Remote industrial sites face a fundamental power challenge that grid-connected facilities never encounter: maintaining stable voltage and frequency without the massive inertia of a centralised grid. When a mine site switches from diesel-only to hybrid renewable power, the inverter technology chosen determines whether the system delivers rock-solid reliability or constant voltage fluctuations that damage equipment and halt operations.
The difference between grid-forming and grid-following inverters isn’t just technical specification – it’s the distinction between a power system that behaves like utility-grade infrastructure and one that requires constant diesel generator backup to maintain stability. For operations in the Pilbara, Kimberley, and Goldfields regions where grid connection isn’t an option, this choice directly impacts diesel consumption, maintenance costs, and operational uptime.
Understanding Grid-Following Inverter Limitations
Grid-following inverters – also called grid-tied inverters – were designed for a specific purpose: feeding solar power into an existing strong grid. These systems act as current sources, synchronising to the voltage and frequency already established by the grid. In metropolitan Perth or Adelaide where massive synchronous generators maintain grid stability, grid-following inverters perform adequately because they’re following something inherently stable.
The problem emerges in remote locations where diesel generators create the “grid.” A 500 kW diesel genset lacks the massive rotating inertia of a utility-scale power station. When cloud cover reduces solar output by 300 kW in 15 seconds, grid-following inverters simply reduce their output accordingly. The diesel generator must instantly ramp up to fill the gap – causing voltage sags, frequency deviations, and mechanical stress on the generator.
This limitation explains why many early solar-diesel hybrid installations achieved disappointing diesel offset results. The solar system could only contribute power when conditions were perfect and load was stable. Any transient event – a motor starting, cloud transient, or load step change – forced the diesel generator to carry the full load until stability returned.
Grid-following technology fundamentally cannot provide the voltage and frequency reference that utility-grade stand-alone power systems require. These inverters need something else to follow, which means diesel generators must remain online and synchronised even when solar production exceeds site demand. The result: diesel continues running, fuel savings plateau at 30-40%, and the business case for renewable integration weakens.
How Grid-Forming Inverter Technology Changes Remote Power
Grid-forming inverter technology operates on an entirely different principle. Rather than following an existing voltage and frequency reference, grid-forming inverters establish the reference themselves. These systems function as voltage sources, creating stable 50 Hz AC power with regulated voltage regardless of what other generation sources are doing.
This capability transforms what’s possible in remote power systems. A properly designed grid-forming inverter can maintain stable voltage and frequency while:
- Diesel generators start and synchronise to the system
- Large induction motors draw starting currents
- Cloud transients cause rapid solar production changes
- Battery storage systems charge or discharge at high rates
- Load steps occur as equipment cycles on and off
The technical distinction lies in the control algorithms. Grid-following inverters use Phase-Locked Loop (PLL) technology to detect and match the existing grid frequency. Grid-forming inverters use voltage and frequency droop control, similar to synchronous generators, allowing multiple power sources to share load naturally without complex communication protocols.
For mine sites and industrial facilities, this means the solar and battery system can operate as the primary power source, with diesel generators serving as backup rather than baseload. When solar production exceeds demand and batteries are fully charged, diesel generators can shut down completely – something impossible with grid-following technology.
The Modulus Battery Energy Storage System Architecture
CDI Energy‘s Modulus system represents a specific implementation of grid-forming inverter technology designed for utility-grade stand-alone power systems in the harsh conditions and demanding applications of Australian remote sites. Rather than adapting residential or light commercial equipment for industrial use, the Modulus architecture was engineered specifically for mine sites, pastoral stations, and remote industrial facilities where utility-grade reliability isn’t optional.
The system uses bi-directional battery inverters rated from 125 kVA to 500 kVA per unit, configured to provide genuine grid-forming capability. Unlike systems that claim “grid-forming” capability but require diesel generators to remain synchronised, the Modulus system can establish and maintain stable three-phase power independently.
Battery capacity scales from 250 kWh to multi-MWh configurations, with lithium iron phosphate (LFP) chemistry selected for thermal stability in ambient temperatures exceeding 45°C. The battery management system monitors individual cell voltages, temperatures, and state-of-charge with millisecond-level precision, ensuring safe operation across the full depth-of-discharge range.
Integration with CDI Energy’s Rapid Solar Module creates a complete microgrid where solar generation, battery storage, and diesel backup operate as a coordinated system. The control architecture allows seamless transitions between operating modes without voltage transients or frequency deviations that would trip protection relays or damage sensitive electronic equipment.
Practical Performance: Voltage and Frequency Regulation
The performance difference between grid-forming and grid-following systems becomes measurable in voltage regulation and frequency stability metrics. Australian Standard AS 61000.3.100 specifies voltage variation limits for low voltage installations: ±10% for normal operation, with frequency maintained within ±0.5 Hz of nominal.
Grid-following systems in remote applications struggle to meet these standards during transient events. When a 100 kW load suddenly disconnects, grid-following inverters cannot instantly adjust their output because they’re synchronising to a diesel generator that’s also responding to the load change. The result: frequency spikes to 51-52 Hz for several seconds until governor controls stabilise the diesel, then voltage overshoots as the automatic voltage regulator compensates.
Grid-forming inverter technology in the Modulus system responds to the same transient in under 50 milliseconds. The battery inverters instantly absorb or supply power to maintain voltage and frequency regulation within ±0.2 Hz and voltage within ±2%. Diesel generators, if running, don’t experience sudden load changes because the battery system buffers all transients.
This performance level matters for operations running variable frequency drives (VFDs), programmable logic controllers (PLCs), and other equipment sensitive to power quality. A gold processing plant in the Goldfields region running flotation cells and grinding mills cannot tolerate voltage sags that cause VFD faults and production interruptions. The grid-forming capability of properly designed hybrid energy systems ensures power quality matches or exceeds what utility grids provide.
Diesel Generator Interaction and Load Sharing
One of the most significant advantages of grid-forming inverters appears in how they interact with diesel generators. In grid-following systems, diesel generators must remain synchronised and carrying minimum load (typically 30-40% of rated capacity) to maintain grid stability. This requirement limits diesel offset and forces generators to run inefficiently.
Grid-forming systems reverse this relationship. The battery inverters establish voltage and frequency, allowing diesel generators to start, synchronise, and load up only when needed. When solar production drops or battery state-of-charge reaches minimum thresholds, diesel generators can synchronise to the existing stable grid created by the battery system.
Load sharing between battery inverters and diesel generators occurs naturally through frequency droop characteristics. As load increases, frequency drops slightly (within regulation limits), causing diesel generators to increase output proportionally. This mimics how synchronous generators share load in utility grids, requiring no complex communication protocols or master controllers that create single points of failure.
The practical result: diesel generators can shut down completely during periods of high solar production and adequate battery charge. A mine site in the Pilbara running the Modulus system with 1 MW of solar PV and 2 MWh of battery storage achieves 80-85% diesel offset – nearly double what grid-following systems deliver in the same application.
Blackstart Capability and System Resilience
Blackstart capability – the ability to restore power after a complete system shutdown without external power sources – represents a critical requirement for remote industrial sites. When a fault condition or emergency shutdown de-energises the entire site, operators need to restore power quickly and safely.
Grid-following inverters cannot perform blackstart because they require an existing voltage and frequency reference to synchronise. This means diesel generators must always start first, establish stable power, then wait for solar inverters to detect the grid and begin contributing. The process takes 5-10 minutes and requires manual intervention if automatic sequences fail.
The Modulus system’s grid-forming architecture enables true blackstart from battery storage alone. After a site-wide shutdown, the battery inverters can energise the electrical system, establish stable voltage and frequency, and begin powering critical loads within 30 seconds. Solar inverters then synchronise to the stable grid created by the batteries, and diesel generators start only if battery capacity or solar production proves insufficient for the load.
This capability proved essential for a remote telecommunications facility in the Kimberley region. When lightning strikes caused grid protection to trip, the Modulus system automatically restored power to critical communications equipment before diesel generators completed their start sequence. The 45-second power restoration prevented loss of telecommunications services across a 200 km radius.
Integration with Renewable Energy Sources
While battery energy storage provides the grid-forming capability, integration with solar PV determines overall system efficiency and diesel offset performance. The control system must coordinate solar production, battery charging/discharging, diesel generator operation, and load demand without creating instabilities or inefficiencies.
CDI Energy’s approach integrates the Rapid Solar Module ground-mount arrays with the Modulus battery system through a coordinated control architecture. Solar inverters operate in grid-following mode, synchronising to the stable voltage and frequency established by the battery system. This configuration allows solar to contribute maximum available power while the battery system handles all transient events and frequency regulation.
The control system implements several operating modes based on solar production, battery state-of-charge, and load demand:
- Solar-Battery Mode: During daytime with adequate solar production, batteries maintain grid voltage and frequency while solar provides load power and charges batteries. Diesel generators remain offline.
- Battery-Only Mode: During evening and night hours, batteries supply all load power while maintaining stable grid conditions. Diesel generators start only if battery state-of-charge reaches minimum thresholds.
- Hybrid Mode: When load exceeds solar production and battery discharge limits, diesel generators synchronise to the battery-established grid and share load proportionally.
- Generator-Priority Mode: During extended low-solar periods or high-load events, diesel generators carry baseload while batteries provide peak shaving and power quality support.
These modes transition automatically based on system conditions, requiring no operator intervention. The result: maximum diesel offset while maintaining utility-grade power quality and system reliability.
Modular Scalability for Growing Operations
Remote industrial operations rarely remain static. Mine sites expand production, processing facilities add equipment, and pastoral stations increase pumping capacity as operations grow. Power systems must scale accordingly without requiring complete replacement of existing infrastructure.
The Modulus system architecture supports modular expansion in both battery capacity and inverter power rating. A site initially installed with 500 kWh of storage and 250 kW of battery inverter capacity can add additional battery modules and inverter units as load grows. The grid-forming control system automatically incorporates new units into the coordinated system without reprogramming or reconfiguration.
This scalability contrasts sharply with grid-following systems where adding capacity often requires upgrading the diesel generators to provide adequate grid strength for the larger inverter capacity. The capital cost and installation complexity of replacing generators makes expansion prohibitively expensive for many operations.
A gold mine in the Eastern Goldfields demonstrates this advantage. The site initially installed a 1 MW solar array with 1 MWh Modulus battery system in 2019. As ore processing expanded in 2022, the operation added another 500 kWh of battery capacity and 500 kW of solar without modifying existing equipment. The grid-forming architecture seamlessly integrated the new capacity, increasing diesel offset from 65% to 78% while maintaining the same power quality metrics.
Cost-Benefit Analysis: Grid-Forming vs Grid-Following Systems
The capital cost premium for grid-forming inverter technology typically adds 15-20% to battery system costs compared to grid-following alternatives. For a 1 MWh system, this represents approximately AUD 150,000-200,000 additional upfront investment. The question becomes whether improved diesel offset and operational benefits justify this premium.
Analysis of installations across Western Australian remote sites shows grid-forming systems achieve 75-85% diesel offset compared to 30-45% for grid-following systems in similar applications. For a mine site consuming 2,000 litres of diesel per day at AUD 1.80 per litre, the difference amounts to AUD 1,100-1,400 per day in fuel savings – over AUD 400,000 annually.
Additional operational benefits compound these savings:
- Reduced generator maintenance: Running diesel generators 50-60% less operating hours extends service intervals and reduces maintenance costs by AUD 80,000-120,000 annually for typical mine site installations.
- Improved power quality: Fewer voltage transients and frequency deviations reduce VFD faults, PLC errors, and equipment damage, saving AUD 30,000-50,000 annually in avoided downtime and repairs.
- Extended generator lifespan: Operating diesel generators primarily as backup rather than baseload extends overhaul intervals from 15,000 hours to 25,000+ hours, deferring capital replacement costs.
When these factors combine, the payback period for the grid-forming technology premium typically falls between 4-8 months – a compelling return that explains why sophisticated remote operations increasingly specify grid-forming capability as a mandatory requirement.
Maintenance and Operational Considerations
Grid-forming inverter systems require different maintenance approaches compared to grid-following alternatives. The increased complexity of voltage and frequency control algorithms demands more sophisticated monitoring and diagnostics, but properly designed systems translate this complexity into improved reliability rather than increased maintenance burden.
The Modulus system implements remote monitoring that tracks voltage regulation performance, frequency stability, battery state-of-health, and inverter operating parameters in real-time. Algorithms detect degrading performance before failures occur, triggering maintenance alerts when parameters drift outside normal ranges.
Typical maintenance requirements include:
- Quarterly inspections: Visual inspection of battery modules, inverter cabinets, cooling systems, and electrical connections. Thermal imaging identifies developing hot spots before they cause failures.
- Annual testing: Verification of voltage regulation accuracy, frequency response characteristics, and protection relay coordination. Battery capacity testing confirms state-of-health meets specifications.
- Firmware updates: Control algorithm improvements and feature additions deployed remotely without site visits or system downtime.
For remote sites where maintenance access is limited and technician availability constrained, this predictive maintenance approach proves far more practical than reactive maintenance triggered by failures. A pastoral station 400 km from the nearest service centre cannot afford unplanned downtime waiting for technicians and parts.
Conclusion
The evolution from grid-following to grid-forming inverter technology represents more than incremental improvement – it’s a fundamental shift in what’s possible for remote industrial power systems. Sites that previously achieved 30-40% diesel offset with solar-only systems now reach 75-85% with properly designed battery storage using grid-forming inverters.
This performance difference directly impacts operating costs, environmental footprint, and system reliability. For mine sites, pastoral stations, and remote industrial facilities where diesel fuel costs AUD 1.50-2.00 per litre delivered, the economic case for grid-forming technology delivers payback periods measured in months rather than years.
Beyond economics, grid-forming capability enables true energy independence. Sites can operate indefinitely on solar and battery power alone, with diesel generators serving as backup rather than baseload generation. This operational flexibility proves essential for operations targeting net-zero emissions, reducing carbon footprint, or simply insulating themselves from diesel price volatility and supply disruptions.
The Modulus battery energy storage system demonstrates how grid-forming technology translates utility-grade stand-alone power systems into practical, reliable remote power solutions. By establishing stable voltage and frequency independent of diesel generators, the system delivers utility-grade power quality while maximising renewable energy contribution and minimising fossil fuel consumption.
For operations evaluating renewable energy integration, the choice between grid-following and grid-forming inverters determines whether the system delivers incremental improvement or transformational change. As remote industrial sites increasingly demand higher diesel offset, improved reliability, and genuine energy independence, grid-forming technology shifts from optional enhancement to essential requirement.
Remote operations considering hybrid power systems should get in touch with CDI Energy for site-specific feasibility analysis. Every site presents unique load profiles, solar resources, and operational requirements that influence optimal system configuration. Professional assessment ensures the selected technology delivers maximum diesel offset while maintaining the power quality and reliability that remote industrial operations demand.