Geoffrey James

COORDINATION OF DISTRIBUTED ENERGY RESOURCE AGENTS

This article describes our research in technologies for the management and control of distributed energy resources. An agent-based management and control system is being developed to enable large-scale deployment of distributed energy resources. Local intelligent agents will allow consumers who are connected at low levels in the distribution network to manage their energy requirements and participate in coordination responses to network stimuli. Such responses can be used to reduce the volatility of wholesale electricity prices and assist constrained networks during summer and winter demand peaks. In our system, the coordination of energy resources is decentralized. Energy resources coordinate each other to realize efficient autonomous matching of supply and demand in large power distribution networks. The information exchange is through indirect (or stigmergic) communications between agents. The coordination mechanism is asynchronous and adapts to change in an unsupervised manner, making it intrinsically scalable and robust.

The Future of Renewables Linked by a Transnational Asian Grid

In this paper, we argue that Asias unique geography, abundant low-emission energy resources, rapid economic growth, and rising energy demands merit consideration of a Pan-Asian Energy Infrastructure. In our study, we focus on development of wind and solar resources in Australia, China, Mongolia, and Vietnam as the potential foundation for an electricity grid stretching from China to Australia. Hourly climate data for a full year are used to estimate renewable energy generation, electricity demand, generation capacity are projected forward to the year 2025, and economic dispatch in an international market is simulated to demonstrate cost benefits. Intermittency, connectivity, future dispatch orders, storage, line losses, and engineering and financial issues are all addressed.

Impacts of large scale wind power on power system transient stability

Wind power generation changes the load flow, the swing modes and transient stability of the integrated power system. The characteristic of power transient stability is well studied for large scale wind power integration in this paper. Different wind power generator models, including fixed speed induction generator (FSIG) and double-fed induction generator (DFIG), are considered in the analysis, as well as different penetration levels, faults locations and faults clearing time. By using extended equal area criterion (EEAC), it was revealed that large scale wind power integration may change the unstable mode (UM), namely the pattern of dividing all generators into the critical cluster (CC) and the remaining one (RC), the times of the swing for an unstable case, or the change rate of the swing stability margin for a stable case. If some traditional synchronous generators within the CC are replaced with wind power generators, power system transient stability degree can be either decreased or increased. Similarly, these phenomena might also appear if the replacement occurs in the RC. Based on EEAC, this paper presents such cases with simulations, and conducts theoretical and quantitative analyses to explain the mechanisms behind. The impacts of large scale wind power on system power transient stability can be mainly ascribed to the change of the equivalent generalized inertia of the CC and that of the RC, and their equivalent accelerating power.

A study on the harmonic issues at CSIRO Microgrid

With increasing number of photovoltaic (PV) systems connected to the electricity network in Australia, power quality becomes a major concern. There is an increasing interest in Microgrids due to their potential to provide a solution to integrate renewable energy into the wider grid. This paper presents a study on the harmonic issues in a Microgrid. Different experimental scenarios have been carried out to characterize the voltage and current distortions under different operation conditions. Matlab/Simulink simulation and field experimental results have been provided. The results showed that the harmonic current emission can be affected by the output power level of PV inverter. In addition, the current and voltage waveforms distortion at the Point of Common Coupling to the grid is significantly increased when the net power follow through the bus is close to zero.

Economic Analysis of Two Microgrid Prototypes

A microgrid is an excellent supplement for both urban and rural utility grids. It assists in the integration of different kinds of renewable and distributed generation and it has the potential to make the distribution system more flexible and reliable. A microgrid is a combination of two or several energy resources like natural gas, wind, photovoltaic, biomass or diesel generators. Different energy resources together with battery storage system can complement one another to provide a more continuous power output. Two microgrid prototypes are discussed and, optional configurations are estimated using the economic analysis tool HOMER. Economic benefits and greenhouse-gas emissions of microgrids are calculated and compared. Results show that microgrids with optimal sizing and operation can achieve both cost efficiency and lower emissions.

Recurrence relations for spherical waves

This paper derives new recurrence relations for scalar spherical waves in Cartesian coordinates and compares the performance of these relations with that of traditional recurrence relations. They are numerically stable for travelling waves and some standing waves, and are faster for evaluating scalar spherical waves up to order 40 on a nonspherical surface. Because of their algebraic simplicity, they will be especially useful for symbolic-algebra computer programs, allowing explicit expressions for scalar and vector spherical waves to be obtained using a succinct procedure.