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Satisfying fault ride-through requirements, solar photovoltaic (PV) plant remains connected to the grid even during a fault. With current limiting feature, the plant current during a fault becomes comparable to its rated current. This imposes challenges to conventional local data-based protection methods employed in the relay on PV-side. In such a situation, the selectivity of a protection scheme is crucial for maintaining an uninterrupted supply to customers. In this article, a q-axis component-based protection scheme is proposed for the distribution system with a PV plant. The method extracts the second-order harmonic components of q-axis voltage and current at relaying point for fault detection and direction identification. Using this direction information at both ends of a line segment to be protected, internal and external faults are discriminated. The performance of the proposed method is tested on 14-bus distribution system for various fault cases. A comparative analysis with existing techniques shows the strength of the proposed method. Hardware-in-loop testing using OPAL-RT simulator as system and Arduino NANO microcontroller as relay validates the performance of the proposed method in real-time. [ABSTRACT FROM AUTHOR]

For fault ride-through requirement, solar photovoltaic (PV) plant remains connected to the grid during a fault. In such a situation, a PV plant operates in different modes and supplies current to comply with the requirements of the grid. The relative magnitude of phase current contributed by a PV plant during a fault is at par with the nominal current. Such a fault behavior restricts the application of available phase current based relaying approaches while protecting the distribution system with a PV plant. A protection method using local positive sequence voltage and current is proposed to protect a distribution system with PV plant. The method selects pickup current using proposed current-voltage curve for fault detection. A three-dimensional time-current-voltage characteristic is proposed for trip time calculation. Performance of the proposed method is tested for relays on both PV plant side and grid end using DigSilent PowerFactory simulation data for a CIGRE 14-bus distribution system with PV plant having different modes of operations. The method is found to be accurate and comparative assessment reveals its superiority. [ABSTRACT FROM AUTHOR]

Distribution lines are generally protected by overcurrent relays. With the integration of an inverter-interfaced solar photovoltaic (PV) plant having a current-limiting feature, the fault current seen by the relay on the PV side of that feeder becomes comparable to the load current. The conventional overcurrent relaying principle is not suitable for distribution line protection. Distance relay may be a viable option for protection of distribution lines connecting the solar PV plant. However, positive- and negative-sequence source impedances of the PV plant depend on an inverter controller, which results in limited performance of fixed setting distance relay. This article proposes an adaptive distance relay setting to protect distribution line connecting the PV plant, using prefault voltage and current data at the relaying point. The method calculates positive- and negative-sequence PV source impedances for boundary setting of distance relay at the PV side. The proposed trip boundary is modified adaptively with the change in prefault conditions of the PV plant. Performance of the proposed method is tested for different control strategies and operating capacities of the PV plant and variation in the grid source impedance on a 34-bus distribution system. Real-time application of the proposed method is validated in hardware-in-the-loop using OPAL-RT simulators with IEC 61850 as the communication protocol and found to be accurate. [ABSTRACT FROM AUTHOR]

As grid codes evolve, inverter-interfaced renewable generation may be required to take greater responsibility for grid support. It may be obliged to source a large current during a short-circuit fault in the grid and provide large dynamic reactive power, beyond the inverter rating, for voltage recovery after the fault clearance. In this sense, the inverter-interfaced generating system would behave more similarly to a conventional synchronous machine. This is not yet mandatory but current technology cannot readily support it if required in the future, because the power semiconductors would overheat unless they are drastically derated. This study proposes a method to increase the power semiconductor's transient thermal capacity, and hence its short-term over-current capability, by integrating a phase-change material inside the power semiconductor module. Experiment and thermodynamic simulation across different materials are used to illustrate the feasibility of the concept and the factors that should be considered in such a design. The study shows that 1.5 p.u. (per unit) overcurrent could be achieved for 30 s, which is typical of synchronous generators; and 3.0 p.u. fault current could be achieved for 3 s. A custom-made 1200-V, 50-A IGBT half-bridge module integrating a liquid metal as the phase change material is compared with a conventional commercially available module. A validated simulation model is then used to further evaluate the proposal, regarding a 1700-V, 1000-A IGBT module for use in a wind turbine. [ABSTRACT FROM AUTHOR]