JPH01160312A - Digital processor - Google Patents

Abstract

PURPOSE:To improve reliability and to reduce size of a device, by modifying operation sequence of an analog switch of a switched capacitor filter thereby inverting the phase of an output signal and inspecting the device. CONSTITUTION:When inspecting operation is performed by inverting an input signal, polarity of a clock signal to be applied onto switched capacitor filters 1, 2 is inverted based on a phase inversion signal fed from a phase inversion control section 13 so as to modify driving sequence of an analog switch thus inverting the phase of output signals from the filters 1, 2. Then filtered data are employed in a relay operation processing section for operating detection of fault and function of a relay is checked based on the fault operation result. If the relay does not function, it is judged that an A/D converter 6, a processing section 12 or the filters 1, 2 is abnormal and the abnormality is displayed. If the relay functions, it is judged that the converter 6, the processing section 12 and the filters 1, 2 are functioning normally.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital arithmetic processing device, and particularly to inspection means suitable for a digital protection relay for a power system using a switched capacitor filter circuit as an input circuit.

[Conventional technology]

In conventional digital protection relays, when inspecting the input section, the characteristics of the switched capacitor filter are changed by changing the clock frequency of the switched capacitor filter, as described in Japanese Patent Laid-Open No. 61-227628. Accordingly, abnormalities in the switched capacitor filter and the protective relay are detected by determining the magnitude of the output of the switched capacitor filter relative to the input.

[Problem that the invention seeks to solve]

In the above conventional technology, when inspecting the input section, when the clock signal is set high for the bandpass filter,
The center frequency becomes higher, the output signal becomes smaller relative to the input signal during inspection, and abnormalities can be detected. However, with regard to low-pass filters, even if the clock frequency is increased, the output signal relative to the input signal during inspection does not become smaller, and there is a problem that abnormality detection cannot be performed. Furthermore, there is a problem in that the relay elements targeted for abnormality detection are only overcurrent and undervoltage relay elements, and abnormality detection cannot be performed on reactance relays.

An object of the present invention is to perform the switch capacitor filter in accordance with an inspection command during inspection of a digital arithmetic processing device equipped with a switch capacitor filter for input signal filtering.
It is an object of the present invention to provide a digital arithmetic processing device that can inspect the filter including the capacitor filter by changing the output signal with respect to the input signal of the filter, regardless of whether the capacitor filter is a band pass filter or a low pass filter.

[Means for solving problems]

The above problem is solved by using a switched capacitor filter that uses a switched capacitor circuit, which consists of an analog switch and a capacitor that are driven in a predetermined drive order by a clock signal of a predetermined frequency, and constitutes a circuit equivalent to a resistor. In a digital arithmetic processing device that converts the output signal of the switched capacitor filter into a digital quantity and performs processing based on a predetermined arithmetic algorithm, the driving order of the analog switches is changed to convert the output signal of the switched capacitor filter into a digital quantity. The present invention is solved by providing a phase inversion control means for inverting the phase of the output signal.

[Effect]

In the above configuration, the phase inversion control means outputs a clock signal in which the polarity of a clock signal of a predetermined frequency that drives the analog switch of the switched capacitor circuit constituting the equivalent resistance circuit of the switched capacitor filter is inverted. The capacitor filter changes the driving order of the analog switches based on the clock signal and the inverted clock signal to invert the phase of the output signal.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 9b.

FIG. 1 is a block diagram showing the configuration of an embodiment in which the present invention is applied to a digital protection relay (digital processing unit). In FIG. 1, switched capacitor filters 1 and 2 are connected to a voltage input signal V20 and a current input signal I, respectively.
21 to remove harmonic components of the input signal and prevent sampling aliasing errors. In Figure 1, only two sets of input signals and filters are shown, but
It is also possible to install more than one. The sampling and holding circuit (S/H) 3.4 samples and holds the output signals of the switched capacitor filters 1 and 2 in the previous stage at every sampling period t. The multiplexer 5 receives output signals from a plurality of sampling and holding circuits and sequentially switches and selects one of them.

An analog/digital converter (A/D) 6 converts analog data into digital data. The relay arithmetic processing section 12 performs arithmetic operations based on input signals to determine the operation of the protection relay, and is comprised of the following components. The setting section 7 sets the setting value of the protection relay. The digital input/output circuit (Ilo) 8 inputs and outputs digital data. The CPU 9 performs processing according to an arithmetic algorithm. RAMl0 stores input data and calculation data. The ROMII stores programs and data for operating the CPU 9, and is a read-only memory. The above components constitute the relay calculation processing section 12. The phase inversion control section 13 (phase inversion control means) sends out a control signal for inverting the phase of the output signals of the switched capacitor filters 1 and 2.

Before explaining the details of the operation shown in FIG. 1, a detailed explanation will be given of a switched capacitor circuit, a switched capacitor filter using the same, and phase inversion control.

FIGS. 2(a) and 2(b) are intended to explain in principle how an equivalent resistance can be obtained by a switched capacitor. In FIG. 2, when the voltages at terminals ■ and ■ are Vl and V2, respectively, and switch S2 is turned on as shown in FIG. 2(a), capacitor C has:
This means that a charge Q2 expressed by Q z =CV 2 is being charged. In this state, when switch s1 is turned on as shown in FIG. 2(b), the charge on capacitor C becomes Q1=CV 1 , and the charge Δ is the difference between Ql and Q2.
Q will flow from terminal ■. That is, the charge ΔQ is as follows.

ΔQ=Q engineering Qz=C(Vt-Vz) ・=(
1) Now, switch S2 again as shown in FIG. 2(C).
is turned on, the charge Qz of the capacitor C = CV2, and the same amount of charge as the charge ΔQ shown in equation (1) is transferred to the capacitor C.
It is clear that it flows from the terminal ■ to the terminal ■. Therefore, if the above operation is repeated at a period T, the charge ΔQ will move through the capacitor C at a period T, and as a result, a current i shown by equation (2) will flow from the terminal ■ to the terminal ■.
will flow on average.

i = A Q/T = C(Vz Vz)/T
-(2)-Resistance R as shown in Figure 2 (d)
If the voltages at each end of are Vl and Vx, respectively.

The current i flowing through the resistor R is as follows.

1r=(Vt-Vz)/R-- (3) where i=i,
Then, the following equation (4) can be obtained from equations (2) and (3).

R=T/C=1/(f − C) (4) where f is the switching frequency.

That is, the equivalent resistance of a switched capacitor is determined by the ratio between the capacitance value C of the capacitor C and the switching period T, and by changing the period T, the equivalent resistance can be freely changed without changing the capacitance of the capacitor C. It is.

The switched capacitor circuit described above is a basic circuit, but in reality, circuits such as those shown in FIGS. 2(e) and 2(f), which are less susceptible to the influence of parasitic capacitance, are used. Figure 2 (
7 in e) and (f) indicates an inverted version of the clock φ, which respectively drives the switch S1-84.

Next, the switched capacitor filter will be explained.

FIG. 3 is a diagram showing the circuit configuration of a switched capacitor filter, in which switched capacitor equivalent resistances 151 to 154 are composed of analog switches 101 to 116 and switched capacitor equivalent resistance capacitors 121 to 124.
, integrating capacitors 131, 132, and operational amplifier (
OP amplifier) 141 and 142.

FIG. 4 is a diagram showing an example of the waveform of a clock for operating the switched capacitor filter of FIG. 3.

In the switched capacitor filter shown in FIG.
, 109, 110, 113 and 116 are turned on when the clock φ shown in FIG.
It is set to turn off when the L ll level is reached. Also, analog switches 103, 104° 107, 108, 111
, 112, 114 and 115 are turned on when the clock 7 shown in FIG. 4 is at the "H" level, and are turned off when the clock is at the "ILL" level. These series of operations are expressed as period TF
By repeating each time, V o u i in Fig. 3
Outputs expressed by the transfer functions shown below can be obtained from s and Vout 2.

Note that V o u c 1 is a band pass filter (B P
F) Shows the output, Voutz is a low pass filter (L
PF) shows the output.

(Voutt) [Voutt 2. ) However, H: Gain coefficient ω0: Angular frequency Q: Selectivity Also, the switched capacitor equivalent resistance capacitors 121 to 124 and the integrating capacitor 131 shown in FIG.
, 132, Crt, Crz.

Assuming Cra, Cra + and Ct p C2, the characteristic constant of the filter can be expressed by the following equation.

(Voutl) Crz (Voutz) r4 However, fo: center frequency Q: selectivity H: gain coefficient Next, phase inversion control of the switched capacitor filter will be explained.

FIG. 5 is a diagram showing a configuration in which the switched capacitor filter shown in FIG. 3 and a phase inversion control section 13 are added thereto. The phase inversion control section 13 includes an inverter 161 and a switch 171.

Next, the phase inversion operation of the switched capacitor filter shown in FIG. 5 will be explained. In FIG. 5, the switch 171 is normally connected to the a side so that the same clock signal φ is applied to all the switched capacitor equivalent resistances 151 to 154. Therefore, the outputs of the switched capacitor filter v o ut and V o
At u t 2, outputs shown by equations (5) and (6) are obtained.

In order to invert the phase of the output of the switched capacitor filter, the switch 171 is connected to the b side and the clock signal is sent out via the inverter 161. That is, C in the switched capacitor filter equivalent resistance 151
A clock signal with inverted polarity is applied to the analog switches 102 and 104 shown in FIG. Due to the above operation, the analog switch 102 causes the clock signal φ to go “L”.
The analog switch 104 turns on when the clock signal T is low and turns off when the clock signal T is high. analog switch 101
and 104 are turned on at the same time.

analog switches 102 and 103 are turned on and off simultaneously.

Therefore, as a result of this operation, the phase of the output of the switched capacitor filter is reversed.

FIG. 6 is a diagram showing the waveform of the clock applied to each analog switch of the switched capacitor equivalent resistance 151 shown in FIG. That is, analog switches 101 to 10
4, clock signals φ1 to φ4 are applied. In FIG. 6, signal S is a phase inversion command signal for operating switch 171 in FIG. From Figure 6, signal S is
It can be seen that the polarities of clock signals φ3 and φ4 are inverted when they reach H''' level.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be described in detail. The inspection operation performed by inverting the input signals of a digital protection relay that performs protection operations based on a plurality of input signals will be explained using a flow diagram, and the flow diagram is shown in FIG. In block 201 of FIG. 7, the phase inversion control section 13 shown in FIG. 1 inverts the phase of the switched capacitor filter 1.2. As explained earlier using FIG.
By inverting the polarity of the clock signal applied to the capacitor filters 1 and 2, the switched capacitor filters 1 and 2
This is to invert the phase of the second output signal. Here, the switched capacitor filter that is inverted is only the switched capacitor filter 1 side to which the voltage signal V20 is input, and the switched capacitor filter 2 side to which the current signal I21 is input is not inverted.

Next, in block 202 of FIG. 7, the filtered data is used to perform an accident detection calculation in the relay calculation processing section 12 shown in FIG. As an example of accident detection calculation, the following formula is used.

5=(I −Z−V)I −Z −(13
) However, I: Current V: Voltage 2: Set value In this way, S is determined for each fault calculation cycle, and when ΣS≧K holds true for a predetermined value K, the relay operates. In block 203, based on the result of the accident calculation performed in block 202 as described above, it is determined whether a relay (for example, a reactance element using a reactance relay) has operated. This flow is to perform a check operation, and in block 202, conditions are created to forcibly operate the relay, and if it does not operate, the analog-to-digital converter (A/D) 6. There is an abnormality in the relay arithmetic processing section 12 or the switched capacitor filters 1 and 2. Therefore, when there is no operation, the process moves to block 204 and displays an abnormality.
If the relay operates, the analog/digital converter (A/
D) 6, the relay arithmetic processing unit 12, and the switched capacitor filters 1 and 2 are both operating normally.

By the above operation, switch capacitor filter 1
, 2, and other digital protection relays can be easily automatically inspected.

FIG. 8 is a waveform example of each block shown in FIG. 1 for explaining the inspection operation. In Fig. 8, the inspection input is
Voltage input signal V20 and current input signal I2 from the power grid
1 is shown. 1 side filter output is current input signal I2
1, and the V-side filter output shows the filter output of voltage input signal V20. Here, a phase reversal command signal is output as an inspection command. In this case, only the voltage input signal V2O side is used. Therefore, after the phase inversion command signal is output, the phase of the V-side filter output is inverted. As a result, the relay output becomes "operational" a predetermined time after the phase inversion command signal is output. In this case, it indicates that it is operating normally. FIGS. 9a and 9b show relay characteristics expressed as impedances calculated using R-X coordinates in order to explain the inspection method of this embodiment. 30
1 indicates the characteristics of a reactance relay, which has an operating range and a non-operating range, Z indicates a setting value, and is 302°30
3 indicates the impedance obtained after the arithmetic processing. FIG. 9a shows the impedance 302 before the phase reversal command signal is outputted as the inspection command, and since it is in the non-operating region at this time, the relay does not operate. FIG. 9b shows the impedance 303 after the phase reversal command signal is output as an inspection command. By forcibly reversing the phase of the V-side filter output, the impedance 303 enters the operating range and the relay becomes operational. Detecting the operating signal of this relay,
Finish checking the relay (normal operation).

The above-mentioned inspection method is carried out every cycle TN,
By managing this, automatic inspection of relays including filters can be easily performed.

The reverse of the method described above is also performed. That is, by leaving the V side filter as it is and performing the same inspection by inverting the phase of the output of the ■ side filter, even more reliable automatic inspection can be achieved. Further I
Check whether the relay changes from active to inactive by leaving the phase of the output of the filter on the side inverted and inverting the phase of the output of the filter on the V side.

According to the present embodiment described above, since a special inspection input signal input device for inspection is not required, the circuit can be made smaller and lower in cost. Furthermore, automatic inspection of the protection relay including the input filter can be realized, which has the effect of increasing the reliability of the protection relay.

FIG. 10 is a block diagram showing another applied embodiment of the present invention. FIG. 10 shows the configuration of FIG. 1, including a CPU 14 that manages the input/output signals of the inspection input signal, a digital-to-analog converter 15 that converts inspection data into digital and analog and uses it as an inspection input signal, and a switch capacitor filter 1.
, 2 are added with changeover switches 16 and 17 for switching the input signal paths.

Next, the inspection operation of this applied example will be explained.

First, when inspecting, turn on the changeover switches 16 and 17.

Connect to b' side (inspection input signal side). Thereafter, preset inspection data, for example power system simulation data, is transferred to the digital-to-analog converter 15 under the control of the CPU 14, and the analog-converted inspection input signal is sent to the switched capacitor via the changeover switch 16.17. According to this applied example, the inspection data can be easily created using software, such as 0 or more applied to the filters 1 and 2, and a special inspection input signal input device can be made unnecessary. In addition, since the frequency, amplitude, offset value, content rate of harmonic components, etc. of inspection data can be changed arbitrarily, highly accurate inspection is possible.Furthermore, it is protected to eliminate the need for a special inspection input signal input device. This has the effect of reducing the size of the relay device.

〔Effect of the invention〕

According to the present invention, in a digital arithmetic processing device equipped with a switched capacitor filter for filtering an input signal, by changing the operating order of the analog switches of the switched capacitor filter, the output signal of the switched capacitor filter is By inverting the phase of the output signal, the digital arithmetic processing unit including the switched capacitor filter can be inspected based on the inverted output signal, thereby improving the reliability of the device and providing a special inspection input for inspection. Since no signal input device is used, there is an excellent effect that the device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment according to the present invention, and FIG. 2 (
a) to (f) are circuit diagrams of a switched capacitor equivalent resistance circuit, Figure 3 is a circuit diagram of a switched capacitor filter, and Figure 4 is a clock that drives the analog switch of the switched capacitor filter shown in Figure 3. Figure 5 is a diagram showing waveforms, and Figure 5 is a circuit configuration diagram of the switched capacitor filter and its phase inversion control section shown in Figure 1.
The figure shows the clock waveform that drives the analog switch shown in Figure 5, Figure 7 is a flowchart showing the inspection operation of Figure 1, Figure 8 is a waveform diagram of each block during inspection, and Figure 9a. and FIG. 9b are relay characteristic diagrams, and FIG. 10 is a block diagram of another different applied embodiment of the present invention. 1.2... switch capacitor filter, 6...
- Analog-to-digital converter, 12... Relay calculation processing section, 13... Phase inversion control section.

Claims (1)

[Claims] 1. Equipped with a switched capacitor filter for filtering the input signal, which uses a switched capacitor circuit that consists of an analog switch and a capacitor that are driven in a predetermined drive order by a clock signal of a predetermined frequency, and constitutes a circuit equivalent to a resistor. , regarding a digital arithmetic processing device that converts the output signal of the switched capacitor filter into a digital quantity and performs processing based on a predetermined arithmetic algorithm, the driving order of the analog switches is changed to change the output signal of the switched capacitor filter. A digital arithmetic processing device characterized by comprising phase inversion control means for inverting the phase of a signal.