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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]

Communication-assisted distance protection schemes are widely used for three-terminal line protection and are susceptible to power swings. The available differential protection scheme is also considered to be suited to protect three-terminal lines and is free from problems associated with the power swing. However, the performance of the current differential protection scheme may be affected if an outfeed condition occurs during an internal fault. This paper presents a new technique for protecting three-terminal transmission lines immune to power swing. The technique uses synchronized voltage and current measurements from three terminals for calculating voltage at the tee-point. The maximum magnitude of the superimposed component of positive-sequence voltage estimated at the tee-point is compared with the maximum magnitude of superimposed componentas of the positive-sequence voltage measured at three terminals of the line to discriminate a fault from power swing. The method is accurate even for an outfeed condition during the internal fault, current-transformer saturation during severe internal or external faults, large load rejection, and different prefault loading conditions occur during the power swing. The proposed algorithm is verified using data simulated through EMTDC/PSCAD for a 400-kV double-circuit three-terminal system. [ABSTRACT FROM AUTHOR]

A distance relaying scheme is susceptible to power swing. To avoid unintended trip operation during such conditions, a power swing blocking function is utilized in distance relays. However, if a fault occurs during power swing, the relay should detect the fault and trip as soon as possible. The detection of fault in a series-compensated line during the power swing is further complicated due to complex transients produced by series capacitor and the metal–oxide varistor (MOV) protecting it. This paper proposes a negative-sequence current-based technique for detecting all types of faults during the power swing in a series-compensated line. The technique is tested for different series-compensated systems including a 9-bus 3-machine power system. Different types of faults: symmetrical, asymmetrical, and high resistance occurring during the power swing are simulated through EMTDC/PSCAD to test the algorithm. The method is compared with available techniques and found to be accurate and fast. [ABSTRACT FROM PUBLISHER]