UHV DC electromagnetic transient model effectiveness evaluation method and system

Abstract

The invention discloses an ultra-high voltage direct current electromagnetic transient model effectiveness evaluation method and system, and the method comprises the steps: determining a model main body structure, the types of included elements, and a corresponding connection mode according to a hardware circuit structure standard of an ultra-high voltage direct current transmission system electromagnetic transient model; according to a control system structure standard of the model, respectively determining control loops of three levels of master control, pole control and trigger control under selection type and amplitude limiting type conditions; and performing steady-state output operation test and transient process test on the model, comparing a test result with known parameters and recorded waves of the black-box direct-current model, calculating an error value and similarity of related electrical quantities, and comparing a given evaluation index to verify the effectiveness of the model. According to the method, evaluation standards of a model hardware circuit and a control system are defined, specific verification steps and evaluation indexes are provided, the verification process is simple, convenient and clear, and simulation results show that the method can well cover steady-state and transient-state processes.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high voltage direct current (UHV DC) transmission system modeling for electric power systems, and in particular to an effectiveness evaluation method and system for an ultra-high voltage direct current (UHV DC) electromagnetic transient model. Background Art

[0002] Ultra-high voltage direct current transmission has the advantages of fast response speed and low line loss, and plays an important role in my country's "West-to-East Power Transmission" and other projects. In the current software simulation, the modeling methods of ultra-high voltage direct current transmission can be divided into electromechanical transient modeling and electromagnetic transient modeling. Compared with the electromechanical transient modeling of the ultra-high voltage direct current system, the electromagnetic transient modeling can better describe the dynamic characteristics of the ultra-high voltage direct current system itself and the interaction with the AC system under the non-fundamental or asymmetric conditions of the AC-DC hybrid power system, and has higher accuracy in studying the fault process of ultra-high voltage direct current transmission. However, there is no unified and clear evaluation standard for the electromagnetic transient modeling of ultra-high voltage direct current, which often leads to misjudgment of the system structure during the modeling process, and it is impossible to effectively evaluate the effectiveness of the model. Therefore, for a given black box direct current model, how to determine the basic structure and form of hardware circuits and control loops in electromagnetic transient modeling, and at the same time clarify the standards for verifying the effectiveness of the model building, has become one of the important issues that need to be solved in the power system.

[0003] At present, there are many modeling methods and engineering simulation examples for electromagnetic transient modeling of UHV DC, such as: 1. Wang Can et al. published "±800kV Qi Shao UHV DC Electromagnetic Transient Modeling Based on PSCAD / EMTDC" Hunan Electric Power, 2017, 37(06): 1-4. Based on the main technical parameters of Qi Shao UHV DC, this article formulated the basic control strategy of the DC model, that is, the control loop adopts constant current control on the rectifier side and constant arc extinction angle control on the inverter side. On this basis, a UHV DC electromagnetic transient model was built in the PSCAD / EMTDC electromagnetic simulation platform, and the model was simulated and tested in steady state and transient state respectively. The effectiveness of the model was verified by analyzing the errors between the relevant parameters and the rated values ​​during the stable operation of the model, as well as the changes in the relevant current, voltage and power waveforms during DC current step and AC / DC fault. 2. "Simulation Model of DC Transmission Control System Based on Actual Project" published by Wan Lei et al., Power System Technology, 2013, 37(03): 629-634. Based on the actual controller of the DC transmission project, this article established a small-scale DC transmission system example in the PSCAD / EMTDC electromagnetic simulation platform, and analyzed the principles and implementation methods of each control module in the DC transmission control system model at three levels: main control, pole control, and trigger control. Finally, the calculation error and interface error caused by the control system hierarchy were compensated, and the accuracy of the model was verified by comparing the single-phase short-circuit experimental recordings of the rectifier and inverter sides in the commissioning of the Debao DC system and the Longzheng DC system with the model simulation results. 3. Cheng Gaihong et al. published “Efficient Modeling Method for Electromagnetic Transient Simulation of Large-Scale AC and DC Power Systems”, Power System Technology, 2017, 41(06): 1919-1926. This article simplifies the conventional ±800kV UHV DC transmission system, replaces the bipolar 12-pulse converter with an equivalent valve group, simplifies the DC transmission line, and completes the initialization of the generator by modifying the initial data of the generator. This method improves the model simulation calculation speed in the electromagnetic software. The article built a four-machine two-area system in PSCAD software as a verification of the DC equivalent model, tested symmetrical faults and asymmetrical faults respectively, and verified the accuracy of the model construction by comparing the system dynamic response and related physical quantity changes before and after the model simplification.

[0004] In summary, most of the existing electromagnetic transient modeling methods for ultra-high voltage DC systems build simulation models based on existing engineering examples or software examples. The hardware circuits and control system main structures of the models are mostly the same, but the scale of the valve group in the converter station and the form of the control loop are somewhat different. At the same time, the current model validity verification method mainly consists of two parts: steady-state and transient verification. When verifying the transient process, the specific fault conditions and related electrical quantity types that need to be verified and the allowable range of simulation errors have not yet formed a unified standard. For this reason, there is an urgent need for an electromagnetic transient validity verification standard for black box DC models to clarify the basic structure and form of hardware circuits and control loops when modeling DC systems on electromagnetic platforms, and at the same time unify the simulation results and allowable error ranges required for comparison when verifying the model validity. Summary of the invention

[0005] In view of the above existing problems, the present invention is proposed.

[0006] Therefore, the present invention provides a method and system for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model to solve the problem that there is currently no clear effectiveness evaluation standard when performing electromagnetic transient modeling on an ultra-high voltage direct current black box model.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model, comprising: determining the main structure of the model and the types of components included and the corresponding connection methods according to the hardware circuit structure standard of the electromagnetic transient model of the ultra-high voltage direct current transmission system; determining the control loops at three levels, namely, main control, pole control and trigger control, in the selective and limiting cases according to the control system structure standard of the electromagnetic transient model of the ultra-high voltage direct current transmission system; performing a steady-state output operation test and a transient process test on the model based on the basic structure and control system structure of the electromagnetic transient model of the ultra-high voltage direct current transmission system; comparing the results of the steady-state output operation test and the transient process test with the recorded waveform of the black box direct current model, and calculating the error value and similarity of the relevant electrical quantities; and using the results of the comparison and calculation to compare with given evaluation indicators to verify the effectiveness of the electromagnetic transient model of the ultra-high voltage direct current transmission system.

[0009] As a preferred solution of the method for evaluating the effectiveness of the UHV DC electromagnetic transient model of the present invention, the method for determining the main structure of the model and the types of components included and the corresponding connection methods includes:

[0010] The electromagnetic transient model of the UHV DC transmission system includes two parts: a main circuit and a reactive power compensation device, wherein the main circuit includes a converter transformer, a converter, a smoothing reactor, a DC filter and a DC transmission line;

[0011] The AC systems on the rectifier and inverter sides both adopt an equivalent AC system model, and the main circuit is divided into two basic types: unipolar operation and bipolar operation according to the structure and connection method of the converter station and its valve group.

[0012] As a preferred solution of the effectiveness evaluation method of the UHV DC electromagnetic transient model of the present invention, the control loops for determining the three levels of main control, pole control and trigger control in the selective and limiting cases respectively include:

[0013] The control system of the electromagnetic transient model of the UHV DC transmission system includes two control modes: selective control and limiting control. The control system is divided into three parts: main control, pole control and trigger control according to different control levels. The main control receives pole control instructions and generates trigger pulses to control the shutdown of the entire UHV DC transmission system. The pole control realizes power transfer between converter stations, current margin compensation, low voltage current limiting, DC line fault, and no-load pressurization functions. The trigger control receives pole control instructions to control the operation of the converter valve;

[0014] The control system of the electromagnetic transient model of the ultra-high voltage direct current transmission system adopts different pole control links, including constant current control, constant voltage control, trigger angle control and fixed shutdown angle control.

[0015] As a preferred solution of the method for evaluating the effectiveness of the UHV DC electromagnetic transient model described in the present invention, it includes:

[0016] Based on the basic structure of the electromagnetic transient model of the UHV DC power transmission system and the control system structure, a steady-state output operation test and a transient process test are performed on the model, that is, simulation results of the steady-state process, DC current step process and commutation failure fault process of the electromagnetic transient model of the UHV DC power transmission system are measured;

[0017] The results of the steady-state output operation test and the transient process test are compared with the known parameters and waveforms of the black box DC model, and the error values ​​and similarities of the relevant electrical quantities are calculated.

[0018] As a preferred solution of the method for evaluating the effectiveness of the UHV DC electromagnetic transient model of the present invention, the comparison process includes:

[0019] When the electromagnetic transient model of the ultra-high voltage direct current transmission system is in steady-state operation, a simulation test is performed on the electrical quantities related to the electromagnetic transient model of the ultra-high voltage direct current transmission system, and according to the results of the simulation test, it is verified whether the steady-state average value error and the steady-state error maximum value are within the effective specified error range;

[0020] To ensure the modeling accuracy and stability of the converter station, the trigger angle on the rectifier side and the turn-off angle on the inverter side must meet the average error allowable value index requirements in the steady-state range.

[0021] As a preferred solution of the method for evaluating the effectiveness of the UHV DC electromagnetic transient model of the present invention, the comparison process further comprises:

[0022] Performing a DC current step test on the electromagnetic transient model of the UHV DC transmission system, wherein the DC current step test includes testing the simulated waveforms of the DC current, DC voltage, AC current and AC voltage at both the rectifier side and the inverter side during the process from the start of the DC current step to the recovery of the steady state;

[0023] The simulated waveform obtained by the DC current step test is compared with the recorded waveform of the black box DC model to verify whether the relevant waveform meets the prescribed similarity standard.

[0024] As a preferred solution of the method for evaluating the effectiveness of the UHV DC electromagnetic transient model of the present invention, the comparison process further comprises:

[0025] On the basis that the steady-state and DC current step tests meet the requirements, a commutation failure fault test is performed on the electromagnetic transient model of the UHV DC power transmission system, wherein the commutation failure fault is generated by a three-phase ground short circuit on the inverter-side busbar;

[0026] According to the results of the commutation failure fault test, it is verified whether the relevant electrical quantities in the steady-state interval meet the steady-state average error allowable value and the steady-state interval error maximum allowable value standards, and at the same time, it is verified whether the test waveforms of the relevant electrical quantities from the occurrence of the fault to the recovery meet the overall similarity standard.

[0027] In a second aspect, the present invention provides a UHV DC electromagnetic transient model effectiveness evaluation system, comprising:

[0028] A hardware circuit construction module is used to determine the main structure of the model and the types of components included and the corresponding connection methods according to the hardware circuit structure standard of the electromagnetic transient model of the UHV DC transmission system;

[0029] A control system building module, for determining control loops at three levels, namely, main control, pole control and trigger control, in the selective and limiting cases, according to the control system structure standard of the electromagnetic transient model of the UHV DC transmission system;

[0030] An operation test module is used to perform a steady-state output operation test and a transient process test on the model based on the basic structure of the electromagnetic transient model of the UHV DC power transmission system and the control system structure;

[0031] The effectiveness evaluation module is used to compare the results of the steady-state output operation test and the transient process test with the recorded waveform of the black box DC model, and calculate the error value and similarity of the relevant electrical quantities; and use the results of the comparison and calculation to compare with the given evaluation index to verify the effectiveness of the electromagnetic transient model of the ultra-high voltage DC transmission system.

[0032] In a third aspect, the present invention provides a computing device, comprising:

[0033] Memory and processor;

[0034] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model are implemented.

[0035] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for evaluating the effectiveness of the ultra-high voltage direct current electromagnetic transient model.

[0036] Compared with the prior art, the present invention has the following beneficial effects: for the electromagnetic transient model of the UHV DC transmission system, the present invention provides a modeling evaluation standard for the black box DC model, stipulates the hardware circuit and control system structure and form of the electromagnetic transient model of the UHV DC transmission system, and provides the effectiveness method and evaluation index of the model. Based on the current modeling methods and examples of most UHV DC electromagnetic platforms, this method provides an effectiveness evaluation method for the UHV electromagnetic transient model. Compared with the current effectiveness verification method of the UHV DC transmission system, this method has higher accuracy, more complete coverage, and is easy to implement in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0038] Figure 1 A schematic diagram of the overall process logic of a method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to an embodiment of the present invention;

[0039] Figure 2 A standard structure diagram of an electromagnetic transient model of an ultra-high voltage direct current transmission system according to an ultra-high voltage direct current electromagnetic transient model effectiveness evaluation method described in an embodiment of the present invention;

[0040] Figure 3 A structural diagram of an electromagnetic transient model selection control system for an ultra-high voltage direct current transmission system according to an ultra-high voltage direct current electromagnetic transient model effectiveness evaluation method according to an embodiment of the present invention;

[0041] Figure 4 A structural diagram of a limiting control system of an electromagnetic transient model of a UHV DC power transmission system according to a method for evaluating the effectiveness of an electromagnetic transient model of a UHV DC power transmission system according to an embodiment of the present invention;

[0042] Figure 5 A schematic diagram showing comparison of simulation results of some electrical quantities to be measured in a steady-state process of a UHV DC power transmission system according to a method for evaluating the effectiveness of an UHV DC electromagnetic transient model according to an embodiment of the present invention;

[0043] Figure 6 A schematic diagram showing comparison of simulation results of some electrical quantities to be measured in a DC current step process of a UHV DC power transmission system according to a method for evaluating the effectiveness of an UHV DC electromagnetic transient model according to an embodiment of the present invention;

[0044] Figure 7 A schematic diagram showing comparison of simulation results of some electrical quantities to be measured during a commutation failure process of a UHV DC power transmission system according to a method for evaluating the effectiveness of an UHV DC electromagnetic transient model described in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0046] Example 1

[0047] Reference Figure 1-Figure 7 As an embodiment of the present invention, a method for evaluating the effectiveness of a UHV DC electromagnetic transient model is provided. Figure 1 The specific steps shown include:

[0048] S100: Determine the main structure of the model and the types of components included and the corresponding connection methods according to the hardware circuit structure standard of the electromagnetic transient model of the UHV DC transmission system;

[0049] S200: According to the control system structure standard of the electromagnetic transient model of the UHV DC transmission system, the control loops at the three levels of master control, pole control and trigger control are determined under the two control methods of selective control and limiting control;

[0050] S300: Based on the basic structure of the electromagnetic transient model of the UHV DC transmission system and the control system structure, the model is tested for steady-state output operation and transient process;

[0051] S400: Compare the results of the steady-state output operation test and the transient process test with the known parameters and waveforms of the black box DC model, and calculate the error values ​​and similarities of the relevant electrical quantities;

[0052] S500: Use the comparison and calculation results to compare the given evaluation indicators to verify the effectiveness of the electromagnetic transient model of the UHV DC transmission system.

[0053] It should be noted that, for the electromagnetic transient model of the UHV DC transmission system, the present invention provides a modeling evaluation standard for the black box DC model, stipulates the hardware circuit and control system structure and form of the electromagnetic transient model of the UHV DC transmission system, and provides the effectiveness method and evaluation index of the model. Based on the current modeling methods and examples of most UHV DC electromagnetic platforms, this method provides an effectiveness evaluation method for the UHV electromagnetic transient model. Compared with the current effectiveness verification method of the UHV DC transmission system, it has higher accuracy, more complete coverage, and is easy to implement in engineering.

[0054] It should be noted that the method provided in this embodiment is based on a black box model of a UHV DC transmission system covering various models, and proposes a validity verification standard after the model is built on the electromagnetic platform. The standard includes the modeling standard for the hardware circuit structure of the model, the modeling standard for the main control link of the control system and the control loop of each control part, the validity verification method of the model and the corresponding error tolerance range. Before modeling the UHV DC transmission system, the error tolerance standard can be formulated according to the actual engineering requirements. For example, when the transient overvoltage peak of the UHV DC transmission system needs to be studied in the project, the numerical similarity should be preferred; if the application direction of the model is to study the interaction in the UHV DC transmission system during the transient process, such as the impact of DC faults on the sending end bus, it is necessary to focus on shape similarity.

[0055] In the embodiment of the present application, the above step S100 includes:

[0056] The electromagnetic transient model of the UHV DC transmission system consists of two parts: the main circuit and the reactive compensation device. The main circuit includes converter transformers, converters, smoothing reactors, DC filters and DC transmission lines. The AC systems on the rectifier and inverter sides both use equivalent AC system models. The main circuit is divided into two basic types: unipolar operation and bipolar operation according to the structure and connection method of the converter station and its valve group.

[0057] Specifically, the standard structural diagram of the electromagnetic platform model of the UHV DC transmission system is as follows: Figure 2 As shown, this embodiment takes the classic two-terminal DC transmission system as an example. The model includes two converter stations on the rectifier side and the inverter side. The Thevenin equivalent circuit in the form of a voltage source series impedance is used at the two AC busbars to simulate the input and output of relevant electrical quantity data in the black box model. The UHV DC model on the electromagnetic platform should include the main components such as converters and transformers on both sides of the rectifier and inverter, and should also have filtering devices such as AC filters, smoothing reactors, and DC filters. In addition, the model can be connected to a control and protection system, a motion communication system, and a frequency modulation control system, etc., which can respectively realize protection, monitoring, and frequency modulation functions, which are omitted here.

[0058] In the embodiment of the present application, the above step S200 includes:

[0059] The control system of the electromagnetic transient model of the UHV DC transmission system includes two control modes: selective control and limiting control. Figure 3 The figure shows the structure diagram of the electromagnetic transient model selection control system of the UHV DC transmission system. Figure 4 The figure shows the structure diagram of the limiting control system of the electromagnetic transient model of the UHV DC transmission system;

[0060] The control system is divided into three parts according to the different control levels: main control, pole control and trigger control. Among them, the main control receives the pole control command and generates a trigger pulse to control the shutdown of the entire UHV DC transmission system. The pole control realizes power transfer between converter stations, current margin compensation, low-voltage current limiting, DC line fault, and no-load pressurization functions. The trigger control receives the pole control command to control the operation of the converter valve. The control system of the electromagnetic transient model of the UHV DC transmission system adopts different pole control links, including constant current control, constant voltage control, trigger angle control and fixed shutdown angle control.

[0061] It should be noted that the main control link is the highest control level of the UHV DC transmission system. Its main function is to receive the operating parameters of the UHV DC transmission system from the communication system, and modulate the voltage and power of the DC circuit according to the rated power command and system dispatching command. Among them, the VDCOL module is a low-voltage current limiting link, which can improve the stability of the system and prevent commutation failure caused by DC voltage drop. The commutation failure prediction control link is activated when the AC system on the inverter side fails. By reducing the trigger angle on the inverter side, the commutation margin is improved to avoid commutation failure.

[0062] It should be noted that the control system in the pole control layer includes control links such as constant current control link, constant voltage control link and fixed shut-off angle control link. Among them, the selective UHV DC transmission control system adopts fixed shut-off angle and trigger angle control, while the limiting UHV DC transmission control system adopts constant voltage control and constant current control. In addition, the limiting UHV DC transmission control system has a trigger angle limiting link to ensure the stability of system operation. The trigger control layer implemented by the electromagnetic transient model of UHV DC transmission adopts an equal phase interval triggering method. The specific method is to first record the trigger time of the previous converter valve under the same working condition, and then calculate the trigger interval between the current converter valve and the previous converter valve, so as to determine the trigger time of the current converter valve.

[0063] For example, taking the unipolar operation mode as an example, the changes in physical quantities such as current, voltage and power between the rectifier and inverter sides of the UHV DC system follow the following relationship:

[0064]

[0065] Among them, K 0 Indicates the coefficient generated by the connection method of the rectifier circuit, I d represents the DC transmission current, (the subscripts r and i in the following variables represent the rectifier side and the inverter side respectively), E dr and E di Indicates the DC transmission voltage on both sides, E r and E i Represents the RMS value of the AC voltage on both sides, R r and R i They represent the DC smoothing reactance and the equivalent resistance of the commutation loss, respectively. r and X i is the equivalent reactance of the converter transformer, α and β are the trigger delay angle and trigger advance angle of the converter, γ is the arc extinction angle of the inverter;

[0066]

[0067] Where Z represents the impedance of the DC transmission line;

[0068] P d =E dr I d

[0069] P d =E di I d

[0070] Among them, P d Indicates the DC power of the DC transmission line.

[0071] In the embodiment of the present application, the above steps S300 to S500 include:

[0072] Based on the basic structure of the electromagnetic transient model of the UHV DC transmission system and the control system structure, the model is tested for steady-state output operation and transient process, that is, the simulation results of the steady-state process, DC current step process and commutation failure process of the electromagnetic transient model of the UHV DC transmission system are measured;

[0073] Compare the results of the steady-state output operation test and the transient process test with the known parameters and waveforms of the black box DC model, and calculate the error values ​​and similarities of the relevant electrical quantities;

[0074] The comparison and calculation results are used to compare the given evaluation indicators to verify the effectiveness of the electromagnetic transient model of the UHV DC transmission system.

[0075] Specifically, when the electromagnetic transient model of the UHV DC transmission system is in steady-state operation, simulation tests are performed on the relevant electrical quantities of the electromagnetic transient model of the UHV DC transmission system, and the results of the simulation tests are used to verify whether the steady-state average value error and the steady-state error maximum value are within the effective specified error range; to ensure the modeling accuracy and stability of the converter station, the trigger angle on the rectifier side and the turn-off angle on the inverter side must meet the average error allowable value index requirements in the steady-state interval.

[0076] Specifically, a DC current step test is performed on the electromagnetic transient model of the UHV DC transmission system. The DC current step test includes testing the simulated waveforms of DC current, DC voltage, AC current and AC voltage on both the rectifier side and the inverter side from the beginning of the DC current step to the recovery of the steady state; the simulated waveform obtained from the DC current step test is compared with the recorded waveform of the black box DC model to verify whether the relevant waveforms meet the specified similarity standards.

[0077] Specifically, on the basis that the steady-state and DC current step tests meet the regulations, a commutation failure fault test is carried out on the electromagnetic transient model of the UHV DC transmission system, wherein the commutation failure fault is caused by a three-phase ground short circuit on the inverter-side bus; based on the results of the commutation failure fault test, it is verified whether the relevant electrical quantities in the steady-state interval meet the steady-state average error allowable value and the steady-state interval error maximum allowable value standards, and at the same time, it is verified whether the test waveforms of the relevant electrical quantities from the occurrence of the fault to the recovery meet the total similarity standards.

[0078] In a feasible implementation, the steady-state error verification needs to verify the simulation results of the rectifier side and the inverter side respectively, that is, at the AC bus and the DC transmission line, the waveforms of the DC voltage and DC current, the AC voltage and AC current, the trigger angle and the shutoff angle of the converter valve are tested, and finally the steady-state average error and the maximum error of the above electrical quantities are calculated;

[0079] For example, taking the rectifier side as an example, the black box recording and test value waveforms of some relevant electrical quantities of the electromagnetic platform of the UHV DC transmission system during steady-state operation are compared. Figure 5 As shown, the current and voltage are expressed in per-unit values. Starting from the simulation time t, the waveform of the steady-state time length ΔT is intercepted for error calculation. A series of simulation data are obtained by taking the same time length Δt. The values ​​of ΔT and Δt can be determined according to the actual project's need for accuracy. r Indicates the reference value of electrical quantity related to the external characteristics of the black box model, X h Indicates the simulation data of the electrical quantity corresponding to the model to be verified. Accordingly, the first and last data of the benchmark data and simulation data are represented by K r_Start , K h_Start and K r_End , K h_End The steady-state average error and maximum error of the above-mentioned electrical quantities to be verified are measured respectively, and the average error F between the electromagnetic model simulation result and the black box model source data in the steady-state interval is 1 and the maximum error F 2 The calculation method is as follows:

[0080]

[0081] Based on the above error calculation, the final allowable values ​​of the steady-state average error and maximum error of the relevant electrical quantities are: the steady-state average error F of DC current and DC voltage 1dr No more than 5%, maximum error F 2dr No more than 10%; the steady-state average error F of the AC current and AC voltage at the AC bus 1ac No more than 5%, maximum error F 2ac No more than 10%; the steady-state average error F between the trigger angle on the rectifier side and the turn-off angle on the inverter side 1θ When the steady-state related electrical quantities of the model meet the above-mentioned allowable error index, the effectiveness of the electromagnetic transient model of the UHV DC transmission system in steady state can be verified.

[0082] In a feasible implementation, based on the verification of the steady-state validity of the electromagnetic transient model of the UHV DC transmission system, the DC current step response validity of the model is verified;

[0083] For example, the schematic diagram of the comparison between the black box recording waveform and the electromagnetic model simulation waveform of the above-mentioned part of the electrical quantities is as follows: Figure 6 As shown, the relevant physical quantities are expressed in per unit values. During the test, at t 1 At the moment, the DC current changes from 1.0pu to 0.8pu, t 2 At the moment when the DC current changes from 0.8pu to 1.0pu, t3 The moment is the moment when the DC current returns to steady state. The specific determination method is that from this moment on, the DC current and t 1 The error in steady state before time is less than 5%. After the simulation results are tested, it is necessary to verify t 1 to 3 The error between the relevant electrical quantities of the electromagnetic model of the UHV DC transmission system in the interval and the black box model recording is analyzed by dynamic accuracy analysis of the waveform, that is, calculating t 1 to 3 The numerical similarity and shape similarity of the two waveforms in the transient interval are calculated, and finally the total similarity calculation result is compared with the effectiveness index. When the similarities of the above electrical quantity waveforms meet the index requirements, the UHV DC transmission system model can be considered to be effective.

[0084] The method for calculating numerical similarity is to calculate the distance between the two curves at the same time, that is, the numerical difference. At the same time, in order to avoid distortion of numerical similarity caused by excessive local errors, the mean difference of relative errors in the same time series is used to represent the distance between the curves. 1 to 3 The transient interval is divided into n equal parts, using the sequence x i Represents the recorded values ​​of the black box model, using the sequence y i represents the value of the electrical quantity to be measured in the UHV DC transmission electromagnetic model, then the numerical similarity A between the simulation waveform of the electrical quantity to be measured in the UHV DC transmission electromagnetic model and the recorded waveform of the black box model is calculated as follows:

[0085]

[0086] The calculation method of shape similarity is: suppose the time length of the entire transient process to be measured is T, divide the transient process into k parts from time 0 to time T in units of time length d, where k is rounded down, and on this basis, divide the taken time length d into n equal parts, and number them into a sequence D = (d 1 ,d 2 ,···d n ), offset and scale the elements in sequence D to the sequence element value

[0087]

[0088] Among them, d max and d min are the maximum and minimum values ​​of the n elements in the sequence respectively. It is easy to know The absolute value of is less than 1. The black box recording data obtained by the above division method is set as sequence D a =(d a1 ,d a2 ,···dan ), the electromagnetic model waveform data is set as sequence D b =(d b1 ,d b2 ,···d bn ). For a given similarity threshold ε, if for any positive integer i not greater than n, the following inequalities hold:

[0089]

[0090] It is considered that sequence D a and D b are similar, and the shape similarity is the ratio of the sum of the time lengths of all similar sequences to the total time length of the transient process to be measured. The calculation formula for shape similarity is as follows:

[0091]

[0092] When the numerical similarity and shape similarity are close enough to 100%, the two measured waveforms can be considered to be the same. Considering the different emphasis on waveform numerical value and shape in actual engineering, and to simplify the effectiveness verification index, the present invention introduces the concept of total similarity, that is, introduces the coefficient r to obtain the total similarity S:

[0093] S=rA+(1-r)B

[0094] Among them, r can take different values ​​between 0 and 1 according to the actual engineering needs. The larger r is, the more emphasis is placed on numerical similarity. For example, when the transient overvoltage peak of the UHV DC transmission system needs to be studied in the project, the numerical similarity should be tended to, and r can be 0.6-0.8; if the application direction of the model is to study the interaction in the UHV DC transmission system during the transient process, such as the impact of DC faults on the sending-end bus, it is necessary to focus on the similarity of the current status, and r can be 0.3-0.4.

[0095] Based on the above error calculation, the effectiveness indicators of the step response test of the UHV DC transmission system are as follows: on the rectifier side and the inverter side, the total similarity between the waveform of the electromagnetic model simulation and the DC current, DC voltage and power recorded by the black box is not less than 90%, and the total similarity of the AC voltage and power at the AC bus is not less than 80%.

[0096] In a feasible implementation, based on the verification of the steady-state validity of the electromagnetic transient model of the UHV DC transmission system and the validity of the DC current step response, the validity of the transient process of the model during the commutation failure fault is verified;

[0097] For example, a three-phase ground short circuit fault of the AC busbar on the inverter side triggers a commutation failure fault, which occurs at t 1At this moment, the three-phase ground short circuit fault lasts for Δt. Taking the inverter side commutation failure fault as an example, the black box recording of the relevant electrical quantities and the electromagnetic model simulation waveform comparison diagram are shown in Figure 7 As shown. Figure 7 The time division results of the DC voltage waveform change on the inverter side during the fault are as follows: at t1, the three-phase ground short circuit fault occurs on the AC busbar on the inverter side. The fault lasts for Δt, during which a commutation failure fault occurs. At t2, the DC voltage recovers to within 5% of the value before the fault occurs, which means that the steady-state operation is restored at this time.

[0098] The effectiveness method of the three-phase ground short circuit fault includes: (1) verifying that the steady-state average error and the maximum error before the fault occurs and after the fault is cleared and reaches the steady state do not exceed the error index range, and the error calculation method is the same as (a); (2) verifying that the total similarity of the relevant waveforms in the interval from the occurrence of the fault to the stability of the waveform is within the error index range, and the similarity calculation method is the same as (b);

[0099] Based on the above error calculation, the effectiveness indicators of the commutation failure fault test of the UHV DC transmission system are as follows: before the fault occurs and after the fault is cleared, the steady-state average error of the DC current and DC voltage on the rectifier side and the inverter side does not exceed 5%, and the maximum error does not exceed 10%. The steady-state average error of the AC current and AC voltage on the AC bus does not exceed 7%, and the maximum error does not exceed 15%. The steady-state average error of the trigger angle on the rectifier side and the turn-off angle on the inverter side does not exceed 5%. In the transient interval from the occurrence of the fault to the steady state, the total similarity of the DC current, voltage and power on the rectifier side and the inverter side is not less than 90%, the total similarity of the AC voltage and power at the AC bus is not less than 80%, and the total similarity of the trigger angle on the rectifier side and the turn-off angle on the inverter side is not less than 90%.

[0100] When the simulation results of the electromagnetic model of the UHV DC transmission system and the test results of the steady-state error, DC current step error and commutation failure error of the black box model all meet the standards given in the present invention, the constructed electromagnetic model of the UHV DC transmission system can be considered to be valid.

[0101] It can be seen from the above simulation experiment results that the present invention proposes a validity evaluation standard, which respectively gives the hardware system structure standard and the structure standard of the control system and control loop for the constructed model. At the same time, when verifying the validity of the constructed electromagnetic transient model, the present invention gives a verification method for the validity of the model and the error index of the corresponding electrical quantity. According to this standard, after completing the modeling of the electromagnetic platform of the UHV DC transmission system, the model can be evaluated for validity, and the black box UHV DC model can be compared to verify whether the electromagnetic platform model is valid. Compared with most previous electromagnetic platform model validity evaluation methods, the verification method of the present invention has a more comprehensive verification process, covering aspects such as structural evaluation, steady-state verification and transient verification. It is relatively simple to implement in the actual verification process, and the credibility of the UHV DC electromagnetic model verified by this validity evaluation method is high.

[0102] Example 2

[0103] This embodiment provides a UHV DC electromagnetic transient model effectiveness evaluation system, including a hardware circuit construction module, a control system construction module, an operation test module, and an effectiveness evaluation module;

[0104] Specifically, the hardware circuit construction module is used to determine the main structure of the model and the types of components included and the corresponding connection methods according to the hardware circuit structure standard of the electromagnetic transient model of the ultra-high voltage direct current transmission system;

[0105] Specifically, the control system construction module is used to determine the control loops at three levels, namely, the main control, the pole control and the trigger control, in the selective and limiting cases, according to the control system structure standard of the electromagnetic transient model of the UHV DC transmission system;

[0106] Specifically, the operation test module is used to perform steady-state output operation test and transient process test on the model based on the basic structure of the electromagnetic transient model of the UHV DC transmission system and the control system structure;

[0107] Specifically, the effectiveness evaluation module is used to compare the results of the steady-state output operation test and the transient process test with the recording of the black box DC model, and calculate the error value and similarity of the relevant electrical quantities; using the comparison and calculation results, the effectiveness of the electromagnetic transient model of the UHV DC transmission system is verified by comparing the given evaluation indicators.

[0108] It should be noted that the technical solution of the system for evaluating the effectiveness of the UHV DC electromagnetic transient model and the technical solution of the above-mentioned method for evaluating the effectiveness of the UHV DC electromagnetic transient model belong to the same concept. For the details not described in detail in the technical solution of the system for evaluating the effectiveness of the UHV DC electromagnetic transient model in this embodiment, please refer to the description of the technical solution of the above-mentioned method for evaluating the effectiveness of the UHV DC electromagnetic transient model.

[0109] The above-mentioned unit modules may be embedded in or independent of a processor in a computer device in the form of hardware, or may be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to the above-mentioned modules.

[0110] This embodiment also provides a computing device, which includes a processor, a memory, a communication interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. When the computer program is executed by the processor, a method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a button, trackball or touchpad set on the housing of the computer device, or an external keyboard, touchpad or mouse.

[0111] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method proposed in the above embodiment is implemented.

[0112] The storage medium proposed in this embodiment and the method proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0113] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0114] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0115] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0116] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0117] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0118] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1The steps for the functions specified in one or more boxes.

[0119] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0120] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model, characterized in that: include: According to the hardware circuit structure standard of the electromagnetic transient model of the UHV DC transmission system, determine the main structure of the model and the types of components included and the corresponding connection methods; According to the control system structure standard of the electromagnetic transient model of the UHV DC transmission system, the control loops at three levels, namely, the main control, the pole control and the trigger control, are determined in the selective type and the limiting type respectively; Based on the basic structure of the electromagnetic transient model of the UHV DC transmission system and the control system structure, the model is subjected to steady-state output operation test and transient process test; Comparing the results of the steady-state output operation test and the transient process test with the waveform recording of the black box DC model, and calculating the error value and similarity of the relevant electrical quantities; The comparison and calculation results are used to compare with given evaluation indicators to verify the effectiveness of the electromagnetic transient model of the ultra-high voltage direct current transmission system.

2. The method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to claim 1, characterized in that: The determination of the main structure of the model and the types of components included and the corresponding connection methods includes: The electromagnetic transient model of the UHV DC transmission system includes two parts: a main circuit and a reactive power compensation device, wherein the main circuit includes a converter transformer, a converter, a smoothing reactor, a DC filter and a DC transmission line; The AC systems on the rectifier and inverter sides both adopt an equivalent AC system model, and the main circuit is divided into two basic types: unipolar operation and bipolar operation according to the structure and connection method of the converter station and its valve group.

3. The method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to claim 1, characterized in that: The control loops for determining the three levels of main control, extreme control and trigger control in the selective and limiting cases respectively include: The control system of the electromagnetic transient model of the UHV DC transmission system includes two control modes: selective control and limiting control. The control system is divided into three parts: main control, pole control and trigger control according to different control levels. The main control receives pole control instructions and generates trigger pulses to control the shutdown of the entire UHV DC transmission system. The pole control realizes power transfer between converter stations, current margin compensation, low voltage current limiting, DC line fault, and no-load pressurization functions. The trigger control receives pole control instructions to control the operation of the converter valve; The control system of the electromagnetic transient model of the ultra-high voltage direct current transmission system adopts different pole control links, including constant current control, constant voltage control, trigger angle control and fixed shutdown angle control.

4. The method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to claim 2 or 3, characterized in that: include: Based on the basic structure of the electromagnetic transient model of the UHV DC power transmission system and the control system structure, a steady-state output operation test and a transient process test are performed on the model, that is, simulation results of the steady-state process, DC current step process and commutation failure fault process of the electromagnetic transient model of the UHV DC power transmission system are measured; The results of the steady-state output operation test and the transient process test are compared with the known parameters and waveforms of the black box DC model, and the error values ​​and similarities of the relevant electrical quantities are calculated.

5. The method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to claim 4, characterized in that: The comparison process includes: When the electromagnetic transient model of the ultra-high voltage direct current transmission system is in steady-state operation, a simulation test is performed on the electrical quantities related to the electromagnetic transient model of the ultra-high voltage direct current transmission system, and according to the results of the simulation test, it is verified whether the steady-state average value error and the steady-state error maximum value are within the effective specified error range; To ensure the modeling accuracy and stability of the converter station, the trigger angle on the rectifier side and the turn-off angle on the inverter side must meet the average error allowable value index requirements in the steady-state range.

6. The method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to claim 4, characterized in that: The comparison process also includes: Performing a DC current step test on the electromagnetic transient model of the UHV DC transmission system, wherein the DC current step test includes testing the simulated waveforms of the DC current, DC voltage, AC current and AC voltage at both the rectifier side and the inverter side during the process from the start of the DC current step to the recovery of the steady state; The simulated waveform obtained by the DC current step test is compared with the recorded waveform of the black box DC model to verify whether the relevant waveform meets the prescribed similarity standard.

7. The method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model according to claim 4, characterized in that: The comparison process also includes: On the basis that the steady-state and DC current step tests meet the requirements, a commutation failure fault test is performed on the electromagnetic transient model of the UHV DC power transmission system, wherein the commutation failure fault is generated by a three-phase ground short circuit on the inverter-side busbar; According to the results of the commutation failure fault test, it is verified whether the relevant electrical quantities in the steady-state interval meet the steady-state average error allowable value and the steady-state interval error maximum allowable value standards, and at the same time, it is verified whether the test waveforms of the relevant electrical quantities from the occurrence of the fault to the recovery meet the overall similarity standard.

8. A system using the method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model as claimed in any one of claims 1 to 7, characterized in that: include: A hardware circuit construction module is used to determine the main structure of the model and the types of components included and the corresponding connection methods according to the hardware circuit structure standard of the electromagnetic transient model of the UHV DC transmission system; A control system building module, for determining control loops at three levels, namely, main control, pole control and trigger control, in the selective and limiting cases, according to the control system structure standard of the electromagnetic transient model of the UHV DC transmission system; An operation test module is used to perform a steady-state output operation test and a transient process test on the model based on the basic structure of the electromagnetic transient model of the UHV DC power transmission system and the control system structure; The effectiveness evaluation module is used to compare the results of the steady-state output operation test and the transient process test with the recorded waveform of the black box DC model, and calculate the error value and similarity of the relevant electrical quantities; and use the results of the comparison and calculation to compare with the given evaluation index to verify the effectiveness of the electromagnetic transient model of the ultra-high voltage DC transmission system.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the computer executable instructions are executed by the processor, the steps of the method for evaluating the effectiveness of the ultra-high voltage direct current electromagnetic transient model described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the steps of the method for evaluating the effectiveness of an ultra-high voltage direct current electromagnetic transient model as claimed in any one of claims 1 to 7.

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