The spectrum of power from wind turbines

This paper presents system modeling and control design for fast load voltage regulation using static compensators (STATCOMs). The modeling strategy gives a clear representation of load voltage magnitude and STATCOM reactive current on an instantaneous basis. The particular coordinate transformation employed here also facilitates extraction of linearized system dynamics in conjunction with circuit simulators. It is rigorously shown that the control problem of load voltage regulation using reactive current is nonminimum phase. Linear and nonlinear controllers for the regulation problem are designed and compared via simulation results. Internal dynamics of the STATCOM are modeled using the same strategy. Lyapunov based adaptive controllers are designed for controlling the STATCOM reactive current while maintaining its dc bus voltage. Simulation results of the controlled STATCOM integrated with the load bus voltage controller are presented to show efficacy of the modeling and control design.

Voltage regulation with STATCOMs: modeling, control and results

In order to fully study the electrical, mechanical, and aerodynamic aspects of a wind turbine with a doubly fed induction generator, a detailed model that considers all these aspects must be used. A drawback of many works in the area of wind turbine simulation is that either a very simple mechanical model is used with a detailed electrical model, or vice versa. Hence, the effects of interactions between electrical and mechanical components are not accurately taken into account. In this paper, three simulation programs - TurbSim, FAST, and Simulink - are used to model the wind, mechanical and electrical parts of a wind turbine, and its controllers. Simulation results obtained from the model are used to observe the interaction of all three factors affecting the operation of a wind turbine system. For example, it is shown how an electrical disturbance can cause dangerous tower vibrations under high speed and turbulent wind conditions, which may not be feasible using a simple model of the wind and wind turbine.

Simulation of a Wind Turbine With Doubly Fed Induction Generator by FAST and Simulink

This paper presents a control scheme for grid-connected pulsewidth-modulated voltage-source inverters (VSIs) featuring fast load-voltage regulation and effective mitigation of unbalanced voltage disturbances. To ensure perfect regulation of the voltage at the point of common coupling (PCC) and provide means for rejecting fast and dynamic voltage disturbances, the frequency modes of the disturbances to be eliminated should be included in the stable closed-loop system. Toward this, a hybrid voltage controller combining a linear with variable-structure control element is proposed for an inverter-based distributed-generation interface to regulate the voltage at the PCC. The proposed voltage controller can embed a wide band of frequency modes through an equivalent internal model. Subsequently, a wide range of voltage perturbations, including capacitor-switching disturbances, can be rejected. To account for unbalanced voltage disturbances, a dual-sequence voltage controller is proposed. To provide accurate and robust tracking of the generated active and reactive current trajectories, a newly designed deadbeat current control algorithm is proposed. The controller is designed under the practical considerations of inherent plant delays, which are associated with the digital implementation of the control algorithm, and the uncertain nature of the current dynamics. Theoretical analysis and comparative evaluation tests are presented to demonstrate the effectiveness of the proposed control scheme.

A Control Scheme for PWM Voltage-Source Distributed-Generation Inverters for Fast Load-Voltage Regulation and Effective Mitigation of Unbalanced Voltage Disturbances

The headway of wind power generation is a great blessing to help meet up the electrical power demand day by day. The strongest challenges for wind energy conversion system (WECS) are to handle the intermittency of wind and to maintain the grid reliability. The power electronics and energy storage systems are essential elements of the WECS. This paper attempts to provide various new directions to the future wind energy researchers to improve the wind turbine aerodynamics, electric generators׳ configurations with improved control of power electronics and lower cost energy storage system for designing a reliable wind turbine generator system. This study will work as a guideline for the researchers to understand the development and requirement of a reliable and smart wind energy conversion system.

Future research directions for the wind turbine generator system

Wind energy conversion systems (WECS) produce fluctuating output power, which may cause voltage fluctuations and flicker. Flicker assessment in networks may be difficult since its evaluation requires long computing time and special procedures to calculate the flicker severity index, Pst. In this paper, a frequency domain method to study flicker propagation is presented. This method is based on propagation of frequency components from WECS output currents throughout the grid. In this way, a fast flicker analysis in a network of any size can be performed. Also, an algorithm for flicker measurement in the frequency domain, which allows Pst calculation, is proposed. Several study cases have been performed, and results have been compared with time domain simulations, showing good agreement between them.

Propagation of flicker in electric power networks due to wind energy conversions systems

The implementation of electrification programs in non-interconnected rural areas in Colombia is a challenge for the country in order to reduce the social gap in these regions. This task is responsibility of the Mining and Energy Planning Unit (UPME), which has as challenges the implementation of renewable energy projects that allow diversifying the national energy matrix. For this reason, this paper proposes a support framework for multicriteria decision-making in the electricity supply of non-interconnected rural areas for the Colombian Caribbean Region. The multicriteria method of the Fuzzy Analytical Hierarchical Process (FAHP) was used, which allows the incorporation of a fuzzy triangular scale to improve the imprecision in the judgments made by experts. A hierarchical structure with 6 renewable energy alternatives, 4 criteria and 16 sub-criteria was designed, which allowed the implementation of a paired comparison survey that was answered by 10 experts from the region. The results obtained show the relevance of all alternatives, which is evidenced by a percentage difference of less than 5% between all the options. The best alternative was solar PV (20,27%). Regarding the criteria, the most relevant were economic (39,6%) and environmental (30,8%). The most relevant sub-criterion was the renewable fraction, related to the possible reuse of equipment (20,2%).

C. Vilar Moreno

Papers

Propagation of flicker in electric power networks due to wind energy conversions systems

Decision-Making Support Framework for Electricity Supply in Non-Interconnected Rural Areas Based on FAHP