This paper proposes a novel bridge-type solid-state fault current limiter (BSSFCL) based on one series reactor which operates in ac and dc modes. The proposed BSSFCL includes a rectifier bridge with a reactor. This reactor is used as a dc reactor in normal operation mode and as an ac reactor in fault conditions. The advantages of the proposed BSSFCL over the existing dc reactor-type FCLs are its negligible impedance in normal operation mode and its high impedance during a fault interval using simple and novel switching. In other words, during the normal operation mode, the proposed BSSFCL operates in dc mode and in the fault interval, its topology is changed to the ac mode. This switching decreases the switching transient recovery voltage and introduces considerable impedance during the fault period. MATLAB/Simulink software is used for simulations and a prototype is designed and tested for results verification, and to show the performance of the proposed BSSFCL.

Selective harmonic elimination pulse width modulation (SHEPWM) is a well-known switching technique applied directly to the output voltage waveform of multilevel inverters which aims to omit low-order harmonics. Related equations for this technique are transcendental, so an objective function should be defined in order to cover all constraints. Evolutionary computation is demonstrated to be a promising tool meeting requirements of such problems. In this paper, the standard colonial competitive algorithm (CCA) is improved to be employed for the mentioned technique in two cases of equal and unequal dc sources. The results are compared with two other successful algorithms namely genetic algorithm (GA) and particle swarm optimization (PSO). Results indicate that this method outperforms other methods in terms of convergence rate and tackling local optima. Experimental results verify the simulation results.

In this paper, a new approach for photovoltaic (PV) arrays modeling and maximum power point estimation (MPPE) in real operating conditions is presented. The PV array polynomial model is developed from its single-diode equivalent circuit, and the parameters of the proposed model are estimated by measuring the voltage and current of three points around the maximum power point (MPP). The maximum power point voltage (MPPV) is then calculated from the proposed model, and the PV array voltage is fixed at MPPV. Therefore, unlike the maximum power point tracking (MPPT) algorithms, there is no oscillation around the MPP. Using the PV array polynomial model with only three measurements around the operating point, results in less calculation burden, increases the estimation speed and decreases the I-V curve estimation process loss. In order to validate the proposed MPPE algorithm, we have compared it with the most commonly used perturb and observe (P&O) MPPT algorithm, a zero oscillation adaptive P&O technique, and a fast MPPT method by simulation and experimental results.

In this paper, a novel solid-state fault current-limiting circuit breaker (SSFCLCB) based on a series resonance LC tank is proposed. Since the series configuration of the resonance structure (a capacitor and a reactor) of the SSFCLCB is invisible during normal operation mode, it shows negligible impedance in the line. In fault conditions, the SSFCLCB topology changes to a rectifier bridge and feeds the resonance structure with rectified ac voltage. With the rectified voltage, the series capacitor is charged and, as a result, the faulty line is opened and the fault current is seized. Hence, the suggested SSFCLCB cannot only limit the fault current but can also open the faulty line and acts as a circuit breaker. For confirmation of these aspects, simulations are performed using MATLAB software. Also, a prototype structure is designed and built for results confirmation. This experimental setup is established to prove that SSFCLCB has excellent performance in its startup, normal operation, and current-limiting/breaking conditions. The results show that the SSFCLCB has the ability to improve distribution network reliability and it can decrease the network fault current level successfully.