Research on the impact of grid-connected offshore wind farms on transient overvoltage and characteristics of harmonic resonances

Abstract

Grid-connected offshore wind farms are likely to cause harmonic resonances in the power system that jeopardize the safe operation of the power grid. To this end， the impact of grid-connected offshore wind farms on the transient overvoltage and harmonic resonance characteristics of the onshore power grid PCC （point of common coupling） is studied， and a harmonic resonance management scheme is proposed. Firstly， PSCAD simulation modeling is performed for a grid-connected project of offshore wind farms in Zhejiang Province. Then the transient overvoltage and harmonic resonance characteristics of the grid-connected system under different operation modes are obtained by simulation. The results show that the maximum per-unit value of PCC transient overvoltage is 2.1 p.u.， which is less than the limit value of 3.0 p.u. and meets the safety requirements. Finally， the harmonic suppression strategy of parallel connection with low impedance branch filters five times and seven times respectively at PCC that significantly weakens the harmonic amplification of PCC and reduces the total harmonic distortion rate to less than 1.5%， eliminating the second to seventh low-frequency harmonic amplification.

Keywords

• offshore wind farm
• transient overvoltage
• harmonic resonance
• parallel filter