DCS (distributed control system) control method and SMITH controller

Abstract

The invention relates to a DCS (distributed control system) control method and a SMITH controller. The SMITH controller comprises a regulated variable actual value module, subtraction modules, a PID (proportion, integration and differentiation) controller, an actuator M / A station, an actuator output module, a process quantity module, a set value module, a multiplier, a proportionality coefficient modification function device, a multi-order inertia time constant function device, a pure delay time function device and first-order inertia elements. The control method includes procedures of (1), performing a step response test and determining a transfer function model of a controlled object; (2), configuring a DCS by the aid of the transfer function model, corresponding parameter modules and the corresponding function devices; (3), computing parameters of a unit under a load working condition; (4), inputting the parameters to the configuration graph function devices; (5), mounting the configured DCS in a DCS controller of an application system. The DCS control method and the SMITH controller have the advantages that modification parameters of the controller are computed by the aid of the transfer function model, the DCS is configured by the aid of the modification parameters, accordingly lagging in control procedures of a power plant is reduced or eliminated, and the production running control stability is improved.

Description

technical field [0001] The invention belongs to the technical field of electric power production process control, and relates to a DCS control method and a SMITH controller. Background technique [0002] There are many adjustment lag problems in the control process of thermal power plant production and operation. Due to the pure lag of adjustment, the controlled quantity cannot reflect the disturbance suffered by the system in time. Even if the measurement signal reaches the controller, the action command issued by the adjustment mechanism after receiving the signal , it also needs to pass through the pure lag time τ to affect the controlled quantity. The pure hysteresis problem leads to obvious overshoot in the control process and prolongs the transition process time, making the transition process worse and affecting the stability of the system. The predictor is a commonly used compensation controller, which can better solve the influence of pure lag on the controlled syst...

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Problems solved by technology

[0003] Most of the control of thermal power plants is realized by distributed control system (DCS), and there is no pure delay link in many DCS systems, so the structure of conventional SMITH control cannot be realized in DCS

The SMITH controller has high requirements on the estimation model, namely Must be very close to the transfer function of the actual controlled object , and the models of many thermal power plant control objects are time-varying and related to unit load. If the model mismatch is large, the SMITH prediction control effect will become very poor, so it is difficult to apply SMITH control to DCS

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