Global Perspective on Configuration and Status of Grid Connected Photovoltaic System

Global Perspective on Configuration and Status of Grid Connected Photovoltaic System
-Balamurugan M, Sarat Kumar Sahoo*
School of Electrical Engineering, VIT University, Vellore, India

This article gives an overview of different configuration of Grid Connected Photovoltaic System and its status in Global Power Sector.

The Solar Photovoltaic (PV) panel installation has been increased every year because of the high demand in the power sector. More than 75 GW of PV capacitieshave been added worldwide by the year 2016 and this equivalent to the installation of 31000 PV panels every hour. The total PV capacity has been increased to 303 GW by the end of year which is shown in Fig.1. India is the third largest market for solar PV in Asia and it is ranked fourth in the total global PV additions. The solar PV projects have been largely carried out in India because of the falling price of panels and strong support policy of various governments.

The solar rooftop market has been extended considerably in recent year ant it is contributed only 10% of the country installations and it has to long way to reach the target of 40GW by 2022.

In India one of the most important challenges in PV industry is the grid integration. To address these challenges eight energy corridors are formed throughout the country to transfer the power from one state to another state.

Fig.2. Installed Capacity of PV in GW of different countries(Source: IEA PVPS)

Fig.2. Installed Capacity of PV panels in GW of different countries have been displayed and the violet series indicates the installation up to 2015 and the light blue series addition of further PV in 2016. China is in the first position where the large number of PV capacity installed in the year 2016 and Spain is least capacity of installations during the year 2016.

PV systems rated for domestic, the industrial and commercial application from few kilowatts to several megawatts in rooftop-mounted or building-incorporated systems. Nowadays, most of PV systems are integrated with grid because for stand-alone systems batteries are required to store the energy which will increase the cost of the entire system and also the government announces certain incentives those who are using grid tie inverter, therefore people shift their focus towards the grid connected system.

A grid-tie PV inverter is also called as power inverter that converts direct current (DC) into alternating current (AC) with the capability to synchronize with the utility line. The major difference is that the grid tie PV inverter will generate the energy from the PV Array and send it to the grid and the parameters used for estimate the power are voltage, frequency and phase reference and it also consists of Islanding detection circuit which will cut off the inverter whenever there is not enough power in the grid while in stand-alone or off grid system the energy is generated from the PV Array and it is stored in the batteries and it continuously monitors the load and supply the load as much as the demand.

Configuration of Grid Connected PV System:
Grid Connected Photovoltaic System has been found in different sizes from 100 W to 1GW. It can be classified into three different levels based on the power ratings of the system. The power range of few watts to few tens of kW comes under the small scale system. Few tens of kW to few hundreds of kW comes under the medium scale system and for the large scale system the power range is between few hundreds of kW to several hundreds of MW. PV systems can be further classified based on the PV module arrangements which are single module, multiple modules, string of modules which is shown in Fig.3. Based on the inverter configuration it can be classified as Central Inverter, String Inverter, Multistring Inverter and AC Module Inverter.

In most of the large power plant, centralized topology is installed where the large numbers of panels are connected in series or parallel in one string with central inverter. The major advantages of this topology are the simple structure and less maintenance. This topology has highly suffered due to the partial shading and also fails to determine the peak point because of the centralized MPPT algorithm.

In String topology, the panels are divided into separate sections, where each string is connected to DC/DC converter and DC/AC inverter where the distributed MPPT scheme is applied to improve the power produced the strings. The advantages of these topologies are the higher power production and distributed MPPT scheme. This topology has applicable to small scale systems because of the complex structure and also cost of the topology is very high.
AC-Module topology has one dedicated converter for each module and this topology is widely used in domestic and small scale applications. The drawback of the topology is high cost and complex structure.

Therefore, by combining the merits of centralized topology and string topology the new topology is evolved and it is called as multistring topology. In multistring topology, each PV string is connected to the dc/dc converter and the distributed MPPT control algorithm is connected to the central inverter. This topology has been mostly used in medium voltage high power applications because of the modularity structure and it is easy to increase rating of the system by connecting the additional string to the topology.

Balamurugan M was born in Vellore, Tamilnadu, India. He received his B.E Degree from Anna University Chennai, in 2012, M.Tech Degree from VIT University Vellore in 2014 and currently pursuing Ph.D. degree from VIT University Vellore. His research interests include Multilevel Inverters, Power Electronics application in Renewable energy systems. He is currently working as Junior Research Fellow, School of Electrical Engineering, VIT University, Vellore, India

Sarat Kumar Sahoo was born in Dhenkanal,Orissa, India, in 1973. He received the M. Tech degree from Visveswaraih Technological University, Belgaun, India, in 2002 and Ph.D. degree from JNTU, Hyderabad, India, in 2011. His research interests include renewable energy, power electronics and control of high performance drives. He is currently working as Professor and Head Department of Electrical Engineering, School of Electrical Engineering, VIT University, Vellore, India.