Decentralized Control of a Distributed Energy Buffer Network

A Distributed Energy Buffer Network (DEBN) is an array of “smart” batteries located in the buildings of various electricity consumers, and interconnected with one another for the purpose of transferring electrical energy, and for communicating and carrying out various algorithms in order to accomplish the following tasks: to maximize energy efficiency by minimizing distribution losses, to lower consumer electricity costs by means of optimized power transfer techniques, and to help resolve the problem of high energy/power demand and the related issue of grid instability. A DEBN is therefore beneficial to both the grid operator and the energy consumer.

Below is a block diagram of a single residential node of a DEBN. In this case photovoltaic production has been incorporated, but is not necessary. Such a system would however render a domestic renewable energy system more favorable.

An example of a consumer’s benefit from this technology would be in the case of the purchase of an electric vehicle. Without a DEBN, the consumer would have to upgrade to a higher power electrical service in order to charge the vehicle quickly, and depending on the consumer’s convenience, he/she may not be able to charge at the particular time of day when electricity rates are lowest (during off-peak hours). In this case the consumer will pay a greater fee for the higher power service (maximum kW of instantaneous power available), as well as a higher consumption rate (price per kWh of energy consumed) if the energy is purchased during peak hours. With a DEBN however, the consumer can save on both of these costs because the accumulator can charge from the grid at low power during off-peak hours, then charge the vehicle at high power during peak hours. In this case the consumer doesn’t require a higher power service for the rapid charging, nor does he/she purchase the electricity during peak hours.

The grid operator on the other hand would benefit from being able to implement a full-out smart grid, one which is capable of eliminating the problem of peak demand and grid instability. Due to the increasing demand for electrical power and the increase in renewable energy generation, electrical grid instability has become a growing problem worldwide. The root of this complex problem lies in grid overloading and power generation derived from uncontrollable sources (renewables such as wind and solar). As a result, undesirable fluctuations in voltage and frequency occur due to extreme power source loading variations, and transmission line voltage drop due to conductor overheating caused by excessive active and reactive power flowing in the grid.

A DEBN is based on a distributed control architecture, where each node shares a portion of the processing work and plays a role in making decisions on behalf of the entire network. The grid operator can however monitor all nodes in the network from a central control station, where all other electrical grid data is collected in the conventional manner, via grid smart meters located in the consumer buildings, at grid substations, and in generating plants. Based on the analysis of the historical data, the grid operator can decide whether or not to update the control algorithms by remotely reprogramming each node. An example of the control software could be to simply charge all accumulators of a specific area when there is excess renewable energy production nearby, and to redeliver that energy to the grid at a later time, when there is less renewable energy production and a peak demand for power. This will ensure local use of the generated energy and avoid excessive transmission line losses, as well as prevent grid overloading. Therefore, stability of the electrical grid can be achieved and this can translate to cost savings for the grid operator as well.

One of the main reasons for the choice of a distributed control architecture is for a greater level of fault tolerance. Since the network is not directly controlled by a central control station, but is instead just monitored and updated by it, a major fault in the control center would not necessarily affect operation of the network. Even if the fault causes certain sections of the grid to go down, those specific sections can be islanded from the main grid and they can continue to operate as independent microgrids, running off of the energy stored in the various accumulators pertaining to those sections. The other major reason for the distributed architecture as opposed to a centralized one is for compatibility. Not all grids around the globe are equipped to accomplish such a task, and even though many are equipped on a hardware level, a significant effort would be required to develop the control software, and not all grid operators would be ready to make such an investment this early on. What can be proposed for development is a particular method of implementing the decentralized control of a DEBN, such that the systems can be installed and fully functional without the dependence for a specific infrastructure in the electrical grid.