47 results about "Cascade converter" patented technology

The invention discloses a solid-state transformer seamless fault-tolerant control method based on cascaded H-bridge pre-charging, and the method comprises the steps: carrying out the pre-charging of a bus capacitor of a redundant unit module based on a cascaded H-bridge, dynamically adjusting the modulation wave of a preceding-stage H-bridge of each unit module, and achieving the impact-free charging of the bus capacitor of the redundant unit module. And after the pre-charging of the redundant unit module is finished, controlling a modulation wave signal and a driving pulse of a pre-stage H bridge of the redundant unit module to intermittently charge a bus capacitor of the redundant unit module. According to the invention, the problems of long charging time of the redundant unit module, overload of the residual unit module and overlarge current impact of the alternating current inductor in the process of removing the fault unit module and inserting the redundant unit module in the cascade converter are solved. According to the method, no additional circuit needs to be added, the method is suitable for a power bidirectional flow and unidirectional flow system, quick and smooth switching of the unit modules can be achieved when a fault occurs, and reliable and stable operation of the whole system is guaranteed.

The invention discloses a cable fault diagnosis method and system based on sequence square wave excitation, and the method employs a cascade converter composed of a GaN full-bridge module to output broadband signal excitation, not only ingeniously utilizes the high-frequency characteristic of GaN, but also employs a power electronic topology to overcome the defect that a GaN element cannot bear an overlarge voltage, and improves the reliability of the cable fault diagnosis. The amplitude of the output voltage is greatly enhanced on the excitation source, the high-frequency excitation attenuation effect is overcome, the noise interference resistance of the device is enhanced, and meanwhile the portability is improved.

The invention discloses an impedance-adjustable series hybrid cascade static synchronous compensator and a control method thereof. The method comprises the following steps: acquiring grid-connected point voltage and load current information, and performing positive and negative sequence component analysis on the grid-connected point voltage and load current information; calculating a compensation line current component with the same size and opposite phase as the positive and negative sequence components of the load current so as to compensate the reactive power and the negative sequence current of the grid-connected point load; zero-sequence injection current used for in-phase active power balance is calculated, and reference operation current of each cascade branch is obtained; calculating the output reactive power of each phase based on the cascade branch voltage of each phase and the reference operation current, calculating the corresponding trigger angle of each phase thyristor under the condition that the adjustable impedance bears all phase voltages and generates all reactive power, and generating a pulse control signal to realize the control of the adjustable impedance; and each phase cascade converter adopts quasi-proportional resonance control to track the reference operation current, and generates a corresponding PWM signal to respectively control each phase cascade converter.

The invention discloses a high-voltage high-power cascade converter which comprises rectifier diodes, a direct-current input bar, an IGBT device, a low-inductance busbar, a cascade output bar, a radiator, a cover plate, a shell assembly and a control assembly. The fuse and the supporting capacitor are detachably connected with the converter through the low-inductance busbar. The radiator is located at the bottom of the shell assembly, a cooling medium connector is arranged on the side portion of the radiator, and the cover plate is used for sealing the top of the shell assembly. The plurality of rectifier diodes and the plurality of IGBT devices are installed on the radiator, and the low-inductance busbar is used for connecting terminals of corresponding polarities of the rectifier diodes and the IGBT devices; the direct current input bar and the cascade output bar are both located above the IGBT device and are arranged in a staggered manner; the DC input bar is connected with the support capacitor through the low-inductance busbar. The cascade output bar adopts a copper bar mode; the control assembly is located above the cascade output row. The invention has the advantages of compact structure, convenience in maintenance, high power and the like.

The present invention belongs to the technical field of transformers and specifically relates to a method for calculating voltage stress within a cascaded high-frequency transformer. The method comprises simulating and obtaining the time-domain voltage waveforms at each port of the high-frequency transformer in the DC-DC isolation converter under cascade conditions based on the external cascade mode, internal topology, converter characteristics, and control strategy of the DC-DC isolation converter, extracting spectral information of the voltage waveform through frequency-domain analysis, and finally, analyzing and calculating the internal voltage stress of the high-frequency transformer under the important operating condition of excitation at all ports of the cascaded converter based on a constructed equivalent model of the high-frequency transformer and a method for applying excitation to different ports. This method avoids the limitation of traditional methods that only consider single-ended excitation.

The invention discloses a low-current high-precision acquisition method for a high-power cascade converter, and relates to the technical field of power electronic application, and the method comprises the steps: building the high-power cascade converter with a cascade topological structure, and enabling a power unit to comprise a first-stage power unit and a general power unit; hall sensors with different measuring ranges and insulated gate bipolar transistors with different powers are installed in the first-stage power unit, and the wiring direction is adjusted according to an output port; calculating a current effective value in the first-stage power unit based on a current signal of the Hall sensor, comparing the current effective value with a preset current threshold value, and dynamically adjusting the working mode of the first-stage power unit; the first-stage power unit transmits a sampled current value to a converter control system through a high-speed optical fiber. By designing the wide-dynamic-range high-precision acquisition method for the high-power high-voltage cascade converter, the problem of full-range high-precision measurement of the current of the high-voltage cascade converter is effectively solved.

The invention discloses a photovoltaic module maximum power point tracking and grid-connected control method, in a photovoltaic system, the input of a series converter SLC is connected to an equivalent direct current bus, each photovoltaic string is connected to the equivalent direct current bus through a cascade converter, and the cascade converter adopts a cascade structure of a DAB converter and a BL converter. A DAB converter is used as a first stage, and a BL converter is used as a second stage; the method comprises the following steps: acquiring a real-time main bus voltage, if the main bus voltage is in a normal grid-connected interval, acquiring a real-time equivalent direct current bus voltage by using a central converter, and adjusting the equivalent direct current bus voltage through PI closed-loop control; independently operating an MPPT algorithm for each photovoltaic string by using a BL converter so as to realize maximum power point tracking; a DAB converter is utilized to obtain a real-time intermediate bus voltage, the intermediate bus voltage is kept stable through SPS modulation, and stable power support is provided for a BL converter.

To prevent such a problem that a predetermined volts alternating current required for system interconnection cannot be output from an SST when operation is continued in the case where a part of cells fails.SOLUTION: A plurality of cells each including an AC-DC converter ACDC, a primary-side DC capacitor C1, an insulated DC-DC converter DCDC, and a secondary-side DC capacitor C2 are provided per phase. A plurality of DC systems to which a plurality of secondary side DC capacitors C2 are connected in parallel are provided, and voltages of the plurality of DC systems are supplied to a load or a power source. When a cell fails, the control unit of the AC / DC converter ACDC increases the output voltage on the AC system side of the cell connected to the same DC system as the failed cell, and decreases the output voltage on the AC system side of the cell connected to the other DC system. The third harmonic is superimposed on the AC output voltage of the cell connected to the same DC system as the failed cell, and the third harmonic in the opposite direction is superimposed on the AC output voltage of the cell connected to the DC system different from the failed cell.SELECTED DRAWING: Figure 1

The invention relates to the technical field of power system relay protection, and discloses a DC fault current processing method and system for a DR-MMC hybrid cascade system. The method comprises the following steps: dividing a DC fault process of the DR-MMC hybrid cascade converter into a plurality of fault stages based on fault loop state change; the fault current dynamic change characteristic of each fault stage is analyzed, and a fault current analysis sub-result of the corresponding fault stage is determined; integrating each fault current analysis sub-result according to the time interval of the corresponding fault stage, and determining a fault current analysis result of the DR-MMC hybrid cascade converter covering the DC fault process; and parameter optimization is carried out on the DR-MMC hybrid cascade converter based on the fault current analysis result, and the safe operation boundary of the DR-MMC hybrid cascade system is determined. The method provides a theoretical basis for fault protection design, equipment selection and safe and stable operation of the DR-MMC hybrid cascade system.

The invention provides a control method of a branch parallel current generator suitable for cascade converter test, and the method comprises the steps: generating a reference signal of a test current according to a to-be-tested target cascade converter system model; according to the reference signal of the test current and the sampling signal of the test current, a current controller is adopted to generate basic modulation voltage of a branch parallel current generator; according to the capacitance voltage of each power supply unit and a preset capacitance voltage threshold value, determining a fine tuning balance component of the power supply unit; determining the modulation voltage of the branch parallel type current generator according to the fine adjustment balance component of the power supply unit and the basic modulation voltage of the branch parallel type current generator; and according to the modulation voltage of the branch parallel current generator and a preset modulation method, generating a control pulse signal of the power supply unit, and determining a test current generated by the branch parallel current generator. According to the invention, the test current is accurately controlled while the capacitor voltage of the branch parallel current generator is kept stable.

The application provides a power conversion module and a cascaded converter. First sides of cascaded units in the power conversion module are respectively connected with corresponding windings in coupling inductors in series, and two branches connected in series or in parallel after the connection are connected between two interfaces in a cascaded side of the power conversion module. When multiple power conversion modules are cascaded through the cascaded side, each winding is connected in series, which is equivalent to decomposing centralized reactance in the prior art into multiple distributed inductors. Each winding does not need to be additionally provided with a spacing meeting the ground insulation requirement, thereby reducing the space requirement for external additional insulation of the inductor and improving the power density. Moreover, by adjusting the connection in the power conversion module, the series-parallel relationship between two cascaded units can be converted, so that the power conversion module can meet the large-current requirement and the high-voltage requirement, and the adaptability is further improved.

A cascaded converter architecture comprising a pure switched-capacitor (SC) stage and a resonant SC stage. Multiple switching buses are utilized to connect the first-stage SC converter with second-stage multi-phase resonant SC converters. The flying capacitors of both stages are resonant with the output inductors, so the charge distribution loss is eliminated. Zero-current switching is realized by adjusting the duty ratio and switching frequency. By using the intermediate switching bus, the number of switches can be reduced, and the intermediate bus capacitor is not required; thereby greatly reducing component count and cost while improving power density. Numerous implementation variations are described by way of example and not limitation.

This modular multi-level cascade converter has a plurality of cells per phase, each cell comprising an AC-DC converter ACDC, a primary-side DC capacitor C1, an insulated DC-DC converter DCDC, and a secondary-side DC capacitor C2. The converter has a plurality of DC systems in each of which a plurality of secondary-side DC capacitors C2 are connected in parallel. The voltages of the plurality of DC systems are supplied to a load or a power supply. When a cell fails, a control unit for the AC-DC converter ACDC increases the output voltage on the AC system side of a cell connected to the same DC system as that of the failed cell, and reduces the output voltage on the AC system side of a cell connected to another DC system. A third harmonic is superimposed on the AC output voltage of the cell connected to the same DC system as that of the failed cell, and a reverse third harmonic is superimposed on the AC output voltage of the cell connected to the DC system different from that of the failed cell. This prevents the problem that, when an operation is continued in the event of failure of some of the cells, an SST cannot output a prescribed AC voltage required for system interconnection.

The invention discloses a cascade system bus voltage stability domain evaluation method under small current disturbance, and relates to the technical field of power supply and distribution systems. The method comprises the following steps: constructing an impedance ratio test circuit; introducing non-intrusive current signal interference into bus voltage of the cascade system by an impedance analyzer to excite a feedback loop of the cascade system to operate; the stability criterion of the Middlebrok is simplified, and an improved stability criterion is obtained; according to the corresponding amplitude-frequency Bode diagram data of each load operation point obtained by the impedance ratio test circuit, the amplitude data of the corresponding amplitude-frequency Bode diagram of each load operation point is integrated and fitted through Matlab, and a fitting curved surface based on a test result is obtained; and comparing the fitting curved surface with a judgment area determined based on a stability criterion, and determining a stable operation boundary of the cascade system in a wide load range. According to the invention, the problem of the bus voltage stability of the black box cascade converter system in a wide load range is solved, and a test method without invading a bus line is provided.

The disclosure provides a thyristor device type modular cascaded novel converter topology which completely solves the commutation failure problem, explores the circuit topology principle of thyristor and capacitor providing controllable commutation support and arrester providing energy transfer branch, constructs a thyristor converter module with controllable output voltage and impedance and automatic capacitor input, and proposes a novel converter topology structure which can completely resist commutation failure in the commutation process. Each converter valve is composed of at least two thyristor converter modules in cascade; the thyristor converter module is composed of four groups of thyristor bridge arms and a forced turn-off part. Each two groups of bridge arms are connected in series, left and right symmetrical, and the capacitor branch is connected in parallel with the branch where the arrester is located, and the whole after parallel connection is connected between the four groups of bridge arms as the forced turn-off part.

A gallium nitride Flyback-Buck cascade converter for an unmanned aerial vehicle comprises a magnetic integrated transformer inductor, a gallium nitride power device S1, a gallium nitride power device S2, a diode D1, a diode D2, a capacitor C1, a capacitor C2, a direct current input Vin and a load Vo, one end of the direct current input Vin is connected with the magnetic integrated transformer inductor, and the other end of the direct current input Vin is connected with the load Vo. One end of the inductor is connected with the inductor, the other end of the inductor is connected with the inductor of the magnetic integrated transformer through the gallium nitride power device S1, the inductor of the magnetic integrated transformer is connected with the load Vo and the capacitor C2, the inductor of the magnetic integrated transformer is connected with the diode D1, and the other end of the diode D1 is connected with the gallium nitride power device S2 and the capacitor C1. The other ends of the gallium nitride power device S2 and the capacitor C1 are connected with the magnetic integrated transformer inductor, one end of the diode D2 is connected with the gallium nitride power device S2, the other end of the diode D2 is connected with the magnetic integrated transformer inductor, and by using the magnetic integration technology, the problems that a traditional cascade converter is large in size, low in power density and low in system efficiency are solved.

The invention discloses a cascade converter and a control method. The cascade converter comprises a first buck-boost cascade circuit and a second buck-boost cascade circuit. The first buck-boost cascade circuit comprises a first buck-boost circuit and a first coupling circuit; the second buck-boost cascade circuit comprises a second buck-boost circuit and a second coupling circuit; the input end of the first boost-buck cascade circuit is connected in series with the input end of the second boost-buck cascade circuit, the output end of the first boost-buck circuit is connected to the input end of the first coupling circuit, and the output end of the second boost-buck circuit is connected to the input end of the second coupling circuit. The output end of the first coupling circuit is connected with the output end of the second coupling circuit in parallel. By means of input series connection and output parallel connection, withstand voltage of a switching tube can be reduced, and the device has the advantages that device type selection is convenient, device characteristics are better, so that overall switching loss is reduced, power supply efficiency can be improved, and good economic and social benefits are achieved.

In an example embodiment, a system includes an inverter configured to operate in at least one of a charging mode or a drive mode, a cascaded direct current (DC)-DC converter, the DC-DC converter including a first portion of the inverter and at least one controller configured to selectively couple the first portion of the inverter to a first portion of the cascaded DC-DC converter during the charging mode, and selectively couple the inverter to a second portion of the cascaded DC-DC converter during the drive mode.

The present invention comprises a quantity of m cells per phase (m being an integer of 2 or greater), with each cell comprising an AC / DC converter ACDC, a primary-side DC capacitor C1, an insulated DC / DC converter DCDC, and a secondary-side DC capacitor C2. There are a quantity of x (x being an integer of 2 or greater) DC systems in which a plurality of secondary-side DC capacitors C2 are connected in parallel, and the voltages of the plurality of DC systems are supplied to a load or a power supply. A control unit of the AC / DC converter ACDC adjusts the output voltage on the AC system side of the cell on the basis of the value obtained by dividing the detected power value of each DC system by an average power value of the DC systems. Thus, even if a difference in the load of the DC systems has occurred, the primary-side DC voltages and the voltages of the DC systems are uniformly balanced.

Even if there is a difference in the load on the DC system, the primary DC voltage and the voltage of the DC system are balanced evenly. [Solution] Each phase has m (m: integer equal to or greater than 2) cells, each of which has an AC-DC converter ACDC, a primary-side DC capacitor C1, an isolated DC-DC converter DCDC, and a secondary-side DC capacitor C2. There are x (x: integer equal to or greater than 2) DC systems, each of which has a plurality of secondary-side DC capacitors C2 connected in parallel, and the voltages of the plurality of DC systems are supplied to a load or power source. A control unit of the AC-DC converter ACDC adjusts the output voltage on the AC system side of the cell based on a value obtained by dividing the power detection value of each DC system by the average power of the DC system.

The application discloses a kind of cascaded converter valve intelligentization quick test system, by test power supply, series reactor, charging circuit, quick connecting line / row, control system and measurement system composition.The application is measured valve group test state conversion by quick connecting line / row, without disassembling converter valve internal connection copper row or connecting line, only need to increase quick connecting line / row to realize the erection of test circuit.Measurement system acquires the voltage and current waveform data of each power module in the converter valve to be measured;Automatic test program is integrated in the control system, including charging test, function test, power test and bypass test, the control system realizes one-key start, automatic, batch full device test, and judges the full chain device state of the converter valve to be measured according to the feedback of test system, and automatically generates test report.The application can realize efficient, automatic, full link, batch converter valve test of one-step start, greatly improve test efficiency, reduce cost and manpower investment.

The invention discloses a configuration method for a voltage flexible matching cascade type current conversion system, which comprises the following steps of: firstly, constructing a voltage flexible matching cascade type current conversion topological structure, then establishing an initial distribution relation between the selection of a cascade converter voltage grade and transmission power, and determining a rated voltage division ratio of each station according to a receiving end net rack planning requirement; next, determining a constraint relation between a full-bridge and half-bridge hybrid MMC direct-current voltage operation range and a full-bridge sub-module proportion, calculating a modulation boundary of a unit in a voltage regulation process, and finally establishing a corresponding relation between a power distribution flexible adjustment range and a full-bridge module configuration proportion in a cascade converter operation process; and flexible mutual assistance of active power among different converter stations is realized by cooperatively adjusting the direct-current voltage proportion of the two stations. According to the method, differential matching of receiving end power is achieved in the planning stage, cross-grid flexible power scheduling is achieved in the operation stage, and the scheduling activity and engineering applicability of the cascade direct current power transmission system are remarkably improved.

The present disclosure relates to a power cell for a cascaded converter, and a cascaded converter comprising the power cell. The power cell comprises a cell controller, a rectifier circuit, an inverter circuit, a DC-link capacitor, and a bypass control device, the bypass control device comprises: a bypass switch, disposed between the two output terminals of the inverter circuit; a switch driver, comprising a power supply input, a control input, and a driving output; and a power supply circuit, configured to supply power to the power supply input of the switch driver, wherein the switch driver is configured to receive a handshake signal from the cell controller of the power cell, and to drive the bypass switch to close when at least one of the following conditions is fulfilled: the handshake signal from the cell controller is lost, and a control signal from the cell controller is received by the control input.

This uninterruptible power supply device (10) is provided with a converter (12), a bidirectional chopper (18), and an inverter (20). Each of the converter (12) and the inverter (20) includes a leg circuit having a plurality of converter cells (26) that are cascade connected. The bidirectional chopper (18) includes a plurality of chopper cells (30) connected in series between a DC positive bus (14p) and a DC negative bus (14n). A power storage device includes a plurality of power storage cells that are provided so as to respectively correspond to the plurality of chopper cells, and that are connected in parallel to each other. Each of the plurality of chopper cells (30) includes: a first input / output terminal and a second input / output terminal; a capacitor connected between the first input / output terminal and the second input / output terminal; and a charge / discharge circuit for transmitting / receiving DC power between the capacitor and a corresponding power storage cell.

The present application provides a wind power generation grid-connected cascade converter system, which includes: a generator, a converter group, and a transformer, wherein the output end of the generator is connected to the input end of the converter group, and the output end of the converter group is connected to the input end of the transformer; wherein the converter group includes a first converter, a second converter, and a third converter connected in a cascade manner, wherein the first converter is connected to the second converter and the third converter respectively, and the second converter is connected to the third converter. The present application can achieve an increase in the output power of the wind generator set and an increase in the voltage level of the converter group output voltage by adopting a new converter group with an AC cascade topology. At the same time, the wind power generation grid-connected cascade converter system can achieve self-balancing of the output power, effectively improve the grid-connected performance of the wind generator set, and improve the overall performance of the wind power generation grid-connected cascade converter system.

A spliced converter comprises four capacitors, four switches, a fifth switch, a first inductor, a sixth switch, a second inductor and a seventh switch. The four capacitors comprise a first capacitor, a second capacitor, a third capacitor and a fourth capacitor which are connected in series. The four switches comprise a first switch, a second switch, a third switch and a fourth switch which are connected in series. The fifth switch and the first inductor are jointly connected to the sixth node, the fifth switch is further connected to the first node, and the first inductor is further connected to the fourth node. The sixth switch and the second inductor are jointly connected to the seventh node, the sixth switch is further connected to the third node, and the second inductor is further connected to the fifth node. The seventh switch is connected between the sixth node and the seventh node.

The uninterruptible power supply (UPS) includes a converter (12), a bidirectional chopper (18), and an inverter (20). The converter (12) and inverter (20) each include branch circuits with multiple cascaded converter units (26). The bidirectional chopper (18) includes multiple chopper units (30) connected in series between a DC positive bus (14p) and a DC negative bus (14n). The energy storage device includes multiple energy storage units, each corresponding to and connected in parallel with the multiple chopper units. Each chopper unit (30) includes a first input / output terminal and a second input / output terminal, a capacitor connected between the first input / output terminal and the second input / output terminal, and a charging / discharging circuit for imparting and receiving DC power between the capacitor and the corresponding energy storage unit.

The present invention relates to a method and system for balancing control of parallel battery clusters, and relates to the field of battery energy storage systems. The actual current value and state of charge value of the battery cluster are obtained through a central controller, and the current average value and the state of charge average value are determined. The working state of the battery cluster is determined according to the current average value, and the control target of the battery cluster is determined according to the working state of the battery cluster and the state of charge average value. The output voltage expected value of multiple cascade converters is determined according to the battery cluster control target, and the multiple cascade converters are adjusted according to the output voltage expected value. Compared with the prior art, the present invention adopts a staged control method that combines the state of charge and the highest and lowest voltages of the battery cell, and independently controls the charge and discharge current of each battery cluster, which solves the problem that the existing parallel battery cluster cannot be filled and discharged at the same time, and the available capacity of the energy storage unit is low. It can also reduce the degree of dependence on the accuracy of the state of charge and improve the balancing effect.

A cascaded converter includes four capacitors, four switches, a fifth switch and a first inductor, a sixth switch and a second inductor, and a seventh switch. The four capacitors include a first, a second, a third, and a fourth capacitor connected in series. The four switches include a first, a second, a third, and a fourth switch. The fifth switch and the first inductor are jointly connected at a sixth node, and the fifth switch is further connected to a first node and the first inductor is further connected to a fourth node. The sixth switch and the second inductor are jointly connected at a seventh node, and the sixth switch is further connected to a third node and the second inductor is further connected to a fifth node. The seventh switch is connected between the sixth node and the seventh node.

The application discloses a three-phase non-isolated cascade type power electronic transformer with no-load, and belongs to the technical field of transformers. Each phase input is connected to a neutral point through a cascade converter structure. The cascade converter structure comprises a plurality of rectification-inversion modules, a front stage of which is a cascade rectification structure and a rear stage of which is a cascade inversion structure. The cascade converter structure comprises at least one no-load module, which is arranged at the head end of the cascade converter structure. When the number of the rectification-inversion modules is three, the second rectification-inversion module is a three-bridge-arm structure, and the third rectification-inversion module is a two-bridge-arm structure. When the number of the rectification-inversion modules is greater than three, the rectification-inversion modules after the second one are all two-bridge-arm structures. The application solves the short-circuit path problem of the power electronic transformer with N points, and also makes the input and output realize common ground.