28 results about "Cascade converter" patented technology

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 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.

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 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.

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.

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.

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 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 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.

The application discloses a three-phase common N-point cascade type simplified isolation non-isolation hybrid power electronic transformer, 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, the front stage of the rectification inversion modules is a cascade rectification structure, and the rear stage of the rectification inversion modules is a cascade inversion structure. The cascade converter structure comprises at least one isolation module, and the isolation module is arranged at the first end of the cascade converter structure. When the number of the rectification inversion modules is 3, 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 3, the rectification inversion modules after the second rectification inversion module are all two-bridge-arm structures. The application reduces part of switch tubes of a non-isolation module of a topology, reduces switch loss and tube loss, and avoids the influence of redundant switch states on three-phase common N points.

This invention provides a reliability testing system and method for simulating the operating conditions of a cascaded converter capacitor. The system includes: an operating current loader applying an operating voltage to the capacitor under test using a control signal generated by a current controller; an operating voltage loader applying an operating voltage to the capacitor under test using a control signal generated by a voltage controller; a current filter removing high-frequency harmonic components of the operating current; a temperature and humidity loader applying external ambient temperature and humidity conditions to the capacitor under test; and a pulse discharge circuit performing overcurrent discharge on the capacitor under test. This invention enables the application of electrothermal operating condition simulation tests based on a cascaded converter capacitor to the capacitor under test, as well as constant overvoltage and repetitive overcurrent tests as specified in current national standards. It also allows for online monitoring of the capacitance value and hot spot temperature of the capacitor under test, significantly improving the efficiency, accuracy, and economy of capacitor reliability testing.

To equally balance a primary side DC voltage and a voltage of a DC system even when a difference occurs in a load of the DC system.SOLUTION: M (m: an integer of 2 or more) 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. X (x: an integer of 2 or more) DC systems in 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. The 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 power average value of the DC system.SELECTED DRAWING: Figure 1

The application discloses a series-parallel hybrid cascaded static synchronous compensator with adjustable impedance and a control method thereof, and the method is as follows: obtaining grid-connected point voltage and load current information and performing positive and negative sequence component analysis on the information; calculating compensation line current components with the same size and opposite phase of positive and negative sequence components of the load current to realize compensation of reactive power and negative sequence current of the grid-connected point load; calculating zero sequence injection current for in-phase active power balance and obtaining reference operating currents of cascaded branches; calculating output reactive power of each phase based on cascaded branch voltages of each phase and the reference operating currents; calculating corresponding trigger angles of thyristors of each phase under the condition that the adjustable impedance bears all phase voltages and generates all reactive power, generating pulse control signals to realize control on the adjustable impedance; and each phase cascaded converter adopts quasi-proportional resonance control to track the reference operating current and generate corresponding PWM signals to control each phase cascaded converter.

The uninterruptible power supply includes 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 cascaded converter cells (26). 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). The power storage device includes a plurality of power storage cells connected in parallel to each other and corresponding to the plurality of chopper cells. 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 exchanging DC power with the capacitor and the corresponding power storage cell.

The invention provides a single-phase cascade type optical storage hybrid system power coordination control method and device, and relates to the technical field of photovoltaic system power control, and the method comprises the steps: according to the reference power and the DC side voltage of a photovoltaic module unit, and the reference amplitude of the output voltage of a cascade converter, calculating the power of a single-phase cascade type optical storage hybrid system; determining a modulation factor of the cascade converter when the power of the battery unit is zero; judging the size of the modulation factor and a target threshold value, judging the size of the state of charge of the battery unit and the size of the state of charge threshold value range, and determining a comparison result; and based on the comparison result, determining a corresponding power coordination control strategy to control the operation mode of the single-phase cascaded optical storage hybrid system, and the method solves the technical problems of complex system structure and high over-modulation risk in the prior art. The technical effects of simplifying the hardware architecture, maintaining the system performance and reducing the over-modulation risk are achieved.

The application relates to the technical field of power system relay protection, and discloses a DR-MMC hybrid cascaded system direct-current fault current processing method and system. In the method, based on fault loop state changes, the direct-current fault process of a DR-MMC hybrid cascaded converter is divided into a plurality of fault stages; the dynamic change characteristics of fault current in each fault stage are analyzed, and a fault current analysis sub-result corresponding to the fault stage is determined; each fault current analysis sub-result is integrated according to the time interval of the corresponding fault stage, and a fault current analysis result covering the direct-current fault process of the DR-MMC hybrid cascaded converter is determined; based on the fault current analysis result, the DR-MMC hybrid cascaded converter is subjected to parameter optimization, and the safe operation boundary of the DR-MMC hybrid cascaded system is determined. The application provides a theoretical basis for DR-MMC hybrid cascaded system fault protection design, equipment selection and safe and stable operation.

The invention belongs to the technical field of alternating-current electrified railway traction power supply, and particularly relates to a multi-port new energy conversion device for an electrified railway traction power supply system and a direct-current voltage balance control method, and the multi-port new energy conversion device comprises a transformer, a single-phase rectification system, a direct-current bus system, an energy conversion system and the like. The requirement for the number of windings on the low-voltage side of a transformer is lowered through cascade operation of the alternating current sides of the two AC / DC rectification modules, multiple direct current buses are constructed through parallel operation of the direct current sides of the AC / DC rectification modules at the relative positions of the single-phase rectification system, and each direct current bus is connected with a new energy power generation and energy storage converter. On the basis of direct-current voltage balance control of a traditional cascade converter, active power adjustment can be carried out between the AC / DC rectification modules connected in parallel on the direct-current side, and balance control over the direct-current voltage is further achieved.

The invention relates to a high-power electromagnetic transmitter power supply converter topology and a control method thereof. A power supply converter topology adopts a mode of combining a plurality of modules in an IPOS mode, and each module adopts a Buck + DCX-LLC cascade converter structure; each module is independently controlled through the control method, and the control method comprises the following steps: establishing a state space expression of the converter; obtaining an equivalent discrete mathematical model by using a forward Euler formula; introducing a control time domain and a prediction time domain, and establishing a prediction output equation of the equivalent circuit; introducing a disturbance observer, enabling the lumped influence of disturbance to be equivalent to load current disturbance, taking the load current disturbance as a state variable, and correcting a prediction output equation; and establishing an objective function and optimizing the objective function to obtain an optimal solution of the control quantity. According to the invention, soft switching, low-voltage input and high-voltage high-power output can be realized, the change of the load is quickly responded, and the prediction accuracy of model prediction control is improved through the disturbance observer under the condition that disturbance exists.

The invention provides an electromagnetic transient simulation method and modeling system suitable for any submodule topological structure cascade converter valve, and an electronic device, and the method comprises the steps: carrying out the simulation calculation of each internal submodule through a valve arm element based on the state information of a previous time step and switch triggering information; the obtained result is used for updating the external total Thevenin equivalent resistance and total Thevenin equivalent voltage of the whole valve arm; then, the total Thevenin equivalent resistance and the total Thevenin equivalent voltage are adopted to participate in external large power grid simulation calculation, and valve arm branch current is obtained; and finally, the port current of the internal sub-module is updated according to the current of the valve arm branch in the current time step, and simulation calculation is carried out on each sub-module again to obtain the state of the internal element of the sub-module for the next time step. According to the method, under the condition that the calculation scale is not increased, the effect of accurately performing internal electrical simulation of any topological sub-module can still be achieved.