CN103036230B - A kind of Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied - Google Patents

Abstract

Based on a Dynamic Equivalence for the alternating current-direct current series-parallel connection bulk power grid of engineer applied, belong to and become field of power distribution.Electrical network to be analyzed is divided into electrical network two parts in district's external power grid and district by it; To 500kV electrical network Detailed simulation in region, Equivalent Simplification is carried out to low-voltage network in district's external power grid and district; With the Dynamic Equivalence based on experience, external power grid equivalent generator in district's is obtained simplifying electrical network outside district; With the Dynamic Equivalence of physically based deformation equivalence, Equivalent Simplification is carried out to low-voltage network in district and obtains simplifying electrical network in final district; In district's external power grid dynamic equivalent and district after electrical network dynamic equivalent, respectively equivalent effect is checked; Simplifying electrical network and the dynamic response curve of actual electric network under same fault by comparing, checking the validity of whole dynamic equivalent Principles and ways.Which reduce equivalent system state amount and differential equation number, improve system analysis computation efficiency, the analytical calculation of series-parallel connection bulk power grid and the dispatching management field of electrical network can be widely used in.

Description

A kind of Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied

Technical field

The invention belongs to change, field of power distribution, particularly relate to a kind of Dynamic Equivalence for alternating current-direct current series-parallel connection bulk power grid.

Background technology

At present, China's electric power system develops rapidly, transfers electricity from the west to the east, north and south is interconnected, alternating current-direct current combines transmission of electricity and large regions networking operation makes system day by day huge, complicated.Even if when carrying out off-line electromechanical transient simulation, all very difficult.Because the dynamic element number of large-scale power system is more, electric network composition, characteristic, operational mode are all very complicated, the transient process of system is again nonlinear processes, required Computer Storage amount is very large, computing time is also longer, and during the machine of computer, internal memory, data encasement etc. be often not enough to the analysis and research meeting complicated large-scale power system, also need the full detail (comprising parameter and the operation conditions of all elements in system) knowing whole system, thus seem difficult.A large amount of large power power electronic appliance simultaneously, as: direct current transportation, SVC(StaticVarCompensator, Static Var Compensator), TCSC(ThyristorControlledSeriesCompensation thyristor controlled series capacitor compensation technique) extensive use of equipment and various fast automatic control device, make the dynamic characteristic of electrical network increasingly sophisticated.

Electromechanical transient simulation software based on first-harmonic, phasor, sequence analysis all adopts quasi steady state model to simulate at power electronic equipment such as emulation HVDC system and FACTS etc., all can not reflect the waveform that its fast transient characteristic and non-linear element cause; And electromagnetic transient analysis software makes because the dynamic characteristic of all elements of its system all adopts the differential equation to represent that its material calculation is little, amount of calculation large, therefore, its simulation scale is little.It is very difficult for directly carrying out the analysis of off-line electromechanical transient, electromagnetic transient analysis, online dynamic secure estimation and Control System Design to large-scale electrical power system, so be necessary to carry out Equivalent Simplification to it.

When analyzing and researching large-scale electrical power system dynamic behaviour, often also just to wherein a part of area interest, this subregion needs to describe in detail with the dynamic behaviour accurately reflecting system, usually claims this subregion to be built-in system (Study system); And to remainder region, in research, only consider its impact on built-in system, itself need not describe in detail, can carry out depression of order simplification, the region that this part work done in the manner of a certain author simplifies is called external system.

Being simplified can be given prominence to principal contradiction by system, for the principal character grasping Study system, is very necessary.This reservation Study system is constant, and is ensureing that it is under the undistorted condition of the dynamic response of Study system to external system, and the process of carrying out simplifying is called dynamic equivalent.

Many experimental Dynamic Equivalences are had in history to large-scale power system.Such as, represent away from the generator of survey region, load and network one (or several) equivalent generator or equivalent load, be even reduced to infinite busbar.Correspondingly network also simplifies, cancellation great deal of nodes, and the nonlinear-load on origin node is also displaced to reservation node and gets on.But the shortcoming of these experience equivalences is:

(1) experience and subjective judgement is greatly depended on;

(2) behavioral characteristics of method coarse, low precision, the original system that may distort;

(3) method used not system, not strictly, not general etc.

Shen Qing Publication day is on December 14th, 2011, application publication number is disclose a kind of power grid equivalence method in the Chinese invention patent application of CN102280884A, it simplifies generating set external system to be studied, and it is infinite busbar and dynamic unit that distant place complex large power grid and near-end are distinguished equivalence with bus bar machine group.The method is applicable to being applied to the aspects such as the check of Modeling of excitation system time Domain Parameter and PSS parameter optimization, can better reflect external system characteristic, while simplification electric system simulation calculates, improve simulation calculation precision.But it can only be applicable to the Modeling of excitation system of generating set, cannot be applied in the dynamic equivalent calculating of alternating current-direct current series-parallel connection bulk power grid, also for considering the problem of engineer applied.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied, it carries out Equivalent Simplification to low-pressure system in district's external power grid and district, quantity of state and the differential equation number of valve system such as to greatly reduce, the research to original system is replaced with the research of reciprocity valve system, man power and material can be saved like this, catch principal contradiction, system analysis computation efficiency can be greatly improved under the prerequisite ensureing claimed accuracy, thus effectively can carry out electromechanical transient simulation to large-scale electrical power system, the research of electromagnetic transient simulation and real-time simulation.

Technical scheme of the present invention is: the Dynamic Equivalence providing a kind of alternating current-direct current series-parallel connection bulk power grid based on engineer applied, is characterized in that described Dynamic Equivalence comprises the following steps:

1-1, the target studied according to the difference of electrical network characteristic, the object of dynamic equivalent research and equivalent rear grid simulation, be divided into electrical network two parts in district's external power grid and district by electrical network to be analyzed;

1-2, to the 500kV electrical network Detailed simulation in region, Equivalent Simplification is carried out to the low-voltage network in district's external power grid and district;

1-3, district's external power grid to be adopted based on the Dynamic Equivalence of experience, external power grid equivalent generator in district's is represented, obtains simplifying electrical network outside district;

The Dynamic Equivalence of 1-4, the equivalence of employing physically based deformation, carries out Equivalent Simplification to low-voltage network in district, obtains simplifying electrical network in final district;

1-5, after electrical network dynamic equivalent, respectively equivalent effect to be checked in district's external power grid dynamic equivalent and district;

1-6, simplifying electrical network and the dynamic response curve of actual electric network under same fault by comparing, checking the validity of whole dynamic equivalent Principles and ways.

Dynamic Equivalence Equivalent Simplification electrical network described in it replaces former electrical network to carry out electromagnetic transient simulation and Research on Real-time Simulation, analyze influencing each other between multiple-circuit line, and influencing each other near DC Line Fault and direct current drop point under AC fault between ac and dc systems.

Wherein, described Dynamic Equivalence selects AC fault near direct current locking and direct current drop point as fault set; Based on these fault disturbance, carry out the division of Coherent Generator Group and the dynamic equivalent of system, also check equivalent electrical network simultaneously and whether have under these fault disturbance with the identical dynamic response characteristic of original system.

The method of dynamic equivalent described in it ensure equivalent before and after, under the fault set of 500kV electrical network anticipation such as AC fault near direct current locking fault and direct current drop point in district, there is close dynamic response characteristic.

Dynamic response curve described in it at least comprises the merit angle change curve of generator, busbar voltage change curve and circuit active power change curve.

Concrete, in the Equivalent Simplification step of described district external power grid, in reserved area, all outsides of electrical network are by electric channel; Reserved area outer net delivers to whole DC line and the sending end current conversion station of district's Intranet; Reserved area outer net delivers to the extra-high-voltage alternating current power transmission sequence of district's Intranet; Reserved area outer net extra high voltage line and connected transformer station and power plant; The combination of the duty values such as foreign network low-voltage network employing and equivalent generator is simulated; District's external power grid is simulated the generator of the dynamic response of grid disturbance in district by equivalence; The direct current sending end of foreign network is directly connected with the equivalent generator of foreign network; All the other foreign network networks all simplify.

Wherein, infinitely great unit model all taked by described equivalent generator.

It carries out Equivalent Simplification to described low-voltage network, comprises and carries out equivalence to 220kV in electrical network in district and following low-voltage network.

In the Equivalent Simplification step of described district external power grid, adopt the equivalence method of physically based deformation equivalence, for the 220kV electrical network near direct current drop point, be expressed as the combination of generator and load; Be load for other 220kV network equivalence away from direct current; Its process is as follows: carry out short circuit calculation to given fault set, calculates bus residual voltage, the Region dividing of preliminary certainty equivalents model; Respectively access 220kV and with the capacity of the generating set of lower network and kinetic energy in statistical regions, and the proportion of all generating set capacities and kinetic energy in their territories, occupied area, in conjunction with residual voltage data, determine region 220kV system equivalent model; To different Equivalent Model, Confirming model parameter, obtains simplifying electrical network in district; By waiting performance number of duty value in adjustment district, make the calculation of tidal current in district before and after electrical network simplification consistent; Check the effect of Dynamic Equivalence Schemes again, contrast equivalent under identical disturbance before and after the merit angle change curve of important generator, busbar voltage change curve and circuit active power change curve, whether both observations close; Finally carry out Adaptability Analysis to simplification electrical network, assessment Dynamic Equivalence Schemes is in the validity that other fault types, operational mode change and rack to change etc. in situation.

Wherein, described equivalence is that the concrete steps of load are as follows:

10-1, Load flow calculation is carried out to former network, this 500kV node is connect multiple stage transformer parameter and is polymerized to an equivalent transformer by parallel way, send power under all transformer 220kV sides under adding up this node, after cumulative, be connected to equivalent transformer 220kV side as total load.If any the tertiary winding (35kV), statistics 35kV side reactive power compensation situation, is connected to equivalent 35 kV-side of transformer after cumulative;

10-2, to the laggard row Load flow calculation of equivalence, optimize and revise the equivalent load power value in 220kV side, ensure equivalent before and after system load flow basically identical;

10-3, carry out time-domain-simulation to system after equivalence, corresponding simulation curve before and after contrast is equivalent, Calculation Estimation index, as met the demands, adopts this model; If can not meet the demands, be then further analyzed, consider to adopt load to add the Dynamic Simulation Model of generator.

Equivalence described in it is that the concrete steps of generator application of load model are as follows:

The determination of 11-1, generator capacity and equivalent load capacity

Load flow calculation is carried out to former network, the multiple stage transformer parameter being connected to same bus in this 500kV transformer station is polymerized to an equivalent transformer by parallel way, under adding up this bus all transformer 220kV side, send power, 220kV side can be obtained and go out equivalence and exert oneself as P _∑+ jQ _∑;

If any the 35kV tertiary winding, statistics 35kV side reactive power compensation situation, is connected to equivalent 35 kV-side of transformer after cumulative;

The generator total capacity run in statistics access 220kV subregion, the generator total capacity run in described access 220kV subregion does not comprise the generator be directly connected with 500kV electrical network, obtains equivalent generator capacity, be designated as P after cumulative _g+ jQ _g;

Calculating equivalent load power is: P _l+ jQ _l=(P _∑+ P _g)+j (Q _∑+ Q _g),

The subtranient reactance x of 11-2, equivalent generator " _dthe mode of polymerization is adopted to obtain, namely

$x_d^{\′\′}=\frac{\underset{j\∈g}{\mathrm{\Σ}}{S}_j{x}_{\mathrm{dj}}^{\′\′}}{\underset{j\∈g}{\mathrm{\Σ}}{S}_j}---(2-1)$

In formula, g is generator sum in this subregion, S _jfor the rated capacity of jth platform generator, x " _djfor the subtranient reactance of jth platform generator.

The perunit value that to change into system reference capacity by this parameter be reference, namely

$x_{d\left(S_B\right)}^{\′\′}=x_d^{\′\′}\frac{S_B}{\underset{j\∈g}{\mathrm{\Σ}}{S}_j}---(2-2)$

The requirement that the parameter that generator boosting becomes keeps identical according to equivalent front and back busbar short-circuit electric current is determined;

Before equivalence in network, three-phase shortcircuit on this 500kV bus, adds up the short circuit current I that this bus 220kV provides ";

In flow calculation program BPA, calculate short circuit, do not consider influence on tidal flow, be i.e. E=1, then have

$x_{T1\left(S_B\right)}+x_{T2\left(S_B\right)}+x_{d\left(S_B\right)}^{\′\′}=\frac{1}{I^{\′\′}},$ Namely $x_{T2\left(S_B\right)}=\frac{1}{I^{\′\′}}-x_{T1\left(S_B\right)}-x_{d\left(S_B\right)}^{\′\′}$

In formula, S _bfor system reference capacity, be defaulted as 100MVA, and then calculate step-up transformer equivalent reactance x _t2;

For equivalent generator rotation inertia, following formula is adopted to calculate

$H=\mathrm{\Σ}{H}_N=(H_1\·\frac{S_1}{S_B}+H_2\·\frac{S_2}{S_B}+\·\·\·+H_N\·\frac{S_N}{S_B})\·\frac{S_B}{S_G}$ （2-3）

$=H_1\·\frac{S_1}{S_G}+H_2\·\frac{S_2}{S_G}+\·\·\·+H_N\·\frac{S_N}{S_G}$

In formula, H ₁, H ₂... H _nand S ₁, S ₂... S _nbe respectively moment of inertia and the capacity of generating set in 220kV subregion, S _gfor generating set capacity sum in 220kV subregion;

11-3, to the laggard row Load flow calculation of equivalence, optimize and revise the equivalent load power in 220kV side, meet equivalent before and after system load flow basically identical;

11-4, to the laggard row short circuit calculation of equivalence, optimize and revise generator step-up transformer reactance, meet equivalent before and after system short-circuit electric current basically identical;

11-5, carry out time-domain-simulation to system after equivalence, for corresponding simulation curve before and after equivalent, Calculation Estimation index, as met the demands, adopts this model; If can not meet the demands, be then further analyzed, consider to finely tune model.

Above-mentioned finely tunes model, comprises and weakens excitation system pressure regulation ability and adjust prime mover and speed regulator fm capacity.

Further, to when in described district, low-voltage network carries out Equivalent Simplification, apply short trouble to the associated bus in forecast failure collection or circuit, extracting part partial node is its residual voltage of node calculate representatively, according to the residual voltage situation of representation node, Further Division all subregion in district; For the subregion that residual voltage is lower, consider that equivalence is generator application of load; For the subregion that residual voltage is higher, first equivalence is load, then according to dynamic characteristic before and after equivalent be directly connected into the capacity of 500kV system unit and whether the selection of kinetic energy proportion situation increases the capacity and kinetic energy that are directly connected into 500kV system unit, namely be similar to and add equivalent machine, make the whole volume of equivalent rear generating set roughly the same with before equivalence with kinetic energy.

It is in order to determine the concrete equivalent scheme of described all subregion, to parton region adopt generator application of load and approximate add equivalent machine two kinds of equivalent schemes after the dynamic characteristic that obtains compare analysis; If compare analysis to the dynamic characteristic of certain subregion two kinds of equivalent schemes of difference, whole equivalence is that before the dynamic characteristic of load and equivalence, deviation is larger, before the dynamic characteristic of generator application of load and equivalence, fitting degree is better, then this subregion is adopted to the equivalent scheme of generator application of load; If compare analysis to the dynamic characteristic before and after certain subregion equivalence, all equivalence be fitting degree before dynamic characteristic and the equivalence of load with regard to better, then do not need equivalence to be generator application of load.

After to electrical network dynamic equivalent in described district external power grid dynamic equivalent and district, respectively equivalent effect is checked.

Described checks equivalent effect, comprises and carries out dynamic stability check.

It is to compare in district electrical network and electrical network in the district after equivalence under identical fault disturbance that dynamic stability described in it is checked, whether the change curve of generator's power and angle, busbar voltage and circuit active power is close, whether Changing Pattern is similar, to check the effect of dynamic equivalent.

When carrying out described dynamic stability and checking, choose the elements such as 500kV and the 1000kV bus near representative generator, direct current drop point, 500kV and 1000kV circuit; Under same fault disturbance, be plotted in together by the change curve of these element physical quantitys of equivalent front and back, whether the Changing Pattern compared in the initial value of two curves, steady-state value and simulation time section is consistent or close; If the two is close, show that simplify electrical network has identical dynamic response characteristic with former electrical network under fault disturbance, dynamic equivalent is respond well; If difference is comparatively large, then needs to revise equivalent scheme, re-start equivalence.

Further, whether described Dynamic Equivalence adopts relative root-mean-square error RMS index to weigh the dynamic response of equivalent front and back system under identical disturbance consistent; Described relative root-mean-square error RMS be equivalent before and after the root mean square ratio of curve each point before the root mean square of performance graph each point absolute error and equivalence, namely

Before and after computing system equivalence under same fault the relative root-mean-square error RMS of performance graph, if its error is within the acceptable range, then think that it meets the requirements;

When calculating relative root-mean-square error RMS, the performance graph only chosen before and after forecast failure line active power equivalence carries out quantitative analysis.

Compared with the prior art, advantage of the present invention is:

1. adopt the Dynamic Equivalence based on experience to carry out dynamic equivalent to district's external power grid, the Dynamic Equivalence of physically based deformation equivalence is adopted to carry out dynamic equivalent to electrical network in district, according to different electrical network characteristics, different dynamic equivalent Principles and ways should be adopted to electrical network in district's external power grid and district, can greatly reduce;

2. after in pair district's external power grid and district, electrical network carries out dynamic equivalent respectively, all equivalent effect is assessed, basically identical before busbar voltage, Line Flow and equivalence near direct current drop point, to occur near DC Line Fault and direct current drop point after AC fault, dynamic response also with equivalence before basically identical, and after operational mode and rack change, still there is adaptability;

3. the fitting degree between two curves is weighed in the relative root-mean-square error of employing (RMS), effectively can differentiate the difference of equivalent front and back dynamic response curve, assessment dynamic equivalent effect.

4. simplify electrical network in district and, while greatly simplifying system, also can obtain the simulation analysis result close with former actual electric network, simplify electrical network in district and former actual electric network can be replaced to carry out electromagnetic transient simulation research, there is good engineering practicability.

Accompanying drawing explanation

Fig. 1 is alternating current-direct current series-parallel connection bulk power grid Dynamic Equivalence schematic diagram of the present invention;

Fig. 2 is alternating current-direct current series-parallel connection bulk power grid dynamic equivalent step block diagram of the present invention;

Fig. 3 is a kind of example schematic of fault set;

Fig. 4 is the example schematic of the merit angle change curve of generator;

Fig. 5 is the example schematic of generator's power and angle swing curve;

Fig. 6 is the example schematic of busbar voltage change curve;

Fig. 7 is the example schematic of circuit active power change curve.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

In Fig. 1, in technical solution of the present invention, the operating conditions Shi Dui district external power grid of alternating current-direct current series-parallel connection bulk power grid Dynamic Equivalence adopts the Dynamic Equivalence based on experience, is represented by external power grid equivalent generator in district's, obtains simplifying electrical network outside district; Then adopt the Dynamic Equivalence of physically based deformation equivalence, Equivalent Simplification is carried out to low-voltage network in district, obtain simplifying electrical network in final district.

Simultaneously, in district's external power grid dynamic equivalent and district after electrical network dynamic equivalent, respectively equivalent effect is checked, simplifying electrical network and the dynamic response curve of actual electric network under same fault finally by comparing in district, checking the validity of whole dynamic equivalent Principles and ways.

As seen from the figure, whole dynamic equivalent process is divided into two stages to carry out, and adopts object in this way, is to make Dynamic Equivalence have good practicality in engineering.

The dynamic equivalent model setting up a large-scale electrical power system mainly reduces system state variables, reduces the dimension of system equation, and the principal character of retention system, simplifies external system depression of order according to certain requirement simultaneously.

Because dynamic equivalent carries out Equivalent Simplification to external system, make to wait the dynamic element number in valve system to greatly reduce, so quantity of state and the differential equation number of valve system such as to greatly reduce.The research that can replace original system with the research of reciprocity valve system, man power and material can be saved like this, catch principal contradiction, can greatly improve system analysis computation efficiency under the prerequisite ensureing claimed accuracy, thus effectively can carry out the research of electromechanical transient simulation, electromagnetic transient simulation and real-time simulation to large-scale electrical power system.

In Fig. 2, technical solution of the present invention provides a kind of Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied, it is characterized in that described Dynamic Equivalence comprises the following steps:

1-1, the target studied according to the difference of electrical network characteristic, the object of dynamic equivalent research and equivalent rear grid simulation, be divided into electrical network two parts in district's external power grid and district by electrical network to be analyzed;

1-2, to the 500kV electrical network Detailed simulation in region, Equivalent Simplification is carried out to the low-voltage network in district's external power grid and district;

1-3, district's external power grid to be adopted based on the Dynamic Equivalence of experience, external power grid equivalent generator in district's is represented, obtains simplifying electrical network outside district;

The Dynamic Equivalence of 1-4, the equivalence of employing physically based deformation, carries out Equivalent Simplification to low-voltage network in district, obtains simplifying electrical network in final district;

1-5, after electrical network dynamic equivalent, respectively equivalent effect to be checked in district's external power grid dynamic equivalent and district;

1-6, simplifying electrical network and the dynamic response curve of actual electric network under same fault by comparing, checking the validity of whole dynamic equivalent Principles and ways.

In technical solution of the present invention, former electrical network is replaced to carry out electromagnetic transient simulation and Research on Real-time Simulation with Equivalent Simplification electrical network, analyze influencing each other between multiple-circuit line, and influencing each other near DC Line Fault and direct current drop point under AC fault between ac and dc systems.

Wherein, above-mentioned Dynamic Equivalence selects AC fault near direct current locking and direct current drop point as fault set; Based on these fault disturbance, carry out the division of Coherent Generator Group and the dynamic equivalent of system, also check equivalent electrical network simultaneously and whether have under these fault disturbance with the identical dynamic response characteristic of original system.

In general, the simulation purposes that the forecast failure collection (referred to as being accident set) applying disturbance should simplify electrical network afterwards according to equivalence is reasonably selected.In the technical program, in the object Shi Jiang district external power grid of dynamic equivalent and district, the low-voltage network of electrical network inside simplifies, former electrical network is replaced to carry out electromagnetic transient simulation and Research on Real-time Simulation with Equivalent Simplification electrical network, analyze influencing each other between multiple-circuit line, and influencing each other under DC Line Fault and AC fault between ac and dc systems.Therefore AC fault near direct current locking and direct current drop point can be selected as forecast failure collection.Based on these fault disturbance, carry out the division of Coherent Generator Group and the dynamic equivalent of system, also check equivalent electrical network simultaneously and whether have under these fault disturbance with the identical dynamic response characteristic of original system.

As shown in Figure 3, because fault set is prior art in dynamic simulation and electrical network analysis, therefore it forms implication and concrete purposes no longer describes at this for a typical forecast failure collection.

The method of dynamic equivalent described in it ensure equivalent before and after, under the fault set of 500kV electrical network anticipation such as AC fault near direct current locking fault and direct current drop point in district, there is close dynamic response characteristic.

Dynamic response curve described in it at least comprises the merit angle change curve of generator, busbar voltage change curve and circuit active power change curve.

The example schematic of typical generator's power and angle change curve, generator's power and angle swing curve, busbar voltage change curve and circuit active power change curve as shown in Figures 4 to 7, because these figure are conventionally standard and adopt reference instrument to carry out testing obtained, therefore the implication that its each bar curve and waveform thereof comprise no longer describes at this.

Concrete, in the Equivalent Simplification step of described district external power grid, in reserved area, all outsides of electrical network are by electric channel; Reserved area outer net delivers to whole DC line and the sending end current conversion station of district's Intranet; Reserved area outer net delivers to the extra-high-voltage alternating current power transmission sequence of district's Intranet; Reserved area outer net extra high voltage line and connected transformer station and power plant; The combination of the duty values such as foreign network low-voltage network employing and equivalent generator is simulated; District's external power grid is simulated the generator of the dynamic response of grid disturbance in district by equivalence; The direct current sending end of foreign network is directly connected with the equivalent generator of foreign network; All the other foreign network networks all simplify.

Wherein, infinitely great unit model all taked by described equivalent generator.

It carries out Equivalent Simplification to described low-voltage network, comprises and carries out equivalence to 220kV in electrical network in district and following low-voltage network.

Further, in the Equivalent Simplification step of described district external power grid, adopt the equivalence method of physically based deformation equivalence, for the 220kV electrical network near direct current drop point, be expressed as the combination of generator and load; Be load for other 220kV network equivalence away from direct current; Its process is as follows:

Short circuit calculation is carried out to given fault set, calculates bus residual voltage, the Region dividing of preliminary certainty equivalents model; Respectively access 220kV and with the capacity of the generating set of lower network and kinetic energy in statistical regions, and the proportion of all generating set capacities and kinetic energy in their territories, occupied area, in conjunction with residual voltage data, determine region 220kV system equivalent model; To different Equivalent Model, Confirming model parameter, obtains simplifying electrical network in district; By waiting performance number of duty value in adjustment district, make the calculation of tidal current in district before and after electrical network simplification consistent; Check the effect of Dynamic Equivalence Schemes again, contrast equivalent under identical disturbance before and after the merit angle change curve of important generator, busbar voltage change curve and circuit active power change curve, whether both observations close; Finally carry out Adaptability Analysis to simplification electrical network, assessment Dynamic Equivalence Schemes is in the validity that other fault types, operational mode change and rack to change etc. in situation.

Wherein, A, described equivalence are that the concrete steps of load are as follows:

A1, Load flow calculation is carried out to former network, this 500kV node is connect multiple stage transformer parameter and is polymerized to an equivalent transformer by parallel way, send power under all transformer 220kV sides under adding up this node, after cumulative, be connected to equivalent transformer 220kV side as total load.If any the tertiary winding (35kV), statistics 35kV side reactive power compensation situation, is connected to equivalent 35 kV-side of transformer after cumulative;

A2, to the laggard row Load flow calculation of equivalence, optimize and revise the equivalent load power value in 220kV side, ensure equivalent before and after system load flow basically identical;

A3, carry out time-domain-simulation to system after equivalence, corresponding simulation curve before and after contrast is equivalent, Calculation Estimation index, as met the demands, adopts this model; If can not meet the demands, be then further analyzed, consider to adopt load to add the Dynamic Simulation Model of generator.

B, equivalence described in it are that the concrete steps of generator application of load model are as follows:

The determination of B1, generator capacity and equivalent load capacity

Load flow calculation is carried out to former network, the multiple stage transformer parameter being connected to same bus in this 500kV transformer station is polymerized to an equivalent transformer by parallel way, under adding up this bus all transformer 220kV side, send power, 220kV side can be obtained and go out equivalence and exert oneself as P _∑+ jQ _∑;

If any the 35kV tertiary winding, statistics 35kV side reactive power compensation situation, is connected to equivalent 35 kV-side of transformer after cumulative;

The generator total capacity run in statistics access 220kV subregion, the generator total capacity run in described access 220kV subregion does not comprise the generator be directly connected with 500kV electrical network, obtains equivalent generator capacity, be designated as P after cumulative _g+ jQ _g;

Calculating equivalent load power is: P _l+ jQ _l=(P _∑+ P _g)+j (Q _∑+ Q _g),

The subtranient reactance x of B2, equivalent generator " _dthe mode of polymerization is adopted to obtain, namely

$x_d^{\′\′}=\frac{\underset{j\∈g}{\mathrm{\Σ}}{S}_j{x}_{\mathrm{dj}}^{\′\′}}{\underset{j\∈g}{\mathrm{\Σ}}{S}_j}---(2-1)$

In formula, g is generator sum in this subregion, S _jfor the rated capacity of jth platform generator, x " _djfor the subtranient reactance of jth platform generator.

The perunit value that to change into system reference capacity by this parameter be reference, namely

$x_{d\left(S_B\right)}^{\′\′}=x_d^{\′\′}\frac{S_B}{\underset{j\∈g}{\mathrm{\Σ}}{S}_j}---(2-2)$

The requirement that the parameter that generator boosting becomes keeps identical according to equivalent front and back busbar short-circuit electric current is determined;

Before equivalence in network, three-phase shortcircuit on this 500kV bus, adds up the short circuit current I that this bus 220kV provides ";

In flow calculation program BPA, calculate short circuit, do not consider influence on tidal flow, be i.e. E=1, then have

$x_{T1\left(S_B\right)}+x_{T2\left(S_B\right)}+x_{d\left(S_B\right)}^{\′\′}=\frac{1}{I^{\′\′}},$ Namely $x_{T2\left(S_B\right)}=\frac{1}{I^{\′\′}}-x_{T1\left(S_B\right)}-x_{d\left(S_B\right)}^{\′\′}$

In formula, S _bfor system reference capacity, be defaulted as 100MVA, and then calculate step-up transformer equivalent reactance x _t2;

For equivalent generator rotation inertia, following formula is adopted to calculate

$H=\mathrm{\Σ}{H}_N=(H_1\·\frac{S_1}{S_B}+H_2\·\frac{S_2}{S_B}+\·\·\·+H_N\·\frac{S_N}{S_B})\·\frac{S_B}{S_G}$ （2-3）

$=H_1\·\frac{S_1}{S_G}+H_2\·\frac{S_2}{S_G}+\·\·\·+H_N\·\frac{S_N}{S_G}$

In formula, H ₁, H ₂... H _nand S ₁, S ₂... S _nbe respectively moment of inertia and the capacity of generating set in 220kV subregion, S _gfor generating set capacity sum in 220kV subregion;

B3, to the laggard row Load flow calculation of equivalence, optimize and revise the equivalent load power in 220kV side, meet equivalent before and after system load flow basically identical;

B4, to the laggard row short circuit calculation of equivalence, optimize and revise generator step-up transformer reactance, meet equivalent before and after system short-circuit electric current basically identical;

B5, carry out time-domain-simulation to system after equivalence, for corresponding simulation curve before and after equivalent, Calculation Estimation index, as met the demands, adopts this model; If can not meet the demands, be then further analyzed, consider to finely tune model.

Above-mentioned finely tunes model, comprises and weakens excitation system pressure regulation ability and adjust prime mover and speed regulator fm capacity.

Further, to when in described district, low-voltage network carries out Equivalent Simplification, apply short trouble to the associated bus in forecast failure collection or circuit, extracting part partial node is its residual voltage of node calculate representatively, according to the residual voltage situation of representation node, Further Division all subregion in district; For the subregion that residual voltage is lower, consider that equivalence is generator application of load; For the subregion that residual voltage is higher, first equivalence is load, then according to dynamic characteristic before and after equivalent be directly connected into the capacity of 500kV system unit and whether the selection of kinetic energy proportion situation increases the capacity and kinetic energy that are directly connected into 500kV system unit, namely be similar to and add equivalent machine, make the whole volume of equivalent rear generating set roughly the same with before equivalence with kinetic energy.

In order to determine the concrete equivalent scheme of described all subregion, to parton region adopt generator application of load and approximate add equivalent machine two kinds of equivalent schemes after the dynamic characteristic that obtains compare analysis; If compare analysis to the dynamic characteristic of certain subregion two kinds of equivalent schemes of difference, whole equivalence is that before the dynamic characteristic of load and equivalence, deviation is larger, before the dynamic characteristic of generator application of load and equivalence, fitting degree is better, then this subregion is adopted to the equivalent scheme of generator application of load; If compare analysis to the dynamic characteristic before and after certain subregion equivalence, all equivalence be fitting degree before dynamic characteristic and the equivalence of load with regard to better, then do not need equivalence to be generator application of load.

In Fig. 4 to Fig. 7, give the dynamic characteristic before and after certain subregion equivalence, the reality/thick line in figure is the actual dynamic characteristic before certain subregion equivalence, and the void/fine rule in figure is the dynamic characteristic after certain subregion equivalence.Identical with aforementioned reason, in this is no longer to figure, curve formation and waveform carry out describing.

From above-mentioned accompanying drawing, in case of a fault, simplify electrical network in district and still there is the dynamic response characteristic close with former electrical network, therefore in district, simplify the main dynamic characteristic that electrical network remains former electrical network, meet the needs of constant value principle requirement and Practical Project simulation study.

After above-mentioned simplification, compared with original actual electric network, simplify electrical network scale in district greatly to reduce, nodes is contracted to original 4.4%, the parts numbers such as generator, circuit, transformer also significantly reduce, generator number is reduced to original 9.7%, and circuit number is reduced to original 4.7%, and transformer number is reduced to original 4%.Therefore dynamic equivalent is carried out to original actual electric network, significantly can reduce system scale.

On the basis of having checked electrical network dynamic equivalent effect in district's external power grid dynamic equivalent and district respectively, simplify trend and the dynamic response characteristic of electrical network in more original actual electric network and district, to assess the resultant effect of dynamic equivalent.

One, Static Power Flow comparison:

The active power of contrast equivalent front and back reserved line and busbar voltage, if its error within the acceptable range, then illustrate that the equivalent effect of Static Power Flow is fine, the error of equivalent front and back stability Calculation initial value is less.

Known by the ultra high voltage rack tidal current chart simplifying electrical network in more original actual electric network and district, retain busbar voltage level, reservation ultra high voltage and the distribution of 500kV major network trend before and after equivalent basically identical.

Two, dynamic stability is checked:

Compare simplifying the dynamic response curve of electrical network under same fault in original actual electric network and district, comprise busbar voltage change curve and circuit active power change curve near direct current drop point, as can be seen from the curve chart shown in Fig. 4 to 7, before and after equivalent, system has close dynamic response characteristic, simplify the main dynamic characteristic that electrical network remains original actual electric network in district, meet the needs of constant value principle requirement and Practical Project simulation study.

From Fig. 4 to Fig. 7, basically identical before busbar voltage, Line Flow and equivalence near direct current drop point, occur near DC Line Fault and direct current drop point after AC fault, dynamic response also with equivalence before basically identical, and after operational mode and rack change, still there is adaptability.

In addition, after to electrical network dynamic equivalent in described district external power grid dynamic equivalent and district, all should check equivalent effect respectively.

Described checks equivalent effect, comprises and carries out dynamic stability check.It is to compare in district electrical network and electrical network in the district after equivalence under identical fault disturbance that dynamic stability described in it is checked, whether the change curve of generator's power and angle, busbar voltage and circuit active power is close, whether Changing Pattern is similar, to check the effect of dynamic equivalent.

Concrete, when carrying out described dynamic stability and checking, choose the elements such as 500kV and the 1000kV bus near representative generator, direct current drop point, 500kV and 1000kV circuit; Under same fault disturbance, be plotted in together by the change curve of these element physical quantitys of equivalent front and back, whether the Changing Pattern compared in the initial value of two curves, steady-state value and simulation time section is consistent or close; If the two is close, show that simplify electrical network has identical dynamic response characteristic with former electrical network under fault disturbance, dynamic equivalent is respond well; If difference is comparatively large, then needs to revise equivalent scheme, re-start equivalence.

Further, whether described Dynamic Equivalence adopts relative root-mean-square error RMS index to weigh the dynamic response of equivalent front and back system under identical disturbance consistent; Described relative root-mean-square error RMS be equivalent before and after the root mean square ratio of curve each point before the root mean square of performance graph each point absolute error and equivalence, namely

Before and after computing system equivalence under same fault the relative root-mean-square error RMS of performance graph, if its error is within the acceptable range, then think that it meets the requirements;

When calculating relative root-mean-square error RMS, the performance graph only chosen before and after forecast failure line active power equivalence carries out quantitative analysis.

An actual relative root-mean-square error RMS result of calculation is as follows:

Visible, near fault point, the RMS value of circuit active power change curve is all less, shows that curve is better, indicates equivalent front and back system further quantitatively and have close dynamic response under these disturbances.

The Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied provided by the present invention, its technical scheme carries out Equivalent Simplification to low-pressure system in district's external power grid and district, quantity of state and the differential equation number of valve system such as to greatly reduce, the research to original system is replaced with the research of reciprocity valve system, man power and material can be saved, catch principal contradiction, system analysis computation efficiency can be greatly improved under the prerequisite ensureing claimed accuracy, thus effectively can carry out electromechanical transient simulation to large-scale electrical power system, the research of electromagnetic transient simulation and real-time simulation.

To carry out in district's external power grid dynamic equivalent and district after electrical network dynamic equivalent to actual electric network, obtain simplifying electrical network in district.Simplify in district in electrical network, near direct current drop point, busbar voltage, Line Flow and reality are basically identical, to occur near DC Line Fault and direct current drop point after AC fault, dynamic response is also basically identical with actual electric network, and calculate the RMS value of equivalent front and back dynamic response curve, further illustrate equivalent front and back system, under these disturbances, there is close dynamic response.Simplify electrical network while greatly simplifying system, also can obtain the simulation analysis result close with former actual electric network, simplify electrical network in district and original actual electric network can be replaced to carry out electromagnetic transient simulation research, there is good engineering practicability.

The present invention can be widely used in the analysis of series-parallel connection bulk power grid, the scheduling of calculating and electrical network, management domain.

Claims (5)

1. the Dynamic Equivalence based on the alternating current-direct current series-parallel connection bulk power grid of engineer applied, described Dynamic Equivalence comprises difference, the object of dynamic equivalent research and the target of equivalent rear grid simulation research according to electrical network characteristic, electrical network to be analyzed is divided into electrical network two parts in district's external power grid and district; To the 500kV electrical network Detailed simulation in region, Equivalent Simplification is carried out to the low-voltage network in district's external power grid and district; Dynamic Equivalence based on experience is adopted to district's external power grid, external power grid equivalent generator in district's is represented, obtains simplifying electrical network outside district; Adopt the Dynamic Equivalence of physically based deformation equivalence, Equivalent Simplification is carried out to low-voltage network in district, obtain simplifying electrical network in final district; It is characterized in that:

Described Dynamic Equivalence after electrical network dynamic equivalent, is checked equivalent effect respectively in district's external power grid dynamic equivalent and district;

Simplifying electrical network and the dynamic response curve of actual electric network under same fault by comparing, checking the validity of whole dynamic equivalent Principles and ways;

Wherein, the method for described dynamic equivalent ensure equivalent before and after, under the fault set of 500kV electrical network anticipation such as AC fault near direct current locking fault and direct current drop point in district, there is close dynamic response characteristic;

In the Equivalent Simplification step of described district external power grid, infinitely great unit model all taked by the equivalent generator described in it;

Described Dynamic Equivalence carries out Equivalent Simplification to described low-voltage network, comprises and carries out equivalence to 220kV in electrical network in district and following low-voltage network; It is in order to determine the concrete equivalent scheme of all subregion, to parton region adopt generator application of load and approximate add equivalent machine two kinds of equivalent schemes after the dynamic characteristic that obtains compare analysis;

If compare analysis to the dynamic characteristic of certain subregion two kinds of equivalent schemes of difference, whole equivalence is that before the dynamic characteristic of load and equivalence, deviation is larger, before the dynamic characteristic of generator application of load and equivalence, fitting degree is better, then this subregion is adopted to the equivalent scheme of generator application of load;

If compare analysis to the dynamic characteristic before and after certain subregion equivalence, all equivalence be fitting degree before dynamic characteristic and the equivalence of load with regard to better, then do not need equivalence to be generator application of load;

To when in described district, low-voltage network carries out Equivalent Simplification, short trouble is applied to the associated bus in forecast failure collection or circuit, extracting part partial node is its residual voltage of node calculate representatively, according to the residual voltage situation of representation node, and Further Division all subregion in district;

For the subregion that residual voltage is lower, consider that equivalence is generator application of load;

For the subregion that residual voltage is higher, first equivalence is load, then according to dynamic characteristic before and after equivalent be directly connected into the capacity of 500kV system unit and whether the selection of kinetic energy proportion situation increases the capacity and kinetic energy that are directly connected into 500kV system unit, namely be similar to and add equivalent machine, make the whole volume of equivalent rear generating set roughly the same with before equivalence with kinetic energy.

2., according to the Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied according to claim 1, it is characterized in that after to electrical network dynamic equivalent in described district external power grid dynamic equivalent and district, checking equivalent effect respectively; Described checks equivalent effect, comprises and carries out dynamic stability check.

3. according to the Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied according to claim 2, it is characterized in that described dynamic stability is checked is to compare in district electrical network and electrical network in the district after equivalence under identical fault disturbance, whether the change curve of generator's power and angle, busbar voltage and circuit active power is close, whether Changing Pattern is similar, to check the effect of dynamic equivalent.

4. according to the Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied according to claim 2, it is characterized in that, when carrying out described dynamic stability and checking, choosing the elements such as 500kV and the 1000kV bus near representative generator, direct current drop point, 500kV and 1000kV circuit; Under same fault disturbance, be plotted in together by the change curve of these element physical quantitys of equivalent front and back, whether the Changing Pattern compared in the initial value of two curves, steady-state value and simulation time section is consistent or close;

If the two is close, show that simplify electrical network has identical dynamic response characteristic with former electrical network under fault disturbance, dynamic equivalent is respond well;

If difference is comparatively large, then needs to revise equivalent scheme, re-start equivalence.

5., according to the Dynamic Equivalence of the alternating current-direct current series-parallel connection bulk power grid based on engineer applied according to claim 1, whether unanimously it is characterized in that described Dynamic Equivalence adopts relative root-mean-square error RMS index to weigh the dynamic response of equivalent front and back system under identical disturbance;

When calculating relative root-mean-square error RMS, the performance graph only chosen before and after forecast failure line active power equivalence carries out quantitative analysis.