Configuration and optimization of a novel compressed-air-assisted wind energy conversion system

The increasing concerns over the environmental impact of carbon emissions and the unsustainability of conventional fossil fuel power plants are stimulating interest in the implementation of renewable energy in current power systems. Among all of the renewable energies, wind energy holds a prominent place because of its high output and the maturity of the technology. However, like all of the other renewable energies, integration of wind energy into the power grid causes some quality and control issues, such as overvoltage or undervoltage and frequency excursion. Other issues include: 1) wind power generation may require a broader safety margin of the capacity reserve, 2) the excessive energy may be rejected by the transmission because of the mismatch between generation and load demand, and 3) induction wind turbines may not be able to ride through a voltage sag event because a critical voltage has to be guaranteed to produce the fundamental magnetic field. To mitigate these issues and build a robust wind power system, a novel structure referred to as a compressed-air-assisted wind energy conversion system (CA-WECS) is proposed in this dissertation. The CA-WECS converts the wind-generated mechanical spillage to compressed air when the wind is a surplus and regenerates power from the compressed air storage when the wind is a deficit. The addition of a compressed air storage subsystem decouples wind power and electric power allowing a higher level of dispatchable generation and providing another degree of freedom for power management. The key component of the new system is a variable displacement machine (VDM), which can work as a compressor or air motor/expander depending on the power gap between wind power and load/command. This work addresses the configuration of the CA-WECS in detail. The functions of the system components are explained and the fundamentals of the proposed VDM are explicitly described. A regulation policy for dispatchable generation is simulated and studied. The economical issues associated with the implementation of the proposed system are split into two parts, the sizing problem and the offering problem. The sizing problem refers to finding the proper sizes of different components for the proposed system. The offering problem refers to determining the appropriate offer to the day-ahead electricity market for a wind farm consisting of the proposed system. A two-stage stochastic framework is used to solve the optimization model each problem. The simulation studies validate the benefits of the proposed system. The results show that renewable generation is increased by 15-20% under various wind conditions, accounting for a 20-30% revenue increment in a dynamic market environment