Fang Peng's Z-Source Technology Earns IEEE's Top Power Engineering Honor

In fourth grade, Fang Peng's thumb touched a faulty light socket and left a burn scar. The village in rural China where he grew up had only just received electricity - a single bulb on an extension cord that, as the eldest son, he carried from room to room. That early encounter with electricity's capacity for both illumination and harm shaped the direction of a career that has now earned him the Institute of Electrical and Electronics Engineers' most prestigious award.

This month, Peng - RK Mellon Endowed Chair Professor in Electrical and Computer Engineering at the University of Pittsburgh's Swanson School of Engineering - received the IEEE Medal in Power Engineering. The recognition cites his contributions to Z-source and modular multilevel converters for distribution and transmission networks.

The Problem with Conventional Converters

Power converters - devices that change voltage levels and convert between alternating and direct current - are everywhere in modern electrical systems. They sit between solar panels and the grid, between batteries and motors, between transmission lines and homes. Traditional converter designs have a fundamental constraint: they can either boost voltage or reduce it, not both, and they cannot tolerate short-circuit or open-circuit faults. When a fault occurs, the current either shoots to dangerous levels or the system loses the ability to operate.

Peng's Z-source topology, developed in the early 2000s, bypasses this constraint using a unique network of inductors and capacitors arranged in an impedance source (Z) configuration. Z-source converters can both boost and reduce voltage in a single stage, and their circuit geometry allows them to tolerate short- and open-circuit conditions that would destroy conventional designs.

"Electric arcs can be explosive and destructive. In recent years, we've seen the devastating wildfires in places like Hawaii and California that have been ignited from downed power lines," said Peng, who also co-directs Pitt's Energy GRID Institute. "Since graduate school, I have been developing systems that can handle faults. Even in the power conversion converters and inverters I've developed, they won't create a huge fault and can switch to a self-protection mode."

DC Circuit Breakers: A Specific Hard Problem

Direct current power is increasingly important. Battery storage systems, solar photovoltaic arrays, data centers, and electric vehicles all operate on DC. But interrupting DC during a fault is technically harder than interrupting AC. Alternating current naturally passes through zero 60 times per second, providing a moment when the circuit can open cleanly. DC flows continuously and can sustain an electric arc across a gap long enough to destroy the breaker and ignite surrounding material.

Peng extended the Z-source concept to DC circuit breakers, using the distinctive properties of his impedance network to create conditions in which DC can be safely interrupted. The same principles that prevent catastrophic faults in converters apply to creating artificial zero-crossing points in DC systems.

"The Z-source circuits and controls have been used and adopted in many applications such as DC circuit breakers, power conversion, fault protection, and power grid resiliency enhancement," Peng said.

Modular Multilevel Converters

The second technology cited in Peng's IEEE award - modular multilevel converters - addresses a different scaling challenge. High-voltage direct current (HVDC) transmission, increasingly used for long-distance power delivery and offshore wind connections, requires converters that can operate at voltages far above what individual semiconductor devices can handle.

Modular multilevel converter architectures solve this by stacking identical submodules, each handling a portion of the total voltage. The number of modules can be increased or decreased depending on the application's requirements. This modular approach also improves fault tolerance: if one module fails, the system can continue operating with reduced capacity rather than shutting down entirely.

An Electric Power Renaissance

Peng joins a list of IEEE Medal recipients that includes figures foundational to modern electrical engineering. He is a Fellow of both IEEE and the National Academy of Inventors, a member of the National Academy of Engineering, and a previous winner of the IEEE William E. Newell Power Electronics Award.

"In Pittsburgh right now, there is an electric power and electrical energy renaissance, and I am proud to be a part of that," Peng said. The city that once defined itself through steel production is now positioning itself as a center for grid modernization, battery research, and electrification technology. Peng's work on fault-tolerant converters sits at the practical core of that transition - not as theoretical contribution but as deployed engineering running in systems around the world.