Hysteresis-based charging control of plug-in electric vehicles

The paper develops a hysteresis-based charging control strategy for plug-in electric vehicles (PEVs) that is capable of regulating charging load to satisfy system-wide services, including filling the overnight demand “valley” and balancing fluctuations in renewable generation. The actual state-of-charge (SoC) of a PEV battery follows a nominal SoC profile within a small hysteresis band. This leads to a sequence of ON and OFF cycles for the charger. The paper shows that in steady-state the probability distributions of SoC in the ON and OFF states, normalized around the nominal profile, follow a uniform distribution over the hysteresis deadband. Based on this steady-state behavior, a linearized state-space model has been developed to capture the response of aggregate electricity demand to shifts in the nominal SoC profile. A feedback control law is designed based on this linearized model.