Power Electronics in Power Systems

🔌 The dynamic behaviour of bulk power systems was mainly influenced by synchronous generators, their controls, and load dynamics. The timescales that required analysis were determined by electromechanical phenomena occurring over several milliseconds to minutes. However, the increasing integration of power electronic converters, such as due to the penetration of wind, photovoltaic, and energy storage systems, has shifted power system dynamics towards rapid responses driven by power electronic converters. This change extends the relevant timescales down to microseconds and several milliseconds, requiring the inclusion of faster electromagnetic dynamics in stability assessments. 🔋 Microgrids further accentuate these shifts because of their smaller size and (typically) higher penetration of intermittent Renewable Energy Sources (RES), resulting in lower system inertia, limited short-circuit capacity, and higher feeder R/X ratios, which make their dynamics inherently faster and less predictable than bulk systems. Consequently, there is a strong coupling between voltage and frequency, meaning control actions and disturbances reflect almost instantly across the system. 🔦 In traditional systems, stability was categorised into three types: rotor angle, voltage, and frequency. While the core definitions of these remain unchanged, new stability classes have emerged: Resonance Stability and Converter-driven Stability. Resonance stability includes issues such as subsynchronous resonance, like torsional interactions between series compensation and turbine-generator shafts, and electrical resonance in DFIGs, often referred to as subsynchronous control interaction due to the dominant converter control actions. Converter-driven stability, influenced by rapid dynamic interactions of power electronic controls, is further divided into fast-interaction (high-frequency harmonic instability caused by inner current loops or switching) and slow-interaction (low-frequency oscillations from outer control loops and PLLs, particularly in weak grids). 🔋 For microgrids, instabilities often manifest as fluctuations across all system variables due to the strong voltage-frequency coupling, making root-cause classification more relevant than traditional voltage or frequency distinctions. Additionally, intentional load shedding to sustain operation (beyond fault isolation or voluntary demand response) is generally regarded as causing microgrid instability. Principal challenges in microgrid stability include rapid frequency excursions caused by low inertia, issues with reactive power sharing and voltage regulation among DERs, and other problems resulting from inadequate control schemes or poorly tuned equipment controllers (e.g., Phase-Locked Loops (PLLs), which can compromise stability), introducing negative admittance). #gridmodernization #datacenter #powerelectronics #cleanenrgy #microgrids #technology

A Comprehensive HVDC Power Electronics System in Simulink: A Milestone in Innovation This project presents an advanced High Voltage Direct Current (HVDC) system modeled in Simulink, integrating diverse power electronics components and renewable energy sources into a unified setup. This unique system is a pioneering effort in simulation and modeling, designed to highlight cutting-edge energy transmission and integration techniques. Below is a detailed breakdown of the system and its components. 1. HVDC System Overview Voltage and Distance: The system operates at 230 kV DC and spans a transmission distance of 100 km, enabling high-efficiency long-distance power transfer. Power Transmission: It is designed to transfer a total of 50 MW of power between two Voltage Source Converter (VSC) stations. Grid Integration: The system is connected to an AC grid operating at 220 kV, 50 Hz, with a transformer rated at 220/110 kV to match the transmission voltage. 2. Photovoltaic (PV) Arrays Capacity: The system integrates two 1 MW PV arrays, contributing clean solar energy to the grid. Control Strategy: Each PV array is equipped with Maximum Power Point Tracking (MPPT) controllers to optimize energy harvesting under varying solar irradiance conditions. 3. Wind Energy Integration Wind Turbine: A wind turbine rated at 10 kW is included to supplement the system’s renewable energy input. Boost Converter with MPPT: A boost converter is employed alongside MPPT algorithms to ensure maximum power extraction from the wind turbine under fluctuating wind speeds. 4. Energy Storage System Z-Source Inverter: The system features a Z-source inverter integrated with storage elements, providing robust and reliable energy storage and transfer. Boost Inverter: A boost inverter is included to enhance the storage system’s performance and support the grid during peak demand or renewable energy fluctuations. 5. Key Features and Advantages Modularity: Each component is modularly designed, enabling easy expansion and testing of additional renewable sources or advanced control strategies. Efficiency: The combination of HVDC, advanced inverters, and MPPT controllers maximizes overall system efficiency. Innovation: This is the first published system of its kind to integrate such diverse components, making it a benchmark in power electronics simulation. Conclusion This comprehensive HVDC power electronics system in Simulink serves as a cutting-edge example of modern energy systems. Its ability to integrate solar, wind, and storage solutions into a unified, high-efficiency setup positions it as a vital step toward sustainable and reliable energy solutions. 💡 If you are interested in contributing to scientific publications, sharing insights, or exploring practical applications of this system, feel free to reach out directly. Let’s work together to advance the field and achieve impactful results.

Modern grids are dominated by power electronics, yet many of today’s stability problems are old physics problems we’ve forgotten how to see.   Some of the most useful intuition for today’s converter-dominated systems comes from technologies we rarely talk about anymore. A few years ago, I analysed the behaviour of fixed-speed induction generator (FSIG) wind turbines using real disturbance data and simulations. What stood out wasn’t nostalgia, it was how clearly they exposed stability mechanisms that are still relevant. Not because we should go back to FSIGs, but because they reveal physics that modern grids have to recreate through control design. ➤ FSIGs delivered inertia through physics, instant, natural, and loop-free When frequency dipped: • the rotor slowed • stored kinetic energy was released • power was injected within milliseconds • before any grid-side controller acted. In the animation below: • frequency falls (blue) • inertial power is injected in Stage I (orange) • energy is then recovered in Stage II as rotor speed returns (provided pitch allows re-acceleration) This is physical inertia in action, not synthetic inertia produced by a control loop. ➤ Why this matters for today’s engineering challenges Much of what engineers grapple with, RoCoF sensitivity, fast frequency response tuning, PLL dynamics, coordination of grid-forming controls, is an attempt to recreate, in software, behaviours that used to exist naturally in electromechanical machines. FSIGs help explain: • why historical grids were inherently more forgiving • why frequency used to decline more slowly • why inertia was once a physical property, not a procured service • why synthetic inertia is not the same physical process • why converter-dominated grids demand precise control coordination ➤ We’re not romanticising old technology, we’re extracting timeless principles FSIGs also had real limitations: poor voltage control, limited reactive capability, and constraints that ultimately pushed the industry toward modern turbines. But their inertial behaviour remains a powerful reference for: • how machines exchange torque • how energy moves in the first 200 ms • what stabilises the system before any control loop wakes up As we build a grid dominated by power electronics, we can’t lose the intuition that anchored the synchronous era. The physics hasn’t disappeared. It has moved into software, and that makes understanding it more important, not less. I’m seeing these questions surface increasingly in EMT studies, connection assessments, and early grid-forming control design decisions, not as theory, but as constraints on what actually gets approved. 👉 As we design synthetic inertia and fast frequency response, how do we ensure we’re reproducing not just the equations, but the robustness and predictability that physical inertia once gave us “for free”? #PowerSystems #RenewableEnergy #GridStability #Inertia #InverterBasedResources #GridForming #EnergyTransition

Modular Multilevel Converter via EtherCAT with phase-shifted PWM The Modular Multilevel Converter (MMC) demonstrator with EtherCAT real-time communication, implemented for the purpose of investigating MMC topology suitability for medium-voltage wind turbine applications. The project focuses specifically on the EtherCAT communication architecture, synchronization method, and phase-shifted PWM modulation technique. 🔧 Decentralized submodule control on a standard industrial bus - TwinCAT on an Embedded-PC as EtherCAT Master - EtherCAT IP Core integrated into the FPGA of each submodule ⚡ Real-time performance the converter actually needs - 156 µs minimum cycle time, 5 kHz sampling rate - 20 ns jitter measured across all 18 submodules via Distributed Clocks - Phase-shifted PWM with 1 kHz, automatic capacitor voltage balancing The decentralized control follows the same modular and scalable approach as the power hardware. Doubling the submodule count scales the topology to 6 kV without redesigning the control platform. The same EtherCAT bus that runs the turbine controller runs the converter, which means seamless integration instead of a second isolated control domain. The authors' conclusion, after three years of measurements: "EtherCAT meets the requirements for a direct use in PE converter systems." PC-based Control plus EtherCAT is not just a fieldbus story. For power electronics developers, it is a way to put MMC, grid-forming inverters, and HVDC submodule control on one open, standardized, real-time platform. Research project at the Hochschule Flensburg by, Jan-Henrik Fey, Frank Hinrichsen, Prof. Dr. Regine Mallwitz. Links to the publications in the comments.

⚖️🔧⚡ Transitioning from Grid-Following (GFL) to Grid-Forming (GFM) in Solar + BESS Projects As more renewable projects move toward grid-forming capabilities, it’s critical to understand that success depends on two distinct but equally important layers: 👉 Power Electronics (device level) 👉 GPM – Grid Performance Management (plant/system level) They solve different parts of the problem — and both must evolve together. 🔌 1. Power Electronics – The Foundation Before (GFL): -Inverters follow grid voltage & frequency (PLL-based) -Require a strong grid -Limited stability support (no inertia, -weak voltage control) After (GFM): -Inverters create voltage & frequency -Act like synchronous machines (virtual inertia, droop control) -Operate in weak grids or islanded mode 🔧 Key Changes: Control shift: PLL → Droop / Virtual Synchronous Machine (VSM) Add: Frequency droop (P–f) Voltage droop (Q–V) Synthetic inertia OEM firmware & protection updates (e.g., Sungrow, Tesla, SMA) Integration of BESS for fast dynamic support Enhanced fault response & ride-through capability 🧠 2. GPM – The System-Level Brain GPM coordinates the entire plant: Inverters BESS Plant Power Controller (PPC) Interfaces with utilities (e.g., Oncor) and ISOs (e.g., ERCOT) 🔧 What Changes with GFM: ✔ PPC Upgrades Grid-forming dispatch Multi-unit coordination Voltage & frequency reference control Black start capability ✔ EMS Enhancements BESS dispatch optimization SOC management (maintain headroom for grid support) ✔ Grid Compliance Meet requirements like NOGRR272 Fast frequency response Voltage ride-through Disturbance support ✔ Protection Updates Adaptive protection schemes Revised relay coordination Anti-islanding updates ✔ Operational Modes Grid-connected ↔ Grid-forming Grid-forming ↔ Islanded Black start sequences ⚖️ Power Electronics vs GPM – Key Difference Power Electronics: Creates voltage & frequency (device-level stability) GPM: Coordinates and sustains plant-wide performance ⚡ Real Example: 40 MW Solar + 10 MW / 20 MWh BESS Without GFM: PV becomes unstable in weak grids No meaningful frequency support With GFM: BESS + inverter form the grid Stabilize voltage & frequency GPM ensures: SOC ~50–70% (bidirectional support) Dynamic dispatch Alignment with ERCOT signals 🚧 Key Risks if Not Done Right Control instability (oscillations) BESS depletion → loss of support Protection miscoordination Non-compliance (e.g., NOGRR272) Interconnection delays ✅ Bottom Line ⚡ Power Electronics = “Can we form the grid?” 🧠 GPM = “Can we control it reliably at scale?” 👉 You need both: Power electronics enables the capability GPM ensures it works in real-world grid conditions #SolarEnergy #RenewableEnergy #EnergyStorage #BESS #GridForming #GridFollowing #PowerElectronics #EnergyTransition #ERCOT #GridStability #CleanEnergy #Inverters #Engineering #PowerSystems #EnergyManagement #UtilityScale #SolarProjects #Transmission #Infrastructure