CN104992043A

CN104992043A - Line voltage boosting effect assessment method based on power distribution network series compensation device

Info

Publication number: CN104992043A
Application number: CN201510246910.2A
Authority: CN
Inventors: 刘鹏; 李海; 吕志来; 张东; 喻宜
Original assignee: State Grid Corp of China SGCC; Beijing Xuji Electric Co Ltd
Current assignee: State Grid Corp of China SGCC; Beijing Xuji Electric Co Ltd
Priority date: 2015-05-14
Filing date: 2015-05-14
Publication date: 2015-10-21

Abstract

The invention discloses a line voltage boosting effect assessment method based on a power distribution network series compensation device. The line voltage boosting effect assessment method comprises that A. a power supply node is taken as a balance node, a load node is taken as a PQ node, the voltage phasor of the power supply terminal is U1<*>=U1[phase angle 0 DEG], the voltage phasor of the load terminal is U2<*>=U2 [phase angle fai], and the longitudinal component and the transverse component of voltage drop can be worked out; B. when a capacitor series compensation device is not added, the relation between the head-end voltage phasor and the tail-end voltage phasor is worked out, and the voltage value of the tail end of the line is worked out; and C. after the capacitor series compensation device is added, the voltage value of the tail end of the line is worked out. By employing the line voltage boosting effect assessment method, a complex iteration process can be effectively avoided, and the assessment of the line tail-end voltage boosting effect of the series compensation device can be achieved quickly.

Description

The line voltage distribution mending device based on power distribution network string promotes effect evaluation method

Technical field

The present invention relates to the electric power conveying technology of distribution line, particularly relate to a kind of line voltage distribution lifting effect evaluation method mending device based on power distribution network string.

Background technology

In the distribution line of below 35kV, series connection access capacitor, utilizes the induction reactance of the capacitive reactance compensated line of capacitor, can improve the voltage of line end.The numerical value QX of the terminal voltage that series capacitor promotes _c/ V (i.e. voltage regulation result) changes with load or burden without work size, increases when load is large, and load hour reduces, just consistent with the requirement of pressure regulation.This is a remarkable advantage of series capacitor pressure regulation.

Tradition is used for solving string and mends the method that device promotes circuit terminal voltage effect, is carry out Load flow calculation, but, when known line head end voltage and end load power, need to carry out complicated iterative process.

Summary of the invention

In view of this, fundamental purpose of the present invention is to provide a kind of line voltage distribution lifting effect evaluation method mending device based on power distribution network string, effectively can evade complicated iterative process, thus realize the assessment of string being mended to device line end voltage boosting effect fast.

For achieving the above object, technical scheme of the present invention is achieved in that

The line voltage distribution mending device based on power distribution network string promotes an effect evaluation method, comprises the steps:

A, make power supply node be balance node, load bus is PQ node, and power end voltage phasor is load side voltage phasor is then the vertical component of voltage-drop and horizontal component are respectively:

{ΔV}_{2} = \frac{P \cdot R + Q \cdot X}{U_{2}} = \frac{S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l}{U_{2}} - - - (1)

{δV}_{2} = \frac{P \cdot X - Q \cdot R}{U_{2}} = \frac{S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l}{U_{2}} - - - (2)

Wherein: Δ V ₂for the vertical component of voltage-drop, δ V ₂for the horizontal component of voltage-drop, P and Q represents active power and the reactive power of load bus respectively, R and X represents resistance and the reactance of circuit respectively, S is the applied power of load bus, PF is the power factor of load, r and x is resistivity and the reactance Rate of circuit respectively, and l is the length of circuit;

B, do not add capacitor string mend device time, the pass calculated between first and end voltage phasor by formula (1), (2) is:

{U_{1}}^{2} = {(U_{2} + \frac{S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l}{U_{2}})}^{2} + {(\frac{S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l}{U_{2}})}^{2} - - - (3)

So line end voltage is:

{U_{2}}^{2} = \frac{1}{2} [{U_{1}}^{2} - 2 \cdot A &PlusMinus; \sqrt{{U_{1}}^{4} - 4 \cdot A \cdot {U_{1}}^{2} - 4 \cdot B^{2}}] - - - (4)

Wherein:

A = P \cdot R + Q \cdot X = S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l - - - (6)

B = P \cdot X - Q \cdot R = S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l; - - - (7)

C, when installing series capacitor compensation additional, according to formula (4), (5), line end voltage is:

{U_{2}}^{2} = \frac{1}{2} [{U_{1}}^{2} - 2 \cdot A_{C} &PlusMinus; \sqrt{{U_{1}}^{4} - 4 \cdot A_{C} \cdot {U_{1}}^{2} - 4 \cdot {B_{C}}^{2}}] - - - (8)

Wherein:

A_{C} = P \cdot R + Q \cdot (X - X_{C}) = S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot (x \cdot l - X_{C}) - - - (10)

B_{C} = P \cdot (X - X_{C}) - Q \cdot R = S \cdot PF \cdot (x \cdot l - X_{C}) - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l - - - (11)

In above formula, X _cfor the reactance value of series capacitor.

Wherein, the method is applicable to the distribution line of below 35kV.

The line voltage distribution lifting effect evaluation method mending device based on power distribution network string provided by the present invention, has the following advantages:

Utilize the inventive method, can constant power load model to the certain power factor of the distribution line band of below 35kV time, effectively can evade complicated iterative process, thus realize that device line end voltage boosting effect is mended to string fast and assess.

Accompanying drawing explanation

Fig. 1 is that existing simple power system forms schematic diagram;

Fig. 2 is for the present invention is based on the electric system formation schematic diagram of power distribution network serial connection capacitor compensating device (being called for short " string mends device ");

Fig. 3 be before and after application the inventive method line end voltage with the change curve schematic diagram of circuit series compensation capacitive reactance.

Embodiment

Promote effect evaluation method below in conjunction with accompanying drawing and embodiments of the invention to the line voltage distribution based on power distribution network string benefit device of the present invention to be described in further detail.

Fig. 1 is that existing simple power system forms schematic diagram.As shown in Figure 1, in this simple power system, make power supply node be balance node, load bus is PQ node, and power end voltage phasor is load side voltage phasor is then the vertical component of voltage-drop and horizontal component are respectively:

{ΔV}_{2} = \frac{P \cdot R + Q \cdot X}{U_{2}} = \frac{S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l}{U_{2}} - - - (1)

{δV}_{2} = \frac{P \cdot X - Q \cdot R}{U_{2}} = \frac{S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l}{U_{2}} - - - (2)

Wherein: Δ V ₂for the vertical component of voltage-drop, δ V ₂for the horizontal component of voltage-drop, P and Q represents active power and the reactive power of load bus respectively, R and X represents resistance and the reactance of circuit respectively, S is the applied power of load bus, PF is the power factor of load, r and x is resistivity and the reactance Rate of circuit respectively, and l is the length of circuit.

Do not add line end voltage during capacitor string benefit device, the relation between first and end voltage phasor can be calculated by formula (1), (2):

\begin{matrix} {\overset{\cdot}{U}}_{1} = U_{2} + \frac{P \cdot R + R \cdot X}{U_{2}} + j \frac{P \cdot X - Q \cdot R}{U_{2}} \\ = U_{2} + \frac{S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l}{U_{2}} + j \frac{S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l}{U_{2}} \end{matrix}

That is:

{U_{1}}^{2} = {(U_{2} + \frac{S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l}{U_{2}})}^{2} + {(\frac{S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l}{U_{2}})}^{2} - - - (3)

So line end voltage is:

{U_{2}}^{2} = \frac{1}{2} [{U_{1}}^{2} - 2 \cdot A &PlusMinus; \sqrt{{U_{1}}^{4} - 4 \cdot A \cdot {U_{1}}^{2} - 4 \cdot B^{2}}] - - - (4)

Wherein:

A = P \cdot R + Q \cdot X = S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot x \cdot l - - - (6)

B = P \cdot X - Q \cdot R = S \cdot PF \cdot x \cdot l - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l . - - - (7)

Fig. 2 is for the present invention is based on the electric system formation schematic diagram of power distribution network serial connection capacitor compensating device (being called for short " string mends device ").As shown in Figure 2, when power circuit installs additional string benefit device (as series connection enters electrostatic condenser), the induction reactance of the capacitive reactance compensated line of capacitor is utilized.

When having installed series capacitor compensation additional, above-mentioned formula (4), (5) have become respectively:

{U_{2}}^{2} = \frac{1}{2} [{U_{1}}^{2} - 2 \cdot A_{C} &PlusMinus; \sqrt{{U_{1}}^{4} - 4 \cdot A_{C} \cdot {U_{1}}^{2} - 4 \cdot {B_{C}}^{2}}] - - - (8)

Wherein:

A_{C} = P \cdot R + Q \cdot (X - X_{C}) = S \cdot PF \cdot r \cdot l + S \cdot \sqrt{1 - {PF}^{2}} \cdot (x \cdot l - X_{C}) - - - (10)

B_{C} = P \cdot (X - X_{C}) - Q \cdot R = S \cdot PF \cdot (x \cdot l - X_{C}) - S \cdot \sqrt{1 - {PF}^{2}} \cdot r \cdot l - - - (11)

In above formula, X _cfor the reactance value of series capacitor.

Fig. 3 be before and after application the inventive method line end voltage with the change curve schematic diagram of circuit series compensation capacitive reactance.Method of the present invention is applicable to the distribution line of below 35kV.According to above-mentioned formula (8) ~ (11), utilize emulation experiment can assess the effect of string benefit device lifting circuit terminal voltage, to verify said method.Specific practice is as follows:

Select distribution line model to be LGJ-120, its parameter is as shown in table 1:

The correlation parameter on table 1:LGJ-120 molded line road

The capacitor value X of compensativity needed for compensation of definition capacitor series compensation device _cwith by the original induction reactance value X of compensated line _lratio:

k_{C} = \frac{X_{C}}{X_{L}} . - - - (12)

We are for 10kV power circuit, select conventional LGJ-120 molded line road, and according to the rational transmission power of 10kV power circuit, emulate for 2MVA constant power load model in experiment, and the power factor of load is 0.80, and line length is 20km.Change the capacitive reactance (namely changing the compensativity that string is mended) that string is mended, the simulation result of line end voltage as shown in Figure 3.By the result of emulation experiment, be easy to the difference of alternative route terminal voltage when different series compensation capacitor values and before series compensation, thus assessment and analysis series compensation is to the lifting effect of line voltage distribution.

The above, be only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.

Claims

1. mend a line voltage distribution lifting effect evaluation method for device based on power distribution network string, it is characterized in that, comprise the steps:

So line end voltage is:

Wherein:

In above formula, X _cfor the reactance value of series capacitor.

2. the line voltage distribution lifting effect evaluation method mending device based on power distribution network string according to claim 1, it is characterized in that, the method is applicable to the distribution line of below 35kV.