A harmonic elimination optimised pulse-width modulation (PWM) scheme is an attractive alternative to both natural and regular sampled PWM schemes for voltage source inverter drives used in railway traction. However, i...
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A harmonic elimination optimised pulse-width modulation (PWM) scheme is an attractive alternative to both natural and regular sampled PWM schemes for voltage source inverter drives used in railway traction. However, its application has been limited by the fact that the exact switching angles cannot be calculated online by a microprocessorbased waveform generator. The paper describes an algorithm for calculating the near optimal switching angles, which will permit a fast and efficient realisation in a microprocessor based controller. With this type of PWM scheme, it is possible to show analytically that components at the signalling frequencies are not generated in the DC supply input current, for existing power frequency track circuits. The switching angles calculated with the algorithm agree closely with the exact solutions over most of the range of the fundamental output.
The authors describe the constructional features of a controller for operating an autonomous refrigeration unit powered by a field of photovoltaic panels and backed up by a generator set. The controller enables three ...
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The authors describe the constructional features of a controller for operating an autonomous refrigeration unit powered by a field of photovoltaic panels and backed up by a generator set. The controller enables three voltage levels of operation of an inverter to meet the start, run and off cycle conditions of the refrigerator compressor. The algorithm considers several input and output parameters and status signals from each subsystem of the unit to deduce a control strategy. Such units find application for storage of vaccines and life-saving medicines requiring uninterrupted refrigeration, in medical shops, rural health centres, veterinary laboratories etc.
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