A control method for suppressing interleaved parallel circulation of wind turbine grid-side converters

Abstract

The invention discloses a control method for restraining interleaved ring currents of grid-side converters of a wind driven generator. The control method includes the steps that output currents of a, b and c phases of a power grid are detected and added to obtain a ring current component iz output by the parallel-connection grid-side converters; subtraction is carried out on the ring current component iz output by the parallel connection grid-side converter and a preset ring current component reference value izref, and a difference value obtained through subtraction is adjusted through a proportional-resonant adjustor to achieve indifference control over zero-sequence currents so as to obtain a ring current restraint component Uz1; the ring current restraint component Uz1 is calibrated and matched to obtain a restraint component reference value Uz2; the restraint component reference value Uz2 is superposed to output voltage reference values of all the phases of the power grid. The ring currents between the parallel-connection converters can be restrained, and the control method can be flexibly applied to various wind power generation control algorithms and is capable of efficiently restraining the ring currents on the premise of not changing an existing control strategy or increasing cost.

Description

technical field [0001] The invention relates to a grid-side converter of a wind-driven generator, in particular to a control method for suppressing interleaved parallel circulation of the grid-side converter of a wind-driven generator. Background technique [0002] Multiple grid-side converters connected to wind turbines operate in staggered parallel operation, adopting the staggered parallel operation mode, such as figure 1 As shown in the figure, the interleaved parallel connection method of parallel converters means that two converters are connected with a common bus bar, and at the same time, they are connected in parallel after the AC side through the filter inductor L, and each single converter adopts a three-phase bridge voltage source converter. For different converters, the driving pulse signals of the corresponding phases of parallel converters are staggered by 180°, so that part of the current high-order harmonics cancel each other out and improve the grid-side cu...

AI Technical Summary

Problems solved by technology

However, the staggered parallel operation mode will cause a large circulation between the parallel units at the same time, making the converter equipment unable to work normally

At present, the method of suppressing the circulation between the interleaved parallel converters generally adopts the hardware suppression method, which eliminates the circulation channel on the hardware, that is, an isolation transformer is connected in series on the AC side of the parallel PWM converter, and the isolation transformer is used to block the circulation circuit of the AC side. This method increases the cost of the wind power conversion system, increases the volume of the device, reduces the flexibility of use, and increases the system loss

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