An ANN-Based Power System Emergency Control Scheme in the Presence of High Wind Power Penetration
Green Energy and Technology
Re-evaluation of emergency control and protection schemes for distribution and transmission networks are one of the main problems posed by wind turbines in power systems. Change of operational conditions and dynamic characteristics influence the requirements to control and protection parameters. Introducing a significant wind power into power systems leads to new undesirable oscillations. The local and inter-modal oscillations during large disturbances can cause frequency and voltage relays to
... easure a quantity at a location that is different to the actual underlying system voltage and frequency gradient. From an operational point of view, this issue is important for those networks that use the protective voltage and frequency relays to re-evaluate their tuning strategies. In this chapter, an overview of the key issues in the use of high wind power penetration in power system emergency control is presented. The impact of wind power fluctuation on system frequency, voltage and frequency gradient is analyzed, the need for the revising of tuning strategies for frequency protective relays, automatic under-frequency load shedding (UFLS) and under-voltage load shedding (UFLS) relays are also emphasized. In the present chapter, necessity of considering both system frequency and voltage indices to design an effective power system emergency control plan is shown. Then, an intelligent artificial neural network (ANN) based emergency control scheme considering the dynamic impacts of wind turbines is proposed. In the developed algorithm, following an event, the related contingency is determined by an appropriate ANN using the online measured tie-line powers. A suitable set of voltage sensitivity indices based on a comprehensive voltage stability analysis in the presence of the wind turbines is proposed. Another intelligent ANN is used to A u t h o r P e r s o n a l C o p y A u t h o r P e r s o n a l C o p y 216 H. Bevrani and A.G. Tikdari examine the stability margin by estimating the system power-voltage (P-V) curves. Finally, the system frequency gradient, voltage sensitivity indices and stability information are properly used by an effective load shedding algorithm. The proposed emergency control scheme and discussions are supplemented by computer nonlinear simulations on the IEEE 9-bus test system. In the present chapter, a new intelligent emergency control is proposed. The developed emergency control scheme is summarized in Fig. 10 . Following an event, A u t h o r P e r s o n a l C o p y L. Wang et al. (Eds): Wind Power Systems, Green Energy and Technology, pp. 297-335. springerlink.com Abstract. This chapter presents design of intelligent controllers for a wind-diesel power system equipped with a wind turbine driving an induction generator. The goal for the design is to maintain a good power quality under varying wind and load conditions. On the other hand, the controller has to show acceptable closedloop performance including stability, robustness, optimal energy, and steady-state and transient performance at a permissible level of control effort. Moreover, such a controller has to be highly adaptive to various operating conditions and independent of model parameters that might be uncertain. Toward these goals the concepts of fuzzy-robust controller and fuzzy-neural hybrid controller are applied to design integrated non-linear controllers to provide control input for excitation system and governor system simultaneously. A u t h o r P e r s o n a l C Abstract. Control systems for variable-speed wind turbines (WTs) are continuously evolving toward innovative and more efficient solutions. Among the various techniques, fuzzy logic is gaining reputation due to its simplicity and effectiveness. In this chapter, after a review of fuzzy logic based control applied to wind energy conversion systems, a sensorless peak power tracking control for maximum wind energy extraction and a voltage control allowing compensation of voltage variations at the WT connection point are proposed. Both the controllers are based on fuzzy logic. Before that, a data-driven design methodology is introduced, in order to generate the "best" Takagi-Sugeno-Kang fuzzy model, for the maximum power exploitation from a variable-speed wind turbine. The performance of the variable speed wind systems employing a synchronous generator and a full scale converter endowed with the proposed fuzzy controllers are tested under some common operating conditions. A u t h o r P e r s o n a l C o p y A u t h o r P e r s o n a l C o p y L. Wang et al. (Eds): Wind Power Systems, Green Energy and Technology, pp. 367-382. springerlink.com Abstract. This chapter focuses on the implementation of the TS (Tagaki-Sugino) fuzzy controller for the Doubly Fed Induction Generator (DFIG) based wind generator. The conventional PI control loops for mantaining desired active power and DC capacitor voltage is compared with the TS fuzzy controllers. . DFIG system is represented by a third-order model where electromagnetic transients of the stator are neglected. The effectiveness of the TS-fuzzy controller on the rotor speed oscillations and the DC capacitor voltage variations of the DFIG damping controller on converter ratings is also investigated. The results from the time domain simulations are presented to elucidate the effectiveness of the TS-fuzzy controller over the conventional PI controller in the DFIG system. The proposed TS-fuzzy controller can improve the fault ride through capability of DFIG compared to the conventional PI controller. A u t h o r P e r s o n a l C o p y A u t h o r P e r s o n a l C o p y L. Wang et al. (Eds): Wind Power Systems, Green Energy and Technology, pp. 383-405. springerlink.com Abstract. The wind systems have become more and more complex, namely due to increase of the turbines and wind farms power, what implies higher significance of either system non-linearities or system multivariable characteristics. It adds as direct consequence from wind systems high power that wind farms are becoming active elements in the wind power system. So the wind system performance and behaviour become critical elements of the grid. The performance of the turbine control is improved keeping on the power coefficient always near to maximum value, optimizing the energy extraction from the wind speed and so increasing the global system efficiency. It adds that the operation within a wind farm context demands for optimization of the whole operation. This chapter analyses wind systems biased by the increasing of wind power penetration into the grid and intends to deal with the requirement of controlling either each wind system or wind farm pointing out a methodology to design fuzzy controllers in order to optimize turbine operation and farm operation taking in accounting its operation as power system element. Some results are carried out to validate main conclusions, namely the need of including in the control process data on very short-term wind condition through adopting new techniques of real-time forecasting.