CN104201664A - Distributed grounding electrode design method for high-voltage direct-current transmission system - Google Patents

Abstract

Disclosed is a distributed grounding electrode design method for a high-voltage direct-current transmission system. The distributed grounding electrode design method includes the steps of 1), preliminarily selecting the scope for grounding electrodes to be established according to planning and land expropriation, and determining the best position for the grounding electrodes to be established through a global optimal position mutation particle swam optimization algorithm; 2), determining the biggest potential rise of sub-electrodes according to temperature rise of the grounding electrodes and checking step potential; 3), connecting all the grounding electrodes with newly established sub-electrodes through an overhead line; 4), establishing a unified model for the distributed grounding electrodes and direct-current distribution of a alternating-current network; 5), according to the solved direct-current distribution of the alternating-current network, predicting risks of direct-current magnetic bias occurring to transformers of the alternating-current network; 6), for the transformers with the risks of direct-current magnetic bias in prediction, taking measures to restrain or eliminate negative influence brought by the problem of the direct-current magnetic bias. By the distributed grounding electrode design method, the risks of the direct-current magnetic bias can be reduced, and the degree of the direct-current magnetic bias after establishment of the grounding electrode can be estimated, so that damage brought by the direct-current magnetic bias can be reduced.

Description

A kind of method for designing of the distributed earth electrode for HVDC (High Voltage Direct Current) transmission system

Technical field

The present invention relates to high voltage direct current transmission project design field, specifically a kind of method for designing of the distributed earth electrode for HVDC (High Voltage Direct Current) transmission system.

Background technology

At present, China's receiving end current conversion station drop point is often positioned at developed area, these regional density of population are large, electric network composition is huge and complicated, and underground metallic facility (as oil transportation gas and water supply line etc.) is numerous, this makes direct current grounding pole Site Selection under traditional conventional earth electrode design become more and more difficult.Meanwhile, along with putting into operation in a large number of large capacity ultrahigh voltage DC transmission engineering, the electromagnetic compatibility problem that direct current transportation earth current and current conversion station harmonic wave cause is more outstanding, and direct current transportation earth current produces a series of harmful effects to environment and other system.But traditional current conversion station addressing mainly considers to prevent the problem such as antifouling problem, impact, large equipment transport and the installation of Noise upon Environment of flashover, rarely has and considers the influence degree of direct current transportation earth current to AC network.

Distributed DC earth electrode, sees in geographical position by several sub-earth electrodes (being called for short the sub-utmost point) that are positioned at different regions and forms, and on electric, is to see that multiple sub-utmost points are by the grounding system of feedback Flow Line realization electrical connection.The geographical wiring diagram of distributed earth electrode is shown in Fig. 1.Adopt distributed earth electrode not only can reduce direct current utmost point addressing difficulty, can also reduce the impact of direct current system on AC network, AC network, without taking measures or only marginally taking braking measure, just can obtain good inhibition D.C. magnetic biasing effect.

But, the influence degree of direct current earth current to AC network do not considered in the addressing of traditional distributed earth electrode, so just can not predict the risk of the each transformer generation of AC network D.C. magnetic biasing, cause can not taking measures in advance to there is D.C. magnetic biasing risk higher transformer, so after causing newly-built earth electrode to put into operation because D.C. magnetic biasing problem is brought loss.

Summary of the invention

The invention provides a kind of method for designing of the distributed earth electrode for HVDC (High Voltage Direct Current) transmission system, can in the time of addressing, consider the influence degree of direct current earth current to AC network, and then prediction builds up the risk of the each transformer generation of rear AC network D.C. magnetic biasing, thus the loss bringing because of D.C. magnetic biasing problem after can taking measures in advance to reduce or eliminating newly-built earth electrode and put into operation.

For a method for designing for the distributed earth electrode of HVDC (High Voltage Direct Current) transmission system, comprise the steps:

Step 1, according to the scope of planning and the preliminary selected newly-built earth electrode of expropriation of land, determine the optimum position of newly-built earth electrode by global optimum's position Particle Swarm Optimization Algorithm;

Step 2, raise by the maximum potential of the true stator poles of earth electrode temperature rise, and verification step voltage;

Step 3, by overhead transmission line, all earth electrodes and the newly-built sub-utmost point are connected, form distributed earth electrode, the mode of connection of distributed earth electrode is carried out with reference to the bus arrangement mode of electric power system;

Step 4, set up the unified model that distributed earth electrode and AC network direct current distribute, impact AC network direct current being distributed to assess distributed earth electrode;

Step 5, distribute according to direct current in the AC network solving in above-mentioned steps, the risk of each transformer generation D.C. magnetic biasing in prediction AC network;

Step 6, to there is the transformer of D.C. magnetic biasing risk in prediction, the adverse effect that D.C. magnetic biasing problem is brought of taking measures to suppress even to eliminate.

Wherein, step 1 is specially:

A, objective definition function, in system, the maximum neutral point current minimum of transformer magnetomotive force mean value minimum, the average neutral point current minimum of transformer or transformer is as target function;

The position of b, initialization particle and speed, and obtain initial globally optimal solution g*=min[f (p1) ..., f (pn)], t=0, wherein p1, pn is that initialized n group is separated, and is the abscissa that comprises solution and the bivector of ordinate information, f (p1), f (pn) is p1 ..., the target function value that pn difference is corresponding; T optimizes the cycle-index of calculating, and the original position of particle and speed should be evenly distributed among effective codomain of whole inverted parameters

$x_i^{t=0}=x_{\min }+{\mathrm{\η}}_i(x_{\max }-x_{\min })---\left(1\right)$

$y_i^{t=0}=y_{\min }+{\mathrm{\η}}_i(y_{\max }-y_{\min })---\left(2\right)$

In formula (1), (2), x _max, y _maxand x _min, y _minbe respectively maximum and the minimum value of newly-built direct current grounding pole or transformer station's horizontal stroke, ordinate, η _ibe the random number between 0～1, the starting velocity of particle is generally made as 0,

C, t=t+1, to all n _pindividual particle, uses formula (3) to produce new speed v ti, then presses formula (4) and upgrades particle position, and calculate the target function of each particle, upgrades the optimal location x*i of each particle, and obtains current globally optimal solution g*;

$p_i^{t+1}{=p}_i^t+v_i^{t+1}---\left(4\right)$

In formula (1), pi and vi are respectively speed and the position of particle i, and θ is inertia weight, and its effect is the inertia that keeps Particles Moving, make algorithm have the trend in expanded search space and have the ability to explore new region, θ ∈ [0.5,0.9], ε ₁and ε ₂be two 2 dimension 0～1 between random vector; X ⊙ y=[xi*yi], α and β are accelerator coefficient;

If d target function value no longer reduces or exceeds iterations, Output rusults, otherwise t=t+1, proceed to step c.

Beneficial effect of the present invention:

1, by the best site selection of the newly-built direct current grounding pole of global optimum's position Particle Swarm Optimization Algorithm calculative determination in early stage, reduce D.C. magnetic biasing risk and can estimate the rear D.C. magnetic biasing degree of building up, reduce the harm that D.C. magnetic biasing causes.

2, in the time of newly-built earth electrode addressing just prediction build up after the risk of the each transformer generation of AC network D.C. magnetic biasing, thereby the loss bringing because of D.C. magnetic biasing problem after can taking measures in advance to reduce or eliminating newly-built earth electrode and put into operation.

Brief description of the drawings

Fig. 1 is distributed ground electrode system wiring schematic diagram;

Fig. 2 is the schematic flow sheet of the present invention for the method for designing of the distributed earth electrode of HVDC (High Voltage Direct Current) transmission system.

Embodiment

Below in conjunction with the accompanying drawing in the present invention, the technical scheme in the present invention is clearly and completely described.

The method for designing that the invention provides a kind of distributed earth electrode for HVDC (High Voltage Direct Current) transmission system, comprises the steps:

Step 1, according to the scope of planning and the preliminary selected newly-built earth electrode of expropriation of land, determine the optimum position of newly-built earth electrode by global optimum's position Particle Swarm Optimization Algorithm.

Concrete, step 1 is specially:

A, objective definition function, can be in system transformer magnetomotive force mean value minimum, the average neutral point current minimum of transformer or the maximum neutral point current minimum of transformer as target function.Independent variable p=(x, y), represents the coordinate of newly-built direct current grounding pole or transformer station.

The position of b, initialization particle and speed, and obtain initial globally optimal solution g*=min[f (p1) ..., f (pn)], t=0, wherein p1, pn is that initialized n group is separated, and is the abscissa that comprises solution and the bivector of ordinate information, f (p1), f (pn) is p1 ..., the target function value that pn difference is corresponding; T optimizes the cycle-index of calculating.The original position of particle and speed should be evenly distributed among effective codomain of whole inverted parameters

$x_i^{t=0}=x_{\min }+{\mathrm{\η}}_i(x_{\max }-x_{\min })---\left(1\right)$

$y_i^{t=0}=y_{\min }+{\mathrm{\η}}_i(y_{\max }-y_{\min })---\left(2\right)$

In formula (1), (2), x _max, y _maxand x _min, y _minbe respectively maximum and the minimum value of newly-built direct current grounding pole or transformer station's horizontal stroke, ordinate, η _iit is the random number between 0～1.The starting velocity of particle is generally made as 0,

C, t=t+1, to all n _pindividual particle, uses formula (3) to produce new speed v ti, then presses formula (4) and upgrades particle position, and calculate the target function of each particle, upgrades the optimal location x*i of each particle, and obtains current globally optimal solution g*.

$p_i^{t+1}{=p}_i^t+v_i^{t+1}---\left(4\right)$

In formula (1), p _iand v _ibe respectively speed and the position of particle i, θ is inertia weight, and its effect is the inertia that keeps Particles Moving, make algorithm there is the trend in expanded search space and have the ability to explore new region, and θ ∈ [0.5,0.9], the present embodiment is got θ=0.7; ε ₁and ε ₂be two 2 dimension 0～1 between random vector; X ⊙ y=[xi*yi], α and β are accelerator coefficient, generally α=β=2.In addition, arbitrarily value of vi, but the bound that speed should be set in practice prevents from dispersing, and the bound of speed is generally set according to element interval range.

If d target function value no longer reduces or exceeds iterations, Output rusults, otherwise t=t+1, proceed to step c.

The present invention, by the best site selection of the newly-built direct current grounding pole of global optimum's position Particle Swarm Optimization Algorithm calculative determination, can reduce D.C. magnetic biasing risk and can estimate the rear D.C. magnetic biasing degree of building up, and reduces the harm that D.C. magnetic biasing causes.

Step 2, raise by the maximum potential of the true stator poles of earth electrode temperature rise, and verification step voltage:

$V_e=\sqrt{2\mathrm{\λ\ρ}({\mathrm{\ρ}}_{\mathrm{my}}-{\mathrm{\θ}}_c)}---\left(5\right)$

In above formula (5), Ve is the potential rise (V) that earth electrode allows, the thermal conductivity (W/m/ DEG C) that λ is soil, resistivity that ρ is soil (Ω m), θ _cfor the maximum the earth temperature in the utmost point location of earth electrode (DEG C), θ _myfor design allow earth electrode maximum temperature (DEG C).

Step voltage can be by following formula verification Em:

E _m＝7.42+0.0318ρ _s (6)

In formula (6), ρ s is top layer ground resistivity.

Step 3, by overhead transmission line, all earth electrodes and the newly-built sub-utmost point are connected, form distributed earth electrode, the mode of connection of distributed earth electrode can be carried out with reference to multiple bus arrangement modes of electric power system, as shown in Figure 1.

Step 4, set up the unified model that distributed earth electrode and AC network direct current distribute, impact AC network direct current being distributed to assess distributed earth electrode.

The nodal voltage equation of distributed earth electrode and AC network direct current distribution Unified Network:

YU＝J (7)

In formula (7), Y is that node electricity is led battle array, and U is node voltage battle array, and J is node Injection Current vector, and its expression formula is respectively

U＝[U _A；U _D] (8)

$Y=\left[\begin{array}{cc}{Y}_A& 0\\ 0& Y_D\end{array}\right]---\left(9\right)$

Definition by node Injection Current vector has:

J＝H′GP (10)

In above formula (10), H ' GP is that the equivalent current of all nodes of Unified Network injects vector; H is transformer station's node and all internodal incidence matrices, the transposition that H ' is H; P is the induced potential column vector of transformer station.

$H=\left[\begin{array}{cc}{H}_A& 0\\ 0& H_D\end{array}\right]---\left(11\right)$

In above formula (8)-(11) formula, the variable of subscripting A represents the variable of AC network, and the variable of subscripting D represents the variable of distributed earth electrode.

Have for grounding conductance:

$G=R^{-1}={\left[\begin{array}{cccc}{R}_{A1}& 0& 0& 0\\ 0& ...& 0& 0\\ 0& 0& R_{D1}& 0\\ 0& 0& 0& ...\end{array}\right]}^{-1}---\left(12\right)$

Have for induced potential:

P＝MI (13)

In formula (13), M represents the mutual resistance matrix of the large system of transformer station and sub-utmost point composition in Unified Network, and I representative is the earth current column vector of transformer station and the sub-utmost point.Definition by earth current has:

I＝G(HU-P) (14)

Simultaneous formula (7), (11), (13) and (14) can complete the unified model of whole distributed earth electrode and AC network direct current distribution calculating, obtain final solution formula as follows:

C＝[Y-H′GM(R+M) ^-1H]U (15)

(15 equation, the node voltage that can obtain unified model distributes solution formula, and then can distribute in the hope of the direct current of whole electrical network.

Step 5, distribute according to direct current in the AC network solving in above-mentioned steps, the risk of each transformer generation D.C. magnetic biasing in prediction AC network.If the absolute value of the transformer neutral point electric current monitoring in AC network is respectively: A1, A2 ... An, to single transformer, can be according to DL/T 437-2012 " shape high voltage DC earthing pole technology directive/guide " requirement, or according to local conditions, neutral point direct current threshold value I is set _λ, for neutral point current A _i>I _λtransformer, can think after newly-built earth electrode puts into operation, there is D.C. magnetic biasing risk.

Step 6, to having the transformer of D.C. magnetic biasing risk in prediction, can take neutral point to add resistance, electric capacity, maybe can take even to eliminate every inhibition such as straight measures the adverse effect that D.C. magnetic biasing problem is brought.

With very example of certain direct current in Hubei Province, suppose due to exploration and expropriation of land problem, the circumscription of newly-built direct current grounding pole is (111.37,30.51), (111.50,30.51), (111.50,30.63), (111.37,30.63) in region, newly-built direct current grounding pole earth current 3000A, 0.2 ohm of earth resistance, buried depth 3m, use the inventive method to be optimized calculating to earth electrode field, optimization aim is respectively: 1, the average DC magnetic kinetic potential minimum of transformer in 100km scope system; 2, the average neutral point current minimum of transformer in 100km scope system; 3, the maximum neutral point current minimum of transformer in 100km scope system; 4, the maximum DC magnetic kinetic potential of transformer minimum in 100km scope system; 5, the average neutral point current minimum of 500kV transformer in 100km scope system; 6, the interior average neutral point current minimum of 220kV transformer of system within the scope of 100km; 7, the interior average DC magnetic kinetic potential of the 500kV transformer minimum of system within the scope of 100km; 8, the interior average DC magnetic kinetic potential of the 220kV transformer minimum of system within the scope of 100km.In 8 kinds of situations, effect of optimization is in table 1.

Table 1 direct current grounding pole addressing optimum results

As shown in Table 1, no matter get that optimization aim function, global optimum's position Particle Swarm Optimization Algorithm is all obtained good effect, and in practical application, target function is got the average DC magnetic kinetic potential minimum of transformer in 100km scope system.

Claims (2)

1. for a method for designing for the distributed earth electrode of HVDC (High Voltage Direct Current) transmission system, it is characterized in that comprising the steps:

Step 1, according to the scope of planning and the preliminary selected newly-built earth electrode of expropriation of land, determine the optimum position of newly-built earth electrode by global optimum's position Particle Swarm Optimization Algorithm;

Step 2, raise by the maximum potential of the true stator poles of earth electrode temperature rise, and verification step voltage;

Step 3, by overhead transmission line, all earth electrodes and the newly-built sub-utmost point are connected, form distributed earth electrode, the mode of connection of distributed earth electrode is carried out with reference to the bus arrangement mode of electric power system;

Step 4, set up the unified model that distributed earth electrode and AC network direct current distribute, impact AC network direct current being distributed to assess distributed earth electrode;

Step 5, distribute according to direct current in the AC network solving in above-mentioned steps, the risk of each transformer generation D.C. magnetic biasing in prediction AC network;

Step 6, to there is the transformer of D.C. magnetic biasing risk in prediction, the adverse effect that D.C. magnetic biasing problem is brought of taking measures to suppress even to eliminate.

2. the method for designing of the distributed earth electrode for HVDC (High Voltage Direct Current) transmission system as claimed in claim 1, is characterized in that step 1 is specially:

A, objective definition function, in system, the maximum neutral point current minimum of transformer magnetomotive force mean value minimum, the average neutral point current minimum of transformer or transformer is as target function;

The position of b, initialization particle and speed, and obtain initial globally optimal solution g*=min[f (p1), ..., f (pn)], t=0, wherein p1 ..., pn is that initialized n group is separated, be the abscissa that comprises solution and the bivector of ordinate information, f (p1) ..., f (pn) is p1, the target function value that pn difference is corresponding, t optimizes the cycle-index of calculating, and the original position of particle and speed should be evenly distributed among effective codomain of whole inverted parameters

$x_i^{t=0}=x_{\min }+{\mathrm{\η}}_i(x_{\max }-x_{\min })---\left(1\right)$

$y_i^{t=0}=y_{\min }+{\mathrm{\η}}_i(y_{\max }-y_{\min })---\left(2\right)$

In formula (1), (2), x _max, y _maxand x _min, y _minbe respectively maximum and the minimum value of newly-built direct current grounding pole or transformer station's horizontal stroke, ordinate, η _ibe the random number between 0～1, the starting velocity of particle is made as 0,

C, t=t+1, to all n _pindividual particle, uses formula (3) to produce new speed v t _i, then press formula (4) and upgrade particle position, and calculate the target function of each particle, upgrade the optimal location x*i of each particle, and obtain current globally optimal solution g*;

$p_i^{t+1}{=p}_i^t+v_i^{t+1}---\left(4\right)$

In formula (1), p _iand v _ibe respectively speed and the position of particle i, θ is inertia weight, and its effect is the inertia that keeps Particles Moving, makes algorithm have the trend in expanded search space and has the ability to explore new region, θ ∈ [0.5,0.9], ε ₁and ε ₂be two 2 dimension 0～1 between random vector; X ⊙ y=[xi*yi], α and β are accelerator coefficient;

If d target function value no longer reduces or exceeds iterations, Output rusults, otherwise t=t+1, proceed to step c.