Grid Inertia Support From Electrified Rail Transportation

With the large-scale integration of renewable energy sources (RESs) and the increasing phasing out of traditional generators, the inertia support from the load side can benefit the frequency control of low-inertia power systems. In this article, inertia support from trajectory regulation of electric trains is first explored with a novel reference time sliding (RTS) method. To imitate the inertia response of traditional generators, frequency deviation is fed into the reference time of the scheduled train trajectory. By generating the regulated trajectory via sliding the standard reference time in the scheduled trajectory, the unified control of power response and train operation restoration is realized. The resulting train operation delay can be smoothly recovered by offsetting the sliding time deviation via a proportional-integral (PI) controller. To tackle the possible rapid train speed variation due to the inertia delivery, a robust trajectory tracking controller considering actuator saturation is adopted to track the regulated trajectory in perturbed realistic environments. Comprehensive simulations based on IEEE 39-bus system show that the rate of change of frequency (RoCoF) can be reduced by around 1/2 and the frequency nadir can be improved by 16.9%–18.0% in the considered 1%–5% power imbalance events with trains’ participation, demonstrating the effectiveness of the proposed method and the significant inertia-supporting capability of electrified rail transportation.