Rapid synchronization control of compressed gas energy storage generator during power grid contingent and extended contingent events.
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
Electric power system (EPS) operates with economy, supply reliability, and renewability in mind. This means that the power generated must be cheap, clean, and can rapidly maintain the EPS frequency within the nominal range following the loss of an EPS asset to prevent causing damages to the connected equipments. To maintain frequency during contingent events, fast responding generation units called instantaneous reserves (IR) are o ered, and these are typically provided by spinning hydro turbines in New Zealand. The gradual increase in price, reduction in supply and the damage caused to the en- vironment of using nonrenewable energy sources such as fossil fuel and nuclear energy are attracting the interests in the research and development of clean energy produc- tion technologies such as photovoltaics (PV), wind turbines, and tidal power to supply the electric grid. These nonrenewable energies are however restricted by environmental conditions such as the sun's illumination, wind direction, wind intensity and tidal ow velocities. For these reasons, a fast responding and steady output cannot be always be guaranteed, making these intermittent generation resources unsuitable to be used as instantaneous reserves. Callaghan Innovation scientists and engineers have proposed a novel energy storage system which stores the excess energy in a form of compressed gas at a capacity capable of meeting the time required by the FIR speci cation without losing the energy that is typically observed in a tail-water depressed hydro reserve unit. The proposed system is able to o er torque via compressed air and hydraulics such that a generator able to reach synchronization speed within 0.4 seconds, and is cheaper to be o ered as instantaneous reserve compared to a small scale hydro-turbines. To ful ll the master thesis requirement, a rapid synchronization control scheme is de- veloped to ensure that the generator is able to spin up to the power system frequency, synchronize with the distorted power system voltages, and begin delivering power within 1 second of receiving the FIR dispatch signal. This thesis describes the operation of the proposed compressed gas energy storage system, documents the instrumentation algo- rithm selection and implementation process, details the modeling and control strategy design techniques utilized to achieve successful simulated synchronization outcome, and provides a stability study of generator rotors following the synchronization breaker clo- sure as a result of using the developed synchronization control scheme.