Variable structure PWM controller for high efficient PV inverters

In general, the output voltage level of PV array varies widely at various irradiances and temperatures. The MPP (maximum power point) range of a medium- or high-power PV PCS is normally 450~830 Vdc or 300~600 Vdc. This means the PV PCS should operate in a wide range of modulation index. The PV PCS should satisfy the harmonic current requirement that TDD (total demand distortion) shall not exceed 5%. This paper proposes a new PWM control method for the medium- or high-power PV PCS which increases the efficiency of power conversion in all operation range with acceptable harmonic ripple currents. This paper compares and analyzes appropriate PWM schemes for the PV PCS in the view points of conversion efficiency and current harmonics.