Lack of charging facilities is still a significant barrier for electrification of the logistic system. How to effectively schedule the electric vehicle (EV) charging power to reduce the charging station operating cost when the number of chargers was limited becomes an important issue. To tackle this issue, an optimal charging scheduling method by responding to the time-of-used (TOU) electricity price is proposed. First, the uncontrolled charging model to fully charge EVs as fast as possible is established. Then, an optimal charging scheduling model by considering the limited number of chargers is proposed to both reduce the charging cost and guarantee the charging demand of each EVs. The proposed model is formulated as a bilevel programming (BP) model. The charger index and available charging duration for each EV are determined at upper level, while the charging power of each EV at each time slot is determined at the lower level. After that, a solving approach is introduced for the proposed BP model. The efficacy and performance of the proposed charging scheduling method is verified by simulation results.

The increasing of electric vehicles (EVs) alleviates the faced environmental problems but brings challenges to the optimal operation of transportation network (TN) and distribution network (DN). However, the most of existing research works consider EV charging station assignment and navigation services in the TN separately from charging station power scheduling services in the DN. To overcome this research gap, this paper proposes a collaborative optimal routing and scheduling (CORS) method, providing optimal route to charging stations and designing optimized charging scheduling schemes for each EV. In the order of reporting, whenever an EV reports its charging demand, a CORS optimization model is built and solved so that a specific charging scheme is designed for that EV. Then, the TN and DN status is updated to guide the subsequent EVs operating. The proposed CORS integrates the real-time state of the TN and DN, and effects positive benefits in helping EVs to avoid traffic congestion, improving the utilization level of charging facilities and enhancing charging economy. The combined distributed biased min consensus algorithm and generalized benders decomposition algorithm are adopted to solve the complex nonlinear optimization problem. Through comparing with the existing methods, better effectiveness is verified by simulation results.

With the rapid development of high-speed and heavy-load electrified railway, the peak impact and the regenerative braking energy content of traction load become increasingly significant, which has become an important problem affecting the construction and operation benefits of electrified railway. On the basis of comprehensively solving the power quality problems of electrified railway, a multi-application strategy based on the railway static power conditioner (RPC) with the energy storage system (ESS) is proposed in this paper to improve the economic benefits of the traction system. Through the implementation of the peak clipping and the recuperation and utilization of regenerative braking energy of traction load with the guidance of such strategy, the comprehensive economic benefits of the traction system can be improved. By analyzing the mathematical relationship between the comprehensive economic benefits and the parameters such as peak clipping rate and regenerative braking energy utilization rate of the system, an optimization model with the goal of maximizing the comprehensive economic benefits is established. Therefore, the optimal configuration capacity of the ESS is obtained. Finally, the experiments are carried out in MATLAB. The results show that, with the multi-application strategy, the peak load clipping and the recuperation and utilization of regenerative braking energy can be simultaneously realized. It is also demonstrated that the comprehensive economic benefits and environmental benefits can be improved while improving energy efficiency.

This paper proposes a distributed fractional-order predefined-time sliding mode controller (DFOPTSMC) to adjust the external energy storage to improve the transient stability of the power system with time delay and input saturation. The time delay is able to worsen the performance of the power system, and even bring about instability. Based on the Artstein transform theorem, the model of the power system with communication delay is transformed into a model without delay. Meanwhile, the output of the external energy storage should be limited in practical power systems. The saturation compensation system is proposed to remedy the influence of input saturation of the external energy storage. Therefore, a DFOPTSMC considering communication delay and input saturation is proposed to adjust the energy storage device, which has fast response ability and strong regulation capability, to increase transient stability of the power system. The predefined-time stability of the power system under the DFOPTSMC is analyzed through the Lyapunov function. Finally, simulations are taken to verify that the proposed DFOPTSMC is able to raise the transient stability of the power system as well as ensure that the power system returns to stability region under a large delay margin.

Frequency and voltage are the most significant indicators in AC microgrids (MGs). To maintain the stability of grid frequency and bus voltage, this paper proposes a distributed secondary control scheme based on bi-limit homogeneity for frequency restoration, average voltage recovery, active and reactive power sharing among DGs in AC MGs subjected to non-uniform communication delays and actuator saturations. First, a state-transformation-based strategy by virtue of the past information of the control input is designed to deal with non-uniform delays, which can fully alleviate the adverse effects of communication delays. Additionally, the hyperbolic tangent function is introduced to approximate the non-smooth saturation function and to design anti-saturation fixed-time controller, which can mitigate the impact caused by actuator saturations. Then, by constructing an auxiliary bi-limit homogeneous system, the fixed-time stability of the close-loop control system with the constraint of actuator saturation can be demonstrated. Finally, several simulation cases are conducted to evaluate the performance of the proposed strategy on a test MG system, and the results are compared with other existing methods. Simulation and comparison results reveal the proposed method's validity, robustness and flexibility in restoring the MG's frequency/average bus voltage and achieving accurate active/reactive power sharing.

The frequency and voltage restoration along with power sharing is imperative for the safe, reliable and stable operation of the islanded AC microgrids (MGs). In this paper, a novel distributed fractional-order predefined-time sliding mode controller (DFOPTSMC) is proposed as a secondary controller for the islanded AC MGs. The proposed DFOPTSMC can ensure that frequency and estimated average voltage (EAV) converge to reference value along with accurate power sharing within a setting predefined time. The fractional calculus algorithm is implemented to design the DFOPTSMC, which increases the degree of freedom of parameter adjustment and greatly enhances the flexibility of the DFOPTSMC. In addition, a distributed predefined-time observer is presented to achieve the EAV within a setting predefined time. The upper bound convergence time of the islanded AC MGs under the proposed DFOPTSMC is directly equal to a tunable parameter, thus overcoming the disadvantages of finite-time control and fixed-time control. The Lyapunov function is applied to present rigorous proof to analyze the stability of the islanded AC MGs under the proposed DFOPTSMC. An islanded AC MG is taken into simulation on the Matlab/Simulink 2021a platform and the experimental platform to test and verify the effectiveness and superior performance of the proposed DFOPTSMC. The results indicate that the proposed DFOPTSMC can significantly enhance the dynamic performances of the islanded AC MGs.