This simulator models a static excitation system — the field-control loop that feeds a synchronous generator's rotor through slip rings and shapes both terminal voltage and reactive power exchange. Switch between island and grid operation, compare AVR voltage control against grid var control, tune regulator gain and field time constant, and see how limiters and protection respond to faults.
• A 3D cutaway of the static excitation system, including the stator enclosure, with camera views for the full machine and an auto-rotate option, plus a labeled component legend describing each part's function. • A network mode selector for island (constant-impedance load) versus grid (infinite bus) operation, and an excitation control selector for AVR voltage control with grid Q droop, dedicated var control on the grid, or manual field demand. • Time controls to run, step (100 ms, 1 s, 10 s) the simulation, open the breaker, initialize the connection, and reset a trip. • Trend charts of terminal voltage, field current and exciter drive in per-unit, and of real (MW) and reactive (MVAr) power exported. • A voltage phasor diagram (E = V + jXsI, resistance neglected) and an illustrative P–Q operating-point capability chart. • Model equations and measurements on a 5 MVA, 6.6 kV, 50 Hz base, including the field time-constant relationship dIf/dt = (drive − If)/τ. • Guided experiments, a diagnostic challenge question about grid voltage stiffness versus excitation, a model verification bench, and OEL/UEL limiter and protection-envelope testing with field-supply or voltage-sensing failure injection.
A static exciter rectifies and regulates a supply to feed DC field current into the rotor winding through slip rings and brushes. That field current sets the internal EMF, E, and the automatic voltage regulator continuously adjusts it to hold terminal voltage at a reference, subject to a field time constant τ that governs how quickly field current can follow a change in exciter drive (dIf/dt = (drive − If)/τ).
On an island, with no stiff external voltage source, raising or lowering excitation directly moves terminal voltage, and the load — modeled as constant impedance at a given power factor — draws real and reactive power that both vary with voltage squared. On a strong grid, the bus itself fixes terminal voltage, so the AVR's error term becomes Vref − V − droop × Q: raising excitation mostly changes reactive power exchange rather than terminal voltage, which is the basis for the simulator's built-in diagnostic challenge question. A separate var-control mode instead regulates directly to a reactive-power setpoint, Qref − Q, useful when a plant is dispatched on vars rather than voltage.
The excitation system includes overexcitation and underexcitation limiter (OEL/UEL) behavior and stator-current constraints applied as instantaneous teaching limits on drive demand — they also act in manual mode. The underexcitation limit uses a fixed minimum reactive power rather than a machine-specific curve, and a generic protection envelope monitor (roughly 250 ms) can trip the unit, rather than device-specific 40 (loss of field), 24 (volts/hertz) or 59 (overvoltage) relay coordination.
This is a representative static exciter: switching ripple, rectifier harmonics, brush wear and detailed power-electronics behavior are not calculated, frequency is fixed and electrical states are quasi-steady. No saturation curve, magnetic transients, turbine/governor dynamics, power system stabilizer, synchronizing transient, or full generator capability curve is represented — initializing the grid connection sets up an algebraic match rather than modeling an actual synchronizing sequence.
A static exciter rectifies and regulates a supply, then feeds DC field current to the generator's rotor winding through slip rings and brushes. The automatic voltage regulator adjusts this field current continuously to control the generator's internal EMF and, through it, terminal voltage or reactive power output.
On a stiff infinite bus, terminal voltage is fixed by the grid itself, not by the generator alone. Increasing field current raises the generator's internal EMF relative to that fixed terminal voltage, and the resulting phasor difference is absorbed almost entirely as reactive power (MVAr) exchange rather than a change in terminal voltage.
AVR mode regulates the error between a voltage reference and measured terminal voltage (with an optional reactive-power droop term on the grid), directly controlling voltage. Var control mode instead regulates the error between a reactive-power reference and measured Q, useful when the plant is dispatched on a reactive-power setpoint rather than a voltage target.
The overexcitation limiter (OEL) and underexcitation limiter (UEL) cap the field-current demand at its high and low ends as instantaneous teaching limits, including in manual mode. The underexcitation limit here uses a fixed minimum reactive-power value rather than a manufacturer-specific curve, and a generic protection envelope can disconnect the unit if it operates outside acceptable bounds.