The vapor-water type heat exchanger is one of the most important equipmentsin thermal power station. It has some dynamic characteristics of non-linearity, time-varying volatility of parameters, and time-delay, etc. Firstly, the related requirements of central heating technological process and automatic control are analyzed synthetically, and the constitutional plants of vapor-water type heat exchanger are modeled respectively. A cascade control strategy of water supply temperature fractional order proportional integral derivative controller (WST-FOPIDC) as the main controller and steam flow fractional order proportional integral controller (SF-FOPIC) as the secondary controller is determined. Secondly, a modified particle swarm optimization algorithm (MPSOA) is applied to tune the optimal values of eight parameters of WST-FOPIDC and SF-FOPIC, respectively. Finally, by means of MATLAB tool, the proposed cascade system is configured and the corresponding control effect is simulated numerically. The results show that this cascade control system is feasible in theory, which can obtain more satisfactory control effect, and the corresponding control effect of water supply temperature is
obviously better than that of water supply temperature PID-steam flow PI cascade control system based on Ziegler-Nichols tuning method for the parameters of these two controllers.