KR20000050367A - power-factor improvement apparatus of air-conditioner - Google Patents

Abstract

PURPOSE: An apparatus for improving power-factor of an air conditioner is provided to control a turn-on time of a switching element according to a change of load and restrain power high-harmonic components. CONSTITUTION: An apparatus for improving power-factor of an air conditioner including a converter element(100) for converting AC input power to DC power, an inverter element for converting the DC power to three-phase AC power of a desired frequency, and a compressor for rotating by the three-phase AC power output, includes a voltage sensing element(120) for sensing a size of an input voltage from a power input terminal, a voltage phase sensing element(130) for sensing a phase of the input voltage from the power input terminal, a control element(140) for making a phase of an input current close to the phase of the input voltage by synchronization with a zero potential point of the input voltage from the voltage phase sensing element, and a power-factor improving element(150) for improving power-factor by making the input current phase close to the input voltage phase according to a switching signal output from the control element.

Description

Power-factor improvement apparatus of air-conditioner

The present invention relates to an inverter air conditioner for varying an operating frequency of a compressor according to cooling or heating capacity, and in particular, an air conditioner for improving an operating power factor of an air conditioner by connecting an inductor and a switching element having an energy accumulation path to a converter means. The present invention relates to a device for improving power factor.

In general, the inverter device of the air conditioner, as shown in Fig. 1, the converter unit 3 for converting the AC input power input from the power input terminal 1 to the DC power, in accordance with the outdoor conditions and the instructions of the indoor unit A control unit 5 which determines an operating frequency of the compressor 9 and outputs an inverter driving signal, and is output from the control unit 5 so as to rotate the compressor 9 according to the operating frequency determined by the control unit 5. The inverter unit 7 is configured to alternately turn on or turn off a power transistor, not shown, in accordance with the drive signal to convert the DC power output from the converter unit 3 into a three-phase AC power source.

The converter unit 3 filters the ripple component included in the bridge rectifier 11 for full-wave rectifying the AC input power at a predetermined DC voltage, and the ripple component included in the DC voltage full-wave rectified by the bridge rectifier 11. And a smoothing capacitor C1 connected to the output terminal of the bridge rectifier 11 to charge the full-wave rectified DC voltage.

In the inverter air conditioner configured as described above, when AC input power is applied from the power input terminal 1, the AC input power is rectified to a predetermined DC power through the bridge rectifier 11 of the converter unit 3, and the bridge rectifier The ripple component included in the DC power source rectified by (11) is filtered through the smoothing capacitor C1.

In this case, the inverter unit 7 alternately turns on or off the six power transistors (not shown) according to the driving signal output from the controller 5 to generate three-phase DC power output from the converter unit 3. u-phase, v-phase, w-phase) The compressor 9 is driven by switching to AC power.

As described above, the converter unit 3 for converting the AC input power to the DC power source uses a relatively large capacity smoothing capacitor C1 to obtain DC having a small ripple, but the input current is affected by the smoothing capacitor C1. As shown in FIG. 2, the distortion is distorted into an unsine waveform, so that the power factor of the system has a low value of about 0.5 to 0.7.

The low power factor of such a system is accompanied by an increase in power harmonics, which generates noise and EMI, increases reactive power, and causes a larger current to flow than that required by the system. Due to various problems, the European and advanced countries are taking measures to prevent the export of products that do not satisfy the legislation of power harmonics.

Accordingly, a power factor improving device for improving the power factor of the system has been devised. As a power factor improving device, there are largely active methods and passive methods.

First, as shown in FIG. 1, the passive method prevents an instantaneous increase in current at the output terminal or the power input terminal 1 of the bridge rectifier 11 and compensates for the power factor by releasing the accumulated energy when the direction of the current increase is changed. And a coil (L1) to be connected in parallel with the coil (L1) to advance the current phase and the capacitor (C2) for compensating the power factor by complementary action with the coil (L1) is connected to adjust the impedance appropriately.

The passive method described above has a small impedance for the first harmonic (base wave) of the input current and a high impedance for the other harmonics to improve the waveform of the input current, and is widely used in general inverter air conditioners. have.

The impedance seen from the bridge rectifier 11 is as follows.

Where s = jw

By using the above formula, the appropriate L and C values are selected to have zero impedance for the first harmonic and infinite impedance for the other harmonics.

Therefore, it is intended to have a relatively small impedance for the first order and a relatively large impedance for the third and fifth harmonics that have the greatest influence on the distortion.

In the conventional manual power factor improving device, however, the reactance capacity of the coil L1 and the capacitance of the capacitor C2, which are power factor correction circuits, are independent of the load fluctuation of the compressor 9 and the power factor of the air conditioner set. Since the initial design value is fixed, the power factor increases when the load of the compressor (9) is high, and the power factor decreases when the load of the compressor (9) is reduced, while satisfying the reference value above the standard rated load (eg, rated load power factor of 90). Or more), the power factor decreases proportionally as the minimum load is lower than the rated load, so that the minimum load power factor falls below the reference value (for example, the minimum load power factor is less than 75%). (Link) voltage is changed according to the load (compressor), there is a problem that can not suppress the power harmonics because there is no countermeasure.

Next, as an active method, a DC / DC converter is connected between a bridge rectifier and a smoothing capacitor to make a current in a waveform of power voltage and in phase, and is disclosed in Korean Patent Application No. 95-39229 filed by the present applicant. It is.

The active power factor correction device disclosed in this publication can achieve the effect of a full band pass of power factor and power harmonics of almost 1, but it can cause reliability problems due to complicated control circuits and high switching frequency, which is itself a noise source. As a result, there was a problem accompanied by difficulty in designing a noise filter and an increase in material cost.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems, by connecting an inductor having an energy accumulation path to the converter means and a switching element, and controlling the turn-on time of the switching element according to the load change of the air conditioner. The purpose of the present invention is to provide a power factor improving apparatus for an air conditioner that can satisfy the criteria of the standard (EN60555-2) that limits the harmonic currents by improving the operating power factor and suppressing the power harmonic components.

In order to achieve the above object, a power factor improving apparatus for an air conditioner according to the present invention includes: converter means for converting alternating current at a power input stage into a direct current by a rectifying unit and a smoothing capacitor; An air conditioner comprising: an inverter means for converting into a phase alternating current power supply; and a compressor rotating by a three-phase alternating current power output from the inverter means, comprising: an inductor for compensating the phase of an input current between the rectifier and the smoothing capacitor; A switching element for switching an input current to the inductor is connected, and a voltage phase sensing means for sensing a phase of an input voltage is connected between the power supply input terminal and the rectifying unit, and a voltage phase sensing means for sensing the phase of the input voltage. The turn-on time of the switching element is proportional to the operating frequency of the compressor according to the phase. And control means for changing the basic control value to be controlled.

1 is a manual power factor improvement circuit diagram of a conventional inverter device;

2 is a voltage and current waveform diagram when there is no L-C filter shown in FIG. 1;

3 is a circuit block diagram of an active power factor improving apparatus according to an embodiment of the present invention;

4 is a detailed circuit diagram of the voltage sensing means and the voltage phase sensing means of FIG.

5 is a gate signal and a current operating waveform diagram of an inductor and a switching device according to the present invention;

6 is a basic data explanatory diagram of an operating frequency band switching element of a compressor according to the present invention;

7 is a flowchart illustrating a control operation of a switching device according to a compressor operating frequency of the present invention.

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

100: converter means 110: current sensing means

120: voltage detection means 130: voltage phase detection means

140: control means 150: power factor improvement means

160: inverter means 162: compressor

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

3 is a circuit block diagram of an active power factor improving apparatus according to an embodiment of the present invention, Figure 4 is a detailed circuit diagram of the voltage sensing means and voltage phase sensing means of FIG.

As shown in Figs. 3 and 4, the converter means 100 rectifies and smoothes the AC input power input from the power input terminal 1 to convert it into DC power, and the converter means 100 is the power input terminal. (1) filter the ripple component contained in the rectifying unit 102 for full-wave rectifying the AC input power input from the predetermined DC power, and the full-wave rectification at the same time It consists of the smoothing capacitor C1 connected to the output terminal of the said rectification part 102 so that the charged DC voltage may be charged.

Current sensing means 110 detects the power current of the AC input power input from the power input terminal (1).

In addition, the voltage sensing means 120 senses the power supply voltage of the AC input power input from the power input terminal 1, and the voltage sensing means 120 receives the AC input power input from the power input terminal 1. A decompression transformer TX1 applied to the primary side and decompressed to a predetermined low voltage and induced to the secondary side; a resistor R1 for limiting a current component of the AC voltage boosted by the decompression transformer TX1; and the decompression transformer. Bridge rectifier 122 for full-wave rectifying the AC voltage reduced by TX1 to a predetermined DC voltage, and the bridge rectifier to filter the ripple component included in the DC voltage full-wave rectified by the bridge rectifier 122. A zener diode for supplying a constant voltage of a constant potential by bypassing a smoothing capacitor C2 connected to an output terminal of 122) and a breakdown voltage of a predetermined level or more from a DC voltage filtered by the smoothing capacitor C2. (Dz), a diode (D7) for limiting the maximum value of the breakdown voltage bypassed by the zener diode (Dz), and a resistor for inputting the DC voltage filtered by the smoothing capacitor (C2) to the control means described later. It consists of (R2).

The voltage phase detection means 130 detects the voltage phase (power frequency) of the AC input power input from the power input terminal 1, and the voltage phase detection means 130 decompresses the voltage by the decompression transformer TX1. The bidirectional photocoupler 132 which is inputted through the resistors R3 and R4 to be operated on at the zero potential point of the AC input voltage, and the voltage applied from the outside during the on operation of the photocoupler 132 ( 5V is inputted through the resistors R5 and R6 to turn on the transistor TR1 and a voltage 5V applied from the outside during the turn-on operation of the transistor TR1 through the resistor R7 and turned on. A transistor TR2 that operates, a capacitor C3, C4 that maintains the potential of the control means stably during the turn-on operation of the transistors TR1, TR2, and prevents a malfunction of the control means, and the transistor TR2 In synchronization with the zero potential of the AC input voltage during the turn-on It consists of a voltage signal of a level resistance (R8) to input to the control means.

In addition, the control means 140 is a waveform of the input power current input from the power input terminal 1 in synchronization with the zero potential point signal (low level voltage signal) of the AC input voltage input from the voltage phase detection means 130. As a microcomputer that outputs a switching signal so as to be close to the sine wave, and determines an operating frequency of the compressor 162 according to outdoor conditions and an indoor unit's instruction, and outputs an inverter driving signal. The frequency band voltage (F / V) data for maintaining the air gap flux (V / F) of the compressor 162 at the rated value and the operating frequency of the compressor 162 according to the power supply voltage level input from the voltage sensing means 120 The basic control value (turn-on time) of the corresponding switching element SW1 is stored on the ROM table.

In addition, the power factor improving means 150 receives the switching signal output from the control means 140 and improves the power factor by bringing the phase of the input current closer to the phase of the input voltage. It is connected to the output terminal of the rectifier 102 of the converter means 100 and accumulates the current when the positive voltage is applied, and the current continues to flow in the same direction by the accumulated amount when the negative voltage is applied. An inductor L5 for delaying a phase of the chopper, and a chopper connected to the inductor L5 and turned on / off in accordance with a switching signal from the control means 140 to force a current to flow in the inductor L5. A switching element SW1, a diode D5 through which current accumulated in the inductor L5 flows during the turn-off operation of the switching element SW1, and a protection diode D6 of the switching element SW1. It is.

In addition, in the drawing, the inverter means 160 alternately turns on or turns off six power-transistors (not shown) according to a driving signal output from the control means 140 to be output from the converter means 100. The DC power is converted into a three-phase (u-phase, v-phase, w-phase) AC power having a variable frequency and a variable voltage suitable for the operation frequency of the compressor 162, and is supplied to the compressor 162.

Hereinafter, the effect of the power factor improving device of the air conditioner configured as described above will be described.

When AC input power is applied from the power input terminal 1, the AC input power is rectified to a predetermined DC power through the rectifying unit 102 of the converter means 100 and included in the DC power rectified by the rectifying unit 102. The ripple component is filtered through the smoothing capacitor C1 and converted into DC power.

As described above, the converter means 100 for converting the AC input power to the DC power source uses a relatively large capacity smoothing capacitor C1 to obtain a DC having a small ripple, which is influenced by the smoothing capacitor C1. As shown in Fig. 2, Is is distorted into a non-sinusoidal pulse waveform.

Therefore, in the present invention, the inductor L5 having the energy accumulation path and the chopper switching element SW1 are connected to the converter means 100 so as to control the phase of the current to be a little more matched to the phase of the voltage.

First, the current flowing through the inductor L5 connected to the output terminal of the rectifying unit 102 of the converter means 100 determines the input power current. The current flowing through the inductor L5 is controlled by the voltage across the inductor L5. do.

When a positive voltage is applied across the inductor L5, the inductor L5 acts as a sink so that a current flows in the inductor L5, and this current accumulates in the inductor L5, and is negative. When the voltage is applied, the inductor L5 acts as a source, so that the inductor L5 has a relatively large value by using the characteristic of the inductor L5 that the current continues to flow in the same direction by the accumulated amount. As in (a), the current Is flows with a large phase delay.

In this case, when the energy accumulation path forcing the inductor L5 to the positive phase is formed in the previous phase delay part, the current Is flows as shown in the dotted line of FIG. In order to force current to flow in L5), a chopper switching element SW1 such as an insulated gate bipolar transistor (IGBT) is connected to a DC (-) terminal at the rear end of the inductor L5 to switch the current to flow in a desired section. To control.

Next, let's look at the energy accumulation operation mechanism of the inductor (L5).

When the AC input power input from the power supply input terminal 1 to the primary side of the decompression transformer TX1 is decompressed to a predetermined AC voltage and induced to the secondary side, the AC voltage decompressed by the decompression transformer TX1 is resistance R3 ( It is applied to the photocoupler 132 of the voltage phase detection means 130 through R4) and the photocoupler 132 operates on at the zero potential point of the AC input voltage.

When the photocoupler 132 is turned on, the transistors TR1 and TR2 are turned on so that a low-level voltage signal synchronized with the zero potential point of the AC input voltage from the voltage phase sensing means 130 is controlled. Is entered.

Therefore, in the control means 140, the phase of the input current flowing through the inductor L5 in synchronization with the zero potential point signal (low level voltage signal) of the AC input voltage input from the voltage phase detection means 130 is The switching signal of FIG. 5 (b) for approaching the phase is output to the gate terminal of the switching element SW1.

When the switching device SW1 is turned on according to the switching signal from the control unit 140, both ends of the inductor L5 are directly short-circuited to the output of the rectifier 102 and the DC (−) terminal, so that both ends of the inductor L5 are switched. Since the current flows while the positive voltage is applied at the same time as the device SW1 is turned on, a portion in which the current Is rises in the dotted line in FIG. 5 (a) is the same as in FIG. 5 (b). When SW1 is turned on, as shown in FIG. 5C, the current flows through the inductor L5 and the switching device SW1 by force.

At this time, according to the power source frequency and the load (compressor) current of the switching device SW1, when a predetermined time elapses in the control unit 140, the current accumulated by turning off the switching device SW1 is switched to the switching device SW1. After the turn-off, the current flows through the diode D5, and the current Is decreases slightly in the dotted line in FIG.

Thereafter, both ends of the inductor L5 have a positive voltage while the DC link voltage becomes smaller than the voltage Vd at the front end of the inductor L5, thereby increasing the current, and again, the voltage at the front end of the inductor L5 exceeds the DC link voltage. As it decreases, a negative voltage is applied to both ends of the inductor L5. At this time, current from the power supply does not flow and flows while the accumulated current decreases.

In this way, the charging current of the forcibly flowing inductor L5 and the actual load current are combined to compensate for the phase of the current to be closer to the phase of the voltage. Therefore, the power factor of the system is defined by the phase difference of voltage and current and the basic size of current as shown in the following formula, so that the power factor of the system and the regulation satisfaction of power harmonics can be improved by controlling θ and Is ₁ in the above manner. .

Next, operation control of the switching element SW1 according to the load change (operation frequency of the compressor) will be described with reference to FIGS. 6 and 7.

FIG. 7 is a flowchart showing a control operation of a switching element according to the compressor operating frequency of the present invention, in which S denotes a step.

First, in step S1, the control means 140 includes a basic data (turn-on time) of the switching element SW1 for increasing or decreasing the turn-on time of the switching element SW1 according to the operating frequency of the compressor 162, and the power supply voltage. The frequency band voltage (F / V) data for maintaining the air gap magnetic flux (V / F) of the compressor 162 at the rated value is set on the ROM table according to the size of.

The basic data value of the switching element SW1 is to increase the amount of energy accumulated in the inductor L5 by increasing the turn-on time (conduction angle) of the switching element SW1 when the operating frequency of the compressor 162 increases. As the load current increases, the input current Is in FIG. 5 (a) increases because the current value flowing in the Dymmy path is sufficiently increased so that the input current is close to the fundamental wave component value. In this case, the turn-on time of the switching element SW1 is controlled to sufficiently increase the current value of the dotted line portion.

Subsequently, in step S2, the voltage phase detection means 130 detects the voltage phase of the AC input power input from the power input terminal 1, determines whether the power frequency is 50 Hz, and if it is 50 Hz (YES), proceeds to step S3. The control means 140 determines the operating frequency of the compressor 162 according to the outdoor conditions and the instructions of the indoor unit, and then determines the turn-on time of the switching element SW1 corresponding to the operating frequency from the ROM table set in step S1. .

As a result of the discrimination in step S2, if it is not 50Hz (NO), it is determined that the power supply is 60Hz as a basic example, and the control means 140 proceeds to step S21. In step S3, the turn-on time of the switching element SW1 is shortened as much as Dt1 (e.g., 0.1 ms) in the data value, that is, as the power supply frequency is increased.

Subsequently, in step S4, the voltage sensing unit 120 senses the magnitude of the power supply voltage of the AC input power input from the power supply input terminal 1 to determine whether the power supply voltage level is a low voltage. Further, the optimum frequency band voltage (F / V) corresponding to the power supply voltage level is determined from the plurality of ROM tables set in step S1.

This is because one frequency band voltage (F / V) table defined for the operation of the compressor 162 in regions with large fluctuations in power supply voltage, such as China, is used in the low frequency operation region at low voltage (180 V or less). Since the voltage drop generated by the primary winding resistance of the motor is large and the air gap magnetic flux (V / F) of the compressor 162 is lowered, the torque is lowered and the starting torque is insufficient.

In addition, during high voltage, power factor and efficiency are lowered due to an increase in the excitation current caused by the magnetic saturation of the motor of the compressor 162 due to the application of an abnormally high line voltage, making it difficult to match the frequency band voltage (F / V) characteristics. Therefore, after setting a plurality of frequency band voltage (F / V) data by precomputation, the optimum F / V which does not decrease the efficiency according to the power supply voltage level is determined and the air gap flux (V / F) of the compressor 162 is determined. ) Is maintained at the rated value.

As a result of the discrimination in step S4, if the power supply voltage level is low (YES), the torque is insufficient in the high-speed range due to the lack of voltage, and the control means 140 proceeds to the step S41. Since the compressor 162 is operated by setting the operation frequency lower than the preset basic maximum operating frequency, stable operation is maintained in the entire operation region.

Subsequently, in step S6, the inverter means 160 alternately turns on or turns off six power transistors (not shown) according to the inverter driving signal output from the control means 140 to be output from the converter means 100. The compressor 162 is rotated by converting the DC power supply into a three-phase (u-phase, v-phase, w-phase) AC power source.

At the same time, the voltage sensing unit 120 and the voltage phase sensing unit 130 detect the phase (power frequency) and input voltage value (change of F / V data) of the input voltage to bring the phase of the input current closer to the phase of the voltage. The control device controls the turn-on time of the switching element SW1 according to the operating frequency (load change) of the compressor 162 to sufficiently satisfy the current harmonic regulation of EN60555-2 while maintaining the power factor of the pre-operation area control at about 0.95. The control operation becomes possible.

As a result of experimenting by mounting the power factor improving device according to the present invention on an air conditioner set, it shows a significantly higher power factor than the conventional manual method and regulated by the International Electronical Commission (IEC) (EN60555-2). It can satisfy the harmonics, and has similar power factor to the conventional active method, but the low operation frequency improves the reliability, simplifying the design and control of the EMI noise filter, and makes it possible to use the inverter system in all devices. It can be used for power factor and harmonic devices.

According to the power factor improvement apparatus of the air conditioner according to the present invention as described above, the air conditioner is connected by connecting an inductor having an energy accumulation path to the converter means and a switching element, and controlling the turn-on time of the switching element according to the load change. By improving the operating power factor of the device and suppressing the power harmonic components, there is an effect that it can satisfy the standard of the standard (EN60555-2) that limits the harmonic current.

Claims (7)

Converter means for converting AC input power at the power input stage into DC power, inverter means for converting the DC power converted by the converter means into three-phase AC power of a desired frequency, and three-phase AC power output from the inverter means. In an air conditioner having a compressor that rotates by Voltage sensing means for sensing a magnitude of an input voltage input from the power input terminal; Voltage phase detection means for sensing a phase of an input voltage input from the power input terminal; Control means for outputting a switching signal for bringing the phase of the input current closer to the phase of the input voltage in synchronization with the zero potential point of the input voltage input from the voltage phase sensing means; And a power factor improving means for improving the power factor by bringing the phase of the input current closer to the phase of the input voltage according to the switching signal output from the control means. The method of claim 1, The power factor improving means includes an inductor for compensating the phase of an input current and a switching element switched according to a switching signal from the control means so that an input current flows through the inductor. Device. The method of claim 1, The control means changes the frequency band voltage control value of the compressor according to the input voltage level sensed by the voltage sensing means, and if the input voltage is a low voltage, the air conditioner characterized in that to control by lowering the maximum operating frequency of the compressor Power factor improver. The method according to claim 1 or 2, The control means stores a basic control value for proportionally controlling the turn-on time of the switching element according to the operating frequency of the compressor, and changes the basic control value according to the phase of the input voltage sensed by the voltage phase detection means. The power factor improvement apparatus of the air conditioner, characterized in that. Converter means for converting alternating current of the power input stage into direct current by a rectifying unit and a smoothing capacitor, inverter means for converting the direct current converted by the converter means into a three-phase AC power source of a desired frequency, and three-phase AC output from the inverter means. In an air conditioner having a compressor that rotates by a power source, An inductor and a switching element are connected between the rectifier and the smoothing capacitor, and the turn-on time of the switching element is proportionally controlled according to the operating frequency of the compressor. Converter means for converting the alternating current of the power input stage into the direct current by the rectifying unit and the smoothing capacitor, an inverter means for converting the direct current converted by the converter means into a three-phase AC power source of a desired frequency, and a three-phase alternating current output from the inverter means. In an air conditioner having a compressor that rotates by a power source, An inductor for compensating the phase of an input current and a switching device for switching an input current to flow through the inductor are connected between the rectifier and the smoothing capacitor, and the switching device is turned on according to an operating frequency of the compressor. A power factor improvement apparatus for an air conditioner, wherein a control means for proportionally controlling time is connected. Converter means for converting the alternating current of the power input stage into the direct current by the rectifying unit and the smoothing capacitor, an inverter means for converting the direct current converted by the converter means into a three-phase AC power source of a desired frequency, and a three-phase alternating current output from the inverter means. In an air conditioner having a compressor that rotates by a power source, An inductor for compensating the phase of the input current is connected between the rectifier and the smoothing capacitor, and a switching element for switching the input current to flow through the inductor, and a voltage phase detection for sensing the phase of the input voltage between the power input terminal and the rectifier. And means for connecting a means and changing a basic control value for controlling the turn-on time of the switching element in proportion to the operating frequency of the compressor in accordance with the phase of the input voltage sensed by the voltage phase sensing means. Power factor improving device for air conditioners.