Electronic Power Transformer Control Strategy in Wind Energy Conversion Systems for Low Voltage Ride-through Capability Enhancement of Directly Driven Wind Turbines with Permanent Magnet Synchronous Generators (D-PMSGs)

Abstract

This paper investigates the use of an Electronic Power Transformer (EPT) incorporated with an energy storage system to smooth the wind power fluctuations and enhance the low voltage ride-through (LVRT) capability of directly driven wind turbines with permanent magnet synchronous generators (D-PMSGs). The decoupled control schemes of the system, including the grid side converter control scheme, generator side converter control scheme and the control scheme of the energy storage system, are presented in detail. Under normal operating conditions, the energy storage system absorbs the high frequency component of the D-PMSG output power to smooth the wind power fluctuations. Under grid fault conditions, the energy storage system absorbs the redundant power, which could not be transferred to the grid by the EPT, to help the D-PMSG to ride through low voltage conditions. This coordinated control strategy is validated by simulation studies using MATLAB/Simulink. With the proposed control strategy, the output wind power quality is improved and the D-PMSG can ride through severe grid fault conditions.

Low Voltage Ride-Through Capability Solutions for Permanent Magnet Synchronous Wind Generators

“…In order to deal with the current negative sequence components in power converters connected to the grid during unbalanced voltage conditions, several papers in literature propose different methods to control this component [14,16,20,[33][34][35][36][37][38][39].…”

“…One of the most common methods applied to grid connected converters is the dual controller [24,33,34], also reported for the FC-PMSG technology [14]. This strategy employs two control structures, one controlling the positive sequence component oriented in the positive reference frame and other dealing with negative sequence component oriented in the negative sequence reference frame.…”

“…Nevertheless, during voltage sags, the capability of the converter to supply active power to the grid is reduced, and then the power that is converted by turbines/generators may increase the DC-link voltage. Therefore, several works propose solutions to improve the RTFC of PMSG WECS [12][13][14][15][16][17][18][19][20][21].…”

“…References [13,14] propose the use of energy storage systems to store the surplus energy. Although the stored energy can be used for other purposes, this solution has a higher cost compared to the braking chopper.…”

“…Huang et al [14] employs an independent control of positive and negative sequence components of grid currents, a well-known strategy for grid connected voltage source converters (VSC). The feedforward of negative sequence grid voltage is used in [16,20].…”