JPS5864822A - Frequency voltage converting circuit - Google Patents

Abstract

PURPOSE:To output a voltage with less ripple in response to the frequency change of an AC power supply system through increased pulse number at one period of the AC power supply, by increasing the oscillating frequency of pulsive signals and decreasing the period with a voltage controlled oscillator. CONSTITUTION:An oscillating frequency f2 of a voltage controlled oscillator 8 is selected as (n) times an oscillating frequency f1, where the f1 is the frequency of an AC power supply system with the period T1 of a zero point detection signal (e) determined by the frequency of the AC power supply, then a period of an output signal (h) of the oscillator 8 becomes T1/n and the number of pulses in one period of the AC power supply is increased. The pulsive output signal (h) is taken as an input signal of a monostable multivibrator 9, and a rectangular wave signal (i) having a prescribed pulse width determined with the monostable multivibrator 9 passes through an integration circuit 10 to become an output voltage V'0. Thus, the oscillating frequency of the pulsive signal (h) is increased and the period is decreased, allowing to increase the number of pulses of one period of the AC power source. Thus, the ripple of the output voltage V'0 is less and the output voltage becomes a voltage in response to the frequency change of the AC power source.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power conversion device, and particularly to a frequency-voltage conversion circuit that outputs a voltage according to frequency changes in an AC power system.

In a power conversion device connected to the AC power supply system of the Kurodo generator, a row of frequency-voltage conversion circuits provided to control the control device of the power conversion device with a voltage corresponding to frequency changes of the AC power supply system of the generator. is shown in Figure 1. In FIG. 1, U, V, and W are phase voltages obtained by a synchronous power supply transformer 5 connected to an AC power system, and 1 is a synchronous power supply configured by each phase power supply zero point detection circuit 11, 12, and 13. A zero point detection circuit, 21 is an OR circuit of ICs, 3 is a monostable multivibrator, and 4 is an integration circuit constituted by an operational amplifier.

FIG. 2 is a time chart for explaining the operation of the frequency-voltage conversion circuit shown in FIG. 1.

a) is the phase voltage waveform s b) m ”) s d) is the U phase, ■
Phase and W phase power supply voltage zero point detection circuit 11.1
The zero point detection signal detected by 2.13, e) is b),
A signal obtained by ORing the zero point detection signals of c) and d) with the IC 21, f) is a square wave signal with a pulse width t from the monostable multivibrator 3, and g) is the output waveform of the integrating circuit 4.

The operation of the frequency-voltage conversion circuit shown in FIG. 1 will be explained using FIG. 2. Each phase power supply voltage U, V, W obtained through the synchronous power supply transformer 5 connected to the AC power supply system of the motor generator
When inputting to each phase power supply zero point detection circuit 11, 12, 13, each U, V.

Zero point detection signal b)sCLd) synchronized with the zero point of the W-phase power supply
is detected. If the signal e) obtained by ORing these signals b), c), and d) with the OR circuit 2 is used as the input signal to the monostable multivibrator 30, the pulse width t determined by the constant of this monostable multivibrator is A square wave signal f) is output, and this square wave signal f) is passed through an integrating circuit 4 to an output voltage V as shown in g). is obtained.

Here, the pulse width t of the square wave signal shown in f) is determined by the monostable multivibrator 3, so even if the frequency of the AC power supply system changes, it remains constant regardless of this frequency change, but the period T is determined by the monostable multivibrator 3. Change according to change. From the above, the output voltage ■. has the following relationship.

Vo E・－・・・・・・・・・・・・(1) Here,
'o (fo: frequency of the AC power system), so vo, fo......(2
). That is, 1. Integrating circuit 4. The output voltage V. As shown in equation (2), a value proportional to the frequency of the AC power system is output. Here, the integrating circuit 4
The output voltage V. is the constant 1(,i,l(,f
, (:' Since charging and discharging are repeated with the time constant determined by f, ripples are included as shown in Figure 1. If this ripple is large, it becomes a problem.For example, when the coil of a nuclear fusion device Since the thyristor conversion device of the power supply is connected to the AC power supply system of the motor generator, its frequency fluctuates widely. Therefore, the phase control device of the conversion device uses the voltage converted by the frequency-voltage conversion circuit described above. However, in this case, the output voltage ripple of the frequency-voltage conversion circuit becomes a problem, and a voltage with small ripple is required.As a method to reduce the ripple of this output voltage v0, integration Although the time constant τ=l'ji−Cf of circuit 4 may be increased, this τ
If you increase , the output voltage of the frequency-voltage conversion circuit■. There is a problem that the response time when the frequency changes is slow. Therefore, there is a method as shown in FIG.

In Fig. 3, %1 and 6 are each phase power supply zero point detection circuit 11~
13. Synchronous power supply zero point detection circuit composed of 61 to 63, 2
3 is a monostable multivibrator, 4 is an integrating circuit, 5 and 7 are synchronous power supply transformers, and phase voltage U obtained by the synchronous power supply transformers 5 and 7.

There is a phase difference of 30 degrees between V and W and tr/, v/, and w/. Therefore, by calculating the logical sum of the zero point detection signals that detect the zero point of each phase synchronous power source, the signal e) has a larger number of pulses in one cycle of the AC power source than in the case of Fig. 1, and the period T becomes 1/2. Therefore, the noggle width t determined by the monostable multivibrator 3 also needs to be narrower than in the case of FIG. 1, but if the ratio t/T is constant, the output voltage V of the integrating circuit 4. It is possible to reduce the ripple. That is, it can be seen that in order to reduce the ripple, it is sufficient to increase the number of pulses of the input signal of the monostable multivibrator 3 and shorten the period T thereof. However, in order to increase the number of pulses of the input signal e) of the monostable multivibrator 3 using the method shown in FIG. There are two sets of transformers and their phase difference is 30
In the case of 24 pulses, it is necessary to provide four sets of synchronous power transformers with a phase difference of 15 degrees. Therefore, it is not easy to increase the number of pulses in one cycle of the AC power supply using this method because the device becomes larger.

An object of the present invention is to provide a frequency-voltage conversion circuit that outputs a voltage with small ripples in response to frequency changes in an AC power supply system.

In order to realize a frequency-voltage conversion circuit that responds to frequency changes in an AC power supply system and outputs a voltage with a small tipple, it is necessary to shorten the period of the repetitive square wave signal that serves as the input signal to the integrating circuit. When creating a square wave signal with a short period using a monostable multivibrator or the like, it is necessary to shorten the period by increasing the number of pulses of the input signal that serves as a reference for this square wave signal. Therefore, the present invention is based on the above-mentioned concept of increasing the number of pulses and shortening the cycle.An embodiment of the present invention is shown in FIG. 4 below. Phase voltages U, V, W and U/
, V/, and W/ are omitted. In FIG. 4, 8 is a voltage controlled oscillator, and 9 is a monostable multivibrator.

10 is an integrating circuit, and the final output voltage is v'.

becomes.

FIG. 5 is a time chart for explaining the operation of the embodiment of the present invention shown in FIG. e) is a signal obtained by ORing the zero point detection signal of each phase with OR circuit 2, f) is a square wave signal with pulse width t from monostable multivibrator 3, g) is the output of integrating circuit 4, h ) is the output signal of the voltage controlled oscillator 8, i) is a square wave signal with pulse width tt from the monostable multivibrator 9, and j) is the output waveform of the integrating circuit 10.

The operation shown in FIG. 4 will be explained below using FIG. 5.

In FIG. 4, the configuration before A is the same as that in FIG. 3.

That is, the phase voltage U obtained by the synchronous power transformers 5 and 7 connected to the AC power system. 79w and U/, V/,
W/ is input to the synchronous power supply zero point detection circuits 1 and 6, the zero point detection signals synchronized with the zero points of these phase voltages are detected, and each of these signals is ORed by the OR circuit 2 to become the output signal e). . Next, the monostable multivibrator 3 outputs the signal e) as a square wave signal with a pulse width t1, and the integrating circuit 4 outputs the voltage v0 shown in FIG. 5g). Next, the voltage controlled oscillator 8 is an oscillator that generates a pulse-like signal with a frequency proportional to the magnitude of the input voltage. Therefore, in a single circuit configuration, it oscillates at a frequency corresponding to the output voltage vo of the integrating circuit 4, and oscillates a signal as shown in FIG. 5h).

Here, for the frequency f□ when the period of the zero point detection signal e) determined by the frequency of the AC power supply system is T,
Let f be the oscillation frequency of the voltage controlled oscillator 8, and set it to a constant so that the oscillation frequency is n times f8, then the period T of the output signal h) of the voltage controlled oscillator 8 becomes T1/n, and the AC The number of pulses in one cycle of power supply increases. This pulsed output signal h) is used as an input signal to a monostable multivibrator 9, and is made into a square wave signal i) with a pulse width t2 determined by this monostable multivibrator 9, and is passed through an integrating circuit 10 to produce an output voltage V shown in j). ' is output. Thus, by the voltage controlled oscillator 8.

Final output V. By increasing the oscillation frequency and shortening the period of the pulse-like signal h) connected to AC power source 1,
The number of pulses per cycle can be increased. As a result, the ripple in the output voltage v0' of the integrating circuit 10 becomes small, almost eliminated in some cases, and the voltage becomes responsive to the frequency change of the AC power supply system.

FIG. 6 shows another embodiment of the invention. FIG. 6 shows the configuration after A in FIG. 4. In FIG. 6, 11 is a flip-flop circuit, 4.10 is an integrating circuit, 12 is a voltage-frequency converter, and 13 is a frequency dividing circuit. Here, the voltage-frequency converter 12 generates a repetitive square wave signal with a frequency (period) depending on the magnitude of the input voltage.

The operation of FIG. 6 will be explained below.

In FIG. 6, the flip-flop circuit 11 is s e
) is used as a set signal, and the output signal n) of the frequency divider circuit 13 is used as a reset signal, so that the output signal k) of the flip-flop circuit 11 becomes a repetitive square wave signal. This signal k) is input to the integrating circuit 4 and the output voltage v
Get 0. Next, this voltage ■. When is the input voltage of the voltage-frequency converter, a repetitive square wave signal m) with a period T corresponding to vo is obtained as an output signal. here,
The period T2 of this repetitive square wave signal m) is:

The period is set to l/n of the period T1 of the zero point detection signal e). Therefore, the input signal m of the integrating circuit 10
) has a shorter period than the zero point detection signal e).

As a result, the ripple in the output voltage v0' of the integrating circuit 10 becomes small and, in some cases, almost eliminated, and furthermore, it is possible to obtain a voltage that corresponds to the frequency variation of the AC power supply system. In addition, the square wave signal m) becomes an input signal of the integrating circuit 100, and is used as an input signal of the frequency dividing circuit 13, and this frequency dividing circuit 13 converts n, which is a signal corresponding to the period T1 of the zero point detection signal e).
) is output as a reset signal for the flip-flop circuit 11. That is, the period T of the zero point detection signal e),
Assuming that the frequency is f1, the period T2 of the output signal m) of the voltage-frequency converter 12 and the oscillation frequency f2 are set to be n times fl.
The frequency is divided so that the oscillation frequency becomes n.

Although this embodiment describes the case where two sets of synchronous power transformers are used, the present invention can also be applied to a case where only one set of synchronous power transformers is used.

According to the present invention, it is possible to obtain a voltage with small ripples that corresponds to frequency changes in an AC power supply system.

[Brief explanation of the drawing]

Figure 1 is a diagram of the frequency-voltage conversion circuit, Figure 2 is an operational diagram of Figure 1, Figure 3 is the frequency-voltage conversion circuit (g, Figure 4 is a block diagram of an embodiment of the present invention, and Figure 5 is a FIG.

Claims (1)

[Claims] 1. A synchronous power supply transformer connected to an AC power system. Detect the zero point of the phase voltage, obtained by this transformer. a synchronous power supply zero point detection circuit, an OR circuit that ORs the zero point detection signal of this synchronous power supply zero point detection circuit, a monostable multivibrator that outputs a square wave signal based on the signal from this OR circuit, and a monostable multivibrator that outputs a square wave signal based on the signal from this OR circuit. In a frequency-voltage conversion circuit that has an integral circuit that integrates an output signal of a vibrator as its basic structure and outputs a voltage according to a frequency change of an AC power supply system, the frequency-voltage conversion circuit is configured based on the period of the zero-point detection signal obtained from the synchronous power supply zero-point detection circuit. . A frequency-voltage conversion circuit, comprising means for generating a signal having a cycle shorter than the cycle of the zero point detection signal and increasing the number of pulses in one cycle of the AC power supply.