Improving Stability of TPP Load Center by Optimization of Startup Modes of Synchronous Motors

This article analyzes a TPP load center of a metal plant that supplies electric power to synchronous utility motors. During TPP operation, one of the generators can be stopped to perform maintenance works, resulting in a significant reduction of voltage in 10 kV buses. Due to this, it is crucial to facilitate the smooth operation of synchronous utility motors, especially in startup modes. Conducting experiments with a TPP load center, the authors found out that the use of synchronous motors does not facilitate the required compensation for the reactive power, which led to the voltage level reduction by up to 6.7%. Therefore, to analyze the stability of synchronous motors at the startup, the authors developed and presented a mathematical model for the TPP load center with special attention given to the modeling of synchronous motor electrics. This article reviews the most efficient methods of maintaining the required voltage level in TPP buses. Following the results of complex experiments performed with the developed model, the authors selected two possible options: introducing the voltage feedback for high-power line-operated synchronous motors and connecting capacitor banks to the synchronous motor terminals. Correction systems were installed on operating automated excitation control equipment, which allowed reducing the amounts of synchronous motor idle times caused by the line voltage drops by 40%.