Current control method of pulse phase change stage and computing method of expression

Abstract

The invention discloses a current control method of a pulse phase change stage. A way of combining a feedforward control and a feedback control is utilized for controlling loop current of the pulse phase change stage. As time lapses, the feedforward control controls output quantity to gradually increase according to speed controlled by feedforward control parameters, and the feedback control utilizes ratio control of current deviation. Through well coordinating the relationship of the motor speed rise of the pulse phase change stage and the system loop circuit, the control method can supply continuous forward torque to the motor rotating, achieve quick increasing of the current and loop current which is kept at a certain level in future at the same time, and improve the rapidity and smoothness of starting the motor in the pulse phase change stage. The invention further discloses a computing method of a current control expression of the pulse phase change stage.

Description

technical field [0001] The invention belongs to the technical fields of electromechanics and power electronics, and in particular relates to a current control method in the pulse commutation stage when a synchronous motor is started at rest with variable frequency. Background technique [0002] Static frequency conversion systems, such as figure 1 As shown, the three-phase fully-controlled rectifier bridge and the DC reactor form a DC current source. By controlling the inverter bridge, the DC current is converted into an AC current with gradually increasing frequency and input to the motor stator, so that the motor speeds up from static to the required speed. When the rotation frequency of the motor is low (such as less than 5Hz), the voltage value induced by the machine terminal is low, which is not enough to make the thyristor of the inverter bridge turn off naturally under the action of the reverse voltage: at the moment of commutation, artificially control the rectificat...

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Problems solved by technology

The duration of the current control process, t3+t4, can be as short as 20ms. The intermittent current and the short duration of the control process bring difficulties to the control of the current recovery after each commutation in the pulse commutation stage. The existing control methods cannot handle this well. One problem is that the motor fails to start due to the inability to provide a sufficient continuous current, and the adaptability of its control parameters is not good

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