Specification
Title of invention: Control device for rolling system and rolling system
Technical field
[0001]
　The present invention relates to a rolling system controller and a rolling system.
Background technology
[0002]
　As a background art of this technical field, in the abstract of Patent Document 1 below, "provides a converter that maintains stable operation and reduces loss of switching elements against fluctuations in power supply voltage and load" and "PWM. The modulation factor of the modulated wave that generates the signal and the modulation factor of the carrier wave are fixed, and the power factor 1 control and the constant voltage control of the DC voltage are performed.For the power factor 1 control, in order to make the alternating current and the power supply voltage in phase, The phase is adjusted. The DC voltage is controlled by changing the size of the dead time."
Prior art documents
Patent literature
[0003]
Patent Document 1: JP-A-11-299245
Summary of the invention
Problems to be Solved by the Invention
[0004]
　The converter that realizes the control of the power factor of 1.0 described above is also applied to the driving of a rolling mill motor as a variable speed drive device. Here, auxiliary equipment such as a pump and a fan are provided around the rolling mill. Most of these incidental equipment is a motor load, and is often driven by on/off control at a constant rotation speed, and the steady power factor is about 0.5 to 0.8. The entire system of the rolling mill system is complicatedly combined with a variable speed drive device having a power factor of 1.0 and various auxiliary equipment. In order to reduce the reactive power of the whole system, a reactive power compensator, a power factor compensator, etc. have been applied.
　However, the operating conditions of the rolling system and ancillary equipment are fluctuating moment by moment, and depending on the operating conditions and the selection of the power factor correction device, a strict target power factor may cause a difference. Therefore, it has been difficult to continuously achieve the target power factor (for example, 1.0 or 0.995) in the entire system. Further, in order to achieve the severe target power factor of recent years with only the reactive power compensating device, it is necessary to select a fine capacity, and it is necessary to combine and select the reactive power compensating devices with various capacities. Furthermore, installing a dedicated reactive power compensator causes problems in increasing equipment cost and securing installation space. Further, it is difficult to perform highly accurate power factor compensation only with the power factor improving capacitor.
　The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a rolling system control device and a rolling system that are inexpensive and can realize highly accurate power factor compensation.
Means for solving the problem
[0005]
　In order to solve the above problems, the control device for a rolling system of the present invention drives a motor for driving a rolling mill, and a measuring unit that is attached to an electric line and measures electric line power factor information for specifying a power factor in the electric line. A variable speed drive device for converting the frequency of the AC voltage input from the electric circuit to another frequency for output, and a receiving terminal for receiving the electric power factor information from the measuring unit. And a command value generation unit that outputs a command value for generating reactive power having a leading power factor or a lagging power factor to the variable speed drive device based on the electric path power factor information. ..
Effect of the invention
[0006]
　According to the present invention, it is possible to realize highly accurate power factor compensation while being inexpensive.
Brief description of the drawings
[0007]
FIG. 1 is a power supply system diagram of a rolling system according to an embodiment of the present invention.
FIG. 2 is a block diagram of a control unit.
FIG. 3 is a vector diagram in a comparative example.
FIG. 4 is a vector diagram according to the present embodiment.
FIG. 5 is another vector diagram according to the present embodiment.
MODE FOR CARRYING OUT THE INVENTION
[0008]

　FIG. 1 is a power supply system diagram of a rolling system 1 according to an embodiment of the present invention.
　The rolling system 1 includes a transformer 22 (transformer), a circuit breaker (circuit breaker) 24, an instrument transformer 26 (potential transformer), an instrument current transformer 28 (current transformer), and a measuring unit 30. A power factor correction capacitor 32, a control unit 40 (rolling system control device), and an in-facility electric circuit 50 are provided. Further, the rolling system 1 includes M (M is a plurality) circuit breakers 52-1 to 52-M (hereinafter sometimes collectively referred to as circuit breakers 52) and the same number of transformers 58-1 to 58-M. (The same transformer 58), the same number of converters 60-1 to 60-M (the same converter 60), the same number of inverters 62-1 to 62-M (the same inverter 62), and the same number of circuit breakers 64. -1 to 64-M (same as circuit breaker 64) and the same number of rolling mill driving motors 66-1 to 66-M (same as motor 66). Further, the rolling system 1 includes a plurality of circuit breakers 51, a plurality of transformers 55, and a plurality of power distribution systems 57. The rolling mill driving motors 66-1 to 66-M are for driving a rolling mill (not shown).
[0009]
　In the transformer 22, the primary winding 22a is connected to the power receiving system 20, the voltage received from the power receiving system 20 is stepped down, and the voltage is output from the secondary winding 22b. The circuit breaker 24 is connected between the secondary winding 22b and the in-facility electric circuit 50, and is turned off to protect the rolling system 1 when a predetermined overcurrent flows. The instrument transformer 26 measures the output voltage of the secondary winding 22b, and the instrument current transformer 28 measures the output current from the secondary winding 22b. The measurement unit 30 measures the reactive current, the reactive power, and the power factor in the secondary winding 22b based on the measurement results of the instrument transformer 26 and the instrument current transformer 28, and sends the measurement result to the control unit 40. Supply. Since all of these pieces of information are information that can identify the power factor in the in-facility electric circuit 50, these pieces of information may be referred to as “electric circuit power factor information”.
[0010]
　The transformer 58 converts the voltage of the in-facility electric circuit 50 into a voltage suitable for the converter 60. The converter 60 converts the supplied AC voltage into DC voltage. The inverter 62 performs PWM (Pulse Width Modulation) modulation on the supplied DC voltage and supplies the DC voltage to the motor 66. Thereby, the motor 66 can be driven at a desired rotation speed. Therefore, the converter 60 and the inverter 62 each function as a “variable speed drive device” for the corresponding motor 66. When a predetermined overcurrent flows, the circuit breaker 52 is turned off to protect the corresponding transformer 58 or the like. Further, the circuit breaker 64 turns on/off the connection between the corresponding inverter 62 and the motor 66.
[0011]
　The in-facility electric circuit 50 is connected to a plurality of power distribution systems 57 via a plurality of circuit breakers 51 and transformers 55, respectively. Although details of the power distribution system 57 are omitted, each power distribution system 57 includes auxiliary equipment such as a pump and a fan, lighting equipment, and air conditioning equipment. The devices included in these incidental facilities have many inductive loads, and the overall steady power factor of the plurality of power distribution systems 57 is about 0.5 to 0.8. Therefore, the power factor correction capacitor 32 is connected to the in-facility electric circuit 50 to bring the power factor in the in-facility electric circuit 50 close to 1.0.
[0012]
　FIG. 2 is a block diagram of the control unit 40.
　The control unit 40 includes hardware as a general computer such as a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a RAM (Random Access Memory), and a ROM (Read Only Memory). , A control program executed by the CPU, a microprogram executed by the DSP, various data, and the like are stored. In FIG. 2, inside the control unit 40, the functions realized by the control program, the micro program, and the like are shown as blocks.
[0013]
　In FIG. 2, the control unit 40 receives the reactive power signal Pq, which is the measurement result of the reactive power, from the measuring unit 30 (see FIG. 1) via the receiving terminal 43. The filter 41 attenuates the high frequency component of the reactive power signal Pq, and outputs the result as the reactive power signal Pqave. The subtractor 42 subtracts the reactive power signal Pqave from the predetermined reactive power target value Pqtg, and outputs the result as the total reactive power calculated value Pq*. Here, the reactive power target value Pqtg is, for example, zero.
[0014]
　Distribution rate output units 44-1 to 44-M respectively output distribution rates A1 to AM when distributing total reactive power calculated value Pq* corresponding to converters 60-1 to 60-M. Here, when the reactive power that can be generated in a certain converter 60-k (1≦k≦M) is the reactive power generation capacity Ppk (that is, Pp1 to PpM), the distribution ratio Ak is “Ak=Ppk/(Pp1+Pp2+... +PpM)”. In the present embodiment, the reactive power generation capacity Ppk is a constant according to the capacity of the converter 60-k.
[0015]
　Reactive power calculation units 46-1 to 46-M multiply the total reactive power calculated value Pq* by the corresponding distribution ratios A1 to AM, and output the multiplication result as reactive power calculated values ​​Pq01* to Pq0M*. To do. Command value generation units 48-1 to 48-M perform correction processing on reactive power calculation values ​​Pq01* to Pq0M* and output the results as reactive power command values ​​Pq1* to PqM*. The correction processing in the command value generation units 48-1 to 48-M includes dead zone processing and limit processing described below.
[0016]
　Here, the dead zone process is a process of setting the reactive power command value Pqk* to zero when the reactive power calculation value Pq0k* (where 1≦k≦M) is within a predetermined range including zero. .. This is because when the reactive power calculation value Pq0k* is sufficiently small, the reactive power signal Pqave of the entire rolling system 1 is also small, so that the reactive power compensation is stopped and the operating efficiency of the converter 60-k is prioritized. is there.
[0017]
　In addition, the limit processing means that when the reactive power calculation value Pq0k* exceeds the reactive power generation capacity (reactive power that can be generated) of the converter 60-k, the reactive power command value Pqk* is set to the reactive power in the converter 60-k. This is a process of limiting the value to a value less than or equal to the power generation capacity. Thus, the reactive power generated for all converters 60-k can be set to a value equal to or less than the reactive power generation capacity of each. Each of the converters 60-1 to 60-M generates reactive power based on the supplied reactive power command values ​​Pq1* to PqM*. Thereby, the reactive power of the whole rolling system 1 is compensated.
[0018]

　Here, a comparative example of the present embodiment will be described. In this comparative example, the control unit 40 shown in FIG. 1 is not provided, and the reactive power of the rolling system 1 is compensated for only the power factor correction capacitor 32 with respect to the in-facility electric circuit 50. Each converter 60 independently controls reactive power so that its power factor approaches 1.0.
　FIG. 3 is a vector diagram in this comparative example. The illustrated current vectors I1, Ih, and Ix are all current vectors in the secondary winding 22b of the transformer 22. First, the current vector I1 is a current vector of a target power factor (for example, 1.0 or 0.995).
[0019]
　The current vector Ix is a current vector at a steady power factor that flows through the plurality of circuit breakers 51 to the plurality of power distribution systems 57. As described above, the power distribution system 57 includes auxiliary equipment such as a pump and a fan. The current vector Ic is a current vector generated by the power factor correction capacitor 32. The current vector Ih is a current vector obtained as a result of the power factor being improved by the current vector Ic.
[0020]
　In order to set the entire power factor of the rolling system 1 to 1.0, it is preferable to set the current vector Ic so that the current vector I1 and the current vector Ih match. That is, the capacity of the power factor correction capacitor 32 may be set so as to realize such a current vector Ic. However, depending on the overall operating state of the rolling system 1, the operating conditions of the auxiliary equipment such as the pump and the fan change every moment, and the current vector Ix also changes. Therefore, even if the steady power factor of the current vector Ih is set to the target power factor, a lead phase or a lag phase is generated instantaneously, and the current vector Ih includes the reactive current component Ihx as shown in the figure. become.
　As described above, when the power factor of the rolling system 1 is improved only by the power factor improving capacitor 32, a deviation from the power factor of 1.0 is likely to occur, and it becomes difficult to achieve the preset power factor target.
[0021]

　FIG. 4 is a vector diagram in this embodiment.
　The meanings of the current vectors I1, Ix, Ic, and Ih are the same as those in FIG. The current vector Iv1 is a lead phase current vector, and the current vector Iv2 is a lag phase current vector. These current vectors Iv1 and Iv2 represent the range of current vectors that can be generated by the control unit 40 and the converter 60. This allows the control unit 40 and the converter 60 to compensate for a phase that cannot be completely compensated by the current vector Ic by the power factor correction capacitor 32, and the current vector Ih can be compensated for by the target power factor (for example, 1.0 or 0.995). Etc.) of the current vector I1.
[0022]
　Further, according to the present embodiment, the converter 60 can be made to generate the current vector Iv2 or the like of the delay power factor. Therefore, the control unit 40 can bring the current vector Ih close to the current vector I1 of the target power factor regardless of whether the power factor in the in-facility electric circuit 50 is the advanced power factor or the delayed power factor.
[0023]
　FIG. 5 is another vector diagram in the present embodiment, and shows an operating state when the operation of the power factor correction capacitor 32 is stopped.
　In FIG. 5, the meanings of the current vectors I1, Ix, Ih, Iv1, Iv2 are the same as those in FIG. Further, since the operation of the power factor correction capacitor 32 is stopped, the one corresponding to the current vector Ic (see FIG. 4) is not shown. In this example, by controlling the power factor of converter 60, current vector Ih can be brought close to current vector I1 of the target power factor.
[0024]
As described
　above, the rolling system control device (40) according to the present embodiment is based on the receiving terminal (43) for receiving the electric power factor information from the measuring unit (30) and the electric power factor information. And a command value generation unit (48-1 to 48-) that outputs a command value (Pq1* to PqM*) for generating the reactive power of the leading power factor or the lagging power factor to the variable speed drive device (60, 62). M), and.
　By generating reactive power of the leading power factor or the lagging power factor to the variable speed drive device (60, 62) based on the electric power factor information, it is possible to realize highly accurate power factor compensation at low cost.
[0025]
　Further, the command value generation units (48-1 to 48-M) output command values ​​(Pq1* to PqM*) so as to set the power factor in the electric circuit (50) within a predetermined range.
　Thereby, the power factor in the electric circuit (50) can be set within a predetermined range.
[0026]
　In the rolling system (1), a plurality of variable speed drive devices (60, 62) are provided, and the rolling system control device (40) controls the reactive power generation capacity (Ppk) of each variable speed drive device (60, 62). ), and further includes a distribution rate output unit (44-1 to 44-M) for outputting the distribution ratio (A1 to AM), and the command value generation unit (48-1 to 48-M) is A command value (Pq1* to PqM*) is output for each variable speed drive device (60, 62) according to A1 to AM).
　This makes it possible to generate command values ​​(Pq1* to PqM*) according to the reactive power generation capacity (Ppk) of each variable speed drive device (60, 62).
[0027]
　The rolling system control device (40) outputs the reactive power calculation values ​​(Pq01* to Pq0M*) corresponding to the variable speed drive devices (60, 62) according to the distribution ratio (A1 to AM). The electric power calculation unit (46-1 to 46-M) is further provided, and the command value generation unit (48-1 to 48-M) has a predetermined reactive power calculation value (Pq01* to Pq0M*) including zero. When the value is within the range, the command value (Pq1* to PqM*) is set to zero.
　Thereby, when the generated reactive power is small, the compensation of the reactive power can be stopped and the efficiency of the variable speed drive device (60, 62) can be improved.
[0028]
[Modification] The
　present invention is not limited to the above-described embodiment, and various modifications can be made. The above-described embodiment is provided as an example in order to facilitate understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, another configuration may be added to the configuration of the above embodiment, and a part of the configuration may be replaced with another configuration. Further, the control lines and information lines shown in the figure are those considered to be necessary for explanation, and not all the control lines and information lines necessary for the product are shown. In practice, it may be considered that almost all the configurations are connected to each other. The possible modifications to the above embodiment are, for example, as follows.
[0029]
(1) In the above-described embodiment, the control unit 40 receives the reactive power signal Pq from the measuring unit 30, but instead of the reactive power signal Pq, other power line power factor information (for example, reactive current, power factor, etc.). Alternatively, the reactive power command values ​​Pq1* to PqM* may be generated based on the reception.
[0030]
(2) In the control unit 40 of the above embodiment, the command value generation units 48-1 to 48-M output the reactive power command values ​​Pq1* to PqM* to the converters 60-1 to 60-M. However, instead of this, the command value of the reactive current to be generated by each of the converters 60-1 to 60-M may be output. It goes without saying that commanding the reactive current to each of the converters 60-1 to 60-M is equivalent to commanding the reactive power.
[0031]
(3) In the above embodiment, the reactive power generation capacity Ppk is a constant according to the capacity of the converter 60-k. However, the reactive power generation capacity Ppk may be changed according to the operating state of the converter 60-k. For example, in the converter 60-k, the smaller the active power supplied from the in-facility electric circuit 50 (the power output to the corresponding inverter 62-k), the more the converter 60-k has a surplus power. The reactive power generation capacity Ppk may be increased.
[0032]
(4) In the above embodiment, the example in which the present invention is applied to the rolling system 1 has been described, but the present invention is applied not only to the rolling system 1 but also to various electric power equipment, factory equipment, railway vehicles, ships and the like. You may. That is, the control unit 40 generally includes: "a measuring unit that is attached to an electric line and measures electric line power factor information for specifying a power factor in the electric line; and an AC voltage input from the electric line. A converter that outputs, and a receiving terminal that receives the electric path power factor information from the measurement unit, and a lead power factor or a delayed power factor for the converter based on the electric path power factor information. And a command value generating unit that outputs a command value that generates reactive power".
Explanation of symbols
[0033]
1 rolling system
30 measuring unit
40 control unit (rolling system control device)
43 receiving terminals
44-1 to 44-M distribution ratio output units
46-1 to 46-M reactive power calculation units
48-1 to 48-M command values Generator
50 In-facility electric circuit (electric circuit)
60-1 to 60-M Converter (variable speed drive device)
62-1 to 62-M Inverter (variable speed drive device)
66-1 to 66-M Motor
A1 to AM Distribution ratio
Ppk Reactive power generation capacity
Pq01* to Pq0M* Reactive power calculation value
Pq1* to PqM* Reactive power command value
The scope of the claims
[Claim 1]
　A measuring unit which is attached to an electric line and measures electric line power factor information for specifying a power factor in the electric line, and a frequency of an AC voltage input from the electric line for driving a motor for driving a rolling mill to another frequency. A variable speed drive device for converting and outputting the variable speed drive device, and a variable speed drive device
　based on the receiving terminal for receiving the electric circuit power factor information from the measuring unit and the electric circuit power factor information. And a command value generation unit that outputs a command value for generating reactive power with a leading power factor or a lagging power factor,
　and a controller for a rolling system.
[Claim 2]
　2.
　The rolling system control device according to claim 1, wherein the command value generation unit outputs the command value so as to set the power factor in the electric path within a predetermined range .
[Claim 3]
　In the rolling system, a plurality of the variable speed drive devices are provided,
　further including a distribution ratio output unit that outputs a distribution ratio according to the reactive power generation capacity in each of the variable speed drive devices, and the
　command value generation unit,
　The rolling system control device according to claim 2, wherein the command value is output for each of the variable speed drive devices according to the distribution ratio .
[Claim 4]
　The reactive power calculation unit that outputs a reactive power calculation value corresponding to the variable speed drive device according to the distribution ratio is further included, and the
　command value generation unit has a predetermined reactive power calculation value including zero.
　The rolling system control device according to claim 3 , wherein the command value is set to zero when the value is within a range .
[Claim 5]
　A measuring unit which is attached to an electric line and measures electric line power factor information for specifying a power factor in the electric line, and
　a frequency of an AC voltage input from the electric line for driving a motor for driving a rolling mill to another frequency. And a variable speed drive device for converting and outputting to a variable speed drive device
　for a rolling system that outputs a command value for generating reactive power of a leading power factor or a lagging power factor to the variable speed drive device based on the electric power factor information. And a control device.