Research On Load Frequency Control Optimization Of Thermal Power Unit Under Flexible Operation

With the deepening of China's energy transformation,new energy is transiting to the main position.And the research on the stability of high proportion of new energy power system has become the current research hotspot.At present,China's power system does not have enough flexibility,which leads to serious abandonment of wind and light.In order to enhance the flexibility of power system and promote new energy consumption,most thermal power units actively participate in the flexibility transformation.After the flexible transformation,the thermal power units have different active power regulation characteristics under different operating conditions.The flexible operation of thermal power units in a large range will cause the change of active power regulation characteristics in the system.This paper focuses on the frequency stability of power system.Under the background of energy transformation and flexibility transformation,it will comprehensively analyze the impact of flexibility transformation of thermal power unit on the unit itself and the frequency regulation ability of power system.Therefore,this paper will carry out research work from the following aspects:(1)Based on the mechanism analysis,the calculation method of the parameters of the steam turbine and its governing system model is deduced in this paper.Based on the historical operation data,the linear models of the steam turbine and its governing system under multiple working conditions after the flexibility transformation are established.By analyzing the simulation results,it is found that the response rate of steam turbine and its governing system decreases with the decrease of load,which is not conducive to peak load regulation and frequency regulation.(2)According to the general form of primary frequency regulation response process,the limit utilization form of boiler thermal storage is determined,and a comprehensive evaluation method of primary frequency regulation is proposed.In this paper,a solution algorithm is designed for each parameter in the evaluation method,and then the limit response process of primary frequency regulation under all working conditions is quantitatively described by using the historical operation data of the demonstration unit,and the differential adjustment coefficients under different working conditions are calculated according to the results.The results show that with the decrease of unit load,the total heat released by the boiler gradually decreases,while the time needed to support the primary frequency regulation process increases due to the influence of low flow and low flow rate flue gas.Generally speaking,the response performance of primary frequency regulation of the unit decreases with the decrease of the load,and the adjustment coefficient also decreases with the decrease of the unit operation condition.(3)Considering the regulation function of primary and secondary regulation,the response ability of flexible operation thermal power unit to frequency difference is analyzed.In the single unit operation scenario,the restraining ability of the unit side to the load disturbance decreases with the decrease of the unit operation point.However,there is a problem of unit commitment in multi unit operation,so it is difficult to get a universal conclusion.Therefore,this paper considers two typical operation modes of the power side,and completes the simple power system modeling under the framework of load frequency control.The simulation results show that no matter the thermal power unit adopts the deep operation or start-up and stop operation mode,with the increase of wind power penetration,the regulation ability of the system to the load disturbance shows a downward trend,but the deep operation mode can retain the moment of inertia of the system,and then retain the anti load disturbance ability of the system.(4)The development of thermal power flexibility increases the complexity of multi machine coordination in the system.In this paper,an optimal control strategy based on power factor dynamic trajectory planning is proposed.Firstly,the power distribution factors of each unit in the LFC frequency regulation area are set to free state,and the dynamic trajectory of the power distribution factors in the oscillation area is dynamically planned based on the idea of UAV dynamic trajectory optimization,The complementary coordination problem is transformed into a multi-objective optimization problem.The algorithm is simulated with a typical three region nine generating unit system.The simulation results show that the algorithm can call different advantages of different units in the LFC process,and simultaneously enhance the frequency adjustment effect and adjust the economy in the adjustment process.Finally,the stability of the algorithm is verified by Monte Carlo simulation.(5)In order to deal with the deterioration of power system frequency stability under the high proportion of new energy access,aiming at the characteristics of modern power system such as scale and complexity,this paper proposes an improved fuzzy ADRC method,which adds fuzzy rules to the improved ADRC and provides adaptive compensation for the parameters of ADRC,The simulation results based on IEEE 9-bus model verify the effectiveness of the algorithm.