JPS6016175A - Digital controller of controlled rectifier - Google Patents

Abstract

PURPOSE:To prevent commutation failure caused by variations in frequency by detecting the variation in the power source frequency and correcting the control phase angle. CONSTITUTION:A frequency detector 11 which inputs a reference pulse theta0 from a zero cross detector 10 and outputs a frequency detection signal (f) is provided, and a pulse generator 8A has an input terminal for reading out the signal (f) as a correction signal. The detector 11 has a clock pulse generator for generating a pulse at every prescribed period and a counter for counting the pulse during a period of the pulse theta0, and outputs the counted value of the counter as the signal (f). Accordingly, when the frequency of the power source is small, the counted value (f) of the counter is large, and when the frequency is high, the counted value (f) is, on the contrary, small, and the generator 8A performs the correcting operation so that the value (f) becomes zero correction in case of rated frequency f0.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a digital control device, and particularly to a digital control device that corrects fluctuations in a control phase angle due to fluctuations in power supply frequency when controlling the control timing of a control rectifier by digital control. The present invention relates to a digital control device for a controlled rectifier.

[Technical background of the invention and its problems]

An example of current control by a conventional digital control device for a controlled rectifier is shown in the block diagram of FIG.

The control rectifier 2, which is fully supplied with electric power from the AC power source 1, converts the AC voltage into a DC voltage and causes the current to flow through the load 3. This current is detected by a current detection circuit 5, and a current detection signal having a value proportional to the average value of the current is output as a digital value and inputted to a current control circuit 6.

This current detection signal is compared with the current reference signal input as a digital value from the current reference circuit 4 by the current control circuit 6, and outputted as a phase control circuit or a digital value obtained by differential proportional integral calculation. This phase control signal
The control phase angle signal .theta. is inputted manually, converted to -1x, outputted as a digital value control phase angle signal .theta., and inputted to the pulse generation circuit 8.

On the other hand, the reference pulse θ0 generated from the zero cross detection circuit 10 is input to the pulse generation circuit 8 every time the voltage polarity of the AC power supply 1 is reversed, and the power supply voltage has a phase angle corresponding to the control phase angle signal θ. At this time, a control pulse C is generated and input to the pulse amplification circuit 9.

The pulse amplification circuit 9 uses the control pulse C to output a gate signal GP that controls the conduction and non-conduction of each of the two control rectifier elements constituting the control rectifier 2, and controls the current flowing through the load 3 to a value corresponding to the current reference signal. ing.

The pulse generation circuit 8 includes a clock pulse generation circuit that generates high-frequency clock pulses with a constant period (not shown), and counts the clock pulses to obtain a period τ! A frequency divider circuit that generates a check pulse CP at In preparation for this, the increment of the phase control signal θ is equal to the period τ1 when the power supply frequency is the rated frequency fo.
is given as the incremental phase angle corresponding to .

Therefore, the power supply voltage e1 corresponding to the control phase angle signal θ given in units of incremental phase angle (1 in period) of the rated frequency fo
As shown in the time chart of FIG. 2, the control phase angle of is determined from time t1 when the polarity of the power supply voltage es is reversed to time t2 when the number of check pulses CP given by the control phase angle signal θ is generated, i.e. , tl is the phase angle after τ2 has elapsed.

However, in the conventional digital control device having the above configuration, when the frequency of the power source deviates from the rated frequency fo, the control phase angle also deviates. For example, as shown in the power supply voltage e,' in Fig. 2, when the power supply frequency decreases to fl, the time for the phase angle increases, but the control time τ2 by the control phase angle signal θ remains the same as in the case of the rated frequency f. The control phase angle is f1
/fo decreases, causing an error. This control error appears as a change in control gain, and also causes a non-negligible error in the control phase angle limit values (α limit, β limit, not shown) inside the current control circuit 6, causing a commutation failure. It appears as

[Purpose of the invention]

The present invention has been removed in order to eliminate the above-mentioned problems,
Provides a digital control device for a controlled rectifier that detects fluctuations in the power supply frequency and corrects the control phase angle to prevent the error in the control phase angle caused by the phase control signal from increasing even when the power supply frequency fluctuates, improving reliability. The purpose is to.

[Summary of the invention]

In order to achieve the above object, the present invention includes a controlled rectifier that is supplied with power from an AC power source and supplies power to a load, a zero-cross detection circuit that generates a reference pulse every time the voltage polarity of the AC power source is reversed, and a digital rectifier that supplies power to a load. In a digital control device for a controlled rectifier, the digital control device for a controlled rectifier includes a phase control circuit that receives a controlled phase angle signal of a value and the reference pulse and controls the phase of the controlled rectifier with a voltage phase corresponding to the controlled phase angle signal. a check pulse generating means for generating a check pulse at a predetermined timing determined by the reference pulse; and a value determined by the control phase angle signal is initially set at a predetermined timing determined by the reference pulse, and when the check pulse is counted by the initially set number of pulses, the control phase angle is determined. check pulse counting means for outputting a timing signal; frequency detection means for detecting a frequency detection signal of a digital value corresponding to the frequency of the AC power source; and frequency correction means for correcting the control phase angle timing signal using the frequency detection signal. This is a digital control device for a controlled rectifier that can control the controlled rectifier with an accurate control phase angle according to the controlled phase angle signal even if the power supply frequency fluctuates, and has improved reliability.

[Embodiments of the invention]

A digital control device for a controlled rectifier according to the present invention will be explained using an embodiment shown in the block diagram of FIG. The same reference numerals as in FIG. 1 indicate that the functions of the elements are the same.

In the embodiment shown in FIG. 3, a frequency detection circuit 11 is newly provided which inputs the reference pulse θof from the zero cross detection circuit 10 and outputs a frequency detection signal f, and the pulse generation circuit 8A receives this detection signal ff: a correction signal. A new input terminal has been provided to read the data as .

The frequency detection circuit 11 includes a clock pulse generation circuit (not shown) that generates pulses at regular intervals and a counter that counts the pulses during the period of the reference pulse θ0, and the count value of this counter is used as the frequency detection signal f. Output as . Therefore, when the frequency of the power supply is low, the count value f of the counter is large, and when the frequency is high, the count value f becomes small, and in the case of the 8 pulse generation circuits, the count value f when the power supply frequency is f is zero correction. Correcting operations are being carried out to ensure this.

FIG. 4 is a flowchart for explaining the operation of the pulse generating circuit 8A, and FIG. 5 is a functional block configuration diagram thereof. That is, the eight pulse generating circuits have a phase control signal reading means 21 for reading the control phase angle signal θ at the timing of the reference pulse θ0, and a frequency detection signal reading means 22 for reading the frequency detection signal fi. The control signal reading means 21 initializes the check pulse counting means 23 using the control phase angle signal θ, and the frequency detection signal reading means 22 sets the frequency detection signal fi in the check pulse period correction means 24 and generates it in the check pulse generating means 25. The period τ1 of the check pulse to be detected is corrected so that it is proportional to the total frequency detection signal f. In this case, as described above, the electric rating frequency f is set to zero correction. .

The check pulse CP obtained from the check pulse generating means 25 is counted by the check pulse counting means 23, and when it reaches the initially set value of the control phase angle signal θ, the control pulse CP is outputted from the control pulse generating means 26. issue instructions to.

Therefore, even if the power supply frequency changes and the period of the AC voltage changes, the period τl of the check pulse is similarly corrected, and the control rectifier 2 is accurately controlled by the control pulse C at the phase given by the control phase angle signal θ. be able to.

[Other embodiments of the invention]

Another embodiment of the pulse generating circuit 8A using the digital control device for a controlled rectifier according to the present invention is shown in the flowchart of FIG. 6 and the functional block diagram of FIG. 7.

In this embodiment, the control phase angle signal θ initially set in the check pulse counting means 23 is corrected by keeping the period τ1 of the check pulse constant. That is, the frequency detection signal f read by the frequency detection signal reading means 22
is input to the dividing means 27 to obtain the electric rating frequency fO of the detection frequency f.
The frequency ratio K ('/fo) is calculated and inputted to the multiplier 28 (2).

The multiplier 28 multiplies this frequency ratio K by the control phase angle signal θ to calculate θs (=K·θ), corrects this, and initializes the check pulse counting means 23 from the t-controlled control phase angle signal type 1. .

Therefore, since the initial setting value is corrected according to the change in frequency, even if the frequency changes by counting check pulses at a constant period, the control pulse C can be generated with the phase given by the control phase angle signal θ. I can do it.

〔Effect of the invention〕

According to the present invention, the control phase of the controlled rectifier is correctly controlled even if the frequency of the power source fluctuates, thereby completely preventing commutation failures due to frequency fluctuations, and providing a digital control device for the controlled rectifier with improved reliability. be able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional digital control device for a controlled rectifier, FIG. 2 is a timing chart for explaining the operation, FIG. 3 is a block diagram of a digital control device for a controlled rectifier according to the present invention, and FIG. 4 is a block diagram of a digital control device for a controlled rectifier according to the present invention. Pulse generating circuit 8A of the invention
5 is a functional block diagram thereof; FIG. 6 is a flowchart illustrating a pulse generation circuit 8A according to another embodiment of the present invention; and FIG. 7 is a functional block diagram thereof. . l... AC power supply 2... Control rectifier 2 people... Control rectifier element 3... Load 4... Current reference circuit 5.
...Current detection circuit 6...Current control circuit 7...Function circuit 8.8A...Pulse generation circuit 9...Pulse amplification circuit IO...Zero cross detection circuit 11...Frequency detection circuit 21 ...Phase control signal reading means 22...Frequency detection signal reading means 23...Check pulse counting means 24...Check pulse period complementing means 25...Check pulse generating means 26...Control pulse generating means 27... Division means 28... Multiplication means (7317)
Agent Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 1 Figure 3 Figure 1 Figure 4 Figure 5 θ f Figure 6

Claims (3)

[Claims] (1) A control rectifier that is supplied with power from an AC power source and supplies power to a load, a zero cross detection circuit that generates a reference pulse every time the voltage polarity of the AC power source is reversed, and a control phase angle signal that is a digital value. In a digital control device for a control rectifier including a phase control circuit which receives the reference pulse and controls the phase of the control rectifier with a voltage phase corresponding to the control phase angle signal, a check pulse is generated at a predetermined period. pulse generating means; and a check pulse for outputting a control phase angle timing signal when a value determined by the control phase angle signal is initially set at a predetermined timing determined by the reference pulse and the check pulse is counted by the initially set number of pulses. A counting means, a frequency detection means for detecting a frequency detection signal of a digital value corresponding to the frequency of the AC power supply, and a frequency correction means for correcting the control phase angle timing signal using the frequency detection signal. Control rectifier digital controller. (2) The frequency correction means is a check pulse period correction means for correcting the period of the check pulse according to the frequency detection signal, and the check pulse generation means performs the check pulse period correction means based on a command from the check pulse period correction means. A digital control device for a controlled rectifier as claimed in claim 1 and configured to generate pulses. (3) The frequency correction means includes a division means for calculating a frequency ratio using the frequency detection signal and a signal determined by the rated frequency, and a multiplication means for calculating the product of the control phase angle signal and the frequency ratio, 2. A digital control device for a controlled rectifier according to claim 1, wherein a value is initially set in said check pulse counting means.