175 results about "Cascade converter" patented technology

A circuit and a method for controlling output current of cascaded switching power converters having a buck type output stage are disclosed. The circuit comprises two comparators for sensing input and output current, a logic gate for processing the output states of the comparators, and a pulse width modulator circuit for receiving the output of the logic gate and for controlling a switching power converter in accordance with this output. The method comprises simultaneous monitoring current in the stages of the converter, comparing the currents to the corresponding reference levels, generating the corresponding error signals, and controlling a pulse-width modulator circuit of a switching converter in accordance with these error signals.

A method of providing power to a load is provided. A first series resonant converter is provided. A second SRC is operably coupled to the first SRC in a cascade connected arrangement. First and second zero voltage switching (ZVS)-assistance networks are operably coupled between the first SRC and the second SRC, such that the first and second ZVS-assistance networks are providing first and second ZVS-assistant currents flowing from each ZVS-assistance network to the cascade connected arrangement of SRCs. Power from a power source is received at the cascade connected arrangement of first and second SRCs, power from a power source. The cascade connected arrangement of first and second SRCs supplies an output voltage to the load in response to receiving power from the power source.

A line voltage LED Lamp produces variable illumination in response to industry standard lighting dimmers, through the use of an input voltage monitoring circuit which variably controls the current output of an integral driver in response to sensed changes in the input voltage. A cascaded converter circuit is used to achieve a very high step-down ratio, enabling the LEDs to be driven from a high input voltage without the need for a power transformer. Electrolytic capacitors are avoided, increasing the life of the driver circuit in the high ambient temperatures typically encountered in the base of similar lamps. The circuit employed drives high power LEDs, and the lamp is adapted to fit common MR16 size fixtures. Illumination output equivalent to similar size halogen bulbs is achieved.

A method of providing power to a load is provided. A first series resonant converter is provided. A second SRC is operably coupled to the first SRC in a cascade connected arrangement. First and second zero voltage switching (ZVS)-assistance networks are operably coupled between the first SRC and the second SRC, such that the first and second ZVS-assistance networks are providing first and second ZVS-assistant currents flowing from each ZVS-assistance network to the cascade connected arrangement of SRCs. Power from a power source is received at the cascade connected arrangement of first and second SRCs, power from a power source. The cascade connected arrangement of first and second SRCs supplies an output voltage to the load in response to receiving power from the power source.

A cascaded electric power converter and a method of operating a cascaded electric power converter are disclosed. The cascaded converter includes: a converter cell including a cell capacitor and at least one phase leg having at least two electric valves, the at least one phase leg being connected in parallel to the cell capacitor; and a control system for controlling the switching of the electric valves of the at least one phase leg. The control system is configured to, upon detection of a need to by-pass the converter cell, control the switching of the electric valves in a manner so that the cell capacitor is short circuited via a phase leg, so as to obtain a current surge through the phase leg, thereby creating a permanent current path through the converter cell.

The present invention provides a multi-port modular multilevel converter for multi-end flexible direct-current transmission application. The multi-port modular multilevel converter is composed of (2n+1) cascaded converters; each cascaded converter is composed of three bridge arms; N sub-modules and corresponding bridge arm impedors are connected in series to form each bridge arm; according to the modular multilevel converter (MMC), the (2n+1) cascaded converters altogether form (2n+1) neutral points; and a direct-current transmission line positive pole bus-bar is led out from the neutral point of the cascaded converter (0), and 2n negative pole direct-current transmission lines are led out from the neutral points of the other 2n cascaded converters, so that 2n direct-current transmission lines can be formed. According to the multi-port modular multilevel converter of the invention, the bridge arms can be multiplexed, so that the total number of power devices can be decreased, loss and the total number of capacitors can be reduced; and under a condition that a high-voltage direct-current circuit breaker is not adopted, the blocking of any malfunctioned line can be realized through the direct-current fault blocking ability of the converter with normal operation of the other power transmission lines not affected.

The invention discloses a novel cascaded three-phase bridge converter and belongs to alternating current (AC) / direct current (DC) converters. The converter comprises three-phase AC power supplies, three input inductors and three cascaded three-phase voltage type bridge converters, wherein the three-phase AC power supplies are in star connection and do not have a neutral line. A voltage stress of a switching tube is reduced by using a connection mode of cascaded superposition of three-phase input line voltages, so the converter is applicable to high-voltage and high-power level occasions; and when three-phase input power supplies are unbalanced, inter-phase energy can be compensated for each other, so DC output voltages of each three-phase bridge are automatically equalized. By using cascade connection between bridge arms of the three-phase bridges, compared with a three-phase cascaded converter which is cascaded in same level (m level) and consists of single-phase H-bridge cascaded converters, the novel cascaded three-phase bridge converter has the advantage that: six active switching tubes and m+1 output capacitors are eliminated, so the cost and volume of the converter are reduced.

The invention relates to a redundant power supply of an H-bridge cascading converter. The redundant power supply is composed of 3N power modules with identical structures, each power module comprises an equalizing resistor, a controllable switch, a DC / AC converter, a single-input three-output four-winding isolation transformer, three AC / DC converters, six output diodes, a direct current input side and three direct current output sides. Each power module corresponds to an H-bridge chain link, the input ends of the power modules are connected to the positive electrodes and the negative electrodes of the direct current bus supporting capacitors of the corresponding chain links in parallel, and the three output ends of the power modules provide control power supplies for the corresponding chain links and two chain links most adjacent to the power modules respectively. According to the scheme of the redundant power supply, each H-bridge chain link is provided with three channels of control power inputs, and the three channels of power inputs are from the power module corresponding to each H-bridge chain link and the power modules corresponding to two chain links most adjacent to each H-bridge chain link respectively, and are connected together in parallel to provide the control power supplies for each H-bridge chain link.

A line voltage LED Lamp produces variable illumination in response to industry standard lighting dimmers, through the use of an input voltage monitoring circuit which variably controls the current output of an integral driver in response to sensed changes in the input voltage. A cascaded converter circuit is used to achieve a very high step-down ratio, enabling the LEDs to be driven from a high input voltage without the need for a power transformer. Electrolytic capacitors are avoided, increasing the life of the driver circuit in the high ambient temperatures typically encountered in the base of similar lamps. The circuit employed drives high power LEDs, and the lamp is adapted to fit common MR16 size fixtures. Illumination output equivalent to similar size halogen bulbs is achieved.

The invention provides a modulation method applied to a cascade converter, which comprises the following steps: obtaining a linear modulation region, a first over-modulation region and a second over-modulation region according to the direct current voltage value, the control command reference voltage vector and the power unit number of each phase of a bridge voltage source type power unit; and setting Edc as the direct current voltage value of the bridge voltage source type power unit, V<*> as the control command reference voltage vector, and n as the power unit number of each phase so that the modulation ratio m is equal to (pi|V<*> / 2n|) / 2Edc, wherein the interval that m is more than or equal to 0 and less than or equal to 0.906 is the linear modulation region, the interval that m is more than or equal to 0.906 and less than or equal to 0.951 is the first over-modulation region, and the interval that m is more than or equal to 0.951 and less than or equal to 1 is the second over-modulation region. The modulation method can simplify the judgment time of the vector areas.

The invention provides a cascaded converter and a protection method thereof. A discharge loop and a bypass circuit are added into the converter, and simultaneously, an active voltage equalizing method or an overvoltage protection method is used for monitoring the converter to ensure that the direct-current bus voltage of each transformer in the cascaded converter is in a balanced state, or the overvoltage protection is performed when the voltage is overhigh. In the invention, the active voltage equalizing method obtains a good effect through tests. In the invention, the overvoltage protection method and the active voltage equalizing control method adopt the same circuit, a fast protection method is provided, a good protection effect can be obtained, the failure-free operation time of a system is prolonged, and a foundation is provided for the application of the cascaded converter. The invention has important significance for the application of cascaded converters in the future.

The invention discloses a testing device for operation of a current changing chain and a control method. The testing device comprises two current changing chains, wherein one end of each current changing chain is connected with a reactor in series; and a single-phase system transmits current to the current changing chain by a soft circuit and the reactor so as to charge the two current changing chains. Inverse outputs of the two current changing chains are started simultaneously, and the output currents are increased gradually and respectively, so that one current changing chain works in a capacitive output state, and the other current changing chain works in a sensible output state till the two current changing chains meet the testing conditions. By test, whether the current chaining chains can operate normally to meet the designed capacity and overload capability under various working conditions can be judged. The invention has the advantages that the circuit is simple, and all parts of a cascade converter can be completely utilized without need of adding a special testing part additionally; long-time and high-power test can not cause influence on the system, and the power waste is reduced; and the requirement on the system capacity is very low without need of capacity expansion and modification on a power supply.

The invention discloses a triangular connection type comprehensive compensation system integrated with a cascaded active filter and a reactive compensator. The system comprises triangular connection type N-grade cascaded converters and a three-phase filter inductor connected with each N-grade cascaded converter; triangular connection type thyristor reactors and star-shaped connection type thyristors are used for switching the reactive compensator composed of fixed capacitors; and the triangular connection type N-grade cascaded converters and the reactive compensator are connected in parallel between a connection node and a ground node of an input power grid voltage and a load. According to the system provided by the invention, reactive power and harmonic current in a medium-voltage power grid are subjected to dynamic compensation and the efficiency of the power grid is improved; when the system is used for compensating, the system has no negative influences on the power grid, and has advantages of stable system, simple structure, strong stability and flexibility in compensation.

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 discloses a power electronic transformer suitable for a hybrid micro-grid and a coordinated control and mode switching method thereof. The transformer includes an input stage, an isolation conversion stage, and an output stage. The input stage includes an H-bridge cascade converter. The isolation conversion stage includes dual active bridge converters. The output stage includes a three-phase voltage source inverter. A high-voltage alternating current input port is connected with the alternating current side of the H-bridge cascade converter. The high-voltage side of each dual active bridge converter is connected with the direct current capacitor of the H-bridge cascade converter, and the low-voltage side is connected in parallel with a low-voltage direct current output port.The direct current side of the three-phase voltage source inverter is connected with the low-voltage direct current output port, and the alternating current side is connected with a low-voltage alternating current output port. The low-voltage direct current output port is connected with the low-voltage direct current grid of the hybrid micro-grid system. According to the invention, multi-mode flexible operation of the hybrid micro-grid is realized; the problem of alternating current-direct current micro-grid power imbalance caused by the off hybrid micro-grid is solved; and the problem of power quality deterioration caused by operating mode switching is solved.

The invention discloses a two level conversion type AC-DC Power electronic transformer which includes three filter inductors Lga, Lgb and Lgc, three cascade converters CCA, CCB and CCC, three low frequency blocking capacitors CLFB1, CLFB2 and CLFB3, three high frequency isolation transformers THF1, THF2 and THF3, and three high frequency rectifiers REC1, REC2 and REC3. The two level conversion type AC-DC Power electronic transformer includes two level transformation involving a direct AC / AC conversion from lower frequency AC to high frequency AC and an AC / DC conversion from high frequency AC to DC. The cascade converters CCA, CCB and CCC realize direct AC / AC conversion of power which changes from lower frequency AC to high frequency AC, and the high frequency rectifiers REC1, REC2 and REC3 realize high frequency AC / DC conversion of power. Compared with existed topology of power electronic transformers, according to the invention, the two level conversion type AC-DC Power electronic transformer herein has less transformation levels, has less switch devices and high operation efficiency.

The invention discloses a variable-modal cascade converter. Output of a PFC converter is connected with input of a full-bridge converter to form the variable-modal cascade converter; the input of the PFC converter and the output of the full-bridge converter are input and output of the variable-modal cascade converter respectively; output voltage of the PFC converter controls a target value; the output voltage is determined according to the input voltage size; and the full-bridge converter selectively works in a half-bridge mode or a full-bridge mode according to the output voltage. According to the variable-modal cascade converter, the problem of low circuit efficiency when input voltage is low in related technologies is solved; high efficiency within a full range is achieved; and the overall performance of a circuit is improved.

The invention provides a control system for a cascaded converter multi-submodule multi-working condition simulation device. A simulation device includes a current generator used for generating testingcurrent and a submodule system; the submodule system includes upper and lower bridge testing units which are in series connection, and used for receiving the current generated by the current generator and output capacitance and voltage signals of submodules; a cascaded converter system parameter module is used for outputting current and voltage reference signals corresponding to actual cascaded converter system parameters and operation working conditions to a current controller and a voltage controller; the current controller is used for generating a control signal of the current generator; and the voltage controller is used for generating the control signal of switch devices in each testing unit of the submodule system. A control method is simultaneously provided. The system can realizethe operation working condition simulation of any submodules of a cascaded converter, and realize the simultaneous testing of the multiple submodules under multiple working conditions, so that testingcosts can be saved, and testing efficiency and accuracy can be enhanced.

The invention discloses a cascading static synchronous reactive compensator topology with an energy exchange unit and a control method thereof, and relates to the power unit capacitor voltage balance control technology of a cascaded reactive compensation device. The cascading static synchronous reactive compensator topology with the energy exchange unit and the control method thereof aim at solving the problems existing in the method adopted by an existing star connection cascade converter for the capacitor voltage unbalance among phases that the output current of the converter changes and breaks the control reliability and extracting of positive and negative sequence components has lowpass filtering and influences the dynamic performance of the cascading static synchronous compensator. The cascading static synchronous reactive compensator topology comprises N-1 power modules which adopt the star connection, and the N is a positive integer; the N power module adopts the energy exchange unit EEU, the energy exchange unit EEU is connected with a star point, the energy exchange unit EEU comprises a three-phase bridge and two common capacitors, and the three-phase bridge and the common capacitors adopt the star connection. The cascading static synchronous reactive compensator topology with the energy exchange unit and the control method thereof are used in the cascaded reactive compensation device based on the power unit.

The invention discloses a mixing cascaded multi-electric-level converter topology based on a T type APF. The mixing cascaded multi-electric-level converter topology comprises the T type APF and three single-phase H bridge inverters, wherein the T type APF is used for restraining higher harmonics and high-frequency on-off ripple waves generated by the converters, and the three single-phase H bridge inverters operate at high voltage, medium voltage and low voltage respectively. The three single-phase H bridge inverters are connected in an end-to-end mode to be used for generating multi-electric-level voltage high in quality, and the T type APF is connected with the low-voltage single-phase H bridge inverter. The mixing cascaded multi-electric-level converter topology has the advantages that the defects that the number of modules of a traditional cascaded converter is large, and reliability is low are overcome, and meanwhile the problems that existing mixing cascaded multi-electric-level topology fails to sufficiently utilize the voltage withstanding characteristic advantage of all kinds of power electronic devices, the high-frequency on-off ripple waves and higher harmonics of the converter lead to poor electromagnetic compatibility, and high-frequency resonance between a device and a power grid is prone to being generated are solved. According to the topology structure, the operation voltage of the H bridge units at high voltage, medium voltage and low voltage is allocated according to the proportion of 6:2:1, so that advantages of an IGCT, an IGCB and other semiconductor devices are brought into full play.

The invention discloses a working condition simulation test circuit and method for a cascaded converter sub-module. The circuit comprises a current generator which is used for generating a current needed by a to-be-tested sub-module; the to-be-tested sub-module which is used for receiving a current signal and outputting a capacitor voltage signal; a voltage controller which is used for receiving the capacitor voltage signal and generating a voltage regulation signal, so that the capacitor voltage of the to-be-tested sub-module is consistent with a reference voltage; a current controller whichis used for receiving the current signal and the voltage regulation signal and generating a control signal of the current generator to control the running state of the current generator; an auxiliarybridge arm which is switched on when the to-be-tested sub-module operates in a cut-off state and matches the current generator to carry out auxiliary adjustment on the output current of the current generator; an auxiliary bridge arm controller which is used for controlling the auxiliary bridge arm; and a converter system model which is used for controlling the to-be-tested sub-module, the currentcontroller and the voltage controller. According to the invention, the test cost is reduced, and the safety is improved.

The invention provides a prebias switch machine circuit and a prebias circuit and method of a multi-cascade converter, and is applied to the field of communication. The prebias switch machine circuit comprises a detection module and a control module, wherein the detection module is connected with an output end of the multi-cascade converter and is used for detecting an output signal of the multi-cascade converter, and the control module is connected with a push-pull circuit of the multi-cascade converter and is used for generating a prebias signal according to the detected output signal when the output signal is a preset output signal and controlling a rectification tube driving switch circuit of the push-pull circuit according to the prebias signal. Compared with the prior art, the prebias switch machine circuit has the advantages that the prebias switch machine circuit is additionally arranged in a DC converter, whether a prebias switch machine is needed or not is judged by detecting the output signal of the multi-cascade converter, the prebias switch machine circuit is simple to implement, and accurate control of an entry point is achieved. By the prebias switch machine circuit, the problem of device damage due to excessively large reverse current of a freewheeling switching tube caused by a prebias voltage of a load is solved, and the drop of an output voltage of the converter is also prevented.

Provided in the invention is a three-stage type alternating-current / direct-current hybrid three-port power electronic transformer comprising three filter inductors LgA, LgB, and LgC, three cascaded converters CCA, CCB, and CCC, six low-frequency blocking capacitors CLFB1, CLFB2, CLFB3, CLFB4, CLFB5 and CLFB6, three high-frequency isolation transformers THF1, THF2 and THF3, and a three-phase four-wire inverter INV. According to the three-stage type alternating-current / direct-current hybrid three-port power electronic transformer, with the cascaded converters CCA, CCB, and CCC, direct AC / AC conversion form the low-frequency alternating current to the high-frequency alternating current is realized; with the high-frequency isolation transformers THF1, THF2 and THF3, direct AC / AC conversion ofthe high-frequency alternating current of electric energy is realized; and with the three-phase four-wire inverter INV, direct conversion from the high-frequency alternating current to the low-frequency alternating current and direct current is realized.

The invention provides a novel static var compensator based on a single-stage conversion module cascade converter. The novel static var compensator based on a single-stage conversion module cascade converter includes multiple single-phase and three-phase main power circuits which are formed through cascade connection of a plurality of module units, and a plurality of branches which are formed through serial connection of inductors and capacitors and are in parallel connection with the main power circuits. The novel static var compensator based on a single-stage conversion module cascade converter has the advantages of being high in the SVG dynamic response speed, being low in the harmonic wave content, being low in power dissipation of the device, being small in volume, being light in weight, being simple in SVC control, and being low in price. The novel static var compensator is formed on the basis of a controllable rectifier circuit transmitting the energy in single direction; the branches which are formed through serial connection of inductors and capacitors and are in parallel connection with the controllable rectifier; the branches can provide advanced fundamental wave reactive power and can also filter the low-order harmonics so as to achieve the aim of providing continuously adjustable reactive power for the system by controlling the input current of the controllable rectifier and restrain or eliminate the power grid current harmonics.

An n-buck cascade converter, where the DC conversion ratio is Un where U is the duty ratio. The converter comprises n inductors, n capacitors, (2n-1) diodes and a MOSFET transistor. The cascading configuration uses the minimum number of active switches while avoiding complex control circuitry. It is assumed that this converter operates in continuous condition mode, i.e., all the inductor currents never decay to zero. The corresponding formulae for the ripples in the capacitor voltages and the inductor currents are given. This allows designing in principle a specific converter following some specifications.

The invention relates to the technical field of power electronic converters, in particular to topology of an energy-fed three-port cascade converter of hexagonal structure and a control method, The topology effectively combines a hexagonal converter with a traditional H-bridge cascaded multilevel converter driven by the existing medium and high voltage system motors, and then connects it with theAC power network through the multi-winding phase-shifting transformer, so that it can be extended to a three-port structure with single input and two outputs, which can meet the operating requirementsof the two-motor system under different operating conditions. As the front-end input is added to the module units on part of the bridge arm of the hexagonal converter, the number of power electronicdevices and the secondary side windings of the phase-shifting transformer required by the converter can be greatly reduced. At the same time, in order to solve the problem of system power imbalance caused by the default of front-end input of some units, the internal relationship between loop current and converter bridge arm power is further analyzed. Through a power balance method based on loop current control, the topology can realize stable operation and energy interaction.

The invention provides a testing circuit for cascaded converter multi-submodule multi-working condition simulation. The circuit includes a current generator and a submodule system; the current generator is used for generating testing current and includes a three-port converter and corresponding filters; the submodule system includes an upper bridge arm testing unit module and a lower bridge arm testing unit module which are in series connection; the upper bridge arm testing unit module includes multiple upper bridge arm testing units in series connection; the lower bridge arm testing unit module includes multiple lower bridge arm testing units in series connection; each testing unit includes two detected submodules in reverse series connection; and the upper and lower bridge arm testing units receive the testing current generated by the current generator and output voltage signals, or the voltage signals and current signals of the detected submodules in each testing unit to external. The circuit can realize the operation working condition simulation of any submodules of a cascaded converter, and realize the simultaneous testing of the multiple submodules under multiple working conditions, so that testing costs can be saved, and testing efficiency can be enhanced.

The invention discloses a cascade converter valve, a DC power transmission system and a control method thereof. The cascade converter valve is provided with a high voltage valve group and a low voltage valve group which are connected in series in the DC side. The high voltage valve group is a first converter. The low voltage valve group comprises a second converter and a third converter which areconnected in parallel. At least one of the converters is a hybrid multilevel output converter. The AC side of the first converter and the AC side of the third converter are connected in parallel through a transformer to form the first AC end of the cascade converter valve. The AC side of the second converter forms the second AC end of the cascade converter valve. The cascade converter valve has multiple working modes and AC system access modes, high-voltage, high-capacity and long-distance DC power transmission and receiving AC network hierarchical access and asynchronous partition interconnection can be simultaneously realized under the premise of reducing the total manufacturing cost and area occupation of the DC system and thus the system stability and reliability can be enhanced. The cascade converter valve is suitable for the electric power system of multiple DC feed-in points.

The invention discloses a double-bootstrap three-level Zeta converter and belongs to the technical field of power electronic converters. The invention aims to solve the problems that loss in a conversion circuit and a cascade converter which do not need to be isolated is high, the equipment size is large and the cost is high when a topological structure of a direct current converter main circuit is changed by means of adding a transformer or utilizing cascade connection at present. According to the double-bootstrap three-level Zeta converter, a switching inductor circuit with an auxiliary switch is added on the basis of a topological structure of an original two-level Zeta converter circuit, so that a conversion ratio of the direct current converter is improved. The switching loss of the double-bootstrap three-level Zeta converter is 3 / 2n the switching loss under the condition that n circuits are in cascade connection with one another on the premise of the same effect with the traditional mode of increase of transformers and cascade connection of n circuits; and moreover the transformer equipment is reduced, so that the total equipment size is reduced, and the cost is saved. The invention is applied to modification of the topological structure of the direct current converter main circuit.

A power conversion device includes a plurality of cascaded converter cells. In each of the converter cells, each of a plurality of arms forming a bridge circuit is provided with a plurality of semiconductor switching elements in parallel. A drive controller of each of the converter cells is configured to, when none of a plurality of predetermined abnormality modes is detected, control the bridge circuit in accordance with an externally provided command. The drive controller is configured to, when at least one of the plurality of abnormality modes is detected, turn on all semiconductor switching elements provided in at least one of the plurality of arms forming the bridge circuit, to thereby establish a short circuit between first and second input / output nodes.