JPH04293A - Current detecting system for thyristor leonard device - Google Patents

Abstract

PURPOSE:To detect the average value of current conducted through a DC machine with high speed and accuracy by a method wherein the sampling and processing of data are effected simultaneously and the summing average of data in a buffer is obtained as an instantaneous current while the change of the instantaneous current is detected by the processing of the instantaneous current. CONSTITUTION:Two sets of direct memory access(DMA) channels, two sets of buffers in a RAM 12 and an A/D converter 8, repeating sampling at all times and storing the data directly into the buffers by the DMAs, are provided. Data is read into a CPU bus from a sample and hold circuit 7 through the A/D converter 8 and an input port 9. Sampling and processing of the data are effected simultaneously and the data in the buffer are reconstituted to detect a division, in which current is zero, while the summing average of the data in the buffer is changed into instantaneous current and the change of the instantaneous current is detected by processing the instantaneous current.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a current detection method for a thyristor Leonard device that digitally controls a DC motor, and in particular to a DMA (
The present invention relates to a current detection method that utilizes the Direct Memory Acce+ss) method.

B1 Overview of the Invention The present invention is a current detection system for a thyristor Leonard device that digitally controls a motor, and includes two DMA channels, two buffers, and an A/D device that constantly repeats sampling and stores the data directly in the buffer using DMA. It is equipped with a D converter, simultaneously samples and processes data, reconstructs the data in the buffer to detect the zero current section, takes the average of the data in the buffer as an instantaneous current, and by that processing, the instantaneous current By detecting changes in the current, the average value of the current flowing through the DC machine can be detected at high speed and with high accuracy, and software can process processes such as detecting whether the current is continuous or intermittent and detecting the ripple width to improve the hardware. The present invention provides a technique that is simple and resistant to noise superimposed on the input to the A/D converter.

C0 Prior Art In a thyristor Leonard device, a digitally controlled thyristor Leonard device is provided with a current detection circuit to perform overcurrent suppression control, etc., and conventionally detects current as described below.

FIG. 6 is a configuration diagram showing an example of a conventional thyristor Leonard device. In the figure, 61 is a three-phase AC power supply, 62 is two thyristor rectifier circuits connected in antiparallel, 63 is a DC motor, 64 is a voltage detection transformer, and 65 is a current detection current transformer.

In the figure, a current flowing through a DC motor 63 is taken into the CPU bus from a current detecting current transformer (CT) 65 via a rectifier 66° active filter 67 and an A/D converter 68. Further, whether or not this current is intermittent is detected by comparing the output value of the rectifier 66 with a set value by a comparator 69, and inputting the result to the CPU bus via a shift register 70.

The CPU bus includes CPU71. RAM72 and ROM7
3 is connected. The voltage detected by the transformer 64 is input to the synchronization detection circuit 74 and drives the shift register 70 and the gate output port door 5, and via the gate output port door 5, the CPU 71 drives the anti-parallel thyristor circuit. Controls 62 gates.

D1 Problems to be Solved by the Invention However, the conventional current detection method has the following drawbacks. FIG. 7 is a time chart showing each waveform of the device shown in FIG. The thick line at the bottom shows the intermittent current detection waveform, and the broken line shows the reference (ref) set to the comparator 69.
), and when the thick line falls below the broken line, the comparator 69 outputs a rectangular wave shown at the bottom.

As is clear from FIG. 7, the device shown in FIG. 6: (1) To obtain the average value of current detection including ripples,
The input to the A/D converter 68 is connected to the active filter 67.
However, this active filter 67 causes a delay in detection.

(2) Even through the active filter 67, it is difficult to completely remove ripples, and the accuracy deteriorates depending on the sampling time of the A/D converter 68. Furthermore, the ripple waveform of current detection changes depending on various constants of the motor and the gate phase angle of the thyristor.

(3) The accuracy of the current detection described above depends on the resolution (number of bits) of the A/D converter 68.

(4) It is necessary to perform current intermittent detection in order to speed up the arm switching of the anti-parallel thyristor circuit 62 and compensate for the current intermittent, but in the above device, detection by the comparator 69 and accumulation in the shift register 70 are used instead. .

(5) In the hardware configuration as described above, the set value b of the comparator reference (ref) is at a small level, and malfunctions are likely to occur. There are many issues that need to be resolved.

The present invention was created in view of these problems, and
The average value of the current flowing through the DC machine is detected quickly and with high precision, and software processes such as detecting whether the current is continuous or intermittent and detecting the ripple width, simplifying the hardware. It is an object of the present invention to provide a current detection method for a thyristor Leonard device that is resistant to noise superimposed on the input to the thyristor Leonard device.

80 Means for Solving the Problems Means for solving the above problems in the present invention is a current detection method of a digitally controlled thyristor Leonard device, which includes two DMA channels, two buffers, continuous sampling, and the like. Equipped with an A/D converter that directly stores data in the buffer using DMA, performs data sampling and processing simultaneously, reconstructs the data in the buffer, detects the zero current section, and adds the data in the buffer. This is based on the current detection method of a thyristor Leonard device, which uses the average as instantaneous current and processes it to detect changes in instantaneous current.

11 Effects The present invention utilizes the well-known DMA method, which is a method for directly inputting and outputting data to memory without bothering the CPU, by controlling the input/output ports with a dedicated controller, to control the current flowing through the DC machine. It detects the average value at high speed and with high precision, and can detect whether the current is continuous or intermittent and detect the ripple width using software. Current is detected using the following process.

(1) For example, the electrical angle is 1.2° (55.5μ at 60Hz)
s) A fixed timer is used to constantly sample the current from the A/D converter.

(2) The sampled data is alternately stored in two buffers in the RAM using DMA every 60 degrees, for example, in synchronization with the power supply.

(3) A current detection calculation by software is started by an interrupt using a synchronization signal of the above power supply every 60°, for example.

(4) In the above interrupt processing, the average value and zero current interval are calculated by referring to the contents of the buffer that is not being stored out of the two buffers.

(5) Furthermore, the above calculation results are used to calculate current control and thyristor firing angle control.

G. Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the present invention.

In the figure, ■ is a three-phase AC power supply, 2 is two thyristor rectifier circuits connected in antiparallel, 3 is a DC motor, 4 is a voltage detection transformer, and 5 is a current detection current transformer. In the figure, the current flowing through the DC motor 3 is taken out from the current detection transformer (CT) 5 to the rectifier 6, but in this device, a sample and hold circuit 7 is connected to the rectifier 6. CP via A/D converter 8 and input port 9
Import data to U bus. The A/D converter 8 constantly samples current data from the sample and hold circuit 7 at fixed time intervals using a timer 10 that generates a trigger at a fixed cycle. The shorter the sampling period, the better in order to improve the accuracy of the average value calculation performed in software processing, which will be described later. However, in this embodiment, the response time of the sample hold circuit 7 and the conversion time of the A/D converter 8 are Considering, 50μ
Set to approximately s (1 to 1.2 degrees electrical angle).

A CPU II, a RAM 12, a DMA controller (hereinafter abbreviated as DMAC) 13, and a synchronization detection circuit 14 are connected to the CPU bus. Note that the voltage detected by the transformer 4 is used by the synchronization detection circuit 14.

When the A/D conversion is completed, the terminal E of the A/D converter 8
Generates a DMA request to OC (End Or Convert).

FIG. 2 is a time chart of waveforms in the above embodiment.

In the figure, (a) shows the synchronization detection state, and (b) shows the DMA RO (buffer 0).

(C) is DMA R1 (buffer 1), (d) is CPU
II shows the current detection calculation, (e) shows the CPU II current control calculation, and (f) shows the output current.

The synchronization detection in (a) is a synchronization signal with an electrical angle of 60°, and the first
It is sent to the gate logic from the synchronization detection circuit 14 in the figure.
The DMA request is distributed to RO or R1 of the DMAC 13. The DMAC 13 controls the input port 9 in accordance with this request, and stores the data from the A/D converter 8 in buffer 0 or buffer 1 of the RAM 12, the memory configuration of which is shown in FIG.

At this time, it goes without saying that the DMAC 13 controls the number of people on the CPtJPt memory, so the arithmetic processing of the CPU II is not affected at all. In this way, sampling data for several dozen times within 60" is always stored in buffer 0 and buffer l. The synchronization signal from the power supply may not always be 60 degrees due to external or internal factors.
It is not constant (there is a fluctuation of about ±2°, but DMACl
As shown in Figure 3, a counter for counting the number of stored data is provided for each buffer, and if this counter is read as a base when taking the average value, the calculation result based on the number of samples can be calculated. The fluctuation of will disappear.

The current detection calculation in this embodiment is performed by the synchronous detection circuit 14.
It is activated at the timing shown in FIG. 2 by interrupting the CPU II with a synchronization detection signal every .degree.

FIG. 4 is a flowchart showing an example of the software processing of the current detection calculation. In the same figure, when the flow starts, first, the level of the synchronization detection signal shown in FIG. 2 (a) is ON or OFF. , and selects the buffer to process (the buffer that was storing data until just before will be selected). Next, add all the contents of the selected buffers. The number of data to be added is DMACl
This is N read from the counter of No. 3. Subsequently, the total sum value (SUM) is divided by this N to obtain the average current value (Ia) within the 60' interval.

FIG. 5 is a time chart explaining intermittent detection. The flow shown in FIG. 4 will be explained below with reference to FIG. The flow moves to search for a zero current section, first transfers the previous sample data, and connects it to the current buffer. In this process, as shown in FIG. 5, since the phases of the synchronizing signal and the actual current are not constant, the search sections shown by n in the figure overlap. For this reason, if the buffer currently being processed is, for example, buffer O with the memory configuration shown in FIG.
For example, one 11N-2 to il of buffer 1 shown in FIG.
Transfer N immediately before buffer 0. At this time, the source buffer, that is, buffer 1, is storing the current value in order from the beginning, but the data up to the last 5 to 10 degrees, indicated by the length n at the bottom of the memory in Figure 3, has not been stored and has not been stored previously. data will remain unchanged and will not be affected.

Here, the flow in FIG. 4 converts the counter value in the zero section to ZCC.
, the calculated value is ZCX, the data length is ZCN, the actual interval is Z
If N, then initialize the counter value ZCC and the calculated value zCX, add n to the actual interval N, and search for the longest number of data that is less than or equal to the zero current setting threshold Z rer. , find the length zCX of the zero current section.

At this time, the search range includes data including the last tail of the previous search, as shown by NQ+n in the memory of FIG.

The average current 1a obtained in the above process is used for current control calculation in the subsequent flow, and the length of the zero current section zCX is
Furthermore, in the subsequent part of the flow, it is used for switching between forward and reverse thyristor arms, phase angle control, current intermittent compensation, etc.

This example has the following effects.

(1) Since the current flowing through the digitally controlled thyristor Leonard is sampled at a high speed of about 50 μs and the average value is calculated, accuracy higher than the resolution of the A/D converter can be obtained.

(2) Since data is stored in two buffers in synchronization with 60° of the power supply, sampling and data processing are performed simultaneously, resulting in high-speed detection.

(3) Since the average value is used, it is less susceptible to malfunctions.

(4) Since the current value is constantly sampled and stored, subsequent data processing is easy.

(5) The detected current value is not affected by fluctuations in the synchronization signal or the phase of the current ripple.

H1 Effects of the Invention As described above, according to the present invention, the average value of the current flowing through a DC machine can be detected at high speed and with high precision, and software can be used to detect whether the current is continuous or intermittent and to detect the ripple width. It is possible to provide a current detection method for a thyristor Leonard device that simplifies the processing and hardware and is resistant to noise superimposed on the input to the A/D converter.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a time chart of waveforms of the embodiment, Fig. 3 is a block diagram of a memory used in the embodiment, and Fig. 4 is a diagram of the operation of the embodiment. 5 is a time chart explaining intermittent detection, FIG. 6 is a configuration diagram of a conventional example, and FIG. 7 is a time chart of waveforms of a conventional example. 1.61...3-phase AC power supply, 2.62...Anti-parallel connection SIRISK rectifier circuit, 3,63...DC motor, 4
．． 64... Voltage detection transformer, 5, 65... Current detection current transformer, 6, 66... Rectifier, 7... Sample hold circuit, 8, 68... A/D converter, 9・-・Input boat, 10・-・Timer 11.71・・CPU
, 12゜72...RAM, 13...DMAC114
, 74-9, synchronous detection circuit, 67... active filter, 69... comparator, 70... shift register, 73... ROM, 75... gate output port.

Claims (1)

[Claims] (1) In the current detection method of a digitally controlled thyristor Leonard device, it is equipped with two DMA channels, two buffers, and an A/D converter that constantly repeats sampling and stores the data directly in the buffer by DMA, Data is sampled and processed simultaneously, the data in the buffer is reconstructed to detect the zero current section, the average of the data in the buffer is taken as the instantaneous current, and changes in the instantaneous current are detected by this processing. Characteristic current detection method of thyristor Leonard device.