A method and system for dynamic reactive power compensation of a hybrid submarine cable system based on submarine cable aging intervention

Abstract

The application relates to the technical field of hybrid submarine cable system management, in particular to a hybrid submarine cable system dynamic reactive power compensation method and system based on submarine cable aging intervention, wherein the hybrid submarine cable system is a three-phase power transmission loop adopting XLPE submarine cables for one phase and oil-filled submarine cables for two phases, the method comprises the following steps: constructing an electromagnetic transient simulation model; calculating equivalent parameters of the XLPE submarine cables before aging, and determining initial static reactive power compensation of the system; obtaining current parameters to perform electromagnetic-thermal coupling simulation to obtain average temperature of an insulation layer; designing an accelerated thermal aging test to obtain the relationship between dielectric constant, dielectric loss angle and aging time; establishing a time-varying mathematical model of equivalent capacitance and equivalent resistance changing with service time, introducing a voltage offset correction coefficient to obtain a reactive power compensation correction model; and calculating a final reactive power compensation power value to perform compensation. The application can dynamically track parameter drift caused by XLPE submarine cable thermal aging, and effectively suppresses three-phase voltage imbalance in the whole life cycle.

Description

Technical Field

[0001] This application relates to the field of hybrid submarine cable system management technology, specifically to a dynamic reactive power compensation method and system for hybrid submarine cable systems based on submarine cable aging intervention. Background Technology

[0002] With the large-scale development of offshore wind power, high-voltage AC submarine cables, as core equipment for offshore power transmission, directly affect the safety and stability of the entire power transmission system due to their operational reliability. In some cross-sea interconnection projects, due to historical laying limitations, differences in the remaining lifespan of existing submarine cables, and the technological iteration requirements of newly constructed submarine cables, hybrid submarine cable transmission systems composed of submarine cables of different types and commissioning times have emerged. For example, in a three-phase transmission circuit structure, one phase uses cross-linked polyethylene (XLPE) insulated submarine cable, while the other two phases use oil-filled submarine cables, and the XLPE submarine cable is often in a single-core current-carrying asymmetrical operating state, forming a hybrid submarine cable system. This hybrid configuration needs to adapt to limited marine corridor resources and balance the need for continued use of existing submarine cables with the introduction of new technologies.

[0003] To address the reactive power generation issue arising from the large line-to-ground capacitance in long-distance AC submarine cable transmission systems, current engineering practices typically employ parallel high-voltage reactors for static reactive power compensation to offset capacitive reactive power and suppress power frequency overvoltage. For transmission systems composed of submarine cables of different types or insulation media, existing technologies utilize phase-independent controlled static var compensators (SVCs) or static synchronous compensators (STATCOMs) to configure different inductive reactive power compensation amounts based on the differences in capacitance parameters of each phase, thereby mitigating voltage imbalances caused by three-phase parameter asymmetry. Furthermore, in recent years, dynamic reactive power regulation based on real-time voltage or power fluctuation signals from the power grid has emerged. By monitoring the electrical quantities on the power grid side online, the output of the compensation device is dynamically adjusted to cope with changes in system operation.

[0004] However, the aforementioned existing technologies, when addressing the reactive power compensation problem in hybrid submarine cable systems, all treat the electrical parameters of the submarine cables as constant values ​​that do not change with service time. For hybrid submarine cable systems containing XLPE and oil-filled cables, especially when the XLPE cable is in single-core current-carrying mode, the alternating magnetic field of the current-carrying phase core cannot be canceled by the other cores, generating significant induced circulating currents in the metal sheath and armor layer. This leads to increased additional Joule heat loss, and the insulation layer operating temperature is significantly higher than under symmetrical operating conditions. This continuous thermal stress accelerates the thermo-oxidative degradation process of the XLPE insulation material, altering its dielectric constant and dielectric loss angle, thus causing the equivalent capacitance and equivalent conductance of the XLPE cable to drift over service time. In contrast, the electrical parameters of oil-filled cables change relatively little with aging due to the physical repair effect of the insulating oil. Therefore, during the long-term service of hybrid submarine cable systems, the parameter differences between XLPE and oil-filled cables will change asynchronously with aging time, resulting in a deviation between the initial static reactive power compensation configuration and actual requirements. When this deviation accumulates to a certain extent, the three-phase voltage imbalance will exceed the safety threshold. However, the existing dynamic compensation technology only relies on the passive feedback of electrical quantities at the grid end and fails to establish a correlation mechanism between the aging state of submarine cable insulation and reactive power compensation demand, making it difficult to feedforward compensation for the time-varying parameters driven by aging. Summary of the Invention

[0005] To address the technical problem that existing static reactive power compensation technologies for hybrid submarine cable systems treat the electrical parameters of the submarine cable as constant values ​​and rely solely on passive feedback from the power grid for dynamic compensation, lacking a mechanism for feedforward adjustment of parameters caused by thermal aging under the operating conditions of a single core of XLPE submarine cable, this application provides a dynamic reactive power compensation method and system for hybrid submarine cable systems based on submarine cable aging intervention. By establishing a time-varying mathematical model of the equivalent capacitance and equivalent resistance of the XLPE submarine cable changing with service time and introducing a voltage offset correction coefficient, the dynamic reactive power compensation correction amount is superimposed with the initial static compensation amount, realizing adaptive tracking of the aging process of the submarine cable and dynamic correction of the compensation amount throughout the entire life cycle, thereby effectively suppressing the growth of three-phase voltage imbalance.

[0006] Firstly, this application provides a dynamic reactive power compensation method for a hybrid submarine cable system based on submarine cable aging intervention. The hybrid submarine cable system is a three-phase transmission circuit, where one phase uses XLPE submarine cable and the other two phases use oil-filled submarine cables of the same specification. The steps include: S1. Obtain the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, and construct an electromagnetic transient simulation model of the hybrid submarine cable system based on the standard electrical parameters; S2. In the electromagnetic transient simulation model, short-circuit and open-circuit tests are performed on the current-carrying phase of the XLPE submarine cable. The short-circuit voltage, short-circuit current, open-circuit voltage and open-circuit charging current are measured. The equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance and equivalent capacitance of the XLPE submarine cable before aging are calculated. The initial static reactive power compensation of the system is determined based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system. S3. Obtain the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model. Using the current parameters as boundary conditions, perform electromagnetic-thermal coupling simulation on the XLPE submarine cable under single-core operation conditions to obtain the average temperature of the insulation layer. S4. Take several sets of submarine cable samples from the insulation layer of XLPE submarine cable, design and perform accelerated thermal aging tests on the submarine cable samples based on the average temperature of the insulation layer, and obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. S5. Based on the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and the aging time, a time-varying mathematical model of the equivalent capacitance and equivalent resistance of the XLPE submarine cable as a function of service time is established. Then, a voltage offset correction coefficient is introduced to obtain a reactive power compensation correction model. S6. Calculate the dynamic reactive power compensation correction amount based on the service time and reactive power compensation correction model of the hybrid submarine cable system. Superimpose the dynamic reactive power compensation correction amount with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation power value. Perform reactive power compensation on the hybrid submarine cable system based on the final reactive power compensation power value.

[0007] It should be further noted that in step S1, the standard electrical parameters include positive sequence resistance, positive sequence reactance, positive sequence capacitance, zero sequence resistance, zero sequence reactance, and zero sequence capacitance.

[0008] It should be further noted that, in step S1, constructing the electromagnetic transient simulation model of the hybrid submarine cable system specifically includes: Based on a real-time digital simulation system, a full electromagnetic transient model is constructed, including all submarine cables, submarine cable terminal stations, overhead lines, and substations in a hybrid submarine cable system.

[0009] It should be further noted that when constructing the full electromagnetic transient model, dynamic equivalent technology is used to simplify the topology of the main grid with voltage levels of 220kV and above, while retaining coastal hub switching stations, substations and offshore converter platforms as key nodes.

[0010] It should be further noted that when constructing the all-electromagnetic transient model, the Bergeron model is used to represent the 500kV long-distance transmission line as a lumped parameter line; the dynamic equivalent method based on Thevenin's theorem is used to represent the 220kV secondary grid as a voltage source with internal impedance, while retaining the saturation characteristics of the converter transformer as the core nonlinear element.

[0011] It should be further noted that in step S1, when constructing the electromagnetic transient simulation model of the hybrid submarine cable system, the hybrid submarine cable segment is modeled using a π-type equivalent circuit.

[0012] It should be further noted that step S2, which involves conducting a short-circuit test on the current-carrying phase of the XLPE submarine cable, specifically includes: Disconnect the terminal stations on both sides of the XLPE submarine cable, ground the beginning and end of the non-current phase conductor, metal sheath and armor layer of the XLPE submarine cable, apply the rated power frequency voltage source to the beginning of the current phase conductor, short-circuit the end to ground, and measure the voltage phasor at the beginning as the short-circuit voltage and the current phasor as the short-circuit current. The open-circuit test of the current-carrying phase of the XLPE submarine cable specifically includes: Disconnect the terminal stations on both sides of the XLPE submarine cable, ground the beginning and end of the non-current phase conductor, metal sheath and armor layer of the XLPE submarine cable, apply the rated power frequency voltage source to the beginning of the current phase conductor, open the end, measure the voltage phasor at the beginning as the open circuit voltage and the current phasor as the open circuit charging current.

[0013] It should be further noted that in step S2, the formulas for calculating the equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance of the XLPE submarine cable before aging are as follows:

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] in, The equivalent impedance before aging; This is the short-circuit voltage; This is the short-circuit current; This is the equivalent admittance before aging; This is the open-circuit voltage; This is the open-circuit charging current; This represents the phase difference between the short-circuit voltage and the short-circuit current. The equivalent resistance before aging; The equivalent reactance before aging; This is the phase difference between the open-circuit voltage and the open-circuit charging current. The equivalent conductivity before aging; The equivalent capacitance before aging; It is the power frequency.

[0020] It should be further explained that the specific method for determining the initial static reactive power compensation of the system in step S2 is as follows: Based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system, the no-load charging reactive power of each phase is calculated. The phase with the smallest no-load charging reactive power is used as the system balance benchmark, and the inductive reactive power compensation value of this phase is set to zero. Inductive reactive power compensation values ​​are configured for the remaining phases to make the capacitive reactive power injected into the system equal in all three phases, i.e., satisfying:

[0021] in, , , These are the net capacitive reactive power injected into the system after compensation for phases A, B, and C, respectively. The net capacitive reactive power injected into the system for each phase is equal to the no-load charging reactive power of that phase minus the inductive reactive power compensation value configured for that phase.

[0022] It should be further noted that the no-load charging reactive power of the XLPE submarine cable phase... The calculation formula is:

[0023]

[0024] in, The equivalent susceptance of the XLPE submarine cable; This is the system's rated phase voltage; No-load charging reactive power of oil-filled submarine cable phase The calculation formula is:

[0025]

[0026] in, The equivalent susceptance for oil-filled submarine cables; The positive sequence capacitance per unit length of oil-filled submarine cable; This refers to the physical laying length of a single-phase oil-filled submarine cable.

[0027] It should be further noted that step S3, which involves electromagnetic-thermal coupling simulation of the XLPE submarine cable, specifically includes: Based on the actual specifications of XLPE submarine cable, a two-dimensional cross-sectional model of XLPE submarine cable is established in the finite element simulation platform. The components in the two-dimensional cross-sectional model include the conductive core, conductor shielding layer, XLPE insulation layer, inner sheath, lead sheath, filler and outer sheath of XLPE cable. Set the electrical conductivity, relative permittivity, thermal conductivity, specific heat capacity, and density parameters of each component of the XLPE submarine cable at power frequency; Set the seabed environmental boundary conditions, including the water depth at the location of the submarine cable, the burial depth in the saturated sediment on the seabed, the thermal conductivity of the saturated sediment and seawater, and the ambient temperature. The current amplitude of the current-carrying phase of the XLPE submarine cable obtained from the electromagnetic transient simulation model is used as the current excitation source input, and the non-current-carrying phase core, the metal sheath of each phase and the armor layer are set to the ground potential; the electromagnetic-thermal coupling field is solved. Extracting the inner layer temperature of XLPE insulation layer in an electromagnetic-thermal coupling field and outer layer temperature ; The formula for calculating the average temperature of the insulation layer is:

[0028] in, This represents the average temperature of the insulation layer.

[0029] It should be further noted that step S4, which involves designing an accelerated thermal aging test based on the average temperature of the insulation layer, specifically includes: S401. Calculate aging acceleration factors The formula is:

[0030] in, Boltzmann's constant; The activation energy of the XLPE insulation material in the XLPE submarine cable; This refers to the actual operating temperature, specifically the temperature value obtained by converting the average temperature of the insulation layer into an absolute temperature. The absolute temperature of the preset accelerated aging thermal test; S402. Calculate the total duration of the accelerated thermal aging test. The formula is:

[0031] in, The preset ideal service life of XLPE submarine cables; S403. Total duration of accelerated thermal aging test Several sampling time points are set in the middle.

[0032] It should be further noted that in step S4, performing an accelerated thermal aging test on the submarine cable sample to obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and the aging time specifically includes: Accelerated thermal aging tests were performed on submarine cable samples according to the absolute temperature and total duration of the accelerated thermal aging test. At least one set of submarine cable samples was taken out, and aluminum electrodes were deposited on their surfaces. Then, a broadband dielectric spectrometer was used to measure their dielectric constant and dielectric loss angle within the preset test frequency range. The relationship between the measurement results and the cumulative aging time corresponding to the sampling time node was recorded.

[0033] It should be further noted that the test frequency range is 10. -1 Hz-10 6 Hz.

[0034] It should be further noted that the sampling time points include 360h, 720h, 1080h, and 1440h.

[0035] It should be further noted that in step S5, the time-varying mathematical model includes the time-varying equivalent capacitance model and the time-varying equivalent resistance model of the XLPE submarine cable, wherein: The expression for the time-varying equivalent capacitance model is:

[0036] It is the vacuum permittivity; The outer radius of the XLPE insulation layer; The inner radius of the XLPE insulation layer; This is a function of dielectric constant as a function of aging time obtained by fitting the dielectric constant of each sampling time point measured in the accelerated thermal aging test with the corresponding cumulative aging time. The time-varying equivalent capacitance model is represented as the equivalent resistance. The function that varies with service time is the equivalent resistance before aging. The data was obtained by fitting the equivalent resistance values ​​at each time point after aging.

[0037] It should be further explained that, The function that changes with service time follows a linear growth law.

[0038] It should be further noted that in step S5, the reactive power compensation correction model is a dynamic reactive power compensation correction amount. With service time The function of change is expressed as:

[0039] in The equivalent capacitance changes over service time; The equivalent capacitance before aging; This is the system's rated phase voltage; This is the voltage offset correction factor.

[0040] It should be further noted that the formula for calculating the voltage offset correction factor is as follows:

[0041] in, Indicates the service life of XLPE submarine cables The actual operating voltage at that time is expressed as:

[0042] For XLPE submarine cables during service life The longitudinal voltage drop at that time is expressed as:

[0043] in, The baseline active load transmitted in the hybrid submarine cable system is obtained from the electromagnetic transient simulation model; The baseline reactive load is obtained from the electromagnetic transient simulation model; The equivalent resistance varies with service time; The equivalent capacitance changes over service time; This is the equivalent reactance before aging; This is the system's rated phase voltage; It is the power frequency.

[0044] It should be further explained that, in step S6, the calculation of the dynamic reactive power compensation correction amount based on the service time of the hybrid submarine cable system and the reactive power compensation correction model is as follows: The service life of the hybrid submarine cable system is directly substituted into the reactive power compensation correction model to solve for the dynamic reactive power compensation correction. .

[0045] In another specific embodiment of this application, in step S6, calculating the dynamic reactive power compensation correction based on the service time of the hybrid submarine cable system and the reactive power compensation correction model specifically involves using the dynamic reactive power compensation correction. The simplified engineering model is used to calculate the dynamic reactive power compensation correction. The simplified engineering model is expressed as follows:

[0046] in, The solution obtained using the reactive power compensation correction model when the service time t approaches infinity. The limit value is calculated by substituting multiple discrete aging times into the reactive power compensation correction model. The value is obtained by performing exponential fitting; The time constant represents From 0 to of The required time is calculated by substituting multiple discrete aging times into the reactive power compensation correction model. The value is obtained by performing exponential fitting.

[0047] It should be further explained that, in step S6, the specific method for performing reactive power compensation on the phase containing the oil-filled submarine cable in the hybrid submarine cable system based on the final reactive power compensation power value is as follows: The final reactive power compensation value is used as a control command to output the corresponding amount of inductive reactive power to each phase of the oil-filled submarine cable, so as to compensate for the three-phase reactive power difference caused by the aging of the XLPE submarine cable insulation in real time.

[0048] Secondly, this application provides a dynamic reactive power compensation system for a hybrid submarine cable system based on submarine cable aging intervention, used to implement the aforementioned dynamic reactive power compensation method for the hybrid submarine cable system, including: The electromagnetic transient simulation model building module is used to obtain the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, and to build an electromagnetic transient simulation model of the hybrid submarine cable system based on the standard electrical parameters. The initial parameter calculation module is used to perform short-circuit and open-circuit tests on the current-carrying phase of the XLPE submarine cable in the electromagnetic transient simulation model, measure the short-circuit voltage, short-circuit current, open-circuit voltage, and open-circuit charging current, and calculate the equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance of the XLPE submarine cable before aging; and determine the initial static reactive power compensation of the system based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system. The electromagnetic-thermal coupling simulation module is used to obtain the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model. Using the current parameters as boundary conditions, electromagnetic-thermal coupling simulation is performed on the XLPE submarine cable under single-core operation to obtain the average temperature of the insulation layer. The accelerated thermal aging test module is used to cut several sets of submarine cable samples from the insulation layer of XLPE submarine cable, design and perform accelerated thermal aging tests on the submarine cable samples based on the average temperature of the insulation layer, and obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. The reactive power compensation correction model construction module is used to establish a time-varying mathematical model of the equivalent capacitance and equivalent resistance of XLPE submarine cable with service time based on the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and aging time. Then, the voltage offset correction coefficient is introduced to obtain the reactive power compensation correction model. The reactive power compensation execution module is used to calculate the dynamic reactive power compensation correction amount based on the service time of the hybrid submarine cable system and the reactive power compensation correction model. The dynamic reactive power compensation correction amount is superimposed with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation power value, and reactive power compensation is performed on the hybrid submarine cable system according to the final reactive power compensation power value.

[0049] Thirdly, this application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described dynamic reactive power compensation method for a hybrid submarine cable system.

[0050] Fourthly, this application provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of the above-described dynamic reactive power compensation method for a hybrid submarine cable system.

[0051] As can be seen from the above technical solutions, this application has the following advantages: 1. The dynamic reactive power compensation method for hybrid submarine cable systems based on submarine cable aging intervention provided in this application establishes a time-varying mathematical model of the equivalent capacitance and equivalent resistance of XLPE submarine cables changing with service time, and introduces a voltage offset correction coefficient to obtain a reactive power compensation correction model. Finally, the dynamic reactive power compensation correction amount is superimposed with the initial static reactive power compensation amount to compensate the system. This method can dynamically track the electrical parameter drift of XLPE submarine cables caused by thermal aging throughout the entire life cycle of the hybrid submarine cable system, so that the reactive power compensation amount is adaptively adjusted with the aging process, effectively suppressing the growth of three-phase voltage imbalance and extending the safe service life of the hybrid submarine cable system.

[0052] 2. This application conducts short-circuit and open-circuit tests on the current-carrying phases of the XLPE submarine cable, measures the short-circuit voltage, short-circuit current, open-circuit voltage, and open-circuit charging current, calculates the equivalent impedance and equivalent admittance of the XLPE submarine cable before aging, and determines the initial static reactive power compensation of the system based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system. This can accurately obtain the three-phase parameter mismatch reference at the initial stage of the hybrid submarine cable system's commissioning, providing an accurate starting point for subsequent dynamic correction and avoiding subsequent cumulative errors caused by initial compensation deviations.

[0053] 3. This application obtains the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model as boundary conditions, and performs electromagnetic-thermal coupling simulation on the XLPE submarine cable under single-core operation conditions to obtain the average temperature of the insulation layer. This can quantitatively reflect the actual thermal field distribution of the XLPE submarine cable under asymmetric operation conditions, overcome the defect of simply equating the operating temperature of the submarine cable with the ambient temperature or rated load temperature, and provide a temperature basis consistent with the field conditions for accelerating thermal aging tests, making the aging test results closer to the actual service state.

[0054] 4. This application extracts several sets of submarine cable samples from the insulation layer of XLPE submarine cables. Based on the average temperature of the insulation layer, it designs and performs accelerated thermal aging tests on the submarine cable samples to obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. It can obtain the dielectric property evolution data of XLPE insulation material under long-term thermal stress in a short time through accelerated aging, overcoming the time cost problem of long-term on-site tracking tests. At the same time, it obtains dielectric parameters at multiple frequency points through broadband dielectric spectrum measurement, providing multi-dimensional data support for the establishment of time-varying mathematical models.

[0055] 5. This application establishes a time-varying mathematical model of the equivalent capacitance and equivalent resistance of XLPE submarine cables as a function of service time based on the relationship between the dielectric constant and dielectric loss angle of submarine cable samples and aging time. A voltage offset correction coefficient is introduced to obtain a reactive power compensation correction model, which can transform the microscopic changes in the dielectric properties of materials into the macroscopic time-varying laws of line parameters. By taking into account the impact of the increase in active power loss and voltage drop caused by aging on the reactive power compensation requirements through the voltage offset correction coefficient, it overcomes the defect of traditional methods that ignore the actual operating voltage changes during the aging process and improves the compensation accuracy. Attached Figure Description

[0056] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a flowchart of a dynamic reactive power compensation method for a hybrid submarine cable system based on submarine cable aging intervention in one embodiment of this application.

[0058] Figure 2 This is an equivalent wiring diagram of a hybrid submarine cable system in an electromagnetic transient simulation model of one embodiment of this application.

[0059] Figure 3 This is a thermal field distribution diagram of an XLPE submarine cable obtained from electromagnetic-thermal coupling simulation under single-core operation conditions in one embodiment of this application.

[0060] Figure 4 This is a schematic diagram of the thermal aging test platform architecture used to perform accelerated thermal aging tests on submarine cable samples in one embodiment of this application.

[0061] Figure 5 This is a graph showing the relationship between the dielectric constant of a submarine cable sample and the test frequency at different sampling time points in one embodiment of this application.

[0062] Figure 6 This is a graph showing the relationship between the dielectric loss angle of a submarine cable sample and the test frequency at different sampling time points in one embodiment of this application.

[0063] Figure 7 This is a bar chart showing the simulation results of the voltage negative sequence imbalance of an important site in a hybrid submarine cable system under static reactive power compensation mode, according to one embodiment of this application.

[0064] Figure 8This is a bar chart showing the simulation results of the voltage negative sequence imbalance of an important site in a hybrid submarine cable system under dynamic reactive power compensation mode, according to one embodiment of this application.

[0065] Figure 9 This is a schematic block diagram of a dynamic reactive power compensation system for a hybrid submarine cable system based on submarine cable aging intervention in one embodiment of this application. Detailed Implementation

[0066] To make the purpose, features, and advantages of this application more apparent and understandable, specific embodiments and accompanying drawings will be used to clearly and completely describe the technical solution protected by this application. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0067] The following describes in detail the dynamic reactive power compensation method for hybrid submarine cable systems involved in this application. Specific details, such as particular system structures and technologies, are presented for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details.

[0068] In the dynamic reactive power compensation method for hybrid submarine cable systems involved in this application, the term "comprising" indicates the presence of the described feature, whole, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or collections thereof. The terms "comprising," "including," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0069] To facilitate a clear description of the technical solutions of this application, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" do not necessarily imply that they are different.

[0070] The terms "one embodiment" or "some embodiments" used in this application mean that one or more embodiments of this application include the specific features, structures, or characteristics described in that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this application do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0071] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0072] The dynamic reactive power compensation method for hybrid submarine cable systems provided in this application embodiment is executed by computer equipment. Correspondingly, the dynamic reactive power compensation system for hybrid submarine cable systems based on submarine cable aging intervention runs in the computer equipment.

[0073] Figure 1 This is a flowchart of a dynamic reactive power compensation method for a hybrid submarine cable system based on submarine cable aging intervention, according to an embodiment of this application. The hybrid submarine cable system is a three-phase transmission circuit, where one phase uses XLPE submarine cable and the other two phases use oil-filled submarine cables of the same specification. Figure 1 The implementing entity can be a hybrid submarine cable system dynamic reactive power compensation system. Depending on different requirements, the order of steps in this flowchart can be changed, and some steps can be omitted.

[0074] like Figure 1 As shown, the dynamic reactive power compensation method for hybrid submarine cable systems based on submarine cable aging intervention includes: Step S1: Obtain the standard electrical parameters of the oil-filled submarine cable and the XLPE submarine cable, and construct an electromagnetic transient simulation model of the hybrid submarine cable system based on the standard electrical parameters.

[0075] By acquiring the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables and constructing an electromagnetic transient simulation model of the hybrid submarine cable system based on them, all short-circuit tests, open-circuit tests, electromagnetic-thermal coupling simulations, and reactive power compensation calculations are all based on a simulation platform that can accurately reflect the parameter differences between the two heterogeneous submarine cables. This ensures the consistency of the simulation basis for the entire compensation chain from initial static compensation to dynamic correction.

[0076] In some specific embodiments, standard electrical parameters include positive sequence resistance, positive sequence reactance, positive sequence capacitance, zero sequence resistance, zero sequence reactance, and zero sequence capacitance.

[0077] By specifically defining the standard electrical parameters as positive-sequence resistance, positive-sequence reactance, positive-sequence capacitance, zero-sequence resistance, zero-sequence reactance, and zero-sequence capacitance, the constructed electromagnetic transient simulation model can comprehensively reflect the electrical behavior of the hybrid submarine cable system under three-phase symmetrical and asymmetrical fault conditions, providing accurate parameter benchmarks for short-circuit tests, open-circuit tests, and reactive power compensation calculations.

[0078] In some specific embodiments, constructing an electromagnetic transient simulation model of a hybrid submarine cable system specifically includes: Based on a real-time digital simulation system, a full electromagnetic transient model is constructed, including all submarine cables, submarine cable terminal stations, overhead lines, and substations in a hybrid submarine cable system.

[0079] By constructing a full electromagnetic transient model based on a real-time digital simulation system, including all submarine cables, cable terminal stations, overhead lines, and substations in the hybrid submarine cable system, the simulation model fully covers the complete power transmission channel from the submarine cable body to the power grids at both ends, thus enabling accurate simulation of the electromagnetic transient process of the hybrid submarine cable system in the actual power grid environment.

[0080] In some specific embodiments, when constructing the all-electromagnetic transient model, dynamic equivalent technology is used to simplify the topology of the main grid with voltage levels of 220kV and above, while retaining coastal hub switching stations, substations and offshore converter platforms as key nodes.

[0081] By employing dynamic equivalent techniques to simplify the topology of the main grid structure at voltage levels of 220kV and above when constructing the full electromagnetic transient model, and retaining coastal hub switching stations, substations, and offshore converter platforms as key nodes, the complexity of large-scale power grid models is significantly reduced while ensuring simulation accuracy, thereby improving the computational efficiency and engineering practicality of electromagnetic transient simulation.

[0082] In some specific embodiments, when constructing the all-electromagnetic transient model, the Bergeron model is used to represent the 500kV long-distance transmission line as a lumped parameter line; the dynamic equivalent method based on Thevenin's theorem is adopted to represent the 220kV secondary grid as a voltage source with internal impedance, while retaining the saturation characteristics of the converter transformer as the core nonlinear element.

[0083] By constructing a fully electromagnetic transient model, the 500kV long-distance transmission line is equivalent to a lumped parameter line using the Bergeron model, and the 220kV secondary grid is equivalent to a voltage source with internal impedance using a dynamic equivalent method based on Thevenin's theorem. At the same time, the saturation characteristics of the converter transformer are retained as the core nonlinear element. This simplifies the external power grid while accurately preserving the key nonlinear factors affecting the reactive power characteristics of the hybrid submarine cable system, thereby improving the accuracy of voltage and current phasor measurements in short-circuit and open-circuit tests.

[0084] In some specific embodiments, when constructing the electromagnetic transient simulation model of the hybrid submarine cable system, the hybrid submarine cable segment is modeled using a π-type equivalent circuit.

[0085] By using a π-type equivalent circuit to model the hybrid submarine cable segment when constructing the electromagnetic transient simulation model, the distributed parameter characteristics of the submarine cable can be concisely expressed in the form of lumped parameters, thereby reducing the computational burden of electromagnetic transient simulation while ensuring the simulation accuracy of power frequency and nearby frequencies.

[0086] In one specific embodiment, the equivalent wiring diagram of the hybrid submarine cable system in the electromagnetic transient simulation model is as follows: Figure 2As shown. According to Figure 2 As can be seen, the figure takes the hybrid submarine cable segment containing XLPE submarine cable and oil-filled submarine cable as the core of the study, and retains the key sites connected to it (such as submarine cable terminal stations, coastal hub switching stations, substations, etc.) as network nodes, which fully cover the complete power transmission channel from the submarine cable body to the power grids at both ends in the simulation.

[0087] Step S2: In the electromagnetic transient simulation model, short-circuit and open-circuit tests are performed on the current-carrying phase of the XLPE submarine cable. The short-circuit voltage, short-circuit current, open-circuit voltage and open-circuit charging current are measured. The equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance and equivalent capacitance of the XLPE submarine cable before aging are calculated. The initial static reactive power compensation of the system is determined based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system.

[0088] By conducting short-circuit and open-circuit tests on the current-carrying phase of the XLPE submarine cable in an electromagnetic transient simulation model to measure the short-circuit voltage, short-circuit current, open-circuit voltage, and open-circuit charging current, the equivalent impedance and equivalent admittance of the XLPE submarine cable before aging are calculated. Then, based on the equivalent admittance, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system, the initial static reactive power compensation of the system is determined. This allows the three-phase reactive power imbalance caused by the difference in capacitance parameters of heterogeneous submarine cables in the early stage of operation of the hybrid submarine cable system to be quantitatively anchored and forcibly compensated, thereby eliminating the initial voltage imbalance caused by structural asymmetry.

[0089] In some specific embodiments, short-circuit testing of the current-carrying phase of the XLPE submarine cable specifically includes: Disconnect the terminal stations on both sides of the XLPE submarine cable, ground the beginning and end of the non-current phase conductor, metal sheath and armor layer of the XLPE submarine cable, apply the rated power frequency voltage source to the beginning of the current phase conductor, short-circuit the end to ground, and measure the voltage phasor at the beginning as the short-circuit voltage and the current phasor as the short-circuit current. The open-circuit test of the current-carrying phase of the XLPE submarine cable specifically includes: Disconnect the terminal stations on both sides of the XLPE submarine cable, ground the beginning and end of the non-current phase conductor, metal sheath and armor layer of the XLPE submarine cable, apply the rated power frequency voltage source to the beginning of the current phase conductor, open the end, measure the voltage phasor at the beginning as the open circuit voltage and the current phasor as the open circuit charging current.

[0090] By disconnecting the terminal stations on both sides of the XLPE submarine cable during the short-circuit test and grounding the beginning and end of the non-current phase conductor, metal sheath, and armor layer, a rated power frequency voltage source is applied to the beginning of the current phase conductor and the end is short-circuited to ground to measure the short-circuit voltage and short-circuit current. In the open-circuit test, the end is opened to measure the open-circuit voltage and open-circuit charging current. This allows the short-circuit test to accurately eliminate the interference of capacitor charging current on impedance measurement and the open-circuit test to accurately eliminate the interference of inductance voltage drop on admittance measurement. Thus, the equivalent impedance and equivalent admittance of the XLPE submarine cable under single-core operating conditions can be obtained independently.

[0091] In some specific embodiments, the formulas for calculating the equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance of the XLPE submarine cable before aging are as follows:

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] in, The equivalent impedance before aging; This is the short-circuit voltage; This is the short-circuit current; This is the equivalent admittance before aging; This is the open-circuit voltage; This is the open-circuit charging current; This represents the phase difference between the short-circuit voltage and the short-circuit current. The equivalent resistance before aging; The equivalent reactance before aging; This is the phase difference between the open-circuit voltage and the open-circuit charging current. The equivalent conductivity before aging; The equivalent capacitance before aging; It is the power frequency.

[0098] By clarifying the calculation formulas for equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance, the equivalent electrical parameters of the XLPE submarine cable before aging can be quantitatively decoupled from the voltage and current phasors measured by short-circuit and open-circuit tests, thus providing an accurate numerical basis for determining the initial static reactive power compensation of the system.

[0099] In some specific embodiments, the method for determining the initial static reactive power compensation of the system is as follows: Based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system, the no-load charging reactive power of each phase is calculated. The phase with the smallest no-load charging reactive power is used as the system balance benchmark, and the inductive reactive power compensation value of this phase is set to zero. Inductive reactive power compensation values ​​are configured for the remaining phases to make the capacitive reactive power injected into the system equal in all three phases, i.e., satisfying:

[0100] in, , , These are the net capacitive reactive power injected into the system after compensation for phases A, B, and C, respectively. The net capacitive reactive power injected into the system for each phase is equal to the no-load charging reactive power of that phase minus the inductive reactive power compensation value configured for that phase.

[0101] By calculating the no-load charging reactive power of each phase based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system, and taking the phase with the smallest no-load charging reactive power as the system balance benchmark, the inductive reactive power compensation value of this phase is set to zero, while the inductive reactive power compensation values ​​are configured for the other phases to make the capacitive reactive power injected into the system equal in the three phases. This enables the forced balance of three-phase reactive power in the initial stage of the hybrid submarine cable system operation, thereby suppressing the voltage imbalance caused by the difference in capacitance parameters of heterogeneous submarine cables from the source.

[0102] In some specific embodiments, the no-load charging reactive power of the XLPE submarine cable phase The calculation formula is:

[0103]

[0104] in, The equivalent susceptance of the XLPE submarine cable; This is the system's rated phase voltage; No-load charging reactive power of oil-filled submarine cable phase The calculation formula is:

[0105]

[0106] in, The equivalent susceptance for oil-filled submarine cables; The positive sequence capacitance per unit length of oil-filled submarine cable; This refers to the physical laying length of a single-phase oil-filled submarine cable.

[0107] By clearly defining the no-load charging reactive power of the XLPE submarine cable phase and the oil-filled submarine cable phase, the capacitive reactive power difference caused by the different insulation media of the two heterogeneous submarine cables can be quantitatively characterized, thus providing an engineering-calcifiable expression for configuring the inductive compensation amount based on the phase with the minimum reactive power.

[0108] Step S3: Obtain the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model. Using the current parameters as boundary conditions, perform electromagnetic-thermal coupling simulation on the XLPE submarine cable under single-core operation conditions to obtain the average temperature of the insulation layer.

[0109] By obtaining the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model as boundary conditions and performing electromagnetic-thermal coupling simulation on the XLPE submarine cable under single-core operation conditions, the average temperature of the insulation layer is obtained. This allows the additional heating caused by the disappearance of the magnetic field cancellation effect during single-core current carrying to be accurately included in the thermal field calculation, thus obtaining an insulation layer temperature value that is highly consistent with the actual operating conditions on site.

[0110] In some specific embodiments, electromagnetic-thermal coupling simulation of XLPE submarine cables specifically includes: Based on the actual specifications of XLPE submarine cable, a two-dimensional cross-sectional model of XLPE submarine cable is established in the finite element simulation platform. The components in the two-dimensional cross-sectional model include the conductive core, conductor shielding layer, XLPE insulation layer, inner sheath, lead sheath, filler and outer sheath of XLPE cable. Set the electrical conductivity, relative permittivity, thermal conductivity, specific heat capacity, and density parameters of each component of the XLPE submarine cable at power frequency; Set the seabed environmental boundary conditions, including the water depth at the location of the submarine cable, the burial depth in the saturated sediment on the seabed, the thermal conductivity of the saturated sediment and seawater, and the ambient temperature. The current amplitude of the current-carrying phase of the XLPE submarine cable obtained from the electromagnetic transient simulation model is used as the current excitation source input, and the non-current-carrying phase core, the metal sheath of each phase and the armor layer are set to the ground potential; the electromagnetic-thermal coupling field is solved. Extracting the inner layer temperature of XLPE insulation layer in an electromagnetic-thermal coupling field and outer layer temperature ; The formula for calculating the average temperature of the insulation layer is:

[0111] in, This represents the average temperature of the insulation layer.

[0112] By establishing a two-dimensional cross-sectional model of the XLPE submarine cable in the finite element simulation platform and setting the material parameters of each component and the boundary conditions of the seabed environment, and then using the current amplitude obtained from the electromagnetic transient simulation model as the excitation source, and setting the non-current-carrying phase core, metal sheath and armor layer to ground potential, the electromagnetic-thermal coupling field is solved. Finally, the inner and outer temperatures of the insulation layer are extracted and the average temperature of the insulation layer is calculated using the logarithmic average formula. This allows the abnormal temperature rise caused by induced circulating current under single-core operating conditions to be accurately quantified, thus providing a temperature benchmark consistent with the field operating conditions for accelerated thermal aging tests.

[0113] In one specific embodiment, the thermal field distribution diagram of the XLPE submarine cable obtained by electromagnetic-thermal coupling simulation under single-core operation is shown below. Figure 3 As shown.

[0114] Step S4: Cut several sets of submarine cable samples from the insulation layer of the XLPE submarine cable, design and perform accelerated thermal aging tests on the submarine cable samples based on the average temperature of the insulation layer, and obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. Figure 3 The color gradient clearly shows the temperature diffusion process from the inner conductive core to the outer sheath. Simulation results also indicate that under single-core current-carrying conditions with the other two phases, metal sheath, and armor layer grounded, the XLPE insulation layer experiences abnormal temperature rise due to additional Joule heat loss caused by induced circulating current, with the inner layer temperature... The outer layer temperature reached 87.9℃. The average temperature of the insulation layer was calculated to be 81.3℃. The temperature was 84.57°C. Several sets of submarine cable samples were cut from the insulation layer of the XLPE submarine cable. An accelerated thermal aging test was designed based on the average temperature of the insulation layer and the test was performed on the samples. The relationship between the dielectric constant and dielectric loss angle of the samples and the aging time was obtained. This accelerated the reproduction of the thermo-oxidative degradation process of XLPE insulation material at the actual operating temperature, and thus obtained a complete evolution curve of dielectric parameters with aging time within a limited time.

[0115] In some specific embodiments, the accelerated thermal aging test designed based on the average temperature of the insulation layer specifically includes: S401. Calculate aging acceleration factors The formula is:

[0116] in, Boltzmann's constant; The activation energy of the XLPE insulation material in the XLPE submarine cable; This refers to the actual operating temperature, specifically the temperature value obtained by converting the average temperature of the insulation layer into an absolute temperature. The absolute temperature of the preset accelerated aging thermal test; S402. Calculate the total duration of the accelerated thermal aging test. The formula is:

[0117] in, The preset ideal service life of XLPE submarine cables; S403. Total duration of accelerated thermal aging test Several sampling time points are set in the middle.

[0118] The aging acceleration factor was calculated using the Arrhenius equation. And according to After calculating the total duration of the accelerated thermal aging test, several sampling time nodes are set within this total duration, so that the duration and sampling nodes of the accelerated thermal aging test are quantitatively mapped to the actual service life, thereby obtaining dielectric property evolution data covering the entire life cycle of the XLPE submarine cable in a short period of time.

[0119] In some specific embodiments, accelerated thermal aging tests are performed on submarine cable samples to obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time, specifically including: Accelerated thermal aging tests were performed on submarine cable samples according to the absolute temperature and total duration of the accelerated thermal aging test. At least one set of submarine cable samples was taken at each sampling time point, and aluminum electrodes were deposited on their surface. Then, a broadband dielectric spectrometer was used to measure their dielectric constant and dielectric loss angle within the preset test frequency range. The relationship between the measurement results and the cumulative aging time corresponding to the sampling time point was recorded.

[0120] By performing accelerated thermal aging tests on submarine cable samples according to the absolute temperature and total duration of the accelerated aging thermal test, and taking at least one set of samples at each sampling time point, depositing aluminum electrodes on their surface, and then using a broadband dielectric spectrometer to measure the dielectric constant and dielectric loss angle within the preset test frequency range and recording the relationship with the cumulative aging time, the changes in the dielectric properties of XLPE insulation material during the thermal aging process are continuously and quantitatively captured at multiple frequency points, thus providing original experimental data for establishing a time-varying mathematical model.

[0121] In one specific embodiment, a schematic diagram of the thermal aging test platform architecture used to perform accelerated thermal aging tests on submarine cable samples is shown below. Figure 4 As shown.

[0122] In some specific embodiments, the test frequency range is 10. -1 Hz-10 6 Hz.

[0123] By limiting the test frequency range to 10 -1 Hz-10 6 The Hz allows for wideband dielectric spectrum measurement to cover a broad frequency range from power frequency to higher frequencies, thus enabling comprehensive capture of the response characteristics of dipole orientation polarization, interface polarization, and conductivity loss caused by thermal aging at different frequencies.

[0124] In some specific embodiments, the sampling time points include 360h, 720h, 1080h, and 1440h.

[0125] In one specific embodiment, the curves showing the relationship between the dielectric constant of the submarine cable sample and the test frequency at different sampling time points are as follows: Figure 5 As shown in the figure, the dielectric loss angle of the submarine cable sample varies with the test frequency at different sampling time points. Figure 6 As shown.

[0126] Figure 5 The curves show that as the thermal aging time increases, the dielectric constant at all frequencies generally shows an upward trend. This quantitative relationship verifies that thermo-oxidative aging leads to an increase in polar groups in XLPE materials, thereby causing macroscopic changes in microscopic dielectric properties. Figure 6 The curves show that the dielectric loss angle deteriorated drastically with the aging process. The loss angle of the unaged sample (0h) was extremely small, while the curve rose significantly with the increase of aging time. The loss peak of the sample aged for 1440h could be several times that of the healthy sample, reflecting that thermal aging caused a sharp increase in the material's electrical conductivity loss.

[0127] Step S5: Based on the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and the aging time, establish a time-varying mathematical model of the equivalent capacitance and equivalent resistance of the XLPE submarine cable as a function of service time. Then, introduce the voltage offset correction coefficient to obtain the reactive power compensation correction model.

[0128] By establishing a time-varying mathematical model of the equivalent capacitance and equivalent resistance of XLPE submarine cable with service time based on the relationship between dielectric constant and dielectric loss angle of submarine cable samples and aging time, and introducing a voltage offset correction coefficient to obtain a reactive power compensation correction model, the aging law of microscopic material dielectric properties is transformed into a time-varying mathematical description of macroscopic line parameters, and the impact of voltage drop caused by aging on reactive power compensation requirements is taken into account.

[0129] In some specific embodiments, the time-varying mathematical model includes a time-varying equivalent capacitance model and a time-varying equivalent resistance model for the XLPE submarine cable, wherein: The expression for the time-varying equivalent capacitance model is:

[0130] It is the vacuum permittivity; The outer radius of the XLPE insulation layer; The inner radius of the XLPE insulation layer; This is a function of dielectric constant as a function of aging time obtained by fitting the dielectric constant of each sampling time point measured in the accelerated thermal aging test with the corresponding cumulative aging time. The time-varying equivalent capacitance model is represented as the equivalent resistance. The function that varies with service time is the equivalent resistance before aging. The data was obtained by fitting the equivalent resistance values ​​at each time point after aging.

[0131] By constructing functions for time-varying equivalent capacitance and time-varying equivalent resistance models, the dielectric constant and equivalent resistance data obtained from accelerated thermal aging tests are transformed into mathematical expressions that change continuously with service time, thus providing analytically calculable time-varying parameter inputs for the reactive power compensation correction model.

[0132] In some specific embodiments, The function that changes with service time follows a linear growth law.

[0133] By The function that changes with service time is constrained to follow a linear growth law, which simplifies the slow increase of the equivalent resistance of XLPE submarine cable during thermal aging into a linear model. This reduces the complexity of the time-varying mathematical model and the difficulty of parameter identification while ensuring engineering accuracy.

[0134] In some specific embodiments, the reactive power compensation correction model is a dynamic reactive power compensation correction amount. With service time The function of change is expressed as:

[0135] in The equivalent capacitance changes over service time; The equivalent capacitance before aging; This is the system's rated phase voltage; This is the voltage offset correction factor.

[0136] By clarifying the expression of the reactive power compensation correction model, the change in capacitive reactive power caused by the aging and drift of the equivalent capacitor is quantitatively calculated and a voltage offset correction coefficient is introduced for correction. At the same time, the impact of the increase in capacitive reactive power caused by the increase in dielectric constant and the decrease in actual operating voltage on the compensation demand are considered.

[0137] In some specific embodiments, the formula for calculating the voltage offset correction factor is as follows:

[0138] in, Indicates the service life of XLPE submarine cables The actual operating voltage at that time is expressed as:

[0139] For XLPE submarine cables during service life The longitudinal voltage drop at that time is expressed as:

[0140] in, The baseline active load transmitted in the hybrid submarine cable system is obtained from the electromagnetic transient simulation model; The baseline reactive load is obtained from the electromagnetic transient simulation model; The equivalent resistance varies with service time; The equivalent capacitance changes over service time; This is the equivalent reactance before aging; This is the system's rated phase voltage; It is the power frequency.

[0141] By clarifying the calculation formula for the voltage offset correction coefficient, the coupling effect of the increase in equivalent resistance and equivalent capacitance caused by aging of XLPE submarine cables on voltage drop along the line is quantitatively incorporated into the correction model, thereby improving the calculation accuracy of dynamic reactive power compensation correction throughout the entire life cycle.

[0142] Step S6: Calculate the dynamic reactive power compensation correction amount based on the service time of the hybrid submarine cable system and the reactive power compensation correction model. Superimpose the dynamic reactive power compensation correction amount with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation power value, and perform reactive power compensation on the hybrid submarine cable system according to the final reactive power compensation power value.

[0143] The dynamic reactive power compensation correction amount is calculated based on the service time of the hybrid submarine cable system and the reactive power compensation correction model. This correction amount is then superimposed with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation value. Reactive power compensation is then performed on the hybrid submarine cable system based on this final value, so that the reactive power compensation amount can adaptively increase or decrease with the aging process of the XLPE submarine cable, thereby dynamically maintaining the three-phase reactive power balance throughout the entire life cycle.

[0144] In some specific embodiments, the dynamic reactive power compensation correction amount is calculated based on the service time of the hybrid submarine cable system and the reactive power compensation correction model as follows: The service life of the hybrid submarine cable system is directly substituted into the reactive power compensation correction model to solve for the dynamic reactive power compensation correction. .

[0145] The dynamic reactive power compensation correction amount is solved by directly substituting the service time of the hybrid submarine cable system into the reactive power compensation correction model. This enables the reactive power compensation correction model to output the corresponding compensation correction value in real time according to the input service time, thereby realizing open-loop feedforward compensation control based on the aging time of submarine cables.

[0146] In other specific embodiments of this application, calculating the dynamic reactive power compensation correction based on the service time of the hybrid submarine cable system and the reactive power compensation correction model specifically involves using the dynamic reactive power compensation correction. The simplified engineering model is used to calculate the dynamic reactive power compensation correction. The simplified engineering model is expressed as follows:

[0147] in, The solution obtained using the reactive power compensation correction model when the service time t approaches infinity. The limit value is calculated by substituting multiple discrete aging times into the reactive power compensation correction model. The value is obtained by performing exponential fitting; The time constant represents From 0 to of The required time is calculated by substituting multiple discrete aging times into the reactive power compensation correction model. The value is obtained by performing exponential fitting.

[0148] By using a simplified engineering model to calculate the dynamic reactive power compensation correction, the originally complex nonlinear time-varying model is simplified into a single exponential function, thereby significantly reducing the online computing burden while ensuring that the calculation error is less than 2%.

[0149] In some specific embodiments, the specific method for reactive power compensation of the phase containing the oil-filled submarine cable in the hybrid submarine cable system based on the final reactive power compensation power value is as follows: The final reactive power compensation value is used as a control command to output the corresponding amount of inductive reactive power to each phase of the oil-filled submarine cable, so as to compensate for the three-phase reactive power difference caused by the aging of the XLPE submarine cable insulation in real time.

[0150] By using the final reactive power compensation value as a control command, the corresponding inductive reactive power is output to each phase of the oil-filled submarine cable to compensate for the three-phase reactive power difference caused by the aging of the XLPE submarine cable insulation in real time. This allows the output of the reactive power compensation device to adjust the inductive compensation amount of the oil-filled submarine cable phase synchronously with the aging process of the XLPE submarine cable, thereby maintaining the equal capacitive reactive power of the three-phase net injection system throughout the entire life cycle.

[0151] The dynamic reactive power compensation method for the hybrid submarine cable system in this application is taken as the dynamic reactive power compensation mode, and the conventional static reactive power compensation method for the hybrid submarine cable system is taken as the static reactive power compensation mode. Simulation analysis of the voltage negative sequence imbalance at important sites of the hybrid submarine cable system is performed under both the static and dynamic reactive power compensation modes. The bar chart of the analysis results corresponding to the static reactive power compensation mode is shown below. Figure 7 The bar chart showing the analysis results corresponding to the dynamic reactive power compensation mode is shown below. Figure 8 As shown.

[0152] in, Figure 7 The results show that throughout the entire service life of the system, the voltage negative sequence imbalance at each important station increases monotonically with aging time. At the end of the service life (corresponding to 1440h), the imbalance at some stations has increased to close to or even exceeded 0.3%. Figure 8 The results show that after applying the dynamic reactive power compensation strategy based on aging intervention provided in this application, the voltage negative sequence imbalance of the same site within the same service cycle is effectively constrained within a very narrow and low-level range, and is strictly suppressed to below the safety threshold of 0.2% throughout the entire process.

[0153] Figures 7-8 The stark contrast demonstrates that traditional static compensation cannot cope with the time-varying parameters caused by the aging of XLPE submarine cables, and the imbalance will continue to worsen; while the dynamic compensation strategy provided in this application can accurately track and compensate for the reactive power difference caused by aging, and maintain the three-phase voltage imbalance of the system within a safe range throughout the entire life cycle, effectively ensuring the long-term stable operation of the system.

[0154] The following are embodiments of the dynamic reactive power compensation system for hybrid submarine cable systems based on submarine cable aging intervention provided in this application. This dynamic reactive power compensation system for hybrid submarine cable systems based on submarine cable aging intervention belongs to the same inventive concept as the dynamic reactive power compensation method for hybrid submarine cable systems in the above embodiments. For details not described in detail in the embodiments of the dynamic reactive power compensation system for hybrid submarine cable systems, please refer to the embodiments of the dynamic reactive power compensation method for hybrid submarine cable systems based on submarine cable aging intervention described above.

[0155] like Figure 9 As shown, the dynamic reactive power compensation system for a hybrid submarine cable system based on submarine cable aging intervention includes: The electromagnetic transient simulation model building module is used to obtain the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, and to build an electromagnetic transient simulation model of the hybrid submarine cable system based on the standard electrical parameters. The initial parameter calculation module is used to perform short-circuit and open-circuit tests on the current-carrying phase of the XLPE submarine cable in the electromagnetic transient simulation model, measure the short-circuit voltage, short-circuit current, open-circuit voltage, and open-circuit charging current, and calculate the equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance of the XLPE submarine cable before aging; and determine the initial static reactive power compensation of the system based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system. The electromagnetic-thermal coupling simulation module is used to obtain the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model. Using the current parameters as boundary conditions, electromagnetic-thermal coupling simulation is performed on the XLPE submarine cable under single-core operation to obtain the average temperature of the insulation layer. The accelerated thermal aging test module is used to cut several sets of submarine cable samples from the insulation layer of XLPE submarine cable, design and perform accelerated thermal aging tests on the submarine cable samples based on the average temperature of the insulation layer, and obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. The reactive power compensation correction model construction module is used to establish a time-varying mathematical model of the equivalent capacitance and equivalent resistance of XLPE submarine cable with service time based on the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and aging time. Then, the voltage offset correction coefficient is introduced to obtain the reactive power compensation correction model. The reactive power compensation execution module is used to calculate the dynamic reactive power compensation correction amount based on the service time of the hybrid submarine cable system and the reactive power compensation correction model. The dynamic reactive power compensation correction amount is superimposed with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation power value, and reactive power compensation is performed on the hybrid submarine cable system according to the final reactive power compensation power value.

[0156] The dynamic reactive power compensation system for hybrid submarine cable systems in this embodiment is used to implement a dynamic reactive power compensation method for hybrid submarine cable systems based on submarine cable aging intervention.

[0157] This application also provides an electronic device for implementing various embodiments of this application, including a memory, a processor, and a computer program stored in the memory and executable on the processor.

[0158] Those skilled in the art will understand that the electronic device structure involved in the embodiments of this application does not constitute a limitation on the electronic device. The electronic device may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements.

[0159] In embodiments of this application, electronic devices include, but are not limited to, laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic devices may also represent various forms of mobile devices and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the embodiments of this application described and / or claimed herein.

[0160] In this application embodiment, the processor can be implemented using at least one of an Application-Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a processor, a controller, a microcontroller, a microprocessor, or an electronic unit designed to perform the functions described herein. In some cases, such implementations can be implemented within a controller. For software implementations, implementations such as processes or functions can be implemented with separate software modules that allow the performance of at least one function or operation. The software code can be implemented by a software application (or program) written in any suitable programming language, and the software code can be stored in memory and executed by the controller.

[0161] In addition, the electronic device includes some functional modules not shown, which will not be described in detail here.

[0162] Those skilled in the art will understand that the various aspects of the electronic device provided in this application can be implemented as a system, method, or program product. Therefore, the various aspects of this application can be specifically implemented in the following forms: a completely hardware implementation, a completely software implementation (including firmware, microcode, etc.), or a combination of hardware and software aspects, collectively referred to herein as a "circuit," "module," or "system."

[0163] This application also provides a storage medium storing a program product capable of implementing a dynamic reactive power compensation method for a hybrid submarine cable system based on submarine cable aging intervention. In some possible implementations, various aspects of this application can also be implemented as a program product comprising program code that, when run on a terminal device, causes the terminal device to perform the steps described in the "Exemplary Methods" section of this specification according to various exemplary embodiments of this application.

[0164] The storage medium may be any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example,, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of readable storage media include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0165] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dynamic reactive power compensation method for a hybrid submarine cable system based on submarine cable aging intervention, characterized in that, include: The hybrid submarine cable system is a three-phase transmission circuit, with one phase using XLPE submarine cable and the other two phases using oil-filled submarine cables. The two oil-filled submarine cables are of the same specification. The steps include: S1. Obtain the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, and construct an electromagnetic transient simulation model of the hybrid submarine cable system based on the standard electrical parameters; S2. In the electromagnetic transient simulation model, short-circuit and open-circuit tests are performed on the current-carrying phase of the XLPE submarine cable. The short-circuit voltage, short-circuit current, open-circuit voltage and open-circuit charging current are measured. The equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance and equivalent capacitance of the XLPE submarine cable before aging are calculated. The initial static reactive power compensation of the system is determined based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system. S3. Obtain the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model. Using the current parameters as boundary conditions, perform electromagnetic-thermal coupling simulation on the XLPE submarine cable under single-core operation conditions to obtain the average temperature of the insulation layer. S4. Take several sets of submarine cable samples from the insulation layer of XLPE submarine cable, design and perform accelerated thermal aging tests on the submarine cable samples based on the average temperature of the insulation layer, and obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. S5. Based on the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and the aging time, a time-varying mathematical model of the equivalent capacitance and equivalent resistance of the XLPE submarine cable as a function of service time is established. Then, a voltage offset correction coefficient is introduced to obtain a reactive power compensation correction model. The reactive power compensation correction model is a dynamic reactive power compensation correction amount. With service time The function of change is expressed as: in The equivalent capacitance changes over service time; The equivalent capacitance before aging; This is the system's rated phase voltage; The voltage offset correction factor is calculated using the following formula: in, Indicates the service life of XLPE submarine cables The actual operating voltage at that time is expressed as: For XLPE submarine cables during service life The longitudinal voltage drop at that time is expressed as: in, The baseline active load transmitted in the hybrid submarine cable system is obtained from the electromagnetic transient simulation model; The baseline reactive load is obtained from the electromagnetic transient simulation model; The equivalent resistance varies with service time; The equivalent capacitance changes over service time; This is the equivalent reactance before aging; This is the system's rated phase voltage; It is the power frequency; S6. Calculate the dynamic reactive power compensation correction amount based on the service time and reactive power compensation correction model of the hybrid submarine cable system. Superimpose the dynamic reactive power compensation correction amount with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation power value. Perform reactive power compensation on the hybrid submarine cable system based on the final reactive power compensation power value.

2. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 1, characterized in that, In step S1, the standard electrical parameters include positive sequence resistance, positive sequence reactance, positive sequence capacitance, zero sequence resistance, zero sequence reactance, and zero sequence capacitance.

3. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 1, characterized in that, Step S2, specifically the short-circuit test of the current-carrying phase of the XLPE submarine cable, includes: Disconnect the terminal stations on both sides of the XLPE submarine cable, ground the beginning and end of the non-current phase conductor, metal sheath and armor layer of the XLPE submarine cable, apply the rated power frequency voltage source to the beginning of the current phase conductor, short-circuit the end to ground, and measure the voltage phasor at the beginning as the short-circuit voltage and the current phasor as the short-circuit current. The open-circuit test of the current-carrying phase of the XLPE submarine cable specifically includes: Disconnect the terminal stations on both sides of the XLPE submarine cable, ground the beginning and end of the non-current phase conductor, metal sheath and armor layer of the XLPE submarine cable, apply the rated power frequency voltage source to the beginning of the current phase conductor, open the end, measure the voltage phasor at the beginning as the open circuit voltage and the current phasor as the open circuit charging current.

4. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 1, characterized in that, In step S2, the formulas for calculating the equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance of the XLPE submarine cable before aging are as follows: in, The equivalent impedance before aging; This is the short-circuit voltage; This is the short-circuit current; This is the equivalent admittance before aging; This is the open-circuit voltage; This is the open-circuit charging current; This represents the phase difference between the short-circuit voltage and the short-circuit current. The equivalent resistance before aging; The equivalent reactance before aging; This is the phase difference between the open-circuit voltage and the open-circuit charging current. The equivalent conductivity before aging; The equivalent capacitance before aging; It is the power frequency.

5. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 1, characterized in that, In step S2, the specific method for determining the initial static reactive power compensation of the system is as follows: Based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system, the no-load charging reactive power of each phase is calculated. The phase with the smallest no-load charging reactive power is used as the system balance benchmark, and the inductive reactive power compensation value of this phase is set to zero. Inductive reactive power compensation values ​​are configured for the remaining phases to make the capacitive reactive power injected into the system equal in all three phases, i.e., satisfying: in, , , These are the net capacitive reactive power injected into the system after compensation for phases A, B, and C, respectively. The net capacitive reactive power injected into the system for each phase is equal to the no-load charging reactive power of that phase minus the inductive reactive power compensation value configured for that phase.

6. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 1, characterized in that, Step S3, specifically the electromagnetic-thermal coupling simulation of the XLPE submarine cable, includes: Based on the actual specifications of XLPE submarine cable, a two-dimensional cross-sectional model of XLPE submarine cable is established in the finite element simulation platform. The components in the two-dimensional cross-sectional model include the conductive core, conductor shielding layer, XLPE insulation layer, inner sheath, lead sheath, filler and outer sheath of XLPE cable. Set the electrical conductivity, relative permittivity, thermal conductivity, specific heat capacity, and density parameters of each component of the XLPE submarine cable at power frequency; Set the seabed environmental boundary conditions, including the water depth at the location of the submarine cable, the burial depth in the saturated sediment on the seabed, the thermal conductivity of the saturated sediment and seawater, and the ambient temperature. The current amplitude of the current-carrying phase of the XLPE submarine cable obtained from the electromagnetic transient simulation model is used as the current excitation source input, and the non-current-carrying phase core, the metal sheath of each phase and the armor layer are set to the ground potential; the electromagnetic-thermal coupling field is solved. Extracting the inner layer temperature of XLPE insulation layer in an electromagnetic-thermal coupling field and outer layer temperature ; The formula for calculating the average temperature of the insulation layer is: in, This represents the average temperature of the insulation layer.

7. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 1, characterized in that, Step S4, which designs the accelerated thermal aging test based on the average temperature of the insulation layer, specifically includes: S401. Calculate aging acceleration factors The formula is: in, Boltzmann's constant; The activation energy of the XLPE insulation material in the XLPE submarine cable; This refers to the actual operating temperature, specifically the temperature value obtained by converting the average temperature of the insulation layer into an absolute temperature. The absolute temperature of the preset accelerated aging thermal test; S402. Calculate the total duration of the accelerated thermal aging test. The formula is: in, The preset ideal service life of XLPE submarine cables; S403. Total duration of accelerated thermal aging test Several sampling time points are set in the middle.

8. The dynamic reactive power compensation method for a hybrid submarine cable system as described in claim 7, characterized in that, In step S5, the time-varying mathematical model includes the time-varying equivalent capacitance model and the time-varying equivalent resistance model of the XLPE submarine cable, wherein: The expression for the time-varying equivalent capacitance model is: It is the vacuum permittivity; The outer radius of the XLPE insulation layer; The inner radius of the XLPE insulation layer; This is a function of dielectric constant as a function of aging time obtained by fitting the dielectric constant of each sampling time point measured in the accelerated thermal aging test with the corresponding cumulative aging time. The time-varying equivalent capacitance model is represented as the equivalent resistance. The function that varies with service time is the equivalent resistance before aging. The data was obtained by fitting the equivalent resistance values ​​at each time point after aging.

9. A dynamic reactive power compensation system for a hybrid submarine cable system based on submarine cable aging intervention, characterized in that, The method for implementing dynamic reactive power compensation of a hybrid submarine cable system as described in any one of claims 1-8 includes: The electromagnetic transient simulation model building module is used to obtain the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, and to build an electromagnetic transient simulation model of the hybrid submarine cable system based on the standard electrical parameters. The initial parameter calculation module is used to perform short-circuit and open-circuit tests on the current-carrying phase of the XLPE submarine cable in the electromagnetic transient simulation model, measure the short-circuit voltage, short-circuit current, open-circuit voltage, and open-circuit charging current, and calculate the equivalent impedance, equivalent admittance, equivalent resistance, equivalent reactance, equivalent conductance, and equivalent capacitance of the XLPE submarine cable before aging; and determine the initial static reactive power compensation of the system based on the equivalent admittance of the XLPE submarine cable before aging, the standard electrical parameters of the oil-filled submarine cable, and the rated phase voltage of the system. The electromagnetic-thermal coupling simulation module is used to obtain the current parameters of the current-carrying phase of the XLPE submarine cable from the electromagnetic transient model. Using the current parameters as boundary conditions, electromagnetic-thermal coupling simulation is performed on the XLPE submarine cable under single-core operation to obtain the average temperature of the insulation layer. The accelerated thermal aging test module is used to cut several sets of submarine cable samples from the insulation layer of XLPE submarine cable, design and perform accelerated thermal aging tests on the submarine cable samples based on the average temperature of the insulation layer, and obtain the relationship between the dielectric constant and dielectric loss angle of the submarine cable samples and the aging time. The reactive power compensation correction model construction module is used to establish a time-varying mathematical model of the equivalent capacitance and equivalent resistance of XLPE submarine cable with service time based on the relationship between the dielectric constant and dielectric loss angle of the submarine cable sample and aging time. Then, the voltage offset correction coefficient is introduced to obtain the reactive power compensation correction model. The reactive power compensation execution module is used to calculate the dynamic reactive power compensation correction amount based on the service time of the hybrid submarine cable system and the reactive power compensation correction model. The dynamic reactive power compensation correction amount is superimposed with the initial static reactive power compensation amount of the system to obtain the final reactive power compensation power value, and reactive power compensation is performed on the hybrid submarine cable system according to the final reactive power compensation power value.

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