Modeling and Simulation of the Interface between Geothermal Power Plant Based on Organic Rankine Cycle and the Electric Grid

Abstract

A geothermal power plant is to be designed that uses oil field geothermal fluids with Organic Rankin Cycle (ORC) technology. The ORC engine will use low temperature (T<150 oC) geothermal water to generate electricity which will be sold to a local electric utility. With oil production at the site requiring a significant power load, this plant will be both an electricity generator and a customer. Thus, it will maintain a symbiotic relationship with electric grid at all times. The fewer instabilities and interruptions there are in plant-grid interactions, the more productively and consistently the plant can supply power to consumers. As a result, a complex set of regulatory and unique engineering challenges have to be satisfied while integrating the plant into the grid. This study presents a simulation of the interface between the power plant and electric grid for a stable and reliable flow of power. Using a set of preliminary data, a simulation model of the plant in a MATLAB/SIMULINK environment with connection to the electric grid through an AC-DC-AC converter is developed and tested. The voltage obtained from the generator is first rectified by a six pulse diode bridge. The filtered DC voltage is then applied to an IGBT based inverter which generates a 60 Hz AC voltage. The resulting voltage is connected to the regulated grid.