UC San Diego
Inverter-Based Disturbance Rejection of Real and Reactive Power
- Author(s): Gwynn, Benjamin
- Advisor(s): de Callafon, Raymond A
- et al.
Electric grid transients stress power systems and can have cascading effects leading to widespread
damage. Transient effects and oscillations are made worse by an increased portion of power supplied by sources without any rotational inertia, such as DC to AC inverters connected to photovoltaics or energy storage media. Yet, the solid state architecture of modern inverters allows
unprecedented response time, enabling novel control schemes.
It is difficult to leverage the speed of modern inverters because of the comparably slower
response rate of microprocessors. Electric grid transients are characterized by a mix of gridfrequency and lower frequency components, and a high levels of harmonic distortion that accompanies the most common inverter architectures, forming challenges in signal processing. Furthermore, the complexity of electric grids makes model development and validation difficult.
This dissertation makes contributions toward overcoming these difficulties and demonstrates
feasibility of controlling inverter output to mitigate transient effects on an electric grid. A gridxix
connected reference circuit allows recreation of power oscillations when an inductive load is
switched in. Parallel processing via a field programmable gate array allows signal processing that
demodulates and filters inverter-supplied power, removing grid frequency components and higher
harmonics. The result is clean real-time active and reactive power signals sent to a microprocessor
for control. This data is used for system identification, greatly reducing the burden of model development. Finally the improved signal serves as input to a robust control scheme that adjusts inverter
active and reactive power output for disturbance rejection of transients created by the reference