Abstract
The synchronizing units adaptive to instability of the mains voltage amplitude for the network forced power semiconductor converters are considered. In order to reduce switching and pulse interference in the synchronizing unit with tracing fixation of selfswitching points the first-order aperiodic filters are used, regulated to the shift of input sinusoidal voltage to the angle of minus 30 or 60 electrical degrees that is determined by the level of interference from mains voltage. As a result the auxiliary three-phase voltage system is created which is processed further with the help of comparators and binary-decimal decoders. From the gained series of numbers the needed ones are chosen and combined by the function “OR”. The logic signal is gained as a result, the width of which corresponds to the required synchronization interval of the semiconductor converter. In the second case the synchronization signal affects the self-oscillating integrating sweep converters transferring them to the forced switching mode with the mains voltage frequency. Together with this each of the synchronization channels gets the properties of the first-order aperiodic filters with time constant determined by the value of the amplitude and frequency of mains voltage. The closed-circuited structure of the sweep converters and the presence of the integrator in the direct control channel contribute to the high level of metrological characteristics of such synchronizing units. The waveform diagram of the synchronizing units and the recommendations concerning the choice of the parameters of their elements are given.
Highlights
Modern power systems both stationary and autonomic-based are characterized by the high level of interference with difficultly predicted parameters, often exceeding the allowable norms of interference and serving as destabilizing factors in the work of semiconductor converters (SC) but process installations in whole [1,2,3]
The drawback of the synchronizing units (SU) of F–relay element (RE) type is obvious – when the amplitude and/or the frequency of mains voltage is changed the specified synchronization angle is significantly changed [6,7], which affects the characteristics of the SC on the whole and in some cases can even lead to its emergency switching
For the power line with the low level of interference time constant of smoothing filters can be chosen at the level of minus 30 electrical degrees
Summary
Modern power systems both stationary and autonomic-based are characterized by the high level of interference with difficultly predicted parameters, often exceeding the allowable norms of interference and serving as destabilizing factors in the work of semiconductor converters (SC) but process installations in whole [1,2,3]. In the second case the synchronization signal affects the self-oscillating integrating sweep converters transferring them to the forced switching mode with the mains voltage frequency. Together with this each of the synchronization channels gets the properties of the first-order aperiodic filters with time constant determined by the value of the amplitude and frequency of mains voltage.
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