JP5272319B2 - Power converter - Google Patents

Description

The present invention relates to a power conversion device using an inverter.

  A conventional power factor improvement type power converter described in Patent Document 1 will be described with reference to FIG. As shown in FIG. 5, the conventional power conversion apparatus 300 includes a reactor 202 having one end connected to one output end of the single-phase AC power supply 201, and a short-circuit unit 203 that short-circuits the AC power supply 201 via the reactor 202. A rectifier circuit 204 connected via the input current detection circuit 230 between the other end of the AC power supply 201 not connected to the AC power supply 201 and a smoothing capacitor 206 connected in series to both ends of the DC output of the rectifier circuit 204. One of the AC inputs of the rectifier circuit 204, a control circuit 207 that outputs a short-circuit pulse signal 296 that operates the short-circuit means 203 using a zero-cross signal 292 that detects a zero-cross of the AC power supply 201 as a reference timing, and an input from the AC power supply 201 The input current detection circuit 23 detects the input current Is and outputs the input current value 298 to the control circuit 207. When, and a DC voltage detection circuit 211 which outputs a DC voltage value 293 detects the voltage across the smoothing capacitor 206 to the control circuit 207. In addition, a motor drive unit 301 including an inverter circuit 210 connected to a DC output of the power conversion device 300 and a compressor 220 incorporating a motor is also shown.

  The zero-cross detection circuit 208 inputs the voltage across the AC power supply 201, and outputs a zero-cross signal 292 that outputs a falling signal or a rising signal when the AC voltage of the AC power supply 201 passes through the zero-crossing point and the polarity changes. Input to the control circuit 207.

  The control circuit 207 uses the rising or falling edge of the input zero-cross signal 292 as a reference timing, the delay time T1 from which the short-circuit means 203 starts the short-circuit operation, and the operation time T2 that is the short-circuit period. And short circuit pulse signal 296 is output to short circuit means 203. The delay time T1 and the operation time T2 are previously stored in the control circuit 207 or calculated by the control circuit 207.

  The short-circuit means 203 is composed of a power semiconductor switching element, and short-circuits the AC power supply 201 via the reactor 202 according to the short-circuit pulse signal 296. The power factor of the AC power supply 201 is improved by this short-circuit opening operation.

  The power conversion device 300 of the conventional example performs an operation of short-circuiting the AC power supply 201 through the reactor 202 once or a plurality of times in a half cycle of the power supply, widening the conduction angle of the power supply current and improving the power supply power factor. , AC power is converted to DC power.

The delay time T1 and the operation time T2 are controlled so as to make the DC voltage Vd constant by utilizing the relationship that the sum of the delay time T1 and the operation time T2 is equal if the input current is detected within a predetermined interval. It is what is done. In addition, the delay time T1 and the operation time T2 are independently controlled using functions according to the input current.
JP 2006-180700 A

  In the prior art, the input current of the AC power source is used to determine the delay time T1 and the operation time T2, and it is necessary to detect the input current.

  By calculating the inverter output power from the DC voltage and the inverter output current, and determining the delay time T1 and the operation time T2, the power converter is controlled without detecting the input current.

(Embodiment 1)
The power conversion device according to claim 1, claim 2, claim 4, and claim 6 will be described with reference to FIGS. 1, 2, 3, and 4. FIG.

  FIG. 1 is a block diagram in which the present invention is used for driving a motor. Reactor 2 having one end connected to single-phase AC power supply 1, short-circuit means 3 for short-circuiting AC power supply 1 via reactor 2, side not connected to AC power supply 1 of reactor 2, and the other end of AC power supply 1 The rectifier circuit 4 connected in between, the smoothing capacitor 6 connected in parallel to both ends of the DC output of the rectifier circuit 4, and the short-circuit pulse for operating the short-circuit means 3 using the zero-cross signal 92 for detecting the zero-cross of the AC power supply 1 as a reference timing A control circuit 7 that outputs a signal 96; an inverter drive unit 12 that is built in the control circuit 7 and controls the inverter; an inverter circuit 10 that is connected in parallel to the smoothing capacitor 6; and an inverter output current that is output from the inverter circuit 10 An inverter output current detection circuit 9 that detects Io (hereinafter referred to as Io) and outputs an inverter output current value 98 to the inverter drive unit 12. The DC voltage detection circuit 11 detects the voltage Vd (hereinafter referred to as Vd) across the smoothing capacitor 6 and outputs a DC voltage value 93 to the inverter drive unit 12. The inverter drive unit 12 corresponds to the inverter output current value 98. The motor 20 driven by the output is connected.

FIG. 2 shows the relationship between the AC voltage of the AC power source 1, the zero-cross signal 92, and the delay time T1 (hereinafter T1) and operation time T2 (hereinafter T2) of the short-circuit pulse signal 96. Zero-cross detecting circuit 8 receives the voltage across the AC power source 1, passes through the AC voltage Va of the AC power source 1 (hereinafter Va) is the zero-cross point, the rising signal at a timing at which the polarity is changed or the output of the falling signal, This is input to the control circuit 7 as a zero cross signal 92. The control circuit 7 uses, as a reference, the rising or falling edge of the input zero-cross signal 92 as a delay time T1 that is a period until the short-circuit means 3 operates and an operation time T2 that is a short-circuiting period. The short-circuit pulse signal 96 is output to the short-circuit means 3. The short-circuit means 3 is configured by a semiconductor switching element such as a diode bridge and IGBT, and improves the power factor of the AC power supply 1 by short-circuiting the AC power supply 1 via the reactor 2 according to the short-circuit pulse signal 96.

  A method for calculating the inverter output power Wi (hereinafter referred to as Wi) will be described with reference to FIG. Wi is a function of the output voltage Vo (hereinafter referred to as Vo) and Io of the inverter and the phase difference φ. In order to control the motor 20 by the inverter drive circuit 12, Vo is a vector on the dq axis from the drive signal of Vd and the inverter.

として算出されている。ｄｑ軸はモータ制御において既知であるので説明を省略する。Ｉｏはインバータ出力電流検出回路９のインバータ電流出力９８にてインバータ駆動部１２に入力され、同じくｄｑ軸上のベクトル

It is calculated as. Since the dq axis is known in motor control, the description thereof is omitted. Io is input to the inverter drive unit 12 at the inverter current output 98 of the inverter output current detection circuit 9, and is also a vector on the dq axis

として算出されている。また、位相差φはｄｑ軸上でＶｏとＩｏの角度差で表され、図３に示すベクトル図となる。このとき電力Ｗｉは、

It is calculated as. Further, the phase difference φ is represented by an angular difference between Vo and Io on the dq axis, and becomes a vector diagram shown in FIG. At this time, the power Wi is

と定義できる。右辺はベクトルの内積の計算式でもあるので、

Can be defined. Since the right side is also the calculation formula for the inner product of vectors,

となる。ここで、

It becomes. here,

と置き換えると、

Is replaced by

としてＷｉが計算される。

Wi is calculated as follows.

  Next, a method for determining T1 and T2 will be described with reference to FIG. FIG. 4 shows the relationship between Wi, T1, and T2 optimum power factor points obtained by simulation. It can be seen that T1 monotonically decreases with respect to Wi, and T2 monotonically increases with respect to Wi. That is, the operation at the power factor optimum point can be performed by changing T1 and T2 with respect to the change in Wi. Usually, Vd decreases as Wi increases. Therefore, when control is performed to keep Vd constant, T1 and T2 are power factor optimum points 150 (hereinafter referred to as T1a) including T1 Vd correction in FIG. It changes like a power factor optimum point 151 (hereinafter referred to as T2a) including the correction of Vd.

  Since the change in T1 with respect to the change in Wi is smaller than T2, T1 is controlled by the Wi function described with reference to FIG. 3 in order to perform more stable control, and T2 is determined by simulation or actual measurement. By storing in advance and setting the value of T2a according to the value of Wi, control can be performed so that T1 and T2 become power factor optimum points.

(Embodiment 2)
The power conversion device according to claims 3 and 5 will be described. The circuit configuration, the relationship between the zero cross signal and T1, T2, and the method for determining T1 are the same as those in the first embodiment.

  When operating with Vd kept constant, T1 monotonously decreases with respect to Wi, and T2 monotonously increases with respect to Wi. That is, the operation at the power factor optimum point can be performed by changing T1 and T2 with respect to the change in Wi. If T1 is determined using the Wi function described in FIG. 3, T2 can be controlled to be the power factor optimum point by performing known PI control.

  The same effect can be obtained by using not only a current transformer but also a shunt resistor for Io detection.

  Moreover, even if there are a plurality of inverter loads, if each output current is detected, the power factor improvement control can be performed by adding them. Further, even if the power consumption of the circuits other than the inverter load is smaller than that of the inverter load, the power factor is small even if the control is performed by ignoring it.

  The power converter of the present invention can be widely applied to applications having inverter loads by improving the power factor using the power converter.

The block diagram of the power converter device in Embodiment 1, 2 of this invention Diagram showing T1, T2 of AC voltage, zero cross signal, short circuit pulse output of the present invention Explanatory drawing of calculation formula and inner product of Wi in Embodiments 1 and 2 of the present invention Explanatory drawing showing the relationship between T1, T2 and Wi in Embodiments 1 and 2 of the present invention Block diagram of a control device in a conventional embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Reactor 3 Short circuit means 4 Rectifier circuit 6 Smoothing capacitor 7 Control circuit 8 Zero cross detection circuit 9 Inverter output current detection means 10 Inverter circuit 11 DC voltage detection circuit 12 Inverter drive part 20 Motor 92 Zero cross signal 93 DC voltage value 96 Short circuit Pulse signal 100 Power conversion unit 150 Power factor optimum point including correction of Vd of T2 151 Power factor optimum point including correction of Vd of T1 201 AC power source 202 Reactor 203 Short-circuit means 204 Rectifier circuit 206 Smoothing capacitor 207 Control circuit 208 Zero cross detection Circuit 210 Inverter circuit 211 DC voltage detection circuit 220 Compressor 230 Input current detection means 291 AC power supply waveform 292 Zero cross signal 293 DC voltage 296 Short-circuit pulse signal 298 Input current value 300 Power conversion Location 301 motor driver

Claims (3)

A reactor having one end connected to an AC power supply, an AC power supply short-circuit means connected to the other end of the reactor, a rectifier circuit connected in parallel with the AC power-supply short-circuit means, and connected in parallel to the output end of the rectifier circuit A smoothing capacitor, a zero-crossing detection circuit that detects a zero-crossing of the AC power supply and outputs it as a zero- cross signal, a voltage detection circuit that detects the voltage of the smoothing capacitor, and an inverter having an input terminal connected to the output terminal of the rectifying circuit A circuit, a control circuit for controlling the AC power supply short-circuit means and the inverter circuit, and an inverter output current detection circuit for detecting a current flowing through an inverter load connected to an output terminal of the inverter circuit. A delay time T1 from the zero cross until the short circuit operation is started and an operation time T2 that is a short circuit period are set to Control using scan signal and the output of said voltage detecting circuit and an output of the inverter output current detecting circuit A power converter,
In inverter function of the output power the control circuit and the inverter output current output of the DC voltage output the inverter output current detecting circuit is calculated from the inverter drive output that is an output of said voltage detection circuit, controls the delay time T1 The power converter characterized by doing. The power conversion device according to claim 1, wherein the operation time T2 is controlled using a deviation from a target. A reactor having one end connected to an AC power supply, an AC power supply short-circuit means connected to the other end of the reactor, a rectifier circuit connected in parallel with the AC power-supply short-circuit means, and connected in parallel to the output end of the rectifier circuit A smoothing capacitor, a zero-crossing detection circuit that detects a zero-crossing of the AC power supply and outputs it as a zero- cross signal, a voltage detection circuit that detects the voltage of the smoothing capacitor, and an inverter having an input terminal connected to the output terminal of the rectifying circuit A circuit, a control circuit for controlling the AC power supply short-circuit means and the inverter circuit, and an inverter output current detection circuit for detecting a current flowing through an inverter load connected to an output terminal of the inverter circuit. A delay time T1 from the zero cross until the short circuit operation is started and an operation time T2 that is a short circuit period are set to Control using scan signal and the output of said voltage detecting circuit and an output of the inverter output current detecting circuit A power converter,
Using a power factor model value modeling the best point of the power factor obtained from the inverter output power and the DC voltage output at the time of stoppage, which is detected before the operation of the inverter circuit and the AC power supply short-circuit means. The power conversion device controls the operation time T2.

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