Elettronica di potenza: rivoluzionare i sistemi energetici mondiali del futuro

Power Electronics (PE) is not a topic of everyday discussion. Nevertheless, it is a vital transformational technology that is quietly operating in the background – unseen and unheard – yet, embedded into products that people use every day to make life more enjoyable. 

We use Power Electronics to charge our smartphones and electric vehicles, and we use it to increase cooking efficiency through induction cooktops/hobs. The world’s industries are also becoming increasingly dependent on PE to increase efficiency in solutions. For example, PE is used to power large-scale aluminum production and efficiently transmit power across countries and seas. Power Electronics is revolutionizing the world’s energy systems – and can be increasingly found everywhere!

Therefore, it is not surprising that 70% of electrical energy today is processed by Power Electronics1, and this will increase in the coming decades. 

Power Electronics is the application of semiconductor electronics to the control and conversion of electric power². 

These semiconductors are the power transistors and diodes that switch the input voltage on and off into a network of passive components to transform it to different voltage levels. Advancements in power semiconductor technology have enabled the power processing to even higher efficiency levels.

To correctly operate, the power conversion systems need to be controlled through embedded digital computers that run sophisticated algorithms thousands of times per second. The controller supervises the operation and adapts the behavior based on various parameters and set goals. This ability to change is embedded into digital algorithms which comprise the system and application knowledge.

PE is where the digital bits (information) meet the flow of electrons to perform optimal work. The combination of PE and digital technologies is the key enabler of the electrical power grid that will serve as the backbone of the carbon-neutral energy system.

The presence and growth of Power Electronics in society come from its extreme flexibility and capability to adapt for the purpose. Power Electronics is a ‘multitool’ ready at hand for solving the many new challenges arising from a dynamic and accelerated transformation towards a carbon-neutral energy system. And the big winners are global society as well as the planet!

In the last twenty years, Power Electronics and its ability to enable game-changing technologies, bringing efficiency, compactness (less use of our planet’s land and resources) and reliability (keeping production on, even in extreme conditions) has strongly contributed to the journey towards carbon-neutral targets. Its speed of reaction, flexibility of control, and the scalability across power and voltage levels are key attributes that will ensure resiliency of the future energy system. PE is enabling the electrification of remote urban areas, converting polluting industrial processes and transportation infrastructure toward greener alternatives and improving the wealth of the population through more affordable energy – in line with the UN Sustainable Development Goal 7. 

In recent decades the power grid was supplied by traditional rotating generation sources that had a main role in maintaining grid stability. Large-scale renewable power generation was just emerging, and bulk generation was concentrated in a few locations, while high voltage AC lines transmitted the energy from the generation sources to the load centers. 

In the energy sector, PE applications were highly specialized solutions at the high and medium voltage level. High Voltage Direct Current (HVDC), for one, connected separated AC grids where AC transmission could not be used due to excessive losses, cost or differences in frequency. HVDC makes possible the provision of reliable energy to remote places and islands such as Shetland Islands in Scotland and Rio Madeira in Brazil while enabling a holistic power system across geographies and frequencies such as the Japanese power system in Higashi-Shimizu. Flexible AC Transmission Systems (FACTS), meanwhile, strengthened the AC network and power quality in weak nodes, while static frequency converter solutions electrified rail networks, decoupling the voltage and frequency of the rail network from that of the grid. Hitachi ABB Power Grids pioneered most of these PE applications.

The energy system is today undergoing a tremendous transformation, which due to its speed and outcome could be called a ‘revolution’. Increasing sustainability and environmental attention, sup-porting regulatory frameworks and new technology developments in the power sector are making electricity the backbone of the future energy system.

In this new and evolving situation, the role of Power Electronics has drastically changed.

Power Electronics connects renewable DC sources (e.g. solar PV) to the AC grid and is used to increase the controllability and efficiency of AC generation such as wind turbines and hydro power plants. HVDC technology realizes very efficient, long distance and fully controllable power transmission, allowing connection of offshore wind generation and interconnection of countries, enabling more energy trading. FACTS have become instrumental in solving the new power quality issues helping the existing infrastructure to cope with the new dynamic power flow even when the grid strength is reduced. From generation to consumption, Power Electronics is enabling solutions such as battery energy storage systems, pumped hydro storage, hydrogen production and conversion back to electricity.

Transportation is undergoing a real revolution towards electrification. 

The rapid development of Power Electronics in the transportation sector allows for faster and more reliable charging of electrical vehicles, being cars, buses or trucks – which greatly contributes to the adoption of e-mobility across the world. 

Power Electronics connects a world where both AC and DC power solutions coexist. It allows a smooth integration of various energy resources like solar PV, wind turbines, batteries, electrical vehicles and diesel backup power generation within an industrial facility like a mine, a data center and even across islands – in a form of a microgrid. Power Electronics improves efficiency and resilience of our grid from generation to consumption. The journey to a more sustainable energy system will continue to drive this metamorphosis in the years to come.

The power semiconductors are at the heart of the converter for a full range of systems from kilo-watts to gigawatts. The transistor and diode manufacturing process starts with a pure silicon wafer, and then different elements and metal patterns are added to form the correct physical structure to control the flow of current. Some no larger than 5mm by 5mm, are less than 1mm thick, but are able to switch hundreds of amps and hundreds of volts in microseconds. The largest power devices can control gigawatts of power and are the diameter of a coffee cup. 

The operating speed of the power semiconductors and PE systems are orders of magnitude faster than the power grid. The fast speed is what enables the fast control of the power grid. By employing silicon carbide (SiC) power transistors instead of silicon, the power converter becomes more efficient, smaller and responds faster to any grid changes. Hitachi ABB Power Grids has over the last two decades been directly involved in bringing SiC and its benefits into PE systems.

Power Electronics systems are supervised and controlled by digital controllers, as performance is important in obtaining the optimal system operation. The controllers perform millions of calculations per second using many inputs that are measured thousands of times per second, and continuously for more than twenty years. 

The evolution of digital technologies facilitates even higher controllability of the system and improves visibility by gathering and analyzing data thus improving decision making and control outcomes. Edge and cloud solutions help to increase controllability of the asset, the fleet, and the interaction of PE solutions with the power grid. Augmented reality, machine learning and digital-twin technologies bring the next level of customer experience when it comes to serviceability and health management and allow new concepts of training and safety assurance.

These applications require an excellent knowledge about the process in the background, the constraints and the operating boundaries of the system as well as the interaction between all assets used in the application.
 

• For example, flash charging (600 kW with immediate power transfer at connection) of electric buses at bus stops allows for an improved design of the electric buses, reducing the need for a large battery and making room for more passengers to be carried instead, while a sophisticated digital algorithm can turn a battery energy storage system into a virtual synchronous generator, providing essential support to the grid.

• Power Electronics is playing a crucial role in the electrification of rail. It allows power supply from the main grid instead – and hence removing the use of polluting diesel trains – providing different AC voltages and frequencies, as well as DC voltage, enabling the development of electric and sustainable transportation solutions based on high-speed trains, metro and trams.
• Through the applications of STATCOM and Power Quality Filters, Power Electronics ensures a reliable and resilient power supply, stabilizing current and voltage fluctuations and therefore increasing the productivity of industrial facilities and facilitating smooth integration of variable renewable power plants based on wind and solar power. 
• HVDC solutions provide high-efficiency bulk power transfer from offshore wind to on-shore or between countries that are separated by sea. For example, the IFA2 HVDC link that connects the power grids of France and the UK can instantaneously respond to e.g. generation outages in the UK by increasing the delivery of power from France.
  
  All the above solutions are using semiconductors and control systems, but the way they are designed and programmed makes them suitable for specific applications. 

Power Electronics is already proven to be providing great value today and is enabling the energy sector to evolve. 

Three technological aspects need further urgent development and mastery: 

1. Semiconductors and system design

• New power semiconductor devices for higher voltage, higher currents, higher efficiency e.g. wide bandgap devices are needed. They will change how the layout of the power circuits is done as the switching is so fast, while making a robust EMI/EMC³ design more challenging.
• Advanced Power Electronic systems will challenge the power quality and EMC of the power grid in both the low and high (>150kHz) frequency ranges. To meet international standards, the output filter damping needs to be increased and this will adversely affect power grid impedance making it more prone to instability and incompatibility issues. Thus, there will be a need for more advanced control and impedance shaping strategies to maintain grid performance.
• Increasing integration at component-, converter-, and system-level demands new concepts to address challenges in thermal, insulation, testing, manufacturing, and cost reduction. Life cycle analysis, including recycling to ensure the sustainability of power electronic products, is of increasing importance.
• To design Power Electronics products even better and more optimized, then multi-domain analysis is needed e.g., thermal, electrical, mechanical, humidity, and material properties are included in a three-dimensional structure.
• High reliability of the power conversion and application is achieved by “Design for Reliability” and is based on models that describe the relationship between the application profile and expected failures over time.

2. New applications

• The increased use of the Power Electronic converters, both at generation and consumption points, will challenge the power system stability over a wide frequency range. Methods to analyze, assess and mitigate such problems are needed, including analyzing thousands of power converters at the same time in real-time simulation systems.
• Advanced sector coupling (e.g. electrical & heat/cooling) architectures and control strategies for 100% integration of renewable energy generation (e.g. on-site) for high energy consumers/applications such as Data Centers and Power-to-X⁴ are also important.

3. Digitalization
 

• A wave of digitalization possibilities is emerging due to increased connectivity and handling of big data. It will continually give a better understanding and ability to optimize the products’ design.
• Digital Twins can also use data to enable condition monitoring and preventive maintenance, thus enabling better serviceability of Power Electronics solutions.
• Artificial Intelligence (AI) algorithms are being introduced for different purposes e.g. fast simulation of complicated systems, for system design and optimization or reliability calculations and assessments.

¹ https://www.et.aau.dk/research-programmes/efficient-and-reliable-power-electronics/

² https://en.wikipedia.org/wiki/Power_electronics

³ EMI = Electromagnetic Interference; EMC – Electromagnetic Compatibility

⁴ Power-to-X refers to the solutions that convert electrical power into other energy forms such as gas or hydrogen.