Patent ID: 6058028
Filing Date: 2000-05-02
Classification: H02M

Abstract:
A method of controlling the flow of current through a DC matrix converter between a DC load and a set of three-phase AC mains, said DC matrix converter comprising a plurality of top switches, each connected between a corresponding one of said AC mains and a first DC output of said DC matrix converter, and a plurality of bottom switches, each connected between a corresponding one of said AC mains and a second DC output of said DC matrix converter, comprising:operating said switches in a manner so that each switch, when operated to connect a corresponding one of said AC mains to a related specific one of said DC outputs, remains operated until another switch has operated to connect one of said AC mains to said specific DC output, and so that one of said top switches is operated contemporaneously with one of said bottom switches, said switches being operated in pairs, each pair including a top switch related to one AC main and a bottom switch related to an AC main other than said one AC main, and said switches also being operated in sets, each set including a top switch and a bottom switch both related to the same AC main;providing a voltage command signal, V*, indicative of the voltage to be provided by said DC output terminals to said load;providing a modulation command, m*, as the ratio of said voltage command signal, V*, to the instantaneous magnitude of voltage, V, of said AC mains in stationary d, q coordinates; andproviding an in-phase modulation command component, mq=m* cos .theta. and a quadrature modulation command component md=m* sin .theta.;providing a quantity m1=.sqroot.3md/2-mq/2;providing a quantity m2=.sqroot.3md/2+mq/2;providing an in-phase component, Vq, and a quadrature component, Vd, of the instantaneous AC mains voltage in orthogonal coordinates aligned with the phase of a given one of said AC mains; andproviding, when .vertline.Vd.sqroot.3.vertline.<.vertline.Vq.vertline., a first fraction d.alpha.=-m1 if Vq>0 and d.alpha.=m1 if Vq<0, and a second fraction d.beta.=m2 if Vq>0 and d.beta.=-m2 if Vq<0;providing when VdVq.sqroot.3>Vq.sup.2, said first fraction d.alpha.=-m2 if Vq>0 and d.alpha.=m2 if Vq<0, and said second fraction d.beta.=mq if Vq>0 and d.beta.=-mq if Vq<0; andproviding, when neither .vertline.Vd.sqroot.3.vertline.<.vertline.Vq.vertline. nor Vd.sqroot.3>Vq, said first fraction d.alpha.=mq if Vq>0 and d.alpha.=-mq if Vq<0, and said second fraction d.beta.=-m1 if Vq>0 and d.beta.=-m1 if Vq<0; andin each of a continuous sequence of modulation periods which are small compared with the period of voltage of said AC mains, operating a first pair of said switches for said first fraction, d.alpha., of said period, operating a second pair of said switches for said second fraction, d.beta., of said period, and operating a set of switches for the remainder of said period.