CN201569704U - Harmonic impedance measurement device - Google Patents
Harmonic impedance measurement device Download PDFInfo
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- CN201569704U CN201569704U CN2009202738166U CN200920273816U CN201569704U CN 201569704 U CN201569704 U CN 201569704U CN 2009202738166 U CN2009202738166 U CN 2009202738166U CN 200920273816 U CN200920273816 U CN 200920273816U CN 201569704 U CN201569704 U CN 201569704U
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Abstract
A harmonic impedance measurement device comprises a voltage transformer, a current transformer, a low pass filter, a voltage and a current program control amplifiers, an analog-to-digital converter, a MCU (microprogrammed control unit) or a DSP (digital signal processing) controller and a display operating interface which are orderly electrically connected. The utility model is characterized in that the device also comprises a sampling frequency and system frequency synchronous circuit and a phase and system period synchronous circuit; the sampling frequency and system frequency synchronous circuit comprises an amplitude limit amplifier, a bandpass filter, a zero crossing point detection circuit, a phase locking frequency doubling loop, a N frequency divider and a synchronous sampling pulse loop; the amplitude limit amplifier, the bandpass filter, the zero crossing point detection circuit, the phase locking frequency doubling loop and the N frequency divider are orderly electrically connected; the zero crossing point detection circuit is connected with the MCU or the DSP controller, and the synchronous sampling pulse loop is respectively connected with the phase locking frequency doubling loop and the MCU or the DSP controller; the phase and system period synchronous circuit comprises an amplifying circuit a, a primary low pass filter, a secondary high pass filter, a phase adjusting circuit, an amplifying circuit b and a signal zero crossing point detection circuit which are orderly electrically connected. The device having the advantages of simple principle and easy implementation achieves practical engineering level and solves harmonic impedance measurement problems in electric production.
Description
Technical field
The utility model relates to a kind of harmonic impedance measurement mechanism, belongs to quality of power supply control and improvement, quality of power supply measuring method and device field.
Background technology
Harmonic impedance is important parameters very in the electrical production, no matter is the design electric-power filter, still assesses the harmonics level that disturbance load produces, and system harmonic impedance is the most basic underlying parameter; Adopt the harmonic trend software for calculation that grid is carried out frequency sweeping, drawing harmonic impedance is common method, but since the network high-frequency difficult parameters to obtain; In addition, the three-phase geometric parameter of system not exclusively symmetry, each mutually between and parameter such as ground capacitance very big to the influence of result of calculation degree of accuracy, make the result of calculation deviation very big.Therefore actual measurement is an effective means of obtaining system harmonic impedance.But harmonic impedance is measured and is still lacked effective, practical method and device up to now, becomes one of difficult problem in the electrical production." method of addition " is a kind of comparatively feasible measuring method, the harmonic current that passes through the measurement disturbance load of this method and the harmonic impedance that voltage increment calculates system or load.Among Fig. 1, the system harmonic impedance of seeing into to system from the PCC point is Z
Sh, the harmonic voltage of this point, electric current satisfy relation:
The size of distortion load is changed, promptly produce a disturbance, the h subharmonic voltage that PCC is ordered, electric current will be from changing preceding sample window c's
Become sample window a's
(b is a disturbance transient process window among Fig. 2), and system harmonic impedance Z
ShWith background harmonics voltage
Substantially remain unchanged, as shown in the formula:
Can get the harmonic impedance Z of system by (2) formula
Sh:
When using following formula, suppose that the harmonic voltage of different time and current vector are all with reference to the constant voltage vector of same phase place
Because this is closely related with reference to vector and system frequency, when frequency changes,
Phase place can change, thereby introduce bigger measuring error.Therefore and how the fluctuation within the specific limits always of the frequency of electric system eliminates error that frequency change introduces and is the key that can this method engineering demands.As seen from Figure 2, any frequency error measurement will make the voltage of sample window c, a, the phase angle between the current vector produce deviation, thereby make voltage and current increment Delta U
h, Δ I
hProduce bigger deviation.Promptly there are the following problems for this method: before and after (1) disturbance produced, signal sampling must have common constant fixed phase
Just can measure the harmonic wave phase angle of voltage before and after changing, electric current.But the load impedance variation can cause the phase angle of points of common connection (PCC) voltage
Change; (2)
With system frequency f
0Change, therefore
F must can be followed the tracks of
0Variation.(3) before and after increment produced, sample frequency must be followed the tracks of f
0Variation, promptly must with system frequency f
0Synchronously, otherwise frequency deviation f
0To cause bigger synchronous error.
Existing " method of addition " can not keep constant voltage vector as with reference to vectorial for the harmonic voltage of different time and current vector are provided with a phase place with frequency jitter, causes when frequency changes reference vector
Phase place can change, thereby introduce bigger measuring error.
Summary of the invention
The purpose of this utility model is to provide a kind of harmonic impedance measurement mechanism, measuring principle and existing problem according to " method of addition ", the utility model proposes " two synchronous method of addition " and be intended to the error problem that the resolution system frequency change is introduced, improve measuring accuracy, make it engineering demands.
The technical solution of the utility model is: a kind of harmonic impedance measurement mechanism, comprise voltage transformer (VT), and current transformer, low-pass filter, voltage, current-programmed amplifier, A/D converter, MCU or dsp controller, the display operation interface is electrically connected successively; It is characterized in that: also comprise sample frequency and system frequency synchronizing circuit and phase place and system cycle synchronizing circuit, sample frequency and system frequency synchronizing circuit comprise limiting amplifier, bandpass filter, zero-crossing detection circuit, phase locking frequency multiplying loop, Fractional-N frequency device and Synchronous Sampling Pulse loop; Limiting amplifier, bandpass filter, zero-crossing detection circuit, phase locking frequency multiplying loop and Fractional-N frequency device are electrically connected successively, zero-crossing detection circuit is connected with MCU or dsp controller, and the Synchronous Sampling Pulse loop is connected respectively with phase locking frequency multiplying loop, MCU or dsp controller; Phase place comprises that with the system cycle synchronizing circuit amplifying circuit a, low-pass first order filter, bivalent high-pass filter, phase-adjusting circuit, amplifying circuit b and signal zero crossing testing circuit are electrically connected successively.
A kind of harmonic impedance measurement mechanism of the present utility model, the method that is adopted is: produce the front and back fixed phase for obtaining disturbance, introduce the voltage signal of upper level or adjacent bus
As with reference to vector, with the starting point of this point voltage cycle signal zero-cross point, promptly with the sampling fixed phase of this voltage signal as sample window c, a before and after the disturbance as sampling before and after the disturbance; It is characterized in that: fixed phase and system cycle T
0Synchronously, to solve the problem that fixed phase is drifted about with frequency change, make the time interval t between two sample windows of c, a
AcFor system cycle is synchronizing signal T
0Integral multiple, the zero crossing of getting synchronizing signal is as reference phase place or sampling starting point; By hardware phase locking frequency multiplying loop, the variation of tracker frequency, sample frequency is then produced by the phase locking frequency multiplying loop, makes sample frequency and system frequency synchronous.
The harmonic impedance measuring method that the utility model device is used, in turn include the following steps: beginning, initialization, be carved into when the detection of synchronizing signal zero crossing, synchronizing signal zero crossing, enter sample window c, be carved into when sampling M cycle, disturbance generation command signal, P the cycle of delaying time, the detection of synchronizing signal zero crossing, synchronizing signal zero crossing, enter sample window a, sample three-phase voltage, the electric current each harmonic vector of M cycle, calculating sampling window c, the three-phase voltage of calculating sampling window a, electric current each harmonic vector; By sample window c, a three-phase voltage, current harmonics vector calculation harmonic wave increment and harmonic impedance, the harmonic impedance measurement result is stored, shows and is uploaded, and finishes.
Principle of work of the present utility model is: produce the front and back fixed phase for obtaining disturbance, introduce the voltage signal of upper level or adjacent bus
As with reference to vector, with the starting point of this point voltage cycle signal zero-cross point as sampling before and after the disturbance, promptly with the sampling fixed phase of this voltage signal as sample window c, a before and after the disturbance, and this fixed phase must with system cycle T
0Synchronously, sample frequency must be synchronous with system frequency, i.e. so-called " two synchronous method of addition ".The utility model has mainly solved following problem.
1) eliminates the error that the fixed phase drift is introduced
By (4) formula as seen, the fixed phase skew can cause great measuring error.The Δ Z of each harmonic
Sh/ Z
ShWith
Change curve be shown in Fig. 3.From top to bottom each straight line corresponding h=17, h=15, h=13, h=11, h=7, h=5, h=3 and h=1 respectively among Fig. 3.As seen overtone order is high more, and error is big more.As
Δ U
h/ E
Sh h=2%, Δ Z
Sh/ Z
Sh≈ 13% (h=11).
2) eliminate the error that frequency change is introduced
General using discrete Fourier transform (DFT) (DFT) calculates the incremental vector of each harmonic voltage, electric current earlier, calculates harmonic impedance by (6) formula again.If mains frequency is f
0(=1/T
0), since frequency jitter, sample frequency f
iCan not accurate tracking f
0Variation then can cause harmonic wave amplitude measurement error:
ΔC
h/C
h≈nπ|ΔT
0/T
0|(5)
Wherein, Δ C
h/ C
hBe the relative error of h subharmonic amplitude, Δ C
h/ C
hWith frequency deviation T
0=1/ Δ f
0And h is directly proportional.Δ T for example
0/ T
0=0.64%, to 5 subharmonic Δ C
5/ C
5≈ 10%; Therefore if f
iCan not accurate tracking f
0Variation, very big to the influence of the measuring accuracy of harmonic impedance.
Core of the present utility model is " two synchronous method of addition ", and the voltage signal that fixed phase is introduced upper level or adjacent bus only is a kind of supplementary means, and inessential.
The beneficial effects of the utility model are: by the utility model proposes " two synchronous method of addition ", solved the error problem that is caused by reference phase and system frequency fluctuation etc. in " method of addition "; Principle of device is simple, easy to implement; Institute's extracting method and measurement mechanism reach the engineering realistic scale, and the harmonic impedance that can efficiently solve in the electrical production is measured a difficult problem.
Description of drawings
Fig. 1 is " method of addition " harmonic wave equivalent circuit synoptic diagram.
Fig. 2 is " method of addition " sample window synoptic diagram.
Fig. 3 is the Δ Z of " method of addition " each harmonic
Sh/ Z
ShWith
Change curve.
Fig. 4 is the utility model embodiment harmonic impedance measurement mechanism schematic diagram.
Fig. 5 is the utility model embodiment synchronization waveform figure.
Fig. 6 is the utility model embodiment phase place and system cycle synchronizing circuit schematic diagram.
Fig. 7 is the utility model embodiment sample frequency and system frequency synchronizing circuit schematic diagram.
Fig. 8 is the utility model embodiment workflow synoptic diagram.
Fig. 9 is the utility model embodiment 1 pilot system synoptic diagram.
Figure 10 is the Z of the utility model embodiment 1
h=f (h) curve synoptic diagram.
Embodiment
Below in conjunction with drawings and Examples the utility model is described further.
The explanation of mark among Fig. 4: 1-voltage transformer (VT) (TV), 2-current transformer (TA), 3-low-pass filter, the 4-programmable amplifier, 5-six road A/D converters, 6-MCU or dsp controller, 7-display operation interface, the 8-limiting amplifier, the 9-bandpass filter, 10-zero-crossing detection circuit, 11-phase locking frequency multiplying loop, the 12-N frequency divider, 13-Synchronous Sampling Pulse loop.
The explanation of mark among Fig. 6: 14-amplifying circuit a, 15-low-pass first order filter, 16-bivalent high-pass filter, 17-phase-adjusting circuit, 18-amplifying circuit b.
The explanation of mark among Fig. 9: 19-10kV bus, 20-400kV bus, 21-six pulsed rectifiers, 22-resistive load, 23-harmonic impedance measurement mechanism.
The utility model embodiment harmonic impedance measurement mechanism theory of constitution is shown in accompanying drawing 4: enter low-pass filter 3 after three-phase current, current signal process accurate voltage TV1, the electric current TA2 decay conditioning, filtering is higher than the component of the cutoff frequency of sampling; Be amplified near the input of the full scale of A/D converter A/D through six distance control amplifiers 4 again, enter six road A/D converters 5 then analog signal conversion is become digital signal; A/D starts the zero crossing control (accompanying drawing 5) of conversion by synchronizing signal, and six road A/D converters 5 are gathered simultaneously under the control of fi, guarantee that three-phase voltage, current signal do not have the time-delay synchronized sampling.
In window c arrival constantly, the zero crossing startup A/D by synchronizing signal begins to gather three-phase voltage, a current signal M cycle; Surveying instrument sends and produces the disturbance order thereupon, and P cycle of time-delay, to avoid the voltage fluctuation of measured point; Be carved into during time-delay, surveying instrument starts A/D collection three-phase voltage, a current signal M cycle (accompanying drawing 5) at the zero crossing of synchronizing signal once more.
One of the proposition of the utility model embodiment harmonic impedance method is synchronous, is to make fixed phase and system cycle T
0Synchronously, to solve the problem that fixed phase is drifted about with frequency change.Make the time interval t between two sample windows of c, a
AcBe system cycle (synchronizing signal) T
0Integral multiple, the zero crossing of getting synchronizing signal is as reference phase place (sampling starting point).That is:
t
ac＝P×T
0(6)
P in the formula 〉=1 generally gets 10～20.So, even system frequency f
0Change, but each power frequency period T
0Electrical angle be 2 π, make t
Ac=P * (2 π) * T
0, by the periodicity of sine function:
By following formula as seen, so can guarantee to have same fixed phase before and after the system frequency fluctuation
Phase place and system cycle produce the loop synchronously and are shown in accompanying drawing 6.Form by following circuit: amplifying circuit a14, low-pass first order filter 15, bivalent high-pass filter 16, phase-adjusting circuit 17, amplifying circuit b18 and signal zero crossing testing circuit 10 are electrically connected successively.
It is synchronous two that the utility model embodiment harmonic impedance method proposes, by hardware phase locking frequency multiplying loop 11, and the tracker frequency change, sample frequency is produced by phase locking frequency multiplying loop 11, makes sample frequency f
iWith the tracker frequency f
0Variation.The resolution system frequency f
0Change the error of " leakage effect " introducing that causes, even the sample frequency f of A/D
iWith system frequency f
0Synchronously:
f
i＝M×N×f
0(10)
N is weekly the sampling number of phase in the following formula, and M is for adopting window width.As system frequency f
0During variation, the sampling period τ of each sampled point
i=1/f
iWith f
0Variation regulate sampling period τ automatically
i=T
0The size of/N guarantees that the sampled data in a sample window is the integral multiple of system cycle.
Sample frequency f
iWith system frequency f
0Produce the loop synchronously and be shown in accompanying drawing 7, form by following circuit: limiting amplifier 8, bandpass filter 9, zero-crossing detection circuit 10, phase locking frequency multiplying loop 11, Fractional-N frequency device 12 and Synchronous Sampling Pulse loop 13; Limiting amplifier 8, bandpass filter 9, zero-crossing detection circuit 10, phase locking frequency multiplying loop 11 and Fractional-N frequency device 12 are electrically connected successively, zero-crossing detection circuit 10 is connected with MCU or dsp controller 6, and Synchronous Sampling Pulse loop 13 is connected respectively with phase locking frequency multiplying loop 11, MCU or dsp controller 6;
The utility model embodiment harmonic impedance method implementing procedure is illustrated in accompanying drawing 8, its steps in sequence comprises: beginning, initialization, be carved into when the detection of synchronizing signal zero crossing, synchronizing signal zero crossing, enter sample window c, be carved into when sampling M cycle, disturbance generation command signal, P the cycle of delaying time, the detection of synchronizing signal zero crossing, synchronizing signal zero crossing, enter sample window a, the sample three-phase voltage of M cycle, calculating sampling window c, the each harmonic vector of electric current, the three-phase voltage of calculating sampling window a, electric current each harmonic vector; By the each harmonic vector calculation each harmonic vector increment of sample window c, a three-phase voltage, electric current and the impedance of each harmonic, the harmonic impedance measurement result is stored, shows and is uploaded, and finishes.
Experimental system is shown in accompanying drawing 9.The capacity of short circuit of 10kV bus 19 is 319MVA; Transformer capacity is 315kVA, and impedance voltage is 4.2%; The impedance of fundamental frequency of 400kV bus 20 is 0.008+j0.023 (Ω).Interference source is six pulsed rectifiers 21, and direct current resistance load 22 is 2 Power Resistors (100kVA/5 Ω/platforms).Utilize this system to carry out measured test, with check " two synchronous method of addition " and harmonic impedance measurement mechanism 23.
Synchronizing signal is got the light distribution transformer 220V side voltage signal of this 110kV transformer station.Drop into a resistor during test earlier, drop into second resistor subsequently,, promptly produce harmonic voltage, current increment, extract harmonic voltage, the current signal of disturbance front and back respectively, calculate the each harmonic impedance of system by (3) formula in order to produce disturbance quantity.Because the characteristic harmonics of six pulsed rectifiers 21 is 6k ± 1 time, the harmonic content of other number of times is very little in the system, and measurement result is only effective to 6k ± 1 subharmonic.Measure altogether 5 times, the mean value of 5 measurement results of three-phase is listed in subordinate list 1, Z
h=f (h) curve is plotted in Figure 10.
In h≤17,5 measurement result basically identicals; The harmonic voltage increment is very little more than 17 times, so 5 measurement result dispersivenesses are bigger; Active component is also like this.Because the harmonic impedance of this system is mainly by the transformer impedance decision, so Z
hLinear substantially with h.
| h | X ah(Ω) | R bh(Ω) | X bh(Ω) | R ch(Ω) | X ch(Ω) |
| 1 | 0.0258 | 0.0078 | 0.0232 | 0.009 | 0.0246 |
| 5 | 0.1424 | 0.0376 | 0.1312 | 0.0332 | 0.1322 |
| 7 | 0.1878 | 0.0304 | 0.1836 | 0.0456 | 0.1736 |
| 11 | 0.3002 | 0.0612 | 0.2646 | 0.05 | 0.2776 |
| 13 | 0.3504 | 0.0488 | 0.3292 | 0.0632 | 0.3132 |
| 17 | 0.464 | 0.0532 | 0.4048 | 0.055 | 0.4184 |
| h | X ah(Ω) | R bh(Ω) | X bh(Ω) | R ch(Ω) | X ch(Ω) |
| 19 | 0.52 | 0.041 | 0.4664 | 0.0658 | 0.429 |
| 23 | 0.6006 | 0.1112 | 0.5872 | 0.07 | 0.5884 |
| 25 | 0.6262 | 0.1054 | 0.719 | 0.0876 | 0.5528 |
| 29 | 0.7248 | 0.161 | 0.66 | 0.2326 | 0.698 |
| 31 | 0.6632 | 0.1604 | 0.748 | 0.1744 | 0.6734 |
| 35 | 0.9762 | 0.173 | 0.9266 | 0.1424 | 0.8224 |
| 37 | 0.8132 | 0.2106 | 0.9798 | 0.1362 | 0.9114 |
Claims (1)
1. a harmonic impedance measurement mechanism comprises voltage transformer (VT), current transformer, and low-pass filter, voltage, current-programmed amplifier, A/D converter, MCU or dsp controller, the display operation interface is electrically connected successively; It is characterized in that: also comprise sample frequency and system frequency synchronizing circuit and phase place and system cycle synchronizing circuit, sample frequency and system frequency synchronizing circuit comprise limiting amplifier, bandpass filter, zero-crossing detection circuit, phase locking frequency multiplying loop, Fractional-N frequency device and Synchronous Sampling Pulse loop; Limiting amplifier, bandpass filter, zero-crossing detection circuit, phase locking frequency multiplying loop and Fractional-N frequency device are electrically connected successively, zero-crossing detection circuit is connected with MCU or dsp controller, and the Synchronous Sampling Pulse loop is connected respectively with phase locking frequency multiplying loop, MCU or dsp controller; Phase place comprises that with the system cycle synchronizing circuit amplifying circuit a, low-pass first order filter, bivalent high-pass filter, phase-adjusting circuit, amplifying circuit b and signal zero crossing testing circuit are electrically connected successively.
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|---|---|---|---|
| CN2009202738166U CN201569704U (en) | 2009-11-25 | 2009-11-25 | Harmonic impedance measurement device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009202738166U CN201569704U (en) | 2009-11-25 | 2009-11-25 | Harmonic impedance measurement device |
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| CN201569704U true CN201569704U (en) | 2010-09-01 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102749521A (en) * | 2012-07-18 | 2012-10-24 | 华北电力大学（保定） | Method for computing harmonic impedance of power system |
| CN106526321A (en) * | 2015-09-15 | 2017-03-22 | 日置电机株式会社 | Impedance measuring device and impedance measuring method |
| CN111077375A (en) * | 2019-12-13 | 2020-04-28 | 合肥工业大学 | Online identification method for power grid impedance under background harmonic influence based on frequency domain subtraction |
| CN112098741A (en) * | 2020-07-24 | 2020-12-18 | 合肥工业大学 | Three-phase power grid impedance online identification method under influence of background noise based on time domain subtraction |
| CN112098742A (en) * | 2020-07-24 | 2020-12-18 | 合肥工业大学 | Online identification method for impedance of balanced power grid under influence of background noise based on time domain subtraction |
| CN115825560A (en) * | 2023-02-17 | 2023-03-21 | 青岛鼎信通讯股份有限公司 | Intelligent low-voltage power grid phase checking device and method based on frequency tracking technology |
-
2009
- 2009-11-25 CN CN2009202738166U patent/CN201569704U/en not_active Expired - Lifetime
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102749521A (en) * | 2012-07-18 | 2012-10-24 | 华北电力大学（保定） | Method for computing harmonic impedance of power system |
| CN102749521B (en) * | 2012-07-18 | 2015-04-08 | 华北电力大学（保定） | Method for computing harmonic impedance of power system |
| CN106526321A (en) * | 2015-09-15 | 2017-03-22 | 日置电机株式会社 | Impedance measuring device and impedance measuring method |
| CN111077375A (en) * | 2019-12-13 | 2020-04-28 | 合肥工业大学 | Online identification method for power grid impedance under background harmonic influence based on frequency domain subtraction |
| CN111077375B (en) * | 2019-12-13 | 2020-12-29 | 合肥工业大学 | Online identification method for power grid impedance under background harmonic influence based on frequency domain subtraction |
| CN112098741A (en) * | 2020-07-24 | 2020-12-18 | 合肥工业大学 | Three-phase power grid impedance online identification method under influence of background noise based on time domain subtraction |
| CN112098742A (en) * | 2020-07-24 | 2020-12-18 | 合肥工业大学 | Online identification method for impedance of balanced power grid under influence of background noise based on time domain subtraction |
| CN115825560A (en) * | 2023-02-17 | 2023-03-21 | 青岛鼎信通讯股份有限公司 | Intelligent low-voltage power grid phase checking device and method based on frequency tracking technology |
| CN115825560B (en) * | 2023-02-17 | 2023-05-23 | 青岛鼎信通讯股份有限公司 | Intelligent phase checking method of electric power network based on frequency tracking technology |
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|---|---|---|---|
| C14 | Grant of patent or utility model | ||
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Granted publication date: 20100901 Effective date of abandoning: 20091125 |