43results about How to "Limit fault current" patented technology

The invention discloses a cascaded converter-based multifunctional high-speed switch device which structurally comprises a main switch module, an auxiliary switch K1, an auxiliary switch K2 and an auxiliary switch K3; the main switch module is connected with a power source by the auxiliary switch K1 and is connected with a load by the auxiliary switch K3, and the main switch module is connected with the auxiliary switch K1 and the auxiliary switch K3 with each other in series and is connected with the auxiliary switch K2 in parallel with each other; and the main switch module comprises a cascaded H bridge converter and a wave filtering link, an output end of the cascaded H bridge converter is connected with the wave filtering link, and the cascaded H bridge converter comprises n H bridge converter cascaded units which are connected with one another in series. The cascaded converter-based multifunctional high-speed switch device is flexibly applicable to various connection modes between the power source and the load, has various functions of superspeed switching, voltage compensating, fault current limiting and the like, and is applicable to the middle and high voltage occasion due to a cascaded structure.

This application provides a method for determining parameters of DC power grid components. The DC power grid includes at least two converter stations and at least one DC line between the converter stations. The method includes: determining the component parameters of the power grid to be determined; based on the topology of the power grid and the Component parameters determine the state matrix; based on the state matrix and the DC line fault current time domain expression, determine the relationship between the DC line fault current changing with time with one component parameter of the power grid as a variable; based on the DC line fault current The suppression requirements of fault current on the line determine the range of component parameters of the power grid.

The invention discloses a flexible DC short-circuit fault protection method based on a thyristor chain and a superconducting current limiter. The converter used in the flexible DC power transmission system is a modular multi-level converter based on cascaded half-bridge sub-modules: ABC three-phase structure, each phase includes an upper bridge arm and a lower bridge arm, each bridge arm is composed of several half-bridge sub-modules and a bridge arm inductor; the output port of the modular multi-level converter AC side is connected in parallel with a thyristor A superconducting current limiter is connected in series with each of the three-phase lines on the AC side of the modular multilevel converter; the upper ends of the three-phase upper arms of the modular multilevel converter are short-circuited and connected to the DC side through the first mechanical switch , the lower end of the three-phase lower bridge arm is short-circuited and then connected to the DC side through the second mechanical switch. The protection method realizes the current isolation of the AC and DC sides under fault conditions by opening the thyristor chain and reduces the fault current of the DC side to zero, and limits the fault current of the AC side through the superconducting current limiter, thereby realizing the DC short-circuit fault protection of the flexible DC transmission system.

The invention relates to an AC-DC hybrid distribution network based on flexible multi-state switches, the distribution network includes N AC power supply networks, where N is an integer greater than or equal to 2; each AC power supply network includes at least one pivot node , at least one terminal node and at least two branch nodes, the power distribution network further includes at least N flexible multi-state switches, the AC terminals of the flexible multi-state switches are connected to the AC power grid, which can realize AC and DC voltage conversion, and the DC port leads out; The invention also relates to a control test method including the above distribution network, which can realize active power balance, stabilize the system frequency and voltage, and improve the reliability of the distribution network.

The disclosed current limiter for short circuit fault is constituted by adding a cascaded capacitor to positive / negative DC ends of rectification bridge of existed current limiter for short circuit fault respectively; two capacitors and two current limiting inductances are connected in shape of number '8'. The disclosed current limiter can restrict peak value of fault current, restrict ascending velocity of fault current at any time, improves distortion of stable current generated by current limiter. Under condition of canceling bias voltage, size and cost can be reduced. Based on connection method of existed current limiter for short circuit fault, the invention can constitute multiple circuit structures. Advantages are: simple structure, high current limiting capacity, raised quality, stability, safety and reliability of power network.

The present invention proposes a through-type in-phase traction power supply system based on a balance transformer and four-port MMC. Traction transformer T in the form of two-phase balanced connection 1 and T 2 , a static power converter SPC with three input and one output ports; T 1 and T 2 The three-phase primary side port of the circuit breaker is connected to the three-phase synchronous public AC grid, T 1 and T 2 The three-phase secondary ports of the SPC are respectively connected to the three input ports of the SPC, and the output ports of the SPC are connected to the traction bus; the SPC is composed of k four-port modular multilevel converters 4P-MMC connected in parallel, and each 4P-MMC Each includes four phases, and each phase is composed of upper and lower bridge arms in series. The three-phase midpoints of each 4P‑MMC are respectively connected to the corresponding input ports of the SPC through a three-phase circuit breaker, and the fourth phase midpoints of each 4P‑MMC are respectively connected by The circuit breaker is connected to the output port of the SPC. The invention has the advantages of simple wiring and low cost.

The invention discloses a comprehensive protection method and device of a direct current collection cable, and relates to the technical field of fault protection of a direct current collection grid-connected system. The method can inhibit the fault current and accurately position the direct current cable fault position. The method mainly comprises the steps that a direct current capacitor discharging equivalent circuit of the starting end or terminal end of the direct current cable is built, wherein the equivalent circuit comprises series connection current limiting reactors used by the method; according to the capacitor discharging equivalent circuit and protection constraint conditions, the reactance parameter values of the current limiting reactors are calculated; the current limiting reactors with the reactance parameter values are connected in series in the direct current cable; the voltage values on the current limiting reactors connected in series in the direct current cable areobtained; according to the voltage values of the current limiting reactors, the fault types of the direct current cable are judged, wherein the fault types include a positive electrode fault, a negative electrode fault and an interelectrode fault; according to the fault types, the position of fault points is calculated and positioned. The method and the device are mainly applied to fault protection and fault positioning of the direct current cable in new energy source direct current collection networks and other direct current power transmission and power distribution networks.

The present application provides a flexible multi-state switch and a control method: the flexible multi-state switch includes two chain converters; the chain converter includes three multi-level commutation chains, and three multi-level commutation chains The head and tail of the chain are connected to each other to form an angle connection, and the ends are drawn out and connected to the AC power grid; the multi-level commutation chain includes N four-port power modules and at least one damping unit, and N is an integer greater than or equal to 1; so The four-port power module is composed of a DC capacitor, a power component, a first switch unit and a second switch unit; the DC capacitor is connected to the power component, and the power component includes four groups of power semiconductor devices to form two bridge arms, that is, a full bridge connection In the form, the midpoint of the two bridge arms is defined as the AC end of the four-port power module; one end of the first switch unit is connected to the positive or negative electrode of the DC capacitor, and the other end is connected to one end of the second switch unit. The first switch unit is connected to The connection point of the second switch unit is defined as the first DC port; the other end of the second switch unit is defined as the second DC port.

The invention relates to a mixed excitation type economical three-phase magnetic saturation fault current limiter comprising a magnetic core, a coil winding, three current limiting inductors and a direct current excitation power source, wherein the magnetic core comprises two pillars with an air gap therebetween, and left A, B and C phase side pillars and right A, B and C phase side pillars positioned on two sides of the central pillars; and the coil winding comprises a first coil and a second coil wound on a left A pillar, a third coil and a fourth coil wound on a left B pillar, a fifth coiland a sixth coil wound on a left C pillar, a seventh coil and an eighth coil wound on a right A pillar, a ninth coil and a tenth coil wound on a left B pillar, and an eleventh coil and a twelfth coilwound on a left C pillar. According to the mixed excitation type economical three-phase magnetic saturation fault current limiter, the three phase current limiter is integrated, the good limiting effect is achieved for a short-circuit current with various fault types, and the magnetic material and installation area are greatly saved. Furthermore, the loss in the iron core is also greatly reduced.

The invention discloses a novel combined DC circuit breaker topology, which adopts only one main breaker switch, one malfunctioning auxiliary switch, one transfer switch TS0 connected in series with the main breaker switch, two groups of diodes in different directions, and a transfer switch TS1 corresponding to m lines on each DC bus bar, wherein, the main breaker switch TS0 is connected with themain breaker switch TS0, and the main breaker switch TS1 is connected with the main breaker switch TS0-TSm. The transfer switch TS0 is connected in parallel with the failed auxiliary switch in serieswith the main disconnect switch, one end of the main disconnect switch is connected with the DC bus bar, the other end is connected with the diode group in the direction of the inflow line through thetransfer switch TS0, and is also connected with the diode group in the direction of the outflow line through the failed auxiliary switch. The transfer switch TS1-TSm is respectively connected to thebus bar and the corresponding line 1-Line m. When the system is in normal operation, the voltage on both ends of the switches of each part of the novel combined DC circuit breaker is zero, which can effectively reduce the breakdown probability of the device, improve the operation reliability of the system as a whole, adopt fewer main devices, and have better economy.

A flexible switching station interconnection structure with comprehensive distribution of multiple electric energies. The interconnection structure of the flexible switch station is composed of several flexible switch stations. The input end of each flexible switch station is connected to the high-voltage AC bus, and the output of the flexible switch station is respectively connected to the low-voltage AC bus and the low-voltage DC bus; the end of the low-voltage AC bus It is connected through a flexible multi-state switch, and the ends of the low-voltage DC bus are connected through a DC-DC converter; both the low-voltage AC bus and the low-voltage DC bus are connected with loads, energy storage components and distributed power sources. The invention interconnects the flexible switching station with functions of AC and DC voltage conversion and power distribution through flexible multi-state switches and DC-DC converters. Compared with traditional substations, the flexible switch station interconnection system has the advantages of active power flow control, flexible topology construction, distributed energy consumption, multi-voltage level interconnection, and unified distribution of AC and DC, which improves the reliability and diversity of power supply.

The invention discloses a short-circuit fault current limiter and relates to a short-circuit fault current limiter for a transmission and distribution power grid. The short-circuit fault current limiter is composed of a first electric reactor, a second electric reactor, a double-splitting electric reactor, a capacitor and a switch, wherein a first winding of the double-splitting electric reactor is connected with a second winding in parallel after being connected with the switch in series and then is connected with the capacitor in parallel, a parallel circuit is connected with the second electric reactor in series, and the whole series-parallel circuit and the first electric reactor are connected in parallel to form the short-circuit fault current limiter. According to the short-circuit fault current limiter, through the cooperation between the double-splitting electric reactor and the switch, impedance change and rapid short circuit of the capacitor are achieved during current limiting, the electric reactors are put into use fast, overcurrent impact and overvoltage impact when the double-splitting electric reactor cooperates with the switch are relieved through the parallel connection of the first electric reactor, and the operating reliability and the current limiting capacity of the limiter are improved.

The invention provides an energy storage optimization control method for an energy router device applied to wind and solar energy storage, and relates to the technical field of energy systems. The device includes a bidirectional rectifier unit, a resonant bidirectional DC-DC conversion unit, a photovoltaic Boost conversion unit, a bidirectional DC-DC conversion unit, a soft-switching single-phase full-bridge inverter unit, a three-phase PWM rectifier unit, a high-voltage DC bus, a low-voltage DC bus, DSP controller, voltage sensor and current sensor; at the same time, the device adopts a hybrid energy storage coordinated control strategy of a stochastic robust optimization method, including 7 working modes; the invention also provides an energy router device applied to wind and solar energy storage A control method for energy storage optimization. The energy router device and control method applied to wind and solar energy storage provided by the present invention, the multi-unit topology adopted by the device determines that it can provide electric energy of various voltage levels, meet the needs of various loads and energy storage equipment, and can control The method and hardware structure realize the effect of photovoltaic and wind turbine complementary power generation.