Modified Filter for Enhancement of Power Quality in Distribution Networks

The recent rise in renewable energy sources has brought with it a corresponding rise in the utilization of Voltage Source Converters (VSCs). These typically contain a Pulse Width Modulation (PWM) switched element that can introduce harmonics into the power grid, resulting in equipment damage and failure. In order to suppress excessive harmonics and improve performance, various lowpass filters are inserted between the VSC and grid. This paper presents a comparative and systematic analysis of the LCL filter and its derivatives based on both theoretical and simulation results. The paper details the impact of each parameter on the system behaviour, as well as a performance analysis between different filter structures such as the conventional LCL filter, LLCL filter, LCL-LC filter and others. Then a design process of the modified filter is introduced with particular focus on development of a formal model which allows the filter components to be determined while maintaining filter performance and reducing damping loss.