Abstract: Under economical operation mode of throttle admission steam turbines, the sliding pressure operation mode will be enabled with fully-opened high-pressure control valve. However, under this circumstance, the capability of increasing load for primary frequency regulation will be weakened, which makes it difficult to meet the requirement of quick load response to large power grid frequency deviation. Therefore, there exists big contradiction between the economic operation mode and the capability of primary frequency control. In this paper, the technologies of overload control valve adjustment, energy storage utilization in LP and HP regenerative systems, as well as in heat supply system are studied for primary frequency regulation. With the combination of these technologies, in the case of high-pressure control valve at full opening, the unit will increase the load fast when the power grid frequency is low. These technologies may also be used in the steam turbines adopting sequence valve admission to complement the original primary frequency regulation capacity at large frequency deviation.

Key words: throttle admission, primary frequency modulation, low power grid frequency, economical operation