LVRT Test Bench for Wind Turbines Based on Virtual Voltage Divider

With high penetration of wind energy, the low voltage ride through (LVRT) ability of wind turbines (WTs) connected to the grid is included in recent grid codes. A novel LVRT testing method for full scale power converter WTs and the corresponding control strategies are proposed in this paper, which can emulate different types of grid faults. A virtual voltage divider is presented to realize linear control of the point of common coupling (PCC) voltage during the asymmetrical fault and makes the PCC voltage fit the standard LVRT voltage profile accurately. To validate the control strategies, a regular 2MW permanent magnet synchronous generator (PMSG) with the full scale power converter connected to the VSC-based test bench is modeled in PSCAD/EMTDC. The simulation results have shown that LVRT testing for wind turbines under different grid faults can be realized by utilizing the proposed bench.

I. Introduction

With the rapid development of wind energy, strict requirements are imposed to ensure that wind farms can remain connected with power system and support reactive power to sustain the PCC voltage under the fault condition. The LVRT ability is vital to wind turbines because of the high wind energy penetration in power system. Once the connection between wind farms and power systems is cut off, severe consequences will occur in the power system. Therefore, many recent researches focus on enhancing the LVRT ability of wind farms [1]-[3]. Meanwhile, the LVRT requirement is standardized by transmission system operators (TSOs) in many countries [4].