4607results 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.

A fault ride-through method and apparatus for a new energy transmission system, and an electronic apparatus, relating to the technical field of new energy grid connection and flexible direct-current power transmission. The method comprises: acquiring a voltage parameter of a grid-connected inverter and a voltage of an alternating-current system, the voltage parameter comprising at least one of the following: an alternating-current voltage of the grid-connected inverter, a direct-current voltage of the grid-connected inverter, and a direct-current voltage change rate; on the basis of at least one of the voltage parameter and the voltage of the alternating-current system, determining whether a low-voltage fault has occurred in a new energy transmission system; and when a low-voltage fault has occurred in the new energy transmission system, adjusting the new energy transmission system at least according to a preset adjustment method, so that the new energy transmission system carries out fault ride-through within a preset duration, the preset adjustment method comprising at least one of the following: adjusting the active current of the grid-connected inverter and adjusting the integral element of a flexible direct-current system. The problem of lack of a fault ride-through method suitable for a large-scale new energy flexible direct-current transmission system is solved.

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 online prediction method and device for node voltage of a time-varying topology direct-current power distribution network, and the method comprises the steps: building a simulation model based on the historical operation data of the direct-current power distribution network in combination with the real topology of a power grid, and generating a time sequence training data set containing voltage, power and line states through dynamic topology simulation; based on the training data set, constructing a dynamic space-time diagram neural network fused with topology dynamic change, and learning a voltage time sequence evolution rule in combination with a time sequence module; node power data and topology information are collected in real time by using a dynamic space-time diagram neural network, network topology input is dynamically updated, and a future short-time domain voltage predicted value is output; and for a power grid topology change scene, graph connection parameters associated with change nodes are updated, rapid fine adjustment of the model is realized, and stable prediction is carried out. According to the method, network topology information can be dynamically input under the condition that the topology of the direct-current power distribution network is changed, and rapid and stable prediction of the node voltage of the direct-current power distribution network under the time-varying topology is achieved.

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 power matching-based current limiting method, system and equipment for a network construction type flexible direct current system. Relates to flexible direct current transmission. An existing current limiting method affects system stability and control accuracy. The current limiting condition is equivalently converted into the power limiting condition under the characteristic that the output voltage of the grid-forming converter is stable, the power limiting condition is converted into the angular frequency judgment condition under the characteristic of droop control, and when the angular frequency of the system is smaller than the lower limit of the angular frequency threshold value, it is judged that the system has overcurrent under large disturbance, and then the system is controlled. And the power matching module is connected, the output power of the converter is limited to be the maximum value, and then the current is limited to be the maximum value allowed to be output by the converter. According to the technical scheme, the current limiting effect of the converter can be achieved on the premise of not changing the network construction type frequency modulation control characteristics, complex parameter measurement and setting are not needed, the potential operation scene of the flexible direct current system can be effectively dealt with, and safe and reliable operation of the network construction type flexible direct current system is ensured.

The invention relates to a regional power grid flexible interconnection planning method giving consideration to global consumption capability and investment income of new energy. The method comprises the following steps: firstly, constructing a regional power grid flexible interconnection device locating and sizing and new energy consumption index evaluation system and a to-be-planned interconnection line position-capacity set; secondly, a regional power grid flexible interconnection double-layer planning model is constructed, an upper layer decides an interconnection device locating and sizing scheme, and a lower layer evaluates the system new energy consumption capability after the flexible device is constructed and decides the new energy grid-connected access quantity; and finally, determining a target planning scheme by adopting an improved multi-target particle swarm algorithm. According to the method, the new technology of flexible interconnection between regional power grids is considered, and the model selection, site selection and capacity determination scheme of the cross-regional interconnection line is determined through the new indexes of the node topology connection degree, the neighbor node center support force and the node vulnerability resistance, so that the problem that the traditional regional power grid planning method cannot directly match the source load is solved; and the capability of flexible consumption of new energy and mutual aid of resources among regional power grids is improved.

The invention discloses an offshore wind power low-frequency networking system based on hybrid topology and a control method, in N onshore receiving end nodes of the offshore wind power low-frequency networking system, one node adopts an M3C current converter, N-1 nodes adopt DRU and MMC current converters, an offshore low-frequency power grid voltage is established through the M3C current converter, and the M3C current converter is connected with the M3C current converter; the power flow control of other power control nodes is realized through the DRU and the MMC, and by adopting the technical scheme of the invention, the engineering construction cost can be obviously reduced under the condition of ensuring the reliable operation of the system, and the method has a good application prospect.

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 provides an alternating-current fault ride-through control method of a direct-current sending-out system and storage equipment thereof. The method comprises the steps that the operation condition of a wind power flexible direct-current system is monitored in real time; when it is detected that the direct current side voltage of the wind power flexible direct current system is larger than a set threshold value at the receiving end converter station, a direct current side energy consumption device of the flexible direct current system is started to dissipate surplus power; when an alternating current fault is detected at the sending end converter station based on the direct current side voltage, the sending end converter station is switched to a current limiting mode, a fan and a power transmission system of the wind power flexible direct current system are controlled, and surplus power is dissipated again through an unloading circuit; when the AC voltage recovers, the sending-end converter station is adjusted back to a normal mode; and power transmission of the wind power flexible direct current system is recovered. According to the invention, on the basis of the operation condition of the receiving-end and sending-end converter station direct-current voltage monitoring system, the energy consumption device, the fan, the power transmission system and other links are used for cooperative control, power can be balanced, equipment can be protected, and the system stability can be enhanced.

The invention relates to the technical field of power electronics and energy management. The invention provides an AC / DC power supply system monitoring device and method. The method comprises the following steps: constructing a historical data set; preprocessing the historical data set to obtain a preprocessed data set; based on the preprocessed data set and a machine learning algorithm, constructing a system monitoring model, and presetting a voltage anomaly judgment threshold value of the system monitoring model; acquiring real-time power data of the AC / DC power supply system and real-time operation state and load change data of the power grid, inputting the data into the system monitoring model, and identifying the mode, trend and potential abnormity of voltage fluctuation of the AC / DC power supply system; and dynamically adjusting a preset voltage abnormity judgment threshold value, and giving a corresponding AC / DC power supply system adjustment strategy and early warning information. The problems that in the prior art, an alternating-current and direct-current power supply system monitoring method is low in efficiency, frequent in false alarm and missing alarm conditions, difficult to adapt to a complex and changeable power grid environment and lack of intelligent analysis and early warning functions are solved.

The invention belongs to the technical field of inertia evaluation, and discloses a direct current delivery system minimum inertia demand evaluation method considering multi-frequency modulation resource support characteristic difference, and the method comprises the steps: firstly analyzing the frequency response characteristics of each frequency modulation resource in a direct current delivery system in a typical control mode; a system frequency response model considering wind power, photovoltaic and extra-high voltage direct current frequency response characteristic differences is established, and an influence mechanism of different frequency modulation resources on system frequency characteristics is disclosed. Secondly, constructing a system equivalent inertia calculation model considering a wind power and photovoltaic inertia support effect, and providing a minimum inertia demand evaluation method based on an initial frequency change rate as a constraint; and then, considering the influence of a direct current frequency limit controller on the maximum frequency deviation, designing a direct current delivery system minimum inertia evaluation scheme considering the frequency dynamic safety constraint so as to support efficient, stable and continuous delivery of new energy power generation.

The invention discloses a parameter design method and device for an impedance correction device of a direct-current power transmission system, and the method comprises the steps: obtaining a voltage parameter and a harmonic parameter of an alternating-current system according to a constructed target direct-current power transmission system topology, and designing an amplitude-phase corrector parameter optimization model; in different operation modes, impedance characteristics of the alternating current and direct current system are obtained respectively; in response to the impedance characteristic, performing simulation through an amplitude-phase corrector parameter optimization model to obtain element stress of the amplitude-phase corrector in a corresponding fluctuation state; in the corrector configuration link, parameters of an amplitude-phase corrector are determined according to the voltage fluctuation ratio of the alternating current system and the operation power range of the direct current system, and the parameters are optimized based on element stress so as to configure the amplitude-phase corrector; and after the amplitude-phase corrector is configured, the corrector configuration link is repeated until the equivalent harmonic impedance of the direct-current power transmission system meets a preset system oscillation index. Harmonic oscillation in a direct-current power transmission system can be effectively reduced by optimizing parameters of the amplitude-phase corrector.

The invention relates to the technical field of new energy control, and discloses a flexible DC system comprehensive coordination control method giving consideration to frequency active support and DC overvoltage suppression, and the method comprises the steps: obtaining a sending end frequency deviation delta fS, a receiving end system frequency deviation delta fR and a DC voltage deviation delta Udc of a flexible DC interconnection system; when the absolute value of the sending end frequency deviation is greater than the frequency dead zone value, an MMC adaptive control strategy for supporting the sending end system frequency stability is executed; when the absolute value of the frequency deviation of the receiving end system is greater than 0, inertia support control is carried out; and after inertia support control, if the absolute value of the direct-current voltage deviation is greater than the direct-current voltage dead zone value UdcH, an MMC adaptive control strategy giving consideration to receiving end system frequency support and direct-current overvoltage suppression functions is executed. According to the invention, the active frequency support and fault ride-through capability of the flexible DC power transmission system can be improved.

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 present application provides a reactive power feedback control-based control method for a commutation failure in a hybrid cascaded high-voltage direct-current power transmission system, a storage medium and an electronic apparatus, and particularly relates to a reactive power feedback control-based control method for a commutation failure in a hybrid cascade high-voltage direct-current power transmission system. The method mainly comprises the following steps: acquiring power data of a hybrid cascaded high-voltage direct-current power transmission system; calculating the reactive power supply of an inverter-side MMC-end alternating-current system, the reactive power supply of an inverter-side alternating-current filter, and the reactive power supply of an inverter-side LCC-end alternating-current system; solving a reactive power control instruction of an inverter-side MMC converter; and, on the basis of a critical voltage, determining whether to implement the reactive power feedback control-based control method for a commutation failure in the hybrid cascaded power transmission system. The method can effectively reduce the probability of commutation failures in hybrid cascaded power transmission systems, thus guaranteeing safe and stable operation of large-scale power grids.

The invention relates to the technical field of photovoltaic grid connection, and particularly provides an active support control method and an active support control device for transient voltage of a transmitting end power grid of an LCC-HVDC (line commutated converter high voltage direct current power transmission) system, and the active support control method and the active support control device for the transient voltage of the transmitting end power grid of the LCC-HVDC system. Comprising the following steps: correcting an output voltage phase of a synchronization link in a virtual synchronous generator control strategy based on active power and frequency output by a network construction type photovoltaic converter, and correcting an output voltage amplitude of a voltage amplitude link in the virtual synchronous generator control strategy based on a measured value of a sending end power grid voltage; and using the virtual synchronous generator control strategy to control the network construction type photovoltaic current converter in the LCC-HVDC system containing the network construction type photovoltaic current converter. According to the technical scheme provided by the invention, the stability of photovoltaic access to the weak power grid can be improved, and the reactive power output by the converter can be automatically adjusted after the transient voltage of the sending-end power grid occurs due to the commutation failure of the LCC-HVDC system, so that the transient voltage is effectively supported, and the phenomenon of reverse adjustment of the reactive power is prevented.

A method and device for supporting weak networks in an AC / DC distribution network are provided. The method includes the following steps: constructing a topology of the AC / DC distribution network, where the topology is configured to support the weak networks and isolate faults actively, and the topology is a multi-terminal ring structure; establishing a distributed optimization method for the AC / DC distribution network based on the topology; obtaining power fluctuations of the AC / DC distribution network, where the AC / DC distribution network can switch a droop control mode automatically according to the power fluctuations; and obtaining frequency fluctuations of the AC / DC distribution network, where the AC / DC distribution network performs energy dispatching according to the frequency fluctuations to match the droop control mode of the AC / DC distribution network.

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 new energy voltage ride-through parameter optimization method considering polymorphic voltage stability constraint, a storage medium and equipment, and belongs to the technical field of power system safety and stability improvement. In order to solve the problem that an existing new energy voltage ride-through parameter optimization method is only suitable for a single fault scene and only aims at a voltage stable form to optimize a new energy voltage ride-through parameter, the invention provides a new energy voltage ride-through parameter optimization method. Based on the dynamic characteristics of the new energy during the power grid fault period, the new energy general control model is established so as to determine the dominant control parameters influencing the dynamic characteristics of the new energy during the high / low voltage penetration period, the influence of the dominant control parameters on the voltage stability under different faults is considered, and the voltage regulation capability and the power regulation cost of the new energy are considered. A new energy voltage ride-through parameter optimization model considering polymorphic voltage stability constraints is established, and the optimization model is solved by adopting a particle swarm optimization algorithm. The method is used for voltage ride-through parameter optimization of new energy.

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 discloses an optimized reactive power control and fault ride-through method and system for a hybrid commutation converter, and the method comprises the steps: introducing reactive power control and considering the constant voltage control of negative turn-off angle limitation, achieving the control of an extremely low turn-off angle through the active turn-off of a full-control device in the converter under a steady-state working condition, and further meeting the demands of a high power factor; the investment of passive filter equipment is reduced; under the alternating current fault working condition, forced commutation and negative turn-off angle operation are achieved through active turn-off of a full-control device, the receiving end power grid voltage is effectively supported while commutation failure of a half-control thyristor in the hybrid commutation converter is avoided, and the active power transmission level during the fault period is improved. The full-control characteristic of the reverse blocking type integrated gate commutation thyristor in the hybrid commutation converter is fully utilized, reactive power control under the steady-state working condition and stable power transmission under the alternating-current fault are achieved by optimizing active turn-off control, and the method has wide applicability and good application prospects.

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 discloses a direct current control method and system for improving transient stability of a grid-connected converter, and the method comprises the steps: judging whether a power angle out-of-limit-based fault judgment module or a voltage out-of-limit-based fault judgment module has a voltage drop or phase jump fault or not when any one module judges that a power grid has a voltage drop or phase jump fault; processing an angular velocity control signal of a synchronous control link through a direct current port transient energy correction module, and performing temporary storage unbalanced power-oriented lifting and inertia correction-oriented lifting on a direct current voltage reference value; the voltage value of the direct-current port capacitor is compared with a direct-current voltage reference value, and is processed by the steady-state direct-current voltage control module to obtain a direct-current voltage control reference value; the output data of the converter at the common coupling point obtains a synchronous control signal according to a synchronous control link; and based on the synchronous control signal, an internal potential reference value is obtained according to an internal potential control link, and then a converter driving signal is generated. According to the invention, the stability problem of the grid-connected converter when the power grid has a transient fault can be effectively solved.

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.