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Glossary

Glossary: solar forecasting and power-market terms.

Plain definitions of the terms used in solar forecasting, plant operations and South-East European power markets, as we use them on this site.

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How the error is measurednMAE = Σ |forecast − actual| ÷ (hours × AC capacity)

Forecast accuracy

nMAE (normalised mean absolute error)
The average absolute difference between forecast and metered production, divided by a stated normaliser. DYNVOLT normalises by installed AC capacity and scores daytime hours only, so a 5.1% nMAE means the hourly forecast misses by 5.1% of the plant's capacity on average. How we measure it →
Normalisation basis
The denominator an error is divided by. The same forecasts give very different percentages against installed capacity, against mean production, or with night hours included, which is why a forecast error is meaningless without its basis.
Daytime filter
Scoring only the hours when the sun is more than 5° above the horizon. Night hours have zero output and zero error, so including them makes any forecast look better than it is.
P10, P50, P90
Quantiles of a probabilistic forecast. P50 is the central estimate; actual output should fall below P10 about 10% of the time and below P90 about 90% of the time, so a well-calibrated P10 to P90 band contains the actual about 80% of the time. Our measured band coverage →
Smart persistence
A baseline forecast that assumes tomorrow looks like today, adjusted for the sun's position. A forecasting model is only useful if it beats it.
Skill score
How much a forecast improves on a baseline, as 1 minus the ratio of their errors. A skill of 0 means no better than the baseline; positive values mean better.
Out-of-sample (walk-forward) evaluation
Scoring a model only on periods it was never trained or tuned on, with each month predicted by a model trained on earlier months. It is the honest way to test a model before it has a live record.
Issued-forecast record
Scores computed on the forecasts that were actually sent before the gate, not regenerated later. It is the evidence that cannot be tuned after the fact. Our live record →

Markets

Day-ahead market
The auction where electricity for each hour or quarter-hour of tomorrow is bought and sold, cleared once per day after the gate closes.
Gate closure
The deadline for submitting day-ahead orders. On MEMO (North Macedonia) it is 10:00 local time; the SDAC-coupled markets such as HUPX, SEEPEX, OPCOM, IBEX, HEnEx and Germany close at 12:00 CET.
Nomination
The schedule of energy a producer commits to deliver for each period. Deviations from it settle as imbalance.
Imbalance settlement
The charge or payment for the difference between nominated and delivered energy, priced by the transmission system operator after the fact.
BRP (balance responsible party)
The market participant financially responsible for a portfolio's imbalances. A plant owner can be its own BRP or use one; DYNVOLT prepares the plan and the BRP submits it.
Intraday market
Trading after the day-ahead auction and up to shortly before delivery, through intraday auctions or continuous trading, used to correct positions as forecasts improve.
MEMO
The Macedonian electricity market operator, which runs the day-ahead market for North Macedonia.

Plant operations

SCADA
Supervisory control and data acquisition: the layer that polls inverters, loggers and meters, shows what the plant is doing, raises alarms and writes set-points. DYNVOLT SCADA →
EMS (energy management system)
The decision layer above plant control. It uses production and price forecasts to plan nominations, curtailment and battery dispatch. DYNVOLT EMS →
PPC (power plant controller)
The controller that keeps the plant within grid-code limits at the point of connection, on a timescale of milliseconds to seconds.
Edge node
A computer on site that polls the plant, stores data locally and enforces limits without depending on the internet.
Peer-relative string detection
Comparing each string with strings facing the same way, so weather affects both sides equally. DYNVOLT flags a string that stays below 70% of its peers across several days. Fault detection →
I-V curve
A sweep of a string's current against voltage. Its shape reveals shading, soiling, damaged cells and connection faults.
Curtailment
Deliberately limiting a plant's output, for example when prices are negative or the grid operator asks. DYNVOLT clamps every limit to the plant's export permit.
Export permit
The maximum power a plant is allowed to feed into the grid at its connection point.

Batteries

State of charge (SOC)
How full a battery is, as a share of usable capacity.
Warranty envelope
The limits a battery manufacturer requires to keep the warranty valid: state-of-charge range, cycles per day, power and temperature. DYNVOLT treats them as hard constraints in dispatch. BESS optimization →
Arbitrage
Charging when power is cheap and discharging when it is expensive.
aFRR and FCR
Balancing reserves a battery can be paid to hold available: automatic frequency restoration reserve and frequency containment reserve.

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