CN204009909U - A kind of three-phase ac electric arc furnace adaptive modeling device - Google Patents

Abstract

The utility model relates to power quality analysis and control field, is specially a kind of three-phase ac electric arc furnace adaptive modeling device.The adaptive modeling device of three-phawse arc furnace can not only reflect the three-phase imbalance problem of electric arc furnaces, and can change accordingly model parameter with corresponding with it according to the change of operating mode.The utility model is optimized and adjusts simulation parameters according to actual operating mode, can more accurately reflect that electric arc furnaces truly uses electrical characteristics, thereby be the arc furnace power quality phenomenon under the different operating conditions of research, promote electrical network and receive arc furnace load ability, provide fundamental basis.

Description

A kind of three-phase ac electric arc furnace adaptive modeling device

Technical field

The utility model relates to power quality analysis and control field, is specially a kind of three-phase ac electric arc furnace adaptive modeling device.

Background technology

In recent years, the increase of various nonlinear-loads causes electric power quality problem day by day serious, jeopardizes the safety and economic operation of electric system.Ac arc furnace is typical nonlinear-load, is also one of load that the quality of power supply is had the greatest impact.

Electric arc furnaces modeling is the prerequisite of arc furnace power quality analytical work.Model accurately whether, rationally whether, whether applicability has determined that by force can follow-up work launch smoothly.Electric arc furnaces operating condition is complicated and changeable, so need to set up a kind of electric arc furnaces model building device that is applicable to various working.

Current electric arc furnaces model is often supposed three-phase equilibrium, represents three-phase research with single-phase arc funace, mainly comprises nonlinear time-varying Resistance model for prediction, nonlinear time-varying voltage source model, the time-varying reactance model based on energy conservation etc.And actual arc stove three phase power unequal, three-phase imbalance problem is serious, carries out the electric arc furnaces model that above-mentioned hypothesis obtains and is difficult to reflect electric arc furnaces actual motion state.And this single-phase arc funace model often can not be adjusted according to the change of electric arc furnaces operating mode, cannot be corresponding with actual condition.

Utility model content

(1) technical matters that will solve

(1) according to the real-time adjustment model of the variation of three phase power;

(2) study the arc furnace power quality problem under different operating conditions.

(2) technical scheme

In order to solve the problems of the technologies described above, the utility model provides a kind of three-phase ac electric arc furnace adaptive modeling device, it is characterized in that, described three-phase ac electric arc furnace adaptive modeling device comprises: bus 1, electric arc furnaces 3, tester 6, comprehensive modeling machine 7 and basic modeling engine 8; On described bus 1, be electrically connected with respectively transformer 2, electric arc furnaces 3 and voltage transformer (VT) 5; Described electric arc furnaces 3 is provided with current transformer 4; The secondary side of described voltage transformer (VT) 5 is electrically connected with the voltage waveform input end of described tester 6; The secondary side of described current transformer 4 is electrically connected with the current waveform input end of described tester 6; The data output end of described tester 6 is connected with the service data collection terminal of described comprehensive modeling machine 7; The model communication terminal of described basic modeling engine 8 is connected with the model communication terminal of described comprehensive modeling machine 7 by ethernet line 9.

(3) beneficial effect

The adaptive modeling device of three-phawse arc furnace can not only reflect the three-phase imbalance problem of electric arc furnaces, and can change accordingly model parameter with corresponding with it according to the change of operating mode.The utility model is optimized and adjusts simulation parameters according to actual operating mode, can more accurately reflect that electric arc furnaces truly uses electrical characteristics, thereby be the arc furnace power quality phenomenon under the different operating conditions of research, promote electrical network and receive arc furnace load ability, provide fundamental basis.

Brief description of the drawings

In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only embodiment more of the present utility model, for those of ordinary skill in the art, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is according to the structural representation of an embodiment of a kind of three-phase ac electric arc furnace adaptive modeling of the utility model device;

Fig. 2 is the electric arc furnaces output I-V family curve according to an embodiment of a kind of three-phase ac electric arc furnace adaptive modeling of the utility model device;

Fig. 3 is according to the three-phase ac electric arc furnace model equivalent electrical circuit of an embodiment of a kind of three-phase ac electric arc furnace adaptive modeling of the utility model device.

Embodiment

Below in conjunction with Figure of description and embodiment, embodiment of the present utility model is described in further detail.Following examples are only for the utility model is described, but can not be used for limiting scope of the present utility model.

The utility model provides a kind of three-phase ac electric arc furnace adaptive modeling device, comprises bus 1, electric arc furnaces 3, tester 6, comprehensive modeling machine 7 and basic modeling engine 8.On bus 1, be electrically connected with respectively transformer 2, electric arc furnaces 3 and voltage transformer (VT) 5; On electric arc furnaces 3, be provided with current transformer 4.The secondary side of voltage transformer (VT) 5 is electrically connected with the voltage waveform input end of tester 6; the secondary side of current transformer 9 is electrically connected with the current waveform input end of tester 6; the data output end of tester 6 is connected with the service data collection terminal of comprehensive modeling machine 7; the model communication terminal of basis modeling engine 8 is connected with the model communication terminal of comprehensive modeling machine 7 by ethernet line 9, realizes both-way communication.

The method of applying device-adaptive modeling described in the utility model, comprises the following steps:

The first step, the secondary side of voltage transformer (VT) 5 is electrically connected with the voltage waveform input end of tester 6; the secondary side of current transformer 9 is electrically connected with the current waveform input end of tester 6, and the data output end of tester 6 is connected with the service data collection terminal of comprehensive modeling machine 7.Tester 6 is tested and is added up the real-time running data of electric arc furnaces 2, and test data result is transferred to comprehensive modeling machine 7.

Second step, the electric arc furnaces parameter of collecting is input in basic modeling engine 8; basis modeling engine 8 is according to the basic model of electric arc furnaces 3 and typing parameter; set up the equivalent model adapting with it; and calculate through simplifying; form corresponding mathematics model, transfer in comprehensive modeling machine 7 setting up mathematical model by both-way communication.

The 3rd step, the mathematical model of exporting according to the measured data of tester 6 in first two steps and basic modeling engine 8; 7 computings of comprehensive modeling machine draw the unified model and the parameter that are applicable to this electric arc furnaces operational system; finally draw close to electric arc furnaces 3 it is really the realistic model of operating condition, and the data export function that supplies a model.

Apply device-adaptive modeling and simulating algorithm described in the utility model, comprise the following steps:

The first step: set up the three-phase ac electric arc furnace equivalent model of concentrated expression arc furnace power quality problem, contain the parameter that need to ask for according to actual condition in equivalent model.

As shown in Figure 2, the relation between electric arc furnaces voltage and electric current is nonlinear to electric arc furnaces output I-V family curve as seen from the figure, and this makes modeling very difficult.For this reason, carried out staging treating.First stage: electric arc starts to light, when arc voltage is elevated to zero, electric current is zero crossing also.Equivalent electrical circuit can be regarded as an open circuit, and leakage current exists, in this stage with a constant resistance (V _g/ i _g) relation of voltage and current described; Subordinate phase: electric arc is set up, in arc-melting process, arc voltage declines suddenly, then tends towards stability.This process is described with the reciprocal function of time constant (b1) with one.Phase III, electric arc starts to extinguish, the decline that arc voltage is milder.This process is still described with a reciprocal function, wherein with time constant be b2.Obtain in sum the mathematical model (taking A mutually as example) of the electric arc furnaces output characteristics as shown in formula (1).

Wherein i _mfor the amplitude of electric current, unit is ampere; i _gfor invariable current, unit is ampere, V _gfor fixed voltage; B1 and b2 are time constants; V _a(t) be A phase electric arc furnaces voltage, unit is volt, i _a(t) be A phase current, unit is ampere; V _d1electric arc furnaces magnitude of voltage while trending towards maximal value for electric current, unit is volt.

Second step: electric power system is carried out to equivalence, and to the electric arc furnaces model simplification in the first step to facilitate calculating, and then set up electric arc furnaces and electric power system mathematical model thereof.Wherein in electric arc furnaces simplified model, also can reflect the output characteristics of electric arc furnaces containing parameter to be determined.

The equivalent circuit diagram of electric arc furnaces and electric power system thereof as shown in Figure 3.Wherein, for convenience of calculation by three-phawse arc furnace model simplification is:

$V_a\left(t\right)=\left\{\begin{array}{cc}{V}_{d1}& i_a\left(t\right)\&GreaterEqual;0\\ -V_{d1}& i_a\left(t\right)<0\end{array}\right.---\left(2\right)$

$V_b\left(t\right)=\left\{\begin{array}{cc}{V}_{d2}& i_b\left(t\right)\&GreaterEqual;0\\ -V_{d2}& i_b\left(t\right)<0\end{array}\right.---\left(3\right)$

$V_c\left(t\right)=\left\{\begin{array}{cc}{V}_{d3}& i_c\left(t\right)\&GreaterEqual;0\\ -V_{d3}& i_c\left(t\right)<0\end{array}\right.---\left(4\right)$

In formula, V _a(t), V _b(t), V _c(t) be respectively electric arc furnaces A, B, C phase voltage, unit is volt; V _d1, V _d2, V _d3be respectively A, B, C phase current corresponding electric arc furnaces voltage while trending towards maximal value, unit is volt.

Can obtain according to Fig. 3 and Thevenin theorem:

$i_a\left(t\right)R+L\frac{{\mathrm{di}}_a\left(t\right)}{\mathrm{dt}}=U_A+\frac{-2V_a\left(t\right)+V_b\left(t\right)+V_c\left(t\right)}{3}---\left(5\right)$

$i_b\left(t\right)R+L\frac{{\mathrm{di}}_b\left(t\right)}{\mathrm{dt}}=U_B+\frac{V_a\left(t\right)-{2V}_b\left(t\right)+V_c\left(t\right)}{3}---\left(6\right)$

$i_c\left(t\right)R+L\frac{{\mathrm{di}}_c\left(t\right)}{\mathrm{dt}}=U_C+\frac{V_a\left(t\right)+V_b\left(t\right)-{2V}_c\left(t\right)}{3}---\left(7\right)$

Wherein R and L represent respectively electric power system line resistance and the inductance reduction value to Circuit Fault on Secondary Transformer, and unit is respectively ohm and prosperous.U _a, U _b, U _cfor supply voltage reduction is to the three-phase voltage of Circuit Fault on Secondary Transformer, expression formula is:

U _A＝U _msin(wt)、 $U_B=U_m\sin (\mathrm{wt}-\frac{2\mathrm{\&pi;}}{3}),U_C=U_m\sin (\mathrm{wt}-\frac{4\mathrm{\&pi;}}{3})$

The 3rd step: according to supply line and transformer parameter, the mathematical model in electric arc furnaces three-phase operation power and second step, determines three-phawse arc furnace adaptive algorithm, in the hope of getting electric arc furnaces model parameter.

Because Va, Vb, Vc are the discrete functions about the time, be inconvenient to calculate, carried out Fourier decomposition and got first 4:

Wherein represent respectively three-phase current i _a, i _b, i _cinitial phase angle.

It is brought into respectively in formula (5)～(7), can try to achieve the expression formula of ia, ib, ic, then try to achieve P _a, P _b, P _cexpression formula.As follows:

Wherein

$\mathrm{\&phi;}=\arctan \frac{\mathrm{awL}}{R}$

Wherein

Because so can obtain according to formula (11)-(13):

Make P _a, P _b, P _cequal electric arc furnaces three-phase actual motion power P _a,n, P _b,n, P _c,n, can obtain other three and describe V _d1, V _d2, V _d3, equation:

Utilize process of iteration to ask the system of equations being formed by equation (17)～(22) can try to achieve the V corresponding to actual motion power _d1, V _d2, V _d3value.Ask for thereby realized corresponding to the self-adaptation of the parameter of actual condition.Whenever changing, operating mode can utilize this algorithm to ask for corresponding model parameter.

The 4th: by the model parameter value substitution formula (1) of asking in the 3rd step, obtain reflecting the three-phase model of electric arc furnaces actual motion state.

In conjunction with actual power situation, adopt the model of above-mentioned foundation can analyze arc furnace power quality relevant issues under different operating modes.

This model building device and emulation mode thereof are that connection type is simple based on conventional electric energy quality test instrument and Modeling Analysis System, focus on simulation calculation and are combined with measured data, and modeling and simulating visual result is accurate.

Above embodiment is only for the utility model is described, but not to restriction of the present utility model.Although the utility model is had been described in detail with reference to embodiment, those of ordinary skill in the art is to be understood that, the technical solution of the utility model is carried out to various combinations, revises or is equal to replacement, do not depart from the spirit and scope of technical solutions of the utility model, all should be encompassed in the middle of claim scope of the present utility model.

Claims (1)

1. a three-phase ac electric arc furnace adaptive modeling device, it is characterized in that, described three-phase ac electric arc furnace adaptive modeling device comprises: bus (1), electric arc furnaces (3), tester (6), comprehensive modeling machine (7) and basic modeling engine (8); On described bus (1), be electrically connected with respectively transformer (2), electric arc furnaces (3) and voltage transformer (VT) (5); Described electric arc furnaces (3) is provided with current transformer (4); The secondary side of described voltage transformer (VT) (5) is electrically connected with the voltage waveform input end of described tester (6); The secondary side of described current transformer (4) is electrically connected with the current waveform input end of described tester (6); The data output end of described tester (6) is connected with the service data collection terminal of described comprehensive modeling machine (7); The model communication terminal of described basic modeling engine (8) is connected with the model communication terminal of described comprehensive modeling machine (7) by ethernet line (9).