Supervisory hybrid control of a wind energy conversion and battery storage system

This thesis presents a supervisory hybrid controller for the automatic operation and control of a wind energy conversion and battery storage system. The supervisory hybrid control scheme is based on a radically different approach of modeling and control design, proposed for the subject wind energy conversion and battery storage system.;A finite hybrid-automata based model of the wind energy conversion and storage system has been proposed that captures the different operating regimes of the system during grid-connected and in islanded operating modes. The hybrid model of the subject system defines allowable operating states and predefines the transition paths between these operating states. A modular control design approach has been adapted in which the wind energy conversion and storage system has been partitioned along the dc bus into three independent system modules. Traditional control schemes using linear proportional-plus-integral compensators have been used for each system module with suitable modifications where necessary in order to achieve the required steady state and transient performance objectives. A supervisory control layer has been used to combine and configure control schemes of the three system modules to suite the requirements of system operation during any one operating state depicted by the hybrid model of the system. Transition management strategies have been devised and implemented through the supervisory control layer to ensure smooth inter-state transitions and bumpless switching among controllers.;It has been concluded based on frequency domain linear analysis and time domain electromagnetic transient simulations that the proposed supervisory hybrid controller is capable of operating the wind energy conversion and storage system in both grid-connected and in islanded modes under changing operating conditions including temporary faults on the utility grid.;The wind energy conversion unit is composed of a 360kW horizontal axis wind turbine mechanically coupled to an induction generator through a gearbox. The assembly is electrically interfaced to the dc bus through a thyristor-controlled rectifier to enable variable speed operation of the unit. Static capacitor banks have been used to meet reactive power requirements of the unit. A battery storage device is connected to the dc bus through a dc-dc converter to support operation of the wind energy conversion unit during islanded conditions. Islanding is assumed to occur when the tiebreaker to the utility feeder is in open position. The wind energy conversion unit and battery storage system is interfaced to the utility grid at the point of common coupling through a 25km long, 13.8kV feeder using a voltage-sourced converter unit. A bank of static (constant impedance) and dynamic (induction motor) loads is connected to the point of common coupling through a step down transformer.