Interfacing of PV Array with AC Grid using Twelve Pulse Converter

Author Name(s): Yasir Sheikh, Sudarshan Khond, Dr. M. M. Renge
Author Email: sheikhmn@rknec.edu

Abstract

Owing to continuously booming energy demand, if the reliance is on fossil fuel only then energy crunch is very near within few decades. To explore renewable green energy sources is the empirical solution which can dodge the energy crunch. In order to bridge the energy gap, solar energy is used widely. In interfacing of grid with voltage source inverter, the pivotal concern is Synchronization. In the proposed scheme, interfacing of solar PV panels and Ac grid is implemented using line commutated twelve pulse converter and it does not necessitate additional synchronizing circuit. The performance of PV array is affected by variation in irradiance and temperature. As a consequence, the Maximum Power Point (MPP) also shifts. A Maximum Power Point Tracking (MPPT) controller is modelled in order to utilize maximum power from PV array. It is developed by using hill climbing (Perturb and Observe) method.

Introduction

Solar energy is growing in popularity in electricity generation being clean, affordable, and sustainable. Thus, it is an apt replacement of conventional energy sources that have serious environmental issues. The energy produced by solar radiation is in Direct Current (DC) form. This DC need to be converted into AC form as most of the electrical appliances work on Alternating Current (AC). The most popular device to convert DC into AC is Voltage Source Inverter (VSI). Most Popular topology utilised for interfacing PV array with grid is Voltage source inverter (VSI). The quality of power injected is improved by using two-level VSI with help of PWM techniques [3][4]. For high power, in order to minimise switching losses there is restriction on switching frequency in PWM technology. Further to inject high quality power in grid at low switching frequency [5][6]. Some other configurations are demonstrated in [7] which can be effective for grid interfaced PV applications. These converters need separate frequency synchronizing controllers. Synchronization of grid is pivotal task in interfacing of converters with the grid. The information regarding phase angle of grid voltage is required to transfer the power from converters in synchronization. The techniques used to maintain synchronism are Fourier analysis techniques, Phase Locked Loop, etc. [8]. However there is always change in voltage and frequency. VSI needs to follow frequency changes and synchronization.

Conclusion

The simulated results are compared and verified with the theoretical results to validate the proposed methodology for interfacing of PV array to ac grid. There is no need of additional synchronizing circuit to maintain synchronism and track the grid voltage waveform. The simulated results showed that the MPPT mechanism developed is effective and easy to track the MPP.

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