Role of Converters in Grid Integration

Grid-Forming Inverters: Quietly Solving a Crisis We Don’t Talk About As renewables scale, one thing is quietly disappearing from our grids: Inertia. Spinning turbines in coal, gas, and hydro plants used to stabilize frequency. But inverter-based solar and storage don’t provide that naturally. Enter Grid-Forming Inverters (GFIs), not just feeding power, but actively supporting the grid. ✅ Create voltage and frequency reference — no need to follow others ✅ Provide virtual inertia for smoother post-fault recovery ✅ Enable black start capability (restart a dead grid) ✅ Stabilize weak grids — vital for remote and developing regions In short: they help solar + BESS act like conventional generation and that changes everything. 📊 A few numbers to keep in mind: • Australia targets 80% of new inverters to be grid-forming by 2035 • Systems with over 60% inverter-based generation become unstable without GFIs • IRENA notes that with >60% inverter-based generation, systems without GFIs face serious stability risks 🔍 Curious how others are integrating GFIs into their systems? Let’s exchange notes — strategy, challenges, and lessons learned. #GridStability #RenewableEnergyTech #SolarAndStorage #PowerSystemsInnovation

🔌 Grid-forming (GFM) inverters gained significant interest because of their potential to enhance grid stability and reliability, particularly as the limitations of grid-following converters became clear. However, the GFM converter faces substantial challenges in current limiting during fault conditions. The core challenge is protecting the inverter hardware from thermal damage due to excessive output currents. The ideal current limiter must act swiftly and accurately to curtail overcurrent; however, engaging the current limiter alters the entire control architecture. This typically leads to different dynamic output behaviours that may introduce small-signal instability or excessive output voltage and current harmonics.   ⚡ Current limiting methods for GFM inverters can be categorised into direct and indirect approaches. The current limiters are highlighted in red colours in the figure. Direct current limiters aim to curtail the inverter output current by manipulating the current-reference control signals or directly controlling the semiconductor switch signals. For instance, the current-reference saturation limiter dynamically scales the current-reference signal based on the maximum allowable current, ensuring that the output current does not exceed predefined limits. The other option is the switch-level current limiting method, which directly modulates the switching signals fed to the bridge. This method achieves the fastest response as it bypasses the other control loops. However, the unavoidable consequence of bypassing the control loops is the sacrifice of power quality and even controller stability, which leads to integrator windups in the hierarchical control loops.   ⚡ Indirect current limiters, on the other hand, work by manipulating voltage-reference and power-reference signals in the inverter controls. These approaches can be slower than direct methods but avoid the windup issues associated with them. For example, voltage-based current limiting reduces the voltage reference in response to overcurrent conditions, effectively limiting the output current while maintaining control over the voltage and current phasors. This method can enhance transient stability during faults but may also lead to challenges in frequency stability and post-fault recovery. The last group of limiters that has been explored are hybrid solutions that combine the strengths of both direct and indirect methods, aiming to improve reliability and stability during current-limited operations. One of the promising approaches is combining a VI current limiter and a current-reference saturation limiter. First, the saturation limiter kicks in and limits the current to Imax. After the initial phase of fault passes, the VI current limiter takes over because the threshold current for the VI current limiter is set lower than Imax. #gridforming #microgrids #powerelectronics #battery #energystorage #gridmodernization #cleanenergy #renewables

The 28 April #blackout impacting #Spain and #Portugal is yet another reminder of the complexities we face in modern #powersystems. It is still too early to pinpoint the exact cause, initial analysis (and many excellent posts here) points towards subsynchronous #oscillations across the European network leading to sequential generation disconnections (have we seen this before South Australia?), ultimately tripping the critical France-Spain interconnector and resulting in a total system loss.   Such events inevitably bring greater focus to #GridForming (GFM) converters essential in weaker systems like Australia's but increasingly relevant even in strong grids like the European due to their oscillation damping capabilities.   Yet, as promising as #GFMs are, it is crucial to acknowledge their inherent limitations. After all, they're still #powerelectronics #converters. They have their own [power] comfort zone, they are serious about their [current] boundaries and they do sometimes have commitment [#synchronisation] issues 😁 .   Our recently published work highlights some of these limitations: 1. Synchronisation challenges: GFM converters are prone to synchronisation instability when active power references cannot be reached due to limits in the converter current and the requirement for current limiters. This can lead to instabilities in GFM converters after being subjected to large frequency disturbances as the current limiter restricts the power transfer capability of GFM converters. Our work led by Tony Xu can be found here: (Composite Power-Frequency Synchronization Loop for Enhanced Frequency Response Considering Current and Power Limits of Grid-Forming Converters: https://lnkd.in/gJhNZ9DB )   2. Effective Damping of GFMs under power and current limitations: While we can design the GFM with a certain damping coefficient in its control, power limiters will reduce the available damping power during large disturbances. This might lead to frequency / power oscillations due to insufficient damping against what we originally designed. In a worst-case scenario, the damping power can drop to zero if a fully loaded GFM converter needs to respond to a frequency drop. The work led by Shan Jiang, Ye Zhu demonstrated such occasions (Bandwise Power-Synchronization Loop for Frequency Response Improvement in Grid-Forming Converters: https://lnkd.in/gUTKxnta)   Phase Jumps: In #GFL systems, a larger phase jump typically means worse conditions for the converter. However, the synchronisation modes of GFMs set different requirements, and smaller phase jumps closer to a critical angle can actually create worse conditions for a GFM converter (more on this from Shan in June 😊 )   Such incidents underscore the urgent need to rethink grid connection standards and consider mandating site-specific testing for increasingly power electronics-defined power systems. #gridintegration #renewables #stability

Grid-forming control to achieve a 100% power electronics interfaced power transmission systems by Taoufik Qoria -”Nouvelles lois de contrˆole pour former des r´eseaux de transport avec 100% d’´electronique de puissance” ´ECOLE DOCTORALE SCIENCES ET M´ETIERS DE L’ING´ENIEUR L2EP - Campus de Lille  Abstract: The rapid development of intermittent renewable generation and HVDC links yields an important increase of the penetration rate of power electronic converters in the transmission systems. Today, power converters have the main function of injecting power into the main grid, while relying on synchronous machines that guaranty all system needs. This operation mode of power converters is called "Grid-following". Grid-following converters have several limitations: their inability to operate in a standalone mode, their stability issues under weak-grids and faulty conditions and their negative side effect on the system inertia.To meet these challenges, the grid-forming control is a good solution to respond to the system needs and allow a stable and safe operation of power system with high penetration rate of power electronic converters, up to a 100%. Firstly, three grid-forming control strategies are proposed to guarantee four main features: voltage control, power control, inertia emulation and frequency support. The system dynamics and robustness based on each control have been analyzed and discussed. Then, depending on the converter topology, the connection with the AC grid may require additional filters and control loops. In this thesis, two converter topologies have been considered (2-Level VSC and VSC-MMC) and the implementation associated with each one has been discussed. Finally, the questions of the grid-forming converters protection against overcurrent and their post-fault synchronization have been investigated, and then a hybrid current limitation and resynchronization algorithms have been proposed to enhance the transient stability of the system. At the end, an experimental test bench has been developed to confirm the theoretical approach.  VIEW FULL THESIS: https://lnkd.in/dcTJU-9v

🔋 Powering the Future: Grid-Forming Inverters for Stable Renewable Integration 🌍⚡ As the energy landscape rapidly evolves with increasing contributions from renewable sources like solar and wind, maintaining grid stability has become more challenging. Enter Grid-Forming Inverters—the game-changers in modern power systems. A grid-forming inverter is a power electronic device that plays a crucial role in the operation and stability of electrical power grids What Makes Grid-Forming Inverters Essential? Unlike traditional grid-following inverters that merely follow grid voltage and frequency, Grid-Forming Inverters actively control voltage and frequency, making them vital in microgrids and regions with unreliable access to main power grids. They continuously monitor grid conditions and adjust their output to maintain stability and synchronization, addressing the lack of rotational inertia in inverter-based resources. 💡 Key Control Techniques in Grid-Forming Inverters: 📍 Voltage and Frequency Droop Control: Regulates voltage and frequency in multi-generating setups, ensuring smooth operation. 📍 Virtual Inertia & Frequency Support: Mimics traditional rotating masses by controlling the rate of change of output power, enhancing grid stability. 📍 Phase-Locked Loop (PLL): Ensures precise synchronization by accurately detecting grid frequency and phase. 📍 Fault Ride-Through: Keeps inverters connected during grid faults, ensuring uninterrupted power and system reliability. 📌 Why It Matters: Grid-forming inverters are not just about integrating renewables; they are about redefining grid reliability and stability. By actively managing power quality and ensuring synchronization, they play a critical role in the clean energy transition. 📈 Why Now? With 94% of new U.S. electric-generating capacity in 2024 expected to come from inverter-based resources like solar and wind, the shift to grid-forming technology is not just beneficial—it's essential for a sustainable energy future. 📖 Reference: For a comprehensive dive into the critical role of grid-forming inverters, check out the Introduction to Grid Forming Inverters by Ben Kroposki, Director at the Power Systems Engineering Center, National Renewable Energy Laboratory (NREL). This document outlines why GFM inverters are vital in today's evolving energy landscape. #GridFormingInverters #RenewableEnergy #PowerGridStability #InverterTechnology #EnergyTransition

Grid Forming Inverters in Focus and how they're reshaping our energy systems Take a look back at older power grids. These traditional grid-following inverters struggled. They couldn't maintain power supply or stability without a main grid connection. But that's changing. Grid Forming Inverters (GFIs)... - excel in their ability to maintain grid stability and operate autonomously. - can function in both high-inertia and low-inertia environments. - adapt to varied grid conditions with remarkable efficiency. This makes them invaluable in integrating renewable energy sources like solar PV, wind power plants, and hybrid systems into the grid. Want proof? 💡 Hornsdale Power Reserve showcased the efficiency of its Battery Energy Storage System (BESS) in handling grid disturbances following the Callide coal plant explosion in Queensland, especially its "virtual machine mode". 💡 California Imperial Irrigation District BESS successfully synchronized a 44 MW natural gas turbine generator with the grid. 💡 Sint Eustatius, Netherlands used GFIs to enable the use of solar power for 46% of its electricity needs, maintaining grid stability for over 10 hours with solar energy exceeding 100% of the power demand. 💡 Santa Rita Jail Microgrid uses about 1.5 MW of solar power, a 1.0 MW fuel cell, and diesel generators, with a 2 MW battery managed by GFIs for balancing, allowing operations in both grid-connected and islanded modes. The future of energy is not just about being cleaner and greener. It's about being smarter and more resilient. I think GFIs are a key piece of this puzzle. What's your perspective on GFIs? #innovation #technology #energy #sustainability ASEC ENGINEERS - Engineering your success, delivering precision and innovation in every project since 1991.