This document presents a summary of previous research on electronic load controllers (ELCs) for synchronous generators. It discusses 16 previous studies that developed and analyzed ELC models and designs. The studies aimed to develop ELCs that can smoothly control voltage and frequency for small hydroelectric systems serving remote areas. Various ELC designs are summarized, including those using thyristors, IGBTs, PWM control, and rectifier and chopper circuits. The goals, methods, and results of each study are briefly described.