A control method and device for a doubly-fed motor under the condition of deeply asymmetric power grid

Abstract

The invention discloses a control method and device of a double-fed motor under the working condition of asymmetric depth of a power grid. The method adopts a vector control strategy of double closedloops, wherein an outer loop controls active power and reactive power, an inner loop controls a rotor current, a double-sequence phase-locked loop is utilized to separate positive and negative sequence components of a grid voltage, a given value of a negative sequence of the rotor current can be obtained by directly controlling the negative sequence rotor voltage to be zero according to a steady-state equation of the rotor voltage of a double-fed motor under a reverse synchronous coordinate system, and the rotor negative sequence voltage is reduced by controlling the rotor negative sequence current, so that the amplitude of the rotor voltage is reduced to be within a controlled range of a machine side converter. The control method and device further widen the asymmetric operation range ofthe double-fed machine side converter, and the machine side converter can still be in a controlled state to perform active output and perform reactive support on the power grid under the condition ofasymmetric depth of the power grid.

Description

technical field [0001] The invention relates to a control method and device for a doubly-fed motor under the deeply asymmetric working condition of a power grid, and belongs to the technical field of motor control. Background technique [0002] The vast majority of grid faults are asymmetric faults. When the grid voltage is asymmetrical, regardless of the influence of the rotor current, the relationship between the positive sequence rotor voltage amplitude and the positive sequence stator voltage amplitude is approximately the slip times, while the negative sequence rotor voltage amplitude and the negative sequence stator voltage amplitude are approximately It is the relationship of (2-slip rate) times. In actual operation, the slip rate range of double-fed motor is generally between -0.2 and 0.2, so that the smaller negative sequence component of the stator voltage will be greatly increased on the rotor. With the increase of the grid voltage unbalance, the negative sequen...

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Problems solved by technology

In this way, the machine-side converter completely loses its current control capability, and the rotor voltage injects energy into the DC side through uncontrolled rectification, resulting in repeated switching of the DC side energy discharge resistor.

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