How to Assure Grid Stability While Tapping Third-Party Energy Sources

The California Public Utilities Commission approved a pilot program in December that incentivizes utilities to use more distributed energy resources. These resources are defined as renewable generation sources, energy efficiency, energy storage, electric vehicles, and demand response technologies. As part of the pilot, the utilities must identify where distributed resources can be placed on the grid utilizing a seven step process. Several tools are available to help utilities plan and identify optimal locations on the grid for third-party energy resources.

Currently, the grid is designed to carry electricity one way from centralized generating facilities to consumers. Distributed resources allow for a two-way stream of electricity that offers advantages such as selling electricity to make up for deficiencies in different parts of the grid, but causes some uncertainty. Because the grid is not designed to handle reverse flows of electricity, high levels of distributed resource penetration could exceed energy consumption and cause high-voltage swings. These could harm or put stress on customer equipment such as circuit breakers, and make operation of the distribution system more difficult.

Analyses of multiple scenarios and energy flows moving in many directions across the electric grid need to be conducted to ensure grid stability. Stress testing and faster response times could help relieve concerns and confirm distributed resources are capable of providing electricity. Algorithms could provide fast decision routines and real-time feedback control, but they are not easily tailored to the grid’s unique assets. System complexity is exacerbated by cyber threats.

Planning for third-party energy sources must include assessments of highly volatile supply and demand that result from customer behavior. This is demonstrated by electric vehicles which are expected to become more common, especially in high-income areas with environmentally conscious consumers. As more people need to charge electric vehicles, the peak to average electricity demand could increase, reduce capacity utilization and increase rates depending on when they are charged. If cars are charged when users return home from work, they could significantly add to peak energy consumption, but if electric vehicles are charged overnight energy demand would increase unlike now when it is typically low.

Utilities could use management systems to assess the impacts of distributed resources. Advanced Distribution Management Systems allow utilities to understand conditions across service territory with communication, intelligence, and visibility of the distribution grid in real-time. In addition, the Distributed Energy Resource Management Systems allow utilities to dispatch resources and forecast supply and demand conditions up to 24–48 hours in advance, and integrate data with other utility systems.

Grid operators and distribution utilities need to be able to locate electricity and plan for the grid to operate correctly. However, some distributed energy resources are located “behind the meter,” where the electricity produced is intended for on-site use such as a home or office building. Because operators cannot locate or plan for such resources, regional blackouts could occur where difficulty is experienced meeting energy demand in extreme circumstances. Other distributed resources such as solar and wind power are dependent on weather conditions, and variability can create extreme changes in power output over short periods. Hence, system operators experience difficulty when attempting to match generation load at every moment, potentially creating grid instability.

Data and information are necessary for operators and providers to properly manage the electric grid. Information, such as hosting capacity analysis, interconnection studies, and short and long term operational planning, allow for the optimization of different distributed resources specific to their location on the grid.  Access to other types of information and data also allow regulators to make better decisions about the performance of the distributed system. However, sharing such data requires navigating challenging issues about privacy, security and the market design of the grid.

Increased situational awareness is vital to the stable operation of distributed resources on the grid.  Phasor measurement units utilize sensors to monitor characteristics in small increments, about 30 to 120 samples per second, and are time-stamped and synced with other units to get a clear picture of activity. Such data allow control systems and operators to see disturbances as they begin to develop, analyze the situation in relation to information from other parts of the grid and take corrective action. This data can be used by system operators to anticipate contingencies, reduce the risks of wide-area blackouts, enhance system efficiency and improve system models.

There may be times when a distributed resource is unable to operate or experiences disruption. The pilot program requires utilities to develop contingency plans to allow for uninterrupted flow of quality electricity. Such plans could minimize the economic effects if electricity supply is interrupted. Furthermore, transparency and cross-jurisdictional cooperation between grids along with infrastructure upgrades and new distributed control systems would increase electricity reserves and prevent interruptions.

The success and competitiveness of the U.S. economy is dependent on the uninterrupted flow of quality electricity. Such disruptions come in different forms and durations and are not always predictable or preventable. Utilities in California will increasingly need to utilize analytic tools available to increase situational awareness, and identify optimal locations for distributed resources on the grid. Such instruments will ensure third-party energy resources operate successfully and will help create backup plans to minimize reliability problems.