Aime Francis Okou

An integrated reduced inertial sensor system — RISS / GPS for land vehicle

This paper demonstrates a low cost navigation solution that can efficiently work, in real-time, in denied GPS environment. It explores a reduced inertial sensor system (RISS) involving single-axis gyroscope and two-axis accelerometers together with a speed sensor to provide full navigation solution in denied GPS environments. With the assumption that the vehicle mostly stay in the horizontal plane, the vehicle speed obtained from the speed sensor are used together with the heading information obtained from the gyroscope to determine the velocities along the East and North directions. Consequently, the vehiclespsila longitude and latitude are determined. The position and velocity errors are estimated by Kalman filter (KF) relying on RISS dynamic error model and GPS position and velocity updates. The two accelerometers pointing towards the forward and transverse directions are used together with a reliable gravity model to determine the pitch and roll angles. This paper analyzes and discusses the merits and limitations of the proposed RISS system and its integration with GPS. The performance of the proposed method is examined by conducting road test experiment in a land vehicle.

Experimental Results on an Integrated GPS and Multisensor System for Land Vehicle Positioning

Global position system (GPS) is being widely used in land vehicles to provide positioning information. However, in urban canyons, rural tree canopies, and tunnels, the GPS satellite signal is usually blocked and there is an interruption in the positioning information. To obtain positioning solution during GPS outages, GPS can be augmented with an inertial navigation system (INS). However, the utilization of full inertial measurement unit (IMU) in land vehicles could be quite expensive despite the use of the microelectromechanical system (MEMS)-based sensors. Contemporary research is focused on reducing the number of inertial sensors inside an IMU. This paper explores a multisensor system (MSS) involving single-axis gyroscope and an odometer to provide full 2D positioning solution in denied GPS environments. Furthermore, a Kalman filter (KF) model is utilized to predict and compensate the position errors of the proposed MSS. The performance of the proposed method is examined by conducting several road tests trajectories using both MEMS and tactical grade inertial sensors. It was found that by using proposed MSS algorithm, the positional inaccuracies caused by GPS signal blockages are adequately compensated and resulting positional information can be used to steer the land vehicles during GPS outages with relatively small position errors.

Control of variable speed wind energy conversion system using a wind speed sensorless optimum speed MPPT control method

This paper presents a wind speed sensorless maximum power point tracking (MPPT) controller for variable speed wind energy conversion systems (WECS). The proposed controller generates at its output the optimum speed (OS) command for the speed control loop of the vector controlled machine side converter control system without requiring the knowledge of wind speed. The MPPT control of the WECS is achieved using optimum speed-power curve of the WECS taking into account the variation of the system efficiency while operating at various operating points due to the change in wind speed. The method is based on the fact that the optimum output power of a WECS at a certain wind speed depends upon the total mechanical power developed by the turbine and efficiency of the WECS at the corresponding OS of rotation of the turbine. The controller algorithm implementation requires the knowledge of turbine parameters and output power and air density as its inputs. The proposed concept is analyzed in a variable speed direct drive permanent magnet synchronous generator (PMSG) WECS. Experimental results show good tracking capability of the proposed controller.

A Power Oscillation Damping Control Scheme Based on Bang-Bang Modulation of FACTS Signals

In this paper, we develop a new damping control scheme for FACTS devices, using bang-bang modulation of FACTS signals. The scheme is used to attenuate quickly the systems most dominant mode which is identified using online Prony analysis. An analysis framework to evaluate the robustness of the control schemes to changes in operating conditions and to time-delay is also proposed. Simulation results on various test systems show that following large disturbances, the proposed control scheme is very effective to mitigate the power system critical modes of oscillation. Furthermore, the problem of control interactions is completely avoided with the proposed control scheme.

Nonlinear control of non-minimum phase systems: application to the voltage and speed regulation of power systems

A novel control scheme for nonlinear multi-input multi-output (MIMO) systems which have unstable zero dynamics is presented. The proposed approach consists of a state-feedback controller which simultaneously achieves the input-output linearization of the nonlinear system and stabilizes the internal dynamics using a Lyapunov-based scheme. The approach is used to design a nonlinear MIMO voltage and speed regulator for a single machine infinite bus power system.

Selection of input/output signals for wide area control loops

This paper studies the various aspects of input/output selection for wide-area damping controllers, targeted at the power system inter-area oscillation modes. The objectives is to choose a control loop which has large impact to a few selected modes, while does not affect the other system modes, hence the interactions problem can be greatly reduced. For this purpose, a new modal interaction index is proposed. Non linear simulations are also carried out to validate the modal analysis results.

Trends in naval ship propulsion drive motor technology

Electric drive propulsion system for naval ships is a very active and fast-growing research area driven by the rapid growth in power electronics and advancement in machine design. Propulsion motors and associated drive control systems form the heart of modern all-electric ships (AES). This paper presents the technology trends in propulsion drive motors for AES propulsion systems. The induction motor (IM), permanent magnet synchronous motor (PMSM), the high temperature superconducting synchronous motor (HTSSM) and the superconducting homopolar DC motor (SHDCM) are examined. These machines are preferred over others mainly because of their higher power densities and efficiencies, allowing a more compact and efficient propulsion system design.

Contribution of PV generators with energy storage to grid frequency and voltage regulation via nonlinear control techniques

This paper proposes a nonlinear control strategy for a hybrid PV-battery system insuring frequency and voltage support of the power system. The hybrid system includes a PV panel and battery connected to three-phase DC-AC inverter via DC-DC boost converter and bidirectional DC-DC boost converter. A synchronous generator represents the power grid. The voltage regulators control DC-DC boost converter and DC-AC inverter while the frequency regulator controls the bidirectional DC-DC boost converter. A conventional MPPT is used to adjust the reference for nonlinear PV voltage regulator. The voltage regulator is designed based on multi-input multi-output exact feedback linearization technique. It consists of a module that uses the terminal voltage deviation to generate q-axis voltage component. A module that maintains the DC-link voltage is also added to generate d-axis voltage component as well. The proposed frequency regulator includes a module that changes the reference signal of a battery current control module when the frequency deviation is significant. The battery current regulator is designed based on partial input-output feedback linearization strategy. The proposed control system is evaluated in simulation. The results reveal that with the proposed control scheme, the PV-battery generator reacts like a conventional synchronous generator when the grid frequency changes considerably.

An optimum speed MPPT controller for variable speed PMSG wind energy conversion systems

A maximum power point tracking (MPPT) controller for variable speed permanent magnet synchronous generator (PMSG) wind energy conversion systems (WECS) is proposed. The proposed controller, without requiring the knowledge of wind speed, generates at its output, the optimum speed (OS) reference signal for the speed control loop of the vector controlled machine side converter control system, thus, allowing maximum power extraction. Optimum speed - power curve of the WECS, used by the controller, takes into account the changes in system efficiency while operating at different operating points due to the change in wind speed. The method proposed is based on the fact that the optimum output power of a WECS at a certain wind speed depends upon the total mechanical power developed by the turbine and efficiency of the WECS at the corresponding OS of rotation of the turbine. The controller requires the active power and air density as its inputs to generate optimum reference speed. The proposed controller is validated experimentally in a variable speed direct drive PMSG WECS using a wind turbine emulator.

Control strategy insuring contribution of DFIG-Based wind turbines to primary and secondary frequency regulation

A new control strategy of DFIG-based wind turbines is proposed by this paper. The turbine is connected to a network where it contributes to primary and secondary frequency as well as voltage regulation. The originality of the proposed control strategy is that it allows the wind turbine to have a similar response to changes in grid frequency as that of a conventional generator. The effectiveness of the method is tested by simulation in Matlabs SimPowerSystems blockset.