Robust control method for LCL‐type shunt active power filter under weak grid condition

Abstract

This study presents an improved double closed-loop current (fundamental and harmonics current) control method for inductive-capacitive-inductive (LCL) type shunt active power filter (SAPF), which is designed to enhance the robustness of the SAPF system to adapt weak grid application condition. Due to the variation of weak grid impedance, fundamental current control loop based on grid current feedback control method may become unstable, a robust parameters design method in discrete zdomain according to amplitude-frequency and phase-frequency characteristics is proposed to fit the grid impedance variation. The harmonics current of non-linear load exists in a wide frequency range, normal resonant controller will cause the system unstable due to the negative −180° cross of phase at high-frequency range, a digital phase-lead resonant controller (PL-RC) is proposed to extend the bandwidth of the harmonics current control, then the quantities of the PL-RCs used to suppress harmonics can be increased considerably compared with normal resonant controller. Experimental results are presented to verify the effectiveness of the robust parameters design method and the proposed PL-RC.

Harmonic impedance optimization scheme for multi‐resonance systems to suppress resonance

“…Terminal control requires the installation of harmonic compensation equipment near non-linear loads to reduce or eliminate harmonics flowing into the grid. Harmonic compensation devices include passive power filters (PPFs), active power filters (APFs) and hybrid active power filters [16][17][18][19]. However, PPFs cause new resonances at other frequency points; APF applications are also hindered by the complex control [20,21].…”

High voltage low quiescent current LDO with self-regulation impedance buffer

“…PCA (programmable capacitor array) is also suffered from more die size and high cost [10]. Reference [11] employed the structure called super-source-follower that can decrease the buffer output impedance greatly without much tail current [12], but the problem is the negative feedback loop cannot be stable in all cases, especially when driving a capacitive load [13]. FVF (flipped voltage follower) is also a good way to enhance the transient response but more transistors and current will be consumed [14].…”

A comparative analysis of PI & FLC based grid connected PV system with power backup to improve power quality

“…This type of proposed apology also shows the reactive power compensation and harmonic mitigation at PCC by using even mentioned controllers and this controller also ensures that grid current is purely sinusoidal. To mitigate this type of power quality issue several authors use the filters circuit at PCC [13,14]. In the proposed work inverter controller itself mitigate the power quality issue at PCC and also maintain power flow control.…”