Transmission System Operators (TSOs) and Distribution System Operators (DSOs) employ hands-on operations, directing and controlling the energy grid. A TSO runs overall grid system security and function, and a DSO operates a distribution network. Distributed Energy Resources Management Systems (DERMSs) are platforms of hardware and software manipulated by the DSOs based on Distributed Energy Resources (DERs). “DERs can provide services to both Distribution System Operators (“DSOs”) and Transmission System Operators (“TSOs”). Distributed energy resources (DERs) are typically installed and interconnected to electricity networks that may or may not be completely controlled, monitored, or analyzed by the power system operators themselves.” (1) The integration of TSO and DSO responsibilities regarding DERs reflects various framework options for coordinating DER DERMS services at wholesale (flow of power), transmission (flow of services), and distribution (flow of operational signals) levels using both the TSO and DSO positions in fluent communication. This communication necessarily is both computer and human-oriented. Several types of feedback systems are required by both the TSO and DSO working together.
Screen Shot from IRENA “Co-Operation Between Transmission and Distribution Systems Operators”
TSOs monitor power flow through power lines and substations to the electric grid. DSOs communicate with the TSOs to ensure the power flow continues efficiently and uninterrupted at the electric grid. To do this, the DSO provides steady readings of the DERs and alerts TSOs to electric power supply deficiencies. Feedback communication models on the wholesale value of the TSO's continued supply include decentralized power stations and forecast futures “day ahead” TSO to DSO estimates of power flow availability. In the decentralized feedback model, individual TSO power stations represent single points on a network that communicate with the electric grid and DSO, apart from an integrated TSO representing several substations or an entire regional area of power lines. These solo network points subsidize normal DER ranges when the DSO consults higher than usual activity on the electric grid. Forecast future feedback models rely on estimates from the TSO substations and “last known” power flow averages to give the DSO a decision on how much of the wholesale market power will be available for DER operations. DERMSs regulate this interchange through the DSO. A TSO comes “field ready” to scout and verify alternate area exchange values. When the TSO and DSO communicate decentralized electricity value adds and forecast energy power flow service needs predictions, a DERMS electricity transaction decision adds efficiencies and voltage controls back to the DERs.
When a substation or power line transmission stops or malfunctions, a centralized emergency communication feedback model carries information from the TSO to the DSO so that the DSO can manage the electric grid to transmit to the DERs without power flow interruption. In this emergency feedback model, the DSO needs access to decentralized wholesale electricity to combat electricity transmission depletion. Crisis feedback communications management coordinates between the TSO and DSO. The TSO gives the DSO a “heads up” for power service distribution re-direction. The DSO is necessary to direct acquired power for emergency transmissions through the electric grid to the affected DERs using the DERMS. The DERMS networks substations and power lines for cut-offs and transfers. “This means that consumers should be able to aggregate regardless of their connection points and that exclusive markets limited to a particular DSO area would imply an inefficient limitation of the potential of aggregation of consumers.” (2) Emergency communication reflecting amber alerts or red alerts between the DSO and TSO (at times initiated by the DERMS) can help pinpoint the root cause of the interruption of the flow of electricity for services.
The power flow service of the TSO goes directly to the DER. This type of DER feedback at the TSO level records power flow transmission without necessarily going through the DERMS. The DSO and TSO monitor this power flow of service from DER operational signal feedback through the DERMS and communications directly to one another. SMART devices communicate directly from the DER to the TSO and the DSO. The touchback feedback model ensures the DSO at the electric grid stays informed through the DERMS by DER SMART devices on operational signal failures and power flow distribution interruptions. The DERMS controls the DSO distribution electric grid functions in a vertical platform and reaches the TSO transmission power flow in a horizontal model. Operational signals from the DSO to the DERs create a user environment connected to the electric grid network monitored and measured by a DERMS. “To keep transmission systems operation secure and stable, distribution systems need to be more flexible when exchanging power at the interface with the overlaying grid.” (3) Off-grid DER communication interacts with the TSO for power flow service transmission. These DERs do not communicate with the DSOs DERMS monitoring even voltage, alternate distribution for efficiencies and emergencies, and forecast or problem-solving analytics. This positions off-grid DERs for frequent failures.
Controversy over TSO and DSO requirements for integrated communications exists in some utilities arenas. With the constant DER DERMS interface of power flow, service transmission, and operational signals occurring with the DSOs, TSOs seem to be dispensable. TSOs remain in a position to relay and solve power transmission details and issues. DSOs gather DERMS information about power transmissions arbitrarily, but DSOs concern their operations with electricity distribution. This is a line in the sand. Electricity transmission and power distribution are two separate functions. Since both of these functions are interconnected to the end result of equipping the DERs with electric power service, it makes sense to establish good communications between TSOs and DSOs regarding field and operations decisions independent of the communications fed to and from the DERs and DSOs by the DERMS. Feedback models for decentralization, forecasting, emergencies, and touchbacks all coordinate important information useful for both TSOs and DSOs. The benefit to the DERs as end recipients of electricity transmission and distribution services of continued integration of the TSOs and DSOs in these communication models comes from good management with good customer service. DERs rely on TSO and DSO cooperation. Looking at a DERMS, DERs on-grid must have access to DSO and TSO input and output. The DSO electric grid operation is equipped while the TSO point of value is often neglected. As stated before, a DERMS must be seen as both a hardware and software energy resources management system. It makes sense to include the TSOs' positions of hardware as substations, power lines, etc. as part of a DERMS horizontal platform. This leaves room for expansion of DERMS operations. A TSO and a DSO interdepend functions. These functions are not assumable by a DERMS software umbrella only focused on the DER balanced on the electric grid. Building a complete DERMS environment includes the TSO, DSO, and- of course- the DER.
Resources:
1. Birk, M., Chaves-Avila, J.P., Gomez, T., and Tabors, R., Massachusetts Institute of Technology, “ TSO/DSO COORDINATION IN A CONTEXT OF DISTRIBUTED ENERGY RESOURCE PENETRATION” (October, 2017)
2. Entsoe-E, “Towards smarter grids: Developing TSO and DSO roles and interactions for the benefit of consumers”, eepublicdownloads.entsoe.eu
3. IEEE (PES)- Power and Energy Sector, “IEEE Transactions on Power Systems- Real World Challenges of TSO-DSO Coordination” (2022)