JPH08336234A - Power receiving facility - Google Patents

Abstract

PURPOSE: To obtain a power receiving facility in which the power factor can be improved appropriately through automatic control even under a light load by closing the switching means for each main capacitor selectively at the main control section of a power factor regulator depending on the reactive power under a normal load where the effective power of a load side bus exceeds a first reference level. CONSTITUTION: Effective and reactive powers of a load side bus 6 are determined at the power operating section of a power factor regulator 16. When the effective power thus determined exceeds a first set reference level for detecting a light load, the switch 13 for each main capacitor 10 is closed selectively at a main control section 18 depending on the reactive power. The switch 13 for sub-capacitor 11 is closed at a sub-control section 19 during an interval when the effective power is higher than a second set reference level for detecting a light load but lower than the first set reference level. The switch 13 for sub-capacitor 11 is opened at the sub-control section 19 when the effective power drops below the second set reference level. This constitution can improve the power factor appropriately through automatic control even under a light load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power receiving and transforming facility such as a building in which power demand is significantly reduced depending on the time of day.

[0002]

2. Description of the Related Art Conventionally, in power receiving and transforming facilities such as buildings,
A power factor regulator consisting of a reactive power relay in which one or more capacitors for power factor improvement are connected to the load side (secondary side) busbars of the transformer for receiving and transforming via switches for switching on and off respectively. The reactive power of the load side busbar is detected by the above, and each switch is controlled according to this reactive power, and each capacitor is turned on / off to improve the power factor of the load side busbar to be close to 1. .

At this time, the capacity of the capacitor necessary for improving the power factor is calculated and determined from the maximum load capacity of the equipment.

Further, the number and the capacity of the power factor improving capacitors are set so as to share about 20 to 30% of the installed capacity. Therefore, in the case of a power receiving and transforming facility of about 1000 KVA, each power factor improving capacitor generally has a large capacity for compensating for about 100 to 300 KVar.

[0005]

In the case of the conventional power receiving and transforming facility, each power factor improving capacitor is set to a large capacity according to the maximum load capacity of the facility, so that the power demand is remarkably increased depending on the time of day. There is a problem that the power factor cannot be improved appropriately in the case of facilities that are decreasing.

For example, in a facility such as a tenant building in which many stores and offices are housed, which has a significantly lighter load at night than in the daytime, the reactive power generated at night (during light load) is also in the daytime. This is significantly smaller than that under normal load, and at this time, the capacity of the power factor improving capacitor becomes excessive with respect to the capacity required for improving the power factor.

Therefore, in many cases, during such a light load, the power factor improving capacitor is not turned on, and the equipment is operated with the delay power factor based on the reactive power, so that the power factor is appropriately improved. Cannot be done.

In order to solve this problem, as a power factor improving capacitor, a small-capacity capacitor (base capacitor) of about several% of the installed capacity is provided together with the originally large-capacity capacitor. It is conceivable that the operation may be manually turned on and off as required, or may be always connected to the load side busbar.

In this case, when the load is light such as at night, all the original capacitors are turned off and only the base capacitor is turned on, so that a small amount of reactive power can be controlled by the base capacitor and the power factor can be improved. become.

However, in the construction in which the base capacitor is turned on and off manually, it is necessary to monitor the load condition and turn on and off the base capacitor, and the power factor improvement cannot be automated. Moreover, the reactive power enters the capacitor for power factor improvement,
It also changes when the load is turned off.Especially when the load is light, the power factor improving capacitor has a large effect on the reactive power, and it is not easy to detect the load state from the reactive power. It is difficult to turn on and off properly, and proper power factor improvement cannot be performed.

Further, in the configuration in which the base capacitor is always connected to the load side bus bar and kept in the closed state at all times, the base capacitor is turned off even when the load becomes lighter and the reactive power becomes extremely small during a light load such as at night. They cannot be separated, and even in this case, the power factor cannot be improved properly at light load.

An object of the present invention is to enable appropriate power factor improvement by automatic control even when the load is light.

[0013]

In order to achieve the above-mentioned object, in the power receiving and transforming equipment of the present invention, the power factor improvement is connected to the load side busbars of the transformer for power receiving and transforming via the switching means, respectively. Control a plurality of main capacitors for power supply, one sub-capacitor that is set to a smaller capacity than each main capacitor, and is connected to the load side bus bar through the switching means, and the switching means for each capacitor And a power factor adjuster for improving the power factor. The power factor adjuster includes a power calculation unit for obtaining active power and reactive power of the load side bus based on detection of voltage and current of the load side bus, and an effective power factor adjuster. When the power is above the first reference value for light load detection, the switching means of each main capacitor is selectively closed according to the reactive power, and when the active power becomes smaller than the first reference value, each main capacitor is closed. Main control that locks the opening / closing means of the capacitor in the open state When the active power is equal to or higher than the second reference value for light load detection smaller than the first reference value, the sub-capacitor opening / closing means is closed at least while the active power is lower than the first reference value. And a sub-control unit for locking the opening / closing means of the sub-capacitor in the open state when the value becomes smaller than the second reference value.

To improve the power factor under a light load more accurately and effectively, a plurality of power factor improving sub-capacitors are provided, and the sub-control unit serves as a load-side bus bar of the transformer for receiving and transforming. When the active power of the sub-capacitor becomes equal to or larger than the second reference value, the opening / closing means of each sub-capacitor is selectively closed according to the active power at least while the active power becomes smaller than the first reference value. It is preferable to provide means for locking the opening / closing means of each sub-capacitor in the open state when the value becomes smaller than the reference value of 2.

Further, in a small-scale facility or the like, in order to simplify the structure, etc., a single main capacitor for improving the power factor is used, and the main control unit serves as a main bus for the load side busbar of the transformer for receiving and transforming. Open / close the main capacitor opening / closing means in response to the reactive power when the active power of is above the first reference value, and open the main capacitor opening / closing means at a light load when the active power becomes smaller than the first reference value. Means for locking the state may be provided.

[0016]

In the case of the power receiving and transforming equipment of the present invention configured as described above, each of the large-capacity main capacitors which are the original capacitors for power factor improvement and the small-capacity sub-capacitor for power factor improvement at light load. Are respectively connected to the load side busbars of the transformer for receiving and transforming electricity via the switching means.

Further, the active power and reactive power of the load side busbar are obtained by the power calculation unit of the power factor adjuster which controls each switching means.

Then, when the active power becomes larger than the first reference value under normal load, the main controller of the power factor regulator selectively closes the opening / closing means of each main capacitor according to the reactive power, The power factor is improved by the large main capacitor.

Next, when the active power is less than the first reference value and the load is light, the main control unit opens and locks all the opening and closing means of the main capacitors, and the main capacitors are disconnected from the load-side bus bar.

At this time, the sub-control unit of the power factor adjuster
While the active power is at least smaller than the first reference value and equal to or more than the second reference value, the opening / closing means of the sub-capacitor is closed, and the power factor is improved by the small-capacity sub-capacitor corresponding to the load.

Further, the load becomes lighter and the active power becomes second.
When the value becomes smaller than the reference value, the opening / closing means of the sub-capacitor is opened and locked by the sub-control unit, the sub-capacitor is also disconnected from the load side bus bar, and the improvement of the power factor stops.

Since the load state (light or heavy) of the load side bus bar is detected from the active power, the load state is not affected even when the power factor improving capacitors are turned on or off even when the load is light. Is accurately detected.

Therefore, especially when the load is light, the sub-capacitor is automatically turned on and off according to the load condition, and when the load becomes extremely light and the sub-capacitor becomes excessive, the sub-capacitor is also removed from the load side busbar. The power factor can be improved by automatic disconnection.

If a plurality of sub-capacitors are provided and the sub-control unit selectively closes the opening / closing means of each sub-capacitor according to the load when the load is light, each sub-capacitor is selectively turned on / off. The power factor can be improved more appropriately according to the load.

Further, each of the main capacitor and the sub-capacitor for improving the power factor is one, and the main control section of the power factor adjuster responds to the reactive power at the time of the normal load in which the active power exceeds the first reference value. By opening and closing the opening and closing means of the main capacitor to improve the power factor, the power factor can be improved appropriately with the simplest configuration, and a substation facility suitable for small-scale facilities can be provided.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIGS. (One Embodiment) One embodiment will be described with reference to FIGS. FIG. 1 shows a configuration in the case of, for example, a 3-phase 3-wire type 22KV power receiving and transforming facility such as a tenant building.
The system power of the 2KV system bus 1 is supplied to the primary side of the transformer 4 for receiving and transforming 22 / 6.6KV, 5000KVA through the circuit breaker 2 and the transformer 3 for transaction instruments.

The system power source is 6.6 by the transformer 4.
It is stepped down to KV, and this 6.6KV power source is used for the transformer 4-2.
The load is supplied from the next side to the load-side bus bar 6 via the circuit breaker 5, and each load connected to the bus bar 6 via the circuit breaker 7 is driven.

Further, a power bank improving capacitor bank section 9 is connected to the load side bus bar 6 via a circuit breaker 8. This bank section 9 is usually used in the daytime when the maximum load capacity of the equipment is about 3000 kW. As a capacitor for improving the power factor at the time of load, there are three main capacitors 10 (three groups) each having a large capacity of 300 KVar, which corresponds to about 20 to 30% of the maximum load capacity of the equipment. As the capacitor for improving the power factor of, for example, one sub capacitor 11 having a small capacity of 50 KVar is provided.

The capacitors 10 and 11 are respectively a series resistor 12 and a switch 1 as a switching means.
It is connected to the circuit breaker 8 via 3, and is connected to the load side bus bar 6 via this circuit breaker 8.

An instrument current transformer 14 is provided between the circuit breaker 5 and the load side bus bar 6, and the current transformer 14 detects the line current of each phase of the load side bus bar 16.

Further, a grounding type instrument transformer 15 is connected to the load side bus bar 6, and this transformer 15 detects the voltage of each phase of the load side bus bar 6.

Then, the detection signal of each line current of the current transformer 14 and the voltage detection signal of each phase of the transformer 15 are the power factor adjuster 16.
2, the regulator 16 is configured using an arithmetic unit, a logic gate, etc. as shown in FIG.
7, a main controller 18, and a sub controller 19 are provided.

Further, since the power calculation unit 17 obtains the active power and the reactive power of the load side bus bar 6, the reactive power unit 2
0 and the active power unit 21, and the detection signal of the line current of each phase of the current transformer 14 and the voltage detection signal of each phase delayed by π / 2 by the voltage phase shifter 22 are multiplied by the reactive power unit 20. It is supplied to the block 23.

This multiplication block 23 multiplies both detection signals for each phase and obtains the reactive power of each phase of the following formula 1 consisting of the DC component and the ripple component of the double frequency.

[Equation 1] Qu = V · I · [sin θ−sin (2ωt−θ)] Qv = V · I · [sin θ−sin {2ωt− (θ + 2)
/ 3 · π)}] Qw = V · I · [sin θ−sin {2ωt− (θ + 4
/ 3 · π)}] where Qu, Qv, Qw are reactive powers of each phase, V is the effective value of the bus voltage, I is the effective value of the bus current, and θ is the phase.

Further, the calculation result of the reactive power of each phase of the multiplication block 23 is added by removing the ripple component of the double frequency by the addition block 24, and by this addition, the reactive power of the three-phase batch (Q = V.multidot.V). I · sin θ) is calculated,
A reactive power detection signal whose amplitude changes according to this reactive power is formed.

Further, the multiplication block 25 of the active voltage unit 21 performs the same calculation as that of the multiplication block 23 on the basis of the line current detection signal of each phase of the current transformer 14 and the voltage detection signal of each phase of the transformer 15. The active power of each phase obtained by replacing each sine (sin) term of Equation 1 with a cosine (cos) term is obtained.

Further, the active powers of the respective phases of the operation block 25 are added by the addition block 26 similar to the addition block 24, and by this addition, the active powers of all the three phases (P = V).
I · cos θ) is obtained, and an active power detection signal whose amplitude changes according to this active power is formed.

The reactive power detection signal of the addition block 24 is supplied to the input gate 27 such as an analog switch of the main control section 18, and the active power detection signal of the addition block 26 is supplied to the sub control section 19.

The sub-control unit 19 detects the load state of the load side bus bar 6 by comparing the active power based on the active power detection signal with each of the first and second reference values set for light load detection. .

In this embodiment, the sub capacitor 1
The power factor improvement range covered by 1 is 50 to 20 KVar, and the first and second reference values have a required capacity of 50 K for power factor improvement.
It is settled to the magnitude of active power in the load states of Var and 20 KVar, respectively.

In a tenant building or the like, there is no abrupt power factor fluctuation like in a factory or the like, and the phase θ is almost constant, so that the first and second reference values can be easily adjusted based on preliminary measurements. Can be set to.

There is much power demand, and active power is the first
During normal load such as daytime when the value exceeds the reference value of
The high-active ON command A and OFF command A ′ of the switch 11 output from 9 both become low level, and the switch 13 of the sub-capacitor 11 is turned off and is disconnected from the load side bus bar 6. To be kept.

Further, the output of the OR gate 28 to which both commands A and A'are supplied becomes low level, the input gate 27 is turned on by this low level, and the reactive power detection signal of the addition block 24 is passed through the input gate 27. And is supplied to the control output unit 29 of the main control unit 18.

The control output unit 29 compares, for example, reactive power with a plurality of threshold values, determines the number of main capacitors 10 connected to the load-side bus 6 according to the reactive power, and opens / closes each main capacitor 10. High active ON command B ₁ , B ₂ , B ₃ or OFF command B ₁ ′, B ₂ ′, B ₃ ′ of the device 13
Is selectively set to a high level, and the switch 13 of each main capacitor 10 is selectively opened and closed according to the reactive power.

By the selective opening and closing, each main capacitor 10 is selectively turned on according to the reactive power, and the power factor of the load side bus bar 6 is improved.

Next, at the time of light load when the demand for electric power is significantly reduced at night, 50 to 20 covered by the sub-capacitor 11
During the power factor improvement range of KVar, the condition of (first reference value)> (active power) ≧ (second reference value) is satisfied.
Becomes high level.

The high level of the ON command A is supplied to the input gate 27 via the OR gate 28, the gate 27 is turned off, and the OFF commands B ₁ ', B ₂ ' and B ₃ '
Becomes high level, the switches 13 of each main capacitor 10 are opened, and all the main capacitors 10 are disconnected from the load-side bus bar 6. Further, the switch 13 of the sub-capacitor 11 is closed by the high level of the ON command A, and the power factor is improved by the sub-capacitor 11 having a small capacity corresponding to the load.

Next, when the power demand further decreases below the coverage of the sub-capacitor 11, the active power becomes smaller than the second reference value. At this time, the ON command A returns to the low level and the OFF command A'is high. Become a level.

The output of the OR gate 28 is held at a high level by the high level of this OFF command A ', the input gate 27 is continuously turned off, and each main capacitor 10 is kept in a state of being disconnected from the load side bus bar 6. Be drunk Further, the switch 13 of the sub-capacitor 11 is opened by the high level of the off command A ′, and the sub-capacitor 11 is also disconnected from the load side bus bar 6.

Therefore, when the load is light, the sub-capacitor 11 is automatically turned on and off according to the load condition, and the sub-capacitor 1
When the load becomes light to such an extent that the capacity of 1 becomes excessive, the sub-capacitor 11 is also automatically disconnected from the load side bus bar 6, and automatic power control can perform an appropriate power factor improvement.

By the way, the number and capacities of the main capacitors 10 and the capacities of the sub capacitors 11 are not limited to those in the embodiment. And when making the simplest configuration,
One main capacitor 10 and one sub capacitor 11 are provided, and one set of ON command and OFF command is output from the control output unit 29 of the main control unit 18, and at the time of normal load, one main capacitor 10 is turned on and off. Power factor should be improved.

The sub-capacitor 11 has a small capacity,
Even if the sub-capacitor 11 is continuously connected to the load-side bus 6 during a normal load, it does not pose a problem in practical use. Therefore, the switch 1 of the sub-capacitor 11 is maintained while the active power is equal to or higher than the second reference value.
3 may be kept in the closed state.

(Other Embodiments) Next, another embodiment corresponding to claim 2 will be described with reference to FIGS. In FIGS. 3 and 4, the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding ones. The equipment of this embodiment is the same as the equipment of one embodiment in order to improve the accuracy of the power factor improvement under light load. The following points (i) and (ii) are different.

(I) As shown in FIG. 3, for example, the capacitor bank section 9 is provided with two sub capacitors 11a and 11b each having a capacity about half that of the sub capacitor 11 of the first embodiment, and both sub capacitors 11a and 11b are provided. Points connected to the circuit breaker 8 via the series reactor 12 and the switch 13, respectively.

(Ii) As shown in FIG. 4, the power factor adjuster 16
2 is provided with a sub-control unit 19 ′ and an OR gate 28 ′ in place of the sub-control unit 19 and the OR gate 28 in FIG.
Compares the active power with the first and second reference values for light load detection, and the power factor improvement range is less than 50KVar and less than 20KVar.
When the load is higher than Var, for example, based on an appropriate threshold value between them, the ON commands Aa and Ab or the OFF commands Aa 'and Ab' of the sub capacitors 11a and 11b are selectively set to the high level, and both the sub capacitors 11a. , 11b of the switch 13 are selectively opened and closed equivalently in accordance with the reactive power based on the active power.

When the load factor of the power factor improvement range is less than 50 KVar and more than 20 KVar, the switch 13 of the sub-capacitors 11a and 11b is selectively closed according to the size, and the sub-capacitors 11a and 11b are closed. It is selectively connected to the load-side bus bar 6, and the input capacity for power factor improvement is varied in two steps, so that the power factor is improved with higher accuracy.

The required capacity for power factor improvement is 20 KVa.
When it becomes smaller than r, both the OFF commands Aa 'and Ab' become high level, and the sub capacitors 11a and 11b are both disconnected from the load side bus bar 6.

Further, the required capacity for power factor improvement is 50 KVar.
When the above normal load is applied, the ON commands Aa, Ab and the OFF commands Aa ', Ab' are all at the low level, and at this time, the input gate 27 is turned on by the output of the OR gate 28 '. Similarly, the ON command B of the main control unit 29
_{Based on 1} , B ₂ , B ₃ , and OFF commands B ₁ ′, B ₂ ′, B ₃ ′, the power factor is improved by the plurality of main capacitors 10. Therefore, the power factor at the time of a light load is accurately corrected to match the load.

It is also possible to provide three or more sub-capacitors for more accurate power factor improvement. Also,
Based on the capacitance setting of each sub-capacitor, the power factor may be improved over a wider range of reactive power than in the case of the embodiment.

Needless to say, the capacities of the sub-capacitors do not have to be the same, and the sub-capacitors may continue to be turned on at the normal load when the active power is equal to or higher than the first reference value.

[0062]

Since the present invention is configured as described above, it has the following effects. When the active power of the load-side bus 6 is equal to or higher than the first reference value, the main controller 18 of the power factor adjuster 16 selectively closes the opening / closing means of each main capacitor 10 according to the reactive power. The large-capacity main capacitor 10 improves the power factor by automatic control.

Next, when the active power of the load-side bus bar 6 is smaller than the first reference value, the main controller 18 opens and locks all the main capacitors 10 so that the main capacitors 10 are locked. It is disconnected from the load-side bus bar 6, and at this time, the sub-control unit 19 closes the opening / closing means of the sub-capacitor 11 while the active power is at least smaller than the first reference value and equal to or more than the second reference value. The power factor is improved by the small-capacity sub-capacitor 11 commensurate with.

Further, when the load becomes lighter and the active power becomes smaller than the second reference value, the opening / closing means of the sub-capacitor 11 is opened and locked by the sub-control unit 19, and the sub-capacitor 11 is also disconnected from the load side bus bar 6. The power factor improvement is stopped by being released.

Then, the load state (light, amount) of the load side bus bar 6 is detected from the active power, and each capacitor 1 for improving the power factor is detected.
Since 0 and 11 are automatically turned on and off, the load state can be accurately detected without being affected by the turning on and off of the power factor improving capacitors 10 and 11 even when the load is light.

Therefore, it is possible to perform an appropriate power factor improvement suitable for the load, and particularly when the load is light, when the sub-capacitor 11 is automatically turned on and off according to the load state, and when the load becomes extremely light. The sub-capacitor 11 is also disconnected from the load-side bus bar 6, and automatic control can perform an appropriate power factor improvement suitable for the load state.

Then, a plurality of sub capacitors 11a, 1
1b, the sub-control unit 19 'selectively closes the opening / closing means of the sub-capacitors 11a, 11b according to the load state when the sub-capacitors 11a, 11b are selectively turned on / off. Therefore, the power factor can be improved more accurately and appropriately according to the load.

Further, the main factor and the sub-capacitor for power factor improvement are each set to one, and the main controller of the power factor adjuster responds to the reactive power at the time of the normal load in which the active power is equal to or higher than the first reference value. If the power factor is improved by opening and closing the opening / closing means of the main capacitor, the power factor can be appropriately improved with the simplest configuration, and it is possible to provide the power receiving and transforming equipment suitable for small-scale facilities.

[Brief description of drawings]

FIG. 1 is a system diagram of one embodiment of the present invention.

2 is a detailed block connection diagram of a part of FIG. 1. FIG.

FIG. 3 is a system diagram of another embodiment of the present invention.

4 is a detailed block connection diagram of part of FIG. 3. FIG.

[Explanation of symbols]

 4 Transformer for receiving and transforming power 10 Main capacitor for improving power factor 11, 11a, 11b Sub-capacitor for improving power factor 13 Switch as switching means 14 Current transformer for instrument 15 Transformer for instrument 16 Power factor regulator 17 Power Calculation Unit 18 Main Control Unit 19, 19 'Sub Control Unit

Claims (3)

[Claims] 1. A plurality of main capacitors for power factor improvement, each of which is connected to a load-side bus of a transformer for receiving and transforming via switching means, and a main capacitor set to have a smaller capacity than each main capacitor, and the load. A power factor improving one sub-capacitor connected to the side bus through an opening / closing means, and a power factor adjuster for controlling the opening / closing means of each of the capacitors to improve the power factor are provided. A power calculator for determining active power and reactive power of the load-side bus based on detection of voltage and current of the load-side bus, and when the active power is equal to or higher than a first reference value for light load detection, A main unit that selectively closes the opening / closing means of each main capacitor according to the reactive power, and locks the opening / closing means of each main capacitor in an open state when the active power becomes smaller than the first reference value. A control unit, wherein the active power is the first When the active load is smaller than the second reference value for light load detection smaller than the first reference value, the opening / closing means of the sub-capacitor is closed at least while the active power is smaller than the first reference value. A power receiving and transforming facility, comprising: a sub-control unit that locks the opening / closing means of the sub-capacitor in an open state when the value becomes smaller than the reference value of 2. 2. The power receiving and transforming equipment according to claim 1, wherein a plurality of power factor improving sub-capacitors are provided in place of one power factor improving sub-capacitor, and a sub-control unit for power receiving and transforming is provided. When the active power of the load-side bus of the transformer is equal to or higher than the second reference value for light load detection, at least while the active power is smaller than the first reference value for light load detection, the switching means for opening and closing each sub-capacitor is provided. A means is provided for selectively closing in accordance with the active power and for locking the opening / closing means of each of the sub-capacitors in an open state when the active power becomes smaller than the second reference value. Substation equipment to be used. 3. The power receiving and transforming equipment according to claim 1, wherein one main capacitor for power factor improvement is provided in place of the plurality of main capacitors for power factor improvement, and a main control unit for power receiving and transforming is provided. When the active power of the load-side bus of the transformer is equal to or higher than the first reference value for light load detection, the switching means of the main capacitor is opened and closed according to the reactive power, and the active power is the first reference value. A power receiving and transforming facility comprising means for locking the opening / closing means of the main capacitor in an open state when the load becomes smaller and lighter.