A parameter design method and device for impedance correction in a DC transmission system

Abstract

This invention discloses a parameter design method and apparatus for an impedance correction device in a DC transmission system. The method includes: obtaining the voltage and harmonic parameters of the AC system based on the constructed target DC transmission system topology, and designing an amplitude-phase corrector parameter optimization model; obtaining the impedance characteristics of the AC and DC systems under different operating modes; simulating the component stress of the amplitude-phase corrector under corresponding fluctuation states using the amplitude-phase corrector parameter optimization model in response to the impedance characteristics; determining the parameters of the amplitude-phase corrector based on the voltage fluctuation rate of the AC system and the operating power range of the DC system in the corrector configuration stage, and optimizing the parameters based on the component stress to configure the amplitude-phase corrector; repeating the corrector configuration stage after configuring the amplitude-phase corrector until the equivalent harmonic impedance of the DC transmission system meets the preset system oscillation index. This method can effectively reduce harmonic oscillations in the DC transmission system by optimizing the parameters of the amplitude-phase corrector.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology, and in particular to a parameter design method and apparatus for an impedance correction device for a DC power transmission system. Background Technology

[0002] Multi-source adaptive commutator (SLCC) DC transmission technology is a novel DC transmission technology that combines the characteristics of grid-connected commutator (LCC) and high-capacity static var filter (SVF) technologies. It integrates the mature technology of high-voltage, high-power transmission from traditional DC transmission with the technical characteristics of new power electronic devices. Employing valve-side reactive power compensation and harmonic filtering technologies, it improves the adaptability of DC to weak AC systems, reduces the safety hazards of converter transformers, lowers the risk of DC commutation failure, eliminates the need for amplitude and phase correctors, reduces equipment noise levels, and saves on land area.

[0003] In scenarios such as new energy-SLCC and weak AC system-SLCC, many power electronic devices are characterized by high-frequency switching operation. The impedance of the entire power grid and the SLCC DC interconnection system exhibits nonlinear characteristics. As the switching frequency increases, the control delay caused by measurement, communication, and calculation processes has a greater impact on the system's response characteristics, leading to frequent mid-to-high frequency broadband oscillations. To address this issue, a hardware suppression solution can be adopted by configuring amplitude and phase correctors on the AC bus. However, existing amplitude and phase correctors are not very effective at improving the impedance characteristics of SLCC converters, resulting in an inability to effectively suppress harmonic oscillations and affecting the stable operation of the transmission system.

[0004] Therefore, how to improve the amplitude and phase correction device has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a parameter design method and apparatus for an impedance correction device in a DC transmission system, which addresses how to improve the design of the parameters of the amplitude-phase correction device to enhance its impedance regulation capability and ensure the stable operation of the transmission system.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a parameter design method for an impedance correction device in a DC transmission system, comprising:

[0007] Based on the constructed target DC transmission system topology, obtain the voltage and harmonic parameters of the AC system, and design an optimization model for the amplitude and phase corrector parameters;

[0008] The impedance characteristics of the AC / DC system of the target DC transmission system topology were obtained under different preset operating modes.

[0009] In response to the impedance characteristics, the component stress of the amplitude-phase corrector under the corresponding fluctuation state is simulated by the amplitude-phase corrector parameter optimization model;

[0010] In the calibration configuration stage, the initial parameters of the amplitude-phase calibration are determined based on the voltage fluctuation rate of the AC system and the operating power range of the DC system, and the initial parameters are optimized based on the component stress to configure the amplitude-phase calibration.

[0011] After configuring the amplitude and phase corrector, repeat the corrector configuration process until the equivalent harmonic impedance of the target DC transmission system topology meets the preset transmission system oscillation index.

[0012] Furthermore, the design of the amplitude-phase corrector parameter optimization model includes:

[0013] Under extreme power frequency conditions, based on the obtained rated voltage, steady-state voltage, and extreme voltage of the AC system, a parameter optimization model for the power frequency amplitude and phase corrector is designed.

[0014] Based on the obtained background harmonic voltage and harmonic current at the AC bus of the target DC transmission system topology, an optimization model for the parameters of the harmonic amplitude and phase corrector is designed.

[0015] Furthermore, the impedance characteristics of the target DC transmission system topology AC / DC system are obtained under different preset operating modes:

[0016] Using the AC bus of the target DC transmission system topology as the port, the first impedance characteristics of the AC system within a preset frequency range under different disconnection methods are obtained; and,

[0017] Obtain the second impedance characteristics of a broadband DC system under different operating modes.

[0018] Further, the step of simulating the element stress of the amplitude-phase corrector under the corresponding fluctuation state through the amplitude-phase corrector parameter optimization model in response to the impedance characteristics includes:

[0019] In response to the impedance characteristics, the first stress distribution of the AC system under extreme power frequency conditions is calculated using the power frequency amplitude-phase corrector parameter optimization model.

[0020] Close / open the target switch in the parameter optimization model of the harmonic amplitude and phase corrector to obtain the second stress distribution generated by the AC system under the influence of harmonics.

[0021] Furthermore, the corrector configuration step also includes:

[0022] Calculate the component settings of the configured amplitude-phase corrector based on the harmonic parameters;

[0023] The component settings are analyzed in order to optimize and adjust the parameters of the amplitude-phase corrector.

[0024] Furthermore, the voltage fluctuation rate is controlled to be within 1%.

[0025] Furthermore, the different wire breakage methods include three types of wire breakage methods: N-0, N-1, and N-2, within the three-level cross-section.

[0026] Furthermore, the different operating modes include bipolar operation, monopolar operation, and monopolar metal operation.

[0027] Another embodiment of the present invention provides a DC transmission system impedance correction device, which is applied to the parameter design method of the above-mentioned DC transmission system impedance correction device. The device includes: a multi-source adaptive DC transmission system and the amplitude-phase corrector.

[0028] The multi-source adaptive DC transmission system includes a grid-commutated converter, a converter transformer, and a filter;

[0029] The amplitude and phase correctors are configured on both sides of the multi-source adaptive DC transmission system.

[0030] Furthermore, the amplitude-phase corrector is configured as a C-type amplitude-phase corrector consisting of a high-voltage capacitor, a low-voltage capacitor, a reactor, and a resistor connected in series and parallel.

[0031] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0032] This invention designs amplitude and phase correction calculation models under different conditions to determine the component stress of the amplitude and phase corrector under extreme voltage and harmonic fluctuation conditions and the impedance response of the DC system, so as to adjust the parameters of the amplitude and phase corrector. By comprehensively considering the background harmonic voltage of the AC system and the effect of the harmonic current injected by the converter, the component settings of the amplitude and phase corrector can be accurately calculated, thereby achieving the optimized design of parameters. Attached Figure Description

[0033] Figure 1 This is a schematic flowchart of the parameter design method for an impedance correction device for a DC transmission system in one embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the amplitude and phase corrector calculation model under power frequency conditions in one embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the calculation model of the amplitude and phase corrector under harmonic effects in one embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of a DC power transmission system structure in one embodiment of the present invention;

[0037] Figure 5 This is a schematic diagram of the C-type amplitude and phase corrector structure in one embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0040] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0041] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0042] One embodiment of the present invention provides a parameter design method for an impedance correction device for a DC transmission system. For details, please refer to [link to relevant documentation]. Figure 1 , Figure 1 The diagram shown is a schematic flowchart of a parameter design method for a DC transmission system impedance correction device according to one embodiment of the present invention, including the following steps:

[0043] S1. Obtain the voltage and harmonic parameters of the AC system based on the constructed target DC transmission system topology, and design an amplitude and phase corrector parameter optimization model.

[0044] This step involves constructing the topology and designing the computational model for the amplitude-phase corrector. This embodiment considers the advantages of multi-source adaptive commutator transmission systems, constructs the topology based on this, and obtains the voltage and harmonic parameters of the AC system within the topology.

[0045] Understandably, voltage parameters include rated voltage, steady-state voltage, and extreme voltage. The highest steady-state voltage refers to the highest voltage value the system may reach under normal operating conditions, while the lowest steady-state voltage refers to the lowest voltage value the system may reach under normal operating conditions. Extreme voltage is the highest or lowest voltage value that an AC system may experience under specific conditions (such as faults, lightning strikes, etc.).

[0046] Based on this, this embodiment designs a parameter optimization model for the power frequency amplitude and phase corrector under extreme power frequency conditions, according to the obtained rated voltage, steady-state voltage, and extreme voltage of the AC system. For details, please refer to... Figure 2 , Figure 2 The diagram illustrates a calculation model of the amplitude-phase corrector under power frequency conditions in one embodiment of the present invention. This embodiment aims to design an amplitude-phase corrector parameter optimization model based on power frequency conditions such as the highest / lowest steady-state voltage and the highest / lowest extreme voltage, for calculating the stress of an AC system under extreme power frequency voltage conditions.

[0047] Accordingly, harmonic parameters refer to the background harmonic voltage and harmonic current at the AC bus of the target DC transmission system topology. Therefore, this embodiment designs a parameter optimization model for the harmonic amplitude and phase corrector based on the obtained background harmonic voltage and harmonic current. It is worth noting that the background harmonic voltage of the AC system includes at least the 1st to 50th harmonics, while the harmonic current includes at least the 2nd to 50th converter-injected harmonic current.

[0048] For details, please refer to Figure 3 , Figure 3 The diagram shown is a schematic of a calculation model for an amplitude-phase corrector under harmonic effects in one embodiment of the present invention. This model is used to calculate the component stress under various harmonics.

[0049] This embodiment uses a computational model to evaluate the stress conditions of the amplitude-phase corrector and its components under different voltage / harmonic conditions, including system stress under normal, extreme, and harmonic conditions, providing data support for the parameter design of the amplitude-phase corrector. Based on these two corrector parameter optimization models, the parameters of the amplitude-phase corrector can be optimized to ensure its normal operation under various conditions, while improving the stability and efficiency of the system.

[0050] S2. Under different preset operating modes, obtain the impedance characteristics of the AC / DC system of the target DC transmission system topology.

[0051] This embodiment uses the AC bus of the target DC transmission system topology as the port to obtain the system's impedance characteristics. Specifically,

[0052] Under different disconnection methods, the first impedance characteristics of the AC system within a preset frequency range are obtained; and the second impedance characteristics of the broadband DC system under different operating modes are obtained.

[0053] Understandably, a broken wire can cause changes in the system's impedance characteristics, leading to problems such as harmonic resonance. Therefore, considering the impedance under the broken wire can help accurately select the parameters of the amplitude-phase corrector. In some embodiments of this invention, the broken wire methods include three types within a three-level cross-section: N-0, N-1, and N-2.

[0054] For example, the following operations are included:

[0055] 1) Turn on the SLCC DC transmission system;

[0056] 2) With a step size of 5Hz, the scanning range, i.e. the frequency range, is set from 0 to 2500Hz, taking into account the different disconnection methods of N-0, N-1, and N-2 in the three-level cross-section.

[0057] The operating modes include bipolar operation, monopolar operation, and monopolar metallic operation. These operating modes affect the current, voltage, and other parameters of the DC system, thereby affecting its impedance characteristics.

[0058] Impedance characteristics can be obtained by determining the specific conditions of the disconnection method or operating mode, such as the location, number of disconnections, and operating power. During the simulation process, simulation analysis is performed based on the constructed topology and mathematical model to obtain impedance characteristic parameters, such as impedance value and phase angle.

[0059] S3. In response to the impedance characteristics, the component stress of the amplitude-phase corrector under the corresponding fluctuation state is obtained by simulating the amplitude-phase corrector parameter optimization model.

[0060] This step is the process of simulating parameters. Based on the obtained impedance characteristics, the stress of components in the power transmission system under different operating conditions is simulated through the amplitude and phase corrector parameter optimization model.

[0061] Understandably, the stress tolerance of components must be fully considered when designing an amplitude-phase corrector. If the stress on a component exceeds its tolerance, it may lead to component damage or performance degradation, thereby affecting the overall performance of the amplitude-phase corrector. Based on this, this embodiment calculates the first stress distribution of the AC system under extreme power frequency conditions using the power frequency amplitude-phase corrector parameter optimization model.

[0062] And by closing / opening the target switch in the harmonic amplitude and phase corrector parameter optimization model, the second stress distribution generated by the AC system under the influence of harmonics is obtained. Figure 3 As shown,

[0063] When switches SW1-SW2 are closed and SW3 is open, the model represents the stress on the amplitude-phase corrector components caused by harmonics generated by the converter.

[0064] When switches SW1-SW2 are open and SW3 is closed, the model represents the stress caused by the background harmonic voltage of the AC system.

[0065] In the model that determines stress by harmonic currents generated by the converter, the harmonic current I... nc Multiply by a factor of 1.1 to accommodate a wider frequency range in AC systems and component Z. nF The error. In the model where stress is determined by background harmonics, the harmonic impedance Z of the AC system... nN The choice of [element] is to make it resonate continuously or nearly continuously with the impedance of the amplitude-phase corrector at various background harmonic voltage frequencies, so that the current flowing through the amplitude-phase corrector reaches its maximum value.

[0066] S4. In the calibration configuration stage, the initial parameters of the amplitude-phase calibration are determined based on the voltage fluctuation rate of the AC system and the operating power range of the DC system, and the initial parameters are optimized based on the component stress to configure the amplitude-phase calibration.

[0067] In some embodiments of the present invention, by analyzing the structure, load characteristics, and possible fault conditions of the power system, the allowable voltage fluctuation range of the system can be calculated, thereby determining the voltage fluctuation rate requirement. Furthermore, by analyzing the operating characteristics of the DC system and the stability requirements of the power network, the operating power range of the DC system can be calculated. It is understood that the voltage fluctuation rate should be controlled within 1%.

[0068] After determining the required voltage fluctuation rate of the AC system and the operating power range of the DC system, parameters such as the reactive power compensation required by the AC system under different operating power conditions can be calculated. Based on the calculation results, initial parameters such as the fundamental frequency reactive power capacity of the amplitude-phase corrector, the control strategy of the amplitude-phase corrector, the response time, and the adjustment range are selected to meet the reactive power requirements of the AC system. These parameters are used to configure the appropriate amplitude-phase corrector.

[0069] Furthermore, in some embodiments of the present invention, during the configuration process, the component settings of the configured amplitude-phase corrector are calculated based on the harmonic parameters, namely the obtained harmonic current and voltage, and the component settings are analyzed to optimize and adjust the parameters of the amplitude-phase corrector.

[0070] S5. After configuring the amplitude and phase corrector, repeat the corrector configuration step until the equivalent harmonic impedance of the target DC transmission system topology meets the preset transmission system oscillation index.

[0071] As is understandable, equivalent harmonic impedance is a parameter describing the impedance characteristics of a power transmission system at harmonic frequencies. Based on this, after configuring the amplitude-phase corrector, it is calculated whether the harmonic impedance of the AC system and the equivalent impedance of the DC transmission system meet the system oscillation index. In some embodiments of this invention, this preset power transmission system oscillation index may include oscillation frequency, amplitude, damping ratio, etc., used to evaluate the oscillation of the power transmission system under specific conditions.

[0072] Repeat the above configuration, evaluation and adjustment process until the system's equivalent harmonic impedance meets the preset oscillation index. At that time, it can be determined that the configured amplitude and phase corrector can give full play to its impedance adjustment capability, suppress the harmonics generated by the system, and maintain the stable operation of the system.

[0073] In summary, this embodiment aims to optimize the amplitude-phase compensator parameters in the target DC transmission system topology to ensure that the system's equivalent harmonic impedance meets the preset transmission system oscillation index. In response to the acquired impedance characteristics of the AC / DC system under different operating modes, simulation analysis is performed using a designed amplitude-phase compensator parameter optimization model to obtain the component stress of the amplitude-phase compensator under corresponding fluctuation states. In the compensator configuration stage, the initial parameters of the amplitude-phase compensator are determined based on the voltage fluctuation rate of the AC system and the operating power range of the DC system. Then, the initial parameters are optimized based on the simulation results of the component stress to configure the amplitude-phase compensator. By optimizing the amplitude-phase compensator parameters, harmonic oscillations in the DC transmission system can be effectively reduced, improving the system's stability and reliability.

[0074] One embodiment of the present invention provides an impedance correction device for a DC transmission system, and applies a parameter design method to the aforementioned DC transmission system impedance correction device. For details, please refer to [link to relevant documentation]. Figure 4 , Figure 4 The diagram shown is a schematic diagram of a DC transmission system in one embodiment of the present invention. It can be seen that the device includes: a multi-source adaptive DC transmission system and an amplitude and phase corrector.

[0075] The multi-source adaptive DC transmission system includes a grid-commutated converter, a converter transformer, and a filter; the amplitude and phase corrector is configured on both sides of the multi-source adaptive DC transmission system.

[0076] It is understood that the multi-source adaptive phase-commutation converter (SLCC) DC transmission system of this invention is a DC transmission system that combines a grid-commutated phase-commutation converter (LCC) and a large-capacity static var filter (SVF).

[0077] For example, such as Figure 4 As shown, the DC transmission system impedance correction device in this embodiment consists of two twelve-pulse LCC DC converter valves per pole. Each converter valve and converter transformer is equipped with an SVF (Synchronous Variable Voltage Filter) for reactive power compensation and filtering on the valve side. Each twelve-pulse converter valve is equipped with two three-phase SVFs. The converter valves, SVFs, and converter transformer together form an SLCC converter. All converters at the sending and receiving ends can be connected to the AC bus in layers (connected to the same AC bus in the figure). The amplitude-phase corrector is connected to the AC bus on the AC side of the converter transformer.

[0078] Depend on Figure 5 As shown, Figure 5 The diagram shown is a schematic diagram of a C-type amplitude-phase corrector in one embodiment of the present invention. It can be seen that the amplitude-phase corrector is configured as a C-type amplitude-phase corrector consisting of a high-voltage capacitor, a low-voltage capacitor, a reactor, and a resistor connected in series and parallel.

[0079] It is worth noting that when calculating the harmonic current injected into the converter, the harmonic current generated by the LCC converter and the harmonic current filtered by the SVF should be taken into account.

[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A parameter design method for an impedance correction device in a DC transmission system, characterized in that, include: Based on the constructed target DC transmission system topology, obtain the voltage and harmonic parameters of the AC system, and design an optimization model for the amplitude and phase corrector parameters; The design of the amplitude-phase corrector parameter optimization model is specifically as follows: under the extreme power frequency conditions, based on the obtained rated voltage, steady-state voltage, and extreme voltage of the AC system, a power frequency amplitude-phase corrector parameter optimization model is designed; based on the obtained background harmonic voltage and harmonic current at the AC bus of the target DC transmission system topology, a harmonic amplitude-phase corrector parameter optimization model is designed. The impedance characteristics of the AC / DC system of the target DC transmission system topology were obtained under different preset operating modes. In response to the impedance characteristics, the component stress of the amplitude-phase corrector under the corresponding fluctuation state is simulated by the amplitude-phase corrector parameter optimization model; In the calibration configuration stage, the initial parameters of the amplitude-phase calibration are determined based on the voltage fluctuation rate of the AC system and the operating power range of the DC system, and the initial parameters are optimized based on the component stress to configure the amplitude-phase calibration. After configuring the amplitude and phase corrector, repeat the corrector configuration process until the equivalent harmonic impedance of the target DC transmission system topology meets the preset transmission system oscillation index.

2. The parameter design method for the impedance correction device of a DC transmission system as described in claim 1, characterized in that, The impedance characteristics of the target DC transmission system topology AC / DC system are obtained under different preset operating modes: Using the AC bus of the target DC transmission system topology as the port, the first impedance characteristics of the AC system within a preset frequency range under different disconnection methods are obtained; and, Obtain the second impedance characteristics of a broadband DC system under different operating modes.

3. The parameter design method for the impedance correction device of a DC transmission system as described in claim 1, characterized in that, The element stress of the amplitude-phase corrector under the corresponding fluctuation state is obtained by simulating the amplitude-phase corrector component through the amplitude-phase corrector parameter optimization model in response to the impedance characteristics, including: In response to the impedance characteristics, the first stress distribution of the AC system under extreme power frequency conditions is calculated using the power frequency amplitude-phase corrector parameter optimization model. Close / open the target switch in the parameter optimization model of the harmonic amplitude and phase corrector to obtain the second stress distribution generated by the AC system under the influence of harmonics.

4. The parameter design method for the impedance correction device of a DC transmission system as described in claim 1, characterized in that, The corrector configuration step also includes: Calculate the component settings of the configured amplitude-phase corrector based on the harmonic parameters; The component settings are analyzed in order to optimize and adjust the parameters of the amplitude-phase corrector.

5. The parameter design method for the impedance correction device of a DC transmission system as described in claim 1, characterized in that, The voltage fluctuation rate is controlled to be within 1%.

6. The parameter design method for the impedance correction device of a DC transmission system as described in claim 2, characterized in that, The different breakage methods include three breakage methods: N-0, N-1, and N-2, within the three-level cross-section.

7. The parameter design method for the impedance correction device of a DC transmission system as described in claim 2, characterized in that, The different operating modes include bipolar operation, monopolar operation, and monopolar metal operation.

8. A DC transmission system impedance correction device, applied to the parameter design method of the DC transmission system impedance correction device according to claims 1-7, characterized in that, The device includes: a multi-source adaptive DC transmission system and the amplitude-phase corrector; The multi-source adaptive DC transmission system includes a grid-commutated converter, a converter transformer, and a filter; The amplitude and phase correctors are configured on both sides of the multi-source adaptive DC transmission system.

9. The impedance correction device for a DC transmission system as described in claim 8, characterized in that, The amplitude-phase corrector is configured as a C-type amplitude-phase corrector consisting of a high-voltage capacitor, a low-voltage capacitor, a reactor, and a resistor connected in series and parallel.

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