Quasi-steady-state calculation method and apparatus for converters

Abstract

This invention discloses a method and apparatus for quasi-steady-state calculation of a converter. The method includes: acquiring circuit parameters related to high-voltage direct current (HVDC) transmission; obtaining circuit equations before and after a HVDC transmission fault based on the circuit parameters and calculating the actual AC voltage phase at the time of the fault; constructing a three-phase AC voltage using the actual AC voltage phase and inputting the three-phase AC voltage into a phase-locked loop (PLL) to obtain the PLL output synchronization phase; obtaining the phase deviation based on the actual AC voltage phase and the PLL output synchronization phase, and calculating the actual firing angle using the phase deviation, so as to calculate the actual DC voltage based on the actual firing angle and the actual DC current. This invention can calculate the DC voltage by acquiring the DC current and firing angle, and can perform equivalent calculations locally at the converter station, enabling fast and accurate equivalent calculations of the converter.

Description

Technical Field

[0001] This invention relates to the field of power system simulation technology, and in particular to a method and apparatus for quasi-steady-state calculation of converters. Background Technology

[0002] LCC-HVDC high-voltage direct current transmission, with its low price, huge transmission capacity and flexible control methods, has gradually become the main component of my country's high-voltage direct current transmission. my country has formed the world's largest AC-DC hybrid power grid.

[0003] Due to the strong time-varying and nonlinear characteristics of high-voltage direct current (HVDC) transmission, the dynamic characteristics of AC / DC hybrid power grids differ from those of traditional AC power grids, attracting significant attention. The equivalent simulation of converters has become a focal point. Currently, converter equivalent simulations are mainly divided into electromagnetic transient simulation models and electromechanical transient simulation models. Electromagnetic transient simulation models provide numerical solutions, making it difficult to analyze the dynamic characteristics of AC / DC hybrid power grids from a physical mechanism perspective. From an analytical calculation perspective, electromechanical transient simulation models primarily utilize quasi-steady-state models. These models are based on the idea of ​​power frequency periodic average values, reflecting the dynamic adjustment behavior of the controller and the impact of AC voltage RMS changes on DC voltage. However, this model does not consider the influence of phase-locked loops (PLLs) during transients. Furthermore, because it uses AC voltage RMS values ​​for calculation, it struggles to reflect the impact of AC voltage phase changes on the DC system, resulting in higher errors when AC voltage phase changes occur, thus affecting the accuracy of converter equivalent simulations. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] To address the issue that quasi-steady-state models cannot consider the impact of AC voltage phase changes on DC voltage, this invention proposes a quasi-steady-state calculation method for converters. Furthermore, it studies the impact of AC voltage phase changes on the calculation accuracy of quasi-steady-state models and presents a quasi-steady-state model calculation method that considers the AC power supply short-circuit ratio, thus overcoming the disadvantage of traditional quasi-steady-state models that cannot characterize the impact of AC voltage phase changes on DC voltage.

[0006] Another objective of this invention is to provide a converter quasi-steady-state calculation device.

[0007] To achieve the above objectives, this invention provides a quasi-steady-state calculation method for a converter, comprising:

[0008] Obtain circuit parameters related to high-voltage direct current transmission;

[0009] Based on the circuit parameters, the circuit equations before and after the high-voltage direct current transmission fault are obtained, and the actual AC voltage phase at the time of the fault is calculated.

[0010] A three-phase AC voltage is constructed using the actual AC voltage phase, and the three-phase AC voltage is input into a phase-locked loop to obtain the phase-locked loop output synchronization phase;

[0011] The phase deviation is obtained based on the actual AC voltage phase and the phase-locked loop output synchronization phase, and the actual firing angle is calculated using the phase deviation. The actual DC voltage is then calculated based on the actual firing angle and the actual DC current.

[0012] In addition, the converter quasi-steady-state calculation method according to the above embodiments of the present invention may also have the following additional technical features:

[0013] Furthermore, in one embodiment of the present invention, the circuit parameters include the effective value U of the rectifier-side AC line voltage. N Compared to short circuit K SCR And the rated DC voltage U during steady-state operation. d0 Rated DC current I d0 and initial trigger angle α r0 .

[0014] Furthermore, in one embodiment of the present invention, the circuit equations obtained based on the circuit parameters before and after the high-voltage direct current transmission fault are as follows:

[0015]

[0016] Where E is the equivalent electromotive force of the AC power supply, and I d α r , ω represents the DC current, firing angle, and AC voltage phase during actual operation, k represents the power frequency angular velocity, and k represents the proportionality coefficient for converting DC current to the effective value of AC current.

[0017] Furthermore, in one embodiment of the present invention, the calculation of the actual AC voltage phase at the time of the fault is as follows:

[0018]

[0019] in, This represents the actual AC voltage phase.

[0020] Furthermore, in one embodiment of the present invention, the step of constructing a three-phase AC voltage using the actual AC voltage phase and inputting the three-phase AC voltage into a phase-locked loop to obtain the phase-locked loop output synchronization phase includes:

[0021] Through the actual AC voltage phase Constructing three-phase AC voltage As the input to the phase-locked loop (PLL), the output yields the PLL output synchronization phase θ.r :

[0022]

[0023] Among them, K I K is the integral constant of the phase-locked loop PI element. G U is the proportional constant of the phase-locked loop PI element. α u β error, x i PI and PI are intermediate variables in PLL modeling, t represents time, and Δt represents the calculation step size.

[0024] Furthermore, in one embodiment of the present invention, the actual AC voltage phase is utilized. Subtract the phase-locked loop output synchronization phase θ r Receive phase deviation

[0025]

[0026] Furthermore, in one embodiment of the present invention, the phase offset is utilized. Calculate the actual firing angle α:

[0027]

[0028] Furthermore, in one embodiment of the present invention, based on the actual firing angle α and the actual DC current I... d The actual DC voltage U is calculated. d :

[0029]

[0030] To achieve the above objectives, another aspect of the present invention provides a converter quasi-steady-state calculation device, comprising:

[0031] The initial data acquisition module is used to acquire circuit parameters related to high-voltage direct current transmission; the AC voltage phase calculation module is used to obtain the circuit equations before and after the high-voltage direct current transmission fault based on the circuit parameters and to calculate the actual AC voltage phase at the time of the fault.

[0032] The synchronization phase calculation module is used to construct a three-phase AC voltage using the actual AC voltage phase, and input the three-phase AC voltage into the phase-locked loop to obtain the synchronization phase output of the phase-locked loop;

[0033] The DC voltage calculation module is used to obtain the phase deviation based on the actual AC voltage phase and the phase-locked loop output synchronization phase, and to calculate the actual firing angle using the phase deviation, so as to calculate the actual DC voltage based on the actual firing angle and the actual DC current.

[0034] The converter quasi-steady-state calculation method and apparatus of the present invention consider the converter calculation model of AC power supply short-circuit ratio. At the same time, it does not require real-time collection of detailed AC voltage information. It only needs to obtain the relevant rated electrical information during stable operation. The DC voltage can be calculated by collecting DC current and firing angle. The equivalent calculation can be performed locally at the converter station, which can quickly and accurately perform the equivalent calculation of the converter.

[0035] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0037] Figure 1 This is a flowchart of a converter quasi-steady-state calculation method according to an embodiment of the present invention;

[0038] Figure 2 This is a flowchart illustrating the quasi-steady-state calculation method for a converter according to an embodiment of the present invention.

[0039] Figure 3 This is a comparison chart of the calculation results of the rectifier-side DC voltage according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the converter quasi-steady-state calculation device according to an embodiment of the present invention. Detailed Implementation

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0043] The converter quasi-steady-state calculation method and apparatus according to embodiments of the present invention are described below with reference to the accompanying drawings.

[0044] Figure 1 This is a flowchart of the converter quasi-steady-state calculation method according to an embodiment of the present invention.

[0045] like Figure 1 As shown, the method includes, but is not limited to, the following steps:

[0046] S1, obtain circuit parameters related to high-voltage direct current transmission;

[0047] S2, based on the circuit parameters, obtain the circuit equations before and after the fault in the high voltage direct current transmission and calculate the actual AC voltage phase at the time of the fault;

[0048] S3, construct a three-phase AC voltage using the actual AC voltage phase, and input the three-phase AC voltage into the phase-locked loop to obtain the phase-locked loop output synchronization phase;

[0049] S4 obtains the phase deviation based on the actual AC voltage phase and the phase-locked loop output synchronization phase, and uses the phase deviation to calculate the actual firing angle, so as to calculate the actual DC voltage based on the actual firing angle and the actual DC current.

[0050] The converter quasi-steady-state calculation method of this invention considers the converter calculation model of AC power supply short-circuit ratio. At the same time, it does not require real-time collection of detailed AC voltage information. It only needs to obtain the relevant rated electrical information during stable operation. The DC voltage can be calculated by collecting DC current and firing angle. The equivalent calculation can be performed locally at the converter station, which can quickly and accurately perform the equivalent calculation of the converter.

[0051] like Figure 2 The above is a specific flowchart of the converter quasi-steady-state calculation method according to an embodiment of the present invention, as follows: Figure 2 As shown:

[0052] Step S101: Read in the effective value U of the AC line voltage on the rectifier side of the LCC-HVDC high-voltage direct current transmission. N and short-circuit ratio K SCR And the rated DC voltage U during steady-state operation of the LCC-HVDC. d0 DC current I d0 Trigger angle α r0 .

[0053] Step S102: Based on the output parameters of step S101, write the circuit equations before and after the fault respectively:

[0054]

[0055] Where E is the equivalent electromotive force of the AC power supply, and I d α r , For the actual operating DC current, firing angle, and AC voltage phase, where I d α rω is the power frequency angular velocity, obtained from DC side measurements and controller output. k is the proportionality coefficient for converting DC current to the effective value of AC current.

[0056] Step S103: Solve for the actual AC voltage phase based on the circuit equations before and after the fault:

[0057]

[0058] Step S104: Through actual phase Constructing three-phase AC voltage As the input to the phase-locked loop (PLL), the synchronous phase θ of the PLL output is obtained. r :

[0059]

[0060] Among them, K I K is the integral constant of the phase-locked loop PI element. G U is the proportional constant of the phase-locked loop PI element. α u β error, x i PI and PI are intermediate variables in PLL modeling, t represents time, and Δt represents the calculation step size.

[0061] Step S105: Utilize the actual phase Subtract the phase-locked loop output synchronization phase θ r The phase deviation can be obtained. Used to compensate for the trigger angle.

[0062]

[0063] Step S106: Utilize phase offset Calculate the actual firing angle α r .

[0064]

[0065] Where, α rord The trigger angle command is obtained from an external controller.

[0066] Step S107: Calculate the actual firing angle and the acquired DC current I using the converter calculation model. d The DC voltage U is calculated. d :

[0067]

[0068] Furthermore, the converter quasi-steady-state calculation method of the present invention embodiments is compared and verified, such as... Figure 3As shown, the model of the present invention can be compared with the calculation results of the traditional quasi-steady-state model. The model of the present invention does not need to collect detailed AC voltage information in real time. It only needs to obtain the relevant rated electrical information during stable operation. The DC voltage can be calculated by collecting DC current and firing angle. The equivalent calculation can be performed locally at the converter station. It can express the influence of voltage phase change on DC voltage that the traditional quasi-steady-state model cannot express.

[0069] The converter quasi-steady-state calculation method according to embodiments of the present invention overcomes the disadvantage of traditional quasi-steady-state models that cannot characterize the impact of AC voltage phase changes on DC voltage, which is beneficial to improving the equivalent accuracy of quasi-steady-state models and laying a computational foundation for small disturbance analysis and power flow calculation of AC / DC hybrid power grids.

[0070] To achieve the above embodiments, such as Figure 4 As shown, this embodiment also provides a converter quasi-steady-state calculation device 10, which includes an initial data acquisition module 100, an AC voltage phase calculation module 200, a synchronous phase calculation module 300, and a DC voltage calculation module 400.

[0071] The initial data acquisition module 100 is used to acquire circuit parameters related to high voltage direct current transmission.

[0072] The AC voltage phase calculation module 200 is used to obtain the circuit equations before and after the fault in the high voltage DC transmission based on the circuit parameters and to calculate the actual AC voltage phase at the time of the fault.

[0073] The synchronization phase calculation module 300 is used to construct a three-phase AC voltage using the actual AC voltage phase, and input the three-phase AC voltage into the phase-locked loop to obtain the synchronization phase output of the phase-locked loop;

[0074] The DC voltage calculation module 400 is used to obtain the phase deviation based on the actual AC voltage phase and the phase-locked loop output synchronization phase, and to calculate the actual firing angle using the phase deviation, so as to calculate the actual DC voltage based on the actual firing angle and the actual DC current.

[0075] Furthermore, the circuit parameters in the aforementioned initial data acquisition module 100 include the effective value U of the rectifier-side AC line voltage. N Compared to short circuit K SCR And the rated DC voltage U during steady-state operation. d0 Rated DC current I d0 and initial trigger angle α r0 .

[0076] Furthermore, the circuit equations obtained by the AC voltage phase calculation module 200 based on the circuit parameters before and after the high-voltage direct current transmission fault are as follows:

[0077]

[0078] Where E is the equivalent electromotive force of the AC power supply, and I d α r , ω represents the DC current, firing angle, and AC voltage phase during actual operation, k represents the power frequency angular velocity, and k represents the proportionality coefficient for converting DC current to the effective value of AC current.

[0079] Furthermore, the AC voltage phase calculation module 200 calculates the actual AC voltage phase at the time of the fault:

[0080]

[0081] in, This represents the actual AC voltage phase.

[0082] Furthermore, the aforementioned synchronization phase calculation module 300 is also used for:

[0083] Through the actual AC voltage phase Constructing three-phase AC voltage As the input to the phase-locked loop (PLL), the output yields the PLL output synchronization phase θ. r :

[0084]

[0085] Among them, K I K is the integral constant of the phase-locked loop PI element. G U is the proportional constant of the phase-locked loop PI element. α u β error, x i PI and PI are intermediate variables in PLL modeling, t represents time, and Δt represents the calculation step size.

[0086] Furthermore, the DC voltage calculation module 400 described above utilizes the actual AC voltage phase. Subtract the phase-locked loop output synchronization phase θ r Receive phase deviation

[0087]

[0088] Furthermore, the DC voltage calculation module 400 described above utilizes phase offset. Calculate the actual firing angle α:

[0089]

[0090] Where, α rordThe trigger angle command is obtained from an external controller.

[0091] Furthermore, the DC voltage calculation module 400 above calculates the actual firing angle α and the actual DC current I. d The actual DC voltage U is calculated. d :

[0092]

[0093] The converter quasi-steady-state calculation device according to the present invention overcomes the disadvantage of traditional quasi-steady-state models that cannot characterize the influence of AC voltage phase changes on DC voltage, which is beneficial to improving the equivalent accuracy of quasi-steady-state models and laying a computational foundation for small disturbance analysis and power flow calculation of AC / DC hybrid power grids.

[0094] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0095] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. A method of quasi-steady state calculation of a converter, characterized in that, Includes the following steps: Obtain circuit parameters related to high-voltage direct current transmission; Based on the circuit parameters, the circuit equations before and after the high-voltage direct current transmission fault are obtained, and the actual AC voltage phase at the time of the fault is calculated. A three-phase AC voltage is constructed using the actual AC voltage phase, and the three-phase AC voltage is input into a phase-locked loop to obtain the phase-locked loop output synchronization phase; The phase deviation is obtained based on the actual AC voltage phase and the phase-locked loop output synchronization phase, and the actual firing angle is calculated using the phase deviation. The actual DC voltage is then calculated based on the actual firing angle and the actual DC current.

2. The method according to claim 1, characterized in that, The circuit parameters include the rectifier side AC line voltage effective value U N And short circuit ratio K SCR And rated DC voltage in steady state operation U d0 Rated DC current I d0 And initial trigger angle α r0 .

3. The method of claim 2, wherein, The circuit equations before and after the high-voltage direct current transmission fault, obtained based on the circuit parameters, are as follows: in, E This is the equivalent electromotive force of the AC power supply. I d , α r , φ The actual operating parameters are DC current, firing angle, and AC voltage phase. ω For power frequency angular velocity, k This is the proportionality coefficient for converting DC current to the effective value of AC current.

4. The method according to claim 3, characterized in that, The actual AC voltage phase at the time of the fault was calculated as follows: in, φ This represents the actual AC voltage phase.

5. The method according to claim 4, characterized in that, The process of constructing a three-phase AC voltage using the actual AC voltage phase and inputting the three-phase AC voltage into a phase-locked loop (PLL) to obtain the PLL output synchronization phase includes: Through the actual AC voltage phase φ Constructing three-phase AC voltage u a = U N sin( ωt + φ ), u b = U N sin( ωt + φ -2 π / 3) u c = U N sin( ωt + φ +2 π / 3), as the input of the phase-locked loop (PLL), the output yields the PLL output synchronization phase. θ r : in, KI Let be the integral constant of the phase-locked loop PI element. KG The proportional constant of the PI element in the phase-locked loop. uα , uβ , error , xi , PI These are intermediate variables used for PLL modeling. t Indicates time, Δ t This indicates the calculation step size.

6. The method according to claim 5, characterized in that, Using the actual AC voltage phase φ Subtract the phase-locked loop output synchronization phase θ r The phase deviation Δ is obtained φ r : 。 7. The method according to claim 6, characterized in that, Using the phase deviation Δ φ r Calculate the actual firing angle : in, α rord The trigger angle command is obtained from an external controller.

8. The method according to claim 7, characterized in that, Based on the actual trigger angle and actual DC current I d The actual DC voltage was calculated. U d : 。 9. A converter quasi-steady-state calculation device, characterized in that, include: The initial data acquisition module is used to acquire circuit parameters related to high-voltage direct current transmission. The AC voltage phase calculation module is used to obtain the circuit equations before and after the fault in the high voltage direct current transmission based on the circuit parameters and to calculate the actual AC voltage phase at the time of the fault. The synchronization phase calculation module is used to construct a three-phase AC voltage using the actual AC voltage phase, and input the three-phase AC voltage into the phase-locked loop to obtain the synchronization phase output of the phase-locked loop; The DC voltage calculation module is used to obtain the phase deviation based on the actual AC voltage phase and the phase-locked loop output synchronization phase, and to calculate the actual firing angle using the phase deviation, so as to calculate the actual DC voltage based on the actual firing angle and the actual DC current.

10. The apparatus according to claim 9, characterized in that, The circuit parameters in the initial data acquisition module include the effective value of the rectifier-side AC line voltage. U N Compared to short circuit K SCR and the rated DC voltage during steady-state operation. U d0 Rated DC current I d0 and initial trigger angle α r0 .

11. The apparatus according to claim 10, characterized in that, The AC voltage phase calculation module obtains the following circuit equations before and after the HVDC transmission fault based on the circuit parameters: in, E This is the equivalent electromotive force of the AC power supply. I d , α r , φ The actual operating parameters are DC current, firing angle, and AC voltage phase. ω For power frequency angular velocity, k This is the proportionality coefficient for converting DC current to the effective value of AC current.

12. The apparatus according to claim 11, characterized in that, The AC voltage phase calculation module calculates the actual AC voltage phase at the time of the fault: in, φ This represents the actual AC voltage phase.

13. The apparatus according to claim 12, characterized in that, The synchronization phase calculation module is also used for: Through the actual AC voltage phase φ Constructing three-phase AC voltage u a = U N sin( ωt + φ ), u b = U N sin( ωt + φ -2 π / 3) u c = U N sin( ωt + φ +2 π / 3), as the input of the phase-locked loop (PLL), the output yields the PLL output synchronization phase. θ r : in, KI Let be the integral constant of the phase-locked loop PI element. KG The proportional constant of the PI element in the phase-locked loop. uα , uβ , error , xi , PI These are intermediate variables used for PLL modeling. t Indicates time, Δ t This indicates the calculation step size.

14. The apparatus according to claim 13, characterized in that, The DC voltage calculation module utilizes the actual AC voltage phase. φ Subtract the phase-locked loop output synchronization phase θ r The phase deviation Δ is obtained φ r : 。 15. The apparatus according to claim 14, characterized in that, The DC voltage calculation module utilizes the phase deviation Δ φ r Calculate the actual firing angle : in, α rord The trigger angle command is obtained from an external controller.

16. The apparatus according to claim 15, characterized in that, The DC voltage calculation module calculates the actual firing angle. α and actual DC current I d The actual DC voltage was calculated. U d : 。

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