CN103036230A - Dynamic equivalence method of alternating-current-direct-current serial-parallel large power system based on engineering application - Google Patents

Abstract

The invention discloses a dynamic equivalence method of an alternating-current-direct-current serial-parallel large power system based on engineering application, and belongs to the field of electric transformation and distribution. The method of the alternating-current-direct-current serial-parallel large power system based on the engineering application comprises dividing a power grid to be analysed into two parts including an external power grid and an internal power grid, detailedly imitating a 500 kV power grid inside an area, carrying out equivalence simplification on the external power grid and an internal low voltage power grid, obtaining an external simplified power grid from the external power grid through an equivalence generator by using a dynamic equivalence method based on experience, obtaining a final internal simplified power grid by carrying out equivalence simplification on the internal low voltage power grid by using the dynamic equivalence method based on physical equivalent, respectively checking equivalence effects after the external power grid and the internal power grid are in dynamic equivalence, and checking effectiveness of the entire dynamic equivalence principle and method through comparing dynamic response curves of a simplified power grid and an actual power grid in the same fault. The method of the alternating-current-direct-current serial-parallel large power system based on the engineering application has the advantages of reducing quantity of equivalence system state and the number of differential equation, improving system analysis computational efficiency, and being capable of being widely used for analytical calculation of a serial-parallel large power grid and used in the field of dispatching management of power grids.

Description

A kind of Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering

Technical field

The invention belongs to change, distribution field, relate in particular to a kind of Dynamic Equivalence for the large electrical network of alternating current-direct current series-parallel connection.

Background technology

At present, China's electric power system develops rapidly, and transferring electricity from the west to the east, interconnected, the alternating current-direct current in north and south are united transmission of electricity and large area networking operation so that system is day by day huge, complicated.Even when carrying out the 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, desired Computer Storage amount is very large, computing time is also longer, and during the machine of computer, internal memory, data prepare etc. often to be not enough to satisfy the analysis and research of complicated large-scale power system, also need know the full detail (parameter and the operation conditions that comprise all elements in the system) of whole system, thereby seem difficult.Simultaneously a large amount of large power power electronic appliances, as: direct current transportation, SVC(StaticVar Compensator, Static Var Compensator), TCSC(Thyristor Controlled SeriesCompensation thyristor controlled series capacitor compensation technique) extensive use of equipment and various fast automatic control device so that the dynamic characteristic of electrical network is increasingly sophisticated.

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

When analysis and research large-scale electrical power system dynamic behaviour, often also just to wherein part zone is interested, this subregion need to be described the dynamic behaviour with accurate reflection system in detail, claims that usually this subregion is built-in system (Study system); And to the remainder zone, only consider it in the research to the impact of built-in system, and itself needn't describe in detail, can carry out depression of order to simplify, the zone that this part work done in the manner of a certain author is simplified is called external system.

Can give prominence to principal contradiction by system simplification, for the principal character of grasping Study system, be very necessary.This reservation Study system is constant, and external system is being guaranteed that under the undistorted condition of its dynamic response to Study system, the process of simplifying is called dynamic equivalent.

In history large-scale power system there are many experimental Dynamic Equivalences.For example, will represent with one (or several) equivalent generator or equivalent load away from generator, load and the network of survey region, even be reduced to infinite busbar.Correspondingly network is also simplified, the cancellation great deal of nodes, and the nonlinear-load on the origin node also is displaced to the reservation node and gets on.But the shortcoming of these experience equivalences is:

(1) greatly depends on experience and subjective judgement;

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

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

Shen Qing Publication day is on December 14th, 2011, application publication number is to disclose a kind of power grid equivalence method in the Chinese invention patent application of CN 102280884A, it is simplified generating set external system to be studied, is infinite busbar and dynamic unit with distant place complex large power grid and near-end with bus bar machine group difference equivalence.The method is fit to be applied to the aspects such as the check of Modeling of excitation system time Domain Parameter and PSS parameter optimization, can better reflect the external system characteristic, when simplifying electric system simulation calculating, improves the simulation calculation precision.But it can only be applicable to the Modeling of excitation system of generating set, can't be applied in the dynamic equivalent calculating of the large electrical network of alternating current-direct current series-parallel connection, also the problem for considering that engineering is used.

Summary of the invention

Technical problem to be solved by this invention provides a kind of Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering, it carries out Equivalent Simplification to low-pressure system in district's external power grid and the district, quantity of state and the differential equation number of valve system such as greatly reduce, replace research to original system with the research of reciprocity valve system, can save the man power and material like this, caught principal contradiction, under the prerequisite that guarantees claimed accuracy, can greatly improve system analysis computation efficient, thereby can effectively 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: a kind of Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering is provided, it is characterized in that described Dynamic Equivalence comprises the following steps:

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

1-2, to the zone in the 500kV electrical network simulate in detail, to the district external power grid and the district in the low-voltage network carry out Equivalent Simplification;

1-3, district's external power grid is adopted Dynamic Equivalence based on experience, will distinguish external power grid and represent with equivalent generator, obtain distinguishing outer simplification electrical network;

1-4, adopt the Dynamic Equivalence based on the physics equivalence, carry out Equivalent Simplification to distinguishing interior low-voltage network, obtain simplification electrical network final district in;

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

1-6, by relatively simplifying electrical network and the actual electric network dynamic response curve under same fault, check the validity of whole dynamic equivalent principle and method.

Its described Dynamic Equivalence replaces former electrical network to carry out electromagnetic transient simulation and Research on Real-time Simulation with the Equivalent Simplification electrical network, analyze influencing each other between many times direct currents, and near influencing each other between the ac and dc systems under AC fault DC Line Fault and the direct current drop point.

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

The method of its described dynamic equivalent guarantees equivalent front and back, and the 500kV electrical network has close dynamic response characteristic in the district under near the fault collection of the anticipations such as AC fault direct current locking fault and the direct current drop point.

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

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

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

It carries out Equivalent Simplification to described low-voltage network, comprises that 220kV and following low-voltage network carry out equivalence in the interior electrical network to distinguishing.

In the Equivalent Simplification step of described district external power grid, adopt the equivalence method based on the physics equivalence, near the 220kV electrical network for the direct current drop point is expressed as the combination of generator and load; Be load for other 220kV network equivalence away from direct current; Its process is as follows: given fault collection is carried out short circuit calculation, calculate the bus residual voltage, the zone of preliminary certainty equivalents model is divided; Access 220kV and with capacity and the kinetic energy of the generating set of lower network in the statistical regions respectively, and the proportion of all generating set capacities and kinetic energy in their territories, occupied area, in conjunction with the residual voltage data, definite area 220kV system equivalent model; To different Equivalent Model, determine model parameter, obtain distinguishing interior simplification electrical network; By adjusting the performance number that waits duty value in the district, so that the calculation of tidal current before and after electrical network is simplified in the district is consistent; Check again the effect of Dynamic Equivalence Schemes, contrast under the identical disturbance merit angle change curve, busbar voltage change curve and the circuit active power change curve of generator important before and after equivalent, observe both and whether approach; Carry out Adaptability Analysis to simplifying electrical network at last, the assessment Dynamic Equivalence Schemes changes and rack the validity in the situation such as change in other fault types, operational mode.

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

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

10-2, the laggard row trend of equivalence is calculated, is optimized and revised the equivalent load power value of 220kV side, guarantee equivalent before and after system load flow basically identical;

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

Its described equivalence is that the concrete steps of generator application of load model are as follows:

Determining of 11-1, generator capacity and equivalent load capacity

Former network is carried out trend calculate, many transformer parameters that are connected to same bus in this 500kV transformer station are polymerized to an equivalent transformer by parallel way, add up under all transformer 220kV sides of this bus and send power, can get the 220kV side and go out equivalence and exert oneself and be 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 adding up;

The generator total capacity of moving in the statistics access 220kV subregion, the generator total capacity of moving in the described access 220kV subregion does not comprise the generator that directly links to each other with the 500kV electrical network, obtains equivalent generator capacity after adding up, and is designated as P _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 " _dAdopt the mode of polymerization 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 the formula, g is generator sum in this subregion, S _jBe the rated capacity of j platform generator, x " _DjIt is the subtranient reactance of j platform generator.

This parameter is changed into perunit value take system's reference capacity as reference, namely

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

The generator parameter that becomes of boosting keeps identical requirement to determine according to busbar short-circuit electric current before and after equivalent;

In the network, three-phase shortcircuit on this 500kV bus is added up the short circuit current I that this bus 220kV provides before equivalent ";

Calculate short circuit in flow calculation program BPA, do not consider influence on tidal flow, namely E=1 then has

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

In the formula, S _BFor system's reference capacity, be defaulted as 100MVA, and then calculate step-up transformer equivalent reactance x _T2

For equivalent generator moment of inertia, adopt following formula 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 the formula, H ₁, H ₂... H _NAnd S ₁, S ₂... S _NBe respectively moment of inertia and the capacity of generating set in the 220kV subregion, S _GBe generating set capacity sum in the 220kV subregion;

11-3, the laggard row trend of equivalence is calculated, is optimized and revised the equivalent load power of 220kV side, satisfy equivalent before and after system load flow basically identical;

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

11-5, system behind the equivalence is carried out time-domain-simulation, for corresponding simulation curve before and after equivalent, calculate evaluation index, as meet the demands, adopt this model; If can not meet the demands, then be further analyzed, consider model is finely tuned.

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

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

It is in order to determine the concrete equivalent scheme of described all subregion, to adopting the generator application of load and approximately add the dynamic characteristic that obtains after two kinds of equivalent schemes of equivalent machine and compare analysis in the parton zone; If the dynamic characteristic to two kinds of equivalent schemes of difference of certain subregion compares analysis, all equivalence is larger with equivalent front deviation for the dynamic characteristic of load, the dynamic characteristic of generator application of load is better with equivalent front fitting degree, then this subregion is adopted the equivalent scheme of generator application of load; If the dynamic characteristic before and after certain subregion equivalence is compared analysis, all equivalence is just better with equivalent front fitting degree for the dynamic characteristic of load, does not then need the equivalent generator application of load that is.

In to described district external power grid dynamic equivalent and district, after the electrical network dynamic equivalent, respectively equivalent effect is checked.

Described equivalent effect is checked, comprise that carrying out dynamic stability checks.

Its described dynamic stability check be in the district that relatively distinguishes behind interior electrical network and the equivalence electrical network under identical fault disturbance, whether the change curve of generator's power and angle, busbar voltage and circuit active power approaches, whether Changing Pattern is similar, with the effect of check dynamic equivalent.

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

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

The relative root-mean-square error RMS of computing system equivalence front and back performance graph under same fault if its error within the acceptable range, thinks that then it meets the requirements;

When calculating relative root-mean-square error RMS, the performance graph of only choosing circuit active power equivalence front and back under the forecast failure carries out quantitative analysis.

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

1. adopt the Dynamic Equivalence based on experience that district's external power grid is carried out dynamic equivalent, employing is carried out dynamic equivalent based on the Dynamic Equivalence of physics equivalence to distinguishing interior electrical network, according to different electrical network characteristics, should adopt different dynamic equivalent principle and method to electrical network in district's external power grid and the district, can greatly reduce;

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

3. adopt relative root-mean-square error (RMS) to weigh two fitting degree between the curve, can effectively differentiate the difference of equivalent front and back dynamic response curve, assessment dynamic equivalent effect.

4. simplify the interior electrical network in district when greatly simplifying system, also can obtain the simulation analysis result close with former actual electric network, simplify electrical network in the district and can replace former actual electric network to carry out electromagnetic transient simulation research, have good engineering practicability.

Description of drawings

Fig. 1 is the large electrical network Dynamic Equivalence of alternating current-direct current series-parallel connection of the present invention schematic diagram;

Fig. 2 is the large electrical network dynamic equivalent of alternating current-direct current series-parallel connection of the present invention step block diagram;

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

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

The present invention will be further described below in conjunction with accompanying drawing.

Among Fig. 1, the crucial thinking of the large electrical network Dynamic Equivalence of alternating current-direct current series-parallel connection is to the Dynamic Equivalence of district's external power grid employing based on experience in the technical solution of the present invention, will distinguish external power grid and represent with equivalent generator, obtains distinguishing outer simplification electrical network; Then adopt the Dynamic Equivalence based on the physics equivalence, carry out Equivalent Simplification to distinguishing interior low-voltage network, obtain simplifying in the final district electrical network.

Simultaneously, in district's external power grid dynamic equivalent and district after the electrical network dynamic equivalent, respectively equivalent effect is checked, by relatively simplifying electrical network and the dynamic response curve of actual electric network under same fault in the district, check the validity of whole dynamic equivalent principle and method at last.

As seen from the figure, whole dynamic equivalent process is divided into two stages carries out, and adopts the purpose of this mode, is in order to make Dynamic Equivalence have good practicality in engineering.

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

Because dynamic equivalent carries out Equivalent Simplification to external system, so that wait the dynamic element number in the valve system to greatly reduce, so quantity of state and the differential equation number of valve system such as greatly reduce.Can replace with the research of reciprocity valve system the research to original system, can save the man power and material like this, caught principal contradiction, under the prerequisite that guarantees claimed accuracy, system analysis computation efficient can be greatly improved, thereby the research of electromechanical transient simulation, electromagnetic transient simulation and real-time simulation can be effectively carried out to large-scale electrical power system.

Among Fig. 2, technical solution of the present invention provides a kind of Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering, it is characterized in that described Dynamic Equivalence comprises the following steps:

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

1-2, to the zone in the 500kV electrical network simulate in detail, to the district external power grid and the district in the low-voltage network carry out Equivalent Simplification;

1-3, district's external power grid is adopted Dynamic Equivalence based on experience, will distinguish external power grid and represent with equivalent generator, obtain distinguishing outer simplification electrical network;

1-4, adopt the Dynamic Equivalence based on the physics equivalence, carry out Equivalent Simplification to distinguishing interior low-voltage network, obtain simplification electrical network final district in;

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

1-6, by relatively simplifying electrical network and the actual electric network dynamic response curve under same fault, check the validity of whole dynamic equivalent principle and method.

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

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

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

A typical forecast failure collection as shown in Figure 3 because fault integrates in dynamic simulation and electrical network analysis as prior art, thus its consist of implication and specifically purposes no longer narrate at this.

The method of its described dynamic equivalent guarantees equivalent front and back, and the 500kV electrical network has close dynamic response characteristic in the district under near the fault collection of the anticipations such as AC fault direct current locking fault and the direct current drop point.

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

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 such as Fig. 4 are to shown in Figure 7, because these figure are according to the prior art standard and to adopt reference instrument to test resulting, therefore the implication that its each bar curve and waveform thereof comprise is no longer narrated at this.

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

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

It carries out Equivalent Simplification to described low-voltage network, comprises that 220kV and following low-voltage network carry out equivalence in the interior electrical network to distinguishing.

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

Given fault collection is carried out short circuit calculation, calculate the bus residual voltage, the zone of preliminary certainty equivalents model is divided; Access 220kV and with capacity and the kinetic energy of the generating set of lower network in the statistical regions respectively, and the proportion of all generating set capacities and kinetic energy in their territories, occupied area, in conjunction with the residual voltage data, definite area 220kV system equivalent model; To different Equivalent Model, determine model parameter, obtain distinguishing interior simplification electrical network; By adjusting the performance number that waits duty value in the district, so that the calculation of tidal current before and after electrical network is simplified in the district is consistent; Check again the effect of Dynamic Equivalence Schemes, contrast under the identical disturbance merit angle change curve, busbar voltage change curve and the circuit active power change curve of generator important before and after equivalent, observe both and whether approach; Carry out Adaptability Analysis to simplifying electrical network at last, the assessment Dynamic Equivalence Schemes changes and rack the validity in the situation such as change in other fault types, operational mode.

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

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

A2, the laggard row trend of equivalence is calculated, is optimized and revised the equivalent load power value of 220kV side, guarantee equivalent before and after system load flow basically identical;

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

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

Determining of B1, generator capacity and equivalent load capacity

Former network is carried out trend calculate, many transformer parameters that are connected to same bus in this 500kV transformer station are polymerized to an equivalent transformer by parallel way, add up under all transformer 220kV sides of this bus and send power, can get the 220kV side and go out equivalence and exert oneself and be 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 adding up;

The generator total capacity of moving in the statistics access 220kV subregion, the generator total capacity of moving in the described access 220kV subregion does not comprise the generator that directly links to each other with the 500kV electrical network, obtains equivalent generator capacity after adding up, and is designated as P _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 " _dAdopt the mode of polymerization 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 the formula, g is generator sum in this subregion, S _jBe the rated capacity of j platform generator, x " _DjIt is the subtranient reactance of j platform generator.

This parameter is changed into perunit value take system's reference capacity as reference, namely

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

The generator parameter that becomes of boosting keeps identical requirement to determine according to busbar short-circuit electric current before and after equivalent;

In the network, three-phase shortcircuit on this 500kV bus is added up the short circuit current I that this bus 220kV provides before equivalent ";

Calculate short circuit in flow calculation program BPA, do not consider influence on tidal flow, namely E=1 then has

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

In the formula, S _BFor system's reference capacity, be defaulted as 100MVA, and then calculate step-up transformer equivalent reactance x _T2

For equivalent generator moment of inertia, adopt following formula 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 the formula, H ₁, H ₂... H _NAnd S ₁, S ₂... S _NBe respectively moment of inertia and the capacity of generating set in the 220kV subregion, S _GBe generating set capacity sum in the 220kV subregion;

B3, the laggard row trend of equivalence is calculated, is optimized and revised the equivalent load power of 220kV side, satisfy equivalent before and after system load flow basically identical;

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

B5, system behind the equivalence is carried out time-domain-simulation, for corresponding simulation curve before and after equivalent, calculate evaluation index, as meet the demands, adopt this model; If can not meet the demands, then be further analyzed, consider model is finely tuned.

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

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

In order to determine the concrete equivalent scheme of described all subregion, to adopting the generator application of load and approximately add the dynamic characteristic that obtains after two kinds of equivalent schemes of equivalent machine and compare analysis in the parton zone; If the dynamic characteristic to two kinds of equivalent schemes of difference of certain subregion compares analysis, all equivalence is larger with equivalent front deviation for the dynamic characteristic of load, the dynamic characteristic of generator application of load is better with equivalent front fitting degree, then this subregion is adopted the equivalent scheme of generator application of load; If the dynamic characteristic before and after certain subregion equivalence is compared analysis, all equivalence is just better with equivalent front fitting degree for the dynamic characteristic of load, does not then need the equivalent generator application of load that is.

In Fig. 4 to Fig. 7, provided the dynamic characteristic of certain subregion equivalence front and back, the reality/thick line among the figure is the actual dynamic characteristic before certain subregion equivalence, the void/fine rule among the figure is the dynamic characteristic behind certain subregion equivalence.Identical with aforementioned reason, this no longer to figure in curve consist of and waveform is narrated.

By above-mentioned accompanying drawing as can be known, under failure condition, simplify electrical network in the district and still have the dynamic response characteristic close with former electrical network, therefore simplify the main dynamic characteristic that electrical network has kept former electrical network in the district, satisfy the needs of equivalent principles and requirements and Practical Project simulation study.

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

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

One, Static Power Flow comparison:

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

Ultra high voltage rack tidal current chart by simplifying electrical network in more original actual electric network and the district keeps the busbar voltage level before and after equivalent, keeps ultra high voltage and 500kV major network trend distributes basically identical as can be known.

Two, dynamic stability is checked:

Compare simplifying the dynamic response curve of electrical network under same fault in original actual electric network and the district, comprise near the busbar voltage change curve of direct current drop point and circuit active power change curve, can be found out by the curve chart shown in Fig. 4 to 7, system has close dynamic response characteristic before and after equivalent, simplify the main dynamic characteristic that electrical network has kept original actual electric network in the district, satisfy the needs of equivalent principles and requirements and Practical Project simulation study.

By Fig. 4 to Fig. 7 as can be known, basically identical before busbar voltage, Line Flow and the equivalence near the direct current drop point, behind the AC fault, dynamic response is also with equivalent front basically identical near generation DC Line Fault and the direct current drop point, and after operational mode and rack change, still has adaptability.

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

Described equivalent effect is checked, comprise that carrying out dynamic stability checks.Its described dynamic stability check be in the district that relatively distinguishes behind interior electrical network and the equivalence electrical network under identical fault disturbance, whether the change curve of generator's power and angle, busbar voltage and circuit active power approaches, whether Changing Pattern is similar, with the effect of check dynamic equivalent.

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

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

The relative root-mean-square error RMS of computing system equivalence front and back performance graph under same fault if its error within the acceptable range, thinks that then it meets the requirements;

When calculating relative root-mean-square error RMS, the performance graph of only choosing circuit active power equivalence front and back under the forecast failure carries out quantitative analysis.

The relative root-mean-square error RMS result of calculation of a reality is as follows:

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

The Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering provided by the present invention, its technical scheme is carried out Equivalent Simplification to low-pressure system in district's external power grid and the district, quantity of state and the differential equation number of valve system such as greatly reduce, replace research to original system with the research of reciprocity valve system, can save the man power and material, caught principal contradiction, under the prerequisite that guarantees claimed accuracy, can greatly improve system analysis computation efficient, thereby can effectively carry out electromechanical transient simulation to large-scale electrical power system, the research of electromagnetic transient simulation and real-time simulation.

Behind electrical network dynamic equivalent in actual electric network district external power grid dynamic equivalent and the district, obtain distinguishing interior simplification electrical network.In the district, simplify in the electrical network, busbar voltage, Line Flow and actual basically identical near the direct current drop point, after near the AC fault of DC Line Fault and direct current drop point occurs, dynamic response is also basically identical with actual electric network, and the RMS value of the equivalent front and back of calculating dynamic response curve, further illustrate equivalence front and back system and under these disturbances, have close dynamic response.Simplify electrical network when greatly simplifying system, also can obtain the simulation analysis result close with former actual electric network, simplify electrical network in the district and can replace original actual electric network to carry out electromagnetic transient simulation research, have good engineering practicability.

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

Claims (18)

1. the Dynamic Equivalence based on the large electrical network of alternating current-direct current series-parallel connection of engineering application is characterized in that described Dynamic Equivalence comprises the following steps:

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

1-2, to the zone in the 500kV electrical network simulate in detail, to the district external power grid and the district in the low-voltage network carry out Equivalent Simplification;

1-3, district's external power grid is adopted Dynamic Equivalence based on experience, will distinguish external power grid and represent with equivalent generator, obtain distinguishing outer simplification electrical network;

1-4, adopt the Dynamic Equivalence based on the physics equivalence, carry out Equivalent Simplification to distinguishing interior low-voltage network, obtain simplification electrical network final district in;

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

1-6, by relatively simplifying electrical network and the actual electric network dynamic response curve under same fault, check the validity of whole dynamic equivalent principle and method.

2. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, it is characterized in that described Dynamic Equivalence replaces former electrical network to carry out electromagnetic transient simulation and Research on Real-time Simulation with the Equivalent Simplification electrical network, analyze influencing each other between many times direct currents, and near influencing each other between the ac and dc systems under AC fault DC Line Fault and the direct current drop point.

3. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, it is characterized in that described Dynamic Equivalence selects near direct current locking and the direct current drop point AC fault as the fault collection; Based on these fault disturbances, carry out the division of Coherent Generator Group and the dynamic equivalent of system, also check equivalent electrical network simultaneously and under these fault disturbances, whether have with the identical dynamic response characteristic of original system.

4. according to the Dynamic Equivalence of claim 1 or the 3 described large electrical networks of alternating current-direct current series-parallel connection of using based on engineering, the method that it is characterized in that described dynamic equivalent guarantees equivalent front and back, and the 500kV electrical network has close dynamic response characteristic in the district under near the fault collection of the anticipations such as AC fault direct current locking fault and the direct current drop point.

5. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, it is characterized in that described dynamic response curve comprises merit angle change curve, busbar voltage change curve and the circuit active power change curve of generator at least.

6. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, it is characterized in that in the Equivalent Simplification step of described district external power grid,

All outsides of electrical network are subjected to electric channel in the reserved area;

The reserved area outer net is delivered to whole DC line and the sending end current conversion station of district's Intranet;

The reserved area outer net is delivered to the extra-high-voltage alternating current power transmission sequence of district's Intranet;

Reserved area outer net extra high voltage line and continuous transformer station and power plant;

The combination of the duty values such as foreign network low-voltage network using and equivalent generator is simulated;

District's external power grid is simulated by the generator of equivalence the dynamic response of distinguishing interior grid disturbance;

The direct current sending end of foreign network directly links to each other with the equivalent generator of foreign network;

All the other foreign network networks are all simplified.

7. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 6, it is characterized in that described equivalent generator all takes infinitely great unit model.

8. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, it is characterized in that described low-voltage network is carried out Equivalent Simplification, comprise that 220kV and following low-voltage network carry out equivalence in the interior electrical network to distinguishing.

9. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 6, it is characterized in that in the Equivalent Simplification step of described district external power grid, employing is based on the equivalence method of physics equivalence, near for the direct current drop point 220kV electrical network is expressed as the combination of generator and load; Be load for other 220kV network equivalence away from direct current; Its process is as follows:

Given fault collection is carried out short circuit calculation, calculate the bus residual voltage, the zone of preliminary certainty equivalents model is divided;

Access 220kV and with capacity and the kinetic energy of the generating set of lower network in the statistical regions respectively, and the proportion of all generating set capacities and kinetic energy in their territories, occupied area, in conjunction with the residual voltage data, definite area 220kV system equivalent model;

To different Equivalent Model, determine model parameter, obtain distinguishing interior simplification electrical network;

By adjusting the performance number that waits duty value in the district, so that the calculation of tidal current before and after electrical network is simplified in the district is consistent;

Check again the effect of Dynamic Equivalence Schemes, contrast under the identical disturbance merit angle change curve, busbar voltage change curve and the circuit active power change curve of generator important before and after equivalent, observe both and whether approach;

Carry out Adaptability Analysis to simplifying electrical network at last, the assessment Dynamic Equivalence Schemes changes and rack the validity in the situation such as change in other fault types, operational mode.

10. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 6, it is characterized in that described equivalence is as follows for the concrete steps of load:

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

10-2, the laggard row trend of equivalence is calculated, is optimized and revised the equivalent load power value of 220kV side, guarantee equivalent before and after system load flow basically identical;

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

11. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 6, it is characterized in that described equivalence is that the concrete steps of generator application of load model are as follows:

Determining of 11-1, generator capacity and equivalent load capacity

Former network is carried out trend calculate, many transformer parameters that are connected to same bus in this 500kV transformer station are polymerized to an equivalent transformer by parallel way, add up under all transformer 220kV sides of this bus and send power, can get the 220kV side and go out equivalence and exert oneself and be 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 adding up;

The generator total capacity of moving in the statistics access 220kV subregion, the generator total capacity of moving in the described access 220kV subregion does not comprise the generator that directly links to each other with the 500kV electrical network, obtains equivalent generator capacity after adding up, and is designated as P _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 " _dAdopt the mode of polymerization 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 the formula, g is generator sum in this subregion, S _jBe the rated capacity of j platform generator, x " _DjIt is the subtranient reactance of j platform generator.

This parameter is changed into perunit value take system's reference capacity as reference, namely

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

The generator parameter that becomes of boosting keeps identical requirement to determine according to busbar short-circuit electric current before and after equivalent;

In the network, three-phase shortcircuit on this 500kV bus is added up the short circuit current I that this bus 220kV provides before equivalent ";

Calculate short circuit in flow calculation program BPA, do not consider influence on tidal flow, namely E=1 then has

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

In the formula, S _BFor system's reference capacity, be defaulted as 100MVA, and then calculate step-up transformer equivalent reactance x _T2

For equivalent generator moment of inertia, adopt following formula 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 the formula, H ₁, H ₂... H _NAnd S ₁, S ₂... S _NBe respectively moment of inertia and the capacity of generating set in the 220kV subregion, S _GBe generating set capacity sum in the 220kV subregion;

11-3, the laggard row trend of equivalence is calculated, is optimized and revised the equivalent load power of 220kV side, satisfy equivalent before and after system load flow basically identical;

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

11-5, system behind the equivalence is carried out time-domain-simulation, for corresponding simulation curve before and after equivalent, calculate evaluation index, as meet the demands, adopt this model; If can not meet the demands, then be further analyzed, consider model is finely tuned.

12. according to the Dynamic Equivalence of the described large electrical network of alternating current-direct current series-parallel connection of using based on engineering of claim 11, it is characterized in that described model being finely tuned, comprise reduction excitation system pressure regulation ability and adjust prime mover and speed regulator fm capacity.

13. the Dynamic Equivalence according to the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, when it is characterized in that the low-voltage network carries out Equivalent Simplification in to described district, associated bus in the forecast failure collection or circuit are applied short trouble, the extracting part partial node calculates its residual voltage as representation node, according to the residual voltage situation of representation node, middle Further Division all subregion in the district; For the lower subregion of residual voltage, consider that equivalence is the generator application of load; For the higher subregion of residual voltage, equivalent for loading first, then whether increase capacity and the kinetic energy that directly is connected into 500kV system unit according to dynamic characteristic before and after equivalent and the capacity and the selection of kinetic energy proportion situation that directly are connected into 500kV system unit, namely approximately add equivalent machine, make equivalent after the whole volume of generating set and kinetic energy with equivalent front roughly the same.

14. the Dynamic Equivalence according to the described large electrical network of alternating current-direct current series-parallel connection of using based on engineering of claim 13, it is characterized in that in order to determine the concrete equivalent scheme of described all subregion, to adopting the generator application of load and approximately add the dynamic characteristic that obtains after two kinds of equivalent schemes of equivalent machine and compare analysis in the parton zone;

If the dynamic characteristic to two kinds of equivalent schemes of difference of certain subregion compares analysis, all equivalence is larger with equivalent front deviation for the dynamic characteristic of load, the dynamic characteristic of generator application of load is better with equivalent front fitting degree, then this subregion is adopted the equivalent scheme of generator application of load;

If the dynamic characteristic before and after certain subregion equivalence is compared analysis, all equivalence is just better with equivalent front fitting degree for the dynamic characteristic of load, does not then need the equivalent generator application of load that is.

15. the Dynamic Equivalence according to the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1 is characterized in that after the electrical network dynamic equivalent, respectively equivalent effect being checked in to described district external power grid dynamic equivalent and district; Described equivalent effect is checked, comprise that carrying out dynamic stability checks.

16. the Dynamic Equivalence according to the described large electrical network of alternating current-direct current series-parallel connection of using based on engineering of claim 15, it is characterized in that described dynamic stability check be in the district that relatively distinguishes behind interior electrical network and the equivalence electrical network under identical fault disturbance, whether the change curve of generator's power and angle, busbar voltage and circuit active power approaches, whether Changing Pattern is similar, with the effect of check dynamic equivalent.

17. the Dynamic Equivalence according to the described large electrical network of alternating current-direct current series-parallel connection of using based on engineering of claim 15, it is characterized in that when carrying out described dynamic stability check, choose representative generator, near 500kV and the elements such as 1000kV bus, 500kV and 1000kV circuit of direct current drop point; Under same fault disturbance, the change curve of these element physical quantitys before and after equivalent is plotted in together, relatively whether the Changing Pattern in initial value, steady-state value and the simulation time section of two curves is consistent or close;

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

If difference is larger, then need to revise equivalent scheme, re-start equivalence.

18. according to the Dynamic Equivalence of the large electrical network of alternating current-direct current series-parallel connection of using based on engineering claimed in claim 1, it is characterized in that described Dynamic Equivalence adopt relative root-mean-square error RMS index weigh equivalent before and after the dynamic response of system under identical disturbance whether consistent;

Described relative root-mean-square error RMS is the root mean square of equivalent front and back performance graph each point absolute error and the root mean square ratio of equivalent front curve each point, namely

The relative root-mean-square error RMS of computing system equivalence front and back performance graph under same fault if its error within the acceptable range, thinks that then it meets the requirements;

When calculating relative root-mean-square error RMS, the performance graph of only choosing circuit active power equivalence front and back under the forecast failure carries out quantitative analysis.

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