ANALYSIS, DESIGN AND IMPLEMENTATION OF THE SPACE-VECTOR MODULATOR FOR FORCED-COMMUTATED CYCLOCONVERTORS

Novel research results on control of forced-commutated cycloconvertors (FCCs) with matrix topology are summarised. The space-vector-modulation (SVM) technique for control of the 3-phase/3-phase matrix convertor is presented. The SVM technique provides FCC output voltages of any frequency, from zero to a maximum value constrained by the switching frequency, and any amplitude, up to square-root(3)/2 of the input voltage amplitude, without low-frequency harmonics. Time-domain-simulation results and spectral analysis of the output voltages and input currents are shown. The space-vector modulator is digitally implemented in a microprocessor system with reduced real-time computation. The switching times are precalculated offline and the results are stored in EPROMs. A multistepped switching procedure for safe control of the matrix-convertor switches is also presented. The safe-control algorithm is implemented with a sequential circuit by using a PROM lookup table. The FCC space-vector modulator is experimentally verified.