JP2002359930A - Device and method for controlling power factor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power factor control device and its method which enable power factor control, keeping the balance of power factors and voltages, when system non-interconnection parallel operation by the use of generators of different specifications and capacities is carried out. SOLUTION: This control device is fitted with a target power factor setting means (9a) for setting at constant periods each range of power factors which a plurality of generators (1a-1d) aim at, a comparison means (9a) for comparing the voltage of a bus-bar (10) with a specified voltage value range at the constant periods, a first control means (9a) which performs control, so as to lower the voltage of at least one generator of the lowest power factor, when it is found by the result of this comparison means that the voltage of the bus-bar is higher than the voltage value range, and to raise the voltage of at least one generator of the highest power factor, when the voltage of the bus-bar is lower than the voltage value range, and a second control means (9a) which controls the power factor of a generator being out of the power factor range so as to correct the power factor of the generator into the power factor range, when the voltage of the bus-bar lies within the voltage value range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power factor control apparatus and method for controlling a power factor of a plurality of generators when the generators are operated in parallel.

[0002]

2. Description of the Related Art Conventionally, when a plurality of generators are operated in parallel without being connected to a power company system (system non-cooperative parallel operation), the power factor balance between the generators is maintained as follows. This is performed by a power factor compensation circuit as shown.

FIG. 4 is a diagram showing a configuration of a reactive current control device to which a power factor compensation circuit disclosed in Japanese Patent Application Laid-Open No. 51-103209 is applied. In this device, when there is a difference between the power factors of the two generators 11a and 11b, each generator 1a
There is a difference between the outputs of the power factor detectors 12a and 12b corresponding to 1a and 11b. At this time, the power factor of the load (bus) 10a is intermediate between the power factors of the generators 11a and 11b. Therefore, the output of the power factor detector 12c corresponding to the bus 10a is intermediate between the outputs of the power factor detectors 12a and 12b, and the difference signal between the power factor detectors 12c and 12a and the power factor detectors 12c and 12c.
The polarity is opposite to the difference signal of b.

When the voltages of the generators 11a and 11b are adjusted in this state, the polarities of the signals of the automatic voltage regulators 13a and 13b are reversed. That is, the generators 11a, 11b
The power factor of each of the generators 11a and 11b is made equal by operating to increase one voltage and decrease the other voltage. Thus, the power factor balance between the generators is maintained without control from external equipment.

[0005]

However, in the above-described conventional control method, when a plurality of small-capacity generators are used to respond to, for example, a load in a factory or the like, a plurality of automatic voltage regulators are connected to each of the generators. Are sequentially output, so that there is a problem that each generator cannot follow a sudden load change. In addition, if the power factor balance of each generator is poor when connected to the grid of the power company, it is difficult to recover the power factor balance when starting isolated operation when disconnected from the grid at the time of power failure etc. The motor trips due to overexcitation or overload.

The above-described control method is effective when the generators have the same specifications and the same capacity. However, problems arise when the generators have different specifications (eg, different manufacturers) or different capacities. . In other words, since the characteristics of the generator generated by the power factor compensation circuit differ for each manufacturer of the generator, the response of each generator receiving a signal from each automatic voltage regulator is not unified, and the power factor balance and the voltage balance of the load are not uniform. We cannot expect retention.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power factor control apparatus and method capable of performing power factor control during non-system parallel operation using generators having different specifications and capacities while maintaining a balance between power factor and voltage. To provide.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the object, a power factor control apparatus and method according to the present invention are configured as follows.

(1) A power factor control device according to the present invention is a power factor control device for controlling power factors of a plurality of generators connected to a bus. Target power factor setting means for setting at a constant cycle, comparing means for comparing the voltage of the bus with a predetermined voltage value range at the constant cycle, and as a result of the comparing means, the voltage of the bus is set to the voltage value When the voltage is higher than the range, the voltage of at least one generator having the lowest power factor is reduced, and when the voltage of the bus is lower than the voltage value range, the voltage of at least one generator having the highest power factor is controlled to increase. As a result of the first control means and the comparing means, when the voltage of the bus is within the voltage value range, control is performed such that the power factor of the generator outside the power factor range is corrected to be within the power factor range. And second control means for That.

(2) The power factor control method according to the present invention is the power factor control method for controlling the power factor of a plurality of generators connected to a bus. Setting at a fixed cycle, and comparing the voltage of the bus with a predetermined voltage value range at the fixed cycle.As a result of the comparison, when the voltage of the bus is higher than the voltage value range, Controlling the voltage of at least one generator having a low power factor to increase the voltage of the at least one generator having the highest power factor when the voltage of the bus is lower than the voltage value range; and As a result, when the voltage of the bus is within the voltage value range, controlling the power factor of the generator outside the power factor range to be corrected to the power factor range.

[0011]

FIG. 1 is a circuit diagram showing a configuration of a power factor control device according to an embodiment of the present invention. In this embodiment, four generators 1a, 1b,
Control is performed to maintain the power factor balance between 1c and 1d.

In FIG. 1, four automatic voltage regulators 2a, 2b, 2c, 2d are connected to a power factor control section 9a. The automatic voltage regulators 2a, 2b, 2c, 2d control the voltage of the generators 1a, 1b, 1c, 1d via the field windings 3a, 3b, 3c, 3d, respectively.

The generators 1a, 1b, 1c, 1d are connected to a bus 10 via circuit breakers 6a, 6b, 6c, 6d in a switchboard 8a, respectively. The grid L of the power company is
It is connected to bus 10 via circuit breaker 6e in switchboard 8a.

In the switchboard 8a, the current transformer 5 for the instrument is provided.
a, 5b, 5c, 5d and instrument transformers 4a, 4b, 4
Each of c, 4d, and 4e is connected to the composite analog signal converter 7a.

FIG. 2 is a flowchart showing a control procedure by the power factor control device having the above-described configuration. In addition, the bus 10 is in a state of being disconnected from the grid L of the power company by the circuit breaker 6e.

First, in step S1, the power factor control section 9a compares the reactive power and active power borne by each of the generators 1a, 1b, 1c, 1d with a constant sampling period (500 ms).
To set a target power factor range (82-88% in the present embodiment) of each generator. In this case, the composite analog signal converter 7a detects each voltage of each of the generators 1a to 1d from the respective transformers 4a to 4d, and detects each current of each of the generators 1a to 1d. Detectors 5a to 5d, converts them into analog signals, and outputs them to the power factor controller 9a. Power factor control section 9a
Calculates the power factor of each of the generators 1a to 1d from the input signal and sets a target power factor range.

Next, in step S2, the power factor control section 9a detects the voltage of the bus 10. In this case, the composite analog signal converter 7a detects the voltage of the bus 10 from the instrument transformer 4e, converts the voltage to an analog signal, and outputs the analog signal to the power factor control unit 9a.

In step S3, the voltage of the bus 10 is set to the target voltage value (10.7 to 11.3 k in this embodiment).
V is higher than the maximum value (11.3 kV), the power factor controller 9a executes the voltage lowering correction power factor control mode in step S4. In this mode, the power factor control unit 9a
The power factor of each of the generators 1a to 1d is calculated as described above, and a voltage reduction signal is output to the automatic voltage regulators 2a to 2d corresponding to the generators 1a to 1d having the lowest power factor. Upon receiving this signal, the automatic voltage regulators 2a to 2d control the currents of the field windings 3a to 3d in the corresponding generators 1a to 1d, and lower the voltages of the generators 1a to 1d. After that, the power factor control section 9a sets the target power factor in step S1 again.

For example, in step S4, the generators 1a to 1a
When each power factor of 1d is 80%, 85%, 87%, and 90%, the power factor controller 9a lowers the voltage of the generator 1a, and the power factor falls within the target power factor range (82 to 88%). Is controlled so that

In step S3, the voltage of the bus 10 is not higher than the maximum value of the target voltage, and in step S5,
The voltage of the bus 10 is the minimum value of the target voltage value (10.7 k
If it is lower than V), in step S6, the power factor control section 9a executes the voltage upward correction power factor control mode. In this mode, the power factor control unit 9a calculates the power factor of each of the generators 1a to 1d as described above, and the generators 1a to 1 having the highest power factor.
A voltage increase signal is output to the automatic voltage regulators 2a to 2d corresponding to 1d. Automatic voltage regulators 2a to 2
2d is a field winding 3 in the corresponding generators 1a to 1d.
The currents a to 3d are controlled to increase the voltage of the generators 1a to 1d. After that, the power factor control section 9a sets the target power factor in step S1 again.

For example, in step S6, the generators 1a to 1a
When each power factor of 1d is 80%, 85%, 87%, and 90%, the power factor control unit 9a increases the voltage of the generator 1d, and the power factor is in the target power factor range (82 to 88%). Is controlled so that

In step S5, if the voltage of the bus 10 is not lower than the minimum value of the target voltage value, step S7
Then, the power factor control unit 9a calculates the power factor of each of the generators 1a to 1d as described above, and determines that each power factor is in the target power factor range (82 to 8).
8%), the target power factor is set again in step S1.

If there is a power factor that is not within the target power factor range in step S7, a power factor control unit 9 is executed in step S8.
a executes the power factor control mode. In this case, the power factor control unit 9a determines that the generators 1a to 1 have the largest absolute value deviation of the power factor from the target minimum power factor 82% or the target maximum power factor 88%.
A voltage increase signal or a voltage decrease signal is output to the automatic voltage regulators 2a to 2d corresponding to d. Upon receiving this signal, the automatic voltage regulators 2a to 2d control the currents of the field windings 3a to 3d in the corresponding generators 1a to 1d, and increase or decrease the voltages of the generators 1a to 1d. afterwards,
The power factor control section 9a sets the target power factor again in step S1.

For example, in step S8, the generators 1a to 1a
When each power factor of 1d is 80%, 83%, 86%, and 89%, the power factor controller 9a lowers the voltage of the generator 1a, and the power factor falls within the target power factor range (82 to 88%). Is controlled so that

As described above, in the power factor control device according to the present embodiment, the control is performed by the programming according to the above-described procedure without using the power factor compensation circuit as in the related art. The basis of the control is to output a voltage reduction signal to a generator with a low power factor and to raise a voltage to a generator with a high power factor, which is conventionally used when cooperating with the grid of a power company. This is in accordance with the method of outputting a signal. However, if these controls are performed when the system is not linked, the balance between the power factor and the voltage is greatly lost, and appropriate control cannot be performed. Therefore, in the present embodiment, the following control is performed.

(1). Measure the reactive power and active power of multiple generators at fixed intervals to set each target power factor, check whether the bus voltage is within the specified value range, and further deviate from the target power factor Check for the presence of a generator.

(2). If the bus voltage is higher than the specified value,
Outputs a voltage reduction signal to the generator with the lowest power factor,
When the bus voltage is lower than the specified value, a voltage increase signal is output to the generator having the highest power factor.

(3). (1) is performed, and even if the control of (2) based on the previous sampling result is not completed, the latest sampling result is prioritized to shift to the next target control (2).

FIGS. 3A and 3B are diagrams showing power factor / voltage data when two power generators are controlled by the above-described power factor control device. FIGS. 3A and 3B show the results of parallel operation of two generators A and B in a state where the bus 10 is disconnected from the power company's system L by the circuit breaker 6e. From FIG. 3A, the power factor of both generators A and B is within the target power factor range (40 to 60%), and the voltage of the bus 10 is within the target voltage value range (around 11.0 kV). It can be seen that the state is constant. As described above, according to the present power factor control device, the operation control of a plurality of generators having different specifications and capacities can be performed while maintaining the balance between the power factor and the voltage when the system is not linked.

It should be noted that the present invention is not limited to only the above-described embodiment, and can be appropriately modified and implemented without changing the gist. For example, in the above embodiment, the number of generators is four or two.
Although the case of a single unit has been described, the present invention is not limited to this, and a plurality of units can be implemented.

In the above-described embodiment, the number of generators for performing power factor control is one for each cycle, but two or more generators may be controlled simultaneously. For example, in the case of controlling two units at a time, in step S4, a voltage drop signal is output to each of the automatic voltage regulators 2a to 2d corresponding to the generator having the lowest power factor and the generator having the second lowest power factor. In step S6, a voltage increase signal is output to each of the automatic voltage regulators corresponding to the generator having the highest power factor and the generator having the second highest power factor. In step S8, a voltage increase signal or a voltage decrease is sent to each automatic voltage regulator corresponding to the generator having the largest absolute value deviation of the power factor from the target minimum power factor or the target maximum power factor and the generator having the second largest absolute value deviation. Output a signal.

In the above embodiment, the sampling period (program execution period) is set to 500 ms. However, the present invention is not limited to this, and can be changed in an adjustment range of, for example, 10 ms or more. Further, the followability of each generator with respect to the signal can be adjusted within the setting range of the power factor control section 9a.

The present invention can be implemented for a plurality of generators having the same specifications and the same capacity, and can be implemented in a state where the generator is connected to a power company system.

[0034]

According to the power factor control device and method of the present invention, it is possible to prevent the generator from tripping due to a power factor balance collapse that occurs at the time of transition to non-cooperative operation due to a commercial power failure or the like. At the same time, it is possible to suppress the fluctuation of the voltage accompanying the fluctuation of the power factor. Thereby, power factor control at the time of system non-cooperation parallel operation using generators of different specifications and capacities can be established.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a power factor control device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure by the power factor control device according to the embodiment of the present invention.

FIG. 3 is a diagram showing power factor / voltage data according to the embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a reactive current control device according to a conventional example.

[Explanation of symbols]

 1a, 1b, 1c, 1d: Generators 2a, 2b, 2c, 2d: Automatic voltage regulators 3a, 3b, 3c, 3d: Field windings 4a, 4b, 4c, 4d: Instrument transformers 5a, 5b, 5c, 5d: current transformer for instrument 6a, 6b, 6c, 6d, 6e: circuit breaker 7a: composite analog signal converter 8a: switchboard 9a: power factor control unit 10: bus L: system

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Koyanagi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Hirofumi Araki 6-14 Maruo-cho, Nagasaki City, Nagasaki Prefecture Mitsubishi Electric F-term in Plant Engineering Co., Ltd. (reference) 5G066 FA01 FB17 FC11 5H590 AA12 AB03 AB06 CC01 CC29 CE02 DD64 EA16 EB12 EB16 FA06 GA02 GA08 HA02 HA04 HB02 HB03

Claims (2)

[Claims] 1. A power factor control device for controlling a power factor of a plurality of generators connected to a bus, wherein a target power factor setting for setting a target power factor range of the plurality of generators at a constant cycle. Means, comparing means for comparing the voltage of the bus with a predetermined voltage value range at the fixed cycle, and as a result of the comparing means, when the voltage of the bus is higher than the voltage value range, the power factor is the lowest. First control means for reducing the voltage of at least one generator, and controlling to increase the voltage of at least one generator having the highest power factor when the voltage of the bus is lower than the voltage value range; and the comparing means As a result, when the voltage of the bus is within the voltage value range, a second control unit that controls the power factor of the generator outside the power factor range to be corrected to within the power factor range. A power factor control device characterized in that: 2. A power factor control method for controlling a power factor of a plurality of generators connected to a bus, comprising: setting a target power factor range of the plurality of generators at a constant cycle; Comparing the voltage of the bus with a predetermined voltage value range at the fixed cycle; and, as a result of the comparison, when the voltage of the bus is higher than the voltage value range, at least one of the generators having the lowest power factor Controlling the voltage to be lower and increasing the voltage of at least one generator having the highest power factor when the voltage of the bus is lower than the voltage value range; and as a result of the comparison, the voltage of the bus is higher than the voltage value. Controlling the power factor of the generator outside the power factor range to be within the power factor range if the power factor is within the range.