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In this thesis, a directly-converted-type dc/ac and ac/ac
converter topology for UPS is proposed. Using the technique of
the Buck-Boost circuit, a reliable sinusoidal ac output is
presented at load end for the case of ac or dc input. Voltage-
mode and current-mode control methods are investigated to deal
with various loads and sources. Good output characteristics are
achieved in the voltage-mode control for dc input. However,
when ac input is applied, the output will distort. In order to
solve this problem , the current- mode control is addressed. In
the current mode control, by way of additional current feedback
loop is used, the proposed system can obtain the better output
profile. To verify the proposed scheme, the prototype is
implemented. The experiment results are agreed with the
theoretical analysis.
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