Combined Cycle Performance Evaluation and Dynamic Response Simulation

ABSTRACT Power plants operating in combined cycle present higher thermal efficiency (over 60%) and increased power generation when compared to traditional simple cycles, such as gas or steam turbines operating alone. Considering that the power plant evaluated in this paper is already operational, a further development concerning to the power plant control system is required in order to evaluate disturbances and frequency variations, generated by the electrical grid during normal operation, as the loads applied to the turbines are intrinsically associated to the grid frequency. A computer program able to simulate the control system was developed to cope with these instabilities and to guarantee the necessary protection to the power plant operation. The develop program was made using MATLAB Simulink®. The main components of the power plant consists of 2 gas turbines of 90 MW each and a steam turbine of 320 MW, totalizing 500 MW. Firstly, the power plant main components were constructed separately. Once obtained stable models, the exhaust from the gas turbine was connected to the water-steam cycle through the heat recovery steam generator. The main parameters necessary to adjust the model such as gains, limits and constants were obtained from the power plant operational data. The simulation results allowed the evaluation of some key parameters; others are possible but not shown, such as power, exhaust gas temperature, fuel flow and variable stator angles during grid instabilities. The studies were conducted by testing the robustness, response time, transient analysis, steady state analysis and reliability of the proposed model.

摘要 相较于传统简单循环（如单独运行的燃气轮机或蒸汽轮机），联合循环运行的发电厂拥有更高的热效率（超过60%）与更大的发电量。考虑到本文所评估的发电厂已投入运营，由于汽轮机承受的负荷与电网频率存在内在关联，因此需要对该发电厂的控制系统开展进一步开发，以评估电网在正常运行期间产生的扰动与频率变化。为应对此类运行不稳定性并保障发电厂运行所需的安全保护机制，研究人员开发了一款可模拟该控制系统的计算机程序，本程序基于MATLAB Simulink®开发完成。该发电厂的核心组件包含2台单机容量90兆瓦的燃气轮机与1台320兆瓦的蒸汽轮机，总装机容量达500兆瓦。研究首先分别构建了发电厂的各主要组件模型，待各模型均实现稳定运行后，将燃气轮机的排气通过余热回收蒸汽发生器接入水-蒸汽循环系统。用于模型调试的核心参数（包括增益、限值与常数）均取自该发电厂的实际运行数据。仿真结果可用于评估若干关键参数；其余参数虽可被观测但未在此展示，例如电网扰动工况下的功率、排气温度、燃料流量与可变静子角度。本研究通过测试所提模型的鲁棒性、响应时间、暂态分析、稳态分析与可靠性，完成了全部验证工作。