KR100653284B1 - Digital uninterruptible power supply system for three phases - Google Patents

Abstract

A digital UPS(Uninterruptible Power Supply) system for three phases is provided to prevent the disconnection of output voltage by rapidly detecting the voltage of three phases input/single phase output. In a digital UPS system for three phases, a first transformer(12) transforms power inputted through a three phases input switch(11) to a single phase. A distribution switch(13) switches the power inputted from the first transformer(12). A second transformer(10) outputs the power to a load side through a primary coil. A chopper circuit(20) controls the voltage/current of a secondary coil of the second transformer(10) and the output for input of the second transformer(10). A first inverter(30) controls the voltage and current of the chopper circuit(20). A battery(40) supplies uninterruptible power. A second inverter(50) transforms the battery power to AC power during the interruption of power. A third transformer(60) is connected between the second inverter(50) and an output load side of the second transformer(10). A high speed detecting unit(80) detects input voltage(Vi) and input current(Is) from the rear end of the input switch(11), output voltage(Vo) and output current(Ip) from the connecting end of the load side, and DC voltage from the battery(40). A microprocessor(900) controls the uninterruptible power, an automatic voltage regulating function, and various monitoring, displaying, and protections functions. A gate driver(70) outputs pulse width modulation control signals of the first inverter(30) and the second inverter(50). A key pad(100) is manipulated by an operator for setting various functions and monitoring control. An LCD(110) displays various states and menus for setting functions.

Description

Digital uninterruptible power supply system for three phases}

1 is a block diagram of a UPS / AVR combined power supply according to the prior art.

Figure 2 is a configuration of a UPS system showing an embodiment according to the present invention.

3 is an internal functional block diagram of the microprocessor of FIG.

4 is a configuration diagram of another embodiment of the UPS system according to the present invention;

5 is a simplified circuit diagram of a UPS system according to the present invention.

6A to 6F are explanatory diagrams showing power flow paths for respective operation modes of the UPS system according to the present invention;

Figure 7 is an exemplary control panel of the keypad and LCD of the UPS system according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10: second transformer 11: three-phase input switch

12: first transformer 13: distribution switch

14: SCR 20: Chopper Circuit

30: first inverter 40: battery

50: second inverter 60: third transformer

70: gate driver 80: high speed detection unit

90: microprocessor 91: pulse width modulation (PWM) generator

92: output voltage control unit 93: main control unit

94: battery charge control unit 95: three-phase voltage monitoring unit

96: mode setting unit 100: keypad

110: LCD 120: input / output controller

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital uninterruptible power supply (UPS) system, which is a high-efficiency, high-performance online UPS that controls the inverter output voltage at a constant voltage while outputting the output and the input and input power. Serial and parallel type 3-phase input / single-phase output online digital type that performs the function of automatic voltage regulator (hereinafter referred to as 'AVR') to control the buffer voltage of the controller. It is about a PS system.

In general, in case of medium and large information processing devices, when the power supply is interrupted such as a power failure, the data of the uninterruptible power supply (hereinafter referred to as a UPS) is supplied so that working data is lost during an emergency such as a power failure. I am preparing for a problem.

That is, in general, the computer stores the working data in RAM, so if the power supply is interrupted during the operation, many data in the work disappear, and there is no way to restore the data, so it is inconvenient to rework. There is this. Therefore, in computer systems that perform important tasks such as large computers, an uninterruptible power supply (UPS) is installed so that the computer can be supplied with power even when the power supply from the power company is interrupted.

On the other hand, even in a personal computer (PC), the need for a UPS to cope with unforeseen accidents due to a power outage during work is the same, but the conventional UPS is expensive and bulky and requires a separate installation space is not easily used However, in recent years, due to the rapid spread of personal computers, the necessity and utilization of the above-mentioned UPS are increasing in offices and homes.

In addition, the AVR (Automatic Voltage Regulator) is a device that constantly outputs irregular voltage caused by the change of the input voltage. It is mainly used with the UPS, and thus the power failure compensation function and the voltage regulation function are used simultaneously. Various products having the functions of the UPS and the AVR are being developed.

1 is a block diagram of a UPS / AVR combined power supply according to the prior art.

Referring to FIG. 1, the conventional UPS / AVR composite power supply apparatus includes an A / D converter 4 for converting a commercial AC power into a DC, and a D / A converting the DC power into AC power and supplying it to a load. Of the inverter 7, the charger 5 for converting the commercial power into direct current to charge the battery Batt, the DC-DC converter 6 for maintaining a constant voltage, and the D / A inverter 7 In case of abnormality or overload, the synchronous transfer switch unit 8 and the input power are selectively monitored by applying the AC power of the commercial AC power source or the D / A inverter 7 as an output AC power source to the external system. It consists of CPU1 which controls the operation | movement of the switching switch part 8. As shown in FIG. In the drawing, reference numeral 2 denotes a front panel for displaying a charging state and a power supply state of a battery, and 3 and 9 are noise filters.

Hereinafter, the operation of the conventional UPS / AVR combined power supply device will be described.

First, the commercial AC power input via the input terminal is converted from the A / D converter 4 to the DC power during normal operation, which charges a plurality of batteries provided in the charger 5. In addition, the DC power of the A / D converter 4 is converted into the AC power in the D / A inverter 7 and applied to the external system through the synchronous transfer switch unit 8 and the plurality of output terminals. At this time, the DC-DC converter 6 adjusts the low voltage and the overvoltage step by step to uniformly output the irregular voltage caused by the change of the input voltage.

When commercial AC power is interrupted in the above state, the DC power of the battery charged with the predetermined voltage passes through the DC-DC converter 6 and the diode D, and then the D / A inverter 7 is converted into AC power. By being converted and applied to an external system through the synchronous transfer switch section 8, the external system can operate stably despite a power failure.

If the commercial AC power is applied again during this operation, the charger 5 again charges the battery BATT.

In addition, when an abnormality occurs in the D / A inverter 7, the CPU 1 detects this and bypasses the commercial AC power supply directly to an external system by a switching operation of the synchronous transfer switch unit 8. In this case, the user may recognize that an abnormality occurs by looking at the battery state on the front panel 2.

According to the prior art, for example, a single computer system includes a computer main body, a monitor, a printer, a digitizer, a hub, a plotter, an external modem, and the like, which requires and does not require power compensation during a power failure. On the other hand, because there are weak equipment in the irregular power supply, by using the UPS and the AVR function, there is an advantage that you do not have to pay expensive costs because you do not purchase the UPS and AVR separately.

However, in the conventional uninterruptible power supply, the uninterruptible power supply has caused a lot of deterioration in the reliability of the power supply line, such as a decrease in efficiency of the commercial line, generation of harmonic noise, and power factor distortion. In particular, due to the recent increase in capacitive loads, there are disturbances in power plants due to harmonic currents, and the problem of peak power is so severe that there is a need for countermeasures caused by the uninterruptible power supply itself.

In addition, in terms of load, the output distortion of the uninterruptible power supply in the nonlinear load adversely affects the neighboring devices, thereby hindering the supply of high-quality used power, thereby increasing the need for fundamental improvement.

Therefore, the present invention devised to solve the above problems is to use the main controller as a microprocessor, all the functions are softwareized, including the generation of inverter pulse width modulation (PWM) and bypass power semiconductor switching pulse signal generation The purpose is to provide a highly functional UPS by setting various parameters related to the system to be memorized.

In addition, the present invention is to provide a UPS that the LCD control for keypad input signal processing and monitoring is processed in communication with the main controller using an 8-BIT PIC micro-controller to be strong and separated operation in the electrical external environment. will be.

In addition, the present invention is to provide an on-line PUS that is output so that the output voltage is not disconnected in connection with the line voltage and the transfer time is ignored through a rapid detection technique of the three-phase input / single phase output voltage.

In addition, the present invention supplies energy to the load through the line with high efficiency under normal three-phase input / single-phase output voltage, and the inverter generates a voltage almost the same as the three-phase input / single-phase output voltage to charge the abnormal voltage while charging It is to provide the UPS.

UPS according to the present invention for achieving the above object, and a first transformer for converting the input power input through the three-phase input switch into a single phase; A distribution switch for switching the input power input through the first transformer; A second transformer for outputting the power input through the distribution switch to the load side through the primary coil, and controlling the output for the input to output the load to the load side; A chopper circuit for controlling the voltage / current of the secondary coil of the second transformer to control the output to the input of the second transformer; A first inverter for controlling the voltage and current of the chopper circuit; A battery for supplying uninterruptible power; A second inverter for converting the battery power into an AC power and outputting it to a load side during a power failure, or receiving the Iric power from the load side and converting the battery power into a DC power to charge the battery; A third transformer connected between the second inverter and the output load side of the second transformer and outputting a load side output power to the inverter during a normal power supply and an output of the inverter to the load side power during a power failure; An input voltage Vi and an input current Is at the rear end of the input switch, an output voltage Vo and an output current Ip at the load side connection terminal, and a DC voltage Vd at the battery are respectively detected. A high speed detector for detecting a signal detected using the CT and the transformer PT at high speed without delay time by a resistance circuit; Input / output voltage and current and DC voltage detected by the high speed detection unit are input, and various functions are set by key input to control uninterruptible control, automatic voltage control (AVR) function, various monitoring, display and protection functions, etc. A microprocessor for; A gate driver configured to output a pulse width modulation (PWM) control signal of the first inverter and the second inverter based on a pulse width modulation (PWM) control signal of the microprocessor; It includes a keypad for allowing the operator to operate for various function setting, monitoring control, and set value control, and various status displays, as well as an LCD for displaying menus and setting value indicators when setting functions.

The microprocessor includes: an output voltage controller for controlling the output voltage by controlling the first inverter for the AVR function and controlling the secondary side of the second transformer through the chopper circuit; A battery charging control unit controlling a charging voltage and a charging current of the battery; A line voltage monitoring unit for monitoring input and output voltages and performing display control and alarm control thereof; A mode setting unit for storing and managing various mode setting values; A main control unit for controlling each unit and controlling selection of system operating conditions, alarm control, various protection functions and bypasses; And a pulse width modulation generator for generating a pulse width modulation signal for controlling the gate of the first inverter and the second inverter under the control of the main controller, and outputting the pulse width modulation signal to the gate driver. .

When the keypad and the LCD are separately configured, an 8-bit microcontroller can be used as an input / output controller to communicate with the microprocessor so that independent configuration is possible and the key input processing and display control functions of the microprocessor are controlled. Can be configured to share.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram of a UPS system showing an embodiment according to the present invention, FIG. 3 is a block diagram illustrating an internal function of the microprocessor of FIG. 2, and FIG. 4 is a block diagram of another embodiment of the UPS system according to the present invention. 5 is a simplified circuit diagram of a UPS system according to the present invention.

2 to 5, the UPS system according to the present invention includes a first transformer 12 for converting an input power input through a three-phase input switch 11 into a single phase, and the first transformer 12. Distribution switch 13 for switching the power input through the) and outputs the power input through the distribution switch 13 to the load side through the primary coil, the output to the load side by controlling the output for the input A chopper circuit 20 for controlling the voltage / current of the second transformer 10 and the secondary coil of the second transformer 10 to control the load side output to the input of the second transformer 10, and The first inverter 30 for controlling the voltage and current of the chopper circuit 20, the battery 40 for supplying the uninterruptible power, and the battery 40 in the case of power failure are converted to AC power and output to the load side. Or from the load side at the time of normal It is connected between the second inverter 50 and the output load side of the second inverter 50 and the second transformer 10 for charging the battery 40 by converting the power into DC power and receiving a normal power source. A third transformer 60 outputting an output of the load-side output power to the second inverter 50, an output of the second inverter 50 to the load-side power during a power failure, and an input voltage at a rear end of the input switch 11. (Vi) and the input current (Is), the output voltage (Vo) and the output current (Ip) at the load-side connection terminal, and the DC voltage (Vd) at the battery 40, respectively, PT) and a current transformer (CT) to detect a signal detected by the resistance circuit at high speed without delay, the input / output voltage detected by the high speed detector 80 and Receives current and DC voltage and various inputs by key input The microprocessor 900 for controlling the uninterruptible control, automatic voltage control (AVR) function, species monitoring, display and protection functions by setting the function, and the pulse width modulation control signal of the microprocessor The gate driver 70 which outputs a signal to the pulse width modulation control of the first inverter 30 and the second inverter 50, and the driver to operate for various function setting and monitoring control and set value control It comprises a keypad 100 and an LCD 110 for displaying various statuses, as well as displaying menus and setting value indicators at the time of function setting.

Here, the transformer (PT), the current transformer (CT) for detecting the voltage and current of the input terminal and the output terminal in the drawing is not shown in the drawing, but this detection in the UPS system circuit is obvious to those skilled in the art. To omit them.

In addition, the SCR 12 is installed in any one-phase power line of the three-phase power line in parallel with the second transformer 10 and configured to control the emergency shutoff by the microprocessor 900.

On the other hand, the microprocessor 900 is to control the core functions of the present invention by a program as shown in FIG.

The microprocessor 900, an output voltage control unit for controlling the output voltage by controlling the secondary side of the second transformer 10 through the chopper circuit 20 by controlling the first inverter 30 for the AVR function (92), the battery charging control unit 94 for controlling the charging voltage and the charging current of the battery 40, and the line voltage monitoring unit for monitoring the input and output voltage to display and control information on the input and output voltage 95, a mode setting unit 96 for storing and managing setting values for various modes, control of each unit, selection of system operating conditions, test operation, alarm control, various protection functions, bypass, etc. A pulse width for controlling the gate of the first inverter 30 and the second inverter 50 under the control of the main control unit 93 and the main control unit 93 according to the control function of each unit. Generating a modulated signal And a pulse width modulation generator 91 for outputting to the gate driver 70.

As shown in FIG. 7, when the keypad and the LCD are configured as independent controllers, as shown in FIG. 4, an 8-bit microcontroller is used as the input / output controller 120 and the microprocessor 900. Communication allows for independent configuration and can be configured to share the microprocessor's keystroke processing and display control functions.

Referring to the operation and effects of the present invention configured as described above are as follows.

The present invention performs an AVR function simultaneously with a function as an uninterruptible power supply, and operates as a high-efficiency, high-performance online PC by converting the main word into software. To maximize the efficiency at the available line voltage, the inverter controls the output voltage to a constant voltage while the AVR function controls the buffer voltage between the output and the input so that the output power is supplied from the line. All functions are software-configured and the various parameters associated with the system are stored on the keypad.

First, referring to the circuit of FIG. 5, the basic flow will be described. The input power Vi input through the three-phase input switch 11 is converted into a single phase through the first transformer 12 to convert the distribution switch 13. Through the primary coil of the second transformer 12 and output to the load side. At this time, the voltage and current of the secondary coil of the second transformer 10 are controlled by the chopper circuit 20 to control the output voltage Vo to perform the AVR function. The chopper circuit 20 is controlled by the first inverter 30. The first inverter 30 is PWM controlled by the control of the microprocessor 900.

In a normal power input situation, the output load side voltage Vo is connected to the second inverter 50 through the third transformer 60, and the second inverter 50 is controlled by the microprocessor 900. After conversion to the battery 40 is charged.

When the input power is out of power, the second inverter 50 is controlled by the control of the microprocessor 900 so that the DC power of the battery 40 is converted into AC power, and the output load side is transferred through the third transformer 60. It is supplied to and operated as an uninterruptible power supply.

The pulse width modulation (PWM) control of the present invention is used for the inverter sine wave voltage control, and uses a unipolar PWM method that is more complicated in the control method than the conventional bipolar PWM method, but the ripple voltage can be reduced by about 2 times. . This is controlled by the PWM generator 91 on the internal program of the microprocessor 900 of FIG. The sinusoidal frequency output from the inverter may be set by the keypad and may be operated differently from the line frequency. That is, when the high speed detector 80 detects the input voltage Vi, the frequency is detected by zero crossing of the voltage, and when the input frequency and the output frequency are different, the pulse width modulation is controlled according to the set output frequency to automatically output the frequency. Can be set to the set frequency.

The output voltage controller 92 controls the function of the automatic voltage regulator (AVR) that matches the measured output voltage with the reference output voltage. The voltage control and output is performed to obtain responsiveness and stability to the load. Perform the current compensation control function. The high speed detector 80 detects an input voltage and an input current, an output voltage and an output current, and performs calculation processing to match the set output voltage and output current to PWM control the first inverter 30. Accordingly, the voltage and current of the secondary coil of the second transformer 10 are controlled through the chopper circuit 20 to compensate for the output voltage and the output current, thereby performing the AVR function.

The battery charge control unit 94 performs a floating charge for charging up to a general float charging voltage, and even charging for charging up to a maximum charging voltage at the time of initial installation or charging after being discharged to a battery low voltage. Limited to maximum charging current. When the charging current reaches 10% or less of the maximum charging current value during even charging, it enters the floating charging. The charging current control calculates the effective current based on the difference between the input current and the output current and detects the battery charging current.When charging by limiting to the maximum charging current value and reaching full charge, the charging current is reduced by the constant voltage control function. Charge current responsiveness is determined by the charge control gain. In the temperature compensation of the even charging voltage, if the temperature drops below room temperature, the charging voltage is increased. Temperature compensation at temperatures above room temperature uses positive temperature compensation, and compensation at low temperatures uses negative temperature compensation.

The three-phase voltage monitoring unit 95 determines whether the normal and abnormality of the three-phase voltage is a voltage difference from the normal voltage, and if the value is larger than the specified value, the inverters are operated. This is to monitor and control the input voltage, and it is possible to eliminate the frequent change between the three-phase operation and the inverter operation through the hysteresis voltage at the boundary of the three-phase voltage drop when detecting the three-phase voltage.

In detecting abnormality of three-phase voltage, the detection time constant of the three-phase voltage can be used to reduce the sensitivity of the three-phase voltage. Only the inverter operates and sends the output to the battery voltage.

In other words, the voltage monitoring applies the system hysteresis voltage, reduces the frequent change by using the system voltage time constant, and operates the inverter only without operating as a three-phase voltage when it is out of the system abnormal frequency or the system abnormal voltage. Operating only the inverter without operating with the three-phase voltage is to cut off the three-phase voltage, that is, the input voltage to the output load by blocking the SCR 14 under the control of the microprocessor 900, the second inverter 50 ) To convert the charging power of the battery 40 to AC power to output to the load side output voltage (Vo).

The setting unit 96 for each mode is for setting various setting values, and sets and stores various setting values by menu selection of the keypad 100. Then, as a selection function, it is possible to select whether the operating frequency of the system is 60Hz or 50Hz, select whether or not to operate the system automatically when all batteries are discharged by the inverter operation and 3 phase voltage comes in. Relay contact terminal (a contact and b contact) Select the operation method.

Also, if the gain is not correct when accepting or outputting numerical values from analog data for fine calibration, an error will occur in the processor, and the gain needs to be readjusted.

This can be adjusted in fine calibration parameters, where the battery voltage gain is the measurement gain of the battery voltage, the output voltage gain is the measurement gain of the output voltage, the output current gain is the measurement gain of the output current, and the charge current gain is the charge current. The measured gain of the input voltage gain adjusts the measured gain of the input voltage. These variables are displayed on the LCD 110 using the rated output current. As the output voltage gain increases, the value displayed on the LCD in 3-phase mode increases and decreases in constant voltage control in inverter mode.

The main controller 93 controls the respective units and controls the PWM generator 91 according to the control function of each unit to execute the main control of the actual UPS system. In the alarm function, the buzzer does not sound at the normal three-phase voltage, and the buzzer sounds when the inverter is operated at an abnormal three-phase voltage. Buzzer sounds differently by distinguishing inverter operation, abnormality caused by protection function, battery low status, etc.

When the inverter is operating, the buzzer sounds, and when the alarm silent switch of the keypad 100 is pressed, the buzzer does not sound without pressing the switch again. In case of an abnormal state, the buzzer will sound continuously, and if the momentary overload is not abnormal, the buzzer will sound continuously and if the overload is released, the buzzer will not sound. The buzzer also sounds when the UPS system is stopped.

The protection function controls the battery undervoltage state, overcurrent, overload, battery abnormality, bypass overcurrent and the like as a protection function.

The battery undervoltage generates a battery undervoltage signal when the battery voltage is discharged to 85% of the rated voltage and the output voltage is not maintained to the allowable value. At this time, the inverter operates for 30 seconds at maximum. When the 3-phase voltage is restored from the battery low voltage, the inverter returns to normal operation.

The overcurrent stops the system in order to protect the inverter when the overcurrent continuously occurs over 300% due to the output current exceeding the load state in the inverter operation.

Overload is to protect the inverter from overload. If the output current is greater than the accumulated amount of up to 1 minute due to the overload set during operation over the rated current, it is recognized as overload.

Battery abnormality generates an abnormal signal and stops the inverter when the battery voltage is discharged to 85% of the rated voltage in the inverter operation. If the input power is applied, the battery will be alarmed even when the battery is open. In this case, the inverter will continue to operate and will return to normal when the battery is connected.

Bypass overcurrent turns off the bypass switch to protect the bypass switch when an output short or fault occurs when operating on a three-phase voltage. The reference value of the abnormal current is an overcurrent value.

When the test terminal of the keypad is pressed to test the inverter regardless of the three-phase voltage, the test function turns off the SCR 14 to operate the inverter for 10 seconds before entering normal operation.

Initialization functions include fault initialization, parameter initialization, and system initialization. Fault initialization removes past fault records and prepares them for readiness. Parameter initialization sets all variables or selection functions to their default values. System initialization restarts the system.

Meanwhile, when the keypad and the LCD are configured as independent controllers, the input / output controller 120 which is an 8-bit microcontroller communicating with the microprocessor 900 may be further configured as shown in FIG. 4. Independently configured keypad and LCD control panel has three LEDs at the top, as shown in Figure 7 "Line" indicating the normality of the input power, and is operated by the inverter due to the abnormal input power And "Flt" to indicate system abnormality.

In the LCD 110, the first line represents the overall situation of the UE, and the second line represents various internal variables of the UE. Battery voltage capacity, battery voltage, battery current, output voltage, output current, input voltage. Input current, output frequency, temperature, status display and the number of times of power outage, date and time, etc., the display selection to read the value using the up and down keys of the keypad (100).

The "Menu ESC" of the keypad 100 enters or exits a menu and controls the shifting of variables. Up and down keys change the value of the variable value, change the menu type and display variable, alarm changes the on / off status of the alarm, "SET RUN STP", the menu is selected or the variable is set, Stop and run, restart the system in case of failure.

The UPS system of the present invention by the microprocessor performing the above functions, the three-phase operation, the inverter operation and the bypass control, the state is as shown in Figure 6a to 6f.

Normal operation is a three-phase operation mode, the input power is output to the load side, as shown in Figure 6a, the first inverter 30 through the chopper circuit 20 to the secondary coil of the second transformer 10 By controlling, only the AVR function is controlled, and the battery 40 is charged by the function of the second inverter 50.

As illustrated in FIG. 6B, the power failure operation is operated as an inverter mode in which the power of the battery 40 is output to the load side by controlling the second inverter 50 when the power failure of the input power is detected.

In the power failure return, as shown in FIG. 6C, the input is output to the load side, and the power fed back from the output is operated as the charging mode to the battery 40 through the second inverter, and the first inverter 30 and the chopper circuit ( The secondary side of the second transformer 10 is controlled through 30 to return to normal operation with the AVR function.

Bypass, as shown in Fig. 6D, does not control the inverter, that is, the UPS does not operate and controls the bypass function in which the input power is transferred to the load side as it is.

Emergency bypass is a maintenance bypass switch (MBS) is provided in parallel with the UPS system of the present invention, as shown in Figure 6e is to transmit the input power to the load side through the emergency switch, and cut off the SCR It is to prevent the operation of the PS in case of troubleshooting or other emergency.

6F, the input power is automatically output to the load side by the bypass path by not operating the inverter as shown in FIG. 6F, and is operated when it cannot be handled within the system.

As described in detail above, the present invention is a digital UPS system, which can also function as an AVR function in order to maximize efficiency at a three-phase input voltage. It has the effect of providing a power factor, a high-performance PU system.

Claims (3)

A first transformer for converting the input power input through the three-phase input switch into a single phase; A distribution switch for switching the input power input through the first transformer; A second transformer for outputting the power input through the distribution switch to the load side through the primary coil, and controlling the output for the input to output the load to the load side; A chopper circuit for controlling an output of an input of the second transformer by controlling the voltage / current of the secondary coil of the second transformer; A first inverter for controlling the voltage and current of the chopper circuit; A battery for supplying uninterruptible power; A second inverter for converting the battery power into an AC power and outputting it to a load side during a power failure, or receiving the input power from the load side in normal operation, converting the battery power into a DC power, and charging the battery; A third transformer connected between the second inverter and the output load side of the second transformer and outputting a load side output power to the inverter during a normal power supply and an output of the inverter to the load side power during a power failure; An input voltage Vi and an input current Is at the rear end of the input switch, an output voltage Vo and an output current Ip at the load side connection terminal, and a DC voltage Vd at the battery are respectively detected. A high speed detector for detecting a signal detected using the CT and the transformer PT at high speed without delay time by a resistance circuit; Receiving input / output voltage and current and DC voltage detected by the high speed detector, and setting various functions by key input to control uninterruptible control, automatic voltage control (AVR) function, and various monitoring, display and protection functions. A microprocessor for; A gate driver configured to output a pulse width modulation (PWM) control signal of the first inverter and the second inverter based on a pulse width modulation (PWM) control signal of the microprocessor; And 3, characterized in that it comprises a keypad for allowing the operator to operate for various function setting and monitoring control and set value control, and a status display, and a display (LCD) for displaying menus and setting values when setting functions. 3-phase digital PC system. The method of claim 1, The microprocessor includes an output voltage controller for controlling the output voltage by controlling the first inverter to control the secondary voltage of the second transformer through a chopper circuit for an automatic voltage control (AVR) function; A battery charging control unit controlling a charging voltage and a charging current of the battery; A three-phase voltage monitoring unit configured to monitor the input and output voltages and perform alarm control and display control thereon; A mode setting unit for storing and managing various mode setting values; A main control unit for controlling each unit and controlling selection of system operating conditions, alarm control, various protection functions, and bypass; And A pulse width modulation (PWM) signal for generating a pulse width modulation (PWM) signal for controlling the gate of the first inverter and the second inverter by the control of the main controller according to the control function of each unit Three-phase digital UPS system, characterized in that composed of a generator. The method according to claim 1 or 2, Three-phase digital, characterized in that the keypad and display (LCD) are configured as independent controllers by communicating with the microprocessor using an 8-bit microcontroller that shares key input processing and display control functions as an input / output controller. UPS system.

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