Synchronization of Photo-voltaic system with a Grid

Abstract

The study addresses the architecture of a hybrid PLL circuit technique for synchronizing a PV system with single phase grid. For determination of synchronization, the PV system is based on a reference system .The reference system is controlled by a microcontroller and pulse width modulation technique is used within the microcontroller to trigger the inverter in order to achieve efficient synchronization. Optocoupler is used to detect the real-time zero crossing detection and the digital phase lock loop system is used to control the phase angle and frequency of the system. The architecture of system is designed in Proteus simulator. The proposed architecture has performed well in reducing the harmonics produced because of inverter switching. Also if there are any abrupt changes in frequency or phase angle, the system can effectively manage changes. Keywords: PV Array, Grid synchronization, Microcontroller, Optocoupler, DPLL, PWM and Power Quality. I. Introduction The power generated through photo-voltaic system is used to operate the different types of loads. Solar energy is harnessed by means of photovoltaic (PV) systems(1), which use arrays of PV panels that convert solar energy into electrical energy. It is cheap and is more reliable as compare to other generating systems.The PV systems are suitable for applications such as battery charging, lighting and water pumping in remote areas. The solar energy charges a battery (DC supply) which is further connected to a DC-AC inverter that finally operates AC loads. This system can be used on small as well as for domestic use to fulfill the consumer demand for power.It is used as a backup Source for purpose when the load on the power station increases.For such purpose we synchronize our system to the Grid(2)(3)to overcome low power problems. The inverter must convert the renewable energy stored in the battery bank into pure sinusoidal voltage that tracks the grid voltage in amplitude, frequency and phase. For this purpose the inverter must be synchronized with grid. The interconnection of photo-voltaic (PV) system(4) with a Grid requires an accurate control of synchronism between converter and grid. The parameters including voltage, phase and frequency of both systems need to be synchronized.There are different types of techniques (5)(6)developed to achieve synchronization but the system used in this study is simple,reliable,requires small area for installation and need small circuitry. The proposed system is designed for 1.5kw.The main goal is to share the load during the peak load time on the power station as well as an accurate measuring of the phase-angle of the grid voltage.The parameters of the reference system (Grid) and photo-voltaic system must be equal for efficient synchronization.