CN105891738B - Commutation frequency measuring circuit and over-excitation protection method for over-excitation protection - Google Patents
Commutation frequency measuring circuit and over-excitation protection method for over-excitation protection Download PDFInfo
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- CN105891738B CN105891738B CN201610368898.7A CN201610368898A CN105891738B CN 105891738 B CN105891738 B CN 105891738B CN 201610368898 A CN201610368898 A CN 201610368898A CN 105891738 B CN105891738 B CN 105891738B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
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Abstract
Provided by the present invention for the commutation frequency measuring circuit and over-excitation protection method of over-excitation protection; the circuit can measure overexcitation multiple in real time; conversion speed is fast; precision is high; it is small by frequency influence under suitable circuit parameter; and due to not having to differentiate zero crossing, protection inherent delay is short, effectively meets demand of the over-excitation protection to actuation time and time of return；Using temperature-compensation circuit, the trueness error that temperature change can be effectively prevent to bring.Measuring circuit is converted by said frequencies and converts measured signal to the over-excitation protection method that d. c. voltage signal exports, judges that the mode whether protection acts is flexible, and hardware judgement both can be used directly, also can indirectly have been judged by software sampling；Using multistage Parabolic Fit inverse-time curve, it can solve the problems, such as that time change is rough in match point；The cumulative effect of history value in too drastic magnetic value dynamic changing process is really reflected using fuel factor accumulation distinguished number.
Description
Technical field
The present invention relates to a kind of commutation frequency measuring circuits and over-excitation protection method for over-excitation protection, belong to electricity
Force system Main Equipment Protection Technology field.
Background technology
In the large and medium-sized generator of electric system or tranformer protection, inverse time lag over-excitation protection is when preventing overexcitation
The protection that causes iron core to overheat and must match.Conventional inverse time lag over-excitation protection generally use software calculating method realizes overexcitation
The measurement of multiple, is generally realized with the following method：Voltage is introduced by voltage transformer, sampled voltage signal obtains voltage transient
Value, respectively numerical calculation voltage U values and frequency quantity f values, then composite calulation U/f values；Or the zero crossing of first measured waveform, meter
The integral of pulse shape value between two zero crossings is calculated, U/f values are further converted into.
It is had the following problems using above two algorithm：
(1) due to will measured waveform zero crossing, so time and the size of frequency that protection calculates have relationship, frequency
Smaller, data window is longer, and calculating speed is slower, and inherent delay is longer, and protection act and time of return are longer；
(2) it when measuring zero crossing, the case where being non-sampled point for zero crossing, needs to be simulated with interpolation method, frequency
There are errors for rate measurement；
(3) algorithm of trapezoidal fitting is generally adopted by when calculating integral of pulse shape value, there are errors for result of calculation.
Inverse-time curve used in over-excitation protection is generator or the practical overexcitation limit that transformer manufacturing producer provides
Curve, different generators or transformer correspond to different inverse-time curves, it is difficult to be described instead come accurate with a kind of mathematic(al) representation
Time limit relationship is fitted inverse-time curve frequently with more broken lines, is calculated according to these broken lines dynamic under different overexcitation multiple values
Make time limit ts, then compared with timer tj values, as tj >=ts, over-excitation protection action.
It is had the following problems using above-mentioned algorithm：
(1) polygometry calculating action time limit ts changes unsmooth near match point, when overexcitation value generates smaller shaking
When, the ts errors being calculated are larger, often cannot be satisfied time precision requirement；
(2) time criterion be built upon the too drastic magnetic value into inverse-time curve it is static it is constant under conditions of, and practical mistake
Excitatory value is dynamic change, if not accounting for the influence of the too drastic magnetic value of history, can bring uncertain time deviation.
Therefore propose one kind can transient measurement overexcitation multiple, calculate iron core heat accumulation situation special overexcitation algorithm
It will be necessary.
Invention content
The present invention provides a kind of for over-excitation protection to solve drawbacks described above and deficiency existing in the prior art
Commutation frequency measuring circuit and over-excitation protection method.
In order to solve the above technical problems, the present invention provides a kind of commutation frequency measuring circuit for over-excitation protection, packet
Include power vd D, ground GND, operational amplifier A 1, operational amplifier A 2, diode V1, diode V2, sampling resistor R1, sampling electricity
Hold C1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, filter resistance R8 and filter capacitor C2；Letter to be measured
The other end of one end of number Vi connection sampling resistors R1, R1 is grounded GND by sampling capacitance C1 respectively, is connected to by resistance R3
The positive input terminal of operational amplifier A 1, the positive input terminal that operational amplifier A 2 is connected to by resistance R6；Operational amplifier A 1
Negative input end is connected with one end of the cathode of diode V1 and resistance R4 respectively, and is grounded GND, operational amplifier by resistance R2
The output end of A1 is connected with the cathode of the anode of diode V1 and diode V2 respectively；The anode of diode V2 is another with resistance R4's
One end is connected, and the negative input end of operational amplifier A 2 is connected to by resistance R5, and resistance R7 is defeated by bearing for operational amplifier A 2
The output end for entering end and operational amplifier A 2 links together；The output end of operational amplifier A 2 passes through filter resistance R8 and output
Signal Vo is connected, and output signal Vo is grounded GND by filter capacitor C2.
Further, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7 resistance value meet following relationship：
R2=R3=R4=R5=R6, R7=2R2.
Further, the measuring circuit further includes protection circuit, and the protection circuit includes voltage-stabiliser tube VD1 and voltage-stabiliser tube
The anode of VD2, voltage-stabiliser tube VD1 and the cathode of voltage-stabiliser tube VD2 are connected with the junction of sampling resistor R1 and sampling capacitance C1, surely
The cathode of pressure pipe VD1 meets power vd D, the plus earth GND of voltage-stabiliser tube VD2.
Further, the measuring circuit further includes temperature-compensation circuit, and the temperature-compensation circuit includes anti-temperature coefficient
Capacitance C3, anti-temperature coefficient capacitance C4, anti-temperature coefficient capacitance C3 are connected in parallel with sampling capacitance C1, anti-temperature coefficient capacitance C4
It is connected in parallel with filter capacitor C2.
Over-excitation protection method, includes the following steps：
Step 1, measured signal is accessed into claim 1-4 any one of them commutation frequency measuring circuits, the frequency
Converting measuring circuit will be in the size conversion to the amplitude of alternating voltage of measured signal frequency so that the amplitude of output voltage and frequency
Rate is inversely proportional, meanwhile, the commutation frequency measuring circuit carries out fine full-wave rectification to the waveform of output voltage, is exported after filtering
D. c. voltage signal, by adjusting corresponding resistance value and capacitance in circuit make DC voltage value and overexcitation multiple value at
Direct ratio；
Step 2, judge to judge that two methods determine whether protection acts with indirect using direct.
Wherein, direct judgment method is to be compared DC voltage value and setting voltage value using comparator, work as direct current
When voltage value is more than setting voltage value, protection transmits and trips.
Indirect judgment method specifically includes following steps：
Step 2.1, the direct current signal generated to step 1 samples to obtain overexcitation instantaneous value Uf；
Step 2.2, discrete practical overexcitation inverse-time curve, obtains one group of definite value (Uf0,t0), (Uf1,t1) ... (Ufn,
tn) ..., (Ufm,tm), it is used in combination multistage curve-parabola-fitting method to realize that curve matching, specific algorithm are as follows：
Work as Uf＜ Uf0When, time definite value ts=t0；
Work as Ufn-1≤Uf＜ Ufn＜ Ufn+1, and when 1≤n ＜ m, time definite value tsCalculation formula be：
Work as Ufm-1≤Uf＜ UfmWhen, time definite value tsCalculation formula be：
Work as Uf≥UfmWhen, time definite value ts=tm；
Step 2.3, it carries out fuel factor and accumulates operation, obtain heat accumulation value M；
Step 2.4, judge whether protection acts according to heat accumulation value M：As M >=1, protection transmits and trips；Work as M<1
When, protection returns.
The step 2.3 is specially：
For the K moment, overexcitation instantaneous value is Uf(k)：As overexcitation instantaneous value Uf(k) it is less than inverse-time curve minimum value
When, heat accumulation value M is reset；As overexcitation instantaneous value Uf(k) when being more than inverse-time curve minimum value, in conjunction with Uf(k) and step 2.2
Instantaneous time definite value t is calculated in the calculation formula of obtained Parabolic Fit curves(k)；
Interval time △ t (k)=t (k)-t (k-1) that measurement is calculated away from the last time, t (k) are the absolute time at current time
Mark, t (k-1) are the absolute time mark at upper one calculating moment；
Calculate heat accumulation value M：Work as Uf(k) ＜ Uf0When, M=0；Work as Uf(k)≥Uf0When,Wherein, Uf0
For first match point of inverse-time curve.
The advantageous effects that the present invention is reached：
Provided by the present invention for the commutation frequency measuring circuit of over-excitation protection, which can measure overexcitation in real time
Multiple, conversion speed is fast, and precision is high, small by frequency influence under suitable circuit parameter, and due to not having to differentiate zero crossing, protects
It is short to protect inherent delay, effectively meets demand of the over-excitation protection to actuation time and time of return；Using temperature-compensation circuit,
The trueness error that temperature change can be effectively prevent to bring.
The present invention also provides a kind of over-excitation protection method, this method converts measuring circuit by letter to be measured by said frequencies
It number is converted into d. c. voltage signal output, judges that the mode whether protection acts is flexible, hardware judgement both can be used directly, also may be used
Judged indirectly by software sampling, calculation amount is few when judging indirectly, and real-time is good；Using the multistage Parabolic Fit inverse time lag
Curve can solve the problems, such as that time change is rough in match point, enhancing action time precision；Sentenced using fuel factor accumulation
Other algorithm, which can overcome in conventional comparison expression time, algorithm inverse time lag, can not accurately reflect too drastic magnetic value dynamic changing process
Defect really reflects the cumulative effect of history value in too drastic magnetic value dynamic changing process, operating time of protection precision higher, object
It manages meaning definitely, differentiates that more science is accurate.
Description of the drawings
The commutation frequency measuring circuit schematic diagram of Fig. 1 present invention；
The protection circuit of Fig. 2 present invention and commutation frequency measuring circuit connection diagram；
The temperature-compensation circuit of Fig. 3 present invention and commutation frequency measuring circuit connection diagram；
Commutation frequency measuring circuit figure in Fig. 4 embodiments of the present invention；
The over-excitation protection method flow schematic diagram of Fig. 5 present invention；
The multistage curve-parabola-fitting method schematic diagram of Fig. 6 present invention.
Specific implementation mode
The invention will be further described below in conjunction with the accompanying drawings.Following embodiment is only used for clearly illustrating the present invention
Technical solution, and not intended to limit the protection scope of the present invention.
As shown in Figure 1, provided by the present invention for the commutation frequency measuring circuit of over-excitation protection, including power vd D, ground
GND, operational amplifier A 1, operational amplifier A 2, diode V1, diode V2, sampling resistor R1, sampling capacitance C1, resistance R2,
Resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, filter resistance R8 and filter capacitor C2；Measured signal Vi connections sample
The other end of one end of resistance R1, R1 is grounded GND by sampling capacitance C1 respectively, is connected to operational amplifier A 1 by resistance R3
Positive input terminal, be connected to by resistance R6 the positive input terminal of operational amplifier A 2；The negative input end of operational amplifier A 1 is distinguished
It is connected with one end of the cathode of diode V1 and resistance R4, and GND, the output end point of operational amplifier A 1 is grounded by resistance R2
It is not connected with the cathode of the anode of diode V1 and diode V2；The anode of diode V2 is connected with the other end of resistance R4, and
The negative input end of operational amplifier A 2 is connected to by resistance R5, resistance R7 puts the negative input end of operational amplifier A 2 and operation
The output end of big device A2 links together；The output end of operational amplifier A 2 is connected by filter resistance R8 with output signal Vo,
Output signal Vo is grounded GND by filter capacitor C2.In use, in order to preferably ensure the voltage value of output signal with
Overexcitation multiple value is directly proportional, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7 resistance value meet following pass
It is formula：R2=R3=R4=R5=R6, R7=2R2.
In order to protect operational amplifier A 1, operational amplifier A 2 and subsequent circuit not to damage, the measuring circuit further includes
It includes voltage-stabiliser tube VD1 and voltage-stabiliser tube VD2 to protect circuit, the protection circuit, and voltage-stabiliser tube VD1's is positive and voltage-stabiliser tube VD2 negative
Extremely it is connected with the junction of sampling resistor R1 and sampling capacitance C1, the cathode of voltage-stabiliser tube VD1 meets power vd D, voltage-stabiliser tube VD2's
Plus earth GND, as shown in Figure 2.
The measuring circuit further includes temperature-compensation circuit, it is possible to reduce influence of the temperature drift to circuit measuring precision, it is described
Temperature-compensation circuit includes anti-temperature coefficient capacitance C3, anti-temperature coefficient capacitance C4, and anti-temperature coefficient capacitance C3 is with sampling capacitance
C1 is connected in parallel, and anti-temperature coefficient capacitance C4 is connected in parallel with filter capacitor C2, as shown in Figure 3.
As the specific implementation mode of the present invention, as shown in figure 4, the design parameter of required electronic component is in circuit：
R1=220K, R2=R3=R4=R5=R6=10K, R7=20K, R8=120K, C1=0.1u, C2=0.047u, diode
The model of V1 and diode V2 are 1SS355, can better illustrate the frequency folding provided by the present invention for over-excitation protection
Calculate the technique effect of measuring circuit.
The circuit can convert the size of measured signal frequency onto the amplitude of alternating voltage so that the width of output voltage
Value is inversely proportional with frequency, figure 4, it is seen that output voltageWherein f is the frequency of input signal, because
This, it can be seen that output voltage VjAmplitude it is directly proportional to overexcitation multiple, and conversion speed is fast.
Output voltage VjSignal V is obtained after 1 processing of circuit of operational amplifier Az, calculation formula is：Signal VzOutput letter is obtained after 2 processing of circuit of operational amplifier A
Number Vo, calculation formula are：
By VzResult of calculation bring above formula into, can obtain：
To sum up, commutation frequency measuring circuit can measure overexcitation multiple in real time, and result conversion speed is fast, and precision is high,
It is small by frequency influence, and due to not having to differentiate zero crossing, protection inherent delay is short, when effectively meeting over-excitation protection to action
Between and time of return demand.
As shown in figure 5, the present invention provides a kind of over-excitation protection method, include the following steps：
Step 1, measured signal is accessed into claim 1-4 any one of them commutation frequency measuring circuits, the frequency
Converting measuring circuit will be in the size conversion to the amplitude of alternating voltage of measured signal frequency so that the amplitude of output voltage and frequency
Rate is inversely proportional, meanwhile, the commutation frequency measuring circuit carries out fine full-wave rectification to the waveform of output voltage, is exported after filtering
D. c. voltage signal, by adjusting corresponding resistance value and capacitance in circuit make DC voltage value and overexcitation multiple value at
Direct ratio；
Step 2, judge to judge that two methods determine whether protection acts with indirect using direct.
Wherein, direct judgment method is to be compared DC voltage value and setting voltage value using comparator, work as direct current
When voltage value is more than setting voltage value, protection transmits and trips.
Indirect judgment method specifically includes following steps：
Step 2.1, the direct current signal generated to step 1 samples to obtain overexcitation instantaneous value Uf；
Step 2.2, discrete practical overexcitation inverse-time curve is used in combination multistage curve-parabola-fitting method to realize curve matching.It is existing
There is general algorithm in technology to use polygometry matched curve, error is larger, and changes unsmooth, slope generation near definite value point
Mutation, when overexcitation value generates smaller shaking, the time error being calculated is also larger.As shown in fig. 6, using multistage
Curve-parabola-fitting method carries out curve fitting, and matched curve error is small, relatively more flat closer to actual curve, and near definite value point
It is sliding, it not will produce the problem of slope is mutated, fitting algorithm is as follows：
Discrete practical overexcitation inverse-time curve, obtains one group of definite value (Uf0,t0), (Uf1,t1) ... (Ufn,tn) ...,
(Ufm,tm), it is used in combination multistage curve-parabola-fitting method to realize that curve matching, specific algorithm are as follows：
Work as Uf＜ Uf0When, time definite value ts=t0；
Work as Ufn-1≤Uf＜ Ufn＜ Ufn+1, and when 1≤n ＜ m, time definite value tsCalculation formula be：
Work as Ufm-1≤Uf＜ UfmWhen, time definite value tsCalculation formula be：
Work as Uf≥UfmWhen, time definite value ts=tm；
Step 2.3, it carries out fuel factor and accumulates operation, obtain heat accumulation value M；
For the K moment, overexcitation instantaneous value is Uf(k)：As overexcitation instantaneous value Uf(k) it is less than inverse-time curve minimum value
When, heat accumulation value M is reset；As overexcitation instantaneous value Uf(k) when being more than inverse-time curve minimum value, in conjunction with Uf(k) and step 2.2
Instantaneous time definite value t is calculated in the calculation formula of obtained Parabolic Fit curves(k)；
Interval time △ t (k)=t (k)-t (k-1) that measurement is calculated away from the last time, t (k) are the absolute time at current time
Mark, t (k-1) are the absolute time mark at upper one calculating moment；
Calculate heat accumulation value M：Work as Uf(k) ＜ Uf0When, M=0；Work as Uf(k)≥Uf0When,Wherein, Uf0
For first match point of inverse-time curve.
Step 2.4, judge whether protection acts according to heat accumulation value M：As M >=1, protection transmits and trips；Work as M<1
When, protection returns.
Can be overcome using fuel factor accumulation distinguished number can not be accurately anti-in conventional comparison expression time, algorithm inverse time lag
The defect for reflecting too drastic magnetic value dynamic changing process, really reflects the cumulative effect of history value in overexcitation dynamic changing process.
The above is only a preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, without departing from the technical principles of the invention, several improvement and deformations can also be made, these improvement and deformations
Also it should be regarded as protection scope of the present invention.
Claims (8)
1. the commutation frequency measuring circuit for over-excitation protection, it is characterised in that：Including power vd D, ground GND, operation amplifier
Device A1, operational amplifier A 2, diode V1, diode V2, sampling resistor R1, sampling capacitance C1, resistance R2, resistance R3, resistance
R4, resistance R5, resistance R6, resistance R7, filter resistance R8 and filter capacitor C2；The one of measured signal Vi connection sampling resistors R1
The other end at end, R1 is grounded GND by sampling capacitance C1 respectively, is connected to the positive input of operational amplifier A 1 by resistance R3
End passes through the positive input terminal of resistance R6 and connecting pin operational amplifier A 2；The negative input end of operational amplifier A 1 respectively with two poles
The cathode of pipe V1 is connected with one end of resistance R4, and is grounded GND by resistance R2, and the output end of operational amplifier A 1 is respectively with two
The anode of pole pipe V1 is connected with the cathode of diode V2；The anode of diode V2 is connected with the other end of resistance R4, and passes through electricity
Resistance R5 is connected to the negative input end of operational amplifier A 2, and resistance R7 is by the negative input end of operational amplifier A 2 and operational amplifier A 2
Output end link together；The output end of operational amplifier A 2 is connected by filter resistance R8 with output signal Vo, output letter
Number Vo passes through filter capacitor C2 and is grounded GND.
2. the commutation frequency measuring circuit according to claim 1 for over-excitation protection, it is characterised in that：Resistance R2,
Resistance R3, resistance R4, resistance R5, resistance R6, resistance R7 resistance value meet following relationship：R2=R3=R4=R5=R6, R7
=2R2.
3. the commutation frequency measuring circuit according to claim 1 for over-excitation protection, it is characterised in that：The measurement
Circuit further includes protection circuit, and the protection circuit includes voltage-stabiliser tube VD1 and voltage-stabiliser tube VD2, the anode of voltage-stabiliser tube VD1 and voltage stabilizing
The cathode of pipe VD2 is connected with the junction of sampling resistor R1 and sampling capacitance C1, and the cathode of voltage-stabiliser tube VD1 meets power vd D, surely
The plus earth GND of pressure pipe VD2.
4. the commutation frequency measuring circuit according to claim 1 for over-excitation protection, it is characterised in that：The measurement
Circuit further includes temperature-compensation circuit, and the temperature-compensation circuit includes anti-temperature coefficient capacitance C3, anti-temperature coefficient capacitance C4,
Anti- temperature coefficient capacitance C3 is connected in parallel with sampling capacitance C1, and anti-temperature coefficient capacitance C4 is connected in parallel with filter capacitor C2.
5. over-excitation protection method, which is characterized in that include the following steps：
Step 1, measured signal is accessed into claim 1-4 any one of them commutation frequency measuring circuits, the commutation frequency
Measuring circuit will measured signal frequency size conversion in the amplitude of alternating voltage so that the amplitude of output voltage and frequency at
Inverse ratio, meanwhile, the commutation frequency measuring circuit carries out fine full-wave rectification to the waveform of output voltage, and direct current is exported after filtering
Voltage signal makes DC voltage value with overexcitation multiple value at just by adjusting corresponding resistance value and capacitance in circuit
Than；
Step 2, judge to judge that two methods determine whether protection acts with indirect using direct.
6. over-excitation protection method according to claim 5, it is characterised in that：Direct judgment method is to use comparator
DC voltage value and setting voltage value are compared, when DC voltage value is more than setting voltage value, protection transmits and trips.
7. over-excitation protection method according to claim 5, it is characterised in that：Indirect judgment method specifically includes following step
Suddenly：
Step 2.1, the d. c. voltage signal generated to step 1 samples to obtain overexcitation instantaneous value Uf；
Step 2.2, discrete practical overexcitation inverse-time curve, obtains one group of definite value (Uf0,t0), (Uf1,t1) ... (Ufn,
tn) ..., (Ufm,tm), it is used in combination multistage curve-parabola-fitting method to realize that curve matching, specific algorithm are as follows：
Work as Uf＜ Uf0When, time definite value ts=t0；
Work as Ufn-1≤Uf＜ Ufn＜ Ufn+1, and when 1≤n ＜ m, time definite value tsCalculation formula be：
Work as Ufm-1≤Uf＜ UfmWhen, time definite value tsCalculation formula be：
Work as Uf≥UfmWhen, time definite value ts=tm；
Step 2.3, it carries out fuel factor and accumulates operation, obtain heat accumulation value M；
Step 2.4, judge whether protection acts according to heat accumulation value M：As M >=1, protection transmits and trips；Work as M<When 1, protect
Shield returns.
8. over-excitation protection method according to claim 7, which is characterized in that the step 2.3 is specially：
For the K moment, overexcitation instantaneous value is Uf(k)：As overexcitation instantaneous value Uf(k) when being less than inverse-time curve minimum value, heat
Accumulating value M is reset；As overexcitation instantaneous value Uf(k) when being more than inverse-time curve minimum value, in conjunction with Uf(k) it is obtained with step 2.2
Instantaneous time definite value t is calculated in the calculation formula of Parabolic Fit curves(k)；
Interval time △ t (k)=t (k)-t (k-1) that measurement is calculated away from the last time, t (k) are the absolute time mark at current time, t
(k-1) it is upper one absolute time mark for calculating the moment；
Calculate heat accumulation value M：Work as Uf(k) ＜ Uf0When, M=0；Work as Uf(k)≥Uf0When,Wherein, Uf0For inverse time
Limit first match point of curve.
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| CN108199350B (en) * | 2017-11-27 | 2019-11-05 | 上海电气电站设备有限公司 | A kind of generator overexcitation limitation guard method |
| CN109980604A (en) * | 2017-12-28 | 2019-07-05 | 沈阳新松机器人自动化股份有限公司 | The thermal overload protection method and computer readable storage medium of robot motor |
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