Daniel Roye

Energy-Reliability Optimization of Wind Energy Conversion Systems by Sliding Mode Control

This paper describes a manner in which the energy-reliability optimization of wind energy conversion systemspsila operation can be achieved by means of the sliding mode control. The proposed approach aims at designing a tradeoff between maximizing the power harvested from wind by a horizontal-axis-grid-connected variable-speed doubly-fed-induction-generator-based wind power system and minimizing its mechanical stress. An appropriate sliding surface has been found in the speed-power plane, which allows the operation more or less close to the optimal regimes characteristic. Thus, by torque controlling the generator, an energy-reliability optimization of the wind turbine behavior is performed. The proposed control law is validated by both off-line and real-time simulation; the latter on a dedicated experimental rig, based upon the hardware-in-the-loop simulation concept. The results show that the control objective is fully accomplished.

Hardware-in-the-Loop-based Simulator for a Class of Variable-speed Wind Energy Conversion Systems: Design and Performance Assessment

This paper focuses on the design, building, error evaluation, and performance assessment of a physical simulator for a variable-speed wind energy conversion system (WECS). Such simulator, dedicated to control algorithms validation, must replicate the dynamical behavior of the WECS physically in real time. To this end, software parts, which model subsystems of the plant, and hardware parts, taken as they are from the plant, are closed-loop connected, thus implementing a hardware-in-the-loop (HIL) simulator. The simulator interacts with a software-simulated environment-in this case, the wind velocity-in order to run experiments under controllable conditions. Controllers to be tested interact directly with the hardware part of the simulator, thus better approaching the behavior of the real-world WECS. A complete grid-connected generation chain employing a horizontal-axis fixed-pitch three-bladed rotor permanent-magnet-synchronous-generator-based WECS is chosen as example for the design and performance assessment of an HIL simulator, both in frequency and time domain.

Adaptive MPPT Applied to Variable-Speed Microhydropower Plant

Variable-speed microhydropower energy systems have recently received significant attention in the renewable energy field, due to its overall efficiency and great potential available worldwide. This emergent technology combined with maximum power point tracking (MPPT) techniques allows us to replace the burden classical governing mechanical systems, being a very effective way of ensuring high energy efficiency when operating in free water flows. In this paper, a variable-speed microhydropower plant based on a semi-Kaplan turbine is employed and a novel adaptive high-performance MPPT technique is proposed. This allows high tracking quality due to superior dynamic response and high output power quality due to steady-state oscillations cancellation. This approach has been experimentally validated by using a dedicated test rig.

Real-Time Analysis of the Control Structure and Management Functions of a Hybrid Microgrid System

Due to their non-controllable nature renewable energy sources (RES) participation in the network operation is currently rather deficient. In this paper the microgrid concept is presented as an innovative solution to improve RES integration into the grid. In this study an example of a hybrid microgrid composed of RES generators and a programmable support device together with a centralized management system is considered. The microgrid can operate both in grid-connected mode and in islanded mode. Its control structure as well as its management functions to assure successful performances in both operation modes and in the transitions between them are analyzed in detail and tested in real-time conditions with a physical control device

Optimal operation for a wind-hydro power plant to participate to ancillary services

To limit the impact of the intermittence of wind power, a water storage ability of the hydraulic storage plant combined with a wind power plant, called the wind-hydro power system (WS), is used. The main objective is to limit the active power output variations of wind energy resource taking into account the grid needs and the available stored energy. The problem is formulated as an optimization problem with constraints by using the linear programming (LP). Based on the forecast information of the wind power, the power demand of the grid, the penalty cost, an optimal operation strategy is proposed to help the WS system for better using of wind energy and storage management. An example study case is presented. A comparison with classical approach of economic gain is also given to illustrate the interest of the proposed method.

Micro-hydro water current turbine control for grid connected or islanding operation

This paper deals with the up-to-date issue of renewable energy production systems. For their exploitation these systems need advanced integrated controls that include power electronics facilities. A study of a micro- hydro water turbine based energy production system is presented. This study is oriented on controlling the micro- hydro generation system in grid-connected and in islanded operation. For each of this two operation modes, the roles of power electronics converters have been assigned and control structures have been proposed. Simulations and experimental tests have been realized to verify the feasibility of the system and the response of the control loops.

Reactive power control for variable speed wind turbines to low voltage ride through grid code compliance

This paper is dealing with the reactive power management of two kinds of variable speed wind turbine (WT) technologies in order to respect the grid code requirements during voltage dips. Nowadays, the WT systems are asked to fulfil with many grid connection requirements, especially to provide reactive power during dip voltage with the aim of better voltage recovering. Specific controls applied to Double Fed Induction generator WT (DFIG) and Permanent Magnet Synchronous Generator fully interfaced (PMSG) are proposed in this paper to meet with these requirements. The control laws are studied through simulations; results analysis shows their efficiency and their limits.

Management and Control of Operating Regimes of Cross-Flow Water Turbines

This paper deals with a generation system based on cross-flow water turbines (CFWTs) operating in a river stream. It is equipped with a permanent-magnet synchronous generator and can feed a power grid or an insulated load through a back-to-back power electronics converter. This paper concerns the control of these two operating regimes with focus on the manner of achieving a soft switching between them, in order to ensure the balance between the generated and the provided power and to alleviate transients. The control laws and the switching sequences have been experimentally validated on a real-time CFWT simulator equipped with the same type of generator and power electronics converter. This paper aims at offering a synthetic vision of how the CFWT-based generation system should be controlled across the main operating regimes in order to preserve its continuity of service.

Modeling and control of variable-speed micro-hydropower plant based on Axial-flow turbine and permanent magnet synchronous generator (MHPP-PMSG)

This paper presents a grid connected variable-speed micro hydropower plant, based on a micro Axial-flow turbine (semi-Kaplan) coupled to permanent magnet synchronous generator (MHPP-PMSG); Two back-to-back Voltage Source Inverters are interfacing the generator. The main idea is to show the feasibility and interest of variable speed operation of the considered system. The scope of the presented work is similar to that used for wind and tidal generators. A MPPT algorithm (perturb & Observe) is used for controlling the MHPP-PMSG for optimizing the operating efficiency by finding the optimal rotation speed. PI controllers are used to control the power electronics interface converters and DC-link voltage. The proposed scheme of MHPP-PMSG has been simulated under Matlab Simulink and the results obtained show the benefit of variable speed for micro hydropower.

Operation of Grid-Connected Cross-Flow Water Turbines in the Stall Region by Direct Power Control

This paper proposes a new method of controlling cross-flow-water-turbine (CFWT)-based generation systems, having fixed pitch, by power regulation. The method consists of directly controlling the electrical generator power, as imposed by a dispatcher, without employing an inner rotational speed control loop. The proposed control approach represents the base for the operation framework (i.e., output power and rotational speed limitations, start-up, and stopping) for the entire operating range up to the cut-out water flow speed. A permanent-magnet synchronous generator is used in this paper. The system is operated at low rotational speed values, i.e., in the so-called hydrodynamic stall region, where mechanical and hydrodynamic stresses are lower. Given that this region corresponds to an unstable dynamic behavior, the power regulation relies upon an inner loop of rotational-speed stabilization. Consequently, the innermost (electrical machine current) control loop is fed by a reference having two components, namely, the driving and stabilization currents. The embodied control laws and the output power and rotational speed limitation sequences have been experimentally validated on a real-time simulator of CFWT-based generation systems.