Dual-mode smooth transition control method of PWM rectifier

Abstract

The invention discloses a dual-mode smooth transition control method of a PWM rectifier. According to the method, a modulation ratio soft start controller is additionally arranged between a double-closed-loop controller of the PWM rectifier and a PWM pulse signal generating module; a modulation ratio is gradually reduced to a steady state value from large to small when the PWM rectifier is startedthrough the modulation ratio soft start controller, so that a starting impact current of the PWM rectifier is inhibited; the structure of the modulation ratio soft start controller is divided into three parts; a mathematical model of the modulation ratio soft start controller meets a condition that k=0 before controllable rectification starting of the PWM rectifier; in a range between a startingmoment t0 and a starting termination moment t1, the mathematical model of the modulation ratio soft start controller meets a condition that k=k2-k1t, and the mathematical model of the modulation ratiosoft start controller meets a condition that k=1 after modulation ratio soft start is terminated; and the modulation ratio soft start controller is started in a segmented mode, so that the impact current generated at the starting moment of the PWM rectifier is completely eliminated, and the purpose of smooth transition is achieved.

Description

technical field [0001] The invention relates to a control method for a three-phase voltage PWM rectifier, in particular to a safety control method for the PWM rectifier without current impact. Background technique [0002] Because the PWM rectifier mainly controls the charging and discharging time of the AC side filter inductor to supply power to the DC side through the on-off of the bridge arm IGBT when it starts up, so the three-phase PWM rectifier can be divided into two types from the state of the filter inductor, one is the inductor Charging, saving energy; the other is that the inductor discharges to charge the DC side, and when the charging time and discharging time reach a balance, the DC side voltage will be stable; when the PWM rectifier starts, if the initial modulation ratio amplitude is small, it will lead to the first One kind of circuit state time is too long. At this time, the inductance is approximately connected between the two-phase power supply on the AC ...

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Problems solved by technology

[0002] Because the PWM rectifier mainly controls the charge and discharge time of the AC side filter inductor to supply power to the DC side through the on-off of the bridge arm IGBT when it starts up, so the three-phase PWM rectifier can be divided into two types from the state of the filter inductor, one is the inductor Charging, saving energy; the other is that the inductor discharges to charge the DC side, and when the charging time and discharging time reach a balance, the DC side voltage will be stable; when the PWM rectifier is started, if the initial modulation ratio amplitude is small, it will lead to the first One kind of circuit state time is too long, at this time the inductance is approximately connected between the two-phase power supply on the AC side, the current growth rate is faster, causing a large inrush current to affect the life and safety of the system

[0003] Commonly used starting surge current suppression methods are: clipping method, such as publication number: CN104734481A; target voltage value parabolic law starting method, such as publication number: CN103904873A; vector soft start method, such as publication number: CN107196496A, and parabolic Superimposed ramp function startup method, such as the publication number: CN105915039A, according to the formula , the common point of these methods is to reduce the output value of the voltage outer loop PI regulator, that is, the reference value of the current inner loop d-axis i d * , when the actual current increases more than the reference value i d * hour, m d will increase, thereby reducing the charging time of the grid-side inductance and reducing the inrush current, but the common point of these methods is that the current of the actual system is greater than the rated current, that is, the suppression effect will not be produced until the inrush current is generated. Unable to suppress the inrush current caused by too small modulation ratio at the beginning of start-up

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