47 results about "Doubly fed induction generator dfig" patented technology

A system for modulating a frequency output of a generator coupled to an electric distribution network is described herein. The system includes: a doubly-fed induction generator coupled to a power source selected from at least one of hydropower and fuel combustion, the generator providing an electrical power output having a first frequency based on a rotational speed of the generator; a controller for selecting the rotational speed of the generator; and a converter coupled to the generator for changing the frequency of the output to a selected value, in response to selecting the rotational speed. Methods for modulating a frequency output of a generator coupled to an electric distribution network are also described.

Systems and methods for allocating reactive power production in a doubly-fed induction generator (DFIG) wind turbine system including a DFIG and a power converter including a line side converter and a rotor side converter are provided. A method can include obtaining a reactive power production requirement, obtaining one or more operating parameters for the DFIG and the line side converter, and determining a priority ratio based at least in part on the one or more operating parameters. The priority ratio can be a ratio of reactive power production between the DFIG and the line side converter. The method can further include controlling the DFIG and the line side converter based at least in part on the reactive power production requirement and the priority ratio such that the combined reactive power production from the DFIG and the line side converter meet the reactive power production requirement.

A DFIG power system defines a generator power path and a converter power path. The generator power path has a DFIG with a rotor and a stator. The converter power path has a power converter with a rotor-side converter coupled to a line-side converter via a DC link. The power converter has at least two power bridge circuits connected in parallel. A method of operating the DFIG power system includes monitoring, via one or more sensors, at least one electrical condition thereof. The method also includes comparing, via a control system, the at least one electrical condition to a predetermined threshold, the predetermined threshold being indicative of an occurrence of a transient overloading event. Further, the method includes alternating between non-interleaving and interleaving intervals if the at least one electrical condition exceeds the predetermined threshold so as to reduce harmonics of the DFIG power system.

A wind farm is presented. The wind farm includes a plurality of wind turbine stations, where each wind turbine station includes a wind turbine and a generator sub-system. The generator sub-system includes a doubly-fed induction generator configured to generate an alternating current voltage and a wind turbine station power converter. The wind farm further includes a power collection sub-system that includes a power bus and a sub-station power converter. The wind farm also includes a control system configured to determine a wind speed metric, estimate a corresponding frequency metric, calculate a desirable frequency based on the wind speed metric and frequency compensation ranges of the wind turbine station power converters, and generate and communicate control commands to the sub-station power converter based on the desirable frequency to allow the sub-station power converter to update a line frequency of a power bus voltage based on the desirable frequency.

The invention provides a method and device for controlling the stator current of a grid-connected doubly-fed induction generator. The method includes: performing coordinate transformation on the collected parameters of the doubly-fed induction generator to obtain The stator voltage vector U sαβ and the stator current vector I sαβ ; Calculate the stator current vector I of the doubly-fed induction generator sαβ α, β axis command; according to the DFIG stator current α, β axis command and the actual measured feedback value, calculate the rotor voltage command U' under the stator two-phase stationary coordinate system rαβ ;To the rotor voltage command U' rαβ Carry out coordinate transformation to obtain the rotor voltage command U in the rotor two-phase static α-β coordinate system rαβ ;According to the rotor voltage command U rαβ A set of PWM signals are obtained to control the rotor converter of the doubly-fed induction generator. The technical scheme provided by the invention simplifies the design and implementation process of the control system, and enhances the adaptability of the control system to generator parameter changes.

The present invention relates to a method of controlling a doubly fed induction generator wind turbine converter system in case of a sub-synchronous resonance event, the method comprising the steps of detecting the sub-synchronous resonance event, and switching from a first control mode to a second control mode in response to detecting the predetermined event, wherein the second control mode comprises the step of setting at least one rotor current controller parameter on the basis of a generator speed of the doubly fed induction generator. The predetermined event may also be a fault ride through event. The present invention further relates to a doubly fed induction generator wind turbine converter system being capable of handling such events.

Aspects of the present invention relate to a method for controlling an amount of reactive current provided from a wind turbine generator to a power grid during an abnormal power grid event, said wind turbine generator comprising a doubly-fed induction generator having a rotor and a stator, and a power converter coupling the rotor to the power grid, the power converter comprising a grid-side inverter, wherein the method comprises the step of balancing the reactive current provided to the power grid between a reactive stator current and a reactive grid-side inverter current, wherein the reactive grid-side inverter current is controlled in accordance with a reactive current capacity of a grid breaker receiving the reactive current provided by the grid-side inverter. Aspects of the present invention also relate to a wind turbine generator being capable of performing the method.

The invention provides a stochastic stability analysis method for a power system containing wind power based on Markov theory, establishes a Markov model of wind speed and a stochastic dynamic model of a doubly-fed induction generator, and establishes a stochastic Markov dynamic of a power system containing a doubly-fed induction generator Model, put forward the criterion applicable to the system stochastic Markov dynamic model. Based on the stochastic Markov theory, the present invention analyzes the system stability by establishing a stochastic Markov dynamic model of the wind power system. According to the definition of random mean square stability of the system, using the relevant knowledge of the M matrix, the random Markov dynamic model based on the system is used to determine the randomness of the system. Practical criterion of mean square stability; the present invention overcomes the limitations of stochastic equations, and can more accurately describe the dynamic behavior of wind power systems in the case of large-scale random fluctuations in wind speed, based on the stochastic Markov dynamic model derived from the system Compared with other criteria, the criterion is more practical, more concise and has a wider scope of application.

The invention discloses a parameterless predictive current control method of an independent brushless double-fed induction generator, which belongs to the technical field of brushless double-fed induction generator control. The method includes: real-time monitoring of the control winding voltage and current information of the motor at the previous two moments and the current moment, calculating the predicted current with delay compensation, and determining the optimal switching state of the power electronic device in the control winding side converter through the cost function , and finally use the single-vector modulation algorithm to determine the duty cycle and generate a reasonable and effective switching sequence to drive the control winding side converter to realize real-time control of the control winding current. The control method predicts and controls the winding current through real-time motor state information, which can effectively avoid dependence on motor parameters. The control system is hardly affected by changes in motor parameters, and has strong robustness and more stable operation.

In order to detect the fault of doubly-fed induction generator, a fault detection method of doubly-fed induction generator based on sliding mode observer is proposed here. Due to the advantages of the sliding mode observer such as simple structure, not easily affected by parameters, and strong anti-interference ability, the invention applies the sliding mode observer to the fault detection of the doubly-fed induction motor. First, the present invention builds a sliding mode observer based on the mathematical model of the doubly-fed induction generator, observes the rotor current and speed, and realizes fault self-detection by comparing the residual between the actual rotor current value and the observed value. Then the present invention provides three kinds of faults, namely grid end voltage drop fault, doubly-fed induction generator stator turn-to-turn fault and rotor current sensor fault, to prove that the sliding mode observer can perform fault detection on faults occurring at different positions. , and it can be seen that the sliding mode observer has the characteristics of fast response and good stability.

The invention relates to a method for analyzing the three-phase short-circuit current of a doubly-fed induction wind generator after the protection action of a crowbar, and belongs to the technical field of wind power generation system fault analysis. The invention uses the DFIG stator and rotor voltage equations and stator and rotor flux linkage equations after the crowbar protection action to deduce the three-phase short-circuit current of the double-fed induction wind generator after the crowbar protection action, which simplifies the calculation process. The method can accurately calculate the three-phase short-circuit current of the doubly-fed induction wind turbine after the protection action of the crowbar, and is of great significance to the selection of power system equipment and the analysis of the protection action characteristics of the doubly-fed induction wind turbine.