This paper presents a single-phase five-level photovoltaic (PV) inverter topology for a grid-connected system. The PV arrays are connected to a five-level inverter. By implementing maximum power point tracking algorithm, more power is produced from the PV array. The DC power from the PV array is applied to PWM inverter, which is controlled by the PID controller. The output of the inverter is AC supply, which is connected to the grid. A digital Proportional-Integral-Derivative (PID) current control algorithm is implemented in MATLAB version 7.5. Dynamic performance of the grid current is almost sinusoidal. The total harmonic distortion produced by the inverter is less.

In recent years, the demand for renewable energy is more because of shortage of fossil fuels. The renewable energy source has a long effective life, is maintenance-free and does not create pollution. The solar energy is the most effective power generation, compared to other renewable energy sources. The solar energy is directly converted to electric energy. The photovoltaic (PV) energy conversion technology is the most useful way of harnessing solar energy. The PV cells generate DC electricity without the involvement of any mechanical generators. The electrical energy output from the solar PV cells depends upon the intensity of sunlight, conversion efficiency and temperature of operation. Energy conversion devices are used to convert sunlight to electricity by the use of the PV effect. The maximum power point tracking algorithm is implemented to obtain maximum energy for PV arrays. The PV array output power is applied to multilevel inverter. The inverter is used for conversion of DC to AC voltage. The cascaded H-bridge inverter is one of the common methods. The modulation and control strategies have been developed using sinusoidal Pulse Width Modulation (PWM). A five-level PWM inverter output voltage can be represented in the following five levels: zero, +1/2 Vdc, + Vdc, -1/2 Vdc, and - Vdc. This inverter topology uses two reference signals, instead of one, to generate PWM signals for the switches. Both the reference signals V_ref1 and V_ref2 are identical, except for an offset value equivalent to the amplitude of the carrier signal V_carrier. Because the inverter is used in a PV system, a Proportional-Integral-Derivative (PID) current control scheme is employed to keep the output current sinusoidal, to have high dynamic performance under rapidly changing atmospheric conditions and to maintain the power factor at near unity. Simulation results are presented to validate the proposed inverter configuration. The inverter offers lower Total Harmonics Distortion (THD) and quality of power.

A solar cell is basically a p-n junction fabricated in a thin wafer or layer of semiconductor. The electromagnetic radiation of solar energy can be directly converted to electricity through the PV effect. Being exposed to sunlight, photons with energy greater than the band-gap energy of the semiconductor are absorbed and create some electron-hole pairs proportional to the incident irradiation. Under the influence of the internal electric fields of the p-n junction, these carriers are swept apart and create a photocurrent, which is directly proportional to solar insolation. The PV system naturally exhibits a nonlinear I-V and P-V characteristics, which vary with the radiant intensity and cell temperature.

Electrical and Electronics Engineering Journal, Grid-Connected PV System, PID Controller, Power Point Tracking Algorithm, Electromagnetic Radiation, Proposed Inverter Topology, Modulation Technique, Control System Algorithms, Grid-Connected Applications, Photovoltaic Models, Mathematical Calculations.