1858 results about "High voltage direct current transmission" patented technology

The invention discloses an intelligent fault classification and location method for an ultra-high voltage direct current transmission line, and belongs to the technical field of relay protection of power systems. The method comprises the following steps of: classifying fault data by using a neural network by adopting a layered and distributed neural network model; distinguishing fault types; sending the classified data into different neural networks respectively for performing fault location; when the direct current transmission line has a fault and a sampling frequency is 10 kHz, selecting a discrete line mode voltage signal which has the sampling sequence length of 100 after the fault and performing S-transform, wherein a transform result is a complex time-frequency matrix of 51*100; solving the modulus of each element in the complex matrix to obtain transient energy distribution of the line mode voltage at all frequencies; selecting first five energy spectrums as sample properties; selecting a transfer function and a learning rule; setting proper neural network parameters for constructing a BP network model; and performing fault classification and fault location. A large number of simulation results show that the method has a good effect.

A power electronic converter for use in high voltage direct current power transmission and reactive power compensation comprises a plurality of switching elements interconnecting in use a DC network and one or more AC networks, the plurality of switching elements being controllable in use to facilitate power conversion between the AC and DC networks, wherein in use, the plurality of switching elements are controllable to form one or more short circuits within the power electronic converter so as to define one or more primary current flow paths, the or each primary current flow path including a respective one of the AC networks and the power electronic converter and bypassing the DC network.

A high-voltage direct-current breaker is composed of an initial current path (1) and a fail current interdicting path (2). The initial current path (1) comprises at least one electric electronic switch module (3) and a mechanical switch (4), and the fail current interdicting path (2) comprises an initial capacitor (C) and a modular switching subunit series connection component (5). The modular switching subunit series connection component (5) is formed by connecting a plurality of sub units (6) in series. When a high-voltage direct-current electric transmission line fails, the opening and closing of a fail electric transmission line can be rapidly achieved.

The invention discloses a series hybrid bipolar direct-current transmission system with direct-current fault ride-through capability. The series hybrid bipolar direct-current transmission system comprises a rectifier station and an inverter station, wherein the rectifier station is connected with the inverter station through a direct-current transmission line; positive electrodes and negative electrodes of the rectifier station and the inverter station are formed by connecting thyristor converters and modular converters in series; and each modular converter is formed by connecting one or more modular multilevel converters in parallel. The series hybrid bipolar direct-current transmission system has the advantages of low construction cost, low loss, high reliability and the like of the traditional thyristor converters, and has the advantages of flexible control, low harmonic wave, active and reactive power decoupling control, voltage support capacity on an alternating-current system access point and the like of the modular multilevel converters; the system is divided into the positive electrode and the negative electrode; the operation reliability is enhanced; and a direct-current fault can be removed by the actions of the converters under various faults. Therefore, the series hybrid bipolar direct-current transmission system is suitable for high-voltage direct-current transmission occasions of a remote high-capacity overhead line, has a wide development space and is worthy of strong popularization.

The invention discloses a total bridge type MMC (Microsoft Management Console)-HVDC (High Voltage Direct Current Transmission) sub-module fault in-situ diagnosing and protecting method, belonging to the technical field of power transmission and distribution. According to the technical scheme, the method comprises the following steps: realizing fault in-situ diagnosis through an electric amount and a communication state of a monitoring sub-module, and transmitting a fault signal to a valve base controller (VBC); then locking a fault sub module through a sub module controller (SMC), and triggering a bypass fault sub module of a bypass device, so that the fault sub module and the system can be protected. The invention provides the total bridge type MMC-HVDC sub-module fault in-situ diagnosing and protecting method, which can be used for monitoring the state of the sub module in real time, and protect the system and the fault sub module after the sub module has a fault, and provides a method capable of keeping the system to stably operate when a signal transmission channel is caused by the fault of the superior controller of the communication fault or sub module controller (SMC).

The invention discloses a control method of an alternating voltage sensorless high voltage direct current transmission converter, belonging to the technical field of electrical equipment and comprising the following steps: establishing a stator resistor and an inductor for a virtual motor; building relative position relationships among a current vector, a voltage vector and a flux linkage vector, and analyzing a vectorgram; establishing a converter and flux linkage mathematic model, and calculating a virtual flux linkage vector of a system to obtain a power feedback quantity of the system; acquiring an active control signal and a reactive control signal of the system through a direct power control algorithm, and generating a PWM trigger converter for respectively and independently controlling the active power and reactive power of the system; and utilizing MATLAB simulation software to set up a system model for verifying, and obtaining a systematic selection device when the verification is successful. By utilizing Matlab / Simulink to set up a corresponding simulation model, the designed method is verified to have rapid response speed, the voltage and power after startup can still reach stable values after about 2 power frequency periods and have high steady state precision.

The present invention discloses an LCC and MMC series-connected HVDC system with DC fault ride-through capacity, comprising rectifier and inverter linked by DC transmission line; Both the positive pole and the negative pole of the rectifier and the inverter consist of line-commutated converter and modular converter in series-connection; the modular converter adopts one MMC or several parallel-connected MMCs. The present invention has the advantage of low cost, low power loss and high reliability of the LCC, as well as flexible control, low harmonics and AC voltage support of the MMC. Further, the present invention is able to deal with DC fault by itself, hence additional DC fault clearing equipment is not needed. As a result, the present invention is suitable for the field of long-distance large-capacity power transmission and has broad development potential.

The invention discloses a method for current differential protection of a direct current electric transmission line, which comprises the following steps: according to a distributed parameter model of the electric transmission line, using mode transformation in a time domain to transform sampling values of direct current and direct current voltage into a modulus; then using the mode voltage and the current of two ends from two ends of a line respectively to calculate mode current of certain point of the line at each moment; and using the mode current to directly construct a current differential protection criterion, or synthesizing electrode current through electrode mode inverse transformation, and then constructing the current differential protection criterion according to the electrode current. The method can improve the sensitivity and the reliability of direct current line protection, has good controllability and high security, has a complete setting theory, overcomes the defects of the conventional traveling-wave protection as the main protection of a high-voltage direct current line, and requires no recognition of a traveling-wave wave head; besides, the calculation is simple. The method is mainly used for the current differential protection of the direct current electric transmission line in an electric power system, in particular for the protection of an ultra / extra high-voltage direct current electric transmission line.

The invention relates to a training examination system, in particular to a training examination system for technical staffs about operation and maintenance of a converter station of a high voltage direct current power transmission system. The intelligent training examination system of the high voltage direct current power transmission technology consists of a direct current power transmission simulation system, a database, a training examination system server, a router, a remote access server and an instructor subscriber terminal, and a plurality of local student subscriber terminals or a plurality of remote student subscriber terminals. The system can be adopted to undergo on-line learning, training and examination which comprises a theory training examination and a direct current power transmission system practical operation training examination, thereby automatically building the questions, timing, estimating scores and forming score reports based on the set question types and difficulties and meeting demands of normalized and intelligentized training and examination on primary workers, secondary workers and advanced workers for the operation and the maintenance of the direct current power transmission system.

The invention discloses a high-voltage direct current transmission line internal fault and external fault identification method based on backward traveling waves. The high-voltage direct current transmission line internal fault and external fault identification method comprises the following steps that firstly, a voltage transformer and a current transformer installed on the rectification station line side and an inversion station line side of a direct current transmission system collect voltage and current across the two ends of a positive electrode line and voltage and current across the two ends of a negative electrode line respectively; secondly, the voltage leap amount and current leap amount of the two ends of the positive electrode line and the voltage leap amount and current leap amount of the two ends of the negative electrode line are calculated; thirdly, the voltage leap amount and current leap amount of each electrode line are transformed into corresponding line mode voltage component and line mode current component; fourthly, the voltage backward waves at the two ends of the direct current line are worked out according to the line mode voltage component and the line mode current component, and integration of backward wave amplitude values is conducted in specific time; fifthly, a specific value of the backward wave amplitude value integral on the rectification side of the direct current line to the backward wave amplitude value integral on the inversion side of the direct current line is calculated, and faults are judged according to the specific value. By means of the method, the internal faults and the external faults can be quickly and accurately recognized, correct actions can still be conducted under the high-resistance faults at the line tail end and the noise interferences, and reliability and sensitivity are high.

The invention discloses a determination method of network side harmonic current of a high-voltage direct current power transmission system. The determination method comprises the following steps: if the harmonic current voltage at a direct current power transmission line inlet is zero, decoupling and equalizing a rectifying side and an inverting side into a plurality of independent six-pulse moving bridge units; dividing a work period of the six-pulse moving bridge units into six phase converting sections and six non-phase converting sections; calculating a phase converting overlapping angle of each phase converting section; equalizing a current converter into a harmonic current voltage source containing internal resistance; calculating the direct current side harmonic current according to the concrete forms of a smoothing reactor and a direct current filter; obtaining valve side harmonic current according to an equivalent circuit of the current converter; and converting the valve side harmonic current to a network side according to a connecting structure of a transformer to obtain the network side harmonic current. The invention considers background harmonic current and other nonideal factors, and can quickly and accurately obtain the harmonic current at the network side of a converter transformer, accelerate the period for designing an alternating current filter in the high-voltage direct current power transmission engineering and improve the design quality and the design efficiency.

A direct current to alternating current inverter sub-system is for a HVDC distribution system. The DC to AC inverter sub-system includes an enclosure and a DC to DC galvanically isolated buck converter having a DC input electrically connectable to a HVDC cable and a DC output. A DC to AC inverter includes a DC input electrically connected to the DC output of the DC to DC galvanically isolated buck converter and an AC output electrically connectable to an AC transmission line. The DC to AC inverter is mounted in an enclosure with the DC to DC galvanically isolated buck converter, in order that the DC output of the DC to DC galvanically isolated buck converter is directly electrically connected within the enclosure to the DC input of the DC to AC inverter.

The invention relates to a high-voltage capacitor imbalance protecting method for a high-voltage DC transmission system, comprising the following steps of: (1) analyzing imbalance current of a high-voltage capacitor in breakdown of a capacitor element during failure development in a high-voltage DC transmission system; (2) judging a symmetrical or dissymmetrical failure of the high-voltage capacitor in the high-voltage DC transmission system; and (3) proposing a corresponding setting principle and an action strategy aiming at the symmetrical or dissymmetrical failure. The high-voltage capacitor imbalance protecting method for a high-voltage DC transmission system has simple structure, convenience and practicability.

The invention discloses a method for starting an ultra-weak receiving-end high-voltage direct-current (HVDC) power transmission system by using a static synchronous compensator (STATCOM), belonging to the technical field of HVDC power transmission. The system is characterized in that a STATCOM and HVDC are connected to a same bus of an alternating-current system in parallel, and a STATCOM subsystem is connected with the same bus of an HVDC subsystem receiving-end alternating-current system through a current conversion reactor (X1). According to the method, a substep starting manner is adopted, and during starting, the STATCOM subsystem is subjected to the composite control of a series-connection current limiting resistor and current decoupling and voltage feedforward control; and soft wart is adopted for the HVDC subsystem, and the setting value of a current regulator is gradually increased in a start process till the finish of the start. According to the invention, the HVDC system can be started to a rated running state under the condition that a receiving end system is an ultra-weak alternating-current system, the voltage property of the HVDC receiving-end alternating system is improved, and the HVDC system is prevented from failed commutation.

The invention relates to an ultra-high voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics, and belongs to the technical field of power system relay protection. When voltage of an ultra-high voltage direct current transmission line fluctuates, positive voltage and negative voltage of the initial 5ms are monitored; the relevancy between voltage of each electrode and voltage of each axis is calculated, and the lightning stroke interference is recognized according to the relevancy; the recognition of fault classifications is shifted to if the interference is caused by a fault; an additional component of line modal voltage is calculated, and seven dimension decomposition is performed on the additional component by utilizing a db3 wavelet; and the ratio of high frequency energy to low frequency energy is calculated, fault categories are distinguished, and fault protection is performed. According to the method, the signal acquisition time is short, the sample acquisition scale is small, and the voltage relevancy theory is used for recognizing lightning stroke interference and fault, so that the thought is clear, and the accuracy is high; the transient state energy distribution characteristics obtained through wavelet transformation are used for recognizing lightning stroke fault and short circuit fault, and the effect is obvious; and the method is easy to implement and is not easily influenced by system parameters and transition resistance.

The invention provides an audible noise calculating method for a high-voltage direct current electric transmission line of 4 to 8 bundle conducting wires and can effectively solve the audible noise prediction problem of an extra-high-voltage direct current electric transmission line. The calculating method comprises three parts that (1) the surface electric field intensity of the conducting of the high-voltage direct current electric transmission line is calculated; (2) the audible noise level (in summer) of the high-voltage direct current electric transmission line is calculated; and (3) the audible noise level of other seasons is obtained through adding or reducing correction items. The calculating method is simple, the implementation is easy, the audible noise of the direct current line corona of the 4 to 8 bundle conducting wires obtained through the calculation can be preferably coincided with the measuring results of testing line in China through being compared with calculation results of other formulas. The direct current corona audible noise of multiple conducting wires, obtained through calculation by the calculating method provided by the invention can more adapt to the environment climate condition in China. The audible noise calculating method is particularly suitable for the extra-high-voltage direct current corona audible noise calculation when during the 4 to 8 bundle conducting wire adoption in north China.

The invention relates to an extra-high-voltage DC power transmission line area internal and external fault identification method, and belongs to the technical field of high-voltage DC power transmission system relay protection. Fault current data are acquired firstly, current traveling wave direction is determined by comparing polarity of fault current at waveform mutation points, and then whether a fault signal comes from the outside of a rectification side area or the inside or the outside of an inversion side area is judged. A problem of double-end information interaction can be solved by adopting a single-end current transient protection method so that whole line protection is realized, and the method is used for distinguishing the fault outside the rectification side area, the fault inside the area and the fault outside the inversion side area.

The invention relates to the field of relay protection of direct-current transmission lines of power systems, in particular to a single-ended electrical quantity full-time quick-action protection method for recognizing faults inside and outside a high-voltage direct-current transmission line region. The faults inside and outside the high-voltage direct-current transmission line region are recognized by using an amplitude of a special frequency component of electrical quantity of the direct-current line side of a single-ended convertor station. The invention is mainly used in single-ended electrical quantity full-line quick-action protection of the direct-current transmission line in the power system, only needs to adopt the singe-ended electrical quantity, has low requirement on the sampling frequency and a simple algorithm, is easy to realize on the engineering, has the advantages of high action speed, good selectivity and high reliability, and is complete in theory and easy to integrate. The protection method in the invention can be used as the main protection of the direct-current transmission line instead of the traditional traveling wave protection, and is especially suitable for full-line quick-action protection of extra / super high-voltage direct-current transmission lines by using single-ended electrical quantity.

The invention relates to a traveling wave analysis and recognition method for distinguishing lightning shielding failure from lightning counterattack of direct current transmission line. The lightning shielding failure of line is that lightning avoids the lightning shield line and directly strokes on the transmission line, while lightning counterattack of line is that lightning directly strokes on the lightning shield line or the tower. Because the earth resistance of tower exists, the potential on tower top suddenly increases and causes insulation flashover. The electromagnetic transient component generation mechanism of the high voltage direct current transmission line and the propagation path of lightning electromagnetic transient of the line in the lightning shielding failure are different from those in the lightning counterattack, the size and polarity of the initial surge voltage and the second surge voltage of the voltage transient signal exist significant difference. The traveling wave analysis and recognition method of the invention analyzes zero mode voltage using wavelet and distinguishes the lightning shielding failure and lightning counterattack failure according to the size and polarity of the initial surge voltage and the second surge voltage of the zero mode voltage in the traveling wave analysis and high-speed acquisition system of the protection zone. A lot of simulation results show that the method is reliable and effect. The physical concept of the invention is visible and clear, the method is easy to achieve and wide to use in the direct current system protector, also provides accurate initial data for researching lightning characteristics, analyzing lightning accident, discussing lightning protection countermeasure of transmission line and designing insulation coordination in the power system.

The invention relates to a method of a boundary element utilizing polar wave S transform energy ratio to determine ultra high-voltage (UHV) direct current (DC) transmission line faults, belonging to the technical field of power system relay protection. The method is as follows: a starting element is started when a DC line breaks down, the polar wave voltages of the positive and negative lines are calculated according to dipolar DC voltages and DC currents measured at a protective installation part; a discrete polar wave voltage signal the sampling sequence length of which is 200 after faults is subjected to S transform, the transform result is a 101*200 time-frequency complex matrix, and mode operation is carried out on each element in the complex matrix. High-frequency component and low-frequency component of the polar wave voltage are extracted according to the obtained modular matrix, and then the ratio of the high-frequency energy to the low-frequency energy of the polar wave voltage is figured out; and whether the fault is interior or exterior is distinguished according to the value of the ratio of the high-frequency energy to the low-frequency energy. A large number of simulation results show that the invention has good effect.

The invention discloses a high voltage direct current power transmission line protection method based on a voltage and current mutation direction. The method comprises the following steps that when a fault exists in a line area, the directions of the voltage mutation quantity and the current mutation quantity at the protection measurement of a rectifying side are opposite, and the directions of the voltage mutation quantity and the current mutation quantity at an inverter side are the same; the feature is also applicable for anode lines and cathode lines; and faults at other areas do not satisfy the condition. Thus, the protection criterion of the high voltage direct current transmission line is structured and the protection method is disclosed. As the method provided by the invention is adopted in the protection of the direct current transmission line, actions can be performed fast and accurately when fault lightning, high impedance earthing faults and pole-pole faults exist in the line area; no error action is carried out under the situations of lightning disturbance, faults outside the line protection area and the like; the protection method is simple and clear; the requirement on communication channels is not high; the requirements on data calculating speed and sampling frequency are low; no synchronizing processing is required for sampled data; and various operation ways of a bipolar direct current power transmission system are applicable, and the practical value is high.

The invention relates to a high voltage DC power transmission line shielding failure current waveform inversion recovery method. When the transmission line suffers the lightning stroke, the transient state traveling wave is spread and transmitted by the power transmission line, so the transient response at the protection installation place is different. The transmission line is equivalent to a natural lightning current air-termination system, and when the shielding failure happens, the prior traveling wave fault location technology can precisely locate the lightning stroke point; the parameters of the power transmission line can be obtained by measuring and analyzing on line; and with the transfer function of the transmission line deduced by the method, the lightning current waveform at the lightning stroke point can be finally obtained by carrying out the phase amplitude transformation, noise reduction, and Prony fit process, and deconvolution operation of on the transient voltage which is obtained through a high-speed collection at the protection installation place of the transmission line.

The invention relates to a method for identifying extra-high voltage direct current transmission line area inside and outside fault wavelet energy. The method comprises the following steps of: starting a starting element when a direct current fails and selecting bipolar direct current voltage data detected at a protection installation part after 5 ms of the fault, wherein the direct current voltage data are a discrete signal with sampling frequency of 100 kHz and sample sequence length of 500; finding out a direct current system line-mode voltage for four layers of wavelet decomposition by utilizing the bipolar direct current voltage so as to obtain low frequency coefficients and high frequency coefficients of the wavelet decomposition at different scales; and finding out wavelet high frequency energy from first scale to fourth scale and wavelet low frequency energy at the fourth scale according to the definition of wavelet energy of the signal at a certain scale, finding out the ratio of the wavelet high frequency energy to the wavelet low frequency energy, and comparing the size of the ratio of the wavelet high frequency energy to the wavelet low frequency energy so as to distinguish the inside faults and the outside faults. A large amount of simulation results show that the invention has good effect.

The invention discloses a hybrid DC (direct current) electric power transmission system comprising a passive filter, a rectifier converter transformer, a thyristor converter, a flat wave reactor, a DC electric power line, a multi-level converter and an inverse converter transformer. A twelve-pulse bridge converter based on a thyristor is arranged at a sending-end rectifier side, and a modularized multi-level converter is arranged at a receiving-end inverter side, thus eliminating the phase conversion failure of the traditional DC electric power transmission system fundamentally and being suitable for supplying power for multi-DC droppoint areas, passive networks or weak alternating current systems and other occasions. Compared with a light-type high-voltage DC electric transmission system, the hybrid DC electric power transmission system provided by the invention has the advantages that the number of expensive full-control devices is greatly decreased, the cost is reduced, the loss is reduced, the reliability is high, the control is flexible, and fewer reactive compensation devices are used. In addition, the hybrid DC electric power transmission system provided by the invention can be used as a black start power supply of a receiving-end alternating current system and is good in engineering application value.

The invention relates to a high-voltage direct-current transmission detecting system and relative method, wherein it is formed by data collector, server and user terminal; the server comprises a forward data server, a real-time data server, a communication manage server and a history data server; the user terminal displays variable data information and supply graph detecting operation; he collector converts the collected analogue signal into digit signal, via network to be sent to the forward data server; the forward data server processes and calculates out relative signal value, and transmits the data to the real-time data server; the real-time data server stores the digit signal value, according to the request of user terminal, to send displayed data to relative user terminal, or transmit the user operation command via forward data server to the operator; the operator will control the executer to complete the operation; the server has stable and reliable operation; the user interface is friend, with simple operation.

The invention provides a compound type high-voltage direct current transmission system which comprises at least one rectifier station, a contravariant station and an aerial electric power transmission line. The rectifier station and the contravariant station both comprise positive electrodes and negative electrodes, a thyristor current converter is adopted in the rectifier station, a positive electrode and a negative electrode of the thyristor current converter both comprise at least one twelve-impulse thyristor current converter, a voltage source current converter which has direct current fault processing capacity is adopted in the contravariant station, and a positive electrode and a negative electrode of voltage source current converter both comprise at least one multi-level current converter with two series-wound modules. Connection points of the positive electrodes and negative electrodes of each station are connected with a grounding electrode or a local network according to operation mode, a double electrode ground return wire or a single ground return wire or a single electrode metal return wire, of the direct current transmission system. By means of the compound type high-voltage direct current transmission system, a commutation failure of the contravariant station in the direct current transmission system is avoided, operation mode is flexible, reliability is high, and project cost is reduced. Besides, the advantages of the thyristor current converter and the voltage source current converter are integrated, and thus the compound type high-voltage direct current transmission system has direct current side fault processing capacity.

The invention provides a method for high-voltage direct-current transmission commutation failure prevention. The method comprises the following steps that: whether commutation failure caused by alternating current-side faults occurs or not is judged; a commutation failure prevention system outputs rectangular wave commands to a control protection system; and rectangular waves are subtracted from trigger angle commands in the control protection system, and a thyristor is triggered in advance. With the method adopted, commutation failure can be prevented when grounding faults or interphase short-circuit faults occur on an alternating current system, and the reduction amplitude of direct-current voltage and power transmission can be lowered after the faults occur.

The invention relates to a double 12-pulse valve bank coordinated-control method for an ultra-high voltage direct-current transmission system. The method is realized in a way that: two valve banks at each pole are connected in series, one ends are connected with each other, and the other ends are respectively connected to an polar high voltage bus and a polar neutral bus; the pole control system is divided into a dipole\pole control layer and a valve bank control layer, the valve bank control layer realizes trigger control on the high-voltage valve bank and the low-voltage valve bank, each valve bank control only collects the respective 12-pulse valve bank conversion flow bus voltage as the synchronous voltage of the trigger pulse, the trigger angle of the two 12-pulse valve banks in series can be adjusted to maintain the direct-current current and the direct current voltage, and the trigger angle between the valve banks in series can be coordinated and controlled to realize balanced operation of the valve banks in series; and the dipole\pole control layer generates a current command and simultaneously transmits the current command to high voltage and low voltage, i.e. master-slave valve bank control. The invention solves the problems of trigger angle deviation of high-voltage valve bank and low-voltage bank in series, and unbalanced voltage distribution caused by competitive control between valve banks in series, measuring errors and other factors.