The Internet of Things (IoT) promises significant cost savings when fully implemented in smart building and smart campus environments. Managing energy will provide one of the greatest savings, as managing environmental controls provides optimal comfort for residents while minimizing energy usage. Factories and industrial complexes will also benefit from more robust and connected IoT-based energy management systems. Collecting and controlling all points of power transmission and consumption will require a wider rollout of energy measurement and management devices.

MCU manufacturers have long targeted energy measurement and management applications, and modern MCUs have several advanced features that make them very efficient in these applications. Additionally, reference designs are often available to provide complete system solutions for common energy measurement, control, and concentrator applications. This article will explore some of these reference designs to illustrate how they can significantly simplify the implementation of your next energy measurement and management design and speed up your time to market.

Energy Management in Smart Grids

Smart grids are a new way of thinking and building energy infrastructure. It applies to all aspects of energy generation, distribution and utilization. If all three elements are in place and operational, a smarter and more efficient “smart grid” can be built. A smart grid will optimize the generation, delivery and consumption of energy by measuring and predicting the energy needed, then generating and delivering it efficiently. A key element of a smart grid is the perception, monitoring and communication of energy usage by consumers. Once energy usage is understood and ideally forecasted through the use of big data analytics, generation and delivery can be better managed. Additional efficiencies can be gained if consumption can be managed according to the availability of the energy produced.

Figure 1 illustrates the evolution of the smart grid. On the left, the previous energy system focused on generating electricity. Smart grids take a more distributed approach to power generation, using multiple sources as well as communication and sensor networks to better manage energy delivery and utilization. Sensors are used throughout the smart grid to measure power. This is implemented not only at every point of use, but at every point of generation and distribution, so real-time decisions can be made to optimize the efficiency of the entire system.



Figure 1: Smart grid evolution (courtesy STMicroelectronics)

Energy Metering Evaluation Kit

Energy metering in smart homes can be a key element in smart grids. An energy metering solution typically includes an MCU used in conjunction with an energy measurement IC. Figure 2 shows a simplified block diagram of a typical smart meter that utilizes STMicroelectronics STM32F series MCU, STPM10 energy metering IC, and several supporting components to provide Power Line Modem (PLM) communication, additional memory, security, and power. STPM10 measures active, reactive and apparent energy in power line systems using current transformers and shunt sensors in single-phase or multi-phase metering systems.



Figure 2: Energy metering in the smart home. (Provided by STMicroelectronics)

The analog portion of the STPM10 includes a preamplifier and first-order sigma-delta A/D converter, a bandgap voltage reference, and a low-dropout regulator. The digital section includes system control, oscillator, configuration and calibration non-volatile memory, DSP and SPI interface. From the pair of sigma-delta output signals produced by the analog section, the DSP unit calculates the amount of active, reactive and apparent energy consumed, as well as RMS and instantaneous voltage and current values. The result of the calculation is available as the pulse frequency and status of the device’s digital outputs, or as data bits in a data stream that can be read from the device via the SPI interface. The STEVAL-IPE15V1 evaluation kit can be used to simplify prototyping.

Energy Metering and Communication Reference Design

The evaluation kits described above help speed up your development cycle by quickly putting working hardware at your fingertips. The development process can be further accelerated when a software tool including a graphical user interface (GUI) is provided to observe the operation of the target evaluation kit or reference design. For example, the Cirrus Logic CDB5480U-Z reference design platform includes a target board and an associated GUI that communicates with the board to configure and observe operations. Figure 3 shows the target board on the left and sample output from the GUI showing the histogram of the collected data. The mean, standard deviation, variance, maximum and minimum values ​​are displayed on the left side of the window. A full-featured target board combined with advanced configuration and measurement tools and an easy-to-use GUI can be particularly effective in accelerating your development cycle.



Figure 3: Reference design board and user interface display (courtesy of Cirrus Logic)

MCU manufacturers also provide reference designs for the communications portion of the smart grid. Power line communication is a popular method of sending and receiving data in smart grids, and MCUs are often used as the central control element for these types of systems. Some MCUs are optimized for these applications and provide extensive communication capabilities for smart grid implementations. Figure 4 shows a block diagram of the Texas Instruments TMDSICE3359 industrial communication engine reference design and TI AM335x processors optimized for communication. Note the broad set of communication interfaces supported, including dual Ethernet, USB, CAN/PROFIBUS, I 2 C, SPI, and UART.



Figure 4: Texas Instruments Smart Grid Communications Reference Design Block Diagram (Courtesy of Texas Instruments)

TI’s AM3352MCU is powerful enough to implement a wide range of intelligent algorithms for sensing and controlling energy usage in lighting, HVAC, signage, occupancy, material transportation and process control. The TI TMDSICE3359 reference design contains extensive code collected in the SYS/BIOS Industrial SDK. The SDK includes an open source RTOS, bootloader, peripheral drivers, industrial communication protocol stack evaluation versions for EtherCAT Slave Stack, PROFIBUS Slave Stack, EtherNet/IP Adapter/Slave Stack, Profinet IO Device Stack, and examples Demonstrate applications for industrial input/output data exchange via various industrial communication protocols. The inclusion of these critical functions greatly speeds time-to-market by eliminating the need to create these complex functions from scratch.

In summary, making a smart grid “smart” requires control and metering of every key element of the grid (generation, distribution, and consumption). By using MCU-based power measurement systems, the grid can collect the vast amounts of data needed to improve system efficiency, and MCU-based communication systems can send and receive this data within the smart grid. As we have shown, evaluation kits and reference designs are readily available to help you accelerate the development of these smart grid design solutions.

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