Double-fed induction motor system direct torque controller capable of reducing torque ripple

Abstract

The invention relates to a double-fed induction motor system direct torque controller capable of reducing torque ripple, and belongs to the fields of power electronics and motor control. A new logical judgment manner is adopted, a new switching state table is redesigned by changing the switching state of a switching element in a double-fed motor control system, and the magnetic flux trace is closer to a circle, so that the torque ripple, rotor magnetic flux and direct-current bus voltage fluctuation of the system are greatly reduced, the steady-state characteristics of a double-fed wind power generation system are improved, the dynamic response for motor speed when a wind speed changes is increased, the control level of the system is also improved, and the utilization rate of wind energy is improved. The double-fed induction motor system direct torque controller is simple in control method and good in control effect, and has wide application prospects in practical engineering.

Description

technical field [0001] The invention relates to a direct torque controller of a doubly-fed induction motor system for reducing torque fluctuation, which belongs to the field of power electronics and motor control. Background technique [0002] The doubly-fed induction machine (DFIG) is currently the most widely used wind power machine. It consists of a wound asynchronous generator whose stator winding is directly connected to a fixed-frequency three-phase grid and a bidirectional back-to-back voltage source converter installed on the rotor winding. There are various control methods, and direct torque control is one of them. [0003] In the 1980s, German scholar Depenbrock proposed direct torque control. The idea was to regard the motor and the drive converter as a whole, and use the space voltage vector analysis method to calculate the magnetic flux and torque in the stator coordinate system. The switching state of the tracking PWM converter directly controls the torque. C...

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Problems solved by technology

The main reasons are: because the hysteresis comparator is used in the torque and flux regulator, the torque ripple is inevitably caused; after the motor runs for a period of time, the temperature of the motor rises, and the resistance value of the stator resistance changes, so that The estimation accuracy of the stator flux linkage is reduced, resulting in a large pulsation of the electromagnetic torque; the switching frequency of the converter will also affect the size of the torque pulsation, the higher the switching frequency, the smaller the torque pulsation, and vice versa, the lower the switching frequency The larger the torque ripple

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