The invention discloses a
transformer-free type low-leakage-current photovoltaic grid-connected
inverter circuit with an
active clamp and a modulation method thereof. The
transformer-free type low-leakage-current photovoltaic grid-connected
inverter circuit with the
active clamp comprises two filter capacitors Cdc1, Cdc2, eight switch tubes S1, S2, S3, S4, S5, S6, S7, S8 and two filter inductors L1, L2, and is characterized in that an
active switch tube is additionally arranged in the circuit so as to form a clamping unit, common-mode
voltage in a grid-connected
inductance follow current stage is clamped to the midpoint of a
bus capacitor by being matched with an appropriate switching sequence, common-mode
voltage disturbance of the
system is removed, and thus a suspension problem of common-mode
voltage of a decoupling
inverter in zero level output is solved; and
parasitic oscillation of a common-mode circuit is removed at the same time, and a phenomenon of common-mode
resonance is suppressed. The photovoltaic grid-connected inverter circuit disclosed by the invention has the advantages of
simple circuit structure, high efficiency, simple modulation method and the like. The photovoltaic grid-connected inverter circuit can ensure an inverter not to be affected by a current
zero crossing point in unit
power factor running, and can avoid current
waveform distortion caused by influences of grid power fluctuations or operations at a non unit
power factor.