List of thesis topics in Power Electronics

1. Design and control of multilevel converters for grid interface of Battery Energy Storage Systems (BESS)

The research activity aims to investigate the possibility of using multilevel converters, such as the Cascaded H-Bridge (CHB), the Modular Multilevel Converter (MMC) or reconfigurable multilevel structures, to replace the conventional two-level inverter in BESS grid interface. The main reason is related to the possibility of subdividing the battery pack cells into smaller groups with reduced supply voltage directly connected to the individual cells of the multilevel converter. Ideally, each module is connected to a single battery cell. The advantages of using this application solution include the possibility of using low-power semiconductor devices, reducing costs and losses, eliminating the need for a BMS whose functions can be directly managed by the converter’s individual cells, improving the quality of voltage and current waveforms, resulting in increased efficiency, and reducing the volumes and costs of filters and passive elements of the converter.

However, the complications from a topological, constructional, and control point of view pose challenges for the implementation of this technology in the automotive field, representing highly current and innovative research topics. Thesis activities in this field can include:

• Design and construction aspects related to the optimization of topologies, devices, and PCBs.
• Hardware implementation of experimental prototypes and testing.
• Development of innovative modulation techniques to improve system performance, power quality, and efficiency.
• Development of control techniques for battery-side management (balanced management of battery cell charging and discharging).
• Study and comparison of different topological solutions with respect to current standards of efficiency, performance, volumes, weights, and costs.

2. Multi-port Converters for the Integration of Energy Storage Systems and Renewable Energy Sources in modern DC microgrids

DC microgrids are more and more becoming an interesting solution adopted in modern power grids. A DC microgrid is a localized power system that distributes and manages direct current (DC) electricity among interconnected sources (like solar panels, fuel cells, and batteries) and DC loads (such as LED lighting, electronics, and EV chargers). Unlike traditional AC microgrids, DC microgrids eliminate multiple AC/DC conversions, improving efficiency, reliability, and compatibility with renewable energy and storage systems. They are increasingly used in remote areas, data centers, and smart buildings, offering flexible, resilient, and energy-efficient power management solutions.

This activity aims to develop innovative architectures for the integration of storage systems with RES within DC microgrids, exploring multi-stage and/or multi-port conversion topologies with a minimal number of components, high efficiency, low cost, and optimized control systems for power flow management, in order to maximize energy extraction from RES and storage efficiency.

Thesis topics in this area may include:

• Study, design, and development of multi-stage and/or multi-port bidirectional conversion architectures for the integration of storage systems, RES, in a DC microgrids including a port for eventual AC connection, aimed at maximizing power extraction from RES, conversion and storage efficiency, reliability, and power quality.

• Design and construction aspects of converters focused on topology optimization regarding efficiency, cost, and power density.

• Development and implementation of control systems for power flow management.

• Study and development of innovative modulation and control techniques for the interface between batteries and RES.

3. Modelling and Control of power Converters Connected to power electronic dense grids to Improve Stability and Power Quality

With the advent of smart grids, the increase in distributed generation, and the spread of loads requiring regulated power supplies, more and more power electronic converters are being connected to the electrical distribution system. This increases the injection of harmonics into the grid with power quality reduction and generate unwanted interactions among different converters. This issue is particularly critical in weak or isolated networks, such as microgrids or those on ships and airplanes. In these contexts, converters—often from different manufacturers—interact in an uncoordinated manner. Although designed for standalone operation, once integrated into the same network, their performance degrades, often causing instability.

This research activity aims to investigate innovative solutions for integrating converters and systems into the grid through advanced power flow control techniques. These include the estimation of network impedance and parameters as seen from the converter and optimizing control actions based on the grid’s status and predefined cost functions.

Thesis topics in this area may include:

• Study of the effects of converters on grid stability and system modeling.

• Development and implementation of techniques for estimating the network impedance seen at the terminals of connected converters.

• Development and implementation of optimized control techniques based on the type and state of the network in which the converter is integrated.

4. Advanced Control Strategies for Converters and Electric Drives

In recent years, due to the increasingly widespread use of converters and electric drives and the significant advances in digital systems used for control implementation, numerous high-performance control strategies have been researched, including Model Predictive Control (MPC).

MPC determines the optimal control action at each time step by minimizing a cost function based on the prediction of future errors. There are two types of MPC:

• Implicit MPC calculates the control action for the next time step based on a model of the system and predictions of its transient response. This method is computationally intensive but can be implemented using FPGA systems.

• In power electronic converters, finite-state MPC is often used instead, where the control action is selected from a limited set of possible converter states. This approach is easier to implement but results in lower steady-state performance. Research in this area includes the study and implementation of modulated MPC and long prediction horizon strategies.

Thesis topics in this area may include:

• Digital development and implementation of implicit MPC techniques, pushing the limits of computational systems (microcontrollers, DSPs, FPGAs) to maximize transient performance of the converter.

• Digital development and implementation of finite-state MPC techniques, focusing on modulated strategies and those with long prediction horizons.

• Use of MPC techniques for estimating the impedance and network parameters as seen by the converter.

5. Artificial Intelligence applications to Power Electronics

6. Power Electronics for nuclear fusion applications

Nuclear fusion represents a cutting edge technology under development and a central topic for many academic institutions and companies around the world. Europe currently leads the most ambitious fusion experiment, ITER, located in Cadarache, France. Italy contributes to this effort through the Divertor Tokamak Test facility in Frascati.
In a fusion reactor, plasma at extraordinary high temperatures must be confined in vacuum using magnetic fields generated by currents controlled by power electronics devices, making this branch of engineering fundamental for achieving stable plasma confinement.
A thesis in this area may deal with the design and optimization of a power electronics converter and the control strategies required to generate the currents used for plasma confinement. Alternatively, it may address the characterization of electrical systems dedicated to plasma heating, such as neutral or negative beam injection units. The main challenges set by such a thesis are not only the control of the converters but also the management of very high currents which can reach up to tens of kA.
A work project of this kind would imply:

– studying the fundamentals of plasma fusion and the role of coils and actuators inside the reactor
– modelling the most suitable converter architecture to meet plasma-current requirements
– design of the most suitable control strategy for the converters
– analysis of the semiconductors devices needed to implement the system

7. Isolated DC/DC converters for Transportation Energy and Data Centers applications

Isolated DC-DC converters, such as Dual Active Bridge (DAB) converters and LLC resonant converters, are fundamental components across diverse sectors due to their high efficiency, compact size, and galvanic isolation, which ensures safe and reliable power transfer between voltage domains. They enable critical functions in:

• Data center power supplies: used to obtain a low-voltage (LV) DC output (e.g., 12 V or 48 V) from a typical 400 V DC bus, or from the emerging
800 V DC power supply architectures.
• Medium-voltage DC (MVDC) grids: for integrating renewable energy sources, interconnecting different voltage levels, and providing galvanic
isolation to enhance system reliability.
• Electric and hybrid vehicles (EVs and HEVs): to derive a low-voltage DC (LVDC) bus from the high-voltage (HV) battery pack.
• Transportation systems beyond EVs and HEVs, including railways and more-electric aircraft, where their high power density and efficiency contribute to reduced size and weight.

Thesis topics in this area include:
• Design and simulation of DAB converters using conventional or novel control schemes.
• Design and simulation of LLC converters in open-loop operation or with voltage control.
• Frequency-domain and time-domain modeling techniques for DAB and LLC converters.
• Efficiency evaluation through analytical and simulation-based methods.