A method, system, device and medium for reactive power compensation of a hybrid submarine cable system

Abstract

The application relates to the technical field of mixed submarine cable system maintenance, in particular to a reactive power compensation method, system, equipment and medium for a mixed submarine cable system, which comprises the following steps: acquiring standard electrical parameters of oil-filled submarine cables and XLPE submarine cables; constructing an electromagnetic transient simulation model of the mixed submarine cable system; calculating an ideal electric reactance compensation range; setting multiple groups of series electric reactance compensation schemes and applying each scheme in the electromagnetic transient simulation model; simulating and calculating three-phase power distribution, total transmission power and voltage unbalance degree under each series electric reactance compensation scheme; comparing simulation results of each series electric reactance compensation scheme; selecting a series electric reactance compensation scheme with the maximum total transmission power under the premise that the three-phase power unbalance degree is lower than a preset balance constraint condition as an optimal compensation scheme; and applying the optimal compensation scheme in the mixed submarine cable system. The application can simultaneously realize three-phase power balance and maximum total transmission power of the mixed submarine cable system.

Description

Technical Field

[0001] This application relates to the field of maintenance technology for hybrid submarine cable systems, specifically to a reactive power compensation method, system, equipment, and medium for hybrid submarine cable systems. Background Technology

[0002] With the large-scale integration of renewable energy and the increasing demand for long-distance power transmission, the efficient operation of submarine cable systems is becoming increasingly important, leading to ever-increasing technical complexity and reliability requirements. In the field of high-voltage power transmission, the mixed operation of cables with different insulation materials has become an important means to improve the economic efficiency of engineering projects, such as hybrid submarine cable systems that combine XLPE (cross-linked polyethylene) submarine cables with oil-filled submarine cables. How to achieve stable and efficient operation of hybrid submarine cable systems is an important issue in this field.

[0003] In existing technologies, the three-phase imbalance problem in hybrid submarine cable transmission lines is typically addressed using series reactive power compensation. For example, by connecting reactors or capacitors in series with the line to offset the inductive / capacitive reactance, power distribution is optimized, overvoltage is suppressed, or transmission capacity is increased. This method has become a standardized solution in conventional cable lines of the same type.

[0004] However, in hybrid submarine cable systems where XLPE and oil-filled submarine cables operate together, existing technologies have significant shortcomings: the positive-sequence resistance, reactance, capacitance, and zero-sequence parameters of the two types of cables differ significantly (e.g., the capacitance per unit length of XLPE submarine cables is about 40% lower than that of oil-filled submarine cables), resulting in inherent asymmetry in the electrical parameters of the three-phase transmission circuit. Existing compensation methods do not consider the special transient characteristics of such heterogeneous submarine cable coupling systems, making it difficult to accurately match reactance compensation values ​​to simultaneously achieve power balance and maximize transmission capacity. Furthermore, there is a lack of electromagnetic transient simulation verification mechanisms for hybrid submarine cable systems, making it impossible to intuitively quantify the compensation effects of different compensation schemes. Summary of the Invention

[0005] To address the technical problem that existing compensation methods for hybrid submarine cable systems cannot quantify and match the optimal compensation scheme for the significant parameter differences between XLPE and oil-filled submarine cables, this application provides a reactive power compensation method, system, equipment, and medium for hybrid submarine cable systems. The optimal reactance compensation value is selected and implemented through an electromagnetic transient simulation model, while simultaneously achieving three-phase power balance and maximizing the total transmission power of the hybrid submarine cable system.

[0006] In a first aspect, this application provides a reactive power compensation method for a hybrid submarine cable system, comprising the following steps:

[0007] S1. Obtain the standard electrical parameters for oil-filled submarine cables and XLPE (cross-linked polyethylene) submarine cables;

[0008] S2. Construct an electromagnetic transient simulation model of a hybrid submarine cable system based on standard electrical parameters. The hybrid submarine cable system is a three-phase transmission circuit, in which one phase uses XLPE submarine cable and the other two phases use oil-filled submarine cables. The two oil-filled submarine cables are of the same specification, and the three submarine cables are electrically connected through a multi-conductor coupled line unit.

[0009] S3. Calculate the total phase resistance of the XLPE submarine cable based on standard electrical parameters. XLPE submarine cable phase total reactance Total resistance of oil-filled submarine cable phase Total reactance of oil-filled submarine cable phase ;

[0010] Solve for the theoretical equilibrium reactance compensation value :

[0011]

[0012] Based on the theoretical equalization reactance compensation value Determine the range of ideal reactance compensation :

[0013]

[0014] in, , This is the proportionality constant, 0 < < <1;

[0015] S4. Set up multiple series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range, apply each series reactance compensation scheme in the electromagnetic transient simulation model, and superimpose the corresponding reactance compensation values ​​in the two oil-filled submarine cable phases. Simulate and calculate the three-phase transmission power distribution, total transmission power and voltage imbalance under each series reactance compensation scheme.

[0016] S5. Compare the simulation results of each series reactance compensation scheme, and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme;

[0017] S6. Apply the optimal compensation scheme to the hybrid submarine cable system, and apply the series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively.

[0018] 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.

[0019] It should be further explained that in step S3, , The calculation formula is:

[0020]

[0021]

[0022] in, For the system capacitance ratio, , The total ground capacitance of the oil-filled submarine cable phase.

[0023] In another embodiment of this application, in step S3, 0.2 ≤ < ≤0.3.

[0024] It should be further explained that in step S5, after selecting the optimal compensation scheme, the optimal compensation scheme is applied in the electromagnetic transient simulation model, and then a safety verification is performed. If the safety verification fails, another series reactance compensation scheme is selected as the new optimal compensation scheme; if the safety verification passes, step S6 is continued.

[0025] It should be further noted that security verification includes:

[0026] Obtain the negative-sequence current and zero-sequence current in the electromagnetic transient simulation model, and determine whether the following conditions are met:

[0027] The negative sequence current is lower than the preset negative sequence current protection setting.

[0028] The zero-sequence current is lower than the preset zero-sequence current protection setting.

[0029] Perform a power frequency resonant overvoltage test under non-full-phase operating conditions to determine whether the following conditions are met:

[0030] The residual voltage at the end of the disconnected phase line is lower than the preset residual voltage safety threshold.

[0031] The power frequency overvoltage of the healthy phase line is lower than the preset overvoltage safety threshold;

[0032] If any condition is not met, the security verification is deemed to have failed; if all conditions are met, the security verification is deemed to have passed.

[0033] It should be further noted that the value range of the negative sequence current protection setting is 0.1-0.3 times the rated phase current of the transmission circuit;

[0034] The value range of the zero-sequence current protection setting is 0.05-0.2 times the rated phase current of the transmission circuit;

[0035] The residual voltage safety threshold ranges from 0.2 to 0.3 times the rated phase voltage of the transmission circuit;

[0036] The overvoltage safety threshold ranges from 1.3 to 1.5 times the rated phase voltage of the transmission circuit.

[0037] It should be further noted that the power frequency resonant overvoltage test under non-full-phase operating conditions shall be carried out according to the following steps:

[0038] S501. Disconnect any one phase of the submarine cable line in the electromagnetic transient simulation model;

[0039] S502. Apply rated power frequency voltage to the remaining intact phase submarine cable lines;

[0040] S503. Measure the residual voltage at the end of the disconnected phase line and the overvoltage amplitude of the intact phase line.

[0041] It should be further explained that, in step S6, the method of applying series reactance compensation to the oil-filled submarine cable is to connect a reactor with the corresponding reactance value in series to the line of the oil-filled submarine cable phase.

[0042] Secondly, this application provides a reactive power compensation system for a hybrid submarine cable system, used to implement the above-mentioned reactive power compensation method, including:

[0043] Standard electrical parameter acquisition module, used to acquire standard electrical parameters of oil-filled submarine cables and XLPE submarine cables;

[0044] The simulation model building module is used to build electromagnetic transient simulation models of hybrid submarine cable systems based on standard electrical parameters.

[0045] The ideal reactance compensation range calculation module is used to determine the ideal reactance compensation range;

[0046] The simulation calculation module sets up multiple series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range. Each series reactance compensation scheme is applied in the electromagnetic transient simulation model. At the same time, the corresponding reactance compensation values ​​are superimposed on the two oil-filled submarine cable phases. The simulation calculation is performed on the three-phase transmission power distribution, total transmission power and voltage imbalance under each series reactance compensation scheme.

[0047] The optimal solution selection module is used to compare the simulation results of each series reactance compensation scheme and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme.

[0048] The optimal solution execution module is used to apply the optimal compensation scheme in a hybrid submarine cable system, and to apply the series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively.

[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 reactive power compensation method.

[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 reactive power compensation method.

[0051] As can be seen from the above technical solutions, this application has the following advantages:

[0052] 1. This application obtains the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, and constructs an electromagnetic transient simulation model of the hybrid submarine cable system based on these parameters. This enables accurate electrical connection modeling of multi-conductor coupled line units, providing a realistic working condition basis for compensation scheme design.

[0053] 2. This application overcomes the shortcomings of existing technologies in that they cannot quantitatively evaluate the compensation effect of hybrid submarine cable systems by pre-setting multiple sets of reactance compensation schemes in the electromagnetic transient simulation model and simulating and calculating the three-phase power distribution, total transmission power and voltage imbalance. It achieves the screening of the optimal series reactance compensation value from the dual dimensions of power balance and transmission capacity, ensuring that the three-phase transmission power distribution is balanced and the total transmission power is maximized.

[0054] 3. This application selects the optimal compensation scheme by comparing simulation results and applies corresponding series reactance compensation to the two oil-filled submarine cables, which solves the parameter imbalance problem caused by compensation value mismatch in the prior art. It can significantly reduce voltage imbalance and release transmission capacity, thereby improving the power quality and economy of the hybrid submarine cable system. Attached Figure Description

[0055] 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.

[0056] Figure 1 This is a flowchart of a reactive power compensation method for a hybrid submarine cable system in one embodiment of this application.

[0057] Figure 2 This is a topology diagram of a hybrid submarine cable system in one embodiment of this application.

[0058] Figure 3 This is a schematic block diagram of a reactive power compensation system for a hybrid submarine cable system in one embodiment of this application.

[0059] Figure 4This is a schematic diagram of the hardware structure of an electronic device in one embodiment of this application. Detailed Implementation

[0060] 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.

[0061] The reactive power compensation method involved in this application will be described in detail below. 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.

[0062] In the reactive power compensation methods involved in this application, the term "comprising" indicates the presence of the described feature, integral, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integrals, 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.

[0063] 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.

[0064] 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.

[0065] The following is a definition of some terms used in this plan to facilitate a better understanding of the plan:

[0066] XLPE submarine cable: XLPE submarine cable, also known as cross-linked polyethylene insulated submarine cable, is a submarine cable with cross-linked polyethylene (XLPE) as the insulation material. It is mainly used for submarine power transmission and is widely used in offshore wind power, inter-island interconnection, submarine communication base station power supply and other scenarios.

[0067] Oil-filled submarine cable: An oil-filled submarine cable is a submarine cable that uses insulating oil as the insulating medium and maintains oil pressure through an oil supply system.

[0068] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0069] The reactive power compensation method provided in this application embodiment is executed by computer equipment. Accordingly, the reactive power compensation system of the hybrid submarine cable system runs in the computer equipment.

[0070] Figure 1 This is a flowchart of a reactive power compensation method for a hybrid submarine cable system according to an embodiment of this application. Figure 1 The implementing entity can be a reactive power compensation system. Depending on different requirements, the order of steps in this flowchart can be changed, and some steps can be omitted.

[0071] like Figure 1 As shown, the reactive power compensation method for this hybrid submarine cable system includes:

[0072] Step S1: Obtain the standard electrical parameters of the oil-filled submarine cable and the XLPE submarine cable.

[0073] By acquiring the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables, basic data collection on the electrical characteristics of the two cable types was achieved, providing a complete parameter set required for system modeling, thereby ensuring the accuracy and representativeness of the subsequent electromagnetic transient simulation model.

[0074] 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.

[0075] By limiting the range of standard electrical parameters, a comprehensive coverage of the electrical characteristics of hybrid submarine cable systems is achieved. This allows for accurate description of the system's impedance, admittance, and coupling behavior under symmetrical and asymmetrical operating conditions, thus providing a complete and reliable data input foundation for the subsequent construction of electromagnetic transient simulation models.

[0076] Step S2: Construct an electromagnetic transient simulation model of the hybrid submarine cable system based on standard electrical parameters. The hybrid submarine cable system is a three-phase transmission circuit, in which one phase uses XLPE submarine cable and the other two phases use oil-filled submarine cable. The two oil-filled submarine cables are of the same specification, and the three submarine cables are electrically connected through a multi-conductor coupled line unit.

[0077] By constructing an electromagnetic transient simulation model of a hybrid submarine cable system based on standard electrical parameters, a dynamic simulation platform for the electrical behavior of the system was realized. This platform can accurately reflect the coupling effect and transient response between different submarine cable phases, thus providing a reliable basis for the simulation of compensation schemes.

[0078] Step S3: Calculate the total phase resistance of the XLPE submarine cable based on standard electrical parameters. XLPE submarine cable phase total reactance Total resistance of oil-filled submarine cable phase Total reactance of oil-filled submarine cable phase ;

[0079] Solve for the theoretical equilibrium reactance compensation value :

[0080]

[0081] Based on the theoretical equalization reactance compensation value Determine the range of ideal reactance compensation :

[0082]

[0083] in, , This is the proportionality constant, 0 < < <1.

[0084] Theoretical equalization reactance compensation value The derivation process of the solution formula is as follows:

[0085] Define the formula for calculating the transmission power of a two-phase submarine cable:

[0086]

[0087]

[0088] in, For the transmission power of the XLPE submarine cable, For the transmission power of the oil-filled submarine cable, The reactance value applied to the oil-filled submarine cable;

[0089] Assuming the three-phase power is perfectly balanced, ,at this time:

[0090]

[0091] Solving for the given information, we get:

[0092]

[0093] However, the theoretical optimal value While it can balance power, it can lead to the following problems:

[0094] Total power decreases when At this time, the imaginary part of the phase impedance of the oil-filled submarine cable increases dramatically, and its current is excessively suppressed. Although the power of the XLPE phase increases slightly, the power attenuation of the two-phase oil-filled submarine cable far exceeds the single-phase gain, which violates the goal of maximizing transmission.

[0095] Resonance risk: High compensation reactance Approaching the ground capacitance of the submarine cable This may induce series resonance; when At this time, the system damping weakens, causing voltage distortion and insulation overstress;

[0096] Therefore, this scheme is based on the principle of engineering trade-offs and adopts the theoretical balanced reactance compensation value. Part of the ideal reactance compensation range While suppressing capacitive circulating current and improving balance, it avoids power decay and resonance risks, achieving Pareto optimization of total power and stability.

[0097] In some specific embodiments, , The calculation formula is:

[0098]

[0099]

[0100] in, For the system capacitance ratio, , The total ground capacitance of the oil-filled submarine cable phase.

[0101] Through the volumetric ratio Dynamically generating proportional coefficients can overcome the limitations of traditional fixed-proportion compensation and significantly improve system performance: especially for short-distance high-capacitance submarine cables ( <0.05, compressing the compensation range to 15%-20% of the theoretical value to avoid the risk of series resonance caused by overcompensation; and for long-distance low-capacitance submarine cables ( If the value is greater than 0.15, the compensation range can be expanded to 26%-32% of the theoretical value, fully optimizing the three-phase power balance. This adaptive mechanism can reduce the total power loss while reducing the three-phase power imbalance, and ensure that the system stays away from the resonant instability region.

[0102] In some specific embodiments, 0.2≤ < ≤0.3.

[0103] Step S4: Set multiple sets of series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range. Apply each set of series reactance compensation schemes in the electromagnetic transient simulation model. Simultaneously, superimpose the corresponding reactance compensation values ​​in the two oil-filled submarine cable phases. Simulate and calculate the three-phase transmission power distribution, total transmission power, and voltage imbalance under each series reactance compensation scheme.

[0104] By applying each set of series reactance compensation schemes in the electromagnetic transient simulation model, and superimposing the corresponding reactance compensation values ​​in the two oil-filled submarine cable phases, and simulating and calculating the three-phase transmission power distribution, total transmission power and voltage imbalance under each scheme, a quantitative evaluation of the performance of the compensation schemes is realized. The power balance, transmission efficiency and voltage quality of different schemes can be objectively compared, thereby supporting data-driven optimization decisions.

[0105] Step S5: Compare the simulation results of each series reactance compensation scheme, and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme.

[0106] By comparing the simulation results of each series reactance compensation scheme, and selecting the scheme that maximizes the three-phase power distribution and the total transmission power as the optimal compensation scheme, a scheme selection based on clear criteria is achieved. This can simultaneously optimize the system's power quality and transmission capacity, thereby determining the most effective compensation strategy.

[0107] In some specific embodiments, after selecting the optimal compensation scheme, the optimal compensation scheme is applied in the electromagnetic transient simulation model, and then a safety verification is performed. If the safety verification fails, another series reactance compensation scheme is selected as the new optimal compensation scheme; if the safety verification passes, step S6 is continued.

[0108] By adding a security verification step and setting up a feedback mechanism, dynamic assessment and iterative optimization of the security risks of the optimal compensation scheme are achieved. Schemes that do not meet the security conditions can be eliminated in a timely manner, thereby ensuring the reliability and robustness of the system operation.

[0109] In some specific embodiments, security verification includes:

[0110] Obtain the negative-sequence current and zero-sequence current in the electromagnetic transient simulation model, and determine whether the following conditions are met:

[0111] The negative sequence current is lower than the preset negative sequence current protection setting.

[0112] The zero-sequence current is lower than the preset zero-sequence current protection setting.

[0113] Perform a power frequency resonant overvoltage test under non-full-phase operating conditions to determine whether the following conditions are met:

[0114] The residual voltage at the end of the disconnected phase line is lower than the preset residual voltage safety threshold.

[0115] The power frequency overvoltage of the healthy phase line is lower than the preset overvoltage safety threshold;

[0116] If any condition is not met, the security verification is deemed to have failed; if all conditions are met, the security verification is deemed to have passed.

[0117] By specifying the content of safety verification, comprehensive detection of potential system failure conditions is achieved, which can identify and prevent risks such as current imbalance and resonant overvoltage, thereby ensuring the safety of the compensation scheme under extreme conditions.

[0118] In some specific embodiments, the value range of the negative sequence current protection setting is 0.1-0.3 times the rated phase current of the transmission circuit;

[0119] The value range of the zero-sequence current protection setting is 0.05-0.2 times the rated phase current of the transmission circuit;

[0120] The residual voltage safety threshold ranges from 0.2 to 0.3 times the rated phase voltage of the transmission circuit;

[0121] The overvoltage safety threshold ranges from 1.3 to 1.5 times the rated phase voltage of the transmission circuit.

[0122] By limiting the range of negative sequence current protection settings, zero sequence current protection settings, residual voltage safety threshold, and overvoltage safety threshold, reasonable range settings for protection parameters are achieved, which can be adapted to the actual system protection requirements, avoid false tripping or failure to trip of protection devices, and thus improve system stability and safety margin.

[0123] In some specific embodiments, the power frequency resonant overvoltage test under non-full-phase operating conditions is performed according to the following steps:

[0124] S501. Disconnect any one phase of the submarine cable line in the electromagnetic transient simulation model;

[0125] S502. Apply rated power frequency voltage to the remaining intact phase submarine cable lines;

[0126] S503. Measure the residual voltage at the end of the disconnected phase line and the overvoltage amplitude of the intact phase line.

[0127] By standardizing the power frequency resonant overvoltage test procedure under non-full-phase operating conditions, a quantitative assessment of resonant risk is achieved. This allows for accurate simulation of voltage behavior under fault scenarios, thus providing objective and repeatable test data for safety verification.

[0128] Step S6: Apply the optimal compensation scheme to the hybrid submarine cable system and apply the series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively.

[0129] By applying the optimal compensation scheme in the hybrid submarine cable system and applying the series reactance compensation corresponding to the optimal scheme to the two oil-filled submarine cables respectively, the physical deployment of the optimal scheme is realized. Compensation can be directly introduced into the phase of the oil-filled submarine cable, thereby improving the three-phase power distribution, increasing the total transmission power and reducing the system voltage imbalance.

[0130] In some specific embodiments, the method for applying series reactance compensation to the oil-filled submarine cable is to connect a reactor with the corresponding reactance value in series into the line of the oil-filled submarine cable phase.

[0131] By clarifying the method of applying series reactor compensation to oil-filled submarine cables, the physical implementation of the compensation scheme is standardized, which can ensure the simple and reliable integration of reactors and submarine cable lines, thereby directly improving the electrical performance of oil-filled submarine cable phases and reducing implementation complexity.

[0132] In one specific embodiment, the reactive power compensation method for a hybrid submarine cable system is applied in a cross-sea power transmission project, comprising the following steps:

[0133] Step S1: Obtain the standard electrical parameters of the oil-filled submarine cable and the XLPE submarine cable. The standard electrical parameters include positive sequence resistance, positive sequence reactance, positive sequence capacitance, zero sequence resistance, zero sequence reactance, and zero sequence capacitance. The standard electrical parameters of the oil-filled submarine cable and the XLPE submarine cable are shown in Table 1.

[0134] Table 1 Standard Electrical Parameters of Submarine Cables

[0135]

[0136] Step S2: Construct an electromagnetic transient simulation model of the hybrid submarine cable system based on standard electrical parameters. 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, and the three submarine cables are electrically connected through a multi-conductor coupled line unit. The specific construction process is as follows:

[0137] Establish such a simulation platform on the electromagnetic transient simulation platform Figure 2The hybrid submarine cable system topology diagram shown employs dynamic equivalent techniques to simplify the 220kV and above main grid: coastal hub substations (several stations A and B) and offshore converter platforms are retained as key nodes, while 500kV long-distance transmission lines are equivalent to lumped parameter lines using the Bergeron model. For voltage level transition nodes (such as 500kV / 220kV interconnection transformers), a dynamic equivalent method based on Thevenin's theorem is used to convert the secondary grid into a voltage source with internal impedance, while retaining core nonlinear components such as the saturation characteristics of converter transformers.

[0138] according to Figure 2 As can be seen, in the hybrid submarine cable system, the mainland substation is connected to the onshore converter station via a 220kV overhead line, while the island substation is connected to the island's power grid via a submarine cable terminal station, forming a "mainland-ocean-island" energy transmission channel. The left end is the mainland end, and the right end is the island end; the substations at both ends are connected to the submarine cable terminal station via overhead lines. The submarine cable is planned to have four sections, including two 37.6km cross-linked polyethylene (XLPE) submarine cables and two 31km oil-filled submarine cables. One phase of one oil-filled submarine cable is damaged; it is proposed to replace the damaged phase with one core of a three-core XLPE submarine cable, forming a hybrid transmission line composed of a single-phase XLPE submarine cable and two-phase oil-filled submarine cables. Its topology is accurately modeled in the electromagnetic transient simulation model using multi-conductor coupled line units.

[0139] Step S3: Calculate the total phase resistance of the XLPE submarine cable based on standard electrical parameters. XLPE submarine cable phase total reactance Total resistance of oil-filled submarine cable phase Total reactance of oil-filled submarine cable phase ;

[0140] Solve for the theoretical equilibrium reactance compensation value :

[0141]

[0142] Based on the theoretical equalization reactance compensation value Determine the range of ideal reactance compensation :

[0143]

[0144] in, , This is the proportionality constant, 0 < < <1;

[0145] , The calculation formula is:

[0146]

[0147]

[0148] in, For the system capacitance ratio, , The total ground capacitance of the oil-filled submarine cable phase.

[0149] Step S4: Set multiple sets of series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range. Apply each set of series reactance compensation schemes in the electromagnetic transient simulation model. Simultaneously, superimpose the corresponding reactance compensation values ​​in the two oil-filled submarine cable phases. Simulate and calculate the three-phase transmission power distribution, total transmission power, and voltage imbalance under each series reactance compensation scheme.

[0150] Step S5: Compare the simulation results of each series reactance compensation scheme, and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme.

[0151] After selecting the optimal compensation scheme, apply the optimal compensation scheme in the electromagnetic transient simulation model, and then perform safety verification. If the safety verification fails, select another series reactance compensation scheme as the new optimal compensation scheme; if the safety verification succeeds, continue to step S6.

[0152] Security verification includes:

[0153] Obtain the negative-sequence current and zero-sequence current in the electromagnetic transient simulation model, and determine whether the following conditions are met:

[0154] The negative sequence current is lower than the preset negative sequence current protection setting.

[0155] The zero-sequence current is lower than the preset zero-sequence current protection setting.

[0156] Perform a power frequency resonant overvoltage test under non-full-phase operating conditions to determine whether the following conditions are met:

[0157] The residual voltage at the end of the disconnected phase line is lower than the preset residual voltage safety threshold.

[0158] The power frequency overvoltage of the healthy phase line is lower than the preset overvoltage safety threshold;

[0159] If any one condition is not met, the security verification is deemed to have failed; if all conditions are met, the security verification is deemed to have passed.

[0160] The value range of the negative sequence current protection setting is 0.1-0.3 times the rated phase current of the transmission circuit;

[0161] The value range of the zero-sequence current protection setting is 0.05-0.2 times the rated phase current of the transmission circuit;

[0162] The residual voltage safety threshold ranges from 0.2 to 0.3 times the rated phase voltage of the transmission circuit;

[0163] The overvoltage safety threshold ranges from 1.3 to 1.5 times the rated phase voltage of the transmission circuit;

[0164] The power frequency resonant overvoltage test under non-full-phase operating conditions shall be performed according to the following steps:

[0165] S501. Disconnect any one phase of the submarine cable line in the electromagnetic transient simulation model;

[0166] S502. Apply rated power frequency voltage to the remaining intact phase submarine cable lines;

[0167] S503. Measure the residual voltage at the end of the disconnected phase line and the overvoltage amplitude of the intact phase line.

[0168] Step S6: Apply the optimal compensation scheme to the hybrid submarine cable system. Apply series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively. The compensation method is to connect the reactor with the corresponding reactance value in series to the line of the oil-filled submarine cable phase.

[0169] The following are embodiments of the reactive power compensation system for a hybrid submarine cable system provided in this application. This reactive power compensation system for a hybrid submarine cable system belongs to the same inventive concept as the reactive power compensation methods in the above embodiments. For details not described in detail in the embodiments of the reactive power compensation system, please refer to the embodiments of the reactive power compensation methods for the hybrid submarine cable system described above.

[0170] like Figure 3 As shown, the reactive power compensation system of the hybrid submarine cable system includes:

[0171] Standard electrical parameter acquisition module, used to acquire standard electrical parameters of oil-filled submarine cables and XLPE submarine cables;

[0172] The simulation model building module is used to build electromagnetic transient simulation models of hybrid submarine cable systems based on standard electrical parameters.

[0173] The ideal reactance compensation range calculation module is used to determine the ideal reactance compensation range;

[0174] The simulation calculation module sets up multiple series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range. Each series reactance compensation scheme is applied in the electromagnetic transient simulation model. At the same time, the corresponding reactance compensation values ​​are superimposed on the two oil-filled submarine cable phases. The simulation calculation is performed on the three-phase transmission power distribution, total transmission power and voltage imbalance under each series reactance compensation scheme.

[0175] The optimal solution selection module is used to compare the simulation results of each series reactance compensation scheme and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme.

[0176] The optimal solution execution module is used to apply the optimal compensation scheme in a hybrid submarine cable system, and to apply the series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively.

[0177] The reactive power compensation system in this embodiment is used to implement a reactive power compensation method for a hybrid submarine cable system.

[0178] This application also provides an electronic device for implementing the various embodiments of this application. Figure 4 To illustrate the hardware structure of an electronic device according to various embodiments of this application, as shown in the following diagram... Figure 4 As shown, the electronic device includes a memory, a processor, and a computer program stored in the memory and capable of running on the processor.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] In addition, the electronic device includes some functional modules not shown, which will not be described in detail here.

[0183] 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."

[0184] This application also provides a storage medium storing a program product capable of implementing a reactive power compensation method for a hybrid submarine cable system. 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.

[0185] 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.

[0186] 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 reactive power compensation method for a hybrid submarine cable system, characterized in that, include: S1. Obtain the standard electrical parameters of oil-filled submarine cables and XLPE submarine cables; S2. Construct an electromagnetic transient simulation model of a hybrid submarine cable system based on standard electrical parameters. The hybrid submarine cable system is a three-phase transmission circuit, in which one phase uses XLPE submarine cable and the other two phases use oil-filled submarine cables. The two oil-filled submarine cables are of the same specification, and the three submarine cables are electrically connected through a multi-conductor coupled line unit. S3. Calculate the total phase resistance of the XLPE submarine cable based on standard electrical parameters. XLPE submarine cable phase total reactance Total resistance of oil-filled submarine cable phase Total reactance of oil-filled submarine cable phase ; Solve for the theoretical equilibrium reactance compensation value : Based on the theoretical equalization reactance compensation value Determine the range of ideal reactance compensation : in, , This is the proportionality coefficient, 0 < < <1; S4. Set up multiple series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range, apply each series reactance compensation scheme in the electromagnetic transient simulation model, and superimpose the corresponding reactance compensation values ​​in the two oil-filled submarine cable phases. Simulate and calculate the three-phase transmission power distribution, total transmission power and voltage imbalance under each series reactance compensation scheme. S5. Compare the simulation results of each series reactance compensation scheme, and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme; S6. Apply the optimal compensation scheme to the hybrid submarine cable system, and apply the series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively.

2. The reactive power compensation method 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 reactive power compensation method as described in claim 1, characterized in that, In step S3, , The calculation formula is: in, For the system capacitance ratio, , The total capacitance to ground of the oil-filled submarine cable phase.

4. The reactive power compensation method as described in claim 1, characterized in that, In step S5, after selecting the optimal compensation scheme, the optimal compensation scheme is applied in the electromagnetic transient simulation model, and then a safety verification is performed. If the safety verification fails, another series reactance compensation scheme is selected as the new optimal compensation scheme; if the safety verification succeeds, step S6 is continued.

5. The reactive power compensation method as described in claim 4, characterized in that, Security verification includes: Obtain the negative-sequence current and zero-sequence current in the electromagnetic transient simulation model, and determine whether the following conditions are met: The negative sequence current is lower than the preset negative sequence current protection setting. The zero-sequence current is lower than the preset zero-sequence current protection setting. Perform a power frequency resonant overvoltage test under non-full-phase operating conditions to determine whether the following conditions are met: The residual voltage at the end of the disconnected phase line is lower than the preset residual voltage safety threshold. The power frequency overvoltage of the healthy phase line is lower than the preset overvoltage safety threshold; If any condition is not met, the security verification is deemed to have failed; if all conditions are met, the security verification is deemed to have passed.

6. The reactive power compensation method as described in claim 5, characterized in that, The power frequency resonant overvoltage test under non-full-phase operating conditions shall be performed according to the following steps: S501. Disconnect any one phase of the submarine cable line in the electromagnetic transient simulation model; S502. Apply rated power frequency voltage to the remaining intact phase submarine cable lines; S503. Measure the residual voltage at the end of the disconnected phase line and the overvoltage amplitude of the intact phase line.

7. The reactive power compensation method as described in claim 1, characterized in that, The method for applying series reactance compensation to oil-filled submarine cables is to connect reactors with corresponding reactance values ​​in series to the line of the oil-filled submarine cable phase.

8. A reactive power compensation system for a hybrid submarine cable system, characterized in that, To implement the reactive power compensation method as described in any one of claims 1-7, the method includes: Standard electrical parameter acquisition module, used to acquire standard electrical parameters of oil-filled submarine cables and XLPE submarine cables; The simulation model building module is used to build electromagnetic transient simulation models of hybrid submarine cable systems based on standard electrical parameters. The ideal reactance compensation range calculation module is used to determine the ideal reactance compensation range; The simulation calculation module sets up multiple series reactance compensation schemes with reactance compensation values ​​within the ideal reactance compensation range. Each series reactance compensation scheme is applied in the electromagnetic transient simulation model. At the same time, the corresponding reactance compensation values ​​are superimposed on the two oil-filled submarine cable phases. The simulation calculation is performed on the three-phase transmission power distribution, total transmission power and voltage imbalance under each series reactance compensation scheme. The optimal solution selection module is used to compare the simulation results of each series reactance compensation scheme and select the series reactance compensation scheme with the largest total transmission power under the premise that the three-phase power imbalance is lower than the preset balance constraint as the optimal compensation scheme. The optimal solution execution module is used to apply the optimal compensation scheme in a hybrid submarine cable system, and to apply the series reactance compensation corresponding to the optimal compensation scheme to the two oil-filled submarine cables respectively.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor is used to execute a computer program, it implements the steps of the reactive power compensation method as described in any one of claims 1-7.

10. A storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the reactive power compensation method as described in any one of claims 1-7.

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