Overview

Approximately 1.2 billion people will need to gain access to electricity to achieve the universal access goal by 2030. The only viable way to achieve this is through a combination of undergrids (main grid extensions) and microgrids.

Aided by new technologies, stronger policies, and innovative business models, microgrids now have the potential to provide quality energy for productive uses to communities that would otherwise wait years for a grid connection.

Furthermore, microgrids are a resilient and reliable alternative to the traditional powergrid due to their diverse set of generation resources; this diversity is particularly advantageous for geographies where there are unpredictable grid failures.

A typical microgrid comprises a set of generators such as solar PV or diesel, often coupled with energy storage. These components are usually referred to as Distributed Energy Resource (DER).

To make the most of the available DERs, an intelligent control system is required to provide monitoring, control and optimised operation of the microgrid. Such a control system comprises:

  • a collection of mediation devices which are the local DER integration points

  • sensors for additional data capture which can influence the microgrid operation

  • cloud computing services for information processing and online human interactions

Smarter Microgrid Ltd (SML) has developed a distributed microgrid controller which exploits open source software and standardised IoT protocols to integrate the generation and consumption sources across a microgrid; utilising affordable single board computers as its mediation devices.

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Unified Management System (UMS) overview

The Unified Management System (UMS) is part of the Internet-of-Things (IoT) revolution enabled by smart digitalisation; it helps to transform electricity generation and distribution by improving the management of new and existing minigrids.

These IoT transformations are enabled by the combination of:

  • widely available off-the-shelf low cost but powerful single board computers

  • sophisticated and reliable open source operating system and application software

  • flexible distributed application software development toolkits developed for the web

  • comprehensive cloud-based computation, data storage and comms facilities

UMS Features

UMS provides three key facilities Instrumentation, Control and Policy. These are each outlined below

Instrumentation, Collection, Persistence and Monitoring

Every DER is equipped with a control system which is responsible for its operation and being the interface for human intervention.

UMS collects and processes the available data from DER’s control system, consumers and any additional sensors within the microgrid. There is no constraint on the data source, therefore, external data such as “upcoming weather events” or “the price and availability of diesel” can also be integrated into UMS for further data correlation and analysis.

The collected data is backed up, prepared and presented through the UMS’s online user interface.

Control

UMS provides intelligent control of the microgrid’s DERs and consumers to address the requirements set by the microgrid operator.

These objectives are typically intended to optimise the overall microgrid efficiency. The improvements are achieved by: UMS facilitating all the microgrid components to coherently work together Maximisation of the productive use of electricity from the valuable, and sometimes limited DERs Consumer management and control based on energy availability, time of day tariffs or any other desired policy variations

UMS’s active notification capability enables the microgrid operator to set relevant thresholds on any important measurements. The system automatically distributes alerts to a predefined list of people once the threshold is met.

The same alert distribution technology is also capable of sending scheduled reports and information streams at any required frequency or resolution.

Policy

UMS implements a user configurable policy engine to provide flexible system behaviour configurable by the local operator and therefore not requiring code changes by the system developer to adapt to the inevitable changes in the system’s environment.

This dynamic adaptability to changing circumstances ensures consistent performance from the initial commissioning and system improvement and as the minigrid evolves over time.

The UMS’s policy system is expressed in the form of spreadsheets:

Rules are expressed in MS Excel formula, referring to signals originating as real time MQTT topics Signal topics are logically connected to particular spreadsheet cells The spreadsheets are compiled into a directed acyclic graph representation, facilitating parts of the graph to be distributed to mediation devices, based on affinity to signals The graph segments are re-evaluated once per time-step using current signal values

Policy decisions are further improved as UMS integrates extra data points from different sensor types such as temperature, sound, light, rainfall or any other accessible data.

Mediation Device

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Functionality

Implementation of the UMS onto a minigrid is accomplished by deployment of a number of low-cost computer devices by the minigrid DERs; UMS refers to these as Mediation Devices.

Mediation devices facilitate the communication ‘through link’ and integration of the DERs into the UMS platform by performing the following functions:

  • Intelligent syntactic and semantic protocol conversion of each of the minigrid’s various DER to the USM’s common internal attribute representation communicated using the industry standard MQTT protocol

  • monitoring and local management of each DER. e.g. Mediation Devices provide a local policy execution point that continue to function in the event of loss of communications with the upstream monitoring systems

Portability

All UMS features have been developed to run on very low cost single board computers with the initial target being the Raspberry Pi 3b. Built using the popular Python programming language running on the freeware open Linux OS, all UMS software is easily portable to the continuing flow of ever cheaper single board computers as they become available over time e.g. the Raspberry Pi 4. In the rare event that more power is needed for a particular task, any computer that supports Linux can be applied.

We have used a combination of Python code for mediation devices, and TypeScript/Node.js for microservices.

Powerful Remote Supportability

UMS is implemented on the BalenaOS version of Linux, developed specifically for the IoT deployment environment. Balena provides sophisticated multi application support using containerisation.

The Balena Cloud / Open Balena provides:

  • Remote node monitoring

  • Over-The-Air (OTA) software updates - OTA eliminates the need for physical proximity to the Mediation Device for the application of both OS and application software updates. This is especially advantageous in the context of rural minigrids in remote areas.