DFIG unbalanced power grid voltage compensation method based on phase-locked-loop-free self-synchronization control

Abstract

The invention discloses a DFIG unbalanced power grid voltage compensation method based on phase-locked-loop-free self-synchronization control, and the method comprises the steps: avoiding the introduction of a phase-locked loop by presetting a fixed rotation angular frequency dq coordinate system on the basis of conventional direct power control, and compensating a power grid voltage unbalanced component by adding a direct resonator, so multi-coordinate transformation is not needed. The system is simple in control structure, and can be used for quickly compensating when the power grid voltageis unbalanced and drops, so the power quality of a power grid is improved. Meanwhile, the method can flexibly set the compensation coefficient, can achieve the full-range compensation of the PCC voltage, and gives consideration to the power quality of a power grid and the operation performance of a unit.

Description

technical field [0001] The invention belongs to the technical field of motor control, and in particular relates to a DFIG unbalanced grid voltage compensation method based on self-synchronization control without a phase-locked loop. Background technique [0002] Since the doubly-fed induction generator (DFIG) has the advantages of small converter capacity and flexible and adjustable power, the proportion of wind turbines based on DFIG in new energy power generation is increasing. The system structure of DFIG generators is as follows: figure 1 shown. At present, most of the wind farms in my country are distributed in remote areas, so the line impedance is relatively large, usually showing the characteristics of a weak grid; under the condition of a weak grid, wind power grid connection points (PCC) usually have large power quality problems, such as voltage fluctuations, voltage unbalanced etc. [0003] Due to the randomness of wind power generation, DFIG-based generators usu...

AI Technical Summary

Problems solved by technology

However, the traditional unbalanced voltage compensation method based on PCC voltage closed-loop has some shortcomings: 1) In the voltage closed-loop, the reference value of the negative sequence voltage can only be set to 0, which will seriously threaten the operation performance of the unit; 2) It is necessary to extract the positive and negative sequence components of voltage and current, and control it in multiple rotating coordinate systems. The structure is complex and highly dependent on motor parameters.

However, under non-ideal grid conditions, the PLL cannot quickly and accurately track the grid voltage signal, which will affect the control of DFIG and have potential stability problems

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