Generator Rotor Angle Control for Low-Frequency Oscillation Damping
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Solution Overview
Problem
Existing power system control technologies, such as PSS, are ineffective in damping inter-area low-frequency oscillations between generators due to insufficient use of wide-area information and signal delay issues, leading to fluctuations in power transmission.
Innovation Solution
A method and system that measure the absolute rotor angle of power generators using GPS reference vectors and control the rotor speed to align with a target angle upon each GPS PPS signal arrival, utilizing PID controllers for mechanical power output, energy storage, and excitation voltage adjustments to maintain zero steady-state error and suppress low-frequency oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wide area damping control is implemented to damp inter-area oscillation, then oscillation damping capability is improved, but signal transmission delay worsens control effect
Solution Approach 1:
The patent replaces the mechanical signal transmission system with an absolute rotor angle measurement system based on GPS time synchronization. This substitution eliminates signal transmission delays by using independently measured absolute angles referenced to GPS time, rather than transmitting relative angle signals across the network.
2Reliability
If rotor angle control is implemented to eliminate low frequency oscillation, then oscillation elimination is improved, but control system complexity increases
Solution Approach 1:
The patent implements self-service through automatic PID control that continuously adjusts rotor angle based on real-time measurements. The system autonomously detects oscillations and applies corrective control without manual intervention, simplifying operation while maintaining sophisticated control functionality through standardized PID algorithms.
Data Source
AI summary
A method and system for eliminating the low-frequency oscillation between generators. By way of measuring the absolute rotor angle of a generator and controlling the rotor rotational speed, the absolute rotor angles obtained through measurement are the same when each GPS pulse per second signal arrives. The absolute rotor angles are angles of the internal potential Eq of the generator leading a GPS reference vector. Through the absolute rotor angle, zero steady state error control of the frequency and the rotor angle is achieved and the position of the generator rotor can remain unchanged in the PPS determined rotating coordinate system, thus suppressing the low-frequency oscillation better even without the need of remote measurement and achieving automatic local balance of active power during variation of loads. Accordingly, the power fluctuation on transmission lines is decreased while safe and stable operation of a large-scale interconnected power grid is achieved.