Understanding Electrical Systems

Eight Misconceptions Around the “Merit Order” Misconception 1: Marginal pricing is unique to electricity markets. It’s not. All commodities price on the margin. The “Merit Order” is what is conventionally called a short-term supply curve. Marginal costs determine prices of crude oil, natural gas, bananas, coffee beans, solar cells, cloud computing, etc. Misconception 2: The Merit Order Model is mandatory or prescriptive. It’s not. It describes how independent, profit-maximizing firms behave in free, competitive markets. Marginal pricing is not a rule or law – firms can bid any price they want. The Merit Order is not a policy; it is a description of how a free market works. The Merit Order Model is descriptive, not prescriptive. Misconception 3: Marginal pricing is an artificial and arbitrary rule. It’s not. Marginal pricing is not one among many sensible alternatives that we can pick and choose from. In fact, it is the only price that underpins a market equilibrium. Setting any other price requires rationing, i.e. excluding consumers from the market or forcing generators to produce. Misconception 4: Contribution margins are windfall profits. They are not. The difference between the electricity price and variable costs pays for investment. Misconception 5: Pay-as-bid would lead to different prices. It would not. If the pricing rule in an auction were changed – say, the EPEX SPOT day-ahead auction – market parties would adjust their bidding strategy immediately. Instead of bidding their own variable cost, they would estimate the variable cost of the marginal plant and bid just below. The resulting price would hardly change. Misconception 6: The Merit Order is a model of the day-ahead auction. It is not. It’s an equilibrium model of the entire short-term electricity market, not just one segment. Even if the pricing rule in a particular day-ahead auction (say, Nordpool Spot) were changed, the merit order would remain a valid model for predicting equilibrium power prices. Generators would simply adjust their bids or use different market platforms for trading. Misconception 7: The power price is coupled to the gas price by law. It’s not. It is economic mechanisms, not regulation, that make these prices move hand-in-hand. They do not always move in parallel — when gas plants are not needed to serve demand, gas prices have no impact on power prices. Misconception 8: It’s only about spot prices. It is not. Most consumers and producers hedge, i.e. they lock in prices months or years in advance of delivery by trading on forward markets. Hence spot price fluctuations do not immediately spill over to retail prices levels.

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

🔴 The Spanish power system collapsed within seconds following a double contingency in its interconnection lines with France. First, a 400 kV line disconnected, and less than a second later, a second line also failed, suddenly isolating Spain while it was exporting 5 GW of power. The frequency rose abruptly, triggering the automatic disconnection of approximately 10 GW of renewable generation, programmed to shut down when exceeding 50.2 Hz. This led to a sudden energy shortfall, a sharp frequency drop, and within just nine seconds, a total system blackout. 🪕 The causes of the incident are attributed to low rotational inertia (only about 10 GW of synchronous generation online), identically configured renewable protections that reacted simultaneously, reserves that were inadequate for such a high share of renewables, and an under-dimensioned interconnection with France. Could this have been avoided? Several measures could help prevent similar situations in the future, such as requiring synthetic inertia in large power plants, reinforcing the interconnection with France, and establishing a fast frequency response market, among others. 💡 In this context, Battery Energy Storage Systems (BESS) are more essential than ever. These systems can provide synthetic inertia, ultra-fast frequency response, and backup power in critical situations—capabilities that today’s renewable-dominated system cannot ensure on its own. By reacting in milliseconds, BESS help stabilize the grid during sudden frequency deviations, preventing massive disconnections and buying time for other reserves to activate. Their strategic deployment, combined with appropriate regulation, would make these systems a cornerstone of a more secure and resilient future power system. ... ✋️Please note that this post was written based on the information published on or before its release. Root cause analysis is still ongoing and updates will be released with the outcomes of the investigation. The goal is to show the features that can be provided by BESS within the wide portfolio of solutions applicable in these cases. All inisghts are highly welcome and appreciated in order to enrich our collective understanding. ... 📸 Reid Gardner Battery Energy Storage System (Nevada, USA) A real-world example of how BESS ensures grid stability by delivering synthetic inertia and fast frequency response—essential in a renewable-heavy energy mix.

🔋 Why Grid Frequency Matters – and How Inertia Keeps the Lights On Did you know that the stability of our entire power grid depends on keeping frequency within ±0.1 Hz of its target value (50 Hz or 60 Hz worldwide)? If it drifts ±0.5 Hz outside the norm, grids enter emergency mode, risking blackouts. A more extreme deviation? It could lead to a full system failure—costing economies millions and endangering lives. At the heart of frequency stability is inertia—the kinetic energy stored in the spinning turbines of synchronous generators. This “rotating mass” acts like a shock absorber, slowing down frequency changes when sudden disruptions occur (like losing a 1 GW power plant). 🛁 Imagine it like a bathtub: The tap = power generation (flowing in) The drain = consumption (flowing out) The water level = frequency The size of the tub = inertia As long as inflow and outflow are equal, the water level (frequency) stays stable. But if the flow changes? The level moves. And the bigger the tub (more inertia), the slower and smaller the change. ⚡️ As we transition to renewables (which often lack inherent inertia), maintaining frequency stability becomes even more challenging, and innovative solutions are needed to “artificially” replicate inertia in modern grids. 👉 What role do you see for battery storage, synthetic inertia, or demand response in solving this challenge? Let’s talk about the future of grid stability. #Energy #PowerSystems #GridFrequency #Inertia #Renewables #Electricity #SmartGrid #EnergyTransition #PowerQuality

Cyberattacks could exploit home solar panels to disrupt power grids - New Scientist The growth of domestic solar installations opens the possibility of hackers targeting their smart inverter devices as a way to cause widespread power-system failures Power grids around the world are increasingly under threat from cyberattacks because of the vulnerabilities of home solar installations. As distributed energy resources like rooftop solar become more prevalent, grids are increasingly reliant on smart inverters, which manage connections to local power networks. “While these technologies offer many benefits, they also introduce new operational and cybersecurity challenges,” says Sid Chau at CSIRO, an Australian government research agency. Smart inverters convert the direct current produced by solar panels into the alternating current needed to power appliances. They also optimise energy storage and enable remote monitoring via the internet. These web connections mean they pose a threat not just to home solar systems, but also to the wider power-generation network, Chau and his colleagues warn. The team identified multiple ways that smart inverters could be hacked, including exploitation of the security flaws in the physical hardware and software of smart inverters. Malicious actors could trick users into granting excessive permissions for apps connected to the inverter or work with manufacturers to embed malicious code into the hardware. Chau and his colleagues only modelled the threat from inverters in Australia, where around a third of homes have rooftop solar. But the situation is similar for power grids throughout parts of the world where private solar systems are becoming more common. While any attack would require careful orchestration and planning, the researchers found that, if vulnerabilities align, relatively few solar smart inverters would need to be hacked to cause disruption. Once the smart inverter has been compromised, hackers can then mount coordinated attacks on the broader power grid, according to the researchers. #cybersecurity #solarpanels #smartinverter #IoT #OT

🔌 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

Keeping the same impedance along a serial channel in a PCB is crucial to achieve good #signalintergity. I've published an animation of a trace with a stub in the middle that changes the impedance, and some people said that the discontinuity was electrically small for most signals and wouldn't affect SI (would affect only high frequency signals or the small 10ps rise time I used). So here I created an animation of a 6in microstrip only with a half an inch stub in the middle which change its width in #Ansys HFSS and SIwave. You can clearly see that the "electrically small" stub affects S-parameters (look at reflections around 1GHz!), TDR, near fields and especially an eye diagram of a real DDR4-2300MHz signal. Again, it's all about the impedance discontinuity, we don't need to have to have resonances to affect your signals and electromagnetic fields. So, whenever someone says that small details won't affect SI or #EMI for MHz range signals, be skeptical! Extract the frequency response of your channel, simulate, measure, and take your own conclusions :)

Signal Integrity Simplified: The One Concept That Unlocks High-Speed Design "It takes years to master high-speed PCB design." If you've heard this, you're not alone. This belief keeps countless engineers from pursuing advanced PCB design skills. But what if understanding ONE core concept could dramatically accelerate your path to high-speed design competence? The Transmission Line Revelation Early in my career, I avoided high-speed design. It seemed impossibly complex - filled with arcane formulas, specialized tools, and terminology I didn't understand. It was where the 'real' electrical engineers did 'black magic'. Then I had a breakthrough that changed everything: ALL signal integrity issues at their core relate to transmission line theory. Once I deeply understood how signals propagate along PCB traces as transmission lines, suddenly: - Impedance control made intuitive sense - Reflection problems became predictable - Cross-talk had clear solutions - EMI sources became obvious This single concept - viewing PCB traces as transmission lines rather than simple connections - unlocked an entire field that previously seemed impenetrable. From Concept to Competence in Weeks, Not Years Here's the step-by-step path I took to rapidly build signal integrity expertise: Master transmission line fundamentals (2 weeks) Learn to calculate and control impedance (1 week) Understand reflection mechanics and termination (1 week) Apply principles to real designs (4 weeks) Within just 8 weeks of focused learning, I was confidently handling 1Gbps+ designs that previously would have intimidated me. The Practical Application That Proves It Works Recently, one of my mentees (just 6 months into his hardware career) was tasked with designing a board with LPDDR4 memory - typically considered an advanced challenge. Rather than memorizing DDR4 design rules, he focused on understanding the transmission line characteristics of the signals. The result? His first DDR4 design passed simulation and validation on the first attempt - something his manager couldn't believe. When asked how long he'd been doing high-speed design, expecting to hear "years," his answer was simply: "About 6 weeks of focused study on the right things." Accelerate Your Own Mastery If you want to rapidly develop signal integrity expertise: Start with transmission line fundamentals - not just tools or checklists Use simple test boards to validate your understanding Focus on WHY rules exist, not just memorizing them Simplify complex problems by relating them back to basic principles You can develop professional-level signal integrity skills in MONTHS, not years - but only if you focus on the fundamental concepts that everything else builds upon. Question for hardware engineers: What's one "advanced" PCB design concept you've been avoiding because it seems too complex? #SignalIntegrity #PCBDesign #HighSpeedDesign #HardwareEngineering

For most of the last century, generators stabilised the grid as a by-product of producing energy. Today, we are building assets that stabilise the grid without producing energy at all. That shift identifies the binding constraint. Electricity system transition is no longer constrained by renewable resource availability. It is constrained by deliverability and operability. In inverter-dominated systems under rapid load growth, the binding constraints are: - transmission and major substation capacity - system strength, fault levels, frequency and voltage control - connection and commissioning throughput - secure operation under worst-day conditions - execution pace across networks and system services Generation capacity remains necessary. On its own, it no longer delivers firm supply or supports large new loads. Historically, synchronous generators supplied energy and stability together. Inertia, fault current, voltage support, and controllability were implicit. As synchronous plant retires, these services must be provided explicitly. Stability shifts from physics-led to control-led. System behaviour becomes more sensitive to modelling accuracy, protection coordination, control settings, and real-time visibility. Curtailment is not excess energy. It is a deliverability or security constraint. When transmission and substations lag generation, congestion and curtailment rise. Independent analysis shows that delay increases prices and emissions by extending reliance on higher-cost thermal generation. Distribution networks are no longer passive. They now host distributed generation, storage, EV charging, and large loads at the edge of transmission. Voltage control, protection coordination, hosting capacity, and connection throughput now constrain both decarbonisation and industrial growth. Firming is a hard requirement. Batteries provide fast frequency response and contingency arrest. They do not provide multi-day energy and do not replace networks or system strength in weak grids. Demand response reduces peaks. It cannot be relied upon for system-wide security under stress. Execution speed is critical. Slow delivery increases congestion duration, curtailment exposure, reserve requirements, and reliance on ageing plant. These effects flow directly into costs, emissions, and reliability. This is why electricity bills can rise even when average wholesale prices fall. Costs are driven by peak demand, contingencies, and security, not average energy. Large digital and industrial loads are transmission-scale, continuous, and failure-intolerant. They increase contingency size and correlation risk. At that scale, loads do not connect to the grid, they shape it. Supporting growth requires time-to-power, transmission and substation capacity in load corridors, explicit system strength and fault levels, operable firming under worst-day conditions, scalable connection and commissioning, and early procurement of long lead time HV equipment. #energy

Star-Delta (Y-Δ) Connection in Motors. is a common method used to start three-phase induction motors with reduced starting current. It is particularly useful for high-power motors where a direct start would cause excessive current draw and voltage drops in the power supply. 1. How Star-Delta Starting Works The motor is initially connected in Star (Y) configuration during startup and then switched to Delta (Δ) configuration** for normal operation. Steps in Star-Delta Starting: 1. Start in Star (Y) Mode - The motor windings are connected in a star configuration. - Voltage per phase= \( \frac{V_{line}}{\sqrt{3}} \) (e.g., 400V line → ~230V per phase). - Starting current is reduced to ~1/3 of direct-on-line (DOL) starting current. - Torque is also reduced to ~1/3 of full-load torque. 2. After a Delay (Few Seconds), Switch to Delta (Δ) Mode - The motor windings are reconfigured into a delta connection. -Full line voltage (400V) is applied across each winding. - The motor runs at full torque and speed . 2. Why Use Star-Delta Starting? ✔ Reduces starting current (helps avoid tripping circuit breakers). ✔ Minimizes voltage dips in the power supply. ✔ **Suitable for high-inertia loads(e.g., pumps, compressors, fans). ✖ Not ideal for heavy-load startups (since torque is reduced in star mode). ✖ Requires 6 motor terminals (not all motors support star-delta). 3. Wiring Diagram & Connection A star-delta starter uses: - 3 contactors (Main, Star, Delta) - A timer relay (to switch from Star to Delta) Connection Steps: 1. Star (Y) Connection: - Main + Star contactors close. - The motor windings are connected in star (one end of each winding is shorted). 2. Delta (Δ) Connection: - Star contactor opens, Delta contactor closes. - The windings are reconfigured in delta (end-to-end connection). 4. Limitations of Star-Delta Starter - Not suitable for high starting torque applications (e.g., crushers, conveyors). - Switching transient: A brief power interruption occurs during the transition. - Requires a motor with all 6 terminals accessible. 5. Alternatives to Star-Delta Starting - Soft Starter (Smooth voltage ramp-up). - Variable Frequency Drive (VFD) (Best for speed & torque control) . - Auto-transformer starter** (For very large motors) Conclusion Star-delta starting is a cost-effective way to reduce inrush current in three-phase motors, but it sacrifices starting torque. It is best suited for applications with **low starting load but high running power, such as pumps and fans.