Managing Power Sources in Island Mode Operations

⚙️ Gas Turbine Control Philosophy Explained Droop vs Isochronous vs Megawatt PID Control Understanding turbine governing modes is critical for stable power generation — especially in grid-connected and isolated systems. Here’s a simplified technical breakdown 👇 🎛 1️⃣ Droop Control – Grid Friendly Mode Droop control allows multiple machines to operate in parallel and share load proportionally. 🔹 Load sharing based on rated capacity 🔹 Responds to frequency deviations 🔹 Typical droop setting: 4% 🔹 Frequency drops → Machine increases load 📌 Example from the slide: Two turbines: • GT1 rated 100 MW • GT2 rated 20 MW • Both with 4% droop If system frequency drops by 1%: ✔️ GT1 increases from 50 MW → 75 MW ✔️ GT2 increases from 10 MW → 15 MW Each machine picks up load proportional to its rating. As grid frequency restores to 50 Hz, machines return to original load. 👉 This makes droop control ideal for utility-connected systems. 📊 Droop Philosophy (Graph Insight) The sloped characteristic curve shows: ⬇️ Frequency decreases ⬆️ Load increases Speed setpoint adjustments shift the operating line but maintain proportional sharing. This ensures: ✔️ Stability ✔️ Load balance ✔️ Grid compliance ⚡ 2️⃣ Isochronous Control – Constant Speed Mode Isochronous means: 🎯 “Constant Speed” operation In this mode: 🔹 Governor maintains exact speed setpoint (typically 50 Hz) 🔹 Load changes do NOT cause steady-state frequency changes 🔹 Controller adjusts fuel to restore frequency instantly ⚠️ Important Limitation: Multiple machines cannot normally operate in isochronous mode in parallel — one machine will take full load while the other unloads. 👉 Best suited for isolated plants. 📈 Isochronous Philosophy (Graph Insight) The curve is horizontal. No frequency change with load. Controller continuously corrects to bring speed back to setpoint. Perfect for: ✔️ Islanded operation ✔️ Small captive plants 🔥 3️⃣ Megawatt PID Control – Load Control Mode This mode uses: Proportional – Integral – Derivative (PID) control blocks. Key features: 🔹 Controls turbine based on desired MW output 🔹 Adjusts governor output to achieve load setpoint 🔹 Does NOT respond to system frequency ⚠️ Not typically suitable for utility-connected turbines where droop response is mandatory. Commonly used in: ✔️ Isolated systems ✔️ Plants where specific turbines must run at fixed load ✔️ Hybrid droop + isochronous coordination setups #PowerPlant #GasTurbine #ControlSystems #PowerGeneration #EngineeringLearning

🔌 Grid Synchronisation of a Captive Power Plant Startup, Synchronising & Shutdown Logic – Explained with SLD Grid synchronisation is one of the most critical operations in a captive power plant. It is not just about matching voltage and frequency, but about logic, interlocks, and protection coordination. Below is a practical overview based on a typical Grid–Captive Power Plant Single Line Diagram (SLD). 🔹 1️⃣ Generator Startup Logic (Island Mode) Preconditions: Generator CB & Bus Coupler → OPEN All protections healthy AVR in AUTO, Governor in speed mode Auxiliaries (LO, cooling, sealing) available Sequence: Start turbine / prime mover Generator reaches rated speed (50 Hz) AVR builds up generator voltage Close Generator CB Generator feeds captive plant bus in island mode 🔹 2️⃣ Synchronising Logic (Generator ↔ Grid) Synchronising Conditions: Voltage difference ≤ ±5% Frequency difference ≤ ±0.1–0.2 Hz Phase sequence match (RYB) Phase angle ≈ 0° Sequence: Grid CB closed, grid healthy Sync panel compares Grid PT & Generator PT Governor fine-tunes frequency AVR fine-tunes voltage When conditions are satisfied → Bus Coupler CLOSE After Parallel Operation: Governor controls Active Power (MW) AVR controls Reactive Power (MVAR) / Voltage 🔹 3️⃣ Normal Shutdown / De-Synchronising Logic Gradually reduce generator MW to near zero Ensure no reverse power (32 relay supervision) Open Bus Coupler Open Generator CB Stop turbine and auxiliary systems sequentially ➡ Generator is safely disconnected without disturbing the grid. 🔹 4️⃣ Emergency Trip Logic Triggered by: Generator faults (87G, 40, 50/51, 50N/51N) Reverse power Grid failure / severe disturbance Turbine trip Action: Generator CB trips Bus Coupler opens (anti-islanding) System shifts to safe condition 🔑 Key Takeaways ✔ Generator is always started in island mode ✔ Synchronisation is protection-driven, not manual judgment ✔ MW is controlled by Governor, MVAR by AVR ✔ Proper shutdown logic prevents grid disturbances ✔ Protection relays are the final safety layer 💡 Understanding startup, synchronising, and shutdown logic is essential for safe and reliable captive power plant operation. #PowerPlant #GridSynchronization #ElectricalEngineering #CaptivePowerPlant #SLD #GeneratorProtection #AVR #Governor #RelayProtection #HTSystems

Addressing challenges in islanded microgrids (IMGs) is crucial for enhancing grid stability. Virtual synchronous generators (VSGs) have been pivotal in mitigating low-inertia issues, yet they can lead to low-frequency oscillations (LFOs) due to swing equation replication. This innovative approach optimizes VSG power allocation based on production costs, boosting efficiency while addressing virtual damping constraints. By prioritizing cost-effective VSGs, the method optimizes grid performance, albeit at the expense of reduced damping and inertia levels. To counteract LFOs and ensure seamless grid operations, a novel concept of virtual inductance in the voltage magnitude loop of VSGs is introduced. This adjustment, requiring minimal tuning, effectively dampens oscillations while maintaining high virtual inertia for rate-of-change-of-frequency (RoCoF) compliance. The optimization process leverages small-signal stability analysis through teaching-learning-based techniques, ensuring robust performance under diverse operating conditions. Furthermore, the proposed method accommodates smooth mode transitions, intricate multi-VSG interactions, and voltage drop limitations. Extensive validation through mathematical proofs, simulations, real-time experiments, and eigenvalue analyses underscores its reliability and superiority over conventional damping strategies. Comparative assessments with feedback-based, feedforward-based, and voltage magnitude-based approaches reaffirm its efficacy, particularly in hybrid cost function scenarios. Notably, the economic advantages of adopting this cost-based VSG strategy are quantified, showcasing substantial potential savings in power generation expenses. This comprehensive approach not only addresses existing grid challenges but also lays a foundation for cost-efficient and stable IMG operations.

Formidable grid support and resiliency! The combination of a gas turbine and a battery will provide all TSO abbreviations (FCR-x, xFRR, FFR) with fast reactive power for voltage control, physical inertia, and short-circuit current, in addition to normal active power generation. Black start and island mode are readily available... This is the lot for any grid operator's wish list! Recent work by Norris Martinsson and Hannes Steiner has shown that the large on-site battery can increase the gas turbine's fault ride-through (FRT) capability during brown-outs (low or zero voltage and short circuits) by a substantial amount of time by controlling the generator load angle swings. Gas turbines can utilize a plethora of renewable fuels, and the battery will provide spinning reserve even without firing the gas turbine. The latter is important from a NOx perspective. Adding an SSS Clutch / SSS Gears will further enhance capability by allowing the spinning generator to operate without firing the gas turbine. Hence, instant reactive power and short-circuit current at hand! The combination is utter elegance and flexibility, and the battery sizing is limited to cover less than 10 minutes of gas turbine operation. The resiliency perspective is covered from all aspects... Johan Bergström

⚡ Mastering Grid-Forming Control for Stable & Resilient Power Systems 🌍 In the era of renewable energy and microgrids, Grid-Forming (GFM) inverters are a game-changer. Unlike grid-following inverters that depend on the grid’s voltage and frequency, GFM inverters actively set and stabilize these parameters, making them essential for islanded operation, black start, and weak grid conditions. The control strategy shown here integrates Voltage Control, Current Control, and Active Power Control in a multi-loop GFM architecture. 1. Reference Voltage Generation Inputs: egd0*, egq0*, Q*, Q, igd, igq Output: Voltage references egd*, egq* Role: Maintains the desired voltage magnitude and provides reactive power support. 2. Voltage Control Loop (Outer Loop) Compares measured voltages egd, egq with references egd*, egq*. PI control laws: isd* = kpv × (egd* − egd) + (kiv / s) × (egd* − egd) isq* = kpv × (egq* − egq) + (kiv / s) × (egq* − egq) Purpose: Generates current references to support voltage formation and stability. 3. Current Control Loop (Inner Loop) Tracks reference currents isd*, isq* with high bandwidth. PI control laws: vmd* = kpi × (isd* − isd) + (kii / s) × (isd* − isd) vmq* = kpi × (isq* − isq) + (kii / s) × (isq* − isq) Outputs: Voltage commands in dq-frame, converted to vmabc* for inverter switching. 4. Active Power Control & Frequency Droop Regulates inverter output frequency according to active power deviation: ωeg = ωB + kp × (P* − P) Integrates ωeg to get phase θeg, enabling grid-forming capability. Why This Matters Voltage-forming ability: Maintains stable voltage without relying on the grid. Black start capability: Can energize a dead grid. Frequency support: Uses droop control for power sharing among multiple GFMs. Islanded & Weak Grid Support: Operates reliably where grid-following inverters would fail. ✅ Applications: Microgrid island operation Renewable plants in weak grids Battery energy storage systems Hybrid power systems with PV, wind, and storage 💡 Final Note: Grid-Forming Control is the future backbone of inverter-based power systems, ensuring resilience, stability, and seamless renewable integration in both grid-connected and islanded modes. #gridforming #renewableenergy #powerelectronics #invertercontrol #microgrid #voltagecontrol #currentcontrol #activepowercontrol #droopcontrol #energystorage #smartgrid #powerquality #electricalengineering #sustainableenergy #microgridstability

Electrical Deliverables for FPSO – FEED Phase 🔌 1. Electrical System Studies & Reports Load List (normal, essential, emergency, critical loads) Load Flow, Short Circuit, and Motor Starting Study Transient Stability / Generator Load Rejection Study Power Factor & Harmonics Analysis (especially with large VFDs for compressors) Generator Sizing & Spinning Reserve Study Emergency Power Balance & Black Start Study FPSO-Specific Earthing Study (floating hull = special grounding considerations) 🏗️ 2. System Architecture & Key Diagrams Power Distribution SLDs (HV/LV generation and distribution, segregated zones) PMS Architecture Diagram (generators, transformers, tie breakers, busbars) UPS and DC System SLDs Emergency and ESD Power SLDs Electrical Zoning Plan (Hazardous/Non-hazardous) Shore Power Interconnect SLD (if applicable during commissioning) 📐 3. Layout Drawings & Interface Plans Substation/Electrical Room GA Layouts Cable Tray Routing Layouts (by deck/module) Equipment Layouts with Clearances (transformers, MCCs, panels) Lighting Layouts (internal/external/hazardous areas) Earthing & Bonding Layout (for topsides + hull interface) Lightning Protection Layout Junction Box, Local Control Panel, and Ex Equipment Location Layouts 📋 4. Datasheets & Equipment Specifications Generators (Gas Turbine or Diesel) – marine certified HV/LV Switchgear (Ex-rated where required) Transformers (cast resin/dry type for marine use) UPS & Battery Systems (redundant, for ICSS/ESD) Motors (pump/compressor, Ex-certified) Lighting (Zone 1/2 certified), Emergency Lighting Cables (offshore/marine grade, LSZH, UV/rodent resistant) 🧠 5. Control, PMS & Protection Design Power Management System (PMS) Functional Description Protection Philosophy & Preliminary Relay Settings Synchronizing and Load Shedding Schemes Generator Load Sharing & Islanded Operation Strategy Control Interface with ICSS/DCS Fire & Gas System Electrical Interfacing (shutdown signals, power) 📑 6. Hazardous Area & Certification Deliverables Hazardous Area Classification Layout (IEC/ATEX) Equipment Zone Classification Datasheets ATEX/IECEx Compliance Matrix Marine Class Society Compliance Summary (ABS, DNV, etc.) Ex Equipment Lists and Certificates 💰 7. Procurement & Costing Electrical MTO/BOQ Long Lead Equipment List (with lead times) Preliminary Vendor Lists and RFQs CAPEX Estimate (Electrical Systems) Weight & Space Estimate for Electrical Modules 🛠️ 8. Supporting Deliverables Electrical Basis of Design (FPSO-specific) Design Criteria Document Project Specification for Electrical Installation Construction Strategy & Installation Constraints (modularization, integration) Offshore Commissioning & Testing Strategy (electrical scope) ✅ Optional Add-ons (Often in EPC Tender or Pre-EPC Stage) Arc Flash Hazard Study (if required by client/operator) Dynamic Simulation (e.g., blackout scenarios) Topside–Hull power interface studies (risers, glands, penetrations) #FEED #Electricaldesign

𝐌𝐢𝐜𝐫𝐨𝐠𝐫𝐢𝐝 𝐒𝐞𝐚𝐦𝐥𝐞𝐬𝐬 𝐓𝐫𝐚𝐧𝐬𝐢𝐭𝐢𝐨𝐧𝐬 𝐁𝐞𝐭𝐰𝐞𝐞𝐧 𝐆𝐫𝐢𝐝 𝐂𝐨𝐧𝐧𝐞𝐜𝐭𝐞𝐝 𝐚𝐧𝐝 𝐈𝐬𝐥𝐚𝐧𝐝𝐞𝐝 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧 The simulation demonstrates the #seamless #transition of the Battery Energy Storage System (#BESS) from #grid #connected to #islanded operation mode, which involves #transition from grid #following to grid #forming mode and vis versa. This functionality has been validated through software #simulation using MATLAB Simulink. Additionally, the simulation includes a #resynchronization process to ensure #smooth #reconnection of the #microgrid to the #transmission system after #islanded operation. 𝟏.         𝐊𝐞𝐲 𝐀𝐝𝐯𝐚𝐧𝐭𝐚𝐠𝐞𝐬 𝐨𝐟 𝐌𝐢𝐜𝐫𝐨𝐠𝐫𝐢𝐝 𝐎𝐩𝐞𝐫𝐚𝐭𝐢𝐨𝐧 One of the primary benefits of a microgrid is its ability to #operate in both #grid #connected and #islanded modes. In each mode, #BESS #inverters can function under different control strategies: 𝗚𝗿𝗶𝗱 𝗖𝗼𝗻𝗻𝗲𝗰𝘁𝗲𝗱 𝗠𝗼𝗱𝗲: BESS #inverters operate under #current #source #control. 𝗜𝘀𝗹𝗮𝗻𝗱𝗲𝗱 𝗠𝗼𝗱𝗲: BESS #inverters operate under #voltage #source #control. 𝟐.         𝐂𝐡𝐚𝐥𝐥𝐞𝐧𝐠𝐞𝐬 𝐚𝐧𝐝 𝐂𝐨𝐧𝐭𝐫𝐨𝐥 𝐒𝐭𝐫𝐚𝐭𝐞𝐠𝐲 𝐂𝐨𝐧𝐭𝐫𝐨𝐥 𝐌𝐨𝐝𝐞: In grid #connected operation, the #BESS functions in grid #following mode, #synchronizing with the grid’s #voltage and #frequency. In #islanded operation, it must switch to grid #forming mode to establish its #own #voltage and #frequency. The #transition between these two fundamentally different control strategies must be #seamless. 𝐏𝐨𝐰𝐞𝐫 𝐈𝐦𝐛𝐚𝐥𝐚𝐧𝐜𝐞: At the moment of #disconnection, #power #exchange with the main #grid immediately #drops to zero. This sudden change creates either a #power #surplus or #deficit within the #microgrid, resulting in #deviations in #frequency and #voltage. 𝐑𝐞-𝐬𝐲𝐧𝐜𝐡𝐫𝐨𝐧𝐢𝐳𝐚𝐭𝐢𝐨𝐧 𝐮𝐩𝐨𝐧 𝐑𝐞𝐜𝐨𝐧𝐧𝐞𝐜𝐭𝐢𝐨𝐧: Before #reconnecting to the main #grid, the #microgrid must achieve #perfect #synchronization by matching: - #voltage #magnitude, - #frequency, - and #phase #angle. Any significant mismatch can cause large #transient currents, potentially damaging #equipment and #triggering #protection systems. 𝐏𝐫𝐨𝐭𝐞𝐜𝐭𝐢𝐨𝐧 𝐂𝐨𝐨𝐫𝐝𝐢𝐧𝐚𝐭𝐢𝐨𝐧: Fault #current levels are significantly #lower in islanded mode compared to grid #connected mode. Conventional #overcurrent protection may not function #correctly in both scenarios, leading to #risks such as #fault #detection #failure or nuisance #tripping. 𝐋𝐨𝐚𝐝 𝐚𝐧𝐝 𝐆𝐞𝐧𝐞𝐫𝐚𝐭𝐢𝐨𝐧 𝐒𝐡𝐞𝐝𝐝𝐢𝐧𝐠: The #BESS has limited #power and #energy capacity. If the #microgrid is #importing or #exporting significant #power at the time of #grid #failure, the 3BESS may not be able to support all connected #loads or #generation. Without rapid load and generation #shedding, the entire microgrid could become #unstable and #collapse.