Power grid synchronization method based on frequency self-adaptive virtual flux linkage estimation
A technology of frequency self-adaptation and virtual flux linkage, applied in the direction of single-network parallel feeding arrangement, etc., can solve problems such as cascading delay in transient response, sensitivity to power grid frequency changes, and no grid synchronization method proposed
Active Publication Date: 2014-07-02
CHINA UNIV OF MINING & TECH
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[0006] The purpose of the present invention is to provide a grid synchronization method based on frequency-adaptive virtual flux linkage estimation, which solves three problems existing in existing grid synchronization methods based on virtual flux linkage. The virtual flux linkage estimation method is sensitive to grid frequency changes; second, the method based on cascaded flux linkage and positive and negative sequence separation has cascaded delays in transient response under unbalanced grid conditions; third, no harmonic Problems with grid synchronization methods under grid conditions, to achieve positive and negative sequence separation of harmonics
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Embodiment 1
[0055] Embodiment 1: The power grid synchronization method has six steps in total, including: 1. Output voltage reconstruction on the two-phase bridge arm side; 2. Converter and grid resistance voltage compensation; 3. Harmonic decoupling; 4. Virtual flux linkage and Separation of positive and negative sequences of current; 5. Grid frequency estimation; 6. Converter and grid total inductance flux compensation; the specific steps are as follows:
[0056] Step 1. Output voltage reconstruction on the two-phase bridge arm side: the output voltage of the converter on the two-phase bridge arm side is obtained from the duty cycle of the three-phase bridge arm switching device of the converter and the DC voltage obtained by sampling;
[0057] Step 2. Compensation of converter and grid resistance voltage: Sampling the output current of the converter, and the output voltage of the two-phase bridge arm side converter obtained according to step 1, the total resistance of the converter and ...
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The invention belongs to power grid synchronization methods and provides a power grid synchronization method based on frequency self-adaptive virtual flux linkage estimation. According to the power grid synchronization method, a harmonic decoupling unit HDN completes detection of the harmonic components of the voltage and the current of a power grid. The output of the harmonic decoupling unit HDN passes by positive and negative separating cells MPNSC (alpha and beta), positive sequence components and negative sequence components of each harmonic of the voltage and the current are obtained. A frequency tracking unit FLL obtains the fundamental frequency of the power grid. The harmonic decoupling unit HDN of the voltage and the current completes decoupling under the condition that the fundamental frequency is tracked. According to the flux linkage and the current which are obtained through the positive and negative separating cells MPNSC (alpha and beta), flux linkage minus inductance flux linkage dip is the flux linkage of a virtual point of common coupling. By the adoption of the power grid synchronization method based on frequency self-adaptive virtual flux linkage estimation, the sensitivity of a virtual flux linkage estimation method to the change of grid frequency is reduced, the voltage phase of the power grid is accurately tracked, cascade delay for transient response under the condition of unbalance of the power grid is eliminated, and the power grid synchronization method under the condition of a harmonic power grid is put forward for the first time.
Description
technical field [0001] The invention relates to a method for synchronizing with a power grid, in particular to a method for synchronizing a power grid based on frequency-adaptive virtual flux linkage estimation. Background technique [0002] As the use of power electronic converters continues to grow, the voltage source converter (VSC) has become the dominant topology for modular and standardized grid-connected converter units over a wide power range. In the scientific literature, a large number of grid synchronization methods and voltage source converter control methods have been proposed and analyzed. Voltage-free sensor technology is also gaining attention in grid synchronization because it can reduce costs, enable system modularization and, in some cases, even increase the stability of grid-connected converters. The estimation method using voltage-free sensor technology can improve the performance of the converter by estimating the grid situation at the remote end of th...
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Inventor 王颖杰伍小杰刘海媛陈文强韩雪龙张永磊王康安唐建波文炳林闫浩浩
Owner CHINA UNIV OF MINING & TECH