A three-phase four-wire parallel apf double closed-loop nonlinear composite control method

Abstract

The invention provides a double-close-loop nonlinear compound control method for a three-phase four-wire parallel APF (active power filter). A voltage outer loop adopts a sliding-mode PI composite nonlinear control algorithm, and a current inner loop adopts a repeated PI nonlinear control algorithm. The method comprises the steps as follows: firstly, a low-order system model of a dq coordinate system is established by synchronous rotation coordinate transformation, a PI feedforward decoupling controller is designed according to a dq DC model, a PI repetitive controller is designed based on internal model control, and a control output function of the PI repetitive controller of the current inner loop is established; in order to obtain a current reference value of the current inner loop accurately and quickly, a novel sliding-mode PI nonlinear control algorithm for DC side voltage is proposed, a sliding-mode surface switching function is designed according to an exponential reaching law form, and a control function of a sliding-mode PI controller of the voltage outer loop is established. With adoption of the outer loop sliding-mode PI compound control algorithm, the steady-state performance and the response speed of the DC side voltage can be improved, and voltage fluctuation is effectively reduced; with adoption of the repetitive PI nonlinear control algorithm, zero static error tracking of a current signal can be realized, and the tracking control accuracy of a harmonic compensation current instruction is improved.

Description

technical field [0001] The invention belongs to the field of active filter control, in particular to a three-phase four-wire parallel APF double-closed-loop nonlinear composite control method. Background technique [0002] Parallel active power filter (Active Power Filter, APF) is an effective means to solve the harmonic pollution of the power grid. It can realize accurate, real-time and effective compensation for the harmonics, negative sequence current and reactive power existing in the power grid system. The output compensation characteristics of the active filter mainly depend on the control method of the current and voltage, and the main circuit topology of the converter device used. The earliest control strategy applied to the active power filter is that the current loop adopts single PI control, and the DC side voltage is added with an independent power supply device. At present, the research on the topology of active filters is relatively mature, and now basically n...

AI Technical Summary

Problems solved by technology

The traditional PI control algorithm can achieve good tracking control when the reference signal is DC, but it cannot achieve static error-free tracking for the harmonic command signal that changes from time to time

Hysteresis control is a transient feedback control system. Although it has the advantages of high precision and fast response, it can obtain better tracking performance, but its switching frequency fluctuates greatly, and the output filter design is difficult.

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