Effects of POD control on a DFIG wind turbine structural system

This paper investigates the effects power oscillation damping (POD) controller could have on a wind turbine structural system. Most of the published work in this area has been done using relatively simple aerodynamic and structural models of a wind turbine which cannot be used to investigate the detailed interactions between electrical and mechanical components of the wind turbine. Therefore, a detailed model that combines electrical, structural and aerodynamic characteristics of a grid-connected Doubly Fed Induction Generator (DFIG) based wind turbine has been developed by adapting the NREL (National Renewable Energy Laboratory) 5MW wind turbine model within FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code. This detailed model is used to evaluate the effects of POD controller on the wind turbine system. The results appear to indicate that the effects of POD control on the WT structural system are comparable or less significant as those caused by wind speed variations. Furthermore, the results also reveal that the effects of a transient three-phase short circuit fault on the WT structural system are much larger than those caused by the POD controller

Nonlinear self-tuning control for power oscillation damping

Power systems exhibit nonlinear behavior especially during disturbances, necessitating the application of appropriate nonlinear control techniques. Lack of availability of accurate and updated models for the whole power system adds to the challenge. Conventional damping control design approaches consider a single operating condition of the system, which are obviously simple but tend to lack performance robustness. Objective of this research work is to design a measurement based self-tuning controller, which does not rely on accurate models and deals with nonlinearities in system response. Designed controller is required to ensure settling of inter-area oscillations within 10−12s, following disturbance such as a line outage. The neural network (NN) model is illustrated for the representation of nonlinear power systems. An optimization based algorithm, Levenberg-Marquardt (LM), for online estimation of power system dynamic behavior is proposed in batch mode to improve the model estimation. Careful study shows that the LM algorithm yields better closed loop performance, compared to conventional recursive least square (RLS) approach with the pole-shifting controller (PSC) in linear framework. Exploiting the capability of LM, a special form of neural network compatible with feedback linearization technique, is applied. Validation of the performance of proposed algorithm is done through the modeling and simulating heavy loading of transmission lines, when the nonlinearities are pronounced. Nonlinear NN model in the Feedback Linearization (FLNN) form gives better estimation than the autoregressive with an external input (ARX) form. The proposed identifier (FLNN with LM algorithm) is then tested on a 4−machine, 2−area power system in conjunction with the feedback linearization controller (FBLC) under varying operating conditions. This case study indicates that the developed closed loop strategy performs better than the linear NN with PSC. Extension of FLNN with FBLC structure in a multi-variable setup is also done. LM algorithm is successfully employed with the multi-input multi-output FLNN structure in a sliding window batch mode, and FBLC controller generates multiple control signals for FACTS. Case studies on a large scale 16−machine, 5−area power system are reported for different power flow scenarios, to prove the superiority of proposed schemes: both MIMO and MISO against a conventional model based controller. A coefficient vector for FBLC is derived, and utilized online at each time instant, to enhance the damping performance of controller, transforming into a time varying controller

Stability Analysis and Control of Nonlinear Power System Oscillations

This work investigates the nonlinear oscillatory behaviors of multi-machine power systems. New model-based and measurement-based approaches are proposed for stability analysis and control of nonlinear oscillations. For stability analysis, a recently proposed model-based nonlinear oscillation analysis method, nonlinear modal decoupling (NMD), is investigated on its ability in capturing the stability information of a multi-machine power system. From the differential-equation model of the power system, the NMD inversely constructs a set of 1-degree-of-freedom nonlinear oscillators, referred to as decoupled oscillators or subsystems, with each one corresponding to an oscillation mode of the original system. It is shown that retaining high order polynomial terms in the differential equation of each decoupled oscillator can make it more accurately represent the nonlinear modal dynamics and conditions of stability regarding the corresponding oscillation mode. For power system analysis, keeping the polynomial terms up to the 3rd-order during the decoupling is acceptable for the purpose of approximating assessment for transient stability. A transient stability analysis approach is proposed to apply the NMD for early warning of transient instability caused by inter-area oscillations. This new approach simplifies the real-time monitoring of the whole power system to the monitoring of only a few critical modes by checking the dynamics of the corresponding decoupled oscillators and their stability boundaries. Thus, when a critical oscillation mode is going to evolve into a mode of instability, this approach can provide early warning to the power system operator. For stability control, a direct damping feedback control method is proposed to control the damping ratio of a target dominant mode to closely follow a pre-set value by utilizing power converter-interfaced energy resources, e.g. battery-based energy storage devices. The direct damping feedback controller is designed to consist of a proportional-integral controller, a low-pass filter and a power system module that includes a reduced single-oscillator power system equivalent on the target oscillation mode and its measurement-based damping estimation algorithm. The parameters of the PI controller are optimized by considering the trade-off between the requirements of robustness and control performance. The power system module is represented by a transfer function based on the zeroth-order parametric resonance phenomenon. By identifying a nonlinear oscillator to fit dynamics of the target mode under both small and large disturbances, the measurement-based real-time damping estimation algorithm provides a feedback signal to the direct damping feedback controller. Numerical studies on the 48-machine Northeast Power Coordinating Council system validate the effectiveness of the proposed damping control method

Passivity - Based Control and Stability Analysis for Hydro-Solar Power Systems

Los sistemas de energía modernos se están transformando debido a la inclusión de renovables no convencionales fuentes de energía como la generación eólica y fotovoltaica. A pesar de que estas fuentes de energía son buenas alternativas para el aprovechamiento sostenible de la energía, afectan el funcionamiento y la estabilidad del sistema de energía, debido a su naturaleza inherentemente estocástica y dependencia de las condiciones climáticas. Además, los parques solares y eólicos tienen una capacidad de inercia reducida que debe ser compensada por grandes generadores síncronos en sistemas hidro térmicos convencionales, o por almacenamiento de energía dispositivos. En este contexto, la interacción dinámica entre fuentes convencionales y renovables debe ser estudiado en detalle. Para 2030, el Gobierno de Colombia proyecta que el poder colombiano El sistema integrará en su matriz energética al menos 1,2 GW de generación solar fotovoltaica. Por esta razón, es necesario diseñar controladores robustos que mejoren la estabilidad en los sistemas de energía. Con alta penetración de generación fotovoltaica e hidroeléctrica. Esta disertación estudia nuevas alternativas para mejorar el sistema de potencia de respuesta dinámica durante y después de grandes perturbaciones usando pasividad control basado. Esto se debe a que los componentes del sistema de alimentación son inherentemente pasivos y permiten formulaciones hamiltonianas, explotando así las propiedades de pasividad de sistemas eléctricos. Las principales contribuciones de esta disertación son: una pasividad descentralizada basada control de los sistemas de control de turbinas hidráulicas para sistemas de energía de múltiples máquinas para estabilizar el rotor acelerar y regular el voltaje terminal de cada sistema de control de turbinas hidráulicas en el sistema como, así como un control basado en PI pasividad para las plantas solares fotovoltaicas