JPS6110992A - Power factor detector of current type inverter - Google Patents

Abstract

PURPOSE:To obtain a detector having high accuracy and excellent responsiveness by detecting the input power factor from the AC side voltage of an inveter and a DC side voltage or a signal equivalent thereto. CONSTITUTION:The AC side output voltage of an inverter 3 is detected by a transformer 5, rectified by a rectifier 6 to become a signal (a). On the other hand, the DC side input voltage of the inverter 3 is detected by a detector 7 to become a signal (b). The output of a 6f pulse circuit 8 becomes a signal (c), and the pulse becomes 6f frequency. Then, the signals (a), (b) are respectively integrated by integrators 9, 10 during 1/6f time determined by the pulse of the signal (c) to become the integrated value output of the signals (d), (e). The signals (d), (e) are input to a divider 11. The input power factor of the induction motor can be detected from the output signal of the divider 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a current source inverter that drives an induction motor, and more particularly to a power factor detection device for a current source inverter that can detect the human power factor of an induction motor.

[Technical background and problems]

Conventionally, when controlling the primary frequency of an induction motor using a current source inverter, it was difficult to control the input power factor of the induction motor without speed detection, which was an obstacle to stable operation. . The input power factor itself is also detected using the inverter output voltage.

Since the current waveform is a distorted wave, it is difficult to accurately detect it with a short sampling time.

If a method for detecting the input power factor of an induction motor with high accuracy and excellent responsiveness could be developed, it would be possible to easily construct a stall detection circuit or a stall prevention circuit. Furthermore, characteristics during acceleration/deceleration and characteristics during load fluctuations can be improved.

[Purpose of the invention]

An object of the present invention is to detect the input power factor of an induction motor driven by a current source inverter using a simple structure and method using the AC side voltage and DC side voltage of the inverter of the current source inverter or a signal equivalent thereto. It is an object of the present invention to provide a power factor detection device that is equipped with a current source inverter and is characterized in that it performs the following.

[Summary of the invention]

According to the present invention, the above object is to convert a signal obtained by full-wave rectification of the AC tJlt side voltage of the inverter and the DC side voltage of the inverter into one commutation of the inverter in the N1m type inverter device. This method attempts to detect the input power factor of an induction motor by comparing signals integrated over a period or an integral multiple of one commutation period.

Hereinafter, in explaining the present invention, the principle of the present invention will be explained with reference to the configuration diagram of an electric type inverter shown in FIG. 3 to which the present invention is applied.

In FIG. 3, 1 is a forward converter connected to an AC power source;
2 is a DC reactor, 8 is an inverter, and 4 is an induction motor. If the effective value of the line voltage of the induction motor fi4 is vM, and the average value of the input side DC voltage vd of the inverter is Vd, then V
d and ■. is related to the following equation.

3v'! vd=-VM l1ffll (1) Here, co
Sz is equal to the input power factor of the induction motor.

Now, FIG. 4 shows the waveform of the inverter functional voltage vd.

In Figures 1 and 4, a is the waveform obtained by full-wave rectification of the inverter AC side voltage, b is the waveform of the inverter DC side voltage, and c is the timing 2 pulses of the gate that commands the inverter. The inverter DC voltage is 6 times the frequency f of the induction motor 4.
It is sufficient to consider a time that is an integral multiple of the repetition period at twice the frequency. In other words, a signal obtained by rectifying the inverter AC side voltage can be obtained directly. Now, from these two signals, (
1) Formula [Embodiment of the Invention] An embodiment of the present invention is shown in FIG. In FIG. 1, the constituent elements given the same numbers as in FIG. 8 are the same 2 elements. In the figure, 5 is a transformer that detects the AC side output voltage of the inverter 3, 6 is a rectifier that full-wave rectifies the output of the transformer 5, and 7 is a voltage detector that detects the DC side input voltage of the inverter 3. 8 is a 6f pulse circuit that generates the pulse shown in FIG.
．． The timing of the f-pulse circuit 8 (an integrator that integrates from two points; 10 is an integrator that integrates the output of the 61-pulse circuit 8 according to the timing of the 61-pulse circuit 8; 11 is a divider that compares the outputs of the integrators 9 and 10; Dechiru.

The AC side output voltage of the inverter 3 is detected by the transformer 5 and rectified by the rectifier 6 to become the signal a shown in FIG. On the other hand, the DC side input voltage of the inverter 3 is sent to the detector 7.
is detected and becomes the signal shown in Figure 4. The output of the 6f Hals circuit 8 is a pulse of signal C, which pulse has a 61 frequency. Next, the signal d is integrated by the signal integrator 9.10.
, e is the integral value output. At the falling edge of the pulse of the signal C, for example t, the integral values a/, b/ start integration from zero, hold the integral values 3/, b/, and output the equity value output signal d.

It is output to the comparator 11 as 8. 1. After holding the integral value at this time point 92, the integral it+\a', b' is reset, and the integration is started again from the time point t3. Therefore, since the output signals of the integrators 9 and 10 can always be supplied to the comparator 11 as the output signals d and e even at the time between the pulses of the signal C, the input power factor of the induction motor obtained as the output signal of the comparator 11 is can be detected at all times.

As described above, according to the present invention, the input power factor of the induction motor can be easily detected by simply detecting the AC side voltage and direct side voltage of the inverter. Furthermore, since integration is used as the detection method, the influence of high frequency component noise such as commutation surge can be removed.

Another embodiment of the invention is shown in FIG. The difference between FIG. 2 and FIG. 1 is that the inverter DC side voltage synthesis circuit 12 is
This is an added point. If the DC side voltage of the inverter is a high voltage, it is necessary to step down and insulate it using a voltage dividing resistor and an insulator. There is no need to provide one.

In other words, the voltage on the AC side of the inverter is stepped down using a transformer.

Combining the inverter DC side voltage from the isolated voltages has the advantage of simplifying the detection circuit.

In FIG. 2, the inverter AC side voltage detected by the transformer 5 is turned on by the inverter DC side voltage synthesis circuit 12 in synchronization with the inverter gate pulse.

If it is turned off, a signal equivalent to the voltage I>' can be obtained. Therefore, it is clear that the same effect as in FIG. 1 can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the input power factor of an induction motor driven by an electric inverter can be detected simply by detecting the voltages on the AC side and DC side of the inverter, so that various types of control can be performed. It can be used for.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a block diagram showing another embodiment of the invention, and Fig. 3 is a basic configuration diagram of a current source inverter device to which the present invention can be applied. ,
Figure 4 is an operational waveform diagram for explaining the present invention. 1... Forward converter, 2... DC reactor, 3...
Inverse converter, 4... Induction motor, 5... Voltage detection copying pressure device, 6... Rectifier, 7... Voltage detector, 8 ・6f
Pulse circuit, 9... Integrator, 10... Integrator, 11
...Divider, 12...Inverter current side voltage synthesis circuit (73) 7) Agent Bu ``Scientist Noriyuki 1Qte1 Yu (and 1 other person) Figure 1 Figure 2 Figure 3 - Figure 1

Claims (1)

[Claims] A forward converter that is connected to an AC power source and converts AC to DC;
A current source inverter comprising an inverter whose DC side circuit is connected to the forward converter via a DC reactor, and an induction motor driven by the inverter,
A voltage obtained by full-wave rectification of the AC side voltage of the inverter, and a DC side voltage of the inverter or a voltage corresponding thereto, respectively, during one commutation period or an integral multiple of one commutation period of the inverter. first and second integrators that integrate over time;
A power factor detection device for a current source inverter, comprising a divider that detects the input power factor of the induction motor from the ratio of the outputs of the first and second integrators.