A Novel Control for Enhancing Voltage Regulation of Electric Springs in Low-Voltage Distribution Networks

Abstract

Electric springs (ES) have been reported as a distributed means to address the voltage instability issues at the point of common coupling (PCC) in low-voltage distribution networks (LVDN). In the reported research works on the control methods of the ES, it is generally assumed that the grid networks are predominately inductive. This assumption is fundamentally flawed as the line impedances are significantly resistive in LVDN, which leads to deteriorated voltage regulation effects. To address this, a novel <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\boldsymbol{\gamma }}$</tex-math></inline-formula> control method is proposed to enhance the voltage regulation performances of the ES in LVDN. A comprehensive steady-state model of the ES-based smart load considering different Thevenin's equivalent line impedances is developed in this article. Equivalent regulation points and optimal operating regions of this smart load are derived analytically. The proposed control embeds a smart load model and enables adaptive control boundaries of the ES, which can avoid the suboptimal or positive-feedback operations in the PCC voltage regulation. Besides, a hysteresis proportional integral (PI) controller is designed to mitigate the voltage flickers. Experimental and simulation results have been provided to verify the effectiveness of the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\boldsymbol{\gamma }}$</tex-math></inline-formula> control.