Impact of Passive Cell (PC) and Active Distributive Network Cell (ADNC) on Power System Oscillation John B. Oladosu Abdrazak A. Olawoye Department of Computer Science and Engineering, Department of Computer Science and Engineering, Ladoke Akintola University of Technology, Ogbomoso, Ladoke Akintola University of Technology, Ogbomoso, Nigeria Nigeria Correspondence Authors (johnoladosu@gmail.com) aaolawoye@student.lautech.edu.ng ABSTRACT Distribution Network Cell (ADNC) and to analyze the small and Impact of Active Distribution Network Cell (ADNC) Study on large signal stability changes and to analyze the power flow Power System Oscillation requires modelling of power system signal [1,7]. components. The system covers the well knows Two Areas- System benchmark which studies low frequency electro- 2. METHODOLOGY mechanical oscillations in large interconnected power system. Impact of Active Distribution Network Cell Study on Power This study examined the effect of passive cell on Active System Oscillation requires modelling of power system Distributive Network Cell (ADNC). The method adopted was components. The system covers the well knows Two Areas- modelled using Power System Analysis Toolbox in MATLAB System benchmark. The benchmark is a model was created by environment. The result was varied by analysizing the effect of Canadian Association to presents the various types of passive cell at different position and Active Distributive oscillations that may happen in large/small power systems. It is Network Cell (ADNC) at different positions. The damping also known as Kunder’s system which “is specifically designed effect is also analyse through reactive and real (active) power to study low frequency electromechanical oscillations in large profile. interconnected power systems” [1]. CCS Concepts 2.1 System Model The 2-Area System was modelled using Power System Analysis • General and reference ➝Cross-computing tools and Toolbox (PSAT) embedded in Matlab Environment. Figure 1 techniques ➝Experimentation shows the design overview. The analysis of the system model is summarized below: Keywords ADNC, Passive Cell, PSS i.) The System consists of two areas: Area I region is indicated by the buses on the left half side of Figure 1 1. INTRODUCTION and Area II region is indicated by the buses on the The types of load in modern power systems range “from simple right half. resistive load to more complicated loads with electronic controllers” [1-14]. Power system complexity and their ii.) The two areas are connected together by a characteristic nonlinearity increase with increase in controllers transmission line of power, voltage rating and and loads. This in turn makes power systems to exhibit frequency of 100MVA, 20kV and 60Hz respectively. increasing instability problem. Power instability problems can iii.) The system generally consists of 4 PSSs, 4 AVRs, 5 cause partial or total blackout. This problems can be categorized Synchronous Generators, 3 PV Generators, 3 ZIP into “voltage, phase angle and frequency related problems” [1- Loads, 3 PQ Constants, 11 Buses, 5 Transformers, 5 7]. transmission lines, 1 Slack Bus, and 1 Induction In order to address power systems disturbances many devices Machine. have been invented and a number of solutions have been iv.) Each of the Area consists of 2 Synchronous proffered to enhance the effectiveness of these devices. These Generators, each of rating 900MVA of Power and include fast exciter or Automatic Voltage Regulators (AVR), 20kV of Voltage. Power System Stabilizer (PSS) which helps to produce the fine adjustment needed to damp out electromechanical or low v.) Each generator is equipped with AVR and PSS. frequency oscillations in power systems [1, 7-10]. Existing study vi.) The loads are applied at Bus 6 and Bus 5. [1] examined the “Impact of Active Distribution Network Cell (ADNC) on Power System Oscillation.” The objective of the vii.) The Slack Bus, PSS, AVR, Synchronous Generator, work is to examined the impact of Passive Cell (PC) on Active Transformers, and Transmission Lines are all linked together by Buses of rating 20kV. CoRI’16, Sept 7–9, 2016, Ibadan, Nigeria. 152 Figure 1: The Two Area System (PSAT Implementation) 3. IMPLEMENTATION AND RESULTS 2.2 Design Approach There are three cases considered in the system design, namely: 3.1 Base Case Analysis Base Case, in which the system is considered neutrally as The base case load benchmark is P= 2734 MW, with 100 MW depicted in Figure 1; Passive Cell (PC) Case and Active transferred from Area I to Area II over the tie-line. Results in Distributive Network Cell (ADNC) which are varied at Bus 5 Figures 3 and 4 show the power flow and the eigenvalues for the and Bus 6 as shown in Figure 2 (a) and 2 (b) respectively. base case system. The system with passive network cell consists of Induction Machine, constant PQ load and ZIP load. Figure 2: (a)Passive Cell Figure 2:(b) ADNC Figure 3: Power flow curve The Active Distributive Network Cell consists of the following: ZIP Load, Back-to-Back Converter, Synchronous Generator and Inductor Motor [1]. 153 Figure 4: Eigenvalues diagram of Two Area System (Base Case) 3.2 System with Passive Cell (Loads and IM) In order to study and analyze the impact of Passive Cell in the Power System Oscillation, Passive Cells which consists of Loads (ZIP and PQ) and Induction Machine are applied to the system (Figure 5). Figure 5: PSAT Implementation of the Study with Passive Cell 154 The power flow of system with PC at bus 6, Area II is as shown in Figure 6. Figure 7 is the eigenvalues curve for the system with PC. Figure 8: Power flow analysis of the passive cell at Area I Figure 6: Power Flow by the System with PC (Area II) Figure 9: Eigenvalue report of passive cell at Area I Figure 7: Eigenvalues report at Area II for system with PC Figure 8 shows the power flow analysis of the system with PC 3.3 IMPLEMENTATION OF ADNC implementation at Area I while Figure 9 is the eigenvalue for the Figure 10 represents the implementation of the two Area System same system. of the study by replacing the Induction Machine as shown in Figure 5 with Synchronous Machine. The ADNC consists of Synchronous Machine, ZIP load and constant PQ load. 155 Figure 10: Power System with ADNC (PSAT Implementation) Figure 11 is the power flow analysis of the implementation with ADNC at Area II and Figure 12 is the eigenvalue. Figure 12: Eigen value report of ADNC at Area II Figure 11: Power flow of ADNC system at Area II For implementation of the ADNC system at Area I, the power flow analysis is shown in Figure 13 and the eigenvalue graph is It can be seen from Figure 11 that power flow maximum shown in Figure 14 convergency error at bus 6 is the same as that for PC at Bus 6 (Figure 8). 156 Table 1: Global Summary Report Figure 13: Power flow in ADNC at Area I 4.1 Comparison between existing model and new model In term of the design model, when solving the power flow from the existing design, there are errors generated, shown as follows: Definition of system connections ... Error: Block cannot be connected to block . Error: Block cannot be connected to block . Error: Block cannot be connected to block . Figure 14: Eigenvalue report at Area I Error: Block cannot be connected to block . *** Failed conversion from Simulink model: Simulink model is not 4. DISCUSSION well-formed (check links). Table 1 shows the report of the Total Generation, Total Load and Total Losses of both Real and Reactive Power of the model Attempted to access idx(2); index out of bounds because for each of the cases i.e. base case, PC case and ADNC case. numel(idx)=1. From the table, it can be seen that ADNC has a great impact on Data conversion failed. power system oscillation than any of the other in term of the total generation, total losses and total load of the model. These errors make the existing model heavily error-prone. The errors are corrected using the new model by removing the transmission lines (compare Figure 15 with Figure 16). 157 Figure 15: Existing model Figure 16: New Model 158 Since the existing model is invalidated, some of the responses of [3] He, J., & Malik, O. 1997. An adaptive power system the analysis analyzed are not gotten when using the new model. stabilizer based on recurrent neural networks. Energy New dimensions were then taken to analyze the impact of both Conversion, IEEE Transactions on, 12(4), 413–418. passive cell and active distribution network cell on power system [4] Hemmingsson, M. 2003. Power system oscillations- oscillation. detection, estimation and control, Lund University. In term of the continuous and time domain analysis, only the base [5] Hsu, Y.-Y., & Chen, C.-R. 1991. Tuning of power system case has continuous and time domain flow. The passive cell and stabilizers using an artificial neural network. Energy ADNC (both Area I and Area II) do not have continuous state Conversion, IEEE Transactions on, 6(4), 1991, 612–619. variable. [6] K. Prasertwong,, N. Mithulananthan, & D. Thakur. (n.d.). 5. CONCLUSION Understanding low frequency oscillation in power systems. As shown by the simulation of the base case, where there is no Power and Energy System Group, School of Information additional elements connected to the two area system, it has been Technology and Electrical Engineering, The University of found that all the PSS types exhibit damping effect under small Queensland, St. Lucia Campus, Brisbane, Qld 4072, disturbances. Australia: Electric Power System Management, Energy Field of Study, Asian Institute of Technology, Klongluang, P.O. Then, in the subsequent simulation model, adding a regular load Box 4, Pathumthani, Thailand. Retrieved from and induction motor as a passive cell, in different locations, and mithulan@itee.uq.edu.au their impact on the system loading have been analyzed. The [7] Kauhaniemi, K., & Kumpulainen, L. 2004. Impact of results revealed that the system becomes instable when the distributed generation on the protection of distribution passive cell is connected at the midpoint of tie line. 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