Investingation Done To Improve Load Response Capacity Of Large Scale(Ultra) Super Critical Units

With the features of little heat accumulation and long time delay of boiler response, large scale (ultra) super critical units can not well meet the power grid dispatching demands of the load response capability.According to the requirements of European power grid and the properties of the turbo-generator unit, a condensate throttling technology to realize the fast load response of the turbo-generator unit was proposed by SIEMENS AG. The principle of the condensate throttling technology is to change the condensate flow quickly, so that the thermal balances in the LP-preheaters and the deaerator are broken, and the extraction steam to the LP-preheaters and the deaerator therefore is changed correspondingly. The result is a short and rapid change of electric power output.By using the control strategy of the condensate throttling, even though the steam turbine governing valves are full open, the unit is also has a favorable load response capacity, so that it can not only satisfy the load response demands of the power grid dispatching, but also decrease the throttling loss of the steam turbine governing valves. This technology has been applied to the control of the actual turbo-generator unit by SIEMENSE AG. Because it is a commercial software, as a technology application, it still has many limits. In order to apply it to the other turbo-generator units in china, this paper firstly analyzes the load response property of the large scale (ultra) super critical unit and the features of traditional turbine-boiler coordinated control system, and then establishes the simplified mathematical models of the pre-heaters and the deaerator through the mechanism analysis, and deeply studies the load regulation by the condensate water, based on the coordinated control system, constructs a new control system architecture with rapid load response. Combined with the test data of the domestic related super critical unit, a coordinated control system with the load regulation by condensate water is developed in this paper, and its validity is proved by the simulation. This research results is also suitable for the other similar large scale (ultra) super critical units’control systems, and it can commendably satisfy the power grid requirements of rapid load response.