52results about How to "Improve traversal ability" patented technology

Power supply systems and methods can enable an electromagnetic device, such as an electrical contactor, to ride-through both voltage sags and dropouts. In an illustrative embodiment, a rectifier is used to generate a DC input voltage from an AC supply voltage. An interface circuit supplies the DC input voltage to an electrical contactor to provide the necessary power for operating the contactor. In general, an electrical contactor that is intended to operate from an AC voltage will operate equally well from a lower magnitude DC voltage. The interface circuit uses this difference in magnitudes between the AC voltage source and an operationally equivalent DC voltage source to maintain the DC input voltage at a desired level even if the AC voltage source sags below its normal operating level. In addition, an energy storage device may be used to store at least some of the DC input voltage. When a sag or dropout occurs in the AC voltage source, the interface circuit is able to maintain the operation of the electrical contactor for a period of time by using the stored DC input voltage as a power source. The energy storage device thus provides a power reservoir that can be accessed during severe voltage sags or even dropouts to ensure continuous operation of the electrical contactor.

The invention discloses a double-fed type wind generating set low-voltage-ride-through control method based on an electromagnetic transient algorithm. The double-fed type wind generating set low-voltage-ride-through control method is characterized in that when falling fault happens to power grid voltages, a control system controls double-fed motor stator flux linkage decoupling, transient state compensating current computing and composition and rotor current loop closing, so that a low-voltage-ride-through purpose of a double-fed type wind generating set is achieved. According to the requirement that transient state voltage impact at a double-fed motor rotor end is lowered when a power grid falls, transient state compensating currents are injected into the double-fed motor rotor end, the angle of the double-fed motor rotor end is set, so that the transient state voltages at the rotor end is optimally controlled when the power grid voltages fall, and accordingly impact from the transient state voltages on the double-fed type wind generating set when the voltages fall is lowered, and meanwhile decay speed of stator direct current flux linkage can be increased, a transient state process of a system is shortened, and influence from a flux linkage negative sequence component on the wind generating set is lowered. Accordingly, through the low-cost high-reliability control method, the voltage fault range which the double-fed type wind generating set can ride through is expanded, and the low-voltage-ride-through performance of the double-fed type wind generating set is greatly improved.

The invention discloses a method for controlling low voltage ride-through of a direct-drive type wind power system. The method comprises the following steps that (1) load torque of an electric generator is changed through a machine side current transformer of a permanent magnet direct drive wind generation set so as to achieve maximum wind energy utilization; (2) under the situation of matching with a direct-current side unloading circuit, when a depth power grid fails, the aim of rapidly and smoothly adjusting the power grid is achieved through the combination of the control strategy that a grid-side current transformer runs in a reactive priority output mode and a reactive compensation circuit additionally arranged on a grid side; (3) a zero d-axis current control strategy is adopted in an electric generator side current transformer to adjust the electromagnetic torque output by the electric generator so as to adjust the rotating speed of the electric generator; (4) a power grid voltage oriented vector control strategy is adopted in the grid-side current transformer, double-loop control is adopted, an outer ring is a direct-current side voltage ring, the direct-current side voltage can be stabilized under the situation that the power grid is normal, the inner ring is a current ring, and the decoupling control over output of active power and reactive power is achieved.

The invention discloses a low voltage ride through control method for a network side inverter of a permanent magnet direct drive wind power system. The low voltage ride through control method comprises a power detector a, a power detector b, a power change detector and a control circuit are adopted, wherein the power change detector is used for receiving output signals from the power detectors a and b to record power changes; a comparator is arranged in the power change detector and is used for comparing an output power of a wind motor and an output power of a network side inverter to generate a practical power difference signal delta P, and inputting the signal delta P into an outer loop controller of the control circuit; and the control circuit is used for realizing current decoupling and generating a PWM (pulse width modulation) control signal to drive the inverter. According to the control method using a power outer loop, stability of the system during a voltage drop and a grid connection period can be guaranteed, reactive power can be compensated along with the power grid drop depth, and overcurrent of the network side inverter can be limited at the same time, therefore, the network side inverter can be guaranteed to work stably.

The invention discloses a voltage fast detection algorithm suitable for a grid power system low voltage ride through function. The voltage fast detection algorithm suitable for the grid power system low voltage ride through function comprises the following steps: (1) acquiring amplitude value information under the normal operation of a power grid based on a phase-locked loop of a synchronous reference coordinate frame, (2) separating the voltage of a sampled power grid into three-phase of A, B, C, conducting a period of delay to the sampled power grid, and acquiring the absolute value of an difference value, (3) setting a voltage threshold value and comparing the difference value in the step (2) with the voltage threshold value, (4) if the difference value is smaller than the voltage threshold value, then judging that the voltage is normal, if the difference value is larger than the voltage threshold value, then turning to step (5), (5) sending real-time voltage signals into a maximum value tracking module and an over zero point tracking module through each of the phrases of voltage, after judging that the system enters into a low voltage status, and (6) recording the maximum value tracking module and the over zero point tracking module to acquire an amplitude value after the voltage of the power gird drops.

The invention provides a dual inverse impedance type submodule, a control method and a modular multi-level converter. The dual inverse impedance type submodule comprises a first inverse impedance typeunit, a second inverse impedance type unit, a clamping diode D3 and a clamping diode D4. The dual inverse impedance type submodule is simple in structure, and can block direct-current fault current,improve the passing-through capacity in case of a fault of a direct current power grid and improve the operation reliability of the direct current power grid; on the premise of an equal output level number, the direct-current fault current block capacity and the clearing speed are equivalent to the direct-current fault current block capacity and the clearing speed of a full-bridge type submodule;and furthermore, the number of used instruments and the additional loss are less than the number of used instruments and the additional loss of a clamping dual module, so that no extra investment is required for a fault isolation function, and the cost is reduced. According to the dual inverse impedance type submodule disclosed by the invention, states of all instruments of the dual inverse impedance type submodule under a normal mode and a closed mode are analyzed, and output voltages of the dual inverse impedance type submodule in different states are provided; and the dual inverse impedancetype submodule can directly adopt modulation and control strategies of a half-bridge type submodule, and a control process is simple and easy to realize.

The invention discloses a comprehensive control method of a double-fed wind power system under the asymmetrical grid voltage condition, which is characterized by comprising the following steps of: 1, establishing a POI (point of interconnection) positive sequence voltage and negative sequence voltage mathematical model of a wind power generator under the condition of asymmetrical voltage sag so as to obtain control methods for controlling POI currents to carry out positive sequence voltage support and negative sequence voltage rejection in sequence; 2, establishing a stable-state mathematicalmodel of a double-fed generator; 3, establishing a decoupling and synthetizing control method of positive sequence active and reactive voltage and negative sequence active and reactive voltage of a converter; 4, establishing the optimum allocation plan of positive and negative sequence currents in the positive sequence voltage support and negative sequence voltage rejection methods, and calculating amplitude values and phase positions of positive and negative sequence synthesizing currents of targets output by a generator system; and 5, carrying out PWM (pulse width modulation) voltage control of a current closed-loop on the converter. The method is used to obviously improve grid-connected conditions of the double-fed wind power system in a wind power station under the asymmetrical grid voltage condition.

The invention discloses a method for using a unified power flow controller in wind turbine generator grid-connected operation, and belongs to the technical field of power electronics. An active and inactive independent control system is established on the series side of a UPFC, compensating voltage is output to an electric transmission line, the power flow distribution capability of the system for optimizing a wind power gird-connected system is researched, and a model is established in Matlab/Simulink software. Simulation results indicate that the UPFC can obviously improve the low voltage ride through capability and optimized power flow distribution of the wind power grid-connected system based on powerful reactive compensation capability and power flow control capability of the UPFC.

The invention provides a low-voltage ride-through simulation system of a wind power generation set and an application method of the low-voltage ride-through simulation system. The simulation system comprises a simulation power system and a static var generator (SVG), wherein the simulation power system is built by using a real time digital system (RTDS) and is used for simulating the wind power generation set connected to a power grid through a transformer, an AC bus and a power transmission circuit, the power transmission circuit is provided with a short-circuit fault point, a grounding resistor is connected to the short-circuit fault point, and the SVG is connected to the AC bus of the simulation power system. By the low-voltage ride-through simulation system, the low-voltage ride-through capability of the system is inspected on the condition of no influence on the running of the real power system, whether the SVG is needed to be additionally arranged is determined to assist the system to improve the low-voltage ride-through capability, the required output capacity of an SVG device is determined, and thus, a reliable basis is provided for a situation that the SVG is additionally arranged in the real power system to improve the low-voltage ride-through capability.

The invention discloses a low-voltage ride through method of a winding type brushless double-fed wind power generator set. The low-voltage ride through method comprises the following steps of S1, calculating a voltage amplitude and a voltage drop depth of a power grid; S2, switching a control strategy of a power generator to a low-voltage ride through control strategy from a normal control strategy if the power grid drops; S3, detecting a current of a control winding of the brushless double-fed power generator in real time, calculating the size of reactive current which shall be injected to the power grid according to the voltage drop depth of the power grid if the current amplitude of the control winding is smaller than a threshold value of the rated current of the control winding, taking the reactive current as a current loop instruction of the control winding, and injecting the reactive current to the power grid to help recovery the voltage of the power grid by a machine-side current converter; S4, detecting the voltage of the power grid in real time, and judging whether a fault of the power grid is eliminated or not; and S5, switching the low-voltage ride through control strategy of the winding type brushless double-fed power generator to the normal control strategy. By the low-voltage ride through method, extra hardware is not additionally arranged, and the low-voltage ride through capability of the power generator can be improved.

The invention discloses a child non-standard balloon dilating catheter, and belongs to the field of medical instruments. The child non-standard balloon dilating catheter comprises an outer tube, a balloon, an inner tube and a connector, the balloon is a sectional tubular cavity and provided with a far-end portion, a middle-end portion and a near-end portion, the cross sections of the far-end portion, the middle-end portion and the near-end portion are elliptical, the middle-end portion can be expanded to reach a dilating diameter larger than the far-end portion, the near-end portion can be expanded to reach a dilating diameter larger than the middle-end portion, the far-end portion, the middle-end portion and the near-end portion of the balloon are provided with tapered transition structures, and the diameters of the tapered transition structures are gradually increased from the far end to the near end of the balloon. The child non-standard balloon dilating catheter has the advantagesthat lesion vessels can be progressively increased from small diameters to large diameters to realize sequential expansion of the balloon dilating catheter, the risk of vascular rupture can be decreased, the balloon dilating catheter can be closely fitted with the vessels in a dilating surgery, and surgical safety and stability are ensured.

The invention discloses a grid-connected PWM converter anti-power-grid-disturbance method which is to reduce the influence of power grid voltage waveform distortion disturbance on the operation of a grid-connected PWM converter. The method comprises judging whether a power grid has waveform transient disturbance in real time by detecting the voltage of the power grid; if power grid disturbance is detected and meanwhile, the grid-connected PWM converter has instantaneous overcurrent, allowing the grid-connected PWM converter to work temporarily under the state of overcurrent in a current hardware clamping manner to prevent fault shutdown to the largest degree; if duration time of the overcurrent state exceeds a set value, causing fault shutdown, but after a fixed time delay, and fault state is restored automatically, putting the converter into operation again; and if no power grid disturbance is detected and meanwhile overcurrent occurs, triggering overcurrent protection, and carrying out direct fault shutdown, fault being not restored automatically. The method can greatly improve anti-power-grid-disturbance capability of the grid-connected PWM converter, and the anti-interference level of the converter is improved.

The invention discloses a doubly-fed motor rotor string dynamic resistance low-voltage ride-through control method, and belongs to the technical field of wind power generation control. According to avoltage drop amplitude and a rotor current threshold value, a rotor side is connected in series with a double dynamic resistor RSDDR, the RSDDR is divided into Rrs1 and Rrs2, the two resistors are flexibly switched according to the voltage drop depth and the rotor current when the low voltage passes through LVRT, a switching strategy of the double dynamic resistors is designed by adopting fuzzy control, a comprehensive rotor resistance input rule is formulated, and the input of the resistor Rrs1 or Rrs2 can be accurately controlled. According to the doubly-fed motor rotor string dynamic resistance low-voltage ride-through control method, a rotor series connection double-dynamic-resistor structure is adopted, according to different voltage drop depths, fuzzy control is adopted for controlling the switching strategy of the double dynamic resistors connected with the rotor in series, fuzzy control has the advantages of being good in dynamic performance and high in adaptability, the stability of a system can be effectively enhanced, and the low-voltage ride through performance is improved.

The invention discloses a self-locking clamping head device of a great saphenous vein stripping catheter. The device comprises a clamping head nut and a self-locking screw, a jamming position is arranged at the top of the self-locking screw, a self-locking thread is arranged in the middle of the outer side of the self-locking screw, a taper guiding piece is arranged at the lower end of the self-locking screw, and a longitudinal assembling groove is formed in the inner side of the self-locking screw; a longitudinal inner thread matched with the self-locking screw is arranged in the middle of the inner side of the clamping head nut, a taper groove is formed in the lower end of the inner side of the clamping head nut, a round hole concentric with the longitudinal assembling groove of the self-locking screw is formed in the bottom of the clamping head nut, and the round hole is communicated with the taper groove. The self-locking clamping head device is simple in structure, a blood vessel and a stripping head are fixed with an arc clamping head nut body and the self-locking screw, operation threads used in traditional operations are substituted for fixing the blood vessel and the stripping head, the working efficiency can be effectively improved, operation time can be effectively shortened, and patient pains can be alleviated.

The invention relates to a method for improving the low voltage ride through capacity of a wind generating set. Electric power storage equipment is additionally arranged in a frequency conversion system of the wind generating set and comprises a charging controller and a battery, wherein the battery is connected to a direct current bus of a frequency converter; and the charging controller has the characteristic of quick charging. The electric power storage equipment comprises the working steps of: under a normal operation state of a power grid, if the active power P1 generated by the wind generating set is higher than the active power P2 required by the power grid, introducing the exceeded power deltaP into the electric power storage equipment for storing; in the fault state of the grid, storing the energy of an impulse current into the battery when the impulse current occurs to the direct current bus of the frequency converter at the beginning of a grid failure; and discharging to the power grid by the electric power storage equipment when a power grid voltage restores to 90% of a rated voltage Un so that the active power P1 generated by the wind generating set is in balance with the active power P2 required by the power grid.

The invention discloses a method for improving the crossing ability of grid-connected photovoltaic power generation under asymmetric operating conditions. The method comprises the following steps: determining the optimal resistance value of a superconducting current limiter based on a superconducting current limiter resistance fixing method; setting the superconducting current limiter with the optimal resistance value in a grid-connected photovoltaic power generation system to limit the active power down level of an on-line current limiting method of the grid-connected photovoltaic power generation system during a sag period; and improving the grid-side voltage of the grid-connected photovoltaic power generation system based on the on-line current limitation method of the grid-connected photovoltaic power generation system to realize transient current limitation of the grid-connected photovoltaic power generation system. In an existing grid-connected photovoltaic power generation system, the on-line current limiting method is used to set the superconducting current limiter resistance fixing method which matches an on-line current limiting strategy, thereby ensuring the optimal selection of the resistance value of the superconducting current limiter, and saving the calculation amount. Through reasonable installation of the superconducting current limiter, the economical efficiency of a coordinated operation method is maximized, thereby improving the smooth asymmetric operating condition crossing ability of grid-connected photovoltaic power generation.

The invention provides a phenothiazine-containing iridium complex as well as a preparation method and application thereof, and belongs to the technical field of photosensitizers. On the basis that a central iridium atom of the metal iridium complex is a heavy atom, the long-life triplet excitation state of the metal iridium complex is regulated and controlled through phenothiazine, the emission spectrum of the designed iridium complex containing the phenothiazine structure is located in a near-infrared region, and the iridium complex belongs to near-infrared phosphorescence emission iridium complexes. The phenothiazine structure is introduced into the N^N ligand of the iridium complex, so that the capability of generating <1>O2 by the iridium complex can be improved. The iridium complex provided by the invention can generate singlet oxygen in both a solution and tumor cells under the illumination condition of more than 470nm, has the capability of photodynamically killing cancer cells, and provides possibility for photodynamic therapy.