CN103983842A - Substation power measurement error compensation method - Google Patents

Abstract

The invention discloses a substation power measurement error compensation method which comprises the steps that a phase shift detector is used for measuring voltage phase shift phi 1 caused by a voltage transformer; the phase shift detector is used for measuring current phase shift phi 2 caused by a current transformer; a phase difference compensation coefficient lambda is calculated; a power analyzer is used for measuring active power P'; the power analyzer is used for measuring reactive power Q'; corrected active power P is calculated; corrected reactive power Q is calculated. According to the substation power measurement error compensation method, compensation for the transformer phase difference can be effectively conducted through error measuring and compensation calculating, and therefore the power can be accurately measured. In addition, errors caused by PT and CT phase shift can be effectively eliminated, and meanwhile high precision can be achieved under the condition of different power factors.

Description

The power measurement error compensation method of a kind of transformer station

Technical field

The invention belongs to transformer station's field of measuring technique, particularly relate to the power measurement error compensation method of a kind of transformer station.

Background technology

Conventionally due to the reason of electrical network capacitive or inductive load, between alternating voltage and electric current, there is certain phase differential θ, in measuring process, mutual inductor can make signal produce certain phase shift φ (the leading or very little angle φ that lags behind), the impact of current transformer of take is example, and the displacement producing between alternating voltage and current signal as shown in Figure 1.

And power calculation and electric energy metrical require electric current and voltage sample uniformly-spaced and synchronously, but in actual hardware designs, because the difference of measuring current transformer and voltage transformer (VT) phase shift also reaches 10 ' left and right, this brings very large error to power measurement and electric energy metrical.Actual active power can be expressed as:

P＝UIcosθ (1)

And due to current transformer, to electric current, phase shift makes the active power measuring be:

P′＝UIcos(θ+φ) (2)

So for active power, measuring error is:

$E=1-\frac{P^{\′}}{P}=1-\frac{\cos (\mathrm{\θ}+\mathrm{\φ})}{\cos \mathrm{\θ}}---\left(3\right)$

Equally, for reactive power, measuring error is:

$E=1-\frac{Q^{\′}}{Q}=1-\frac{\sin (\mathrm{\θ}+\mathrm{\φ})}{\sin \mathrm{\θ}}---\left(4\right)$

From above formula, error function is a nonlinear function of power factor, when power factor is during close to 1 (current/voltage differs θ and approaches 0), active power error is very little, negligible, but along with the decline of power factor, error increases gradually, for example, when power factor is 0.5, every degree phase shift will cause 3% error.In real system, 10 ' phase shift causes, and 5 ‰ error is unacceptable completely for the power measuring terminal of 0.5S level.

In like manner, the measuring error of reactive power is minimum close to 0 time error in power factor, but along with power factor increases, the error that mutual inductor phase shift causes becomes obviously very soon, when power factor is close to 1 time, error will far surpass 3%/degree, and in using so actual, phase shift is more far more than the measurement of active power for the impact of reactive power measurement.

Because the voltage transformer (VT) of sampling is probably not identical with the phase deviation that current transformer produces signal in actual applications, thereby the measurement of the parameters of electric power such as power is caused to very large error, so must process such situation.

Summary of the invention

In order to address the above problem, the object of the present invention is to provide the power measurement error compensation method of a kind of transformer station.

In order to achieve the above object, transformer station provided by the invention power measurement error compensation method comprises the following step of carrying out in order:

Step 1, the voltage phase shift φ 1 that utilizes phase shift detection instrument measuring voltage mutual inductor to cause;

Step 2, the electric current phase shift φ 2 that utilizes phase shift detection instrument measurement current transformer to cause;

Step 3, calculating differ penalty coefficient λ: utilize the voltage phase shift φ 1 and the electric current phase shift φ 2 that obtain, calculate and differ penalty coefficient λ;

Step 4, utilize power analyzer measure active-power P ';

Step 5, utilize power analyzer measure reactive power Q ';

Step 6, calculate active-power P after calibration: utilize and differ penalty coefficient λ to the active-power P measuring by step 4 ' calibrate, obtain calibrating rear active-power P;

Step 7, calculate reactive power Q after calibration: utilize and differ penalty coefficient λ to the reactive power Q measuring by step 5 ' calibrate, obtain calibrating rear reactive power Q.

In step 3, the computing formula that described calculating differs penalty coefficient λ is: $\mathrm{\λ}=\frac{1}{\mathrm{tg}(\mathrm{\φ}1-\mathrm{\φ}2)}.$

In step 6, after described calibration, the computing formula of active-power P is: P=P '+Q '/λ.

In step 7, after described calibration, the computing formula of reactive power Q is: Q=Q '-P '/λ.

Transformer station provided by the invention power measurement error compensation method can and be calculated compensation by measuring error and effectively mutual inductor phase differential be compensated, thereby realizes the accurate measurement to power.In addition, it can eliminate the error of bringing due to PT, CT phase shift effectively, can under different capacity factor condition, obtain higher precision simultaneously.

Accompanying drawing explanation

Fig. 1 is the displacement oscillogram between alternating voltage and current signal in electrical network capacitive character or inductive load in prior art.

Embodiment

Below in conjunction with specific embodiment, transformer station provided by the invention power measurement error compensation method is elaborated.

1, ultimate principle

Suppose in thering is the alternating current sampling circuit that the voltage transformer (VT) of desired phase characteristic and current transformer form, actual power input P and the power P measuring ' ratio be ideal power coefficient.Wherein, desirable phase propetry refers to that voltage transformer (VT) equates with the phase shift that current transformer produces signal.If ideal power coefficient is designated as K:

K＝P/P′ (2-22)

If external input voltage input current through mutual inductor conversion, then A/D is converted to digital quantity, and the effective value calculating is respectively U ₀and I ₀, ideal power coefficient also can be expressed as:

$K=\frac{\mathrm{UI}}{U_0{I}_0}---(2-23)$

In formula, U and I are respectively voltage and electric current effective value, U ₀and I ₀be respectively voltage and electric current effective value.Ideal power coefficient is not with input voltage and electric current between phase differential change and change.

In actual measuring system, the phase shift that voltage transformer (VT) and current transformer cause signal is unequal, if the difference of the phase shift that the two produces signal is φ, the power P that now if same definition measures ' with the ratio of actual power input P be real power coefficient, real power coefficient can be with input voltage and electric current between phase differential change and change, but the difference φ value of phase shift generally do not change with the phase differential between voltage and electric current, for specific hardware, it is a constant.

Be defined in input voltage and electric current between real power coefficient under the phase differential condition that is 0 be zero phase angle power coefficient:

K′＝P/P′ (2-24)

Input voltage and electric current between phase differential be 0 o'clock, respectively after voltage transformer (VT) summation current transformer, differing as φ between the two, measure power and be:

P′＝U ₀I ₀cosφ (2-25)

So can obtain following formula:

$K^{\′}=P/P^{\′}=\frac{\mathrm{UI}}{U_0{I}_0\cos \mathrm{\φ}}---(2-26)$

Be defined in input voltage simultaneously and electric current between under the phase differential condition that is 0, the active power that actual measurement obtains and the ratio of reactive power are for differing penalty coefficient λ:

$\mathrm{\λ}=P^{\′}/Q^{\′}=U_0{I}_0\cos \mathrm{\φ}/U_0{I}_0\sin \mathrm{\φ}=\frac{1}{\mathrm{tg\φ}}---(2-27)$

So, establish input voltage and electric current between phase differential be θ, after mutual inductor, voltage signal and current signal differ as (θ+φ), the active-power P that actual measurement obtains ' (without differing compensation) can be expressed as:

P′＝U ₀I ₀cos(θ+φ)·K′ (2-28)

Power coefficient K ' used herein is zero phase angle power coefficient, at input voltage and electric current between phase differential while being θ, still use the active-power P that this coefficient calculations obtains ' be exactly without the active power that differs compensation.

Formula (2-26) substitution formula (2-28) is obtained:

$P^{\′}=U_0{I}_0\cos (\mathrm{\θ}+\mathrm{\φ})\·\frac{\mathrm{UI}}{U_0{I}_0\cos \mathrm{\φ}}=\mathrm{UI}\frac{\cos (\mathrm{\θ}+\mathrm{\φ})}{\cos \mathrm{\φ}}---(2-29)$

Apply following trigonometric function formula:

cos(α+β)＝cosαcosβ-sinαsinβ (2-30)

Decompose power P ' expression formula:

$P^{\′}=\mathrm{UI}\frac{\cos \mathrm{\θ}\cos \mathrm{\φ}-\sin \mathrm{\θ}\sin \mathrm{\φ}}{\cos \mathrm{\φ}}=\mathrm{UI}\cos \mathrm{\θ}-\mathrm{UI}\sin \mathrm{\θ}\·\mathrm{tg\φ}---(2-31)$

Because UIcos θ is the active-power P of outside actual input, and UIsin θ is the reactive power Q of outside actual input, and tg φ is the inverse that differs penalty coefficient λ, thereby obtains following expression:

P′＝P-Q/λ (2-32)

Equally, the reactive power Q of actual measurement ' (without differing compensation) can be expressed as:

Q′＝U ₀I ₀sin(θ+φ)·K′ (2-33)

Use the decomposable process same with active power can obtain following expression:

Q′＝Q+P/λ (2-34)

Association type (2-32) solves with formula (2-34):

$P=\frac{P^{\′}\·{\mathrm{\λ}}^2+Q^{\′}\·\mathrm{\λ}}{{\mathrm{\λ}}^2+1}---(2-35a)$

$Q=\frac{Q^{\′}\·{\mathrm{\λ}}^2-P^{\′}\·\mathrm{\λ}}{{\mathrm{\λ}}^2+1}---(2-35b)$

In actual measuring system, the difference of phase shift signal being caused due to voltage transformer (VT) summation current transformer is about 10 ', so conventionally λ generally more than 300, so can be the λ in two expression formulas above ²+ 1 is approximately λ ², can obtain the following final compensation expression formula that differs:

P＝P′+Q′/λ (2-36a)

Q＝Q′-P′/λ (2-36b)

At above two, differ in compensation expression formula, P is the actual active power of outside input, and P ' is the active power that adopts zero phase angle power coefficient to calculate; Q is the actual reactive power of outside input, and Q ' is the reactive power that adopts zero phase angle power coefficient to calculate.

2, transformer station provided by the invention power measurement error compensation method comprises the following step of carrying out in order:

Step 1, the voltage phase shift φ 1 that utilizes phase shift detection instrument measuring voltage mutual inductor to cause;

Step 2, the electric current phase shift φ 2 that utilizes phase shift detection instrument measurement current transformer to cause;

Step 3, calculating differ penalty coefficient λ: utilize the voltage phase shift φ 1 and the electric current phase shift φ 2 that obtain, calculate and differ penalty coefficient λ;

Step 4, utilize power analyzer measure active-power P ';

Step 5, utilize power analyzer measure reactive power Q ';

Step 6, calculate active-power P after calibration: utilize and differ penalty coefficient λ to the active-power P measuring by step 4 ' calibrate the active-power P after being calibrated;

Step 7, calculate reactive power Q after calibration: utilize and differ penalty coefficient λ to the reactive power Q measuring by step 5 ' calibrate the reactive power Q after being calibrated.

In step 3, the computing formula that described calculating differs penalty coefficient λ is: $\mathrm{\λ}=\frac{1}{\mathrm{tg}(\mathrm{\φ}1-\mathrm{\φ}2)}.$

In step 6, the computing formula of the active-power P after described calibration is: P=P '+Q '/λ.

In step 7, the computing formula of the reactive power Q after described calibration is: Q=Q '-P '/λ.

Embodiment:

If input voltage U=cos (ω t), input current I=cos (ω t), input active-power P=1/2, reactive power Q=0, if voltage U phase shift after mutual inductor is φ 1=2, measuring voltage U '=cos (ω t-2), electric current I phase shift after mutual inductor is φ 2=1, measure electric current I '=cos (ω t-1), measure applied power S '=1/2.

Differ penalty coefficient $\mathrm{\λ}=\frac{1}{\mathrm{tg}(\mathrm{\φ}1-\mathrm{\φ}2)}=\frac{1}{\mathrm{tg}\left(1\right)}=57.28$

Measure active-power P '=S ' cos (1)

Measure reactive power Q '=S ' sin (1)

Active-power P=P '+Q '/λ=P '=S ' cos (1)+S ' sin (1) * tg (1)=0.49992384 after compensation

Reactive power Q=Q '-P '/λ=S ' sin (1)-S ' cos (1) * tg (1)=0 after compensation.

Claims (4)

1. The power measurement error compensation method of 1.Yi Zhong transformer station, is characterized in that: described transformer station's power measurement error compensation method comprises the following step of carrying out in order:

   Step 1, the voltage phase shift φ 1 that utilizes phase shift detection instrument measuring voltage mutual inductor to cause;

   Step 2, the electric current phase shift φ 2 that utilizes phase shift detection instrument measurement current transformer to cause;

   Step 3, calculating differ penalty coefficient λ: utilize the voltage phase shift φ 1 and the electric current phase shift φ 2 that obtain, calculate and differ penalty coefficient λ;

   Step 4, utilize power analyzer measure active-power P ';

   Step 5, utilize power analyzer measure reactive power Q ';

   Step 6, calculate active-power P after calibration: utilize and differ penalty coefficient λ to the active-power P measuring by step 4 ' calibrate, obtain calibrating rear active-power P;

   Step 7, calculate reactive power Q after calibration: utilize and differ penalty coefficient λ to the reactive power Q measuring by step 5 ' calibrate, obtain calibrating rear reactive power Q.
2. 2. transformer station according to claim 1 power measurement error compensation method, is characterized in that: in step 3, the computing formula that described calculating differs penalty coefficient λ is: $\mathrm{\λ}=\frac{1}{\mathrm{tg}(\mathrm{\φ}1-\mathrm{\φ}2)}.$
3. 3. transformer station according to claim 1 power measurement error compensation method, is characterized in that: in step 6, after described calibration, the computing formula of active-power P is: P=P '+Q '/λ.
4. 4. transformer station according to claim 1 power measurement error compensation method, is characterized in that: in step 7, after described calibration, the computing formula of reactive power Q is: Q=Q '-P '/λ.