Photovoltaic(PV) power system converts infinite solar energy directly into electrical energy. PV system has been considered to be the most reliable renewable energy source, because it supplies green energy without emitting greenhouse gases like CO2. However, the high initial installation cost prevented its usage from terrestrial applications except an installation for special purpose such as pilot plant and local power plant.
It is important to reduce the harmonic component of inverter output with solar-cell in an utility-connected inverter system. In order to reduce the output harmornics, various methods such as using a output L-C filter, and a PWM switching pattern, etc., are currently being investigated.
This paper proposes a new PWM(Pulse Width Modulation) method which is derived by shifting its phase at a conventional SPWM(Sinusoidal Pulse Width Modulation) on-off time. The PWM on-off time was calculated from simultaneous equation induced fourier series.
To verify a validity of the proposed algorithm, computer simulation and experimental test has been implemented. The experimental result showed that the ratio of each harmonics to the fundamental component are decreased by the proposed PWM, and the 3rd harmonic is decreased from 30.15[%] to 10.5[%]. Also it is confirmed that the output current waveform comes to be nearly a sinusoidal waveform.