BESS CONTROL LOOP ARCHITECTURE

Cascaded PI control structure — EMS grid code + plant level

Interactive reference diagram for Battery Energy Storage System power plant controllers. Showing the full signal chain from frequency measurement through droop response, PI control, rate/power limiting, and dispatch to PCS units. Click any block for tuning details and Fingrid SJV2024 requirements.

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BESS CONTROL ARCHITECTURE — EMS + PLANT LEVELFrequency response → PI controller → rate/power limiting → dispatch → PCS · Click blocks for detailsFINGRID RESERVE PRODUCTS:FCR-N (Normal)49.9–50.1 Hz · ~3 minFCR-D (Disturbance)< 49.9 Hz · 5s/30sFFR (Fast Frequency)< 49.5 Hz · 0.7–1.3sP_base(market / SCADA)EMS / GRID CODE PATH← signal flowFREQ METERf_meas at POIPLL / zero-crossDEADBAND±10 mHzconfigurableGCC Grid Code ControllerDROOP / P(f)ΔP = −(Pn/R)·Δf/fnR = 2–12% · FCR-N/D/FFRΔPΣP_refLFSM-O> 50.5 Hz · droop 4% · mandatoryΔPΣ+−errorPI ControllerKp·e + Ki·∫e dtanti-windupPPC Plant Power ControllerLimiterRate Power clampsHybrid limitsP_cmdPower Dispatchsplit to N unitsSOC balancingunit availabilityQ CONTROLcos φ · Q(U) · Q setpoint · see details ↓P₁P₂PₙPCS #1inner PIPCS #2inner PIPCS #Ninner PIPOIGRIDPOWER METERP_meas (10s avg) · CT/VT at POIP_measured feedbackFor a 9 MW Type B BESS: LFSM-O is mandatory. FCR-N, FCR-D, FFR participation requires prequalification tests.Frequency measurement is local (no Fingrid activation signal). Each product has its own droop/deadband settings.━━ signal flow╍╍ feedback / routingΣ summing junction▸ click blocks for info┈┈ GCC boundary┈┈ PPC boundaryEMS100ms–3minPPC100–500ms
Click any control block in the diagram above to see details, tuning parameters, and Fingrid requirements

REACTIVE POWER CONTROL REQUIREMENTS

Fingrid SJV2024 — Type B (0.1–10 MW) and Type C (10–75 MW)

Reactive power capability and voltage control requirements for BESS connected to the Finnish grid. The PQ envelope, control modes, and response requirements differ significantly between Type B and Type C. Click any block in the diagram below for details.

REACTIVE POWER REQUIREMENTS — TYPE B vs TYPE CPQ capability envelopes · Q control modes · voltage range · Fingrid SJV2024 · Click blocks for detailsTYPE B (0.1–10 MW)Q/PmaxP/Pmax00.51.0+0.33−0.33cos φ = 0.95 capcos φ = 0.95 indTYPE C (10–75 MW)Q/PmaxP/Pmax00.20.51.0+0.33−0.33Q = +0.33 PmaxQ = −0.33 Pmax~0.2 PminQ CONTROL MODESFIXED cos φType B: primary · Type C: availableFIXED Q SETPOINTType C: remote SCADA dispatchQ(U) VOLTAGE DROOPType C: mandatory · Type B: optionalQ(P) MODEType C: available · power-dependent QVOLTAGE RANGE & RESPONSESTEADY-STATE VOLTAGE RANGE0.90–1.10 p.u. · both typesQ STEP RESPONSEType C: ≤ 1s · Type B: not specifiedREMOTE Q DISPATCH (SCADA)Type C: mandatory · Type B: not requiredType B: PQ envelope is triangular (cos φ ≥ 0.95). Q narrows linearly as P → 0. Fixed cos φ is the primary operating mode.Type C: PQ envelope is rectangular (±0.33 Pmax above ~0.2 Pmax). Q(U) droop is mandatory. Remote SCADA Q dispatch required.EH-0430 PCS supports cos φ down to 0.8 (over/under-excited) — exceeds both Type B and Type C reactive capability requirements.━━ PQ boundary╋╋ Pmax edge■ Type B (cos φ ≥ 0.95)■ Type C (±0.33 rectangular)▸ click blocks for infocap = capacitive · ind = inductive
Click any control mode or requirement block in the reactive power diagram above to see details

REACTIVE POWER REQUIREMENTS — TYPE B vs TYPE C COMPARISON

RequirementType B (0.1–10 MW)Type C (10–75 MW)
Q range at Pmax±0.33 Pmax (cos φ ≥ 0.95)±0.33 Pmax (rectangular envelope)
PQ envelope shapeTriangular — Q narrows to 0 as P → 0Rectangular — full Q from ~0.2 Pmax upward
Q control modesFixed cos φ (primary)Fixed cos φ, Q setpoint, Q(U), Q(P)
Q(U) voltage droopOptional (DSO may request)Mandatory — droop 2–5%, configurable
Remote Q dispatchNot requiredMandatory via SCADA / EMS
Q step responseNot specified≤ 1 s to 90% of new setpoint
Voltage range0.90–1.10 p.u. at POC0.90–1.10 p.u. at POC
FRT Q priorityNot mandatoryIq priority during fault (k-factor)
Grid-forming QOptionalRequired for voltage source behaviour
BESS Control Loop Reference · Fingrid SJV2024 Type B (0.1–10 MW) & Type C (10–75 MW) · Active & Reactive Power Control