[Show abstract][Hide abstract] ABSTRACT: Wind power represents a growing portion of the energy and power produced in modern electrical power systems. They have to be integrated and interconnected with conventional generation, mostly based on synchronous generators. Utility grid codes have evolved to allow integration in a manner that preserves the integrity and security of the overall power system, taking into account the fact that wind power displaces some of the conventional generators. This paper examines the requirements that wind power plants are asked or may be asked to meet in order to maintain the integrity of the power system. These requirements are similar to those that synchronous generators normally fulfil. They include the Low-Voltage Ride-Through (LVRT) capability, the Power System Stabilizer (PSS) function, and the inertial response emulation. The paper demonstrates that wind turbine generators can be designed to meet these requirements, with the added flexibility provided by the power electronic converter interfaces. In the presence of increased wind penetration, wind turbine generators can take over the functions normally carried out by conventional generators by means of supplementary controls. For each requirements and associated control function, supplementary loops are defined and design considerations are given. Typical implementations are illustrated and performance results presented. Specific implementation issues refer to the more common wind turbine generator technology, the Doubly Fed Induction Generator (DFIG). However, the designs can be extended to other converter-based wind turbine generators. The specific implementation of supplementary control loops will depend upon design criteria and choices defined and technologies adopted by wind turbine manufacturers.
[Show abstract][Hide abstract] ABSTRACT: Variable-speed wind generators are decoupled from the grid frequency by their power electronic interfaces. These generators do not naturally exhibit inertial response or any other form of frequency support in generation deficit situations. This study assesses and quantifies the capability of wind turbines with doubly-fed induction generators for emulating the inertial response of conventional generators by providing temporary extra active power on top of the available production. Special attention is given to the underproduction phase that follows overproduction due to rotor speed recovery. Results show that the inertial contribution strongly depends on the wind turbine operating conditions and the allowed underproduction level.
[Show abstract][Hide abstract] ABSTRACT: The increasing penetration of modern wind plants may cause primary frequency regulation to fall below acceptable levels, especially in isolated grids. This paper investigates the contribution of variable speed wind generators to short-term frequency support. First, the extractable inertial power from a DFIG wind turbine is quantified. Based on that, a controller is designed to transiently release part of the stored kinetic energy in the rotating masses. This can be very helpful in the critical few seconds following a load-generation mismatch. Through time-domain simulations, performance of the proposed controller is examined against earlier implementations of inertial response. Results show that the proposed controller is effective in arresting the initial frequency dip and capable of bringing together the advantages of earlier implementations for better integration of wind generators.
[Show abstract][Hide abstract] ABSTRACT: The paper examines two major implementations of inertial response in variable-speed wind turbine generators. Through time-domain simulations, these supplementary loops are compared based on their impact on grid frequency and the wind plant. Testing is performed on an isolated, hydrodominated power system benchmark, to which a DFIG-based wind plant is connected. The results show that when these implementations are combined, with proper coordination, the resulting controller is capable of superior performance.