This paper presents a discrete-time domain control scheme for balanced voltage sag compensation using a Dynamic Voltage Restorer (DVR), which is recognized to be an appropriate and economical power electronic device with which to ameliorate these disturbances. The proposed control method is implemented in the synchronous reference frame (SRF), with two nested regulators, one of which includes an integral action. This algorithm has some advantages with respect to other control algorithms, such as the fact that the proposed methodology permits all the closed-loop poles of the DVR system to be placed in the desired locations in order to define the dynamical behavior with a reduction in the number of the electrical magnitudes to be measured and without the need for state observers, as occurs in traditional control methods. What is more, the well-known inner current loop implemented in other control schemes, which is employed to attenuate the resonance of the plant, is unnecessary. Furthermore, the unbalanced voltage sag compensation can be achieved by adding a “plug-in” controller and following the same methodology presented for balanced voltage sags to design the controller. The good performance of the proposed control scheme is validated by means of simulation and experimental results carried out with a 5 kW DVR laboratory prototype. The discrete-time control method is also compared with two control schemes previously proposed in literature.

Inductive power transfer (IPT) systems have become a very effective technology when charging the batteries of electric vehicles (EVs), with numerous research works devoted to this field in recent years. In the battery charging process, the EV consumes energy from the grid, and this concept is called Grid-to-Vehicle (G2V). Nevertheless, the EV can also be used to inject part of the energy stored in the battery into the grid, according to the so-called Vehicle-to-Grid (V2G) scheme. This bidirectional feature can be applied to a better development of distributed generation systems, thus improving the integration of EVs into the grid (including IPT-powered EVs). Over the past few years, some works have begun to pay attention to bidirectional IPT systems applied to EVs, focusing on aspects such as the compensation topology, the design of the magnetic coupler or the power electronic configuration. Nevertheless, the design of the control system has not been extensively studied. This paper is focused on the design of a control system applied to a bidirectional IPT charger, which can operate in both the G2V and V2G modes. The procedure design of the control system is thoroughly explained and classical control techniques are applied to tailor the control scheme. One of the advantages of the proposed control scheme is the robustness when there is a mismatch between the coupling factor used in the model and the real value. Moreover, the control system can be used to limit the peak value of the primary side current when this value increases, thus protecting the IPT system. Simulation results obtained with PSCAD^TM/EMTDC^TM show the good performance of the overall system when working in both G2V and V2G modes, while experimental results validate the control system behavior in the G2V mode.

This paper proposes an adaptive operation of an IPT system that can manage significant variations in the value of the magnetic coupling coefficient $k$. It employs a proportional-integral (PI) and a predictive-integral (Pred-I) controller to regulate the DC bus voltage and the battery current on the vehicle assembly (VA) side, respectively. Furthermore, an expert controller is implemented at a higher hierarchical level to monitor the behavior of both control loops and to determine when it is necessary to adapt the IPT system operation. The control tasks are managed solely by the EV, and the charger placed on the parking side operates with no control loop applied. Consequently, the need for real-time data exchange for control purposes between both sides of the magnetic coupling is avoided, and the operation and implementation of the ground assembly (GA) side are simplified. The experimental validation of the proposed operation was conducted on a 3-kW prototype featuring three different air gaps, which is capable of operating either with both a Series-Series (SS) or an LCC compensation network. As a result, the proper operation and adaptation of the system was assessed considering a variation of more than 100% between the lower an higher values of $k$.

The use of compensation networks increases the power transfer capability of inductive power transfer (IPT) systems in the battery charging process of electric vehicles (EVs). Among the proposed topologies, the Series-Series (SS) and the LCC networks are currently in widespread use in wireless battery chargers based on IPT systems. This paper focuses on the study of the behavior of both compensation topologies when they are detuned due to the tolerances of their components. To compare their performances, a Monte-Carlo analysis was carried out using Simulink and MATLAB. The tolerance values, assigned independently to each component, fall within a [ $-20$ , 20] % range according to a normal distribution. Histograms and scatter plots were used for comparison purposes. The analysis reveals that the LCC network allows a tighter control over the currents that flow through the magnetic coupler coils. Moreover, it was found that the increments in those currents can be limited to some extent by selecting capacitors featuring low tolerance values in the LCC compensation. Nevertheless, the SS network remains an appropriate choice if size and cost are essential constraints in a given design.

High-Voltage Direct Current (HVDC) systems are a feasible solution that allows the transmission of energy between several power networks. As a consequence of the use of HVDC systems, renewable energy sources can be integrated more easily into distribution grids and smart grids. Furthermore, HVDC systems can contribute to improving the power quality (PQ) of the grids to which they are connected. This paper presents a multiterminal HVDC system that not only controls the flows of active power between four different networks, but also compensates imbalances and harmonics in the grid currents to maintain balanced and sinusoidal voltages at the point of common coupling of the various grids. The compensation is carried out by the voltage-source converters (VSCs) connected to their respective AC grids. A control scheme based on the use of resonant regulators and proportional–integral (PI) controllers is responsible for of achieving the necessary power flow control with the amelioration of the PQ. A case study of a multiterminal HVDC system that comprises four terminals sharing a DC bus of 80 kV is simulated by means of PSCAD^TM/EMTDC^TM (Power System Computer-Aided Design; Electromagnetic Transients including Direct Current), where the AC grids associated with the terminals suffer from voltage imbalances and voltage harmonics owing to the connection of unbalanced loads and nonlinear loads. The obtained simulation results show the performance of the complete system in terms of active power flow, voltage regulation, and harmonic distortions of the grid current and the grid voltage.