KR100445463B1 - Method and device for power factor compensation in inverter airconditioner - Google Patents

Abstract

The present invention relates to a power factor correction method and apparatus for an inverter air conditioner, and more particularly, to an inverter air conditioner for variably controlling a partial switching on time for power factor correction based on a DC LINK voltage driving a compressor. It relates to a power factor correction method and apparatus. The present invention controls the power factor as high as possible by automatically controlling the partial switching on time so that the DC link voltage driving the compressor is kept constant. To this end, the present invention adjusts the target switch-on time based on the sensed DC link voltage, and controls to reach the target DC link voltage.

Description

Method and device for power factor compensation in inverter air conditioner

The present invention relates to a power factor correction method and apparatus for an inverter air conditioner, and more particularly, to an inverter air conditioner for variably controlling a partial switching on time for power factor correction based on a DC LINK voltage driving a compressor. It relates to a power factor correction method and apparatus.

An air conditioner is a home appliance for maintaining indoor air in a state most suitable for use and purpose. For example, in summer, the room is cooled to a cool state, in winter, the room is heated to a warm state, and also the humidity of the room, and the air in the room to a comfortable clean state. As life convenience products such as air conditioners are gradually expanded and used, consumers are demanding high energy use efficiency, performance improvement and convenience products.

In addition, the increasing use of home appliances and electronic devices in homes, businesses, and factories has led many countries and organizations to regulate the use of their products in various ways. For example, there is a harmonic standard (standard number EN61000-3-2, Limit for Harmonic current emissions). The limitation in the Harmonic (alternatively referred to as 'harmonics') standard is to regulate the amount of distortion of the frequency. This is because harmonic disturbances not only accelerate the deterioration of various power devices, shorten the lifespan and increase the risk of fire due to overheating, but also increase the reactive power and increase the power consumption. For this reason, the inverter air conditioner performs various controls for improving the power factor to reduce harmonic disturbances.

FIG. 1A is a control circuit diagram of an inverter air conditioner employing a conventional passive system, and FIG. 1B shows output waveforms of voltage and current accordingly.

As shown, the control circuit of the conventional passive inverter air conditioner improves the power factor from the output of the rectifier circuit 3 and the rectifier circuit 3 for primary rectifying the input AC voltage by a rectifier circuit composed of bridge diodes. And a reactor 5 and a capacitor 6 which are passive filters.

The passive filter stores energy in the reactor 5, continues charging and discharging with the capacitor 6, and when there is a sudden change in the input current, the reactor 5 serves to compensate for the current, thereby harmonic distortion. Is to reduce the impact.

The signal whose power factor is improved in the passive filter is applied to the DC voltage generator 7 formed of a capacitor. The DC voltage generator 7 generates a DC voltage necessary for driving the compressor. The DC voltage generated from the DC voltage generator 7 is supplied to the compressor 11 under the control of the inverter 9.

In the conventional passive inverter air conditioner configured as described above, the passive filter repeatedly charges and discharges the input current at predetermined time intervals. Therefore, when there is a sudden change in the input current, it serves to supplement the current in the reactor (5) to obtain a current waveform with reduced harmonic distortion. In addition, the phase of the input current and the voltage is adjusted by the accumulation time in which energy is accumulated by the reactor 5 and the discharge time of energy stored in the capacitor 6, and the charge and discharge time is consistent with the harmonic components. The maximum power factor improvement is achieved.

However, when the charge and discharge time is inconsistent with the harmonic component, the power factor improvement effect is inevitably deteriorated. Furthermore, the charge and discharge time determined by the reactor 5 and the capacitor 6 can be actively controlled according to the harmonic component. Rather, the power factor improvement effect was not high because it was set at a preset value. That is, as shown in FIG. 1B, the power factor is inevitably lowered while a very large phase difference occurs in the input current waveform with respect to the input voltage waveform. Therefore, the conventional passive inverter air conditioner did not satisfy the harmonic standard.

Next, FIG. 2A shows a control circuit diagram of a conventional active inverter air conditioner, and FIG. 2B shows an input voltage waveform and an input current waveform according to power factor improvement control.

As shown, the control circuit of the conventional active inverter air conditioner includes a rectifying circuit 23 for primary rectifying the input AC voltage 31 by a rectifying circuit constituted by a bridge diode. An active filter is provided to input the output of the rectifier circuit 23 and to actively match the phase of the voltage and the current.

The active filter includes a reactor 25 for inputting the output of the rectifier circuit 23 and a reverse current prevention diode 21 connected to the output terminal of the reactor 25, and a phase difference between the voltage and the current of the output signal. An IGBT switch 19 for high speed switching control to be hardly generated, and a PFC controller 27 for performing PWM control to control the switching operation of the IGBT switch 19 are included. Accordingly, the active filter performs high-speed switching control of the IGBT switch 19 such that the phase of the current of the reactor 25 follows the phase of the input voltage by the PWM control of the PFC controller 27.

In addition, the signal whose power factor is improved in the active filter is applied to the DC voltage generator 13 formed of a capacitor. The DC voltage generator 13 generates a DC voltage required for driving the compressor. The DC voltage generated from the DC voltage generator 13 is supplied to the compressor 17 under the control of the inverter unit 15.

In the control circuit of the conventional active inverter air conditioner configured as described above, when the IGBT switch 19 is turned on, the reactor 25 receives the rectified voltage from the rectifier circuit 23, and the reactor current increases linearly. . The diode 21 is turned off due to a reverse voltage applied, and the energy charged in the capacitor 13 is supplied to the compressor 17.

On the contrary, when the Insulated Gate Bipolar Transistor (IGBT) switch 19 is turned off by the PFC control unit 27 (Power Factor Correction), the diode 21 conducts, and the reactor 25 has a voltage obtained by subtracting the input voltage from the output voltage. And reactor current decreases linearly. At this time, the power is supplied from the input end to the output end, the capacitor 13 is charged and energy is supplied to the compressor. If this operation is repeated, the power factor is improved as the reactor current follows the phase of the input voltage. At this time, the PFC control unit 27 performs PWM control under the control of a control unit (not shown).

In this way, the voltage of which the power factor is improved in the active filter is supplied to the DC voltage generator 13, and the DC voltage generator 13 generates a DC voltage necessary for driving the compressor. The DC voltage generated from the DC voltage generator 13 is supplied to the compressor 17 under the control of the inverter unit 15.

2B illustrates a state in which a power factor at which a phase difference between an input voltage and a current hardly occurs due to an on / off switching operation of the IGBT IGBT switch 19 in a control circuit of a conventional active inverter air conditioner is maximally improved. However, this method has a problem in that the manufacturing cost of semiconductor devices and peripheral circuits increases because the IGBT switch 19 must perform a very high high speed switching control (about 20 KHz). For example, the diode 21 and the reactor 25 connected to the IGBT switch 19 should use a device suitable for high speed switching. In addition, in order to dissipate the reverse current flowing from the diode 21 to the IGBT switch 19 in the switching operation of the IGBT switch 19, there is a problem that a large capacity heat sink and a large capacity fan must be used. .

Accordingly, the passive and active power factor improvement control circuits in the conventional inverter air conditioner do not satisfy the harmonic standard or have to use expensive electric elements.

Accordingly, an object of the present invention is to provide a power factor correction apparatus and a control method of an inverter air conditioner by partial switching control which can be manufactured at low cost while satisfying the harmonic standard.

1A is a control block diagram for power factor correction of a conventional passive inverter air conditioner,

Figure 1b is a comparison waveform diagram of the input voltage and the input current of the conventional passive inverter air conditioner,

2a is a control block diagram for power factor correction of a conventional active inverter air conditioner,

Figure 2b is a comparison waveform diagram of the input voltage and the input current of the conventional active inverter Aiken,

3A is a control block diagram for power factor correction of an inverter air conditioner according to the present invention;

Figure 3b is a comparison waveform diagram of the input current to the input voltage in the inverter air conditioner according to the present invention,

4A to 4C are control process diagrams for power factor correction according to a first embodiment of the present invention;

5 is a control process diagram for power factor correction according to a second embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

50: power 52: reactor

54: IGBT switch 56: rectifier

58: DC voltage generating unit 60: inverter unit

62 compressor 64 inverter drive unit

66: DC link voltage detection unit 68: IGBT switch control unit

70: microcontroller 72: input voltage phase detection unit

74: input voltage detector

A power factor correction apparatus for an inverter air conditioner according to the present invention for achieving the above object includes a reactor for passing only a specific frequency in the commercial AC power input; A power factor correction unit for performing a partial switching operation to compensate for the power factor of the power passing through the reactor; A DC voltage generator which inputs power output from the power factor correction unit and generates a DC voltage having a predetermined size; An inverter unit inverting the output voltage of the DC voltage generation unit and supplying the output voltage to the compressor; A DC voltage detector configured to detect a magnitude of the DC voltage generated by the DC voltage generator; An input voltage phase detector for detecting a phase of a voltage input into the product; Whenever the phase of the input voltage detected by the input voltage phase detector is zero crossing time, the switching operation of the power factor correction unit is controlled once, and the power factor is set so that the magnitude of the voltage detected by the DC voltage detector reaches a set value. And control means for variably controlling the switching on time of the compensator.

In addition, the power factor correction method of the inverter air conditioner according to the present invention for achieving the above object, the power factor correction unit for switching the input power to control the power factor; A DC voltage generator which inputs power output from the power factor correction unit and generates a DC voltage having a predetermined size; An inverter air conditioner comprising an inverter unit for inverting an output voltage of the DC voltage generator and supplying the compressor to a compressor, comprising: a setting step of setting a DC voltage when a power factor correction value of a product becomes the highest to a target DC voltage; A sensing step of sensing a magnitude of a current DC voltage generated by the DC voltage generator during driving of a compressor; And a control step of adjusting the partial switching operation time of the power factor correction unit until the DC voltage sensed in the sensing step reaches a target DC voltage.

In the setting step, the ratio of the current input voltage to the standard input voltage of the product is calculated, and the target DC voltage is set based on the calculated ratio.

The present invention may further include a detecting step for detecting a phase of a voltage input into the product, and when the phase of the voltage detected in the detecting step is at a zero crossing point, the switching operation of the power factor correction unit is performed once. It is characterized by.

Hereinafter, a power factor correction apparatus and a method of an inverter air conditioner according to the present invention will be described in detail with reference to the accompanying drawings.

The present invention performs partial switching control to maintain a constant DC LINK voltage for driving the compressor. To this end, the present invention includes a control circuit as shown in Fig. 3A.

That is, as shown in the drawing, the reactor 52 is connected to the power supply terminal 50. The rectifier circuit 56 and the IGBT switch 54 are connected in parallel to the rear end of the reactor 52. The IGBT switch 54 is switched on / off under the control of the IGBT switch control unit 68 described later. Next, the DC link voltage generator 58 is connected to the next stage of the rectifier circuit 56, and the high-voltage DC link voltage generated by the DC link voltage generator 58 is compressed through the inverter unit 60. And to be delivered to 62.

In this configuration, the control of the IGBT switch 54 and the inverter unit 60 is required to supply the voltage of the power supply terminal to the compressor 62 at a high-voltage DC link voltage. For the above control, the present invention includes an inverter driver 64 for driving the inverter unit 60 under the control of the microcontroller 70. And an IGBT switch controller 68 for controlling the on / off operation of the IGBT switch 54 under the control of the microcontroller 70.

In addition, the present invention is provided with a DC link voltage detection unit 66 for detecting the generated voltage of the DC link voltage generation unit 58, an input voltage phase detection unit for detecting the phase of the input voltage input into the product 72 is provided. The magnitude of the DC voltage sensed by the DC link voltage detector 66 and the phase of the input voltage sensed by the input voltage phase detector 72 are input to the microcontroller 70.

Therefore, from the above configuration, the microcontroller 70 can recognize the phase of the input voltage and can also recognize the magnitude of the generated DC voltage. The microcontroller 70 controls the partial switching operation of the IGBT switch 54 so that the perceived DC voltage is always constant.

In addition, the input voltage detection unit 74 is further included in the present invention. The input voltage detector 74 is configured to detect the magnitude of the voltage input into the product and provide the detected voltage to the microcontroller 70.

Next, a process of controlling power factor compensation in the inverter air conditioner according to the present invention having the above configuration will be described.

4A to 4C are control procedures for power factor correction according to a first embodiment of the present invention.

When the driving is started under the control of the microcontroller 70, the power of the power supply unit 50 is transmitted to the reactor 52 while the power is input into the product. The power passing through the reactor 52 is supplied to the rectifier circuit 56 and primary rectified. The signal rectified by the rectifier circuit 56 is applied to the DC link voltage generator 58. In addition, a high DC voltage is generated in the DC link voltage generator 58 and supplied to the compressor 62 through the inverter unit 60.

On the other hand, when a voltage is applied to the compressor 62 through the above path, the DC link voltage detector 66 detects the generated DC voltage and provides it to the microcontroller 70. In addition, the input voltage phase detection unit 72 detects the phase of the voltage input into the product and provides it to the microcontroller 70 (step 100 of FIG. 4A).

When the phase of the voltage input in step 100 is zero crossing time, the microcontroller 70 commands the IGBT switch controller 68 to turn on the IGBT switch 54. At this time, the IGBT switch controller 68 turns on the IGBT switch 54 (step 103).

While the IGBT switch 54 is turned on, the reactor 52 receives an input voltage, and the phase of the current passing through the reactor 52 rises linearly, as shown in FIG. 3B. It is adjusted close to the phase of. At this time, the energy rectified by the rectifier 56 and charged in the DC link voltage generator 58 is supplied to the compressor 62.

The on operation of the IGBT switch 54 is the same as the above operation, and the phase of the input voltage is repeatedly performed at the time of zero crossing, and the on operation time is a target switch on time (target switch) set to reach a target DC link voltage described later. ON time) (step 106). That is, in step 106, the IGBT switch 54 is turned on and the target switch on time data is stored in the timer counter Ton for how long to turn it on.

Therefore, after the IGBT switch 54 is turned on, the microcontroller 70 decreases the Ton time set at a predetermined time interval by using the built-in timer (step 200 of FIG. 4B). When the set time has elapsed (step 203), the switch controller 68 is instructed to turn off the IGBT switch 54 (step 206).

When the IGBT switch 54 is turned off by the 206th step, the reactor 52 receives a voltage obtained by subtracting the input voltage from the output voltage, and the reactor current is linear as opposed to the on operation of the IGBT switch 54. Decreases. In this case, power is supplied from the input to the output to charge the DC link voltage generator 58 and energy is supplied to the compressor 62.

In the present invention, the IGBT switch 54 is turned on and off, and the phase of the input voltage is made once every zero crossing time point.

Next, a description will be given of a process of setting a target switch on time Ton, which is an on operation time of the IGBT switch 54, when the IGBT switch 54 is turned on.

First, the DC link voltage with the highest power factor is first set as the target DC link voltage in the experimental stage for each product. The set target DC link voltage is stored in the microcontroller 70. In addition, a target switch on time (Ton) until reaching the target DC link voltage is set. The target switch on time Ton is a value according to an experimental value and is stored in the microcontroller 70.

The DC link voltage detector 66 detects the DC link voltage generated by the DC link voltage generator 58 and transmits the detected DC link voltage to the microcontroller 70 (S300). The microcontroller 70 compares the current DC link voltage input in step 300 with a predetermined target DC link voltage. In operation 303, it is determined whether the current DC link voltage is higher than the target DC link voltage.

If the current DC link voltage is higher than the target DC link voltage in step 303, the predetermined target switch-on time Ton is reduced (step 306). However, if the current DC link voltage is lower than the target DC link voltage in step 303, the predetermined target switch-on time Ton is increased (step 309).

The adjusted target switch-on time Ton determines the operation time of the IGBT switch 54 by the control of FIG. 4B.

That is, in steps 306 and 309, when the target DC link voltage is high, the target switch-on time is increased when the target DC link voltage is high, and the target switch is low when the target DC link voltage is low. By reducing the on time, the target DC link voltage is kept constant. Therefore, the present invention is to perform the control to maintain the DC link voltage constant while automatically changing the target switch-on time (Ton) even if the DC link voltage is changed by the load change.

Therefore, the first embodiment of the present invention satisfies the harmonic specification while automatically controlling the partial switching on time so as to keep the DC link voltage driving the compressor constant so that the power factor is as high as possible. In the first embodiment of the present invention, the target DC link voltage always uses a predetermined value.

Next, FIG. 5 is a control process for power factor correction according to a second embodiment of the present invention.

In the power factor correction control process according to the second embodiment of the present invention, the partial switching on time is controlled to maintain the constant by correcting the DC link voltage driving the compressor according to the input voltage. That is, the purpose is to maintain the maximum power factor regardless of the variation of the input voltage. To this end, in the second embodiment of the present invention, the target DC link voltage is varied according to the input voltage.

In the second embodiment of the present invention, the phase of the input voltage is sensed, and the on-state operation of the IGBT switch 54 is controlled at the voltage crossing point zero as in the first embodiment. In addition, when a target switch on time is determined according to a target DC link voltage, a process of turning on the IGBT switch 54 for the determined time and turning off the IGBT switch 54 when the target switch on time Ton elapses. The same is true.

However, in the second embodiment of the present invention, unlike the first embodiment, the target DC link voltage is variably adjusted according to the magnitude of the input voltage instead of using a preset value according to the product.

Therefore, in the second embodiment of the present invention, only the process of setting the target switch on time Ton, which is the on operation time of the IGBT switch 54, is set according to the variable target DC link voltage.

First, the input voltage detecting unit 74 detects the magnitude of the voltage input into the product and provides the detected voltage to the microcontroller 70 (operation 400).

The microcontroller 70 calculates a target DC link voltage according to the input voltage by applying the input voltage input in operation 400 to a predetermined target DC link voltage calculation formula (operation 403).

The target DC link voltage calculation formula set in step 403 is as follows.

(Current Input Voltage / Standard Input Voltage) * Standard DC Link Voltage = Target DC Link Voltage

Here, the standard input voltage indicates a standard input voltage of each product use environment, and sets the optimal DC link voltage to the standard DC link voltage at the standard input voltage.

When the target DC link voltage is set according to the magnitude of the voltage input in step 403, the microcontroller 70 recognizes the target switch on time Ton according to the set target DC link voltage. The target switch-on time Ton is a value which is preset and stored according to the target DC link voltage according to an experimental value. That is, the microcontroller 70 stores and stores in the internal memory a target switch on time suitable for various target DC link voltages.

As described above, while the target DC link voltage is set in step 403, the DC link voltage detector 66 detects the DC link voltage generated by the DC link voltage generator 58 to detect the microcontroller 70. (Step 406).

The microcontroller 70 compares the current DC link voltage input in step 406 with the target DC link voltage set in step 403 (step 409).

If the current DC link voltage is higher than the target DC link voltage in step 409, the target switch on time Ton allocated to the target DC link voltage is reduced (step 412). However, if the current DC link voltage is lower than the target DC link voltage in step 409, the target switch on time Ton is increased (step 415).

The adjusted target switch-on time Ton determines the operation time of the IGBT switch 54 by the control of FIG. 4B.

That is, in steps 412 and 415, the currently detected DC link voltage is compared with the target DC link voltage, and the target switch on time is increased when the target DC link voltage is high, and the target switch is low when the target DC link voltage is low. By reducing the on time, the target DC link voltage is kept constant.

As described above, the second embodiment of the present invention sets the DC link voltage at which the maximum power factor is automatically obtained according to the change of the input voltage to the target DC link voltage, and automatically changes the target switch-on time, thereby changing the DC link voltage for each input voltage. By keeping it constant, you get high power factor compensation.

As described above, the present invention is characterized in that the phase of the input voltage is sensed and the IGBT switch is turned on when the phase of the input voltage is zero crossing. Therefore, the IGBT switch repeats the on operation at each zero crossing time point, but does not perform the fast switching operation as in the conventional active type.

In addition, the present invention sets the timing control for turning off the IGBT switch operated on at the zero crossing timing to the timing at which the target DC link voltage is reached. Therefore, in the present invention, it is possible to always obtain a constant target DC link voltage regardless of load variation.

In the present invention, the target DC link voltage is variably adjusted according to the magnitude of the input voltage. This is to obtain the maximum power factor improvement effect even if the input voltage fluctuates.

The present invention described above can obtain the following effects.

First, it is possible to keep the DC link voltage driving the compressor constant while inducing the automatic switching operation of the IGBT switch at a phase of zero crossing of the input voltage. At this time, the DC link voltage is set to a value that obtains the maximum power factor, so the present invention can satisfy the harmonic standard by increasing the power factor as much as possible.

Second, the IGBT switch is controlled on time according to the target DC link voltage. Therefore, even if a load change occurs, the on-time of the IGBT switch is automatically changed to maintain a constant DC link voltage. Therefore, it is possible to constantly adjust the DC link voltage for driving the compressor.

Third, the present invention employs a partial switching control scheme in which the IGBT switch is turned on at every zero crossing point of the input voltage. Therefore, it is possible to use a low-cost device, such as the peripheral device including the IGBT switch, it is possible to lower the manufacturing cost.

Fourthly, in the present invention, the target DC link voltage is variably set according to the variation of the input voltage. Therefore, it is possible to compensate the power factor to the maximum state regardless of the variation of the input voltage.

Claims (4)

A power factor correction unit configured to control switching of the input power to compensate for the power factor; A DC voltage generator which inputs power output from the power factor correction unit and generates a DC voltage having a predetermined size; In the inverter air conditioner having an inverter unit for inverting the output voltage of the DC voltage generating unit to supply to the compressor: A setting step of setting the DC voltage when the power factor correction value of the product becomes the highest to the target DC voltage; A sensing step of sensing a magnitude of a current DC voltage generated by the DC voltage generator during driving of a compressor; And a control step of adjusting a partial switching operation time of the power factor correction unit until the DC voltage sensed in the sensing step reaches a target DC voltage. The method of claim 1 wherein: The setting step may include calculating a ratio of a current input voltage to a standard input voltage of a product, and setting a target DC voltage based on the calculated ratio. The method of claim 1 or 2, wherein: Further comprising a detecting step for detecting the phase of the voltage input into the product, And a switching operation of the power factor correction unit is performed once when the phase of the voltage detected in the detection step is zero crossing time. A reactor for passing only a specific frequency in an input commercial AC power source; A power factor correction unit for performing a partial switching operation to compensate for the power factor of the power passing through the reactor; A DC voltage generator which inputs power output from the power factor correction unit and generates a DC voltage having a predetermined size; An inverter unit inverting the output voltage of the DC voltage generation unit and supplying the output voltage to the compressor; A DC voltage detector configured to detect a magnitude of the DC voltage generated by the DC voltage generator; An input voltage phase detector for detecting a phase of a voltage input into the product; Whenever the phase of the input voltage detected by the input voltage phase detector is zero crossing time, the switching operation of the power factor correction unit is controlled once, and the power factor is set so that the magnitude of the voltage detected by the DC voltage detector reaches a set value. The power factor correction apparatus of the inverter air conditioner comprising a control means for variably controlling the switching on time of the compensator.