| dc.description.abstract |
Distributed generation (DG) is related with the use of small generating units installed at locations of load centres. DG can be used in an isolated way, supplying consumers’ local demand, or integrated into grid supplying the energy to the remainder of the electric power
system. DG technologies can run on renewable energy resources, and its capacity ranges in size from less than kilowatt to tens of megawatts. DG has attracted a lot of attention world wide, since it decreases the dependency on fossil fuel and also in reducing the emission of the greenhouse gases. The power derived from renewable sources such as wind flows and solar irradiance are unreliable owing to its seasonal and diurnal variations. To surmount the said defiance, power electronics and controls are used to coordinate the renewable power systems. This thesis is focused on modelling, control and power management of electronically interfaced distributed energy resources. To this end, mathematical model of each energy conversion system is developed and they are interfaced through power converters. For this integrated hybrid system, frequency control, voltage amplitude regulation and moderation of generation-demand (G-D) mismatch are the primary control requirements. In order to achieve this control schemes are proposed for the power electronic converters to regulate the power flow under balanced and unbalanced load conditions.
For the hybrid scheme to operate effectively in integrated mode, effective control has to be done in order to meet the changing demand, despite variation in generation. An objective function is formulated to forecast the power harvested from the renewable sources. Moreover, the objective function also estimates the energy reserve available to meet the demand. In order to maintain the dc-link voltage constant, despite variations in G-D gap, an adaptive control technique is devised. In this technique, dc-link voltage is shown to be maintained by adaptive gain control that relates dc-link voltage to the power output of battery system. Further, the proposed objective function is such that, it can quantify the uncertainty with renewable generation forecast and battery power output. Further, this research work is extended to provide reactive power support by connecting static compensator (STATCOM) at point of common coupling. With this, it is possible to provide control measures to protect the system under emergency situations like sudden rise in demand. The STATCOM control is modified to maintain balance currents in the converter, despite unbalanced load conditions. |
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