LCL filter design for VSC-HVDC systems supplying passive grids

This paper presents an LCL passive filter design methodology for high voltage direct current systems based on voltage source converters (VSC-HVDC) connected to passive grids. Power quality of passive grids is largely dependent on the VSC operation. Therefore, the filter design should take into consideration power quality issues. The LCL filter model is developed considering its losses and the passive grid impedance. If the grid impedance is considered, a sequential calculation of parameters is not feasible. Therefore, after modeling, parameter calculation algorithms are presented. The algorithms are divided into two steps: a design algorithm called the Multi-Pair Calculation Algorithm and an algorithm that selects the best solution, called the Selection Algorithm. The design methodology and calculation algorithms were exemplified using the IEEE 34 node test system as a passive grid. The results confirm that the proposed algorithms perform an optimal definition of filter parameters and that the quality of the passive grid voltage is a crucial element for the VSC filter design.