A Compensation Modeling and Diagnosis of Low-Frequency Oscillation Caused by Thermal Power Units

Under the background of establishing a new power system, all kinds of renewable energy are connected to the grid on a large scale. Because of the fluctuation and instability of renewable energy output, their grid connection has a great impact on the stability and security of the grid. This problem makes thermal power units need to respond to frequent fluctuations of the power grid and compensate for the tasks of deep peak adjustment and frequent load change. As a result, the operation state of thermal power units has changed greatly, from infrequent operation of high load to frequent operation of large range now. The prime mover side, especially the nonlinear part, is easy to produce low-frequency oscillation in the running state. Low-frequency oscillations are difficult to identify. Once it occurs, it may spread to the entire power grid, endangering the security of the power grid and even causing economic losses. This paper retrofits the compensation side model. A method to evaluate the safety level of power oscillations is designed to diagnose the low-frequency oscillation modes. It has been proved that the duration to diagnose the emergences of low-frequency oscillations is reduced by about 30 seconds.