JPH0668514B2 - AC line voltage peak value detection circuit - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an AC line voltage peak value detection circuit that detects an instantaneous peak value of an AC line voltage.

[Prior art]

FIG. 6 shows a conventional three-phase AC line voltage peak value detection circuit for obtaining the peak value of a three-phase AC voltage. In FIG. 6, reference numeral 12 denotes the three-phase AC voltages V _U , V _V , V _W. A three-phase AC power supply for outputting, 1, 2, 3, 4, 5, and 6 are diode rectifier circuits 1 for full-wave rectifying the three-phase AC voltages V _U , V _V , and V _W.
6 rectifying diodes forming 3, 3, 8 and 9 are voltage dividing resistors for dividing the full-wave rectified voltage, 10 are capacitors for reducing ripple voltage of the divided voltage, 1
Reference numeral 1 is an isolation amplifier that isolates the obtained voltage and transmits it to the control circuit. Here, it is assumed that the gain of the isolation amplifier 11 is 1. Next, the operation will be described. However, consider the case where there is no capacitor 10 for reducing the ripple voltage in FIG. 7 and 8 are explanatory views of the operation waveforms of FIG. The phase voltages V _U , V _V , V _W of each phase are as shown in FIG.
The voltages are out of phase by 2 / 3π. That is, _{V 1} the voltage rectified by the diode rectifier circuit 13, and when the divided voltage that is insulated by an insulating amplifier 11 by the resistor 7, 8, 9 and _{V 2,} the waveform of the voltage _V 1, _{V 2} eighth It becomes like the figure. Here, it can be said that V ₂ = V ₁ × r ₂ / (2r ₁ + r ₂ ) ... (2). As is clear from FIG. 8, the rectified voltage V ₁ is
It can be seen that it is the peak value of the line voltage of the three-phase AC, and the circuit of FIG. 6 is a circuit that detects the peak value of the three-phase line voltage. Here, the maximum value of _{V 1 V} IH, the minimum value of _{V 1 V 1L}
Then, in FIG. 8, for example, V ₁ when ωt = 2π / 3
Is V _1H and V ₁ is V _1L when ωt = 5π / 6. Therefore, if V _1H and V _1L are expressed using the equation (1), Becomes In this case, defining the voltage ripple rate as Δ = (V _1H −V _1L ) / V _1L (5) Becomes From the equation (2), Δ in V ₂ has the same value as the equation (6).

[Problems to be Solved by the Invention]

Since the conventional AC line voltage peak value detection circuit is configured as described above, there is a problem that the ripple voltage becomes large. This AC line voltage peak value detection circuit is used together with the power conversion circuit 20 as shown in FIG. 9, for example. The power conversion circuit 20 converts the alternating current of the alternating current power source 12 into direct current and regenerates the direct current voltage to the alternating current input side.
And a capacitor 22 connected between the output terminals of the regenerative converter 21, and an inverter 24 that converts the DC output of the capacitor 22 into an AC output and supplies the AC output to a motor 23 as a load. Reference numeral 25 is an isolation amplifier that detects the terminal voltage of the capacitor 22, and 26 is a comparator that compares the outputs of the isolation amplifiers 11 and 25. Based on the comparison result, the regenerative converter 2
The switching element, which is the first component, is turned on and off. In the above configuration, the regenerative energy from the motor 23 is supplied to the capacitor 22 via the inverter 24. The output voltage of the isolation amplifier 25 that detects the terminal voltage _VDC of the capacitor 22 is the output voltage V of the isolation amplifier 11.
_When it becomes higher than _2, the switching element of the regenerative converter 21 is turned on by the output signal of the comparator 25, and the AC power supply 12
Power is regenerated to the side. This regeneration is most preferably performed in a state close to the condition of _VDC > V ₁ where the terminal voltage _VDC of the capacitor 22> the peak voltage V _{1 of the} AC power supply. However,
As described above, when the ripple of the output voltage V ₂ of the isolation amplifier 11 is large, a regeneration instruction, that is, a command to turn on the switching element of the regenerative converter 21 is issued at the time point t ₁ shown in the tenth point, and t ₂ after a short time. At this time point, a powering instruction, that is, an instruction to turn off the switching element 21 of the regenerative converter 21 is issued, and regeneration is frequently performed every time the AC output is synchronized. However, when the regeneration is performed, the switching element of the regenerative converter 21 causes a loss. Therefore, it is not preferable that the regeneration is performed frequently as described above. Therefore, in order to reduce the ripple of the output voltage V ₂ of the isolation amplifier 11, the capacitor 10 is inserted between the input terminals of the isolation amplifier 11, but in this case, there is a problem that a detection delay occurs. The present invention has been made to solve the above problems, and an object thereof is to obtain an AC line voltage peak value detection circuit capable of reducing the ripple of the output voltage without detection delay.

[Means for solving problems]

In the AC line voltage peak value detection circuit according to the present invention, a resistor having a resistance value whose ratio to the resistance value of the voltage dividing resistor provided in the output path of the diode rectifier circuit minimizes the ripple rate of the output voltage is set to an AC power supply. And a diode rectifier circuit connected to each line.

[Action]

A mode in which a plurality of diodes are simultaneously turned on is created by the ratio of the resistance value of the resistance provided in each line connecting the AC power supply and the diode rectifier circuit in the present invention to the resistance value provided in the output path of the diode rectifier circuit, The output voltage ripple is reduced without detection delay.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention.
9 and 11 to 13, the same parts as those of the conventional voltage detecting circuit shown in FIG.
Reference numerals 15, 16 and 17 are resistors respectively connected to the lines connecting the AC power supply 12 and the diode rectifier circuit 13.
These resistors 15, 16 and 17 all have the same resistance value r ₃ . As an example, the operation of the circuit of the present invention shown in FIG. 1 and the operation of the conventional circuit shown in FIG. In the circuit of FIG. 6, in the period of I The maximum value of V _U-phase voltage up, since V _W is the minimum value, the diode 1,6 are turned on, After that, V _V is the maximum value of phase voltage and V _W is the minimum value,
Although the diodes 2 and 6 are turned on, they are different in FIG.
This will be explained below. FIG. 2 shows the equivalent circuit of FIG. 1 in this period I. From equation (1) It can be melted. In addition, r ₄ = 2r ₁ + r ₂ (9) In addition, the U and V phase line currents are I _U and I _VC , respectively.
Then, the voltage V ₃ is set as shown in the figure. In the period I, as described above, in the circuit of FIG. 6, the conduction state of the diodes 1 and 6 shifts to the conduction state of the diodes 2 and 6, but in the circuit of FIG.
A mode occurs in which the two turn on at the same time. However, in either case, in the period I, the diodes 3, 4, and 5 are turned off, and if the diodes are considered to be ideal diodes having a forward drop voltage of 0, the diode 6 can be omitted, so that FIG. 2 is obtained. FIG. 3 shows the line voltage V _UW , V in the period I of FIG.
_VW and V _UW ′, V _VW ′ are drawn, and both the vertical axis and the horizontal axis are enlarged as compared with FIG. 7. Here, the broken _lines V _UW ′ and V _VW ′ are V _UW ′ = (r ₃ + r ₄ ) × V _UW / (2r ₃ +
r ₄ ), ... (10) V _VW ′ = (r ₃ + r ₄ ) × V _VW / (2r ₃ + r ₄ ). Here, only the diodes 1 and 6 are turned on until time t = t ₁ , that is, until ωt = ωt _1, so V ₃ = V _UW ′ = in FIG.
(R ₃ + r ₄ ) · V _UV / (2r ₃ + r ₄ ) (period II). At time t ₁ , V _VW > V ₃ = V _UW ′, so the diode 2 is turned on. At this time, I _U >
Since it is 0, the diode 1 is also on. Therefore, t = t
After _1, that is, after ωt = ωt _1, the diodes 1, 2, 6 are turned on at the same time. These diodes 1, 2, 6
The following is a consideration of the period (period III) in which both are turned on at the same time. According to Kirchhoff's second law, V _UW = (I _U + I _V ) (r ₃ + r ₄ ) + I _{U. r3}
(11) V _VW = (I _U + I _V ) (r ₃ + r ₄ ) + I _{V. r3}
… (12) Sort out (11) and (12) From equation (13) And then substituting equations (7) and (8), From equation (14) Using equation (15) Becomes This V ₃ is drawn and is shown by the broken line in FIG. On the other hand, when r ₃ is 0, in FIG. Up to V ₃ = V _UW ′, After that, V ₃ = V _VW ′, and therefore the broken line portion in FIG. As can be seen by comparing FIGS. 4 and 5, it can be seen that when r ₃ is added, the voltage ripple of V ₃ is considerably reduced as compared with the case where r ₃ is not added. In Figure 4, And the point When the voltage of V _{3 at} the point is equal, the ripple rate is most reduced. That is, in equation (7) When substituting into equation (10), Therefore, in Eqs. (17) and (16), Since the expressions The ripple rate can be minimized by selecting the ratio of r ₃ and r ₄ to be equal to the equation (19). Next, the ripple rate at this time is calculated. First, t _{1 in} FIG.
Ask for. t ₁ is V ₃ = V obtained from the equations (7) and (10)
_Since it is the time when _UW 'and Eq. (16) match [] Are the same, so Becomes Therefore, the ripple rate is Therefore, the ripple rate Δ when there is no r ₃ is reduced to about 23% as compared with the equation of 0.15 (6). As a result, by using the AC line voltage peak value detection circuit of the present invention together with the power conversion circuit shown in FIG. 9, the regenerative operation can be performed in a state close to the condition of _VDC > V ₁ . In the above embodiment, the case where the AC voltage waveform has three phases has been described, but the same effect can be obtained by adding a resistor between the AC power supply and the diode rectifier circuit for single-phase or multi-phase AC. . Further, the AC voltage waveform may of course be the output voltage of the inverter, and the same effect as that of the above embodiment is obtained.

【The invention's effect】

As described above, according to the present invention, the output of the diode rectifier circuit is connected to the line connecting the AC power supply and the diode current circuit.
A resistor with a resistance value that minimizes the ripple ratio of the output voltage is connected to the resistance value of the voltage dividing resistor provided in the path, so the output voltage ripple can be reduced without detection delay with a simple and inexpensive circuit configuration. There is an effect that can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an AC line voltage peak value detection circuit according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram in a certain period for explaining FIG. FIG. 3 is a waveform explanatory view of FIG. 6, FIGS. 4 and 5 are waveform explanatory diagrams of FIG.
FIG. 7 is a circuit diagram showing a conventional AC line voltage peak value detection circuit, FIG. 7 is a waveform diagram showing a three-phase AC phase voltage, FIG. 8 is a waveform diagram showing the operation of FIG. 6, and FIG. A circuit diagram in which the line voltage peak value detection circuit is also used in the power conversion circuit, and FIG. 10 is a waveform diagram showing a regenerative operation. In the figure, 1 to 6 are diodes, 7 to 9 are resistors, and 11
Is an isolation amplifier, 12 is an AC power supply, 13 is a diode rectifier circuit, and 15 to 17 are resistors. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An AC line voltage peak value detection circuit for detecting an instantaneous peak value of an AC line voltage by rectifying an output voltage of an AC power supply by a diode rectifier circuit, wherein the AC line voltage peak value detection circuit is provided in an output path of the diode rectifier circuit. A resistance of the voltage dividing resistor having a resistance value that minimizes the ripple rate of the output voltage is connected to each line that connects the AC power source and the diode rectifier circuit. Voltage peak value detection circuit.