阅读说明：本技术 一种大规模交直流电网在线安全评估方法 (Online safety assessment method for large-scale alternating current and direct current power grid ) 是由 冯煜尧 赵乐 熊雪君 于 2021-08-30 设计创作，主要内容包括：本发明提供一种大规模交直流电网在线安全评估方法,用于对由多个交流系统和高压直流输电系统构成的大规模复杂电网进行在线安全评估,包含步骤：S1、基于大规模交直流电网架构构建机电-电磁暂态混合仿真平台；S2、选取大规模交直流电网在线安全评估指标,制定安全稳定标准；S3、基于机电-电磁暂态混合仿真平台和安全稳定标准,实施大规模交直流电网在线安全评估。本发明采取机电-电磁暂态混合仿真的方式,可对含有大量电力电子设备的高压直流输电系统进行详细精确的描述,又具有较高的计算速度,可以解决纯电磁暂态仿真速度慢、规模小,纯机电暂态仿真无法准确反映交直流系统交互影响的技术问题。(The invention provides an online safety assessment method for a large-scale alternating current and direct current power grid, which is used for online safety assessment of a large-scale complex power grid consisting of a plurality of alternating current systems and a high-voltage direct current power transmission system and comprises the following steps: s1, constructing an electromechanical-electromagnetic transient hybrid simulation platform based on a large-scale alternating current and direct current power grid architecture; s2, selecting large-scale AC/DC power grid online safety assessment indexes, and making a safety and stability standard; and S3, performing large-scale AC/DC power grid online safety evaluation based on an electromechanical-electromagnetic transient hybrid simulation platform and a safety and stability standard. The invention adopts an electromechanical-electromagnetic transient hybrid simulation mode, can describe a high-voltage direct-current power transmission system containing a large amount of power electronic equipment in detail and accurately, has higher calculation speed, and can solve the technical problems that the pure electromagnetic transient simulation speed is low, the scale is small, and the interaction influence of an alternating-current and direct-current system cannot be accurately reflected by the pure electromechanical transient simulation.)

1. An online safety assessment method for a large-scale alternating current and direct current power grid is used for online safety assessment of a large-scale complex power grid composed of a plurality of alternating current systems and a high-voltage direct current transmission system, and is characterized by comprising the following steps:

s1, constructing an electromechanical-electromagnetic transient hybrid simulation platform based on the large-scale alternating current and direct current power grid architecture;

s2, selecting the large-scale AC/DC power grid online safety assessment index, and making a safety and stability standard;

and S3, performing online safety assessment on the large-scale alternating current and direct current power grid based on the electromechanical-electromagnetic transient hybrid simulation platform and the safety and stability standard.

2. The large-scale alternating current and direct current power grid online safety evaluation method according to claim 1, wherein the step S1 comprises:

s11, designing a basic framework of an electromechanical-electromagnetic transient hybrid simulation platform consisting of a plurality of electromechanical transient simulation systems and one electromagnetic transient simulation system;

s12, designing the time sequence of the electromechanical transient simulation system, the electromagnetic transient simulation system and the interface between the simulation systems;

and S13, establishing an equivalent model of the alternating current system in the electromagnetic transient simulation system.

3. The large-scale AC/DC power grid online safety assessment method according to claim 1, wherein in step S2,

the online safety assessment indexes of the large-scale alternating current and direct current power grid are selected as follows: the steady-state frequency deviation, the steady-state voltage deviation, the transmission line power, the transient frequency range, the transient voltage range and the power angle difference range are 6 safety evaluation indexes;

the safety and stability standard is as follows:

steady state frequency deviation: | Δ f | < 0.05 Hz;

steady state voltage deviation: | Δ U | < 0.1 p.u.;

transmission line power: p < P_max；

Transient frequency range: 49.25 Hz-51.5 Hz;

transient voltage range: 1.3p.u. to 0.85 p.u.;

power angle difference range: delta delta is less than 360 degrees.

4. The large-scale alternating current and direct current power grid online safety evaluation method according to claim 1, wherein the step S3 comprises:

s31, mixed simulation analysis:

updating the running data of the large-scale alternating current and direct current power grid to be evaluated in real time based on the constructed large-scale alternating current and direct current power grid electromechanical-electromagnetic transient hybrid simulation platform, and performing real-time hybrid simulation analysis;

s32, safety assessment:

screening output variables corresponding to 6 large-scale AC/DC interconnected power grid online safety assessment indexes from the data of the hybrid simulation analysis, and comparing the output variables with the established safety and stability standard:

if all the output variables are within the safety and stability standard limit range, the large-scale alternating current and direct current power grid system is safe and stable, and the evaluation result of 'system safety and stability' and various evaluation data are returned;

and if all or part of the output variables exceed the safety and stability standard limit range, the large-scale alternating current and direct current power grid system has potential safety hazards, and the evaluation result of system safety early warning and various evaluation data are returned.

5. The large-scale alternating current and direct current power grid online safety evaluation method according to claim 2, wherein the step S11 comprises:

s111, designing an electromechanical transient simulation model area and an electromagnetic transient simulation model area:

dividing the multiple alternating current systems of the large-scale alternating current and direct current power grid into a plurality of corresponding electromechanical transient simulation model areas, and adopting electromechanical transient simulation;

dividing the high-voltage direct-current power transmission system of the large-scale alternating-current and direct-current power grid into an electromagnetic transient simulation model area, and performing electromagnetic transient simulation;

s112, determining simulation software and modeling;

and S113, designing the interface position and the interface form between the electromechanical transient simulation system and the electromagnetic transient simulation system.

6. The large-scale ac/dc power grid online safety assessment method according to claim 5, wherein step S112 comprises: and determining that the electromechanical transient simulation adopts electromechanical transient software PSS/E, modeling the plurality of electromechanical transient simulation model areas in the PSS/E, and establishing a plurality of corresponding electromechanical transient simulation systems.

7. The large-scale ac/dc power grid online safety assessment method according to claim 5, wherein step S112 comprises: and determining that the electromagnetic transient simulation adopts electromagnetic transient simulation software RTDS, modeling the electromagnetic transient simulation model region in the RTDS, and establishing the electromagnetic transient simulation system.

8. The large-scale ac/dc power grid online safety assessment method according to claim 2, wherein in step S12, the method for designing the timing sequence of the interface between the simulation systems is to set the inter-system data transfer time variable of the electromechanical transient simulation system and the electromagnetic transient simulation system as the simulation step termination time of each of the electromechanical transient simulation systems.

9. The large-scale alternating current and direct current power grid online safety evaluation method according to claim 2, wherein the step S13 comprises: in the electromagnetic transient simulation system, an equivalent model of the plurality of alternating current systems of the large-scale alternating current and direct current power grid is established in a multi-port Thevenin equivalent mode, and the equivalent model is used for simulating the interaction between the electromechanical transient simulation system and the electromagnetic transient simulation system in the electromagnetic transient simulation system.

Technical Field

The invention relates to the field of electric power system analysis, in particular to an online safety assessment method for a large-scale alternating current and direct current power grid.

Background

The distribution and the demand of the power resources in China have reverse distribution and structural contradiction, the electrical loads of the frontier regions such as the northwest, the northeast, the southwest and the like with rich renewable power resources are relatively small, and the power resources are relatively less in the load center region in the coastal region of the eastern part. In order to solve the problems, a large-scale alternating current-direct current series-parallel power grid is preliminarily established in China, the alternating current-direct current series-parallel power grid not only has ultrahigh voltage alternating current and traditional direct current, but also has back-to-back flexible direct current, double-end and multi-end flexible direct current, and LCC-VSC (power grid commutation converter-voltage source converter) multi-end mixed direct current, and typical projects comprise a Zhang Bei flexible direct current transmission system, a Kunlong three-end mixed direct current transmission system, a Longzheng direct current transmission system, a Yubei back-to-back direct current transmission system and the like. In addition, with the access of large-scale renewable energy sources to the power grid, modern power grids are further developing towards the trend of "double high" with a high proportion of new energy power generation and a high proportion of power electronic equipment. Due to the complex interaction between the high-voltage direct-current power electronic equipment and the alternating-current system, the large-scale alternating-current and direct-current power grid faces complex safety challenges and needs to be reliably evaluated.

At present, many safety assessment methods for large-scale alternating current and direct current power grids exist, such as a time domain simulation method and a direct method. The simulation software commonly used in the time domain simulation method comprises PSD-BPA (power system analysis software), PSS/E (power system simulation software), DSATOols (power system safety analysis software package) and the like; the direct method includes an energy function method, a voltage source equivalent method and the like. However, in the method, both the high-voltage direct-current transmission system model and the renewable energy source model based on power electronic device grid connection adopt steady-state models, and the process and phenomenon of fault propagation between the alternating-current subsystem and the direct-current subsystem cannot be accurately reflected, for example, a fault of an alternating-current system may cause a commutation failure or a locking failure of the direct-current system. Electromagnetic transient simulation systems, such as RTDS (real time digital simulator) and PSCAD (computer aided design) systems, can accurately reflect the detailed dynamics of high voltage direct current, but the electromagnetic transient simulation has relatively low computational efficiency and cannot meet the requirements of online safety assessment. Therefore, an online safety assessment method with accuracy, fineness and high efficiency is needed for a large-scale alternating current and direct current power grid.

Disclosure of Invention

The invention aims to provide an online safety assessment method for a large-scale alternating current and direct current power grid, which adopts an electromechanical-electromagnetic transient hybrid simulation mode, can describe a high-voltage direct current power transmission system containing a large amount of power electronic equipment in detail and accurately, has higher calculation speed, and can solve the technical problems that pure electromagnetic transient simulation is slow in speed and small in scale, and interaction influence of the alternating current and direct current system cannot be accurately reflected by pure electromechanical transient simulation.

In order to achieve the purpose, the invention is realized by the following technical scheme:

an online safety assessment method for a large-scale alternating current and direct current power grid is used for online safety assessment of a large-scale complex power grid composed of a plurality of alternating current systems and a high-voltage direct current transmission system, and comprises the following steps:

s1, constructing an electromechanical-electromagnetic transient hybrid simulation platform based on the large-scale alternating current and direct current power grid architecture;

s2, selecting the large-scale AC/DC power grid online safety assessment index, and making a safety and stability standard;

and S3, performing online safety assessment on the large-scale alternating current and direct current power grid based on the electromechanical-electromagnetic transient hybrid simulation platform and the safety and stability standard.

Preferably, step S1 includes:

s11, designing a basic framework of an electromechanical-electromagnetic transient hybrid simulation platform consisting of a plurality of electromechanical transient simulation systems and one electromagnetic transient simulation system;

s12, designing the time sequence of the electromechanical transient simulation system, the electromagnetic transient simulation system and the interface between the simulation systems;

and S13, establishing an equivalent model of the alternating current system in the electromagnetic transient simulation system.

Preferably, in step S2,

the online safety assessment indexes of the large-scale alternating current and direct current power grid are selected as follows: the steady-state frequency deviation, the steady-state voltage deviation, the transmission line power, the transient frequency range, the transient voltage range and the power angle difference range are 6 safety evaluation indexes;

the safety and stability standard is as follows:

steady state frequency deviation: | Δ f | < 0.05 Hz;

steady state voltage deviation: | Δ U | < 0.1 p.u.;

transmission line power: p < P_max；

Transient frequency range: 49.25 Hz-51.5 Hz;

transient voltage range: 1.3p.u. to 0.85 p.u.;

power angle difference range: delta delta is less than 360 degrees.

Preferably, step S3 includes:

s31, mixed simulation analysis:

updating the running data of the large-scale alternating current and direct current power grid to be evaluated in real time based on the constructed large-scale alternating current and direct current power grid electromechanical-electromagnetic transient hybrid simulation platform, and performing real-time hybrid simulation analysis;

s32, safety assessment:

screening output variables corresponding to 6 large-scale AC/DC interconnected power grid online safety assessment indexes from the data of the hybrid simulation analysis, and comparing the output variables with the established safety and stability standard:

if all the output variables are within the safety and stability standard limit range, the large-scale alternating current and direct current power grid system is safe and stable, and the evaluation result of 'system safety and stability' and various evaluation data are returned;

and if all or part of the output variables exceed the safety and stability standard limit range, the large-scale alternating current and direct current power grid system has potential safety hazards, and the evaluation result of system safety early warning and various evaluation data are returned.

Preferably, step S11 includes:

s111, designing an electromechanical transient simulation model area and an electromagnetic transient simulation model area:

dividing the multiple alternating current systems of the large-scale alternating current and direct current power grid into a plurality of corresponding electromechanical transient simulation model areas, and adopting electromechanical transient simulation;

dividing the high-voltage direct-current power transmission system of the large-scale alternating-current and direct-current power grid into an electromagnetic transient simulation model area, and performing electromagnetic transient simulation;

s112, determining simulation software and modeling;

and S113, designing the interface position and the interface form between the electromechanical transient simulation system and the electromagnetic transient simulation system.

Further, step S112 includes: and determining that the electromechanical transient simulation adopts electromechanical transient software PSS/E, modeling the plurality of electromechanical transient simulation model areas in the PSS/E, and establishing a plurality of corresponding electromechanical transient simulation systems.

Further, step S112 includes: and determining that the electromagnetic transient simulation adopts electromagnetic transient simulation software RTDS, modeling the electromagnetic transient simulation model region in the RTDS, and establishing the electromagnetic transient simulation system.

Preferably, in step S12, the method for designing the timing sequence of the interface between the simulation systems is to set the inter-system data transfer time variable of the electromechanical transient simulation system and the electromagnetic transient simulation system as the simulation step termination time of each of the electromechanical transient simulation systems.

Preferably, step S13 includes: in the electromagnetic transient simulation system, an equivalent model of the plurality of alternating current systems of the large-scale alternating current and direct current power grid is established in a multi-port Thevenin equivalent mode, and the equivalent model is used for simulating the interaction between the electromechanical transient simulation system and the electromagnetic transient simulation system in the electromagnetic transient simulation system.

In summary, compared with the prior art, the large-scale ac/dc power grid online safety evaluation method provided by the invention has the following beneficial effects:

1. the invention can describe a high-voltage direct-current transmission system containing a large amount of power electronic equipment in detail and accurately, has higher calculation speed, better realizes the online safety evaluation of a power grid containing a large-scale alternating current and direct current system, and solves the technical problems that the pure electromagnetic transient simulation speed is low, the scale is small, and the interaction influence of the alternating current and direct current system cannot be accurately reflected by the pure electromechanical transient simulation;

2. the method adopts an electromechanical-electromagnetic transient hybrid simulation mode, the high-voltage direct-current power transmission system can more truly and accurately evaluate the safety and stability of a large-scale alternating-current and direct-current power system through electromagnetic transient modeling, and the problems that the influence of voltage waveform distortion on commutation failure is ignored by adopting electromechanical transient simulation, so that the simulation result has errors, the safety and stability analysis is inaccurate, the system has potential safety hazards and the like are solved.

Drawings

FIG. 1 is a schematic diagram of a large-scale AC/DC power grid online safety evaluation method according to the present invention;

FIG. 2 is a model schematic diagram of a large-scale AC/DC power grid according to the present invention;

FIG. 3 is a schematic diagram of the electromagnetic transient simulation system and electromechanical transient simulation system interface of the present invention;

fig. 4 is a schematic diagram of interface data interfacing between the electromagnetic transient simulation system and the electromechanical transient simulation system according to the present invention.

Detailed Description

The method for online safety assessment of a large-scale ac/dc power grid according to the present invention is further described in detail with reference to the accompanying drawings and the detailed description. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are simplified in form and not to precise scale, and are only used for convenience and clarity to assist in describing the embodiments of the present invention, but not for limiting the conditions of the embodiments of the present invention, and therefore, the present invention is not limited by the technical spirit, and any structural modifications, changes in the proportional relationship, or adjustments in size, should fall within the scope of the technical content of the present invention without affecting the function and the achievable purpose of the present invention.

It is to be noted that, in the present invention, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

With reference to fig. 1 to 4, the embodiment provides an online safety assessment method for a large-scale alternating current/direct current power grid, which is used for performing online safety assessment on a large-scale complex power grid composed of a plurality of alternating current systems and a high-voltage direct current power transmission system. As shown in fig. 2, in the present embodiment, the ac system is composed of a first ac system and a second ac system, and the high-voltage dc transmission system is a double-ended dc transmission system, wherein the double-ended dc transmission system is electrically connected to an ac bus 1 of the first ac system through a first converter transformer 3, and is electrically connected to an ac bus 2 of the second ac system through a second converter transformer 4, so as to form a large-scale ac/dc power grid.

As shown in the attached figure 1, the large-scale alternating current and direct current power grid online safety evaluation method comprises the following steps:

s1, constructing an electromechanical-electromagnetic transient hybrid simulation platform based on a large-scale alternating current and direct current network architecture, comprising the following steps:

s11, designing a basic architecture of an electromechanical-electromagnetic transient hybrid simulation platform consisting of a plurality of electromechanical transient simulation systems and an electromagnetic transient simulation system, comprising the following steps:

s111, designing an electromechanical transient simulation model area and an electromagnetic transient simulation model area:

dividing a plurality of alternating current systems of a large-scale alternating current and direct current power grid into a plurality of corresponding electromechanical transient simulation model areas, and adopting electromechanical transient simulation;

a high-voltage direct-current power transmission system of a large-scale alternating-current and direct-current power grid is divided into an electromagnetic transient simulation model area, and electromagnetic transient simulation is adopted.

Due to the complexity and large calculation amount of the electromagnetic transient simulation model, in order to improve the calculation speed as much as possible, an optimal scheme for dividing the electromechanical transient simulation model and the electromagnetic transient simulation model and the position of a simulation interface needs to be selected, so that the electromagnetic transient simulation model area is reduced as much as possible on the basis of reflecting the system characteristics. In this embodiment, an alternating current bus 1 of a first alternating current system and an alternating current bus 2 of a second alternating current system are used as a boundary line of an electromechanical transient simulation model region and an electromagnetic transient simulation model region, the first alternating current system and the second alternating current system are respectively divided into the first electromechanical transient simulation model region and the second electromechanical transient simulation model region, and electromechanical transient simulation is adopted; and dividing the double-end direct-current power transmission system into an electromagnetic transient simulation model area, and adopting electromagnetic transient simulation.

S112, determining simulation software and modeling:

determining that electromechanical transient simulation adopts electromechanical transient software PSS/E, modeling a plurality of electromechanical transient simulation model areas in the PSS/E, and establishing a plurality of corresponding electromechanical transient simulation systems;

and determining electromagnetic transient simulation, namely, adopting an electromagnetic transient simulation software RTDS (real time digital simulator), modeling an electromagnetic transient simulation model region in the RTDS, and establishing an electromagnetic transient simulation system.

In the embodiment, a first electromechanical transient simulation model area and a second electromechanical transient simulation model area are respectively modeled in a PSS/E, and a first electromechanical transient simulation system and a second electromechanical transient simulation system are established; modeling an electromagnetic transient simulation model area in the RTDS, and establishing an electromagnetic transient simulation system.

S113, designing interface positions and interface forms between simulation systems of the electromechanical transient simulation system and the electromagnetic transient simulation system;

in this embodiment, the alternating current bus 1 is set as an interface position between simulation systems of the first electromechanical transient simulation system and the electromagnetic transient simulation system, and the alternating current bus 2 is set as an interface position between simulation systems of the second electromechanical transient simulation system and the electromagnetic transient simulation system; as shown in fig. 3, a GTFPGA (bidirectional high-speed communication board) of the conventional RTDS is used as an interface between simulation systems of the electromechanical transient simulation system and the electromagnetic transient simulation system, so as to implement unified simulation of a complete large-scale ac/dc power grid under an integral framework.

S12, designing the electromechanical transient simulation system, the electromagnetic transient simulation system and the time sequence of the interface between the simulation systems, including the steps:

s121, setting an electromagnetic transient simulation system to simulate according to a common electromagnetic transient simulation step size, wherein the setting is 50us in the embodiment;

s122, setting an electromechanical transient simulation system to simulate according to a common electromechanical transient simulation step length, wherein the time is set to 0.002S in the embodiment;

and S123, setting the inter-system data transfer time variable of the electromechanical transient simulation system and the electromagnetic transient simulation system as the simulation step length termination time of each electromechanical transient simulation system, wherein the time variable is 0.002S in the embodiment.

S13, establishing an equivalent model of the alternating current system in the electromagnetic transient simulation system:

in the electromagnetic transient simulation system, equivalent models of a plurality of alternating current systems of a large-scale alternating current-direct current power grid are established and used for simulating the interaction of the electromechanical transient simulation system and the electromagnetic transient simulation system in the electromagnetic transient simulation system. In this embodiment, an equivalent model of the first alternating current system and the second alternating current system is respectively established in the RTDS by using a multi-port thevenin equivalent method.

Meanwhile, an equivalent model of a high-voltage direct-current power transmission system of a large-scale alternating-current and direct-current power grid can be established in the electromechanical transient simulation system, and the equivalent model is used for simulating the interaction of the electromechanical transient simulation system and the electromagnetic transient simulation system in the electromechanical transient simulation system. The present embodiment does not build an equivalent model in the PSS/E.

And at this point, the construction of an electromechanical-electromagnetic transient hybrid simulation platform of a large-scale alternating current and direct current power grid is completed.

S2, selecting a large-scale AC/DC power grid online safety assessment index, and formulating a safety and stability standard:

according to frequency deviation of a power quality power system (GB/T15945) 2008 and temporary overvoltage and transient overvoltage of power quality (GB/T18481 2001), by combining actual operation experience of a large-scale alternating current and direct current power grid, 6 large-scale alternating current and direct current interconnected power grid online safety evaluation indexes are selected to establish a safety and stability standard:

(1) steady state frequency deviation: | Δ f | < 0.05 Hz;

(2) steady state voltage deviation: | Δ U | < 0.1 p.u.;

(3) transmission line power: p < P_max；

(4) Transient frequency range: 49.25 Hz-51.5 Hz;

(5) transient voltage range: 1.3p.u. to 0.85 p.u.;

(6) power angle difference range: delta delta is less than 360 degrees.

S3, implementing online safety assessment of a large-scale alternating current-direct current power grid based on the electromechanical-electromagnetic transient hybrid simulation platform and the safety and stability standard, and the specific process is as follows:

s31, mixed simulation analysis:

updating the running data of the large-scale alternating current and direct current power grid to be evaluated in real time based on the constructed large-scale alternating current and direct current power grid electromechanical-electromagnetic transient hybrid simulation platform, and performing real-time hybrid simulation analysis;

s32, safety assessment:

screening output variables corresponding to 6 large-scale AC/DC interconnected power grid online safety assessment indexes from the mixed simulation analysis data, and comparing the output variables with the established safety and stability standard:

if all the output variables are within the safety and stability standard limit range, the system is safe and stable, and the evaluation result of the system safety and stability and all the evaluation data are returned;

if all or part of the output variables exceed the safety and stability standard limit range, the system has potential safety hazards, and the evaluation result of the system safety early warning and various evaluation data are returned.

In conclusion, the method for online safety assessment of the large-scale alternating current and direct current power grid can describe a high-voltage direct current power transmission system containing a large amount of power electronic equipment in detail and accurately, has high calculation speed, and can perform online safety assessment on the power grid containing the large-scale alternating current and direct current system so as to solve the problems that pure electromagnetic transient simulation speed is low, the scale is small, and interaction influence of the alternating current and direct current system cannot be reflected accurately by pure electromechanical transient simulation; due to the adoption of an electromechanical-electromagnetic transient hybrid simulation mode, the safety and stability of a large-scale alternating current and direct current power system can be more truly and accurately evaluated through electromagnetic transient modeling, and the problems that the influence of voltage waveform distortion on commutation failure is neglected by adopting electromechanical transient simulation, so that the simulation result has errors, the safety and stability analysis is inaccurate, the system has potential safety hazards and the like are solved.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.