Application of Advanced Process Control systems in Enel Thermal Generation (Eleonora Porro, Giorgio Mazzola, Giordano Proietti Marini)

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1 AIS - ISA Italy - AUTOMATION INSTRUMENTATION SUMMIT Castello di Belgioioso (Pavia) - Italy, July 4 th & 5 th, 2018 Application of Advanced Process Control systems in Enel Thermal Generation (Eleonora Porro, Giorgio Mazzola, Giordano Proietti Marini)

2 Contents Advanced Process Control (APC) in enel Thermal Generation APC Technology Deployment Plan Scope and Benefits Case Study: Primary Frequency Regulation with Steam Turbine 2 Application of Advanced Process Control systems in Enel Thermal Generation

3 APC how it works? PID vs APC Set point v.s. current value APC CONTROLLER Other field measurements The APC controller elaborates new external variable set points to the base PID controller Based on multivariable models, provides more stability and possibility to work closer to the limit current value Runs on dedicated HW PID Selecting unit Possibility to switch back to PID at any time minimizing risks in case of any failure of hardware, data exchange or involved measures. APC PID Measures Process 3

4 APC how it works? PID vs APC Conventional control systems based on PID controllers lose significantly accuracy when working out of the design point and typically increase the fluctuations of the controlled signal around the set-point Advanced Process Controls allows to operate the power plant closer to the design point by minimizing the fluctuations due to unstable loops. The APC controller elaborates new set-point requests to the control by using additional process measures that normally represent disturbs for traditional controllers APC elaboration is based on accurate process models created and trained on the basis of systems real behavior i.e it Includes several measured variables and feed forward effects of changed PP operating conditions

5 APC how it works? Predictive Control vs. Adaptive Predictive Process Control 1 Predictive Control Requires a process model, built with historical data and /or step tests; Able to predict the evolution of the controlled variables and act in order to let the predicted evolution equal to the desired evolution; Control performance deterioration could occur with changes in the process dynamics 2 Adaptive Predictive Process Control Easy to implement, no need for performing step tests; The predictive model is based on correlations among the variables and on expert rules; The system is self tuning and continuously updates the parameters of the predictive model, according to the changes in process characteristics

6 APC start of application in Enel Pilot APC applications COAL POWER PLANTS PREDICTIVE CONTROL ADAPTIVE PREDICTIVE PROCESS CONTROL 1 UNIT USC 1 Unit Sub-critical 1 Unit Subcritical AIR/ FUEL DeNOx DeSOx STEAM TEMP. AIR/ FUEL STEAM TEMP.

7 Advanced Process Control Coal-fired USC Unit : Boiler combustion TARGETS Minimization of secondary air flow rate and balance between boiler sides A/B, controlling NO x and CO emissions O2 conc. avg TEST RESULTS Long term tests (~ 4 weeks, up to 24 hours/d) with combustion and SCR APC systems, under variable load and coals (Colombian and Russian coals) Air excess bias O2 sides A/B decrease of the oxygen concentration at the ECO outlet of 0,25% (avg) equilibrate the oxygen between the two sides decreasing the delta of 0,2% (*) * mean load profile 590 MW, considering similar operating periods: 7-10 Feb 2017 (APC OFF) and and Feb 2017 (APC ON) Sides A/B balance bias

8 Advanced Process Control Coal-fired Sub-Critical Unit: Main steam Temperature control and Boiler combustion Control of the main Steam pressure and Power output generated in the turbine, through the control of the coal input and the regulation of the main steam valve TARGETS Control of the excess of Oxygen at the outlet of the boiler and CO emissions through the control of the air input and the combustion process in the boiler Control of the final superheater steam temperature, through the control of the attemperation water flow T control performance with & w/o APC TEST RESULTS A 50% reduction on the instability and oscillation of the superheater steam temperature A significant advance in ramping capabilities, increase from 3 to 5MW/min keeping similar control standards A more controlled level of the CO emissions avoiding peaking after load changes A more stable level of the O 2 excess at the outlet of the boiler without requiring the intervention of the operator, and an overall reduction of O 2 excess of 0,5% An average reduction of NOx levels in the range of mg/nm 3 O 2 and CO with & w/o APC O 2 and CO with & w/o APC

9 APC Looking ahead Deployment Plan CCGT: Adv. Humming Ctrl.; SH/RH; Drum Levels: Fast Start; Primary Freq. Ctrl. Coal: Combustion; SH/RH; DeNOx; DeSOx

10 APC Scope and benefits Plant Technology APC application Expected Benefits Steam power plants (mainly coal) Combustion optimization: Minimization of secondary air flow rate and balance between boiler sides A/B, controlling NOx and CO emissions. DeNOx/DeSOx: Reduction of the reagent. Heat rate improvement (through reduction of O 2 excess) and/or NOx reduction Improvement in emissions and in chemicals consumption SH/RH steam temperature: Optimization of max steam temp. The adaptive controller modifies control parameters during the operation. ~+4 C max T setting, HR improvement CCGT PFR regulation with ST: Ancillary grid services, GT reliability improvement Fast start-up Increased revenues for primary frequency control and spinning reserve services, GT working at max load with HR optimized & less burner pressure fluctuation with subsequent reliability improvement Economic incoming from the reduction of fuel consumption. 10

11 APC for CCGT Case Study One example from on-going PFR APC installation at Italian CCGT (Supplier Siemens P3000) Preliminary activities & Plant analysis Commissioning Tuning Installation Performance test Some tests in order to: Evaluate of the steam buffering capability of the boiler Evaluate losses due to the throttling Max/Min allowed steam pressure Min. steam turbine load Min. gas turbine load 11

12 APC for CCGT Plant characteristics Type: CCGT 1+1 multi shaft w/o auxiliary burners w/o by-pass stack BOILER: GAS TURBINE: Type: Siemens V94.3A Generator: Siemens TLRI kV GT load: 264 MW Fuel: natural gas (nominal Nm³/h) Manufacturer: Ansaldo Caldaie S.p.A. Boiler type: Horizontal HRSG with 3 pressure levels and 3 drums Nominal steam flow (HP/IP/LP): 262 / 297 / 326 t/h HP steam parameters: 545 C / 81 bar Attemperator layout: 1 spray attemperator in between SH 1 & 2 IP steam parameters: 545 C / 12 bar Attemperator layout: 1 spray attemperator in between RH 1 & 2

13 APC for CCGT Plant characteristics STEAM TURBINE: Type: FRANCO TOSI Meccanica W27R2 Condensing ST w/o extraction Generator: MARELLI 20KV ST load: 114 MW (downsized from 250 MW) 120 MW short-term overload allowed Admission: 8 governor valves (full-arc and partial-arc operation) no reaction control stage usually working in natural sliding pressure (VWO) Stages: 1 x HP ; 1 x IP ; 1 x LP Nominal steam parameters: HP 540 C ; 110 bar (design) / 90 bar (real) IP 540 C; 19 bar (design) / 12 bar (real) Condenser type: Sea-water cooling

14 APC for CCGT Primary Frequency Control Key Issues Minimum requirements for primary frequency control: When Italy and Sicily are connected: the standard primary reserve is 5 % of the reregistered power within 30 s. When Sicily is disconnected from the continent: the primary frequency reserve must be increased to 10% of the registered power. The primary reserve needs to compensate a frequency deviation in less than 30 s. Fast response to load changes requests The provided primary reserve power must be kept stable for at least 15 minutes consecutively.

15 APC for CCGT Primary Frequency Control with Steam Turbine The load response to the frequency deviation is faster with the steam turbine and complies with the request of Terna Use of steam turbine for frequency control by mobilizing thermal storage Correction of minor frequency deviations only by steam turbine Gas turbine only activated in the event of major frequency deviations 15 Unit control performs predictive management of thermal storage by coordinated gas and steam turbine operation on the basis of dynamic models.

16 APC for CCGT Model of the HRSG 16 Fundamental is the evaluation of the steam buffering capability of the boiler. Throttling the steam flow with the turbine valves increases the steam pressure and stores the heat in the boiler. With a throttling of 25 bar, the buffer is able to produce >13 MW for a period of 3 min with a gross peak at 20.5 MW after 20 s (the unit net load increases by 18.9 MW).

17 APC for CCGT Working of the Optimizer Controlled variables: GT COMPRESSOR INLET AIR TEMPERATURE SPINNING RESERVE UNIT LOAD DEMAND DEVIATION STEAM TURBINE CONTROLLER GROSS ACTIVE POWER TG FREQ DEP LOAD SETP kdf act GROSS ACTIVE POWER - TV STEAM TEMPERATURE AT OUTLET SH2 STEAM PRESSURE RH AT INLET OF TURBINE. SET_POINT_AP CC HP Steam pressure SP POSITION TURBINE VALVE Manipulated variables: CORRECTION OF PRESSURE SET POINT CORRECTION OF THE KDF GT CORRECTION GT LOAD SET POINT

18 APC for CCGT Target and Summary of Results The coordinated response of GT and ST contributes to a better stabilization of the grid. With the max load plus solution, the CCPP enlarges its load range available for the load dispatcher. In terms of primary frequency control, it is possible to increase the service offered to the grid. The current participation of 15.1 MW to the frequency support can be increased to 37.8 MW with faster performance When Sicily is connected (continental mode), the ±5.7 MW PFC support is available until a unit load of 372 MW instead of the present 370 MW. When Sicily is disconnected (island mode), the ±37.8 MW PFC support can be provided until 335 MW instead of 324 MW. It is also possible to increase the secondary frequency participation offered to the grid. The current participation of ±20 MW to the secondary reserve can be increased to 30 MW at least, with faster performance

19 APC for CCGT Drawing some conclusions APC is not a magic wand, it is necessary to verify if process has enough margins to let APC work APC can help to improve the efficiency of the power plant.