In this paper, a design fuzzy logic controller for a variable speed permanent magnet wind generator connected to a grid system through a LC-filter is proposed. A new current control method of grid side conversion is developed by integrating the fuzzy controller, in which both active and reactive power, delivered to a power grid system, is controlled effectively. The fuzzy logic controller is designed to adjust the gain parameters of the PI controllers under any operating conditions, so that the dynamic stability is enhanced. A new simple method, based on frequency response of the bode diagram, is proposed in the design of the fuzzy logic controller. To evaluate the controller system capabilities, simulation analyses are performed on a small wind farm model system including an induction wind generator connected to an infinite bus. The simulations have been performed using PSCAD/EMTDC. Simulation results show that the proposed control scheme is more effective for enhancing the stability of wind farms during temporary and permanent network disturbances and randomly fluctuating wind speed, compared with that of a conventional PI controller.

Wind farm (WF) grid codes require wind generators to have low voltage ride through (LVRT) capability, which means that normal power production should be resumed quickly once the nominal grid voltage has been recovered. However, WFs with fixed-speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) have failed to fulfill the LVRT requirement, which has a significant impact on power system stability. On the other hand, variable-speed wind turbines with doubly fed induction generators (VSWT-DFIGs) have sufficient LVRT augmentation capability and can control the active and reactive power delivered to the grid. However, the DFIG is more expensive than the SCIG due to its AC/DC/AC converter. Therefore, the combined use of SCIGs and DFIGs in a WF could be an effective solution. The design of the rotor-side converter (RSC) controller is crucial because the RSC controller contributes to the system stability. The cascaded control strategy based on four conventional PI controllers is widely used to control the RSC of the DFIG, which can inject only a small amount of reactive power during fault conditions. Therefore, the conventional strategy can stabilize the lower rating of the SCIG. In the present paper, a new control strategy based on fuzzy logic is proposed in the RSC controller of the DFIG in order to enhance the LVRT capability of the SCIG in a WF. The proposed fuzzy logic controller (FLC) is used to control the reactive power delivered to the grid during fault conditions. Moreover, reactive power injection can be increased in the proposed control strategy. Extensive simulations executed in the PSCAD/EMTDC environment for both the proposed and conventional PI controllers of the RSC of the DFIG reveal that the proposed control strategy can stabilize the higher rating of the SCIG.

This paper presents a method to calculate various losses in wind turbine generation system (WTGS) as a function of wind speed, which is based on the steady state analysis. Variable speed WTGS using a doubly-fed induction generator (DFIG) and power converters (inverter and converter) is mainly considered in this paper. By using the proposed method, wind turbine power, generated power, generator losses, gearbox loss, power converter losses and energy efficiency can be calculated quickly. Moreover, annual energy production and capacity factor of the wind farm can be obtained by using the wind speed characteristic expressed by Weibull distribution function. Therefore, if the Weibull distribution function of wind speed is available, we can calculate the annual energy production without using real annual wind speed data. Using the data of Weibull distribution function of some different areas, capacity factor of each area is calculated and compared with those of other types of WTGSs such as Permanent Magnet Synchronous Generator (PMSG) and Squirrel-Cage Induction Generator (IG).

This paper addresses a controller for a full converter of variable-speed wind generators (VSWTs) composed of permanent magnet synchronous generators. Conventionally, several proportional-integral (PI) controllers and a phase lock loop (PLL) are used in the full converter for voltage-oriented control. The use of cascaded control loops with PI controllers degrades the control performance due to the wind-up of the integrators and complicates the tuning task. In this paper, we propose a new full converter control scheme based on predictive control and a single P-controller in the α-β stationary frame to replace the integrators and the PLL. The proposed controller can reduce the parameter tuning effort, is free from integrator wind-up and is robust to symmetrical and asymmetrical voltage dips. The effectiveness of the proposed method is verified through simulations.

This paper proposes a novel coordinated control method of wind farms (WFs) and hydrogen production systems (HPSs). In a grid-connected system where the WF and the HPS are connected to the grid, the WF can supply the power to the grid, producing hydrogen in the HPS. Moreover, the output fluctuation of the WF can be mitigated when the HPS produces hydrogen from the output surplus. The purpose of the grid-connected system is to smooth the WF output fluctuation sufficiently, produce hydrogen constantly, and maintain a high capacity factor in the HPS. The proposed coordinated control achieves the mitigation of the WF output and the high capacity factor in the HPS. The key ideas are 1) utilizing the kinetic energy of wind generators and 2) virtual discharge of the HPS. The fluctuation components of the WF output are compensated by both the WF and the HPS. The proposed coordinated controller enables us to produce hydrogen constantly in the HPS with a low-rated power. The advantage of the proposed coordinated control is verified by a comparative analysis with conventional methods through simulations using real wind data.