Design, Modeling, and Performance Analysis of an Enhanced Doubly Fed Reluctance Generator (DFRG) for Efficient and Reliable Renewable Energy Systems

Abstract

This study investigates the performance and control strategies of an Enhanced Doubly Fed Reluctance Generator (DFRG) system, with the aim of improving torque generation, efficiency, and voltage stability in renewable energy applications. The motivation stems from limitations in traditional generators such as the Permanent Magnet Synchronous Generator (PMSG) and Doubly Fed Induction Generator (DFIG), including higher costs, reduced reliability under transient loads, and limited efficiency across operating ranges. The study addresses these challenges by employing analytical modeling and simulation to analyze the magnetic and dynamic behavior of the DFRG system. A comprehensive methodology was implemented using MATLAB/Simulink to simulate and evaluate the inductance variation, torque production mechanisms, stator voltage dynamics, vector and direct torque control strategies, and battery 
state-of-charge under hybrid scenarios. The study also conducted a comparative assessment of efficiency, power quality (THD), cost, reliability, and voltage regulation under diverse load conditions. Quantitatively, the DFRG system demonstrated a smooth inductance variation between 0.05 H and 0.15 H, producing torque peaks up to ±884 Nm with stator current at 420 A. Under vector control, torque reached 45 Nm, while DTC yielded 38 Nm, showing robust response. Voltage peaks were observed near 220 V, with flux linkage around 63 Wb. Efficiency under rated load was 92%, and up to 97% under high-speed, full-load conditions, surpassing the PMSG’s 96% peak. In fault conditions, efficiency dropped to 0%, indicating critical reliability issues in abnormal operations. The DFRG also maintained a THD of 2.1% under rated load, rising to 28.7% during faults. Voltage regulation was within 4.17%, confirming voltage stability. The hybrid system simulation showed effective energy cycling with a battery SOC increase from 50% to nearly 100%, and a discharge down to 10% within a 24-hour period. Cost and reliability analysis revealed DFRG as the most cost-effective ($800/kW) and reliable (0.98) compared to DFIG ($950/kW, 0.95) and PMSG ($1100/kW, 0.97). The findings support policy implications favoring the deployment of DFRG systems in renewable integration strategies where cost, efficiency, and reliability are prioritized. Recommendations include the incorporation of fault mitigationstrategies and filtering technologies to maintain power quality and continuity in hybrid and variable-speed operations