Effect of PLL Structure on Equivalent Output Impedance of Grid-Side Inverters in Offshore Wind Turbines

Effect of PLL Structure on Equivalent Output Impedance of Grid-Side Inverters in Offshore Wind Turbines: MSc Thesis Report

Kremers, Arjen (TU Delft Electrical Engineering, Mathematics and Computer Science)

Qin, Z. (mentor)
Bauer, P. (graduation committee)
Tindemans, S.H. (graduation committee)

Delft University of Technology

Electrical Engineering | Electrical Power Engineering

2019-09-03

Offshore wind power plants are subject to adverse electrical conditions that are more severe than onshore cases, due to the long cable connection to the shore. Among these conditions are amplified voltage distortion at (inter)harmonic frequencies, as well as stability issues. An important aspect of wind turbine generator control is the phase-locked loop (PLL), a method to synchronize the output current with the grid voltage. In the case of voltage distortion, an error occurs in the estimated phase-angle of the PLL, which results in an additional distortion in the output current. This research focuses on 5 different variants of PLLs and compares their behaviour when implemented in a grid-side inverter of a wind turbine. The comparison is based on deriving the equivalent small-signal output impedance of the inverter for each PLL, which can be used for stability analysis of the wind farm connected to the onshore grid by a typical cable connection. A conclusion is drawn on the effect of each PLL variant on the output distortion as well as the stability.

phase-locked loop
offshore wind power plants
Voltage Source Converter
harmonic distortion
small-signal
stability
equivalent impedance
grid-side inverter

http://resolver.tudelft.nl/uuid:ed5a6bee-f524-4a78-9a24-b5c7da458228

2024-09-01

Student theses

master thesis

© 2019 Arjen Kremers