Energy security is one of the most crucial factor in the development of any nation. Interconnections among different power system networks are made to lower the overall price of power generation as well as enhance the reliability and the security of electric power supply. Different types of interconnection technologies are employed, such as AC interconnections, DC interconnections, synchronous interconnections, and asynchronous interconnections. It is necessary to control the power flow between the interconnected electric power networks. The power flow controllers are used to (i) enhance the operational flexibility and controllability of the electric power system networks, (ii) improve the system stability and (iii) accomplish better utilization of existing power transmission systems. These controllers can be built using power electronic devices, electromechanical devices or the hybrid of these devices. In this paper, control techniques for power system networks are discussed. It includes both centralized and decentralized control techniques for power system networks. This paper also presents a comprehensive review of HVDC interconnections, asynchronous AC interconnections, synchronous AC interconnections and different types of power flow controllers used in these interconnections. Moreover, some important and multivariable flexible AC transmission system (FACTS) devices such as UPFC and IPFC are also discussed with their merits and limitations. Finally, a new asynchronous AC link called flexible asynchronous AC link (FASAL) system is also described in detail. At last, a summary of the comparative analysis of power system link and power flow controllers is given based on recent publications. More than 400 research articles and papers on the topic of power transfer control are covered in this review and appended for a quick reference.

Fast rotating machines require special attention to ensure accurate rotor placement within the air gap. For this reason, the active magnetic bearings (AMB) system is used to levitate the rotor in the air gap using an electromagnetic feedback control force. The contact-less support AMB system improves the rotor dynamic performance and helps in the success of machine operations. However, the control design for the five degrees-of-freedom (DOF) AMB system is intricate because of its complex nonlinear dynamics. Moreover, these systems are often subjected to model uncertainties, harmonic disturbances, and sensor noises. Therefore, this paper proposes a robust control strategy using an adaptive second-order non-singular fast terminal sliding mode control (SMC) design. The proposed control law employs the higher-order SMC scheme to alleviate the chattering problem from the discontinuous SMC input, which would otherwise restrict its practical applicability. Further, a non-singular fast terminal sliding surface is selected to achieve a faster system response. The adaptive law estimates the switching gain to relax the upper bound assumption of disturbance. The theoretical stability analysis of the proposed methodology proves the finite-time convergence of system states to a small residual bound in the neighborhood of zero. The numerical analysis with a comparative study is also carried out to illustrate the efficacy of the proposed strategy.

This paper presents a robust artificial time delay based attitude regulation control of a small spacecraft under the influence of parametric uncertainties, surrounding disturbances, and time-varying actuator faults. In the artificial time delay (ATD) approach, the input-output information of the previous time instant is utilized to estimate the uncertain dynamical parts. The proposed attitude controller is designed by integrating the time delay approach with a feedback control technique. Under the proposed composite control scheme, the system states are proved to be uniformly ultimately bounded (UUB) stable using the Lyapunov analysis. Moreover, the problem of unwinding in the quaternion representation, due to which the spacecraft consumes more time and energy, is also resolved under the proposed scheme. The performance of the proposed control methodology has been validated using numerical simulations. Furthermore, two different control schemes are also compared to illustrate the efficacy of the proposed strategy.

With an accurate state of charge (SOC) estimation, lithium-ion batteries (LIBs) can be protected from overcharge, deep discharge, and thermal runaway. However, selecting appropriate algorithms to maintain the trade-off between accuracy and computational efficiency is challenging, especially under dynamic load profiles such as electric vehicles. In this study, seven different widely utilized online SOC estimation algorithms were considered with the following goals: (a) to compare the accuracy of the different algorithms; (b) to compare the computational time in the simulation. Since the 2-RC battery model is highly accurate and not very computationally complex, it was selected for implementing the considered algorithms for the model-based SOC estimation. The considered online SOC estimation performance was evaluated using measurement data obtained from experimental tests on commercial lithium manganese cobalt oxide batteries. The experimental analysis consisted of a dynamic current profile comprising a worldwide harmonized light vehicle test procedure (WLTP) cycle and constant current discharging pulses. In addition, the performance of the considered different algorithms was compared in terms of estimation error and computational time to understand the challenges of each algorithm. The results indicated that the extended Kalman filter (EKF) and sliding mode observer (SMO) were the best choices because of their estimation accuracy and computation time. However, achieving the SOC estimation accuracy depended on the battery modeling. On the other hand, the estimated SOC root means square error (RMSE) using a backpropagation neural network (BPNN) was less than that using a Luenberger observer (LO). Moreover, with the advantages of BPNNs, such as no need for battery modeling, the estimation error could be further reduced using a large size dataset.

This paper proposes a robust event-driven control for attitude regulation in flexible spacecraft affected by inertial parametric uncertainties and external disturbances. The bandwidth constraint of the communication channel between controller and system requires an event-based control design. Under the action of proposed control law, the system trajectories are ensured to be uniformly ultimately bounded (UUB) in a small vicinity of their equilibrium points. Apart from the boundedness of states, the proposed event-triggered controller also satisfies bandwidth restrictions by achieving a substantially low control usage. The results obtained from numerical simulations are indeed encouraging. It demonstrates the proposed controller as a potential alternative to the periodically sampled data controllers. Moreover, the proposed control strategy successfully eludes the unwanted unwinding phenomenon encountered in quaternion based attitude control of the spacecraft.