KR100875530B1 - Transformerless Power Inverter Using Chopper Technology - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformerless power converter using chopper technology, and in particular, harmonics flowing back to the input side through pulse width modulation (PWM) regardless of voltages of commercial AC power (208V, 380V, 440V, 480V). A rectifying part for reducing the content to extract the AC current waveform and phase, and connecting to the rectifying part to convert the DC step-down voltage or the DC step-up voltage according to the voltage of the AC power source to charge or output the normal load to the battery The neutral point is always maintained at a constant level with respect to the neutral point shift phenomenon which may occur due to the DC link unit connecting the converter unit, the battery, and controlling the charge / discharge voltage and current of the battery, and the isolation transformer of the output circuit. Neutral point adjuster to extract the absolute value of current by applying unbalanced load Inverter section and two silicon control rectifier circuits (SCRs) for controlling the pulse width by dividing a plurality of pulses in a half cycle of the output waveform to stabilize the output voltage and stabilize the power of the variable load by eliminating or reducing the voltage. A total of three pairs in series are connected to each line (= RST line) in series and connected in parallel to the output peaks of the commercial AC power supply and the inverter unit, and outputs load power by removing overcurrent and high frequency of the commercial AC power supply. The present invention relates to a transformerless power converter using a chopper technology, characterized by a bypass circuit portion.

Description

Transformerless power converter using chopper technology {TRANSFORMERLESS POWER CONVERSION DEVICE USING CHOPPER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformerless power converter using chopper technology, and in particular, harmonics flowing back to the input side through pulse width modulation (PWM) regardless of voltages of commercial AC power (208V, 380V, 440V, 480V). Reduce the content to extract the AC current waveform and phase, convert to DC step-down voltage or DC step-up voltage according to the voltage of the AC power source to charge or output the normal load to the battery, connect the battery, and It controls the charge / discharge voltage and current of the battery, extracts the absolute value of the current by applying an unbalanced load so that the neutral point is always at a constant level against the neutral point shift phenomenon that may occur due to the absence of an isolation transformer of the output circuit, To eliminate or reduce harmonics to ensure fast control of the output voltage and stabilize the power supply of variable loads The pulses in the half cycle of the output waveform are divided into plural, and each pulse width is controlled by two pairs of control and silicon controlled rectifier circuits (SCRs), and a total of three pairs are connected in series to each line (= RST line). The present invention relates to a transformerless power converter using a chopper technology, which is connected in parallel to a power supply and an output peak of the inverter unit, and outputs load power by removing overcurrent and high frequency of the commercial AC power.

In general, in the case of medium and large information processing devices, when the power supply is interrupted, such as a power failure, the power converter is supplied with power to prepare for a problem in which data is lost during an emergency such as a power failure.

To this end, in a computer system that performs important tasks such as a large computer, a power converter is installed so that the computer can continue to 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 power converter to cope with unforeseen accidents due to power outages during work is the same, but the existing power converter is expensive and bulky, requiring a separate installation space for easy use This is not true. However, in recent years, due to the rapid spread of personal computers, the necessity and utilization of the above-described power converter in offices and homes is increasing.

In addition, the AVR (Automatic Voltage Regulator) is a device for constantly outputting an irregular voltage caused by the change in the input voltage, mainly used in conjunction with the above-described power conversion device to utilize the power failure compensation function and voltage adjustment function, Recently, various products having the functions of the power converter and the AVR have been developed.

1 and 2 is a block diagram of a power converter or a UPS / AVR combined power supply according to the prior art.

As shown in FIG. 1, the conventional power converter or UPS / AVR composite power supply device includes an A / D converter 4 for converting a commercial AC power into a DC, and converts the DC power into AC power. A D / A inverter (7) for supplying a load, a charger (5) for converting the commercial power into direct current to charge a battery (BATT), a DC-DC converter (6) for maintaining a constant voltage, and the D Synchronous switching unit 8 for selectively applying to the external system by using AC power of commercial AC power or D / A inverter 7 as output AC power in case of abnormality or overload of A / A inverter 7 and And a CPU 1 that monitors the input power and controls the operation of the synchronous transfer switch section 8. In the drawing, reference numeral 2 denotes a front panel for indicating a charging state and a power supply state of the battery Batt, 3 and 9 are noise filters, and D is a diode.

Hereinafter, the operation of the conventional power converter or UPS / AVR combined power supply 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 in normal operation, which charges a plurality of batteries BATT included 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.

In the above state, when commercial AC power is interrupted, the DC power of the battery BAT charged with the predetermined voltage passes through the DC-DC converter 6 and the diode D, and then the D / A inverter 7 By converting into an AC power source and applied to an external system through the synchronous transfer switch unit 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 directly to an external system by 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 having the above-described configuration, there is a computer main body, a monitor, a printer, a digitizer, a hub, a plotter, an external modem, and the like even in one computer system. On the other hand, there is a weak equipment in the irregular power supply, because the power converter or UPS and AVR function is used together, there is an advantage that does not have to pay a high cost because you do not purchase a power converter or UPS and AVR separately.

However, in the conventional uninterruptible power supply device, the uninterruptible power supply device causes a lot of deterioration in the reliability of the power supply line, such as deterioration of efficiency of the commercial line, generation of harmonic noise, and power factor distortion. In particular, the recent increase in capacitive load is causing the power plant to fail 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, from the load side, the output distortion of the uninterruptible power supply device in a non-linear load adversely affects the neighboring devices, thereby hindering the supply of high-quality used power, which necessitates the need for fundamental improvement.

In order to solve this problem, a power converter has been disclosed that prevents the output voltage from disconnecting and is strong in an electrical external environment. Hereinafter, another conventional power converter device will be described with reference to FIG. 2.

As shown in FIG. 2, the power converter or UPS / AVR combined power supply according to the related art outputs the input power input through the input switch 511 to the load side through the primary coil, but outputs the input. To control the load-side output to the input of the first transformer 513 by controlling the voltage and current of the first transformer 513 and the output of the first transformer 513 and the secondary coil of the first transformer 513 A filter circuit 514, a first inverter 515 for controlling the voltage and current of the filter circuit 514, a battery 516 for supplying uninterruptible power, and a power source for the battery 516 in case of power failure A second inverter 517 and the second inverter 517 for charging the battery 516 by converting it into an AC power and outputting it to the load side or receiving the input power from the load side in a normal state and converting it into a DC power source; And the first site A second transformer connected between the output load side of the transformer 513 and outputting the load side output power at the normal power to the second inverter 517 and outputting the output of the second inverter 517 to the load side power at the time of power failure; 518, an input voltage Vi and an input current iS at the rear end of the input switch 511, an output voltage VO and an output current iP at the load side connection terminal, and a direct current from the battery 516. Input and output detected by the high-speed detector 80 and the high-speed detector 80 for detecting the voltage (Vd), respectively, at high speed without a delay time by the resistor circuit to detect the signal detected using CT and PT A microprocessor 90 for receiving voltage, current and DC voltage, and setting various functions by key input to control uninterruptible control, automatic voltage control (AVR) function, and various monitoring, display and protection functions, and the like. PWM control of the microprocessor 90 The gate driver 70 outputs a signal for the PWM control of the first inverter 515 and the second inverter 517 based on the call, and the driver can operate the controller for various function setting, monitoring control, and setting value control. It comprises a keypad 100 to enable, and the LCD 110 for displaying the menu and set value indicator when setting the function as well as various status display.

However, in the composite power supply having the above-described configuration, the overcurrent is controlled by connecting one SCR 512 to the input switch 511 and the load line.

Accordingly, the SCR 512 has a disadvantage in that it is impossible to control overcurrent and abnormality generation in the power converter due to disconnection and inability, and it is impossible to detect the overcurrent flowing in the power converter even in normal operation.

An object of the present invention for solving the above problems of the prior art is to operate as a step-down chopper when charging the battery and to convert to a constant voltage suitable for the battery to charge, the original rectified voltage when the battery discharges during input power failure To provide a transformerless power converter using a chopper technology to convert the magnitude of the DC power to a switching power conversion technology for supplying a DC voltage to the inverter by operating as a boost chopper to boost to the same size.

Transformerless power converter using the chopper technology according to the present invention,

A rectifying unit for reducing the harmonic content flowing back to the input side through pulse width modulation (PWM) regardless of the voltages (208V, 380V, 440V, 480V) of the commercial AC power source to extract the AC current waveform and phase;

A bidirectional converter connected to the rectifier to convert a DC boosted voltage or a DC boosted voltage according to the voltage of the AC power source to charge or output a normal load to a battery;

A DC link unit connecting the battery and controlling the charge / discharge voltage and current of the battery;

A neutral point adjuster for extracting an absolute value of current by applying an unbalanced load to maintain the neutral point at a constant level with respect to the neutral point shift phenomenon which may occur due to the absence of an isolation transformer of an output circuit;

An inverter unit for controlling each pulse width by dividing a plurality of pulses in a half period of an output waveform to control high speed of the output voltage and stabilize the power of the variable load by removing or reducing harmonics; And

A total of three pairs are connected in series with each line (= RST line) by making a pair of two silicon controlled rectifier circuits (SCRs) in parallel to the commercial AC power supply and the output peak of the inverter unit, and the overcurrent of the commercial AC power supply. And a bypass circuit unit outputting a load power by removing high frequency.

The rectifier is connected to a total of three pairs of IGBTs in parallel by using two IGBTs as a pair of IGBTs, and each of the top and the other ends of the reactor and the capacitor connected one by one. Each of the pair of IGBT (IGBT) is characterized in that connecting the peak and the neutral (= N).

The bidirectional converter unit connects two IGBTs in parallel to the rectifying unit, and connects one reactor and one capacitor to each of the two IGBTs to one IGBT once. It is characterized in that the stepped chopper or the stepped up chopper by connecting the other end to the peak and the neutral line (= N).

The DC link unit connects a total of two pairs of capacitors in parallel using two capacitors as a pair, and simultaneously connects the two capacitors in parallel to the bidirectional converter unit and the two pairs of capacitors to input DC charge with a battery or stabilize the DC in the battery. Characterized in that the output.

The neutral point adjusting unit may connect two IGBTs in parallel to the DC link unit, and connect the vertex and the neutral line (= N) between the two IGBTs with one reactor.

Maintaining the constant level, the current of the reactor is detected by comparing the absolute value of the +,-current characterized in that the pulse width is adjusted so that the neutral point is always the center peak.

The inverter unit connects a total of three pairs of IGBTs in parallel to the neutral point adjusting unit using two IGBTs as a pair of IGBTs, and connects one reactor and one capacitor to each other. The vertex and the other end vertex are characterized in that a vertex and a neutral line (= N) are connected between the pair of IGBTs, respectively.

The present invention having the above-mentioned means for solving the problems is a transformerless power converter using chopper technology, which does not require an input and output transformer of the power converter, significantly reducing the installation area and weight, greatly improving efficiency, and reducing power costs, Cost reduction, harmonics reduction has the advantage.

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

3 is a block diagram of a transformerless power converter using a chopper technology according to an embodiment of the present invention, FIG. 4 is an internal functional block diagram of the microprocessor of FIG. 1, and FIG. 6 is a simplified circuit diagram of an uninterruptible power supply system of a transformerless power converter, and FIG. 6 is an exemplary view of a keypad and an LCD control panel of the power converter according to the present invention.

3 to 6, the transformerless power converter using the chopper technology according to the present invention, the rectifier (51, 251), the bi-directional converter (52, 252), the DC link (53, 253), the neutral point adjuster (54, 254) , Inverter unit 55, 255, bypass circuit unit 61, 261, gate drive 91, pulse width modulation (PWM) generator 92, microprocessor 93, input / output controller 94, keypad 96 , LCD 95, high-speed detection unit 97 constitutes a three-phase line with a temperature sensor and an alarm. In order to form a separate line from the input lines of the rectifiers 51 and 251, a total of three pairs are connected in series to each line (= RST line) by using two pairs of silicon-controlled rectifier circuits (SCRs). By connecting in parallel to the output peak of the commercial AC power supply and the inverter unit, the over-current and high frequency of the commercial AC power supply is removed to form a load power supply. That is, the normal power is output to the load side through the three phases (R, S, T), and the three phase (R, S, T) lines are formed in two places, and the two places are connected in parallel to bypass one place. The line is charged, the other one at normal load output. Neutral points without transformers are formed by forming a neutral line (= N, see FIG. 5) grounded at one point of a capacitor or a reactor, which is each element connected to the rectifiers 51 and 251, the neutral point adjuster 54 and 254, and the inverter units 55 and 255. To maintain.

Here, the rectifiers 51 and 251 reduce the harmonic content flowing back to the input side through the pulse width modulation PWM regardless of voltages 208 V, 380 V, 440 V, and 480 V of a commercial AC power source to adjust the AC current waveform and phase. Eject.

Here, the rectifiers 51 and 251 connect two IGBTs as a pair of IGBTs and connect a total of three pairs of IGBTs in parallel and connect one reactor and one capacitor to each other. The vertex and the other vertex are connected to the vertex and the neutral line (= N) between the pair of IGBTs, respectively. At this time, the circuit connecting the reactor and the capacitor is a smoothing circuit.

Here, the rectifiers 51 and 251 are used to control the sine wave voltage of the inverter unit 55 and use a unipolar PWM method in which the ripple voltage can be reduced by 2 times. The PWM signal is generated and controlled by the PWM generator 92 mounted on the internal program of the microprocessor 93. The sine wave frequency output from the inverter units 5 and 255 may be set by the keypad 96 and may be operated differently from the line frequency. That is, when the high speed detector 97 detects the input voltage Vin, frequency is detected by zero-crossing of the voltage, and when the input frequency and the output frequency are different, PWM is controlled according to the set output frequency. The output frequency can be set automatically to the set frequency.

Here, the bidirectional converters 52 and 252 are connected to the rectifiers 51 and 251 to convert the DC step-down voltage or the DC step-up voltage according to the voltage of the AC power to charge or output a normal load to the battery. That is, for example, in the case of a normal power supply, the bidirectional converters 52 and 252 output a normal load of 800V voltage, and step down some of the voltages to 400V, which is a charging voltage, to output the charging. In the case of a power failure operation, the 400V output voltage of the DC link units 53 and 253 is boosted to 800V voltage through the bidirectional converters 52 and 252 to output a 800V voltage to the bidirectional converters 52 and 252. Output it.

Here, the bidirectional converters 52 and 252 connect two IGBTs in parallel to the rectifier, and connect one reactor and one capacitor to each one of the two IGBTs. Step-down choppers or step-up choppers are connected to the IGBT once the peak and the neutral end (= N). In this case, the one end of the reactor and the capacitor and the neutral line (= N) are connected to operate as the step-down chopper during normal power operation and the step-up chopper during electrostatic power operation.

Here, the DC link units 53 and 253 connect the battery and control the charge / discharge voltage and current of the battery.

Here, the DC link units 53 and 253 connect two capacitors in parallel using two capacitors as a pair of capacitors, and simultaneously connect the two capacitors 52 and 252 and the two pairs of capacitors to a battery. DC charging input or DC stabilized output from the battery.

Here, the neutral point adjusters 54 and 254 extract an absolute value of current by applying an unbalanced load to maintain the neutral point at a constant level with respect to the neutral point shift phenomenon that may occur due to the absence of an isolation transformer of an output circuit. The method of maintaining the constant level detects the current in the reactor and compares the absolute value of the + and-currents to adjust the pulse width so that the neutral point is always the center vertex.

Here, the neutral point adjusters 54 and 254 connect two IGBTs connected in series to the DC link units 53 and 253 in series and connect a peak between the two IGBTs and the neutral line (= N). Connect to one reactor.

Here, the inverters 55 and 255 control the respective pulse widths by dividing a plurality of pulses within a half period of the output waveform in order to remove or reduce harmonics to stabilize the output voltage and stabilize the power of the variable load.

Here, the inverter units 55 and 255 connect two IGBTs to one pair of IGBTs and connect a total of three pairs of IGBTs to the neutral point adjusting units 54 and 254 in parallel. And one end of each of the capacitors and the other end of the vertex connect the vertex between the pair of IGBTs and the neutral line (= N), respectively.

Here, the bypass circuits 61 and 261 may connect a total of three pairs in series to each line (= RST line) with two pairs of silicon control rectifier circuits (SCRs) in series and the commercial AC power supply and the inverter units 55 and 255. The output power of the load is removed by parallel connection to the output peak of the power supply) and the overcurrent and high frequency of the commercial AC power supply are removed.

The microprocessor 93 includes an output voltage controller 931, a battery charge controller 932, a line voltage monitor 933, a mode setting unit 934, and a main controller 935.

Here, the output voltage control unit 931 controls the first inverter for the automatic voltage control (AVR) function to control the secondary side of the first IGBT through a filter circuit to control the output voltage. .

Here, the battery charging control unit 932 controls the charging voltage and the charging current of the battery.

Here, the line voltage monitoring unit 933 monitors the input and output voltages to perform display control and alarm control.

Here, the mode setting unit 934 stores and manages various mode setting values.

Here, the main control unit 935 controls each unit of the microprocessor 93, and also controls the selection of system operating conditions, alarm control, various protection functions, and bypass.

Here, the pulse width modulation (PWM) generator 92 controls the gates of the bidirectional converters 52 and 252 and the inverters 55 and 255 under the control of the main controller according to the control function of each of the micro processes 93. A pulse width modulation (PWM) signal for control is generated and output to the gate driver.

In addition, an 8-bit microcontroller, which shares key input processing and display control functions, is used as an input controller and an output controller to communicate with the microprocessor so that the keypad 96 and the display 95 are independent controllers. use.

Referring to the basic flow with reference to the configuration and circuit of the transformerless power converter using the chopper technology of Figures 3 and 5, first, the input power (Vin) is input through the input of the commercial power supply to the load side through the bypass circuit (61,261) Is output to At this time, the voltage and current of the reactor and the capacitor circuit of the rectifiers 51 and 251 are controlled to control the output voltage Vout to perform the AVR function. At this time, the rectifiers 51 and 251 reduce the harmonic content flowing back to the input side through the pulse width modulation PWM regardless of the voltages 208 V, 380 V, 440 V, and 480 V of the commercial AC power source to adjust the AC current waveform and phase. Eject.

Subsequently, the bidirectional converters 52 and 252 convert the DC voltage into DC voltage or DC voltage according to the voltage of the AC power to charge or output a normal load to the battery. In this case, the rectifiers 51 and 251 control the voltage, current, and frequency, and insulated gate bipolar transistor (IGBT) pulse width modulation (IGBT) using a high frequency switching method in accordance with circuit protection and load variation from abnormal occurrence such as overload, short circuit, and ground fault. PWM).

Subsequently, the DC link units 53 and 253 control the charge / discharge voltage and current of the battery.

Subsequently, the composition point adjusting unit 54 or 254 applies an unbalanced load to extract the absolute value of the current so that the neutral point can always maintain a constant level with respect to the neutral point shift phenomenon that may occur due to the absence of an isolation transformer of the output circuit.

Next, the AC power output from the rectifiers 51 and 251 is directly supplied to the load side by the inverters 55 and 255. At this time, the AC power is converted into a DC power and output to the battery for charging. In this case, only the converted DC power passes through the inverter units 55 and 255 and the DC link units 53 and 253 to charge the battery. In addition, when there is a power failure or when there is no input power for commercial power, DC power output from the battery is passed through the DC link units 53 and 253 and the inverter units 55 and 255 to be converted into AC power and supplied to the load side. That is, when the input power is out of power, the inverter units 55 and 255 are controlled by the control of the microprocessor 93 so that the DC power of the battery is controlled by the DC link units 53 and 253, the neutral point adjusting unit 54 and 254, and the inverter unit ( 55,255) is converted into AC power and the output power is supplied to the load side to operate as an uninterruptible power supply. In this case, the bidirectional converters 52 and 252 convert the voltage into the DC step-down voltage or the DC step-up voltage according to the voltage of the AC power to charge or output a normal load to the battery.

The high-speed detection unit 97 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 rectifiers 51 and 251.

The battery charging control unit 932 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. If 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 to detect 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 line voltage monitoring unit 933 determines whether the line voltage is normal or abnormal as a voltage difference from the normal voltage, and when the value is larger than the specified value, the inverter is operated. This is to monitor and control the input voltage, and it is possible to eliminate frequent changes between the line operation and the inverter operation through the hysteresis voltage at the boundary of the line voltage drop when detecting the line voltage.

In detecting whether the line voltage is abnormal, the sensitivity of the line voltage can be desensitized by using the detection time constant of the line voltage. If the frequency of the line voltage is out of the allowable range from the specified value, the inverter is operated without operating the line. The output is sent in 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 the line voltage when it is out of the system abnormal frequency or the system abnormal voltage. Operating only the inverter without operating at the line voltage is to cut off the bypass voltage unit 61 and 261 under the control of the microprocessor 93 so that the line voltage, that is, the input voltage is not output to the output load, and the inverter unit 55 and 255 are operated. ) To convert the battery's charging power to AC power and output it to the load side output voltage (Vout).

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 to operate the system automatically when all the batteries are discharged by the inverter operation and the line voltage is input. Select the operating method of contact terminals (a contact and b contact). In addition, 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. Therefore, the gain needs to be readjusted.

This can be adjusted in the fine calibration parameter, 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 95 using the rated output current. As the output voltage gain increases, the value appearing on the LCD 95 in line mode increases and decreases in constant voltage control in inverter mode.

The main control unit 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 power converter.

In the alarm function, the buzzer does not sound at normal line voltage, and the buzzer sounds when the inverter is operated at abnormal line voltage. The buzzer sounds differently by distinguishing inverter operation, abnormality caused by protection function, and battery low status.

When the inverter operates, the buzzer sounds, and when the alarm silent switch of the keypad 96 is pressed, the buzzer does not sound and the buzzer sounds when the switch is pressed again.

In case of an abnormal state, the buzzer will sound continuously. If the 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 power converter is stopped.

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

The battery undervoltage generates a battery undervoltage signal if the battery voltage is discharged to 85% of its rated voltage and fails to maintain the output voltage to an acceptable level. At this time, the inverter operates for 30 seconds at maximum. When the line voltage is restored from the battery low voltage, the inverter returns to normal operation.

The over current stops the system in order to protect the inverter when the overcurrent is continuously generated by 300% or more because the output current exceeds 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.

The 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 run and will return to normal when the battery is connected.

Bypass overcurrent causes an output short or fault when operating at line voltage to turn off the bypass switch to protect the bypass switch. The reference value of the abnormal current is an overcurrent value.

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. In system initialization, restart the system.

On the other hand, when the keypad 96 and the LCD 95 are configured as independent controllers, an input / output controller 94 which is an 8-bit microcontroller communicating with the microprocessor 93 as shown in FIG. 3 is further added. The control panel by the keypad 96 and the LCD 95, which are configured independently, has a state diagram showing the flow of the system at the top and two LEDs as shown in FIG. "Line" indicating normal, "Inverter" indicating that the inverter is operating, "Bypass" which input power is supplied to the output, "Fault" and "Overload" indicating that the system is abnormal.

In the LCD 95 configuration, the first line represents the overall situation of the power converter, and the second line represents various internal variables of the power converter. Displays the battery voltage capacity, battery voltage, battery current, output voltage, output current, input voltage, input current, output frequency, temperature, status display and power failure count, date and time, and the display selection is up and down of the keypad 96. Use keys to read the value.

"Mode" of the keypad 96 enters or exits a menu and controls the movement of a variable, and the up and down keys change the type and display variables of a variable value, and an alarm is turned on. Toggles the on / off status, "O", "I" means that the menu is selected or the parameter is set, the system is stopped and operated, and the system is restarted in the event of a fault.

In the power converter of the present invention operated by the microprocessor 93 performing the above functions, the commercial power supply operation and the battery power operation control are performed.

The normal operation is a commercial power supply operation mode, which removes the overcurrent and the high frequency of the input power, is controlled and output to the desired power on the load side, and is rectified by the rectifiers 51 and 251 by the high frequency switching method. Only the AVR function is controlled through a chopper circuit formed of a reactor and a capacitor so as to control modulation (PWM), and power fed back from the output is connected to the inverter units 55 and 255 and the DC link units 53 and 253. The battery is operated in the charging mode to return to normal operation.

The power failure operation is operated as a battery power operation mode in which the power of the battery is output to the load side by controlling the inverter units 55 and 255 and the DC link units 53 and 253 when a power failure of the input power is detected.

In case of power failure return, input power is outputted to the load side through the bypass circuits 61 and 261, and power fed back from the output is charged to the battery through the inverter units 55 and 255 and the DC link units 53 and 253, and is operated normally. Is returned.

As described above, the transformerless power conversion device using the chopper technology of the present invention operates the bidirectional converter unit as a step-down chopper when charging the battery, and converts the DC high voltage rectified by the rectifier into a constant voltage suitable for the battery and charges the battery during an input power failure. Is discharged by switching power conversion technology that supplies DC voltage to the inverter by operating as a boost chopper to boost to the same size as the original rectified voltage. As a result, the installation area and weight are greatly reduced, and the efficiency is greatly improved, thereby reducing power costs, cost reduction, and harmonics.

Although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto, and the technical spirit of the present invention and the claims to be described below by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents.

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

2 is a simplified circuit diagram of yet another conventional power converter or UPS / AVR combined power supply.

Figure 3 is a schematic diagram of a transformerless power converter using a chopper technology showing an embodiment according to the present invention.

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

5 is a simplified circuit diagram of an uninterruptible power supply system of a transformerless power converter using the chopper technology according to the present invention.

Figure 6 is an exemplary control panel of the keypad and LCD of the power converter according to the present invention.

<Description of the symbols for the main parts of the drawings>

51,251: rectifier 52,252: bidirectional converter

53,253: DC link unit 54,254: neutral point adjustment unit

55,255: inverter 61,261: bypass circuit

91: gate drive 92: pulse width modulation (PWM) generator

93 microprocessor 94 input / output controller

95: LCD 96: keypad

931: output voltage control unit 932: battery charge control unit

933: line voltage monitoring unit 934: setting unit for each mode

935 main controller

Claims (7)

A rectifying unit for reducing the harmonic content flowing back to the input side through pulse width modulation (PWM) regardless of the voltages (208V, 380V, 440V, 480V) of the commercial AC power source to extract the AC current waveform and phase; A bidirectional converter connected to the rectifier to convert a DC boosted voltage or a DC boosted voltage according to the voltage of the AC power source to charge or output a normal load to a battery; A DC link unit connecting the battery and controlling the charge / discharge voltage and current of the battery; A neutral point adjuster for extracting an absolute value of current by applying an unbalanced load to maintain the neutral point at a constant level with respect to the neutral point shift phenomenon which may occur due to the absence of an isolation transformer of an output circuit; An inverter unit for controlling each pulse width by dividing a plurality of pulses in a half period of an output waveform to control high speed of the output voltage and stabilize the power of the variable load by removing or reducing harmonics; And A total of three pairs are connected in series with each line (= RST line) by making a pair of two silicon controlled rectifier circuits (SCRs) in parallel to the commercial AC power supply and the output peak of the inverter unit, and the overcurrent of the commercial AC power supply. And a bypass circuit unit for outputting a load power by removing high frequency waves. The method of claim 1, The rectifying unit, A total of three pairs of IGBTs are connected in parallel using two IGBTs as a pair of IGBTs, and one reactor and one capacitor are connected to each other. Transformerless power converter using chopper technology characterized by connecting the peak and the neutral (= N) between a pair of IGBT (IGBT). The method of claim 1, The bidirectional converter unit, Two IGBTs are connected in parallel to the rectifier, and one reactor and one capacitor are connected to one of the two IGBTs, and the vertex and the neutral line (= A transformerless power converter using a chopper technology, characterized in that the step-down chopper or the step-up chopper is connected by connecting the other end to N). The method of claim 1, The DC link unit, A total of two pairs of capacitors are connected in parallel using two capacitors as a pair, and the DC charging input is performed by a battery or a DC stabilization output is performed from the battery by simultaneously connecting the two capacitors in parallel to the bidirectional converter unit and the two pairs of capacitors. Transformerless power converter using chopper technology. The method of claim 1, The neutral point adjustment unit, Transformerless using chopper technology, wherein two IGBTs are connected in parallel to the DC link unit, and a peak and a neutral line (= N) between the two IGBTs are connected by one reactor. Power inverter. The method of claim 1, Maintain the constant level, A transformerless power converter using a chopper technique that detects current in a reactor and compares absolute values of + and-currents to adjust the pulse width so that the neutral point is always the center peak. The method of claim 1, The inverter unit, A total of three pairs of IGBTs are connected in parallel to the neutral point controller with two IGBTs as one pair of IGBTs, and one reactor and one capacitor are connected to each other. Transformerless power converter using the chopper technology, characterized in that connecting the peak and the neutral (= N) between the pair of IGBT (IGBT), respectively.

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