CN203054128U - Electric power parameter detection system - Google Patents

Abstract

The utility model discloses an electric power parameter detection system. The detection system comprises a sensor module connected with an electric power system; an analog switch circuit, an amplification circuit and a low pass filter circuit which are sequentially connected with the output end of the sensor module; a data acquisition circuit for acquiring the voltage, current data of each phase of the electric power system, wherein the data acquisition circuit is connected with the output end of the low pass filter circuit; and a computer for calculating each electric power parameter of the electric power system according to the voltage, current data of each phase, wherein the computer is connected with the data acquisition circuit. The voltage, current signal of each phase acquired by a voltage transformer and a current transformer is acquired by one data acquisition card, each electric power parameter of the electric power system is calculated by the computer according to the voltage, current signal of each phase, and the electric power parameter is precisely detected, so as to provide an objective basis for measuring the quality of the electric power system, and the electric power parameter detection system has the advantages of simple structure, strong practicability or the like.

Description

The parameters of electric power detection system

Technical field

The utility model relates to a kind of detection system, especially relates to a kind of for the parameters of electric power detection system of weighing the quality of power supply.

Background technology

Along with social development, power quality problem more and more receives electric power enterprise and user's common concern, and power quality problem is related to the interests of each side, and therefore, it is inexorable trend that the quality of power supply is carried out the real-time online detection.

The prerequisite of weighing quality of power supply quality and electric energy and quality improvement is the detection of parameters of electric power index.Traditional parameters of electric power index pick-up unit is to adopt the simulating signal analysis, different parameters of electric power indexs detects uses different instrument and meters, as: traditional current voltmeter, power meter, frequency meter, humorous wave table, tri-phase unbalance factor meter, voltage fluctuation and flickermeter etc., this class pick-up unit weak point is that measurement is loaded down with trivial details, the instrument versatility is poor, and automaticity is low.

Along with microprocessor and DSP are that the digital instrument of new generation of core is used by extensive exploitation, domestic many Power Quality Detection devices also adopt this mode to design and develop.This class detecting instrument device is fixed, so all be subjected to the processing speed of hardware and the restriction of capacity at aspects such as signal processing, data storages.The shortcoming of such detector is that exchanges data and sharing are strong, very flexible, analytical algorithm is simple, memory data output is little, upgrading difficulty relatively.

The utility model content

For overcoming the defective of prior art, the utility model proposes a kind of parameters of electric power detection system that is used for weighing the quality of power supply accurate, that practicality is stronger that detects.

The utility model adopts following technical scheme to realize: a kind of parameters of electric power detection system, and it comprises: the sensor assembly that connects electric system; Be connected to analog switching circuit, amplifying circuit and the low-pass filter circuit of described sensor assembly output terminal in turn; Be used for gathering the data acquisition circuit of each phase voltage of electric system, current data, described data acquisition circuit is connected the output terminal of described low-pass filter circuit; Be used for calculating according to each phase voltage, current data the computing machine of every parameters of electric power of electric system, described computing machine connects described data acquisition circuit.

Wherein, described sensor assembly comprises voltage transformer (VT) and the current transformer that connects electric system respectively.

Wherein, described analog switching circuit is the analog multiplexer of 16 passages/pair 8 passages, and four control ports of described analog multiplexer connect described data acquisition circuit.

Wherein, described low-pass filter circuit is the fertile low-pass filter now of the program-controlled quadravalence Bart of cutoff frequency.

Wherein, described data acquisition circuit connects described computing machine by pci bus interface.

Compared with prior art, the utlity model has following beneficial effect:

The utility model can be gathered each phase voltage, the current signal of being gathered by voltage transformer (VT) and current transformer by a blocks of data capture card, calculated each parameters of electric power index of electric system according to each phase voltage, current signal by computing machine, parameters of electric power detects accurately, for the quality of power supply of weighing electric system provides objective foundation, and have advantages such as simple in structure, practical.

Description of drawings

Fig. 1 is structural representation of the present utility model.

Fig. 2 is the circuit diagram of current transformer

Fig. 3 is the circuit diagram of analog switch.

Fig. 4 is the circuit diagram of amplifying circuit.

Embodiment

As shown in Figure 1, the utility model proposes a kind of parameters of electric power detection system that is used for weighing the quality of power supply accurate, that practicality is stronger that detects, it comprises: connect the sensor assembly 1 of electric system, comprise voltage transformer (VT) 11 and current transformer 12 (circuit diagram of current transformer 12 as shown in Figure 2); The analog switching circuit 2, amplifying circuit 3, low-pass filter circuit 4 and the data acquisition circuit 5 that connect the output terminal of the output terminal of voltage transformer (VT) 11 and current transformer 12 successively; And the computing machine 6 that connects data acquisition circuit 5.

The six road small voltage signals of electric system parameters of electric power after voltage transformer (VT) 11 and current transformer 12 conversion are amplified input to the analog switching circuit 2 of binary channels 16 tunnel/pairs 8 tunnel each road signal are exported in twos, are gained to amplify by amplifying circuit 3 and handle, undertaken being transferred to data acquisition circuit 5 after the low-pass filtering treatment by low-pass filter circuit 4.

Wherein, analog switching circuit 2 adopts 16 passages/pair 8 passages of using U.S. AD company to produce, low leakage, CMOS analog multiplexer AD7507 to realize that the voltage signal that sensor assembly 1 is exported exports amplifying circuit 3 in twos to.The circuit diagram of analog switching circuit 2 is controlled Ua, Ub, Uc by three channel selecting ends and an Enable Pin as shown in Figure 3, and therefore the collections of signal in twos such as Ia, Ib, Ic, need to introduce four control port D0, D1, D2 and D3 from data acquisition circuit 5 altogether.

As shown in Figure 4, amplifying circuit 3 is one can adjust the high precision of enlargement factor, high performance programme-controlled gain amplifying circuit automatically, adopt software programmable gain amplifier (SPGA, Software Programmable Gain Amplifier) the chip AD526CD of the function admirable of U.S. AD company production to realize programme-controlled gain control.The A of AD526CD chip ₂Port, A ₁Port and A ₀Port connects data acquisition circuit 5, is determined the A of AD526CD chip by data acquisition circuit 5 by computing machine 6 ₂Port, A ₁Port and A ₀The different numerical value of port are determined the enlargement factor of AD526CD chip.

And low-pass filter circuit 4 adopts fertile (Butterworth) low-pass filter now of the program-controlled quadravalence Bart of cutoff frequency, send signal by computing machine 6 to data acquisition circuit 5, this signal is sent by the digital output port of data acquisition circuit 5, control low-pass filter 4 is finished different controls by the frequency size, to satisfy more detection needs.

Data acquisition circuit 5 is based on the data acquisition module of pci bus, directly be plugged on the pci bus interface of computing machine 6, realize on-site data gathering is exported to the front end controll plant to computing machine 6 and with the control data of computing machine 6 by data acquisition circuit 5.

In a preferred embodiment, data acquisition circuit 5 adopts the multi-functional 4 passage synchronous data collection cards of DAQ-2010 type of ADLINK company, has 14 A/D resolution, and the highest sample frequency can reach 2MHz.According to the national standard of power grid quality, A level instrument frequency measurement range is 0～2500Hz, and namely the higher hamonic wave of sampled signal is 50 times, and by the Nyquist sampling thheorem as can be known, the highest sample frequency of data acquisition circuit 5 gets final product greater than 5kHz.Therefore, DAQ-2010 can satisfy three-phase voltage fully, electric current quality of power supply A level detects requirement.

After computing machine 6 gets access to A phase, B phase and the C voltage and current mutually of electric system from data acquisition circuit 5, calculate the effective value of each phase voltage, electric current, and calculate active power, applied power, power factor etc. on the basis of the effective value of each phase voltage, electric current.

Known that by Circuit theory to time dependent voltage signal u (t), current signal i (t), its phase voltage, phase current and active power effective value are defined as:

$U_A=\sqrt{\frac{1}{T}\underset{0}{\overset{T}{\∫}}u{\left(t\right)}^2\mathrm{dt}}$ $I_A=\sqrt{\frac{1}{T}\underset{0}{\overset{T}{\∫}}i{\left(t\right)}^2\mathrm{dt}}$ $P_A=\frac{1}{T}\underset{0}{\overset{T}{\∫}}u\left(t\right)i\left(t\right)\mathrm{dt}---(2-3)$

Tested AC signal one-period is carried out N sampling, u _k, i _kBe k time interval voltage, current sample instantaneous value, Δ T _kBe the adjacent double sampling time interval, then the phase voltage under the discrete case, electric current and single-phase active power effective value are respectively:

$U_A=\sqrt{\frac{1}{T}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{u}_{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HSA00000840388200021.png"\; state="\{\{state\}\}">k</figure-callout>}}^2\mathrm{\&Delta;}{T}_k}$ $I_A=\sqrt{\frac{1}{T}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{\mathrm{<figure-callout\; id="2"\; label="i\; k"\; filenames="HSA00000840388200021.png"\; state="\{\{state\}\}">i</figure-callout>}}_k^{}\mathrm{\&Delta;}{T}_k}$ $P_A=\frac{1}{T}\underset{K=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{u}_k{i}_k\mathrm{\&Delta;}{T}_k---(2-4)$

Adopt technology of frequency tracking when sampling, making the interior sampled point of one-period count is N, and the time interval of adjacent double sampling equates, and Δ T _kBe time constant Δ T,

Then:

$U_A=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{u}_k^2}$ $I_A=\sqrt{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{i}_k^2}$ $P_A=\frac{1}{N}\stackrel{N-1}{\underset{K=0}{\mathrm{\&Sigma;}}}{u}_k{i}_k---(2-5)$

Single-phase power factor is:

The total active power of three-phase is: $P=\frac{1}{N}(\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{U}_{\mathrm{ak}}{I}_{\mathrm{ak}}+\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{U}_{\mathrm{bk}}{I}_{\mathrm{bk}}+\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{U}_{\mathrm{ck}}{I}_{\mathrm{ck}})$

The total applied power of three-phase is: S=U _AI _A+ U _BI _B+ U _CI _C

The three-phase total power factor is:

Though and the sample frequency of electric system can't be determined in advance, but electric system inertia is bigger, the frequency change of adjacent two or several cycles is but very little, therefore the frequency of previous (or several) cycle that the available cycle that will sample is adjacent replaces the fundamental frequency of the cycle of sampling, and then definite sampled signal frequency.

When not containing the triple-phase line electric current of zero-sequence component such as three-phase line voltage, no center line in the three-phase electric weight, GB has provided the accurate formula of tri-phase unbalance factor:

${\mathrm{\&epsiv;}}_U=\sqrt{\frac{1-\sqrt{3-6L}}{1+\sqrt{3-6L}}}\&times;100\%,$ $L=\frac{A^4+{\mathrm{<figure-callout\; id="4"\; label="B"\; filenames="HSA00000840388200021.png"\; state="\{\{state\}\}">B</figure-callout>}}^4+C^4}{{(A^2+{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="HSA00000840388200021.png"\; state="\{\{state\}\}">B</figure-callout>}}^2+C^2)}^2}$

Wherein, A, B, C are respectively the amplitude of three-phase line voltage (electric current), as: U _Ab, U _Bc, U _CaOr I _a, I _b, I _c

The principle acquisition phase differential that utilizes two cross-correlation function values during with the time-delay z=0 of sinusoidal signals frequently to be directly proportional with the cosine value of its phase differential.Because noise signal is common and the useful signal correlativity is very little, so this method has good noise inhibiting ability.

Usually, the measurement of voltage fluctuation in the following ways: measure the effective value of each cycle (20ms) in the set time, then above-mentioned effective value is compared, get maximum difference DELTA U (U _Max-U _Min) divided by nominal voltage U _N(rated voltage U _N) percentage represent its relative percentage value, the i.e. size of voltage fluctuation rate d, i.e. voltage fluctuation rate:

$d=\frac{\mathrm{\&Delta;U}}{U_A}\&times;100\%=\frac{U_{\max }-U_{\min }}{U_N}\&times;100\%$

From above-mentioned analysis as can be known, computing machine 6 can obtain parameters of electric power such as each phase voltage effective value, every current effective value, active power, applied power, power factor, mains frequency, tri-phase unbalance factor and phase differential by behind the A phase, B phase and the C voltage and current mutually that get access to electric system from data acquisition circuit 5 by calculating.Therefore, the detection system of the application's proposition can be finished the measurement of firm power parameter preferably and realize Power Quality Detection according to GB.

Claims (5)

1. a parameters of electric power detection system is characterized in that, comprising: the sensor assembly that connects electric system; Be connected to analog switching circuit, amplifying circuit and the low-pass filter circuit of described sensor assembly output terminal in turn; Be used for gathering the data acquisition circuit of each phase voltage of electric system, current data, described data acquisition circuit is connected the output terminal of described low-pass filter circuit; Be used for calculating according to each phase voltage, current data the computing machine of every parameters of electric power of electric system, described computing machine connects described data acquisition circuit.

2. according to the described parameters of electric power detection system of claim 1, it is characterized in that described sensor assembly comprises voltage transformer (VT) and the current transformer that connects electric system respectively.

3. according to the described parameters of electric power detection system of claim 1, it is characterized in that described analog switching circuit is the analog multiplexer of 16 passages/pair 8 passages, four control ports of described analog multiplexer connect described data acquisition circuit.

4. according to the described parameters of electric power detection system of claim 1, it is characterized in that described low-pass filter circuit is the fertile low-pass filter now of the program-controlled quadravalence Bart of cutoff frequency.

5. according to claim 1 or 2 or 3 or 4 described parameters of electric power detection systems, it is characterized in that described data acquisition circuit connects described computing machine by pci bus interface.

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