Synchronized grid-forming systems
The aim of this project is to propose and investigate control solutions for grid-connected converters to favor large integration of renewables in the power systems. In particular, the focus is on the development of control strategies that allow enhancement of system’s stability and flexibility in power-electronic dominated grid, by controlling the instantaneous energy flow between selected generating units through bi-directional communication links.
The European Union has the ambitious target of at least 27% of energy to come from renewable energy sources (RES) by 2030, with an associated CO2 emissions reduction target of at least 40% (relative to 1990) and at least a 27% saving in energy usage by the same date. Some future European energy scenarios even foresee a very high-RES penetration, and Sweden aims for a 100% renewables generation capacity by year 2040. To address the challenges associated with high penetration and integration of RES in the European system, innovation and development in several research areas, such as system integration, interoperable services, novel controllable devices and coordination schemes are needed in order to guarantee the availability and reliability of the power systems.
The electric power grid is a complex system that continuously requires balance between energy production and consumption, due to its inability to store energy. Furthermore, the system must be available, stable and able to cope with large events, such as short-circuit faults. A high penetration of RES, connected to the grid through power-electronic converters, might negatively impact these critical properties.
It has already been reported in the literature that a large amount of power-electronically interfaced RES might lead to several challenges for the power system such as reduced physical inertia and reduced synchronizing capability following disturbances. Conventional synchronous generators tend to automatically provide inertial and dynamic reactive power support due to the inherent nature of the machines. This is not the case for power-electronic based generation units and can lead to stability issues when the majority of the produced electrical power comes from RES.
Several converter-control solutions to overcome the aforementioned problems have been proposed in the literature, to provide the grid with vital functionalities, such as inertia and frequency support, and black start capability. Converters provide these ancillary services only at the connection point based on local measurements and local control action. Depending on the entity of the event as well as on the characteristics of the system, both in terms of number of synchronous machines available and geographical location of the generating units, this might result in large investments both in terms of need for energy storage and converter requirements.
As intelligence and measurements availability will be spread all-over the system, it is reasonable to consider that in the future converters will communicate and cooperate through bi-directional communication links, aiming at taking full advantage of the flexibility, controllability and speed of response that characterize modern power-electronic converters to increase the robustness and resiliency of the future RES-dominated grid.
Project goals:
To achieve its aim and objectives, the project will have the following specific goals:
Goal 1: to have developed, investigated and ranked different control solutions for synchronized grid-forming systems, and to have validated the effectiveness of the different solutions analytically, in simulation and via laboratory validation.
Goal 2: based on different grid scenarios and RES penetration level, to have identified the minimum number of synchronized generating units needed to guarantee system stability and resiliency.
Goal 3: to have evaluated the impact of system communication latency and delays on system performance.
Goal 4: to have compared the developed concepts with more traditional control strategies based on local measurements and control.
Involved in the project:
Kavian Kamalinejad, Massimo Bongiorno, Mebtu Beza, Anant Narula, Jan R. Svensson, Robert Eriksson, Daniel Karlsson, Lisa Göransson, Olof Samuelsson
Partners
Chalmers University of Technology, Hitachi Energy, SVK, DNV, Soltech Energy, Vattenfall Eldistribution, Lund University
Funders
Energimyndigheten Chalmers University of Technology, Hitachi Energy, SVK