Greg Semrau | Rochester Institute of Technology (original) (raw)

Papers by Greg Semrau

ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control, Volume 1, 2011

The key control problems associated with variable speed wind turbines are maximization of extract... more The key control problems associated with variable speed wind turbines are maximization of extracted energy when operating below the rated wind speed, and power and speed regulation when operating above the rated wind speed. In this paper, we develop a nonlinear systems framework to address these problems. The framework is used to visualize and analyze the equilibria of the wind turbine as its operating regimes and controllers change.

Journal of Dynamic Systems, Measurement, and Control, 2015

One of the key control problems associated with variable speed wind turbines is maximization of e... more One of the key control problems associated with variable speed wind turbines is maximization of energy extraction when operating below the rated wind speed and power regulation when operating above the rated wind speed. In this paper, we approach these problems from a nonlinear systems perspective. For below rated wind speeds we adopt existing work appearing in the literature and provide further insight into the characteristics of the resulting equilibrium points. For above rated wind speeds, we propose a nonlinear controller and analyze the stability property of the resulting * Address all correspondence to this author. 1 equilibria. We propose a method for switching between the two regimes that ensures continuity of control input at the transition point. We perform an analytical study of the stability of the equilibria of the closed loop system under switching control. The control laws are verified using a wind turbine model with two different wind speed profiles.

As battery technology has matured, the overwhelming focus has been on increasing energy density w... more As battery technology has matured, the overwhelming focus has been on increasing energy density while power density remains a primary driver for various niche markets. Flight control surfaces (including aircraft and launch vehicle actuation systems) are a primary example of an application that requires high power density energy storage that could benefit from increased capability.

One of the key control problems associated with variable speed wind turbine systems is maximizati... more One of the key control problems associated with variable speed wind turbine systems is maximization of energy extraction when operating below the rated wind speed and power regulation when operating above the rated wind speed. In this paper, we approach these problems from a nonlinear systems perspective. For below rated wind speeds we adopt existing work appearing in the literature and provide further insight into the characteristics of the resulting equilibrium points of the closed-loop system. For above rated wind speeds, we propose a nonlinear controller and analyze the stability property of the resulting equilibria. We also propose a method for switching between the two operating regimes that ensures continuity of control input at the transition point. The control laws are verified using a wind turbine model with a standard turbulent wind speed profile that spans both operating regimes. NOMENCLATURE P Extracted aerodynamic power, W ρ Density of air, kg/m 2 R r Rotor radius, m A Swept area of rotor (= πR 2 r ), m 2 V w Wind velocity, m/s C p Rotor efficiency β Blade pitch, rad λ Tip speed ratiȯ θ r ,θ g Rotor and generator angular speeds, rad/s * Address all correspondence to this author. J r , J g Rotor and generator inertia, kg m 2 D r , D g Damping of rotor and generator inertia, kg m 2 /s D ls , D hs Damping of rotor and generator shafts, kg m 2 /s K ls , K hs Spring constants of rotor and generator shafts, kg m 2 /s 2 T r , T g Rotor and generator torques, kg m 2 /s 2 GR Gearbox transmission ratio V g , i g , R g Generator voltage, current and resistance, V , A, Ω K v , K i Generator back e.m.f and torque constants, V s, Nm/A

ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control, Volume 1, 2011

The key control problems associated with variable speed wind turbines are maximization of extract... more The key control problems associated with variable speed wind turbines are maximization of extracted energy when operating below the rated wind speed, and power and speed regulation when operating above the rated wind speed. In this paper, we develop a nonlinear systems framework to address these problems. The framework is used to visualize and analyze the equilibria of the wind turbine as its operating regimes and controllers change.

Journal of Dynamic Systems, Measurement, and Control, 2015

One of the key control problems associated with variable speed wind turbines is maximization of e... more One of the key control problems associated with variable speed wind turbines is maximization of energy extraction when operating below the rated wind speed and power regulation when operating above the rated wind speed. In this paper, we approach these problems from a nonlinear systems perspective. For below rated wind speeds we adopt existing work appearing in the literature and provide further insight into the characteristics of the resulting equilibrium points. For above rated wind speeds, we propose a nonlinear controller and analyze the stability property of the resulting * Address all correspondence to this author. 1 equilibria. We propose a method for switching between the two regimes that ensures continuity of control input at the transition point. We perform an analytical study of the stability of the equilibria of the closed loop system under switching control. The control laws are verified using a wind turbine model with two different wind speed profiles.

As battery technology has matured, the overwhelming focus has been on increasing energy density w... more As battery technology has matured, the overwhelming focus has been on increasing energy density while power density remains a primary driver for various niche markets. Flight control surfaces (including aircraft and launch vehicle actuation systems) are a primary example of an application that requires high power density energy storage that could benefit from increased capability.

One of the key control problems associated with variable speed wind turbine systems is maximizati... more One of the key control problems associated with variable speed wind turbine systems is maximization of energy extraction when operating below the rated wind speed and power regulation when operating above the rated wind speed. In this paper, we approach these problems from a nonlinear systems perspective. For below rated wind speeds we adopt existing work appearing in the literature and provide further insight into the characteristics of the resulting equilibrium points of the closed-loop system. For above rated wind speeds, we propose a nonlinear controller and analyze the stability property of the resulting equilibria. We also propose a method for switching between the two operating regimes that ensures continuity of control input at the transition point. The control laws are verified using a wind turbine model with a standard turbulent wind speed profile that spans both operating regimes. NOMENCLATURE P Extracted aerodynamic power, W ρ Density of air, kg/m 2 R r Rotor radius, m A Swept area of rotor (= πR 2 r ), m 2 V w Wind velocity, m/s C p Rotor efficiency β Blade pitch, rad λ Tip speed ratiȯ θ r ,θ g Rotor and generator angular speeds, rad/s * Address all correspondence to this author. J r , J g Rotor and generator inertia, kg m 2 D r , D g Damping of rotor and generator inertia, kg m 2 /s D ls , D hs Damping of rotor and generator shafts, kg m 2 /s K ls , K hs Spring constants of rotor and generator shafts, kg m 2 /s 2 T r , T g Rotor and generator torques, kg m 2 /s 2 GR Gearbox transmission ratio V g , i g , R g Generator voltage, current and resistance, V , A, Ω K v , K i Generator back e.m.f and torque constants, V s, Nm/A