Three-ring control method of three-phase PWM (Pulse-Width Modulation) rectifier for LCL (Lower Control Limit) filtering

Abstract

The invention relates to a three-ring control method of a three-phase PWM (Pulse-Width Modulation) rectifier for LCL (Lower Control Limit) filtering and belongs to the field of rectifier control. The three-ring control method is characterized in that an output voltage of a rectifier, a grid-side inductive current, an inductive current at the side of a rectifier bridge are respectively sampled by using a group of voltage detection transmitters and two groups of current detection transmitters so as to control an output direct-current voltage and a grid-side power factor of the three-phase PWM rectifier. The control method provided by the invention has the outstanding advantages that the output direct-current voltage of the three-phase PWM rectifier is controlled with high precision and good stability; the grid-side power factor is high; the capability of resisting voltage distortion interference of a power grid is strong; and a bridge arm switching tube is convenient to protect, the control method has high reliability and the like. Therefore, the control method provided by the invention is very suitable for controlling the three-phase PWM rectifier for the LCL filtering.

Description

technical field [0001] The invention relates to a three-loop control method for an LCL-filtered three-phase PWM rectifier, which is used for realizing the stable control of the LCL-filtered three-phase PWM rectifier, so as to stabilize the output DC voltage of the rectifier and improve the power factor of the grid side. technical background [0002] Since the power grid is connected to the three-phase PWM rectifier through a series LCL filter, it is more conducive to the rectifier to obtain high-quality grid current at a lower switching frequency, improve the input power factor of the grid side, and ensure the stability of the output DC voltage of the rectifier. Therefore, the three-phase PWM rectifier with LCL filter, as the key equipment of static var compensation, power factor correction, active power filter, solar energy, wind energy and other new energy grid-connected power generation systems, has received extensive attention in recent years. However, the introduction o...

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Problems solved by technology

When the current inner loop of the three-phase PWM rectification system adopts the direct single closed-loop control of the typical grid input current, the system is not easy to be stable; the control method of series-parallel damping at the inductor or capacitor end can avoid system instability, but it causes power loss; When the current inner loop adopts the control bridge arm current, or realizes the indirect control method of the grid current by controlling other current variables, the stability of the closed-loop system is improved, but the indirect current control is difficult to achieve the unit power factor operation of the grid input current. And it is easily affected by grid voltage distortion and background harmonic interference

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