KR20050075103A - Method for power factor compensation in inverter airconditioner - Google Patents

Abstract

The present invention relates to a power factor correction control method of an inverter air conditioner, and to switch a reactor passing only a specific frequency in an input commercial AC power supply and switching at each zero crossing time point of an input voltage to compensate for the power factor of the power passing through the reactor. A control method of an inverter air conditioner having a power factor correction unit for performing an operation, wherein the switching operation is performed by varying a time according to an on delay time after a predetermined time has elapsed from a zero crossing time point of an input voltage. do. Therefore, the power factor can be increased by optimal switching for each power consumption, and the loss of unnecessary current can be reduced.

Description

Power factor compensation control method of inverter air conditioner {Method for power factor compensation in inverter airconditioner}

The present invention relates to a power factor correction control method of an inverter air conditioner. In particular, in an inverter air conditioner employing a partial switching control method for power factor correction, an on time point of a switching element is consumed from a zero crossing time point of an input voltage. The present invention relates to a power factor compensation control method of an inverter air conditioner capable of increasing power factor by performing optimal switching for each power consumption by varying power.

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 electronics in homes, businesses, and factories has led many countries and organizations to regulate the use of their products in many 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 disturbance promotes deterioration of various power equipments, shortens the lifespan, increases the risk of fire due to overheating, and increases the reactive power, thereby increasing power consumption. For this reason, the inverter air conditioner performs various controls for improving the power factor in order to reduce harmonic disturbances.

1 shows a control circuit diagram of a conventional active inverter air conditioner, and FIG. 2 shows an input voltage waveform and an input current waveform according to a conventional 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 24 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 24 includes a reactor 25 for inputting the output of the rectifier circuit 23, a reverse current prevention diode 21 connected to the output terminal of the reactor 25, and a voltage and a current of the output signal. Insulated Gate Bipolar Transistor (IGBT) switch 19 for fast switching control so that the phase difference of the PDP is hardly generated, and PFC (Pulse Width Modulation) control for controlling the switching operation of the IGBT switch 19 Power Factor Correction) control unit 27 is included. The PFC control unit 27 performs high-speed switching control of the IGBT switch 19 so that the phase of the current of the reactor 25 follows the phase of the input voltage by PWM control.

When a signal having an improved power factor through the active filter 24 is applied to the DC voltage generator 13 composed of a capacitor, the DC voltage generator 13 generates a DC voltage necessary for driving the compressor, and the DC The voltage 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 rectified voltage is applied to the reactor 25 through the rectifier circuit 23 and the reactor current is linear. Rise to the enemy. At this time, a reverse voltage is applied to the reverse current preventing diode 21 and turned off, and the energy charged in the DC voltage generator 13 is supplied to the compressor 17.

On the contrary, when the IGBT switch 19 is turned off by the PFC control unit 27, the reverse current prevention diode 21 is turned on so that the reactor 25 takes a voltage obtained by subtracting the input voltage from the output voltage, and the reactor current is linear. Decreases. At this time, while the power is supplied from the input terminal to the output terminal, the DC voltage generator 13 is charged and energy is supplied to the compressor.

As described above, while the IGBT switch 19 is repeatedly turned on and off, the reactor current follows the phase of the input voltage, thereby improving the power factor. At this time, the PFC control unit 27 performs PWM control under the control of a control unit (not shown).

The voltage having the improved power factor through the active filter 24 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.

FIG. 2 illustrates a state in which a power factor at which a phase difference between an input voltage and a current hardly occurs by an on / off switching operation of the IGBT switch 19 in a control circuit of a conventional active inverter air conditioner is 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 fast switching control (about 20 KHz). For example, the reverse current prevention 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 reverse current prevention diode 21 to the IGBT switch 19 in the switching operation of the IGBT switch 19, the problem of having to use a large heat sink and a large fan. This occurred.

As the cost increase problem of active inverter air conditioner lowers the purchasing power of the product as a result, the manufacturer has sought a new solution. One of them is partial switching control (PSC: Partial) with high power factor improvement while lowering the manufacturing cost. Swiching Correction).

In the active inverter air conditioner, as shown in FIG. 2, the IGBT switch 19 is continuously switched on / off at a predetermined frequency (for example, 20 KHz), but the partial switching control method is illustrated in FIG. 2. As shown in FIG. 3, a zero crossing time point of the input voltage is detected, the IGBT switch 19 is turned on from the detected time point, and after a predetermined time, the IGBT switch 19 is turned off. Control is performed to maintain the OFF state of the IGBT switch 19 until the next time of zero crossing of the input voltage.

In FIG. 3, (a) is a waveform diagram of an input voltage and an input current according to a partial switching control method, and (b) is a power supply phase detection waveform diagram of detecting a zero crossing point of an input voltage in an input voltage phase detection unit. , (c) is a waveform diagram of partial switching operation of the IGBT switch 19 from the zero crossing time point.

The partial switching control method performs one switching operation for each period when the zero crossing time according to the detection of the input power is divided into periods, and each switching operation is performed for a predetermined time (about 14% to 15% of the period). The ON operation is maintained, and the partial switching operation control of the IGBT switch 19 is performed together with the operation of the compressor 17.

However, according to the conventional partial switching control method described above, the current waveform is made as shown in FIG. 3A by repeating turning on / off the IGBT switch at each zero crossing time of the input voltage. Silver (see Part A) is a loss in terms of power consumption of the inverter air conditioner.

Accordingly, there is a need for a power factor correction method capable of preventing unnecessary current loss in an inverter air conditioner that controls power factor correction using a zero crossing point of an input voltage.

An object of the present invention is to optimize the switching according to the power consumption by varying the on time of the switching element according to the power consumption from the zero crossing time of the input voltage in the inverter air conditioner employing the partial switching control method for power factor correction. To provide a power factor compensation control method of the inverter air conditioner that can increase the power factor.

According to the power factor correction control method of the inverter air conditioner according to the present invention for achieving the above object, a reactor for passing only a specific frequency in the input commercial AC power, and the input voltage to compensate for the power factor of the power passing through the reactor A control method of an inverter air conditioner having a power factor correction unit for performing a switching operation at every zero crossing point of time, wherein the switching operation is performed by varying a time according to an on delay time after a predetermined time has elapsed from the zero crossing point of an input voltage. It characterized in that to perform.

According to an embodiment of the present invention, the predetermined time is preferably a time taken for the voltage phase and the current phase to become equal.

According to one embodiment of the present invention, it is preferable that the on delay time is shortened when the current power consumption is large and long when the current power consumption is small, and the value thereof changes according to the current power consumption.

According to an embodiment of the present invention, the on delay time may include calculating a current power consumption, calculating a power consumption ratio that is a ratio of current power consumption to standard power consumption, and variable delay according to a standard delay time and the power consumption ratio. It is preferable to calculate by performing the step of calculating the time, adding the variable delay time to the standard delay time.

Therefore, according to the present invention, the power factor can be increased by performing optimal switching for each power consumption, and the loss of unnecessary current can be reduced.

Hereinafter, with reference to the accompanying drawings, it will be described in more detail with respect to the power factor correction control method of the inverter air conditioner according to the present invention.

4 is a control block diagram for power factor correction of the inverter air conditioner according to the present invention.

The reactor 52 is connected to the power supply terminal 50, and 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 controller 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 transferred through the inverter unit 60. It is configured to be delivered to the compressor 62.

In order to change the voltage of the power supply stage into a high voltage DC link voltage and supply the compressor 62 with the above configuration, the control of the IGBT switch 54 and the inverter unit 60 is required. 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 detector 66 for detecting the voltage generated by the DC link voltage generator 58, an input for detecting the phase of the input voltage input into the product The voltage phase detection unit 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 detector 74 is further included in the present invention. The input voltage detector 74 detects the magnitude of the voltage input into the product and provides the detected voltage to the microcontroller 70. In addition, reference numeral 76 denotes an input current sensing unit for sensing a magnitude of a current input into the product. The magnitude of the input current sensed by the input current detector 76 is provided to the microcontroller 70. The input current detector 76 is composed of a current transformer.

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

5A to 5C are flowcharts illustrating a method for controlling power factor correction of an inverter air conditioner according to the present invention.

First, a time point for turning on the IGBT switch will be described with reference to FIG. 5A.

When the driving is started under the control of the microcontroller 70 in FIG. 4, power is supplied to the reactor (52 in FIG. 4) while power is input into the product. Power passing through the reactor is supplied to a rectifier circuit (56 in FIG. 4) and is first rectified. The signal rectified in the rectifier circuit is applied to the DC link voltage generator (58 in FIG. 4). In addition, a high DC voltage is generated in the DC link voltage generation unit and supplied to the compressor (62 of FIG. 4) through the inverter unit 60.

On the other hand, when a voltage is applied to the compressor through the path as described above, the DC link voltage detector (66 in FIG. 4) detects the voltage generated by the DC link voltage generator (58 in FIG. 4) and provides it to the microcontroller. Then, the input voltage phase detection unit (72 of FIG. 4) detects the phase of the voltage input into the product and provides it to the microcontroller (step S100).

When the phase of the voltage input in step S100 is at the zero crossing point, the microcontroller determines whether a predetermined time (T1 in FIG. 6C) has elapsed from the zero crossing point (step S110). In this case, the predetermined time T1 means a predetermined time since the time of the zero crossing time point, which is to turn on the IGBT switch (54 in FIG. 4) only when the voltage phase and the current phase are the same.

Subsequently, in the present invention, the IGBT switch is turned on by varying the time according to the power consumption. The variable time is an on delay, which is referred to as a time delayed more than the predetermined time T1 in turning on the IGBT switch. This is called time (T2 in Fig. 6C).

Referring to the method of obtaining the on delay time T2 in the following steps, first, when it is determined in step S110 that the predetermined time T1 has elapsed from the zero crossing time point, the current power consumption is calculated. The current power consumption can be calculated by reading the input current value detected by the input current detector (76 in FIG. 4) and reading the input voltage value detected by the input voltage detector (74 in FIG. 4) and multiplying the two values. (Step S120).

Next, the power consumption ratio representing the ratio of the current power consumption to the standard power consumption is calculated by dividing the current power consumption calculated in the step S120 by the standard power consumption (step S130), and the variable delay time ΔTon is obtained. The variable delay time [Delta] Ton is obtained by substituting an equation (step S140). In this case, the standard power consumption means power consumed as a standard at the rated voltage of the product.

In addition, the following equation (1) calculates the variable delay time? Ton in step S140.

1-(Standard Delay Time * Power Consumption Ratio) = Variable Delay Time (△ Ton) --- Equation (1)

Here, the standard delay time refers to the delay time of the IGBT switch that satisfies the power factor at the standard load and minimizes the loss of unnecessary current.

Subsequently, by adding the variable delay time? Ton with the standard delay time, an on delay time T2 that finally determines the on time of the IGBT switch is obtained (step S150). Herein, the variable delay time ΔTon may be a positive value or a negative value according to the value of current power consumption, and the variable delay time is positive because the current power consumption is small. When the value is positive, the on delay time T2 is longer than the standard delay time, and when the variable delay time becomes negative because the current power consumption is large, the on delay time is increased. The delay time T2 is shorter than the standard delay time.

According to the present invention, in order to determine a time point at which the IGBT switch (54 in FIG. 4) is turned on, a time point at which it is determined that sufficient power factor compensation can be achieved by the partial switching control, that is, a time point that the output power is determined to rise above a certain level. The on time is adjusted according to current power consumption.

Subsequently, when the on delay time T2 obtained according to the above method has passed (step S160), the microcontroller instructs the IGBT switch control unit (68 in FIG. 4) to turn on the IGBT switch. Accordingly, the IGBT switch controller turns on the IGBT switch (S170).

While the IGBT switch is on, the reactor (52 in FIG. 4) receives an input voltage, and the phase of the current passing through the reactor is similar to the portion "B" in FIG. It is shaped to minimize the loss of unnecessary current and then rises linearly to approximate the phase of the voltage waveform. At this time, the energy rectified by the rectifier circuit (56 in FIG. 4) and charged in the DC link voltage generator (58 in FIG. 4) is supplied to the compressor (62 in FIG. 4).

The on operation of the IGBT switch as described above is repeatedly performed when the phase of the input voltage is zero-crossed, and the time for maintaining the on state of the IGBT switch is set to reach a target DC link voltage, which will be described later. (Ton) is made (step S180). That is, the step S180 is to set how long to maintain the on state after the IGBT switch is turned on.

Next, referring to FIG. 5B, a process of turning off the IGBT switch turned on through the process of FIG. 5A will be described.

After the IGBT switch (54 in FIG. 4) is turned on, the microcontroller (70 in FIG. 4) counters and decreases the preset switch-on time Ton at a predetermined time interval using the built-in timer (S200). Thus, when the preset switch-on time Ton becomes "0" (step S210), the microcontroller instructs the IGBT switch control unit (68 in FIG. 4) to turn off the IGBT switch, and thus the IGBT. The switch controller turns off the IGBT switch (S220).

When the IGBT switch is turned off by the step S220, the reactor (52 in FIG. 4) is applied with a voltage equal to the output voltage minus the input voltage, and the reactor current decreases linearly as opposed to when the IGBT switch is turned on. . At this time, while the power is supplied from the input unit to the output unit, energy is charged in the DC link voltage generator (58 of FIG. 4) and energy is also supplied to the compressor (62 of FIG. 4).

Subsequently, a process of setting the switch on time Ton of operation S180 of FIG. 5A will be described with reference to FIG. 5C.

First, the DC link voltage with the highest power factor is set as the target DC link voltage in the experimental stage for each product. The predetermined target DC link voltage is stored in a microcontroller (70 in FIG. 4), and also sets a target switch on time until reaching the target DC link voltage. The target switch-on time is a value according to the experimental value, which is also stored in the microcontroller.

When the DC link voltage detector 66 of FIG. 4 detects the current DC link voltage generated by the DC link voltage generator 58 of FIG. 4 and transmits the current DC link voltage to the microcontroller (step S300), the microcontroller currently connects the DC link. After comparing the voltage with a predetermined target DC link voltage, it is determined whether the current DC link voltage is higher than the predetermined target DC link voltage (S310).

If the current DC link voltage is higher than the predetermined target DC link voltage in step S310, the predetermined target switch-on time is decreased to set the switch-on time Ton (step S320), and the current DC link voltage is set to the predetermined target DC. If it is not higher than the link voltage, the predetermined target switch-on time is increased to set the switch-on time Ton (step S330).

The switch-on time Ton set in this way determines the operation time of the IGBT switch in the process of FIG. 5B.

6 is a waveform diagram of an input voltage and an input current according to a partial switching control method in an inverter air conditioner according to the present invention, (a) is a waveform diagram of an input voltage and an input current according to a partial switching control method, and (b ) Is a power supply phase detection waveform diagram of detecting the zero crossing point of the input voltage in the input voltage phase detection unit, and (c) is a partial switching operation waveform diagram of the IGBT switch from the zero crossing point.

When the voltage phase detection waveform is generated by detecting the zero crossing point of the input voltage from the input voltage phase detection unit (FIG. 5B), after a predetermined time T1 has elapsed from the zero crossing point, S150 in step S120 of FIG. 5A. The IGBT switch is turned on by calculating the on delay time (T2) through the process described in the step.

In this case, the on delay time T2 is determined so that the time at which the IGBT switch is turned on is determined to be a time when it is determined that sufficient power factor compensation can be achieved by partial switching control, that is, a time when the output power has risen above a predetermined level. ) Depends on the current power consumption.

Therefore, according to the present invention, the waveform of the current passing through the reactor can be adjusted to a shape that can minimize the loss of unnecessary current while satisfying the power factor as in the "B" portion of (a).

According to the power factor correction method of the inverter air conditioner according to the present invention, in the inverter air conditioner employing the partial switching control method for power factor correction, the on time of the switching element is changed from the zero crossing time of the input voltage to the power consumption. By varying accordingly, the power factor can be increased by optimal switching for each power consumption, and the loss of unnecessary current can be reduced.

1 is a control block diagram for power factor correction in a conventional active inverter air conditioner.

2 is a waveform diagram of an input voltage and an input current according to power factor compensation of a conventional active inverter air conditioner.

3 is a waveform diagram of an input voltage and an input current according to a partial switching control method in a conventional inverter air conditioner.

4 is a control block diagram for power factor correction in the inverter air conditioner according to the present invention.

5A to 5C are flowcharts illustrating a method for controlling power factor correction of an inverter air conditioner according to the present invention.

6 is a waveform diagram of an input voltage and an input current according to a partial switching control method in an inverter air conditioner according to the present invention.

* Description of the symbols for the main parts of the drawings *

50: power stage 52: reactor

54: IGBT switch 56: rectifier circuit

58: DC voltage generator 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 76: input current detector

Claims (4)

A control method of an inverter air conditioner including a reactor for passing only a specific frequency in an input commercial AC power source and a power factor compensator for performing a switching operation at each zero crossing point of an input voltage to compensate for the power factor of the power source passing through the reactor. To A method for compensating power factor of an inverter air conditioner, wherein the switching operation is performed by varying a time according to an on delay time after a predetermined time elapses from a zero crossing time point of an input voltage. The method of claim 1, The predetermined time is a power factor compensation control method of the inverter air conditioner, characterized in that the time taken for the voltage phase and the current phase to be equal. The method of claim 1, The on-delay time is short when the current power consumption is large, the value is changed according to the current power consumption as long as the current power consumption is small, the power factor compensation control method of the inverter air conditioner, characterized in that . The method of claim 3, wherein The on delay time may include calculating current power consumption, calculating power consumption ratio which is a ratio of current power consumption to standard power consumption, calculating a variable delay time according to a standard delay time and the power consumption ratio, and the standard delay. And calculating the time delay by adding the variable delay time to the power factor correction control method of the inverter air conditioner.