Patent ID: 8493753

Claim:
A photovoltaic powered system providing a direct current (DC) power through a photovoltaic module and converting the DC power into an alternating current (AC) power grid-connected to an AC utility power; the photovoltaic powered system comprising: a coupling capacitance unit electrically connected to the photovoltaic module to filter the DC power outputted from the photovoltaic module; and an AC module electrically connected to the coupling capacitance unit to convert the filtered DC power into a quasi-sinusoidal current; the AC module comprising: an active-clamping circuit having a first clamping switch, a second clamping switch, a first clamping capacitor, and a second clamping capacitor, the active-clamping circuit receiving the filtered DC power and reducing voltage spike of the filtered DC power; wherein the first clamping switch is connected in series to the first clamping capacitor to form a first clamping switch-capacitor assembly; the second clamping switch is connected in series to the second clamping capacitor to form a second clamping switch-capacitor assembly; a power converter electrically connected to the active-clamping circuit and having comprising: an isolated transformer having a first primary side, a second primary side, and a secondary side; a first main switch connected to the first primary side and a second main switch connected to the second primary side; wherein the first main switch is connected in parallel to the first clamping switch-capacitor assembly and the second main switch is connected in parallel to the second clamping switch-capacitor assembly; and a rectifying circuit having two diodes and two filter capacitors; wherein the two diodes and the two filter capacitors are connected to the secondary side; thus receiving the DC power, converting the voltage level of the DC power, and rectifying the DC power; and an AC selection switch circuit electrically connected to the power converter and the AC utility power and having a plurality of power switches forming a full-bridge switch circuit to provide a synchronous switching to the AC utility power; whereby the quasi-sinusoidal current is converted into a sinusoidal current and high-frequency harmonic components of the sinusoidal current are filtered to produce a sinusoidal output current in phase with the AC utility power, thus realizing the maximum power point tracking (MPPT) of the photovoltaic module and feeding unity-power-factor power into the AC utility power.