| Due to the excellent load-following characteristics and low emission level,gas turbines can be used as a reliable power source to participate in the peak shaving of the power grid,which is conducive to the absorption and development of renewable energy and thus promote the optimization of national energy structure.At present,the electric power market has increasingly high requirements on the operation performance and load-following capability of gas turbines,and attaches more and more importance to the stable load regulation ability of units and the avoidance of unstable operation of unit components in the transition process.Therefore,it is of great value to study the dynamic characteristics and ensure the efficient and stable operation of the unit.In this paper,the purpose is to explore the stable regulation of gas turbines under different operating conditions,and based on the dynamic simulation model of gas turbines,the dynamic response characteristics of gas turbines are studied to provide a reference for the operation of actual units.Firstly,considering the influence of variable speed and compressor inlet guide vane(IGV),a single-stage model of the compressor was established,and the whole model of the compressor was constructed by the step-by-step superposition method.Based on the idea of modular modeling,the dynamic model of the conventional gas turbine including the compressor,combustion chamber,turbine,rotor,and the auxiliary module was constructed according to the matching relationship between parameters.To improve the simulation accuracy,the physical property parameters were calculated by the thermal physical property calculation formula.Besides,different load points and load change process were selected to verify the model.The calculation accuracy of the model is high and it can correctly reflect the dynamic response characteristics of the gas turbine in the load change process.Secondly,combined with the corresponding control system,the response characteristics of conventional heavy-duty gas turbines under different disturbances were studied.With the designed temperature control system,the dynamic response characteristics of gas turbines with the constant turbine inlet temperature(T3)and constant turbine exhaust temperature(T4)operation strategies were compared and analyzed.The model can simulate IGV bias,fuel mass flow,and load disturbance,and the system parameters can be rapidly and stably transitioned under control.The change of fuel heat value will cause the fluctuation of system parameters,which is not conducive to the stability of the system.In the process of decreasing the same load,the response trend of system parameters of constant T3 regulating and constant T4 regulating unit is similar,while the adjustment of parameters of constant T3 regulating unit is larger.Thirdly,the dynamic response characteristics of a hydrogen-blending gas turbine were studied when the hydrogen blending ratio fluctuated.Based on a gas turbine with a hydrogen blending ratio of 20%,the components and low heat value of hydrogen-blended fuel were calculated,and the influence of hydrogen blending ratio fluctuation on system components under different loads was analyzed.The results show that the fluctuation of hydrogen blending ratio will cause a large fluctuation of T3.The larger the fluctuation of hydrogen blending ratio is,the larger the fluctuation of system parameters will be,and it will take more time for the system to reach stabilization.In the high load area,T3 will appear overtemperature.However,with the decrease of load,the influence of hydrogen blending ratio fluctuation is gradually weakened.Finally,based on the dynamic model,the control system of the exhaust gas recirculation ratio control unit was designed,and the dynamic response characteristics of the exhaust gas recirculation control unit during load change were studied.By partially recovering the exhaust gas from the heat recover steam generator and then mixing it with the inlet air of the compressor,the inlet mass flow and temperature of the compressor can be adjusted.Same to IGV control,exhaust gas recirculation ratio control can be used as a load regulation approach to realize the rapid and stabilized regulation of load.Affected by the compressor inlet air mass flow,the load adjustable range of the unit with the same exhaust gas recirculation ratio is shortened in the lower load region.Therefore,to achieve deeper load regulation,it is recommended to use exhaust gas recirculation ratio control in highload regions. |
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