HYB25-89
Hardware-in-the-loop island testing: Evaluation and improvement of frequency stability in grids with low inertia
04 HYB25-89
Presented by: Eddie Eriksson
Solvina, Sweden
Grids with a high penetration of renewable converter-interfaced electricity production, microgrids and island grids often have lower inertia and/or fewer units providing frequency control than in large interconnected systems. Therefore, keeping the frequency stable is more challenging. The smaller number of units make achieving good performance at each individual power plant more important. Simulations are often employed to study frequency stability, but on the scale of island grids, the level of detail needed in power plant models is higher. With fewer units, the practice of linearising and “averaging out” nonlinear behaviours is not feasible in the way it is done for larger systems. On the other hand, operating a small island and introducing disturbances is the most realistic test of a power plant’s frequency control, but comes with its own disadvantages. The limits of stability cannot be tested without accepting the risk of disconnections and tripping. At the same time, load characteristics can vary over time, making it difficult to repeat tests under equal conditions.
A balance is struck between realism, safety and repeatability with simulated island tests with hardware-in-the-loop (HIL), the method discussed in this presentation. A power plant stays connected to a larger grid, while an island grid is simulated in the HIL equipment. The frequency controller of the power plant is fed the frequency from the simulation instead of the physical grid frequency, while active power and other relevant quantities are measured. The method has been used to evaluate the ability of power plants to handle stepwise load changes like during energisation of an island grid, to tune the island mode of frequency controllers, and to study simultaneous frequency control provided by multiple units.
A selection of results from different simulated island operation tests is presented, along with insights. This includes tuning of island controllers, tests on individual plants in island grids, and island tests on storage co-located with conventional production.
A balance is struck between realism, safety and repeatability with simulated island tests with hardware-in-the-loop (HIL), the method discussed in this presentation. A power plant stays connected to a larger grid, while an island grid is simulated in the HIL equipment. The frequency controller of the power plant is fed the frequency from the simulation instead of the physical grid frequency, while active power and other relevant quantities are measured. The method has been used to evaluate the ability of power plants to handle stepwise load changes like during energisation of an island grid, to tune the island mode of frequency controllers, and to study simultaneous frequency control provided by multiple units.
A selection of results from different simulated island operation tests is presented, along with insights. This includes tuning of island controllers, tests on individual plants in island grids, and island tests on storage co-located with conventional production.