A method and system for calculating electromagnetic loss of a saturation reactor of a CLCC converter valve

Abstract

This invention belongs to the field of high-voltage direct current (HVDC) transmission, specifically relating to a method and system for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve. The method includes: performing electrical numerical simulation on the HVDC transmission system containing the overall structure of the CLCC converter valve under the operating condition for which electromagnetic loss needs to be calculated, obtaining the voltage and current characteristics of the main or auxiliary branch of the CLCC converter valve; performing electromagnetic field simulation on the saturated reactor of the main or auxiliary branch of the CLCC converter valve according to the characteristic parameters of the main or auxiliary branch, and substituting the corresponding voltage and current characteristics obtained from the electrical numerical simulation into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic loss; and calculating the electromagnetic loss of the saturated reactor in the main or auxiliary branch of the CLCC converter valve under the corresponding operating condition based on the reactor electromagnetic loss calculation equation and the obtained magnetic field distribution data. This method can more accurately evaluate the electromagnetic loss characteristics of the CLCC converter valve down to the specific branch under different operating conditions.

Description

Technical Field

[0001] This invention belongs to the field of high voltage direct current transmission, specifically relating to a method and system for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve. Background Technology

[0002] High-voltage direct current (HVDC) transmission technology has become an important means of long-distance energy transmission due to its advantages such as long transmission distance, low loss, and high transmission capacity. Traditional HVDC transmission systems mainly use thyristor converters (LCCs), but because thyristors cannot self-turn off, commutation failure has become a significant factor affecting system stability. In recent years, controllable line-commutated converters (CLCCs), as a new topology, have been successfully applied in engineering. Their core advantage lies in their ability to achieve current transfer and active commutation through fully controllable devices such as IGBTs, thereby effectively reducing the risk of commutation failure.

[0003] Reference Figure 1 The CLCC converter valve has a complex topology, with the bridge arm containing not only the main branch (main current-carrying loop) but also an auxiliary branch (current transfer loop). To protect the normal operation of core components such as thyristors and IGBTs, both the main and auxiliary branches of the CLCC converter valve include anode reactors. Therefore, studying the electrical stress and electromagnetic loss characteristics of the saturated reactor is crucial for the design and engineering application of CLCC converter valves. Furthermore, the control logic of the CLCC converter valve differs under different operating conditions, leading to variations in the current distribution and saturated reactor loss characteristics in the main and auxiliary branches. Therefore, the insulation design, heat dissipation optimization, and lifespan assessment of the CLCC converter valve must comprehensively consider the reactor loss characteristics of both the main and auxiliary branches to ensure the reliability and efficiency of the saturated reactor and the converter valve.

[0004] Chinese invention patent application publication number CN101975892A discloses a method for calculating the losses of a saturated reactor for a converter valve. This method is a numerical calculation method based on the circuit model of the saturated reactor. It has high calculation accuracy, is easy to implement in numerical program calculation, and is easy to visualize and simulate. The method includes the following steps: (1) Extract the broadband equivalent model of the saturated reactor to obtain the equivalent circuit of the saturated reactor. The iron loss resistor is connected in series with the iron core inductor, and then in series with the air core inductor and the on-state resistor. The stray capacitor is connected in parallel at the output port; (2) Through theoretical analysis and measurement of the actual saturated reactor, it can be obtained that the iron core loss and on-state loss effects are equivalent to the physical resistance respectively. The coil of the saturated reactor is made of metal, and the conductivity of the material is non-ideal. Its loss performance can be equivalently represented by a linear resistor, called the on-state resistance, denoted as Rcu. The iron core loss is closely related to the current amplitude, frequency, and terminal voltage of the saturated reactor. Therefore, it needs to be replaced by a nonlinear resistor Rm. (3) A simulation model of the converter valve system is built in PSCAD software. Based on the system simulation, the values ​​of the voltages uRcu and iRcu across the on-state resistor and the voltages uRm and iRm across the equivalent iron loss resistor are determined. (4) The on-state loss and the core loss are calculated according to the definition of power. The equivalent circuit of the saturated reactor can be established according to the mathematical relationship between physical quantities and the equivalent circuit topology. The voltage and current borne by the saturated reactor in the converter valve can be applied between the terminals of the equivalent circuit to obtain the voltages uRcu and iRcu across the on-state resistor and the voltages uRm and iRm across the equivalent iron loss resistor. The formulas for on-state loss and core loss can be obtained from the definition of loss. The on-state loss and core loss can be obtained by integrating the above two formulas in one cycle. This scheme is difficult to specifically calculate the electromagnetic loss of the reactor corresponding to the influence of the step-by-step characteristics of the electromagnetic field of the reactor in the main branch and the auxiliary branch. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for calculating the electromagnetic loss of saturated reactors in CLCC converter valves, which solves the problem that existing reactor electromagnetic loss calculation schemes are difficult to specifically calculate the electromagnetic loss of reactors corresponding to the influence of the step-by-step characteristics of the electromagnetic field of the reactors in the main branch and auxiliary branch.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve, comprising:

[0007] Under the condition of electromagnetic loss to be calculated, electrical numerical simulation is performed on the DC transmission system including the overall structure of CLCC converter valve to obtain the voltage and current characteristics of the main branch or auxiliary branch of CLCC converter valve.

[0008] Based on the characteristic parameters of the main or auxiliary branch of the CLCC converter valve, electromagnetic field simulation is performed on the saturated reactor of the main or auxiliary branch of the CLCC converter valve. The corresponding voltage and current characteristics obtained from the electrical numerical simulation are substituted into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic losses.

[0009] Based on the electromagnetic loss calculation equation of the reactor and the obtained magnetic field distribution data, calculate the saturated reactor electromagnetic loss of the main branch or auxiliary branch of the CLCC converter valve under the corresponding operating conditions.

[0010] The first aspect of the present invention provides a method for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve. In one possible implementation, the operating conditions under which the electromagnetic loss is to be calculated include: the normal commutation process of the CLCC converter valve under steady-state conditions, and the forced commutation process of the CLCC converter valve under AC system fault conditions.

[0011] The first aspect of this invention provides a method for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve. In one possible implementation, the parameters required for electrical numerical simulation of a DC transmission system including the overall structure of the CLCC converter valve include: electrical parameters of each semiconductor component and damping, voltage equalization circuit component, and saturated reactor component in the main and auxiliary branches of the CLCC converter valve; electrical parameters of the converter transformer component; and the voltage, current, and power of the DC transmission system.

[0012] The first aspect of this invention provides a method for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve. In one possible implementation, the characteristic parameters required for electromagnetic field simulation of the saturated reactor in the main branch of the CLCC converter valve include the geometric and electromagnetic parameters of key components in the main branch of the CLCC converter valve. The key components in the main branch include the saturated reactor core, coil, and filling material. The electromagnetic parameters include conductivity, dielectric constant, and permeability.

[0013] The parameters required for electromagnetic field simulation of the saturated reactor in the auxiliary branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the auxiliary branch of the CLCC converter valve; the key components of the auxiliary branch include the core, coil and filling material of the auxiliary branch saturated reactor; the electromagnetic parameters include conductivity, dielectric constant and permeability.

[0014] The first aspect of the present invention provides a method for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve. In one possible implementation, the electromagnetic loss calculation equation for the reactor includes the Bertotti or Steinmetz loss calculation equation.

[0015] The above-described technical solution of the present invention provides a novel method for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve, the advantages of which include:

[0016] Numerical simulations are performed on the overall DC transmission system where the CLCC converter valve is located. This allows for accurate acquisition of the voltage and current characteristics of each branch of the CLCC converter valve under the operating conditions requiring electromagnetic loss calculation. Based on this, electromagnetic field simulations are performed on the electromagnetic field characteristics of individual branches in the dual-branch structure of the CLCC topology. The voltage and current characteristics of this branch under the operating conditions for which electromagnetic loss is to be calculated are used as the excitation for the electromagnetic field simulation. This results in relatively accurate magnetic field distribution data for specific operating conditions and specific branches, enabling more precise calculation of the electromagnetic loss of the saturated reactor that better reflects actual conditions. This method can evaluate the electromagnetic loss characteristics of the CLCC converter valve down to the specific branch under different operating modes and conditions, providing data support for the insulation design, heat dissipation optimization, and lifespan assessment of the converter valve.

[0017] A second aspect of the present invention provides a saturated reactor electromagnetic loss calculation system for CLCC converter valves, including a power system simulation module and an electromagnetic loss simulation module;

[0018] The power system simulation module is used to perform electrical numerical simulation on a DC transmission system containing the overall structure of the CLCC converter valve under the condition of electromagnetic loss to be calculated, and to obtain the voltage and current characteristics of the main branch or auxiliary branch of the CLCC converter valve.

[0019] The electromagnetic loss simulation module is used to perform electromagnetic field simulation on the saturated reactor of the main or auxiliary branch of the CLCC converter valve according to the characteristic parameters of the main or auxiliary branch. It substitutes the corresponding voltage and current characteristics obtained from the electrical numerical simulation into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic loss. It is also used to calculate the electromagnetic loss of the saturated reactor of the main or auxiliary branch of the CLCC converter valve under the corresponding operating conditions based on the electromagnetic loss calculation equation of the reactor and the obtained magnetic field distribution data.

[0020] The second aspect of the present invention provides a saturated reactor electromagnetic loss calculation system for a CLCC converter valve. In one possible implementation, the operating conditions under which the electromagnetic loss to be calculated include: the normal commutation process of the CLCC converter valve under steady-state conditions, and the forced commutation process of the CLCC converter valve under AC system fault conditions.

[0021] The second aspect of this invention provides a calculation system for the electromagnetic loss of the saturated reactor of a CLCC converter valve. In one possible implementation, the parameters required for electrical numerical simulation of a DC transmission system including the overall structure of the CLCC converter valve include: electrical parameters of each semiconductor component and damping, voltage equalization circuit component, and saturated reactor component in the main and auxiliary branches of the CLCC converter valve; electrical parameters of the converter transformer component; and voltage, current, and power of the DC transmission system.

[0022] The second aspect of this invention provides a system for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve. In one possible implementation, the characteristic parameters required for electromagnetic field simulation of the saturated reactor in the main branch of the CLCC converter valve include the geometric and electromagnetic parameters of key components of the main branch of the CLCC converter valve. The key components of the main branch include the saturated reactor core, coil, and filling material. The electromagnetic parameters include conductivity, dielectric constant, and permeability.

[0023] The parameters required for electromagnetic field simulation of the saturated reactor in the auxiliary branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the auxiliary branch of the CLCC converter valve; the key components of the auxiliary branch include the core, coil and filling material of the auxiliary branch saturated reactor; the electromagnetic parameters include conductivity, dielectric constant and permeability.

[0024] The second aspect of the present invention provides a saturated reactor electromagnetic loss calculation system for a CLCC converter valve. In one possible implementation, the reactor electromagnetic loss calculation equation includes Bertotti or Steinmetz loss calculation equations.

[0025] The technical solution of the electromagnetic loss calculation system for the saturated reactor of the CLCC converter valve described above can achieve the same beneficial effects as the electromagnetic loss calculation method for the saturated reactor of the CLCC converter valve described above. Attached Figure Description

[0026] Figure 1 This is an example diagram of the topology of the CLCC converter valve in the background art of this invention;

[0027] Figure 2 This is a schematic diagram illustrating the principle of the electromagnetic loss calculation method for the saturated reactor in the embodiment of the CLCC converter valve of the present invention.

[0028] Figure 3 This is an example diagram showing the numerical simulation results of voltage and current values ​​of the main branch and auxiliary branch during the normal commutation process of the CLCC converter valve in the embodiment of the electromagnetic loss calculation method of the saturated reactor of the CLCC converter valve of the present invention.

[0029] Figure 4 This is an example diagram of the AC voltage curve corresponding to the AC phase A grounding fault in the embodiment of the CLCC converter valve electromagnetic loss calculation method of the present invention.

[0030] Figure 5 This is an example diagram of the electrical stress curves of the main / auxiliary branches of the CLCC converter valve during the forced commutation process, as shown in the embodiment of the electromagnetic loss calculation method for the saturated reactor of the CLCC converter valve of the present invention.

[0031] Figure 6This is an example diagram showing the magnetic field density distribution of the saturated reactor core during the normal opening process of the main branch of the converter valve in the embodiment of the electromagnetic loss calculation method of the saturated reactor of the CLCC converter valve of the present invention.

[0032] Figure 7 This is an example diagram illustrating the magnetic field density characteristics of the saturated core of the auxiliary branch during the electric opening process of the auxiliary branch of the converter valve in the embodiment of the electromagnetic loss calculation method of the saturated reactor of the CLCC converter valve of the present invention.

[0033] Figure 8 This is a schematic diagram illustrating the structural principle of the electromagnetic loss calculation system for the saturated reactor in the embodiment of the CLCC converter valve of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Implementation Method for Calculating Electromagnetic Losses of Saturated Reactors in CLCC Converter Valves

[0036] This embodiment presents a technical solution for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve. This solution innovatively proposes a method for separately calculating the electromagnetic loss of the main branch and the auxiliary branch in the dual-branch structure of the CLCC topology. It can simulate the reactor loss of the main branch and the auxiliary branch of the CLCC converter valve under different operating conditions.

[0037] The method specifically includes:

[0038] Under the condition of electromagnetic loss to be calculated, electrical numerical simulation is performed on the DC transmission system including the overall structure of CLCC converter valve to obtain the voltage and current characteristics of the main branch or auxiliary branch of CLCC converter valve.

[0039] Based on the characteristic parameters of the main or auxiliary branch of the CLCC converter valve, electromagnetic field simulation is performed on the saturated reactor of the main or auxiliary branch of the CLCC converter valve. The corresponding voltage and current characteristics obtained from the electrical numerical simulation are substituted into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic losses.

[0040] Based on the electromagnetic loss calculation equation of the reactor and the obtained magnetic field distribution data, calculate the saturated reactor electromagnetic loss of the main branch or auxiliary branch of the CLCC converter valve under the corresponding operating conditions.

[0041] This method performs numerical simulations on the overall DC transmission system where the CLCC converter valve is located. It can accurately obtain the voltage and current characteristics of each branch of the CLCC converter valve for the operating conditions requiring electromagnetic loss calculation. Based on this, for the dual-branch structure in the CLCC topology, it performs electromagnetic field simulations on the electromagnetic field characteristics of each individual branch. The voltage and current characteristics of that branch under the operating conditions for which electromagnetic loss is to be calculated are used as the excitation for the electromagnetic field simulation. Finally, it obtains relatively accurate magnetic field distribution data for specific operating conditions and specific branches, thus more accurately calculating the electromagnetic loss of the saturated reactor in a more realistic manner. This method can evaluate the electromagnetic loss characteristics of the CLCC converter valve down to the specific branch under different operating modes of different operating conditions, providing data support for the insulation design, heat dissipation optimization, and life assessment of the converter valve.

[0042] Reference Figure 2 The operating conditions for calculating electromagnetic losses actually include: the normal switching process of the CLCC converter valve under steady-state conditions, and the forced switching process of the CLCC converter valve under AC system fault conditions. In other embodiments, if it is necessary to refine to some more specific operating conditions and the CLCC converter valve's working process, or if there is a need to calculate the electromagnetic losses of the saturated reactor of the CLCC converter valve under other operating conditions, then other operating conditions for calculating electromagnetic losses can be added or replaced accordingly.

[0043] The parameters required for electrical numerical simulation of a DC transmission system including the CLCC converter valve structure include: the electrical parameters of each semiconductor component, damping circuit component, voltage equalization circuit component, and saturated reactor component in the main and auxiliary branches of the CLCC converter valve; the electrical parameters of the converter transformer component; and the voltage, current, and power of the DC transmission system. In other embodiments, if there are other parameters that need to be considered during the simulation of the CLCC converter valve DC transmission system, these parameters can be added or replaced accordingly.

[0044] Similarly, the characteristic parameters required for electromagnetic field simulation of the saturated reactor in the main branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the main branch of the CLCC converter valve; the key components of the main branch include the saturated reactor core, coil and filling material; the electromagnetic parameters include conductivity, dielectric constant and permeability.

[0045] The parameters required for electromagnetic field simulation of the saturated reactor in the auxiliary branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the auxiliary branch of the CLCC converter valve; the key components of the auxiliary branch include the core, coil and filling material of the auxiliary branch saturated reactor; the electromagnetic parameters include conductivity, dielectric constant and permeability.

[0046] In other implementations, if there are other parameters that need to be considered during the simulation of the saturated reactors of the main and auxiliary branches of the CLCC converter valve that need to be simulated, then other parameters can be added or replaced accordingly.

[0047] In this embodiment, the electromagnetic loss calculation equation for the reactor includes the Bertotti or Steinmetz loss calculation equation; in other embodiments, other loss calculation formulas may also be used adaptively.

[0048] In a preferred embodiment, the specific process for performing the above-mentioned electrical numerical simulation, electromagnetic field simulation, and calculation of the electromagnetic loss of the saturated reactor in the main or auxiliary branch of the CLCC converter valve under the corresponding operating conditions is as follows:

[0049] 1. System Modeling: Based on the actual engineering parameters of the high voltage direct current transmission system, a simulation model of the primary system of the CLCC converter valve is established.

[0050] Specifically, based on engineering parameters and equipment electrical parameters, a primary system electrical simulation model of the CLCC converter valve is established. The main topology diagram of the CLCC converter valve is shown below. Figure 1 As shown, each arm (VT1-VT6) in the CLCC converter consists of a main branch and an auxiliary branch connected in parallel. The main branch mainly comprises a high-voltage thyristor valve (V11) and a low-voltage high-current IGBT valve (V12), while the auxiliary branch consists of a high-voltage IGBT valve (V13) and a high-voltage thyristor valve (V14) connected in series. Furthermore, to protect the thyristors and ensure the normal operation of the IGBTs, the CLCC converter valves, in addition to damping and voltage equalization circuits, are equipped with saturated reactors in both the main and auxiliary branches. System-level simulation models of the main and auxiliary branches are established using PSCAD / EMTDC to calculate their current timing characteristics. In the numerical simulation, system parameters such as frequency, voltage, current, and power, as well as device parameters such as thyristors, IGBTs, damping, voltage equalization circuits, and saturated reactors, can be set according to existing engineering conditions or flexibly configured based on engineering or research needs.

[0051] 2. Simulation Verification: Based on the voltage, current, power and converter valve parameters of the converter station, a steady-state simulation is performed to verify the correctness of the model and to obtain the voltage and current signals of the main branch and auxiliary branch under normal commutation and forced commutation modes.

[0052] Specifically, based on simulations of the CLCC converter valve DC transmission system under different operating conditions, the voltage and current characteristics of the main and auxiliary branches were obtained. The numerical simulation results of voltage and current in the main and auxiliary branches (auxiliary branches) during normal commutation of the CLCC converter valve are as follows: Figure 3 As shown.

[0053] Because the control logic of the CLCC converter valve differs under normal and forced commutation conditions, the voltage and current stresses of the main / auxiliary branches differ under AC system fault conditions, leading to different electromagnetic losses in the reactors of the main / auxiliary branches. Therefore, power system simulation is needed for AC system fault conditions, such as single-phase short circuits and phase-to-phase short circuits, during the CLCC forced commutation process. Taking an AC phase A ground fault as an example, the corresponding AC voltage is as follows: Figure 4 As shown, the electrical stress in the main / auxiliary branches during the forced commutation process of the CLCC converter valve is as follows: Figure 5 As shown. Under forced commutation conditions, when the V13 sub-valve is actively closed, the surge arrester operates simultaneously. Therefore, under forced commutation conditions, the current flowing through the auxiliary branch surge arrester is the sum of the current flowing through the V13 valve IGBT and the surge arrester.

[0054] 3. Establishment of three-dimensional electromagnetic loss model for main / auxiliary branches: Based on the key parameters such as the core, coil, and filling material of the actual saturated reactor of the CLCC converter valve, a three-dimensional electromagnetic loss calculation model for the saturated reactor is established.

[0055] Specifically, COMSOL / ANSYS Maxwell is used to perform three-dimensional finite element electromagnetic field simulation to obtain magnetic field distribution and loss data. The electromagnetic field simulation here requires separate simulation of the main and auxiliary branches of the CLCC converter valve, because the geometric and electromagnetic parameter values ​​of the main and auxiliary branches are different. However, the geometric and electromagnetic parameter values ​​of the same branch are the same under different operating conditions. The only difference is the boundary conditions, that is, the excitation of the reactor coil in the electromagnetic field simulation.

[0056] Key simulation parameters for electromagnetic field simulation include the geometric and electromagnetic parameters of critical components such as the saturated reactor core, coils, and filling materials. The modeling process for three-dimensional finite element electromagnetic field simulation follows the steps of geometric modeling, material setting (defining conductivity σ, dielectric constant ε, permeability μ, etc.), boundary conditions and excitation, solver setting, and post-processing.

[0057] 4. Electromagnetic loss calculation: Input the voltage and current signals obtained from the simulation into the three-dimensional electromagnetic loss model as the excitation source of the reactor coil.

[0058] This step is the core step in the calculation method of electromagnetic loss of saturated reactor in CLCC converter valve, that is, the excitation setting of reactor coil in the electromagnetic field simulation process adopts the voltage and current signals obtained from the simulation of CLCC converter valve DC transmission system. In this embodiment, the magnetic field density distribution of saturated reactor core during normal opening of main branch converter valve is as follows: Figure 6 As shown, the characteristics of the saturated iron core magnetic field density of the auxiliary branch during the switching process of the converter valve auxiliary branch are as follows: Figure 7 As shown.

[0059] 5. Loss separation analysis: Based on the Bertotti loss separation model, the electromagnetic losses of the reactors in the main branch and auxiliary branch are calculated, and the loss distribution under different operating modes is quantified.

[0060] In this embodiment, the equation for calculating the electromagnetic loss of the reactor is selected from the equation corresponding to the Bertotti loss separation model. Specifically, based on Bertotti theory, the total core loss calculation model for the silicon steel sheet core under any magnetic flux density waveform is obtained as follows:

[0061]

[0062] in, This represents the total loss of the reactor. For its hysteresis loss. For eddy current losses, For remaining losses, B is the hysteresis loss coefficient. m is the magnetic flux density; α is the magnetic flux density exponent; f is the operating frequency; and These are the eddy current loss coefficient and the residual loss coefficient, respectively. The relevant parameters can be fitted using the least squares algorithm based on the BP curve of the magnetic core provided by the manufacturer.

[0063] Since the current waveforms of the main / auxiliary branches are nonlinear, the instantaneous power curve of the core loss in the time domain can be obtained based on the above calculation model for the total core loss. The total loss of the saturated reactor within one power frequency cycle T... The calculation method is as follows:

[0064]

[0065] During the calculation, the voltage and current signals from the electrical numerical simulation of the aforementioned high-voltage DC system are substituted into the three-dimensional reactor electromagnetic loss simulation model as boundary conditions to calculate the electromagnetic field distribution characteristics of the positively saturated reactor. Specifically, based on the three-dimensional reactor electromagnetic loss simulation model (i.e., electromagnetic field simulation) under these boundary conditions, the magnetic flux density B can be obtained. m (As magnetic field distribution data), it is used to participate in the electromagnetic loss calculation of the Bertotti loss separation model; if the Steinmetz loss calculation equation is used, the magnetic field distribution data used in the electromagnetic loss calculation is also magnetic flux density. That is, based on the simulation and data acquisition results of the DC transmission system including the CLCC converter valve overall structure, the voltage and current loss timing characteristics of the main branch and auxiliary branch are analyzed. For example, it can be used to... Figure 3 CLCC main branch and under normal operating conditions Figure 5The voltage and current signals under abnormal operating conditions are respectively fed into the three-dimensional electromagnetic loss simulation model of the reactor to calculate the electromagnetic field distribution and loss characteristics of the main branch and auxiliary branch during normal commutation and forced commutation processes.

[0066] Then, based on the loss calculation results, optimization design suggestions for the reactor can be proposed to improve the operating efficiency and reliability of the CLCC converter valve, providing reliable data support and technical solutions for engineering applications.

[0067] As can be seen, the above-mentioned method for calculating the electromagnetic loss of the saturated reactor in the CLCC converter valve, combined with PSCAD calculation of the current in each branch of the converter valve, and the establishment of a field-circuit coupling model through COMSOL or ANSYS, accurately evaluates the electromagnetic loss of the reactor in the main and auxiliary branches of the CLCC converter valve based on the Bertotti or Steinmetz loss calculation equations, providing reliable theoretical support for the design optimization and engineering application of the CLCC converter valve.

[0068] Implementation of the electromagnetic loss calculation system for saturated reactors of CLCC converter valves

[0069] This embodiment presents a technical solution for a saturated reactor electromagnetic loss calculation system for a CLCC converter valve, referring to... Figure 8 It includes a power system simulation module and an electromagnetic loss simulation module;

[0070] The power system simulation module is used to perform electrical numerical simulation on a DC transmission system containing the overall structure of the CLCC converter valve under the condition of electromagnetic loss to be calculated, and to obtain the voltage and current characteristics of the main branch or auxiliary branch of the CLCC converter valve.

[0071] The electromagnetic loss simulation module is used to perform electromagnetic field simulation on the saturated reactor of the main or auxiliary branch of the CLCC converter valve according to the characteristic parameters of the main or auxiliary branch. It substitutes the corresponding voltage and current characteristics obtained from the electrical numerical simulation into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic loss. It is also used to calculate the electromagnetic loss of the saturated reactor of the main or auxiliary branch of the CLCC converter valve under the corresponding operating conditions based on the electromagnetic loss calculation equation of the reactor and the obtained magnetic field distribution data.

[0072] This system performs numerical simulations of the overall DC transmission system where the CLCC converter valve is located. It can accurately obtain the voltage and current characteristics of each branch of the CLCC converter valve for the operating conditions requiring electromagnetic loss calculation. Based on this, for the dual-branch structure in the CLCC topology, it performs electromagnetic field simulations on the electromagnetic field characteristics of each individual branch. Using the voltage and current characteristics of that branch under the operating conditions for which electromagnetic loss is to be calculated as the excitation for the electromagnetic field simulation, it ultimately obtains relatively accurate magnetic field distribution data for specific operating conditions and specific branches. This allows for more precise calculation of the electromagnetic loss of the saturated reactor, which is more consistent with actual conditions. This method can evaluate the electromagnetic loss characteristics of the CLCC converter valve down to the specific branch under different operating modes of different conditions, providing data support for the insulation design, heat dissipation optimization, and life assessment of the converter valve.

[0073] In this embodiment, the operating conditions for calculating electromagnetic losses actually include: the normal switching process of the CLCC converter valve under steady-state conditions, and the forced switching process of the CLCC converter valve under AC system fault conditions. In other embodiments, if it is necessary to refine to some more specific operating conditions and the CLCC converter valve's operating process, or if there is a need to calculate the electromagnetic losses of the saturated reactor of the CLCC converter valve under other operating conditions, then other operating conditions for calculating electromagnetic losses can be appropriately added or replaced.

[0074] The parameters required for electrical numerical simulation of a DC transmission system including the CLCC converter valve structure include: the electrical parameters of each semiconductor component, damping circuit component, voltage equalization circuit component, and saturated reactor component in the main and auxiliary branches of the CLCC converter valve; the electrical parameters of the converter transformer component; and the voltage, current, and power of the DC transmission system. In other embodiments, if there are other parameters that need to be considered during the simulation of the CLCC converter valve DC transmission system, these parameters can be added or replaced accordingly.

[0075] Similarly, the characteristic parameters required for electromagnetic field simulation of the saturated reactor in the main branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the main branch of the CLCC converter valve; the key components of the main branch include the saturated reactor core, coil and filling material; the electromagnetic parameters include conductivity, dielectric constant and permeability.

[0076] The parameters required for electromagnetic field simulation of the saturated reactor in the auxiliary branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the auxiliary branch of the CLCC converter valve; the key components of the auxiliary branch include the core, coil and filling material of the auxiliary branch saturated reactor; the electromagnetic parameters include conductivity, dielectric constant and permeability.

[0077] In other implementations, if there are other parameters that need to be considered during the simulation of the saturated reactors of the main and auxiliary branches of the CLCC converter valve that need to be simulated, then other parameters can be added or replaced accordingly.

[0078] In this embodiment, the electromagnetic loss calculation equation for the reactor includes the Bertotti or Steinmetz loss calculation equation; in other embodiments, other loss calculation formulas may also be used adaptively.

[0079] In a preferred embodiment, the specific process for performing the above-mentioned electrical numerical simulation, electromagnetic field simulation, and calculation of the electromagnetic loss of the saturated reactor in the main or auxiliary branch of the CLCC converter valve under the corresponding operating conditions is as follows:

[0080] 1. System Modeling: Based on the actual engineering parameters of the high voltage direct current transmission system, a simulation model of the primary system of the CLCC converter valve is established.

[0081] Specifically, based on engineering parameters and equipment electrical parameters, a primary system electrical simulation model of the CLCC converter valve is established. The main topology diagram of the CLCC converter valve is shown below. Figure 1 As shown, each arm (VT1-VT6) in the CLCC converter consists of a main branch and an auxiliary branch connected in parallel. The main branch mainly comprises a high-voltage thyristor valve (V11) and a low-voltage high-current IGBT valve (V12), while the auxiliary branch consists of a high-voltage IGBT valve (V13) and a high-voltage thyristor valve (V14) connected in series. Furthermore, to protect the thyristors and ensure the normal operation of the IGBTs, the CLCC converter valves, in addition to damping and voltage equalization circuits, are equipped with saturated reactors in both the main and auxiliary branches. System-level simulation models of the main and auxiliary branches are established using PSCAD / EMTDC to calculate their current timing characteristics. In the numerical simulation, system parameters such as frequency, voltage, current, and power, as well as device parameters such as thyristors, IGBTs, damping, voltage equalization circuits, and saturated reactors, can be set according to existing engineering conditions or flexibly configured based on engineering or research needs.

[0082] 2. Simulation Verification: Based on the voltage, current, power and converter valve parameters of the converter station, a steady-state simulation is performed to verify the correctness of the model and to obtain the voltage and current signals of the main branch and auxiliary branch under normal commutation and forced commutation modes.

[0083] Specifically, based on simulations of the CLCC converter valve DC transmission system under different operating conditions, the voltage and current characteristics of the main / auxiliary branches are obtained. Because the control logic of the CLCC converter valve differs under normal and forced commutation conditions, the voltage and current stresses of the main / auxiliary branches differ under AC system fault conditions, leading to different electromagnetic losses in the reactors of the main / auxiliary branches. Therefore, power system simulations are needed for AC system fault conditions, such as single-phase short circuits and phase-to-phase short circuits, during the CLCC forced commutation process. Since the active closure of the V13 sub-valve under forced commutation conditions is accompanied by the operation of the surge arrester, the current flowing through the auxiliary branch surge arrester under forced commutation conditions is the sum of the currents flowing through the V13 valve IGBT and the surge arrester.

[0084] 3. Establishment of three-dimensional electromagnetic loss model for main / auxiliary branches: Based on the key parameters such as the core, coil, and filling material of the actual saturated reactor of the CLCC converter valve, a three-dimensional electromagnetic loss calculation model for the saturated reactor is established.

[0085] Specifically, COMSOL / ANSYS Maxwell is used to perform three-dimensional finite element electromagnetic field simulation to obtain magnetic field distribution and loss data. The electromagnetic field simulation here requires separate simulation of the main and auxiliary branches of the CLCC converter valve, because the geometric and electromagnetic parameter values ​​of the main and auxiliary branches are different. However, the geometric and electromagnetic parameter values ​​of the same branch are the same under different operating conditions. The only difference is the boundary conditions, that is, the excitation of the reactor coil in the electromagnetic field simulation.

[0086] Key simulation parameters for electromagnetic field simulation include the geometric and electromagnetic parameters of critical components such as the saturated reactor core, coils, and filling materials. The modeling process for three-dimensional finite element electromagnetic field simulation follows the steps of geometric modeling, material setting (defining conductivity σ, dielectric constant ε, permeability μ, etc.), boundary conditions and excitation, solver setting, and post-processing.

[0087] 4. Electromagnetic loss calculation: Input the voltage and current signals obtained from the simulation into the three-dimensional electromagnetic loss model as the excitation source of the reactor coil.

[0088] This step is the core step in the calculation method of electromagnetic loss of saturated reactor of CLCC converter valve, that is, the excitation setting of reactor coil in electromagnetic field simulation process adopts the voltage and current signals obtained by simulation of DC transmission system of CLCC converter valve.

[0089] 5. Loss separation analysis: Based on the Bertotti loss separation model, the electromagnetic losses of the reactors in the main branch and auxiliary branch are calculated, and the loss distribution under different operating modes is quantified.

[0090] In this embodiment, the equation for calculating the electromagnetic loss of the reactor is selected from the equation corresponding to the Bertotti loss separation model. Specifically, based on Bertotti theory, the total core loss calculation model for the silicon steel sheet core under any magnetic flux density waveform is obtained as follows:

[0091]

[0092] in, This represents the total loss of the reactor. For its hysteresis loss. For eddy current losses, For remaining losses, B is the hysteresis loss coefficient. m is the magnetic flux density; α is the magnetic flux density exponent; f is the operating frequency; and These are the eddy current loss coefficient and the residual loss coefficient, respectively. The relevant parameters can be fitted using the least squares algorithm based on the BP curve of the magnetic core provided by the manufacturer.

[0093] Since the current waveforms of the main / auxiliary branches are nonlinear, the instantaneous power curve of the core loss in the time domain can be obtained based on the above calculation model for the total core loss. The total loss of the saturated reactor within one power frequency cycle T... The calculation method is as follows:

[0094]

[0095] During the calculation, the voltage and current signals from the electrical numerical simulation of the aforementioned high-voltage DC system are substituted into the three-dimensional reactor electromagnetic loss simulation model as boundary conditions to calculate the electromagnetic field distribution characteristics of the positively saturated reactor. Specifically, based on the three-dimensional reactor electromagnetic loss simulation model (i.e., electromagnetic field simulation) under these boundary conditions, the magnetic flux density B can be obtained. m (As magnetic field distribution data), it is used to participate in the electromagnetic loss calculation of the Bertotti loss separation model; if the Steinmetz loss calculation equation is used, the magnetic field distribution data used in the electromagnetic loss calculation is also magnetic flux density. That is, based on the simulation and data acquisition results of the DC transmission system including the overall structure of the CLCC converter valve, the timing characteristics of voltage and current losses in the main branch and auxiliary branch are analyzed.

[0096] Then, based on the loss calculation results, optimization design suggestions for the reactor can be proposed to improve the operating efficiency and reliability of the CLCC converter valve, providing reliable data support and technical solutions for engineering applications.

[0097] As can be seen, the above-mentioned CLCC converter valve saturated reactor electromagnetic loss calculation system combines PSCAD to calculate the current of each branch of the converter valve, and establishes a field-circuit coupling model through COMSOL or ANSYS. Based on the Bertotti or Steinmetz loss calculation equation, it accurately evaluates the electromagnetic loss of the reactor in the main and auxiliary branches of the CLCC converter valve, providing reliable theoretical support for the design optimization and engineering application of the CLCC converter valve.

[0098] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or explanatory of the principles of the present invention, and do not constitute a limitation thereof.

Claims

1. A method for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve, characterized in that, include: Under the condition of electromagnetic loss to be calculated, electrical numerical simulation is performed on the DC transmission system including the overall structure of CLCC converter valve to obtain the voltage and current characteristics of the main branch or auxiliary branch of CLCC converter valve. Based on the characteristic parameters of the main or auxiliary branch of the CLCC converter valve, electromagnetic field simulation is performed on the saturated reactor of the main or auxiliary branch of the CLCC converter valve. The corresponding voltage and current characteristics obtained from the electrical numerical simulation are substituted into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic losses. Based on the electromagnetic loss calculation equation of the reactor and the obtained magnetic field distribution data, calculate the saturated reactor electromagnetic loss of the main branch or auxiliary branch of the CLCC converter valve under the corresponding operating conditions.

2. The method for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve according to claim 1, characterized in that, The operating conditions under which electromagnetic losses are to be calculated include: the normal switching process of the CLCC converter valve under steady-state conditions, and the forced switching process of the CLCC converter valve under AC system fault conditions.

3. The method for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve according to claim 1 or 2, characterized in that, The parameters required for electrical numerical simulation of a DC transmission system including the overall structure of the CLCC converter valve include: electrical parameters of each semiconductor component, damping, voltage equalization circuit component, and saturated reactor component in the main and auxiliary branches of the CLCC converter valve; electrical parameters of the converter transformer component; and voltage, current, and power of the DC transmission system.

4. The method for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve according to claim 1 or 2, characterized in that, The characteristic parameters required for electromagnetic field simulation of the saturated reactor in the main branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the main branch of the CLCC converter valve; the key components of the main branch include the saturated reactor core, coil and filling material; the electromagnetic parameters include conductivity, dielectric constant and permeability. The parameters required for electromagnetic field simulation of the saturated reactor in the auxiliary branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the auxiliary branch of the CLCC converter valve; the key components of the auxiliary branch include the core, coil and filling material of the auxiliary branch saturated reactor; the electromagnetic parameters include conductivity, dielectric constant and permeability.

5. The method for calculating the electromagnetic loss of the saturated reactor in a CLCC converter valve according to claim 1 or 2, characterized in that, The equations for calculating electromagnetic losses in reactors include the Bertotti or Steinmetz loss calculation equations.

6. A system for calculating the electromagnetic loss of a saturated reactor in a CLCC converter valve, characterized in that, Includes a power system simulation module and an electromagnetic loss simulation module; The power system simulation module is used to perform electrical numerical simulation on a DC transmission system containing the overall structure of the CLCC converter valve under the condition of electromagnetic loss to be calculated, and to obtain the voltage and current characteristics of the main branch or auxiliary branch of the CLCC converter valve. The electromagnetic loss simulation module is used to perform electromagnetic field simulation on the saturated reactor of the main or auxiliary branch of the CLCC converter valve according to the characteristic parameters of the main or auxiliary branch. It substitutes the corresponding voltage and current characteristics obtained from the electrical numerical simulation into the excitation of the reactor coil in the electromagnetic field simulation to obtain the magnetic field distribution data required for calculating electromagnetic loss. It is also used to calculate the electromagnetic loss of the saturated reactor of the main or auxiliary branch of the CLCC converter valve under the corresponding operating conditions based on the electromagnetic loss calculation equation of the reactor and the obtained magnetic field distribution data.

7. The electromagnetic loss calculation system for the saturated reactor of the CLCC converter valve according to claim 6, characterized in that, The operating conditions under which electromagnetic losses are to be calculated include: the normal switching process of the CLCC converter valve under steady-state conditions, and the forced switching process of the CLCC converter valve under AC system fault conditions.

8. The electromagnetic loss calculation system for the saturated reactor of the CLCC converter valve according to claim 6 or 7, characterized in that, The parameters required for electrical numerical simulation of a DC transmission system including the overall structure of the CLCC converter valve include: electrical parameters of each semiconductor component, damping, voltage equalization circuit component, and saturated reactor component in the main and auxiliary branches of the CLCC converter valve; electrical parameters of the converter transformer component; and voltage, current, and power of the DC transmission system.

9. The electromagnetic loss calculation system for the saturated reactor of the CLCC converter valve according to claim 6 or 7, characterized in that, The characteristic parameters required for electromagnetic field simulation of the saturated reactor in the main branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the main branch of the CLCC converter valve; the key components of the main branch include the saturated reactor core, coil and filling material; the electromagnetic parameters include conductivity, dielectric constant and permeability. The parameters required for electromagnetic field simulation of the saturated reactor in the auxiliary branch of the CLCC converter valve include the geometric and electromagnetic parameters of the key components of the auxiliary branch of the CLCC converter valve; the key components of the auxiliary branch include the core, coil and filling material of the auxiliary branch saturated reactor; the electromagnetic parameters include conductivity, dielectric constant and permeability.

10. The electromagnetic loss calculation system for the saturated reactor of the CLCC converter valve according to claim 6 or 7, characterized in that, The equations for calculating electromagnetic losses in reactors include the Bertotti or Steinmetz loss calculation equations.

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