Hi,
I am working on a Simulink model of a generator excitation system in 2025a that includes an IEEE AC11C-type exciter and a UEL2C (Under-Excitation Limiter) block. The complete model runs correctly and produces stable field voltage (Efd) when tested in MATLAB/Simulink R2025a, but the same exact model and parameters, when converted and run in MATLAB/Simulink R2017b, produces a persistent low‑frequency oscillation (~2–3Hz) in the exciter output (Efd), reactive power (Qt), real power (Pt), and various internal UEL2C signals.
The oscillation appears only when the UEL2C output is connected to the AC11C exciter.
If I bypass UEL2C and feed AC11C with a constant input, the oscillation disappears completely in 2017b.
Opening the same 2017b model file in 2025a makes the oscillation disappear again ─ system becomes stable.Hi,
I am working on a Simulink model of a generator excitation system in 2025a that includes an IEEE AC11C-type exciter and a UEL2C (Under-Excitation Limiter) block. The complete model runs correctly and produces stable field voltage (Efd) when tested in MATLAB/Simulink R2025a, but the same exact model and parameters, when converted and run in MATLAB/Simulink R2017b, produces a persistent low‑frequency oscillation (~2–3Hz) in the exciter output (Efd), reactive power (Qt), real power (Pt), and various internal UEL2C signals.
The oscillation appears only when the UEL2C output is connected to the AC11C exciter.
If I bypass UEL2C and feed AC11C with a constant input, the oscillation disappears completely in 2017b.
Opening the same 2017b model file in 2025a makes the oscillation disappear again ─ system becomes stable. Hi,
I am working on a Simulink model of a generator excitation system in 2025a that includes an IEEE AC11C-type exciter and a UEL2C (Under-Excitation Limiter) block. The complete model runs correctly and produces stable field voltage (Efd) when tested in MATLAB/Simulink R2025a, but the same exact model and parameters, when converted and run in MATLAB/Simulink R2017b, produces a persistent low‑frequency oscillation (~2–3Hz) in the exciter output (Efd), reactive power (Qt), real power (Pt), and various internal UEL2C signals.
The oscillation appears only when the UEL2C output is connected to the AC11C exciter.
If I bypass UEL2C and feed AC11C with a constant input, the oscillation disappears completely in 2017b.
Opening the same 2017b model file in 2025a makes the oscillation disappear again ─ system becomes stable. simulink model conversion 2017b, simulink model conversion, 2025a, 2017b MATLAB Answers — New Questions

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