The key obstacle in integrating high-voltage direct current (HVDC) point-to-point networks into meshed multiterminal HVDC networks (MTDC) is the absence of dc circuit breakers (DCCBs), which can timely and reliably isolate the faulty HVDC network from the MTDC. In this paper, a novel hybrid-type superconducting DCCB model (SDCCB) is proposed. The SDCCB has a superconducting fault current limiter (SFCL) located in the main line, to limit the fault current until the final trip signal to the SDCCB is given. After the trip signal, insulated-gate bipolar transistor (IGBT) switches located in the main line will commutate the fault current into a parallel line, where dc current is forced to zero by combination of IGBTs and surge arresters. DC fault current behavior in MTDC and fundamental requirements of DCCB for MTDC were described, followed by an explanation of the working principles of the SDCCB. To prove the viability of the SDCCB, a simulation analysis demonstrating SDCCB current interruption performance was done for changing the intensity of dc fault current. It was observed that the passive current limiting by SFCL caused significant reduction in fault current interruption stress for SDCCB. Furthermore, fundamental design requirements for SFCL, including the effect of SFCL quenching impedance on SFCL voltage rating and energy dissipation capacity, were investigated. Finally, advantages and limitations of the SDCCB were highlighted.
The use of solar energy to produce electricity through photovoltaic (PV) systems has significantly increased in the past decade due to (a) reduction in solar panel costs, (b) climate concerns, and (c) advances in power electronics for grid-tied applications. In conventional rooftop PV deployments, solar panels are connected in series with bypass diode(s) across each panel to reduce the effect of shading. Shading results in hot-spots which affect both short-term (power output reduction) and long-term performance (reliability) of a PV system. This paper presents a new technique to reduce hot-spots in shaded cells along with minimizing power dissipation in an overall PV system. The proposed topology is evaluated and compared with various existing topologies with the proposed technique showing superior performance in reducing hot-spots (by 17%) along with lower losses under shading conditions.
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