Bipolar dc microgrids have been increasingly adopted in different applications due to their versatility in scaling to higher power levels while maintaining the same safety requirements as lower voltage unipolar ones. On the other hand, power imbalance, commonly faced in bipolar systems, can lead to undesirable voltage deviations that may trigger protection devices, cause corrosion, and increase risks of electric shock. To address this issue, several voltage balancing solutions have been proposed, including self-balancing dc-dc converters, and others active balancers. Both approaches are different in terms of hardware implementation, efficiency, and complexity. In this paper, a two-switch buck/boost voltage balancer and a self-balanced current-fed dual active bridge (CF-DAB) converter are experimentally compared for applications in bipolar dc microgrids. Experimental results are presented using a 5-kW prototype. The results demonstrate that both solutions offer different opportunities for system optimization. However, the processed rms current analysis shows the self-balanced solution providing advantages in terms of efficiency, while the conventional buck/boost balancer offers a more cost-effective solution.

Electric vehicle (EV) charging infrastructure will play a critical role in decarbonization during the next decades, energizing a large share of the transportation sector. This will further increase the enabling role of power electronics converters as an energy transition technology in the widespread adoption of clean energy sources and their efficient use. However, this deep transformation comes with challenges, some of which are already unfolding, such as the slow deployment of charging infrastructure and competing charging standards, and others that will have a long-term impact if not addressed timely, such as the reliability of power converters and power system stability due to loss of system inertia, just to name a few. Nevertheless, the inherent transition toward power systems with higher penetration of power electronics and batteries, together with a layer of communications and information technologies, will also bring opportunities for more flexible and intelligent grid integration and services, which could increase the share of renewable energy in the power grid. This work provides an overview of the existing charging infrastructure ecosystem, covering the different charging technologies for different EV classes, their structure, and configurations, including how they can impact the grid in the future.

Future MVDC shipboard power systems will be characterized by a progressive employment of power converters. In this paper, starting from a real case-study, the focus is on two AC/DC power conversion stages forming the MVDC bus of a shipboard power system. A preliminary design of the AC/DC power conversion stages and their control system is provided in order to verify feasible operations. A coordination strategy based on the droop control technique is adopted achieving load power sharing. Simulation results verify proper operation also in case of pulsating loads.

In this paper the Feedback Linearization (FL) control theory is applied to a grid-connected Cascaded H-Bridge (CHB) converter. A DC voltage control is designed taking into account the nonlinear model of the converter and its performances are compared with the performances obtained in case of a conventional PI controller. With the aim to provide a fair comparison, the results are evaluated in terms of: settling time in case of a reference voltage variation, voltage overshoot in case of a load variation and total harmonic distortion of the grid current. Simulation and experimental results demonstrate that the FL-based control provides higher power quality and faster response to reference variations than the PI control. Comparing the performances in terms of responses to the load variations, better dynamics performance can be achieved also with the FL-based control increasing the settling time while maintaining an admissible grid current total harmonic distortion index.

In Distributed Power Generation Systems (DPGS), the control system of the converter, interfacing the electrical source with the main grid, is generally based on a dual loop cascade control structure where the internal loop is in charge of the current control while the outer loop controls the voltage at the DC link. The DC voltage can be subjected to transient conditions due to the change of the power produced by the source. If the system experiences high and abrupt variations of the DC voltage, the control system designed starting from a small signal linearized model can fail. In this paper, a Simplified Feedback Linearization (SFL) control is designed for a single-phase grid-connected converter. The system is compared with a classical dual loop control in terms of stability and dynamics performances. Simulation and experimental results confirms the effectiveness of the SFL control also in case of high variations of the DC voltage reference.

Active damping methods are used to guarantee the stability of LCL-filter-based grid converters. Many methods have been proposed in literature but a deep comparison of their dynamic performance is missing. The aim of this paper is to fill this gap and to provide a criterion to choose the best trade-off between dynamic performances and stability.

In the field of wind energy generation particular interest has been focused in recent years on distributed generation through small wind-turbines (power unit 200 kW) because of their limited size and lower environmental impact. The field of small generation was dominated by the use of asynchronous generators directly connected to the grid, while recently permanent magnet synchronous generators (PMSG) with power converter, either partially or fully controlled, became popular. This paper reviews the control issues related to these small wind-turbine systems: generator torque control, speed/position estimation, pitch control, braking chopper control, dc/dc converter control, and grid converter control. Specific issues for small wind-turbines arise in the wind energy extraction optimization and limitation and in the innovative concept of “universal” wind-turbine operation, that leads these system to operate grid-connected, standalone or in load supporting mode.

This paper is focused on the control of small wind turbines, rated less than 200 kW, in grid-interactive microgrids. The considered system is based on a back-to-back power conversion stage. The management of the active and reactive power exchange in the different operating conditions is the key point to allow a practical integration of wind turbine systems in the main electrical grid. This issue lies in a proper control system design achieving high performance in grid-connection as in stand-alone operation modes. A cascade control loops structure is proposed in the paper. Some simulation and experimental results validate the control algorithm.

Fast change of the irradiance conditions entails failure of the maximum power point tracking (MPPT) algorithm in a photovoltaic system (PVS). In this paper it is proposed the combination of a modified Perturb and Observe (P&O) distributed MPPT and an adaptive algorithm. The MPPT has been tested in case of hard mismatch conditions through simulation showing high performance in terms of efficiency.

Photovoltaic Systems (PVS) can be easily integrated in residential buildings hence they will be the main responsible of making low-voltage grid power flow bidirectional. Control issues on both the PV side and on the grid side have received much attention from manufacturers, competing for efficiency and low distortion and academia proposing new ideas soon become state-of-the-art. This paper aims at reviewing part of these topics (MPPT, current and voltage control) leaving to a future paper to complete the scenario. Implementation issues on Digital Signal Processor (DSP), the mandatory choice in this market segment, are discussed.