Narrow Results

Ferroresonance overvoltage and over-current can be restrained using nonlinear dynamics. However, the ferroresonance simplified model, which cannot reflect the huge ferroresonance circuit in the grid precisely and cannot satisfy real-time analysis, is adopted in the traditional nonlinear control method. Owing to these shortcomings, the strategy of controlling ferroresonance overvoltage based on voltage time series is proposed. Based on the voltage time series analysis methods, the ferroresonance system is identified using the best embedding dimension and the best time delay obtained from the phase space reconstruction. Afterward, the feedback controller is designed based on the platform of the identified model. Results show that fundamental, subharmonic and chaotic ferroresonance overvoltage can all be controlled using the method presented in this paper even without the system parameters and the accurate system model. Therefore, the control strategy is generally more applicable.

A novel method for fundamental ferroresonance suppression is proposed in this paper. The suppression mechanism is analyzed based on the harmonic balance method and a novel method for fundamental ferroresonance suppression is proposed. Experiments show that the fundamental ferroresonance with different saturation degrees can be suppressed by a single damping resistor controlled by the high frequency controllable switches located in the suppression module.

Ferroresonance is one of the most harmful and longest known power quality disturbances in the history of AC power systems. The ability of predicting transient and steady-state ferroresonance simulations mainly depends on the accuracy of the power transformer model. Most existing voltage transformer models apply single-valued nonlinear functions to represent the core nonlinearities. This study, based on our previous work, proposes a newly improved and accurate transformer iron core hysteresis model for ferroresonance simulation by extension of the classical arctangent model. To verify the proposed model’s accuracy and superiority, three different ferroresonant voltage and current waveform simulations were performed using both the proposed model and renowned EMTP Type-96 model under the same system parameters. In addition, simulation results were compared with the corresponding experimental measurements. The results indicate that the proposed model is easily implemented using numerical modeling method with good stability and convergence, and is sufficiently accurate for both transient and steady-state periodic ferroresonance analysis.

In this study, a chaos-theoretic method is proposed to model the case of ferroresonance that can occur under nominal conditions in power systems, and the factors that determine the types of ferroresonance to occur are examined. In the ferroresonance chaotic system modeled in Matlab environment, the length of the transmission line and the breaker capacities in the circuit are fixed and its relationship with the transformer efficiency is investigated. In the proposed chaotic modeling, considering the situations that may occur in practical applications, the ferroresonance situations that occur when the single-phase remains open in the three-phase system are examined. In the study, ferroresonance, which occurs when one phase is open in a three-phase system, is analyzed by considering the situations that may happen during practical implementations. The similarity between the mathematical expressions obtained from the systems that create ferroresonance and Duffing oscillator is evaluated. In the chaotic system, fundamental ferroresonance, subharmonic ferroresonance, and chaotic ferroresonance situations are created depending on the transformer loss. Additionally, ferroresonance that occurs when the chaotic system is of fractional-order is analyzed, and it is observed that results of ferroresonance with different fractional-order values are not different. The results show that transformer loss is a significant element to determine the type of ferroresonance in power transformers. Also, when the chaotic system is operated in the fractional-order setting, the ferroresonance cases that occur are re-examined, and it is observed that the system can exit from the chaotic situation and prevent the formation of ferroresonance when fractional-order control is applied. According to the results, the fractional-order method can be used to control ferroresonance.