316 results about "Rotor side converter" patented technology

A controller (28) for a doubly fed induction generator (12,20) adjusts control signals to a rotor side converter (24) and line side converter (22) to adjust rotor current when a voltage transient on a utility grid (10) occurs, so that the doubly fed induction generator can ride through the transient. The controller can also turn off the transistors of the rotor side converter (24) to reduce rotor current and / or activate a crowbar (42) to reduce the voltage of the DC link (26) connecting the converters (22, 24) when significant voltage transients occur on the grid (10). This permits continued operation of the DFIG system without disconnecting from the grid.

A controller (28) for a doubly fed induction generator (12,20) adjusts control signals to a rotor side converter (24) and line side converter (22) to adjust rotor current when a voltage transient on a utility grid (10) occurs, so that the doubly fed induction generator can ride through the transient. The controller can also turn off the transistors of the rotor side converter (24) to reduce rotor current and / or activate a crowbar (42) to reduce the voltage of the DC link (26) connecting the converters (22, 24) when significant voltage transients occur on the grid (10). This permits continued operation of the DFIG system without disconnecting from the grid.

A method and system for dissipating energy in a direct current (dc) bus of a doubly-fed induction generator (DFIG) converter during a grid event is described. In one aspect, the method comprises monitoring operating conditions of an electrical system, the electrical system comprising at least a DFIG generator and a line side converter and a rotor side converter connected by a dc bus having a dynamic brake connected thereto; detecting an overvoltage on the dc bus or a condition indicative of an overvoltage on the dc link is detected, the overvoltage on the dc bus or condition indicative of the overvoltage caused by a grid event; and causing energy in the dc link to be dissipated using the dynamic brake.

The invention discloses a cooperative control method of high and low voltage ride-through for a doubly-fed wind turbine set. According to the method, according to monitored stator end voltage level of the doubly-fed wind turbine set, the operating state of the doubly-fed wind turbine set is divided into three operating modes, to be specific, a normal node, a low voltage ride-through mode and a high voltage ride-through mode; by modifying a rotor side converter control structure, attenuation of direct current and negative sequence component in stator flux linkage of the doubly-fed wind turbine set after a failure occurs is accelerated, and quick injection of reactive current is made possible; according to rotor three-phase current and direct-current bus voltage level monitored in real time, breakover trigger logic of a hardware protective module is optimized, and operational safety of a set transformer and an alternating-current bus capacitor is protected. Especially, the provided cooperative control of high and low voltage ride-through and a protective scheme are implemented completely on basis of existing low voltage ride-through hardware of the set, no additional hardware protective equipment is required, and a general voltage fault ride-through implementing scheme for handling abrupt changes in grid voltage amplitude is provided.

The invention discloses a coordination control method for double-fed asynchronous wind driven generator high voltage ride through, on the basis of a mathematical model of a double-fed asynchronous wind driven generator and gird side and rotor side converters of the double-fed asynchronous wind driven generator, allocation principles of active and reactive power of the grid side and rotor side converters of the double-fed wind driven generator are calculated, extremity expressions of active and reactive current are given, and a high voltage ride through implementation scheme capable of effectively providing dynamic reactive support for a power grid and eliminating direct current bus voltage, active power, reactive power and electromagnetic torque ripples is provided. The coordination control method in the invention can overcome defects of weak ride through capability and poor power grid stability of a wind driven generator in the prior art, thereby achieving the goal of optimal control of the generator when the power grid voltage is high; and the method can perfectly be implemented on the basis of original low voltage rid through hardware, thereby realizing joining with an existing low voltage ride through scheme of the unit, and forming a generalized voltage fault ride through control strategy capable of coping with a sudden change of amplitude of network voltage.

The invention relates to a low-voltage traversing control method for a double-fed wind power generation system, which belongs to the technical field of wind power generation. The method comprises the following steps: firstly, the stator flux and the rotor flux of a double-fed generator are calculated according to the stator current and the rotor current of the double-fed generator which are measured by a current sensor; secondly, the stator flux is multiplied by a corresponding proportionality factor to serve as the set value of the rotor flux of the double-fed generator, so as to control therotor flux; and thirdly, the rotor flux is controlled in the way that as feedforward compensation decoupling is performed, closed-loop control is conducted to the decoupled system, and a rotor-side converter is controlled after pulse-width modulation is conducted to the obtained voltage control quantity of a rotor-side converter, so as to achieve low-voltage traversing control during failures. The low-voltage traversing control method provided by the invention has fast response, and very good traversing effect when symmetrical and asymmetrical drop failures of the network voltage occur, meanwhile, and oscillation of output electromagnetic torque of the double-fed generator can be effectively inhibited. The control method is simple and suitable for engineering application.

A double fed induction generator (DFIG) system and controller are presented in which the rotor side converter is preloaded with one or more initial values for resuming regulated operation to counteract transients upon deactivation of the crowbar protection circuit to provide grid fault ride through.

The invention is concerned with a controller of side converter to excitation electrical source web of double fed variable speed constant frequency wind generator. It controls current by a deadbeat control based on predicted current control, turns the current command signal of dq coordinate to two-phase immobile coordinate to get positive and negative order current present value of alpha and beta axes. Get present value of current to two-phase immobile coordinate through addition operation and carry immobile coordinate commutation about current of power system to get alpha and beta component of actual current value. Make the difference of command and present value, and get inductance pressure drop according to change ratio of current to count the input voltage, and get impulse signal to control on-off tube through SVPWM (space voltage vector). It keeps the control precision of DC voltage, eliminates influence to rotor side converter of fluctuation to DC side voltage, restrains common-mode voltage and differential-mode voltage output by rotor side converter to reduce burden of processor under lopsided state of power system.

The invention discloses a doubly fed generator system with a protector, as well as a method used for protecting the system. The doubly fed generator system with the protector comprises a doubly fed induction generator (100), a rotor side converter (130), an intermediate DC side converter (110), a grid side converter (120) and a bypass protecting circuit (200), wherein the bypass protecting circuit (200) comprises current limiting resistors (R1, R2 and R3) and thyristors (Q1, Q2, Q3, Q4, Q5 and Q6), the thyristors are divided into three groups, each group comprises two thyristors reversely connected in parallel, and is connected with one current limiting resistor in series, and the three groups of thyristors are connected into a star shape; when the voltage of the intermediate DC side converter (110) exceeds the set threshold U2, the thyristors (Q1, Q2, Q3, Q4, Q5 and Q6) are triggered to be conducted. The invention has the advantages of low cost, simple control and stronger fault ride-through capacity.

The invention discloses a double-fed wind generation set high-voltage penetration method capable of realizing inactive support. The method includes detecting grid-connected point-line voltage UT, and direct-current bus voltage Vdc in real time; when grid-connected point-line voltage UT is smaller than 1.1 times of nominal value, controlling a grid-side converter to work at a unit power factor mode and a rotor-side converter to work at a highest power track mode through an upper computer; when the grid-connected point-line voltage UT is not smaller than 1.1 times of nominal value, controlling the grid-side converter to work at a bus voltage control model and the grid-side converter to work at an inactive power support mode; by a self-adaptation direct-current unloading circuit, judging self on and off according to the size of Vdc. By dynamic inactive current instruction optimization of the grid-side converter and the rotor-side converter and real-time protection of the self-adaptation direct-current unloading circuit, grid-connected operation of a double-fed wind generation set during voltage boosting of a power grid is guaranteed, certain dynamic inactive support is provided for fault power grid, fast restoration of the fault power grid is facilitated, and safe and reliable operation of other grid-connected loads is guaranteed.

The invention belongs to the technical field of the power quality control of wind power generation, in particular a double-fed aerogenerator excitation system based on the hybrid stored energy of a super capacitor and a storage battery. The system is characterized by comprising a rotor side converter 3, a net side converter 4, a chopper A5, a chopper B7, a super capacitor 6, a storage battery 8, a bilateral switch as well as a limiting resistor Rl and a direct current side capacitor C, wherein a hybrid stored energy device comprising the chopper A5, the chopper B7, the supper capacitor 6 and the storage battery 8 is connected to both ends of the direct current capacitor in parallel; the rotor side converter 3 is responsible for providing excitation power to an aerogenerator; the net side converter 4 is responsible for transmitting power exchanging with the output end of the rotor side of the aerogenerator, and exactly controlling the charge and discharge power of the storage battery and the super capacitor by controlling the chopper A5 and the chopper B7 so as to compensate external power fluctuation. The invention has the advantages that the aerogenerator generates stable electrical energy under the condition of the frequent fluctuation of the aerogenerator, the safe stability of large-scale synchronization running of a wind farm is improved, and the excitation system can also be widely used in ocean power generation such as wave-actuated power generation and tidal power generation.

The invention relates to a low-voltage ride through control system and a low-voltage ride through control method for a capacity-optimal energy-storage type double-fed motor. The low-voltage ride through control system comprises a power grid, a coupling transformer, a double-fed induction generator (DFIG), a grid-side converter, a rotor-side converter, a DC (Direct Current)-side capacitor, a geared head and a fan, wherein one path of the power grid is directly connected with the DFIG through the coupling transformer, and another path of the power grid passes through the grid-side transformer, the DC-side capacitor and the rotor-side converter in sequence and is connected with the DFIG; a DC-side energy storage device is connected with the DC-side capacitor through a bidirectional DC / DC converter; and the DFIG is connected with the fan through the geared head. The low-voltage ride through control system and method have the advantages of improving the low-voltage ride through capability of a DFIG wind power generation system when the voltage of the power grid sharply drops, ensuring the fault ride-through of the DFIG, improving the supporting capability of the DFID wind power generation system on the voltage of the power grid during fault, providing a measure for reducing the requirement of the DFIG on the capacity of the energy-storage device in the process of realizing the low-voltage ride through and greatly reducing the cost of the energy storage device.

The invention discloses a method for controlling asymmetric direct power of doubly-fed asynchronous wind power generators. The method comprises the following steps that: by collecting voltage and current signals of a three-phase stator of a DFIG, instantaneous active power and reactive power output by the DFIG stator are calculated; error signals between the instantaneous active / reactive power of the stator and given active / reactive power are regulated by utilizing a proportional regulator and two resonant regulators; output signals of the three regulators are added and then decoupled through feedback compensation so as to obtain a reference voltage signal of a rotor in a rotor-speed rotational coordinate system; a switching signal of the operation of a rotor-side converter is generated through space vector pulse-width modulation so as to control the operation state of the DFIG; and the method can eliminate fundamental-frequency fluctuation and double-frequency fluctuation in the output power of the stator, which are caused by voltage asymmetry of power networks, and does not need to decompose positive / negative-sequence components, thereby avoiding introducing decomposition time delay and errors. Therefore, the method can enhance the capability of controlling wind power generating sets under the circumstance that the power networks have asymmetric faults, and improve the uninterrupted operation capability of the wind power generation systems with the faults.

The invention discloses a low-voltage traversing control method for a double-fed wind power generation system. The method comprises the following steps of: 1) detecting zero frequency transient flux component of a motor; 2) when the motor has zero frequency transient flux component outburst, controlling a rotor current transformer and a network current transformer, and attenuating the zero frequency transient flux components of the current transformers; and 3) controlling torque current and power grid reactive compensation current to inhibit the growth of harmful voltage and prevent the formation of harmful current. The method can really realize the elimination of the transient flux caused by sudden decline and sudden rise of a stator voltage and inhibit negative sequence current so as to avoid offline of the fan power generation system at the same time of protecting the rotor current transformer and the network current transformer; meanwhile, by the method, double times ultrahigh dangerous voltage of rotor induction caused by zero frequency transient flux superposition when the voltage is recovered can be prevented, and power grid-friendly intelligent low-voltage traversing is realized.

The invention discloses an operation control method of a DFIG grid side and a rotor side PWM converter. The operation control method is used to aim at engineering demands of grid-connected wind power generation system simulation analysis. A double-fed induction wind power generator grid side PWM converter mathematical model is established, and a grid side converter control method based on d-axis power grid voltage orientation is designed, and current tracking control and inverter direct current busbar voltage equalization control are realized. A rotor side converter mathematical model is established, and a DFIG rotor current control method of stator magnetic flux linkage orientation is designed. A 2MW double-fed asynchronous power generator simulation analysis model in a PLECS software platform is established and a sub-synchronous state, a super-synchronous state, and a transition process from the sub-synchronous state to the super-synchronous state are analyzed in a detailed way, and according to a result, the designed mathematical model and the control method are feasible.

The invention discloses a stability analysis method for a doubly-fed fan grid-connected system, and belongs to the technical field of electrical engineering. According to the method, small signal impedance models of a rotor side converter port and a network side converter port of a double-fed fan are built under polar coordinates; and a small signal impedance model of a network port of a power grid side is built under the polar coordinates. According to the built small signal impedance models of the rotor side converter port and the network side converter port of the double-fed fan, and smallsignal impedance model of the network port, calculation is performed to obtain generalized impedance of the ports of the double-fed fan and generalized impedance of the network port of the power gridside; the two generalized impedances are divided to obtain a corresponding ratio; and the stability of the doubly-fed fan grid-connected system is judged according to a Nyquist criterion. The method can be used for analyzing the stability of the doubly-fed fan grid-connected system, and provides a theoretical foundation for understanding an oscillation mechanism caused after access of large-scalewind power to a power grid.

The invention discloses a method for suppressing total output reactive power fluctuation by adopting a doubly-fed induction wind power system with series grid-side converters under unbalanced voltage. The method relates to the control of series and parallel grid-side converters and motor-side converters. Pulse-width modulation (PWM) driving signals of the series and parallel grid-side converters are generated through a specific method to control the series and parallel grid-side converters. Under unbalanced grid voltage, a doubly-fed induction generator (DFIG) with the series grid-side converters does not change the control strategies of a rotor-side converter. On the premise that the doubled frequency fluctuation of the output power of the generator does not occur, the doubled frequency fluctuation of the electromagnetic torque does not occur and the three-phase current of a stator and a rotor are in balance, through the coordination control of the series grid-side converters and theparallel grid-side converters, the goal that the doubled frequency fluctuation of the total output reactive power of the entire system does not occur is realized, and the quality of reactive power provided by the DFIG wind power system to the grid under unbalanced grid voltage is improved.

The present subject matter is directed to systems and methods for controlling variable speed generators, particularly converters associated with doubly-fed induction generators (DFIG) to permit use of harmonic attenuating filters that are generally smaller and less costly than previous similar filters. The subject matter provides for controlling line-side and rotor-side converters in such a manner that the frequencies generated by the converters are interleaved in a manner that the filters see a higher switching frequency and thus may be designed based on those higher frequencies, thereby requiring smaller and less expensive components.

The invention discloses a method used for inhibiting double-fed wind power plant grid connection subsynchronous oscillation. First, according to a numerical model of a grid-connected double-fed wind power plant, the frequency range of subsynchronous oscillation that may occur is determined. Then a phase compensation technology is employed for designing a corresponding band rejection filter. Finally, the designed band rejection filter is connected to a current feedback link of converter current inner loop of a rotor side of a double-fed fan. According to the invention, subsynchronous control mutual action of the double-fed wind power plant can be inhibited effectively, so that a distinct inhibition effect on double-fed wind power plant grid connection subsynchronous oscillation is realized.The method has significant realistic meaning in ensuring safe and stable operation of a power system.

Wind turbine systems and methods for operating wind turbine systems are provided. A method includes monitoring an operating condition of the wind turbine system, and determining whether the operating condition has exceeded a predetermined threshold. The method further includes switching a plurality of switches devices in a rotor side converter of a power converter of the wind turbine system in a normal switching mode if the operating condition is less than the predetermined threshold. The method further includes switching the plurality of switching devices in a short circuit switching mode if the operating condition is greater than or equal to the predetermined threshold. The method further includes switching the plurality of switching devices in the normal switching mode after switching in the short circuit mode if the operating condition decreases below the predetermined threshold and a secondary operating condition is below a secondary predetermined threshold.

The invention discloses a low-voltage ride through control method of a dual-feed wind generating set, which comprises the step of controlling a rotor side converter and a network side converter. The low-voltage ride through control method has the technical scheme that: during failure, the rotor side converter controls a wind generating set rotor to accelerate for operation through a manner of limiting a torque current of the wind generating set, unbalance energy in the wind generating set due to voltage drop of a power grid is converted into kinetic energy of the rotor, thus overcurrent in a stator loop and a rotor loop of the wind generating set is reduced; and a feed-forward compensation quantity for reflecting rotor power and direct-current voltage fluctuation is added in a direct-current side voltage control ring of the network side controller, thus momentary fluctuation of the rotor power is balanced and overvoltage of a direct current side is reduced. The low-voltage ride through control method is simple in realization without adding a hardware device, has high reliability and capabilities of effectively improving low-voltage ride through capacity of the dual-feed wind generating set and keeping control of the wind generating set on outputting an active power and a reactive power in a power grid failure period.

The invention discloses a method for controlling a wind turbine to participate in power grid frequency modulation based on virtual inertia and a pitch angle. The method comprises the following steps:when a frequency deviation exists between the rated power of a system power grid and the current frequency, calculating a proportionality factor of a tracking curve of the sub-optimal rotating speed-active power of the wind turbine under the control of the virtual inertia; calculating a reference power of an inverter at a rotor side under the control of the virtual inertia; calculating an introduced electromagnetic power at the rotor side inverter according to the frequency change rate, and accumulating the introduced electromagnetic power and the reference power to obtain a total electromagnetic power of the rotor side inverter; calculating the rotating speed deviation of the wind turbine, and adopting the rotating speed deviation of the wind turbine to calculate the electromagnetic powervariation of the rotor side inverter; obtaining an active power of a pitch angle mechanism according to the total electromagnetic power and the electromagnetic power variation, and calculating the pitch angle of the pitch angle mechanism by adopting the active power of the pitch angle mechanism; and controlling the wind turbine to increase captured wind energy and inject the active power into thepower grid according to the pitch angle.

The invention relates to a method for restraining the current imbalance and aberrance of a stator of a double-feed wind generating set. The voltage of the stator as well as the positive sequence component and the non-positive sequence component of a fundamental wave of the current are obtained by detection and calculation; by comparing and adjusting the active power and the reactive power which are calculated by the specified values of a master active power and a master reactive power, the voltage at the stator side and the positive sequence component and transformation of coordinate, the specified value of the positive sequence current of a rotor in a static coordinate system is obtained; the specified value of the control quantity of a rotor three-phase current restraining the current imbalance and aberrance of the stator is obtained by the non-positive sequence component by calculation, overlapped with the specified value of the positive sequence current of the fundamental wave of the rotor; after adjustment, the specified value of the voltage of the rotor is output which is used for controlling an inverter at the rotor side to feed a needed field current to a rotor winding of the double-feed generator; thereby restraining the adverse effects caused by the current imbalance and aberrance of the stator by detecting the voltage of the stator and the positive sequence component and the non-positive sequence component of the fundamental wave of the current as well as carrying out overlapping control of the rotor current.

A method and arrangement for controlling a doubly-fed induction machine by a frequency converter including a rotor side converter (INU) connected to a rotor circuit of a doubly-fed induction machine (DFIG) and having a control system with rotor flux as a feedback variable, a grid side converter (ISU) connected to an AC power network, and a direct voltage intermediate circuit (DC) connected between the rotor side converter (INU) and the grid side converter (ISU). The method includes forming a rotor flux reference (ψr,ref), forming a damping signal (ψref,D), summing the damping signal and the rotor flux reference for obtaining a modified rotor flux reference (ψref), and feeding the modified rotor flux reference to a controller of the rotor side converter (INU) for damping sub-synchronous resonances.

The invention discloses a method and a device for suppressing subsynchronous resonance through a doubly-fed fan rotor side converter. The method comprises the steps as follows: a rotating speed signal and a subsynchronous resonance frequency of a wind generator rotor are obtained; an additional controller is determined according to the amplitude-frequency characteristics and the phase-frequency characteristics of the relationships of a rotating speed variation and an electromagnetic torque variation; the rotating speed signal is processed through the additional controller to obtain an additional controlled quantity; the additional controller comprises a band-stop filter module, a band-pass filter module and a phase-shift module; the additional controlled quantity is injected into the rotor side converter and is superposed to an original controlled quantity to generate an additional torque; and the phase difference between the additional torque and the rotating speed variation is within a range of 90-270 degrees, so that the target of suppressing the subsynchronous resonance in a doubly-fed fan series compensation transmission system is achieved.

In one aspect, a method for controlling a dual-fed induction generator (DFIG) during a high-voltage grid event is provided. The method includes setting, by a controller, an output of a closed-loop portion of a rotor current regulator to a fixed value such that a predictive feed-forward path sets an internal voltage for the DFIG; and detecting, by the controller, a condition of high dc voltage on a dc link or a condition predictive of high dc voltage on the dc link, and in response reduce a rotor torque producing current command to approximately zero, wherein the dc link connects a line-side converter connected to a system bus and a rotor-side converter connected to a rotor of the DFIG.

The invention discloses an open type grid-connection experiment system of a variable-speed constant-frequency double-fed wind power generator unit and an open type grid-connection experiment method. The open type grid-connection experiment system is applied to a power grid. The open type grid-connection experiment system comprises a plurality of fuses, a plurality of contactors, a first voltage and current transducer, a second voltage and current transducer, a grid-side converter, a DC capacitor, a rotor-side converter and a double-fed motor. The open type grid-connection experiment system is characterized by further comprising a voltage adjustable isolation transformer, a DSP / FPGA control system, an encoder and an optical coupling isolation unit. The voltage adjustable transformer is arranged between the power grid and the fuses in series and can be adjusted manually so as to simulate and achieve grid connection of various voltage amplitudes. The DSP / FPGA control system is used for controlling a first set of control signals and a second set of control signals according to sampling signals of the first voltage and current transducer, wherein the first set of control signals and the second set of control signals are required by the grid-side converter and the rotor-side converter and outputted to the grid-side converter and the rotor-side converter. The encoder is connected with the double-fed motor and used for detecting the rotating speed of the rotor side of the double-fed motor. The optical coupling isolation unit is connected between the encoder and an FPGA unit and used for inputting the signals into the FPGA unit after the signals are subjected to filtering processing.

The present invention discloses a control method capable of enhancing low-voltage ride-through used for a double-fed induction generator under an asymmetrical power grid fault. The method comprises control of a rotor side converter and a grid side converter of the double-fed induction generator. According to the method, by controlling the rotor side converter of the double-fed induction generator, the double frequency fluctuation of the electromagnetic torque of the generator can be effectively suppressed, so that safe and stable fault ride-through operation of a double-fed wind power generation system is realized; meanwhile, on the basis of consideration of converter capacity, a minimum reactive current meeting the requirements of a power grid guide rule can be output, so that the transient voltage level of a power grid during a fault period is improved. According to the method, by controlling the grid side converter of the double-fed induction generator, the double frequency fluctuation of a DC bus voltage can be suppressed, so that the service life of a DC bus capacitor is improved, the double frequency fluctuation of active and reactive power output from the generator can be effectively suppressed via coordinated control with the rotor side converter, and thus the grid-connected power quality is improved. According to the method, by comprehensively considering the capacity of the converter and the operation condition of the generator, the fault ride-through capability of the double-fed induction generator and the power quality of the connected power grid are effectively improved.

Provided is a doubly-fed induction generator system and a self-test method for the active crowbar circuit of the doubly-fed induction generator system. The invention is featured by using the controller of the doubly-fed induction generator system to carry out a self-test procedure to detect the loop current of the active crowbar circuit for determining if the active crowbar circuit can be turned on and off normally. Also, the rotor-side converter and the active crowbar circuit of the doubly-fed induction generator system are forbidden to turn on simultaneously during the execution of the self-test procedure.