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# Zhixin Workshop on Modelling and Simulation of Coal-fired Power Generation and CCS Process

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### Zhixin Workshop on Modelling and Simulation of Coal-fired Power Generation and CCS Process

1. 1. Modelling of Primary Frequency Control and Effect Analyses of Governing System Parameters on the Grid Frequency Zhixin Sun
2. 2. Outline Introduction Mathematical Model of Primary Frequency Control Dynamic Test & Parameter Identification Effects of Parameters of Governing System Effect of dead band Effect of speed droopPage 2 Institute of Turbomachinery, Xi’an Jiaotong University
3. 3. Introduction Power Plant frequency Factory Power Plant Machine Power Plant Power Plant Home User Power Generation load DemandFrequency is an indicator of overall power imbalance. power increases, frequency rises load increases, frequency fallsFrequency deviation must be controlled within a certain range.(±0.2Hz in China) Primary frequency control Frequency Secondary frequency control Page 3 Institute of Turbomachinery, Xi’an Jiaotong University
4. 4. Introduction Primary frequency control (speed droop control) load ref Servo- Steam - + - 1/Speed droop turbine + Rotor motor Dead band load increases, frequency falls frequency deviation is greater than the dead band servo-motor increases governing valve opening of steam turbine power output increases to hold back the decrease of frequencyresponses fastutilizes the heat storage of boilerhas frequency error in steady state Page 4 Institute of Turbomachinery, Xi’an Jiaotong University
5. 5. Introduction Secondary frequency control balances the power and load through fuel regulation responses slowly can eliminate steady state frequency errorPage 5 Institute of Turbomachinery, Xi’an Jiaotong University
6. 6. Mathematical Model of Primary Frequency Control Boiler model load ref Servo- Steam - + - 1/Speed droop turbine + Rotor motor Dead band Main steam pressure is the interface between steam turbine and boiler.Governing valve opening rises Main Steam pressure falls Boiler responses slowlyPage 6 Institute of Turbomachinery, Xi’an Jiaotong University
7. 7. Mathematical Model of Boiler gD gs pD pS gQ gw pD pS 1 1 K sTD sTS PF gQ gw gD 1 1 e −τ s TF s + 1 TW s + 1 gsPage 7 Institute of Turbomachinery, Xi’an Jiaotong University
8. 8. Mathematical Model of Steam TurbineSteam Turbine: three cylinders, single reheat Page 8 Institute of Turbomachinery, Xi’an Jiaotong University
9. 9. Mathematical Model of Steam TurbinePower is assumed to be proportional to the pressure before each cylinder aH+aI+aL=1Page 9 Institute of Turbomachinery, Xi’an Jiaotong University
10. 10. Mathematical Model of Steam TurbinePower over-regulation of HP cylinder Power response of actual unit can reach 60% of regulation target in the first several seconds Power response of simulation only reach 38% Page 10 Institute of Turbomachinery, Xi’an Jiaotong University
11. 11. Mathematical Model of Steam Turbine Improved model of Steam TurbinePower over-regulation coefficient 1 sTCH+1 1 sTRH+1 1 sTCO+1of HP cylinder:λ=f( pressure ratio, adiabatic index ) +- λ ++ New modelpower αH αI αL Classic model + + + + Page 11 Institute of Turbomachinery, Xi’an Jiaotong University
12. 12. Mathematical Model of Steam TurbineSingle Unit Test of primary frequency control: 1.static test of servo-motor for identification of Tact 2.load dump test for identification of Ta 3.dynamic test for identification of the time constants of steam turbine on line, increases or decreases the reference speed (by 25 rpm) Page 12 Institute of Turbomachinery, Xi’an Jiaotong University
13. 13. Dynamic Test & Parameter Identification 1.0 0.8 31 4 2 4 0.6 % 0.4 2 1 0.2 0.0 0 10 20 30 40 50 3 t (s) TCH 2 Pressure TRH 3 Valve opening Power 4 TCOPage 13 Institute of Turbomachinery, Xi’an Jiaotong University
14. 14. Effect of dead bandMulti-unitsTab.1 The responses of units under different load disturbance Dead band Power percentage 1 2 r/min 38.0% 2 3 r/min 41.2% 3 4 r/min 11.0% 4 5 r/min 9.8% Page 14 Institute of Turbomachinery, Xi’an Jiaotong University
15. 15. Effect of dead band Dead band =2 rpm Dead band =3 rpm Dead band =4 rpm Dead band =5 rpm Simulation resultsPage 15 Institute of Turbomachinery, Xi’an Jiaotong University
16. 16. Effect of dead band Tab.2 The responses of units under different load disturbance Load disturbance 5% 7.6% 10% Dead band /r·min-1 2 3 4 5 2 3 4 5 2 3 4 5 Freq variation max /Hz -0.22 -0.21 -0.3 -0.31 -0.31 -0.30 -0.44 -0.45 -0.39 -0.38 -0.56 -0.57 Freq variation Steady -0.15 -0.15 -0.15 -0.15 -0.2 -0.2 -0.2 -0.2 -0.25 -0.25 -0.25 -0.25 state /HzSteady State Frequency deviations<0.2 Hz Tab.3 The relationship between different dead band combination and allowed load disturbance a b c d e f g h 2 r/min capacity 0.25 0.5 0.7 0.9 1 0 0 0 3 r/min capacity 0.25 0.2 0.1 0.1 0 1 0 0 4 r/min capacity 0.25 0.2 0.1 0 0 0 1 0 5 r/min capacity 0.25 0.1 0.1 0 0 0 0 1 Allowed load 7.1 7.6 7.9 8.3 8.4 7.6 6.8 5.9 disturbance/%Page 16 Institute of Turbomachinery, Xi’an Jiaotong University
17. 17. Effect of speed droop speedspeed droop n max − n N δ = × 100 % nN 10% capacity with constant nmax —— no-load speed speed droop of 4% nN —— full-load speed unit with speed droop of 4% unit with speed droop of 6% unit with speed droop of 8% unit with speed droop of 10% Frequency /Hz Load increases by 10% Time /s 90% capacity 10% capacityPage 17 Institute of Turbomachinery, Xi’an Jiaotong University
18. 18. Xian Jiaotong University is a top10 university in China,and was founded in1896. Today, Xian Jiaotong University is a comprehensive researchuniversity offering programs in nine areas with a major emphasis onscience and engineering. Page 18 Institute of Turbomachinery, Xi’an Jiaotong University
19. 19. Page 19 Institute of Turbomachinery, Xi’an Jiaotong University