• Energy Research

This paper focuses on the analysis and design of two multilevel–multicell converters (MMCs), named 3-phase 5-Level E-Type Multilevel–Multicell Rectifier (3Φ5L E-Type MMR) and 3-phase 5-Level E-Type Multilevel–Multicell Inverter (3Φ5L E-Type MMI) to be used in microgrid applications. The proposed 3-phase E-Type multilevel rectifier and inverter have each phase being accomplished by the combination of two I-Type topologies connected to the T-Type topology. The two cells of each phase of the rectifier and inverter are connected in interleaving using an intercell transformer (ICT) in order to reduce the volume of the output filter. Such an E-Type topology arrangement is expected to allow both the high efficiency and power density required for microgrid applications, as well as being capable of providing good performance in terms of quality of the voltage and current waveforms. The proposed hardware design and control interface are supported by the simulation results performed in Matlab/Simulink. The analysis has been then validated in terms of an experimental campaign performed on the converter prototype, which presented a power density of 8.4 kW/dm3 and a specific power of 3.24 kW/kg. The experimental results showed that the proposed converter can achieve a peak efficiency of 99% using only silicon power semiconductors.

This paper focuses on the analysis and design of two multilevel–multicell converters (MMCs), named 3-phase 5-Level E-Type Multilevel–Multicell Rectifier (3Φ5L E-Type MMR) and 3-phase 5-Level E-Type Multilevel–Multicell Inverter (3Φ5L E-Type MMI) to be used in microgrid applications. The proposed 3-phase E-Type multilevel rectifier and inverter have each phase being accomplished by the combination of two I-Type topologies connected to the T-Type topology. The two cells of each phase of the rectifier and inverter are connected in interleaving using an intercell transformer (ICT) in order to reduce the volume of the output filter. Such an E-Type topology arrangement is expected to allow both the high efficiency and power density required for microgrid applications, as well as being capable of providing good performance in terms of quality of the voltage and current waveforms. The proposed hardware design and control interface are supported by the simulation results performed in Matlab/Simulink. The analysis has been then validated in terms of an experimental campaign performed on the converter prototype, which presented a power density of 8.4 kW/dm3 and a specific power of 3.24 kW/kg. The experimental results showed that the proposed converter can achieve a peak efficiency of 99% using only silicon power semiconductors.

This article presents a real-time active damping methodology for front-end inverters connected to the railway catenary in energy recovery applications. The system arrangement comprises a three-phase 2.5 MW inverter connected to the ac grid with a suitable filter. On the opposite side it shares the dc-side with the railway plant where traction inverters and auxiliary systems are connected. The proposed method tries to solve a problem when the energy recovery converter, operating with an almost constant power load, stimulates the catenary power line. This method estimates the dc-side resonant frequency, isolates the dc voltage oscillations around the resonant frequency, and finally attenuates the related effects by acting on the inverter current control strategy. Experimental tests are shown to validate the method using the hardware-in-the-loop real-time emulator. Thanks to the HIL, the complete catenary system has been modeled according to the real data provided by the train operator. The control algorithm and the related control board have the same structure as the architecture used in the field. The results show the effectiveness of the proposed method in detecting the resonance and reducing its effects, increasing the catenary robustness, and making the proper integration of energy recovery systems possible.

This article presents a real-time active damping methodology for front-end inverters connected to the railway catenary in energy recovery applications. The system arrangement comprises a three-phase 2.5 MW inverter connected to the ac grid with a suitable filter. On the opposite side it shares the dc-side with the railway plant where traction inverters and auxiliary systems are connected. The proposed method tries to solve a problem when the energy recovery converter, operating with an almost constant power load, stimulates the catenary power line. This method estimates the dc-side resonant frequency, isolates the dc voltage oscillations around the resonant frequency, and finally attenuates the related effects by acting on the inverter current control strategy. Experimental tests are shown to validate the method using the hardware-in-the-loop real-time emulator. Thanks to the HIL, the complete catenary system has been modeled according to the real data provided by the train operator. The control algorithm and the related control board have the same structure as the architecture used in the field. The results show the effectiveness of the proposed method in detecting the resonance and reducing its effects, increasing the catenary robustness, and making the proper integration of energy recovery systems possible.

This paper presents a comprehensive review of multi-port power electronics converters used for application in AC, DC, or hybrid distribution systems in an Internet of Energy scenario. In particular, multi-port solid-state transformer (SST) topologies have been addressed and classified according to their isolation capabilities and their conversion stages configurations. Non-conventional configurations have been considered. A comparison of the most relevant features and design specifications between popular topologies has been provided through a comprehensive and effective table. Potential benefits of SSTs in distribution applications have been highlighted even with reference to a network active nodes usage. This review also highlights standards and technical regulations in force for connecting SSTs to the electrical distribution system. Finally, two case studies of multi-port topologies have been presented and discussed. The first one is an isolated multi-port bidirectional dual active bridge DC-DC converter useful in fast-charging applications. The second case of study deals with a three-port AC-AC multi-level power converter in H-Bridge configuration able to replicate a network active node and capable of routing and controlling energy under different operating conditions.

This paper presents a comprehensive review of multi-port power electronics converters used for application in AC, DC, or hybrid distribution systems in an Internet of Energy scenario. In particular, multi-port solid-state transformer (SST) topologies have been addressed and classified according to their isolation capabilities and their conversion stages configurations. Non-conventional configurations have been considered. A comparison of the most relevant features and design specifications between popular topologies has been provided through a comprehensive and effective table. Potential benefits of SSTs in distribution applications have been highlighted even with reference to a network active nodes usage. This review also highlights standards and technical regulations in force for connecting SSTs to the electrical distribution system. Finally, two case studies of multi-port topologies have been presented and discussed. The first one is an isolated multi-port bidirectional dual active bridge DC-DC converter useful in fast-charging applications. The second case of study deals with a three-port AC-AC multi-level power converter in H-Bridge configuration able to replicate a network active node and capable of routing and controlling energy under different operating conditions.

Nowadays, many islands worldwide are lack of electrical energy. Thus, it is convenient to exploit available renewable energy sources, among which sea waves near the islands. This paper focuses on the power conversion system coupled with an offshore wave energy device, such as an improved linear generator, to be used for sea wave energy harvesting. Particularly, the design of the linear generator has been proposed to improve the energy efficiency of the entire system. The proposed power conversion system is composed by two Boost Rectifier (BR) directly coupled to the linear generator, and one Voltage Source Inverter (VSI), which it is used as front-end between the DC-bus and the grid. The proposed converters are realized using the Silicon Carbide (SiC) devices in order to improve the efficiency. Furthermore, the control strategy to regulate the generator side and grid side currents has been implemented. The proposed system has been validated using the Hardware-In-the-Loop (HIL) test bench and 20 kW SiC power converters.