- Independent cells with mutually unsynchronized phases and frequencies are connected using DGRs composed of power converters and coordinated transmission lines, which exchange electric energy between selected cells by supplying specified energy directly through power converters to the designated end point defined by an address
- In each synchronized system within a cell, power equipment control devices called digital grid controllers (DGCs) are used to transfer information and thereby to control power equipment such as generators and energy storage devices
- Each DGR and DGC has a CPU, memory and network communications, and are assigned unique IP addresses and communicate using an IP protocol like on the Internet
- For communications, the power transmission line can be used so as to integrate power and information on a single line, or an external data network may also be used
- A DGR may have two types of leg: either with power conversion or without power conversion. Each point-to-point connection is composed of a set of legs, one with power conversion and the other without. This avoids the undesirable and unnecessary double conversion of power.
The Digital Grid as described so far enables a robust wide-area grid through segmentation and planned energy flows. This subset of the Digital Grid concept is a logical extension of the Tres-Amigas* project under construction in Texas, which seeks to connect the three North American primary interconnections through a similar AC/DC/AC link.
However, the Digital Grid supports smaller segments, and has addressable exchange of energy between cells which are not directly connected. The digital grid is a new architecture for the grid, not a single point solution like Tres-Amigas. In order to enable very high penetration of renewables, each cell must be made substantially self sustaining, with pre-planned injections of energy to meet forecast shortfalls. This next stage of diffusion of the Digital Grid will require energy storage.
If each cell has suitable energy storage, it is freed from the conventional restriction of exactly matching generated power with demand each second. With the existing grid, the value of energy is inherently tied to the time it is produced as well as the time it is required, which is the time-related value of electric power.
Our Digital Grid removes this time-related value of energy, and enables true commodity pricing of energy