Four smart grid applications are improving how utilities operate their electrical networks. All of these systems incorporate platform elements and cover protection relays, power monitoring, distribution automation, and field communication applications showing the broad range of use that systems can have when designed around platform elements.
by Brett Burger, National Instruments
When the iPhone was first released, many questioned if it would work for the business user or be relegated to the consumer market. The wealth of productivity and enterprise level applications for businesses have answered this question and made the addressable market for iPhone users essentially all mobile phone users. For a platform to succeed it must be flexible enough to appeal to a broad number of applications. Platforms for the modern utility grid are no exception.
Protecting Grid Assets with a Custom Sub-Synchronous Relay
Wind generation is growing at an impressive rate. According to the Global Wind Energy Council, the wind industry grew new wind installations by 44% with a record of more than 51 GW of new capacity installed in 2014. This growth is creating some challenges that are unique to utilities with large amounts of wind generation. Series compensated transmission lines, frequently used for transmitting energy over the great distance from wind farms to population centers, have capacitors installed to increase the capacity of the line. The capacitors increase the load capability but when combined with the properties of the line itself, create a system with resonant frequencies that can interact with wind turbines and potentially cause catastrophic damage to grid equipment.
Dr. Y. Gong, a Senior Engineer with American Electric Power (AEP), along with his colleagues Y. Xue and B. Mehraban, have been working on a new algorithm to detect these lower frequency oscillations and protect the grid from the harmful impacts. Dr. Gong presented this custom sub-synchronous oscillation (SSO) relay at the CIGRE 2015 Grid of the Future Symposium in Chicago where he went into details on the algorithm, custom filter design, and lab performance validation. One reason Dr. Gong and the AEP team were able to design a new protection relay with a small team is because they designed their application on an off the shelf platform of measurement and control components. By purchasing the lower level components off the shelf as building blocks, the team is able to focus more of their expertise on bringing new algorithms and digital filter designs to the market which benefits wind owning utilities, system operators and energy customers alike (Figure 1).
Improving Grid Utilization with Better Control at the Edge
The typical grid is designed for peak demand, the hottest or coldest day with consideration of possible equipment failure. This results in grids with fairly low utilization rates, sometimes under 50% since most days customers do not use near as much energy as the days when all homes and offices are trying to keep up with extreme weather. Controlling equipment at the edge (like commercial and industrial building loads or distributed generation) would help but that task is difficult because edge devices are usually not owned by the utility company and the control solutions that exist today, such as demand response, do not return real-time information and are not reliable solutions for dispatch.
Innovari, a U.S. based energy innovations company, is working to fix that problem with their Interactive Energy Platform. Their solution uses three different hardware nodes for a variety of measurement and control procedures to improve overall system utilization. One type of node both measures the load of connected circuits and has output signals to control the same circuits to which it is connected. Another device processes Voltage and Current waveform measurements
into analytics such as power quality data, and the final device is designed for controlling distributed generation assets.
The vast network of deployed devices sends data back to an Innovari control center where an algorithm can match the dispatch request from the utility company to the appropriate edge nodes that are controlling lights, air handling units, generators, renewable sources, and other edge devices that can help more efficiently use grid infrastructure. This intelligent system provides the utility with affordable, generation quality, demand-side capacity. The end nodes are embedded systems built around a control and processing board with integrated input and output for connection to building energy sensors and circuits. Innovari built these intelligent nodes using a programmable control and measurement platform for embedded design and focused on developing unique real-time algorithms, helping utilities overcome key challenges, and strengthening relationships among utility companies, large commercial utility customers, and regulators in a win-win-win business model (Figure 1).
Figure 1: From the outside view (a), the new SSO relay looks similar to other devices on the market. The inside (b), shows the modular, programmable hardware elements the AEP team used to develop a custom relay.
Monitoring Power Quality Problems
Inverters convert electricity from direct current, as generated by wind, solar, and battery storage, to the alternating current used on transmission networks around the globe. Inverters are important components that connect clean, renewable energy to grid but by the nature of their design they can impact the quality of the grid through the addition of unwanted harmonics. National Grid UK, the transmission operator for England and Wales, is seeing an increase in energy sources that use inverters, mainly offshore wind farms and shared high voltage direct current (HVDC) interconnects with neighboring countries.
To help grid quality and future transmission planning, an engineering team at National Grid UK designed a monitoring platform to help understand the total harmonic distortion at various points in their grid. Peter Haigh, an engineer at National Grid UK and representative of the design team, recently spoke at the IoT World Congress in Barcelona where he talked about connectivity, programmability, and intelligence for systems to help control and maintain a grid. The team selected an off the shelf measurement, control, and signal processing platform because they understand that the future challenges of the UK grid are likely unseen as of today. One feature today of their smart grid application is a heat map that will ultimately represent THD from over 130 measurement locations on their grid, but their application will likely grow in value as future software updates are released (Figure 2).
Figure 2: Grids are designed to handle peak conditions that only occur infrequently. Intelligent control of devices on the edge of the grid can help alleviate peak demand and improve grid utilization percentage.
Improving Device Communication with a Field Message Bus
Faster control can help manage some of the challenges of the grid, like distributed renewables, but the ability to speed up grid control rates is itself a challenge. Many grid control schemes today are designed such that measurement devices send data to a central control program that in turn responds with commands to control devices. With some communication schemes that round trip is measured in minutes, which is not fast enough to keep up with the dynamic nature of today’s electric network. As an example, clouds can block out the generation of a solar farm in less than a minute.
One plan to improve this latency is being worked on by the Smart Grid Interoperability Panel (SGIP) and it’s called the Open Field Message Bus (OpenFMB) initiative. The OpenFMB project aims to abstract device communication and create a reference architecture utilizing Internet of Things technology. Intelligent devices installed at the edge of the grid, like inverters, protection relays, and controllers, will be able to communicate directly with each other without having to communicate through a central server. Communication capability such as this is an element of modern intelligent grid devices that are designed on a platform. This reference architecture, like many popular smart phone applications, is designed to work on a variety of vendor platforms, an important aspect seeing as how utility grids today use devices from multiple vendors.
The applications discussed here could represent the early stages of a broader adoption of software defined grid applications. The platform centric design, as seen with iPhone and Android in the mobile handset industry, helps developers innovate and upgrade capability at a pace much faster than traditional design. In the case of a phone, consumers can expect two to three software upgrades in the span of a couple of years. For the utility grid, that may translate to two or three software upgrades over a decade. However, it is going to reduce the risk of having costly, stale technology deployed on the grid that is ineffective at solving a future of unknown problems. The pool of expertise for the utility grid is smaller compared to that of iPhone and Android developers. And in the market, platforms serve as a force multiplier empowering engineers and grid experts, like Dr. Yanfeng Gong from AEP and Jim Tillett of Innovari, to focus on the problems facing the grid without having to spend time reinventing the wheel, or in this case the relay, meter, or inverter.
National Instruments, Austin, TX. (512) 794-0100. www.ni.com