Spain’s grid operator, Red Eléctrica, proudly declared that electricity demand across the country’s peninsular system was met entirely by renewable energy sources for the first time on a weekday, on 16 April 2025.
Just 12 days later, at 12.33 p.m. on Monday, 28 April, Spain and Portugal’s grids collapsed completely, plunging some 55 million people into one of the largest blackouts the region has ever seen. Entire cities lost electricity in the middle of the day. In the bustling airports of Madrid, Barcelona, and other key hubs, departure boards went blank. No power. No Internet. Even mobile phone service—something most people take for granted—was severely compromised. It was just disconnection and disruption. On the roads, traffic lights stopped functioning, snarling traffic and leaving people wondering when the power would return.
The size and scale of the impact were unsettling, but the scariest part was the speed at which it happened. Within minutes, the whole of the Iberian Peninsula’s energy generation dropped from roughly 25GW to less than 1.2GW.
While this may sound like a freak accident, incidents like this will continue to happen, especially given the rapid changes to the electrical grid over the past few decades. Worldwide, power systems are evolving from large centralized generation to a multitude of diverse, distributed generation sources, representing a major paradigm shift. This is not merely a “power” problem but is also a “systems” problem. It involves how all the parts of the power grid interact to maintain stability, and it requires a holistic solution.
Power grids are undergoing a massive transformation—from coal- and gas-fired plants to millions of solar panels and wind turbines scattered across vast distances. It’s not just a technology swap. It’s a complete reimagining of how electricity is generated, transmitted, and used. And if we get it wrong, we’re setting ourselves up for more catastrophic blackouts like the one that hit all of Spain and Portugal. The good news is that a solution developed by our group at Illinois Institute of Technology over the last two decades and commercialized by our company, Syndem, has achieved global standardization and is moving into large-scale deployment. It’s called Virtual Synchronous Machines, and it might be the key to keeping the lights on as we transition to a renewable future.
Rapid Deployment of Renewable Energy
The International Energy Agency (IEA) created a Net Zero by 2050 roadmap that calls for nearly 90% of global electricity generation to come from renewable, distributed sources, with solar photovoltaic (PV) and wind accounting for almost 70%. We are witnessing firsthand a paradigm shift in power systems, moving from centralized to distributed generation.
The IEA projects that renewable power installations will more than double between 2025 and 2030, underscoring the urgent need to integrate renewables smoothly into existing power grids. A key technical nuance is that many distributed energy resources (DERs) produce direct current (DC) electricity, while the grid operates on alternating current (AC). To connect these resources to the grid, inverters convert DC into AC. To understand this further, we need to discuss inverter technologies.
Professor Beibei Ren’s team at Texas Tech University built modules for a SYNDEM test bed with 12 modules and a substation module, consisting of 108 converters. Beibei Ren/Texas Tech University
Most of the inverters currently deployed in the field directly control the current (power) injected to the grid while constantly following the grid voltage, often referred to as grid-following inverters. Therefore, this type of inverter is a current source, meaning that its current is controlled, but its terminal voltage is determined by what it connects to. Grid-following inverters rely on a stable grid to inject power from renewable sources and operate properly. This is not a problem when the grid is stable, but it becomes one when the grid is less stable. For instance, when the grid goes down or experiences severe disturbances, grid-following inverters typically trip off, meaning they don’t provide support when the grid needs them most.
In recent years, attempts to address grid instability have led to the rise of grid-forming inverters. As the name suggests, these inverters could help form the grid. These usually refer to an inverter that controls its terminal voltage, including both the amplitude and frequency, which indirectly controls the current injected into the grid. This inverter behaves as a voltage source, meaning that its terminal voltage is regulated, but its current is determined by what it is connected to. Unlike grid-following inverters, grid-forming inverters can operate independently from the grid. This makes them useful in situations where the grid goes down or isn’t available, such as during blackouts. They can also help balance supply and demand, support voltage, and even restart parts of the grid if it shuts down.
One issue is that the term “grid-forming” means different things to different people. Some of them lack clear physical meaning or robust performance under complex grid conditions. Many grid-forming controls are model-based and may not scale properly in large systems. As a result, the design and control of these inverters can vary significantly. Grid-forming inverters made by different companies may not be interoperable, especially in large or complex power systems, which can include grid-scale battery systems, high-voltage DC (HVDC) links, solar PV panels, and wind turbines. The ambiguity of the term is increasingly becoming a barrier for grid-forming inverters, and no standards have been published yet.
Systemic Challenges when Modernizing the Grid
Let’s zoom out for a moment to examine the broader landscape of structural challenges we need to address when transitioning today’s grid into its future state. This transition is often called the democratization of power systems. Just as in politics, where democracy means everyone has a say, this transition in power systems means that every grid player can play a role. The primary difference between a political democracy and a power system is that the power system needs to maintain the stability of its frequency and voltage. If we apply a purely democratic approach to manage the power grid, it will sow the seeds for potential systemic failure.
The second systemic challenge is compatibility. The current power grid was designed long ago for a few big power plants—not for millions of small, intermittent energy sources like solar panels or wind turbines. Ideally, we’d build a whole new grid to fit today’s needs, but that would bring too much disruption, cost too much, and take too long. The only feasible option is to somehow make various grid players compatible with the grid. To better conceptualize this, think about the invention of the modem, which solved the compatibility issues between computers and telephone systems, or the widespread adoption of USB ports. These inventions made many devices, such as cameras, printers, and phones, compatible with computers.
The third systemic challenge is scalability. It’s one thing to hook up a few solar panels to the grid. It’s entirely different to connect millions of them and still keep everything running safely and reliably. It’s like walking one large dog versus walking hundreds of Chihuahuas at once. It is crucial for future power systems to adopt an architecture that can operate at different scales, allowing a power grid to break into smaller grids when needed or reconnect to operate as one grid, all autonomously. This is crucial to ensure resilience during extreme weather events, natural disasters, and/or grid faults.
To address these systemic challenges, the technologies need to undergo a seismic transformation. Today’s power grids are electric-machine-based, with electricity generated by large synchronous machines in centralized facilities, often with slow dynamics. Tomorrow’s grid will run on power electronic converters—small, distributed, and with fast dynamics. It’s a significant change, and one we need to plan carefully for.
The Key is Synchronization
Traditional fossil fuel power plants use synchronous machines to generate electricity, as they can inherently synchronize with each other or the grid when connected. In other words, they autonomously regulate their speeds and the grid frequency around a preset value, meeting a top requirement of power systems. This synchronization mechanism has underpinned the stable operation and organic expansion of power grids for over a century. So, preserving the synchronization mechanism in today’s grids is crucial for addressing the systemic challenges as we transition from today’s grid into the future.
Unlike traditional power plants, inverters are not inherently synchronous, but they need to be. The key enabling technology is called virtual synchronous machines (VSMs). These are not actual machines, but instead are power electronic converters controlled through special software codes to behave like physical turbines. You can think of them as having the body of power converters with the brain of the older spinning synchronous machines. With VSMs, distributed energy resources can synchronize and support the grid, especially when something unexpected happens.
Syndem’s all-in-one reconfigurable and reprogrammable power electronic converter educational kit.SYNDEM
This naturally addresses the systemic challenges of compatibility and scalability. Like conventional synchronous machines, distributed energy resources are now compatible with the grid and can be integrated at any scale. But it gets better. First, inverters can be added to existing power systems without major hardware changes. Second, VSMs support the creation of small, local energy networks—known as microgrids—that can operate independently and reconnect to the main grid when needed. This flexibility is particularly useful during emergencies or power outages. Lastly, VSMs provide an elegant solution for the common concern about inertia, traditionally provided by large spinning machines that help cushion the grid against sudden changes. By design, VSMs can offer similar or even better characteristics of inertia.
VSMs are poised to become mainstream in the coming decade, driven in part by the backing of a global standard. After years of hard work, IEEE approved and published the first global standard on VSM, IEEE Standard 2988-2024. It involved members affiliated with key manufacturers, including General Electric, Siemens, Hitachi Energy, Schneider Electric, and Eaton, in addition to regulators and utilities, including North American Electric Reliability Corporation (NERC), Midcontinent Independent System Operator (MISO), National Grid, Southern California Edison, Duke Energy Corporation, and Energinet.
The Holistic SYNDEM Architecture
Until now, much of the expert discourse has focused primarily on energy generation. But that’s only half of the equation—the other half is demand: how different loads consume the electricity. Their behavior also plays a crucial role in maintaining grid stability, in particular when generation is powered by intermittent renewable energy sources.
There are many different loads, including motors, Internet devices, and lighting, among others. They are physically different, but technically have one thing in common: They will all have a rectifier at the front end because motor applications are more efficient with a motor drive, which consists of a rectifier; and Internet devices and LED lights consume DC electricity, which needs rectifiers at the front end as well. Like inverters, these rectifiers can also be controlled as VSMs, with the only difference being the direction of the power flow. Rectifiers consume electricity while inverters supply electricity.
As a result, most generation and consumption facilities in a future grid can be equipped and unified with the same synchronization mechanism to maintain grid stability in a synchronized-and-democratized (SYNDEM) manner. Yes, you read that correctly. Even devices that use electricity—like motors, computers, and LED lights—can play a similar active role in regulating the grid by autonomously adjusting their power demand according to instantaneous grid conditions. A less critical load can adapt its power demand by a larger percentage as needed, even up to 100%. In comparison, a more critical load can adjust its power demand at a smaller percentage or maintain its power demand. As a result, the power balance in a SYNDEM grid no longer depends predominantly on adjusting the supply but on dynamically adjusting both the supply and the demand, making it easier to maintain grid stability with intermittent renewable energy sources.
For many loads, it is often not a problem to adjust their demand by 5-10% for a short period. Cumulatively, this offers significant support for the grid. Due to the rapid response of VSM, the support provided by such loads is equivalent to inertia and/or spinning reserve—extra power from synchronized generators not at full load. This can reduce the need for large spinning reserves that are currently necessary in power systems and reduce the effort to coordinate generation facilities. It also mitigates the impact of dwindling inertia caused by the retirement of conventional large generating facilities.
In a SYNDEM grid, all active grid players, regardless of size, whether conventional or renewable, supplying or consuming, would follow the same SYNDEM rule of law and play the same equal role in maintaining grid stability, democratizing power systems, and paving the way for autonomous operation. It is worth highlighting that the autonomous operation can be achieved without relying on communication networks or human intervention, lowering costs and improving security.
The SYNDEM architecture takes VSMs to new heights, addressing all three systemic challenges mentioned above: democratization, compatibility, and scalability. With this architecture, you can stack grids at different scales, much like building blocks. Each home grid can be operated on its own, multiple home grids can be connected to form a neighborhood grid, and multiple neighborhood grids can be connected to create a community grid, and so on. Moreover, such a grid can be decomposed into smaller grids when needed and can reconnect to form a single grid, all autonomously, without changing codes or issuing commands.
The holistic theory is established, the enabling technologies are in place, and the governing standard is approved. However, the full realization of VSMs within the SYNDEM architecture depends on joint ventures and global deployment. This isn’t a task for any one group alone. We must act together. Whether you’re a policymaker, innovator, investor, or simply someone who cares about keeping the lights on, you can play a role. Join us to make power systems worldwide stable, reliable, sustainable, and, eventually, fully autonomous.
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