A grid-connected control method for dual-motor wind turbines

Abstract

The invention discloses a grid-connected control method of a dual-motor wind generating set. The wind generating set comprises a first motor, a second motor and a transfer case. Two output shafts of the transfer case are connected with the first motor and the second motor respectively. The first motor is connected with a current transformer. The grid-connected control method comprises the following steps that when the first motor is connected to a grid, the current transformer adjusts the power of the first motor; when the first motor and the second motor are jointly connected to the grid, the current transformer adjusts rotation speeds of the two output shafts so as to adjust power distribution of the first motor and the second motor; and when the second motor is switched in or switched out, the current transformer adjusts the rotation speeds of the two output shafts, in order to enable the second motor to accord with switch-in or switch-out conditions. The invention is simple and reliable in control and easy to implement, and can achieve the best use of wind energy and the large power output of the set.

Description

technical field [0001] The present invention mainly relates to the technical field of wind power generation, in particular to a grid-connected control method for a wind power generating set with two motors. Background technique [0002] In the prior art, large-scale wind power generators mostly adopt the structural types of permanent magnet motor direct drive unit and asynchronous motor double-fed unit, and these two kinds of wind power generators are equipped with a generator. [0003] The wind rotor of the direct-drive wind turbine is directly connected to the input shaft of the motor through a coupling. The generator speed changes with the wind speed. The converter rectifies the alternating current with changing frequency into direct current, and then inverts it into alternating current with the same frequency as the grid. Since the unit needs to use multi-stage low-speed permanent magnet motors, with the increase of the design capacity of the unit, it will bring difficul...

AI Technical Summary

Problems solved by technology

Since the unit needs to use multi-stage low-speed permanent magnet motors, with the increase of the design capacity of the unit, it will bring difficulties to the design, processing and manufacturing of the motor, and it needs a full-power converter, which requires a large investment in equipment.

[0004] The wind wheel of the doubly-fed wind turbine is connected to the input shaft of the motor through a speed increaser, which allows the generator to run within 30% of the synchronous speed. When the load is low, the wind energy utilization coefficient is low and the unit efficiency is low

[0005] In addition, because the angle of attack of the airflow on the blades is constantly changing in the entire operating wind speed range of the unit, if the speed of the wind turbine cannot be adjusted with the change of wind speed, the efficiency of the impeller at low wind speeds will inevitably be reduced (if Setting the maximum efficiency point in the low wind speed region will cause the blade to stall prematurely)

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