JPH02202367A - Power source equipment - Google Patents

Abstract

PURPOSE:To eliminate countermeasure for removing low order harmonics by feeding the output from a rectifier for rectifying AC source voltage directly to an inverter circuit, then performing ON/OFF control of a switching element at suitably high frequency, and reducing low-order harmonics. CONSTITUTION:Output from a rectifier circuit 4 for rectifying AC source voltage is fed, not through a smoothing circuit containing a capacitor, but directly to an inverter circuit 10. In other words, conventional resistor, switch, reactor, capacitor, and fuse are removed and the output from the rectifier circuit 4 is fed directly to the inverter circuit 10. Although high-order harmonics produced through ON/OFF control of the switching element in the inverter circuit 10 is returned, as it is, to the power source line, it has substantially no influence because the frequency exceeds over 1kHz at all times. By such arrangement, low-order harmonics are reduced considerably and countermeasure for removing low-order harmonics can be eliminated.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a power supply device that includes an inverter circuit that controls switching elements on and off, and is particularly suitable for air conditioners. .

(Prior Art) FIG. 12 is a schematic diagram of a conventional power supply device applied to an air conditioner. In the same figure, a commercial AC IL power supply 1
The three-phase AC voltage is manually supplied to a rectifier circuit 4 via a fuse 2 and a magnetic switch 3, and is rectified. The output of the rectifier circuit 4 is applied to a smoothing circuit consisting of a reactor 7 and a capacitor 8 via a parallel connection circuit of a resistor 5 and a switch 6, and is smoothed. Then, the smoothed direct current passes through the fuse 9 and is inputted to the inverter circuit 10 . The inverter circuit 10 converts smoothed direct current into alternating current of variable voltage and variable frequency, and applies the converted alternating current to a compressor motor 11 as a load.

In this case, the rectifier circuit 4 is composed of bridge-connected diodes. Furthermore, the resistor 5 suppresses the inrush current to the capacitor 8 during startup, and by closing the switch 6 when the capacitor 8 is charged to a certain extent, the power loss of the resistor 5 during normal operation is reduced. Make it zero. In addition, the inverter circuit 10 bridge-connects power transistors, and controls these transistors on and off by a control circuit (not shown).
Compressor motor 11 with variable voltage/variable frequency AC
In addition, a compressor (not shown) is operated under capacity control.

This conventional power supply device, viewed from the inverter circuit 10,
Since the input stage is equipped with a capacitor 8, it is widely known as a capacitor input current waveform.

(Problems to be Solved by the Invention) Although a large capacitance capacitor 8 is used as the capacitor 8 constituting the above-mentioned conventional power supply device, and thereby the ripple can be reduced, the input current I^ of the rectifier circuit 4 is as shown in FIG. As shown in , the half waves always look like two lumps.

When the frequency of this input terminal IA was analyzed, as shown in FIG.
It was found that although there are few higher-order harmonic components after the next, it contains many low-order harmonic components such as the 3rd and 5th harmonics, which have high levels.

Therefore, in the conventional power supply device, there was a problem in that a separate measure had to be taken to remove low-order harmonic components that tend to have an adverse effect on the AC power supply line.

This invention was made to solve the above problems, and aims to provide a power supply device that can significantly reduce low-order harmonic components and thereby eliminate the need for measures to remove low-order harmonic components. shall be.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes an inverter circuit that controls switching elements on and off. ! In the S source device, the output of the rectifier circuit that rectifies the AC power supply voltage is supplied to the inverter circuit without going through a smoothing circuit including a capacitor, and at a high frequency that does not adversely affect the AC power line. The present invention is characterized in that the switching element is controlled to turn on and off.

(Function) In the present invention, since the output of the rectifier circuit is supplied to the inverter circuit without going through the smoothing circuit, harmonic components caused by turning the switching element on and off appear on the power supply line. However, if this switching element is controlled on and off at a high frequency, this effect will be reduced, and in fact, low-order harmonic components can be significantly reduced by not using a smoothing circuit including a capacitor.

(Embodiment) FIG. 1 is a schematic diagram of an embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 12 indicate the same elements. The difference from FIG. 12 is that the resistor 5, switch 6, reactor 7, capacitor 8, and fuse 9 in FIG. 12 are removed, and the output of the rectifier circuit 4 is directly supplied to the inverter circuit 10. There is.

According to this configuration, the high-order harmonic components resulting from the on/off control of the switching elements of the inverter circuit 10 are returned to the power supply line as they are, but since the frequency thereof always exceeds IKHz, it has virtually no effect. I won't give anything.

Incidentally, as shown in Figure 2, the input current waveform of the rectifier circuit 4 has high-order harmonics superimposed on the fundamental wave, but low-order harmonics and M waves are significantly reduced.If this waveform is frequency-analyzed, it is shown in Figure 3. become that way. The frequency spectrum shown in Fig. 3 is
When compared with that of the conventional device shown in Figure 4, higher harmonics X1, X2,
Although X3 newly appears, the 3rd harmonic is removed and at the same time the 5th and 7th harmonics are significantly reduced.

In addition, in order to reduce this higher-order descendant one-week wave component, the fourth
As shown in the figure, it is sufficient to add poles (a small capacity noise absorbing electrode 12 and a capacitor 13) that are not intended for voltage smoothing between the rectifier circuit 4 and the inverter circuit 10. The waveform becomes as shown in FIG.

By the way, when the power supply device shown in either FIG. 1 or FIG. 4 is applied to one air conditioning system 20 shown in FIG. 6, the AC input current I of each power supply device 21, 22...
The waveforms of A1 IB... are shown in Figure 7 (a), (b)...
become that way. However, since the higher-order harmonic components change over time and change randomly, the composite current I. The waveform of is leveled as shown in FIG. 7(c).

As shown in Figure 8, the input current waveform when looking at only one air conditioner has a form in which harmonics are superimposed on a sine wave, and its high-order harmonic components X1, X2, and X3 is the ninth
It is relatively large as shown in the figure.

However, when applied to the above-mentioned air conditioning system or when a large number of air conditioners are connected to the same power supply system, the uneven portions are averaged out and the wave becomes approximately rectangular, as shown in Fig. 10. At that time, higher harmonic components X1, X2,
x3 is significantly reduced as shown in FIG.

Thus, according to this embodiment, even if high-order harmonic components appear whose effects can be substantially eliminated, low-order harmonic components can be reliably removed.

In addition, although the above embodiment describes a power supply device applied to an air conditioner, it goes without saying that the present invention can be applied to other devices as well.

〔Effect of the invention〕

As is clear from the above explanation, according to this invention,
The output of the rectifier circuit that rectifies the AC power supply voltage is supplied to the inverter circuit without going through a smoothing circuit including a capacitor, and the switching elements of the inverter circuit are operated at a high frequency that does not adversely affect the AC power supply line. Since the on/off control is performed, it is possible to reduce the low-order harmonic components, thereby making it possible to eliminate the need for measures to remove the low-order harmonic components.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the embodiment, FIG. 3 is a frequency spectrum for explaining the operation, and FIG. 4 is a schematic configuration diagram of another embodiment of the present invention, FIG. 5 is a waveform diagram for explaining the operation of the embodiment, FIG. 6 is a diagram of an air conditioning system to which the above embodiment is applied, and FIGS. Figures 8 and 10 are current waveform diagrams for explaining the operation of the system, Figures 9 and 11 are frequency spectra for explaining the operation, and Figure 12 is a schematic configuration of a conventional power supply device. FIG. 13 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 14 is a frequency spectrum for explaining the operation. 3... Magnet switch, 4... Rectifier circuit, 10
...Inverter circuit, 12...Reactor, 13.
...Condenser, 20...Air conditioning system, 21.
22...Power supply device. Figure 6

Claims (1)

[Claims] In a power supply device equipped with an inverter circuit that controls switching elements on and off, the output of the rectifier circuit that rectifies the AC power supply voltage is supplied to the inverter circuit without going through a smoothing circuit including a capacitor, and A power supply device characterized in that the switching element is controlled on and off at a high frequency that does not adversely affect a power supply line.