In large power grids where converter penetration is presently low and the network impedance is predominantly reactive, the required response from converters during faults is presently specified by phrases such as “maximum reactive output”. However, in marine and aero power systems most faults are unbalanced, the network impedance is resistive, and converter penetration may be high. Therefore a balanced reactive fault current response to an unbalanced fault may lead to over-voltages or over/under frequency events. Instead, this paper presents a method of controlling the converter as a balanced voltage source behind a reactance, thereby emulating the fault response of a synchronous generator (SG) as closely as possible. In this mode there is a risk of converter destruction due to overcurrent. A new way of preventing destruction but still providing fault performance as close to a SG as possible is presented. Demonstrations are presented of simulations and laboratory testing at the 10kVA 400V scale, with balanced and unbalanced faults. Currents can be limited to about 1.5pu while still providing appropriate unbalanced fault response within a resistive network
This section of the journal provides a detailed history of the modern whaling industry, between 1904 and 1963. New techniques, new equipment, and new ships led to the complete overhaul of the traditional industry. The rapid expansion of the trade is linked to the shift in oil technology, and the repurposing of oil for soap and margarine. The section explores, in depth, new whaling techniques; new whaling areas; advances in oil technology; expanding fleets and new fishing grounds; crisis and contraction of the industry; and the sharp decline in the final years of the industry in the wake of the Second World War.
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