KR20140096200A - Apparatus for converting power and air conditioner having the same - Google Patents

Apparatus for converting power and air conditioner having the same Download PDF

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KR20140096200A
KR20140096200A KR1020130004135A KR20130004135A KR20140096200A KR 20140096200 A KR20140096200 A KR 20140096200A KR 1020130004135 A KR1020130004135 A KR 1020130004135A KR 20130004135 A KR20130004135 A KR 20130004135A KR 20140096200 A KR20140096200 A KR 20140096200A
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voltage
input
link
power
current
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KR1020130004135A
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Korean (ko)
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KR101972850B1 (en
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정충일
엄재부
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엘지전자 주식회사
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Abstract

Disclosed are a power converting apparatus supplying power to a load and an air conditioner including the same. Embodiments of the present invention reduce the ripple of a current flowing in a DC link capacitor using the harmonic element of an input voltage. The embodiments of the present invention reduce the capacity of the DC link capacitor by reducing the ripple current of the DC link capacitor in a harmonic regulation satisfying level and reduce costs.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a power conversion apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power conversion apparatus and an air conditioner including the same, and more particularly, to a power conversion apparatus for driving an air conditioner and an air conditioner including the same.

Background Art [0002] In recent years, an air conditioner mainly uses a three-phase motor as a driving motor for a compressor. A three-phase motor power conversion device converts an alternating current, which is a commercial power source, into a direct current, and then drives the three-phase motor by applying the converted direct current to the three-phase motor using an inverter.

The air conditioner uses a motor such as a compressor and a fan, and uses a power conversion device for driving the motor. The power conversion apparatus converts the AC voltage supplied from the input power source into a DC voltage, converts the DC voltage into a pulse-width modulated (PWM) voltage, and supplies the DC voltage to the load.

On the other hand, as the air conditioner requires high performance and high efficiency, problems such as harmonic current, input power factor, and EMC arise. For example, when the harmonic current input to the input power source side and the input power factor characteristic are poor, other electric devices connected to the power system may malfunction and adversely affect the service life. For these reasons, countries are tightening regulations on power factor, harmonics, etc. to improve power quality.

Embodiments of the present invention are directed to a power conversion apparatus that reduces a ripple of a current flowing in a DC link capacitor that supplies power to a load, and an air conditioner including the power conversion apparatus.

According to an embodiment of the present invention, there is provided a power conversion apparatus comprising: a converter including at least one switch, converting an input power source to a DC power source, and operating the switch according to a converter control signal to improve a power factor; A DC link portion connected to a rear end of the converter; And a control unit for generating the converter control signal to the switch, wherein the control unit controls the ripple of the DC link current based on the input voltage of the input power source, the harmonic component of the input voltage, and the DC link voltage across the DC link unit, The duty of the converter control signal is reduced.

The control unit includes: a voltage controller for receiving the DC link voltage, the target DC link voltage for the DC link voltage, the input voltage, and the harmonic components of the input voltage, and outputting a target input current; A current controller receiving the target input current and outputting the duty; And a summer for summing the input voltage and the harmonic components of the input voltage and outputting the sum to the voltage controller. And the harmonic component of the input voltage is a natural number of the power supply frequency of the input power supply. In addition, the harmonic component of the input voltage may have a predetermined ratio with respect to the input voltage.

Embodiments of the present invention reduce a ripple of a current flowing in a DC link capacitor by using a harmonic component of an input voltage in an electric power converter for supplying power to a load and an air conditioner including the same.

Embodiments of the present invention can reduce the capacity of the DC link capacitor by reducing the ripple current of the DC link capacitor at a level satisfying the harmonic regulation, and can save costs.

1 is a circuit diagram showing a power conversion apparatus according to an embodiment;
FIG. 2 is a block diagram showing the detailed configuration of the control unit of FIG. 1;
FIGS. 3 and 4 are circuit diagrams showing detailed configurations of the converters in FIG. 1; FIG.
5 is a graph showing a reduction effect of ripple of a DC link current according to embodiments of the present invention; And
6 is a view illustrating an example of an air conditioner including a power conversion apparatus according to embodiments of the present invention.

The air conditioner including the electric power conversion device will be described in the present invention, but the electric power conversion device can also be used for other electric devices including a compressor and a motor.

6, an air conditioner including a power conversion device according to embodiments of the present invention includes a power conversion device and a plurality of switching devices as described below, An inverter for converting the voltage into a motor driving voltage and outputting it to the motor, and a compressor including a driving motor driven in accordance with the motor driving voltage.

Specifically, the air conditioner includes at least one indoor unit that performs air conditioning, a compressor that compresses the refrigerant at a high temperature and a high pressure, a motor that operates the compressor, and a controller that controls driving of the motor. In addition, the air conditioner includes an outdoor unit connected to at least one indoor unit through a pipe to drive the indoor unit. The control device includes a power conversion device according to the present invention, wherein the power conversion device includes at least one switching device for a power conversion device, and drives the switching device in accordance with a control signal to generate a return path, Compensate. Further, the power conversion apparatus includes a rectifying unit for rectifying the AC voltage of the commercial AC power source and converting the rectified AC voltage into a rectified voltage.

The outdoor unit 10 includes an evaporator 13 for heat-exchanging refrigerant compressed in the compressor with air, an expansion valve 14 for expanding the refrigerant discharged from the evaporator to low temperature and low pressure, And a refrigerant switching valve (17) provided at an outlet of the compressor (12) for guiding the refrigerant compressed in the compressor to the evaporator (13) or the condenser (15) do.

6, a refrigerating cycle including a compressor 12, an evaporator 13, an expansion valve 14 and a condenser 15 is installed inside the case 11, and the case 11 A plurality of suction fans 16 for sucking outside air and exchanging heat with the evaporator 13 are installed on the upper surface or the side surface of the condenser 15 and a medium for supplying cold water or hot water to the indoor units 20 The circulation pipe 30 is connected. A refrigerant switching valve 17 is provided at the outlet of the compressor 12 for switching the refrigerant compressed by the compressor 12 to the direction of the evaporator or the direction of the condenser according to operating conditions.

The refrigerant switching valve 17 is normally a four-way valve. The outdoor unit 10 operates as a cooler during the summer season, while it operates as a heater during the winter season. For example, during the summer, the refrigerant compressed by the compressor 12 at high temperature and high pressure is guided to the evaporator 13 by the refrigerant switching valve, heat-exchanged with the air in the evaporator 13 to be radiated, And then the refrigerant is heat-exchanged with water in the condenser 15 to supply the heat-exchanged water to the indoor units 20 which use the refrigerant as a cooling heat source. Meanwhile, during the winter season, the refrigerant switching valve 17 guides the refrigerant in the direction of the condenser, and the high-temperature and high-pressure refrigerant is heat-exchanged with water in the condenser 15 and supplied to the indoor units 20 using the heat- do.

Referring to FIG. 1, a power conversion apparatus according to an embodiment includes a converter 200, a DC link unit 300, and a controller 400. In addition, the power conversion apparatus may further include an inverter depending on the load. Of course, the inverter may be included in the load 500.

The converter 200 includes one or more switches, converts the input power source 100 to DC power, and operates the switch in accordance with the converter control signal to improve the power factor. The DC link unit 300 is connected to the rear end of the converter 200. The control unit 400 generates a converter control signal to the switch in the converter. The control unit 400 calculates a duty ratio of the converter control signal for reducing the ripple of the DC link current based on the input voltage of the input power source 100, the harmonic component of the input voltage, and the DC link voltage applied to the DC link unit 300 .

The power conversion apparatus may further include an input voltage detection unit (not shown) for detecting an input voltage of the input power source 100. The power conversion apparatus may further include a DC link voltage detection unit (not shown) for detecting a DC link voltage of the DC link unit 300.

Referring to FIG. 3, the converter 200 included in the power converter includes four diodes D1 to D4 as a bridge circuit, and a switch is connected to two diodes D3 and D4 at the bottom . One or more reactors (L) may be connected to the input of the diode bridge circuit. A DC link unit 300 is provided at an output terminal of the diode bridge circuit.

Referring to FIG. 4, the converter may be divided into a rectifying unit and a power factor improving unit. The rectification section rectifies the AC voltage of the input power supply 100. Further, the rectifying part may include a diode bridge circuit, and the circuit may be composed of two diodes. Referring to FIG. 4, it can be seen that two (two-stage) diodes included in the rectifying section are connected in parallel. Two diodes at the lower end of the diode bridge circuit of the rectifying section and two diodes at the lower end of the diode bridge circuit of the power factor improving section can share with each other. In order to fully rectify the AC voltage supplied by the input power source, a diode bridge circuit composed of four diodes is generally required. Therefore, the AC voltage of the input power source is rectified by using two diodes (two stages) included in the rectification section and two diodes (two stages) at the bottom end included in the power factor improvement section. That is, the first diode of the rectifying section and the first diode of the lower stage of the power factor improving section are connected, and the second diode of the rectifying section and the second diode of the lower stage of the power factor improving section are connected in parallel. With such a circuit configuration, the rectifying section can perform the same function as the diode bridge circuit composed of four diodes. As described above, the two diodes provided at the lower end of the power factor improving section are shared by the rectifying section and the power factor improving section, and are used as the rectifying diodes of the rectifying section and rectifying diodes of the power factor improving section.

Referring to FIGS. 3 and 4, the converter 200 operates the switch according to the converter control signal to improve the power factor of the input power source 100. Specifically, the power factor of the input current can be improved by returning the current of the input power source by turning on the switch and storing the returned current in the connected reactor. Here, the switch may be, for example, an Insulated Gate Bipolar Transistor (IGBT), a MOSFET, or the like. The switch interrupts the return path of the input power supply 100 according to the converter control signal. That is, the switching operation of the switch is performed in accordance with the converter control signal so that the input power is returned.

The control unit 400 controls the path of the input power source 100 and the short-circuit conduction time through a switch provided in the converter 200. Here, the short-circuit conduction time can be appropriately selected according to the load or the power value of the input power source in order to rectify the waveform of the current. In addition, the controller 400 may detect a zero crossing point when connected to one end of the input power source. The control unit 400 generates a converter control signal to turn on the switch of the converter to generate a return path of the input power source 100. [ In addition, the control unit controls the short-circuit conduction time of the input power source 100 according to the magnitude of the detected load to improve the power factor.

The reactor is connected between converter 200 and input power supply 100. Specifically, one end of the reactor is connected to one end of the input power supply 100, and the other end of the reactor is connected between the AC terminals of the converter. At this time, there may be a plurality of reactors. The reactor removes the harmonic components and compensates for the power efficiency of the input power supply 100. When the switch of the converter 200 is turned on, the reactor stores the energy of the input power source 100 and short-circuits the input power source 100. That is, when the switch of the converter 200 is turned on according to the converter control signal of the control unit, a return path is formed, and the reactor stores the power of the input power source 100 and forcibly short-circuits the input power source 100.

The DC link unit 300 smoothes the DC voltage rectified by the converter 200. The DC link unit 300 supplies a smooth DC voltage to a load, for example, an inverter and a rear stage. The DC link unit 300 may be composed of one capacitor (DC Link Capacitor) or a simple circuit including the same.

At this time, the control unit 400 may switch the switch of the converter so that the waveform of the input current of the input power source 100 follows the current slope determined by the power frequency and the peak value of the input current. The control unit 400 generates a converter control signal for switching the switch once or plural times based on the zero crossing point by twice the power source frequency of the input power source 100 to determine the waveform of the input current. The power converter uses data on the power consumption, input voltage, and DC link voltage of the load to determine the type of current that satisfies the power factor and harmonic regulation. The waveform of the input current follows the current slope determined by the power frequency and the peak value of the input current. The waveform of the input current is determined by at least one of a delay time of a certain time from the zero crossing point of the input voltage, a current slope, a current ripple due to switching, a switching frequency, and a DC link voltage. Is determined by one or more factors.

Referring to FIG. 2, the controller 400 includes a voltage controller 410, a current controller 420, and a summer 430.

The voltage controller 410 receives the harmonic components of the DC link voltage Vd, the target DC link voltage Vd * , the input voltage Vs, and the input voltage Vs with respect to the DC link voltage Vd, And outputs the current Is * .

The current controller 420 receives the target input current Is * and outputs the duty D for the switch. Here, the duty (D) for the switch can be divided into a linear term (Dc) and a non-linear term (Dn). The controller 400 may further include a summer that sums the duties of components other than the linear component and the linear component.

The summer 430 is provided at the front end of the voltage controller 410. The adder 430 sums the harmonic components of the input voltage Vs and the input voltage Vs and outputs the sum to the voltage controller 410.

The harmonic component of the input voltage Vs is a natural multiple (e.g., N = 1, 2, 3, ...) of the power supply frequency? Of the input power supply 100. [ The harmonic component of the input voltage Vs may have a magnitude of a constant ratio k with respect to the input voltage Vs. The harmonic component of the input voltage Vs can be expressed by the following equation (1).

Figure pat00001

5 is a graph comparing a ripple Ic_ripple1 of a DC link current in the case of a general power conversion apparatus and a case (Ic_ripple2) in which a power conversion apparatus according to the present invention is used.

Referring to FIG. 5, the harmonic components of the input voltage are multiplied by the magnitude of the third harmonic (N = 3) (k = 1 or another value) The ripple (Ic_ripple2) of the DC link current is reduced by about 17% from Ic_ripple1 when the duty is calculated after summing. 3, 220 Vrms and 50 Hz are used as the input power source 100, 240 uH of the reactor 200 reactor, 50? Of the output stage load 500, and 2240 uF of the DC link capacitor.

The power converter for supplying power to the load according to the embodiments of the present invention and the air conditioner including the power converter reduce the ripple of the current flowing in the DC link capacitor by using harmonic components of the input voltage. Embodiments of the present invention can reduce the capacity of the DC link capacitor by reducing the ripple current of the DC link capacitor at a level satisfying the harmonic regulation, and can save costs.

100: Input power 200: Converter
300: DC link unit 400: Control unit

Claims (10)

A converter including at least one switch for converting input power to direct current power and operating the switch according to a converter control signal to improve power factor;
A DC link portion connected to a rear end of the converter; And
And a controller for generating the converter control signal to the switch,
Wherein,
And calculates the duty of the converter control signal for reducing the ripple of the DC link current based on the input voltage of the input power source, the harmonic component of the input voltage, and the DC link voltage applied to the DC link portion. The method according to claim 1,
Wherein,
A voltage controller for receiving a DC link voltage, a target DC link voltage for the DC link voltage, the input voltage, and a harmonic component of the input voltage, and outputting a target input current;
A current controller receiving the target input current and outputting the duty; And
And a summer for summing the input voltage and the harmonic components of the input voltage and outputting the sum to the voltage controller. 3. The method of claim 2,
Wherein the harmonic component of the input voltage is a natural number multiple of the power supply frequency of the input power supply. The method of claim 3,
Wherein the harmonic component of the input voltage has a constant ratio to the input voltage. The method according to claim 1,
The converter includes:
And one or more reactors connected between the power source and the input power source and storing energy according to the switching of the switch. An input voltage detector for detecting an input voltage of an input power source;
A converter that includes at least one switch, converts the input power to direct current power, and operates the switch according to a converter control signal to improve power factor;
A DC link portion connected to a rear end of the converter;
A DC link voltage detecting unit for detecting a DC link voltage of the DC link unit; And
Generating a converter control signal based on a harmonic component of the input voltage having a magnitude of a constant ratio of the input voltage and the input voltage and having a natural multiple of a power frequency of the input power source and outputting the converter control signal to the switch; Power converter. The method according to claim 6,
Wherein,
Wherein the harmonic component is added to the input voltage, the DC link voltage and the target DC link voltage for the DC link voltage are input, and the duty for the converter control signal is output. 8. The method of claim 7,
Wherein,
A voltage controller for receiving the DC link voltage, the target DC link voltage, the input voltage, and the harmonic component and outputting a target input current;
A current controller receiving the target input current and outputting the duty; And
And a summer for summing the input voltage and the harmonic components and outputting the sum to the voltage controller. The method according to claim 6,
Wherein,
And switches the switch so that the waveform of the input current of the input power source tracks the current slope determined by the power supply frequency and the peak value of the input current. 10. A power conversion apparatus according to any one of claims 1 to 9,
An inverter having a plurality of switching elements and converting the direct current power into a motor driving voltage according to an inverter control signal and outputting the converted direct current power to a motor; And
And a compressor having a driving motor driven according to the motor driving voltage.
KR1020130004135A 2013-01-14 2013-01-14 Apparatus for converting power and air conditioner having the same KR101972850B1 (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20000031661A (en) * 1998-11-09 2000-06-05 이구택 Semi-bridge type unit power factor rectifying system and method
KR20070101476A (en) * 2006-04-10 2007-10-17 엘지전자 주식회사 Apparatus and method for supplying dc power source

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20000031661A (en) * 1998-11-09 2000-06-05 이구택 Semi-bridge type unit power factor rectifying system and method
KR20070101476A (en) * 2006-04-10 2007-10-17 엘지전자 주식회사 Apparatus and method for supplying dc power source

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Jin-Wan Yoo et al.,Third Harmonic Injection Circuit to Eliminate Electrolytic Capacitors in Light-Emitting Diode Drivers, Journal of Electrical Engineering and Tech.,Vo.7,Iss.3,pp.358-365(2012.5.31.)* *

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