# References

This section provides links to background information useful to understand this project, the standard and the reference implementations.

TIP

This section is just getting started, filling more as we have the time and energy. Suggestions welcome.

# General Information

DC Distribution Systems and Microgrids (opens new window) Dragičević, T., P. Wheeler and F. Blaabjerg (Editors). London: The Institution of Engineering and Technology, 2018. A good general reference about DC grids. Includes a chapter on stability analysis.

Microgrids: Architectures and Control (opens new window) Hatziargyriou, Nikos (Editor). New York: Wiley-IEEE 34 Press, 2014. Another good reference about the microgrids.

# Microgrid Architecture

DC Local Power Distribution with Microgrids and Nanogrid (opens new window). Nordman, B, and K. Christensen, First International Conference on DC Microgrids, Atlanta, GA, June 2015. Bruce Nordman was an early advocate and innovator for the kinds of microgrids this project is working toward. Bruce's website (opens new window) is a trove of papers, talks and related material.

A Simulation of Local Power Distribution Control Strategies (opens new window). Nordman, B., K. Spears, A. Kahndkar, and M. Pezzola. Second International Conference on DC Microgrids, Nurnburg, Germany, June 2017 - Contains a more detailed description of the LPD power protocols.

Hyphae (opens new window). A project from Sony CSL (opens new window) to define peer-to-peer power distribution in a microgrid. The architecture and software have been offered under open source adopted by LFEnergy. The specification (opens new window) and code are available on the Hyphae GitHub Site (opens new window).

IEEE 2030.10-2021 Standard for DC Microgrids for Rural and Remote Electricity Access Applications (opens new window) Describes the requirements to implement an unmanaged grid operating at a nominal 48V. Includes external wiring recommendations and safety concerns. This project is harmonized with ISO 21780 for 48V automotive electrics.

Tactical Microgrid Standard (opens new window) TMS is a standard for implementing microgrids developed by the US Army and the MIT Lincoln Laboratory. Currently it is focused on AC but they have plans to extend it to DC. The Army seems ambivalent about how open to make this standard. Internally, it is based on DDS (Data Distribution Service) (opens new window) middleware.

# Microgrid Activities and Publications

LFEnergy Microgrid SIG (opens new window): A special interest group for microgrids under the LFEnergy project. LFEnergy (opens new window) is the home of several energy and smart grid-related open source projects operating under the umbrella of the Linux Foundation (opens new window).

Microgrid Knowledge (opens new window) An online newsletter focused on microgrids and distributed energy resources.

# DC Distribution Standards and Systems

# DC Distribution Standards

Current OS Foundation (opens new window) The Foundation is dedicated to promoting Current OS, a microgrid protocol for DC power distribution invented by DC Systems (now a part of Schneider). The web site claims to offer "free access to IP" but so far, it just describes the system via a series of web pages.

EMerge Alliance (opens new window) EMerge is an industry association focused on promoting the use of DC in various forms of power distribution including lighting systems and data centers. It claims to be "open" but access to documents is restricted to members who pay to join.

IEEE P2030.10.1 Standard for Electricity Access Requirements with Safety Extra Low Voltage (SELV) DC for Tier ll and Tier lll of Energy Sector Management Assistance Program (ESMAP) Multi-tier Framework for Household Electricity Supply (opens new window) An IEEE project to define household distribution of power at a nominal 48V. Based on IS 16711.

IS 16711:2017 48 V ELVDC distribution system - Guidelines (opens new window) A standard from the Bureau of Indian Standards for distribution of 48V inside a home with a maximum branch current of 5A. A presentation about the standard is avaiable here (opens new window).

# DC Distribution Vendor Systems

DC Systems (opens new window) Makes products for distribution of DC power at 350V and 700V. These products are designed to work with the Current OS architecture. DC Systems was acquired by Schneider in 2021 and is now a subsidiary of Schneider.

Domatic.io (opens new window) A system for the distribution of ELVDC (~48V) power for commercial and household applications such as lighting, fans etc. utilizing Class 2 wiring and incorporating HD-PLC for communicating between a power hub and application nodes.

Schneider Electric (opens new window). Schneider is a global vendor of power systems components including microgrids. They have an extensive catalog of DC devices including circuit breakers, switches etc.

# Software Defined Power Systems

OwnTech (opens new window): An initiative under CNRS (opens new window) and LAAS (opens new window) to create a library of stackable and reprogrammable hardware and associated software accessible via open source that can be combined to create power systems over a wide range of power levels including both DC and AC. Includes a software API (opens new window) for the modules. The code is available at the OwnTech GitLab Repository (opens new window).

MPLab (opens new window): A Columbia University (opens new window) project to define software defined power systems and motors.

# Off-Grid Energy Access Organizations and Initiatives

African Development Bank (opens new window) Finance organization focused on economic development and social progress in Africa. Offers the Green Mini-Grid Help Desk (opens new window) a resource that offers a wide variety of publications relating to mini-grids from technical advice, finance, commissioning and more.

Alliance for Rural Electrification (ARE) (opens new window) A business association that promotes a sustainable decentralised renewable energy industry.

Africa Minigrid Developers Association (opens new window) A trade association focused on minigrids for Africa.

CLASP (opens new window): An NGO focused on energy efficient appliances to minimize climate change and provide clean energy access. Closely affiliated with other organizations in this section including Efficiency For Access and Verasol.

Efficiency For Access (opens new window): A coalition of NGOs that sponsors activities and funding to support energy access. Offers a library of publications (opens new window) containing reports addressing various aspects of the energy access challenge.

Energy Sector Management Assistance Program (ESMAP) (opens new window): An organization sponsored by the World Bank and other partners to help low and middle-income countries reduce poverty and boost growth through sustainable energy solutions. ESMAP created the multi-tier framework for measruing energy access (opens new window) (full report (opens new window)) that adds clarity and nuance to the concept of lacking energy.

GOGLA - Global Off-Grid Lighting Association (opens new window): Industry association for vendors participating in the off-grid solar industry. Publishes market surveys and coordinates industry standards for interoperablity and quality assurance. In cooperation with Lighting Global, publishes its biannual Global Off-Grid Market Sales Report (opens new window) that provides a detailed breakdown of off-grid market sales. In an attempt to create some standardization of 12V appliances, GOGLA has published The Connect Initiative (opens new window), a recommendation for connectors and electrical requirements.

Lighting Africa (opens new window): World Bank initiative to promote off-grid lighting and electricity specifically focused on sub-Saharan Africa.

Lighting Asia (opens new window): World Bank initiative to promote off-grid lighting and electricity specifically focused on Asia with a regional subgroup focused on India (opens new window).

Lighting Global (opens new window): World Bank initiative to promote off-grid lighting and electricity. Maintains a database of products (opens new window) that have been tested according to well-defined standards. The actual testing of these products has been spun off into a separate organization, Verasol. Lighting Global has regional affiliates Lighting Africa and Lighting Asia.

RMI (opens new window): Rocky Mountain Institute (RMI) is an organization in the United States dedicated to research, publication, consulting, and lecturing in the general field of sustainability, with a special focus on profitable innovations for energy and resource efficiency Wikipedia - RMI (opens new window). One of their initiatives is the Africa Energy Program (opens new window) that seeks to accelerate energy access in sub-Sahran Africa. RMI is based in the US (opens new window) with offices globally.

USAID Toolkit (opens new window) The US Agency for International Development (opens new window) Energy Section (opens new window) offers a tool kit of publications that addresses many aspects of mini-grid development including technical and finance.

Verasol (opens new window): Organization focused on testing and quality assurance for the off-grid energy market, spun-off from Lighting Global. Products are tested against IEC TS 62257-9-8 (opens new window), quality standards for pico-solar products and SHS kits derived from Lighting Global testing procedures. Products that pass are issued a Verasol Certificate.

Wind Empowerment (opens new window): Wind Empowerment is an association for the development of locally manufactured small wind turbines for sustainable rural electrification.

# Off-Grid Energy Access Vendors

Companies currently offering products and services related to Open DC Grid:

Angaza (opens new window): Makes remote management and customer relationship software for off-grid power systems. Angaza is based in the US and Kenya and markets its products globally.

Connected Energy (opens new window): Makes smart monitoring products for off-grid energy including solar and biogas. Connected Energy is based in Scotland and markets its products globally.

INENSUS (opens new window) Software developer and consultancy focused on management software for decentralized utilities. Offers Micropowermanager (opens new window) software as open source with repo on GitHub. Based in Germany (opens new window).

Libre Solar (opens new window): A company founded by Open DC Grid co-founder Martin Jäger that makes PV charge controllers, battery management systems and other hardware for the renewable energy and energy access markets. Libre Solar offers its designs under open source at its GitHub site (opens new window). Libre Solar is based in Germany and collaborates with partners to offer products globally.

MeshPower Rwanda (opens new window): Sells solar powered microgrids and smart meters for the energy access markets. Its business model is to sell energy as a service that does not require the customer to purchase hardware. It is based in Rwanda and its primary market focus is central Africa. MeshPower Rwanda is a subsidiary of Xpower.

OkraSolar (opens new window): Offers tools and hardware for the last mile distribution of power via mesh grids. Okra is based in Cambodia and its primary markets are in East Asia including Cambodia and the Philippines.

Solaris Offgrid (opens new window): Provides software and services for off-grid vendors particularly tools related to pay-as-you-go (PAYGO) billing. Solaris Offgrid is based in London and markets its products globally.

Solshare (opens new window): Interconnects solar home systems into smart peer-to-peer microgrids that allows consumers to monetize excess solar energy by sharing it with neighbors utilizing mobile money. Solshare is based in Bangladesh and its primary markets are in South Asia.

TFE Energy GmbH (opens new window) Consultancy focused on mini-grid markets. Based in Germany (opens new window).

Winch Energy (opens new window): Winch Energy is a global, off-grid energy developer and technology designer and integrator. Focus on Renewable Energy and Energy Efficiency projects in Europe, Africa, Latin America and Asia. Products include Remote Power Unit (RPU) (opens new window) (photo (opens new window)), a containerized turn-key solar minigrid.

Xpower (opens new window): A US company focussed on developing technologies which enable distributed utilities across the developing world to provide rural communities with modern services.

# Vehicle Electrical Standards and Systems

When practical, this standard attempts to harmonize with existing standards for low voltage power distribution used in vehicles.

# Vehicle Electrical Systems

ISO 21780 Road vehicles — Supply voltage of 48 V — Electrical requirements and tests (opens new window) One of the standards this project is intending to harmonize with. It defines functiona state across of range of operating voltages and tests needed to validate that a component will interoperate with other equipment in the vehicle. Based on VDA 320.

VDA 320 - Electric and Electronic Components in Motor Vehicles 48 V On-Board Power Supply (opens new window) A standard from the German auto industry association addressing power distribution at 48V. A good paper about this activity is: 48-Volt Electrical Systems – A Key Technology Paving to the Road to Electric Mobility (opens new window) from ZVEI (opens new window).

LV 124 - A german auto industry standard for electrical components operating at 12V. (Need authoritative reference) A description of the tests is available from WKS Informatik GbmH (opens new window).

LV 148 - A german auto industry standard for electrical components operating at 48V. (Need authoritative reference) A description of the tests is available from WKS Informatik GbmH (opens new window).

SAE 563 Standard for 12 Volt Cigarette Lighters, Power Outlets, and Accessory Plugs (opens new window). The standard that formally describes the ubiquitous cigarette lighter outlet. A 12V link in the project needs to harmonize with devices designed for this outlet. See also Wikipedia: Automobile auxiliary power outlet (opens new window).

ISO 4165:2001 Electrical connections — Double-pole connection (opens new window). The standard that describes the electric outlet used on some European vehicles. Slightly smaller than the American cigarette lighter outlet described by SAE 563. See also: Wikipedia: ISO 4165 (opens new window).

# Electric Vehicle Charging Systems

TU Deflt Open University Overview (opens new window) A good overview of the various standards related to EV charging.

India - Bharat EV Charger Specifications (opens new window) A standard from India for EV charging stations that includes 48V DC charging with currents up to 200A. The DC interface is based on the Chinese EV connector standard GB/T20234.3. The interface includes a CAN with the protocols being a slightly modified version of the Chinese EV charging protocol standard GB/T 27930-2015 which is, in turn, a modified version of SAE J1939.

China - EV DC Charging Connector Standard GB/T20234.3 (opens new window) A standard for a DC charging connector and cable capable of up to 200A.

China - EV Charging Protocol Standard GB/T 27930-2015 (opens new window) The China standard application protocol for EV charging. A modified version of SAE J1939. It uses CAN for electrical connectivity. A CAN newsletter (opens new window) gives an overview of the standard.

IEC 61851 (opens new window) The IEC standard collection for EV charging. Wikipedia (opens new window) has a brief overview of the collection which includes IEC 61851-23:2014 (opens new window) that defines a DC charging station and IEC 61851-24:2014 (opens new window) that defines the DC communications Protocol.

US - EV Charging Communications Standard SAE J1939 (opens new window) A collection of standards for communications relating to EV charging based on CAN. Wikipedia (opens new window) has an overview.

US - EV Charging Connector Standard SAE J1772 (opens new window) The US Standard for an AC charging connector. Wikipedia (opens new window) has an overview.

Open Charge Alliance (opens new window) An association of vendors promoting the Open Charge Point Protocol - an open standard for EV charging.

# V2G - Vehicle to Grid

V2G refers to using the batteries in a vehicle to provide power to a local microgrid or to the utility grid, the inverse of charging, which may be economically advantageous in some circumstances.

SunSpec IEEE 2030.5 / SAE J3072 EV Charging Profile (opens new window) A profile of the IEEE 2030.5 standard for power systems information management that is targeted toward V2G applications.

# Software Standards and Initiatives

OpenAPI Initiative (opens new window): A standard that allows the description of a remote API accessible through HTTP or HTTP-like protocols including CoAP. The API is described in a schema written in JSON. Tools exist to translate the schema into client or server source code in many computer languages and frameworks.

The following items are organized roughly by layer according to the OSI model (opens new window) but note that things don't always fall neatly into that model or span multiple layers.

# Layer 1: Physical Layer

6loWPAN - Transmission of IPv6 over Low-Power Wireless Personal Area Networks (RFC 4944) (opens new window): This RFC addresses using IPv6 in resource constrained devices. It defines how to combine small 127-byte frames into larger packets. The RFC is oriented toward wireless networks but wired communications in resource constrained devices face many of the same issues and can use the same techniques. It is extended by RFC 6282 Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks (opens new window) that addresses header compression.

CAN bus - Controller Area Network (opens new window): A multi-master serial bus originally designed by Robert Bosch, gmbh (opens new window) for use in automobiles but now expanded to many applications, especially automation. It is formally defined by a series of ISO standards (ISO-11898 (opens new window)) that include multiple physical transmission standards and link-layer protocols. The standard does not specify connectors so multiple connector types (opens new window) have been informally adopted. An older version of the standard (opens new window), now superseded by the ISO version is available online. Prototype boards developed by Libre.Solar and used for testing by ODG include CAN bus functionality.

HD-PLC (High definition power line communications) (opens new window): HD-PLC is a profile of IEEE 1901a-2019 managed by the HD-PLC Alliance (opens new window), a vendor trade organization. HD-PLC incorporates "HD-PLC Complete" which is basically the IEEE version and "HD-PLC Multihop" that includes hopping technology described in ITU-T G.9905 (opens new window) to extend the range via retransmitting nodes.

IEEE 1901-2010 Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications (opens new window): A standard for communicating using power lines. The original version was based on FFT OFDM. In 2019, an amendment known as IEEE 1901a-2019 was added to support wavelet OFDM for higher data rates and longer range. Two related standards have been created by the same committee, IEEE 1901.1 which uses mid-frequency (< 12 MHz) OFDM and IEEE 1901.2 low frequency (< 500 kH) for use on wide area power line networks.

LIN - Local Interconnect Network (opens new window): A system for transmitting low-speed data using flat (not twisted pair) wiring. LIN was original designed for use as a less expensive alternative to the CAN bus in automobiles. It is formally defined by a series of ISO standards (ISO-17987 (opens new window)) that include link-layer protocols but good information about its electrical properties is available from semiconductor vendors who offer low-cost transceivers. ODG is primarily interested the use of these transceivers that implement the physical layer.

LoRa (opens new window) A proprietary modulation technique for low-power wide-area communications. LoRa defines the physical layer and a protocol stack defining upper layers is referred to as LoRaWAN. The system is supported and promoted by an industry trade group, the LoRa Alliance (opens new window).

LIN Protocol and Physical Layer Requirements - TI SSLA383-2018 (opens new window): This TI application report provides good details about the LIN physical layer.

OpenPAYGO Link (opens new window): An initiative by Solaris (opens new window) to define a system for low-cost communications between appliances and solar home systems based on a LIN physical layer but supporting dynamic address assignment. Solaris presented an overview during the ODG meeting of August 11, 2020 (opens new window).

# Layer 3: Network Layer

IPv6 - Internet Protocol version 6 (opens new window): The replacement for 32-bit IPv4 that, among other things, extends the address to 128-bits so that every device can have its own unique address in the global internet These addresses are defined in RFC 4291 (opens new window) but there are many related RFCs. Some ODG functions operate without any network or transport layer

# Layer 4: Transport Layer

UDP - User Datagram Protocol (opens new window): One of the foundational protocols of the internet (along with TCP (opens new window)) used to send raw packets without guarantees of delivery. It supports both unicast and multicast transmission. The original definition is RFC 768 (opens new window) that dates back to 1980. Much ODG traffic is conceptually carried in UDP packets but much of it may be elided through various optimizations.

# Layer 5: Session Layer

Constrained Application Protocol (RFC 7252) (opens new window): A transport protocol specialized for use in resource constrained devices. It implements a REST semantics of GET, PUT etc similar to the similar HTML operations with an exponential backoff retry. The RFC describes this as a transport protocol because it can provide delivery guarantees but it typically rides on UDP but other transport bindings are possible including TCP.

# Layer 6: Presentation Layer

CBOR - Concise Binary Object Representation (opens new window): A data interchange format based on JSON but binary encoded for a more concise representation. It is formally defined in RFC 7049 (opens new window).

JSON - Javascript Object Notation (opens new window): A data interchange format based on human-readable text used widely in the internet and in ODG tools and device resources. It is formally defined in RFC 8259 (opens new window).

# Layer 7: Application Layer

Angaza Nexus Channel (opens new window): A transport-agnostic application layer for secure communication between resource-constrained devices particularly focused on implementing PAYGO (pay-as-you-go) in resource constrained devices. Nexus channel implements a subset of OCF, split between the core which implements the resource model and the full channel that addresses security. It is an MIT-licensed open source project with a GitHub repository (opens new window). Angaza presented an overview during the ODG meeting of August 11, 2020 (opens new window).

IEEE 2030.5-2018 - IEEE Standard for Smart Energy Profile Application Protocol (opens new window): A transport-agnostic protocol for the smart metering and automation of demand/response and load control. Similar to OCF, IEEE 2030.5 uses REST to manipulate resources but in this case the methods are HTML and the resources are represented in XML. The models are based on those of SunSpec (opens new window) /IEC 61850 (opens new window) and have origins in Zigbee SEP 2.0 (opens new window). IEEE 2030.5 is the "default protocol" for California Rule 21 (opens new window) on distributed energy resources with the intent that it be implemented by smart inverters attached to the public grid or by intermediate aggregators where IEEE 2030.5 is the communications protocol to access the inverter functionality defined by IEEE 1547 (opens new window). Modbus is an alternative.

IoTivity (opens new window): An Apache-2.0 licensed open source reference implementation of OCF available via a GitHub project (opens new window). It includes a variety tools in various repositories but the primary implementation iotivity-lite (opens new window) is in C and includes a light-weight CoAP implementation.

Modbus (opens new window): A family of communications protocols that span all layers of the OSI model. At its core, Modbus is a simple get/set protocol for basic resources are identified by proprietary station addresses and function codes. The original devices were Modicon (Schneider) programmable logic controllers but the protocol has been applied to many other devices. Of most interest to ODG is a set of Modbus specifications (opens new window) from the SunSpec Alliance (opens new window) that define how to query and manipulate a grid-connected inverter. The latest versions of these standards are semantically equivalent to the IEEE 2030.5 resources.

OCF - Open Connectivity Foundation (opens new window): A multi-vendor initiative to define an application layer protocol to manipulate IOT devices based on rigidly defined resource models that are manipulated using REST-type transactions. The OCF standard documents have been submitted for release as an ISO standard but currently can be downloaded from the OCF web site (opens new window). The models themselves can be downloaded from oneIoTa.org.

oneIoTa (opens new window): A repository of OCF device models. These models are JSON files using the schema defined by the OpenAPI Specification (opens new window) which can be read by the Swagger (opens new window) tool to generate API code in various languages. In some cases these models define a complete API for a device. More commonly a device is expected to combine various models like BinarySwitch (opens new window) - a very long-winded way to describe an on-off switch.

OpenADR (opens new window): An open standard to automate and simplify Demand Response(DR) (opens new window), a mechanism by which a utility grid can ask power consumers to reduce power consumption to match the supply available to the utility. In the context of microgrids, the utility grid would ask the microgrid to reduce its demand at the point of common coupling (opens new window). The microgrid would then adjust its internal power flows to minimize consumption from the utility grid.

ThingSet (opens new window): A transport agnostic protocol for the setting of things. It is a client server protocol where the values are represented in JSON for human readability or CBOR for machine consumption. Information is represented as a tree and can be retrieved via a query that can include an entire branch. Modifications use a mechanism similar to iPATCH as defined in RFC 8132 (opens new window), a potentially multi-valued but idempotent modification of leaf nodes. A full-stack architecture is defined including support for serial, CAN and LoRaWAN physical layers. Code is available at the ThingSet GitHub repository (opens new window).

# Embedded Systems, Development Tools and Firmware

# Embedded Systems - Microcontrollers

Arm Cortex-M (opens new window): A family of 32-bit RISC (opens new window) processor cores based on designs licensed from Arm (opens new window). Microcontrollers based on these cores with varying peripherals are available from many vendors include ST, TI (opens new window) and others. Firmware for these microcontrollers is commonly compiled using the GNU tool chain.

STM32 (opens new window): A family of 32-bit microcontrollers based on the Arm Cortex -M series of processors. These are the microcontrollers most commonly used on ODG demonstration boards. A useful way to get started with STM32 is to purchase one of the family of ST demonstration boards referred to as STM32 Nucleo (opens new window). These are low-cost and many come with pins that support Arduino Shields (opens new window).

# Tools for Embedded Software

Docker (opens new window): A lightweight virtualization tool that allows a host computer to execute virtualized images of other platforms. The docker engine is free and available for Windows, Mac and Linux. For development, docker supports creating an image with all the tools installed with known versions and a known OS so a build can be assured of completing, such as zephyrprojectrtos/zephyr-build (opens new window) which is a snapshot of the official Zephyr project build environment.

Eclipse (opens new window): A free and open source desktop integrated development environment (IDE) that supports plugins for a wide variety of specialized tools. Typically these plugins can be applied to the base Eclipse platform (opens new window) or as a download that has the plugin preinstalled so that the combined environment is ready to run, referred to as packages in the Eclipse world. Some packages that may be of interest to ODG developers include:

GNU Toolchain (opens new window): A set of open-source programming tools from the GNU Project (opens new window). Packages (build-essential) to install the tool chain are available on all flavors of Linux. On Windows these tools are typically installed using mingw-w64 (opens new window). On a Mac, the tool chain can be installed with a package manager such as homebrew (opens new window). The tools include:

OpenAPI Tools (opens new window): A collection of tools to edit OpenAPI schemas, generate client or server code and test the schema.

Platformio (opens new window): An open source tool for developing embedded firmware. It can be run as command line interface (CLI) or as an integrated development environment (IDE) operating as an extension to Visual Studio Code (opens new window) a free code editor from Microsoft.

STM32CubeIDE (opens new window): A repackaged version of Eclipse that contains plugins to simplify development on the SMT32 processors including a pinout configurator.

# Operating Systems for Embedded Software

Zephyr RTOS (opens new window): An open source real time operating system(RTOS) (opens new window) that provides the OS platform for ODG's demonstration boards. It's main repository (opens new window) is hosted on GitHub.

Last Updated: 8/7/2022, 10:38:40 PM