CN115313353A - Method and system for analyzing chain instability operation characteristics of receiving-end system - Google Patents

Abstract

The invention discloses a method and a system for analyzing interlocking instability operation characteristics of a receiving end system, and belongs to the technical field of power systems. The method comprises the following steps: establishing a simulation model of the AC/DC hybrid receiving end system, and performing simulation operation of the AC/DC hybrid receiving end system aiming at the simulation model to obtain a simulation result; and determining whether the operation characteristic of linkage instability exists in the alternating current-direct current series-parallel connection receiving end system or not according to the simulation result. The invention strictly controls the operation boundary conditions of each sub-area of the receiving-end system, and can avoid disordered and repeated work when the required power grid operation mode is adjusted, so that the simulation result is more visual and clear and has analytical significance.

Description

Method and system for analyzing chain instability operation characteristics of receiving-end system

Technical Field

The present invention relates to the field of power system technologies, and in particular, to a method and a system for analyzing chain instability operating characteristics of a receiving end system.

Background

Due to the characteristic that domestic energy centers and loads are not distributed uniformly, a high-voltage direct current (LCC-HVDC) transmission technology based on a power grid commutation converter is developed rapidly by virtue of the advantages of long transmission distance, large transmission power capacity and the like. With the successive operation of ultrahigh voltage and extra-high voltage direct current projects, the number of mixed alternating current and direct current is increased, and a plurality of direct currents are sent out in the same direction or received into a power grid to have the characteristic of strong direct current and weak direct current. China power grids in China, china power grids in east China and south China have presented a multi-direct-current feed-in system structure.

After the power grid breaks down, the multiple loops of direct current may be simultaneously impacted greatly, and the risk of simultaneous or sequential direct current blocking is increased, so that the influence on the alternating current system is serious, and the safe and stable operation of the alternating current and direct current hybrid system is threatened. Therefore, it is necessary to perform fast exploration and analysis of strongly correlated faults and accident chains for the problem of frequent ac/dc coupling in the ac/dc hybrid system, so as to avoid large-scale power flow transfer and power imbalance caused by dc blocking.

Because direct current transmission depends on the coordinated operation of an alternating current and direct current power grid, the operation characteristic analysis of the power grid at the moment usually only considers a certain subregion. According to the traditional analysis scheme, by splitting the connecting lines among all sub-areas in the receiving end system, the fault transmission channel after the system accident is cut off, the analysis process of the alternating current-direct current receiving end system is simplified, and therefore the conduction process and the influence factors after the alternating current-direct current hybrid receiving end system accident cannot be accurately analyzed.

Disclosure of Invention

In order to solve the above problems, the present invention provides a method for analyzing the interlock instability operating characteristics of a receiving end system, including:

establishing a simulation model of the AC/DC hybrid receiving end system, and performing simulation operation of the AC/DC hybrid receiving end system aiming at the simulation model to obtain a simulation result; the simulation operation comprises:

determining a system operation mode of an alternating current-direct current hybrid receiving end system;

according to the system operation mode, risk scanning is carried out on the alternating current-direct current series-parallel connection receiving end system according to regions, and the maximum fault risk affecting operation in each regional power grid is determined;

determining the fault which influences the maximum operation in each regional power grid according to the fault risk;

adjusting the power grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid;

and determining whether the operation characteristic of linkage instability exists in the alternating current-direct current series-parallel connection receiving end system or not according to the simulation result.

Optionally, determining a system operation mode of the alternating current-direct current hybrid receiving end system specifically includes:

determining the maximum operable range, the starting mode and the load working condition of the direct current power in each region of the alternating current and direct current hybrid receiving end system, determining the junctor transmission power among the regions according to the maximum operable range, the starting mode and the load working condition of the direct current power, and determining the system operating mode of the alternating current and direct current hybrid receiving end system according to the junctor transmission power.

Optionally, the failure risk is at least one of: a three-permanent-N-1 fault and a three-permanent-N-2 fault.

Optionally, adjusting the power grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid, specifically including:

selecting any regional power grid in each region of an alternating-current and direct-current parallel-serial receiving end system as a starting point for adjusting an operation mode, changing the load quantity of any regional power grid and the system rotation standby quantity which are equal, and switching on/off a capacitor and a reactor in a preset bus range aiming at any regional power grid to determine a critical instability operation mode of any regional power grid;

and adjusting the sub-area power grids in any one area power grid to a critical stable working condition according to the maximum operation fault in the power grid.

Optionally, determining an operating characteristic that the ac/dc series-parallel receiving end system has linkage instability includes:

monitoring bus voltage, a unit power angle and power exchange conditions of a tie line between each area in each area of the alternating-current and direct-current hybrid receiving end system;

and judging whether the operation characteristic of linkage instability exists in the AC-DC hybrid receiving end system or not according to the bus voltage, the power angle of the unit and the power exchange condition of the connecting lines among the regions.

Optionally, it is determined whether an operation characteristic of linkage instability exists in the ac/dc series-parallel receiving end system, specifically as follows:

determining whether a certain area has a low voltage problem or a plurality of areas have a low voltage problem in each area of the alternating current-direct current hybrid receiving end system according to the bus voltage;

determining whether voltage breakdown problems exist in certain areas or not in all areas of the alternating current-direct current hybrid receiving end system or voltage breakdown problems occur in the whole network according to the bus voltage;

determining whether the power angles of the units in the whole network of the alternating current-direct current hybrid receiving end system are out of step, partially out of step or out of step of the whole network;

determining that the tie lines between the areas are not disconnected and are partially or completely split according to the power exchange condition of the tie lines between the areas in the alternating-current and direct-current hybrid receiving end system;

if a certain area has a low-voltage problem, the power angles of the units in the whole network are not out of step, and the connecting lines among the areas are not disconnected, judging that the low-voltage operation problem only exists in the certain area of the alternating-current and direct-current hybrid receiving end system;

if the low voltage problem exists in a certain area, the power angle of the generator set in the whole network is partially out of step and the partial rows of the interconnection lines among the areas are arranged, judging that the alternating current-direct current hybrid connection receiving end system only has the regional low voltage operation characteristic, and judging the sequence and the cause-effect relationship of the linkage accidents according to the inter-area bus voltage drop time sequence;

if voltage collapse problems exist in some areas, the power angles of the generator sets in the whole network are partially out of step and the connection lines among the areas are partially disconnected, the fact that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the causal relationship of the chain accidents are judged according to the inter-area bus voltage drop time sequence;

if the voltage collapse problem occurs in the whole network, the power angles of the units in the whole network are out of step and the tie lines among the regions are disconnected, judging that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem, and judging the sequence and the causal relationship of the chain accidents according to the bus voltage drop time sequence among the regions.

The invention also provides a system for analyzing the interlocking instability operating characteristics of the receiving end system, which comprises the following components:

the simulation operation unit is used for establishing a simulation model of the alternating current-direct current hybrid receiving end system and performing simulation operation of the alternating current-direct current hybrid receiving end system aiming at the simulation model to obtain a simulation result; the simulation operation comprises:

determining a system operation mode of an alternating current-direct current series-parallel connection receiving end system;

according to the system operation mode, risk scanning is carried out on the alternating current-direct current series-parallel connection receiving end system according to regions, and the maximum fault risk affecting operation in each regional power grid is determined;

determining the fault which influences the maximum operation in each regional power grid according to the fault risk;

adjusting the power grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid;

and the analysis unit is used for determining whether the operation characteristic of linkage instability exists in the alternating current-direct current series-parallel connection receiving end system or not according to the simulation result.

Optionally, the method for determining the system operation mode of the alternating current-direct current hybrid receiving end system specifically comprises the following steps:

determining the maximum operable range, the starting mode and the load working condition of the direct current power in each region of the alternating current and direct current hybrid receiving end system, determining the junctor transmission power among the regions according to the maximum operable range, the starting mode and the load working condition of the direct current power, and determining the system operating mode of the alternating current and direct current hybrid receiving end system according to the junctor transmission power.

Optionally, the risk of failure is at least one of: a triple permanent N-1 fault and a triple permanent N-2 fault.

Optionally, the adjusting the power grid operation mode of any regional power grid in each region to the critical instability operation mode according to the maximum fault in the power grid includes:

selecting any regional power grid in each region of an alternating-current and direct-current parallel-serial receiving end system as a starting point for adjusting an operation mode, changing the load quantity of any regional power grid and the system rotation standby quantity which are equal, and switching on/off a capacitor and a reactor in a preset bus range aiming at any regional power grid to determine a critical instability operation mode of any regional power grid;

and adjusting the sub-area power grids in any area power grid to a critical stable working condition according to the maximum operation fault in the power grid.

Optionally, determining that the ac-dc series-parallel receiving end system has an operation characteristic of linkage instability includes:

monitoring bus voltage, a unit power angle and power exchange conditions of tie lines among all areas of an alternating current-direct current hybrid receiving end system;

and judging whether the operation characteristic of linkage instability exists in the alternating current-direct current hybrid receiving end system or not according to the bus voltage, the power angle of the unit and the power exchange condition of the connecting lines among the regions.

Optionally, it is determined whether an operation characteristic of linkage instability exists in the ac/dc series-parallel receiving end system, specifically as follows:

determining whether a certain area has a low voltage problem or a plurality of areas have a low voltage problem in each area of the alternating current-direct current hybrid receiving end system according to the bus voltage;

determining whether voltage breakdown problems exist in certain areas or not in all areas of the alternating current-direct current hybrid receiving end system or voltage breakdown problems occur in the whole network according to the bus voltage;

determining whether the power angles of the units in the whole network of the alternating current-direct current hybrid receiving end system are out of step, partially out of step or out of step of the whole network;

determining that the tie lines between the areas are not disconnected and are partially or completely cracked according to the power exchange condition of the tie lines between the areas in each area of the alternating-current and direct-current hybrid-link receiving end system;

if a certain area has a low-voltage problem, the power angles of the units in the whole network are not out of step, and the connecting lines among the areas are not disconnected, judging that the low-voltage operation problem only exists in the certain area of the alternating-current and direct-current hybrid receiving end system;

if the low voltage problem exists in a certain area, the power angle of the unit in the whole network is partially out of step and the connecting lines among the areas are partially arranged, judging that the alternating current-direct current hybrid receiving end system only has the regional low voltage operation characteristic, and judging the sequence and the cause-effect relationship of the chain accidents according to the bus voltage drop time sequence among the areas;

the method comprises the steps that voltage collapse problems exist in certain areas, power angles of a unit in the whole network are partially out of step, and connecting lines among the areas are partially disconnected, so that the fact that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the causal relationship of chain accidents are judged according to a bus voltage drop time sequence among the areas;

if the voltage collapse problem occurs in the whole network, the power angles of the units in the whole network are all out of step, and the tie lines among all the regions are all disconnected, the fact that the alternating-current and direct-current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the cause-and-effect relationship of the chain accidents are judged according to the bus voltage collapse time sequence among the regions.

The invention has the advantages that:

(1) The invention strictly controls the operation boundary conditions of each sub-area of the receiving end system, and can avoid disordered and repeated work when the required power grid operation mode is adjusted, so that the simulation result is more visual and clear and has analysis significance;

(2) The method can obtain key factors of the influence degree of the multi-feed-in receiving end system on the transient stability of the system, can obtain the time sequence and the incidence relation of instability of each subarea caused by faults, and is suitable for providing a method for analyzing the safety and the stability of the system in actual engineering;

(3) According to the method, the accuracy of the multi-direct-current feed-in receiving-end system characteristic analysis method is verified through the analysis results of the multiple receiving-end systems and the derived operation mode examples thereof, and the method has strong practicability in engineering analysis.

Drawings

FIG. 1 is a flow chart of an embodiment of the method of the present invention;

FIG. 2 is a structure diagram of a Z-region grid network frame in the embodiment of the method of the invention;

FIG. 3 is a timing diagram of voltage sag of each province after a certain worst three permanent N-1 fault in the province A in the embodiment of the method of the present invention;

FIG. 4 is a graph of the D provincial bus voltage in the embodiment of the method of the present invention;

FIG. 5 is a graph of the voltage curve of the bus in province B in the embodiment of the method of the present invention;

FIG. 6 is a C province bus voltage curve diagram in the embodiment of the method of the present invention;

FIG. 7 is a graph of the voltage of the provincial bus A in the embodiment of the method of the present invention;

FIG. 8 is a graph of the power angle of the D-province unit in the embodiment of the method of the present invention;

FIG. 9 is a graph of the power angle of the province unit B in the embodiment of the method of the present invention;

FIG. 10 is a power angle diagram of a C-province unit in the embodiment of the method of the present invention;

FIG. 11 is a power angle diagram of an A-province unit in the embodiment of the method of the present invention;

FIG. 12 is a graph of the active power of the C province-D province tie I line in the embodiment of the method of the present invention;

FIG. 13 is a graph of the active power of the C province-D province contact II line in the embodiment of the method of the present invention;

FIG. 14 is a graph of the active power of the C province-D province connection III line in the embodiment of the method of the present invention;

FIG. 15 is a graph of the active power of the communication I line between provinces B and D in the embodiment of the method of the present invention;

FIG. 16 is a graph of the active power of the communication II line between provinces B and D in the embodiment of the method of the present invention;

FIG. 17 is a timing diagram of voltage sag of each province after a certain worst triple permanent N-1 fault in province A in the embodiment of the method of the present invention;

FIG. 18 is a graph of the D province bus voltage in the embodiment of the method of the present invention;

FIG. 19 is a graph of the bus voltage of province B in the embodiment of the method of the present invention;

FIG. 20 is a graph of the C-province bus voltage in the embodiment of the method of the present invention;

FIG. 21 is a graph of the voltage of the provincial bus A in the embodiment of the method of the present invention;

FIG. 22 is a graph of the power angle of the D-province unit in the embodiment of the method of the present invention;

FIG. 23 is a power angle diagram of a B-province unit in the embodiment of the method of the present invention;

FIG. 24 is a power angle diagram of a C-province unit in the embodiment of the method of the present invention;

FIG. 25 is a graph of the power angle of the economizer group A in the embodiment of the method of the present invention;

FIG. 26 is a graph of the active power of the C province-D province tie I line in the embodiment of the method of the present invention;

FIG. 27 is a graph of the active power of the C province-D province contact II line in the embodiment of the method of the present invention;

fig. 28 is a graph of the active power of line III of the C-D province tie line in the embodiment of the method of the present invention;

FIG. 29 is a graph of the active power of line I of the province-D province tie line in the embodiment of the method of the present invention;

FIG. 30 is a graph of the active power of line II of the province-D province junctor in the embodiment of the method of the present invention;

FIG. 31 is a graph showing the active power of the tie line between provinces A and D after the most serious failure of province A caused by different startup modes of province A in the embodiment of the method of the present invention;

FIG. 32 is a graph of the voltage of the D-province bus after the most serious failure of the A-province in different boot modes of the A-province in the embodiment of the method of the present invention;

FIG. 33 is a block diagram of the system of the present invention.

Detailed Description

Example embodiments of the present invention will now be described with reference to the accompanying drawings, however, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, which are provided for a complete and complete disclosure of the invention and to fully convey the scope of the invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same unit/element is denoted by the same reference numeral.

Unless otherwise defined, terms (including 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. In addition, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their context in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.

The invention is further illustrated by the following examples:

the invention provides a method for analyzing the interlocking instability operating characteristics of a receiving end system, which comprises the following steps of:

1. determining the transmission power of each inter-domain connecting line according to the maximum operable range of the direct current power in each domain, the starting mode and the load working condition, and further determining the operation mode of a receiving end system;

2. based on the established system operation mode, risk scanning is respectively carried out on the whole network alternating current system according to regions, and the fault risk influencing the maximum operation characteristics of the power grid of each region is obtained, wherein the fault risk is the risk existing in the whole network alternating current system and comprises the following steps: a three-permanent-N-1 fault and a three-permanent-N-2 fault;

3. respectively determining the faults which have the largest influence on the operating characteristics in the power grid of each area;

4. and (3) respectively adjusting the operation modes of the regional power grids to critical instability operation modes according to the known faults in the step (3), wherein the adjustment method comprises the following steps:

1) Selecting a certain regional power grid A as a research object and adjusting an operation mode starting point, changing the load capacity of the region and the system rotation spare quantity equal to the load capacity of the region, switching a capacitor and a reactor around a bus, and ensuring that the regional power grid A operates at the same voltage level in different operation modes, thereby obtaining a critical instability operation mode of the region A;

2) Adjusting the sub-area power grids of the next adjacent area A to a critical stable working condition according to the determined faults of the power grids of the areas in the step 3, and then checking whether the area operates in the critical unstable working condition by using the faults of the power grid A of the selected area;

3) According to the adjusting method 2), adjusting the power grid modes of the remaining sub-areas one by one to a critical stable working condition, and judging whether the whole grid only has the area A to operate in the critical unstable working condition; if only the area A operates in the critical instability working condition, entering the step 5; otherwise, returning to the adjustment method 1), readjusting the area A to the critical instability working condition, and repeating the method 2) until only the area A in the whole network system operates in the critical instability working condition, so that the tide adjustment is finished.

5. According to the simulation result output in the step 4, when only a certain area of the whole network operates under the working condition of critical instability, whether a whole network system has the interlocking instability operation characteristic caused by the certain area is judged, the bus voltage, the unit power angle and the active power exchange condition of the connecting line between the areas in each area need to be monitored, and the judgment rule can be divided into:

5-1) if only one area has a low voltage problem, the power angle of the whole network is not out of step, and the connecting lines among the sub-areas are not disconnected in the simulation result, judging that the low voltage operation problem only exists in one area in the multi-feed receiving end system;

5-2) if a few areas in the simulation result have low voltage problems, the power angle of a unit in a part of areas is out of step and a few inter-area connecting lines have disconnection problems, judging that the multi-feed receiving end system only has regional low voltage operation characteristics, and judging the sequence and the cause-effect relationship of the linkage accidents according to the inter-area bus voltage drop time sequence;

5-3) if voltage collapse exists in some areas, power angles of unit sets in some areas are out of step and disconnection problems occur in some inter-area connecting lines in the simulation result, judging that the multi-feed receiving end system only has the problem of regional voltage collapse, and judging the sequence and the causal relationship of the chain accidents according to inter-area bus voltage drop time sequences;

and 5-4) if the whole-network voltage collapse problem, the power angle of the whole-network unit is out of step and all inter-area connecting lines are disconnected in the simulation result, judging that the multi-feed receiving-end system only has the regional voltage collapse problem, and judging the sequence and the cause-and-effect relationship of the chain accidents according to the inter-area bus voltage drop time sequence.

The method can be realized simply according to a calculation process and an analysis method, is simple and easy to implement, can obviously improve the analysis efficiency by adopting the method in the process of analyzing the running characteristics of the multi-direct-current feed-in receiving-end system, saves manpower and material resources, and quickly determines the running characteristics of the system.

Based on the structure of a regional power grid at the end of 2021 years, the structure comprises 2021-year power grid data uniformly provided by a national power grid dispatching control center, and simulation calculation is performed in different starting operation modes of province A by taking the problem of transient security and stability of a Z-region power grid as a research object.

The calculation program used was the power system comprehensive analysis program psaspp version 7.61.06 (Windows version) of the institute of electrical power science of china.

By the end of 2021, as shown in fig. 2, after the extra-high voltage ring networks in the Z region are sequentially put into operation among the provinces, the power transmission level of the fed-in Z region direct current group is significantly improved, and the connection between four power-saving circuits in the Z region is tighter. The voltage stability problem of each of the four provinces in the original Z region power grid can be caused by a single fault in a severe mode, and the whole region linkage voltage stability problem can be caused. The method is based on two calculation examples, and the influence of a single fault in the province A on the operation characteristics of the power grid in the region Z is analyzed according to the starting level of the power grid in the province A of 1400 ten thousand kilowatts and 1800 ten thousand kilowatts respectively.

1) Instability mode one (A1400 thousands kilowatts of power-saving)

The operation mode of each provincial power grid is as follows: a is saved, the machine starts up to 1400 million kilowatts, A is saved, a certain direct current is 450 million kilowatts, A is saved, 370 million kilowatts are sent out by alternating current, 0 phase modulator is arranged, and A is saved, 8 percent (112 ten thousand kilowatts) of the machine set is rotatably equipped; the load of a province B is 1513 ten thousand kilowatts, the province B is started 658 ten thousand kilowatts, the province B is a direct current 400 ten thousand kilowatts, the province B is exchanged and receives 480 ten thousand kilowatts, the province B is a unit 134 ten thousand kilowatts of the province B and is equipped with 1 phase modulator; load 3204 ten thousand kilowatts are saved in the province D, power is saved in the province D by 3753 ten thousand kilowatts, power is saved in the province C by 310 ten thousand kilowatts, power is saved in the province D by 580 ten thousand kilowatts on the section of the eastern part of the province D in the western part of the province D, the minimum power is met in the province D, and a certain direct current 300 ten thousand kilowatts are saved in the province D. By applying the operation mode of the receiving-end system, only the power grid of the province A runs in a critical instability state after being subjected to a certain most serious three-permanent-magnet N-1 fault of the province A, and as shown in figure 3, the rest three-province power grids in the Z area all run in a critical stable working condition.

By comparing the lowest bus voltage values in each provincial power grid, as shown in fig. 4-7, it can be obtained that only the voltage of the A power grid oscillates around 0.4pu after a fault occurs and cannot be recovered along with time, and at this time, the power grid in the Z region does not have the condition of interlocking instability of the whole power grid.

Then, by comparing the power angle difference values of the units in each provincial power grid, as shown in fig. 8-11, it can be obtained that the power angle of the unit in the A-only provincial power grid is out of step for the power angles of the units in other provinces after the fault occurs, and at this time, the power grid in the Z region does not have the condition of interlocking instability of the whole grid.

Finally, comparing the power of the tie lines among the provinces after the three permanent magnet N-1 fault in the province A is most serious, as shown in figures 12-16, the tie lines among the provinces of the Z-region power grid after the fault can be further determined not to be disconnected, so that the fact that the fault of the power-saving network A only causes the voltage instability of the power grid in the province A in the operation mode of the Z region can be obtained, and the rest three provinces and three networks are not influenced.

2) Instability mode two (A1800 ten thousands kilowatts of power-saving)

The operation modes of the power grids of each province are as follows: a is saved, the machine starts up to 1800 ten thousand kilowatts, A is saved, a certain direct current is 450 ten thousand kilowatts, A is saved, 370 ten thousand kilowatts are sent out by alternating current, 0 phase modifier is arranged, and A is saved, 5 percent (90 ten thousand kilowatts) of a machine set is rotatably prepared; b saves 1513 ten thousand kilowatts of load, B saves and starts 658 ten thousand kilowatts of machine, B saves some direct current 400 ten thousand kilowatts, B saves exchanges and receives 480 ten thousand kilowatts of electricity, B saves the unit 134 ten thousand kilowatts of machine and revolves and is equipped with 1 phase modifier; load 3204 ten thousand kilowatts are saved in the province D, power is saved in the province D by 3753 ten thousand kilowatts, power is saved in the province C by 310 ten thousand kilowatts, power is saved in the province D by 580 ten thousand kilowatts on the section of the eastern part of the province D in the western part of the province D, the minimum power is met in the province D, and a certain direct current 300 ten thousand kilowatts are saved in the province D. By applying the operation mode of the receiving-end system, only the power grid of the province A runs in a critical instability state after being subjected to a certain most serious three-permanent-magnet N-1 fault of the province A, and the rest three-province power grids in the Z area all run in a critical stability working condition.

By comparing the lowest bus voltage values in the power grids of the provinces, the fact that the Z-region power grid has voltage instability after the most serious three-permanent-magnet N-1 fault of the province A, and the Z-region power grid has the condition of whole-network linkage instability at the moment, can be obtained.

As shown in fig. 17, the voltage sag sequences of the provinces are a-D-C-B, and fig. 17-21 show that the voltage instability problem exists only in the south region of the C power saving network.

And comparing the power angle difference values of the units in each province power grid, the power angle loss of each province power grid unit in the Z region to the power angles of other inter-province units after the power angle loss is caused can be obtained, as shown in fig. 22-25, and the power grid in the Z region has the condition of whole-grid interlocking instability.

Finally, comparing the power of the tie lines between each province after the three permanent magnet N-1 fault of the province A which is the most serious, and as shown in the graph 26-30, the active power of the tie lines between each province after the fault is oscillated and exchanged at 0pu, so that the tie lines between each province of the Z-area power grid are determined to be disconnected, and the voltage of the whole Z-area power grid is unstable.

By comparing the power of the interconnection line between the provinces A and the voltage value of the bus in the same region under different starting modes of the provinces A, different influences on the operation characteristics of the power grid in the whole Z region can be obtained after the same fault is generated on different operation boundaries of the power grid of the province A. As shown in fig. 31, in the 1400 kw mode of the province starting up, the active power of the province-D province tie line reaches-14 pu at 1.7s, and then the tie line still has active power exchange; however, in 1800 kilowatt mode of the province A, the active power of the province A-D province junctor reaches-15.5 pu due to the fault, and then the active power of the junctor is zero, which indicates that the junctor is split due to the fault. As can be seen from fig. 32, in the mode of 1400 kw for the province a, the voltage-01 of the province D can be restored to 0.8pu after the fault of the thirty-permanent N-1 of the province a, but in the mode of 1800 kw for the province a, the voltage of the province D is unstable and cannot be restored.

By the method for adjusting the operation mode of the power grid, whether the power grid in the Z area has the linkage instability form or not is judged, and the engineering practicability of the analysis method is verified according to the analysis method provided by the invention.

The present invention further provides a system 200 for analyzing the interlock instability operating characteristics of a receiving end system, as shown in fig. 33, including:

the simulation operation unit 201 is configured to establish a simulation model of the ac/dc hybrid receiving end system, and perform simulation operation of the ac/dc hybrid receiving end system on the simulation model to obtain a simulation result; the simulation operation comprises:

determining a system operation mode of an alternating current-direct current series-parallel connection receiving end system;

according to the system operation mode, risk scanning is carried out on the alternating current-direct current series-parallel connection receiving end system according to regions, and the maximum fault risk affecting operation in each regional power grid is determined;

determining the fault which influences the maximum operation in each regional power grid according to the fault risk;

adjusting the power grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid;

and the analysis unit 202 determines whether the operation characteristic of the cascading instability exists in the alternating current-direct current series-parallel connection receiving end system or not according to the simulation result.

The method for determining the system operation mode of the alternating current-direct current series-parallel connection receiving end system specifically comprises the following steps:

determining the maximum operable range, the starting mode and the load working condition of the direct current power in each region of the alternating current and direct current hybrid receiving end system, determining the junctor transmission power among the regions according to the maximum operable range, the starting mode and the load working condition of the direct current power, and determining the system operating mode of the alternating current and direct current hybrid receiving end system according to the junctor transmission power.

Wherein the failure risk is at least one of: a three-permanent-N-1 fault and a three-permanent-N-2 fault.

The method for adjusting the power grid operation mode of any regional power grid in each region to the critical instability operation mode according to the maximum fault in the power grid specifically comprises the following steps:

selecting any regional power grid in each region of an alternating-current and direct-current series-parallel receiving end system as a starting point for adjusting an operation mode, changing the load quantity of any regional power grid and the system rotation spare quantity which are equal, and switching/cutting a capacitor and a reactor in a preset bus range aiming at any regional power grid to determine the critical instability operation mode of any regional power grid;

and adjusting the sub-area power grids in any one area power grid to a critical stable working condition according to the maximum operation fault in the power grid.

Wherein, confirm that alternating current-direct current series-parallel connection receives the running characteristic that the end system has linkage unstability, include:

monitoring bus voltage, a unit power angle and power exchange conditions of a tie line between each area in each area of the alternating-current and direct-current hybrid receiving end system;

and judging whether the operation characteristic of linkage instability exists in the AC-DC hybrid receiving end system or not according to the bus voltage, the power angle of the unit and the power exchange condition of the connecting lines among the regions.

The method comprises the following steps of judging whether an operation characteristic of linkage instability exists in an alternating current-direct current series-parallel connection receiving end system or not, and specifically comprising the following steps:

determining whether a certain area has a low voltage problem or a plurality of areas have a low voltage problem in each area of the alternating-current and direct-current hybrid receiving end system according to the bus voltage;

determining whether voltage breakdown problems exist in certain areas or not in all areas of the alternating current-direct current hybrid receiving end system or voltage breakdown problems occur in the whole network according to the bus voltage;

determining whether the power angles of the units in the whole network of the alternating-current and direct-current hybrid receiving end system are not out of step, partially out of step or out of step of the whole network;

determining that the tie lines between the areas are not disconnected and are partially or completely split according to the power exchange condition of the tie lines between the areas in the alternating-current and direct-current hybrid receiving end system;

if a certain area has a low-voltage problem, the power angles of the units in the whole network are not out of step, and the connecting lines among the areas are not disconnected, judging that the low-voltage operation problem only exists in the certain area of the alternating-current and direct-current hybrid receiving end system;

if the low voltage problem exists in a certain area, the power angle of the unit in the whole network is partially out of step and the connecting lines among the areas are partially arranged, judging that the alternating current-direct current hybrid receiving end system only has the regional low voltage operation characteristic, and judging the sequence and the cause-effect relationship of the chain accidents according to the bus voltage drop time sequence among the areas;

if voltage collapse problems exist in some areas, the power angles of the generator sets in the whole network are partially out of step and the connection lines among the areas are partially disconnected, the fact that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the causal relationship of the chain accidents are judged according to the inter-area bus voltage drop time sequence;

if the voltage collapse problem occurs in the whole network, the power angles of the units in the whole network are all out of step, and the tie lines among all the regions are all disconnected, the fact that the alternating-current and direct-current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the cause-and-effect relationship of the chain accidents are judged according to the bus voltage collapse time sequence among the regions.

The invention has the advantages that:

(1) The invention strictly controls the operation boundary conditions of each sub-area of the receiving end system, and can avoid disordered and repeated work when the required power grid operation mode is adjusted, so that the simulation result is more visual and clear and has analysis significance;

(2) The method can obtain the key factors of the influence degree of the multi-feed receiving end system on the transient stability of the system, can obtain the time sequence and the incidence relation of the instability of each subarea caused by the fault, and is suitable for providing a method for analyzing the safety and the stability of the system in the actual engineering;

(3) According to the method, the accuracy of the characteristic analysis method of the multi-direct-current feed-in receiving end system is verified through the analysis results of the multiple receiving end systems and the derivative operation mode examples thereof, and the method has high practicability in engineering analysis.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the present application.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims (12)

1. A method for analyzing receive-end system interlock instability operating characteristics, the method comprising:

establishing a simulation model of the AC/DC hybrid receiving end system, and performing simulation operation of the AC/DC hybrid receiving end system aiming at the simulation model to obtain a simulation result; the simulation operation comprises:

determining a system operation mode of an alternating current-direct current series-parallel connection receiving end system;

according to the system operation mode, risk scanning is carried out on the alternating current-direct current series-parallel connection receiving end system according to regions, and the maximum fault risk affecting operation in each regional power grid is determined;

determining the fault which influences the maximum operation in each regional power grid according to the fault risk;

adjusting the power grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid;

and determining whether the operation characteristic of linkage instability exists in the alternating current-direct current series-parallel connection receiving end system or not according to the simulation result.

2. The method according to claim 1, wherein the determining of the system operation mode of the alternating current-direct current hybrid receiving end system specifically comprises:

determining the maximum operable range, the starting mode and the load working condition of the direct current power in each region of the alternating current and direct current hybrid receiving end system, determining the junctor transmission power among the regions according to the maximum operable range, the starting mode and the load working condition of the direct current power, and determining the system operating mode of the alternating current and direct current hybrid receiving end system according to the junctor transmission power.

3. The method of claim 1, the risk of failure being at least one of: a three-permanent-N-1 fault and a three-permanent-N-2 fault.

4. The method according to claim 1, wherein the adjusting the grid operation mode of any regional power grid in each region to the critical instability operation mode according to the maximum fault in the power grid specifically comprises:

selecting any regional power grid in each region of an alternating-current and direct-current series-parallel receiving end system as a starting point for adjusting an operation mode, changing the load quantity of any regional power grid and the system rotation spare quantity which are equal, and switching/cutting a capacitor and a reactor in a preset bus range aiming at any regional power grid to determine the critical instability operation mode of any regional power grid;

and adjusting the sub-area power grids in any one area power grid to a critical stable working condition according to the maximum operation fault in the power grid.

5. The method of claim 1, wherein the determining of the operational characteristics of the ac/dc series-parallel receiving end system with the cascading instability includes:

monitoring bus voltage, a unit power angle and power exchange conditions of tie lines among all areas of an alternating current-direct current hybrid receiving end system;

and judging whether the operation characteristic of linkage instability exists in the AC-DC hybrid receiving end system or not according to the bus voltage, the power angle of the unit and the power exchange condition of the connecting lines among the regions.

6. The method according to claim 5, wherein the operation characteristic of determining whether the cascading instability exists in the ac/dc series-parallel receiving end system is as follows:

determining whether a certain area has a low voltage problem or a plurality of areas have a low voltage problem in each area of the alternating current-direct current hybrid receiving end system according to the bus voltage;

determining whether voltage breakdown problems exist in certain areas or not in all areas of the alternating current-direct current hybrid receiving end system or voltage breakdown problems occur in the whole network according to the bus voltage;

determining whether the power angles of the units in the whole network of the alternating current-direct current hybrid receiving end system are out of step, partially out of step or out of step of the whole network;

determining that the tie lines between the areas are not disconnected and are partially or completely cracked according to the power exchange condition of the tie lines between the areas in each area of the alternating-current and direct-current hybrid-link receiving end system;

if a certain area has a low-voltage problem, the power angle of the generator set in the whole network is not out of step, and the connecting lines between the areas are not disconnected, judging that the low-voltage operation problem only exists in the certain area of the alternating-current and direct-current hybrid receiving end system;

if the low voltage problem exists in a certain area, the power angle of the unit in the whole network is partially out of step and the connecting lines among the areas are partially arranged, judging that the alternating current-direct current hybrid receiving end system only has the regional low voltage operation characteristic, and judging the sequence and the cause-effect relationship of the chain accidents according to the bus voltage drop time sequence among the areas;

if voltage collapse problems exist in some areas, the power angles of the generator sets in the whole network are partially out of step and the connection lines among the areas are partially disconnected, the fact that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the causal relationship of the chain accidents are judged according to the inter-area bus voltage drop time sequence;

if the voltage collapse problem occurs in the whole network, the power angles of the units in the whole network are out of step and the tie lines among the regions are disconnected, judging that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem, and judging the sequence and the causal relationship of the chain accidents according to the bus voltage drop time sequence among the regions.

7. A system for analyzing chain-instability operating characteristics of a receiving-end system, the system comprising:

the simulation operation unit is used for establishing a simulation model of the alternating current-direct current hybrid receiving end system and performing simulation operation of the alternating current-direct current hybrid receiving end system aiming at the simulation model to obtain a simulation result; the simulation operation comprises:

determining a system operation mode of an alternating current-direct current series-parallel connection receiving end system;

according to the system operation mode, risk scanning is carried out on the alternating current-direct current series-parallel connection receiving end system according to regions, and the maximum fault risk affecting operation in each regional power grid is determined;

determining the fault which influences the maximum operation in each regional power grid according to the fault risk;

adjusting the power grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid;

and the analysis unit is used for determining whether the operation characteristic of linkage instability exists in the alternating current-direct current series-parallel connection receiving end system or not according to the simulation result.

8. The system according to claim 7, wherein the determining of the system operation mode of the ac/dc hybrid receiving end system specifically comprises:

determining the maximum operable range, the starting mode and the load working condition of the direct current power in each area of the alternating current-direct current hybrid receiving end system, determining the junctor transmission power among the areas according to the maximum operable range, the starting mode and the load working condition of the direct current power, and determining the system operating mode of the alternating current-direct current hybrid receiving end system according to the junctor transmission power.

9. The system of claim 7, the risk of failure being at least one of: a triple permanent N-1 fault and a triple permanent N-2 fault.

10. The system according to claim 7, wherein the adjusting the grid operation mode of any regional power grid in each region to a critical instability operation mode according to the maximum fault in the power grid comprises:

selecting any regional power grid in each region of an alternating-current and direct-current series-parallel receiving end system as a starting point for adjusting an operation mode, changing the load quantity of any regional power grid and the system rotation spare quantity which are equal, and switching/cutting a capacitor and a reactor in a preset bus range aiming at any regional power grid to determine the critical instability operation mode of any regional power grid;

and adjusting the sub-area power grids in any one area power grid to a critical stable working condition according to the maximum operation fault in the power grid.

11. The system of claim 7, wherein the determining of the operating characteristics of the ac/dc series-parallel receiving end system with the cascading instability comprises:

monitoring bus voltage, a unit power angle and power exchange conditions of tie lines among all areas of an alternating current-direct current hybrid receiving end system;

and judging whether the operation characteristic of linkage instability exists in the alternating current-direct current hybrid receiving end system or not according to the bus voltage, the power angle of the unit and the power exchange condition of the connecting lines among the regions.

12. The system according to claim 11, wherein the operation characteristic of determining whether the cascading instability exists in the ac/dc parallel-serial receiving end system is as follows:

determining whether a certain area has a low voltage problem or a plurality of areas have a low voltage problem in each area of the alternating current-direct current hybrid receiving end system according to the bus voltage;

determining whether voltage breakdown problems exist in certain areas or not in all areas of the alternating current-direct current hybrid receiving end system or voltage breakdown problems occur in the whole network according to the bus voltage;

determining whether the power angles of the units in the whole network of the alternating current-direct current hybrid receiving end system are out of step, partially out of step or out of step of the whole network;

determining that the tie lines between the areas are not disconnected and are partially or completely cracked according to the power exchange condition of the tie lines between the areas in each area of the alternating-current and direct-current hybrid-link receiving end system;

if a certain area has a low-voltage problem, the power angles of the units in the whole network are not out of step, and the connecting lines among the areas are not disconnected, judging that the low-voltage operation problem only exists in the certain area of the alternating-current and direct-current hybrid receiving end system;

if the low voltage problem exists in a certain area, the power angle of the unit in the whole network is partially out of step and the connecting lines among the areas are partially arranged, judging that the alternating current-direct current hybrid receiving end system only has the regional low voltage operation characteristic, and judging the sequence and the cause-effect relationship of the chain accidents according to the bus voltage drop time sequence among the areas;

if voltage collapse problems exist in some areas, the power angles of the generator sets in the whole network are partially out of step and the connection lines among the areas are partially disconnected, the fact that the alternating current-direct current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the causal relationship of the chain accidents are judged according to the inter-area bus voltage drop time sequence;

if the voltage collapse problem occurs in the whole network, the power angles of the units in the whole network are all out of step, and the tie lines among all the regions are all disconnected, the fact that the alternating-current and direct-current hybrid receiving end system only has the regional voltage collapse problem is judged, and the sequence and the cause-and-effect relationship of the chain accidents are judged according to the bus voltage collapse time sequence among the regions.

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