Quantitative Evaluation of DER Smart Inverters for the Mitigation of FIDVR in Distribution Systems

This paper exploits smart inverters of distributed energy resources (DERs) for the mitigation of fault-induced delayed voltage recovery (FIDVR). According to the IEEE Standard 1547-2018, smart inverters with voltage ride-through and var injection capabilities are promising technologies for mitigating FIDVR. This paper quantitatively investigates the effectiveness of smart inverters for FIDVR from a system-wide perspective. It shows that the penetration of smart inverters and induction motors are important factors affecting mitigation success. In addition, the over-voltages at the end of FIDVR due to load disconnections can be prevented with coordinated control of DERs and automated switching capacitors. The control scheme of smart inverters used for FIDVR is extended from the distributed volt/var droop control to include low- and high-voltage ride-through capabilities. The IEEE 13-bus feeder, the 8500-node test feeder, and the IEEE 390-node low-voltage network test system are used to illustrate the impact of DER penetration. For example, one can determine the residential air conditioner penetration level (for a given system at certain DER penetration level) that makes a system susceptible to FIDVR. The effects of solar intermittency are also studied.

I. Introduction

Fault Induced Delayed Voltage Recovery (FIDVR) happens frequently in weak electric systems during peak loading conditions (for example, in the summer). The reason is that induction motors of Residential Air Conditioners (RACs) stall at the low voltage caused by a fault, and they are progressively disconnected by their thermal protections in times between 3 and 22 s. This constrains the system voltage to recover slowly [1]. The consequences of FIDVR include loss of load or, in extreme circumstances, a large-scale blackout caused by a chain reaction [2]. FIDVR is essentially due to insufficient reactive power supply to the stalled RACs. Currently, there are two methods to soften FIDVR impacts: the installation of Static Var Compensators (SVCs) and load shedding. References [3] and [4] report the use of SVCs in Metro Atlanta and Massachusetts. Both show that FIDVR is improved to some degree by installing SVCs at the substations, but these projects are capital intensive [2]. The specifications of SVCs are based on an aggregated load model [5]. Although load shedding is another technique to mitigate FIDVR [6], it should be used only as the last resort in case of emergency.