LOAD RESPONSES BASED OPTIMIZED CASCADED PID CONTROL SCHEME USING PLC-HMI IN HYDRO ELECTRIC PUMPED STORAGE POWER PLANT

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 11, November 2017, pp , Article ID: IJMET_08_11_016 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed LOAD RESPONSES BASED OPTIMIZED CASCADED PID CONTROL SCHEME USING PLC-HMI IN HYDRO ELECTRIC PUMPED STORAGE POWER PLANT ECE Dept, Veltech Dr. RR & Dr. SR University, Avadi, Chennai , India ABSTRACT Load Responses based optimized (CPID) Cascaded PID (Proportional - Integral - Derivative) controller scheme using B&R (Bernecker & Rainer) Industrial Automation PLC - HMI (Programmable Logic Control - Human Machine Interface) for Efficient Energy management and storage of a hydroelectric pumped storage power plant is highlighted. In this work based on various Load responses during dynamic load disturbances and steady state conditions, Optimal PID controller parameters were obtained. In the proposed control scheme, Upper Reservoir tank, Level is cascaded with PID Flow which so as to get fast and smooth response in attaining the load demand. Hydroelectric pumped storage power plant prototype model with 22 digital inputs and 14 potential free outputs is designed with an intention of controlling the variables, flow and level by conventional and the proposed Load Responses based CPID control scheme. There are two tanks in the lab scale setup, lower tank with 2 stages of level and upper tank with 5 stages of level. Monitoring and Control will be easily performed by HMI in Real time. In this paper, Load Responses based CPID control scheme using PLC-HMI is performed and finally compared with the conventional PID method by experimental results and validation has been performed from the hydroelectric pumped storage power plant real time statistics. Key word: Pumped Hydro Energy Storage, Optimization; PLC - HMI; CPID. Cite this Article:, Load Responses Based Optimized Cascaded PID Control Scheme Using PLC-HMI In Hydro Electric Pumped Storage Power Plant, International Journal of Mechanical Engineering and Technology 8(11), 2017, pp editor@iaeme.com

2 Load Responses Based Optimized Cascaded PID Control Scheme Using PLC-HMI In Hydro Electric Pumped Storage Power Plant 1. INTRODUCTION Energy Recapture is a system that allows energy to be stored when electricity is plentiful and released for generation in times of high grid demand. The electrical grid needs to assure the supply at any time, including the time of high demand, which is in the morning and late afternoon; the rest of the day, and especially in night, energy consumption will be lesser. The major goal is to try to uniform this curve, getting the line as close to horizontal as possible, avoiding like that peak demands, which make it necessary to have such quantities of energy available, only for very short periods. To balance the load demand by electrical grid at high peak hours, hydroelectric pumped storage power plant is preferred. Ardizzon et al [2] described that Hydropower is not only a renewable and sustainable energy source, but its flexibility and storage capacity also makes it possible to improve grid stability. Deane et al [3] models large pumped hydro energy storage in a future power system. And derived intertemporal targets for large pumped hydro energy storage that reduce overall system costs when compared to targets derived using a conventional method. Martínez-Lucas et al [5] presented a dynamic simulation model of a laboratory-scale pumped-storage power plant (PSPP) operating in pumping mode with variable speed. To overcome the difficulties such as intrinsic time delay, nonlinearity due to uncertainty of the process and frequent load changes in the existing control schemes, the PLC-HMI based optimized CPID control scheme is developed in hydroelectric pumped storage power plant. This paper is structured as follows: Section 2 deals with the hydro power plant and prototype model. Section 3 describes proposed Cascaded PID control scheme, Section 4 includes the PLC-HMI Visualization. Section 5 deals on Experimental results of the conventional PID and the proposed optimized CPID control scheme. Section 6 deals on conclusions. 2. HYDRO ELECTRIC PUMPED STORAGE POWER PLANT AND PROTOTYPE MODEL The schematic representation of a Hydroelectric pumped storage power plant is shown in Figure.1. Figure 1 Pumped Storage Hydro Electric Power Plant editor@iaeme.com

3 In Pumped storage power plant, Energy is stored by pumping water from lower reservoir to upper reservoir at the time of low power demand and at the time of peak load periods, stored water is utilized to generate and manage load demand. = Ƞ Where P Power (kw) Ƞ - Turbine-Generator Efficiency. Q Discharge (m3/s) Hu Head (m) γ Specific Weight of fluid (N/m3) 2.1 Conventional PID Controller in Hydro Electric Pumped Storage Power Plant The Pumped Storage Hydro Electric Power Plant protype operation is represented in Figure.2. Figure 2 Prototype Model of Hydro Electric Pumped Storage Power Plant The sequences [9][10] followed in hydroelectric pumped storage power plant that is put into operation in the prototype model are illustrated as follows. When the water level in the lower tank reaches the low level, the pump 1 is actuated and the water is taken to the upper tank from the lower tank. In upper tank, when the water level reaches the low level, pump 1 is again switched on and water level raises upto average level. When water level exceeding average level, Gate1 is allowed to open. Similarly when the level attains medium level, the pump 1 actuated and the water raises upto high level. When water is mounting beyond medium level, Gate 1 and Gate 2 is opened and when water level is reached the high level, Gate 1, Gate 2 and Gate 3 is opened. When the level increases beyond the high level, the pump2 is actuated and water is taken back to lower editor@iaeme.com

4 Load Responses Based Optimized Cascaded PID Control Scheme Using PLC-HMI In Hydro Electric Pumped Storage Power Plant tank. If the water level reaches high level in lower tank and exceeding danger level in the upper tank, Gate 1, Gate 2 and Gate 3 will be closed and also the pumps 1 and 2 will be switched off. Prototype model is provided with lower tank of two levels and upper tank of five levels [1]. The upper five levels are Low level, Average level, Medium level, High level and Danger level. Whereas the two levels of the lower tank are Low level and High level. The Block diagram of Hardware set up is shown in Figure.3 which consists of the hardware components Programmable Logic Controller, FT - Flow transmitters, LT - Capacitive level transmitter, Pumps and Valves. Based on the level transmitter (LT) output, the ladder logic is programmed and as per the programmed ladder logic, the pumps and also the opening of gates of the dam are actuated at their respective levels. Figure 3 Block diagram of Hardware Set up The Lab scale Experimental set up is operated based on the sequences demonstrated. The prototype model is shown in Figure. 4. Figure 4 Prototype Model editor@iaeme.com

5 Figure 5 Coventional PID Control Scheme In conventional method as shown in Figure.5 water level in the upper Reservoir and water flow to the Gates will be controlled by PID controllers separately as closed loop depending on the Energy demand. In PID water flow controller, the PID control signal, 1 U ( s) = K p (1 + + TDs) E( s) T s I Where Kp represents Proportional gain, TI represents Integral time, TD represents Derivative time. E(s) represents Error signal & U(s) represents Control signal. The PID controller parameters are obtained by Ziegler Nichol's method from offline tests performed in the prototype model for different increase and decrease in load conditions concerning real time data collected from hydro electric pumped storage plant are shown in Table 2. Table 2 PID Parameters (1) Control loop Water Flow Controller Water Level Controller PID parameters K P K I K D PROPOSED CASCADED PID CONTROL SCHEME During start up [9] [14] power obtained is opposite to the direction of change in valve position. When sudden open in gate is done because of water inertia the flow will not do immediate change instead of that the pressure across the turbine will reduce consistently making power to reduce. When sudden increase or decrease in load occurs the water accelerates until the water flow settles to the new desired value (Falqueto et al., [1] 2007) editor@iaeme.com

6 Load Responses Based Optimized Cascaded PID Control Scheme Using PLC-HMI In Hydro Electric Pumped Storage Power Plant Because of the sudden increase and decrease in load the gate opening/closing operation may have limitation in speed deviation but it formulates damages to turbine/generator shaft. If slow and smooth operation of gate is preferred to prevent this type of damages that will lead to lagging in load due to low pick up of the turbine/generator and also the drop in frequency will occur. So it is necessary to get (Falqueto et al., 2007) a suitable signal so that to operate the gate which will satisfy the sudden load change and also to maintain the constant speed, the proposed Load Responses based(cpid) Cascaded PID (Proportional - Integral - Derivative) controller scheme using PLC - HMI (Programmable Logic Control - Human Machine Interface) is proposed. Figure 6 Load Responses based Cascaded PID Thereby the maximum sudden in and out of load change is expected and equivalent manipulation in valve position is obtained using the proposed scheme. The opening and closing of the gate position is done in three types. It is step closing/opening for sudden change, ramp closing/ opening for velocity and exponential opening/closing for acceleration. The proposed load characteristics based Cascaded PID control scheme for flow and level control is shown in the Figure.6. The output of the water level controller is cascaded with PID water flow controller through water flow manipulator. By comparing the actual water flow with load demand the error signal is obtained and it is taken as input to the water flow controller. The following algorithm is proposed for mimicking each Load characteristic response. Step 1: Initialize K, K and K the Proportional, Integral and Differential gains respectively of p I d PID controller for both water flow and level Control. Step 2: Conduct experiments and plot the response for one behavior for different load conditions. Step 3: Find out deviations between Load characteristics and experimental response at different sampling times. Step 4: Find average of all deviations. Step 5: Adjust Kp, KI and Kd of the water flow and level controllers. Step 6: Repeat the experiment until deviations between load characteristic and experimental response become zero editor@iaeme.com

7 Step 7: Note down the final value of Kp, KI and Kd of the water flow and level controllers, which are taken as optimum PID parameters for particular change in load. Repeat the procedure for all the behaviors mentioned above. In order to obtain optimum PID controller parameters an illustrative response for water flow is shown in Figure. 7. th Point A = f ( k 1) = Experimental Water flow sample at k instant. th Point B = f ( k = Load Characteristics Water flow sample at instant. 1) k1 th Point C = f ( k ) = Experimental Water flow sample at instant. n th Point D = f ( k ) Load Characteristics Water flow sample at instant. n k n 1 k n Figure 7 Load Characteristics and Experimental Responses to obtain optimum PID parameters. Keeping the above optimum PID parameters as guidance, again several simulations were carried out on the lab-scale experimental set-up for all the load responses. Finally, one set of overall optimal PID controller parameter, which will mimic almost same way for all the types of load variations mentioned above was found out. Table 1 Optimal PID controller parameters for different behavior responses PID parameters Load Characteristics K P K I K D Water Water Water Water Water Water Flow Level Flow Level Flow Level 10% change in ramp load from 50% to 60% Open Loop Response (Change in water flow % to 80%) Open Loop Response (Change in water flow % to 100%) Sudden load change due to grid disturbance Sudden Load throw off to House Load The overall optimum PID parameters obtained for water flow and level controllers suitable for any kind of dynamic load variation of hydroelectric pumped storage power plant is mentioned in Table editor@iaeme.com

8 Load Responses Based Optimized Cascaded PID Control Scheme Using PLC-HMI In Hydro Electric Pumped Storage Power Plant Table 2 Overall Optimum PID Controller Parameters for Flow and Level Control. Control loop Optimum PID parameter K P K I K D Flow Controller Level Controller These optimal PID parameters are used to the water flow and level controller through error signal. 4. PLC - HMI VISUALIZATION The overall B&R Hardware with Power supply, PLC, Input/ Output modules is shown in the Figure. 8. In PLC HMI, Visualization is done to design the process that will be user friendly and also useful to follow the ongoing process by monitoring in the screen. With the advancement in touch screen, the inputs can be fed in the PLC and if there any changes in the data can also be updated online. Figure.9. represents the HMI display with Start and Stop buttons. Figure.10. displays the buttons of valves and pumps in the plant. There are 3 valves and 2 pumps in the prototype model. Based on the prototype operation, it will be enabled ON condition and it will be displayed in the HMI. Figure.11. indicates the prototype model of the hydroelectric pumped storage power plant in PLC-HMI. Figure 8 B&R PLC Hardware Set Up Figure 9 Prototype Model in PLC HMI Figure 10 Valves and Pumps in PLC HMI Figure 11 HMI displays start/stop button editor@iaeme.com

9 5. EXPERIMENTAL RESULTS Figure12 and 13 represents the Experimental Results for conventional and the proposed CPID control at the opening of Gates. Assessment based on Performance Evaluation Criteria such as Integral Square Error (ISE) and Integral Absolute Error (IAE) for various changes in load was analyzed and it is shown in Table.3. Figure 12 Load 10 MW 20 MW Gate 1 Opening above average level Set Point m3/sec Control scheme Figure 13 Load 20 MW 40 MW Gate 2 Opening at medium level Set Point m3/sec Table 3 Performance Evaluation Criteria Comparison Control loop Load 10MW-20MW Load 20MW-40MW ISE IAE ISE IAE Conventional PID Water flow Cascaded PID (CPID) Water flow Comparison of the performance evaluation criteria such as Integral Square Error (ISE) and Integral Absolute Error (IAE) was done for both conventional and the proposed Load Responses based CPID control scheme using PLC-HMI is presented in Table editor@iaeme.com

10 Load Responses Based Optimized Cascaded PID Control Scheme Using PLC-HMI In Hydro Electric Pumped Storage Power Plant 6. CONCLUSIONS This work enhances the robustness of the load responses based optimized cascaded PID controller scheme for changes in loads. Because of delay in time sudden open in gate that leads to water inertia and the flow didn t do immediate change whereas by using this proposed load responses based optimized CPID control scheme, gate position is identified and a suitable signal is manipulated to operate the gate which satisfied the sudden load change and maintained constant speed with less settling time. Based on Performance Evaluation criteria analysis, the conventional method has large ISE and IAE errors when compared with the proposed scheme. The proposed load responses based optimized CPID control scheme using PLC-HMI results in least ISE and IAE values for the step changes in load showing 26% improvement for water flow when compared to conventional PID control. The qualitative and quantitative comparisons of the performance of the various control schemes reveal the superiority of the load responses based optimized CPID control scheme over the conventional PID control for optimization in balancing the load demand. REFERENCES [1] J. Falqueto, M.S. Telles, "Automation of diagnosis of electric power transformers in Itaipu Hydroelectric Plant with a fuzzy expert system, ETFA 2007, pp , Sept [2] G. Ardizzon, G. Cavazzini, G. Pavesi, A new generation of small hydro and pumped-hydro power plants: Advances and future challenges Renewable and Sustainable Energy Reviews, 31, pg , [3] J. P. Deane, E. J. McKeogh, and B. P. Ó. Gallachóir, Derivation of Intertemporal Targets for Large Pumped Hydro Energy Storage With Stochastic Optimization, IEEE Transactions on Power Systems, 2012 [4] Helena M. Ramos, Maria P. Amaral, Didia I. C. Covas, Pumped-Storage Solution towards Energy Efficiency and Sustainability: Portugal Contribution and Real Case Studies Journal of Water Resource and Protection, Vol 6, pg , [5] G Martínez-Lucas, J I Pérez-Díaz, J I Sarasúa, G Cavazzini, G Pavesi and GArdizzon, Simulation model of a variable-speed pumped-storage power plant in unstable operating conditions in pumping mode IOP Conf. Series: Journal of Physics: Conf. Series 813 (2017) [6] Juan I. Pérez-Díaz,, M. Chazarra, J. García-González, G. Cavazzini, A. Stoppato, Trends and challenges in the operation of pumped-storage hydropower plants, Renewable and Sustainable Energy Reviews, Vol 44, pg , [7] R Bessa, C Moreira, B Silva, J Filipe and N Fulgêncio, Role of pump hydro in electric power systems, IOP Conf. Series: Journal of Physics: Conf. Series 813 (2017) [8] R. Aihara; A. Yokoyama; F. Nomiyama; H. Kihara, Optimal operation scheduling of pumped storage hydro power plantusing efficient optimization algorithm, IEEE International Conference on Power System Technology, [9] A. Selwin Mich Priyadharson, M.S.Saravanan, N. Gomathi, Vinson Joshua and A. Mutharasan, Energy Efficient Flow and Level Control in a Hydro Power Plant using Fuzzy Logic Journal of Computer Science, Science Publications, USA, Vol 10, Issue 10, Pages , [10] Selwin Mich Priyadharson. A, Ramesh Kumar and M. S. Saravanan, Neural Cascaded with Fuzzy Scheme for Control of a Hydroelectric Power Plant American Journal of Applied Sciences, Science Publications, USA, pg , [11] Ahmad M.El-Fallah Ismail and A.K.Bharadwaj, Enhancement of Static & Dynamic Response of The Three Phase Induction Motor Under The Effect of The External editor@iaeme.com

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