KR20150112406A - Uninterruptible power supply and control method thereof - Google Patents

Abstract

Disclosed is an uninterruptible power supply device. According to an embodiment of the present invention, the uninterruptible power supply device includes: a battery; an inverter converting DC power, outputted from the battery, into AC power; a first control part outputting a first control signal through the input of a difference between a reference voltage and an output voltage of the inverter; a second control part outputting a second control signal, obtained by multiplying the difference between a reference voltage and an output voltage of the inverter by a preset gain, through the input of the difference; a third control part outputting a third control signal through the input of the difference between an output current of the inverter and a reference current and the second control signal; and a fourth control part outputting a fourth control signal for determining an inverter output voltage through the input of effective and ineffective components of the output current of the inverter.

Description

Technical Field [0001] The present invention relates to an uninterruptible power supply apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply and a control method thereof, and more particularly, to an uninterruptible power supply And a control method thereof.

The uninterruptible power supply system (UPS) is a device that supplies good quality stable AC power overcoming the power failure that can occur in commercial power supply. The uninterruptible power supply system supplies normal power to the load side in the event of a power outage or an input power failure. Due to recent development of computer industry equipment, it is required to supply high quality power from the load side. It is widely used for supplying the best power.

Uninterruptible power supplies can be classified into two broad categories: off-line uninterruptible power supplies and on-line uninterruptible power supplies.

FIGS. 1 and 2 are block diagrams for explaining an uninterruptible power supply apparatus of an off-line method and an on-line method according to the related art.

An off-line uninterruptible power supply 10 according to FIG. 1 includes an AC power source 11, a filter 12, a battery 13, an inverter 14 and a switch 15.

In the normal operation mode, the switch 15 is connected to the AC power source 11 side, and the power source is connected to the load end through the AC power source 11, the filter 12, and the switch 15 to charge the battery 13. That is, in normal operation mode, there is no big difference between directly connecting the load equipment to the main line.

Thereafter, when a power failure occurs due to a power failure, an instantaneous voltage drop / rise, an overvoltage, a wire noise, a frequency change, or the like, the switch 15 is switched to the inverter 14 direction. In the off-line mode, the power is supplied to the load stage via the battery 13, the inverter 14 and the switch 15. [ That is, in the power failure situation, the offline uninterruptible power supply 10 supplies power at the lower end for a few minutes or several hours, depending on the capacity of the battery 13.

2 includes an AC power source 21, a filter 22, a rectifier 23, an inverter 24, a battery 25 and a switch 26 .

In the normal operation mode, the AC power source 21 is connected to the load stage via the filter 22, the rectifier 23, the inverter 24 and the switch 26, and charges the battery 25 at the same time. If a power failure occurs during operation, the connection between the AC power source 21 and the lower stage is cut off, and the battery 25 supplies power to the lower stage via the inverter 24 and the switch 26. That is, there is no change in the operation of the switch 26 when the backup mode is entered in the normal operation mode.

The switch 26 operates to directly connect the uninterruptible power supply 20 of the on-line type and the subnet of the AC power supply 21 when maintenance is required. That is, the AC power source 21 is connected to the load terminal via the filter 220 and the switch 26 in the form that the switch 26 is directly connected to the external power source.

On the other hand, although the uninterruptible power supply has to supply a good quality power to the load, there is a problem that a desired output value can not be obtained for a predetermined time due to the transient response generated when each mode is changed.

For example, when the switch is operated when each mode of the offline uninterruptible power supply 10 or the online uninterruptible power supply 20 is switched, the output voltage of the inverter is distorted due to the transient transient, There is a problem that a desired output value can not be obtained due to current generation.

Accordingly, there is a need for a control method capable of minimizing the transient response when the mode is changed in the uninterruptible power supply.

Patent Document 10-2014-0009914

It is an object of the present invention to provide an uninterruptible power supply apparatus capable of minimizing a transient response generated when a mode is changed in an uninterruptible power supply apparatus, And to provide a control method thereof.

The technical objects of the present invention are not limited to the above-mentioned technical problems, and other technical subjects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided an uninterruptible power supply comprising: a battery; An inverter for converting a DC power output from the battery into an AC power; A first controller for outputting a first control signal based on a difference between a reference voltage and an output voltage of the inverter; A second controller for receiving a difference between a reference voltage and an output voltage of the inverter as an input and outputting a second control signal obtained by multiplying a difference between the reference voltage and the inverter output voltage by a predetermined gain; A third controller for outputting a third control signal based on a difference between the second control signal and the reference current and the output current of the inverter; And a fourth control unit for outputting a fourth control signal for determining the inverter output voltage based on the ineffective component and the effective component of the inverter output current.

According to an embodiment of the present invention, the first control signal may be a control signal that increases the output voltage of the inverter in proportion to the difference between the reference voltage and the output voltage of the inverter.

According to an embodiment of the present invention, the third control signal may be a control signal for compensating distortion of the inverter output voltage.

According to an embodiment of the present invention, when the inverter is switched to the lower stage, the third controller detects a rush current applied to the inverter, and outputs a control signal for applying a voltage in a direction opposite to the rush current Can be output.

According to another aspect of the present invention, there is provided a method of controlling an uninterruptible power supply, the method comprising: outputting a first control signal for controlling a magnitude of the inverter output voltage based on a difference between a reference voltage and an inverter output voltage; Outputting a second control signal obtained by multiplying a difference between the reference voltage and the inverter output voltage by a predetermined gain, using a difference between the reference voltage and the inverter output voltage as an input; Outputting a third control signal for compensating distortion of the inverter output voltage by taking a difference between the second control signal and the reference current and the output current of the inverter as an input; And determining the inverter output voltage by inputting an invalid component and an effective component of the inverter output current.

According to the present invention as described above, it is possible to improve the transient response characteristic when the main power supply source is switched from the external commercial power supply to the inverter.

In addition, since distortion of the inverter output voltage is compensated, it is possible to provide an effect that high-quality power can be supplied to the lower stage.

In addition, it is possible to prevent the uninterruptible power supply unit and the bottom end from being damaged by the rush current generated upon switching to the inverter.

FIG. 1 is a view for explaining an uninterruptible power supply apparatus of a conventional offline system.
FIG. 2 is a view for explaining an uninterruptible power supply apparatus of the conventional on-line type.
3 is a block diagram illustrating an uninterruptible power supply according to an embodiment of the present invention.
4 is a conceptual diagram illustrating a method of controlling an uninterruptible power supply according to an embodiment of the present invention.
5 is a view for explaining a proportional-integral control method of a first controller according to an embodiment of the present invention.
6 is a flowchart illustrating a method of controlling an uninterruptible power supply according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

3 is a block diagram illustrating an uninterruptible power supply 300 according to an embodiment of the present invention.

Only the components related to the present embodiment are shown in the uninterruptible power supply 300 shown in Fig. Accordingly, those skilled in the art will recognize that other general-purpose components other than the components shown in FIG. 3 may be further included.

3 includes a battery 310, an inverter 320, a first control unit 330, a second control unit 340, a third control unit 350, and a fourth control unit 360. The battery 310, the inverter 320, .

The battery 310 is used to maintain the operation of the uninterruptible power supply 300 when the commercial power supply is out of order or when the input power is low. In the low-capacity uninterruptible power supply 300, maintenance-free sealed sealed lead acid batteries can be used. In the large uninterruptible power supply 300, long-life batteries or ES type batteries can be used. The operating time of the uninterruptible power supply 300 may be determined by the capacity of the battery 310. [

The inverter 320 converts the DC power output from the battery 310 into an AC power and supplies the AC power to the lower stage. Specifically, the DC side of the inverter is connected to the battery 110, and the AC side is connected to the negative side to convert the energy of the battery 310 into AC power according to the control signal, and then transmits the AC power to the load terminal.

The first controller 330 receives the difference between the reference voltage and the output voltage of the inverter 320 and outputs a first control signal. The magnitude of the first control signal is proportional to the difference between the reference voltage and the output voltage of the inverter 320. The closer the output voltage of the inverter 320 is to the reference voltage,

As described above, as the output voltage of the inverter 320 approaches the reference voltage, the magnitude of the first control signal can be controlled to be finely controlled to approach the reference voltage.

On the other hand, if the uninterruptible power supply 300 is normally controlled and the transient response is not large, the output voltage of the inverter 320 can be controlled within a stable range by using only the first control unit 330 described above. However, A desired result can not be obtained only by the first controller 330 when the transient response by the first controller 330 is present or when the uninterruptible power supply 300 has various modes.

The second controller 340 receives the difference between the output voltage of the inverter 320 and the reference voltage and outputs a second control signal obtained by multiplying the difference by a predetermined gain.

In the off-line mode, the inverter 320 is stopped in the normal mode in which the load is supplied from the external commercial power source. However, the inverter 320 receives the output load of the lower stage and operates at its own frequency as soon as the backup mode is switched out of the voltage range, the frequency range and the efficiency range set in the commercial power supply. At this time, the inverter 320 passes the transient, which causes distortion in the output voltage of the inverter 320.

The second controller 340 outputs a second control signal to be input to the third controller 350 to compensate for the distortion of the output voltage of the inverter 320. The second control signal is input to the difference between the output voltage of the inverter 320 and the reference voltage, and the differential value is multiplied by a predetermined gain and output.

According to one embodiment of the present invention, the current peak gain may vary depending on the difference between the output voltage of the inverter 320 and the reference voltage. For example, when the difference between the output voltage of the inverter 320 and the reference voltage is large, a large second signal is required to compensate for the output voltage distortion. Therefore, Is multiplied by the difference value. On the other hand, when the difference between the output voltage of the inverter 320 and the reference voltage is small, the small gain is multiplied by the difference between the output voltage of the inverter 320 and the reference voltage.

The second control signal output through the above-described process is input to the third control unit 350 and is used to output a third control signal for compensating for the voltage distortion of the inverter 320.

The third control unit 350 receives the difference between the second control signal output to the second control unit 340 and the output current of the inverter 320 and the reference current to output a third control signal.

On the other hand, when the uninterruptible power supply 300 is switched from the normal mode to the backup mode, an inrush current may flow in addition to a phenomenon that the output voltage of the inverter 320 is distorted in a transient state. Specifically, the inverter 320 includes a high frequency transformer. In the normal mode, one terminal of the transformer is kept open with the load terminal. Thereafter, when the mode of the uninterruptible power supply 300 is switched from the normal mode to the backup mode, the open terminals are connected and a large inrush current is instantaneously generated.

The third control unit 350 calculates a rush current included in the inverter 320 at the time of mode switching and outputs a third control signal capable of applying the inverter voltage in the direction opposite to the inrush current to prevent saturation of the transformer And minimize the malfunction of the inverter 320 due to the inrush current.

The fourth controller 360 determines the output voltage of the inverter 320 based on the ineffective component and the effective component of the output current of the inverter 320.

When the uninterruptible power supply 300 is changed from the normal mode to the backup mode, a current that flows to the bypass path flows into the inverter 320, and the inside of the transformer included in the inverter 320 and the reactor So that the voltage drop due to the voltage drop can not be avoided.

That is, since the output voltage of the inverter 320 is the sum of the voltage applied to the lower stage and the junction breakdown due to the reactor, the output current of the inverter 320 is classified into the effective component and the ineffective component, The voltage drop due to the reactor can be compensated.

A method of classifying the invalid component and the effective component from the output current of the inverter 320 is as follows.

The output current,

And multiplying sin ωt to obtain the effective component of the output current,

.

를 구할 수 있고 이 값에 2를 곱하면 유효 성분의 전류 크기를 얻을 수 있다.In case of cos2ωt and sin2ωt in the above equation, it becomes 0 when half-period averaging is performed. Therefore, if the average value is obtained by summing the half-period values in real time by storing them in a buffer in FIFO (First in First Out) Ingredient

And by multiplying this value by 2, the current magnitude of the effective component can be obtained.

Next, multiplying cos ωt to obtain the ineffective component of the output current,

.

를 구할 수 있고, 이 값에 2를 곱하면 무효 성분의 전류 크기를 얻을 수 있게 된다.Likewise, in the above equation, cos2ωt and sin2ωt are equal to zero when half-period averaging is performed, so they are stored in a buffer in FIFO (first in first out) method using a digital buffer for half a period, , A direct current component

If this value is multiplied by 2, the current magnitude of the reactive component can be obtained.

As described above, by controlling the output power of the inverter 320 using a plurality of control units, even when an external disturbance occurs or the uninterruptible power supply 300 has a plurality of modes, the transient response can be minimized, Can be supplied to the lower stage.

Although the first to fourth control units 330 to 340 are described as being independent of each other in the above-described embodiment, the present invention can be implemented in a single configuration to perform independent operations. to be.

Also, the first to fourth control units 330 to 340 may be software or a hardware component such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). Further, each control may be configured to be in an addressable storage medium and configured to execute at least one of the processors.

4 is a conceptual diagram illustrating a method of controlling an uninterruptible power supply according to an embodiment of the present invention.

The first controller 330 receives the reference voltage and the output voltage of the inverter 320 and outputs a first control signal for controlling the output voltage of the inverter 320. According to an embodiment of the present invention, the first controller 330 may perform PI control (proportional-integral control).

The first control unit 330 may output a first control signal to control the output voltage of the inverter 320 in proportion to the difference between the reference voltage and the output voltage of the inverter 320. That is, as the output voltage of the inverter 320 approaches the reference voltage, the magnitude of the first control signal decreases. When the output voltage approaches the reference voltage, integral control for eliminating the residual error, which is a minute error, is performed. The integration control is performed by accumulating minute residual deviations temporally and eliminating the deviation when the cumulative value exceeds a preset reference value.

As described above, by controlling the output voltage of the inverter 320 in a proportional-integral manner, it is possible to minimize the ripple voltage generated around the reference voltage.

The second controller 340 receives the difference between the output voltage of the inverter 320 and the reference voltage and outputs a second control signal obtained by multiplying the difference between the two voltages by a predetermined gain. The second control signal output from the second control unit 340 is input to the third control unit 350.

The third control unit 350 receives the difference between the second control signal and the reference current output from the second control unit 340 and the output current of the inverter 320 and outputs a third control signal. The third control signal outputted from the third control unit 350 can compensate the distortion of the output voltage caused by the instantaneous operation of the inverter 320 by changing the mode of the uninterruptible power supply 300. [

The third controller 350 may further output a control signal capable of canceling the inrush current momentarily generated in the high frequency transformer included in the inverter when the inverter 320 is switched to the lower stage.

Specifically, the third controller 350 detects an inrush current applied to the inverter 320 when the mode of the uninterruptible power supply 300 is switched, and applies a voltage to the inverter 320 in the opposite direction in which the inrush current flows , Saturation of the transformer included in the inverter 320 can be prevented, and malfunction due to the inrush current can be minimized.

The fourth controller 360 receives the ineffective component and the effective component of the output current of the inverter 320 and outputs a fourth control signal for determining the output voltage of the inverter 320.

Specifically, the fourth control unit 360 obtains the ineffective component and the effective component of the output current through the PLL (Phase Locked Loop) from the bypass voltage and outputs a fourth control signal for controlling the output voltage of the inverter 320 .

Such a fourth control signal can compensate for the voltage drop from the reactor inserted into the transformer of the inverter 320 and inserted into the filter, thereby minimizing the transient response.

According to an embodiment of the present invention, the first control unit 330 performs proportional-integral control (PI control), and the second control unit 340 and the third control unit 350 perform proportional control (P control) However, the present invention is not limited thereto, and it is possible to control the uninterruptible power supply 300 by adopting an optimal control method according to the situation.

5 is a view for explaining a proportional-integral control method of a first controller according to an embodiment of the present invention.

The first control unit 330 receives a deviation between the reference voltage 510 and the output voltage 520 of the inverter 320 and outputs a first control signal 530 for controlling the output voltage 520. Since the first control signal 530 is proportional to the difference between the reference voltage 510 and the output voltage 520, the control initial control signal 530 may have a 100% output value.

Thereafter, as the output voltage 520 approaches the reference voltage 510, the operation amount according to the first control signal 530 is reduced, and the residual error, which is a minute error between the output voltage 520 and the reference voltage 510, The integral operation amount 540 is increased.

Specifically, the integration control is performed by accumulating minute residual deviations temporally and eliminating the deviation when the cumulative value exceeds a preset reference value.

In the above-described embodiment, the first controller 330 performs the proportional-integral control. However, the present invention is not limited to this and other control methods may be adopted depending on the situation.

6 is a flowchart illustrating a method of controlling an uninterruptible power supply according to an embodiment of the present invention.

The first control unit 330 receives the difference between the reference voltage and the output voltage of the butter 320 and outputs a first control signal for controlling the magnitude of the output voltage of the inverter 320 (S610). According to an embodiment of the present invention, the first controller 330 may control the output voltage of the inverter 320 through proportional-integral (PI control).

The second controller 340 receives the difference between the reference voltage and the output voltage of the inverter 320, and outputs a second control signal obtained by multiplying the difference by a preset gain (S620). At this time, the predetermined gain may vary depending on the difference between the reference voltage and the output voltage of the inverter 320. [

The third control unit 350 outputs a third control signal for compensating distortion of the inverter output voltage by receiving the second control signal, the difference between the reference current and the inverter output current (S630). In addition, the fourth controller 360 receives the ineffective component of the inverter output current and the effective component, and outputs a fourth control signal for determining the inverter output voltage (S640).

Meanwhile, the above-described method can be implemented in a general-purpose digital computer that can be created as a program that can be executed by a computer and operates the program using a computer-readable recording medium. In addition, the structure of the data used in the above-described method can be recorded on a computer-readable recording medium through various means. The computer-readable recording medium includes a storage medium such as a magnetic storage medium (e.g., ROM, floppy disk, hard disk, etc.), optical reading medium (e.g., CD ROM,

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed methods should be considered from an illustrative point of view, not from a restrictive point of view. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

300: uninterruptible power supply 310: battery
320: inverter 330: first control unit
340: second control unit 350: third control unit
360: fourth control section

Claims (5)

battery;
An inverter for converting a DC power output from the battery into an AC power;
A first controller for outputting a first control signal based on a difference between a reference voltage and an output voltage of the inverter;
A second controller for receiving a difference between a reference voltage and an output voltage of the inverter as an input and outputting a second control signal obtained by multiplying a difference between the reference voltage and the inverter output voltage by a predetermined gain;
A third controller for outputting a third control signal based on a difference between the second control signal and the reference current and the output current of the inverter; And
And a fourth control unit for outputting a fourth control signal for determining the inverter output voltage based on an invalid component and an effective component of the inverter output current. The method according to claim 1,
Wherein the first control signal is a control signal that increases the output voltage of the inverter in proportion to the difference between the reference voltage and the output voltage of the inverter. The method according to claim 1,
Wherein the third control signal is a control signal that compensates for distortion of the inverter output voltage. The method according to claim 1,
And the third control unit,
Wherein the inverter further detects a rush current applied to the inverter and outputs a control signal for applying a voltage in a direction opposite to the rush current when the inverter is switched to the lower stage. Outputting a first control signal for controlling a magnitude of the inverter output voltage by inputting a difference between a reference voltage and an inverter output voltage;
Outputting a second control signal obtained by multiplying a difference between the reference voltage and the inverter output voltage by a predetermined gain, using a difference between the reference voltage and the inverter output voltage as an input;
Outputting a third control signal for compensating distortion of the inverter output voltage by taking a difference between the second control signal and the reference current and the output current of the inverter as an input;
And outputting a fourth control signal for determining the inverter output voltage based on an invalid component and an effective component of the inverter output current.

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