JPH0214316Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a self-control type inversion control device.

Generally, an inverse conversion device of the so-called constant r control method (constant control angle advance angle method of the thyristor) is used in an electric power source. When electricity is controlled by this inverter, the load current I _L as shown in Figure 1
flows. It is known that when this load current I _L changes depending on the load, the overlap angle u also changes accordingly. This overlap angle u is the overlap time uT
Expressed as , it becomes as follows. However, L ₀ is the impedance on the load side, V is the load voltage (output voltage), T ₁ is the time when the load current I _L starts to drop, and T ₂ is the time when the load current I _L passes through the zero point.

uT≒2I _L L ₀ /V∫ ^T2 / _T1 Sin ωt dt Therefore, as the load current I _L increases, the overlap time
uT also becomes larger. Now, the load current shown in Figure 1
When I _L increases from I ₁ to I ₂ , the overlap angle u also increases.
Then, the reverse voltage period IV of the thyristor decreases as shown by the solid line. If this period IV becomes less than the turn-off time of the thyristor, commutation will no longer be possible, resulting in the disadvantage that the inverter cannot operate. In FIG. 1, V is the output voltage and δ is the margin angle.

An inversion control device disclosed in Japanese Patent Publication No. 57-34744 solves the above-mentioned drawbacks. This device performs constant commutation margin time control of the thyristor, and in order to detect the commutation margin time, the control advance angle β is determined from the thyristor firing angle and the zero point of the output voltage, and the thyristor firing angle and load Calculations are performed by detecting the overlap angle from the zero point of the current. In this case, if the load current is intermittent, the current detection signal disappears,
There is a possibility that the overlapping angle cannot be detected, the commutation margin time cannot be detected, and control becomes impossible.

This invention has been made in view of the above circumstances, and aims to provide an inverse conversion control device that allows normal operation at all times even if the load current is intermittent.

An embodiment of this invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of one embodiment. In this figure, 1 is an electric control device, and this device 1 includes a forward conversion device 1a, an inverse conversion device 1b, and a DC reactor 1.
c and a load circuit 1d. Note that 1e is a current transformer, and 1f is a transformer. The output of the current transformer 1e is given to an overlap angle detection circuit 2.
This overlap angle detection circuit 2 is composed of a zero cross detector 2a and an R.S flip-flop 2b. The output of the overlapping angle detection circuit 2 is applied to the input A of the deviation integral amplifier circuit 3 via a gate circuit 12 controlled by the output of a level detection sensor, which will be described later. This amplifier circuit 3 is composed of resistors 3a, 3b, 3c, and 3f, a capacitor 3e, and an operational amplifier 3d. 4 is an adder, which adds the output of the deviation integral amplifier circuit 3 and the output of the start frequency setter 5 of the inverse conversion device 1b, and the added output is supplied to the voltage-frequency conversion circuit 6. . Note that the adder 4, the setting device 5, and the conversion circuit 6 form a setting device. The output C of the conversion circuit 6 is supplied to the reset input R of the flip-flop 2b of the overlap angle detection circuit 2, and is also supplied to the input D of the deviation integral amplifier circuit 3 via a monostable multivibrator circuit 8 (hereinafter referred to as mono-multi). given to. Reference numeral 7 designates a control advance angle detection circuit, and this circuit 7 is constructed from a circuit similar to that of the overlapping angle detection circuit 2, 7a is a zero cross detector, and 7b is an R.S flip-flop. The output of the transformer 1f is applied to the input of the control advance angle detection circuit 7, and the output of the detection circuit 7 is applied to the input B of the deviation integral amplifier circuit 3 through the polarity conversion circuit 7'. Note that the conversion circuit 6
The output C is applied to the reset input R of the flip-flop 7b of the control advance angle detection circuit 7 and also to the frequency dividing circuit 9. The output F of the frequency dividing circuit 9 is given to the first and second gate circuits 10a and 10b.
The output of is given to the gate of a thyristor (not shown) of the inverter 1b. The frequency dividing circuit 9 and the first
The second gate circuits 10a and 10b form an ignition signal generator.

11 is a level sensor detection circuit whose input side is connected to the current transformer 1e;
1, it is detected that the load current is intermittent and the zero current time continues, and the detection signal is used to control the gate circuit 12.
control. That is, when intermittent load current is detected, the gate circuit 12 is closed.

Next, the operation of the above embodiment will be described. To operate the electric control device 1, first, the inverter operating frequency is set using the setting device 5, and the set output is provided to the voltage-frequency conversion circuit 6 via the adder 4. Then, the conversion circuit 6 has the output shown in Fig. 3A.
C ₁ , C ₂ ... pulses are generated. This output C ₁ , C ₂
When the frequency divider circuit 9 is activated at the falling edge of . . . , the outputs f ₁ and f ₂ shown in FIG. With these outputs f ₁ and f ₂ , the first and second gate circuits 10
a, 10b are operated, and the outputs g ₁ , g _{2 .} . . , g ₁ ′, g ₂ ′ . . . shown in FIG. Then, a load current shown in FIG. 4a flows through the load circuit 1d. In addition, in FIG. 4a, V indicates the load voltage.

The outputs C ₁ , C ₂ . . . are applied to the overlap angle detection circuit 2 and the control advance angle detection circuit 7, and reset both detection circuits 2, 7. Then both detection circuits 2 and 7
As shown in FIG. 3E and F, the outputs rise at the reset signal and fall at the outputs A ₁ and B ₁ from the zero cross detection circuits 2a and 7a. Further, the signal _B1 is used as an input signal to the polarity conversion circuit 7'. The output signal ₁ (FIG. 3-G) of the polarity conversion becomes a signal with the same width and the same voltage as the signal _B1 but with a different polarity (positive→negative level voltage). When the outputs C ₁ , C ₂ . . . are input to the monomulti 8, the outputs D ₁ , D _{2 .} . . as shown in FIG. The output signal of the detection circuit 2, the output signal of the polarity conversion circuit 7', and the output signal of the monomulti 8 are combined by a deviation integration amplifier circuit 3, and the deviation thereof is integrated and given to an adder 4. Adder 4 outputs this deviation integral output and setter 5
The time interval between the outputs C ₁ , C _{2 .} . . of the voltage-frequency conversion circuit 6 is changed by the added output.

In other words, the deviation integral amplifier circuit 3 is A ₁ + ₁ + D ₁
The output frequency of the inverter will be operated so that =0. The waveform diagram in FIG. 4 specifically shows such an operation. In FIG. /2 is detected, and the control advance angle detection circuit 7
The amount of T _B is detected from. Since this T _B is made into a negative signal by the polarity reversing circuit 7', the commutation margin time detection time T _S becomes T _S =-T _B +2×T〓'. If the inverter is controlled so that the time detection signal T _S obtained in this manner matches the set time given by the monomulti 8, frequency control can be performed such that the reverse voltage time of the thyristor always corresponds to the set amount.

Here, when the load current is intermittent, the level sensor detection circuit 11 detects this discontinuity, and the gate circuit 1
Close 2. At this time, if the amount of overlap angle is set to T〓' = 0 and controlled so that -T _B = T _S , the control lead angle of the inverter will be equal to the set amount T _S even when the load current is intermittent. Normal operation continues.

As described above, according to this invention, it is possible to normally control the inverter even if the load current is intermittent, and it is also possible to improve the operating efficiency of the inverter. Furthermore, in order to prevent current interruption, a dummy resistor was conventionally required during no-load, but this invention has various effects such as making this resistor unnecessary.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram showing the relationship between load current, voltage, and reverse voltage when electricity is controlled by an inverter, Fig. 2 is a block diagram showing an embodiment of this invention, and Fig. 3 A to 3. Figure 4 is a waveform diagram for explaining the operation of Figure 2, and Figures 4a and 4b are waveform diagrams showing details of the overlap angle and control advance angle detection circuit. DESCRIPTION OF SYMBOLS 1... Electric control device, 2... Overlap angle detection circuit, 3... Deviation integral amplifier circuit, 4... Adder, 5
...Start frequency setter, 6...Voltage-frequency conversion circuit, 7...Control advance angle detection circuit, 7'...
Polarity conversion circuit, 8... monomulti, 9... frequency dividing circuit, 10a, 10b... first and second gate circuits,
11...Level sensor detection circuit, 12...Gate circuit.

Claims (1)

[Scope of utility model registration request] In a control device using a forward conversion device and an inverse conversion device, there is a setting device that sets the operating frequency of the inversion device, a monostable multivibrator that sends out an operating output for a certain period of time using the output signal of this setting device, and a a separate detector for detecting a current zero of the load current and a voltage zero of the load voltage applied to the load;
an overlap angle and control advance angle detection circuit that is controlled by the output of the setting device and sends out outputs with different signs when each of the detectors sends out an output; Amplify the deviation output from the vibrator output,
a deviation output amplification circuit that varies the set value of the setting device by its amplified output; a level sensor detection circuit that detects the intermittent state of the load current; a gate circuit that prevents the output of the angle detection circuit from being supplied to the deviation output amplification circuit; and an ignition signal whose generation time of the ignition signal is variably controlled by the output of the setting device and which provides the control output to the inverse conversion device. An inverse conversion control device comprising a generator.