KR101219799B1 - Smart uninterruptible power supply capable of reducing input peak power and method for controlling uninterruptible power supply - Google Patents

Abstract

PURPOSE: An intelligent uninterruptible power supply system having an input peak power reduction function and a control method thereof are provided to reduce electric charges by reducing peak power load at an input terminal. CONSTITUTION: A PWM rectifier(31) converts inputted AC voltage into DC voltage. The PWM rectifier supplies the voltage to a DC bus terminal. An inverter(35) converts the DC voltage into AC and supplies the AC voltage to a load(36). A bypass switch(34) is operated when a system power supply is directly supplied to the load. A controller(37) measures an input power reserve margin, a load amount, and battery power. [Reference numerals] (30) Input terminal; (30A) System; (31) PWM rectifier; (32) Battery charger and discharger; (34) Bypass switch; (35) Inverter; (36) Load; (37) Controller; (38) Data storage; (39) Control unit; (40) Measurement unit

Description

Smart uninterruptible power supply capable of reducing input peak power and its control method {Smart uninterruptible power supply capable of reducing input peak power and method for controlling uninterruptible power supply}

The present invention relates to an uninterruptible power supply and a control method thereof. More particularly, the present invention relates to an uninterruptible power supply and a control method thereof. An intelligent uninterruptible power supply having a peak power reduction function of an input stage by providing battery power and a control method thereof are provided.

As is well known to those skilled in the art, an uninterruptible power supply is a device that is always installed to supply normal power to the equipment in use when an uninterrupted power failure or excessive voltage drop occurs due to an accident in a device (load) that uses AC power. to be.

Such an uninterruptible power supply system uses an off-line method of supplying power to a load by operating a battery only when an input voltage is abnormal (interruption, instantaneous voltage drop, etc.) and a rectifier (AC / DC) even when a normal input voltage is supplied. ) And the inverter (DC / AC) to supply constant voltage and constant frequency (CVCF) voltage to the load, and in case of abnormal input voltage (interruption, voltage drop, etc.) Double conversion).

In the above-described off-line type of uninterruptible power supply, commercial power (system power) is supplied to the load through a bypass line at normal times (when the state of the input power is normal) as shown in FIG. The inverter / rectifier operates as an inverter to supply energy accumulated in the battery to the load.

This off-line type uninterruptible power supply has an advantage of high efficiency because it supplies power directly to the load stage through the bypass line during normal operation, and this off-line operation is called high efficiency operation.

However, in the off-line type of uninterruptible power supply, a switching time occurs during operation switching from normal operation to battery operation during power failure, but a short time, but an instantaneous power failure of the load stage cannot be avoided.

In addition, in the off-line type of uninterruptible power supply, commercial power is supplied to the load as it is in normal operation, so when the input voltage is unstable, the voltage is transmitted to the load. Therefore, this method is not suitable for loads requiring stable output voltage and frequency.

Meanwhile, in the double conversion type uninterruptible power supply device, the commercial power is normally converted into a DC voltage through a rectifier as shown in FIG. 2, and the voltage is converted into an AC voltage through an inverter, thereby converting the double converted power. Is supplied as a load, and in the case of power failure, the battery power is supplied to the load stage through the inverter, so it is possible to transfer the power to the load stage at the time of power failure, and to supply the load stage by double-converting commercial power during normal operation. Therefore, it is possible to always supply high-quality power of constant voltage and constant frequency to the load stage.

However, the double conversion type uninterruptible power supply shown in FIG. 2 has a disadvantage in that efficiency is lower than that of the off-line type uninterruptible power supply due to switching losses of semiconductor devices generated during the double conversion process. Has

In order to overcome the drawbacks of the uninterruptible power supply of the double conversion type uninterruptible power supply as described above, some products are to enable high efficiency operation depending on the load amount and input voltage. That is, the product based on the patented technology of the patent application No. 10-1070472 (name: high efficiency uninterruptible power supply that can set the operation according to the load amount and input voltage and input frequency) filed by the applicant, the load amount, input voltage and input High efficiency operation is possible depending on the frequency.

However, in the case of the prior art, under a limited input power, when only the operation according to the size of the load proceeds, the burden on the input power supply is increased, and the power due to the distortion of the input voltage or the peak power increase due to the increased input power usage. It causes the rise of the rate.

The problem to be solved by the present invention is to solve the above problems of the prior art, the system and the uninterruptible power supply input stage power reserve and load by measuring the optimal way, the system and the instantaneous increase in load An intelligent uninterruptible power supply having an input peak power reduction function operating to secure a reserve ratio of input power by performing a battery discharge operation so as to reduce the load on the uninterruptible power supply input stage, and a control method thereof. There is a purpose.

In addition, the present invention is to solve the problem of the input power reserve ratio by the optimum operating conditions in the environment in which the uninterruptible power supply is installed, it is possible to perform the peak power reduction operation of the input power with the intelligent control algorithm learned based on the measured data The purpose of the present invention is to provide an intelligent uninterruptible power supply and a control method thereof.

In order to achieve the above object, the uninterruptible power supply apparatus according to the present invention includes a PWM rectifier for converting an AC voltage input from a system into a DC voltage and supplying it to a DC bus terminal; An inverter converting a DC voltage supplied from a battery and the PWM rectifier into an alternating current and supplying it to a load; A bypass switch that operates when directly supplying grid power to the load; And a controller for controlling the PWM rectifier operation capable of ensuring optimal operation according to a situation by accumulating data by receiving power reserve ratio, load amount, and battery power of a system and an uninterruptible power supply input terminal, wherein the controller includes: The uninterruptible power supply is characterized in that it operates the uninterruptible power supply to enable the peak power reduction operation according to the input power, the load amount and the battery power.

Preferably, the controller includes a measuring unit for measuring the input terminal power, the load amount, battery power and grid power; A data storage unit for storing the data measured by the measurement unit; Controlling the PWM rectifier according to each of the modes, and the setting and the control unit for setting the operation according to the power and the battery discharge time in the system power.

Preferably, the controller analyzes the data of the input stage power and the load, the battery power and the system power measured by the measuring unit, and then reserves sufficient input (system and input stage) power, so that the peak power of the input stage needs to be reduced. If not, the PWM rectifier is operated to perform double conversion operation.

Preferably, the controller analyzes data of input stage power, load, battery power, and grid power by a measuring unit, and lacks a reserve ratio of input (system and input stage) power, so that peak power reduction operation of the input stage is required. In this case, the operation of the PWM rectifier is limited, and the peak power reduction operation for replenishing the insufficient power through the battery is performed.

The uninterruptible power supply apparatus according to the present invention measures the input stage power, grid power, load and battery power, and measure the state of the input power according to the use environment and the reserve ratio of power based on the measured data, and measure the input stage under optimum conditions. By constructing an intelligent uninterruptible power supply that can reduce peak power of the system, by securing the input power reserve as well as the constant voltage constant frequency (CVCF) function, which is an advantage of the double conversion type uninterruptible power supply, In addition, it reduces the user's power bill and improves the reliability of the uninterruptible power supply, thereby maximizing the advantages of the uninterruptible power supply.

1 is a block diagram showing a conventional off-line uninterruptible power supply.
2 is a block diagram illustrating a conventional double conversion type uninterruptible power supply device.
3A to 3D are diagrams illustrating an intelligent uninterruptible power supply having an input peak power reduction function according to various embodiments of the present disclosure.
4A to 4B show an embodiment of the operation of the present invention, and FIG. 4A is a power flow diagram (double conversion operation) when the reserve ratio of input power is sufficient and the load is small; 4B is a power flow chart (input power peak cut operation) when the input power reserve is low and the load is large.
5 is a flowchart illustrating operation of a battery according to an input ratio and an output load of an uninterruptible power supply apparatus according to the present invention.

Hereinafter, preferred embodiments of the uninterruptible power supply device according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that detailed descriptions of related well-known technologies or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intention or custom of the user, the operator, and the like. Therefore, the definition should be based on the contents throughout this specification.

Referring to Figure 3a, the uninterruptible power supply according to an embodiment of the present invention is connected to the system 30A, the PWM rectifier 31, the battery 33, the battery between the input terminal 30 and the load 36 stage The charger-discharger 32, the inverter 35, the bypass switch 34 and the controller 37 are connected as shown.

Although the uninterruptible power supply of the present invention shown in FIG. 3A includes a battery charger-discharger 32, in some cases, a battery charger-discharger may be possible as shown in FIG. 3B. Will be self explanatory.

Meanwhile, in the uninterruptible power supply apparatus according to the present invention, the inverter switch 35a may be connected to the rear end of the inverter 35 as shown in FIGS. 3C and 3D.

It will be apparent to those skilled in the art that the present invention may be applicable to all of the uninterruptible power supplies shown in FIGS. 3A-3D. However, in the following description, it will be described with reference to FIG. 3A for simplicity of explanation. Accordingly, FIG. 3B may be understood as a configuration in which the battery charger-discharger is excluded in FIG. 3A, and FIGS. 3C and 3D may be understood as configurations in which an inverter switch is additionally connected to the rear end of the inverter of FIG. 3A.

The PWM rectifier 31 converts an AC voltage input from the input terminal 30 into a DC voltage and supplies the DC voltage to the DC link terminal.

The battery charger-discharger 32 depressurizes the DC bus voltage during charging, supplies the battery 33 to the battery 33, and boosts the battery voltage during discharge, and supplies the DC bus voltage to the DC bus.

The inverter 35 converts the DC voltage supplied from the battery 33 and the PWM rectifier 31 into alternating current and serves to supply the load 36.

The bypass switch 34 serves to operate when the system 30A directly supplies the power to the load 36.

The controller 37 receives the system 30A power, the input terminal 30 power, the load amount, and the battery power, accumulates and stores data, and based on the measured data, the peak power of the input power when the input power reserve ratio is small. By determining whether the reduction operation operation, and serves to control the PWM rectifier 31 and the battery charger-discharger (32).

The PWM rectifier 31 is a PWM control method, and operates as a power factor correction converter capable of controlling unit power factor, thereby converting an AC voltage of a system into DC power and supplying it to a DC bus. .

In the present invention, the controller 37 serves to perform the input power peak cut operation, for this purpose, as shown in FIG. 3, the system 30A power, the input terminal 30 power, and the load 36. Control the measurement unit 40 for measuring the size and power of the battery 33, the data storage unit 38 for storing the measured data value, the battery charger-discharger 32 and the PWM rectifier 31, It includes the setting and the control unit 39 to perform the input power reduction function for the system power, and to set the battery discharge time.

An operation of an intelligent uninterruptible power supply having an input peak power reduction function according to the present invention configured as described above will be described with reference to FIGS. 3A to 5.

4A and 4B illustrate power flow diagrams for an operation for reducing input power according to a reserve ratio of input power during operation of an uninterruptible power supply apparatus according to an embodiment of the present invention.

First, in the uninterruptible power supply of the present invention, the input power reduction operation is determined according to the input power reserve ratio, the load amount, and the state of the battery power of the uninterruptible power supply.

When the values measured by the measuring unit 40 are stored in the data storage unit 38 and the input power is sufficient because the values and conditions calculated by the accumulated data are not necessary, As shown in 4a, a double conversion operation of outputting power of the input terminal 30 to the load through the PWM rectifier 31 and the inverter 35 is performed.

Whether the input power is sufficient, that is, the reserve ratio of the input power, for example, calculates an average value of the input voltage measured by the measuring unit 40, and then obtains a standard deviation to know the amount of change in the voltage at the same time, The reserve ratio of the input power can be predicted (measured) by the amount of change in the input voltage.

For example, the measuring unit 40 of the controller 37 may measure an input voltage and an output current, and the measured data may be accumulated in the data storage unit 38. The voltage data accumulated in the data storage unit 38 at each corresponding time is accumulated together with the time-phase voltage data measured on the other day, and the time-phase variance between the average value of the total voltage measured at the same time and the measured voltage. The standard deviation of time can be obtained. Once the standard deviation over time has been obtained, it can be determined whether the standard deviation exceeds a predetermined set value, for example 2. If the standard deviation value exceeds 2, it can be determined that the input power reserve ratio is low; When the standard deviation value is less than 2 and the value obtained by subtracting the standard deviation from the voltage average value is less than a predetermined value, for example, less than 99% of the rated voltage, it may be determined that the input power reserve ratio is also low. On the other hand, when the standard deviation value is less than 2 and the value obtained by subtracting the standard deviation from the voltage average value is 99% or more of the rated voltage, it can be determined that the input power reserve ratio is high during the time period; When the standard deviation value is smaller than 2, but the voltage deviation exceeds 0, it may be determined that the input power reserve ratio is high.

The values measured by the measurement unit 40 are stored in the data storage unit 38 and determined to be in a state requiring input power reduction operation due to insufficient input power due to values and conditions calculated by accumulated data. In the section, the battery charger-discharger 32 is turned on by the control unit 39 and restricts the operation of the PWM rectifier 31 of the input terminal 30 as shown in FIG. The input power reduction operation shared by 33 is performed.

FIG. 4B measures the data of the reserve ratio of the input power measured by the measuring unit 40 and the load amount, and when the load of the output stage increases, the peak power to be charged by the input terminal 30 and the PWM rectifier 31 is measured. Shows an operation flowchart of the battery charge-discharge operation which is operated to bear the burden, that is, the operation flowchart of the input peak power reduction operation.

Referring to FIG. 5, the controller 37 determines whether the reserve ratio of the input power measured by the measuring unit 40 is less than a predetermined reference value, for example, 80% as described above (S100).

In step S100, when the reserve ratio of the input power exceeds the set reference value, the controller 37 operates by setting the current limit value of the PWM rectifier 31 to an initial setting value, that is, a default value (S150).

In step S100, when the reserve ratio of the input power is less than the set reference value, the controller 37 determines whether the load power measured by the measuring unit 40 is less than 50% of the rated power (S110).

In step S110, when the load power exceeds 50% of the rated power, the controller 37 sets the current limit value of the PWM rectifier 31 to an initial set value (S150); Otherwise, it is determined whether the load power is in the stabilization period (S120). Here, the determination of whether the load power is in the stabilization period may be performed as follows.

That is, the stabilization period of the load power is calculated by calculating the change amount by the derivative of the measured output stage output current, and the change amount is large (for example, the current change amount is averaged from the average value for 10 minutes including the current detection value). When the load power is unstable when the change is more than 10%), and the load power is unstable when the change amount is small ( when the change amount is less than 10% based on the average value from the 10-minute average value including the current detection value) Judging by

In step S120, when the load power is not in the stabilization period, the controller 37 sets the current limit value of the PWM rectifier 31 to an initial setting value (S150); Otherwise, it is determined whether the power of the battery 33 exceeds a battery power set value, for example, 70% (S130).

In step S130, when the battery power is less than the battery power set value, the controller 37 sets the current limit value of the PWM rectifier 31 as the initial set value (S150); Otherwise, the current limit of the PWM rectifier 31 is operated by limiting the current load power to a predetermined value, for example, 50% of the load power, and the shortage according to the limiting operation of the PWM rectifier 31 is caused by the battery charger-discharger 32. ) To be covered by the battery 33 power (S140).

According to the present invention, according to each operation shown in Figure 5, by limiting the operation of the PWM rectifier 31, and determines the operation of the battery charger-discharger 32, to prevent the power accident due to lack of input power reserve ratio In addition, a smooth and stable power can be supplied to the load.

Thus, the present invention is an uninterruptible power supply device capable of double conversion operation and low input power reduction operation according to the input power reserve ratio and the load amount, and the optimum power quality according to the load condition, the battery power, and the reserve ratio of the input power, and in a given situation. Optimum and stable operation can be realized.

So far, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. will be.

Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

31: PWM Rectifier
32: battery charger-discharger
33: battery
34: bypass switch
35: inverter
37: Controller
38: data storage
39: control unit
40:

Claims (9)

In the uninterruptible power supply,
A PWM rectifier converting an AC voltage input from the system into a DC voltage and supplying the DC voltage to a DC bus terminal;
An inverter converting a DC voltage supplied from a battery and the PWM rectifier into an alternating current and supplying it to a load;
A bypass switch that operates when directly supplying grid power to the load;
A controller for measuring input power reserve, load and battery power,
The controller
When the input power reserve ratio is lower than the set first reference value and the load amount is higher than the set second reference value, input peak power reduction operation for limiting the output of the PWM rectifier and supplying power by the battery is performed.
When the input power reserve ratio is higher than the first reference value and the load is lower than the second reference value, a double conversion operation is performed.
Uninterruptible power supply, characterized in that.
The method of claim 1,
The controller
A measuring unit for measuring the input power reserve ratio, the load amount and the battery power;
And a setting and a controller for controlling the PWM rectifier according to a set function, operation or mode, and setting a condition for performing an input power reduction function for the grid power and setting a discharge time of the battery during an input power reduction operation. Uninterruptible power supply, characterized in that made.
delete delete delete The method of claim 1,
When the controller performs the input peak power reduction operation, the controller sets the discharge time of the battery according to the battery power, and performs the input power reduction function only during the set time. .
The method of claim 1,
The controller determines the magnitude and the change of the load amount as an average value of the change in the load amount when measuring the change to the load amount.
The method of claim 1,
The uninterruptible power supply further comprises a battery charger-discharger for reducing the DC bus voltage to supply the battery to the battery, and for boosting the voltage of the battery to supply the battery to the DC bus. And a PWM rectifier, an inverter which converts a DC voltage into an alternating current and supplies the load to the load, a bypass switch that operates when the system power is directly supplied to the load, and a controller for controlling the operation of the bypass switch and the inverter. In the control method of the uninterruptible power supply,
A first step of determining, by the controller, whether the reserve ratio of the input power measured by the measurement unit is less than a predetermined reference value;
In the first step, if the preliminary ratio of the input power exceeds the set reference value, the controller operates the initial set value of the rectifier to operate by setting the current limit value of the PWM rectifier to the initial set value;
In the first step, if the reserve ratio of the input power is less than the set reference value, the controller determines whether the load power measured by the measuring unit is less than the predetermined value of the rated power;
In a second step, if the load power exceeds a predetermined value of the rated power, the controller performs an initial set point operating step of the rectifier; otherwise, a third step of determining whether the load power is in a stabilization period ;
In a third step, if the load power is not in the stabilization period, the controller performs an initial set point operating step of the rectifier, and otherwise determines whether the power of the battery exceeds a predetermined battery power set value. step;
In a fourth step, if the power of the battery is less than the predetermined battery power set value, the controller performs an initial setpoint operation step of the rectifier, otherwise the current limit of the PWM rectifier is set to a predetermined value of the current load power. Operating in a limited manner, wherein the deficit according to the limiting operation of the PWM rectifier is covered by the power of the battery.

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