Smart Grid Needs Smart Meter SoC, Part 2

In part 1 of this blog we started looking at why power companies want to switch to a smart grid. We looked at what end-point equipment is needed (where the power is used) to facilitate the implementation of the smart grid. That's the smart meter. Then we started looking at System-on-Chip requirements for a smart meter.

The main feature of the primary digital core is to run a meter application and a metrology algorithm.

The secondary digital core is a signal processing engine and the PLC protocol stack. It runs the real-time functions to guarantee the real-time control of the data coming from the metrology sub-system. It has to be as accurate as possible. Typically, accuracy should be within a fraction of a percent.

Each core has a dedicated memory. The access time to each memory, for read or write purpose, has to be as low as possible to guarantee a real-time system working.

The metrology subsystem is composed of a net of silicon-based integrated sensors. These sensors have to be really accurate and reliable, because they are driven by a dedicated process unit that communicates directly with the digital core. A failure in one or more of these sensors would cause a malfunction of the main digital core and of the overall system. Moreover there is an analog front-end block that interfaces the analog waveforms with the process unit of the metrology subsystem to protect the sensors and to condition the signals that are the inputs/outputs of the sensors.

To guarantee the communication of the data stored into the memories of the two cores of the SoC, a PLC line driver, including a power line amplifier, is integrated in the SoC. The power line is coupled to the line driver. In turn, it is interfaced to the real-time system core by mean of a digital front-end and an analog front-end system. The communication of the data has to be secured by mean of a cryptographic engine. This guarantees that a failure in the security of the data transmission would not affect the overall system end-to-end security.

A recently released SoC features a programmable PLC signal-processing engine for multi-protocol management and an ARM 32-bit Cortex-M4F subsystem with programmable RAM and flash memory. The analog and digital metering front-end is realized in a three-channel front-end interface having high-accuracy. Moreover, it has a security engine that supports important PLC protocols such as METERS AND MORE, G3-PLC, and IEEE 1901.2. These protocols allow remote reconfiguration. This will support new protocols to be developed at some future date. In turn, this should guarantee a secure and effective end-to-end communication. Moreover, the metrology sub-system supports the PRIME standard for measurement.

Going into deeper details, the metering subsystem exceeds Class 0.2 meter requirements, combining three high-accuracy 24-bit ADCs, integrated filters, and a configurable hardwired DSP for energy calculations. The integrated PLC engine supports output signals up to 28 V peak-to-peak and has extended bandwidth of up to 500 kHz, while the dedicated security engine supports cryptography and multiple security modes for privacy and anti-hacking protection, enhancing the SoC's security.

Have you worked with an SoC similar to the one presented here which integrates a metrology sub-system and the digital cores for the PLC? How important is end-to-end security in a system like this? Did you ever use the METERS AND MORE and G3 PLC protocols for smart grid systems? What do you think of the PRIME standard of measurement?

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6 comments on “Smart Grid Needs Smart Meter SoC, Part 2

  1. eafpres
    November 26, 2013

    Hi Paolo–thanks for all the great details of these integrated designs.  I noted that the PRIME definition suggests 128-bit AES as the approach and has a suggested key management scheme.  In the SoC you are describing here can you comment on what security standards are conded into the security subsystem?  I think in the near future it is possible that 128-bit AES could be replaced by even more secure standards as the computing power catches up to this scheme.

  2. etnapowers
    November 26, 2013

    Hi Blaine,

    you're welcome, this blog owns to the same category of the blog that you posted here on the Integration Nation.

    As concerns the security standards I report here the description on STMicroelectronics site of this product:

    • Cryptographic engine supporting AES 128/192/256 with multiple modes hardware support

    The engine is a dedicated one and the company is working on a further enhancement of the security of the standards utilized as your convinction.


  3. samicksha
    November 28, 2013

    We often see people taking about SoC and their design, and one which hear quite often is if it is not feasible to construct a SoC for a particular application, an alternative is SiP, what do you think including cost factors..

  4. etnapowers
    November 28, 2013

    That's correct , it often happens. Well I think that if the only way to realize a particular application is a SiP instead of a SoC , this solution is good because , talking of reasonable cost factors, loosing a customer would be for sure more expensive.

  5. eafpres
    November 28, 2013

    Some reasons the customers want SoC are lower cost, easier system design, less board space, etc. Many of these are accomplished by SiP as well, but to lesser degree. The step after that is a module, which also offers benefits but higher cost and more parts, including connectors. Typically the decisions are largely based on demand volume and price pressure. However there are myriad factors involved in the final choice of integration.

  6. etnapowers
    December 2, 2013

    Hi Blaine, a very nice comment, as usual. According to me you're right when you say that many factors can play a role in the final choise of integration.

    I want to add that this can apply also to the success of the integration, it depends on many factors that , many times, are non-technical factors.


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