JPS618679A - Direct current value detecting circuit - Google Patents

Abstract

PURPOSE:To improve the detection precision of a DC voltage value by converting the DC voltage level in each ripple section into a frequency signal in synchronism with the period of a ripple in a DC output and counting the frequency signal. CONSTITUTION:A controller 4 determines the turn-on phase of each thyristor of a thyristor converter to control a voltage and a current. A gate pulse generating circuit 5 generates a turn-on pulse to be supplied to the gate of each thyristor according to six turn-on phase references calculated by the controller 4. Further, a voltage-frequency converter 7 converts a DC value containing a ripple component into a rectangular wave pulse signal 8 and a counter 9 counts pulses of the voltage-frequency converted signal 8 in every period of the ripple. Then, the mean frequency calculated by the controller 4 is converted into a voltage to calculate digitally a mean voltage signal corresponding to the ripple period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a DC voltage value detection device for a power conversion device.

[Conventional technology]

The following method has been proposed as a DC value detection device for a conventional power converter of this type. That is, after switching the thyristor of a converter configured with a thyristor to convert it into DC, the output voltage containing the ripple is converted to a voltage as a smoothing means in order to reduce the ripple as much as possible.
A method of frequency conversion (hereinafter abbreviated as '/F conversion),
and analog-to-digital conversion (hereinafter abbreviated as A/D conversion), in which the digitized DC signals are sampled to finally detect the DC value.

However, in the detection method described above, the digitally converted sampling data is averaged at a certain period, regardless of the ripple period determined by the gate pulse of the thyristor, whether it is '/F conversion or '/D conversion. There is a need to do.

Therefore, if the sampling period is fixed and the averaging calculation is performed, the ripple period will inevitably fluctuate in principle.
However, when the ripple period becomes out of synchronization with the sampling period, there are many drawbacks such as an extremely low detection accuracy of DC values.

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and converts the DC voltage level of each ripple section into a frequency signal in synchronization with the ripple period included in the DC output, and converts the DC voltage level into a frequency signal. It is an object of the present invention to provide a DC voltage detection device that can significantly improve the detection accuracy of DC voltage values by counting converted frequency signals.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. First, Figure 1 shows the circuit configuration diagram of the thyristor converter device. In the figure, 1 is the thyristor converter, 2 is the three-phase AC power supply of the thyristor converter 1, and 3 is connected to the DC output side of the thyristor converter 1. Load, 20 is an AC current detector that detects DC current on the AC input side, 2
1 is a rectifier circuit that converts a current source into a voltage source using a load resistor RL. Further, 30 is a DC voltage detector that detects the DC output voltage V. The voltage V of the load 3 of the thyristor converter 1 configured in this manner and the output waveform of the current generator are waveforms including a ripple period determined by the gate pulse of the thyristor, as shown in FIGS. 2(,) and (b), respectively. Become. Further, FIG. 2 shows the waveforms of the voltage V, the current I, and the transition of the gate pulse when the phase control angle α is controlled from α-30° to α=60°. FIG. 3 is a block diagram showing one embodiment of the present invention. In the figure, 4 is a controller that determines the firing phase of each thyristor of the thyristor converter 1 and controls the voltage V and current, and is a controller that is processed by a microprocessor. It is equipped with computing devices such as 5 is a gate pulse generation circuit for generating firing pulses to be applied to the gates of each thyristor based on the 6 firing phase standards calculated by the controller 4, and the signals in FIG. 2(c) are as described above. Take out the gate pulse serially and write it to counter 9.
A gate pulse synchronization signal 7 is inputted to a voltage V or a voltage signal of a current generator, and a frequency converter is used to convert the frequency.A rectangular wave signal 8 having a frequency proportional to the input signal level is generated.

9 is a counter for counting the rectangular wave signal 8f, which counts the rectangular wave for each gate pulse synchronization signal shown in FIG. 2(e), and supplies the frequency for each gate pulse period to the controller 4. Further, 9 also counts the gate pulse period, measures the pulse period, and supplies the pulse period to the controller 4.

Next, the operation of this invention will be explained below. First, as shown in Fig. 2, the region where the phase control angle α is stable at α = 30 or α = 60 has a ripple period of 60° in electrical angle determined by the thyristor converter 1; ), the state of transition from α = 30° to α - 60°,
υ, when the phase control angle signal given to each individual sirisk gate is not stable, the ripple period may deviate from 60 (shown from 00 to θ7 in FIG. 2(c)). Therefore, in order to always perform highly accurate voltage detection, it is necessary to count the output rectangular wave signal 8 of the %''/F converter 1 in synchronization with the gate pulse shown in FIG. 2(c).

Next, the detailed procedure of the operation of the present invention will be shown below. That is, the counter 9 starts counting the rectangular wave signal 8 at the first gate pulse shown in FIG. At the i+1th gate pulse, the count values of both counters are simultaneously latched and temporarily saved in the memory of the controller 4. When the memory is completed, both counters are reset, and the square wave count and the period of the gate pulse are counted. and restart at the same time.

Therefore, the controller 4 is normally the thyristor converter 1
When the gate pulse shown in Fig. 2 (c) arrives, the DC output control calculation is performed according to the pre-programmed procedure shown in the flowchart of Fig. 4, and after the Returns to control calculation operation.

That is, the controller 4 calculates the vh conversion rectangular wave count value (NV
F) Sample k and store 31 in memory.

Then, the controller 4 samples the binary digitalized gate pulse period count value (Nc), stores it in the memory 32, and converts the ``/F-converted rectangular wave count value (NVF) 31 into the 32 gate pulse period counts. The average value 33 is calculated by dividing by the value (Nc) and stored in memory.

The operation of the controller 4 is shown in the flowchart of FIG. That is, the sample value and the average value of the rectangular wave signal 8 are processed every time the gate pulse shown in FIG. 2(C) arrives, and the average value is used as data for controlling the thyristor converter 1.

Note that the sampling and averaging functions described above may be performed by a dedicated arithmetic unit provided separately from the controller 4 that controls the thyristor converter 1.

〔Effect of the invention〕

As described above, according to the present invention, the ripple is subjected to '/F conversion in synchronization with the ripple cycle on the DC output side of the thyristor converter, and the converted frequency is counted and the average value is calculated. As a DC value detection device that includes ripples, it has the advantage of being able to obtain extremely highly accurate DC voltage values.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of the thyristor converter device, Figure 2
The figure is a ripple waveform diagram of the gate pulse of the thyristor and the voltage and current of the converter, Figure 3 is a circuit configuration diagram of a detection circuit showing an embodiment of the present invention, and Figure 4 is a flowchart diagram of the detection method of the present invention. . 1... Thyristor converter, 2... Three-phase AC power supply, 3... Negative (Fr, 4... Controller, 5...
Kate pulse generator, γ...voltage frequency (''/F
) converter, 9... counter.

Claims (1)

[Claims] In a DC voltage value detection device that detects a DC value on the DC output side of a thyristor converter that contains a ripple component after rectifying an AC power source, the ripple period is synchronized by a gate pulse synchronization signal output from a gate pulse generation circuit. Trigger the gate pulse, convert the DC value including the ripple by a voltage/frequency converter, count the number of voltage/frequency converted rectangular wave pulses for each ripple period by a counter, A DC voltage value detection device, characterized in that an average voltage signal corresponding to a ripple period is digitally calculated by converting an average frequency value obtained by calculating an average frequency by a controller into a voltage.