Michael Sankur

Model-Free Optimal Control of VAR Resources in Distribution Systems: An Extremum Seeking Approach

Distributed power electronic reactive power sources-such as smart PV inverters-may play an important role in regulating customer voltages and reducing system losses in future distribution systems. Though it is natural to consider model-based optimal control algorithms to coordinate these resources, those strategies typically require relatively large communications capabilities and accurate models. In this paper we present an alternative way to implement the optimization problem that circumvents these communications and modeling challenges. We present an Extremum Seeking (ES) control algorithm to modulate the reactive power output of VAR resources to minimize total real power delivery at the feeder substation subject to voltage magnitude constraints, without an explicit feeder model. We present results that guarantee a variety of distribution feeder objective functions are convex over a broad range of power flows and perform an analysis showing the convergence of the ES approach. Simulation results demonstrate that the method is equivalent to recently developed convex relaxations used to solve distribution optimal power flow problems.

An architecture for integrated commercial building demand response

Enthusiasm for commercial demand response (DR) has inspired research efforts to create new building electric load control frameworks. In this paper we introduce a software architecture for an integrated building control system, the Central Load Shed Coordinator (CLSC). The CLSC provides functional control over three building systems which are large power consumers: lighting, HVAC, and plug loads. The system acts upon external demand response signals to meet load-shed criteria, while minimizing occupant inconvenience. In this paper, we present the purpose and relevant characteristics of this architecture. In addition, we discuss its deployment in a UC Berkeley building and present results from preliminary testing.

Optimal dispatch of reactive power for voltage regulation and balancing in unbalanced distribution systems

Optimization of distributed power assets is a powerful tool that has the potential to assist utility efforts to ensure customer voltages are within pre-defined tolerances and to improve distribution system operations. While convex relaxations of Optimal Power Flow (OPF) problems have been proposed for both balanced and unbalanced networks, these approaches do not provide universal convexity guarantees and scale inefficiently as network size and the number of constraints increase. In balanced networks, a linearized model of power flow, the LinDistFlow model, has been successfully employed to solve approximate OPF problems quickly and with high degrees of accuracy. In this work, an extension of the LinDistFlow model is proposed for unbalanced distribution systems, and is subsequently used to formulate an approximate unbalanced OPF problem that uses VAR assets for voltage balancing and regulation. Simulation results on the IEEE 13 node test feeder demonstrate the ability of the unbalanced LinDistFlow model to perform voltage regulation and balance system voltages.

An Energy Information Gateway for use in residential and commercial environments

Growing demands for products which enable consumers to manage their energy use more efficiently has led to the development of Energy Information Gateways, which are just beginning to gain traction in the marketplace. Such devices are envisioned to provide a communications and control infrastructure for appliances within their domain of influence, as well as communication with metering equipment. All relevant energy consumption information is expected to be relayed to the occupant in a practical manner. This paper outlines a software architecture for an EIG which is applicable to both residential and commercial environments. The software package utilizes the highly modular Open Services Gateway Initiative (OSGI) JAVA software framework to allow customization of individual EIG functionality and facilitates interoperability for existing smart grid products. In addition, the software in question provides a connection to external demand response resources and hosts a dynamic web based user interface to facilitate occupant interaction.

The next generation energy information gateway for use in residential and commercial environments

Both the current state of technology as well as emerging trends in home/office automation and energy management necessitate the presence of a piece of software dedicated towards facilitating interoperability amongst heterogeneous components; therefore empowering occupants to manage these spaces more effectively. This paper outlines the software architecture of an Energy Information Gateway, which is the latest evolution of an open source reference design that utilizes a modular software architecture to create an environment where dissimilar communicable components can not only exchange energy related information, but participate in supervisory control efforts. This latest version of the software allows for the abstraction of physical devices into a common standard, thereby allowing unlike components to join the home or office energy network. In addition, the software allows for definitions to be made of the hierarchical relationship between devices in the physical world and for these relationships to be dynamically altered.

An architecture for enabling distributed plug load control for commercial building demand response

Traditionally, a commercial buildings responsiveness to a demand response event is limited to actuation of the building HVAC and/or lighting system. However, current technological innovations allow for a more “integrated” energy control system via the incorporation of plug-loads as actionable load. This paper outlines the software architecture of such a system to enable plug-loads as a demand response resource. Distributed local plug-load control is facilitated via the use of smart communicating power strips and Energy Information Gateways (EIGs), which bridge the gap between the central building controller an individual loads. Coordinated control of these distributed EIGs is accomplished via the central building controller, which receives and interprets external demand response signals and hosts a bidding process amongst the EIGs to meet the load shed criteria. The deployment of prototype systems based on this design architecture at UC Berkeley and the United States Air Force Academy will also be discussed.

Optimal Control of Office Plug-Loads for Commercial Building Demand Response

While historically the electrical energy resource a commercial building may utilize during a Demand Response (DR) event has been limited to building HVAC and/or lighting systems, enabling technologies such as smart power strips (SPSs) and Energy Information Gateways (EIGs) have made distributed control over commercial office plug loads a reality. This paper investigates coordinated optimal control over plug loads in a commercial building during a DR event. Control over local office plug loads is accomplished via the use of a software entity, the Energy Information Gateway, which employs a binary integer linear program to determine which loads are shed. Individual EIGs are managed by another piece of software, the Central Building Controller (CBC), which can adjust parameters in the individual EIG optimal control algorithm. The proposed control structure is tested via the EIGs managing physical appliances in an actual office, and in simulations of the CBC managing virtual Gateways.Copyright

Model-Free Optimal Coordination of Distributed Energy Resources for Provisioning Transmission-Level Services

Collective control of distributed energy resources (DER)—such as photovoltaic (PV) inverters or battery storage—have the potential to provide regulation services to the bulk electric grid. While optimal power flow techniques may be used to coordinate DER for this purpose, these approaches typically rely on accurate network models and a large number of system measurements. In this paper, we consider an approach that alleviates these modeling and measurement requirements. Here, we consider a two-dimensional adaptive control scheme known as extremum seeking, or ES, to perform optimization without knowledge of a model of the distribution network. We apply this scheme to enable simultaneous feeder head active power and voltage magnitude reference tracking, as well as feeder voltage regulation. From the perspective of the transmission grid, this approach essentially transforms the distribution feeder into a controllable (P,V) bus. Simulation results confirm the ability of the approach to track substation real power and voltage reference signals while maintaining distribution system voltages within acceptable tolerances.

Model Predictive Control of Commercial Office Plug-Loads and Battery Storage Systems

Commercial demand response (DR) has traditionally relied on HVAC and lighting systems as load-shed resources in buildings. However, improvements in technologies such as Energy Information Gateways and smart power strips are making it possible to incorporate distributed plug-loads as an actionable resource. In this paper we explore the addition of a battery storage system (BSS) as a load-shed resource to supplement plug-loads in an office setting. Furthermore we investigate the value of control of BSS battery charging. We develop a model predictive control (MPC) framework for office plug-loads and a BSS. An experimentally derived model of a BSS is presented along with numerical methods for solving the MPC optimization program. Simulations demonstrate the efficacy of a BSS as a load-shed resource. Simulation results also quantify the benefit of BSS controllable charging for DR and load-following scenarios.Copyright

Towards a hyperbolic acoustic one-way localization system for underwater swarm robotics

A hyperbolic acoustic system for underwater robot self-localization is presented. Anchored transducers send acoustic signals which are observed by a receiver. The system is passive with one-way signal transmission. Time differences of arrival (TDOAs) between the emitted signals are estimated by the receiver via cross-correlation. These TDOAs are fed to an Extended Kalman Filter to estimate the global position of the receiver. We describe the complete signal processing chain as well as challenges in hardware and software design. Experimental results in air and water show the feasibility of the system. This paper demonstrates that acoustic one-way localization is possible with off-the-shelf hardware in experimental test tanks.