A technical report from ENTSO-E on instability detection technologies in power-electronics-dominated systems points to dynamic stability challenges in grids where synchronous inertia is not guaranteed. The document links the issue to the region’s evolving generation mix, market coupling structure, and operational stress patterns. It frames the topic as a shift from debates centered on capacity, prices, and balancing volumes toward faster grid behaviour. For South-East Europe (SEE), the report presents the risk as already embedded in current system conditions.
ENSTO-E’s analysis describes a transition across European power systems from synchronous-machine-dominated networks to converter-dominated operation. In that setting, wind, solar, HVDC interconnections, and power-electronic loads increasingly influence grid behaviour. The report says this transition brings instability types that develop quickly and are more difficult to manage using traditional SCADA-based tools. It also connects the SEE implications to three factors: inverter-based resource deployment, cross-border coupling, and uneven grid-monitoring capability.
SEE generation mix and cross-border coupling exposure
South-East Europe has historically depended on large synchronous assets to provide inertia and damping. The report cites lignite plants, hydro cascades, and nuclear generation in Bulgaria and Romania. It notes that when inertia was abundant, the system could absorb forecast errors, cross-border shocks, and local disturbances with slower operator intervention. That operating condition is described as eroding.
The report highlights rising wind and solar penetration across Romania, Bulgaria, Greece, and the Western Balkans. It also points to HVDC links and phase-shifting transformers increasingly shaping flows at regional borders. In parallel, market coupling is described as enabling faster propagation of disturbances across borders than in earlier arrangements. ENTSO-E states that converter-driven instabilities can appear in milliseconds, faster than traditional frequency control or manual response.
Because of this speed, the report says system strength is no longer only a national characteristic. It describes scenarios where a disturbance initiated in one control area—through inverter interactions, resonance, or fast frequency deviation—can propagate region-wide before neighbouring TSOs react. The document links this propagation risk to whether early-warning detection is available across the interconnected system.
Instability mechanisms highlighted for converter-dominated operation
ENSTO-E identifies low-inertia frequency instability as one mechanism relevant to SEE. The report states that as synchronous generation declines, frequency deviations accelerate after imbalances occur. In a tightly coupled SEE market, it says a sudden loss of wind or an HVDC flow can produce frequency excursions that spread across multiple control zones before primary reserves fully respond.
The report also highlights converter-driven oscillations and resonance. It says inverter-based resources can interact through grid impedance in ways that are difficult to model in advance. It adds that such oscillations may not be visible in standard frequency or voltage magnitudes but can grow until protective relays trip. ENTSO-E notes that the risk is elevated where newer inverter-based assets are connected alongside older infrastructure not designed for these interactions.
A third mechanism described is control interaction across borders. As more assets rely on fast digital control, ENTSO-E says poorly coordinated settings across TSOs can amplify disturbances unintentionally. The report characterizes instability as increasingly a system-of-systems issue rather than a purely local fault.
Limitations of SCADA monitoring and need for high-resolution detection
The report states that conventional SCADA systems are too slow and too coarse for detecting new instability precursors. It specifies that sampling intervals measured in seconds are insufficient when destabilising modes develop over tens of milliseconds. ENTSO-E therefore emphasises measurement-based high-resolution detection approaches rather than relying on slower telemetry alone.
Key technologies highlighted include Phasor Measurement Units (PMUs), waveform-level monitoring, and wide-area monitoring systems. The report says these tools enable observation of phase angles, oscillation modes, harmonic content, and fast frequency dynamics in real time. For SEE, it identifies a monitoring gap tied to density of instrumentation, PMU deployment levels, and real-time data analytics capability across the region.
ENSTO-E describes monitoring unevenness as material for SEE as inverter penetration rises. Some parts of the region are described as well instrumented while others rely heavily on legacy visibility. The report characterizes this unevenness as a regional vulnerability rather than only a national limitation.
Market impacts tied to stability constraints
The implications described by ENTSO-E extend beyond grid engineering into power market outcomes. First, it says balancing and reserve activation will increasingly be driven by stability constraints rather than only energy balance requirements. It adds that TSOs may intervene earlier and more conservatively when instability risk is poorly observed, increasing balancing costs and redispatch volumes.
Second, the report links instability risk to cross-border capacity availability becoming more conditional. If instability risk cannot be monitored and mitigated with confidence, TSOs are described as reducing available transfer capacity to preserve security. ENTSO-E says this affects price convergence, congestion rents, and market efficiency across SEE.
Third, flexibility resources are described as gaining additional strategic value under these conditions. ENTSO-E cites fast frequency response capabilities, grid-forming inverters, synchronous condensers, and advanced hydro controls as stability assets as well as balancing tools. It states that markets failing to recognize and remunerate this value could face under-investment alongside higher systemic risk.
Early warning requirements for deeper regional integration
The report positions SEE as a condensed representation of Europe’s future grid challenge. It combines fast renewable growth with legacy thermal dependence, limited investment headroom, and intense cross-border interdependence. ENTSO-E describes regions like SEE as proving grounds for managing the transition toward power-electronics-dominated systems without sacrificing reliability.
It also emphasizes early detection rather than post-event correction as particularly relevant for SEE conditions. The report states that where balancing depth is limited and political tolerance for outages is low, late intervention carries higher costs. Early detection technologies are described as enabling TSOs to act surgically instead of relying on blanket curtailment, emergency imports, or market suspensions.
For policymakers and TSOs in South-East Europe, ENTSO-E frames grid stability as both a data-and-detection problem and a capacity problem. It lists investment priorities extending beyond generation and interconnection to include dense synchronized measurement across borders; real-time analytics capable of detecting sub-second instability modes; common regional standards for data sharing and early warning; and operational procedures integrating detection outputs into control and market decisions.
The report concludes its discussion by stating that without these layers SEE could enter a regime where markets appear liquid and well coupled while system security depends on conservative constraints alongside rising hidden costs. It characterizes advanced instability detection as necessary infrastructure for deeper market integration, higher renewable penetration, and credible security of supply under power-electronics-dominated conditions.