A Full Bridge converter with Pin-10kW running at 10kHz should be reduced in size
ID: 2290919 • Letter: A
Question
A Full Bridge converter with Pin-10kW running at 10kHz should be reduced in size by increasing the switching frequency to 100kHz. Assume the input voltage to be 400V and duty cycle 90% (out of 50%). The transformer and rectifier losses are assumed to be constant in the frequency range of interest and totally equals 250W. Assume Rdson-50m2 and idealized switching witlh ton-40ns and toff-50ns and neglect gate drive power consumption. Calculate how much the efficiency would be reduced at 100kHz assuming hard switched conditions.Explanation / Answer
A long distance point to point HVDC transmission scheme generally has lower overall investment cost and lower losses than an equivalent AC transmission scheme. HVDC conversion equipment at the terminal stations is costly, but the total DC transmission line costs over long distances are lower than AC line of the same distance. HVDC requires less conductor per unit distance than an AC line, as there is no need to support three phases and there is no skin effect.
Depending on voltage level and construction details, HVDC transmission losses are quoted as about 3.5% per 1,000 km, which are 30 – 40% less than with AC lines, at the same voltage levels.[23] This is because direct current transfers only active power and thus causes lower losses than alternating current, which transfers both active and reactive power.
HVDC transmission may also be selected for other technical benefits. HVDC can transfer power between separate AC networks. HVDC powerflow between separate AC systems can be automatically controlled to support either network during transient conditions, but without the risk that a major power system collapse in one network will lead to a collapse in the second. HVDC improves on system controllability, with at least one HVDC link embedded in an AC grid—in the deregulated environment, the controllability feature is particularly useful where control of energy trading is needed.
The combined economic and technical benefits of HVDC transmission can make it a suitable choice for connecting electricity sources that are located far away from the main users.
Specific applications where HVDC transmission technology provides benefits include:
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