CN117955120B - Load transient voltage instability discrimination method and system based on power factor positive feedback - Google Patents
Load transient voltage instability discrimination method and system based on power factor positive feedback Download PDFInfo
- Publication number
- CN117955120B CN117955120B CN202410069649.2A CN202410069649A CN117955120B CN 117955120 B CN117955120 B CN 117955120B CN 202410069649 A CN202410069649 A CN 202410069649A CN 117955120 B CN117955120 B CN 117955120B
- Authority
- CN
- China
- Prior art keywords
- load
- bus
- transient voltage
- power
- voltage instability
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 230000001052 transient effect Effects 0.000 title claims abstract description 131
- 238000012850 discrimination method Methods 0.000 title claims description 3
- 238000000034 method Methods 0.000 claims abstract description 70
- 230000008569 process Effects 0.000 claims abstract description 35
- 230000004044 response Effects 0.000 claims abstract description 28
- 230000007246 mechanism Effects 0.000 claims abstract description 26
- 230000008859 change Effects 0.000 claims description 20
- 230000002829 reductive effect Effects 0.000 claims description 17
- 238000010521 absorption reaction Methods 0.000 claims description 7
- 230000003211 malignant effect Effects 0.000 claims description 6
- 230000000630 rising effect Effects 0.000 claims description 5
- 238000004590 computer program Methods 0.000 claims description 4
- 238000011084 recovery Methods 0.000 claims description 4
- 230000015556 catabolic process Effects 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims 1
- 238000010586 diagram Methods 0.000 description 6
- 238000009434 installation Methods 0.000 description 5
- 238000005192 partition Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000036961 partial effect Effects 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000368 destabilizing effect Effects 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000001960 triggered effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000001687 destabilization Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 230000010534 mechanism of action Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Classifications
-
- 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
-
- 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
- H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
- H02J3/144—Demand-response operation of the power transmission or distribution network
-
- 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
-
- 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
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
- H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
-
- 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]
-
- 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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
-
- 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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
-
- 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
- H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
- H02J2310/50—The network for supplying or distributing electric power characterised by its spatial reach or by the load for selectively controlling the operation of the loads
- H02J2310/56—The network for supplying or distributing electric power characterised by its spatial reach or by the load for selectively controlling the operation of the loads characterised by the condition upon which the selective controlling is based
- H02J2310/58—The condition being electrical
- H02J2310/60—Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention provides a method and a system for judging the transient voltage instability of a load based on positive feedback of a power factor, which are used for deducing the transient voltage instability process of the load side based on a variable impedance model and determining the mechanism characteristic and the stability characteristic quantity of the transient voltage instability of the load side; carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by using bus power and a power factor angle cotangent value, and determining the response characteristic of transient voltage instability at a load side; and adding additional criteria to reduce the false judgment rate, constructing load transient voltage instability criteria based on positive feedback of the power factor, and judging whether the load transient voltage is unstable or not by using the criteria. The load transient voltage instability criterion based on the power factor positive feedback constructed by the invention directly starts from an instability mechanism, the selected response characteristic is easy to obtain in an actual power grid, and the misjudgment rate of a stable scene is lower on the premise of ensuring accurate identification of the load side voltage instability scene.
Description
Technical Field
The invention belongs to the technical field of power grid stability discrimination, and particularly relates to a method and a system for discriminating transient voltage instability of a load based on positive feedback of a power factor.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Voltage stabilization is a significant conventional stabilization modality, and has long received attention. Among them, effective discrimination of transient voltage instability has been an important issue in voltage stability research. In recent years, with the increasing scale of the receiving end system in China and the increasing penetration of power electronic equipment in a power grid, the problem of transient voltage stability of the power system is more and more remarkable, the defects of transient voltage stability judgment and control technology of traditional scheme event matching are gradually revealed, and the judgment of transient voltage instability based on response characteristics is imperative. A common transient voltage destabilization scenario is generally considered to be an electromechanical transient process dominated by load factors. The power load often includes equipment for adjusting its impedance according to the difference between the power obtained and a predetermined target. It is this mechanism of action that in some cases causes more load reactive power consumption and grid reactive power transmission, potentially causing transient voltage instability.
In the aspect of judging transient voltage instability, the bus voltage amplitude can reflect the voltage level of a power system, partial scholars construct a Lyapunov exponent by utilizing the voltage amplitude change rate of key nodes, and judge whether the transient voltage of the system is stable or not according to whether the exponent is larger than 0 or not. The method is characterized in that a part of foreign scholars realize voltage track tracking through time sequences of characteristic parameters, a system model is not needed, and on the basis, relevant researchers of a national power grid analyze the voltage amplitude change rate-voltage amplitude deviation characteristic curve at the machine end to construct transient voltage instability criteria. According to the method, whether the transient voltage is unstable can be judged by only measuring the bus voltage, but the problems of low judging accuracy and long judging time possibly exist only by using the bus voltage amplitude. Aiming at the challenges brought by new energy distributed grid connection and direct current transmission to the judgment of transient voltage stability at the load side, relevant researchers analyze. When the traditional direct current has serious faults or recovers from the faults, the direct current inverter absorbs a large amount of reactive power from the receiving end system under the action of the control system, so that the voltage of the converting bus is reduced, an unstable region of a nearby variable-impedance load is expanded, and the risk of transient voltage instability is increased. Based on the method, partial scholars establish a direct current receiving end system stability measurement index by analyzing the change condition of each electric quantity of the inversion station when the voltage collapse occurs to the converter bus. If the new energy grid-connected scale is larger, but the number of the reactive power compensation devices of the system is insufficient, the transient voltage stability of the system is affected. In order to accurately judge whether transient voltage instability occurs in a system under the participation of new energy, a part of scholars define indexes such as voltage severity, fault limit cutting time and the like.
Although the above-mentioned researches have proposed methods for discriminating transient voltage instability to some extent, none of these methods has been proposed based on the essential mechanism of transient voltage instability on the load side.
In order to improve the accuracy and timeliness of transient voltage instability criteria, partial scholars combine real-time measurement information, and construct an equivalent circuit by using the Thevenin theorem to provide the transient voltage instability criteria, but the difficulty of constructing the equivalent circuit in a power system containing a large number of power electronic equipment is high. In addition, related researchers find that transient voltage instability at the load side can be accompanied with a positive feedback process of continuously reducing active power of a line and continuously increasing current of the line in principle, so that judgment stability is carried out by monitoring the current of the line, the active power of the line and the voltage of a bus, but misjudgment of part of stable cases and missing judgment reasons of part of unstable cases by the criterion are not clarified.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a load transient voltage instability judging method and system based on positive feedback of a power factor, and a voltage instability criterion based on positive feedback of a bus active power and a bus power factor angle cotangent value is constructed, which directly starts from the most essential mechanism of load transient voltage instability, so that the practicability of the criterion is ensured.
To achieve the above object, a first aspect of the present invention provides a method for discriminating transient voltage instability of a load based on positive feedback of a power factor, comprising:
deducing a transient voltage instability process at a load side based on a variable impedance model, and determining a mechanism characteristic and a stability characteristic quantity of the transient voltage instability at the load side;
carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by using bus power and a power factor angle cotangent value, and determining the response characteristic of transient voltage instability at a load side;
and adding additional criteria to reduce the misjudgment rate, converting a differential form in response characteristics into a differential form, constructing load transient voltage instability criteria based on positive feedback of a power factor, and judging whether the load transient voltage is unstable or not by utilizing the constructed load transient voltage instability criteria.
Further, a load side transient voltage instability process is deduced based on a variable impedance model, and the mechanism characteristics of the load side transient voltage instability are determined, specifically:
When a variable-impedance load enters an unstable domain to generate instability, a malignant positive feedback characteristic exists between impedance change and active power acquisition of load absorption; the load absorbs the active power to obtain the active power preset target and change the impedance, and the impedance change makes the load absorb the active power deviate from the active power preset target further, so that a positive feedback process of load absorb the active power deviation, load change impedance and load absorb the active power deviation is formed.
Further, a transient voltage instability process at the load side is deduced based on a variable impedance model, and a stable characteristic quantity of the transient voltage instability at the load side is determined to be the equivalent impedance of a load bus, specifically:
The first-order differential model of the variable impedance load is shown as follows:
Wherein R Load is an equivalent load resistance; A recovery time constant for conductance; p L0 is an active power preset target; p Load is the load absorption active power;
The stable characteristic quantity of transient voltage instability at the load side is determined as bus equivalent impedance:
wherein X Load is equivalent load reactance.
Further, the measurable expression is implemented on the mechanism characteristic and the stable characteristic quantity by using the bus power and the power factor angle cotangent value, and the response characteristic of the transient voltage instability of the load side is determined, specifically:
When the variable-impedance load is unstable due to the malignant positive feedback process of impedance change and bus power deviation, the equivalent load impedance is continuously reduced, so that the power factor angle cotangent value is continuously reduced, and more reactive power is absorbed, so that voltage breakdown is caused; the bus power factor angle cotangent value and the equivalent load impedance show a one-to-one correspondence, and the bus power factor angle cotangent value is easier to measure, so that the bus power factor angle cotangent value is used for approximately representing the change of the load impedance, and a measurable response characteristic quantity is formed.
Further, the response to determining the load side transient voltage instability is characterized by the following formula:
Wherein P is bus active power; q is bus reactive power; and (5) the value is a bus power factor angle cotangent value.
Further, for a misjudgment scene caused by more than two intersection points of the actual active power of the bus and a preset target active power curve, the misjudgment rate is reduced by increasing the voltage safety threshold value; for a misjudgment scene caused by unstable domain shrinkage in the dynamic voltage rising process, a method for setting a criterion duration threshold is adopted to reduce the misjudgment rate.
Further, adding additional criteria to reduce the misjudgment rate, converting a differential form in response characteristics into a differential form, and constructing load transient voltage instability criteria based on positive feedback of a power factor, wherein the load transient voltage instability criteria specifically comprise:
Wherein P k and Q k are respectively the active power and the reactive power of the bus at the kth moment; p k+N and Q ktN are respectively the active power and the reactive power of the bus at the k+N moment; t is the duration of the bus active power drop and the power factor angle cotangent value drop; t 1 is a criterion duration threshold; the bus voltage at the time of k+N+T 1; u 1 is a voltage safety threshold.
A second aspect of the present invention provides a system for discriminating transient voltage instability of a load based on positive feedback of a power factor, comprising:
A first determination module: a module for determining the mechanism characteristic and the stability characteristic quantity of the transient voltage instability of the load side based on the transient voltage instability process of the load side deduced by the variable impedance model;
a second determination module: the module is used for carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by utilizing the bus power and the power factor angle cotangent value and determining the response characteristic of transient voltage instability at the load side;
And a judging module: and adding additional criteria to reduce the misjudgment rate, converting a differential form in response characteristics into a differential form, constructing load transient voltage instability criteria based on positive feedback of a power factor, and judging whether the load transient voltage is unstable or not by using the constructed load transient voltage instability criteria.
A third aspect of the present invention provides a computer apparatus comprising: the system comprises a processor, a memory and a bus, wherein the memory stores machine-readable instructions executable by the processor, when the computer equipment runs, the processor and the memory are communicated through the bus, and the machine-readable instructions are executed by the processor to execute a load transient voltage instability judging method based on positive feedback of a power factor.
A fourth aspect of the present invention provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, performs a method of discriminating a transient voltage of a load based on positive feedback of a power factor.
The one or more of the above technical solutions have the following beneficial effects:
The method determines the stable characteristic quantity of the transient voltage instability at the load side based on the variable impedance model, reflects the transient voltage instability process caused by the combined action of a plurality of dynamic devices and static devices, and avoids the problem that a single dynamic device cannot accurately represent the transient voltage instability.
The response characteristic of the transient voltage instability of the load side measures the active power and the reactive power on the bus, is easy to obtain in an actual power grid, has high calculation speed, and can more intuitively represent the transient voltage instability process of the load side.
The load transient voltage instability criterion based on the power factor positive feedback constructed by the invention directly starts from an instability mechanism, and converts a differential form which is easy to generate errors into a differential form, so that the misjudgment rate of a stable scene is lower on the premise of ensuring accurate identification of a load side voltage instability scene.
Additional aspects of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.
FIG. 1 is a circuit of a variable impedance model of a medium load according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the relationship between the equivalent load impedance, i.e. the load absorbs active power, bus voltage, and current flowing through the load in accordance with the first embodiment of the present invention;
FIG. 3 is a schematic diagram of the running track of the running point when the running point is located in different areas according to the first embodiment of the present invention;
FIG. 4 is a schematic diagram of erroneous judgment caused by the existence of more than two intersections between the actual active power and the preset target active power in the first embodiment of the present invention;
FIG. 5 is a schematic diagram illustrating erroneous judgment caused by unstable domain shrinkage during dynamic voltage rise in accordance with an embodiment of the present invention;
FIG. 6 is a schematic diagram of solving the active power and reactive power of a bus in accordance with the first embodiment of the present invention;
FIG. 7 is a graph showing voltage images of 1SB15222,2SB10222,3SB032221 of three 220kV stable nodes in accordance with one embodiment of the present invention;
FIG. 8 shows the result of 1SB15222,2SB10222,3SB032221 of three 220kV stable node decisions in a first embodiment of the present invention;
FIG. 9 is a graph of voltage at a 1RB07321 220kV destabilizing node according to an embodiment of the present invention;
fig. 10 is a decision result of a failure node of 1rb07321 kv in the first embodiment of the present invention;
FIG. 11 is a flowchart of a method for determining transient voltage instability of a medium load according to an embodiment of the present invention.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention.
Embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Example 1
As shown in fig. 11, this embodiment discloses a method for discriminating transient voltage instability of a load based on positive feedback of a power factor, which includes:
deducing a transient voltage instability process at a load side based on a variable impedance model, and determining a mechanism characteristic and a stability characteristic quantity of the transient voltage instability at the load side;
carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by using bus power and a power factor angle cotangent value, and determining the response characteristic of transient voltage instability at a load side;
and adding additional criteria to reduce the false judgment rate, constructing load transient voltage instability criteria based on positive feedback of the power factor, and judging whether the load transient voltage is unstable or not by utilizing the constructed load transient voltage instability criteria.
The scheme of the embodiment aims at extracting the transient voltage instability response characteristic of the load side according to the most essential mechanism of the transient voltage instability of the load side, and judging whether the transient voltage of the load side is unstable or not by utilizing the transient voltage instability criterion of the load based on the positive feedback of the power factor.
The method of this embodiment is mainly implemented as follows:
step 1: determining the mechanism characteristic and the stability characteristic quantity of the transient voltage instability at the load side
As shown in FIG. 1, R Line and X Line are line resistances and reactances, R Load and X Load are equivalent load resistances and reactances, and E r is the stand-alone infinite power supply potential.
The equivalent load current is shown as formula (1):
the voltage across the equivalent load is shown as (2):
the load absorbs active power as shown in formula (3):
the load absorbing reactive power is shown as formula (4):
Assuming that the line impedance remains unchanged in the dynamic change process of the system, the simultaneous formulas (1) - (3) obtain equivalent load impedance, namely the load absorbs active power, bus voltage and the relation of the current flowing through the load is shown in figure 2.
The equivalent load resistance first-order model is shown as (5):
wherein P L0 is the active power preset target, Is the recovery time constant of the conductance.
After the power system is greatly disturbed, if a load is positioned between the point O and the point A, P Load<PL0, the load reduces the equivalent impedance of the load to increase the self-consumed active power, and finally the load is stable at the point A; when the load is positioned between the point A and the point C, the P Load>PL0 increases the self equivalent load impedance, the load absorbs active power and increases between the point C and the point B, decreases between the point B and the point A, and finally the point A is stable. When the operating point is located right than the point C, P Load<PL0 is adopted, the load equivalent load impedance is reduced, but the load absorption active power is further reduced instead, and a positive feedback process is formed.
In summary, the marked operating point is located between the point O and the point a, the motion track of the operating point is shown in fig. 3 when the operating point is located in the region about the point C, and the process expression is shown in the formula (6) when the system load is found to be unstable and the equivalent load impedance is continuously reduced, but the load absorbs the positive feedback process that the active power is continuously reduced. Therefore, the load absorbed active power and the equivalent load impedance can be used as transient stability characteristic quantities.
Wherein P Load is the active power absorbed by the load, Z Load is the equivalent load impedance, and the equivalent load impedance is taken as the stable characteristic quantity of transient voltage instability at the load side.
Step 2: determining response characteristics of load side transient voltage instability
In an actual power grid, the amplitude and phase angle of the bus voltage, the bus active power and the bus reactive power can be measured, but the equivalent load impedance cannot be measured, so that the equivalent load impedance needs to be measured to be effectively applied to the actual power grid.
According to the ac circuit model constructed in fig. 1, the expression of the bus power factor angle cotangent value is as follows:
Wherein R 0 is the bus initial time equivalent load resistance, X 0 is the bus initial time equivalent load reactance, v R is the bus equivalent load resistance drop rate, and v X is the bus equivalent load reactance drop rate.
Assuming that v R and v X are not a function of time, let the power factor angle cotangent value be derived over time, equation (8) is given as follows:
If the equivalent load impedance can be approximated by the bus power factor angle cotangent, then the relationship is required to be satisfied as shown in equation (9):
under the condition of equation (9), the bus power factor angle cotangent decreases with decreasing equivalent load impedance, which may cause the load to absorb more reactive power resulting in bus voltage collapse. Thus, transient voltage instability can be described as a positive feedback process in which the bus active power continues to decrease and the bus power factor angle cotangent value continues to decrease, so that the response characterization of load side transient voltage instability is determined as shown in equation (10):
wherein: p is bus active power, Q is bus reactive power, And (5) the value is a bus power factor angle cotangent value.
Step 3: constructing load transient voltage instability criterion based on power factor positive feedback
There are two misjudgment scenarios in the formula (10): (1) More than two intersection points exist between the actual active power curve of the bus and a preset target active power curve; (2) The voltage rise during the dynamic process causes the unstable region to shrink.
When three intersection points exist between the actual active power of the bus and a preset target active power curve, the operation track after the operation points are drawn from the point O to the point A, from the point A to the point B, from the point B to the point C and from the point C is shown in the figure 4, and the operation point can be kept stable in all areas finally through analysis of the operation track of the operation point. However, when the operating point is located from point B to point C, a process of reducing the equivalent load impedance and reducing the active power occurs, which may lead to erroneous judgment.
Aiming at the misjudgment scene caused by more than two intersection points of the actual active power of the bus and the preset target active power curve, the misjudgment rate can be reduced by adopting a method for setting a voltage safety threshold value. According to the method, the voltage safety problem and the voltage stability problem are considered together, and when the voltage is the safety voltage, the criterion is not triggered, so that erroneous judgment is avoided.
In the dynamic voltage rising process, the unstable region shrinkage schematic diagram is shown in fig. 5, the operation point is just located at the point A, and is the unstable region at the moment, and the operation point moves from the point A to the point B; when the operating point is positioned at the point B, the voltage rises, and at the moment, the operating point moves from the point B to the point C and is operated from an unstable domain to a stable domain; after the operating point is located at the point C, if the voltage is unchanged, the operating point will be in the stable domain all the time and finally operate to the stable point. However, when the operating point is in an unstable region, a load transient voltage instability criterion based on positive feedback of the power factor is triggered, so that erroneous judgment occurs.
Aiming at the misjudgment scene caused by unstable domain shrinkage in the dynamic voltage rising process, the misjudgment rate can be reduced by adopting a method for setting a criterion duration time threshold. According to the method, the criterion duration time threshold is increased in the criterion, so that the misjudgment probability of the operating point caused by returning the unstable domain to the stable domain is reduced.
Therefore, on the basis of the load transient voltage instability criterion based on the positive feedback of the power factor, two additional criteria of a voltage safety threshold value and a criterion duration threshold value are added to reduce the misjudgment rate, and the load transient voltage instability criterion based on the positive feedback of the power factor after the additional criteria are added is shown as a formula (11):
Wherein U is bus voltage; u 1 is a set voltage safety threshold; t is the duration of the bus active power drop and the power factor angle cotangent value drop (i.e., the first two rows of equation (11)); t 1 is a criterion duration threshold.
In order to reduce errors generated by power angle dynamic and measurement noise possibly existing in an actual power grid, a method of time sliding window difference instead of differential is adopted, and finally, a load transient voltage instability criterion based on power factor positive feedback is constructed as shown in a formula (12):
Wherein P k and Q k are active power and reactive power of a bus at the kth moment; p k+N and Q k+N are active power and reactive power of the bus at the k+N moment; the bus voltage at the k+N+T 1 time.
And (3) carrying out calculation analysis: the universal node test system of the electric department mainly comprises two subsystems of a transmitting end test system and a receiving end test system. Comprising 10575 three-phase nodes: about 550 synchronous power supplies; 1031 wind/light renewable energy stations; 28958 kilowatts of power supply assembly machine, 17896 kilowatts of conventional assembly machine, 11062 kilowatts of new energy assembly machine (accounting for 38.2 percent of the assembly machine); and 6 loops of direct current, wherein the sending and receiving ends are connected through 3 loops of 800 ten thousand direct current, the sending end 1 loops back to other power grids, and the receiving end 2 loops back to other power grids for feeding.
The end conveying test system takes 500 kilovolts as a main net rack and is divided into 3 areas: the high-proportion new energy wind and fire in the subarea 1S is bundled and sent out; partition 2S conventional load center; the subarea 3S is used for carrying out high-proportion hydropower transmission, and a weak connection section with a main network exists. Comprises 4941 three-phase nodes; a synchronous power supply 295; 392 wind/light renewable energy stations; the power supply assembly machine is 15498 kilowatts, the conventional assembly machine is 8728 kilowatts, the new energy assembly machine is 6770 kilowatts (wind power 5505 kilowatts, photovoltaic 1265 kilowatts accounting for 43.68% of the assembly machine), and 4-cycle direct current (400 kilowatts 1+800 kilowatts 3).
The receiving end test system takes 500 kilovolts as a main net rack and is divided into 4 areas: partition 1R powered on region; partition 2R contains a high proportion of new energy; the subarea 3R is powered by an alternating current-direct current hybrid; partition 4R is a purely power base and is weakly connected to the main network. Comprises 5624 three-phase nodes and 8767 branches; 255 synchronous power supplies; 639 wind/light renewable energy sites; a power supply main installation 13570 kilowatts, a conventional machine installation 9278 kilowatts, a new energy installation 4292 kilowatts (1300 kilowatts of a wind power installation and 2992 kilowatts of a photovoltaic installation: 50% of class A and class B photovoltaic respectively); the 5 feed-in direct currents comprise 4-circuit +800 kilovolt extra-high voltage direct currents, rated power of 800 kilowatts and 1-circuit +660 kilovolt direct currents, and rated power of 400 kilowatts.
In peak 103 mode of operation, load 7795.4 kw. The 5 direct current feeds total 2800 kilowatts, and the direct current feeds account for 35% of the load. The conventional unit generates 3930 kilowatts, the new energy generates 1065.36 kilowatts (93.36 kilowatts when wind power is started and 972 kilowatts when photovoltaic power is started), and the new energy output accounts for 20% of the generated power and 13.6% of the load. The partition 1R is a load center, and a large proportion of alternating current is powered. Load 1736 kilowatts, power generation 855 kilowatts (conventional unit 567 kilowatts, distributed new energy 288 kilowatts: 17% of load); the alternating current power receiving rate is 881 kilowatts, and the power receiving rate is 50%.
And monitoring the bus voltage with load at the receiving end and the active power and reactive power of the relevant line, and respectively summing the active power and the reactive power of the relevant line to obtain the active power and the reactive power of the bus. And applying load transient voltage instability criteria based on positive feedback of the power factor on the bus, and judging the system as transient voltage instability if one bus criterion is met.
Taking fig. 6 as an example, if it is to determine whether the transient voltage of the 220kV node B is stable, the active power and the reactive power of the bus of the 220kV node B need to be respectively obtained according to the formula (13) and the formula (14), and a load transient voltage instability criterion based on positive feedback of the power factor is applied to the node to determine whether the transient voltage instability occurs in the node.
P＝P1+P21+P22+P3 (13)
Q＝Q1+Q21+Q22+Q3 (14)
As shown in FIG. 7, the voltage images of 220kV nodes such as 1SB15222,2SB10222,3SB032221 and the like are all recovered to be more than 0.8pu in 10 seconds, so that the nodes belong to stable nodes. The three nodes are judged by using load transient voltage instability criteria based on positive feedback of the power factor, the results are shown in figure 8, the output of 0 represents no trigger criteria, the output of 1 represents trigger criteria, and all the three nodes have no trigger criteria, so that the three nodes can be judged to be stable correctly.
The voltage image of the node 1RB07321 with the voltage class of 220kV is shown in FIG. 9, and the voltage of the node is not recovered to be more than 0.8pu within 10 seconds, so that the node belongs to a destabilizing node. The node is judged by using load transient voltage instability criteria based on positive feedback of the power factor, and the result is shown in fig. 10, and the output of the judgment result is 1, so that the node can be correctly judged as instability.
Through the analysis, the load transient voltage instability criterion based on the positive feedback of the power factor can correctly judge whether the node is stable.
Example two
An object of the present embodiment is to provide a load transient voltage instability discrimination system based on positive feedback of a power factor, including:
A first determination module: a module for determining the mechanism characteristic and the stability characteristic quantity of the transient voltage instability of the load side based on the transient voltage instability process of the load side deduced by the variable impedance model;
a second determination module: the module is used for carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by utilizing the bus power and the power factor angle cotangent value and determining the response characteristic of transient voltage instability at the load side;
And a judging module: and adding additional criteria to reduce the misjudgment rate, converting a differential form in response characteristics into a differential form, constructing load transient voltage instability criteria based on positive feedback of a power factor, and judging whether the load transient voltage is unstable or not by using the constructed load transient voltage instability criteria.
Example III
It is an object of the present embodiment to provide a computing device comprising: a processor, a memory and a bus, said memory storing machine readable instructions executable by said processor, said processor and said memory communicating over the bus when the computer device is running, said machine readable instructions being executed by said processor to perform the steps of the method described above.
Example IV
An object of the present embodiment is to provide a computer-readable storage medium.
A computer readable storage medium having stored thereon a computer program which when executed by a processor performs the steps of the above method.
The steps involved in the devices of the second, third and fourth embodiments correspond to those of the first embodiment of the method, and the detailed description of the embodiments can be found in the related description section of the first embodiment. The term "computer-readable storage medium" should be taken to include a single medium or multiple media including one or more sets of instructions; it should also be understood to include any medium capable of storing, encoding or carrying a set of instructions for execution by a processor and that cause the processor to perform any one of the methods of the present invention.
It will be appreciated by those skilled in the art that the modules or steps of the invention described above may be implemented by general-purpose computer means, alternatively they may be implemented by program code executable by computing means, whereby they may be stored in storage means for execution by computing means, or they may be made into individual integrated circuit modules separately, or a plurality of modules or steps in them may be made into a single integrated circuit module. The present invention is not limited to any specific combination of hardware and software.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it is intended to cover all modifications or variations within the scope of the invention as defined by the claims of the present invention.
Claims (4)
1. The method for judging the transient voltage instability of the load based on the positive feedback of the power factor is characterized by comprising the following steps:
deducing a transient voltage instability process at a load side based on a variable impedance model, and determining a mechanism characteristic and a stability characteristic quantity of the transient voltage instability at the load side;
The variable impedance model-based deduction load side transient voltage instability process is used for determining the mechanism characteristics of load side transient voltage instability, and specifically comprises the following steps:
When a variable-impedance load enters an unstable domain to generate instability, a malignant positive feedback characteristic exists between impedance change and active power acquisition of load absorption; the load absorbs the active power to obtain the active power preset target and change the impedance, and the impedance change causes the load to absorb the active power to deviate further from the active power preset target, so as to form a positive feedback process of the load absorbing the active power deviation, the load changing impedance and the load absorbing the active power to deviate further;
The variable impedance model-based deduction load side transient voltage instability process is used for determining that the stability characteristic quantity of the load side transient voltage instability is the equivalent impedance of a load bus, and specifically comprises the following steps:
The first-order differential model of the variable impedance load is as follows:
Wherein R Load is an equivalent load resistance; A recovery time constant for conductance; p L0 is an active power preset target; p Load is the load absorption active power;
The stable characteristic quantity of transient voltage instability at the load side is determined as bus equivalent impedance:
Wherein X Load is equivalent load reactance;
carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by using bus power and a power factor angle cotangent value, and determining the response characteristic of transient voltage instability at a load side;
The method is characterized in that measurable expression is implemented on the mechanism characteristic and the stability characteristic quantity by using bus power and a power factor angle cotangent value, and the response characteristic of transient voltage instability at the load side is determined, specifically:
when the variable impedance load is unstable due to the malignant positive feedback process of impedance change and bus power deviation, the equivalent load impedance is continuously reduced, so that the bus power factor angle cotangent value is continuously reduced, and more reactive power is absorbed, so that voltage breakdown is caused; the bus power factor angle cotangent value and the equivalent load impedance show a one-to-one correspondence, and the bus power factor angle cotangent value is easier to measure; therefore, the change of equivalent load impedance is approximately represented by the bus power factor angle cotangent value, and a measurable response characteristic quantity is formed;
the response to determine load side transient voltage instability is characterized as:
Wherein P is bus active power; q is bus reactive power; The power factor angle cotangent value of the bus is;
Adding additional criteria to reduce the misjudgment rate, converting a differential form in response characteristics into a differential form, constructing load transient voltage instability criteria based on positive feedback of a power factor, and judging whether the load transient voltage is unstable or not by utilizing the constructed load transient voltage instability criteria, wherein the method specifically comprises the following steps:
Wherein P k and Q k are respectively the active power and the reactive power of the bus at the kth moment; p k+N and Q k+N are respectively the active power and the reactive power of the bus at the k+N moment; t is the duration of the bus active power drop and the power factor angle cotangent value drop; t 1 is a criterion duration threshold; The bus voltage at the time of k+N+T 1; u 1 is a voltage safety threshold;
For a misjudgment scene caused by more than two intersection points of the actual active power of the bus and a preset target active power curve, the misjudgment rate is reduced by increasing the method for setting the voltage safety threshold value; for a misjudgment scene caused by unstable domain shrinkage in the dynamic voltage rising process, reducing the misjudgment rate by adopting a method for setting a criterion duration threshold;
The additional criteria are a voltage safety threshold and a criterion duration threshold.
2. The load transient voltage unstability discrimination system based on the positive feedback of the power factor is characterized by comprising the following components:
A first determination module: a module for determining the mechanism characteristic and the stability characteristic quantity of the transient voltage instability of the load side based on the transient voltage instability process of the load side deduced by the variable impedance model;
The variable impedance model-based deduction load side transient voltage instability process is used for determining the mechanism characteristics of load side transient voltage instability, and specifically comprises the following steps:
When a variable-impedance load enters an unstable domain to generate instability, a malignant positive feedback characteristic exists between impedance change and active power acquisition of load absorption; the load absorbs the active power to obtain the active power preset target and change the impedance, and the impedance change causes the load to absorb the active power to deviate further from the active power preset target, so as to form a positive feedback process of the load absorbing the active power deviation, the load changing impedance and the load absorbing the active power to deviate further;
The variable impedance model-based deduction load side transient voltage instability process is used for determining that the stability characteristic quantity of the load side transient voltage instability is the equivalent impedance of a load bus, and specifically comprises the following steps:
The first-order differential model of the variable impedance load is as follows:
Wherein R Load is an equivalent load resistance; A recovery time constant for conductance; p L0 is an active power preset target; p Load is the load absorption active power;
The stable characteristic quantity of transient voltage instability at the load side is determined as bus equivalent impedance:
Wherein X Load is equivalent load reactance;
a second determination module: the module is used for carrying out measurable expression on the mechanism characteristic and the stable characteristic quantity by utilizing the bus power and the power factor angle cotangent value and determining the response characteristic of transient voltage instability at the load side;
The method is characterized in that measurable expression is implemented on the mechanism characteristic and the stability characteristic quantity by using bus power and a power factor angle cotangent value, and the response characteristic of transient voltage instability at the load side is determined, specifically:
when the variable impedance load is unstable due to the malignant positive feedback process of impedance change and bus power deviation, the equivalent load impedance is continuously reduced, so that the bus power factor angle cotangent value is continuously reduced, and more reactive power is absorbed, so that voltage breakdown is caused; the bus power factor angle cotangent value and the equivalent load impedance show a one-to-one correspondence, and the bus power factor angle cotangent value is easier to measure; therefore, the change of equivalent load impedance is approximately represented by the bus power factor angle cotangent value, and a measurable response characteristic quantity is formed;
the response to determine load side transient voltage instability is characterized as:
Wherein P is bus active power; q is bus reactive power; The power factor angle cotangent value of the bus is;
and a judging module: the method comprises the steps of adding additional criteria to reduce the misjudgment rate, converting a differential form in response characteristics into a differential form, constructing a load transient voltage instability criterion based on positive feedback of a power factor, and judging whether the load transient voltage is unstable or not by using the constructed load transient voltage instability criterion, wherein the module is specifically as follows:
Wherein P k and Q k are respectively the active power and the reactive power of the bus at the kth moment; p k+N and Q k+N are respectively the active power and the reactive power of the bus at the k+N moment; t is the duration of the bus active power drop and the power factor angle cotangent value drop; t 1 is a criterion duration threshold; The bus voltage at the time of k+N+T 1; u 1 is a voltage safety threshold;
For a misjudgment scene caused by more than two intersection points of the actual active power of the bus and a preset target active power curve, the misjudgment rate is reduced by increasing the method for setting the voltage safety threshold value; for a misjudgment scene caused by unstable domain shrinkage in the dynamic voltage rising process, reducing the misjudgment rate by adopting a method for setting a criterion duration threshold;
The additional criteria are a voltage safety threshold and a criterion duration threshold.
3. A computer device, comprising: a processor, a memory and a bus, said memory storing machine readable instructions executable by said processor, said processor in communication with said memory via the bus when the computer device is running, said machine readable instructions when executed by said processor performing the power factor positive feedback based load transient voltage instability discrimination method according to claim 1.
4. A computer readable storage medium, wherein a computer program is stored on the computer readable storage medium, and the computer program is executed by a processor to perform the method for discriminating load transient voltage instability based on positive feedback of power factor according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410069649.2A CN117955120B (en) | 2024-01-17 | 2024-01-17 | Load transient voltage instability discrimination method and system based on power factor positive feedback |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410069649.2A CN117955120B (en) | 2024-01-17 | 2024-01-17 | Load transient voltage instability discrimination method and system based on power factor positive feedback |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN117955120A CN117955120A (en) | 2024-04-30 |
| CN117955120B true CN117955120B (en) | 2024-09-10 |
Family
ID=90804284
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202410069649.2A Active CN117955120B (en) | 2024-01-17 | 2024-01-17 | Load transient voltage instability discrimination method and system based on power factor positive feedback |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117955120B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111725804A (en) * | 2020-06-10 | 2020-09-29 | 国网新疆电力有限公司 | Comprehensive load model parameter identification method and computer readable storage medium |
| CN113341210A (en) * | 2021-05-20 | 2021-09-03 | 南瑞集团有限公司 | Bus transient voltage stability evaluation method, system, medium and computing device |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101630839B (en) * | 2009-08-06 | 2012-07-18 | 中国电力科学研究院 | Transient state and medium and long-term voltage stability distinguishing method based on power current reversal |
| CN114722333B (en) * | 2022-03-09 | 2024-10-01 | 北京科东电力控制系统有限责任公司 | Method and system for estimating transient voltage stability limit of receiving end system |
| CN115149582A (en) * | 2022-06-23 | 2022-10-04 | 国网浙江省电力有限公司宁波供电公司 | Voltage stability analysis method for photovoltaic grid-connected power system based on monotonic system theory |
-
2024
- 2024-01-17 CN CN202410069649.2A patent/CN117955120B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111725804A (en) * | 2020-06-10 | 2020-09-29 | 国网新疆电力有限公司 | Comprehensive load model parameter identification method and computer readable storage medium |
| CN113341210A (en) * | 2021-05-20 | 2021-09-03 | 南瑞集团有限公司 | Bus transient voltage stability evaluation method, system, medium and computing device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN117955120A (en) | 2024-04-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Kong et al. | Fault detection and location method for mesh-type DC microgrid using pearson correlation coefficient | |
| CN104316786B (en) | A kind of mixing island detection method | |
| CN110198044B (en) | LCC-HVDC commutation failure immunity evaluation method and system considering transmission power limit | |
| CN104793067A (en) | Estimation system and method for power adjustment and electric energy quality of wind power station | |
| CN103606922A (en) | Approximate judgment method for power angle stability of electric power system based on typical fault set | |
| CN115800409A (en) | Active and reactive cooperative control method and device considering new energy multi-station short-circuit ratio | |
| CN107104463B (en) | Converter station considers idle active input amount optimization method during black starting-up | |
| CN117996828A (en) | Method and system for identifying voltage instability of new energy AC/DC power grid in response to driving | |
| CN117955120B (en) | Load transient voltage instability discrimination method and system based on power factor positive feedback | |
| CN103997041A (en) | On-line voltage stability determination system of alternating current and direct current mixing connection system | |
| CN116054224A (en) | Quick evaluation method for commutation failure of multi-feed direct-current transmission system | |
| CN109149636A (en) | Wind power integration point transient stability based on Dynamic Security Region influences research method | |
| CN112217220B (en) | Safety and stability defense method and device for new energy source sending multi-terminal flexible direct current power grid | |
| CN113242018A (en) | Photovoltaic equipment fault diagnosis method and application device thereof | |
| CN102868165A (en) | Reactive power capability estimation method for fan and wind power collection line | |
| CN113725890A (en) | New energy power generation power distribution optimization method and device | |
| Zhang et al. | Key feature selection method for intelligent assessment of transient power angle stability based on physical mechanism and improved Relief | |
| CN105846433A (en) | Power distribution network transient analysis method based on intermittent distributed power supply fluctuation | |
| CN113315100A (en) | Micro-grid protection method and system based on convolutional neural network | |
| CN113917249B (en) | Wind turbine generator high-low voltage fault ride through monitoring method and system | |
| CN116988946B (en) | Wind power system fault discrimination method based on active detection signal injection | |
| CN113139152B (en) | Method and system for evaluating adaptability of instantaneous load of direct-current distribution network of offshore oil production platform | |
| Tian et al. | Optimal Configuration of Distributed Synchronous Condenser For High-Proportion Renewable Sending End Power Grid | |
| Lou et al. | Research on Voltage Stability of HVDC Receiving-end System Based on Power Limit Trajectory | |
| Yu et al. | Analysis of the Influence of System Strength on Transient Overvoltage for Power Systems with Renewable Energy Sources |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |