PWM rectifier control method based on model prediction and voltage square control

Abstract

The invention discloses a PWM rectifier control method based on model prediction and voltage square control. The square of the output direct-current side voltage is controlled to serve as the given inner ring active current, the quick response of a controller is ensured through the linear relation between the square of the voltage and the active current, and the anti-disturbance capacity of a rectifier is further enhanced through the model prediction control of the inner ring current. The cost function of model prediction is quickly obtained through the finite set on-off state so that the control method can be easily achieved on a digital controller. The dynamic response and the anti-disturbance capacity of the whole controller can be enhanced through the selection of the weighting coefficient in the cost function and the coordination with the pre-charging soft start strategy. By means of the double-closed-loop control method, the quick response and the high anti-disturbance capacity for load disturbance are achieved while it is ensured that the alternating-current side of the rectifier reaches the unit power factor and the current total harmonic distortion rate reaches the national standard requirement. By means of the double-closed-loop control method combined with the voltage square model prediction control, the control over the unit power factor and the disturbance resistance of the three-phase voltage type PWM rectifier is achieved, and great reference value is provided for engineering.

Description

technical field [0001] The invention relates to the research fields of a three-phase voltage-type PWM rectifier, a flexible AC-DC converter, etc., and in particular relates to a double closed-loop control method of a three-phase bridge-type full-control rectifier circuit. Background technique [0002] With social progress and industrial development, power electronic devices have been widely used in consumer industries such as industry and agriculture due to their superior performance in power transmission, distribution and transformation of power systems. However, as a nonlinear load, power electronic devices will inject a large amount of reactive power and harmonics into the grid. First of all, reactive power will affect the stability of the power system and affect the power quality of other users at the public connection point of the power system. Secondly, harmonics will make the life of mechanical rotating equipment in the power system such as generators and transformer...

AI Technical Summary

Problems solved by technology

[0004] With the continuous development of PWM rectifiers, the traditional double closed-loop PI control strategy based on voltage oriented control (VOC) will have the following problems in engineering applications: the anti-disturbance ability of the DC side output is not strong enough, and the dynamic response speed is not fast enough

Some studies have proposed a control strategy based on model predictive control. Both the voltage outer loop and the current inner loop are realized by predictive control to achieve fast dynamics that cannot be achieved by traditional PI (proportional-integral controller)-based hysteresis control. response, but this method does not consider the output DC voltage as the given inner loop active current, and its nonlinear relationship will cause inaccurate and inefficient control actions

Moreover, the method of deriving to solve the cost function will consume a huge amount of computing time

As a further improvement, another study proposed a control method for the cost function of the fixed-frequency finite set switch state solution model predictive control, but this method will increase the harmonic content of the AC side current

There is another kind of load feed-forward method proposed to solve the problem of slow response to load disturbance, but the measurement points are added to the hardware, which makes the cost higher

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