KR101173507B1 - Automatic power factor correction system - Google Patents

Abstract

PURPOSE: An automatic power factor correcting system is provided to appropriately manage the power factor of a power facility by extending the life span of a condenser. CONSTITUTION: A first transformer(1) changes voltages and currents. A second transformer(2) drops supplied voltages. An automatic power factor correcting device(10) automatically corrects power factors. An operating unit(120) computes power factor information. A condenser bank(150) comprises one or more condensers. A switch unit(140) comprises switches corresponding to the condensers to selectively connect the condensers to a load. A control unit(130) calculates the capacity of condensers and outputs ring-count type control signals to turn on and off the switches.

Description

Automatic Power Factor Correction System {AUTOMATIC POWER FACTOR CORRECTION SYSTEM}

One embodiment of the present invention relates to an automatic power factor improvement system.

Power factor refers to the ratio of active power to apparent power, and a low power factor means that a large amount of unnecessary reactive power returned to the power supply side is not consumed by power in a load such as an electric motor.

As the reactive power increases, the amount of current flowing through the transmission line increases and transmission loss such as heat loss increases, thereby increasing the capacity of a transformer or switchboard. Therefore, there is a need to improve the load power factor of power consumers.

On the other hand, reactive power (Q) is power that continually circulates between the power supply and the load without doing anything when an AC voltage is applied to the load including the reactance, and when the voltage is V and the current is I in single phase AC. Calculated as 'Q = VIsinθ'.

Active power (P), the power actually consumed at the load, is calculated as 'P = VIcosθ'.

In addition, apparent power (S) is a value generally used to represent an AC load or a power supply capacity, and is calculated as 'S = VI' in the case of single-phase AC. At this time, 'cosθ', which is the ratio of the active power and the apparent power, is called a power factor, and in an ideal case, it is '1' (100% when expressed as a percentage).

In inductive loads of AC circuits, ground currents are generated and power factor is lowered, and reactive power is increased to increase power loss due to high loads of power lines or transformers. You need to spend. At present, the power factor does not exceed 90% in Korea and may reach 60% depending on the nature of the load.

Improving the power factor collectively at the utility company is not an easy task because it takes into account the line and voltage adjustments. Therefore, the capacitor capacity appropriate for the power equipment circuit is generally provided through a capacitor bank composed of a plurality of capacitors at the power receiver. By maintaining the power factor, the power factor is improved.

1A to 1E are block diagrams for explaining the operation of a capacitor bank used in a power factor correction apparatus according to the prior art.

Such a conventional power factor improving apparatus is provided with a capacitor bank including a plurality of capacitors and a switch connected to the plurality of capacitors to connect the capacitors to a load in order to improve the power factor. ), It is generally used to bring the target power factor closer to the target power factor.

1A to 1E, a plurality of capacitors constituting the capacitor bank are started from the bottom according to the power factor of the power equipment circuit (see FIG. 1A), and a small amount of capacitor when the power factor approaches the target power factor value. When the power factor decreases, the number of input of the capacitor increases. The order of the input of the condenser is generally sequentially input from the first to the top side in accordance with the order (see FIG. 1B). Here, as the power factor of the power equipment worsens, the number of inputs of the capacitor is further increased, so that a large amount of capacitors are injected (see FIG. 1C), and as the power factor is improved, the number of inputs of the capacitors decreases, but at this time, the number of inputs of the capacitors is reduced. To reduce the number of inputs by cutting off from the top to the bottom (see Fig. 1d). As a result, when the power factor becomes very good, the input amount of the capacitor is minimized (see FIG. 1E).

Accordingly, after the capacitor bank has been used for a long time, the lower the capacitor, the more deterioration proceeds, and thus may fail or fail. In other words, the capacitor bank used in the conventional power factor improving device has a problem that the life of the power factor improving device is shortened due to the shortening of the life of the capacitor at the front end, because the capacitors are introduced step by step. There was a problem that the deterioration of the capacitor and the occurrence of an explosion accident due to frequent input and opening and closing in the.

One embodiment of the present invention provides an automatic power factor improvement system capable of maintaining a constant life of a capacitor used to improve the power factor of a power plant.

In addition, an embodiment of the present invention provides an automatic power factor improvement system that can properly manage the power factor of the power equipment by extending the life of the capacitor, and further improve the reliability of the reverse product.

Automatic power factor improvement system according to an embodiment of the present invention is a transformer for converting and converting the level of the power meter can measure the voltage and current supplied to the power equipment from the outside, and can supply the power supplied from the outside to the load A transformer for stepping down to a voltage having a predetermined level; and an automatic power factor improving device for automatically adjusting a power factor value according to the voltage and current applied to the transformer between the transformer and the load so as to be within a range of a reference power factor value. A power factor improvement system, wherein the automatic power factor improvement apparatus measures a voltage and a current applied to the transformer, and calculates a power factor information including a phase difference between a voltage and a current, active power, reactive power, and apparent power; A condenser bank consisting of at least one condenser; A switch unit having a switch corresponding to each capacitor of the capacitor bank, and selectively connecting each capacitor to the load according to a switch control signal; And a ring count control signal for calculating a capacity of a capacitor required for power factor control of the load based on the power factor information calculated from the calculator, and for inserting or blocking each capacitor in the capacitor bank according to the calculated result. And a controller for turning on or off the switch by turning on or off each capacitor in a predetermined direction by the control signal.

The control unit inputs the condenser in a first direction on the rear end side opposite to the front end side from the front end on the basis of the preset direction, and the blocking of the condenser is a second direction on the front end side from the rear end side. It is characterized by blocking.

The control unit further includes a time measuring unit for measuring the input time of the input capacitor, so as to limit the input by using the information on the condenser that is input for the most time of the input capacitor measured by the time measuring unit The switch can be controlled.

The control unit further includes a number measuring unit for measuring the number of times of the input capacitor, so as to limit the input by using the information about the capacitor that is input the most number of the input capacitor measured by the number measuring unit The switch can be controlled.

In the automatic power factor improvement system according to an embodiment of the present invention, the order of inputting and disconnecting a plurality of capacitors for power factor improvement and a ring count method, that is, assigning a sequence of lines to a plurality of capacitors, and supplying capacitors according to capacity increase factors If this is increased, it is added only to the front part of the input top direction, and if a factor of capacity decrease occurs, the method of blocking the condenser at the bottom of the input bottom side first from the lower direction of the input to the input top direction is used.

Therefore, according to the automatic power factor improvement system according to an embodiment of the present invention, the overall life of the condenser may be kept constant due to the closing and closing of the ring count circulation system.

In addition, according to the automatic power factor improvement system according to an embodiment of the present invention, in the ring count operation, the capacitor accumulating the total accumulated time and the number of times of the capacitor input and recording the most input time and the cumulative number of times of the condenser By controlling the input to be temporarily held, the running time can be made homogeneous on average.

1A to 1E are circuit diagrams for explaining the operation of a capacitor bank used in a power factor correction apparatus according to the prior art.
2 is a block diagram illustrating an example in which an automatic power factor improving system according to an embodiment of the present invention is used.
3 is a circuit diagram illustrating the structure of the automatic power factor improving apparatus of FIG. 2.
4A to 4H are circuit diagrams for describing an operation of the automatic power factor improving apparatus of FIG. 2.
FIG. 5 is a flowchart illustrating a method of operating the automatic power factor improving apparatus of FIG. 2.
FIG. 6 is a flow chart illustrating a condenser individual input method of an operation method of the automatic power factor improving apparatus of FIG. 5.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

2 is a block diagram illustrating an example in which an automatic power factor improving system according to an embodiment of the present invention is used, FIG. 3 is a circuit diagram illustrating a structure of the automatic power factor improving apparatus of FIG. 2, and FIG. 5 is an automatic diagram of FIG. 2. 6 is a flowchart illustrating an operating method of the power factor improving device, and FIG. 6 is a flowchart illustrating an individual capacitor input method among the operating methods of the automatic power factor improving device of FIG. 5.

2 to 3, an automatic power factor improving system according to an embodiment of the present invention includes a transformer 1, a power meter 3, a transformer 2, and an automatic power factor adjusting device 10.

The transformer (MOF) Metering Out Fit (MOF) 1 and the first auxiliary transformer (PT) (1a) and the first power transformer (PT) so as to reliably measure the high-voltage power supplied from the external power equipment (3) 1 A current transformer (CT) 1b converts a supply voltage and a current into a voltage and a current of a reference level. In addition, the first auxiliary transformer 1a is a device for converting a high voltage into a low voltage (for example, 110V), and the first auxiliary current transformer 1b is for modifying a large current to a small current (for example, 5A). Appliance.

The transformer 2 acts to step down the power supplied from the external power equipment to a voltage at a level capable of supplying the load 4.

The automatic power factor adjustment device 10 is a device for adjusting the power factor of the load 4, the power factor value according to the voltage and current applied to the transformer 2 between the transformer 2 and the load 4, the reference power factor value It is automatically adjusted so that it is within the range of.

The automatic power factor adjusting apparatus 10 includes a calculator 120, a capacitor bank 150, a switch 140, and a controller 130. In addition, the automatic power factor adjustment device 10 further includes a time measuring unit 132 and the number measuring unit 133.

On the other hand, the automatic power factor adjustment device 10 is a secondary transformer 110 including a second transformer (PT) and a second current transformer (CT) when the load (4) installed at the rear end is relatively high in power demand. It is provided with, it is possible to convert the power via the transformer (2) to a level that can be processed by the automatic power factor adjusting device (10).

The calculator 120 measures the voltage and current applied to the transformer 2, and calculates power factor information including a phase difference between the voltage and the current, active power, reactive power, and apparent power. That is, the calculator 120 calculates power factor information such as voltage, current, phase difference between voltage and current, active power (P), reactive power (Q), and apparent power (S).

The power factor information may be configured to calculate a power factor value by using information required for power factor calculation.

The relationship between the active power (P), reactive power (Q), apparent power (S) can be expressed by the following equation (1).

[Equation 1]

[Equation 2]

Meanwhile, the controller 130, which will be described later, receives power factor information from the calculator 120 and adjusts the power factor value according to the voltage and current applied from the transformer 2 to be within a preset value range. In general, since the load 4 connected to the power line is mostly inductive, the controller 130 adjusts the power factor by adjusting the capacitive load to be connected to the power line, but if the load 4 is a capacitive load, the inductive load is adjusted. Power factor can be adjusted, and can be configured to adjust both capacitive load and inductive load, if necessary. That is, the controller 130 may adjust the power factor by adjusting the capacitive load of the capacitor bank 150 or the inductive load of the inductor bank as necessary. In the present invention, the controller 130 adjusts the power factor by adjusting the capacitive load of the capacitor bank 150 as an example.

The capacitor bank 150 includes at least one capacitor. Each capacitor C1 to Cn constituting the capacitor bank 150 may be connected in parallel to both ends of the circuit through each switch constituting the switch unit 140, and various capacities may be set according to a combination of capacitors to be connected to the circuit. have. In addition, the capacity of each capacitor can be configured variously as needed. For example, each capacitor C1-Cn can be comprised so that it may become 2 (n-1) times the basic capacitance C0. As described above, each capacitor constituting the capacitor bank 150 connects the control unit and the load through a switch. Through this, each capacitor can adjust the power factor of the load 4 through the switch on and off by the control of the controller 130.

The switch unit 140 includes a switch corresponding to each condenser of the condenser bank 150, and selectively connects each condenser to a load according to a switch control signal. That is, the switch unit 140 is connected to the load of the capacitor connected to the switch is set to the on / off state of each switch is determined according to the control signal transmitted from the controller 130. Thus, one or more capacitors can be configured with the load to improve the power factor. In this case, each switch constituting the switch unit 140 may be a magnetic switch.

The controller 130 calculates the capacity of the capacitor bank 150 required for power factor control of the load 4 based on the power factor information calculated from the calculator 120, and according to the calculated result, the capacitor bank ( Outputs a ring count control signal to input or cut off each capacitor of 150), and turns on or off the switch by turning on or off each capacitor by rotating the capacitor in a predetermined direction according to the control signal. That is, the controller 130 outputs a ring count control signal to include as many capacitors as necessary for power factor adjustment in the circuit. In order to perform such an operation, the controller 130 may transmit a switch control signal required for power factor adjustment to the switch unit 140 through each output port 1 to n 131. Then, each switch of the switch unit 140 is turned on or off according to the control signal transmitted from the corresponding output port.

The control signal of the ring count method may be inputted in the first direction of the rear end side opposite to the front end side from the front side of the capacitor (ie, connection by switching on) based on a preset direction. The blocking of (i.e., disconnection by switching off) is a control signal of the method of blocking in the second direction of the front end side from the rear end side. Description of the ring count control signal will be described in more detail in the description of FIGS. 4A to 4H.

The time measuring unit 132 serves to measure the input time of the input capacitor. Accordingly, the controller 130 may limit the input by using information on the capacitor that is input for the most time among the input capacitors measured by the time measuring unit 132. That is, the controller 130 may withhold the input of the condenser that is input for the most time among the input capacitors for a predetermined time.

The number measuring unit 133 serves to measure the number of times of the input capacitor. Accordingly, the controller 130 may limit the input using information on the capacitor that is input the most times among the input capacitors measured by the number measuring unit 133. That is, the controller 130 may withhold the input of the capacitor, which is input the most times among the input capacitors, for a predetermined time.

Referring to FIG. 5, the automatic power factor improving apparatus 10 used in the automatic power factor improving system according to an embodiment of the present invention calculates the power factor of the load 4 by the calculation unit 120 (S100), and The controller 130 compares the preset reference power factor value with the calculated result value (that is, the power factor value) (S200). When the controller 130 compares the calculated power factor with the reference power factor (S200), and determines that the number of capacitors should be reduced when the calculated power factor exceeds the reference power factor, the capacitor bank 150 is determined. The switch unit 140 is controlled to cut off the capacitor (S210) from the lower end of the capacitor input. In addition, the controller 130 compares the calculated power factor value with the reference power factor value (S200), and when it is determined that the number of capacitors should be increased when the calculated power factor value is insufficient compared to the reference power factor value, the capacitor bank The switch unit 140 is controlled to inject the condenser (S220) from the condenser input upper end side of the 150. In addition, the controller 130 compares the calculated power factor value with the reference power factor value (S200), and when it is determined that the calculated power factor value is appropriate to the reference power factor value, the operation state at that time is continuously maintained (S230). To control.

In addition, referring to Figure 6, the automatic power factor improving apparatus 10 used in the automatic power factor improving system according to an embodiment of the present invention, as a result of the control unit 130 compared with the calculated power factor value and the reference power factor value, In the case where the capacitor is to be injected, the input signal of the capacitor is transferred to the switch unit 140 (S240) to control the on / off of the switch. In this case, the controller 130 inquires information on the capacitors that are put in the most time among the put capacitors measured by the time measuring unit 132 (S250), and limits the input using them (ie, (Input pending) (S251). Then, the controller 130, inquiring (S260) the information about the capacitor that has been put the most number of the added capacitors measured by the number measuring unit 133 (S260) to limit the input using this ( In other words, it is possible to hold the input (S261). Then, the controller 130 controls the switch unit to input a relatively small number of capacitors (S270) of the input capacitors.

The time measuring unit 132 and the number measuring unit 133 constituting the control unit 130, the operation time (operation time) of the capacitor constituting the condenser bank 150 while the automatic power factor improving device 10 is operating and The input frequency is counted (S280).

Therefore, in the present invention, the input of the capacitor constituting the condenser bank 150 is input from the front end to the first direction of the rear end side opposite to the front end side on the basis of the preset direction, but the blocking of the capacitor is sheared at the rear end side. In principle, it is possible to cut off in the second direction of the side, but it is possible to extend the life of the condenser by limiting the input to the cumulative target value of the operating time after the condenser is input or by prohibiting re-injection within the designated time of the condenser which has been turned on and off once. Will be. That is, in the present invention, the cumulative total input time and the number of inputs are counted during the ring counter operation to adjust the input and the number of capacitors constituting the capacitor bank 150 to accumulate the most input time and the number of inputs among the plurality of capacitors. By recording the condenser temporarily, it is possible to make the recorded capacitors homogeneous on average with the heterogeneous characteristics of the operating time.

4A to 4H are circuit diagrams for describing an operation of the automatic power factor improving apparatus of FIG. 2. 4A to 4H, the number of capacitors constituting the capacitor bank will be described as nine. However, the present invention does not limit the number of capacitors. In addition, in Figs. 4a to 4h will be described using the configuration and the reference numerals of the automatic power factor improving apparatus of FIG.

First, as shown in FIG. 4A, when the control unit 130 compares the calculated power factor and the reference power factor, the order in which the capacitors are input when the power factor becomes worse is increased in the upper direction so that the switching unit 140 is supplied. ), The power factor of the load 4 can be controlled.

As shown in FIG. 4B, while the controller 130 controls the power factor of the load 4, when the power factor is improved to reduce the input amount of the capacitor, the switch unit 140 is controlled to be cut off from the bottom. do.

As shown in FIG. 4C, when the control unit 130 compares the calculated power factor with the reference power factor, when the power factor decreases and the capacitor input amount needs to be increased again, the control unit 130 inserts the capacitor from the upper end. 140).

As shown in FIG. 4D, when the controller 130 controls the power factor of the load 4, when the input amount of the capacitor needs to be reduced, the switch unit 140 is controlled to cut off the capacitor from the lower end again. do.

As shown in FIG. 4E, when the controller 130 controls the power factor of the load 4, the switch unit 140 is increased to increase the number of capacitor inputs to the upper side if it is necessary to increase the number of capacitor inputs. To control. At this time, if it is necessary to reduce the number of input of the capacitor, the control unit 140 to reduce the number of capacitor input from the bottom.

If, as shown in Figure 4f, it is necessary to further increase the number of input of the condenser in the state that the uppermost capacitor is inserted, the control unit 130 increases the number of input of the condenser from the lowest end to the upper direction again. To control the switch unit 140.

At this time, as shown in Figure 4g, when it is necessary to reduce the number of input of the condenser in the state that the uppermost condenser is put, the control unit 130 to switch the switch unit 140 to block the lower direction of the upper side To control.

As shown in FIG. 4H, in this case, when it is necessary to increase the number of inputs of the condenser, the controller 140 controls the switch unit 140 to increase the number of inputs of the condenser from the lower end to the upper direction. .

As described above, in the present invention, by using a ring count control signal to control the closing and closing of the capacitor, it is possible to prevent the deterioration of the life of a specific capacitor that may occur in the appropriate quantity control process of the number of input of the capacitor according to the power factor. In addition, it is possible to maintain an even average of the overall condenser use time, thereby significantly reducing the risk of condenser failure, damage and fire, which are the causes of the chronic failure of the power factor improving device.

What has been described above is only one embodiment for implementing the automatic power factor improvement system according to the present invention, and the present invention is not limited to the above embodiment, and as claimed in the following claims, the gist of the present invention Without departing from the scope of the present invention, any person having ordinary skill in the art will have the technical spirit of the present invention to the extent that various modifications can be made.

1: transformer 2: transformer
3: wattmeter 4: load
10: automatic power factor adjustment device 110: transformer
120: calculator 130: controller
131: control terminal 132: time measuring unit
133: counting unit 140: switch unit
150: capacitor bank

Claims (4)

A transformer for transforming and converting a voltage and a current supplied from an external power source into a power meter, and a transformer for stepping down the voltage supplied from an external power supply to a load; An automatic power factor improving system including an automatic power factor improving device that automatically adjusts a power factor value according to a voltage and a current applied to the transformer between the loads so as to be within a range of a reference power factor value,
The automatic power factor improving device
A calculator for measuring a voltage and a current applied to the transformer and calculating power factor information including a phase difference between the voltage and the current, active power, reactive power, and apparent power;
A condenser bank consisting of at least one condenser;
A switch unit having a switch corresponding to each capacitor of the capacitor bank, and selectively connecting each capacitor to the load according to a switch control signal; And
Based on the power factor information calculated by the calculating unit, a capacity of a capacitor required for power factor control of the load is calculated, and a ring count type control signal is input to block or inject each capacitor in the capacitor bank according to the calculated result. And a control unit which turns on and off the switch by turning on or off each capacitor while rotating the capacitor in a predetermined direction by the control signal.
The control unit inputs the condenser in a first direction on the rear end side opposite to the front end side from the front end on the basis of the preset direction, and the blocking of the condenser is a second direction on the front end side from the rear end side. Automatic power factor improvement system, characterized in that the blocking. delete The method of claim 1,
The control unit further includes a time measuring unit for measuring the input time of the input capacitor, so as to limit the input by using the information on the condenser that is input for the most time of the input capacitor measured by the time measuring unit Automatic power factor improvement system, characterized in that to control the switch. The method of claim 1,
The control unit further includes a number measuring unit for measuring the number of times of the input capacitor, so as to limit the input by using the information about the capacitor that is input the most number of the input capacitor measured by the number measuring unit Automatic power factor improvement system, characterized in that to control the switch.

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