Minghui Yin

Robust Dispatch of High Wind Power-Penetrated Power Systems Against Transient Instability

High-level wind power integration can dramatically affect a power systems dynamic performance and introduce significant uncertainties to systems operation. This paper proposes a robust dispatch method to optimize the power systems operation state while sustaining its transient stability with highly variable and stochastic wind power generation. The problem is first modeled as an augmented optimal power flow model with uncertain variables and differential-algebraic equations. Then, the stability constraints are converted to approximately-equivalent algebraic equations based on one-machine-infinite-bus equivalence technique and trajectory sensitivity analysis. Next, the uncertain wind power generation is represented by a small number of strategically selected testing scenarios. Finally, a decomposition-based computation strategy is developed to divide the original model into a master problem and a series of slave problems which are solved iteratively. Using industry-grade system dynamic models and simulation software, the proposed method is tested on the New England 39-bus system and Nordic32 system, showing high performance on economic optimality, stability robustness, and computational efficiency.

Turbine Stability-Constrained Available Wind Power of Variable Speed Wind Turbines for Active Power Control

The active power control (APC) of variable-speed wind turbines (VSWT) is increasingly required to support the power system operation and control. Besides control strategies, the power reference also exerts a significant influence upon APC performance. Due to the VSWT instability, the optimistic reference which is usually determined according to the conventional available wind power (AWP) based on maximum power point, cannot be sustainably maintained over the dispatch period. This may results in frequent interruption of power reference tracking. On the other hand, the conservative reference will easily lead to excessive pitch regulation. In this letter, the turbine stability-constrained available wind power is defined and analyzed to sustain the power generation of scheduled wind turbines at a maximum level. Simulation results show that the VSWT dispatched according to the proposed AWP can maintain stable power generation with less pitch action and therefore better support secure and economic power system operations.

A new measure of the degree of controllability for linear system with external disturbance and its application to wind turbines

This paper is concerned with the measure of degree of controllability (DOC) for linear system with external disturbance. A new measure of DOC, in which the initial condition is regarded as a random vector, is proposed in this paper by solving the fixed-time expected minimum-energy transfer control problem. Since this new measure is dependent on the statistical information of initial condition rather than its estimated value, it is more suitable to apply the proposed measure in the design and optimization of the structural parameters of controlled plants. Furthermore, the simulations on the NREL (National Renewable Energy Laboratory) CART3 wind turbine demonstrate that the relation of the proposed measure to turbine parameters (including rotor inertia and optimum tip speed ratio) coincides with that of the MPPT efficiency to turbine parameters. This indicates that the proposed measure is applicable to guide the design and optimization of the structural parameters of wind turbines. Meanwhile, a mass-spring-damper system is also simulated to validate the proposed measure.

Maximum Wind Energy Extraction for Variable Speed Wind Turbines With Slow Dynamic Behavior

Currently, the maximization of wind energy extraction for variable speed wind turbines (VSWT) is usually transformed into the maximum power point tracking (MPPT), i.e., the rotor speed is continuously regulated to follow the optimal rotor speed as a function of wind speed. However, it has been recognized that the increasing rotor inertia and the high fluctuation of wind speed result in the turbines’ being unable to instantly track the optimal rotor speed and tracking losses. This indicates that maximizing wind energy extraction based on MPPT is not suitable for large-inertia VSWTs under turbulence. Moreover, it is revealed and demonstrated in this letter that a conservative speed reference matching up with the slow dynamic behavior of VSWTs can effectively improve wind energy production, which provides a new approach for maximizing wind energy extraction of VSWTs under turbulence.

Integrated structure and maximum power point tracking control design for wind turbines based on degree of controllability

A linearization model is obtained for a three-bladed horizontal-axis wind turbine (HAWT) consisting of blades and a drive-train. Sensitivity analysis of the degree of controllability (DOC) and maximum power point tracking (MPPT) efficiency with respect to the structural parameters of wind turbines is discussed by numerical simulations. It is observed from the simulation results that higher MPPT efficiency can be achieved with the increase of DOC. Based on the observation, this paper proposes a new integrated design method based on DOC to design and optimize the structural parameters of a HAWT. The designed turbine is tested by the commercial simulation software of wind turbines named Bladed. It is observed from simulations that when using the identical MPPT control strategy, the wind turbine whose structural parameters are optimized for a larger value of DOC can achieve higher MPPT performance.

Variable parameter nonlinear control for maximum power point tracking considering mitigation of drive-train load

Since mechanical loads exert a significant influence on the life span of wind turbines, the reduction of transient load on drive-train shaft has received more attention when implementing a maximum power point tracking U+0028 MPPT U+0029 controller. Moreover, a trade-off between the efficiency of wind energy extraction and the load level of drive-train shaft becomes a key issue. However, for the existing control strategies based on nonlinear model of wind turbines, the MPPT efficiencies are improved at the cost of the intensive fluctuation of generator torque and significant increase of transient load on drive train shaft. Hence, in this paper, a nonlinear controller with variable parameter is proposed for improving MPPT efficiency and mitigating transient load on drive-train simultaneously. Then, simulations on FAST U+0028 Fatigue, Aerodynamics, Structures, and Turbulence U+0029 code and experiments on the wind turbine simulator U+0028 WTS U+0029 based test bench are presented to verify the efficiency improvement of the proposed control strategy with less cost of drive-train load.