130 results about "Current source converter" patented technology

An integrated torsional mode damping method for a current source converter, including a rectifier, an inverter, and a DC link inductor coupled between the rectifier and the inverter, includes sensing a signal representative of torque on a shaft coupled to the inverter or rectifier; using the sensed signal for detecting a presence of a torsional vibration on the shaft; and damping the torsional vibration by modulating active power through the respective inverter or rectifier.

Current source converter (CSC) based wind energy power conversion systems (WECS) and methods are presented in which a unified DC link current control scheme is employed to facilitate grid fault ride-through conditions, with a multiple-mode converter control system that combines the power flow control capabilities of the generator-side and grid-side converters, in which transitions between normal operation and fault condition are achieved automatically by monitoring the grid voltage without the need for, or with partial additional ride-through components.

Power conversion apparatus and methods are presented for providing electrical power to a grid or other load in which a synchronous machine is driven by a wind turbine or other prime mover to provide generator power to a switching type current source converter (CSC), with a current source rectifier (CSR) of the CSC being switched to provide d-axis control of the synchronous machine current based on grid power factor feedback, and with a current source inverter (CSI) of the CSC being switched to provide leading firing angle control and selective employment of dumping resists to dissipate excess generator energy in a fault mode when a grid voltage drops below a predetermined level.

An integrated torsional mode damping method for a current source converter, including a rectifier, an inverter, and a DC link inductor coupled between the rectifier and the inverter, includes sensing a signal representative of torque on a shaft coupled to the inverter or rectifier; using the sensed signal for detecting a presence of a torsional vibration on the shaft; and damping the torsional vibration by modulating active power through the respective inverter or rectifier.

A converter, and in particular a current source converter, including a bridge having an AC terminal for each of one or more AC lines, and first and second DC terminals. A converter arm is connected between each respective AC terminal and the first DC terminal, and between each respective AC terminal and the second DC terminal. Each converter arm includes a first power semiconductor switching device capable of being turned ‘on’ and ‘off’ by gate control and having a recovery time. The converter is adapted to be operated in one or more inverting modes.

Current source converter (CSC) based motor drives and control techniques are presented in which DC link current is regulated to a level set by the output inverter during dynamic braking operation by pulse width modulation of a braking resistance connection signal to maintain control of motor torque and speed while mitigating or preventing line side regenerative currents.

Current source converter drives and common mode voltage reduction techniques are presented in which a space vector modulation zero vector for current source inverter (or rectifier) control is selected according to the switching state of the current source rectifier (or inverter) and according to the AC input power and the AC output power to control the output common mode voltage.

The invention relates to the field of a power electronic technology and particularly relates to a power transmission system for improving the transmission capability of an alternating-current circuit through using a mixed current converting technology. The power transmission system adopts a tri-polar wiring manner; each-polar wiring comprises a lead wire and converters respectively connected with both ends of the lead wire; and each converter comprises a voltage source converter and a current source converter. The invention designs the mixed power transmission system with sensitivity and economical efficiency by combining the advantages of strong controllability of a voltage source converter, high capacity of the current source converter and low cost. According to the power transmission system provided by the invention, the problems of lead wire use ratio, passive compensation and the like caused by that the alternating-current circuit is improved to a direct-current circuit, can be well solved by using bidirectional conduction capability of the voltage source converter and a bidirectional transistor converter, and matching with a switch converting device, so that the power transmission system has important meanings on overcoming the paradox that the load of large-size cities is continuously increased and the difficulty of newly building circuits is increased.

The invention discloses a superconductive current-limiting energy storage circuit and a control method thereof. A superconducting magnet is connected in series with a power grid through a current source converter, a filter capacitor, a switch, a voltage dependent resistor, a transformer and the like. In a normal state, the voltage of the filter capacitor is changed and the voltage distortion of the power grid is compensated by controlling the current injected into the filter capacitor by the current source converter so as to improve the quality of the power supply voltage of a load. When a circuit is short-circuited, the filter capacitor is disconnected with the power grid through the switch and the voltage dependent resistor, and all the switches of the current source converter are turned on, so that the superconducting magnet is connected in series with the power grid in the form of uncontrolled rectifier so as to limit the fault current.

An integrated torsional mode damping method for a current source converter comprising a rectifier, an inverter and a DC link inductor coupled between the rectifier and inverter, the method comprising: sensing a signal representative of torque on a shaft coupled to the inverter or rectifier; using the sensed signal to detect the presence of torsional vibrations on the shaft; and by regulating real power via the corresponding inverter or rectifier to reduce the torsional vibration.

The invention is a current regulator used in charging and discharging superconductive magnet, composed of a voltage unit, a transformer unit and a current unit, where the voltage unit is a voltage source converter whose DC side is a capacitor, the current unit is a current source converter with a DC side connected with a superconductive magnet, an AC output side of the voltage source converter is connected with a primary side of the transformer and that of the current source converter is connected with a secondary side of the transformer, and the transformer unit can be an ordinary transformer and also a transformer tapped on one side or both two sides. The invention can not only charge the magnet but release the electric energy stored in the magnet, and the charge and discharge voltage can be flexibly regulated. Its structure is compact and simple, its power density is high, and its bulk is small, and thus not only improves the property of the magnet charge-discharge system but can largely reduce the cost.

A converter includes a transformer including primary windings and secondary windings, switches connected to the primary windings, an output inductor connected to the secondary windings, and a controller connected to the switches. The controller turns the switches on and off based on dwell times calculated using space vector modulation with a reference current {right arrow over (I)}ref whose magnitude changes with time.

A plurality of capacitors are interposed between ones of a plurality of input lines. The clamp capacitor is connected between two DC power supply lines. A current-source converter includes a plurality of switch devices, where x represents r, s and t. The switch device selects conduction / non-conduction through a first diode between corresponding one of the input lines and the first DC power supply line and conduction / non-conduction through a second diode between said corresponding one of input lines and the second DC power supply line based on external signals and brings corresponding one of the input lines with the first and second DC power supply lines in a state of not receiving the signals.

A current-source converter includes high-arm side switching elements and low-arm side switching elements. A voltage between the DC power supply lines is detected as a line voltage of an input line, based on a conduction pattern of the high-arm side switching elements and the low-arm side switching elements.

The invention relates to alternating-current to direct-current conversion of electric energy, discloses a four-quadrant multilevel current-source converter with a main circuit based on a thyristor and belongs to improvement to the fact that reactive power compensation is needed to be performed additionally caused by the fact that phase current is restricted and phase voltage is delayed due to a phase shift range of a trigger angle ranging from 0 to 180 when two groups of three-phase bridge-paralleled twelve-pulse thyristor circuits are utilized in high-power places. The converter is characterized in that a paralleling reactor in the topology is replaced by a multilevel injection circuit to enable each group of the three-phase bridges to output stepped multilevel pulse direct current and provide zero-current phase-commutation conditions for the thyristor. The multilevel injection circuit consists of multiple units with the same structure, each unit consists of two components with inverse resistant characteristics and a reactor, and cathodes or anodes of the components are connected with a terminal of the reactor to enable each group to structurally be a three-port unit. Consequently, the multilevel injection circuit and the main circuit are coordinated for controlling to provide the zero-current phase-commutation conditions for a main bridge thyristor, so that controlled turn-off of the thyristor is realized, and the whole circuit can possess four-quadrant operating capability.

The invention discloses a control method of a three-phase DC converter, belonging to a control method of a DC-DC converter. The three-phase DC converter comprises an input power supply, three full-bridge conversion circuits and a filtering circuit, wherein the phases of output rectification voltages of a first full-bridge conversion circuit, a second full-bridge conversion circuit and a third full-bridge conversion circuit are the same, and the total output rectification voltage is achieved to be three times of the output rectification voltage of the single full-bridge conversion circuit. The control method is applicable for an occasion with wide input voltage, the problems of high voltage stress of a traditional voltage source converter diode and large output current pulse of a current source converter are solved, the weight and the volume of a filtering inductor are reduced, the voltage and current stresses of a power switching tube are reduced, and the voltage stress of a diode is reduced.

The invention discloses an active power decoupling device without an additional switching element and a control method therefor. The active power decoupling device is achieved by increasing two additional energy storage capacitors in the topological structure of a conventional single phase current source converter. During each power frequency period, the energy storage capacitors work by turns to complete absorption and release of inherent secondary pulse power of the single phase current source converter. Compared with a conventional active decoupling device, the active power decoupling device provided by the invention requires no additional switching element, thereby helping reducing the system cost and improving the system efficiency. Direct current of the active power decoupling device is timely corrected by a decoupling circuit, and the mean value of voltage of a decoupling capacitor is maintained constant by a rectifier state circuit. The system control is not dependent on accurate system parameters, and the robustness is strong. Only a simple PI controller is required to achieve rapid and error-less tracking of a target, and the controller is easy to design.

The invention discloses a method for suppressing specific harmonic waves of a current source converter under an extremely low switching frequency, which is characterized in that a three-phase currentsource type grid-connected rectifier topological structure is adopted, 5-order and 7-order harmonic components in output PWM current are actively controlled by a novel hybrid modulation method combining asymmetric specific harmonic elimination and bypass pulse injection, and active compensation is carried out on the 5-order and 7-order harmonic components in line current. The control strategy enables the high-power current source converter to have the capability of simultaneously performing active compensation on the 5-order and 7-order harmonic components under the extremely low switching frequency, so that the low-order harmonics of the line current can be effectively reduced under the condition of the voltage distortion of a power grid, the line current electric energy quality of the system is greatly improved, and the safe and stable operation of the system is ensured.

The invention provides a light-weight hybrid converter topology suitable for offshore wind power delivery and a control strategy of the light-weight hybrid converter topology. Large-scale fans are gathered to an offshore alternating-current bus through a converter, an offshore converter carries out rectification, an onshore converter carries out inversion through a direct-current cable and then the current is connected to an alternating-current power grid. The offshore converter adopted by the invention comprises an active commutation type current source converter (CSC) and a diode rectifier (DR), wherein the CSC is cascaded with the DR. In the wind power plant starting stage, the CSC establishes an offshore alternating-current voltage to realize power return; in the power generation sending-out stage of the wind power plant, a fan converter and an offshore sending terminal CSC jointly control active power and alternating voltage / frequency, and an onshore receiving terminal converter adopts constant direct voltage control. The technical scheme provided by the invention has the advantages that the CSC can supply power to the passive system to realize black start of the offshore windplant; the sending terminal converter adopts CSC and DR cascade connection, the size and the weight of the offshore platform can be reduced, and therefore the cost is reduced.

A power transmission and distribution system includes a supplying side having a current source and a receiving side. The receiving side includes a modular converter with plurality of direct current (DC)-alternating current (AC) current source converters connected in series with the current source and a plurality of AC-DC rectifiers connected in parallel to supply power to a multiplicity of loads. Each of the DC-AC current source converters supply power to a corresponding AC-DC rectifier and includes a plurality of reverse blocking fully controllable switches having bidirectional voltage blocking capability. Furthermore, a current from the current source flows in at least one reverse blocking fully controllable switch at any instant.

Provided is a fault protection applied to a wind power plant and an energy stabilization circuit. A power converter is composed of a voltage source converter and a chopper or a current source converter. A direct current end of a rectifier is connected with a switch provided with an antiparallel diode and a buffer absorption circuit in parallel. A primary side of a single-phase transformer is connected with a switch and a resistor in parallel, and a secondary side of the single-phase transformer is connected with an alternative current output end of the rectifier. The primary side of the single-phase transformer is respectively connected with a power grid and a switching-in end of the wind power plant. A three-phase alternative current end of a power converter is connected with the power grid and a switching-in end of the wind power plant through a three-phase filter circuit and a three-phase transformer. A direct current end of the power converter is connected with a direct current end of the rectifier in series and then connected with an energy storage inductor in series. Under a normal condition, power output of the wind power plant is smoothed through charging and discharging of the energy storage inductor. Under a fault condition, the energy storage inductor is firstly utilized to limit current, then a thyristor of the rectifier is turned off, and the energy storage inductor is disengaged from the power grid. Current is limited through the resistor connected with the primary side of the transformer in parallel.

The invention discloses a current source converter minimum DC ripple modulation method. The method comprises the following steps: various parameters such as the converter AC voltage amplitude Vtm, the converter AC A-phase voltage initial phase gamma, the modulation ratio m and the reference current angular displacement initial value theta0 of the system are calculated. Through selecting the most proper modulation mode, the DC ripple reaches the minimum, the performance of the converter is optimized, and the service life of the system is prolonged. Compared with the traditional ripple suppression method, the new method does not need to increase the DC inductance nor the switching loss, the method only needs to improve the modulation algorithm of the converter, and great superiority exists; the limitation of a converter AC-side power factor angle does not exist, the problem of time point switching does not exist, the application range is wider, and the realization is simpler.

A control section controls a current-source converter while a switch is conducting, to render conducting a pair of a high-aim side transistor and a low-arm side transistor (for example, transistors) which are connected to any one of input lines, performs voltage doubler rectification on a voltage between a neutral phase input line on which a resistor is provided and any one of the input lines, to serve for charging of clamp capacitors.

The invention provides a multiport DC / DC system (MDS) topology with stepless DC voltage regulation. The MDS has multiple ports to be interconnected with an external DC system. The ports are configured as a hybrid series converter. An AC side is connected to a common AC bus in the MDS through an AC circuit breaker. In the MDS, transformers match DC lines with different voltage classes. The hybrid series converter is formed by connecting in series a current-source converter unit and a voltage-source converter unit. The current-source converter unit includes a LCC based on a diode or a thyristor. The voltage-source converter unit has a modular multi-level structure. Each bridge arm is formed by cascaded connection of sub-modules with no negative level output capabilities (such as IGBT module, HBSM) and sub-modules with negative level output capabilities (such as FBSM). The MDS has a stepless DC voltage regulation (or even reverse polarity) capability, achieves both DC fault ride through and rapid recovery capabilities, helps to quickly reverse power flow. Therefore, the MDS topology helps to promote the application of the multi-port DC-DC converter in a DC power system.