A shore power supply system with on-line diagnosis function of cross-linked polyethylene cable insulation aging and a control method thereof

Abstract

The present application relates to the technical fields of ship shore power system and cable state monitoring. A shore power supply system with cross-linked polyethylene cable insulation aging online diagnosis function, characterized in that it mainly comprises: an improved frequency conversion power supply module: on the basis of traditional voltage / current double closed loop control, the pulse width modulation link of the inverter is upgraded to make it have the double frequency modulation capacity of fundamental wave and high frequency characteristic signal; a high frequency signal acquisition unit: installed at the output end of the shore side frequency conversion power supply, containing a wide band high precision current transformer and a voltage sensor, specially used for capturing weak high frequency response echo; a state evaluation and early warning host: built-in digital filtering algorithm and cross-scale insulation aging diagnosis model, used for analyzing high frequency echo and outputting the health state index of the cable. The method can realize online accurate evaluation and early warning of the microcosmic insulation degradation state of the cable.

Description

Technical Field

[0001] This invention relates to the field of ship shore power systems and cable condition monitoring technology, specifically to a system and method for online monitoring and diagnosis of the insulation condition of high-voltage cross-linked polyethylene (XLPE) cables using shore power frequency converters. Background Technology

[0002] With increasingly stringent global requirements for energy conservation and emission reduction in ports, cold ironing, as a core means to effectively reduce air pollutant emissions from berthed ships, is being widely constructed and promoted. The basic operating logic of a shore power system is to convert the electrical energy from the main land-based power grid at the dock into electrical energy conforming to ship power standards through high-power frequency converters and other conversion equipment, and then transmit it to the berthed ships via high-voltage flexible cables. In this integrated shore-ship physical architecture consisting of "shore-side main grid – frequency converter – ship system," the high-voltage transmission cables connecting the dock and the ship serve as the link for energy transmission, and their operational reliability directly determines the safety foundation of the entire shore power supply network.

[0003] Currently, shore power systems extensively use cross-linked polyethylene (XLPE) as the main insulation material for high-voltage flexible cables. Unlike conventional land-based power grids where cables are laid in underground utility tunnels or cable trays in relatively fixed locations, shore power cables operate in extremely harsh environments. They are not only exposed year-round to the highly corrosive marine climate characterized by high salt spray, high humidity, and strong ultraviolet radiation, but also endure repeated mechanical dragging, winding friction, and joint plugging and unplugging during frequent berthing and unberthing operations of ships. Furthermore, when shore power frequency converters perform high-speed AC / DC switching conversion, they inevitably generate certain harmonic voltages at the output terminals. These high-frequency harmonics also exert additional long-term electrical stress on the cable insulation layer.

[0004] Under the combined effects of multiple stresses over a long period, the insulation layer of XLPE cables inevitably undergoes irreversible degradation. Moisture and impurities can penetrate into the insulation layer under the influence of alternating electric fields, causing dendritic microcracks, or "water treeing" aging. Localized electric field distortions can further induce the growth of even more lethal "electric treeing." If this continuous degradation of insulation performance is not detected in time, it can easily lead to insulation breakdown during the transient process of sudden addition or removal of high-power loads on ships, and may even cause catastrophic phase-to-phase short circuits or high-risk series arc fires.

[0005] Current engineering methods and academic assessment approaches for aging diagnosis of XLPE cables still have significant limitations. In terms of macroscopic electrical testing, conventional methods mainly rely on preventative DC withstand voltage tests, insulation resistance measurements, or offline partial discharge tests under power outage conditions. However, the degradation of insulation materials often begins with changes in their microstructure. To accurately investigate the aging mechanism and diagnose the degree of degradation in XLPE materials, existing materials science research typically requires obtaining destructive cross-section samples of retired cables and using sophisticated microscopic analysis instruments such as scanning electron microscopy (SEM) to directly observe the damage to the internal crystal morphology, the increase in the free volume of amorphous regions, and the evolution of micropores. Undeniably, using scanning electron microscopy for micromorphological analysis provides the most direct and accurate evidence for aging diagnosis, but this method has insurmountable destructiveness, time lag, and strong laboratory dependence. For flexible power supply cables operating at high frequency at docks, real-time destructive cross-section analysis is clearly impossible, and it is even more impossible to accurately predict sudden insulation collapse under current operating conditions based on past offline data.

[0006] On the other hand, from the perspective of the technological evolution of existing ship-to-shore power equipment, the vast majority of system control strategies focus on how to improve the power quality of the variable frequency power supply output, optimize the PI control parameters of the voltage and current dual closed loop, and deal with "system-level" power supply indicators such as reverse power backflow and low voltage ride-through during grid connection. Existing shore power variable frequency control systems often simply regard the power supply cable as an absolutely reliable ideal energy transmission channel, completely lacking the ability to sense the physical health status of this "transmission artery" itself.

[0007] In summary, existing offline power outage detection technologies cannot meet the continuous requirements of high-frequency shore power operations, while precise microscopic physical testing methods cannot be directly applied to online monitoring in industrial settings. How to cleverly overcome the bottleneck of destructive microscopic detection without interrupting the ship's normal AC fundamental wave power supply, and achieve online, non-destructive, and high-precision dynamic diagnosis of the insulation aging status of high-voltage XLPE cables for shore power, thus eliminating potential hazards at their inception, has become a pressing technical challenge in the field of ship-to-shore power technology. This invention is proposed precisely to fill this monitoring blind spot. Summary of the Invention

[0008] The purpose of this invention is to provide a shore power supply system and control method with online diagnostic function for insulation aging of cross-linked polyethylene cables. This method can achieve online accurate assessment and early warning of the microscopic insulation degradation state of cables.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: 1. System Architecture Level. A shore power supply system (topology) with online diagnostic function for cross-linked polyethylene cable insulation aging is characterized by mainly including: Improved inverter power supply module: Based on the traditional voltage / current dual closed-loop control, the pulse width modulation (PWM) stage of the inverter is upgraded with an algorithm to enable it to have dual-frequency modulation capability of fundamental frequency and high-frequency characteristic signal; High-frequency signal acquisition unit: installed at the output end of the onshore frequency converter (cable head end), including a wide-bandwidth high-precision current transformer and voltage sensor, specifically designed to capture weak high-frequency response echoes; Condition assessment and early warning host: Built-in digital filtering algorithm and cross-scale insulation aging diagnostic model, used to analyze high frequency echoes and output the cable health status index (SOH). The improved variable frequency power supply module, the high-frequency signal acquisition unit, and the status assessment and early warning host together constitute a closed-loop online diagnostic and flexible protection architecture. Their specific interconnections are as follows: (1) Electrical and signal sampling connection: The main power output terminal of the improved frequency converter power supply module is electrically connected to the first end of the high-voltage cross-linked polyethylene (XLPE) shore power cable; the high-frequency signal acquisition unit (including high-frequency current transformer and voltage sensor) is configured between the output terminal and the first end of the cable, and is connected to the main circuit line through electromagnetic coupling and parallel voltage division, for real-time sensing and acquisition of fundamental and high-frequency mixed electrical signals in the cable; (2) Uplink data communication connection: The digital signal output interface of the high-frequency signal acquisition unit is connected to the data acquisition input interface of the status assessment and early warning host through industrial communication links such as optical fiber or shielded twisted pair, and the extracted high-frequency response echo is transmitted back to the host in real time for micro aging mapping calculation. (3) Downlink closed-loop control connection: The control command sending interface of the status assessment and early warning host is connected to the communication interface of the underlying main control board inside the improved frequency converter module through the industrial communication bus; when the assessment host determines that the cable health index is close to the safety threshold, it sends an adaptive damping protection intervention command to the lower-level main control board through this control link.

[0010] Furthermore, the improved frequency converter module is architecturally divided into two parts: the main power hardware circuit (existing conventional components) and the control algorithm module (the improved unit of this invention); Internal components: Main power hardware circuit (existing conventional components): includes a rectifier unit, a DC bus unit, an inverter power unit (IGBT bridge arm), and an output LC filter unit connected in sequence; Control algorithm module: includes a high-frequency signal generation submodule, a multi-band instruction reconfigurator, an adaptive PI regulator, and a dual-frequency space vector pulse width modulation (SVPWM) waveform generation submodule; Interconnection relationships between components: Main power hardware connection relationship: The shore-side AC main grid is connected to the AC input terminal of the rectifier unit, the DC output terminal of the rectifier unit is connected to the DC bus unit, and the DC bus unit is connected to the DC input side of the inverter power unit; the AC output side of the inverter power unit, after passing through the output LC filter unit, serves as the final power output terminal of the entire improved frequency converter power module and is physically connected to the shore power supply cable. The coupling relationship between control algorithm logic and physical drive: In the logic link of the main control chip, the signal output terminal of the high-frequency signal generation submodule is connected to the input terminal of the multi-band instruction reconstructor, which is used to feed forward the generated weak high-frequency characteristic voltage instruction and superimpose it onto the conventional fundamental wave instruction; the parameter tuning receiver of the adaptive PI regulator is connected to the external state assessment and early warning host communication link; the output terminal of the multi-band instruction reconstructor and the output terminal of the adaptive PI regulator are connected together to the instruction input terminal of the dual-frequency SVPWM wave generation submodule; Cross-layer connection between algorithm and hardware: The PWM pulse signal with high frequency duty cycle generated by the dual-frequency SVPWM wave generator module is directly electrically connected to the gate drive circuit of each power switch (IGBT) in the inverter power unit.

[0011] The above structure shows that, without changing the physical topology of the main power hardware of conventional high-capacity frequency converters, the present invention achieves high-frequency signal detection and aging derating protection functions simply by reconstructing the control logic link and upgrading the algorithm components.

[0012] 2. Control and Diagnostic Methods. A control method for a shore power supply system with online diagnostic function for aging of cross-linked polyethylene cable insulation is characterized by the following steps: Step 1, Non-inductive characteristic signal injection: When the control module generates the inverter PWM drive signal, in addition to the conventional 50Hz / 60Hz fundamental wave command, it directionally superimposes a set of weak high-frequency AC voltage commands of a specific frequency; since the amplitude of this high-frequency signal is extremely small and the frequency is much higher than the fundamental wave, it will be naturally attenuated by the ship's own filter network or transformer leakage reactance, and will not cause any power quality pollution to the normal electrical equipment of the docked ship. Step 2, High-frequency response feature extraction: When a high-frequency signal with a specific frequency is transmitted in an XLPE cable, the cable insulation layer (equivalent to a distributed capacitance structure) will generate a corresponding small high-frequency leakage current; the high-frequency signal acquisition unit simultaneously captures the voltage and current waveforms, removes strong fundamental interference through a bandpass filter, and calculates the macroscopic electrical parameters under this specific frequency band, such as the high-frequency equivalent capacitance value and the dielectric loss factor (tanδ). Step 3, Macroscopic Electrical and Microscopic Morphology Mapping Diagnosis: Changes in the macroscopic high-frequency electrical characteristics of insulating materials are essentially caused by the destruction of their microscopic physical structure. This system has a built-in "macroscopic-microscopic" cross-mapping matrix. The baseline data of this matrix is ​​obtained by jointly calibrating the microscopic pore evolution, crystal morphology destruction, and dendritic channel characteristics observed under a scanning electron microscope (SEM) of XLPE materials at different aging stages with the corresponding high-frequency dielectric loss parameters. The system inputs the high-frequency electrical parameters measured in real time into this model, and can then reversely deduce the degree of degradation of the current internal microstructure of the cable. Once the assessed health index is lower than the safety threshold, an early warning mechanism is immediately triggered.

[0013] This invention addresses the technical deficiency of existing ship shore power systems, which struggle to perform real-time, non-destructive monitoring of the insulation aging status of high-voltage cross-linked polyethylene (XLPE) flexible power cables under uninterrupted power supply conditions. Breaking away from traditional offline detection methods during power outages, it cleverly reuses existing shore-based frequency converters as a high-frequency detection signal source. This allows for accurate online assessment and early warning of the cable's microscopic insulation degradation status without interfering with the ship's normal fundamental frequency (50Hz or 60Hz) power supply.

[0014] The beneficial effects of this invention are: 1. Enables online non-destructive monitoring: It completely eliminates the limitation of traditional withstand voltage tests that require power outages and disconnection, and also eliminates the need for destructive cable slicing and sampling for testing, ensuring the operational needs of high-frequency continuous power supply for port shore power.

[0015] 2. Extremely low hardware cost: It innovatively reuses the expensive high-capacity frequency converter power supply in the shore power system as the detection signal source. Only the frequency superposition algorithm needs to be added to the control software and a small high-frequency sensor needs to be installed at the output end. The modification cost is negligible.

[0016] 3. High diagnostic accuracy and foresight: A mapping model based on scanning electron microscope microscopic observation data is introduced, which directly links macroscopic electrical parameter drift with microscopic material crystal degradation. This enables extremely sensitive early warning before it develops into a serious series arc or breakdown short circuit accident, greatly improving the operational safety of shore-ship AC / DC hybrid microgrid system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 This is a flowchart illustrating a specific embodiment of the present invention.

[0019] Figure 2 This is the overall topology diagram of the shore power supply system with online diagnostic function according to the present invention.

[0020] Figure 3 This is a cross-mapping diagram of the health index (SOH) and high-frequency dielectric loss characteristics of this invention.

[0021] Figure 4 This is a comparison chart of cable life cycle monitoring and life evolution under different diagnostic technologies of this invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] Part One: I. System Architecture Level. A shore power supply system (topology) with online diagnostic function for aging of cross-linked polyethylene cable insulation mainly includes: Improved inverter power supply module: Based on the traditional voltage / current dual closed-loop control, the pulse width modulation (PWM) stage of the inverter is upgraded with an algorithm to enable it to have dual-frequency modulation capability of fundamental frequency and high-frequency characteristic signal; High-frequency signal acquisition unit: installed at the output end of the onshore frequency converter (cable head end), including a wide-bandwidth high-precision current transformer and voltage sensor, specifically designed to capture weak high-frequency response echoes; Condition assessment and early warning host: Built-in digital filtering algorithm and cross-scale insulation aging diagnostic model, used to analyze high frequency echoes and output the cable health status index (SOH). The improved variable frequency power supply module, the high-frequency signal acquisition unit, and the status assessment and early warning host together constitute a closed-loop online diagnostic and flexible protection architecture. Their specific interconnections are as follows: (1) Electrical and signal sampling connection: The main power output terminal of the improved frequency converter power supply module is electrically connected to the first end of the high-voltage cross-linked polyethylene (XLPE) shore power cable; the high-frequency signal acquisition unit (including high-frequency current transformer and voltage sensor) is configured between the output terminal and the first end of the cable, and is connected to the main circuit line through electromagnetic coupling and parallel voltage division, for real-time sensing and acquisition of fundamental and high-frequency mixed electrical signals in the cable.

[0024] (2) Uplink data communication connection: The digital signal output interface of the high-frequency signal acquisition unit communicates with the data acquisition input interface of the status assessment and early warning host through industrial communication links such as optical fiber or shielded twisted pair, and transmits the extracted high-frequency response echo back to the host in real time for micro aging mapping calculation.

[0025] (3) Downlink closed-loop control connection: The control command sending interface of the status assessment and early warning host is connected to the communication interface of the underlying main control board inside the improved frequency converter module through the industrial communication bus. When the assessment host determines that the cable health index is approaching the safety threshold, it sends an adaptive damping protection intervention command to the lower-level main control board through this control link.

[0026] The improved frequency converter power supply module is divided into two parts in terms of architecture: the main power hardware circuit (existing conventional components) and the control algorithm module (the improved unit of this invention).

[0027] Internal components: Main power hardware circuit (existing conventional components): includes a rectifier unit, a DC bus unit, an inverter power unit (IGBT bridge arm), and an output LC filter unit connected in sequence.

[0028] Control algorithm module: includes a high-frequency signal generation submodule, a multi-band instruction reconfigurator, an adaptive PI regulator, and a dual-frequency space vector pulse width modulation (SVPWM) waveform generation submodule.

[0029] Interconnection relationships between components: Main power hardware connection relationship: The shore-side AC main grid is connected to the AC input terminal of the rectifier unit, the DC output terminal of the rectifier unit is connected to the DC bus unit, and the DC bus unit is connected to the DC input side of the inverter power unit; the AC output side of the inverter power unit, after passing through the output LC filter unit, serves as the final power output terminal of the entire improved frequency converter power module and is physically connected to the shore power supply cable.

[0030] The coupling relationship between the control algorithm logic and the physical drive: In the logic link of the main control chip, the signal output terminal of the high-frequency signal generation submodule is connected to the input terminal of the multi-band instruction reconstructor, which is used to feed forward the generated weak high-frequency characteristic voltage instruction and superimpose it onto the conventional fundamental wave instruction; the parameter tuning receiver of the adaptive PI regulator is connected to the external state assessment and early warning host communication link; the output terminal of the multi-band instruction reconstructor and the output terminal of the adaptive PI regulator are connected together to the instruction input terminal of the dual-frequency SVPWM wave generation submodule.

[0031] Cross-layer connection between algorithm and hardware: The PWM pulse signal with high frequency duty cycle generated by the dual-frequency SVPWM wave generator module is directly electrically connected to the gate drive circuit of each power switch (IGBT) in the inverter power unit.

[0032] The above structure shows that, without changing the physical topology of the main power hardware of conventional high-capacity frequency converters, the present invention achieves high-frequency signal detection and aging derating protection functions simply by reconstructing the control logic link and upgrading the algorithm components.

[0033] II. Control and Diagnostic Methods. A control method for a shore power supply system with online diagnostic function for cross-linked polyethylene cable insulation aging includes the following specific steps: S001, based on Sensorless injection of multi-band feature detection signals in a rotating coordinate system: The core of this step lies in utilizing the inverter power supply's own underlying control algorithm to covertly "smuggle" the detection signal into the main power flow. Shore power inverter power supplies typically... Decoupling control is performed in a rotating orthogonal coordinate system. express Shaft (active shaft). express To avoid disrupting the stability of the system's original voltage outer loop and current inner loop, the system uses a specific high-frequency detection signal for the shaft (reactive shaft). The feedforward is directly superimposed onto the output of the inner-loop current regulator or the voltage reference command. Let the fundamental angular frequency of the power supply be... ,exist The mathematical model for command reconstruction in the coordinate system is as follows: Subsequently, through the three-phase inverse Park transformation ( arrive (Coordinate transformation) restores the perturbed quadrature voltage command to the target voltage in the three-phase stationary coordinate system that drives the inverter IGBTs. : Due to injection amplitude Strictly constrained to a tiny percentage of the rated fundamental amplitude, and At frequencies well above the fundamental frequency, this operation enables truly "unobtrusive" injection of characteristic signals into the ship's load.

[0034] Variable frequency power inverter Final voltage reference command on the shaft (active shaft).

[0035] Variable frequency power inverter Final voltage reference command on the shaft (reactive shaft).

[0036] Used to generate the fundamental frequency of normal power supply. Shaft base voltage component.

[0037] Used to generate the fundamental frequency of normal power supply. Shaft base voltage component.

[0038] The amplitude of the high-frequency characteristic detection voltage actively injected by the system.

[0039] : The angular frequency of the high-frequency characteristic detection voltage (its value is equal to ,in (The injected non-characteristic frequency).

[0040] : Time variable.

[0041] After coordinate inverse transformation, the three-phase stationary coordinate system target voltage command is output to the underlying PWM transmitter.

[0042] The angular frequency of the fundamental frequency for normal power supply in a shore power system (for 50Hz power supply). ).

[0043] S002, Weak high-frequency response echo extraction based on sidelobe suppression window function: When a voltage containing high-frequency components is applied to a shore power XLPE flexible cable, a weak high-frequency leakage current is induced in the distributed capacitance network of the insulation medium. Faced with the fundamental load current of hundreds of amperes in shore power systems, direct Fourier transform is prone to spectral leakage, causing the high-frequency characteristics to be submerged by the fundamental sidelobes. Therefore, a higher-order Blackman windowing function is introduced into the discrete sampling process. Its discrete expression is: Three-phase mixed current was synchronously acquired using a wideband current transformer. Then, the system accurately separates the target detection frequency using windowed Discrete Fourier Transform (WDFT). High-frequency response current phasor : Similarly, high-frequency voltage phasors can be extracted. This step completes the purification and extraction of weak signals in a port environment with strong electromagnetic interference.

[0044] : No. The weights of the Blackman window function corresponding to each sampling point.

[0045] : Current index of discrete sampling point ( ).

[0046] The total number of discrete sampling points within a single analysis data window.

[0047] The complex phasor of the high-frequency response current at the target detection frequency is obtained after filtering by the algorithm.

[0048] : The extracted high-frequency response voltage complex phasor at the target detection frequency.

[0049] : The discrete time-domain sequence value of a single-phase mixed current acquired by a high-frequency current transformer.

[0050] Imaginary unit.

[0051] : The angular frequency of the high-frequency characteristic detection voltage (its value is equal to ,in (The injected non-characteristic frequency).

[0052] : The sampling time step of the system analog-to-digital converter (ADC).

[0053] : Complex exponential twitch factor of Discrete Fourier Transform (DFT) (where The base of the natural logarithm, also known as the Euler number.

[0054] S003: High-frequency dielectric loss calculation considering temperature and length compensation After obtaining the pure voltage and current phasors, the system treats the entire long-distance XLPE cable as equivalent to a cable with distributed conductivity. and distributed capacitance The system constructs a lumped-parameter complex impedance network. The measured high-frequency complex admittance of the cable is first obtained using Ohm's law in the complex domain division. And by separating the real and imaginary parts, a preliminary equivalent capacitance can be obtained. and high-frequency dielectric loss factor : To mitigate the fluctuations in medium polarizability caused by drastic temperature variations in complex marine environments, a temperature compensation coefficient based on the Arrhenius equation is introduced into the system. Let the measured cable surface temperature be... The reference temperature is Activation energy is The ideal gas constant is The final calibrated standardized dielectric loss The calculation model is as follows: This formula ensures that the calculated macroscopic electrophysiological parameters have reliable longitudinal historical comparability.

[0055] The measured equivalent complex admittance of shore power cables in this high-frequency band.

[0056] : The measured equivalent distributed conductance separated from the complex admittance (representing the actual power loss of the insulating material).

[0057] : The measured equivalent distributed capacitance separated by the complex admittance (reflecting the polarization energy storage characteristics of the insulating layer).

[0058] : The high-frequency dielectric loss factor calculated from actual measurements at the current temperature.

[0059] : The standardized high-frequency dielectric loss factor after temperature compensation.

[0060] : The activation energy (constant, determined by the material properties) of cross-linked polyethylene (XLPE) insulation material during the aging reaction.

[0061] Ideal gas constant (approximately 8.314 J / (mol·K), suffix added here). Specifically designed for use with resistors distinguish).

[0062] : The absolute temperature of the cable surface or operating environment collected in real time by the temperature sensor (unit: Kelvin K).

[0063] The system's preset reference absolute temperature (usually 293.15K, which is the baseline ambient temperature at 20°C).

[0064] S004: Cross-mapping of health index based on SEM microporosity evolution equation Simple macroscopic electrical parameters do not possess intuitive physical meaning regarding aging life. The nonlinear surge in high-frequency dielectric loss of XLPE cables is essentially driven at the microscopic level by the fracture of cross-linked crystal lamellars, the expansion of free volume in amorphous regions, and the aggregation of microvoids. The embedded mapping model in the system is calibrated based on scanning electron microscopy (SEM) observation data. Let the volume fraction of micropores in the insulation layer determined by SEM observation and image processing be... It satisfies the effective medium correction equation with the standardized dielectric loss: in and For materials science prior fitting constants ( The range of values ​​is usually 100. and The value range is typically 1.5 to 4.5. The system solves this physical law in reverse to obtain the equivalent of microscopic degradation inside the insulation layer under the current state. Then, it substitutes this into the lifetime loss function and directly outputs a real-time health index characterizing the remaining mechanical and electrical strength of the cable. : This macro-micro cross-mapping algorithm gives the system the diagnostic ability to "see through" the degradation degree of the cable insulation microcrystalline structure even without power interruption.

[0065] : The inherent reference value of high-frequency dielectric loss of a pure XLPE material under ideal conditions, without any internal pores.

[0066] The volume fraction of micro-voids or water tree clusters within the insulation layer relative to the total material volume.

[0067] : A material science fitting proportionality constant characterizing the influence of micropores on macroscopic dielectric loss (the value range is usually 100%). ).

[0068] : Microstructure index factor reflecting the shape and distribution of micropores (typically ranging from 1.5 to 4.5).

[0069] : Cable in The real-time health index typically ranges from 0 (completely damaged) to 1 (completely healthy).

[0070] : The mapping weight coefficient for the transformation of micro-deterioration into macro-life loss (the specific value range is 0.85~1.15).

[0071] The initial healthy dielectric loss rating of this batch of newly manufactured XLPE shore power cables after temperature normalization.

[0072] The critical dielectric failure threshold set by the system before the insulation is about to experience avalanche breakdown or severe series arcing.

[0073] : A nonlinear degradation index that describes the exponentially accelerating rate of insulation deterioration in cables as they enter the middle and late stages of their lifespan.

[0074] S005: System-level breakdown transient damping and underlying PI parameter adaptive derating protection The early warning host continuously monitors The evolutionary trajectory. When Approaching or even falling below the critical safety threshold (e.g.) When the system determines that microscopic electrical trees inside the insulation have penetrated most of the effective insulation thickness, its ability to withstand sudden voltage surges is extremely vulnerable. At this point, the system not only triggers audible and visual alarms in the shore-side control room, but also directly intervenes in the underlying control circuit of the frequency converter power supply using the feedforward link. This is to prevent damage caused by sudden starts and stops of large ship loads. When a spike breaks down the remaining insulation, the system automatically introduces an exponential damping decay function, affecting the proportional gain of the outer voltage loop PI regulator. and integral coefficient Perform adaptive softening: By dynamically reducing the response gain, the system forcibly slows down the dynamic adjustment rate of the frequency converter when connected to the grid or experiencing sudden load changes. At the cost of sacrificing a very small portion of the transient power quality response speed, it fundamentally suppresses overvoltage spikes, thus achieving a "flexible life extension" operation mechanism for severely aged cables.

[0075] The outer loop of the frequency converter power supply voltage is in The current proportional adjustment gain after adaptive attenuation at any given moment.

[0076] The frequency converter is in a completely healthy state when the power supply network is in good condition (i.e. The nominal initial proportional adjustment gain is set at (time).

[0077] The intervention depth coefficient of transient damping (with a specific value range of 0.30~0.65) determines the maximum limit to which the system can tolerate a decrease in dynamic performance under extreme conditions.

[0078] The exponential decay factor of the damping ratio (specifically ranging from 2.5 to 5.5). The larger this value, the better the system's health index. The more violent the fall reaction, the earlier the protection should be activated.

[0079] Part Two: The inventive point of this invention: 1. Signal Source Multiplexing Technology – Innovation in System Hardware Architecture Traditional cable insulation testing typically requires disconnecting the cable from power and connecting bulky and expensive high-voltage testing equipment. The first breakthrough of this invention lies in breaking away from this conventional approach of "external equipment" and directly "requisitioning" the high-capacity frequency converter power supply of the shore power system itself. By performing "surgical" manipulation of the pulse width modulation algorithm at the underlying level of the frequency converter power supply, the high-frequency detection signal is cleverly and covertly superimposed on the normal... or It is transmitted in the fundamental frequency. This not only eliminates the need for an expensive external high-voltage signal generator, but also truly achieves "seamless" online monitoring without interrupting the ship's normal power supply.

[0080] 2. Precise Extraction of Weak High-Frequency Responses Under Strong Electromagnetic Interference Environments – An Innovation in Signal Processing Algorithms: In the actual operation of shore power at docks, the fundamental current of the power supply often reaches hundreds or even thousands of amperes, while the high-frequency leakage current generated by the insulation layer is only at the milliampere level. Finding weak high-frequency signals under such a strong power frequency background is like finding a needle in a haystack. This invention innovatively introduces a filtering extraction algorithm that combines a specific high-order sidelobe suppression window function with discrete transform. It acts like a highly customized digital noise reduction filter, which can cleanly and efficiently eliminate interference from the fundamental frequency and its harmonics, thereby accurately extracting the high-frequency voltage and current phasors reflecting the insulation state in an extremely noisy electromagnetic environment.

[0081] 3. "Macroscopic Electrical-Microscopic Morphology" Cross-Mapping Diagnostic Model—Core Mechanism and Lifetime Assessment Innovation): This is also the most significant technical barrier of this application. Traditional electrical monitoring often only involves simple comparisons of surface parameters, while this invention forcibly links the macroscopic high-frequency dielectric loss factor with the microscopic degradation of the insulating material. By incorporating a physical mapping evolution equation based on materials science microscopic data, the system is essentially equipped with an "electron microscope" that can see through the internal crystal structure of the cable, enabling direct and quantitative deduction of the cable's real-time health index through minute drifts in external electrical signals.

[0082] 4. Active closed-loop flexible derating protection based on insulation health index – an innovation in underlying control strategy: Conventional monitoring systems, upon detecting potential hazards, typically only issue audible and visual alarms and await manual intervention, lacking proactive intervention capabilities. The final piece of this invention provides the system with a proactive defense mechanism. When the system calculates the cable health index (… When the voltage approaches a critical point and the insulation is extremely weak, the early warning host will directly intervene in the underlying closed-loop control of the frequency converter, adapting the proportional gain of the low-voltage regulator. This forcibly limits the rate of change of transient voltage during sudden changes in ship load. This is equivalent to proactively providing a "flexible life-extending" buffer protection for aging cables before they face the risk of breakdown, thus cutting off the inducing chain of overvoltage breakdown at its source.

[0083] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A shore power supply system with online diagnostic function for aging of cross-linked polyethylene cable insulation, characterized in that... Mainly includes: Improved inverter power supply module: Based on the traditional voltage / current dual closed-loop control, the pulse width modulation stage of the inverter is upgraded with an algorithm to enable it to have dual-frequency modulation capability of fundamental and high-frequency characteristic signals; High-frequency signal acquisition unit: installed at the output end of the shore-side frequency converter power supply, it includes a wide-bandwidth high-precision current transformer and voltage sensor, which is specifically designed to capture weak high-frequency response echoes. Condition assessment and early warning host: Built-in digital filtering algorithm and cross-scale insulation aging diagnostic model, used to analyze high-frequency echoes and output cable health status index; The improved variable frequency power supply module, the high-frequency signal acquisition unit, and the status assessment and early warning host together constitute a closed-loop online diagnostic and flexible protection architecture. Their specific interconnections are as follows: (1) Electrical and signal sampling connection: The main power output terminal of the improved frequency converter power supply module is electrically connected to the first end of the high-voltage cross-linked polyethylene shore power cable; the high-frequency signal acquisition unit is configured between the output terminal and the first end of the cable, and is connected to the main circuit line through electromagnetic coupling and parallel voltage division, for real-time sensing and acquisition of the fundamental wave and high-frequency mixed electrical signal in the cable; (2) Uplink data communication connection: The digital signal output interface of the high-frequency signal acquisition unit is connected to the data acquisition input interface of the status assessment and early warning host through industrial communication links such as optical fiber or shielded twisted pair, and the extracted high-frequency response echo is transmitted back to the host in real time for micro aging mapping calculation. (3) Downlink closed-loop control connection: The control command sending interface of the status assessment and early warning host is connected to the communication interface of the underlying main control board inside the improved frequency converter module through the industrial communication bus; when the assessment host determines that the cable health index is close to the safety threshold, it sends an adaptive damping protection intervention command to the lower-level main control board through this control link.

2. A shore power supply system with online diagnostic function for insulation aging of cross-linked polyethylene cables according to claim 1, characterized in that, The improved frequency converter module is divided into two parts in terms of architecture: the main power hardware circuit and the control algorithm module. Internal components: Main power hardware circuit: includes a rectifier unit, a DC bus unit, an inverter power unit, and an output LC filter unit connected in sequence; Control algorithm module: includes a high-frequency signal generation submodule, a multi-band instruction reconstructor, an adaptive PI regulator, and a dual-frequency space vector pulse width modulation wave generator submodule; Interconnection relationships between components: Main power hardware connection relationship: The shore-side AC main grid is connected to the AC input terminal of the rectifier unit, the DC output terminal of the rectifier unit is connected to the DC bus unit, and the DC bus unit is connected to the DC input side of the inverter power unit; the AC output side of the inverter power unit, after passing through the output LC filter unit, serves as the final power output terminal of the entire improved frequency converter power module and is physically connected to the shore power supply cable. The coupling relationship between control algorithm logic and physical drive: In the logic link of the main control chip, the signal output terminal of the high-frequency signal generation submodule is connected to the input terminal of the multi-band instruction reconstructor, which is used to feed forward the generated weak high-frequency characteristic voltage instruction and superimpose it onto the conventional fundamental wave instruction; the parameter tuning receiver of the adaptive PI regulator is connected to the external state assessment and early warning host communication link; the output terminal of the multi-band instruction reconstructor and the output terminal of the adaptive PI regulator are connected together to the instruction input terminal of the dual-frequency SVPWM wave generation submodule; Cross-layer connection between algorithm and hardware: The PWM pulse signal containing high frequency duty cycle generated by the dual-frequency SVPWM wave generator module is directly electrically connected to the gate drive circuit of each power switch in the inverter power unit.

3. A control method for a shore power supply system with online diagnostic function for insulation aging of cross-linked polyethylene cables, characterized in that... Includes the following steps: Step 1, Non-inductive characteristic signal injection: When the control module generates the inverter PWM drive signal, in addition to the conventional 50Hz / 60Hz fundamental wave command, it directionally superimposes a set of weak high-frequency AC voltage commands of a specific frequency; since the amplitude of this high-frequency signal is extremely small and the frequency is much higher than the fundamental wave, it will be naturally attenuated by the ship's own filter network or transformer leakage reactance, and will not cause any power quality pollution to the normal electrical equipment of the docked ship. Step 2, High-frequency response feature extraction: When a high-frequency signal with a specific frequency is transmitted in an XLPE cable, the cable insulation layer will generate a corresponding small high-frequency leakage current; the high-frequency signal acquisition unit simultaneously captures the voltage and current waveforms, removes strong fundamental wave interference through a bandpass filter, and calculates the macroscopic electrical parameters under this specific frequency band. Step 3, Macroscopic electrical and microscopic morphology mapping diagnosis: The system has a built-in "macroscopic-microscopic" cross-mapping matrix. The baseline data of this matrix is ​​obtained by jointly calibrating the microscopic pore evolution, crystal morphology destruction and dendritic channel characteristics observed under a scanning electron microscope for XLPE materials at different aging stages with the corresponding high-frequency dielectric loss parameters. The system inputs the high-frequency electrical parameters measured in real time into the model, which can then reverse the degree of degradation of the current internal microstructure of the cable. Once the assessed health index is lower than the safety threshold, an early warning mechanism is immediately triggered.

4. The control method for a shore power supply system with online diagnostic function for insulation aging of cross-linked polyethylene cables according to claim 3, characterized in that... In step two, the macroscopic electrical parameters under a specific frequency band are: high-frequency equivalent capacitance and dielectric loss factor.

5. The control method for a shore power supply system with online diagnostic function for insulation aging of cross-linked polyethylene cables according to claim 3, characterized in that... The specific steps include the following: S001, based on Sensorless injection of multi-band feature detection signals in a rotating coordinate system: By utilizing the inverter power supply's own low-level control algorithm, the detection signal is covertly "smuggled" into the main power flow; shore power inverter power supplies typically... Decoupling control is performed in a rotating orthogonal coordinate system. express axis, express To avoid disrupting the stability of the system's original voltage outer loop and current inner loop, the system uses a specific high-frequency detection signal. The feedforward is directly superimposed onto the output of the inner loop current regulator or the voltage reference command; assuming the fundamental frequency of the power supply is... ,exist The mathematical model for command reconstruction in the coordinate system is as follows: Subsequently, through a three-phase inverse Park transformation, the perturbed quadrature voltage command is restored to the three-phase stationary coordinate system target voltage that drives the inverter IGBTs. : Due to injection amplitude Strictly constrained to a tiny percentage of the rated fundamental amplitude, and At frequencies far above the fundamental frequency, this operation enables truly "seamless" injection of characteristic signals into the ship's load; Variable frequency power inverter Final voltage reference command on the axis; Variable frequency power inverter Final voltage reference command on the axis; Used to generate the fundamental frequency of normal power supply. Shaft base voltage components; Used to generate the fundamental frequency of normal power supply. Shaft base voltage components; The amplitude of the high-frequency characteristic detection voltage actively injected by the system; The angular frequency of the high-frequency characteristic detection voltage is equal to... ,in For injected non-characteristic frequencies; Time variable; After coordinate inverse transformation, the three-phase stationary coordinate system target voltage command is output to the underlying PWM transmitter. The angular frequency of the fundamental wave for normal power supply in a shore power system, for a 50Hz power supply. ; S002, Weak high-frequency response echo extraction based on sidelobe suppression window function: When a voltage containing high-frequency components is applied to a shore power XLPE flexible cable, a weak high-frequency leakage current is induced in the distributed capacitance network of the insulation medium. Faced with the fundamental load current of hundreds of amperes in the shore power system, direct Fourier transform is prone to spectral leakage, causing the high-frequency characteristics to be submerged by the fundamental sidelobes. Therefore, a higher-order Blackman windowing function is introduced into the discrete sampling process. Its discrete expression is: Three-phase mixed current was synchronously acquired using a wideband current transformer. Then, the system accurately separates the target detection frequency through windowed discrete Fourier transform. High-frequency response current phasor : Similarly, high-frequency voltage phasors can be extracted. This step completes the purification and extraction of weak signals in a port environment with strong electromagnetic interference. : No. The Blackman window function weights corresponding to each sampling point; : The current index of the discrete sampling point ; The total number of discrete sampling points within a single analysis data window; : The complex phasor of the high-frequency response current at the target detection frequency after filtering by the algorithm; : Extracted high-frequency response voltage complex phasor at the target detection frequency; : The discrete time-domain sequence value of a single-phase mixed current acquired by a high-frequency current transformer; Imaginary unit; The angular frequency of the high-frequency characteristic detection voltage is equal to... ,in For injected non-characteristic frequencies; The sampling time step of the system's analog-to-digital converter; : Complex exponential twitch factor of the discrete Fourier transform, where The base of the natural logarithm; S003: High-frequency dielectric loss calculation considering temperature and length compensation After obtaining the pure voltage and current phasors, the system treats the entire long-distance XLPE cable as equivalent to a cable with distributed conductivity. and distributed capacitance The system constructs a lumped-parameter complex impedance network; the measured high-frequency complex admittance of the cable is first obtained by complex domain division using Ohm's law. And by separating the real and imaginary parts, a preliminary equivalent capacitance can be obtained. and high frequency dielectric loss factor : To eliminate the fluctuations in medium polarizability caused by drastic temperature changes in complex marine environments, the system introduces a temperature compensation coefficient based on the Arrhenius equation; assuming the measured cable surface temperature is... The reference temperature is Activation energy is The ideal gas constant is The final calibrated standardized dielectric loss The calculation model is as follows: This formula ensures that the calculated macroscopic electrophysiological parameters have reliable longitudinal historical comparability; Measured equivalent complex admittance of shore power cables at this high frequency band; The measured equivalent distributed conductance separated from the complex admittance represents the actual power loss of the insulating material; The measured equivalent distributed capacitance separated by the complex admittance reflects the polarization energy storage characteristics of the insulating layer. : The high-frequency dielectric loss factor calculated from actual measurements at the current temperature; Standardized high-frequency dielectric loss factor after temperature compensation conversion; The activation energy of the aging reaction of cross-linked polyethylene insulation materials; The ideal gas constant is 8.314 J / (mol·K), with the suffix added here. Specifically designed for use with resistors distinguish; : The absolute temperature of the cable surface or operating environment collected in real time by the temperature sensor, in Kelvin (K). The system's preset reference absolute temperature is typically set to 293.15K. S004: Cross-mapping of health index based on SEM microporosity evolution equation The nonlinear surge in high-frequency dielectric loss of XLPE cables is essentially driven at the microscopic level by the fracture of cross-linked crystal lamellars, the expansion of free volume in amorphous regions, and the aggregation of micropores. The embedded mapping model in the system is calibrated based on scanning electron microscopy (SEM) observation data. Let the volume fraction of micropores in the insulation layer determined by SEM observation and image processing be... It satisfies the effective medium correction equation with the standardized dielectric loss: in and These are the prior fitting constants in materials science. The range of values ​​is usually 100. , The value range is typically 1.5 to 4.5; the system solves this physical law in reverse to obtain the equivalent of microscopic degradation inside the insulation layer under the current state, and then substitutes it into the lifetime loss function to directly output a real-time health index characterizing the remaining mechanical and electrical strength of the cable. : This macro-micro cross-mapping algorithm gives the system the diagnostic ability to "see through" the degradation degree of the cable insulation micro-crystal structure even without power interruption. The high-frequency dielectric loss intrinsic benchmark value of a pure XLPE material without any internal pores under ideal conditions; The volume fraction of micropores or water tree clusters within the insulation layer relative to the total material volume. : A material science fitting proportionality constant characterizing the influence of micropores on macroscopic dielectric loss intensity; its value typically ranges from 100 to 100. ; : Microstructure index factor reflecting the shape and distribution of micropores, with a value range of 1.5 to 4.5; : Cable in The real-time health index at any given moment typically ranges from 0 to 1, where 0 represents complete damage and 1 represents brand new and healthy. The mapping weight coefficient for the transformation from microscopic degradation to macroscopic lifetime loss, with a specific value range of 0.85 to 1.15; The initial healthy dielectric loss rating of this batch of newly manufactured XLPE shore power cables after temperature normalization; The critical dielectric failure threshold set by the system before the insulation is about to experience avalanche breakdown or severe series arcing; : A nonlinear degradation index that describes the exponentially accelerating rate of insulation deterioration in cables as they enter the middle and late stages of their lifespan; S005: System-level breakdown transient damping and underlying PI parameter adaptive derating protection The early warning host continuously monitors The evolutionary trajectory; when When the voltage approaches or even falls below the critical safety threshold, the system determines that the microscopic electrical trees inside the insulation have penetrated most of the effective insulation thickness, making it extremely vulnerable to sudden voltage surges. At this point, the system not only triggers audible and visual alarms in the shore-side control room but also directly intervenes in the underlying control circuit of the frequency converter power supply using the feedforward link. This is to prevent damage caused by sudden starts and stops of large ship loads. When a spike breaks down the remaining insulation, the system automatically introduces an exponential damping decay function, affecting the proportional gain of the outer voltage loop PI regulator. and integral coefficient Perform adaptive softening: By dynamically reducing the response gain, the system forcibly slows down the dynamic adjustment rate of the frequency converter when connected to the grid or when the load changes suddenly. At the cost of sacrificing a very small part of the transient power quality response speed, it fundamentally suppresses overvoltage spikes and realizes a "flexible life extension" operation mechanism for severely aged cables. The outer loop of the frequency converter power supply voltage is in The current proportional adjustment gain after adaptive attenuation at any given moment; The nominal initial proportional gain of the frequency converter when the power supply network is in a completely healthy state; The intervention depth coefficient of transient damping, specifically ranging from 0.30 to 0.65, determines the maximum tolerance limit of dynamic performance degradation of the system under extreme conditions; The exponential decay factor of the damping ratio, specifically ranging from 2.5 to 5.

5. A larger value indicates a better system health index. The more violent the fall reaction, the earlier the protection should be activated.

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