3216results about "Electric power transfer ac network" patented technology

The invention relates to the technical field of operation prediction, in particular to an optical storage flexible direct current operation prediction method based on deep learning, and the method achieves the precise evaluation of photovoltaic power fluctuation through the analysis of historical operation data and the combination of a power state conversion matrix, guarantees that the energy storage charging and discharging rate can be matched with the load demand distribution, and improves the prediction precision. Power scheduling is optimized, topology analysis and power flow path identification are carried out, topology weight calculation is carried out by using a graph convolutional network, power flow can be dynamically adjusted, the adaptability of an operation mode is improved, the influence of power fluctuation on system stability is reduced, power matching is carried out by adopting an adversarial generative network, photovoltaic output is optimized, and the system stability is improved. The energy storage release path is more reasonable, the power loss is reduced, the overall power distribution efficiency is improved, and the load compensation strategy is optimized through short-period fluctuation detection and long-period trend fitting. And variable correction is performed based on error calculation and anomaly detection, so that the reliability of regulation and control response is improved.

The invention relates to the technical field of power system stability control, in particular to a broadband oscillation suppression method and system for an offshore wind power flexible direct current grid-connected system and a medium, and the method comprises the steps: sequentially injecting positive and negative sequence perturbation sine harmonic signals at a grid-connected point of a wind turbine generator, constructing a multi-input multi-output impedance matrix, reducing the order of the multi-input and multi-output impedance matrix into single-input and single-output equivalent positive sequence impedance; the stability margin of the offshore wind power flexible direct current grid-connected system is obtained based on equivalent positive sequence impedance quantification; when the stability margin is lower than a preset margin threshold value, reconstructing the fan grid-side converter into a matrix control structure by cascading a weighting coefficient matrix between the inner and outer ring control loops of the fan grid-side converter; and iteratively optimizing the matrix type control structure based on impedance sensitivity, and synchronously connecting a low-pass filter in series in a voltage and current feedback channel to carry out impedance remodeling so as to finish broadband oscillation risk suppression. According to the invention, broadband oscillation suppression of the offshore wind power flexible direct current grid-connected system is realized through impedance modeling and a matrix type control strategy.

The invention relates to the field of converter station equipment parameter analysis, and provides a converter station equipment parameter analysis method and system based on multi-parameter fusion monitoring, and the method comprises the following steps: collecting multi-parameter characteristic data of converter station equipment; performing streaming processing and abnormal mode identification on the multi-parameter characteristic data to obtain equipment abnormity early warning information of the converter station equipment; constructing a time-varying graph neural network model based on the multi-parameter feature data, obtaining a space-time dependency relationship among parameters through a causal reasoning method, and dynamically adjusting the feature weight of the time-varying graph neural network model in combination with a reinforcement learning algorithm to obtain a running state evaluation model; and inputting the real-time state feature sequence into the operation state evaluation model to obtain an equipment operation state evaluation result, and visually displaying the equipment operation state evaluation result and the abnormal early warning information to obtain a comprehensive operation state evaluation report of the converter station equipment. According to the invention, real-time monitoring and evaluation of the operation state of the converter station equipment are realized.

The invention discloses an SLCC control method and system based on similar network type SVF assistance, and the method comprises the steps: generating a first SVF voltage instruction value through an active outer ring and a reactive outer ring, processing the first SVF voltage instruction value through a voltage ring, and obtaining a fundamental frequency reactive compensation current instruction value; processing the LCC output current by using a multi-synchronous rotation coordinate method to obtain a harmonic compensation current reference value; and superposing the fundamental frequency reactive compensation current instruction value and the harmonic compensation current reference value, obtaining a second SVF voltage instruction value in combination with a current inner loop controller, and processing the second SVF voltage instruction value by using a voltage-sharing control strategy and a carrier phase-shifting modulation strategy to obtain a switching signal for controlling the SVF. According to the method, the dependence of the SVF on an alternating current system is reduced, stable and independent operation of the SVF in the SLCC by virtue of the self regulation capability is favorably realized, and the operation reliability and stability of the SLCC are improved.

The invention discloses a direct-current power transmission receiving end and a direct-current power transmission system. The direct-current power transmission receiving end comprises an inverter circuit and a receiving end transformer; the inverter circuit comprises a hybrid power grid commutation converter and a modular multi-level converter; a direct current first end of the hybrid power grid commutation converter is used for connecting a direct current power transmission line, a direct current second end of the hybrid power grid commutation converter is connected with a direct current first end of the modular multilevel converter, and an alternating current end of the hybrid power grid commutation converter is connected with a receiving end alternating current bus through a corresponding receiving end transformer; the direct current second end of the modular multilevel converter is grounded, and the alternating current end of the modular multilevel converter is connected with the receiving end alternating current bus through the corresponding receiving end transformer. In the embodiment of the invention, the hybrid power grid commutation converter and the modular multi-level converter which are connected in series are used at the direct-current transmission receiving end, so that the direct-current transmission receiving end has direct-current side fault ride-through capability and alternating-current side fault ride-through capability.

The invention relates to a reliability evaluation method and system for a flexible AC / DC power distribution network containing an optical storage system in the field of flexible AC / DC power distribution networks. The method comprises the following steps: collecting photovoltaic data, energy storage data, AC / DC bus data and the like in real time; constructing a multi-time scale dynamic topology model, and establishing a failure probability distribution function; load flow calculation based on an improved forward-backward substitution method; adopting an N-1 + N-1-1 composite fault screening strategy to simulate a typical disturbance scene; establishing a vulnerability evaluation matrix to calculate power failure probability and other indexes; designing an optimal scheduling strategy based on model predictive control; multi-time-scale reliability evaluation is carried out; and outputting an evaluation report and a topology reconstruction suggestion. The system comprises a data acquisition unit, a dynamic modeling unit and the like, and an evaluation and analysis unit is internally provided with an algorithm module and is configured with an FPGA acceleration card. The method breaks through the limitation of traditional steady state evaluation in the technology level, improves the load flow calculation speed in the calculation efficiency level, reduces the operation cost in the application value level, improves the energy storage efficiency, and provides support for reliability evaluation of a novel power system.

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 discloses a fault ride-through test method for an offshore wind power flexible direct output system, and the method comprises the steps: building a fault equivalent circuit of the offshore wind power flexible direct output system, analyzing the operation characteristics of an AC power grid side under a low-voltage fault, and determining the incidence relation between the DC side excess energy and the power grid voltage drop; establishing a model representing each component in the fault equivalent circuit, wherein the components at least comprise a machine-side converter, a grid-side converter, a direct-current capacitor and an unloading resistor; when a low-voltage fault of an alternating-current power grid side is detected, executing the following cooperative control based on the model: synchronously starting unloading resistance control and reactive power support control, wherein an unloading resistor dissipates excess energy of a direct-current side through a direct-current chopper; the grid-side converter injects a capacitive reactive current which is deeply matched with the voltage drop of the power grid so as to improve the voltage of a grid-connected point; and if the direct-current voltage continuously exceeds the preset threshold value, starting power prompt drop control, and reducing the output power of the unit according to a gradient until the system recovers to be stable.

The invention relates to the technical field of AC / DC module control, and discloses an intelligent control method and system for multi-mode switching of an AC / DC module. According to the method, a dynamic topology mapping model is constructed according to an impedance spectrum matrix, and a physical connection relation is converted into a node admittance relation network; generating an energy distribution state sequence based on the power fluctuation vector, and analyzing migration constraint conditions among different operation modes by adopting an association rule mining algorithm; when an operation mode switching instruction is detected, activating a node admittance relation network in the dynamic topology mapping model, and inputting a current energy distribution state sequence to an association rule mining algorithm; according to a real-time matching result of the node admittance relation network and the migration constraint condition, generating a switching control instruction containing an impedance adjustment gradient and a power distribution weight; and the power semiconductor execution unit transmits the switching control instruction to the AC / DC module. According to the method, multi-mode intelligent switching control of the alternating-current and direct-current module can be realized.

The invention relates to the technical field of power systems, and discloses a broadband oscillation risk assessment method and system for offshore wind power through a flexible direct current sending-out system, and the method comprises the steps: dividing a broadband oscillation risk assessment frequency band into a medium-high frequency band and a sub-super-synchronous frequency band; aiming at different broadband oscillation risk assessment frequency bands, respectively establishing an offshore wind power plant side impedance model and a flexible direct current converter side impedance model in a corresponding offshore wind power flexible direct current sending-out system, and determining an equivalent impedance frequency characteristic curve of the offshore wind power plant side and the flexible direct current converter side. The broadband oscillation risk of the offshore wind power through the flexible direct current sending-out system is comprehensively evaluated by using the equivalent impedance frequency characteristic curve, the topological structure and the operation condition are fully considered, and the accuracy and adaptability of evaluation are improved. And when the broadband oscillation risk occurs, the system is adjusted in a targeted manner according to different evaluation frequency bands, so that the broadband oscillation risk is effectively eliminated, and the operation stability of the offshore wind power output system through the flexible direct current is enhanced.

The invention relates to a controllable turn-off converter valve for a high voltage direct current (HVDC) system, each converter valve arm comprises a valve arm voltage-sharing device and a plurality of cascaded controllable turn-off converter modules, and each controllable turn-off converter module comprises an assembly voltage-sharing device and a plurality of cascaded controllable turn-off converter assemblies. Each controllable turn-off current conversion assembly is configured to comprise at least one voltage-sharing circuit and at least one controllable switching device, and two ends of each controllable switching device are provided with one voltage-sharing circuit in parallel. Therefore, the controllable turn-off converter valve can realize voltage sharing at each level, the requirement of the controllable turn-off converter valve on the consistency of controllable switching devices is reduced, a large number of controllable switching devices can be connected in series in the same converter valve arm, and reliable conversion of extra-high voltage direct current transmission at the voltage level of + / -800 kilovolts and above is realized. The problem of commutation failure of the extra-high-voltage direct-current type converter valve is solved, and safe and stable operation of a power system is ensured.

The invention discloses a direct-current voltage self-balancing method in the high-low voltage ride-through process of a high-voltage frequency converter, and the method comprises the steps: obtaining an electric signal of the high-voltage frequency converter, calculating the Lyapunov index of a system in real time based on the electric signal, so as to quantify the chaotic state of the system, and generating a real-time Lyapunov index sequence; according to the real-time Lyapunov index sequence, the gradient of the real-time Lyapunov index sequence relative to a preset system state variable is determined, and a Lyapunov gradient field is constructed; using the Lyapunov gradient field to generate a basic control quantity through nonlinear mapping; and converting the basic control quantity into a pulse width modulation parameter to form a PWM control signal set to be applied to the high-voltage frequency converter. According to the method, the Lyapunov gradient field is constructed to provide prospective direction guidance for control, so that the chaotic oscillation is quickly suppressed, and the dynamic stability of the system under power grid disturbance is remarkably improved.

The invention provides a power grid frequency modulation method and device based on MMC bridge arm capacitor multiplexing, and relates to the technical field of power grid frequency control. In order to solve the problem of functional conflict between participation of an MMC bridge arm capacitor in power grid frequency control and voltage stabilization and filtering, full-bridge multiplexing transformation is carried out on an MMC bridge arm sub-module, the MMC power throughput capacity is enhanced in a parallel super capacitor mode, regulation and control of the bridge arm capacitor on voltage fluctuation are enhanced, and meanwhile, the supporting capacity on the power grid frequency is improved; by simulating frequency characteristics of a synchronous machine, a principle and a method for the MMC to participate in power grid frequency support are analyzed, a power grid frequency modulation model for the MMC to participate in the MTDC system is constructed, and a power grid frequency modulation method for the MMC to participate in the MTDC system is optimized; the frequency deviation generated when the active power of the power grid and the load demand are unbalanced is used as frequency modulation model input, and a corresponding frequency modulation strategy is adopted based on the frequency modulation demand of the MTDC system. According to the invention, reasonable distribution of power required by frequency modulation can be realized, and the comprehensive stability characteristic of a novel power system is improved.

The invention discloses a cooperative ride-through control method for a new energy flexible direct current transmission system under a receiving end fault, and relates to the technical field of flexible direct current transmission, and the method comprises the steps: periodically collecting the grid-connected point voltage of a receiving end converter station, an output active current reference value, and the real-time data of the online impedance estimation of a converter station side; calculating the minimum possible true values of the converter station side equivalent reactance and the short circuit point voltage; calculating a reactive current reference value and an active current reference value of the flexible DC receiving end converter station after the fault occurs; calculating the input time of the energy consumption resistor; the reactive current reference value, the active current reference value and the energy consumption resistor input moment are sent to a receiving end converter station; and when the receiving-end converter station detects that the voltage drop of the grid-connected point meets the low-voltage crossing starting condition, the receiving-end converter station enters a low-voltage crossing control mode and starts control, and the receiving-end converter station performs corresponding adjustment. By the adoption of the method, the rising speed of the direct-current voltage is reduced fundamentally, the input time or the input frequency of an energy consumption device is reduced, and the economical efficiency of fault ride-through is improved.

The invention belongs to the technical field of DC power grid short-circuit current calculation, and particularly relates to a short-circuit current calculation method for a metal backflow four-terminal bipolar DC power grid, and the method comprises the steps: S1, building an MMC equivalent model; s2, constructing and processing an equivalent circuit of a Bergeron lossy transmission line of the DC line to obtain a Bergeron two-port equivalent model of a single-phase transmission line and a Bergeron equivalent model of a three-phase transmission line; s3, establishing an equivalent model of the metal backflow four-terminal bipolar direct current power grid; s4, establishing an accompanying circuit model of the metal backflow four-terminal bipolar direct current power grid; s5, constructing a conductance matrix G, and forming a node voltage equation; and S6, according to the fault type, modifying a node admittance matrix G in the node voltage equation into an equivalent conductance matrix G ', and then solving the modified node voltage equation to obtain the branch current and the node voltage after the fault. According to the method, the problem that the short-circuit current calculation method of the metal backflow four-terminal bipolar direct-current power grid is insufficient in accuracy can be solved.

The invention provides a multi-direct-current feed-in power grid transformation method and system based on risk assessment. The method comprises the steps that risk assessment comprehensive indexes of flexible transformation schemes of all receiving ends are obtained through an electromechanical electromagnetic hybrid transient simulation model; obtaining a risk evaluation result of each receiving end flexibility transformation scheme according to the risk evaluation comprehensive index, and screening a preset number of receiving end flexibility transformation candidate scheme sets; performing multi-target evaluation by using an evaluation model based on an analytic hierarchy process, and determining a final receiving end flexible transformation candidate scheme; and transforming the multi-direct-current feed-in power grid according to the determined final receiving end flexible transformation candidate scheme. According to the method, comprehensive, accurate and efficient evaluation of the receiving end flexible transformation candidate scheme is realized aiming at the direct current planning requirement of a load concentration large area, and the technical effect of improving the overall stability and the fault handling capacity of a power grid is further achieved.

The invention provides a collaborative suppression method for short-circuit current-subsynchronous oscillation of an offshore wind power flexible direct current system, and the method comprises the steps: 1, determining a common parameter for a broadband coupling problem: determining the common parameter through a system topological structure and theoretical analysis of offshore wind power which is directly connected to a receiving-end power grid through flexible direct current for the short-circuit current and subsynchronous oscillation problem; 3, an upper optimization layer based on the DDQN outputs an optimal adjustment instruction for the generality parameters according to the system state, a lower execution layer receives the adjustment instruction of the upper layer, a new generality parameter value is obtained and output to a current inner loop controller, and a current inner loop controller is constructed; the current inner loop controller generates a modulation signal to control the output of the converter. According to the invention, the dynamic damping controller is designed to optimize common parameters, so that collaborative suppression of short-circuit current and subsynchronous oscillation is realized.

The invention relates to the technical field of building electrics, and particularly provides a control method and system of an optical storage direct flexible system. The control method comprises the following steps: acquiring power load data of a target building within a preset time; acquiring illumination meteorological data in the preset time; obtaining a power load prediction curve according to the illumination meteorological data and the power load data; based on the power load prediction curve, constructing a control relationship between the direct current bus voltage at the grid-connected part of the optical storage direct-flexible system and the total grid-connected power; and based on the control relationship, performing power regulation according to the voltage change condition of the direct current bus. According to the invention, when the real-time power deviates from the predicted optimal load value, such as the inflection point, the optical storage direct-current flexible system can automatically deploy the power of the energy equipment connected to the direct-current bus. And system power response is completed according to the flexible capacity potential of the equipment, so that the system operation state tends to be economically optimal.

The invention relates to the technical field of power grid control, in particular to a control method of a network following / constructing new energy LCC-HVDC grid-connected system, electronic equipment and a storage medium. System optimization control is realized through six key steps: firstly, obtaining basic parameters such as a network construction new energy capacity ratio and a system short-circuit ratio; secondly, calculating reactive vacancy of the system; then determining a system working mode; establishing a new energy mathematical model; a cooperative control strategy is obtained; and finally formulating a high-low penetration control strategy. Therefore, a complete control closed loop is established, and a systematic solution is formed from parameter acquisition to strategy execution. And the advantages of the following network type new energy and the constructed network type new energy are integrated, so that the high efficiency of the following network type new energy is reserved, and the power grid supporting capability of the constructed network type new energy is also realized.

The invention discloses a main and distribution network hierarchical coordinated scheduling method and device considering a unified power flow controller and flexible alternating current and direct current interconnection, which are used for solving the technical problem of poor system dynamic stability of a main and distribution network caused by the existing main and distribution network coordinated scheduling technology based on the unified power flow controller. The method comprises the steps of obtaining main and distribution network power flow data and a topological structure, and generating an initial main network power reference instruction, a node power-voltage sensitivity matrix and converter reference power in combination with a double-voltage source equivalent model of a preset UPFC; and obtaining an initial node cluster converter power instruction and a UPFC active power regulation instruction by using the data and the sensitivity matrix based on a Newton-Raphson method combined power flow model. And calculating a weight coefficient through the initial main network power reference instruction and the UPFC regulation instruction, and correcting the initial instruction and the converter reference power according to the weight coefficient. And finally, a main and distribution network hierarchical coordinated scheduling scheme is formed.

The invention relates to the technical field of power electronic devices, in particular to a low-voltage direct-current circuit breaker, a fault protection method and a related device.The low-voltage direct-current circuit breaker comprises a through-flow branch, a transfer branch and an energy consumption branch which are connected in sequence; the through-current branch comprises an isolating switch and an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) commutation switch which are connected in series; the transfer branch comprises a first power electronic switch group and a buffer branch which are connected in parallel; the energy consumption branch comprises a first metal oxide MOV, a second metal oxide MOV and a second power electronic switch group; the first metal oxide MOV is connected in parallel with the second power electronic switch group; and the second metal oxide MOV is respectively connected with the first metal oxide MOV and the second power electronic switch group. The technical problems that an existing hybrid direct current circuit breaker is not suitable for a low-voltage direct current system and the loss is high in the turn-off process are solved.

The invention discloses a method for improving the stability of a system for sending out deep and far sea wind through a dual-port light converter. The method comprises the following steps: introducing a voltage feed-forward path comprising a phase compensator and a low-pass filter into an MMC differential mode control loop in the dual-port light converter; and a compensator parameter feasible region is calculated based on the phase characteristics of the oscillation risk frequency band, and the cut-off frequency of the filter is set, so that targeted phase compensation and impedance remodeling are realized, and the damping of the dual-port light converter is effectively enhanced. According to the method, the impedance characteristic of the dual-port light-weight current converter in the oscillation risk frequency band is remarkably improved, and a reliable technical path is provided for improving the stability of the dual-port light-weight current converter.

The invention discloses a fault processing method for an offshore wind power direct current parallel sending-out system through a DRU-MMC. The fault processing method comprises the steps that direct current energy consumption devices are arranged at direct current outlets of respective land MMC converter stations of a DRU-HVDC system and an MMC-HVDC system; when the alternating current power grid at the receiving end has an alternating current fault, the direct current energy consumption device is controlled to adopt a direct current voltage suppression strategy; when the DRU-HVDC system and the MMC-HVDC system respectively have direct current faults, different locking and circuit breaker disconnection time sequence control strategies are adopted, and in the direct current fault ride-through period, a direct current suppression strategy and a direct current voltage suppression strategy are controlled to be adopted by a direct current energy consumption device of the DRU-HVDC system. Therefore, the fault ride-through capability of the DRU-MMC direct current parallel sending-out system of the offshore wind power can be effectively improved, and stable operation of the system is ensured.

The invention discloses an offshore wind power collecting and sending-out system and method based on a multi-port multi-frequency alternating current and direct current hybrid integrated platform, and belongs to the field of power transmission and distribution of power systems. The system comprises an intermediate-frequency, power-frequency and low-frequency wind power collection subsystem, an offshore integrated platform, a direct-current sending-out submarine cable, a low-frequency sending-out submarine cable, an onshore converter station and an onshore frequency conversion station. The various wind power collection subsystems respectively collect wind turbine generator group outputs with corresponding frequencies and send the wind turbine generator group outputs to the offshore integrated platform; the offshore integrated platform converts intermediate-frequency, power-frequency and partial low-frequency electric energy into direct current and then transmits the direct current to the onshore converter station through the direct-current sending-out submarine cable, and the converter station converts the direct current into power-frequency alternating current; and after being boosted, the other low-frequency electric energy is sent to a land frequency conversion station through a low-frequency sending-out submarine cable to be converted into power-frequency alternating current, so that efficient collection and grid-connected sending-out of multi-frequency wind power resources are realized. According to the invention, the problem that a plurality of independent platforms need to be built in a complex multi-point grid-connected scene in the prior art can be solved.

The invention discloses a multi-type networking equipment collaborative planning method for multi-scene composite regulation and control contribution, and the method comprises the following steps: calculating a single power flow sensitivity factor according to an interaction relation between branch power flow and node injection power; calculating an overload weight coefficient of each branch based on a multi-power flow blocking scene, calculating a power flow sensitivity factor under multiple scenes based on an interaction relationship between branch power flow and node injection power, and constructing a multi-scene composite regulation and control index; according to the multi-scene composite regulation and control index, selecting a plurality of access positions, and determining network construction type HVDC and network construction type energy storage grid-connected access positions; and according to the network construction type HVDC and the network construction type energy storage grid-connected access position, establishing a double-layer optimization model, and carrying out cooperative solution on the double-layer optimization model to obtain multi-type network construction equipment capacity optimization configuration under multiple scenes. According to the invention, the technical problems that the existing network construction equipment cannot be suitable for multi-scene composite regulation and control and dynamic tidal current congestion under multiple working conditions are solved.

The invention provides a wind-light-heat-storage large-scale new energy base frequency coordination control method, and belongs to the field of power system active power control, and the method comprises the steps: carrying out the simulation analysis based on a wind-light-heat-storage large-scale new energy base DC sending-out system through a photo-thermal power generation system dynamic model, and obtaining a wind-light-heat-storage large-scale new energy base frequency coordination control model; analyzing the frequency modulation energy of the network-following type energy storage and the network-constructing type energy storage, constructing a wind-light-heat storage frequency response model, performing difference analysis on the response speed, and performing off-line solution to obtain a frequency response characteristic table; frequency modulation resources under different operation conditions are researched, and a coordinated output relation is obtained; deviation calculation is carried out to obtain a real-time deviation result, strategy matching is carried out by utilizing a frequency response characteristic table, a frequency modulation strategy is obtained and optimized in combination with a coordinated output relation, and a completely distributed frequency control strategy is obtained; according to the invention, reliable interaction of heterogeneous resource operation states in the primary frequency modulation scale and reasonable distribution of power output are realized.

The invention discloses a hybrid direct current transmission power coordination control device and a control method and equipment thereof, and relates to the technical field of offshore power generation, and the hybrid direct current transmission power coordination control device comprises a diode rectifier unit and a first modular multilevel converter which are connected with an offshore wind plant, the sending-end converter station is used for converting alternating current generated by an offshore wind plant into direct current and outputting the direct current; the second modularized multi-level current converter is connected with the diode rectifier unit and the land power grid and is used for restoring the direct current into the alternating current and transmitting the alternating current to the land power grid; and the control module is connected with the first modular multilevel converter and is used for controlling the DC voltage of the first modular multilevel converter based on the fluctuation power according to the transfer relation between the active power and the DC voltage of the sending end converter station, so that the higher requirement of the rated capacity of the MMC in the related technology is met, and the reliability of the MMC is improved. And the engineering construction cost is increased.

The invention discloses an AC / DC power distribution network coordinated planning method, system, equipment and medium containing a flexible interconnection device, and belongs to the technical field of AC / DC power distribution, and the method comprises the steps: inputting the basic information of a power distribution network, setting the key parameters of a hybrid optimization algorithm, generating an initial particle swarm in an upper model of a three-layer optimization model, forming an initial solution set, and carrying out the optimization of the initial solution set; based on the initial solution set, configuring a scheme for each FID, solving a middle-layer model and a lower-layer model, converting the middle-layer model and the lower-layer model into a single-layer problem through a Lagrangian relaxation technology, carrying out solving in combination with a hybrid intelligent algorithm, evaluating the fitness of each FID scheme by utilizing a simulation result, dynamically updating an optimization algorithm state, and when a termination condition is met, carrying out optimization on the FID scheme. And outputting a global optimal planning scheme. According to the method, the three-layer collaborative planning model is constructed and the hybrid intelligent algorithm is adopted for efficient solving, so that the flexible interconnection capability, the distributed energy consumption rate and the equipment safety of the AC / DC power distribution network are improved, and meanwhile, the network loss and the cost are reduced.

The invention provides a series-parallel high-voltage direct-current power transmission system transient state control method suitable for sending-end alternating-current faults, and belongs to the technical field of power systems. The method comprises the following steps: constructing a direct-current power safe operation boundary of an LCC converter station by combining LCC rectification side safety constraint and LCC inversion side commutation failure risk constraint conditions; constructing a commutation failure suppression strategy model of VSC and LCC cooperative control; and by using the commutation failure suppression strategy model, after a sending end alternating current fault occurs and is eliminated, controlling and suppressing the commutation failure of an LCC inverter station by using a control strategy of VSC dynamic reactive compensation and LCC trigger angle adaptive adjustment cooperation, and completing commutation suppression of the series-parallel high-voltage direct-current power transmission system. According to the invention, the problem of commutation failure caused by a sending end alternating current fault intensified by the interaction influence of conventional high-voltage direct current and flexible direct current is solved.

The invention discloses a direct-current power transmission system based on SVG valve side filtering and a control method. An SLCC transmits active power through an LCC converter valve, provides reactive power through an SVG valve and filters; the rectification side of the LCC converter valve maintains the direct current of the rectification side to be the reference value of the direct current by controlling the trigger angle of the converter, and the receiving end of the LCC converter valve carries out constant direct current voltage control through cooperation of the inversion side converter transformer tap switch and the extinction angle; the active component and the reactive component of the fundamental frequency current are added to serve as a fundamental frequency current instruction, and the fundamental frequency current instruction is input into a fundamental frequency current controller for fundamental frequency current closed-loop control; a harmonic current component needing to be compensated is extracted by analyzing an output current measurement value of an LCC converter valve, serves as a harmonic compensation current instruction after being subjected to delay compensation and is input into a harmonic current controller for harmonic current closed-loop control; and superposing the output of the fundamental frequency current controller, the output of the harmonic current controller and the voltage feedforward to obtain a control reference voltage instruction of the SVG valve.