APPLICATIONS OF TECHNOLOGY:
- Power Distribution and Electricity Market Participation
- Electric Grid Sensors and System Control
- Enables optimal control of active and reactive power injections from photovoltaic inverters in real time
- Obviates the need for the electric utility system model and global real-time consumption information
Optimal control of Distributed Energy Resources (DER) shows promise as a critical component for proper operation of the electric distribution grid in the near future. However, many optimization-based approaches for managing DER require knowledge of the underlying distribution system topology, network impedances, and access to feeder-wide real time load information.
Researchers at the Berkeley Lab have developed a 2-dimensional Extremum Seeking (2D-ES) control scheme to manage DER active and reactive power contributions, utilizing a decaying dither and equilibrium-based switching.
This augmented 2D-ES scheme features an exponentially decaying probing (dither) signal that activates based on an equilibrium-based switching criterion. This dither signal does not utilize any exogenous information about the distribution grid. The dither signal decays exponentially when the individual inverters have optimized their portion of the objective function. Simulation results demonstrate that the approach can enable individual photovoltaic inverters – each controlled by a separate ES controller – to modulate their active and reactive power consumptions/injections in a sinusoidal fashion.
The dither signal has been a major limitation of the ES approach, as it causes persistent exploration of the local decision space, which is needed to estimate gradients for the optimization process. Additionally, its presence may incur an opportunity cost as well as contribute to system losses or cause other undesirable harmonic content. The present work significantly alleviates these concerns through its novel modification, which allows the convergence of each ES controller to a final value that is closer to the true optimizer and within the neighborhood of attraction when the probing signal is active.
Applications of this invention include the fields of utilities and inverter manufacturing. It holds potential in serving as a framework enabling a given feeder to act as an aggregate resource – a step closer to participating in electricity markets or regulation services.
DEVELOPMENT STAGE: Proven principle
STATUS: Patent pending. Available for licensing or collaborative research.
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