Autonomous Wind-diesel System Research Articles

Implementation of Distributed Fuzzy Load Control to an Autonomous Wind Diesel System

Many autonomous power systems are powered by diesel generators alone, which results in greater operating costs than interconnected grids. It is therefore desirable to integrate renewable energy sources such as wind into these mini grids. However, due to the fluctuating power generation from the wind resource, the varying load profile and the relatively low system inertia, technical difficulties arise in terms of system stability and efficient operation. Typically the penetration of wind energy on such systems is limited to 30%. Distributed intelligent load control can be used to increase wind penetration and cut diesel fuel consumption, whilst maintaining system stability. This thesis describes the development and application of a distributed intelligent load control system. The development of a self-tuning fuzzy controller and the construction of a laboratory wind-diesel test rig are discussed. The development of a dynamic Wind-Diesel computer model is also described. Finally the results of tests carried out on a Wind-Diesel system consisting of a 45kW stall regulated wind turbine and a 48kW diesel generator are discussed. The results were encouraging demonstrating that distributed fuzzy load control is a low cost and effective technique, which can be applied to small or large hybrid systems. The simulation results are developed by MATLAB.

Performance Comparison of Reactive Power Controllers in Autonomous Wind-Diesel System

Performance Comparison of Reactive Power Controllers in Autonomous Wind-Diesel System

Dynamic Modeling of Autonomous Wind–Diesel system with Fixed-Speed Wind Turbine

Dynamic Modeling of Autonomous Wind–Diesel system with Fixed-Speed Wind Turbine

Smooth transition from wind only to wind diesel mode in an autonomous wind diesel system with a battery-based energy storage system

High wind penetration wind diesel hybrid systems (WDHS) have three modes of operation: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The WDHS presented in this article consists of a wind turbine generator (WTG), a diesel engine (DE), a synchronous machine (SM), the consumer load, a battery-based energy storage system (BESS), a discrete dump load (DL) and a distributed control system (DCS). The DE can be engaged (DO and WD modes)/disengaged (WO mode) from the SM by means of a clutch. The DCS consists of a sensor node, which measures the SM and DE speeds, calculates the reference active power P REF necessary to balance the active power in the WDHS and communicates this P REF value with a message to the BESS and DL actuator nodes. In the WO mode, the power sources are the WTG and the BESS (temporary) and if there is an active power shortfall, the DCS, to prevent a frequency collapse, must order to start the DE, wait until the DE reaches the SM speed and lock the clutch, changing to the WD mode. With the clutch locked, the combined actuation of the DE+BESS will raise the system frequency to the rated value. This WO to WD transition is simulated in this article showing graphs for frequency, voltage and active powers for the elements of the system. These graphs are compared with the ones obtained if the BESS does not actuate in WD mode. The comparison results show that with the BESS actuation in WD mode the settling time is reduced a 50%, the over and under shooting in the system frequency are eliminated and the system voltage variations are reduced a 40%.

AN AUTONOMOUS WIND-DIESEL SYSTEM WITH UNCOOLED COMPRESSED AIR STORAGE

Energy systems based on wind as an energy source, are affected by the fluctuations in the generation and the variable consumer load demand. In this case, energy storage systems play a very important role in matching up generation and demand. Wind turbine can not supply the required energy continuously and the storage capacity is also limited. To overcome these difficulties, a diesel generator set (DGS) can be connected in parallel with the wind energy conversion system (WECS). In this study, the concept and performance analysis of an autonomous wind-diesel system with uncooled compressed air storage (UCAS) are presented. The main objective of this study is to design a realistic UCAS system that would maximize the wind energy penetration and thereby would minimize the fuel consumption. Computer simulation tools are crucial in modeling and simulating such systems. Various techniques can be used to improve the overall operating efficiency. Control, management, system integration, and measurement are key activities, which must be implemented in the system development. A mathematical model is developed and simulation has been applied to study the system performance. The necessary control system is analyzed and interesting simulation results are obtained.

Neuro-fuzzy control for autonomous wind–diesel systems using biomass

This paper deals with the development of a neuro-fuzzy controller for a wind–diesel system composed of a stall regulated wind turbine with an induction generator connected to an ac bus-bar in parallel with a diesel generator set having a synchronous generator. A gasifier is capable of converting tons of wood chips per day into a gaseous fuel that is fed into a diesel engine. The controller inputs are the engine speed error and its derivative for the governor part of the controller, and the voltage error and its derivative for the automatic voltage regulator. These are readily measurable quantities leading to a simple controller which can be easily implemented. It is shown that by tuning the fuzzy logic controllers, optimal time domain performance of the autonomous wind–diesel system can be achieved in a wide range of operating conditions compared to fixed-parameter fuzzy logic controllers and PID controllers.

Dynamic characteristics of autonomous wind–diesel systems

In this paper the dynamics of a small autonomous system, comprising a diesel generator and a wind turbine, are investigated. The analysis is performed both in the frequency and time domain, using simplified models of the system components and taking into account the diesel engine speed governor and the wind turbine pitch controller (for pitch regulated machines). The investigation is extended to include different types of wind turbines, equipped with induction or synchronous generator and using pitch or stall regulation, as well as operation of the wind turbine in an autonomous or infinite system. The objective is to determine the main factors affecting the behaviour of the system and to illustrate the effect of the speed governor and pitch controller settings on the expected performance. Particular emphasis is placed on identifying the main modes of the system and determining their dependence on the controllers' parameters. A comparative assessment of the dynamic characteristics of different types of wind turbines is also included and the operation of the wind turbine in a small system and against an infinite bus is addressed and discussed.

An advanced control system for the optimal operation and management of medium size power systems with a large penetration from renewable power sources

An advanced control system for the optimal operation and management of autonomous wind-diesel systems is presented. This system minimises the production costs through an on-line optimal scheduling of the power units, which takes into account the technical constraints of the diesel units, as well as short-term forecasts of the load and renewable resources. The power system security is maximised through on-line security assessment modules, which enable the power system to withstand sudden changes in the production of the renewable sources. The control system was evaluated using data from the island of Lemnos, where it has been installed and operated since January 1995.

A flywheel variator energy storage system

Flywheels are proving to be an ideal form of energy storage on account of their high power density, cycle life and storage efficiency. This paper describes an energy storage system comprised of a steel flywheel and mechanical variator, designed to provide the main drive power for a hybrid railcar which can be charged either rapidly at stops on the route, or continuously at a constant rate from an on-board primary low power source. By operation on rails at urban speeds, with brake energy recovery, energy losses and consumption are minimised. A further application of the system is in load matching in autonomous wind diesel systems, as a means of load levelling and absorbing fluctuations in wind power. The results of laboratory tests on the energy storage unit are presented, along with the analysis of performance tests on a hybrid flywheel-battery rail vehicle.

Petri net based specification of a real-time supervisory controller for an autonomous wind-diesel system

The feasibility of a no-storage scenario is gaining acceptance among the scientific community interested in the development and promotion of the wind-diesel power system. In this scenario, the unpredictability of the wind resource is compensated by an adequate management procedure that uses a so-called levelling load (often called a dump load) acting as a virtual spinning reserve. Depending on the power level of this load, appropriate decisions on the allocation of the power production units of the hybrid park are made. The design of the supervisory strategy is not an easy task, especially when the park has numerous power production units of different types, each one having its own operating constraints. This article establishes a formal approach to the development of such a controller by using a design tool well proven in the domain of real-time control: the Petri net. The method chosen to specify the controller makes use of the techniques of modern structured analysis to modularize the system. This methodology is illustrated with the preliminary case study of a specific hybrid park consisting of three diesels and three wind turbines.

Techno-economic study of autonomous wind driven reverse osmosis desalination systems

Abstract This paper summarizes the results of an analytical study carried out to determine the technical and economic feasibility of wind driven reverse osmosis desalination systems. Four different types of reverse osmosis are considered including a diesel engine driven system (used for a baseline comparison), two Autonomous Wind Diesel Systems (AWDS), and a mechanical type wind powered system. A major objective of this work was to model systems comprised of commercially available components (including horizontal axis wind turbines, high pressure positive displacement pumps for use in reverse osmosis applications, and reverse osmosis membranes), in order to determine their present economic performance. The general conclusions from this study show that the AWDS type of system can be economically competitive when higher wind velocities and fuel costs prevail, however, for most average wind velocities and fuel prices, the diesel powered systems are still the most economic. Also, extrapolation of the mechanical type wind driven system showed that using a larger wind turbine than the one initially modeled can result in the production of potable water which is cost competitive in the higher speed wind regimes and fuel cost scenarios.