JPH0630599A - Switching device for detected input - Google Patents

Abstract

PURPOSE:To make highly accurate detection possible by switching operational elements through a method of moving averages between a detection of a three product method and an effective value detection in accordance with the range of variations in constituent elements of an object to be detected such as a generator. CONSTITUTION:In a detected input switching device for an A.C. generator, a main operation control section 20 converts a scan output from a multiplexer 15 into a digital signal by means of an A/D converter 21, and this digital signal is then inputted to a CPU 22 and RAMs 25a and 25b. A timer circuit 24 causes sample-and-hold circuits 14a-14c of a detected input circuit 10 to effect sampling. A CPU 22 causes a switch instruction circuit (D/O) 27 to switch change-over switches 13a and 13b to the A.C. instantaneous value side thereof when the frequency of a generator falls within a rated frequency of + or -3Hz, but, in any other cases, causes that circuit to switch the switches to the effective value converting circuit side thereof. To switch an A.C. instantaneous value input to an effective value input, and vice versa, half cycles of an alternating current are subjected to moving average for six samples, whereby the amount of a detected input is obtained. Hence, highly accurate operation of detection is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection input switching system, and more particularly to a control input signal switching system for switching detection signals when controlling a generator or the like.

[0002]

2. Description of the Related Art A detection input of an AC voltage or an AC current required for controlling voltage adjustment or speed adjustment of an AC generator is passed through a voltage transformer or a current transformer, and then a detection signal for control is sent by a converter. Is taken as.

[0003]

The conventional detection input switching system has the following problems.

(1) Depending on the type of converter, the response time
A response delay of 0.5 to 0.8 seconds occurs, which adversely affects the control response time.

(2) Since a conversion deviation and temperature drift occur due to aging of the converter itself, periodic inspection is required.

(3) The controlled object is a three-phase alternating current, voltage,
It requires a significant number of converters for each current, frequency, active power and reactive power. This causes a problem in terms of cost and accommodation space.

As a means for solving the above problems (1) to (3), it is possible to sample an AC waveform and convert the measured value into an effective value by the three-type method, but a new problem arises. is expected.

That is, although the conventional problems are solved by using the digital method, attention must be paid to the sampling interval that cannot be avoided in the digital method. That is, the three-kind method is basically based on a sample of an AC sine wave having an electrical angle of 30 degrees. However, the generator cannot obtain a correct effective value with a constant-time sample because the rotation speed considerably changes at the time of start-up and load interruption. Therefore, following the change in the rotation speed,
It is necessary to input the measured value of the electrical angle 30 ° sample corresponding to the frequency, and the electrical angle 30 ° sampling method that follows this frequency fluctuation is required, but it is not practical.

The present invention has been made in view of the above problems, and an object of the present invention is to determine an arithmetic element by a three product method and an effective value by a moving average method according to a variation range of a component element to be detected. It is to provide a detection input switching method that enables highly accurate detection by switching.

[0010]

In order to achieve the above-mentioned object, the present invention provides a calculation method for obtaining a value of a detection input signal by performing calculation processing using a detection input signal containing a predetermined element component as an input. When the value of the element component is within a predetermined value range, the calculation processing is performed based on the instantaneous value of the detection signal, and when the value of the element component is outside the predetermined value range, the calculation processing is performed based on the effective value of the detection input signal. It is characterized by switching.

[0011]

In the variation of the component elements included in the object to be detected, the 3-product method is used for detection, and the effective value is detected outside the prescribed range. Since this detection switching is based on the moving average method, there is no differential at the time of switching.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

The figure shows a detection input switching method according to an embodiment of the present invention. 11a to 11f are analog filters, 12a and 12b are effective value conversion circuits, and 13a and 13b.
Is a changeover switch, 14a, 14b and 14c are sample and hold circuits, and 15 is a multiplexer, which constitute the detection signal input section 10. Reference numeral 20 denotes a main arithmetic control unit, which is an analog / digital converter (A / D) 2
1, a main arithmetic circuit (CPU) 22, a memory (E ² PRO
M) 23, timer circuit 24, memory (RAM) 25a,
25b, memory (ROM) 26 and switching command circuit (D
/ O) 27. Reference numeral 30 denotes an auxiliary arithmetic control unit, which is a digital signal processor (DSP) 3
1, memory (RAM) 32 and memory (ROM) 33
Consists of.

In the detection input switching device shown in the figure, in the detection signal input section 10, the analog filter 11a receives the U-phase current signal I _u , the V-phase current signal I _v and the W-phase current signal I _w of the generator as an analog signal. The filter 11b inputs the U-phase voltage signal V _u , the V-phase voltage signal V _v and the W-phase voltage signal V _w of the generator.

The analog filter 11c as an input to the system bus voltage signal V _b, the analog filter 11d is set to enter the guide valve opening signal G _v hydraulic turbine, the analog filter 11
e is the runner valve opening signal R _v of Kaplan turbine, analog filter 11f is an input of excitation current signals of the generator.

The current signal of the analog filter 11a is directly led to the sample hold circuit 14a via the changeover switch 13a, and at the same time, by the effective value conversion circuit 12a.
It is converted into an effective value and guided. Analog filter 11b
The voltage output signal of 1 is introduced into the sample hold circuit 14b either directly via the changeover switch 14b or after being converted into an effective value by the effective value conversion circuit 12b. The voltage output signal of the analog filter 11c is the sample hold circuit 14
The analog filters 11d to 11
The output signal of f is input to the multiplexer 15.

In the main operation control unit 20, the multiplexer 1
The scan output of No. 5 is converted into a digital signal by the A / D converter 21 and input to the CPU 22 and the RAMs 25a and 25b. A reference frequency signal is set in the ROM 26. The timer circuit 24 supplies a sampling timing signal to the sample hold circuits 14a to 14c of the detection input circuit section 10 to cause each sample hold circuit to sample. The switching command circuit when the frequency is within the rated frequency ± 3H _Z of CPU22 the generator based on a sampling signal (D
/ O) 27 switches the changeover switches 13a and 13b to the AC instantaneous value side, and otherwise switches to the effective value conversion circuit side. In the auxiliary operation control unit 30, the reference signal is stored in the ROM 33, and the digital signal processor 31 stores the stored contents of the ROM 32 and the RAMs 25b and 3b.
The stored contents of 2 are read and the frequency is calculated, and the active power is calculated as the reactive power. That is, as a method of switching between the AC instantaneous value input and the effective value input, the moving average method of 6 samples of AC half is executed to obtain the detected input amount by the following equation.

[0018]

[Equation 1]

The following table shows an example of this relationship.

[0020]

[Table 1]

According to the detection input signal switching method of the above embodiment, the three-product method employs a crystal oscillator which is less affected by temperature changes and the constant time sampling method is practical. Also, due to the difference in the operating principle of RMS conversion of the input method, it is expected that a difference in measured values will occur at the time of switching, but this eliminates the difference due to the moving average between the sample data before switching and the sample data after switching. Therefore, smooth switching can be implemented. By using the constant-time sampling method and the RMS conversion circuit to make up for their respective disadvantages, it is possible to solve the newly expected problems.

Further, in the above embodiment, the control at the time of starting the generator or at the time of cutting off the load does not require control of active / reactive power, power factor, etc., and detection input thereof is also unnecessary. Further, when the generator is operated in parallel with the bus, the input of active reactive power etc. is obtained by the three product method.

In the above embodiment, the detection data regarding the AC generator is described, but the present invention is not limited to this.

[0024]

As described above, according to the present invention, when the variation of the component element to be detected is within the predetermined range, the 3-product method is used, and at other times, it is input by the effective value conversion circuit. Since the switching between the 3-product method and the effective value conversion is performed by the moving average method, highly accurate detection calculation can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram for executing a detection input switching method according to an embodiment of the present invention.

[Explanation of symbols]

10 ... Detection signal input section 11a-11f ... Analog filter 12a, 12b ... Effective value conversion circuit 13a, 13b ... Changeover switch 14a-14c ... Sample hold circuit 15 ... Multiplexer 20 ... Main operation control section 21 ... Analog / digital converter 22 ... Main arithmetic circuit 23 ... Memory (E ² PROM) 24 ... Timer 25a, 25b ... Memory (RAM) 26 ... Memory (ROM) 27 ... Switching instruction circuit 30 ... Auxiliary arithmetic control unit 31 ... Digital signal processor 32 ... Memory (RAM) ) 33 ... Memory (ROM)

Claims (1)

[Claims] 1. A calculation method for obtaining a value of a detection input signal by performing a calculation process by using a detection input signal including a predetermined element component as an input, and when the value of the element component is within a predetermined value range, A detection input switching system characterized by performing arithmetic processing based on an instantaneous value and switching to arithmetic processing based on the effective value of the detection input signal when the value of the element component is outside a predetermined value range.