CN108471121A - A kind of optimization method that induction conductivity unstable equilibrium point solves - Google Patents
A kind of optimization method that induction conductivity unstable equilibrium point solves Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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Abstract
The invention discloses the optimization methods that a kind of induction conductivity unstable equilibrium point solves, and are related to electric system.This method is by establishing equivalent circuit, give the modification method of induction conductivity generator terminal reactive power compensator parameter and line parameter circuit value after failure, and by changing induction electric acc power the line is busy road power proportions parameter so that model is more nearly the situation of actual electric network.Using generator terminal voltage as virtual induction electric set end voltage, the non-constant problem of induction electric set end voltage in transient process is avoided after failure；The virtual forward and backward Formula of Electromagnetic of induction conductivity failure is built by the difference of transmission line before and after failure, reactive power compensator parameter, induction conductivity electromagnetic torque, machine torque equations induction conductivity unstable equilibrium point after simultaneous failure, solving precision is set to be improved, assessment for induction motor load Enhancement of Transient Voltage Stability after failure provides important evidence, for instructing actual electric network operation to be of great significance.
Description
Technical field
The present invention relates to electric system, are more particularly to the method for solving of induction conductivity unstable equilibrium point.
Background technology
In recent years, since Voltage-stabilizing Problems cause a lot of large-scale blackouts, voltage-stability safety estimation is also got over
Paid attention to by operations staff and researcher to get over, this also proposed higher want to the method and result of Voltage Stability Analysis
It asks.Induction motor load accounting often reaches 60% or more in electric system, after the system failure, induction electric set end voltage
It is a large amount of idle from power grid absorption in recovery process, the no-power vacancy of system short time is exacerbated, Network Voltage Stability is deteriorated.
An important factor for dynamic step response of induction motor load is influence Transient Voltage Stability in Electric Power System, thus it is how rationally accurate
Influence of the split-phase induction motor load to Transient Voltage Stability in Electric Power System have great importance.
For induction motor load, after system short-circuit fault, electromagnetic torque is dropped rapidly in a short time
Zero, induction conductivity constantly slows down under machine torque effect, and slippage constantly increases.After short trouble excision, induction conductivity
Electromagnetic torque can not saltus step, but be restored to the state more than machine torque after a period of time, in the process, induction
Motor absorption is a large amount of idle, and slippage continues to increase.Failure removal for a period of time after, induction conductivity electromagnetic torque be more than machinery
Torque, rotor start to accelerate, and slippage starts to reduce.In short-circuit process, induction conductivity slippage constantly increases, after failure removal
Induction conductivity slippage continues to increase, until electromagnetic torque is more than machine torque.There are unstable after a failure for induction conductivity
Determine equalization point slippage, induction conductivity slippage increases above unstable equilibrium point slippage after failure, induced electricity after failure removal
Motivation terminal voltage unstability, on the contrary then not unstability (soup gushes Voltage Stability Analysis of Power System [M] Science Presses).
Power system voltage stabilization and line transmission power are closely related, and under conditions of line impedance is certain, circuit passes
Defeated reactive power is higher, and line electricity pressure drop is bigger, is more unfavorable for the voltage stabilization of power grid.Power factor of electric network is to influence circuit
The extremely important factor of transimission power.There are a large amount of induction motor loads in power grid, due to induction motor load characteristic,
Power factor is not high, in order to improve induction conductivity power factor, usually installs reactive-load compensation equipment in induction conductivity generator terminal
To improve power factor of electric network, the reactive power that circuit flows through is reduced, the terminal voltage of induction conductivity is improved.Therefore, it is carrying out
Influence (Sun Huadong, Zhou Xiaoxin, Li Ruo the plum induction electrics of meter and reactive power compensator are needed during actual electric network equivalence
Influence [J] the electric power network techniques of machine load parameter to Transient Voltage Stability in Electric Power System, 2005,29 (23):1-6).Practical electricity
Net load composition it is more complicated, but greatly can equivalent proportional induction motor load add a certain proportion of constant-resistance
Anti- load.Different load ratio is affected to actual electric network voltage stabilization.Constant-impedance load is due to its part throttle characteristics, power
Factor will not change with injecting power and terminal voltage, and when its terminal voltage reduces, active power and reactive power also can
Decline with the decline of voltage, this part throttle characteristics will not aggravate the no-power vacancy of system, therefore advantageous to voltage stabilization.It is permanent
Resistive load proportion is higher, and system transient modelling voltage stability margin is higher.It need to be counted and constant-resistance carrying out actual electric network equivalent time
Anti- load (influence of Sun Huadong, Zhou Xiaoxin, Li Ruo the plum induction motor loads parameter to Transient Voltage Stability in Electric Power System
[J] electric power network techniques, 2005,29 (23):1-6).
Have much method for solving about unstable equilibrium point slippage after induction conductivity failure at present, it is most of to use
After simultaneous failure under induction conductivity stable state terminal voltage electromagnetic torque and machine torque formula come solve (well is gorgeous clear, Li Xingyuan,
Guo Xiaoming waits to consider the quick criterion of Transient Voltage Stability [J] Automation of Electric Systems of induction motor load model,
2011,35 (5):10-14).Such methods have ignored the variation of terminal voltage in induction conductivity transient process, directly utilize failure
Induction conductivity stable state terminal voltage, solving precision be not high afterwards.Therefore, induction conductivity failure can accurately be solved by seeking one kind
The method of unstable equilibrium point slippage is particularly important to assess induction motor load Transient Voltage Stability situation after failure afterwards.
Invention content
The present invention proposes a kind of induction conductivity unstable equilibrium from induction conductivity Transient Voltage Stability mechanism
The method for solving of point, it is continually changing that this method avoids induction electric set end voltage in the transient process that conventional method is encountered
Problem, solving precision greatly improve, for induction motor load Enhancement of Transient Voltage Stability after failure assessment propose it is important
Foundation, for instructing actual electric network reliability service to be of great significance.
In order to achieve the above object, the present invention adopts the following technical scheme that：
A kind of optimization method that induction conductivity unstable equilibrium point solves, this method comprise the steps of：
A, the foundation of actual electric network integrated load model
A1, the reality for establishing meter and line transmission reactance, constant-impedance load, induction motor load and reactive power compensator
Electric network synthetic load model
Induction motor model is rotor resistance RRWith rotor reactance XRAfter series connection with excitation reactance XMParallel connection, then with
Stator reactance XS, stator resistance RSIt is in parallel；Real system constant-impedance load resistance RZWith reactance XZIt connects to indicate；System without
Reactive power compensation installations reactance XCIt indicates；It is X that system, which transmits reactance,l；The transmission reactance of generator G and system is connected, later and constant-resistance
Anti- load, reactive power compensator obtain actual electric network integrated load model after induction conductivity is in parallel；
The reactive power Q of a2, computing system reactive power compensatorCAnd reactance XC
The reactive power Q that reactive power compensator providesCIt is calculated as follows
QC=QM-Q0QPer (1)
In formula：QMFor the reactive power of induction conductivity consumption, QPerThe ratio of bus reactive power rate is consumed for induction conductivity
Example, Q0For induction conductivity plus constant-impedance reactive load power；
The reactance X of reactive power compensatorCIt is calculated as follows
In formula：UMFor induction electric set end voltage；
A3, constant-impedance load power P is determinedZ+jQZWith constant-impedance load impedance RZ+jXZ
Constant-impedance load power PZ+jQZIt is calculated as follows
PZ+jQZ=(1-PPer)P0+j(1-QPer)Q0 (3)
PPerBusbar active power ratio is consumed for induction conductivity, j is imaginary unit；
Constant-impedance load impedance RZ+jXZIt is calculated as follows
In formula：UMFor induction electric set end voltage, PZFor constant-impedance load active power, QZFor constant-impedance reactive load work(
Rate
B, it is based on Thevenin's theorem and solves induction conductivity unstable equilibrium point
B1, virtual induction conductivity is established
By constant-impedance load and reactive power compensator, induction conductivity it is in parallel after with system transmit reactance void in series
Quasi- induction conductivity.Virtual induction conductivity is directly connected with system generator G, and system line fault equivalence is virtual induced electricity
The variation of motivation inner parameter, after virtual induction conductivity is established, failure front voltage UM0=E, terminal voltage U after failureM2
=E；
B2, electromagnetic torque after electromagnetic torque before the virtual induction conductivity failure of Thevenin's theorem structure and failure is utilized
The circuit progress that virtual induction conductivity is entered in terms of rotor circuit port using Thevenin's theorem is equivalent, i.e., will
Induction conductivity excitation reactance, stator impedance, System Reactive Power compensation device, constant-impedance load, system transmit reactance, power generation
Machine partial circuit is equivalent to a voltage sourceWith an impedance Rt+jXtConcatenated circuit；
Virtual induction conductivity Formula of Electromagnetic before b21, failure
The solution formula of virtual induction conductivity Thevenin's equivalence impedance and rotor voltage source voltage is as follows before failure：
Rt0+jXt0=jXC0//(RZ+jXZ)//jXl0+RS+jXS (5)
In formula：R∑+jX∑=(RZ+jXZ)//jXC0, R∑1+jX∑1=R∑+jX∑+RS+jXS+jXM, R∑2+jX∑2=(R∑+
jX∑)//[RS+j(XS+XM)]+jXl0, E is generator voltage, Rt0+jXt0Dimension is worn for virtual induction conductivity before the system failure
Southern equivalent impedance, XC0For reactive power compensator reactance, X before the system failurel0For line transmission reactance, U before the system failuret0For sense
Dai Weinan equivalent voltage sources before induction motor failure；
Electromagnetic torque T before virtual induction conductivity failure is obtained according to the above virtual induction conductivity Equivalent Modele0Formula
Wherein s is induction conductivity slippage；
Virtual induction conductivity Formula of Electromagnetic after b22, failure
Post-fault system reactive power compensator parametric solution formula
QC2=QM2-(Q2-QZ2) (8)
In formula：QC2For the reactive power that reactive power compensator after failure provides, QM2For the idle work(of induction conductivity after failure
Rate, Q2Reactive power, Q are injected for power grid after failureZ2For the reactive power of constant-impedance load absorption after failure, UM2To feel after failure
Induction motor terminal voltage, XC2For reactive power compensator reactance after failure；
Virtual induction conductivity electromagnetic torque T after failuree2Formula
In formula：Ut2For Dai Weinan equivalent voltage sources after virtual induction conductivity failure, Rt2For virtual induction conductivity failure
Dai Weinan equivalent resistances afterwards, Xt2For Dai Weinan equivalent reactances after virtual induction conductivity failure；
C, unstable equilibrium point slippage after solution induction conductivity failure
Calculate induction conductivity machine torque TmUsing following formula：
Tm=T0[A(1-s)2+B(1-s)+C] (11)
In formula：A, B, C indicate that induction conductivity moment coefficient A, moment coefficient B, moment coefficient C, s are induction electric respectively
Machine slippage, T0For induction conductivity initial moment, s0For the initial slippage of induction conductivity；Wherein T0It is calculated as follows
Enable formula Tm=Te2Induction conductivity slippage s is solved, two slippage s can be obtained by solution formula2、su, wherein
Smaller solution s2Stablize slippage, larger solution s for induction conductivity after failureuIt is unstable after induction conductivity failure after failure
Equalization point slippage, that is, unstable equilibrium point after induction conductivity failure.
The present invention can accurately solve induction conductivity unstable equilibrium point slippage, for assessing induction conductivity after failure
Load Transient Voltage Stability situation mainly has the following effects compared with prior art：
(1) actual electric network integrated load model is established, induction conductivity unstable equilibrium point in comprehensive study load model
Method for solving.Transmission reactance, constant-impedance load, induction motor load and induction conductivity are considered when establishing equivalent circuit
Generator terminal reactive power compensator.Give the amendment of induction conductivity generator terminal reactive power compensator parameter and line parameter circuit value after failure
Method, the case where more accurately reflecting actual electric network, road power proportions parameter that the line is busy by changing induction electric acc power
The case where can reflecting different actual electric networks.
(2) virtual induction conductivity is established, using generator terminal voltage as virtual induction electric set end voltage, is avoided
The non-constant problem of induction electric set end voltage in transient process after failure；Pass through transmission line, reactive-load compensation dress before and after failure
The difference for setting parameter builds the virtual forward and backward Formula of Electromagnetic of induction conductivity failure, induction conductivity electromagnetism after simultaneous failure
Torque, machine torque equations induction conductivity unstable equilibrium point, make solving precision greatly increase, and are induced electricity after failure
The assessment of engine load Enhancement of Transient Voltage Stability proposes important foundation, important for instructing actual electric network reliability service to have
Meaning.
Description of the drawings
Fig. 1 is actual electric network integrated load model schematic diagram.
Fig. 2 is virtual induction motor system schematic diagram.
Fig. 3 is virtual induction conductivity thevenin equivalent circuit schematic diagram.
Fig. 4 is the optimization method calculation process that a kind of induction conductivity unstable equilibrium point solves.
Specific implementation mode
The present invention builds one machine infinity bus system by using PSD-BPA and is verified to method correctness, includes mainly
It establishes the practical equivalent circuit of one machine infinity bus system, solve constant-impedance load and the forward and backward reactive power compensator parameter of failure, structure
Virtual induction conductivity Formula of Electromagnetic before and after failure is built, virtual induction conductivity machine torque is derived and solves induction conductivity
Unstable equilibrium point slippage after failure.
Embodiment one
As shown in Figure 1, the optimization method that a kind of induction conductivity unstable equilibrium point solves, this method include following step
Suddenly：
A, the foundation of actual electric network integrated load model
A1, the reality for establishing meter and line transmission reactance, constant-impedance load, induction motor load and reactive power compensator
Electric network synthetic load model
In actual electric network, since reactive power large capacity cannot convey at a distance, induction motor load end usually requires
Add reactive power compensator.In actual electric network calculating process, load model is usually that induction motor load adds constant-impedance negative
Lotus model, as shown in Figure 1.
Induction motor model is rotor resistance RRWith rotor reactance XRAfter series connection with excitation reactance XMParallel connection, then with
Stator reactance XS, stator resistance RSIt is in parallel；Real system constant-impedance load resistance RZWith reactance XZIt connects to indicate；System without
Reactive power compensation installations reactance XCIt indicates；It is X that system, which transmits reactance,l；The transmission reactance of generator G and system is connected, later and constant-resistance
Anti- load, reactive power compensator obtain actual electric network integrated load model after induction conductivity is in parallel；
The reactive power Q of a2, computing system reactive power compensatorCAnd reactance XC
Under normal running (operation) conditions, it is P that power grid, which injects constant-impedance load and the power of induction conductivity,0+jQ0, due to induction
Motor power factor is less than initial power factor, therefore induction conductivity reactive power vacancy is provided by reactive power compensator.
The reactive power Q that reactive power compensator providesCIt is calculated as follows
QC=QM-Q0QPer (1)
In formula：QMFor the reactive power of induction conductivity consumption, QPerThe ratio of bus reactive power rate is consumed for induction conductivity
Example, Q0For induction conductivity plus constant-impedance reactive load power；
The reactance X of reactive power compensatorCIt is calculated as follows
In formula：UMFor induction electric set end voltage；
A3, constant-impedance load power P is determinedZ+jQZWith constant-impedance load impedance RZ+jXZ
In view of influence of the constant-impedance load in Network Voltage Stability, needed by certain when establishing system equivalent circuit
Constant-impedance load is added in ratio.
Constant-impedance load power PZ+jQZIt is calculated as follows
PZ+jQZ=(1-PPer)P0+j(1-QPer)Q0 (3)
PPerBusbar active power ratio is consumed for induction conductivity, j is imaginary unit；
Constant-impedance load impedance RZ+jXZIt is calculated as follows
In formula：UMFor induction electric set end voltage, PZFor constant-impedance load active power, QZFor constant-impedance reactive load work(
Rate
B, it is based on Thevenin's theorem and solves induction conductivity unstable equilibrium point
Line reactance and reactive power compensator parameter change after failure, and virtual induction conductivity parameter need to be repaiied
Just.
B1, virtual induction conductivity is established
Since system is varied less before failure with generator voltage after failure, it is possible to which generator in Fig. 1 is right
Lateral circuit is equivalent to a virtual induction conductivity, as shown in Figure 2.
By constant-impedance load and reactive power compensator, induction conductivity it is in parallel after with system transmit reactance void in series
Quasi- induction conductivity.Virtual induction conductivity is directly connected with system generator G, and system line fault equivalence is virtual induced electricity
The variation of motivation inner parameter, after virtual induction conductivity is established, failure front voltage UM0=E, terminal voltage U after failureM2
=E；
B2, electromagnetic torque after electromagnetic torque before the virtual induction conductivity failure of Thevenin's theorem structure and failure is utilized
In order to establish virtual induction conductivity Formula of Electromagnetic before failure, using Thevenin's theorem by virtual induction electric
Circuit carries out equivalent on the left of machine rotor, as shown in Figure 3.I.e. by induction conductivity excitation reactance, stator impedance, System Reactive Power compensation
Device, constant-impedance load, system transmits reactance and master section circuit equivalent is a voltage sourceWith an impedance Rt+
jXtConcatenated circuit；
Virtual induction conductivity Formula of Electromagnetic before b21, failure
Line reactance and reactive power compensator parameter change after failure, and virtual induction conductivity parameter need to be repaiied
Just.
The solution formula of virtual induction conductivity Thevenin's equivalence impedance and rotor voltage source voltage is as follows before failure：
Rt0+jXt0=jXC0//(RZ+jXZ)//jXl0+RS+jXS (5)
In formula：R∑+jX∑=(RZ+jXZ)//jXC0, R∑1+jX∑1=R∑+jX∑+RS+jXS+jXM, R∑2+jX∑2=(R∑+
jX∑)//[RS+j(XS+XM)]+jXl0, E is generator voltage, Rt0+jXt0Dimension is worn for virtual induction conductivity before the system failure
Southern equivalent impedance, XC0For reactive power compensator reactance, X before the system failurel0For line transmission reactance, U before the system failuret0For sense
Dai Weinan equivalent voltage sources before induction motor failure；
Electromagnetic torque T before virtual induction conductivity failure is obtained according to the above virtual induction conductivity Equivalent Modele0Formula
Wherein s is induction conductivity slippage；
Virtual induction conductivity Formula of Electromagnetic after b22, failure
Post-fault system reactive power compensator parametric solution formula
QC2=QM2-(Q2-QZ2) (8)
In formula：QC2For the reactive power that reactive power compensator after failure provides, QM2For the idle work(of induction conductivity after failure
Rate, Q2Reactive power, Q are injected for power grid after failureZ2For the reactive power of constant-impedance load absorption after failure, UM2To feel after failure
Induction motor terminal voltage, XC2For reactive power compensator reactance after failure；
Virtual induction conductivity electromagnetic torque T after failuree2Formula
In formula：Ut2For Dai Weinan equivalent voltage sources after virtual induction conductivity failure, Rt2For virtual induction conductivity failure
Dai Weinan equivalent resistances afterwards, Xt2For Dai Weinan equivalent reactances after virtual induction conductivity failure；Such as the virtual induction conductivity of Fig. 3
Shown in thevenin equivalent circuit schematic diagram；
C, unstable equilibrium point slippage after solution induction conductivity failure
Calculate induction conductivity machine torque TmUsing following formula：
Tm=T0[A(1-s)2+B(1-s)+C] (11)
In formula：A, B, C indicate that induction conductivity moment coefficient A, moment coefficient B, moment coefficient C, s are induction electric respectively
Machine slippage, T0For induction conductivity initial moment, s0For the initial slippage of induction conductivity；Wherein T0It is calculated as follows
Enable formula Tm=Te2Induction conductivity slippage s is solved, two slippage s can be obtained by solution formula2、su, wherein
Smaller solution s2Stablize slippage, larger solution s for induction conductivity after failureuIt is unstable after induction conductivity failure after failure
Equalization point slippage, that is, unstable equilibrium point after induction conductivity failure, such as a kind of induction conductivity unstable equilibrium point of Fig. 4
Shown in the optimization method calculation process of solution.
Embodiment two
Using two groups of IEEE induction conductivity parameters, it is shown in Table 1.Every group of parameter setting system Transient Voltage Stability limit
90%, 80%, respectively load active power is two kinds of operating modes of 1300MW, 1200MW, and initial power factor is 0.97, circuit
It is 0.095 to transmit reactance；+ 35% constant impedance of 65% induction conductivity of load model, 50% sense are respectively set under each operating mode
Two kinds of load proportions of+50% constant impedance of induction motor carry out simulating, verifying.
1 induction conductivity parameter of table
| Parameter | RS | XS | RR | XR | XM |
| Parameter one | 0.02 | 0.18 | 0.02 | 0.12 | 3.499 |
| Parameter two | 0.031 | 0.1 | 0.018 | 0.18 | 3.2 |
(1) by building model emulation and according to formula (4), (9), (2), before calculating induction conductivity failure, after failure
Reactive power compensator parameter and constant-impedance load impedance parameter are as a result as follows：
2 reactive power compensator of table, constant-impedance load parameter
As can be seen from Table 2, under different parameters, system injecting power is bigger, induction conductivity generator terminal reactive-load compensation reactance
It is bigger；Induction conductivity ratio is higher, and reactive power compensator parameter is smaller.Constant-impedance load parameter is with induction motor load
Ratio increases and increases；Reduce as system injecting power reduces.
(2) since the virtual forward and backward parameter of induction conductivity failure changes, the virtual equivalent electricity of induction conductivity Dai Weinan
Potential source voltage can also change, by formula (6) solving virtual induction conductivity Dai Weinan equivalent voltage source voltages, as a result such as
Under：
3 virtual induction conductivity Dai Weinan equivalent voltage source voltages of table
(3) according to formula (12), induction conductivity initial moment under several operating modes is calculated, it is as a result as follows：
4 virtual induction conductivity initial moment of table
It can be obtained by table 4, induction motor load power is higher, and initial moment is bigger；Induction motor load ratio is smaller,
Initial moment is smaller.
(4) according to unstable equilibrium point slippage after equation group (13) calculating induction conductivity failure, result of calculation is as follows：
The calculating of unstable equilibrium point slippage, simulation result and error after 5 induction conductivity failure of table
Unstable equilibrium after induction conductivity failure is compared under load two kinds of operating modes of active power 1300MW, 1200MW respectively
Point slippage it can be found that with load power decline, unstable equilibrium point slippage increases after induction conductivity failure, and system is temporary
State voltage stability is reinforced；Induction motor load ratio reduces, and unstable equilibrium point slippage increases after induction conductivity failure,
System transient modelling voltage stability is reinforced.It is calculated by methods described herein it can be seen from data in table 5, induction conductivity event
Unstable equilibrium point slippage calculating error is up to 2.58%, minimum 0.62% after barrier, and the overall error that calculates is smaller, is carrying out
Actual electric network Voltage Stability Analysis can carry out Transient stability analysis when calculating using methods described herein.
Claims (1)
1. the optimization method that a kind of induction conductivity unstable equilibrium point solves, which is characterized in that this method comprises the steps of：
A, the foundation of actual electric network integrated load model
A1, the actual electric network for establishing meter and line transmission reactance, constant-impedance load, induction motor load and reactive power compensator
Integrated load model
Induction motor model is rotor resistance RRWith rotor reactance XRAfter series connection with excitation reactance XMParallel connection, then with stator
Reactance XS, stator resistance RSIt is in parallel；Real system constant-impedance load resistance RZWith reactance XZIt connects to indicate；System Reactive Power is mended
Repay device reactance XCIt indicates；It is X that system, which transmits reactance,l；Generator G is connected with system transmission reactance, it is negative with constant-impedance later
Lotus, reactive power compensator obtain actual electric network integrated load model after induction conductivity is in parallel；
The reactive power Q of a2, computing system reactive power compensatorCAnd reactance XC
The reactive power Q that reactive power compensator providesCIt is calculated as follows
QC=QM-Q0QPer (1)
In formula：QMFor the reactive power of induction conductivity consumption, QPerThe ratio of bus reactive power rate, Q are consumed for induction conductivity0
For induction conductivity plus constant-impedance reactive load power；
The reactance X of reactive power compensatorCIt is calculated as follows
In formula：UMFor induction electric set end voltage；
A3, constant-impedance load power P is determinedZ+jQZWith constant-impedance load impedance RZ+jXZ
Constant-impedance load power PZ+jQZIt is calculated as follows
PZ+jQZ=(1-PPer)P0+j(1-QPer)Q0 (3)
PPerBusbar active power ratio is consumed for induction conductivity, j is imaginary unit
Constant-impedance load impedance RZ+jXZIt is calculated as follows
In formula：UMFor induction electric set end voltage, PZFor constant-impedance load active power, QZFor constant-impedance reactive load power.
B, it is based on Thevenin's theorem and solves induction conductivity unstable equilibrium point
B1, virtual induction conductivity is established
By constant-impedance load and reactive power compensator, induction conductivity it is in parallel after with system transmit reactance virtual sense in series
Induction motor.Virtual induction conductivity is directly connected with system generator G, and system line fault equivalence is virtual induction conductivity
The variation of inner parameter, after virtual induction conductivity is established, failure front voltage UM0=E, terminal voltage U after failureM2=E；
B2, electromagnetic torque after electromagnetic torque before the virtual induction conductivity failure of Thevenin's theorem structure and failure is utilized
The circuit progress that virtual induction conductivity is entered in terms of rotor circuit port using Thevenin's theorem is equivalent, i.e., will induction
Motor excitation reactance, stator impedance, System Reactive Power compensation device, constant-impedance load, system transmit reactance, master section electricity
Road is equivalent to a voltage sourceWith an impedance Rt+jXtConcatenated circuit；
Virtual induction conductivity Formula of Electromagnetic before b21, failure
The solution formula of virtual induction conductivity Thevenin's equivalence impedance and rotor voltage source voltage is as follows before failure：
Rt0+jXt0=jXC0//(RZ+jXZ)//jXl0+RS+jXS (5)
In formula：R∑+jX∑=(RZ+jXZ)//jXC0, R∑1+jX∑1=R∑+jX∑+RS+jXS+jXM, R∑2+jX∑2=(R∑+jX∑)//
[RS+j(XS+XM)]+jXl0, E is generator voltage, Rt0+jXt0For virtual induction conductivity Thevenin's equivalence before the system failure
Impedance, XC0For reactive power compensator reactance, X before the system failurel0For line transmission reactance, U before the system failuret0For induction electric
Dai Weinan equivalent voltage sources before machine failure；
Electromagnetic torque T before virtual induction conductivity failure is obtained according to the above virtual induction conductivity Equivalent Modele0Formula
Wherein s is induction conductivity slippage；
Virtual induction conductivity Formula of Electromagnetic after b22, failure
Post-fault system reactive power compensator parametric solution formula
QC2=QM2-(Q2-QZ2) (8)
In formula：QC2For the reactive power that reactive power compensator after failure provides, QM2For induction conductivity reactive power, Q after failure2
Reactive power, Q are injected for power grid after failureZ2For the reactive power of constant-impedance load absorption after failure, UM2For induced electricity after failure
Motivation terminal voltage, XC2For reactive power compensator reactance after failure；
Virtual induction conductivity electromagnetic torque T after failuree2Formula
In formula：Ut2For Dai Weinan equivalent voltage sources after virtual induction conductivity failure, Rt2To be worn after virtual induction conductivity failure
The southern equivalent resistance of dimension, Xt2For Dai Weinan equivalent reactances after virtual induction conductivity failure；
C, unstable equilibrium point slippage after solution induction conductivity failure
Calculate induction conductivity machine torque TmUsing following formula：
Tm=T0[A(1-s)2+B(1-s)+C] (11)
In formula：A, B, C indicate that induction conductivity moment coefficient A, moment coefficient B, moment coefficient C, s are slided for induction conductivity respectively
Difference, T0For induction conductivity initial moment, s0For the initial slippage of induction conductivity；Wherein T0It is calculated as follows
Enable formula Tm=Te2Induction conductivity slippage s is solved, two slippage s can be obtained by solution formula2、su, wherein smaller
Solution s2Stablize slippage, larger solution s for induction conductivity after failureuFor unstable equilibrium after induction conductivity failure after failure
Point slippage, that is, unstable equilibrium point after induction conductivity failure.
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