WO2018131769A1

WO2018131769A1 - Device for controlling power factor and method for controlling power factor

Info

Publication number: WO2018131769A1
Application number: PCT/KR2017/009828
Authority: WO
Inventors: 임금성
Original assignee: 주식회사 모스트파워; 임금성
Priority date: 2017-01-11
Filing date: 2017-09-07
Publication date: 2018-07-19
Also published as: KR101793696B1

Abstract

The present invention relates to a device for controlling a power factor and a method for controlling a power factor which control a power factor by using phase control, and the present invention has an effect of performing power factor control through phase control by sequentially performing on-control and off-control within one period.

Description

Power factor control device and power factor control method

The present invention relates to a power factor control apparatus and a power factor control method, and more particularly, to a power factor control apparatus and a power factor control method for controlling a power factor using phase control.

Current that changes in magnitude and direction periodically with time is called alternating current, and voltage that changes in magnitude and direction periodically with time is called alternating current voltage.

An AC power source having a sinusoidal wave shape may have various frequencies, but generally, an AC power source having a frequency of 50 Hz or 60 Hz is used. In the case of 60Hz, which is mainly used at present, the half cycle time is 8.33ms and the phase angle corresponds to 0 ° ~ 180 °.

In a DC circuit, power = voltage x current, but in an AC circuit, the product of the effective value of the current times the effective value of the voltage does not necessarily become the power. In other words, in the AC circuit, the product of the voltage and the current is called the apparent power, and the power factor is not achieved until the power factor is multiplied. In this case, the power factor means the ratio of the active power to the apparent power.

In general, in the case of an AC power supply, a phase difference θ of voltage and current is generated by a capacitance or inductance component present in a circuit. In this case, the effective power is expressed as voltage x current x cos θ, the cos θ value is referred to as a power factor (PF), and the sin θ value is referred to as inefficiency.

A large power factor means that the active power is close to the apparent power, so that power from the power source is efficiently delivered to the load. However, since the power factor is low, it means that power from the power source is not transmitted to the load efficiently. Therefore, it is necessary to perform power factor control to increase the power factor.

An object of the present invention is to perform efficient power factor control by using phase control in performing power factor control.

The power factor control device according to the present invention for solving the above technical problem, the voltage sensing unit for detecting the phase of the voltage waveform, the current sensing unit for detecting the phase of the current waveform, switching the input signal is output or cut off toward the load And a controller configured to control the switching operation of the switching unit by using the switching unit to perform the switching and the phase information of the voltage and current acquired through the voltage sensing unit and the current sensing unit.

In addition, the power factor control method according to the present invention for solving the above technical problem, the step of detecting the phase of the voltage waveform, the phase of the current waveform, and the input waveform at the time when the voltage waveform has a constant phase And performing phase control on the output waveform when the current waveform has a constant phase.

The present invention has an effect of performing power factor control through phase control by sequentially performing on control and off control in one period.

In addition, the present invention has the effect of enabling power saving control through power factor control.

Fig. 1 shows waveforms of voltage and current in the case of the forward phase.

2 shows waveforms of voltage and current in the case of the ground.

3 shows an example of a signal waveform according to phase on control.

4 shows an example of a signal waveform according to phase off control.

5 is an embodiment illustrating a power factor control method using phase control in the case of fastening.

Fig. 6 shows waveforms after performing power factor control using phase control in the case of true phase.

7 illustrates an embodiment of a power factor control method using phase control in the case of the ground.

8 shows waveforms after performing power factor control using phase control in the case of the ground.

9 shows a power factor control apparatus according to an embodiment of the present invention.

The present invention provides a voltage sensing unit for sensing a phase of a voltage waveform, a current sensing unit for sensing a phase of a current waveform, a switching unit for switching an input signal to be output or cut off toward a load, and the voltage sensing unit and the current. It includes a control unit for controlling the switching operation of the switching unit by using the phase information of the voltage and current obtained through the sensing unit.

In addition, the present invention provides a method for detecting a phase of a voltage waveform, detecting a phase of a current waveform, performing phase control on an input waveform at a time when the voltage waveform has a constant phase, and And performing phase control on the output waveform at a point in time with a constant phase.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows voltage and current waveforms in the case of a leading phase.

As shown in Fig. 1, in the case of the fast phase, the phase of the current precedes the phase of the voltage.

2 shows waveforms of voltage and current in the lagging phase.

As shown in FIG. 2, in the case of the ground, the phase of the voltage precedes the phase of the current.

In the power factor control method according to the present invention, the power factor is controlled to be 1 within the effective period by performing phase on control or phase off control on the current waveform and the voltage waveform.

In general, phase control refers to controlling only a part of all sinusoidal inputs to be output based on a half cycle with respect to an AC voltage. Such phase control methods include a phase on control method and a phase off control method.

The phase on control method does not output a voltage (or current) signal for a predetermined time from the zero crossing time point, and then controls to output a voltage (or current) when a specific time point is reached. That is, since there is no output signal for a predetermined time from the zero crossing time point and output starts at a specific time point, this is called phase-on control.

On the other hand, the phase-off control method outputs a voltage (or current) signal for a predetermined time from the time of zero crossing, and then controls not to output the voltage (or current) when the specific time is reached. That is, since the signal is continuously output from the time of zero crossing and the output is cut off at a specific time, this is called phase-off control.

3 shows an example of a signal waveform according to phase on control.

Referring to FIG. 3, the AC voltage is blocked from the first zero crossing point T11 to the on control point T12. On the other hand, the AC voltage signal starts to be output as soon as the on-control time point T12 is reached, and the output of the AC voltage is continued until the second zero crossing point (phase angle 180 °) T13. Then, the output of the AC voltage is cut off from the second zero crossing time point (phase angle 180 °) T13. The AC voltage is output again from the moment when the on-control time point T14 is reached, and the output of the AC voltage continues until the third zero crossing time point T15 (phase angle 360 °).

4 shows an example of a signal waveform according to phase off control.

Referring to FIG. 4, an AC voltage is output from the first zero crossing point T21 to the off control point T22. Then, the AC voltage starts to be cut off from the OFF control point T22, and the AC voltage is cut off until the second zero crossing point (phase angle 180 °) T23. Then, the AC voltage output starts from the second zero crossing time T23 and continues until the off control time T24. The output of the AC voltage is cut off from the off control point T24 to the instant (phase angle 360 °) of the third zero crossing point T25.

As shown in FIG. 5, in the case of a true phase, power factor control may be performed by performing phase on control at a specific time point based on a voltage waveform and then performing phase off control at a specific time point based on a current waveform. Can be. In this case, the specific time point based on the voltage waveform is preferably a zero crossing time point of the voltage. On the other hand, the specific time point based on the current waveform is preferably a zero crossing time point of the current.

Fig. 6 shows waveforms after performing power factor control using phase control in the case of true phase. That is, the waveforms of the phase-on control are performed at the time point T31 of the valid section and the phase-off control is performed at the end point T32 of the valid section.

As shown in FIG. 6, in the case of a true phase, when the phase on control is performed at the zero crossing point T31 of the voltage and the phase off control is performed at the zero crossing point T32 of the current, it is invalid within the effective period. Since power is lost, the power factor can be set to 1.

As shown in FIG. 7, in the case of the ground, power factor control may be performed by performing phase on control at a specific time point based on a current waveform and then performing phase off control at a specific time point based on a voltage waveform. Can be. In this case, the specific time point based on the current waveform is preferably a zero crossing time point of the current. On the other hand, the specific time point based on the voltage waveform is preferably a zero crossing time point of the voltage.

8 shows waveforms after performing power factor control using phase control in the case of the ground. That is, the waveforms of the phase-on control are performed at the time point T41 of the valid section and the phase-off control is performed at the end point T42 of the valid section.

As shown in FIG. 8, in the case of the ground, when the phase on control is performed at the zero crossing point T41 of the current and the phase off control is performed at the zero crossing point T42 of the voltage, it is invalid within the effective section. Since power is lost, the power factor can be set to 1.

A method of performing the power factor control shown in FIG. 6 by using the power factor control device 90 shown in FIG. 9 will now be described.

The switching unit 92 performs an on operation at the zero crossing time point T31 of the voltage, and performs a switching off operation at the zero crossing time point T32 of the current. That is, when the controller 94 detects the zero crossing point T31 of the voltage through the voltage detector 91, the control unit 94 performs a switching on operation at the zero crossing point T31 of the voltage. . In addition, when the controller 94 detects the zero crossing point T32 of the current through the current detector 97, the control unit 94 performs a switching-off operation at the zero crossing point T32 of the current. .

Meanwhile, a method of performing the power factor control shown in FIG. 8 using the power factor control device 90 shown in FIG. 9 will be described below.

The switching unit 92 performs an on operation at the zero crossing point T41 of the current, and performs a switching off operation at the zero crossing point T42 of the voltage. That is, when the controller 94 detects the zero crossing point T41 of the current through the current detector 97, the control unit 94 performs a switching on operation at the zero crossing point T41 of the current. . In addition, when the controller 94 detects the zero crossing point T42 of the voltage through the voltage detector 91, the control unit 94 performs a switching-off operation at the zero crossing point T42 of the voltage. .

On the other hand, the THD (Total Harmonic Distortion) problem that may occur during phase control is a reactive power generated at high frequency due to the harmonics of the power used and the distortion of the load current. .

9 shows an embodiment in the case of a single phase, but the present invention can be applied not only to a single phase but also to a multiphase.

The present invention can be used to control power factor in an AC circuit.

Claims

A voltage sensing unit sensing a phase of the voltage waveform;

A current sensing unit sensing a phase of the current waveform;

A switching unit which performs switching so that an input signal is output or cut off toward the load; And

Control unit for controlling the switching operation of the switching unit by using the phase information of the voltage and current obtained through the voltage sensing unit and the current sensing unit

Power factor control device comprising a.
The method of claim 1,

The control unit,

When the switching on operation is performed based on the phase information of the voltage, the switching off operation is performed based on the phase information of the current.

When the switching on operation is performed based on the phase information of the current, the control is performed to perform the switching off operation based on the phase information of the voltage.

Control unit for controlling the switching on and switching off operation of the switching unit to be performed alternately

Power factor control device comprising a.
The method of claim 2,

The voltage and phase information of the current is a power factor control device, characterized in that the information on the time of zero crossing of the current and voltage.
The method of claim 3, wherein

And the control unit controls the switching unit to perform a switching on operation at a zero crossing point of voltage, and controls the switching unit to perform a switching off operation at a zero crossing point of current.
The method of claim 4, wherein

Power factor control device characterized in that the phase of the current leads the phase of the voltage
The method of claim 3, wherein

And the control unit controls the switching unit to perform a switching-on operation at a zero crossing point of current, and controls the switching unit to perform a switching-on operation at a zero crossing point of voltage.
The method of claim 6,

And a lagging phase of the current phase.
Sensing the phase of the voltage waveform;

Sensing the phase of the current waveform;

Performing switching control on an input signal when the voltage waveform has a constant phase; And

Performing phase control on an input signal when the current waveform has a constant phase

Power factor control method comprising a.
The method of claim 8,

Perform phase-on control at the zero crossing point of the voltage waveform,

And a phase-off control is performed at the zero crossing point of the current waveform.
The method of claim 8,

Perform phase on control at the zero crossing time point of the current waveform,

And a phase off control is performed at the zero crossing point of the voltage waveform.