Interface bus selection method for electromechanical-real-time hybrid simulation of power systems

Abstract

The present invention discloses a method for selecting an interface bus used in electromechanical real-time hybrid simulation of an electric power system, comprising: step S1, injecting current signals of different frequencies at a plurality of AC busbars respectively; step S2, obtaining the impedance of each AC busbar at different frequencies by calculation; step S3, drawing the impedance characteristic diagram of each AC busbar according to the impedance of each AC busbar at different frequencies; step S4, analyzing the impedance characteristic diagram of each AC busbar obtained in step S3, selecting a plurality of AC busbars, and obtaining an AC busbar as the interface busbar of electromechanical real-time hybrid simulation. The present invention discloses a method for selecting an interface busbar, which is suitable for electromechanical real-time hybrid simulation of an electric power system, and the method avoids the phenomenon that the electromechanical real-time hybrid simulation results are unreliable due to improper interface selection.

Description

Technical Field

[0001] The invention relates to the field of power system simulation, and in particular to a method for selecting an interface bus used in electromechanical-real-time hybrid simulation of a power system. Background Art

[0002] At present, the electromechanical transient simulation and electromagnetic transient simulation are mainly used in power systems. The electromechanical transient simulation process and the electromagnetic transient simulation process are two physical processes represented by different mathematical models and have different time constants. When the main research purpose is network planning and design or the stability of the entire network, quasi-steady-state or steady-state system models are often used for electromechanical transient simulation; when it is necessary to study control and protection strategies, DC valve control systems, power electronic equipment, and subsynchronous resonance in detail, it is necessary to use electromagnetic models for electromagnetic transient simulation. However, with the popularization and large-scale application of direct current transmission (HVDC) and flexible direct current transmission, the scale of contemporary power systems has increased rapidly and the complexity has continued to increase. With the commissioning of more and more power electronic equipment, the simulation and analysis technology of power systems needs to be changed to adapt to the new network scale and model. Electromechanical-real-time hybrid simulation has the advantages of both electromagnetic and electromechanical simulation technologies and has attracted widespread attention. The concept of electromechanical-real-time hybrid simulation was introduced, and two sets of simulation programs were written for AC and DC systems for analysis: the high-voltage direct current transmission system (HVDC) uses electromagnetic transient simulation methods, and other parts are simulated using conventional transient programs, with the converter bus as the interface between the two simulation programs. The correctness of the simulation results in the electromechanical-real-time hybrid simulation process depends entirely on the selection of the boundary bus. In general, symmetrical short-circuit faults will not cause harmonics, while asymmetrical short-circuits will cause harmonic problems in addition to voltage drops. If the boundary bus is not selected properly, the asymmetrical fault point will cause the loss of harmonics in the system when it is on the electromechanical side, resulting in unreliable simulation results in some cases. Summary of the invention

[0003] The present invention aims to solve the above problems. To this end, the present invention provides an interface bus selection method for electric power system electromechanical-real-time hybrid simulation, which is used to solve the problem that the simulation results are unreliable due to improper interface selection in the electromechanical-real-time hybrid simulation process.

[0004] In order to solve the above problems, the present invention is implemented by the following technical solutions:

[0005] The present invention provides a method for selecting an interface bus in a hybrid electromechanical-real-time simulation of a power system, comprising:

[0006] Step S1, injecting current signals of different frequencies into a plurality of AC busbars respectively.

[0007] Step S2: Obtain the impedance of each of the AC busbars at different frequencies by calculation.

[0008] Step S3, drawing an impedance characteristic diagram of each AC bus according to the impedance size of each AC bus at different frequencies.

[0009] Step S4, analyzing the impedance characteristic diagram of each of the AC buses obtained in step S3, selecting a plurality of the AC buses, and obtaining an AC bus as an interface bus for electromechanical-real-time hybrid simulation.

[0010] Optionally, the step S2 further includes:

[0011] Step S21, the time characteristic of the current of each AC bus in the α and β coordinates is:

[0012]

[0013] The time characteristic of the current is linearized to obtain the current formula:

[0014]

[0015] Where: i(t) represents the current-time function; i α represents the projection of the current on the α axis; i β represents the projection of the current on the β axis; i α0 represents the projection of the current on the α-axis at ω0; i β0 represents the projection of the current on the β axis at ω0; Δi α represents the projection of the current on the α-axis at ω0+ω; Δi β represents the projection of the current on the β axis at ω0+ω; represents the projection of the linearized current on the α-axis at ω0-ω; represents the projection of the linearized current on the β axis at ω0-ω; represents the unit vector in the complex plane at ω0; e jωt represents the unit vector in the complex plane at ω; e -jωt represents the inverse vector of the unit vector in the complex plane at ω; j represents the imaginary unit.

[0016] Step S22: perform the linearization process on the time characteristic of the voltage of each of the AC buses to obtain a voltage formula:

[0017]

[0018] Where: u(t) represents the voltage-time function; u α0 represents the projection of the voltage on the α-axis at ω0; u β0represents the projection of the voltage on the β axis at ω0; Δu α represents the projection of the voltage at ω0+ω on the α-axis; Δu β represents the projection of the voltage on the β-axis at ω0+ω; represents the projection of the linearized voltage on the α-axis at ω0-ω; Represents the projection of the linearized voltage on the β-axis at ω0-ω.

[0019] Step S23, obtaining a corresponding impedance equation through the current formula and the voltage formula:

[0020] Δi α +jΔi β =Y(ω0+ω)(Δu α +jΔu β )

[0021]

[0022] Where: Y represents impedance.

[0023] Step S24, solving the impedance equation to obtain the impedance value of each of the AC buses at different frequencies.

[0024] Optionally, step S4 includes: analyzing the impedance characteristic diagram of each of the AC buses obtained in step S3, finding the impedance characteristic diagram with the smallest fluctuation of impedance Y with frequency from all the impedance characteristic diagrams, and selecting the AC bus corresponding to the impedance characteristic diagram with the smallest fluctuation of impedance Y with frequency as the interface bus for electromechanical-real-time hybrid simulation.

[0025] Optionally, the linearization calculation is specifically:

[0026] The real part of the complex plane of the power system can be obtained by the following formula:

[0027]

[0028] Linearizing the above formula, we get:

[0029]

[0030] Where: Re represents the real part; S represents the complex plane modulus of the power system; S(t) represents the complex plane linearization function of the power system; S0 represents the complex plane modulus of the power system at ω0; Δ S represents the complex plane modulus value of the power system at ω0+ω; Δ S * Represents the linearized value of the complex plane modulus value of the power system at ω0-ω.

[0031] Optionally, step S2 further includes: the amplitude of the current at a frequency of ω0+ω is Or at a frequency of ω0-ω, its amplitude is

[0032] The present invention has the following beneficial effects:

[0033] The present invention can solve the problem of harmonic loss of the system caused by asymmetric faults on the interface bus side; and by selecting a suitable interface bus, the credibility of the electromechanical-real-time hybrid simulation results is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of a method for obtaining interface bus selection in electromechanical-real-time hybrid simulation of a power system according to an embodiment of the present invention;

[0035] Figure 2 is an impedance amplitude-frequency characteristic diagram in an impedance characteristic diagram of an embodiment of the present invention;

[0036] Figure 3 is a graph showing the change of the real part of the impedance with the frequency in the impedance characteristic graph according to an embodiment of the present invention;

[0037] Figure 4 FIG. 1 is a graph showing how the imaginary part of impedance changes with frequency in an impedance characteristic graph according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following is combined with Figure 1 The specific implementation method of the present invention is further described in detail for a method for selecting an interface busbar in an electromechanical-real-time hybrid simulation of a power system. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] like Figure 1 As shown, a method for selecting an interface bus in a hybrid electromechanical-real-time simulation of a power system in this embodiment includes:

[0040] Step S1, injecting current signals of different frequencies into a plurality of AC busbars respectively.

[0041] Step S2: Obtain the impedance of each of the AC busbars at different frequencies by calculation.

[0042] Step S3, drawing an impedance characteristic diagram of each AC bus according to the impedance size of each AC bus at different frequencies.

[0043] Step S4, analyzing the impedance characteristic diagram of each of the AC buses obtained in step S3, selecting a plurality of the AC buses, and obtaining an AC bus as an interface bus for electromechanical-real-time hybrid simulation.

[0044] In this embodiment, the step S2 further includes:

[0045] Step S21, the time characteristic of the current of each AC bus in the α and β coordinates is:

[0046]

[0047] The time characteristic of the current is linearized to obtain the current formula:

[0048]

[0049] Where: i(t) represents the current-time function; i α represents the projection of the current on the α axis; i β represents the projection of the current on the β axis; i α0 represents the projection of the current on the α-axis at ω0; i β0 represents the projection of the current on the β axis at ω0; Δi α represents the projection of the current on the α-axis at ω0+ω; Δi β represents the projection of the current on the β axis at ω0+ω; represents the projection of the linearized current on the α-axis at ω0-ω; represents the projection of the linearized current on the β axis at ω0-ω; represents the unit vector in the complex plane at ω0; e jωt represents the unit vector in the complex plane at ω; e -jωt represents the inverse vector of the unit vector in the complex plane at ω; j represents the imaginary unit.

[0050] Step S22: perform the linearization process on the time characteristic of the voltage of each of the AC buses to obtain a voltage formula:

[0051]

[0052] Where: u(t) represents the voltage-time function; u α0 represents the projection of the voltage on the α-axis at ω0; u β0 represents the projection of the voltage on the β axis at ω0; Δu α represents the projection of the voltage at ω0+ω on the α-axis; Δu β represents the projection of the voltage on the β-axis at ω0+ω; represents the projection of the linearized voltage on the α-axis at ω0-ω; Represents the projection of the linearized voltage on the β-axis at ω0-ω.

[0053] Step S23, obtaining a corresponding impedance equation through the current formula and the voltage formula:

[0054] Δi α +jΔi β =Y(ω0+ω)(Δu α +jΔu β ) (4)

[0055]

[0056] Where: Y represents impedance.

[0057] Step S24, solving the impedance equation to obtain the impedance value of each of the AC buses at different frequencies.

[0058] In this embodiment, step S4 includes: analyzing the impedance characteristic diagram of each of the AC buses obtained in step S3, finding the impedance characteristic diagram with the smallest fluctuation of impedance Y with frequency from all the impedance characteristic diagrams, and selecting the AC bus corresponding to the impedance characteristic diagram with the smallest fluctuation of impedance Y with frequency as the interface bus for electromechanical-real-time hybrid simulation.

[0059] In this embodiment, the linearization calculation is specifically:

[0060] The real part of the complex plane of the system S can be obtained by the following formula:

[0061]

[0062] Linearizing the above formula, we get:

[0063]

[0064] Where: Re represents the real part; S represents the complex plane modulus of the power system; S(t) represents the complex plane linearization function of the power system; S0 represents the complex plane modulus of the power system at ω0; Δ S represents the complex plane modulus value of the power system at ω0+ω; Represents the linearized value of the complex plane modulus value of the power system at ω0-ω.

[0065] In this embodiment, the step S2 further includes: the amplitude of the current at the frequency ω0+ω is Or at a frequency of ω0-ω, its amplitude is

[0066] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

[0067] In the preferred embodiment, the current signal of different frequencies in step S1 is a current signal with increasing frequency (1 Hz-100 Hz), and the AC bus (153) is taken as an example for description. The current signal with increasing frequency (1 Hz-100 Hz) is only for describing this embodiment and cannot be used as a limitation of the present invention.

[0068] like Figure 1 As shown, this preferred embodiment includes the following steps:

[0069] Step S1: injecting a current signal with an increasing frequency (1 Hz-100 Hz) into the AC bus (153).

[0070] Step S2: Calculate using the above formulas 1 to 5 to obtain impedance values ​​of the AC bus (153) at different frequencies (1 Hz-100 Hz).

[0071] Step S3, drawing an impedance characteristic diagram of the AC bus (153) according to the impedance values ​​of the AC bus (153) at different frequencies (1 Hz-100 Hz), the impedance characteristic diagram of the AC bus (153) being as shown in FIG. Figure 2 , Figure 3 and Figure 4 shown.

[0072] Step S4: Combination Figure 2 , Figure 3 and Figure 4 , analysis shows that: when the frequency is around 1 Hz or above 100 Hz, the impedance value fluctuates greatly around 1 Hz or above 100 Hz. Therefore, if the AC bus (153) is selected as the interface bus of the electromechanical-real-time hybrid simulation, when an asymmetric fault occurs on the side close to the AC bus (153), the asymmetric fault will cause a voltage drop and harmonic loss of the system on the side close to the AC bus (153), resulting in the frequency problem generated by the system being ignored due to the limitation of the electromechanical-hybrid simulation algorithm, ultimately resulting in inaccurate simulation results. Therefore, the AC bus (153) cannot be used as the interface bus of the electromechanical-real-time hybrid simulation.

[0073] In summary, the present invention provides a method for selecting an interface bus in electromechanical-real-time hybrid simulation of a power system, which solves the problem of inaccurate simulation caused by asymmetric faults on the electromechanical side by selecting a suitable interface bus.

[0074] The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are not in exact proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, please refer to the drawings.

[0075] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportion relationship or adjustment of the size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0077] It should be noted that the devices and methods disclosed in the embodiments of this article can also be implemented in other ways. The device implementation described above is only schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of this article. In this regard, each box in the flowchart or block diagram can represent a part of a module, program or code, and the module, program segment or part of the code contains one or more executable instructions for implementing the specified logical function, and the module, program segment or part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented by a dedicated hardware-based system for performing a specified function or action, or can be implemented by a combination of dedicated hardware and computer instructions.

[0078] In addition, the functional modules in the various embodiments of this document may be integrated together to form an independent part, or each module may exist independently, or two or more modules may be integrated to form an independent part.

[0079] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A method for selecting an interface busbar in a hybrid electromechanical-real-time simulation of a power system, characterized in that: include: Step S1, injecting current signals of different frequencies into a plurality of AC busbars respectively; Step S2, obtaining the impedance of each of the AC bus bars at different frequencies by calculation; Step S3, drawing an impedance characteristic diagram of each AC bus according to the impedance size of each AC bus at different frequencies; Step S4, analyzing the impedance characteristic diagram of each of the AC buses obtained in step S3, selecting a plurality of the AC buses, and obtaining an AC bus as an interface bus for electromechanical-real-time hybrid simulation; The step S2 further includes: Step S21, the time characteristic of the current of each AC bus in the α and β coordinates is: The time characteristic of the current is linearized to obtain the current formula: Where: i(t) represents the current-time function; i α represents the projection of the current on the α axis; i β represents the projection of the current on the β axis; i α0 represents the projection of the current on the α-axis at ω0; i β0 represents the projection of the current on the β axis at ω0; Δi α represents the projection of the current on the α-axis at ω0+ω; Δi β represents the projection of the current on the β axis at ω0+ω; represents the projection of the linearized current on the α-axis at ω0-ω; represents the projection of the linearized current on the β axis at ω0-ω; represents the unit vector in the complex plane at ω0; e jωt represents the unit vector in the complex plane at ω; e -jωt represents the inverse vector of the unit vector in the complex plane at ω; j represents the imaginary unit; Step S22: perform the linearization process on the time characteristic of the voltage of each of the AC buses to obtain a voltage formula: Where: u(t) represents the voltage-time function; u α0 represents the projection of the voltage on the α-axis at ω0; u β0 represents the projection of the voltage on the β axis at ω0; Δu α represents the projection of the voltage at ω0+ω on the α-axis; Δu β represents the projection of the voltage on the β-axis at ω0+ω; represents the projection of the linearized voltage on the α-axis at ω0-ω; represents the projection of the linearized voltage on the β-axis at ω0-ω; Step S23, obtaining a corresponding impedance equation through the current formula and the voltage formula: Yes α +jΔi β =Y(ω0+ω)(Δu α +jΔu β ) Where: Y represents impedance; Step S24, solving the impedance equation to obtain the impedance value of each of the AC buses at different frequencies.

2. The interface bus selection method for the electromechanical-real-time hybrid simulation of the power system according to claim 1, characterized in that: The step S4 includes: analyzing the impedance characteristic diagram of each of the AC buses obtained in the step S3, finding the impedance characteristic diagram with the smallest fluctuation of impedance Y with frequency from all the impedance characteristic diagrams, and selecting the AC bus corresponding to the impedance characteristic diagram with the smallest fluctuation of impedance Y with frequency as the interface bus of the electromechanical-real-time hybrid simulation.

3. The interface bus selection method for the electromechanical-real-time hybrid simulation of the power system according to claim 1, characterized in that: The linearization process is specifically as follows: The real part of the complex plane of the power system is obtained by the following formula: Linearizing the above formula, we get: Where: Re represents the real part; S represents the complex plane modulus of the power system; S(t) represents the complex plane linearization function of the power system; S0 represents the complex plane modulus of the power system at ω0; Δ S represents the complex plane modulus value of the power system at ω0+ω; Δ S * Represents the linearized value of the complex plane modulus value of the power system at ω0-ω.

4. The interface bus selection method for the electromechanical-real-time hybrid simulation of the power system according to claim 3 is characterized in that: The step S2 also includes: the amplitude of the current when the frequency is ω0+ω Or at a frequency of ω0-ω, its amplitude is

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