JP2019075880A - Power factor improvement circuit and power supply circuit - Google Patents

Abstract

To improve an input power factor when using an inverter with three input ends for a single phase AC power supply.SOLUTION: In a power factor improvement circuit 200, since phases of currents I, Iare shifted by a reactor 204 and a capacitor 205, a shape of a waveform of a supply current Ican be improved and an input power factor can be improved. Further, by improving the input power factor, it is possible to make a current value (effective value and the like) lower than in a case where the power factor improvement circuit 200 is not provided. Also, the power factor improvement circuit 200 improves the waveform of the power supply current I, so that harmonics are reduced, and thus noise can also be reduced. Also, due to the improvement of the waveform, a peak value is lowered. For example, when a combination of a direct current battery and an inverter for converting a direct current into an alternating current is adopted as a single-phase alternating current power supply AC, a load on switching elements and the like used for the inverter can be reduced.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power factor correction circuit and a power supply circuit.

  Conventionally, an inverter is known as a circuit used for a power supply circuit. For example, Patent Document 1 discloses a three-phase input, three-phase output inverter.

JP 2000-116137 A

  An inverter having three inputs, such as the inverter described in Patent Document 1, is usually used for a three-phase AC power supply and not for a single-phase AC power supply. If an inverter having three input terminals is used for a single-phase AC power supply, the current input to the inverter is distorted, and the input power factor (the active power of the AC input side of the inverter and the apparent power Ratio) is bad. Although it is conceivable to use an AC reactor or a DC reactor to improve the input power factor, these are effective for a three-phase AC power supply, but almost effective for a single-phase AC power supply. Do not exert.

  An object of the present invention is to improve the input power factor when using an inverter having three input terminals for a single-phase AC power supply.

A power factor correction circuit according to a first aspect of the present invention is
A first input end and a second input end to which a single-phase AC voltage output from a single-phase AC power is input;
A first output end, a second output end, and a third output end connected to each of three input ends provided in the inverter;
A node connected to the first input end;
A first element having one end connected to the node and the other end connected to the first output end;
A second element having one end connected to the node and the other end connected to the second output end,
The second input end and the third output end are connected;
The first element and the second element are two different ones of a resistor, a capacitor and a reactor.

The first element is the reactor,
The second element is the capacitor.
You may do so.

A power supply circuit according to a second aspect of the present invention is
The above power factor improvement circuit,
The inverter comprising the three input ends to which the first output end, the second output end, and the third output end are respectively connected;
Equipped with

  According to the present invention, it is possible to improve the input power factor when using an inverter having three input ends with respect to a single-phase AC power supply as compared with the case where the power factor improvement circuit is not provided.

It is a circuit diagram of a power supply circuit concerning one embodiment of the present invention. (A) is a graph showing the waveform of the current _{I 1,} and a power supply voltage _{V AC} waveform, the. (B) is a graph showing the waveform of the current I _{2 and} the waveform of the power supply voltage V _AC . 5 is a graph showing a waveform of a power supply current I _{AC and} a waveform of a power supply voltage V _AC . It is a graph which shows the waveform of power supply current I _AC when not providing a power factor improvement circuit, and the waveform of power supply voltage V _AC . It is a circuit diagram of the power factor improvement circuit concerning a modification.

  A power supply circuit 100, a power factor improvement circuit 200 and the like according to an embodiment of the present invention will be described with reference to the drawings.

(Configuration of power supply circuit 100)
The power supply circuit 100 is a circuit that converts a single-phase alternating current from a single-phase alternating current power supply AC into a three-phase alternating current and supplies it to the motor M. As shown in FIG. Prepare. An example of a single-phase alternating current power supply AC is a combination of a direct current battery and an inverter that converts direct current into alternating current. An example of the motor M is a motor that raises a gondola used for maintenance of a building or the like. The power supply circuit 100 is mounted on, for example, the gondola.

Power factor correction circuit 200, the power supply current I _AC waveform from the single-phase AC power source AC, that close to the supply voltage V _AC waveform circuit for improving the power factor of the power supplied from single-phase AC power source AC It is. The power factor correction circuit 200 includes input terminals 201 to 202, nodes (nodes) 203, a reactor 204, a capacitor 205, and output terminals 206 to 208.

  A single phase AC power supply AC is connected to the input terminal 201 and the input terminal 202. A node 203 is connected to the input terminal 201. One end of the reactor 204 is connected to the node 203, and the other end of the reactor 204 is connected to the output terminal 206. One end of the capacitor 205 is connected to the node 203, and the other end of the capacitor 205 is connected to the output terminal 207. The input terminal 202 is connected (shorted) to the output terminal 208.

  The inverter 300 converts the alternating current supplied from the single-phase alternating current power supply AC through the power factor correction circuit 200 into a three-phase alternating current and supplies it to the motor M. At this time, the inverter 300 can control the voltage and frequency of the AC voltage output to the motor M.

  The inverter 300 includes input terminals 301 to 303, a rectifier circuit (AC-DC converter) 304, a DC reactor 305, a smoothing capacitor 306, a switching circuit (DC-AC inverter) 307, a controller 308, and an output terminal 309. To 311 and nodes N1 and N2. As the inverter 300, for example, a known inverter of three-phase (R-phase, S-phase, T-phase) input and three-phase (U-phase, V-phase, W-phase) output can be used.

  Output terminals 206 to 208 of the power factor correction circuit 200 are connected to the input terminals 301 to 303, respectively. A rectifier circuit 304 is connected to each of the input terminals 301 to 303. The rectifier circuit 304 is composed of six diodes D1 to D6. The diodes D 1 and D 2 are connected in series, and the midpoint is connected to the input terminal 301. The diodes D 3 and D 4 are connected in series, and the midpoint is connected to the input terminal 302. The diodes D5 and D6 are connected in series, and the middle point thereof is connected to the input terminal 303.

  One end of the DC reactor 305 is connected to one of the two output ends of the rectifier circuit 304. The other end of the DC reactor is connected to the node N1. The other of the two output ends of the rectifier circuit 304 is connected to the node N2. One end of the smoothing capacitor 306 is connected to the node N1, and the other end is connected to the node N2. Furthermore, two input terminals of the switching circuit 307 are also connected to each of the node N1 and the node N2. The switching circuit 307 includes six switching elements S1 to S6 and freewheeling diodes D7 to D12 connected in parallel to the six switching elements S1 to S6, respectively. The switching elements S1 and S2 are connected in series, and the middle point thereof is connected to the output terminal 309. The switching elements S3 and S4 are connected in series, and the middle point thereof is connected to the output terminal 310. The switching elements S5 and S6 are connected in series, and the middle point thereof is connected to the output terminal 311. The motor M is connected to the output terminals 309-311.

  The controller 308 is configured to include a computer and the like. The controller 308 supplies a control signal to each of the switching elements S1 to S6, and controls on / off of these to cause the switching circuit 307 to generate a three-phase AC voltage and output it from the output terminal 309 to the output terminal 311. Thereby, three-phase alternating current is supplied to the motor M from the output terminal 309 to the output terminal 311. The controller 308 controls the voltage value, frequency, and the like of the three-phase AC voltage by controlling the on / off timing of each of the switching elements S1 to S6 (the voltage value and frequency of the three-phase AC voltage are Can be specified by operating a predetermined operation unit). The controller 308 also controls on / off of each of the switching elements S1 to S6 by, for example, PWM (Pulse Width Modulation) control. The controller 308 may control on / off of each of the switching elements S1 to S6 by feedback control (a circuit for feedback can be a known one).

(Operation of power supply circuit 100)
A power supply voltage V _AC (single-phase alternating current voltage) output from the single-phase alternating current power supply AC is applied between the input terminal 201 and the input terminal 202. By application of power supply voltage V _AC , the phase of current I ₁ flowing between node 203 and output terminal 206 is delayed by reactor 204 with respect to power supply voltage V _AC . An example of a relationship between the current _{I 1} and the supply voltage _{V AC} shown in FIG. 2 (A). On the other hand, the phase of the current I ₂ flowing between the node 203 and the output terminal 207 is advanced by the capacitor 205 with respect to the power supply voltage V _AC . An example of the relationship between the current _{I 2} and the supply voltage _{V AC} shown in FIG. 2 (B). The power supply current I _AC (current flowing from the single-phase AC power supply AC) flowing through the input terminal 201 is a combination of the current I ₁ and the current I ₂ . FIG. 3 shows an example of the relationship between the current I _AC and the power supply voltage V _AC . The inductance of the reactor 204 of the power factor correction circuit 200 and the capacitance of the capacitor 205 may be set to have suitable values for power factor correction. For example, the inductance of the reactor 204 is 2.3 mH, and the capacitance of the capacitor 205 is 200 μF.

As a comparative example of FIG. 3, without providing the power factor correction circuit 200 connects the single-phase AC power source AC to the input terminals 301 and 303, the supply voltage V _AC in case the input terminal 302 that no connection _{(single-phase} An example of the relationship between the output voltage of the AC power supply AC and the power supply current I _AC flowing to the input terminal 301 is shown in FIG.

Comparing the waveform of FIG. 3 with the waveform of FIG. 4, the peak value is lower in FIG. 3, and a waveform is obtained which has a long period (T) in which the current value rises and falls in the positive or negative direction. , Close to the waveform (sine wave) of the power supply voltage V _AC . Therefore, the power factor (input power factor) of the power from the single-phase AC power supply AC is improved by using the power factor improvement circuit 200.

  The alternating current from the power factor correction circuit 200 is rectified by the rectification circuit 304, converted to direct current, and smoothed by the smoothing capacitor 306. The DC reactor 305 suppresses the generation of harmonics. The direct current smoothed by the smoothing capacitor 306 is converted into a three-phase alternating current by the switching circuit 307, and is supplied to the motor M through the output terminals 309 to 311.

(Effects in the embodiment etc.)
As described above, in the power factor correction circuit 200, the phases of the currents I ₁ and I ₂ are shifted by the reactor 204 and the capacitor 205. Therefore, the power factor correction circuit 200 can improve the waveform shape of the power supply current I _AC , The power factor (the ratio of the active power on the AC input side of the inverter 300 to the apparent power) can be improved (see FIGS. 2 to 4). Further, by improving the input power factor, it is possible to make the current value (effective value and the like) lower than in the case where the power factor improvement circuit 200 is not provided. Furthermore, the power factor correction circuit 200 improves the waveform of the power supply current I _AC , thereby reducing harmonics and hence noise. In addition, due to the improvement of the waveform, the crest value is lowered. For example, a switching element etc. used in the inverter when a combination of a direct current battery and an inverter for converting direct current into alternating current is adopted as single phase AC power supply AC. It is possible to reduce the load on The circuit configuration of the power factor improvement circuit 200 is simple as shown in FIG. 1, and according to the present embodiment, the input power factor can be improved with a simple circuit configuration.

The inventor of the present application adopts a motor for raising a gondola used for maintenance of a building or the like as the motor M, and employs an inverter built-in control panel mounted on the gondola as the inverter 300 to obtain single-phase AC power supply AC. A combination of a battery and an inverter (AC 200 V) was employed to measure the power supply current I _{AC and the} like. 2 and 3 show an example of the waveform at that time. At this time, the power factor improved from 0.7 to 0.85. During the experiment, the rising gondola was shaken up and down, but no significant influence on the power supply current I _AC was observed. When the power factor correction circuit 200 is not provided, the power supply current I _AC changes little by little due to the effect of swinging the rising gondola up and down. Therefore, by providing the power factor correction circuit 200, it is also possible to provide resistance to load fluctuations.

  If you want to convert single-phase alternating current from single-phase AC power supply AC, the input current to the inverter is distorted whether using a single-phase input inverter or using a three-phase input inverter (such as the inverter 300 above) The input power factor is bad. The input power factor when using a single-phase AC power source is hardly improved by using an AC reactor or a DC reactor generally used to improve power factor. However, as in this embodiment, as the inverter used for single-phase AC power supply AC, three-phase input inverter 300 which is not usually used is daringly adopted, and power factor improvement circuit 200 is used there for better operation. Input power factor can be obtained. In particular, it is also possible to obtain a better power factor than when employing a single-phase input inverter.

(Others)
The expression "connected" such as "connected" includes connecting not only directly through other elements but also through elements which do not impair the circuit's original function.

(Modification)
The present invention is also applicable to power supply circuits used for other applications. For example, the present invention may be applied to a power supply circuit such as an air conditioner. Specifically, a three-phase output, three-phase input inverter is adopted as an inverter of a power supply circuit of an air conditioner, a commercial power supply is adopted as a single phase AC power supply AC, and the commercial power supply and the inverter (corresponding to the inverter 300) And a power factor correction circuit 200 is provided between them. The load connected to the power supply circuit according to the present invention may also be something other than a motor. The single-phase alternating current power supply AC may be a commercial power supply, or may be a combination of a direct current power supply and an inverter that converts direct current into alternating current.

  The inverter 300 may not include the DC reactor 305. The inverter 300 may include an AC reactor. Power factor correction circuit 200 may be externally connected to a conventional three-phase input three-phase output inverter. The output of inverter 300 may be single phase.

  The power factor correction circuit 200 and the inverter 300 may be manufactured as one power supply circuit from the beginning. In such a case, the three output ends (output parts on the circuit) of the power factor correction circuit 200 are directly connected to the three input ends (input parts on the circuit of the rectifier circuit 304) of the inverter 300 without passing through the terminals. It may be connected by wiring or the like. The inverter 300 should just be able to convert the alternating current supplied via the power factor improvement circuit 200. That is, the inverter 300 may be any one having three input terminals, and may not be called a three-phase input inverter (an inverter to which an alternating current whose phase is shifted by 120 degrees is input). With regard to the three-phase input inverter, for example, when the power factor correction circuit and the inverter are manufactured as one power supply circuit, the inverter is taken out from the power supply circuit and the three-phase alternating current is input to the inverter. If it can operate normally and can output an alternating current, the inverter can be said to be a three-phase input inverter.

  Each of the three output terminals 206 to 208 of the power factor correction circuit 200 may be connected to any one of the input terminals 301 to 303 of the inverter 300. For example, the output terminal 206 may be connected to the input terminal 303.

A resistor R may be provided instead of the reactor 204 or the capacitor 205 of the power factor correction circuit 200 (see the power factor correction circuits 200A and 200B in FIGS. 5A and 5B). However, better when using the reactor 204 or capacitor 205, it is possible to increase the difference between the phase and the current I ₂ phase currents I _1, it can be improved more power factor.

(Scope of the present invention)
The present invention is capable of various embodiments and modifications. In addition, the above-described embodiment and modification are for explaining the present invention, and do not limit the scope of the present invention.

Reference Signs List 100 power supply circuit 200 power factor improvement circuit 201 to 202 input terminal 203 node 204 reactor 205 capacitor 206 to 208 output terminal 300 inverter 301 to 303 input terminal 304 rectifier circuit 305 DC reactor 306 smoothing capacitor 307 switching circuit

Claims (3)

A first input end and a second input end to which a single-phase AC voltage output from a single-phase AC power is input;
A first output end, a second output end, and a third output end connected to each of three input ends provided in the inverter;
A node connected to the first input end;
A first element having one end connected to the node and the other end connected to the first output end;
A second element having one end connected to the node and the other end connected to the second output end,
The second input end and the third output end are connected;
The first element and the second element are two different ones of a resistor, a capacitor, and a reactor.
Power factor correction circuit. The first element is the reactor,
The second element is the capacitor.
The power factor correction circuit according to claim 1. A power factor correction circuit according to claim 1 or 2;
The inverter comprising the three input ends to which the first output end, the second output end, and the third output end are respectively connected;
Power supply circuit comprising:

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