Design optimization and electromagnetic performance investigation of a magnetically integrated transformer-type...

The increasing penetration of renewable energy sources and nonlinear loads has intensified the need for continuously controllable and low-distortion reactive-power compensation. This study presents the design optimization and electromagnetic performance evaluation of a magnetically integrated transformer-type controllable reactor (MI-TCR), which combines voltage transformation and inductive reactive-power regulation within a single five-limb electromagnetic structure. The three central limbs perform the transformer function, whereas the two outer limbs employ DC-bias-controlled saturation to regulate the effective AC inductance. A coupled electromagnetic, thermal, and vibro-acoustic finite-element framework was used to evaluate the core geometry, winding configuration, distributed air gaps, magnetic coupling, losses, temperature, harmonic distortion, and acoustic response. The optimization problem was formulated using three objectives: minimization of total loss, maximization of the controllable reactive-power span, and minimization of A-weighted sound level. The selected 10 kVA design achieved a simulated inductive reactive-power absorption range of 0.8-9.6 kVAr and an experimentally measured range of 0.9-9.2 kVAr. The simulated and measured settling times were 72 and 78 ms, respectively, while the corresponding current total harmonic distortion values were 2.3% and 2.5%. Simulated and measured core losses were 285 and 298 W, and the corresponding core hot-spot temperatures were 118.4 and 121.7 °C. Across six linear-scale validation metrics, the mean absolute percentage error was 6.84%; the simulation-experiment sound-level difference was reported separately as 1.9 dB. Relative to the matched conventional MCR-plus-coupling-transformer baseline, the proposed design reduced simulated core loss by 18.6%, current THD by 52.1%, response time by 40.0%, and combined magnetic-core volume by 35.4%. The results demonstrate the feasibility of integrating voltage transformation and continuously controllable inductive reactive-power absorption in a compact electromagnetic device while avoiding unsupported claims concerning bidirectional compensation or network-level grid resilience.