Stability is an important part of ensuring operability of power generation systems. Large transients can cause power systems to become unstable and can eventually lead to blackouts. Power systems need to be designed to withstand large disturbances and maintain stability under changing operating conditions. Devices such as the generator automatic voltage regulator (AVR) and power system stabilizer (PSS) are widely used to manage these system instabilities. These control devices can be attached to power generation systems to help improve stability.
The PSS works together with the AVR to maintain transient stability within a power system. The generator’s output is primarily controlled by the AVR, but this system alone is not fast enough to respond to sudden glitches or faults. A PSS is added to the feedback to dampen rotor angle swings within a broad range of frequencies.
PSS performance is often evaluated based on its local mode damping. A properly tuned and well-performing PSS should provide sufficient damping to local mode oscillations. Frequency analysis can be used to determine the optimum PSS settings based on system characteristics. The PSS should be tuned to provide toque changes in phase with speed changes. Dynamic signal analyzers are commonly used to test the performance of AVR and PSS controls. The frequency response of the system under load can be used to tune the PSS. After tuning the PSS, the frequency response of the PSS can be measured and compared with expected models before being added to the power system.
The CoCo-80X now offers Power System Stabilizer as a new type of signal analysis. The CoCo-80X can help determine the phase-frequency characteristics of the power generation and excitation control systems. The CoCo-80X supplies an output signal to excite the PSS device, while simultaneously measuring the FRF across the PSS. The signal analyzer acquires data across a narrow frequency range to provide local mode stability results. PSS analysis results are provided in a tabularized format for the specified frequency range.