Main loop parameter calculation method and device of SLCC conversion technology and medium

The invention relates to a major loop parameter calculation method for an SLCC (selective line commutation converter) technology, and the method comprises the steps: building a corresponding circuit equivalent model and a circuit simplified equivalent model according to a topological structure of an SLCC; establishing a corresponding phasor diagram according to the circuit equivalent model and the circuit simplified equivalent model; on the basis of the phasor diagram and in combination with a preset control target, calculating a grid-connected point voltage and a front-back deviation angle of the transformer; and according to the grid-connected point voltage and the front and back deviation angles of the transformer, performing steady-state parameter calculation of main loop parameters. According to the technical scheme, by establishing the phasor diagram, the grid side current and the valve side current are separated, main loop parameter calculation is simplified into forward calculation ...

Determination method of network side harmonic current of high-voltage direct current power transmission system

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 ...

Hybrid DC (direct current) electric power transmission system

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 ...

Design method for direct current (DC) filter in high voltage DC transmission project

Mixed MMC-based mixed direct current power transmission system

The invention discloses a mixed MMC-based mixed direct current power transmission system, comprising a rectifying converter station and an inversion converter station, wherein the inversion converter station adopts a mixed MMC. The direct current power transmission system has the active and reactive decoupling control capacity, can transmit power to a reactive network without the phase change failure risk and has direct current fault self-cleaning capacity; under the condition that a feeding end alternating current system has a fault; the mixed MMC has the capacity of outputting a negative level by using a full-bridge submodule, the direct current voltage output by the system can be reduced under the premise of ensuring the controllability and stability of the system, the direct current voltage can be matched with the direct current voltage of a rectifying station, and the direct current power is maintained to be continuously transmitted; due to the optimization on the number of two types ...

Design method for direct current (DC) filter in high voltage DC transmission project

The invention discloses a design method for a DC filter in a high voltage DC transmission project. The design method comprises the following steps of: (1) determining the main capacitance and tuning frequency of the filter according to the system conditions; (2) equalizing the three-tuning filter to 3 single-tuning filters, and calculating the parameters of each single-tuning filter on the restrictive conditions of the main capacitance and tuning frequency of the three-tuning filter; (3) acquiring the parameter of the three-tuning filter based on the parameters of single-tuning filters through an equivalence formula according to the principle of admittance consistency; and (4) performing performance computation for the configured filter, regulating the main capacitance or tuning frequencyof each single-tuning filter if requirements are not met, and then repeating the steps till the requirements are met. The design method is clear in physical concept, convenient in parameter adjustment and ...

Solid-state transformer for direct current collection and delivery of long-distance offshore wind power plant

The invention discloses a solid-state transformer for direct current collection and delivery of a long-distance offshore wind farm, and the transformer comprises a direct current collection boost system which is connected with a multi-level converter MMC through a direct current transmission system; the direct current collection boosting system adopts direct current port fan series connection boosting collection, so that complex control of alternating current collection synchronization is avoided, and the overall reliability of a delivery system is improved; the topology secondary side three-phase full bridge of the DC port fan DC/DC converter adopts diodes, so that the overall cost of the device is effectively reduced. And the power loss in the delivery process is effectively reduced through the delivery of the high-voltage direct-current submarine cable. A multi-level converter MMC is matched with a direct-current energy consumption device to solve the problem of power surplus, the fault ...

DC filter grounding method and system

The invention relates to a DC filter grounding method and system, and the method comprises the steps: determining a grounding mode of a DC filter according to a preset DC filter operation condition; when the direct current filter needs to meet a preset direct current filter operation condition, a pair of grounding type direct current filters is configured at each of two ends of the direct current system, or a pair of grounding type direct current filters is configured at one end of the direct current system, and a group of bridging type direct current filters is configured at the other end of the direct current system; when the direct-current filter does not need to meet the preset direct-current filter operation condition, only a pair of grounded direct-current filters needs to be configured at any end of the direct-current system. The method can deal with the problem that 6-time voltage harmonic waves on the DC side of a DC power transmission system adopting a symmetrical monopole wiring ...

Method and device for calculating harmonic impedance of alternating current system and storage medium

The invention discloses an alternating current system harmonic impedance calculation method and device and a storage medium. The method comprises the steps that a BPA data set and a nonlinear harmonic impedance data set are collected; according to the BPA data set and the nonlinear harmonic impedance data set, an observation node is specified, and a node admittance matrix and an injection current sparse matrix are generated; and calculating the impedance of the observation node under the first frequency according to the node admittance matrix and the injection current sparse matrix. According to the technical scheme provided by the invention, the method can adapt to ever-increasing new energy units in the power grid, and the accuracy of harmonic impedance scanning of the power grid is remarkably improved.

Circulating-current restraining method for three-phase modular multilevel convertor

The invention discloses a circulating-current restraining method for a three-phase modular multilevel convertor. The method comprises the following steps of: processing detected bridge current by utilizing fundamental frequency-doubled rotating coordinates transform based on negative sequences, and then performing signal processing and feedforward compensation link so as to acquire an additional control signal used for restraining circulating current; subtracting the additional control signal from a half of a DC voltage value, superposing an output voltage reference signal on the AC side of the existing converter to acquire a bridge voltage reference signal, and performing pulse width modulation to acquire trigger pulses of various bridges of the converter to ensure that the converter outputs corresponding voltage. The circulating-current restraining method can restrain the circulating current in the converter in a low level under the condition of not increasing the inductance of the bridges ...

Automobile exhaust PM (particle matter) 2.5 catcher based on multiple layers of mesh sieves

The invention discloses an automobile exhaust PM (particle matter) 2.5 catcher based on multiple layers of mesh sieves. A filtering box is arranged in a casing and filled with a solution; the rear end of the box and the rear end of the casing are fixed through a buckle; a gas inlet is formed in the front end of the box and communicated with an exhaust pipe at the front end of the casing; the box is divided into a plurality of intervals by a plurality of vertical gratings, and horizontal gaps and gas channels are formed in each grating; the multiple layers of horizontal mesh sieves are arranged in the box, and each layer of a mesh sieve is fixed into the gaps in the gratings; and a sound attenuation layer is arranged at the upper part of the top mesh sieve. A turbine exhaust pump is arranged at the rear end of the catcher, and an output end of the turbine exhaust pump is connected with a tail exhaust pipe. The automobile exhaust PM2.5 catcher can reduce discharge of PM2.5 in automobile exhaust ...

Calculating method for short-circuit current on direct current side of MMC-MTDC (modular multi-level converter-based multi-terminal direct-current transmission system)

The invention provides a calculating method for short-circuit current on the direct current side of an MMC-MTDC (modular multi-level converter-based multi-terminal direct-current transmission system). The calculating method comprises the steps of (1) calculating an MMC-MTDC direct-current network, and taking calculated steady-state operation current as a steady-state component of the short-circuit current; (2) performing equivalent conversion to obtain an equivalent passive circuit corresponding to an MMC; (3) calculating a fault component of the short-circuit current according to the MMC equivalent passive circuit, a direct-current power transmission line and a fault point direct-current voltage source equivalent calculating network; (4) adding the steady-state component and the fault component to obtain a final short-circuit current calculated result. Therefore, on the premise of guaranteeing the effectiveness, the efficiency for calculating the short-circuit current on the direct current ...

Low-order harmonic filter of high-voltage direct-current power transmission system and parameter setting method of low-order harmonic filter

The invention relates to a low-order harmonic filter of a high-voltage direct-current power transmission system and a parameter setting method of the low-order harmonic filter. The low-order harmonic filter comprises a main capacitor, a first low-end capacitor, a second low-end capacitor, a high-end reactor, a low-end reactor, a first damping resistor and a second damping resistor. One end of the main capacitor is connected with a commutation bus in the DC power transmission system, and the other end of the main capacitor is connected in parallel with one end of the first low-end capacitor and one end of the first damping resistor. The other end of the first low-end capacitor is connected in parallel with one end of the second low-end capacitor, one end of the low-end reactor and one end of the second damping resistor through the high-end reactor, and the other ends of the first damping resistor, the second low-end capacitor, the low-end reactor and the second damping resistor are all directly ...

Circulating-current restraining method for three-phase modular multilevel convertor

The invention discloses a circulating-current restraining method for a three-phase modular multilevel convertor. The method comprises the following steps of: processing detected bridge current by utilizing fundamental frequency-doubled rotating coordinates transform based on negative sequences, and then performing signal processing and feedforward compensation link so as to acquire an additional control signal used for restraining circulating current; subtracting the additional control signal from a half of a DC voltage value, superposing an output voltage reference signal on the AC side of the existing converter to acquire a bridge voltage reference signal, and performing pulse width modulation to acquire trigger pulses of various bridges of the converter to ensure that the converter outputs corresponding voltage. The circulating-current restraining method can restrain the circulating current in the converter in a low level under the condition of not increasing the inductance of the bridges ...

Submodule open-circuit fault diagnosis method and system of MMC under NLM strategy

According to the MMC sub-module open-circuit fault diagnosis method and system under the NLM strategy, the absolute error between the SM capacitor voltage actual value and the predicted value is selected as a diagnosis mark, two MMC sub-module open-circuit faults can be accurately and rapidly diagnosed at different power points, meanwhile, the situation that multiple SM in a bridge arm have faults can be handled, and the fault diagnosis accuracy is improved. And the calculated amount is greatly reduced by using the sorting result of the voltage-sharing control, and the diagnosis process can be completed in one power frequency period, so that the reliability of the modular multilevel converter is improved, and the stable operation of the modular multilevel converter is ensured.

Determination method of high voltage direct current converter commutation overlap angle

The invention discloses a determination method of a high voltage direct current converter commutation overlap angle, aiming to solve the problem that a traditional method for calculating a commutation overlap angle can not take nonideal factors including background harmonics into consider to cause poor design performance of a wave filter. The method comprises the following steps of dividing the working period of a converter into six commutation sections and six non-commutation sections; establishing a differential equation to each commutation section by considering factors such as background harmonic interference, asymmetric fundamental voltage, asymmetric converter trigger angle distances, commutation impedance deviation and the like; and accurately calculating the commutation overlap angle. The invention efficiently enhances the calculation efficiency when ensuring the accuracy and can enhance the design quality of an alternating current converter.

Expansion double-electrode direct current transmission system

The invention discloses an expansion double-electrode direct current transmission system which comprises a rectification convertor station, a rectification side current conversion unit, a three-electrode power transmission circuit, an inversion side current converting unit and an inversion convertor station. When the expansion double-electrode direct current transmission system normally works, the rectification convertor station controls the magnitude of direct currents by controlling the triggering angle of a thyristor and converts the three-phase alternating currents into double-electrode direct currents in a rectification mode; afterwards, the double-electrode direct currents are converted into three-electrode direct currents through current conversion processing, flow through three transmission lines respectively and undergo current conversion reverse processing. The three-electrode currents are converted into the double-electrode direct currents and the direct currents are converted ...

Method for starting three-phase modular multilevel inverter without auxiliary DC power supply

The invention discloses a method for charging and starting a three-phase modular multilevel inverter in a self-excitation way under the condition of no need of an auxiliary DC power supply. In the method, by adopting interphase currents generated by line voltages of an AC system among converter bridge arms, the process of charging capacitors of all the submodules on the bridge arms is completed by controlling switching on and switching off an upper electronic power switch and a lower electronic power switch in the submodules of all the bridge arms when current directions of the bridge arms and capacitor voltages of all the submodules are detected; and all the bridge arms can be simultaneously charged, so that the three-phase modular multilevel inverter can be quickly and normally started in the self-excitation way.

Design method for power transmission system line model

The invention relates to a design method for a power transmission system line model, which comprises the following aspects that: (1) the series expansion mode of the conventional design method is changed, and a hyperbolic sine function sh and hyperbolic cosine function ch series expansion mode adopted by the conventional algorithm is changed into a hyperbolic cotangent function cth and hyperbolic cosecant function csch series expansion mode, so that the problem that high-frequency series and terms are increased is solved, and calculation is simplified on the premise of ensuring accuracy; and (2) the problem that the terms of the series may be not converged in the hyperbolic cotangent function cth and hyperbolic cosecant function csch series expansion mode is solved, a line is subjected to segment processing, and the convergence of the series under the long-line condition is ensured. The invention provides the design method for the power transmission system line model which has high accuracy ...

Designing method of equivalent triple-tuned filter based on single-tuned filter

The invention relates to a designing method of an equivalent triple-tuned filter based on single-tuned filter. The triple-tuned filter is equivalent to three single-tuned filters so as to obtain corresponding parameters of the triple-tuned filter; the designing method specifically comprises the following steps of: (1) according to harmonic characteristic of the system respectively defining the reactive powers to be output by three equivalent single-tuned filters as Q1, Q2 and Q3, and respectively defining harmonic wave times to be inhibited as N1, N2 and N3; (2) computing capacitance inductance parameters of three single-tuned filters; (3) enabling three single-tuned filters to be equivalent to a triple-tuned filter, and obtaining the parameters of the triple-tuned filter through the equivalent formula. A method and an accuracy formula for computing the parameter of the single-tuned filter are provided by the invention; in the process of computing the parameter of the triple-tuned filter ...

Cooperative control method for wind power plant and flexible direct current transmission system for improving inertial level of power system

The invention discloses a cooperative control method for a wind power plant and a flexible direct current transmission system for improving an inertial level of a power system. The control method is used for simulating the inertia of a synchronous generator by virtue of a direct-current capacitor and the kinetic energy of a DFIG (Doubly Fed Induction Generator) rotor. The cooperative control method comprises the steps that a GSVSC (Grid-Side Voltage Source Converter) enables the direct-current capacitor to correspondingly absorb or release energy through the slip frequency control on a direct-current voltage under the disturbance of a power grid; then, a WFVSC (Wind Field Voltage Source Converter) converts the changed direct-current voltage into a wind field side alternating-current system change frequency signal through frequency conversion control after feeling the fluctuation of the direct-current voltage, so that a maritime alternating-current system and a shore alternating-current ...

SVG-based offshore wind power uncontrolled rectification DC power transmission system and control method

The invention provides a static var generator (SVG)-based offshore wind power uncontrolled rectification direct-current power transmission system and a control method, and belongs to the technical field of power electronics. The system comprises an offshore wind power plant, an offshore converter station, positive and negative seabed direct-current submarine cables, an onshore converter station and an onshore power grid; the alternating current side of the offshore wind plant is connected with the alternating current side of the offshore converter station through an offshore alternating current bus; the direct current side of the offshore converter station is connected with the direct current side of the onshore converter station through positive and negative seabed direct current submarine cables; and the alternating current side of the onshore converter station is connected with the onshore power grid. The system can be compatible with the technical advantages of conventional direct current ...

Determination method of high voltage direct current converter commutation overlap angle

The invention discloses a determination method of a high voltage direct current converter commutation overlap angle, aiming to solve the problem that a traditional method for calculating a commutation overlap angle can not take nonideal factors including background harmonics into consider to cause poor design performance of a wave filter. The method comprises the following steps of dividing the working period of a converter into six commutation sections and six non-commutation sections; establishing a differential equation to each commutation section by considering factors such as background harmonic interference, asymmetric fundamental voltage, asymmetric converter trigger angle distances, commutation impedance deviation and the like; and accurately calculating the commutation overlap angle. The invention efficiently enhances the calculation efficiency when ensuring the accuracy and can enhance the design quality of an alternating current converter.

Method for starting three-phase modular multilevel inverter without auxiliary DC power supply

The invention discloses a method for charging and starting a three-phase modular multilevel inverter in a self-excitation way under the condition of no need of an auxiliary DC power supply. In the method, by adopting interphase currents generated by line voltages of an AC system among converter bridge arms, the process of charging capacitors of all the submodules on the bridge arms is completed by controlling switching on and switching off an upper electronic power switch and a lower electronic power switch in the submodules of all the bridge arms when current directions of the bridge arms and capacitor voltages of all the submodules are detected; and all the bridge arms can be simultaneously charged, so that the three-phase modular multilevel inverter can be quickly and normally started in the self-excitation way.