A large penetration of grid connected distributed energy resources (DERs) can cause voltages in the grid to rise and fall, leading to added stress on equipment traditionally used to handle these fluctuations. Additionally, the resulting mismatch in phase between current and voltage manifests as reactive power (measured in VAR), reducing the real power delivered by the grid. Current control architectures in advanced inverters are designed to maximize real power while controlling reactive power in order to mitigate local voltage issues. These systems, based on Volt/VAR control, are fast but sub-optimal and cannot provide stability guarantees under uncertainty, such as the uncertainty introduced by the production of solar energy. To ensure a resilient and high-performance grid under a large penetration of DERs, a more robust solution is necessary.
Researchers at NREL have developed a novel control architecture based on a Volt/VAR/Watt control mechanism. This system manages both real and reactive power output via an optimization approach at each individual inverter. This approach allows the accommodation of many objectives such as the minimization of voltage deviation from a given profile, individual consumer objectives such as maximum real power production and the maximization of stability. Although the controllers are decentralized, the inclusion of AC power-flow equations allows for a network-aware approach where inverter outputs are dependent on their location in the network.
For more information, please contact Erin Beaumont at Erin.Beaumont@nrel.gov
Applications and Industries
- Bulk grid and microgrids
- Residential and commercial PV
- Energy storage and inverters
- Electric utility companies
- Optimizes power output of DERs to the distribution network
- Ensures stability under uncertain conditions
- Accommodates diverse objectives
- Allows decentralized, network aware control of DERs