749 results about "Circulating current" patented technology

The invention discloses a cable sheath ring current fault positioning in-loop simulation method and system based on LABVIEW. The method comprises the following steps: collecting ring current data of cable sheath monitoring points in real time under the control of LABVIEW, and carrying out digital display and graphical display; decomposing circulation data to obtain a wavelet coefficient and calculating features, and inputting a classification model to obtain a fault type when the features are abnormal; calculating a compensation coefficient considering the influence of the electromagnetic field, and calculating the position of a fault point in combination with a double-end traveling wave method; the operation model switches a typical working condition simulation mode, prediction of a Bayesian reasoning correction model is carried out, and the full-life-cycle operation state of the cable is simulated; and performing fault early warning through the LSTM model and risk assessment. The method can effectively improve the cable operation and maintenance efficiency and reliability, and is widely applied to cable fault detection and guarantee of safe and stable operation of a power system.

A method for testing sheath impedance in a high-voltage cable cross-bonding system. Three-phase current data and three-phase grounding circulating current data from a first cable body segment and a last cable body segment in cross-bonding units, and three-phase current data, three-phase grounding circulating current data, and three-phase induced voltage data from a cable body at a cross-bonding box are detected and collected, thereby directly calculating three-phase sheath impedance of the three cable segments and determining whether the three-phase sheath impedance is abnormal (step 5), thus determining whether the tested cross-bonding units have a defect. The present invention involves a simple operation, achieves an accurate testing result, and can achieve energized testing without an external excitation source. By performing real-time testing on the cross-bonding units and calculating the sheath impedance of the three cable segments in the cross-bonding units in real time, the states of the cross-bonding units can be determined in real time, which makes it possible to detect a cable fault immediately, thereby preventing a loss caused due to the cable fault.

The invention provides a modularized multi-level converter current control method based on feedforward analysis. The deviation between the direct-current side voltage and the reference value is stably monitored in real time based on the direct-current bus voltage, a first waveform signal is dynamically generated, and the direct-current side voltage fluctuation range is limited. According to the circulating current interphase voltage sharing, the dynamic deviation between the actual value and the rated value is calculated by collecting the capacitor voltage actual value of the bridge arm sub-module, and a second waveform signal is generated to balance the circulating current distribution of each phase of bridge arm. The loop current suppression based on feedforward analysis generates a third waveform signal to compensate for high-frequency loop current interference through real-time comparison of theoretical modeling and actual loop current components. In the modulation wave generation process, information in all aspects is integrated to accurately control the on-off state of the sub-module, so that the operation effect of the system is improved under the complex working condition, and the real-time performance and predictability of control are considered through combination of closed-loop adjustment and feed-forward compensation, so that the effectiveness of control is improved.

The invention relates to the technical field of cable fault diagnosis and positioning, in particular to a cable fault positioning method and system based on multi-source data space-time correlation, and the method comprises the steps: obtaining partial discharge, traveling wave and temperature multi-source monitoring data from a high-voltage cable-overhead line hybrid power transmission network; on the basis of space-time correlation analysis of partial discharge and temperature data, heat-electricity associated defect points are calibrated; comparing traveling waves of the cable and the overhead line, and identifying and inhibiting cross-domain propagation interference; positioning the traveling wave data which are not identified to obtain temporary coordinates, judging fault characteristics by fusing information such as sheath ring current and the like, and comparing the temporary coordinates with defect points to generate matching identification; and inputting multi-dimensional information such as fault features, defect matching identification and temperature into the fusion model, calculating the confidence coefficient of a fault mode, and outputting a cross validation positioning result. According to the invention, high-reliability positioning of mixed line faults and active early warning of insulation defects are realized by carrying out space-time correlation and fusion decision on multi-source monitoring quantities such as traveling waves, partial discharge, circulation, temperature and the like.

The invention relates to the technical field of converter power averaging and circulating current suppression, in particular to a power averaging and circulating current suppression method for parallel operation of a plurality of grid-forming type energy storage converters, which averages power through communication interaction and generates frequency and voltage compensation quantity by adopting a first regulator and a second regulator to realize accurate power averaging; meanwhile, the total current is measured locally, and virtual impedance feedforward control is adopted, so that rapid suppression of the high-frequency circulating current is realized. According to the invention, high-precision active power and reactive power equalization is realized, the capacity utilization rate is improved, high-frequency circulating current is effectively suppressed, loss and thermal stress are reduced, dynamic performance and system reliability are considered, a cooperative control architecture with complementary advantages is formed, adaptability to complex working conditions and system stability are enhanced, and engineering applicability is improved.

The invention relates to the technical field of parallel three-level converter control, and provides a parallel three-level converter model prediction control method and system, and the method comprises the steps: enabling a parallel three-level converter to be modeled as a series connection of an equivalent voltage source and an equivalent filter inductor according to the Thevenin theorem, enabling the parallel three-level converter to be equivalent to a five-level converter, and enabling the parallel three-level converter to be connected in parallel; a three-layer optimization control strategy is adopted; in the first layer, a candidate vector closest to a reference voltage vector is selected as an optimal five-level basic vector so as to track a parallel total output current; in the second layer, a redundant five-level voltage vector is selected to balance the neutral-point voltage; and in the third layer, selecting the candidate switching state which enables the circulating current suppression value function to be the minimum as the optimal redundant three-level switching state so as to suppress the circulating current. The method can effectively reduce output current harmonics under low switching frequency, and balance of neutral-point voltage and effective suppression of circulating current are realized to ensure safe and stable operation of a parallel converter system.

This invention discloses a method and system for suppressing capacitor voltage fluctuations in SiC MMC submodules, belonging to the field of electronic power technology. Based on the analysis results of the optimal broadband harmonic circulating current injection boundary and order for SiC MMC submodules, an optimized model for submodule capacitor voltage fluctuations is determined that simultaneously injects 2nd, 4th, and 8th harmonic circulating currents and 3rd harmonic voltages, which can fully utilize the higher control bandwidth characteristic of SiC MMC. By solving the optimized model for submodule capacitor voltage fluctuations, the amplitude and phase of the reference values ​​of the 2nd, 4th, and 8th harmonic circulating currents to be injected, as well as the amplitude and phase of the corresponding 3rd harmonic voltage, are determined. Then, by injecting 2nd, 4th, and 8th harmonic circulating currents and jointly injecting the 3rd harmonic voltage, broadband harmonic joint injection is achieved, reducing the capacitor voltage fluctuations of the submodule and realizing a method for suppressing capacitor voltage fluctuations in SiC MMC submodules with high suppression effect.

The invention provides a carrier modulation method and modulation-demodulation system for an MMC circulation suppressor, and the method comprises the following steps: obtaining MMC operation log data, carrying out the spectrum analysis, and extracting the spectrum amplitude distribution characteristics; identifying a bridge arm circulation condition based on the amplitude distribution characteristics, and further detecting bridge arm load abnormity and unit energy abnormity conditions; identifying a circulating current frequency component according to an energy abnormal condition, performing electric energy quality attenuation detection and initial circulating current position tracing, and determining a circulating current generation mechanism; and finally, based on the risk assessment result and the generation mechanism data, constructing a modulation parameter, and generating an adaptive circulation suppressor carrier modulation strategy. Compared with the prior art, the method has the following beneficial effects: through modulation of the circulating current suppressor, modulation of the circulating current suppressor is more accurate, so that the problems of inaccurate analysis of a bridge arm circulating current generation mechanism and inaccurate analysis of an energy abnormal condition of the MMC unit existing in carrier modulation of a traditional circulating current suppressor are solved.

The invention relates to the technical field of battery management, in particular to a lithium ion battery power storage method and system based on a BMS architecture, and the method comprises the steps: carrying out the grouping specification division of a battery pack according to an internal resistance range, and collecting the internal resistance fluctuation amplitude and terminal voltage deviation rate of each cluster in real time under a constant charging current working condition; calculating the internal resistance sensitivity coefficient of each cluster under the corresponding group based on the parameters, so as to quantify the cluster-level circulating current risk level, and synchronously obtaining the number of batteries in the cluster, the internal resistance standard deviation and the charging current working condition; calculating a compensation priority index of the battery cluster by integrating the circulating current risk grade, the number of batteries in the cluster, the internal resistance standard deviation and the charging working condition; and the battery cluster with the highest priority is selected as a reference cluster, internal resistance difference compensation voltage regulation is performed on the non-reference cluster through the BMS, the terminal voltage of each cluster is dynamically balanced, the circulation effect is inhibited, and the stability and energy utilization efficiency of the battery pack in the power storage process are improved.

The invention is suitable for the technical field of flexible power distribution of a power system, and discloses a modular multilevel converter multi-objective optimization method, system and device based on model predictive control and space vector modulation, and a medium. Obtaining an output current reference value and a circulating current reference value; obtaining a reference voltage vector based on the output voltage reference value, and screening out a plurality of groups of redundant voltage vector sequences through a space vector diagram; performing performance evaluation through rolling optimization by combining each redundant voltage vector sequence with a multi-target cost function to obtain an optimal voltage vector sequence; and on the basis of the optimal voltage vector sequence and the corresponding duty ratio, a switching signal for driving each sub-module switching device of the MMC is generated, and multi-target cooperative control is realized. The three targets of reference output current tracking, circulating current suppression and sub-module capacitor voltage balance are met, and the dynamic response capability, efficiency and reliability of MMC system operation are comprehensively improved.

The invention discloses a dynamic virtual impedance control method for multi-machine parallel connection of a network construction type energy storage converter, and belongs to the technical field of power electronics. The method aims to solve the problem that accurate reactive power distribution, circulating current suppression, dynamic response and voltage precision are difficult to consider in a multi-machine parallel system through fixed parameter virtual impedance. A dynamic adjustable virtual impedance module is introduced into the voltage outer loop output end of each converter, and virtual resistance and virtual inductance are calculated in real time based on locally measured output current, bus voltage change rate and adjacent machine reactive power deviation information; and the average reactive power of the system is estimated through a phase synchronization mechanism under the condition of no communication so as to realize multi-machine cooperation. According to the method, the reactive power distribution error is less than 5%, the bus voltage drop is less than 3%, the high-frequency circulating current is controlled within 5% of the rated current under all working conditions, and the dynamic performance and robustness of the system are remarkably improved.

The invention discloses a high-voltage cable line parameter extraction method and system based on online monitoring. The high-voltage cable line parameter extraction method comprises the steps of listing a multi-conductor transmission line equation containing a relation between voltage phasors and current phasors at the two ends of a cable based on a multi-conductor transmission line theory; multiple groups of cable operation data are collected at the two ends of the cable, and moments with different load amplitudes are selected for each group of cable operation data; reducing orders of a chain parameter matrix in the multi-conductor transmission line equation and the voltage phasor and the current phasor of the head end of the cable to obtain a multi-conductor transmission line equation after order reduction; substituting the acquired cable operation data into the multi-conductor transmission line equation after order reduction, and solving a chain parameter matrix after order reduction through matrix operation; and solving the length of the cable line by using the chain parameter matrix and the chain parameter matrix after order reduction. According to the method, the calculation precision of the theoretical value of the sheath circulating current is improved, and the misjudgment rate and the missed judgment rate based on online diagnosis of the sheath circulating current are reduced.

The invention discloses a control method for eliminating low-frequency circulating current of a zero common-mode voltage modulation strategy. The control method is used for eliminating the inherent low-frequency circulating current problem of the zero common-mode voltage modulation strategy. Existing zero common-mode voltage modulation strategies all adopt repeated vector sequences, low-frequency circulating current is inevitably introduced, and the practicability of the method is seriously affected. Therefore, the invention provides a control method for adjusting the switching time sequence, and the method realizes the balanced symmetry of the polarity of the circulating current in any two adjacent carrier wave periods by exchanging the switching signals of the parallel bridge arms or reversing the switching signals of the same bridge arm, thereby eliminating the problem of low-frequency circulating current introduced by an asymmetric sequence. According to the method, by adjusting related bridge arm switching signals, alternating conversion of circulating current polarity is achieved, and an original vector time sequence of an existing zero common mode voltage modulation strategy is not damaged. Therefore, the method achieves the optimal common-mode voltage of an existing algorithm, and further eliminates the inherent low-frequency circulating current.

The invention provides a prediction control method and system for two parallel three-phase converters based on ring current symmetry, and the method comprises the steps: firstly, screening out an optimal vector combination beneficial to ring current suppression, enabling the vector combination to overturn the polarity of the ring current change rate in a single period, and facilitating the optimization of the peak value and the average value of the ring current; on the basis, a brand-new model prediction control set is established; then, on the basis of the provided optimal control set, the circulating current average value is incorporated into a cost function of model prediction control, the provided cost function selects an optimal vector combination in real time by evaluating circulating current average value tracking errors of all combinations in two control periods, suppression of low-frequency circulating current and elimination of direct-current components are achieved, and meanwhile, the low-frequency circulating current and the direct-current components are controlled in real time. Due to the fact that the optimal vector combination achieves loop-to-polarity single-period flipping, the method can further push the loop frequency spectrum up to a high-frequency area. According to the invention, suppression of the low-frequency circulating current is realized, and the direct-current component of the circulating current is completely eliminated.

The invention discloses a power control method, system, equipment and medium for a modular multilevel converter, and belongs to the technical field of power electronics and power system application, and the method comprises the steps: collecting the bridge arm current, the sub-module capacitor voltage, the DC bus voltage and the AC side power of the modular multilevel converter; calculating a power error according to the AC side power and a power reference value, and calculating a sub-module capacitor voltage error according to the sub-module capacitor voltage and a voltage reference value; constructing a Lyapunov function comprising a plurality of control targets, wherein the Lyapunov function comprises a power error term, a sub-module capacitor voltage error term, a circulating current suppression term and a total energy balance term; and determining a control law on the basis that the Lyapunov function meets a stability condition, and controlling the modular multilevel converter according to the control law. According to the method, the coupling control problem of multi-terminal direct current system power distribution and sub-module energy balance is considered and improved.

The invention discloses an optimal switch time sequence design and modulation method for single-phase circulating current suppression of two parallel converters. The method comprises the following steps: firstly, screening 32 switch combinations which only introduces a certain phase of single-phase circulating current or does not introduce any single-phase circulating current from all 64 switch state combinations; secondly, designing a switching time sequence corresponding to the whole vector plane by using 32 switch combinations and considering the balance and switching times of single-phase circulating current in a switching period; in view of mutual overlapping of the time sequence modulation areas, single-phase circulation peak values of the time sequences are further compared to determine the optimal modulation areas, and then in view of redundancy of the time sequences in the optimal modulation areas, single-phase circulation effective values of redundant time sequences are further compared, and final sector division is determined according to the minimum effective values. And finally, designing action rules of modulation waves and carrier waves corresponding to each time sequence. The method solves the problem that an existing modulation method does not suppress the high-frequency single-phase circulating current of the two parallel converters.

The invention discloses a distributed cooperative voltage control method for a hybrid flexible traction substation group, and aims at solving the problems of output voltage cooperation, no-load circulating current suppression and multi-substation load distribution during networking operation of a plurality of hybrid flexible traction substations (HFTSS). Rapid synchronization of output voltage phases of the substations is achieved by introducing an average consistency algorithm, and nearby distribution of train loads among the traction substations is achieved by combining self-adaptive virtual impedance. According to the method, the capacity of the hybrid flexible traction substation for coping with the dynamic change of the external power grid voltage phase can be effectively enhanced, the loss of a contact network is reduced, the regenerative braking energy utilization efficiency is improved, and a feasible path is provided for large-scale application of a low-cost hybrid flexible traction power supply system and improvement of a cooperative control technology system.

The invention relates to the technical field of network construction type converters, in particular to a multi-machine parallel operation circulating current suppression method and system for a network construction type converter. By dynamically adjusting control parameters, cooperatively adjusting current and voltage and introducing a high-frequency impedance adjusting mechanism, generation of circulating current can be accurately inhibited in real time, and by obtaining the high-frequency impedance characteristic and the circulating current amplitude of each converter and generating the corresponding high-frequency impedance adjusting reference, the high-frequency impedance adjusting reference can be accurately adjusted. A high-frequency dynamic impedance adjusting model can be constructed according to power flow data, impedance parameters are further optimized, it is ensured that voltage output of each converter is kept consistent in a parallel system, and therefore the circulating current problem caused by voltage differences is avoided; ring current generation can be effectively reduced, and the electric energy quality and power distribution precision of the system are improved.

The invention provides a grid-connected and off-grid mode switching control method and device and an energy storage parallel operation system, and relates to the technical field of energy storage systems.The method comprises the steps that if the energy storage parallel operation system is not connected to mains supply within a preset voltage range, the energy storage parallel operation system is controlled to enter an off-grid mode; based on the first voltage characteristic information of the energy storage converter host, controlling the energy storage converter slave to adjust the first voltage parameter; if the electric supply in the preset voltage range is connected to the energy storage parallel operation system, controlling the energy storage converter host to enter a tracking pre-synchronization mode from an off-grid mode, controlling the energy storage converter host to track the electric supply and sequentially adjust the second voltage parameter, and controlling the energy storage converter host to track the energy storage converter host and sequentially adjust the third voltage parameter; and controlling the energy storage converter host and the energy storage converter slave to enter a grid-connected mode at the same time. According to the technical scheme, it is ensured that the voltage parameters of the host and the slave are consistent, parallel operation circulating current oscillation can be avoided to a great extent, and the possibility of system faults is reduced.

The invention discloses a method for determining control parameters of a network construction type wind-solar hybrid grid-connected system and electronic equipment. The method relates to the technical field of new energy control, and comprises the following steps: constructing a target function based on first control parameters corresponding to a plurality of units in the wind-solar hybrid grid-connected system; optimizing the first control parameter by taking a minimum function value of the target function as a target to obtain an optimized first control parameter; on the basis of the optimized first control parameters, second control parameters corresponding to the multiple units are optimized, and optimized second control parameters are obtained; and based on the voltage deviation, the angular frequency deviation and the dynamic compensation factor corresponding to the plurality of units, optimizing the third control parameters corresponding to the plurality of units to obtain the optimized third control parameters. According to the method, the technical problems of non-uniform reactive power distribution, serious circulating current and low dynamic response speed caused by different new energy unit types and line equivalent impedance differences are solved.

The invention discloses a multi-port DAB energy storage system directly connected with an elevator frequency converter bus and a cooperative control method of the multi-port DAB energy storage system, and is suitable for an elevator frequency converter direct-current bus direct-connection scene. Aiming at the defects in the aspects of elevator bus transient support, multi-branch extension and parallel operation safety access in the prior art, at least two DAB power branches are adopted, the low-voltage sides of the DAB power branches are connected into the same low-voltage direct-current source in parallel to realize current expansion, and the high-voltage sides of the DAB power branches are connected to a VFD direct-current bus through a parallel operation access switch to realize voltage expansion after being connected in series and laminated; the controller adopts fixed frequency phase shift control, and combines a two-line parallel operation or power-off time sequence and a zero-crossing residence strategy; through multi-branch phase interleaving, mutual exclusion amplitude limiting constraint, ZVS guarantee and a fault striding linkage mechanism, branch power balance, circulating current suppression and bus stable support are realized. According to the invention, the millisecond voltage of the bus can be efficiently suppressed, the response speed, the operation efficiency and the reliability of the system are improved, and the core requirements of elevator bus energy recovery and transient stability control are met.

The invention discloses an open-circuit fault diagnosis method and system based on cooperation of a current residual error and a zero-sequence circulating current, and relates to the technical field of fault diagnosis of a deep-sea wind power system. The method comprises the following steps: establishing a continuous time model based on two parallel two-level wind power converters in a wind power parallel conversion system; performing predictive current control according to the continuous time model, and calculating a current residual error; setting a residual threshold value, starting a window statistical mode based on the converters which trigger residual threshold crossing for the first time, and recording the residual threshold crossing state of each converter by using a plurality of windows; and carrying out open-circuit fault diagnosis and positioning on the wind power parallel conversion system according to the residual threshold crossing state and the zero-sequence circulating current direction information. According to the invention, rapid detection and accurate positioning of the open-circuit fault of the power device in the wind power parallel converter system are realized.

The application provides a high-frequency circulating current calculation method for a motor simulator cascaded coupling parallel structure, comprising the following steps: establishing an equivalent decoupling circuit model of each branch in the cascaded coupling parallel structure based on the voltage relationship of each branch in the motor simulator cascaded coupling parallel structure, wherein the equivalent decoupling circuit of each branch comprises an equivalent voltage source and an equivalent leakage inductance connected in series, and the equivalent leakage inductance is determined based on the self-inductance and mutual inductance of each branch choke; dividing a plurality of duty cycle intervals between 0 and 1, and the number of duty cycle intervals is equal to the number of branches in the cascaded coupling parallel structure; and using the equivalent decoupling circuit model to calculate the high-frequency circulating current of each branch when the duty cycle of the modulation signal of the motor simulator is in each duty cycle interval. The method provided by the application can accurately calculate the high-frequency circulating current of the motor simulator cascaded coupling parallel structure, and provides effective support for the targeted design of a high-frequency circulating current suppression scheme.

This application provides an inverter carrier synchronization system, belonging to the field of inverter control technology. The system includes multiple inverter devices connected via cascaded communication. Each inverter device includes a CPLD unit, a drive unit connected to the CPLD unit, a fault output unit, and a fault identification unit. The CPLD unit generates or forwards a carrier synchronization signal. The first contact of the relay in the fault output unit outputs a fault status signal to the next-level inverter device. The first-level inverter device acts as the master, and the fault status signal output by any normal inverter device is low. When any inverter device loses power or malfunctions, its relay disconnects, causing the output fault status signal to be high. Upon detecting the high-level fault status signal, the next-level inverter device automatically switches to become the master of the downstream inverter device. This system effectively suppresses high-frequency circulating currents in the system, improving system operating efficiency and stability.

Implementations described herein are related to a diode driver that recirculates residual current from an operating current pulse in an inductor. Such recirculation produces a diagnostic current pulse to a diode array for measuring a voltage drop across a portion of the array. For example, after a controller charges an inductor of a diode driver to deliver operating current pulses to a portion of a diode array for illumination, the controller causes a residual current to remain and recirculate in the inductor. In some implementations, in response to the recirculating current reaching a monitoring threshold, the controller delivers a monitoring pulse to the portion of the diode array to measure a voltage drop across the portion of the diode array. In some implementations, the controller may infer defectivity in the portion of the array from such voltage drop measurements over time.

The invention discloses a transformer parallel operation circulating current suppression method and system based on a cloud edge collaborative architecture, and relates to the technical field of power grid control, and the method comprises the steps: an edge node collects the multi-source dynamic data of a parallel transformer in real time, and constructs a local dynamic impedance model of a single transformer; the cloud receives the multi-modal data uploaded by each edge node, inputs the multi-modal data into an LSTM-SVM hybrid model trained based on a historical database, generates an impedance prediction weight of each edge node, and issues the impedance prediction weight to the corresponding edge node; the edge node receives the impedance prediction weight and injects the impedance prediction weight into a local dynamic impedance model to generate a corrected dynamic impedance matrix; and calculating a circulating current suppression instruction according to the corrected dynamic impedance matrix, and executing real-time regulation and control based on the circulating current suppression instruction. According to the method, the impedance prediction weight is generated through real-time collection of the edge nodes and calculation of the cloud, the local dynamic impedance model is effectively corrected, and then the circulating current suppression instruction is accurately calculated.

The invention discloses a hybrid MMC voltage-sharing control method and system based on second harmonic injection, and belongs to the technical field of hybrid MMC control for a flexible DC power transmission system, and the method comprises the steps: collecting the AC side output current of a hybrid MMC, constructing a plurality of input number combinations, and carrying out the voltage-sharing control of the hybrid MMC; obtaining an initial optimal input number combination through a model prediction control algorithm; collecting the capacitor voltage of each sub-module when the bridge arm voltage crosses the zero point for the first time, calculating the voltage difference, and screening out the maximum voltage difference; substituting the maximum voltage difference into a target function, solving by using a Bayesian adaptive direct search hybrid optimization algorithm to obtain a second harmonic circulating current reference value enabling the target function to be minimum, and optimizing to obtain a circulating current reference value; and constructing a combination candidate subset in combination with the initial optimal input combination, and obtaining an optimal input number combination through a model prediction control algorithm, thereby obtaining a control signal by using a capacitor voltage sorting algorithm, and completing efficient and stable hybrid MMC voltage-sharing control.

The invention discloses a multi-parameter collaborative optimization design method for a modular multilevel converter, and belongs to the technical field of modular multilevel converter design. In order to solve the problem of reasonable design of main parameters of the modular multilevel converter, a mathematical model of the modular multilevel converter is constructed; designing a capacitor voltage fluctuation model, a sub-module capacitor capacitance value model and a fluctuation quantity model, and analyzing the relationship between the capacitor voltage fluctuation and the operation condition and the relationship between the sub-module capacitor capacitance value and the operation condition; determining an upper limit value of the bridge arm inductance based on consideration of a system power operation range, determining a design initial value of the bridge arm inductance based on consideration of ring current suppression, determining a lower limit value of the bridge arm inductance based on consideration of resonance avoidance and fault current rise rate limitation, and obtaining a design range of the bridge arm inductance; adjusting the bridge arm inductance to obtain a design value of the designed bridge arm inductance; and according to the capacitance value of the sub-module capacitor and the design value of the designed bridge arm inductor, analyzing the peak voltage and the peak current of the power device IGBT to determine the parameter selection of the power device.

The invention discloses a fault current calculation method and system for a high-voltage alternating-current submarine cable grounding system and a storage medium, and the method comprises the following steps: enabling a power supply device and an electric device to be equivalent to an impedance and series voltage source combination and a load impedance based on the Thevenin equivalence theorem; in combination with the double-end grounding characteristic, a submarine cable loop is equivalent according to a pi type, and a three-phase equivalent circuit is constructed; determining a fault phase, and dividing the submarine cable as a left side and a right side by a fault point; a voltage loop equation is listed based on the Kirchhoff theorem, and a matrix recursion rule is deduced in combination with a double-side elimination principle. And establishing an analytic relationship between the main sections of the submarine cables at the power side and the short-circuit side and the fault circulating current according to a recursion rule. And with a fault point current equation as a boundary condition, left sheath fault circulation distribution is solved simultaneously. And repeating the steps on the right side to obtain right side distribution so as to obtain fault phase whole-line distribution. According to the method, the circulation distribution can be accurately calculated, the fault analysis accuracy and efficiency are improved, and support is provided for submarine cable operation and maintenance and the like.

The invention relates to the technical field of ice prevention and disaster reduction of high-voltage power transmission lines, and discloses a cascaded direct-current ice melting system of a high-voltage power transmission line, a control method and a device. The method comprises the following steps: inputting a test signal to the cascaded direct-current deicing system, and detecting the voltage and current of each node; calculating line impedance distribution based on the voltage and current of each node, and constructing a line equivalent model; calculating the minimum ice melting current based on the ice thickness monitoring data and the weather data, and calculating the output current of each ice melting device based on the minimum ice melting current and the line equivalent model; monitoring circulating current between systems, and calculating virtual compensation voltage based on the circulating current; and adjusting the output voltage of each ice melting device based on the virtual compensation voltage. The ice melting success rate, the safety of the system and the service life of the system can be improved.