, so description thereof will be omitted.

In step S707, the control device 4F compares "K" and "N". If K<N holds (S707: Yes), the control device 4F determines that there is a converter 5 with the K+1th latest arrival time predicted value, and proceeds to step S708.

On the other hand, if K<N does not hold (S707: No), there is no converter with the K+1th late arrival time prediction value, so the control device 4F determines that reactive power compensation by the power factor adjustment device 35 is necessary. It judges, and it progresses to step S709.

In step S708, the controller 4F updates the value of K and returns to step S704. By incrementing the value of the variable K by one, the converter with the (K+1)th latest arrival time prediction value can be specified in step S704.

In step S<b>709 , the control device 4</b>F transmits a reactive power output command Q _TMAPREF to the power factor adjustment device 35 .

The present embodiment configured in this way also has the same effect as the fifth embodiment. In this embodiment, when the power converter 5 alone cannot compensate for the reactive power, it cooperates with the power factor adjustment device 35 to compensate for the reactive power. This can improve the power factor of the entire plant.

A seventh embodiment will be described with reference to FIGS. 28 and 29. FIG. FIG. 28 is a configuration diagram of a control device 4G included in the plant power control system according to this embodiment. A control device 4G according to this embodiment differs from the control device 4 of the first embodiment described with reference to FIG. The alarm display section 39 is connected to the reactive power command determination section 16 and outputs a warning according to the instruction from the reactive power command determination section 16 .

The flowchart of FIG. 29 shows the processing of the reactive power command determination unit 16 provided in the control device 4G. Steps S801 to S808 are the same as steps S701 to S708 described with reference to FIG. 27, so description thereof will be omitted.

In step S809, the control device 4G causes the alarm display section 39 to display a predetermined warning. The predetermined warning is to display a message such as "With N converters, it is not possible to compensate as required for reactive power". An audible warning may be given in place of the display on the display, or together with the display. Note that the predetermined warning does not have to be character information, and may call the user's attention by, for example, turning on an indicator lamp.

Predetermined alerts may include suggestions from the plant power control system. The proposals include short-term proposals and/or long-term proposals. Short-term proposals are those that can be implemented relatively quickly to compensate for reactive power. Short-term suggestions include, for example, modifying the reactive power supply plan of the power factor regulator 35 . That is, if the control device 4G calculates whether or not the reactive power can be compensated by changing at least one of the number of the capacitors 37 to be turned on and off or the timing to turn the capacitors 37 on and off, and determines that the compensation is possible, proposes to the user to modify the reactive power supply scheme of the power factor regulator 35 . Long-term proposals are proposals that are implemented over a longer period of time than short-term proposals. Long-term proposals include proposals for updating the power equipment of the plant, for example replacing or adding power converters 5, replacing or adding power factor regulators 35, and so on.

The present embodiment configured in this way also has the same effect as the first embodiment. Furthermore, in this embodiment, since a warning is output when the reactive power cannot be compensated, the user can confirm the warning and take countermeasures, thereby improving usability for the user.

An eighth embodiment will be described with reference to FIGS. 30 and 31. FIG. FIG. 30 is a configuration diagram of the control device 4H included in the plant power control system according to this embodiment. The control device 4H of the present embodiment is additionally provided with a reactive power comparison unit 40, a log data storage unit 41, and an external interface 33B for inputting/outputting the data in the log data storage unit 41 to the outside. It differs from the control device 4 of the first embodiment.

The reactive power comparator 40 receives the reactive power detected by the reactive power detector 2 via the receiver 20A, and receives information on the reactive power output from each power converter 5 via the receiver 20B. Reactive power comparing section 40 compares the reactive power received from receiving section 20A and the reactive power received from receiving section 20B, and stores predetermined log data in log data storage section 41 when it is determined that the reactive power cannot be compensated. save to

The processing of the reactive power comparison unit 40 provided in the control device 4H will be described using the flowchart of FIG.

The control device 4H reads the reactive power detection value QM from the receiver 20A, and reads the reactive powers _QA , _QB , QC, . . . , _QN from the receiver _20B ( _S901 ).

The controller 4H calculates the total reactive power request Q _REF0 (S902). The total reactive power requirement Q _REF0 can be calculated by Equation 24 below.

制御装置４Ｈは、無効電力Ｑ_Ａ，Ｑ_Ｂ，Ｑ_Ｃ，・・・，Ｑ_Ｎの和Ｑ_{ＴＯＴＡＬ}を計算する（Ｓ９０３）。Ｑ_{ＴＯＴＡＬ}は、下記数２５で表される。前記同様に、Ｑ_ＮのＮは電力変換器の数である。

The controller 4H calculates the sum Q _TOTAL of the reactive powers Q _A , Q _B , Q _C , . . . , Q _N (S903). Q _TOTAL is represented by Equation 25 below. As before, _N in QN is the number of power converters.

制御装置４は、Ｑ_{ＴＯＴＡＬ}とＱ_ＲＥＦ０とを比較する（Ｓ９０４）。Ｑ_{ＴＯＴＡＬ}＜Ｑ_ＲＥＦ０が成立する場合（Ｓ９０４：Ｙｅｓ）、制御装置４Ｈは、ステップＳ９０５へ進む。一方、Ｑ_{ＴＯＴＡＬ}＜Ｑ_ＲＥＦ０が成立しない場合（Ｓ９０４：Ｎｏ）、制御装置４Ｈは、本処理を終了する。

The controller 4 compares Q _TOTAL and Q _REF0 (S904). If Q _TOTAL <Q _REF0 is established (S904: Yes), the control device 4H proceeds to step S905. On the other hand, if Q _TOTAL <Q _REF0 does not hold (S904: No), the control device 4H terminates this process.

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

A user can retrieve and use the log data stored in the log data storage unit 41 via the external interface 33B. These log data can be used, for example, to improve the reactive power allocation method by changing the threshold value, etc., and to determine the rated apparent capacity of the power converter 5 at the time of future facility renewal.

The present embodiment configured in this way also has the same effect as the first embodiment. Furthermore, in this embodiment, since the predetermined log data is saved when the reactive power cannot be compensated, the user can utilize the log data for cause analysis or future equipment update, etc., and the usability for the user is improved.

A ninth embodiment will be described with reference to FIGS. 32 to 35. FIG. FIG. 32 is a configuration diagram of a control device 4J provided in the plant power control system according to this embodiment. The controller 4J of this embodiment additionally includes an active power prediction unit 42, a reactive power shortage prediction unit 43, a receiver 20E, and a transmitter 15A. It is different from the control device 4 of the first embodiment in that a device 35 is connected, and a reactive power prediction value 44 is connected to the receiving section 20E.

FIG. 33 is a configuration diagram of the active power prediction unit 42. As shown in FIG. 34 shows an example of the positional relationship among the steel plate 13, the rollers 11 and 12, and the sensor 21. FIG.

In FIG. 34, it is assumed that the rolling rollers 11A and _12A are arranged at the position XA, the rolling rollers 11B and _12B are arranged at the position XB, and the rolling rollers _11C and 12C are arranged at the position XC. It is assumed that sensor 21A is placed at position _XAS , sensor 21B is placed at position _XBS , and sensor 21C is placed at position _XCS . The left side of FIG. 34 is upstream, the right side is downstream, and the steel plate 13 moves from upstream to downstream.

Time _t41 indicates a state in which rolling of the steel plate 13 by the rolling rollers 11A and 12A has started. Time _t42 indicates a state in which the rolling of the steel plate 13 by the rolling rollers 11A and 12A is completed and the steel plate 13 is positioned downstream of the rolling rollers 11A and 12A. Time _t43 indicates a state in which rolling of the steel plate 13 by the rolling rollers 11B and 12B has started. Time _t44 indicates a state in which the rolling of the steel plate 13 by the rolling rollers 11B and 12B is completed and the steel plate 13 is positioned downstream of the rolling rollers 11B and 12B.

Return to FIG. 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 figure, the name of each component is 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 passes through the power converter 5A (from time _{t41 to time t42), the active power of the power converter 5A is P A_DB , and} the same steel plate 13 passes through the power converter 5B. (From time t43 to time _t44 ), the active power of the power converter 5B is _{defined as PB_DB .} Assuming that the ratio between the active power P A_DB of the power converter 5A and the active power P _{B_DB} of the power converter 5B is a correction factor β, the correction factor β is expressed by _Equation 26 below.

数２６に示す補正係数βを、速度情報やトルク情報などと関連付けて学習させることにより、鋼板１３が電力変換器５Ａを圧延中の有効電力情報Ｐ_Ａと速度情報とトルク情報と補正係数βとに基づいて、同じ鋼板１３が電力変換器５Ｂを圧延した際の有効電力Ｐ_{Ｂ＿ＰＲＥＤ}を数２７から予測することができる。

By learning the correction coefficient β shown in Equation 26 in association with speed information, torque information, etc., the active power information _PA , the speed information, the torque information, and the correction coefficient β while the steel plate 13 is rolling the power converter 5A. , the active power _{PB_PRED} when the same steel plate 13 rolls the power converter 5B can be predicted from Equation 27.

有効電力予測値計算部４７は、将来の任意の時点における有効電力を予測する機能である。将来の任意の時点ｔ＋ｔ_ＡＲＢにおける有効電力の予測値Ｐ_ＰＲＥＤは、下記数２８で計算できる。ただし、ｔ_ＡＲＢは任意の時間である。

The active power prediction value calculator 47 has a function of predicting the active power at an arbitrary point in time in the future. The predicted value P _PRED of the active power at any future point in time t+t _ARB can be calculated by Equation 28 below. However, t _ARB is an arbitrary time.

数２８におけるＰ_{ｉ＿ＰＲＥＤ}（ｔ＋ｔ_ＡＲＢ）は、次のように決定される。すなわち、任意の時刻ｔ＋ｔ_ＡＲＢと到達時刻記憶装置４４に記憶された到達時刻予測値（ｔ_{Ａ＿ＥＳＴ}、ｔ_{Ｂ＿ＥＳＴ}，・・・，ｔ_{Ｎ＿ＥＳＴ}）とを比較し、任意の時刻ｔ＋ｔ_ＡＲＢにおいて鋼板１３が到達したと予測される場合は、有効電力学習部４６で学習した有効電力予測値をＰ_{ｉ＿ＰＲＥＤ}（ｔ＋ｔ_ＡＲＢ）とする。鋼板１３が到達していないと予測される場合は、無負荷時の有効電力を有効電力予測値Ｐ_{ｉ＿ＰＲＥＤ}（ｔ＋ｔ_ＡＲＢ）とする。

P _{i_PRED} (t+t _ARB ) in Equation 28 is determined as follows. That is, an arbitrary time t+t _ARB is compared with the arrival time prediction values (t _{A_EST} , t _{B_EST} , . . . , t _{N_EST} ) stored in the arrival time storage device 44 _to If it is predicted that the active power learning unit 46 has learned the active power prediction value, P _{i_PRED} (t+t _ARB ). When it is predicted that the steel plate 13 has not reached, the active power under no load is set as the predicted active power value P _{i_PRED} (t+t _ARB ).

Processing performed by the reactive power shortage amount prediction unit 43 will be described with reference to the flowchart of FIG. 35 .

The control device 4J _reads the predicted values P _A (t ₊ t _ARB ), P _B (t+t _ARB ), . The predicted value Q _REF0 (t ₊ t _ARB ) of the requested amount is read, and the rated apparent power S _A , S _B , .

The controller 4J calculates a predicted value of reactive power that can be supplied at any time in the future (S1002). A predicted value Q _PRED (t+t _ARB ) of reactive power that can be supplied at an arbitrary time point t+t _ARB in the future can be calculated by Equation 29 below.

制御装置４Ｊは、将来の任意の時点において供給可能な無効電力の予測値Ｑ_ＰＲＥＤ（ｔ＋ｔ_ＡＲＢ）と総無効電力要求量の予測値Ｑ_ＲＥＦ０（ｔ＋ｔ_ＡＲＢ）とを比較する（Ｓ１００３）。Ｑ_ＰＲＥＤ（ｔ＋ｔ_ＡＲＢ）＞Ｑ_ＲＥＦ０（ｔ＋ｔ_ＡＲＢ）が成立する場合（Ｓ１００３：Ｙｅｓ）、制御装置４Ｊは、ステップＳ１００４へ進む。一方、制御装置４Ｊは、Ｑ_ＰＲＥＤ（ｔ＋ｔ_ＡＲＢ）＞Ｑ_ＲＥＦ０（ｔ＋ｔ_ＡＲＢ）が成立しないと判定すると（Ｓ１００３：Ｎｏ）、本処理を終了する。

The controller 4J compares the predicted value Q _PRED (t+t _ARB ) of reactive power that can be supplied at any time in the future with the predicted value Q _REF0 (t+t _ARB ) of the total required reactive power (S1003). If Q _PRED (t+t _ARB )>Q _REF0 (t+t _ARB ) holds (S1003: Yes), the controller 4J proceeds to step S1004. On the other hand, when the control device 4J determines that Q _PRED (t+t _ARB )>Q _REF0 (t+t _ARB ) does not hold (S1003: No), it terminates this process.

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

The present embodiment configured in this way also has the same effect as the first embodiment. Furthermore, in the present embodiment, a command can be given to the power factor adjustment device 35 before the reserve capacity of reactive power of each power converter 5 becomes insufficient with respect to the total required amount of reactive power. As a result, in the present embodiment, the power factor adjustment device 35 can be quickly operated, and a decrease in the power factor due to the response delay time of the power factor adjustment device 35 can be suppressed.

1: power supply, 2: reactive power detector, 3: lagging power factor load facility, 4: control device, 5: power converter, 6: transformer for power converter, 7: transformer for lagging power factor load facility, 8: current detector, 9: power supply voltage detector, 10: electric motor, 11: upper rolling roller, 12: lower rolling roller, 13: steel plate, 15: transmission unit, 16: reactive power command determination unit, 17: arrival time prediction unit, 18: Motor arrangement storage unit, 19: Rated apparent power storage unit, 20: Reception unit, 21: Sensor, 23: Steel plate speed estimation 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 device 30: Speed information storage device 31: Torque information storage device 32: Storage data change unit 33: External interface 34: Force Transformer for 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 unit 41: Log data storage unit 42 : Active power prediction unit 43: Reactive power shortage amount prediction unit 44: Reactive power prediction value

Claims (14)

a power converter provided for each electric motor positioned between the electric power system of the plant and each electric motor;
a reactive power load facility connected to the power system;
a control device that generates a predetermined command that instructs reactive power to be supplied from each of the power converters to the power system;
A plant power control system comprising the reactive power load equipment and a reactive power detection device that detects reactive power at a power receiving point of the power system,
The control device is
Calculating a required amount of reactive power for canceling the reactive power detected by the reactive power detection device with the reactive power supplied from each power converter to the power system;
A command value for distributing the calculated reactive power demand to each of the power converters is determined by using motor arrangement information indicating an installation positional relationship of each motor as predetermined information about the reactive power demand and each of the motors. , calculating for each power converter according to a predicted arrival time value at which an object is predicted to reach each power converter, which is calculated based on the electric motor arrangement information;
Plant power control system. The control device includes, as the predetermined information, motor arrangement information indicating the installation positional relationship of each of the motors, either one of torque information or active power information output by each of the power converters, and each of the power converters. using the angular velocity information of each motor output by and the rated apparent power of the power converter,
The plant power control system according to claim 1. The control device indicates, as predetermined information, the motor arrangement information, either one of the torque information or the active power information, each of the angular velocity information, and the time when the load of each of the power converters increases. using load increase time information;
The plant power control system according to claim 2. The control device calculates the load increase timing based on either one of the active power information or the torque information and the angular velocity information, and determines the predetermined timing from the calculated load increase timing.
The plant power control system according to claim 3. Each of the electric motors applies a predetermined process to the object,
further comprising an object detector that detects the position of the object;
The control device calculates the load increase timing based on either one of the active power information or the torque information, each of the angular velocity information, and the output of the object detector.
The plant power control system according to claim 4. The control device further includes an angular velocity information storage unit that stores the angular velocity information and time information in association with each other,
The control device corrects each of the angular velocity information based on the angular velocity information stored in the angular velocity information storage unit.
The plant power control system according to claim 5. The control device externally rewrites all or part of parameters used for calculating at least one of the reactive power request amount, the command value, the load increase timing, and the predetermined timing.
The plant power control system according to claim 3. The control device is further capable of externally rewriting all or part of at least one of the motor arrangement information, the rated apparent power, and the angular velocity information.
The plant power control system according to claim 7. The control device includes a reactive power supply plan for a reactive power compensator connected to the power system, the motor arrangement information, one of the torque information or the active power information, each angular velocity information, and the calculating the command value for each power converter based on the rated apparent power and the reactive power demand;
The plant power control system according to any one of claims 2-8 . The control device instructs a reactive power compensator connected to the power system to output a shortage of reactive power supplied from each power converter to the power system.
The plant power control system according to any one of claims 1-8. The control device outputs an alert when it is determined that the reactive power supplied from each power converter to the power system and the reactive power detected by the reactive power detection device are not in balance.
The plant power control system according to any one of claims 1-8. When the control device determines that the reactive power supplied from each power converter to the power system and the reactive power detected by the reactive power detection device are not in balance, the control device saves predetermined log data.
The plant power control system according to any one of claims 1-8. The control device is
an active power prediction unit that predicts the active power of each power converter;
a reactive power shortage prediction unit that predicts a reactive power shortage 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. The plant power control system according to any one of claims 2-8 . A control method for a plant power control system, comprising:
The plant power control system includes a power converter provided for each motor and positioned between a plant power system and each motor, a reactive power load facility connected to the power system, and each power converter. A control device for generating a predetermined command that instructs the reactive power to be supplied to the power system from the
The control device is
Calculating a required amount of reactive power for canceling the reactive power detected by the reactive power detection device with the reactive power supplied from each power converter to the power system;
A command value for distributing the calculated reactive power demand to each of the power converters is determined by using motor arrangement information indicating an installation positional relationship of each motor as predetermined information about the reactive power demand and each of the motors. , calculating for each power converter according to a predicted arrival time value at which an object is predicted to arrive at each power converter, which is calculated based on the motor arrangement information;
causing each of the calculated command values to be transmitted to each of the corresponding power converters;
A control method for a plant power control system.

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