Rachel Denton and Roberto Piacentini, National Instruments
March 06, 2014 | 2 Comments
The idea of a “smart grid” has taken center stage — an evolution of advanced technologies that make the availability of a smarter, more efficient electrical power grid possible. These technologies aim to address the complex challenges facing grid systems today, which stem largely from its aging infrastructure and a use case model that has evolved over the years. With power systems over a century old, the field instrumentation on the grid is quickly reaching its life cycle limit, which adversely affects overall grid reliability and efficiency.
With a use case model designed to support the needs of heavy machinery and light bulbs alone, traditional devices on the grid are not prepared to meet modern energy demands, increases in distributed energy sources or changing grid requirements and standards. As a result, there is a lack of support for modern advancements such as computers, fluorescent lights or electric vehicles. This is largely because the grid is based on vendor-defined and closed hardware and software platforms that make it extremely challenging to adapt as grid requirements and standards evolve.
Thus, a re-evaluation of current grid architectures is required where basic automation devices are brought to a higher level of intelligence to enable distributed data acquisition and decentralized decision-making. A new generation of intelligent electronic devices (IEDs) is rapidly being deployed throughout the power system. These devices are equipped with advanced technologies that make two-way digital communication possible where each device on the network is equipped with sensing capabilities to gather important data for wide situational awareness of the grid. Utilizing computer-based remote control and automation, these devices can be efficiently controlled and adjusted at the node level as changes and disturbances on the grid occur. Additionally, these IEDs not only communicate with SCADA systems, but among each other, enabling distributed intelligence to be applied to achieve faster self-healing methodologies and fault location/identification.
At the heart of these advanced devices for the smart grid lies the powerful technology of the FPGA. Once seen as a technology only available to engineers with a deep understanding of digital hardware design, the dramatic advancements in the capabilities and levels of integration of this technology are changing the rules of IED development for smart grid applications.
At the highest level, FPGAs are reprogrammable silicon chips that offer the same flexibility of software running on a processor-based system. However, due to their truly parallel nature, FPGAs are not limited by the number of processor cores available. Additionally, they do not use operating systems and minimize reliability concerns with true parallel execution and deterministic hardware dedicated to every task. Each independent processing task is assigned to a dedicated section of the chip and can function autonomously without any influence from other logic blocks. As a result, the performance of one part of the application is unaffected when additional processing is added.
Figure 1. FPGA circuit – includes a flexible hardware architecture with logic functions and DSP blocks
FPGAs exceed the computing power of computer processors and digital signal processors (DSPs) by breaking the paradigm of sequential execution and accomplishing more per clock cycle. With the ability to control inputs and outputs (I/O) at the hardware level, FPGAs provide faster response times and specialized functionality to closely match application requirements.
Furthermore, FPGA technology powers the embedded instrumentation and control systems for the latest generation of IEDs on the smart grid, yielding additional flexibility and reliability, which enables convergence of multiple functional devices into a single unit, lowering the cost of smart grid systems as a whole. As FPGAs are incorporated into virtual instrumentation platforms, this represents a fundamental shift from traditional hardware-centric instrumentation systems to software-centric systems that explore computing power, productivity, display, and connectivity capabilities of popular desktop computers and workstations. Virtual instrumentation platforms that utilize FPGA technology, such as National Instruments CompactRIO hardware, are able to incorporate future modifications to keep pace with power grid requirements that are continuously changing. Thus, as IEDs for the smart grid mature, functional enhancements can be made through the use of open software and modular hardware without the need to modify the board layout or replace the entire device.
Figure 2. Virtual Instrumentation combines productive software, modular I/O, and scalable platforms to enhance system performance and efficiency.
Virtual instrumentation platforms are being used to develop the latest tools and technologies for the most advanced power quality analysis, which ensures that the power going to electrical power systems are suitable to operate properly. Power quality is critical for the stability of power systems and proper operation of systems/equipment connected to them; without the proper electrical power quality, these systems/equipment can malfunction or fail. Thus, power quality is a major concern for everyone involved in electrical power systems including consumers (domestic and commercial), electrical utilities, industrial facilities, standards and research organizations, and instrument manufacturers.
As an example of a virtual instrumentation device used for electrical power system analysis, the measurement of synchrophasors has become significantly useful for real-time assessment of grid health. Phasor measurement units (PMUs) quantify the flow and phase separation on the grid by measuring the frequency, amplitude, and phase angle differences from multiple points on the grid as these are synchronized using high precision GPS time references. These synchronized measurements increase situational awareness across wide-area power systems, which makes it possible for grid operators to improve the evaluation of grid stability, detect and react to issues before outages occur, and “heal” the grid quickly when faults take place.
Traditionally small-scale and limited to transmission systems, PMU deployments were hindered by system complexity and other limitations associated with network communication, performance, and data management issues. However, with recent breakthroughs in smart grid technologies, advanced PMUs are being developed for deployment worldwide and for integration into distribution networks.
For example, at the University of Bologna, researchers are actively working to create PMUs that acquire data at higher sample rates and measurement precision/quality to accommodate the reduced line length and lower power flows present on the distribution grid. These PMU designs are based on CompactRIO FPGA technology, which provides the necessary high sampling rates and high-fidelity measurements combined with a real-time processor that can handle multiple tasks in parallel without compromise. Such a platform enables customizability that gives distribution systems the capacity to evolve and adapt to changing requirements down to the silicon gate array-level.
Through the advanced capabilities of the FPGA technology combined with tools such as NI LabVIEW system design software, developers at the University of Bologna were able to rapidly implement time-critical algorithms for filtering and signal processing into their designs so that their PMUs could be successfully used in a noisy, low amplitude power distribution infrastructure. Utilizing virtual instrumentation platforms based on FPGA technology and a graphical system design approach, researchers at the University of Bologna were able to achieve shorter response times, better bandwidth utilization, and faster functionality field upgrades, resulting in decision-making and intelligence that is truly integrated with the grid.
Advanced PMU technology is just one example of how power engineers are finding more effective ways to meet smart grid application challenges by adding more flexible and multifunction IEDs to smart grid systems. As smart grids evolve and continue to require real-time monitoring and control of the electrical power grid, experts around the world predict that in the next 3-5 years there will be an increasing need to embed distributed intelligence into transmission and distribution networks. From protection devices such as smart reclosers and sectionalizes to automated metering devices and substation asset monitoring systems, advanced IEDs will proliferate along power systems. Ultimately, providing additional insight into the real-time health status of the grid, enhancing control power/performance with self-healing capabilities, and optimizing response to grid disturbances with distributed intelligence.
Lead image: Transmission lines via Shutterstock