A. INTRODUCTION
CE 3.1
The developed section elaborates the task executed for the completion of the project “Design of Power System Stabilizer Using Harmony Search Algorithm” while I was pursuing my PG degree in the field of Electrical & Electronics engineering, enrolled at Andhra University College of Engineering, located at Visakhapatnam, Andhra Pradesh, India. I did the mentioned project individually from ……… to ………….
B. BACKGROUND
CE 3.2
The problem of stability of power system, which comprises of transformer, loads, generators and transmission lines, is a long-going topic of interest where instability is caused by several parameters such as sudden load change, voltage drop and so on which affects the expected outcomes from the systems. This project focuses on comparing the conventional power system stabilizer (CPSS), which was introduced to reduce the damping, settling time, etc. to provide the stability to the power system, with the harmonic search algorithm (HSA) based PID controller. The stability analysis of both the CPSS and the HSA was carried out. I considered a single machine infinite bus (SMIB) power system using the MATLAB Simulink tool to know the best control system among both. I designed the system models, prepared harmonic search algorithm and provided required parameters for all the systems for operations and compared the results.
CE 3.3
Essential objectives of the work were:
- To conclude the best control system among CPSS and HSA controllers
- To improve the power system stability by reducing the constraints called settling time, peak overshoot and undershoot
- To improve the power output by lowering the oscillation damping in rotor speed
CE 3.4
I was responsible for both the technical works which were the design, simulation and result analysis of the power system stabilizer using harmonic search algorithm and comparing with conventional power stability system, and the managerial works which were preparing the proposal, getting the approval on proposal, conducting and attending the meetings with guide and department staffs, giving the presentation, preparing the project report and making submission.
CE 3.5
Though there were several tasks to be done, main duties to be considered were
- To conduct the design of the model of the SMIB power system for CPSS controllers in the Simulink tool
- To design and implement the algorithm for the HSA based PID controller
- To design the model of the SMIB power system with HSA based PID controller in Simulink
- To provide the necessary parameters for CPSS and SMIB in simulation software
- To carry out the analysis for both CPSS and HSA controllers at different perturbations
- To analyze the result and to conclude the best controller for power systems
- To carry out the documentation works and manage the project
CE 3.6
The hierarchy represents the rank of several individuals involved in the work.
Fig: Organizational hierarchy
C. PERSONAL ENGINEERING ACTIVITY
CE 3.7
I gathered details of current technologies in power stability system design for the design and simulation. I carried out the analysis of stability of single machine infinite bus power system implementing the harmony search algorithm-based controller and the conventional power system stabilizer (CPSS) in the MATLAB Simulink tool. For this, I designed the systems model in the Simulink and provided the considerations data for all the systems and performed the simulation. I compared both the control system and concluded the best controller for providing stability to the system. I considered loading conditions of a wide range while analyzing the power system’s stability with the use of HAS algorithm and CPSS for SMIB systems taking different ratings.
CE 3.8
I applied the theoretical as well as practical knowledge that I gained from the subjects of electrical and electronics engineering such as power design system, power distribution system, power electronics, electrical devices and circuits, control systems, etc. in designing the power system controller models. I utilized my practical knowledge regarding the simulation for using the Matlab Simulink tool for simulating the PID controller using HAS algorithms. I used the technical knowledge for the system damping, peak undershoots and its controlling methods according to which I designed the HSA based PID controller. I followed the IEEE 3001.11 and ISO EN 13849 IEC 62061 for designing of controlled power system equipment. I also followed the ISO 16781:2013 for the simulation of control system for enhancing the system operation. I obeyed the rules of my college and my department during my project span.
CE 3.9
CE 3.9.1
First and foremost, I did the deep research to know the different causes of instability of the electrical system and the different controllers to control the instability of the system. I found the most common factors affecting the stability of the electrical system were the sudden load change, grid failure, etc. and the widely used control system nowadays was conventional power system stabilizer and the harmony search algorithm PID controller. For the performance comparison between both the control systems, I studied the research articles for understanding the system models, working methods, etc. I planned to implement both the control system in the SMIB power system because of its ability on controllers tuning at one machine without considering the other machines’ effect in power system. As this project was the comparison between the controllers in SMIB system, I considered the standard designed model for SMIB without changing any parameters and then employing the decided controllers in it. Firstly, I prepared the SMIB with the conventional power supply stabilizer in the Simulink tool. Here, I provided several summing points in order to add or subtract different signals to provide a single output signal.
CE 3.9.2
I positioned some gain loop in order to provide the proportional value to show the relation between output signal magnitude and the input signal magnitude at a steady state. The gain loop also used to provide less or more power to the system. Next, I placed several transfer functions to the system model to relate the output and the input signal of the control system for each possible input value. I introduced the conventional power system stabilizer in the system model as shown in figure below so to enhance the power system’s dynamic stability. For the addition of Simulink blocks, I used the Simulink library, selected the desired Simulink blocks to design required Simulink diagram, as shown below:
Fig: SMIB system with CPSS
CE 3.9.3
After completing the power system control model with CPSS, I prepared the algorithm and the flow diagram showing the steps involved in the HSA. In implementing the HAS algorithm, firstly I initialized the algorithm parameters such as harmony memory size, pitch adjusting rate, bandwidth, and HM considering rate in order to improve the solution vector. These solution vectors were stored on Harmonic Memory. Then, I performed initialization of the harmony memory with many randomly generated solution vectors i.e. xi = x L/I + rand (1) * (x U/I – x L/I) where the rand (1) were randomly generated numbers from 0 to 1, and x L/I & x U/I were lower bounds and upper bounds. Moving on, I carried out generation of the New Harmony vector using pitch adjustment, memory consideration, and random selection. Then, with pitch adjusting rate, all the components were adjusted for pitch. I defined the decision-making function for the replacement of the old solution vector with the new oneif the new solution vector would have enhanced objective function. Based on this algorithm, I prepared the process flow diagram of the HAS, which is given below:
Fig: HSA
CE 3.9.4
After that, I started to prepare the SMIB system model with the harmony search algorithm PID controller. Here, I designed the SMIB system model providing summing points, gain loops, transfer functions, etc. and connected the HSA based PID controller to the system as shown below:
Fig: SMIB system with HSA based PID controller
After completing both the power control system modeling in the Simulink tool, I scheduled to carry out the comparison between both the controllers on providing better stability to the power system for rotor speed and load angle delta for different perturbations at 0.05 and 0.1 for both the models. I gave the input parameters of power supply stabilizer and the SMIB dynamic constants as shown in the table below:
Fig: PSS Parameters SMIB Dynamic Constants
CE 3.9.5
After the simulation with all the prepared models and the considered data for the systems, I obtained the different comparison graphs for load angle and rotor speed at different perturbations. Some of the comparison graphs are given below:
Fig: Load angle at 0.05 perturbations Fig: Rotor speed at 0.1 perturbations
From the simulated result, I found that the result generated by the harmony search algorithm based PID controller was efficient while being compared to the conventional power system stabilizer. I observed the HSA optimized the parameters faster and also showed better damping performance with optimized gains while the system was perturbed and so the reduction in settling time, peak undershoots and peak overshoot occurred. Due to the reduction of these parameters, the power system attained stability quickly. I shared the comparative analysis with the guide and got good appreciation from him and moved ahead for the final documentation and the project presentation.
CE 3.10
TECHNICAL PROBLEMS AND SOLUTIONS
- During the simulation with the Simulink, the error message appeared that read ‘data logging error’ and then showed ‘end now’ within only 1 second. The ending of the simulation task within 1 second avoided me to carry out the proper simulation output. I checked several settings and parameters of the Simulink tool and found that the start time field value in the tool was set to 0.0 and the stop time was given as 1 second due to which the simulation ended in 1 second. To solve the issue, I changed the stop time to 10 seconds and started to simulate again. Hence, the ending of simulation within 1 second was solved and I obtained proper output result of the power system controllers.
- After I found the simulation graph from Simulink, I noted the graph having improperly defined axes that were complex for understanding the graph. I tried to edit it such as axis, line colors, etc. but the editing option of obtained graph was not available in Simulink. To make the graph easily readable, I saved the data in the .mat file where the mat file stored all the information of Simulink. Next, I opened the corresponding mat file script and performed the editing of obtained graph easily.
CE 3.11
CREATIVE WORK
- Here, I checked the performance of the power stability system using HAS algorithm and compared it with the conventional power stabilizer system. This algorithm overcame the problems like instability of small-signal oscillations which is result of lack of sufficient natural damping by damping the low-frequency oscillations of the system.
- For the simulation of the SMIB power system with CPSS and HSA controllers, I selected the MATLAB Simulink tool in comparison to other simulation tools such as ETAP, PSCAD, PSS/E, Pspice, etc. There were several reasons besides the selection of this software which made my project work with less time consumable and fewer errors in design. The Simulink tool used to carry out any type of simulation and at any point in this environment and allowed the user to access different blocks using Simulink library browser. The design verifier in the Simulink helped the user to identify the design errors such as dead logic, integer overflow, etc.
CE 3.12
During this project, I maintained better collaboration with the department professors, department head, etc. and achieved the useful information from them about the project. I attended the meetings multiple times with my guide to conducting discussions on the project regarding design and issues to execute the project in an efficient way. I also had discussion with the colleagues to collect their ideas about my project and also I delivered my ideas to them about their projects. As the record of my project, I prepared the detailed report of the project with overall explanation of the project works and results. I behaved politely with the externals, management executives, etc. during the project presentation.
D. SUMMARY
CE 3.13
I designed the model of conventional power system stabilizer and the harmony search algorithm (HSA) based PID controllers for the SMIB – single machine infinite bus power system in the Simulink tool. I input the parameters for all the systems and carried out the simulation between both CPSS and HSA control system for load angle and rotor speed at 0.05 and 0.1 perturbations to know the best system among both to provide the power system stability.
CE 3.14
From the analysis, I successfully concluded the control system which was capable to provide better stability to the power system. This PID controller with HAS was successfully capable to reduce the system damping and improve the system output. Also, the HSA system reduced the factors to deliver stability as stated in the objective.
CE 3.15
I improved my engineering skills regarding the design of power stabilizer systems, and at the same time, I also strengthened my skills in simulation using Simulink tools. I took several actions in rectifying the concerns, which consequently enhanced my problem solving abilities. I maintained collaboration with the different individuals at the college and gained better communication skills.