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

Provided in the invention is a flexible multi-state switch comprising a first isolation transformer (T1), a first controlled voltage source (D11), a direct-current bus voltage-stabilizing capacitor (C1), a second controlled voltage source (D22), a second isolation transformer (T2), and a central controller. A first feeder line (K11) is connected to the first controlled voltage source (D11) throughthe first isolation transformer (T1); a second feeder line (K22) and the second controlled voltage source (D22) ) are connected by the second isolation transformer (T2); and the first controlled voltage source (D11) is connected to the second controlled voltage source (D22) through the direct-current bus capacitor (C1). Various functions including bidirectional circulation of active power betweenfeeder lines, reactive compensation control, short-circuit current suppression, power flow optimization and power quality management and the like are realized by applying different control methods onthe first controlled voltage source (D11) and the second controlled voltage source (D22) of the flexible multi-state switch.

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.

The invention, which relates to the technical field of energy systems, provides an energy router device applied to wind-light energy storage and a control method thereof. The device comprises a bidirectional rectifying unit, a resonant bidirectional DC-DC conversion unit, a photovoltaic Boost transform unit, a bidirectional DC-DC conversion unit, a soft switching single-phase full-bridge inverterunit, a three-phase PWM rectifying unit, a high-voltage direct-current bus, a low-voltage direct-current bus, a DSP controller, a voltage sensor and a current sensor. Meanwhile, on the basis of a hybrid energy storage coordinated control strategy of a stochastic robust optimization method, the device has seven kinds of working modes. In addition, the invention also provides a control method of anenergy router device applied to wind-light energy storage. According to the invention, on the basis of the multi-unit topological structure, the electric energy with various voltage levels can be provided and various load and energy storage device's needs are met; and the photovoltaic-fan complementary power generation is realized by the control method and the hardware structure.

The invention discloses a fault current-limiting control method and system for an MMC type flexible direct-current power grid, which belong to the field of power transmission and distribution of powersystems. By introducing a control variable of the modulation coefficient, the number of submodules actually inputted by a bridge arm unit of a converter is determined by the control signal outputtedby a pole controller and the modulation coefficient together, so that the bus voltage of the direct-current side outlet of the converter is positively correlated with the modulation coefficient. For aflexible direct-current power grid constructed by any type of modular multilevel converter, the number of submodules inputted by the bridge arm unit of the converter is obtained by multiplying the control signal outputted by the converter pole controller by the modulation coefficient. Under a fault condition, the modulation coefficient is reduced, the number of submodules inputted by the bridge arm unit is actively reduced by each converter, so that the DC voltage of the DC side outlet of the converter is reduced when a fault occurs, the fault current of the DC power grid is limited, the on-off capacity of the circuit breaker and the energy absorption of the parallel lightning arrester of the DC circuit breaker are reduced, and the cost is reduced.

The invention relates to power systems and automation, in particular to a system and a method for improving FRT (fault ride-though) capability of a DFIG-WT (doubly fed induction generator based wind turbine) on the basis of an SFCL (superconducting fault current limiter) and an SMES (superconducting magnetic energy storage). The system is characterized in the on the basis of the typical DFIG-WT, aresistor type SFCL is mounted on the stator side of the DFIG-WT, and the SMES is mounted on a direct current link of the DFIG-WT through a bidirectional DC/DC converter; the resistor type SFCL is used for limiting stator fault current of the DFIG-WT, improving generator terminal voltage sag of the DFIG-WT and absorbing partial surplus active power in the DFIG-WT; the SMES is used for stabilizingunbalanced power and electromagnetic torque oscillation. According to an FRT method for the DFIG-WT on the basis of the SFCL and the SMES, fault current can be limited under symmetrical faults and asymmetrical faults, voltage change is inhibited, and unbalanced power and electromagnetic torque oscillation are stabilized. Efficient FRT support can be provided for the DFIG-WT during FRT, and transient performance of the DFIG-WT is improved.

The invention discloses a saturated bridge type short circuit fault current limiter, which comprises a saturated reactor and a rectifier bridge. The connecting point of a first diode (D1) and a second diode (D2) of the rectifier bridge (Br) is a first alternating current end (A); the connecting point of a third diode (D3) and a fourth diode (D4) of the rectifier bridge (Br) is a second alternating current end (B); the connecting point of the first diode (D1) and the third diode (D3) of the rectifier bridge (Br) is a first direct current end (M); the connecting point of the second diode (D2) and the fourth diode (D4) of the rectifier bridge (Br) is a second direct current end (N); the saturated reactor (L) is connected between the first direct current end (M) and the second direct current end (N); one end of an alternating current power supply (Uac) is connected to the first alternating current end (A); the other end of the alternating current power supply (Uac) is grounded; one end of a circuit breaker (SW) is connected to the second alternating current end (B); the other end of the circuit breaker (SW) is connected with a load (RL) in series and is then grounded. The saturated reactor is realized by a permanent magnet and a direct current coil.

The invention discloses a multi-terminal flexible DC power grid fault current limiting method and device. Blocking of a converter station can be avoided so as to ensure high power supply reliability.The method comprises the following steps: constructing a topology structure of a current limiting device; determining the current of the current limiting device in the discharge stage of the energy storage capacitor and the input stage of the current limiting resistor; setting the input criterion of the current limiting device; selecting the key parameters of the current limiting device; and controlling on/off of the thyristor in the current limiting device when the DC side of the flexible DC system fails and serially connecting the current limiting resistor in the fault loop to realize faultcurrent limiting.

The invention relates to a hybrid short-circuit fault current limiter and a current limiting method. The hybrid short-circuit fault current limiter comprises a current transfer branch and a fault current limiting branch, wherein the current transfer branch comprises a rapid mechanical switch and a power electronic switch in series. In a steady state, a current passes through the current transfer branch, and the loss during normal running is reduced; when a fault occurs, a switch on the transfer branch acts, and the current is transferred to the fault current limiting branch; the fault currentlimiting branch comprises a dual-split reactor and a switch, and a first winding of the dual-split reactor is connected in series with the switch and is connected in parallel with a second winding; the switch is switched on in the steady state, and the fault current limiting branch shows low impedance; and the switch is switched off when the fault occurs, and the fault current limiting branch shows high impedance. By matching of the current transfer branch and the fault current limiting branch, the loss of the current limiter during normal running is reduced, meanwhile, fault current limitingis achieved by the dual-split reactor, and running economy and reliability of the current limiter are improved.

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 invention relates to the technical field of circuit fault current limiting, and specifically relates to a short-circuit fault current-limiting transformer. The current-limiting transformer comprises a transformer and short-circuit protection circuits. The secondary coil of the transformer is composed of three identical secondary coils. A low-voltage tap is led out from each of the three secondary coils. One short-circuit protection circuit is connected between each low-voltage tap and the high-voltage end of the corresponding coil. Each short-circuit protection circuit is a current limiting loop in which one low-voltage tap is sequentially connected in series with an auxiliary reactor, a short-circuit protection switch and a capacitor and then connected with the high-voltage end of the corresponding secondary coil, wherein the capacitor is connected in parallel with a power supply switch, and the common joint of the power supply switch and the short-circuit protection switch is connected to a power supply circuit. At the moment when a line fails, a large impedance is added between the power supply and the fault point, and thus, the fault current is limited.

The invention relates to the technical field of direct-current converters, particularly provides a high-power high-transformation-ratio high-voltage direct-current converter for a space and a photovoltaic power generation system, and aims to solve a problem of how to transmit super-power electric energy output by a space solar power station to a high-voltage direct-current bus and ensure stable operation of the direct-current bus. The high-voltage direct-current converter comprises a plurality of direct-current conversion modules, and each direct-current conversion module comprises one or moredirect-current conversion sub-modules which are connected in parallel. A direct-current input side of each direct-current conversion module forms a plurality of direct-current input side ports of theconverter, and direct-current output sides of the direct-current conversion modules are sequentially connected through redundant switches to form direct-current output side ports of the converter sothat output voltages of the direct-current conversion modules is boosted in series, and transmission requirements of microwave transmitters connected later are met. When each direct-current conversionmodule breaks down, the corresponding redundant switch can be switched on to bypass the direct-current conversion module so that normal transmission of each microwave transmitter is not affected, andnormal operation of the system is guaranteed.

The invention discloses a flexible direct-current short-circuit fault protection method based on a thyristor chain and superconducting current limiters. A converter used in a flexible direct-current power transmission system is a modularized multi-level converter cascaded based on half-bridge sub-modules and is of an A-B-C three-phase structure, and each phase comprises an upper bridge arm and a lower bridge arm; each bridge arm consists of a plurality of half-bridge sub-modules and a bridge arm inductor; an alternating current side output port of the modular multilevel converter is connected in parallel with the thyristor chain; the three-phase lines of the AC side of the modular multilevel converter are each connected in series with a superconducting current limiter; the upper ends of the three-phase upper bridge arms of the modular multilevel converter are connected to a direct current side through a first mechanical switch after being short-circuited, and the lower ends of the three-phase lower bridge arms are connected to the direct current side through a second mechanical switch after being short-circuited. According to the protection method, alternating-current and direct-current side current isolation under a fault condition is achieved by turning on the thyristor chain, the direct-current side fault current is reduced to zero, the alternating-current side fault current is limited through the superconducting current limiters, and therefore direct-current short-circuit fault protection of the flexible direct-current power transmission system is achieved.

The invention belongs to the technical field of wind power integration, and relates to a parameter optimization method for integrating a wind power plant of a superconducting magnetic energy storage coil into VSC-HVDC. The problem that the effect of the SMES coil is reduced due to the fact that the initial inductance LSMES, the initial current ISMES0 and four PI control parameters (KPi and KIi, i= 1, 2) of the SMES magnetic energy storage coil are not optimized is solved. The method comprises the following steps: taking minimization of a direct current power accumulation error, minimization of a direct current voltage accumulation deviation and minimization of SMES coil initial energy as target functions, enabling a system to show a minimum direct current power fluctuation situation, configuring different weights, and determining an optimal value of a superconducting magnetic energy storage coil parameter according to a particle swarm algorithm. By utilizing the SMES-FCL, DC power fluctuation caused by intermittent wind power generation can be reduced, and the fault current of a DC line is limited.

The invention provides a flexible multi-state switch and a control method. The flexible multi-state switch comprises two chain type current converters. The chain type current converter comprises three multi-level current conversion chains, the three multi-level current conversion chains are mutually connected end to end to form an angle type connection method, and the end parts are led out to be connected with an alternating current power grid; the multi-level current conversion chain comprises N four-port power modules and at least one damping unit, and N is an integer greater than or equal to 1; the four-port power module is composed of a direct current capacitor, a power assembly, a first switch unit and a second switch unit. The direct-current capacitor is connected with the power assembly, the power assembly comprises four groups of power semiconductor devices which form two bridge arms in a full-bridge connection mode, and midpoints of the two bridge arms are led out to be defined as alternating-current ends of the four-port power module; one end of the first switch unit is connected with a positive electrode or a negative electrode of the direct current capacitor, the other end is connected with one end of the second switch unit, and a connection point of the first switch unit and the second switch unit is led out and defined as a first direct current port; and the other end of the second switch unit is defined as a second direct current port.