Alcohol oxidases (AOxs) catalyze the aerobic oxidation of alcohols to the corresponding carbonyl products (aldehydes or ketones), producing only H₂O₂ as the byproduct. The majority of known AOxs, however, have a strong preference for small, primary alcohols, limiting their broad applicability, e.g., in the food industry. To broaden the product scope of AOxs, we performed structure-guided enzyme engineering of a methanol oxidase from Phanerochaete chrysosporium (PcAOx). The substrate preference was extended from methanol to a broad range of benzylic alcohols by modifying the substrate binding pocket. A mutant (PcAOx-EFMH) with four substitutions exhibited improved catalytic activity toward benzyl alcohols with increased conversion and k_cat toward the benzyl alcohol from 11.3 to 88.9% and from 0.5 to 2.6 s^-1, respectively. The molecular basis for the change of substrate selectivity was analyzed by molecular simulation.

In the present work we propose a bienzymatic cascade for the oxyfunctionalisation of cycloalkanes to cyclic alcohols/cyclic ketones. By combining a H₂O₂-dependent peroxygenase with a O₂-consuming and H₂O₂-producing alcohol oxidase an overall aerobic oxidation system was established. A convincing proof-of-concept is presented and some current limitations are outlined.

Unspecific peroxygenases (UPOs) represent an emerging class of catalysts for the selective oxyfunctionalisation of C–H- and C = C groups. Until now, only a few UPOs have been characterised. In this study, we report a new peroxygenase identified from the Unspecific Peroxygenase Database. The UPO from Agaricus bisporus var. bisporus (AbvbUPO) has been heterologously expressed in Aspergillus niger and initially characterised with respect to its basic biochemical features. Furthermore, its catalytic properties were evaluated with enzymatic cascade reactions of choline oxidase (AnChOx) and AbvbUPO, which the AnChOx provided H₂O₂ necessary via reductive activation of oxygen in situ. Three types of oxyfunctionalizations, such as hydroxylation of ethylbenzene, epoxidations of styrene and cyclohexene, sulfoxidations of methyl phenyl sulfide and phenyl vinyl sulfide, were successfully achieved. We also investigated the activity of AbvbUPO on fatty acids in some more detail. The experimental results show that Under the above conditions, AbvbUPO had the higher activity for cyclohexene epoxidation and sulfonation of sulfide substrates. The concentration of epoxy cyclohexane was 2.91 mM, and the concentration of methyl phenyl sulfoxide was 3.69 mM. The regioselectivity of AbvbUPO was ω-1 bonds position of linear saturated fatty acid. All in all, AbvbUPO exhibits some interesting differences which may put the basis for further understanding of the factors determining peroxygenase selectivity.

This article provides a detailed analysis of the power electronics solutions enabling bipolar dc grids. The bipolar dc grid concept has proven to be more efficient, flexible, and higher in quality than the conventional unipolar one. However, despite its many features, these systems still have to overcome their issues with asymmetrical loading to avoid voltage imbalances, besides meeting regulatory and safety requirements that are still under development. Advances in power electronics and the large-scale deployment of dc consumer appliances have put this growing architecture in the spotlight, as it has drawn the attention of different research groups recently. The following provides an insightful discussion regarding the topologies that enable these architectures and their regulatory requirements, besides their features and level of development. In addition, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

During the last decades, AC systems dominated the power transmission and distribution applications almost exclusively. However, a recent convergence of needs originated in different sectors (renewable energy conversion, information technology and transportation) have accelerated the development of DC systems. Nowadays, DC systems are present at both transmission and distribution levels, offering high-performance solutions with enhanced efficiency and reliability, besides reducing the number of power conversion stages involved and uninterrupted power delivery. For LVDC active networks, two kinds of architectures are possible: unipolar and bipolar. Despite being a more sophisticated and technically complex solution, bipolar structure provide several advantages over conventional unipolar ones. Higher availability, efficiency and flexibility are just a few advantages featured by bipolar systems. This chapter presented a brief overview covering the different aspects of bipolar LVDC networks. Distribution converter topologies, balancing stages and also their control schemes are discussed in order to highlight the efforts being made in this growing architecture.

This paper proposes a novel balancing approach for an electric vehicle bipolar dc charging station at the megawatt level, enabled by a grid-tied neutral-point-clamped converter. The study uses the presence of an energy storage stage with access to both of the dc buses to perform the complementary balance. It proposes a generic balancing structure that can achieve balance regardless the kind of energy storage system (ESS) employed. This is aiming to reduce the hardware requirements of the system and maximize the usage of the ESS, whose main function is to perform the energy management related tasks. To meet this purpose, a three-level dc-dc interface is employed, allowing to compensate the dc currents with a single ESS. Furthermore, in order to prevent the appearance of even-order harmonics in the input current during asymmetrical operation, an alternative switching sequence for the central converter is proposed. Results indicate that, without altering dramatically the charging process of the ESS, it is possible to cover the whole load scenario without the need of a balancing circuit. This allows the use of off-the-shelf products both for the rectifier and the fast chargers. In this paper, simulation and experimental results are presented to validate the proposed balancing strategy.

The development of high-power charging stations with fast chargers is a promising solution to shorten the charging time for electric vehicles (EVs). The neutral-point-clamped (NPC) converter-based bipolar-dc-bus-fed charging station brings many merits, but it has inherent voltage balance limits. To solve this issue, a voltage balance control (VBC) method based on a new modulation together with three-level (TL) dc-dc converter-based fast charger is proposed. Additionally, an effective VBC coordination between the TL dc-dc converter and the NPC converter is formulated. Through the proposed VBC coordination, the controllable balancing region is extended so that additional balancing circuits are eliminated. Meanwhile, the quality of the grid-side currents is improved as the NPC converter has more freedom to control currents. The low-frequency voltage fluctuations in dc buses are removed because the TL dc-dc converter performs most of the balancing tasks. Faster VBC perturbation performance is achieved due to higher available balancing current at TL dc-dc converter side. In addition, the voltage balance limits of both the TL dc-dc converter and the NPC converter are explored. The voltage balancing performances are compared when VBC is located at different sides. Simulation and experimental results are provided to verify the proposed VBC and the VBC coordination.

The use of conventional half-bridge submodules in the Modular Multilevel Converters brings important benefits such as the reduction in the power losses and semiconductor devices. However, the system with half-bridge submodule lacks the capability of blocking DC-faults currents. In this paper, a 5-level submodule with DC-fault blocking capability is presented. The proposed submodule allows to operate with different internal capacitances in order to reduce the cost of the system. Furthermore, a control and balance strategy for the novel 5-level submodule is proposed.

This chapter provides an overview of the different charging architectures available for electric vehicles and plug-in hybrid electric vehicles. The charging architectures are addressed following two main categories: onboard chargers, used mainly for slow and semi-fast charging (generally AC connection), and off-board chargers, used for fast charging (DC connection). The chapter focuses on the mainstream solutions available in the industry, and also presents some recent advances and trends found in the literature. In addition, the chapter provides an introduction to well-established charging standards being used by manufacturers. Finally, the control schemes used in charging configurations, including the control schemes for DC-DC and AC-DC converter stages, are discussed, the latter considering both single- and three-phase control schemes.

With the increasing popularity of electric vehicles, there is an urgent demand to shorten the charging time, so the development of high-power charging stations with fast chargers is necessary to alleviate range anxiety for drivers. The charging station based on the neutral-point-clamped (NPC) converter can bring many merits, but it has unbalanced power problems in the bipolar dc bus. To solve this issue, comprehensive dc power balance management (PBM) in conjunction with high-power three-level dc-dc converter based fast charger is proposed in this paper. The active dc power balance management (APBM) is proposed to assist the central NPC converter in balancing power so that the additional balancing circuit is eliminated; while the passive dc power balance management (PPBM) is proposed to eliminate the fluctuating neutral-point currents and to ensure the balanced operation of fast chargers. The principles of APBM and PPBM are researched, the efficient integration between them is studied, and the overall control scheme for the fast charger is proposed. The power balance limits of APBM are explored, while the circulating currents of PPBM are analyzed. Simulation and experimental results are presented to verify the effectiveness of the proposed fast charger with PBM functions.

This paper presents a grid-connected seven-level cascaded H-bridge converter operating as photovoltaic inverter. The main issue with this topology are the natural power imbalances between the power cells and the phases of the converter. The control problem is addressed with a Multiobjective Finite Control Set Model Predictive Control, where a dc-link voltage balance among the cells and good tracking of the active and reactive power references injected to the grid are achieved. Furthermore, an average switching frequency control per cell has been included. The proposed control scheme is validated trough simulation results and tested under dynamic conditions.

This paper proposes a novel architecture for plug-in electric vehicles (PEVs) dc charging station at the megawatt level, through the use of a grid-tied neutral point clamped (NPC) converter. The proposed bipolar dc structure reduces the step-down effort on the dc-dc fast chargers. In addition, this paper proposes a balancing mechanism that allows handling any difference on the dc loads while keeping the midpoint voltage accurately regulated. By formally defining the unbalance operation limit, the proposed control scheme is able to provide complementary balancing capabilities by the use of an additional NPC leg acting as a bidirectional dc-dc stage, simulating the minimal load condition and allowing the modulator to keep the control on the dc voltages under any load scenario. The proposed solution enables fast charging for PEVs concentrating several charging units into a central grid-tied converter. In this paper, simulation and experimental results are presented to validate the proposed charging station architecture.

This paper proposes an effective voltage balance control (VBC) together with a new modulation technique for a high-power bidirectional three-level dc-dc converter based fast charger. The proposed VBC method can assist charging stations in balancing the dc-bus voltages so that additional balancing circuits are eliminated, leading to improved system efficiency. Meanwhile the proposed modulation method is not only intuitive to be implemented, but also have merits of reduced switching frequency, resulting in lower switching losses. The modulation principle is formulated, and its effective combination with the voltage balance control are analysed in detail. Based on which, the overall control scheme for the charging system is proposed. Simulation results are presented to validate the effectiveness of the proposed methods.

This paper proposes a bipolar-dc-bus Electric Vehicle (EV) charging station without a line-frequency transformer at the medium-voltage grid side. It is mainly composed of the Neutral Point Clamped (NPC) converter based central ac-dc station and the parallel isolated three-level DC-DC converter based fast chargers. Due to the elimination of the line-frequency transformer, the volume and cost of the system are reduced. Meanwhile, the isolation and step-down between high dc-bus voltages and low load voltages are performed through the high-frequency transformers, leading to increased voltage utilization of switching devices. In order to guarantee the bipolar dc buses balance and minimize the dc-bus voltage ripples, the 180°-interleaved operation for the two parallel isolated three-level DC-DC converters is proposed to make the total neutral-point current zero so that all fast chargers do not bring any unbalance problems. The proposed 180°-interleaved operating principle has been analyzed in detail, then simulation results are presented to verify its performance.

This investigation presents a grid-connected five-level H-bridge neutral-point-clamped converter operating with a single dc-link as photovoltaic power source. The operation with a single dc-bus is enabled by adding a transformer with open-end winding secondary, where each power cell of the converter is connected. The proposed control scheme is validated trough simulation results and tested under dynamic conditions. It can be implemented with a good tracking of the active and reactive power references injected to the grid. The results serve as a preliminary validation to potential utilization of the converter in large scale photovoltaic energy conversion systems.

This paper presents a generalized multilevel direct power control (ML-DPC) scheme for grid-connected multilevel power converters. The proposed method extends the original DPC operating principle by considering only the closest subset of two-level voltage vectors to the present switching state. The implementation of this principle requires the power derivatives for feedback, which can present numerical problems when applied experimentally, mainly due to high measurement noise sensitivity. Therefore, a derivative estimator is proposed based on the converter-grid model in the synchronous reference frame. In addition, a virtual flux observer is developed to achieve synchronization and improve robustness in the presence of grid voltage harmonics. The proposed method is applicable to any multilevel converter topology of any number of levels. In this paper, simulations and experimental results are presented for a seven-level cascaded H-bridge converter.

This paper proposes a novel architecture for Plugin Electric Vehicles (PEVs) dc charging stations, through the use of a single dc-link 3-level h-bridge (HB) converter as the grid interface. This feature is achieved by the use of an open-ended secondary windings transformer at the grid side. The proposed solution enables fast charging for PEVs concentrating several charging units into a single grid-Tied converter. The selected topology provides a three-level waveform without any balancing requirements, enabling a stable dc-bus. Finally, because of the simple nature of the converter, it can be implemented with off-The-shelf components, enabling a low cost alternative for the grid connection of Level III fast chargers.

The automotive industry is making important changes towards the electrified transportation. Several Electric Vehicles (EVs) and Plug-in Hybrid EVs are currently on the market offering a clean and environment friendly alternative to conventional vehicles. However, limited mileage capacity and long refueling times have lead to a lukewarm reception from the consumers. In order to reduce the charging time fast charging architectures are being developed, usually as off-board solutions located in public installations. This paper presents a centralized charging station architecture, using a bipolar dc grid to power off-board chargers and integrate of DGs and storage systems. The central converter topology is an NPC and a novel balancing technique is implemented to extend the operating range of the power converter.

This paper presents a new grid connected photovoltaic energy conversion system configuration for large scale power plants. The grid-tied converter is based on a modular multilevel converter using voltage source H-bridge cells. The proposed converter is capable of concentrating a multimegawatt PV plant with distributed string MPPT tracking capability, high power quality and increased efficiency compared to the classic two-level voltage source converters. The main challenge is to handle the inherent power unbalances which may occur, not only between the different cells of one phase of the converter, but also between the three phases. The control strategy to deal with these unbalances is analyzed in this paper. Simulation results for a downsized 7 level MMC composed of 18 H-bridge cells and PV strings are presented to validate the proposed topology and control method.