A Novel Design Method of LCL Type Utility Interface for Three-Phase Voltage Source Rectifier

LCL type filter becomes more and more attractive as utility interface for grid-connected voltage source rectifier (VSR). Compared to L type filter, LCL type filter can render better switching harmonics attenuation using lower inductance, which makes it suitable for higher power applications. However, LCL filter design is complex and needs to consider many constraints, such as current ripple through inductors, total impedance of the filter, switching harmonic attenuation, resonance phenomenon and reactive power absorbed by filter capacitors, etc. Try-error method is inconvenient and time-consuming. This paper proposes a novel method for LCL type filter design, which makes the task very convenient. At first, the total inductance should be determined according to current ripple requirement. With filter capacitor insertion, total inductance is split into two parts. A set of equations is obtained to represent the relationship between the impedances at switching frequency with consideration of switching harmonic attenuation and reactive power constrains. The other constraints are considered as the limitation for solvability condition for equations. So the overall design can be easily done by solving the equations. Step-by-step design procedure is described as a design example, which is verified on the experimental set-up