155results about How to "Suppressed circulation" patented technology

A leg garment according to the present invention includes a body portion covering at least an instep, a sole and an ankle of a leg. The leg garment includes a support strip exerting a tightening force larger than that of a portion of the leg garment around the support strip. The support strip is arranged in the shape of an inwardly-wound helix extending from the instep to the ankle through the sole. The support strip includes: a first tightening portion arranged so as to medially extend from the instep to the sole; and a second tightening portion arranged so as to extend obliquely upward from a lateral side to a medial side of a ventral ankle, the second tightening portion compressing the ventral ankle via a surface thereof.

The invention relates to a parallel-type permanent magnet direct-drive wind power converter in a wind driven generation system and a control method thereof, belonging to the technical field of power electronics, which solve the problems of increased system volume and complex control method in a traditional parallel converter when the circular flow problem is solved. The parallel-type permanent magnet direct-drive wind power converter consists of two sets of back-to-back PWM (Pulse-Width Modulation) converter module, two input side three-phase reactors and two output side three-phase reactors, wherein each set of back-to-back PWM converter module consists of a rectifier, an inverter and a capacitor. In the control method, a machine side circular flow controller is adopted at a machine side and the output of the machine side circular flow controller is compensated to the initial three-phase duty ratio of a first machine side rectifier; a net side circular flow controller is adopted at a net side and the output of the net side circular flow controller is compensated to the initial three-phase duty ratio of a first net side inverter, thereby respectively adjusting three-phase duty ratio signals of the back-to-back PWM converter modules and achieving the purpose of inhibiting the circular flow. The invention is used for conveying energy of a higher-power generator to power grid.

The invention discloses an APF (Active Power Filter) parallel system. The APF parallel system comprises a plurality of APFs connected with a power grid, and a detection control unit. High-voltage ends of direct current support capacitors of all the APFs are commonly connected, and low-voltage ends of the direct current support capacitors of all the APFs are commonly connected. The parallel system provided by the invention only needs a set of detection control equipment to control the plurality of APFs, thus, less hardware resource is occupied. Simultaneously, the invention further discloses a control method of the APF parallel system. The control method comprises the following steps of: (1) obtaining state information of the power grid, the loads and the parallel system; (2) extracting a current instruction from the load current; (3) calculating a current error signal; (4) performing repetitive control and PI (proportional integral) regulation on the current error signal to obtain a modulation signal; (5) forming a PWM (Pulse-Width Modulation) signal. The method provided by the invention has higher reactive compensation precision and harmonic suppression capability, and can effectively suppress system circulating current.

The invention discloses an improved droop control method based on a communication network for a distributed power source in a parallel connection operation mode in a micro power grid system. The defect of a traditional droop control method is overcome, the performance of the distributed power source in the parallel connection operation mode is improved, the stability of the system is improved, and the improved droop control method is suitable for control over the parallel connection operation mode in the micro power grid system which integrates with new energy resource distributed power generation. According to the improved droop control method, a communication network is used as the basis, a central controller in the micro power grid system and controllers of all inverter units form an entire control system, the active power and the reactive power of public loads are calculated, and the droop control scheme of each distributed power source is corrected. The scheme is used, a better power flow equalizing effect can be achieved, smaller deviation of busbar voltage frequency and amplitude is achieved, and a good application prospect is achieved.

The invention discloses a fluctuation thermoacoustic generation system, which comprises the following loop parts in sequence: cold junction heat exchanger, heat regenerator, heater, heat buffer pipe, hot junction heat exchanger, ring-shaped connection pipe and line generator in the pipe, wherein the generator contains a cylinder with one end of casing on the pipe and the other end with line sliding bearing; a double-loop magnetic-inductive soft iron with ring orifice is set in the cavity between cylinder and casing; the permanent magnet is inserted in the outer ring magnetic wall of soft iron; the coil rack is fixed on cylinder inner wall with part of coil in the ring orifice; the elastic or quality component is set in the hot junction pipe; the quality component does shift sliding along the elastic element; the elastic or quality phase modulation component is set in the greenhouse pipe; the quality component does shift sliding along the elastic phase modulation element. The invention can adjust the phase difference of pressure fluctuation and bulk flow fluctuation, which feedbacks the acoustic power to accomplish high effective Stirling cycle as well as inhibits the loop ring current to improve property of entire machine.

The invention discloses an equalization control method for the power of a plurality of parallel inverters in an island microgrid. The equalization control method comprises the following steps: constructing an alpha-beta coordinate system in a single-phase control system, and calculating the voltage and the power without need of low-pass filtering in the calculation process; and extracting a phase angle of a filtering capacitor voltage in a local controller of all the inverters, and by using the phase angle as reference, transforming a dq coordinate system back to the alpha-beta coordinate system, wherein electric signals are easily transmitted to the local controller from a centralized controller by low-bandwidth communication. The fundamental component of the voltage of the filtering capacitor participates in adjustment of a first quasi-proportional resonance control for the fundamental voltage; the filtering capacitor voltage containing harmonic voltage participates in adjustment of second quasi-proportional resonance control for the characteristic subharmonic voltage. By application of the equalization control method in an equalization control system for the plurality of parallel inverters in the island microgrid under the complex conditions with non-linear loads, different impedances of feeder lines of all the inverters and inconsistent rated capacities, the inverters also can realize equalization control for the output power, and the loop current among all the inverters is effectively inhibited.

The invention provides a method for averagely controlling parallel power of inverters of a low-voltage micro-grid. A method of multiplying feeder line current and virtual complex impedances to obtain base wave virtual impedance voltage is used, output impedances of the inverters are designed to be ohmic and are matched with features of electrical parameters of a feeder line of the low-voltage micro-grid, and droop control output reference voltage is calculated and synthesized by a method of controlling power droop under the condition of ohmic equivalent output impedances; and a phase angle of the droop control output reference voltage is extracted and replaces a phase angle of common busbar voltage to perform dq/alpha beta coordinate transformation, and delay and distortion which are caused by the reason that the phase angle of the common busbar voltage is transmitted to a local controller from an integrated controller through low-bandwidth communication are avoided. When the method is used for a system for averagely controlling the parallel power of the inverters of the low-voltage micro-grid under the conditions that a nonlinear load exists, the feeder line impedances of the inverters are different, and the rated capacities of the inverters are different and the like, average control on the output power of the inverters can be realized, and circulation of the inverters can be restrained effectively.

The invention provides a flexible island grid-connection control device and method for smart power grids. The device comprises flexible inversion units, single-phase electric power detection units, GPS phase detection units, an island grid-connection detection unit, a communication unit and a master control unit. Each flexible inversion unit comprises an angle form differential voltage topological circuit and a star connection type inverter circuit. Each single-phase electric power detection unit is connected with the output end of the corresponding star connection type inverter circuit and a PCC nodal point. Each GPS phase detection unit is connected to the output end of the corresponding star connection type inverter circuit and a PCC nodal point. The input end of the island grid-connection detection unit is connected to the output ends of the single-phase electric power detection units at the PCC nodal points and the output ends of the GPS phase detection units at the PCC nodal points. The output end of the island grid-connection detection unit is connected with the input end of the master control unit. According to the flexible island grid-connection control device, the flexible inversion units composed of novel topological structures can make a micro power grid and a main power grid conduct flexible grid-connection and conduct switching of islanding modes, so that impact of the micro power grid on the circuits is reduced.

The invention discloses a multivoltage level output variable-frequency power source and a control method thereof. A high-voltage charging circuit is connected with a phase-shifting transformer, which is connected with a frequency converter; and the frequency converter is connected with a contactor. Each phase of the frequency converter of the multivoltage level output variable-frequency power source adopts one basis current conversion chain, wherein the basis current conversion chain comprises a power unit and an electric reactor. A three-phase voltage enters into a phase-shifting input transformer through the high-voltage charging circuit, and supplies power for the power unit of the frequency converter after subjecting to voltage reduction of the phase-shifting input transformer. The power unit outputs a single-phase alternating voltage after subjecting to rectifying, filtering and inverting-inversion; and through changing a switch state of a contactor combination, a series connection way and parallel connection way of each basis current conversion chain are changed, so that outputs of rated capacities of different voltage levels are achieved. By adopting the multivoltage level output variable-frequency power source, the rated capacity outputs of multivoltage levels are achieved, each current conversion chain is connected with a sharing reactor, the parallel connection current-sharing effect is good, the circular current phenomenon generated when the current conversion chains are connected in parallel is avoided, the device and production cost is reduced.

The invention discloses a reactive power compensation device of a double-H-bridge modular multilevel converter (MMC) structure under three-phase unbalance and a control method of the reactive power compensation device, and relates to a reactive power compensation device of an MMC and a control method of the reactive power compensation device. The invention aims to solve the problems of poor energy mobility among three phases, low system working efficiency and poor safety and stability existing in the reactive power compensation device in the prior art when a three-phase power grid is at a voltage unbalance state. In the reactive power compensation device, a first controller of a master control part adopts a double-loop control strategy based on positive and negative sequence separation of feedforward decoupling to generate a three-phase modulation signal, a driving signal is generated by a voltage sequencing control method based on carrier phase shifting, and a second controller adopts the combination of a balance control strategy on capacitive voltage of a second H-bridge unit and a control strategy for suppressing system circulation to generate the three-phase modulation signal on the basis of positive and negative sequence separation on the circulation. By the reactive power compensation device, operation can be rapidly, safely and stably carried out under the condition of the unbalance of the power grid.

A vehicle drive device including a rotating electrical machine; a through shaft extending through a rotor shaft of the electrical machine; a power transmission mechanism that transmits power between the rotor shaft and the through shaft; a lubricant supply that supplies lubricant inside of the rotor shaft by rotation of the power transmission mechanism; a first bearing placed radially outward of the rotor shaft to support the rotor shaft; and a second bearing placed radially outward of the through shaft to support the through shaft. The lubricant supply includes a lubricant storing portion located between the first bearing and the second bearing at a position below a rotation central axis of the through shaft. The lubricant storing portion has a portion that communicates with an opening located on an axial first direction side of the rotor shaft, at a position above a lowermost part of the opening.

The invention relates to a grid-connected inverter parallel system circulating current restraining method under an imbalance condition of inductance, relates to the technical field of the circulating current restraining of grid-connected inverter parallel systems, and aims at solving the problems in the grid-connected inverter parallel system that when the three-phase inductance of the parallel inverter is varied or imbalanced, the circulating current is still large through using the existing circulating current restraining method. Since the circulating current flowing between every two inverters is identical in value and opposite in directions, the circulating current between every two inverters can be restrained only by restraining the circulating current of one inverter, so that a purpose for restraining the system circulating current can be achieved. Under the imbalance of the three-phase inductance of the inverter, compared with a PI control method, for the method, the peak value of the circulating current can be reduced by 40 to 65 percent. The grid-connected inverter parallel system circulating current restraining method is suitable for restraining the circulating current in the grid-connected inverter parallel system.

The invention discloses an off-network inverter control method based on frequency division virtual impedance. The off-network inverter control method comprises the steps of measuring a voltage u<c> of an inverter capacitor, an output current i<L> of an inverter and an output current i<o> of an LC filter; extracting a fundamental wave from the voltage of the capacitor C to obtain u<cf>, and extracting an angular frequency Omega<f> of the u<cf>; giving a reference voltage amplitude /U<ref>/, wherein the reference voltage amplitude /U<ref>/ and the angular frequency Omega<f> form a reference capacitance voltage u<creff>; employing a fundamental wave field P regulator by a current regulation ring; setting frequency division virtual resistances z<vir5>, z<vir7> until z<virh>; obtaining harmonic virtual impedance voltages u<vir5>, u<vir7> until u<virh>; employing harmonic fields PR5, PR7 until PRh regulators by a voltage outer ring, and generating an inductive current reference value; employing harmonic fields P5, P7 until Ph regulators by the current regulation ring to obtain a harmonic field modulation signal; and subtracting the harmonic field modulation signal from the fundamental field modulation signal, and outputting a switch pulse to control switch-on and switch-off of an inverter power device after pulse width modulation (PWM). By the off-network inverter control method, a harmonic current is suppressed, balanced running without circulation current of a parallel inverter is achieved, and the system reliability is improved.

Disclosed is an island micro-grid multi-inverter parallel power split control method. Sliding window discrete Fourier transformation is not included in local controllers of inverters, and transmission quantity of an integrated controller is subjected to dq/alfabeta coordinate transformation by the aid of phase angles of droop control output reference voltage. Fundamental-wave virtual impedance voltage and filter capacitor voltage are subtracted from the droop control output reference voltage to acquire a difference value inputted into first quasi proportional resonant control for voltage regulation; the filter capacitor voltage is added to the hth harmonic-wave virtual impedance voltage to acquire a sum value inputted in second quasi proportional resonant control for voltage regulation; the difference of output quantity of the first quasi proportional resonant control and output quantity of the second quasi proportional resonant control is taken as reference current. The method is applied to an island micro-grid multi-inverter parallel power split control system under complicated conditions of nonlinear load bearing, difference of feeder impedance of the inverters, inconformity of rated capacities and the like, inverter output power split control is realized, and loop currents among the inverters are effectively restrained.

The invention relates to an alternating current direct current hybrid microgrid parallel converter ring current suppression method. An alternating current direct current hybrid microgrid consists of an alternating current sub grid and a direct current sub grid, and the two sub grids are connected through a parallel bidirectional power converter. By adoption of the control method, power interactionof the alternating current sub grid and the direct current sub grid can be realized for mutual power support, and smooth switching of grid connection and island mode can be carried out; and the control links mainly comprise automatic operation control and ring current suppression control. The automatic operation control link is specific to different characteristics of alternating current direct current bus voltages, and performs normalization processing thereon according to the sub grid voltage allowable fluctuation range to realize power bidirectional smooth transmission between the alternating current sub grid and the direct current sub grid; the ring current suppression link adopts dq0 three-axis control to replace the conventional dq two-axis control, and proposes a positive sequencecomponent extraction-based ring current suppression method specific to the ring current problem caused by switch action desynchrony, device model difference and the like, so that ring current generation between the parallel bidirectional converters can be suppressed effectively.

The invention relates to a circulating current suppression method of a power system. The method comprises the steps of respectively calculating three-phase circulating current of various parallel inverters by sampling output current of the parallel inverters; obtaining d-axis components and q-axis components of the circulating current through transformation of the circulating current of the parallel inverters from a three-phase static coordinate to a two-phase synchronous rotating coordinate; and adding the d-axis components and the q-axis components of the circulating current to voltage and current loop control of droop control as disturbance, obtaining reference voltage and generating six paths of PWM drive signals to drive on/off of bridge arm switch tubes of the inverters to control inverter output. The equivalent output impedance is not affected, so that power distribution is not affected and the effects of accurately distributing reactive power and suppressing the circulating current can be achieved.

The invention discloses a low-delay robust power droop multi-loop control method which comprises low-delay robust droop control strategy and a voltage and current dual-loop based on virtual complex impedance. The low-delay robust droop control strategy comprises a low-delay fast power calculation method, a robust droop controller and a restoration mechanism. The low-delay robust power droop multi-loop control method aims at a multi-inverter parallel system of a low-voltage microgrid, and has the advantages of improving the robustness of inverters output power to equivalent output impedance and line impedance, relieving the counterbalance relation of the line impedance and power, achieving the accurate allocation of the load power according to a rated capacity ratio, meanwhile reducing the control hysteresis introduced in power calculation, and improving the real time performance and the dynamics of the system.

A high-voltage circuit breaker includes two arcing contacts, which are capable of moving relative to one another along an axis, an insulating nozzle, a heating volume for accommodating quenching gas, a heating channel, and an overpressure valve. The pressure of the quenching gas is based on the energy of a switching arc, which is formed when the breaker opens and generates arcing gas, and the heating channel opens out, with axial alignment, into the heating volume. The heating channel connects an arc zone, and the overpressure valve limits the pressure of the quenching gas by opening a relief duct, which opens out into an expansion space. In high-current switching, the pressure of the arcing gases in the arc zone is limited, and the quality of the quenching gas stored in the heating volume is improved, due to the relief duct having an outflow section extending in the radial direction.

The invention discloses a circulating current control method for parallel power converters. The method includes the steps of 1, calculating magnitude of circulating current of k moment according to a circulating current value of the k moment; 2, adjusting a phase position of a k moment carrier signal according to a phase shift; 3, calculating magnitude of circulating current of k+g (g>/=1) moment according to a circulating current value of the k+g moment; 4, determining changes in the magnitude of the circulating current before and after phase adjustment; 5, adjusting the phase position of a k+g (g>/=1) moment carrier signal according to the changes in the magnitude of the circulating current. The method has the advantages that circulating current caused by a phase difference among PWM (pulse width modulation) carrier signals of power converters in a parallel power conversion system can be suppressed effectively and reliably, the limitation on the quantity of the parallel power converters in parallel power conversion equipment is avoided, and circulating current suppression is convenient to implement. The invention further discloses a control device employing the circulating current control method for parallel power converters.

The invention discloses a parallel variable frequency power supply for a high power and high voltage test, and belongs to the technical field of electric systems. The parallel variable frequency power supply comprises two or more parallel variable frequency power supply parts with current limiting reactors. The parallel variable frequency power supply solves the problem that a main variable frequency power supply controller decodes falsely due to the fact that the signal transmission quantity of optical fiber communication is large when two or more power supplies run in parallel; the parallel variable frequency power supply ensures that asynchronism of output voltage of the parallel variable frequency power supplies is controlled within 1 microsecond; the output synchronism of the variable frequency power supplies is improved; and circular current of output among the power supply parts is realized. In addition, as guard signals are arranged among a main variable frequency power supply and slave variable frequency power supplies, the deficiency in the prior art that when remedial operation cannot be conducted when the variable frequency power supplies fail is overcome.

A content distribution system in which content transmission/reception is suppressed when there is a high risk of contents being stolen by a third party during communication. A content server acquires a communication distance indicating how far the content server is from a terminal in data communication. The content server conducts content transmission/reception when the communication distance is less than or equal to a predetermined value, and suppresses content transmission/reception when the communication distance exceeds the predetermined value.

The invention provides a low frequency model predictive control method based on a hybrid modular multilevel converter. A low frequency model predictive control policy based on upper, middle and lowerlayer control is realized. The upper-layer control establishes an index function and selects a bridge arm output level which meets current, circulating current and bridge arm capacitor voltage controlrequirements of the alternating current side. The optimization calculation amount is effectively reduced. The middle-layer control uses an H-bridge module control algorithm to stabilize the H-bridgemodule capacitor voltage. The equivalent output level is calculated. The number of switching of a bridge arm half-bridge sub-module is determined. The lower-layer control determines the switching signal of each sub-module according to the optimization control policy of the sub-module capacitance voltage. Balance control of the sub-module capacitance voltage is realized. The average switch frequency of sub-modules is reduced.

The invention relates to a method, a device and a system for inhibiting ring current between large power PWM (Pulse-Width Modulation) rectification power supply modules. The method comprises steps of collecting three phase input current of a first rectification power supply module to obtain ring current between the first rectification power supply module and a second rectification power supply module; obtaining a phase difference of triangular carrier signals of the first rectification power supply module and the second rectification power supply module according to the ring current; calculating a carrier compensation delay time according to the carrier phase difference; and adjusting a phase of the triangular carrier signal of the first rectification power supply module according to the carrier compensation delay time so as to synchronize phases of the triangular carrier signals of the first rectification power supply module and the second rectification power supply module. The invention can effectively inhibit ring current between two rectification power supply modules, balances loads of the two rectification power supply modules, and improves safety and stability of a power distribution network.

The invention provides a PFC power supply device comprising an input power supply U, an input power supply V and an input power supply W, wherein the input power supply U is connected with a couplingtransformer T1 in series; one path of an output end of T1 is connected with a boost inductor L1 in series and is connected to an input end of the boost inductor L1, the other path of output end of theT1 is connected with the input end of an boost inductor L2; the output end of the boost inductor L1 is respectively connected to the anode of a boost diode D1, the cathode of a boost diode D2 and theinput end of a boost switching tube S1; the boost inductor L2 is respectively connected to the anode of a boost diode D3, the cathode of a boost diode D4 and the input end of a boost switching tube S2; the cathodes of the boost diodes D1and D3 are connected to the anode of a bus capacitor C1, the output ends of the boost switching tubes S1 and S2 are connected to the cathode of the bus capacitorC1, and the anodes of the boost diodes D2 and D4 are connected to the cathode of a bus capacitor C2; the connection modes of the input power supply V and the input power supply W are the same as thoseof the input power supply U; and the PFC power supply device has the advantages of simple control, good stability and reliability, and capability of increasing the impedance in the loop.