Increasing Importance of Energy Conservation, Smart Cities, and Load Separation
EMDC relieves the burden of implementing embedded metering functions

Over the past decade or so, electronic electric meters, or e-meters, have been replacing conventional mechanical electric meters. As a result, smart grids with greater accuracy and higher performance are being implemented in a compact and low-cost manner.

As shown in Figure 1a, mechanical electric meters are identified by a rotating disc and a gauge, whereas the e-meter in Figure 1b can be read through an LCD.
Both types of electric meters measure active power, but e-meters can additionally calculate parameters such as voltage, current, power, reactive power, frequency, power factor, and phase angle, which mechanical electric meters cannot calculate.

These parameters indicate power quality, outages, load balancing, and tampering, providing highly insightful information to energy consumers and utility providers.

Energy measurement at e-meters is primarily used to charge consumers, identify load conditions, and monitor for failures.

However, as the importance of energy conservation, smart cities, and load separation is emphasized, many devices including sub-meters, smart plugs, sub-power monitors, protection relays, fault indicators, and circuit breakers have come to require accurate energy measurement.

For example, today's smart devices include embedded metering and wireless connectivity that can improve efficiency and control capabilities. Homeowners or business owners save energy by remotely monitoring and managing these types of devices.
Smart devices are merely one example of a load. Most loads and sources can be classified into single-phase, two-phase, and three-phase configurations. In most homes, the single-phase AC mains power primarily provides one type of voltage based on the neutral line, ranging from 110V to 230V.

The current consumed by the load varies depending on the type of equipment used directly, and power is the instantaneous sum of the products of AC voltage and current. Averaging the power over time yields the same energy.

Power and energy can be easily calculated using one of TI's MSP430 microcontrollers. The MSP430F67xxA and MSP430i20xx MCUs include a 24-bit sigma-delta analog-to-digital converter and other integrated analog and digital modules that capture and process AC waveforms to calculate power, energy, and other parameters.

Engineers designing embedded metering applications may have limited experience when using MCUs, developing algorithms, or processing complex signals.

The hardware design challenge includes implementing analog front-end circuits for the selected voltage and current sensor types. The software design task includes configuring and synchronizing MCU modules and optimizing calculations to obtain a comprehensive series of accurate and stable results.

System-level design challenges can be the most difficult, as they may include integrating everything, implementing and performing calibration, and migrating between MCUs across single and multiphase configurations.

Figure 3 shows the Energy Measurement Design Center (EMDC) graphical user interface (GUI) and software library developed by TI to simplify, automate, and accelerate such embedded metering designs.

Now, instead of developing everything necessary to implement embedded metering functions, engineers can focus on developing other features, such as wireless connectivity, while using EMDC. In fact, design time can be reduced from months to days.
Figure 4 shows the three main components of an embedded metering system.

First, the high-voltage source can be precise test equipment or the AC mains power supply. Next, the system can be an evaluation module or a custom board containing an MCU and sensors. Finally, the GUI or host MCU controls and communicates with the system's MCU.

Here, the EMDC GUI configures software libraries, estimates CPU bandwidth, checks for configuration errors, generates source code for the MCU, performs system calibration, and displays the results. All of this is executed without the need to write a single line of code.
In the EMDC GUI shown in Figure 5, there are icons representing the MCU and sensors, and these icons can be dragged and dropped by the user according to the system configuration. In addition, you can migrate between supported MCUs using the drop-down menu.

For more information on how to use this free tool for design, you can download the EMDC GUI and software library to learn about installation requirements and supported evaluation modules, or refer to pre-configured and pre-calibrated projects and related binary images.

In addition, if the design is similar, this EMDC project can be modified, or in other cases, a new project can be started.

This article is a summary of writings by James Evans, an engineer at Texas Instruments.