Correction: Rahman et al. An Overview of Power System Flexibility: High Renewable Energy Penetration Scenarios. Energies 2024, 17, 6393

Figure Legend

In the original publication [1], there was a mistake in the legend for original Figure 7. Correlation of PSF needs with space perspectives (local/global) over time. The correct legend appears below.

Correlation of PSF needs with space perspectives (local/global) over time. Image reproduced with permission from the ref. [25].

Missing Citation

In the original publication [1], Ref. [25] was not cited in proper location. The citation has now been inserted in Section 4.2 and should read:

4.2. PSF Classification Based on System Needs

To maintain the power flow smooth and continuous in the power system, it is crucial to maintain a stable transfer frequency, global energy supply, and stable power grid voltages and transfer capacities locally. It has been seen that the PSF solutions and resources can be found locally in the power system and regulating these local resources can make the whole power system flexible and sound. Using the four power system parameters, PSF may be locally maintained over an entire power system. Specifically, flexibility in voltage, flexibility in power, flexibility in energy, and flexibility in transfer capacity (Figure 7) [25].

4.2.1. Flexibility for Power

If the supplied power and the power sought by the loads are equal, a fully functional power system is flexible. In a power grid, transmission and distribution typically take place via alternate current (AC) methods. Flexibility for power in an AC transmission system refers to keeping the power system frequency within a predetermined range to avoid frequency instability for brief periods (the range is seconds to an hour). Traditionally, this is accomplished by synchronically managing the active power of the generators [25].

4.2.2. Flexibility for Energy

Supply and demand energy equilibrium implies future demand scenarios where flexibility requirement is the securement of future energy demand for the short to long-term periods (hours to several years). Energy flexibility is ensured for the long-term perspective by stockpiling raw materials (fuels) for plants or using hydro reservoirs to store energy for the future outlook. Maintaining energy flexibility in the power system for the long term is somewhat complex and requires robust optimization due to variable forecasting and future load scenarios. The scheduled exact timing of maintenance of the baseload thermal units provides energy flexibility and ensures energy availability during high demand [25].

4.2.3. Flexibility for Transfer Capacity

In an AC transmission system, the structural topology and capacity of the power grid play a vital role. The remedial actions, which are real-time operation or anticipated topology changes during use, provide cost-free flexibility in the power system. Over short to medium-term periods, this topological flexibility maintains the supply–demand scenarios during increased peak demands, peak supply, and variability of loads [25].

4.2.4. Flexibility for Voltage

For power system stability and improved power quality, the power grid voltages must be maintained within a pre-defined level throughout the power system. In contrast to frequency stability, voltage stability is greatly impacted by the reactive power of the generating units. The modern power system’s increased distributed generation causes operational variances and bidirectional power flow, which raises the risk of voltage instability. To maintain the voltage within pre-defined levels, urgent flexibility solutions must be provided within the power system. Ancillary services from distributed generators, storage medium, and demand-side smart responses are the paramount flexibility solutions for voltage stability over short-term periods [25].

The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.