CN104833886A - Method for evaluating direct-current drop point harmonic waves conducting from high-voltage level to low-voltage level - Google Patents

Abstract

The invention relates to a method for evaluating direct-current drop point harmonic waves conducting from a high-voltage level to a low-voltage level, which comprises the steps of (1) getting into a step (2) if a harmonic wave to be evaluated is located at a common connection point of a power grid, and getting into a step (5) if the harmonic wave to be evaluated is located between different levels of the power grid; (2) acquiring system harmonic impedance Zs, user harmonic impedance Zc and harmonic current I<o1> flowing from the common connection point to the user harmonic impedance Zc; (3) equalizing the harmonic current I<o1> into harmonic current I<equo1> injecting into the common connection point from a user side; (4) comparing a value of the harmonic current I<equo1> with a national standard allowable value and evaluating; (5) acquiring harmonic self impedance Z<ii><h> of a direct current side node, equivalent harmonic impedance Z<L><h> of a linear load of a load side node and harmonic current I<L><h> flowing from the direct current node to the linear load of the load side node; (6) equalizing the harmonic current I<L><h> into injection harmonic current I<eqoL><h> of the load side node; and (7) comparing the harmonic current I<eqoL><h> with a national standard allowable value and evaluating. The invention provides an effective harmonic wave evaluation method for conduction of urban power grid direct-current drop point harmonic waves from the high-voltage level to the low-voltage level.

Description

A kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage

Technical field

The present invention relates to mains by harmonics evaluation method, especially relate to a kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage.

Background technology

In electric system, occur that harmonic voltage and electric current can produce harm to electrical equipment, cause apparatus overheat, insulation ag(e)ing, cause the decay of transmitting energy, the reduction of power factor, therefore, harmonic problem always comes into one's own.Along with a large amount of uses of power electronic element in electric system, they are after improving the quality of power supply, also bring even more serious and complicated harmonic problem to system.

Under the actual conditions of, distance large at China's energy flow flux, country is just embarking powerful UHV transmission network.Transferring electricity from the west to the east, north and south confession mutually, on national network, interior on a large scale resource sharing and the requirement of distributing rationally propose new test to electric utility, and high voltage dc transmission technology arises at the historic moment.The current converter that D.C. high voltage transmission adopts is typical non-linear electronic devices, and the alternating current-direct current side that it can become in the change of current in delivery of electrical energy process produces various harmonic wave.

For the urban distribution network containing direct current drop point, harmonic wave conduction has amphicheirality, and while the humorous wave direction high voltage level diffusion that namely nonlinear-load of undervoltage level produces, the direct current drop point harmonic wave of high voltage level also can conduct to undervoltage level.A large amount of measured data shows, direct current drop point harmonic wave accounts for leading in urban distribution network harmonic propagation.

For this new problem, first, straight interacted system access makes urban distribution network harmonic wave have from voltage levels to low-voltage-grade conduction feature step by step, and the harmonic wave that this and undervoltage level are diffused into high voltage level takes on a different character.But existing harmonic analysis method, comprises harmonic wave GB appraisement system, normally proposed to the diffusion of high voltage level by undervoltage level for harmonic wave in traditional electrical network.For utility network harmonic wave GB/T 14549-1993 standard, the standard specifies the harmonic voltage limit of utility network harmonic wave and inject the allowable harmonic current of points of common connection, be only limitted to public electric wire net harmonic electric current or the electric equipment producing harmonic voltage in public electric wire net to the definition of harmonic source in standard, when specifying allowable harmonic current and the distribution principle of points of common connection, also only for the user-side harmonic source of points of common connection, do not relate to system side harmonic source, the scope of application of whole standard is limited to the situation that traditional mains by harmonics is spread to high voltage level by undervoltage level.If still directly adopt the allowable harmonic current under GB framework to evaluate the harmonic current size of direct current drop point generation, because standard is formulated for user-side harmonic source, and direct current drop point harmonic wave belongs to system side, both concepts are different, this evaluation will lose meaning, lack at present to be a kind ofly applicable to direct current drop point harmonic wave from high voltage level to the analysis and evaluation method of undervoltage level conductive process.

Moreover, direct current drop point harmonic wave after filtering device meets harmonic wave GB at public interface after suppressing, but affects by electric network composition, and especially cable and the inductant-capacitance coupling of pole line ground capacitance in electrical network easily cause higher hamonic wave to amplify, thus affect harmonic wave conductive process, cause harmonic excess.

Therefore, find a kind of urban distribution network direct current drop point harmonic wave from high voltage level to the analysis and evaluation method of undervoltage level transport properties be necessary.

Summary of the invention

Object of the present invention be exactly in order to overcome prior art exist defect and provide a kind of direct current drop point harmonic wave to conducting from high pressure stage to low pressure stage to carry out the method for effective analysis and inspection, harmonic current high voltage level being injected undervoltage level is converted to undervoltage level under harmonic wave GB framework by equivalence principle and injects the harmonic current of high voltage level, and compare with GB allowable harmonic current, to evaluate its influence degree.

Object of the present invention can be achieved through the following technical solutions:

A direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage, comprises the following steps:

(1) judge the position of harmonic wave to be evaluated, if the position of harmonic wave to be evaluated is positioned at electrical network points of common connection, then enter step (2), if between the different level of electrical network, then enter step (5);

(2) computing system harmonic impedance Z _swith user's harmonic impedance Z _c, measure and flow to Z from points of common connection _charmonic current

(3) to produce identical harmonic voltage for equivalent condition, will be equivalent to the harmonic current injecting points of common connection from user side

${\stackrel{\&CenterDot;}{I}}_{\mathrm{eqo}1}=\left|\frac{Z_c}{Z_s}\right|{\stackrel{\&CenterDot;}{I}}_{o1};$

(4) will value compares with this GB Injection Current permissible value, obtains evaluation result, exits;

(5) the harmonic wave self-impedance of DC side node is calculated the linear load of load side node resists the harmonic source measuring DC side node flows to the electric current of the linear load of load side node wherein, h is the number of times of harmonic wave to be evaluated;

(6) to produce identical harmonic voltage for equivalent condition, will be equivalent to the harmonic electric current of load side node

${\stackrel{\&CenterDot;}{I}}_{\mathrm{eqoL}}^h=\left|\frac{Z_L^h}{Z_{\mathrm{jj}}^h}\right|{\stackrel{\&CenterDot;}{I}}_L^h;$

(7) will value compares with this GB Injection Current permissible value, obtains evaluation result, exits.

Described with measuring method is: in branch road, seal in harmonic analysis instrument measure.

Described system harmonic impedance Z _swith user's harmonic impedance Z _ccalculated by mains by harmonics parametric technique and obtain.

Described system harmonic impedance Z _scalculating in eliminate the effect of wave filter.

The harmonic wave self-impedance of described DC side node the linear load of load side node resists calculated by mains by harmonics parametric technique and obtain.

Compared with prior art, the present invention has following effect and advantage:

(1) for the process that urban distribution network direct current drop point harmonic wave conducts from high voltage level to undervoltage level, be the harmonic electric current of undervoltage level by high voltage level harmonic current equivalence, compensate for international harmonic current specify in blank parts.

(2) respectively with regard to the two kind situations of harmonic wave when same common connecting point and different electric pressure conduct, give the equivalency transform method of harmonic current, all can provide corresponding analytical approach for the harmonic wave conduction containing certain point in direct current drop point urban distribution network or certain region, there is adaptability widely.

(3) high voltage level harmonic Current Limits is fixed in standard allowed band, avoid mains by harmonics hazards.

(4) measurements and calculations method is simple, easily realizes, has higher engineering use value.

Accompanying drawing explanation

Fig. 1 is system side and user side equivalent circuit diagram;

Fig. 2 is harmonic propagation illustraton of model between different hierarchical network;

Fig. 3 is certain city partial electric grid computation model figure;

Fig. 4 is 11 each branch road harmonic currents, equivalent Injection Current and GB Injection Current permissible value comparison diagrams;

Fig. 5 is 13 each branch road harmonic currents, equivalent Injection Current and GB Injection Current permissible value comparison diagrams;

Fig. 6 is the process flow diagram of the inventive method.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.The present embodiment is implemented premised on technical solution of the present invention, give detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

Embodiment

As shown in Figure 6, the present embodiment provides a kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage, and concrete steps are:

S1, judges the position of harmonic wave to be evaluated, if be positioned at electrical network points of common connection, then enters step (2), if between the different level of electrical network, then enter step S5;

S2, utilizes mains by harmonics parametric technique computing system harmonic impedance Z _swith user's harmonic impedance Z _c, wherein Z _scalculating in eliminate the effect of wave filter; In user's branch road, seal in harmonic analysis instrument, measure and flow to Z from points of common connection _charmonic current

S3, to produce identical harmonic voltage for equivalent condition, will be equivalent to the harmonic current injecting points of common connection from user side

S4, will value compares with this GB Injection Current permissible value, and evaluates its influence degree, obtains evaluation result, exits.

S5, calculates the harmonic wave self-impedance of DC side node i the linear load equivalent harmonic wave impedance of load side node j in branch road, seal in harmonic analysis instrument, the harmonic source of measured node i flows to the electric current of the linear load of j wherein, h is the number of times of harmonic wave to be evaluated;

S6, to produce identical harmonic voltage for equivalent condition, will be equivalent to the harmonic electric current of node j

S7, will value compares with this GB Injection Current permissible value, and evaluates its influence degree, obtains evaluation result, exits.

Right below with computing method describe in detail:

As shown in Figure 1, when harmonic wave is in same common connecting point conduction, if harmonic voltage it is system side harmonic source the result of independent role, flows to user's harmonic impedance Z at common connecting point _charmonic current be namely

${\stackrel{\&CenterDot;}{I}}_{o1}=\frac{{\stackrel{\&CenterDot;}{V}}_{o1}}{Z_c}$

In like manner, if harmonic voltage it is user-side harmonic source the result of independent role, flows to system harmonic impedance Z at common connecting point _sharmonic current be namely

${\stackrel{\&CenterDot;}{I}}_{o2}=\frac{{\stackrel{\&CenterDot;}{V}}_{o2}}{Z_s}$

Because | Z _c| > > | Z _s|, namely user's harmonic impedance amplitude is much larger than system harmonic impedance amplitude, so produce onesize harmonic voltage, i.e. and V _o1=V _o2time, system side injects public interface harmonic current public interface harmonic current is injected much smaller than user side in order to have an evaluation criteria of equal value to both sides Injection Current under harmonic wave GB framework, system side being injected public interface harmonic current and being equivalent to the harmonic current injecting points of common connection from user side by following formula:

${\stackrel{\&CenterDot;}{I}}_{\mathrm{eqol}}=\left|\frac{Z_c}{Z_s}\right|{\stackrel{\&CenterDot;}{I}}_{o1}$

Calculate according to this formula with there is same effect, directly can weigh its influence degree with GB Injection Current permissible value.

As shown in Figure 2, when harmonic wave is propagated in the different level of electrical network, be described in the example that act as of node j with the nonlinear load harmonic source of the DC side harmonics source of node i and node j, first, the harmonic impedance equation setting up h subharmonic according to harmonic propagation model is:

$\left[\begin{array}{c}{\stackrel{\&CenterDot;}{V}}_i^h\\ {\stackrel{\&CenterDot;}{V}}_j^h\end{array}\right]=\left[\begin{array}{cc}{Z}_{\mathrm{ii}}^h& Z_{\mathrm{ij}}^h\\ Z_{\mathrm{ji}}^h& Z_{\mathrm{jj}}^h\end{array}\right]\left[\begin{array}{c}{\stackrel{\&CenterDot;}{I}}_i^h\\ {\stackrel{\&CenterDot;}{I}}_j^h\end{array}\right]$

Wherein, h the harmonic electric current of node i and node j respectively; be by acting in conjunction, the h subharmonic voltage produced in node i and node j respectively; represent the h subharmonic self-impedance of node i and node j respectively; represent the h subharmonic transimpedance between node j and i, between node i and j respectively.

From above formula, when independent role when node j, the harmonic voltage of generation for:

${\stackrel{\&CenterDot;}{V}}_{\mathrm{ji}}^h=Z_{\mathrm{ji}}^h{\stackrel{\&CenterDot;}{I}}_i^h$

When independent role when node j, the harmonic voltage of generation for:

${\stackrel{\&CenterDot;}{V}}_{\mathrm{jj}}^h=Z_{\mathrm{jj}}^h{\stackrel{\&CenterDot;}{I}}_j^h$

When with time equal:

$Z_{\mathrm{ji}}{\stackrel{\&CenterDot;}{i}}_i^h=Z_{\mathrm{jj}}^h{\stackrel{\&CenterDot;}{I}}_j^h$

Therefore, can by the DC side harmonics source of node i be equivalent to

${\stackrel{\&CenterDot;}{I}}_j^h=\frac{Z_{\mathrm{ji}}^h}{Z_{\mathrm{jj}}^h}{\stackrel{\&CenterDot;}{I}}_i^h$

Calculate according to this formula with there is same effect, but cannot directly measure;

DC side harmonics source actual flow is to the electric current of the linear load of node j for:

${\stackrel{\&CenterDot;}{I}}_L^h=\left|\frac{Z_{\mathrm{ji}}^h}{Z_L^h}\right|{\stackrel{\&CenterDot;}{I}}_i^h$

In formula: it is the equivalent harmonic wave impedance of the linear load of node j.

Under normal circumstances, so can directly measure at the scene.So generation illusion: when during lower than harmonic wave GB permissible value, think that harmonic current is qualified.Therefore, in order to have an evaluation criteria of equal value to both sides Injection Current under harmonic wave GB framework, the harmonic current of measurement should carry out equivalent transformation by following formula, is only the injected value of current under GB meaning:

${\stackrel{\&CenterDot;}{I}}_{\mathrm{eqoL}}^h=\left|\frac{Z_L^h}{Z_{\mathrm{ii}}^h}\right|{\stackrel{\&CenterDot;}{I}}_L^h$

Through such conversion, can by measuring obtain the harmonic current injecting points of common connection from user side of equivalence, then directly weigh its influence degree with GB Injection Current permissible value.

As shown in Figure 3, the harmonic current in-site measurement value of each branch road harmonic wave of 11 times, 13 times in certain city partial electric grid actual and calculated value are compared respectively, result is as shown in table 1:

Table 1 branch road harmonic current

For branch road harmonic current data, Fig. 4, Fig. 5 respectively illustrate the harmonic current of 11 times, 13 times each branch roads, equivalent Injection Current and GB Injection Current permissible value and compare.Can find out, the branch road harmonic current size being evaluated the generation of direct current drop point harmonic wave by the allowable harmonic current under GB framework is nonsensical, because both concepts are different.Harmonic electric current under GB framework refers to from load side and flows to system side, and the harmonic wave of direct current drop point flows to load side from system side, the harmonic voltage of both onesize generations is different, obtains equivalent Injection Current, just had comparability with GB by the present invention do conversion.Concrete, as can be seen from Fig. 4, Fig. 5, if do not adopt the present invention to make equivalent transformation to harmonic current, except line 1 11 times of all the other each branch roads, 13 subharmonic currents are all significantly less than the GB allowable harmonic current of corresponding bus, overall judged result is that the branch road harmonic current that direct current drop point produces is not serious.But, after equivalent transformation is done to harmonic current, equivalence harmonic electric current is approximately more than 7 times of corresponding branch road harmonic current, except change 3 11 times of all the other each branch roads, 13 subharmonic currents have all exceeded the GB allowable harmonic current of corresponding bus, evaluation result illustrates that direct current drop point harmonic wave brings serious harmonic problem.To sum up analyze known, the present invention is applicable to direct current drop point harmonic wave from high voltage level to the analysis of undervoltage level conductive process.

Claims (5)

1. a direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage, is characterized in that, comprise the following steps:

(1) judge the position of harmonic wave to be evaluated, if the position of harmonic wave to be evaluated is positioned at electrical network points of common connection, then enter step (2), if between the different level of electrical network, then enter step (5);

(2) computing system harmonic impedance Z _swith user's harmonic impedance Z _c, measure and flow to Z from points of common connection _charmonic current

(3) to produce identical harmonic voltage for equivalent condition, will be equivalent to the harmonic current injecting points of common connection from user side

${\stackrel{.}{I}}_{\mathrm{eqol}}=\left|\frac{Z_c}{Z_s}\right|{\stackrel{.}{I}}_{\mathrm{ol}};$

(4) will value compares with this GB Injection Current permissible value, obtains evaluation result, exits;

(5) the harmonic wave self-impedance of DC side node is calculated the linear load of load side node resists the harmonic source measuring DC side node flows to the electric current of the linear load of load side node wherein, h is the number of times of harmonic wave to be evaluated;

(6) to produce identical harmonic voltage for equivalent condition, will be equivalent to the harmonic electric current of load side node

${\stackrel{.}{I}}_{\mathrm{eqoL}}^h=\left|\frac{Z_L^h}{Z_{\mathrm{jj}}^h}\right|{\stackrel{.}{I}}_L^h;$

(7) will value compares with this GB Injection Current permissible value, obtains evaluation result, exits.

2. a kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage according to claim 1, is characterized in that, described in with measuring method is: in branch road, seal in harmonic analysis instrument measure.

3. a kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage according to claim 1, is characterized in that, described system harmonic impedance Z _swith user's harmonic impedance Z _ccalculated by mains by harmonics parametric technique and obtain.

4. a kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage according to claim 1, is characterized in that, described system harmonic impedance Z _scalculating in eliminate the effect of wave filter.

5. a kind of direct current drop point harmonic wave evaluation method of conducting from high pressure stage to low pressure stage according to claim 1, is characterized in that, the harmonic wave self-impedance of described DC side node the linear load of load side node resists calculated by mains by harmonics parametric technique and obtain.