Takao Shinji

Supply and Demand Control of Dispersed Type Power Sources in Micro Grid

Renewable energies such as wind power or photovoltaic energy are environmentally focused but the output power fluctuation of the renewable energies may cause excess variation of voltage or frequency of the grid (Ramirez et al., 2004; Oliva and Balda, 2003), Marei et al., 2004), Okuyama et al., 2003). Increase of the amount of renewable energies would violate the quality of the grid (McCusker et al., 2002; Gupta and Pahwa, 2004; Bhowmik et al., 2003), Hernandez, 2003). The micro grid in which dispersed energies compensate the variation from the renewable energies can expand the installation limit of the renewable energies by maintaining the quality of the interconnected grid (Guan et al., 2003; Pregelj et al., 2004; Hayashi et al., 2003). In this paper, how the gas turbines absorb the power variation from the wind generation and load is discussed. In order to control output power, gas turbines must run at partial load operation, which results in lower efficiency. Tie-line power flow and frequency fluctuation caused by imbalance between supply and demand is also discussed. It is shown that gas turbine output control is effective method to absorb output fluctuation from load and wind farm. If the exhausted thermal energy from a gas turbine can be used for co-generation, more energy saving is expected

Experimental Comparison of PV-Smoothing Controllers using Distributed Generators

The power output variability of photovoltaic systems can affect local electrical grids in locations with high renewable energy penetrations or weak distribution or transmission systems. In those rare cases, quick controllable generators (e.g., energy storage systems) or loads can counteract the destabilizing effects by compensating for the power fluctuations. Previously, control algorithms for coordinated and uncoordinated operation of a small natural gas engine-generator (genset) and a battery for smoothing PV plant output were optimized using MATLAB/Simulink simulations. The simulations demonstrated that a traditional generation resource such as a natural gas genset in combination with a battery would smooth the photovoltaic output while using a smaller battery state of charge (SOC) range and extending the life of the battery. This paper reports on the experimental implementation of the coordinated and uncoordinated controllers to verify the simulations and determine the differences in the controllers. The experiments were performed with the PNM PV and energy storage Prosperity site and a gas engine-generator located at the Aperture Center at Mesa Del Sol in Albuquerque, New Mexico. Two field demonstrations were performed to compare the different PV smoothing control algorithms: (1) implementing the coordinated and uncoordinated controls while switching off a subsection of the PVmorexa0» array at precise times on successive clear days, and (2) comparing the results of the battery and genset outputs for the coordinated control on a high variability day with simulations of the coordinated and uncoordinated controls. It was found that for certain PV power profiles the SOC range of the battery may be larger with the coordinated control, but the total amp-hours through the battery-which approximates battery wear-will always be smaller with the coordinated control.«xa0less