Adding Reliability and Resiliency to the Electric Grid
Today's interconnected world requires more resiliency and reliability and, for the electric grid, that means adding cyber-secure intelligent microgrid controls.
By Darrell D. Massie and John M. Carroll
Press reports of cyber-attacks on power grids and critical infrastructure are appearing with increasing frequency. On May 16, 2013, the U.S. Department of Homeland Security (DHS) testified that the number of cyber-incidents involving federal agencies, critical infrastructure and industrial entities increased by 68 percent from 2011 to 2012. Although there is no record of a cyber-attack bringing down a U.S. power grid, the emerging trend can't be ignored.
Microgrids bring new capabilities to the electric power grid through distributed intelligence and control. Successful microgrids integrate diesel generators and other legacy power sources with emerging renewable sources including solar photovoltaics, wind, and fuel cells. Energy storage systems including electric vehicles are also emerging as microgrid components. A sophisticated control system optimizes the microgrid across these diverse components in real time, and also handles prioritized shedding and other load management efforts. Intelligent microgrids deliver reduced energy costs, enhanced reliability, and increased resiliency.
An integral aspect of a successful microgrid is the ability to combine powerful software algorithms with easy access for operations personnel to monitor and adjust power priorities as needed. Microgrids have the ability to integrate various types and sizes of generation sources and energy storage sources and may provide for prioritized load shedding. Generation sources may be controllable (such as a diesel generator); uncontrollable (such as photovoltaic or wind); or, bi-directional, which provides a power source or load depending on need (such as energy storage).
A key feature of a microgrid is its ability to seamlessly isolate from the utility and operating as a self-controlled entity providing reliable power with little or no disruption to critical loads. Resynchronizing and reconnecting to the utility grid must occur in an equally seamless fashion. From an operations standpoint, the microgrid must be as reliable as the utility grid.
Islanding is defined as when the microgrid disconnects from the utility grid and the microgrid continues to provide power to loads. This can be desirable when electrical power from the utility is unstable or unavailable. In addition to grid blackout (a clear indication of a service interruption), methods such as passive, under/over voltage, under/over frequency, may also be used to detect when islanding should occur. Islanding must occur in such a way that it is safe for end-user equipment, provides for the safety of repair crews that may be faced with unexpected live wires, and safely reconnects with no damage to the utility. IEEE 1547 and UL 1741 dictate how this should be done electrically.
In islanded mode, a microgrid controller monitors the status of the microgrid in real time and balances sources, storage and loads. Devices can be added or removed, and the microgrid controller needs to recognize these changes and adjust control algorithms accordingly. It must prevent conditions where uncontrollable sources (photovoltaic or wind) exceed the loads, as this type of condition can damage operating generators on the microgrid. Understanding power generation and load “nodes,” as well as the desired power management profile, is essential to properly sizing the microgrid.
A distributed control system with peer-to-peer architecture ensures no single component (such as a master controller, SCADA system or a central storage unit) is required for operation of the microgrid. With a peer-to-peer architecture, a microgrid can continue operating with the loss of an individual component or generator. With multiple power sources, it can insure even higher levels of reliability.
A plug-and-play capability means that a component can be placed at any point within the microgrid without expensive re-engineering of its controls. A microgrid should offer these functionalities at lower costs than traditional approaches by incorporating peer-to-peer and plug-and-play concepts for each component within the microgrid. This is in sharp contrast to the traditional model, which groups assets at a single point in order to make the electrical integration tasks simpler.
A distributed controls architecture is capable of taking existing, disparate power sources and loads and integrating them into an intelligent, power-sharing micro-grid with decentralized decision-making to manage and optimize system power. Such an approach can distribute decision-making and is more robust to grid failure than a single master-slave controller. In all cases, any optimizing controller should be designed for a fail-safe mode in the event of communication or equipment failure.
A SECURE STRATEGY
Given that a central rationale for implementing a microgrid is increased resiliency in the face of utility grid outages, they must be inherently more secure. Security strategy is therefore of utmost importance in microgrid control system design.
The current approach to effective cyber security is to leverage risk and configuration management methodologies to internally cross-check the process, documents and products provided by microgrid system design and subsequent procurement. Several federal departments as well as national institutes and laboratories are developing frameworks pertaining to information assurance and cyber security (these are summarized in Figure 1). These documents are constantly evolving and partially overlap in their scope. This means it is impossible to conclusively “check the box” for defensive cyber security design. Instead, the best cyber security practices and guidelines require a holistic approach, incorporating relevant aspects of several frameworks simultaneously.
The Smart Power Infrastructure Demonstration for Energy Reliability and Security (SPIDERS) is a joint Department of Defense, Department of Energy and DHS program intended to demonstrate reliable, cyber secure, intelligent microgrid controls in both islanded and grid-connected modes. IPERC won competitive contracts to deliver the controls for all three phases of SPIDERS with its GridMaster control system.
Protect task critical assets from loss of power due to cyber attack.The requirements for success, listed in the SPIDERS program directive are:For SPIDERS, as is typical of most critical infrastructure microgrid requirements, the need for a highly distributed, scalable, self-healing and cyber-secure controls solution was paramount. The selection and development of IPERC’s GridMaster delivered unparalleled performance without a master/slave configuration, eliminating single-points-of-failure within the controls architecture.
- Integrate renewables and other distributed energy generation concepts to power task critical assets.
- Sustain critical operations during prolonged power outages.
- Manage installation electrical power and consumption efficiency, to reduce fuel demand and cost.
To accomplish these goals, IPERC developed a community of cyber-secure, intelligent power controllers where each node houses a single-board computer and represents a specific piece or group of equipment. All of the nodes are in constant peer-to-peer communication with each other. The combined capabilities of the node processors allow complex modeling and optimization algorithms to provide intelligently balance loads and prioritize operations.
GridMaster integrates both new and legacy infrastructure into a unified local power network. The distributed design and construction meets all electrical demand while maximizing efficiency and eliminating single points of failure. Ultimately, the technology is an economical and effective way to achieve maximum energy independence with immediate measurable reduction in cost, reduction in fuel consumption and CO₂ emissions, military-tested security and resilience, optimal integration of renewable energy sources, scalability to meet infrastructure changes, engineering to accommodate emerging technologies, and extremely reliable component of backup power for critical systems. GridMaster can be flexibly scaled and automatically reconfigures to meet ever changing, user priorities.
SPIDERS Phase I was deployed at Joint Base Pearl Harbor-Hickam, Hawaii. The operational demonstration was conducted in January 2013. Operations were conducted at the 15-kV Mamala substation, the waste water treatment plant, Station C (main operations locations for utilities) and a renewable energy facility.
SPIDERS moved to Fort Carson, Colo., for Phase II, with its operational demonstration in October 2013. This 5.5-MW microgrid constituted a major increase in scale and complexity, and included mission-critical base command centers and integrated multiple megawatt-class diesel generators, 1-MW of solar PV, and bi-directional electric vehicles.
Overall, the operational demonstrations associated with Phases I and II were deemed a success based on all measures of effectiveness. They included both planned and unplanned situations as well as cyber-attack concerns. These require the microgrid to adjust to rapid changes in loading and generation in order to ensure the principal directives and goals were met. Critical loads were never dropped.
For phase III, SPIDERS moved back to Hawaii, and design is currently underway at Camp H.M. Smith for a 5-MW microgrid, encompassing the U.S. Navy Pacific Command campus. Phase III also will incorporate further hardened cyber-security features, and will incorporate utility-driven measurements of economic success to better quantify the return on investment. The operational demonstration for Phase III is slated for the summer of 2015.
Following the completion of Phase III, the SPIDERS team will extract lessons from the five-year arc of the project and create frameworks to facilitate the transition of state-of-the-art microgrids from demonstration projects to commercial systems that can be deployed at military and civilian sites across the country and around the world.