Three-level three-phase four-wire SAPF nonlinear control method based on Lyapunov

Abstract

The invention relates to a three-level three-phase four-wire SAPF nonlinear control method based on Lyapunov, and the method comprises the following steps: S1, building a general mathematical model ofa three-level NPC-type three-phase four-wire SAPF in a three-phase static abc coordinate system; S2, converting the obtained general mathematical model of the SAPF in the three-phase static abc coordinate system into a general mathematical model in a dq0 coordinate system; S3, obtaining a mathematical model and a switching function in the dq0 coordinate system in steady state; S4, designing a positive definite energy function and a switching function of an NPC-type three-level SAPF system of an inner current loop according to the mathematical model in the dq0 coordinate system in steady statethrough combining with the Lyapunov theory; S5, obtaining an optimal control gain, and controlling the on and off of a switch on each bridge arm of the SAPF according to the switching function of theNPC-type three-level SAPF system; S6, introducing a regulatory factor, and stabilizing the balance of a DC side voltage of the SAPF. Compared with the prior art, the method is advantageous in that the method improves the dynamic-static characteristics of the system and maintains the balance of the DC side voltage.

Description

technical field [0001] The invention relates to the field of micro-grid technology, in particular to a Lyapunov-based three-level three-phase four-wire SAPF nonlinear control method. Background technique [0002] In recent years, with the widespread use of rectification and frequency conversion devices and the rapid increase of semiconductor nonlinear loads, power systems are facing more and more serious harmonic pollution problems. Using shunt active power filter (Shunt Active PowerFilter, SAPF) to dynamically compensate the harmonics of the power grid in real time has become one of the most effective and promising ways. [0003] Compared with the traditional two-level SAPF, the three-level SAPF has many advantages, such as lower switching frequency and loss, high system withstand voltage, and application in higher voltage systems. The topology of three-level SAPF mainly includes Neutral-Point Clamped (NPC) type, flying capacitor type and cascaded H-bridge type. Among them...

AI Technical Summary

Problems solved by technology

The three-phase four-wire system adds the processing of zero-sequence components, which can not only compensate the harmonics and reactive power of the three-phase balanced system, but also compensate the zero-sequence harmonic components generated by nonlinear loads when the power grid is unbalanced. However, at present, most of the research at home and abroad is based on the three-phase three-wire system and the single-phase half-bridge system, while the research on the three-phase four-wire system is relatively limited.

The existing technology proposes to use the state feedback accurate linearization method to establish its linearization model, which can realize the decoupling control of the SAPF three-phase, but this method needs to establish an accurate system model; the existing research proposes a sliding mode control method, the control strategy Although it can achieve a good compensation effect, it has the problem of high-frequency jitter; adaptive sliding mode control based on passive theory is also a solution that has been proposed so far. Tracking control, but only under balanced load

In addition, the existing technology introduces the nonlinear control method based on the Lyapunov function into the SAPF, which can realize real-time control when the load changes, but the control object is a low-power single-phase SAPF

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