A star-delta transformation network decoupling modeling method

Abstract

The application discloses a star-delta transformation network decoupling modeling method, which comprises the following steps: LINE1 and LINE2 are two transmission lines in a power distribution network which cannot realize long conductor decoupling, the two transmission lines are connected in series to obtain a new line LINE; the new line LINE is subjected to star-delta transformation and equivalent transformation, the wave propagation delay of the new line LINE is prolonged, the purpose of prolonging the transmission line is realized, decoupling and simulation are carried out; in the simulation process, the new line LINE is modeled by using the Bergeron model to obtain simulation results. The network decoupling method expands the application range of the traditional long transmission line decoupling method, thereby providing a new simulation scheme for electromagnetic transient simulation space parallel computation.

Description

Technical Field

[0001] This invention relates to the technical field of power distribution networks, and in particular to a decoupling modeling method based on star-delta transformation networks. Background Technology

[0002] With the widespread use of power electronic components in power grids, traditional AC power grids have evolved into hybrid AC / DC power grids. The planning and operation of power systems can no longer simplify or ignore the transient operating characteristics of power electronic devices such as VSCs. Since power systems are difficult to study experimentally, accurate simulation technology remains a crucial tool for understanding and analyzing power grids. Traditional AC power systems are analyzed through electromechanical transient simulation, which uses quasi-steady-state and steady-state models to simulate power electronic devices. However, the simulation step size is relatively large, making it difficult to analyze the discrete high-frequency switching actions of power electronic converters. If small-step electromagnetic transient simulation is used to simulate large-scale power system networks, the computational load becomes extremely large, resulting in very low computational efficiency.

[0003] To resolve the conflict between computational efficiency and accuracy, parallel computing can be used to improve system simulation efficiency. Spatial parallel computing is the most commonly used method in parallel computing. Its core idea is to decompose the power system into multiple sub-regions according to its topology, and then assign each sub-region to a CPU for simulation calculation, thereby improving the simulation speed of the power system.

[0004] The long transmission line decoupling method is a common spatial parallel computing approach. Its basic idea is to achieve natural decoupling of the power system network based on the Berylon model of the transmission line. Voltage and current are transmitted in the form of electromagnetic waves along the line. When the simulation step size Δt is less than or equal to the wave propagation time on the line, the networks at both ends of the long transmission line can be simulated in parallel, achieving natural decoupling of the system. However, the long transmission line decoupling method can only be used when the system contains long transmission lines and a sufficiently small integration step size is employed, thus limiting its application scenarios.

[0005] In typical power distribution networks, long transmission lines are absent, making it impossible to directly apply the long transmission line decoupling method. Using the long transmission line decoupling method would require reducing the simulation step size, thereby increasing the computational load and reducing the simulation speed. This invention provides a new long transmission line decoupling method. When long transmission lines are absent in the power distribution network, series transmission lines can be merged to obtain a longer transmission line. If the propagation time of the new transmission line is greater than the network simulation step size, the networks at both ends of the new transmission line can be naturally decoupled, thus enabling parallel computing simulation. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the decoupling modeling method based on star-delta transformation network, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to provide a decoupling modeling method based on star-triangle transformation network.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: LINE1 and LINE2 are two transmission lines in the power distribution network that cannot be decoupled from long conductors. They are connected in series to obtain a new line LINE.

[0010] The new line LINE undergoes star-delta transformation and equivalent transformation to extend the wave propagation delay of the new line LINE, thereby achieving the purpose of extending the transmission line, and performing decoupling and simulation.

[0011] During the simulation, the new LINE was modeled using the Berylon model, and the simulation results were obtained.

[0012] As a preferred embodiment of the star-delta transformation network decoupling modeling method described in this invention, wherein: LINE1 includes R1, L1, G1, and C1, and LINE2 includes R2, L2, G2, and C2; star-delta transformation is performed on R1, L1, G1, C1, R2, L2, G2, and C2 to obtain the values ​​of each parameter in the circuit after the star-delta transformation;

[0013] Wherein, R1, L1, G1, and C1 are the line resistance, line inductance, circuit conductance, and capacitance to ground of LINE1, respectively, and R2, L2, G2, and C2 are the line resistance, line inductance, circuit conductance, and capacitance to ground of LINE2, respectively.

[0014] As a preferred embodiment of the star-delta transformation network decoupling modeling method described in this invention, the parameter values ​​of the circuit after the star-delta transformation are:

[0015]

[0016]

[0017] R2'=(-G1L1L2-C1L1R2-C1L2R1)w 2 +R1+R2+G1R1R2

[0018] X2'=w(L1+L2+G1L1R2+G1L2R1+C1R1R2)-C1L1L2w 3

[0019]

[0020] Where w is the angular frequency of the power grid, and R1', X1', R2', X2', R3', and X3' are the equivalent resistance and equivalent reactance that appear in the circuit transformation.

[0021] As a preferred embodiment of the star-delta transform network decoupling modeling method described in this invention, the new line LINE after series connection is equivalently transformed to restore R2', X2', G2, and C2, and the circuit after equivalent transformation is converted into a transmission line model. According to the model, R2' is the equivalent resistance of the new line LINE, and X2' is the equivalent reactance of the new line LINE.

[0022] As a preferred embodiment of the star-delta transform network decoupling modeling method described in this invention, the values ​​of R2' and X2' are determined. When R2' is greater than zero and X2' is greater than the equivalent impedance of LINE1 and LINE2, the new line LINE achieves network decoupling, as shown in the following formula:

[0023] R2′=R1+R2+R1R2G1-w 2 L1L2G1-w 2 L2R1C1-w 2 L1R2C1>0

[0024] wL1+wL2+wL2R1G1+wL1R2G1+wC1R1R2-w 3 L1L2C1>wL1

[0025] wL1+wL2+wL2R1G1+wL1R2G1+wC1R1R2-w 3 L1L2C1>wL2

[0026] Among them, wL1 and wL2 are the equivalent reactances of LINE1 and LINE2.

[0027] As a preferred embodiment of the star-delta transformation network decoupling modeling method described in this invention, the new line LINE is simulated using the Balon model, and R1', X1' and R3', X3' are modeled using a lumped parameter model.

[0028] As a preferred embodiment of the star-delta transformation network decoupling modeling method described in this invention, the values ​​of X1' and X3' are determined to be positive or negative.

[0029] As a preferred embodiment of the star-delta transform network decoupling modeling method described in this invention, if the values ​​of X1' and X3' are greater than zero, the Norton equivalent circuit of the inductor model is used for modeling; if the values ​​of X1' and X3' are less than zero, the Norton equivalent circuit of the capacitor model is used for simulation.

[0030] As a preferred embodiment of the star-delta transformation network decoupling modeling method described in this invention, the sign of the values ​​of R1' and R3' is determined.

[0031] As a preferred embodiment of the star-delta transformation network decoupling modeling method described in this invention, if the values ​​of R1' and R3' are greater than zero, a positive resistance model is used for simulation; if the values ​​of R1' and R3' are less than zero, a negative resistance model is used for simulation.

[0032] The beneficial effects of this invention are as follows: Addressing the issue of the absence of long transmission lines in power distribution networks, which precludes parallel simulation using long transmission line decoupling methods, this patent proposes a network decoupling modeling method based on star-delta transformation. First, a star-delta transformation is performed on the series equivalent circuit of two short transmission lines connected in series, converting the original star circuit into a delta circuit. If the transmission time of the new line is longer than the simulation step size, natural network decoupling can be achieved. This network decoupling method expands the application scope of traditional long transmission line decoupling methods, thus providing a new simulation scheme for spatial parallel computation of electromagnetic transient simulations. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0034] Figure 1 The transmission lines LINE1 and LINE2 described in this invention, based on the star-delta transformation network decoupling modeling method, are connected in series through bus BUS1 to obtain a new line LINE.

[0035] Figure 2 This is the equivalent circuit diagram of LINE1 and LINE2 in series, as described in the star-delta transformation network decoupling modeling method of this invention.

[0036] Figure 3 This is a circuit diagram of the new LINE line after star-delta transformation, based on the star-delta transformation network decoupling modeling method of the present invention.

[0037] Figure 4 The circuit diagram is the equivalent transformation of the star-delta transformation network decoupling modeling method of this invention.

[0038] Figure 5 This invention provides an equivalent transmission line model based on the star-delta transformation network decoupling modeling method.

[0039] Figure 6 This invention relates to the Norton equivalent circuit of an inductor based on the star-delta transformation network decoupling modeling method.

[0040] Figure 7 This invention presents the Norton equivalent circuit of a capacitor based on the star-delta transformation network decoupling modeling method.

[0041] Figure 8 This is the resistance simulation model based on the star-delta transformation network decoupling modeling method of the present invention.

[0042] Figure 9 This is a flowchart of the decoupling modeling method based on star-triangle transformation network of the present invention.

[0043] Figure 10 This is a circuit model diagram.

[0044] Figure 11 This is a simulation model of a PI-shaped transmission line.

[0045] Figure 12 This is a comparison diagram of the waveform of phase a of current L1.

[0046] Figure 13 This is a comparison chart of voltage VLOAD results. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0049] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0050] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0051] Example 1

[0052] Reference Figures 1-9 A decoupling modeling method based on star-triangle transformation network includes:

[0053] S1: Connect two transmission lines LINE1 and LINE2 in the distribution network, which cannot be decoupled by long conductors, in series via bus BUS1 to obtain a new line LINE, such as... Figure 1 As shown, draw the equivalent circuit diagram of the new line LINE. Figure 2 As shown. It should be noted that:

[0054] LINE1 includes R1, L1, G1, and C1. R1 is the line resistance of LINE1, L1 is the line inductance of LINE1, G1 is the circuit conductance of LINE1, and C1 is the capacitance to ground of LINE1. LINE2 includes R2, L2, G2, and C2. R2 is the line resistance of LINE2, L2 is the line inductance of LINE2, G2 is the circuit conductance of LINE2, and C2 is the capacitance to ground of LINE2.

[0055] S2: Perform a star-delta transformation on the new LINE after series connection. The circuit diagram after the star-delta transformation is as follows: Figure 3 As shown. It should be noted that:

[0056] Figure 3 The values ​​of each parameter are as follows. In the formula, w is the angular frequency of the power grid, and R1', X1', R2', X2', R3', and X3' are the equivalent resistance and equivalent reactance that appear in the circuit transformation, which have no clear physical meaning.

[0057]

[0058]

[0059] R2'=(-G1L1L2-C1L1R2-C1L2R1)w 2 +R1+R2+G1R1R2

[0060] X2'=w(L1+L2+G1L1R2+G1L2R1+C1R1R2)-C1L1L2w 3

[0061]

[0062] S3: Perform an equivalent transformation on the new LINE after the star-delta transformation, such as... Figure 4 As shown, and based on the equivalent circuit of the new LINE, R2', X2', G2, and C2 can be restored to the new transmission line, as follows. Figure 5 As shown.

[0063] Therefore, the equivalent resistance of the new line LINE is R2' and the equivalent reactance is X2'. Calculate the values ​​of the equivalent resistance R2' and equivalent reactance X2' of the new line LINE, and determine whether the value of R2' is greater than 0 and whether the value of X2' is greater than the equivalent reactance values ​​of LINE1 and LINE2.

[0064] If the following formula is satisfied, then the equivalent resistance R2' is greater than zero, and the equivalent reactance of the new line LINE is X2', which is greater than the equivalent reactance of LINE1 and LINE2; where wL1 and wL2 are the equivalent reactances of LINE1 and LINE2.

[0065] R2′=R1+R2+R1R2G1-w 2 L1L2G1-w 2 L2R1C1-w 2 L1R2C1>0

[0066] wL1+wL2+wL2R1G1+wL1R2G1+wC1R1R2-w 3 L1L2C1>wL1

[0067] wL1+wL2+wL2R1G1+wL1R2G1+wC1R1R2-w 3 L1L2C1>wL2

[0068] The wave propagation delay of the new LINE line is Since the equivalent reactance of the new LINE is X2′, which is greater than the equivalent reactance of LINE1 and LINE2, the wave propagation delay of the new LINE is longer, thus achieving the purpose of extending the transmission line; when At this time, Δt is the simulation step size, and the new line LINE achieves decoupling.

[0069] S4: During the simulation, the new LINE is modeled using the Berylon model, and X1 and X3 are modeled using lumped parameters.

[0070] If the values ​​of X1' and X3' are greater than zero, the Norton equivalent circuit model of the inductor is used. The Norton model of the inductor is as follows: Figure 6 As shown in the figure, V k and V m It is the port voltage of the equivalent circuit, Reff It is an equivalent resistor, and its value is L is the simulated inductance value, Δt is the simulated step size, and i km It is the current flowing into the inductor, and its direction is shown in the figure below, I history(t-Δt) For historical items, their value is

[0071]

[0072] If the values ​​of X1 and X3 are less than zero, the Norton equivalent circuit of the capacitor model is used for simulation, such as... Figure 7 As shown; where V k and V m It is the port voltage of the equivalent circuit, R eff It is an equivalent resistor, and its value is C is the simulated inductance value, Δt is the simulated step size, and i km This is the current flowing into the capacitor, and its direction is shown in the diagram below;

[0073] I history (t-Δt) represents the historical term, and its value is...

[0074] S5: During the simulation, the new LINE line is modeled using the Berylon model, and R1' and R3' are modeled using lumped parameters.

[0075] If the values ​​of R1' and R3' are greater than zero, the positive resistance model is used for simulation; if the values ​​of R1' and R3' are less than zero, the negative resistance model is used for simulation, and the simulation results are obtained.

[0076] Its simulation model is as follows Figure 8 As shown, where V k and V m R is the port voltage of the equivalent circuit. When the simulated resistor is a positive resistor, R is greater than 0 in the simulation model; when the simulated resistor is a negative resistor, R is less than 0 in the simulation model.

[0077] Since there are no long transmission lines in the distribution network, the long transmission line decoupling method cannot be used for parallel simulation; the process of this method is as follows: Figure 9 As shown, firstly, two transmission lines LINE1 and LINE2 in the distribution network, which cannot be decoupled by long conductors, are connected in series via bus BUS1 to obtain a new line LINE. Then, a star-delta transformation is performed on the equivalent circuit of the new line LINE, converting the star circuit in the original circuit into a delta circuit. If the transmission time of the new line LINE is greater than the simulation step size, natural decoupling of the network can be achieved. This network decoupling method expands the application scope of traditional long transmission line decoupling methods, thus providing a new simulation scheme for spatial parallel computing of electromagnetic transient simulations.

[0078] Example 2

[0079] Reference Figures 10-13 This embodiment is the second embodiment of the present invention. Unlike the first embodiment, this embodiment provides a verification test based on the star-delta transformation network decoupling modeling method to verify and explain the technical effects used in this method.

[0080] by Figure 10 Taking the circuit diagram as an example, the transmission line is simulated using the PI-type simulation model and the transmission line model proposed in this paper. The PI-type simulation model is as follows: Figure 11 As shown.

[0081] Where R is the resistance of the transmission line, L is the inductance of the transmission line, C is the capacitance to ground of the transmission line, and the waveform of phase a of current I1 is compared as follows. Figure 12 As shown, voltage V LOAD The comparison results are as follows Figure 13 As shown.

[0082] The error can be calculated using the following formula:

[0083]

[0084] Where a1 is the simulation data vector of the PI-type simulation model, a2 is the simulation data vector of the simulation method in this paper, and the current I1 and voltage V are respectively. LOAD The error values ​​are shown in the table below:

[0085] Comparison waveforms error I1 current a phase 0.1965 I1 current in phase b 0.2174 I1 current c phase 0.2162 VLOAD voltage phase a 0.0550 VLOAD voltage phase b 0.0550 VLOAD voltage c phase 0.0550

[0086] Simulation algorithm efficiency analysis:

[0087] Using the simulation method described above, the simulation efficiency of different nodes was tested, and the simulation time of the network was compared as follows (network simulation time is 10s, simulation step size is 0.0001s):

[0088] Number of network nodes Simulation time (s) for PI-type transmission line Simulation time (s) for the proposed scheme 39 11.54 7.50 926 50.86 36.12 1565 70.23 50.45

[0089] The results above show that the method presented in this paper can effectively improve the simulation efficiency of networks.

[0090] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A network decoupling modeling method based on star-triangle transformation, characterized in that: include, LINE1 and LINE2 are two transmission lines in the distribution network that cannot be decoupled from long conductors. They are connected in series to obtain a new line LINE. The new line LINE undergoes star-delta transformation and equivalent transformation to extend the wave propagation delay of the new line LINE, thereby achieving the purpose of extending the transmission line, and performing decoupling and simulation. During the simulation process, the new LINE was modeled using the Berylon model, and the simulation results were obtained. Then, the new LINE after being connected in series is transformed into an equivalent form to restore the original LINE. R 2 ， , X 2 ， G2 and C2 transform the equivalent circuit into a transmission line model, and based on the Berylon model, the following is derived: R 2 ， Let be the equivalent resistance of the new line LINE. X 2 ， The equivalent reactance of the new line LINE; judge R 2 ， and X 2 ， The value of , when satisfying R 2 ， Greater than zero, X 2 ， The new line LINE, with impedance greater than the equivalent impedances of LINE1 and LINE2, achieves network decoupling, as shown in the following formula: ， ， ， in, wL 1 and wL 2 It is the equivalent reactance of LINE1 and LINE2. The angular frequency of the power grid; The new LINE line was simulated using the Berylon model. R 1 ， 、X 1 ， and R 3 ， 、X 3 ， Modeling is done using a lumped parameter model.

2. The network decoupling modeling method based on star-triangle transformation as described in claim 1, characterized in that: The LINE1 includes R 1 , L 1. G 1. C 1. The LINE2 includes R 2. L 2. G 2. C 2. Regarding R 1. L 1. G 1. C 1. R 2. L 2. G 2. C 2. Perform a star-delta transformation to obtain the values ​​of each parameter in the circuit after the star-delta transformation; in, R 1. L 1. G 1. C 1 represents the line resistance, line inductance, circuit conductance, and capacitance to ground of LINE1, respectively. R 2. L 2. G 2. C 2 represents the line resistance, line inductance, circuit conductance, and capacitance to ground of LINE2, respectively.

3. The network decoupling modeling method based on star-triangle transformation as described in claim 2, characterized in that: The circuit parameters after the star-delta transformation are: ， ， ， ， ， in, The angular frequency of the power grid. R 1 ， , X 1 ， , R 2 ， , X 2 ， , R 3 ， , X 3 ， These are the equivalent resistance and equivalent reactance that appear during circuit transformation.

4. The network decoupling modeling method based on star-triangle transformation as described in claim 1, characterized in that: judge X 1 ， 、X 3 ， The value is positive or negative, and the corresponding model is selected for simulation.

5. The network decoupling modeling method based on star-delta transformation as described in claim 4, characterized in that: like X 1 ， 、X 3 ， If the value is greater than zero, Norton's equivalent circuit model is used with the inductance model. X 1 ， 、X 3 ， If the value is less than zero, the Norton equivalent circuit of the capacitor model is used for simulation.

6. The network decoupling modeling method based on star-delta transformation as described in claim 1, characterized in that: judge R 1 ， 、R 3 ， The sign of the value determines the corresponding model to be used for simulation.

7. The network decoupling modeling method based on star-delta transformation as described in claim 6, characterized in that: like R 1 ， 、R 3 ， If the value is greater than zero, use the positive resistance model for simulation. R 1 ， 、R 3 ， If the value is less than zero, a negative resistance model is used for simulation.

Images