Integration of Grid Connected Photovoltaic System with Active Power Filtering Functionality

Abstract

The development in the field of power electronics has led to its optimum and efficient use in domestic and industrial arena especially in control and automation processes. In turn this has created a threat in terms of power quality issues. The main issue with such devices and the associated circuits is that they act as non linear loads on the system. Due to this the source/grid current in which they are connected gets polluted. The solution for such problems is the use of power filters. Passive filters have certain drawbacks and hence active filters are predominantly used. To some extent, solution to power quality issues is obtained again using power electronic devices in the form of active power filtering. On the other hand, due to social and environmental issues, there is a rising awareness among masses to use renewable sources of energy. In many places renewable sources like photovoltaic systems are being connected to the grid. Renewable sources such as photovoltaic cells and fuel cells need conversion stage before connecting to the utility grid. Normally a DC-AC inverter is used for this purpose. Hence the performance of such system considerably depends upon the type of inverter used. In order to avail better performance, a multilevel inverter is preferred. But the complexity of control circuitry and the number of devices required are the issues of concern with this type of inverters. Here, an attempt is being made to address these two aspects in a common domain. The features of active filtering can be combined with the PV source connected to the grid so that active and reactive power transfer takes place at the point of common coupling (PCC). In this work a PV source is connected to the grid through a dual inverter which also acts as active power filter. A dual inverter topology is simple three level inverter topology compared to existing multi level topologies. A grid connected photovoltaic system is integrated with active power filtering functionality to address both issues of real power injection and harmonic filtering. The performance of such system is enhanced by using multilevel inverters. A transformer fed from both ends at its primary terminals with two independent voltage source inverters is used to replace a filter inductance of a conventional system.iv In this dissertation firstly a grid connected PV system through a dual inverter topology is modeled and simulated. The system performance is verified under different load and solar cell operating conditions. Secondly, in a power distribution system with nonlinear loads an active power filter is developed with three level (dual inverter) inverter. The source current THD and the source displacement power factor are improved at different loads. Finally, two systems are integrated such that grid connected PV system with active power filter functionality is obtained. This system is tested for different atmospheric as well as load conditions.