Thermal Analysis of Multilevel Grid-Side Converters for 10-MW Wind Turbines Under Low-Voltage Ride Through

<span>The capability of low-voltage ride-through (LVRT) of doubly fed induction generator (DFIG) has been considered as an essence for grid code requirements. Any unbalance on the grid side causes the rotor current of the generator to rise which leads to saturate the dc-link of the back-to-back converter or even destroy it. To meet this requirement, a dynamic voltage restorer (DVR) without dc-link energy storage elements is utilized to compensate any disturbance imposed to the DFIG wind turbine system. On the time of any disturbance or fault, DFIG and DVR are properly controlled in order to compensate the specified faulty phase uninterruptedly. DVR is connected in series to the grid and by injecting instantaneous compensating voltage, prevents the stator voltage from rapid changing; consequently, the rotor side converter can accomplish its normal operation. As voltage dips are the most common grid faults subjected to DFIGs, this paper investigates both symmetrical and asymmetrical voltage dips caused by grid faults. The independent and instantaneous phase voltage compensation, less volume, weight, and cost are the merits to utilize the proposed DVR along with DFIG wind turbines. PSCAD/EMTDC based simulations verifies the capabilities of the proposed technique for the LVRT capability of DFIG.</span>

Download Full-text

Optimal Transient Search Algorithm-Based PI Controllers for Enhancing Low Voltage Ride-Through Ability of Grid-Linked PMSG-Based Wind Turbine

Electronics ◽

10.3390/electronics9111807 ◽

2020 ◽

Vol 9 (11) ◽

pp. 1807

Author(s):

Mohammed H. Qais ◽

Hany M. Hasanien ◽

Saad Alghuwainem

Keyword(s):

Wind Turbine ◽

Low Voltage ◽

Search Algorithm ◽

Fitness Function ◽

Synchronous Generator ◽

Pi Control ◽

Low Voltage Ride Through ◽

Control Scheme ◽

Pi Controllers ◽

Grid Side

This paper depicts a new attempt to apply a novel transient search optimization (TSO) algorithm to optimally design the proportional-integral (PI) controllers. Optimal PI controllers are utilized in all converters of a grid-linked permanent magnet synchronous generator (PMSG) powered by a variable-speed wind turbine. The converters of such wind energy systems contain a generator-side converter (GSC) and a grid-side inverter (GSI). Both of these converters are optimally controlled by the proposed TSO-based PI controllers using a vector control scheme. The GSC is responsible for regulating the maximum power point, the reactive generator power, and the generator currents. In addition, the GSI is essentially controlled to control the point of common coupling (PCC) voltage, DC link voltage, and the grid currents. The TSO is applied to minimize the fitness function, which has the sum of these variables’ squared error. The optimization problem’s constraints include the range of the proportional and integral gains of the PI controllers. All the simulation studies, including the TSO code, are implemented using PSCAD software. This represents a salient and new contribution of this study, where the TSO is coded using Fortran language within PSCAD software. The TSO-PI control scheme’s effectiveness is compared with that achieved by using a recent grey wolf optimization (GWO) algorithm–PI control scheme. The validity of the proposed TSO–PI controllers is tested under several network disturbances, such as subjecting the system to balanced and unbalanced faults. With the optimal TSO–PI controller, the low voltage ride-through ability of the grid-linked PMSG can be further improved.

Download Full-text