Designing optimal controllers for doubly fed induction generators using a genetic algorithm
ABSTRACT This work presents a design procedure based on evolutionary computation, more specifically on a genetic algorithm combined with the formal pole placement project, to obtain optimal controllers to the rotor-side converter of doubly fed induction generators (DFIGs), in variable-speed wind generation systems connected to the electrical grid. With this procedure it is intended to improve the global system dynamic behaviour during and after the fault period, also increasing the transient stability margin of the power system and the fault ride-through capability. The control action of the DFIG converters is accomplished by proportional and integral controllers, whose gainspsila adjustment is not a trivial task, because of the high complexity of the system. The results obtained confirm the efficiency of the proposed control design procedure.
SourceAvailable from: Jafar Mohammadi[Show abstract] [Hide abstract]
ABSTRACT: In this paper, a combined vector and direct power control (CVDPC) is proposed for the rotor side converter (RSC) of doubly fed induction generators (DFIGs). The control system is based on a direct current control by selecting appropriate voltage vectors from a switching table. In fact, the proposed CVDPC enjoys the benefits of vector control (VC) and direct power control (DPC) in a compacted control system. Its benefits in comparison with VC include fast dynamic response, robustness against the machine parameters variation, lower computation, and simple implementation. On the other hand, it has benefits in comparison with DPC, including less harmonic distortion and lower power ripple. An extensive simulation study, using MATLAB/Simulink, is conducted on a 9-MW wind farm composed of six 1.5-MW DFIG-based wind turbines. The performance of the proposed CVDPC method is compared with both VC and DPC under steady-state and transient conditions. Simulation results confirm the superiority of the CVDPC over either VC or DPC.IEEE Transactions on Sustainable Energy 07/2014; 5(3):767-775. DOI:10.1109/TSTE.2014.2301675 · 3.84 Impact Factor
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ABSTRACT: This paper proposes a new computational intel ligence-based control strategy, to enhance the low voltage ride-through capability of grid-connected wind turbines (WTs) with doubly fed induction generators (DFIGs). Grid codes world-wide require that WTs should supply reactive power to the grid during and after the fault, in order to support the grid voltage. The conventional crowbar-based systems that were initially applied in order to protect the rotor-side converter at the occurrence of grid faults, do not fulfill this requirement, as during the connection of the crowbar, the DFIG behaves as a squirrel cage machine, absorbing reactive power from the grid. This drawback led to the design of control systems that eliminate or even avoid the use of the crowbar. In order to conform to the above-mentioned requirement, this paper proposes a coordinated control strategy of the DFIG converters during a grid fault, managing to ride-through the fault without the use of any auxiliary hardware. The coordination of the two controllers is achieved via a fuzzy controller which is properly tuned using genetic algorithms. To validate the proposed control strategy, a case study of a 1.5-MW DFIG supplying a relatively weak electrical system is carried out by simulation.IEEE Transactions on Power Systems 05/2014; 29(3):1325-1334. DOI:10.1109/TPWRS.2013.2290622 · 3.53 Impact Factor
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ABSTRACT: SUMMARY The work reported in this paper adds damping to the inter-area mode of oscillation in a power system with relatively high penetration of wind power, by modulating active power output of the permanent magnet synchronous generator wind turbines (PMSG-WTs) using local information. The dc-link voltage of the voltage source converter is used as a local signal for controller input. This input signal is processed through phase compensator blocks, and the output of the controller is used to vary the active power reference signal of the machine side converter controller. The results are compared to the cases of the same supplementary controller loop with a global signal as its input, added to the both PMSG-WTs and doubly fed induction generator wind turbines. An optimization-based approach is proposed to adjust and coordinate various control loops of the grid-connected PMSG-WTs. The performance of the supplementary damping control loop is evaluated, employing modal analysis and time domain simulations of a power system test case. Copyright © 2012 John Wiley & Sons, Ltd.International Transactions on Electrical Energy Systems 10/2013; 23(7). DOI:10.1002/etep.1646 · 0.63 Impact Factor