Current-zero detection in thyristor convertors

The recently developed high-frequency link or power-system intertie incorporates two naturally commutated cycloconvertors (NCCs) with a high-frequency passive resonating tank circuit. A new circuit configuration of thyristors for the NCC has been developed which achieves improved operating characteristics compared to the conventional NCC. The theoretical and practical results of the new NCC show improved output voltage distortion and reduced input reactive loading compared to the standard NCC, both of which are advantageous when used in high-frequency links. Implementation of the new NCC is discussed together with a critical comparison between the two types. List of symbols and abbreviations± V 1 phase tphase harm 'phase react I phase real iRMS m,n,p,q,u NCC r SCR t Vfund a etc. = coefficients of Fourier series used for spectrum of input current to new cycloconvertor = coefficients of Fourier series used for spectrum of output voltage from new cycloconvertor = average DC output voltage of the 'flywheel' SCR NCC for the particular 'firing' angle a, depending on the output voltage polarity V, and output current polarity / = assumed peak sinusoidal output phase current of 'flywheel SCR' NCC = instantaneous input current for a single-phase output circulating currentfree 'flywheel SCR' NCC = unwanted frequency components in 1 phase = fundamental reactive component of * phase= fundamental real component of iphase = RMS input current of 'flywheel SCR' NCC = integers = naturally commutated cycloconvertor = output voltage ratio between the maximum fundamental sine-wave output to the required fundamental sine-wave output (i.e. 0 < r < 1) = silicon-controlled rectifier = time = required fundamental component of output phase-to-neutral voltage waveform = instantaneous output phase voltage with required fundamental component of V fund = peak input phase voltage to NCC = 'firing' angle, in radians, for particular phase delayed from the line voltage zero crossover (i.e. blue-red line voltage for red phase etc.) = cos" 1 [1 -\r sin Paper 2470C (P6, P9),

show abstract

“…(a) sensing the voltage across all convertor thyristors (low thyristor voltage indicates thyristor conduction) [11][12][13][14][15].…”

Section: Zero-current Detection For Bank Selection In 'Flywheel Scr' mentioning

confidence: 99%