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Method and system for controlling current of grid-side converter of wind driven generator under unbalanced power grid condition

A grid-side converter and unbalanced grid technology, applied in wind power generation, single grid parallel feeding arrangement, AC network to reduce harmonics/ripples, etc., can solve problems such as grid-side current distortion

Inactive Publication Date: 2012-09-26
NORTH CHINA UNIVERSITY OF TECHNOLOGY
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Problems solved by technology

Since the actual power grid is usually unbalanced, if the control strategy is not changed, there will be double-frequency fluctuations on the DC bus voltage, which will cause distortion of the grid-side current

Method used

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  • Method and system for controlling current of grid-side converter of wind driven generator under unbalanced power grid condition
  • Method and system for controlling current of grid-side converter of wind driven generator under unbalanced power grid condition
  • Method and system for controlling current of grid-side converter of wind driven generator under unbalanced power grid condition

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Embodiment Construction

[0021] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0022] figure 1 It is the control block diagram of the doubly-fed asynchronous wind generator system when the grid voltage is unbalanced, including wind turbines, gearboxes, doubly-fed asynchronous generators, grid-side converters and machine-side converters, etc. The present invention is aimed at Grid-side converter.

[0023] figure 2 It is the hardware structure diagram of the grid-side converter of the wind turbine, including the three-phase grid voltage, filter inductance, rectifier bridge main circuit, DC side capacitor, voltage and current sensors and sampling processing circuit, DSP controller and drive protection circuit. The voltage sensor and the current sensor respectively measure the grid voltage and current and the DC side voltage of the converter, which are converted into digital signals by the sampling processing circuit and then entered into th...

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Abstract

Disclosed are a method and a system for controlling current of a grid-side converter of a doubly-fed wind driven generator under an unbalanced power grid condition. The method includes combining voltage of a power grid, alternating-current-side voltage of the grid-side converter and delay signals of the power grid and the grid-side converter with given active power and given reactive power, and analyzing and computing to obtain an instruction value of alternating-current-side current of the converter; and further computing to obtain alternating-current-side instruction voltage of the grid-side converter according to a mathematic module of the grid-side converter and a principle that an actual current value of a next time interval is equal to the instruction value, and then generating a pulse signal for controlling on and off of a switching tube via SVPWM (space vector pulse width modulation). In the method, rotational coordinate transformation and positive and negative sequence decomposition are not required, grid-side current and inductance parameters are either not required, fluctuation of direct-current-side voltage of the grid-side converter can be suppressed under an unbalanced voltage condition of the power grid, grid-side harmonic current is reduced, and unity power factor is maintained.

Description

Technical field [0001] The invention relates to a method and system for controlling a grid-side converter of a doubly-fed wind generator, in particular to a current control method and system of a grid-side converter of a doubly-fed wind generator when the grid is unbalanced, and belongs to the technical field of wind power generation. Background technique [0002] Wind energy is a clean and reliable energy source and can be installed quickly. It has become the fastest growing renewable energy source around the world. Among the various types of wind power generation, doubly-fed asynchronous wind generators are very popular in the wind power market due to their advantages such as variable speed and constant frequency operation, flexible active and reactive power control, and relatively small converter power. The doubly-fed asynchronous generator is connected to the grid through a back-to-back converter. The machine-side converter provides excitation power for the doubly-fed generat...

Claims

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Application Information

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IPC IPC(8): H02J3/46H02J3/01
CPCY02E10/763Y02E10/76Y02E40/40
Inventor 张永昌李正熙
Owner NORTH CHINA UNIVERSITY OF TECHNOLOGY
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