Experimental study on excitation phenomena of renewable energy source driven induction generator for isolated rural community loads

Abstract

Induction machines (IMs) are one of the most popular electric machines due to their many advantages. It is well known that the IM can be utilized as a motor and generator at below and above synchronous speeds, respectively. However, an induction generator (IG) in the off-grid mode is not a self-started generator. A proper rating of the reactive power supply to the core of the generator and maintaining the rotor speed above the synchronous speed are key challenges in the off-grid mode for exciting the IG to generate the voltage and frequency at desired values. The voltage and frequency are dependent on the amount of reactive power supplied to the stator of the generator and the rotor speed. Since these two factors play a significant role, a key finding is presented in this paper by conducting various experiments on a three-phase IM and investigate the allowable upper and lower limits to avoid over and under-excitation issues during the self-excitation process. Additionally, different methods for the calculation of the required reactive power have been studied in this paper to identify the best method. The proposed study is advantageous for making effective use of IM as an IG for isolated rural applications.

Keywords

• Induction generator (IG)
• Reactive power (VAR/Var)
• Excitation capacitance
• Synchronous speed
• Self excited induction generator (SEIG)