128 results about "Current source converter" patented technology

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 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 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 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.

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.

A multi-terminal DC power system includes: a DC network connecting together multiple terminals. Each terminal is represented by one of: a voltage source converter having a capacitor at an interface to the DC network, wherein a difference between a converter-side current and a network-side current charges the capacitor, and a current source converter having an inductor at an interface to the DC network, wherein a difference between a converter-side voltage and a network-side voltage drives current through the inductor. A local controller for each terminal directly controls the converter-side current of each voltage source controller and the converter-side voltage of each current source converter, independent of the terminals, leaving network-side currents and voltages to be determined by the network, resulting in simplified terminal control and avoidance of the need for high-speed communication among all terminals at all times.

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.

The invention discloses a five-level specific harmonic elimination method for a parallel current source converter. Common-mode voltage of the converter can be reduced at a relatively low switching frequency, current sharing of DC bridge arms is achieved and the AC harmonic characteristics are ensured. The five-level specific harmonic elimination method comprises the steps of (1) determining 19 PWMcurrent and corresponding switching states of the parallel current source converter according to switching constraint conditions of the current source converter and dividing the PWM current into large, medium, small and zero four classes according to the magnitudes of the PWM current; (2) analyzing common-mode voltage corresponding to each PWM current and selecting the PWM current with relativelylow common-mode voltage for modulation; (3) analyzing the influences of redundant switching states of the PWM current for modulation on current sharing of the DC bridge arms; (4) building a five-level modulation waveform by using the PWM current participating into modulation; and (5) outputting a drive signal according to the modulation waveform in the step (4) and the switching states determinedin the step (3).